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a digital indicator diagram generation system for the ricardo e6 engine

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1. 3 000 3 000 0 002 2 4 922 0 001 0 037 in T AV 7 3 000 5 000 0 006 2 0 547 0 001 0 045 in also Ny YT 2 E Y V 7 DS 3 000 4 375 30 925 in By equation 17 AIMEP _ 0 054 0 037 0 045 IMEP 30 925 t 30 9258 9 056 5 7 139 APPENDIX I SAMPLE RESULTS Complete Results at 20 Degrees Spark Advance 250 EM P psia vs M CinX 5 RESULTS Fnaine speed 1360 54 rom Compression ratio dg Work Gross work output 171 59 Teln Valve loss cr JE Net work 156 19 ft Ib Indicated horsepower Sewer hp IMEF 0553 psi Averaged over 20 cycles 140 y ct y 3 pH e V in 3 Angle deg mM 3 169 3 3 97 aen cue id 173 3 3 3 7 3 176 9 2 87 EI 3 30 9 2 987 p D 33 3 89 72 55 O E 7 SE 1 Le 6 CLA rne go un p uu Mi Uo Sa LT D LA N a a0 Au YO dd asese LM y DD DD EN T LT fo a 1 Si pa mb Hs Trem A op UD uad e m Ay LL 1 Lit pP 0 Cu UD A AN l CC ID O Dn i 5 x D Q bd Fa I gt OPIN Po tt LA gt LU Po I nD LA gt Nin ho C2 UDP D N 106 236 7 107 228 3 103 239 9 T ip Or DCN o EE od CODO O N T CC fess
2. 98 Subroutine An is a calling subprogram that analyses the data to determine the work done by the cycle indicated horsepower and IMEP It then calls Print to print the results on the computer screen and produce a hard copy if desired by the user 10800 10810 1 0820 10830 10840 10850 10860 10870 99 Function FNCalc rpm DEF FNCalc rpm Period ICalculates rpm of engine Variables and constants used Period Period of engine cycle secs RETURN 60 2 Per1iod FNEND Function FNCalc rpm calculates the rpm of the engine based on the period in seconds per cycle of the engine 7110 7120 7130 7140 7150 7160 7170 7180 7190 7200 7210 7220 7230 7240 7250 7260 7270 7280 7230 7300 7310 7320 7330 7340 7350 7360 7370 7380 7380 7400 7410 7420 7430 7440 7450 7460 7470 7480 7480 7500 7510 100 Subroutine Work SUB Work A 11 12 13 Pw Nw Ntw P This subroutine calculates the work done by the engine cycle in ft lbs IUariables and constants used A Array holding data I1 12 13 Points where piston at IDC Pw Work done in upper or power loop of the diagram Nw Pumping losses Ntw Net indicated work done by entire cycle P Phase of cycle used P 1 if Il at end of compression stroke P 2 if Il at end of exhaust stroke ODC1 0DCZ2 Points where piston at ODC i Power_stroke Exhaust stroke Intare stroke Compr_stroke Work done dur
3. ID ID Doe OO OO DOONN MWNNNNNNN Mn Y CT CT unum un un 0 9 O UD 09 J MUI CO P2 OO CO Y O39 UT O MN 00D CO YO UP P CO 141 236 39 28 5 40 1 b4 40 91 79 41 73 94 42 66 09 43 36 24 44 18 39 45 5E 46 2 46 63 9 47 45 03 48 26 2 49 08 37 49 89 54 50 71 7 1 513553 88 62 14 0 06 53 15 Dees 53 98 0 41 54 739 0 59 Dur 0 78 56 43 0 96 are 1 15 53 06 1 34 58 87 Lane 59 59 1 72 50 5 1 31 Blade 2 1 52 14 21523 62 96 2 49 53 77 2 59 64 59 2 89 BS 4 3 09 65 22 3 3 67 04 3 5 67 85 Da Boers 3 91 69 49 4 12 70 32 4 32 1412 4 53 71 94 4 74 lav 4 95 13 5 Gal 74530 5 38 Pare 33253 75 02 5 81 76 83 6 02 77 565 6 24 73 47 6 45 79 28 6 67 380 1 A A A rr Ae l DO LO OO e OL DO D Y DD LS LO OLI OU 0 NDAN D tops DP PDA br a S PO gt No c 210 LO CON UN p Wh Po Pa PR PS RS Pu RO n P9 PPP PI PS MO J CO 3 DE Pu 224 noron fo RO nm no 00 Y UN 13 Y Ye Ld 230 231 232 233 234 BN GIU UU tN NSN Y Y INULAN N 0 NNN o CO UT SU UD C9 E 3 A e 3 3 e L a WwW D XD D CO cO CO cs NN MJ 4 7 0D PO NJ PO TO PO CO Q3 CO G
4. N to exit program segment 10 11 122 HC DATA Produces hardcopy of modified data pressure volume and crank angle for one engine cycle END Causes program exit The GET DATA soft key must be used first since obviously data must be taken before it can be plotted or analyzed Press the GET DATA soft key k0 You will now be prompted to input three values needed by the program the engine compression ratio the charge amplified Range setting and the number of engine cycles to be averaged You must press the CONTINUE key after each response After inputting values the program requests confirmation If your input value is correct enter Y of y then press CONTINUE Now the program begins data acquisition and displays GATHERING DATA on the screen When finished DATA GATHERING COMPLETE is printed on the screen You may select from any of the soft keys at this point If GET DATA is selected the compression ratio range setting and number of cycles to be averaged must be entered again Remember that the CONTINUE key must be pressed after each input by the user in all program segments When finished with the program press the END soft key to exit the program or just turn off the computer Turn off the Ricardo engine following the instructions in the Stopping the Engine section of Ricardo Operating Instructions Spark Ignition Running Disassemble the diagram generation equipment The coolin
5. 1090 OUTPUT 712 ACQUIRE MODE AUG NUMAU 4 1100 WAIT 40 S div 4 1110 Get waveform 1120 OUTPUT 712 CURUE 1130 ENTER 712 USING B AC 1140 OUTPUT 712 ACQ MODE NORMAL 1150 SUBEND The Read avg4 chl subroutine acquires the waveform from Channel 1 averaged over 4 acquisitions and downloads it to the computer It was found that averaging over 4 waveforms produces a sufficiently smooth result that it can be analyzed by the Period subroutine below If less than 4 waveforms were averaged the rising edge of the resultant curve is sometimes too rough for use in Period The DATA specified in the first OUTPUT statement specifies the data source for the acquisition to be Channel 1 the shaft encoder The data encoding ENC RPR is set to Right Justified Positive Binary which means that the data is encoded in 256 vertical increments from 0 to 255 with 0 volts 69 corresponding to the integer 127 ACQUIRE MODE AVG NUMAVG 4 sets the scope to acquire in the AVERAGE mode over 4 waveforms The WAIT statement allows time for the waveforms to be acquired and averaged The resultant waveform is then requested using the CURVE command and is entered into the computer with the ENTER statement specifying binary encoding B into array A Array A is a column array for maximum speed of data downloading The last OUTPUT statement then returns the acquisition mode to NORMAL the mode assumed initially by the subprograms which
6. 950 960 970 66 Subroutine Init setup SUB Init setup Sec div Volts chl Uolts ch2 This subroutine initializes the scope settings for each new run IUariahles and constants used Sec div Horizontal scope setting Volts chl Volts ch2 Volts div scope setting for Chl and Ch2 respectively ISubprograms used None OUTPUT 712 DEBUG ON Set the scope to power up state OUTPUT 712 INIT PANEL WAIT 3 1Set up Channels 1 amp 2 Volts div and sec div OUTPUT 7123 UMODE CH1 0N CH2 0FF OUTPUT TI23 GHI VOLTS 2 Volts_chi 2 OUTPUT 712 CHZ VOLTS 27 Volts_ch2 2 OUTPUT 712 HOR ASEC 1 Sec divs l ITrigger from Channel 1 on positive Islope of square uave OUTPUT 7123 ATRIG MOD NOR S0U CH1 OUTPUT 712 ATRIG COU DC LEU zZ OUTPUT 1 1 ATRIG SLD lt PLU POSS OUTPUT 712 RUN ACQUIRE SUBEND Init setup initializes the scope settings so that they are the same at the start of each run The INIT PANEL OUTPUT statement sets all scope settings to the powerup state see 2430 Instrument Interfacing Guide pgs 24 67 25 The VMODE statement turns Channel 1 on and Channel 2 off on the scope display The scope scale settings are then set at 2 Volts div CH1 VOLTS and CH2 VOLTS and the horizontal scale is set to 100 msec div HOR ASEC This horizontal setting allows 2 secs of Channel 1 data to be displayed on the screen which means that the engine can be running at as
7. OUTPUT 712 UMODE CHZ UN OUTPUT 712 DATA ENC RFB lt S0U CH2 3930 R_ch2 OUTPUT 712 ACQUIRE MOD lt NORMAL 5840 3950 3980 597 0 3980 3990 4000 4010 4020 4050 4040 4050 WAIT Interval OUTPUT 712 CURVUE ENTER 712 USING B A IF ACI1 gt ACT2 THEN FOR I TO 1024 IditI sIdlClotOCl9 NEXT I Counti Count1 1 ELSE FOR I TO 1024 1d2 1 1d2 1 At 1 NEXT I 81 82 4050 Counti2 Count2 4070 END IF 4080 IF Count1 N AND Count2 lt N THEN 4090 GOTO R_ch2 4100 END IF 4110 IF Counti N THEN 4120 FOR I 1 TO 1024 4130 B 1 1 gt 1d1 1 N 4140 NEXT I 4150 Phase 1 4150 ERSE 4170 FOR I 1 TO 1024 4180 BCT 1 dE T N 4190 NEXT 1 4200 Phase 2 4210 END IF 4220 SUBEND The purpose of subroutine Acq ch2 is to acquire the curve from Channel 2 and average over N waveforms The phase of the resultant curve must also be returned through the parameter statement Since the engine cycle occurs over two rotations of the drive shaft the signal from the shaft encoder goes high twice per engine cycle Thus the scope can be triggered at two points in the engine cycle so that it captures two types of curves see Fig A1 below These curve types must be kept sorted with the result based on only one type or one phase With this understood this subroutine will now be explained Three internal arrays are used in this subroutine Array A allows the fast downloading of the waveform from the oscilloscope Arr
8. Oo Ld e 010 Y Y WA ID Q2 CO C C CO CO LO CO CO A 400 09 00 NNW CO CO D I QUO UT LO OO NUTR SLUT 145 O U oO O U D U U U a oo y LO UN y y UN UA 10 Y ON ONS OO N UO Q2 CO DN WD UN SDD UA UN 032 CO ON WIA CO NON Y UN UN YA gt gt 0 Y 03 YU UTN M 4 Y Y y D 00 CO CO O LO LO UO LO hd dd 146 MJ J an D ETICO DINO a e O OVTOO0 0 7S MS mM KH PIMP NMP WwWWWwWh DB O 2010 ce e e e e a e e e e e D N Y 0 IW Y DC J Ul UN DD Y 0 O Y gt 0 Y CO O MN Yun 0D CO gt 0 N UNO O N UN WAUWWINONWWWWUNUIMWNNWOWW 0 Y 00 00 U1 NOANA Q9 Un un un UT Ul CO UT XO Q9 OD QUA CO Co C9 gt Un OO PO n9 o nono NN 147 490 519 T3 ee eee eee hd A EE NNW UI Y O D 9 Y y UN Y CO cO DUI ND MD UTI CO YN CO CO NANA YN CO Y CO ON C0 CO UY CO CO CO GO CO LO LO CO CO CO CO IIq I I Rf 680 5004 CO CO Y Q2 Y CO Y Y CO CO CO CO QO CO D to P D P DR PD PD HEP po oo Ss o UNI LN IN A UN LA UN e c SR fl DW o NO NU OY D o2 Ce DNS 148 149 541 19 5 4 22 12 24 542 19 5 4 27 13 16 543 19 1 4 32 13 98 544 19 1 4 38 14 73 5 45 18 7 4 44 15 61 546 19 5 4 5 16 43 547 19 5 4 56 17 2 548 18 3 4 63 18 06 549 19 5 4 7 13 87 550 19 3 4 77 19 63 551 18 9
9. during which the voltage increases from 0 to five 5 Volts The rise time was measured and found to be constant from 250 to 2500 rpm In order for the computer software to detect the rise in encoder output a threshold value is chosen The software sorts through the digitized encoder ouput downloaded from the oscilloscope and compares it to the threshold value to determine when the encoder output can be called high The angle that the crank goes through between the point where the encoder output starts to rise and the point where it reaches the threshold value increases of course with rpm In the computer software discussed here the threshold value assigned is 148 vertical increments The oscilloscope Screen contains 256 vertical increments fullscale so that 148 is 20 increments above O Volts There are 25 increments per vertical division on the scope The software sets the Volts division setting of the scope to 52 2 Volts division on the channel monitoring the encoder output The crank angle error due to the risetime of the encoder output will now be calculated at 1200 and 3000 rpm 25 increments div 5 Volts total rise 2 Valea aia 62 5 increments total rise 20 increments to threshold 65 5 increments total e 0 150 msec total risetime 0 048 msec to threshold Crank angle error at 1200 rpm 1200 rpm 20 rev sec 7200 degrees sec 7200 degrees sec 0 048 msec 0 346 degrees error Crank an
10. 10570 10580 10590 10600 10610 10620 10630 10640 10650 10660 10670 10680 10690 10700 10710 10720 10730 10740 10750 10760 10770 PRINT selected PRINT Then press CONTINUE key PRINT INPUT Range PRINT are you sure Y N then CONTINUE INPUT Confirms IF Confirm Y OR Confirm y THEN FOR I 1 TO 18 PRINT NEXT I ELSE PRINT GOTO Resp END IF SUBEND SUB Get_num_avg N IThis subroutine prompts the user to enter Ithe number of engine cycles to be averaged tover and returns the number IVariables and constants used N Number of waveforms to be averaged Confirm String to allow user to confirm input I ISubprograms used None DIM Confirm C Resp PRINT Enter the number of cycles over PRINT which you would like to average INPUT N PRINT PRINT Are you sure Y N then CONTINUE INPUT Confirm IF Confirm Y OR Confirm y THEN FOR I 1 TO 18 PRINT NEXT I ELSE PRINT GOTO Resp END IF SUBEND 65 Get comp ratio Get ca range and Get num avg are interactive prompting the user to enter the compression ratio charge amplifier range and the number of cycles to be averaged respectively from the computer keyboard These parameters must be set for each run and the user is required to confirm the value input 680 690 700 710 720 730 740 750 760 770 780 790 800 810 820 830 840 850 869 870 880 890 900 910 920 930 940
11. 4 85 20 51 552 18 9 4 92 21 32 553 19 7 5 01 22 14 554 18 5 5 09 22 96 555 19 9 5 18 23 77 556 19 5 5 27 24 59 557 20 1 5 36 25 4 558 19 3 5 46 26 22 559 19 7 5 56 27 04 560 19 3 5 66 27 25 56 1 19 1 5 76 28 67 562 19 3 5 87 29 493 563 18 7 5 98 30 3 564 18 9 6 09 31 12 565 19 1 6 21 31 94 566 18 1 6 32 29 75 567 18 3 6 44 23 57 568 19 3 6 57 34 38 569 18 9 6 69 365 2 570 18 3 6 82 36 02 571 19 1 6 95 26 62 572 17 1 7 09 37 65 573 18 3 7 22 38 47 574 18 1 7 36 39 28 575 18 1 7 5 40 1 576 17 3 7 64 40 91 577 18 1 7 79 41 73 578 17 9 7 94 42 55 579 17 7 8 09 43 36 580 17 7 8 24 44 18 581 17 5 8 39 E 582 17 3 8 55 45 81 583 17 1 8 71 46 63 584 Zi 8 87 47 45 585 17 3 3 03 43 26 586 17 1 9 2 49 08 587 17 1 9 37 49 89 588 17 7 9 54 50 71 589 16 7 9 71 51 53 590 16 9 3 88 52 34 591 17 1 10 06 Ed 16 610 621 LIA e dd dr o e ds 0 LY C0 CORO IN INON P 00000 GUID a py ds DO SI IM Ji UTI SIC CO UD EO U1 GO BEGET Q9 O OQUD NO 9 a 69 OL 2 DI A NO RQ lI LA Rb Rc IL o ll oo OUI qd 97 4 0101019101010 MM mun 0 mu 71 1 1U1 O 1 1 DATAN NAND c ou CO CO CO LO 00 CO OO CO Y Y Y 4 40009 25600 Mu Ul OH UR DP AR P O2 NO O 38 va Y UU I un Ao Jr et 26 89 7 1 53 34 3 16 38 Taa
12. 770 i529 93s 199 71 losl 33 85 200 1 2 14 7 33 77 200 73 15 5 33 69 201 774 15 3 33 61 202 775 15 3 J3452 2113 776 15 3 33 43 204 77 1553 33 34 205 7 7 98 15 3 33 25 205 t13 Ss 3 33 15 206 780 15 5 33 05 20 781 16 1 323 99 208 182 16 3 32 84 209 33 15 5 desde 209 784 16 3 32 62 210 785 15 3 32 51 24 785 16 1 32 39 21 7 97 15 9 32 27 21 79898 16 3 32 15 21 389 16 3 22 03 21 7 90 16 3 31 9 21 7 31 I5 7 31 21 7 92 16 5 31 64 21 793 16 5 31 5 21 7 94 16 1 31 37 21 795 toad 31 23 21 SNL OO O7 On Dro LON 9 C 154 796 16 1 31 08 220 51 797 15 9 30 94 521 32 798 16 5 30 79 222 14 799 16 1 30 64 222 36 300 16 3 30 49 223 77 301 16 5 3053 224 59 302 16 9 30 18 225 4 203 15 9 30 03 226 22 304 15 9 29 87 223704 305 15 9 29 7 227 85 306 16 9 29 54 208 67 307 16 5 29 237 229 49 308 16 3 29 2 230 3 309 16 7 29 03 231 19 810 15 9 28 86 231 94 311 16 9 28 69 292 75 912 16 5 28 51 233 57 313 16 9 28 33 234 32 314 627 28 15 235 2 315 16 7 27 97 236 05 316 16 9 27 79 236 03 817 ies 275 23785 318 16 7 27 42 238 47 219 16 5 27529 239 28 820 16 9 27 04 240 1 321 17 1 26 84 240 91 322 16 3 26 65 241 73 323 17 1 26 46 242 GE 824 16 7 26 26 243 36 325 17 1 26 06 244 18 326 16 9 25 86 245 327 17 5 25 66 245 81 828 16 9 25 46 246 63 329 17 3 25 26 247 4 830 17 9 25 05 248 26 331 17 9 24 85 249 08 932 17 9 24 64 249 89 333 17 9 24 44 250 71 834 17 5 24 23 251 53 335 18 5 24 02 252 34 93
13. Computation 2nd Edition Harper and Row 1977 Karlekar B V Thermodynamics for Engineers Prentice Hall Inc 1983 Lancaster D R R B Krieger J H Lienesch Measurement and Analysis of Engine Pressure Data SAE Publication 750026 Feb 1975 Nagao F M Ikegami Errors of an Indicator Due to a Connecting Passage Bulletin of JSME Vol 8 No 29 1965 pp 98 108 Nagao F Y Shimamoto H Nagano Y Ueno Influence of the Connecting Passage of a Low Pressure Indicator on Recording Bulletin of JSME Vol 6 No 21 1963 pp 78 85 Pish R H A New Generation Cylinder Performance Indicator Mechanical Engineering Dec 1984 Taylor C F The Internal Combustion Engine in Theory and Practice Vol I The MIT Press Second Edition 1985 90 APPENDIX A DERIVATION OF THERMAL EFFICIENCY OF AIR STANDARD OTTO CYCLE IN TERMS OF COMRPESSION RATIO The compression ratio re is defined as the ratio of the maximum cylinder volume volume at ODC to the minimum volume volume at IDC or where y is the ratio of specific heats of the gas From the Ideal Gas Law pV mRT _ mRT P Y lwY 1x7Y mRT V Vi mRT V ME T _ E ya 1 v 1 T Vi rY The result is that from substituting above into equation 4 ol APPENDIX B CALCULATIONS OF ERROR IN CRANK ANGLE DUE TO RISE TIME OF SHAFT ENCODER OUTPUT The output voltage of the shaft encoder has a rise time of 0 150 msec
14. D JO C9 UI C gt U1CO I I HEP HE Seon YN d NW Q9 CO CO NN CO y 09 DUO UT NW FUT U1 U1 JU1CO LO U1LO CO LD UA N SJ NW JU CO oO CD e QA xA WR AAA QA a A Sd ar h dr s I C20 CO I CO CO I7 P CO p 00 I5 I 43 UT p DE 00 D DU BUT E CO E DI PI 02 UA CO CO I 2000 DY Y y ON DDS corp mnie Wie do e WA doo PIM POPS PO NY f a wee e e na we a NE DN D DD l a PO N WIS O DN oop oN Ji i i r CO CO 0 CO WO DO LO P3 RO o ho ho 7 151 719 PMNMEWOLHPMOEMEHPOMHEPWWAMIMEPMHLHEMOWPHPHEHPWOHPHPWWWWWWWOWWWHEWOhPwHPwWtwfrsL Y UN UN DA U1 Y CO LO UN J UO SIO Y UN CO Y CO UO YN YY Y CO Y CO UN LO UN LO CO CO U1 Yu CO CO to NI OID 152 745 14 7 34 79 172 746 14 7 34 79 179 747 15 1 34 79 180 748 14 1 34 79 181 749 eres 34 7 182 750 14 9 34 77 182 51 14 9 34 76 183 752 loaz 34 74 184 oS 14 9 34 72 ras 54 14 7 34 7 185 2 755 14 9 34 57 187 56 145 34 65 1 57 14 7 a4 51 138 58 Loe 34 58 189 59 14 9 34 54 1305 760 14 3 34 5 191 61 14 5 34 46 ITs 762 15 49 34 41 132 763 14 7 34 36 64 1549 34 31 134 765 eel 34 2 A 66 1543 34 19 196 67 14 5 34 13 196 7 68 1545 34 06 197 69 15 1 33 99 198
15. Hewlett Packard model 2671G HPIB cable Hewlett Packard HP10833 A or B HPIB cable Hewlett Packard HP10631 A or B 2 10X oscilloscope probes Tektronix model TEK PG133 112 Setting up the components of the digital system is simple The steps are listed below 1 Connect the printer to the port labeled SELECT CODE 7 on the back of the computer using the HP10631 cable Connect the oscilloscope GPIB port on the back of the scope to the same computer port SELECT CODE 7 as the printer by stacking the cable terminals at the computer port Use the HP10833 cable for this Attach the scope probes to the CH1 and CH2 ports on the front of the oscilloscope Make sure that the probes are properly set up with a retractable hook probe tip and an alligator ground tip on each to assure proper contact With the oscilloscope probes set up as described above the scope can be used as a voltmeter It is convenient to use the scope to measure the excitation voltage for the shaft encoder when you get to that section below The last thing that must be done is to set up the oscilloscope output GPIB so that it will be able to communicate effectively with the daput To accomplish this turn on the scope and allow it to go through its startup sequence Then perform the following three steps e Press the OUTPUT button on the front of the scope The output menu will be displayed on the bottom of the scope screen Press the button on the scre
16. I C2 LE MN a A a a EE CO O IO DO 7 Y GT UT ls CD FT C 5 242 7 285 Iu 203553 E a 244 7 1 22 14 44 3 mua Pucci 244 3 18 Catt 244 3 vel 24 59 1 245 i 25 4 243 Ab eee 243 1 b 27 04 242 1 bh ue 241 1 PD b 240 1 PY A QJ CA GO Po 2 Po 3 a PQ PO PO Mo aj LA LL 9 dl e IM 4 NOAM YN LA LA LA CA LA LO LA LAO LS PEPE HH os os e os o HOP LU aD gi iD Gu 238 3 698 0 3 i 09 3 5 E 234 1 2 31 94 72320 yu PE CoLa Dio de 53 eae 6 44 Sof PM 5 57 34 38 c E LA GU og N l EV MO O CO 05 74 0n UN pP O2 Pa O D 00 N OO UT P Co py Ps Wd J wp uo Ln AJ a OO o3 gt Qo NNN et vO d bh b Beams oe UO co CI cu CO 0 YN UN pw PM OL 20 Y Oi UN EO CL UA pa Pa PD PER WW WWD ho o AGANO C1 Y Y LO UN SNS 00 J Ulud w YY Ed YY CO CO LO UN WD N Lal 05 NS uo CO un LO e od e dd e L dl Ro il e6 ii coo e ld e dd e dd e i 3 ID O TCT OOO P mn 0020 CY a Ye a BUI e e e a uOUI JCO D U 100 O CO UT CO P 4 O PO U1 0 PO UT NI Y N
17. before running the engine under more than a moderate load Until this oil temperature is reached the engine should be run at about 1500 rpm with a moderate load To shorten the oil heating time the electric oil heater control on the Dynamometer Control Unit can be turned on and the heat exchanger bypass valve should be full open To maintain the oil at a suitable operating temperature say 60 C the flow of the oil through the oil water heat exchanger can be controlled using oil heat exchanger bypass valve It can also be controlled by regulating the water flow through the heat exchanger with the Engine Oil Heat Exchanger Valve Cooling Water Outlet Temperature The outlet temperature of the water circulating through the engine jacket should be maintained at about 70 C This temperature can be monitored by the thermometer in the water outlet line To regulate this temperature the Engine Coolant H E Valve the middle valve can be kept partially closed This reduces the flow of the line water through the heat exchanger and allows the water circulated through the jacket to heat up The Cooling Water Valve can be partially closed to throttle the flow of the cooling water through the jacket but as a fair flowrate is required to maintain a uniform cylinder temperature this valve should be used with moderation 171 The Armature Volts should be kept high to keep the Armature Amps at a minimum However the armature Volts should not be al
18. carburetor which is located under the air filter and heating unit Close the Main Fuel Valve fully seating it firmly but gently Set the Main Throttle Valve at a position about half way between the 0 and 1 marks of its scale Make sure that the Starting Carburetor Valve is closed the knob being fully away from you or in its right most position Close the Fuel Line Valve shown in Fig 1 near the engine Check the two small needle valves at the X intersection under the Calibrated cylinder the horizontally oriented valve should be open and the lower vertically oriented valve should be closed Open the fuel line valve directly under the fuel tank You should now see fuel entering the fuel lines and the Calibrated Cylinder Fully open the Oil H E Bypass Valve This allows the lubricating oil to bypass the oil H E so that it can heat up faster when the engine is first running Check the settings of the control screws on the carburetor as follows The idle adjustment screw should now be fully tightened and then backed out 13 turns Fully tighten the fuel flow screw and then back it out 1 turn While the engine is running the main throttle valve is the only carburetor valve used to control the engine speed Make sure that the Master Switch of the Dynamometer Control Unit is in the off position The Air Heater Control should be off this can be 10 11 12 13 14 15 168 turned on to shorten the time
19. determination of the 33 P psia vs V in 3 100 50 10 15 20 25 30 35 Fig ll Indicator Diagram Engine Motored at 230 rpm Actual Results 34 actual manifold pressure will be left for further work on this system The value of the reference pressure does not affect the principal values IMEP and Ihp determined from an indicator diagram Investigation of the logP logV plot Fig 12 of the compression stroke shows that there is a curvature during the initial part of the stroke This again indicates that the reference pressure is suspect The slope of the plot is 1 02 which is lower than expected This may be due to the relatively low compression ratio used and the low engine speed The aspect of the motoring data that was given particular attention in this project is the phasing between pressure and crank angle data The phasing was thought to be crucial since it has a profound effect on the indicator program produced Phasing problems were anticipated because of the difficulty in aligning the shaft of the shaft encoder and the crank shaft as well as the presence of a flexible coupling between the two shafts The flexible coupling contains a rubber spider which would most likely compress proportionally with the engine speed causing shaft encoder data to lag pressure data increasingly with rpm An empirical investigation of the relation between angle of peak pressure and engine speed while motoring the engine was made Th
20. few as 60 rpm for an entire engine cycle 2 encoder cycles to be captured The ATRIG commands control the trigger settings of the scope The trigger mode MOD is set to NORMAL which means that the trigger source Ch1 must be specified as well as the coupling COU DC the level 2 Volts from the LEV 2 command and the slope positive from the SLO PLU command This means that the scope triggers when the shaft encoder goes high The trigger position POS setting of 1 places the trigger point at the leftmost position possible on the waveform captured so that a maximum number of data points occurs after the trigger The trigger point is therefore off the screen since at powerup the scope displays the central 10 horizontal divisions out of the 20 divisions of data captured To observe the trigger point use the HORIZONTAL POSITION knob on the front panel of the scope The last output statement in Init setup is RUN ACQUIRE which causes the scope to begin waveform acquisition from Channel 1 under the conditions set This subroutine prepares the scope for the actual initial waveform downloading to the computer 68 Subroutine Read avg4 chl 1000 SUB Read avg4 chl A 8 div 1010 Acquire binary data from Channel 1 1020 averaging over 4 uaves 1030 1040 Uariables and constants used 1050 A 1 D array to hold waveform 1060 S div Scope time scale setting 1070 1080 OUTPUT 712 DATA ENC RPB S0U CH1
21. interact with the user or the oscilloscope and subroutines otherwise was followed Note that because of the nature of the HP 9826 computer editor subprograms cannot be inserted into a file but must be appended to the end of the file The subprograms therefore do not appear in a logical order in the file listing The subprograms listed under the segments that call them are as follows MAIN program Start up Get offset New Get comp ratio Get ca range Get num avg Init setup Read avg4 chl Period Scale hor Turn on ch2 Scale ch2 v Max ch2 Acq ch2 Conv degs Adj angle Caroi Conv volume Press Graph ind An Calc rpm Work Trap Horsepower Ind mep Prnt Print data 55 A brief explanation of the main program and each subprogram follows in the order given above 10 20 30 40 50 60 70 BO 90 100 110 120 130 140 150 160 170 180 130 200 210 220 230 240 250 b 270 280 290 300 310 320 330 340 350 360 370 380 330 400 410 420 430 440 56 MAIN Program Program Name IND Ricardo engine indicator diagram By Peggy A Faber Written Summer 1386 Purpose Generate indicator diagram for Ricardo EB variable compression engine This program is to be used in conjunction with the Ricardo Indicator Diagram User s Manual MAIN PROGRAM Variables and constants Dat Array holding data Column 1 Pressure Column 2 Volume Column 5 Crank an
22. may have to be done repeatedly until the engine is warm enough to run smoothly on the main carburetor alone NOTE If during this part of the starting procedure the engine begins to rev over 1 500 rpm by the tachometer on the wall and seems to be getting away form you just SHORT OUT THE IGNITION BY CLIPPING THE ALLIGATOR CLIP TO THE SCREW This will stop the engine very soon Do not let the engine rev over 1 500 rpm for any length of time at this stage 16 When the engine has run fairly smoothly for a few minutes a moderate load should be applied Go to the Dynamometer Control Unit and reduce the Field Volts and the Armature Supply Volts to zero fully off Turn the Master Switch to the load position Now slowly increase the Field Volts to about 30 V If the engine begins to die you are probably applying the load too abruptly Reduce the Field Volts and adjust the main carburetor until the engine runs smoothly again The engine should be run with a moderate load of about 50 Field Volts at 1 500 rpm until the oil temperature reaches at least 60 C RUNNING THE ENGINE This section consists of a list of engine operating variables that must be monitored while the engine is running and some adjustments that can be made to regulate the running of the engine Also refer to the manual on the engine by Ricardo and Co Engineers Ltd 170 Operating Variables to Monitor Oil Temperature The oil temperature should be at least 60 C
23. of the data and the resolution of the computer screen and printer However increasing the number of waveforms averaged produces a smoother plot 9450 9460 9470 9480 9490 9500 3510 3520 3530 3540 3550 3550 9570 9580 9590 5600 39610 39620 3530 9640 9650 9660 39670 9680 9690 9700 9710 9720 9730 9740 9750 9760 9770 9780 3730 3800 3810 3820 9830 9840 97 Subroutine An SUB An A 3 11 12 13 Per Cr Ph N This subroutine calls subroutines that lanalyze the results determining work lhorsepover and IMEP The results are then printed on the screen lvith the option of a hardcopy lUariables and constants used A Array holding data 11 12 13 Points where piston at IDC Per Period of engine cycle Cr Compression ratio Ph Specifies phase of data N Number of waveforms averaged Rpm Rev min Pw Work of power loop Nu Pumping losses Ntw Net work of cycle Hp Horsepower Imep Indicated mean effective pressure Subprograms used FNCalc_rpm Returns rev min Work Calculates Pu Nw Ntu in ft los FNHorsepower Returns horsepower FNInd_mep Returns IMEP Prnt Prints results with optional hardcopy OFF KEY OFF KEY OFF KEY OFF KEY OFF KEY Rpm FNCalc_rpmiPer CALL Work A 3 11 12 13 Pw Nuw Ntw Ph Hp FNHorsepower Ntw Per Imep FNInd_mep At Pw I1 12 CALL Prnt Cr N Rpm Pu Nw Ntw Hp Imep SUBEND Wr C p
24. the field voltage at 40 V The engine oil temperature was about 50 C and the inlet and outlet engine jacket cooling water temperatures were maintained at a temperature of 53 C See Appendices G and H for data and calculations for this section Figure 14 compares the measured and air standard power loops The measured data was taken with the spark advance set at 20 degrees The peak pressure of the real cycle is much lower than and occurs later than that of the air standard cycle This is to be expected Comparing Fig 14 with Fig 5 reveals that when comparing the experimental cycle with an air standard cycle the measured compression stroke process line actually falls below the air standard compression stroke line whereas Fig 5 indicates that the real compression stroke lies below the air standard The experimental results agree with theory because the air standard compression stroke is computed based on constant entropy while compressing air that has a ratio of specific heats of 1 4 In the real cycle there is a mixture of air and fuel say octene 39 sdooT 19M60J DIBDUB1G Iry pue enjoy jo uostiedwog 91314 YF AUNTOA 1 1 l Y 9 25 9n3oy 9T2 9 DIBDUB1S ITY 00 009 Q Q v 009 004 008 gted aunssaig 40 where octene has a ratio of specific heats of about 1 05 Ref 1 pg 46 This would serve to lower the value of y of the charge in the cylinder of a real cycle to b
25. value Top_axis Max value of vertical axis Right axis Max value of horizontal axis Left axis Min value of horizontal asis ISubprograms used DIM OFF OFF OFF OFF OFF Maxv Minv Max and min volume values Resp i KEY KEY KEY KEY KEY P Ol tJ GINIT GRAPHICS ON FOR 1 TO 18 PRINT NEXT I Find extrema of data for scaling LET LET EET FOR IF IF IF Maxp 500 Maxv 500 Minv 500 Idel TO Ides CCI t gt Maxp THEN Maxp C 1 1 C 1 2 gt Maxv THEN Maxv C 1 2 BCT 2 lt Minv THEN Inv 6 T NEXT I I5cale axes Top_ axis INT Maxpt 5 1 Right_axis INT Maxvt 5 d 6420 6430 6440 6450 5450 6470 6480 6490 6500 6510 6520 6530 6540 6550 6560 6570 6580 6590 6600 6610 6620 6650 6640 6650 5660 6670 6680 6690 5700 6710 6720 6730 6740 6750 6760 6770 6780 6790 6800 95 Left_axis WINDOW Left_axis Right_axis 20 Top_ax1s AXES 5 10 0 0 2 5 Label axes LORG 9 MOVE Right_axis 2 Top_axis 10 LABEL P psia vs V in 3 LORG 6 FOR IsLeft axis TO Right axis STEP 5 MOVE 1 0 LABEL I NEXT I LORG 8 FOR 1 50 TO Top axis STEP 50 MOVE I LABEL I NEXT I Plot curve MOVE CC ide 2 6 idel 19 FOR I Idciti TO Idc3 DRAW CCI 2 2 C I 1 NEXT I Prompt for hardcopy PRINT Press P for a hard copy PRINT or Q to proceed then CONTINUE PRINT Choice INPUT Resp IF Resp Q OR Resp q TH
26. 035 Btu 1bm Specific Gravity of octene 0 702 flowrate of octene 0 1890 cc sec 090 ER y o 19 4 2 925x10 lbm sec 19 035 Btu lbm 2 925x107 1bn sec 4 een PI 60 sec 2 rev 12 in min 1560 ey 1 min G SYO 1 ifr 4 588 4 in lb cycle Q from octene Determination of State Values and i Law Chart for Air Standard Cycle Table A2 State Values of Air Standard Cycle 127 Table A3 First Law Chart for Air Standard Cycle 8r an Law Gato 1 2 Properties of air in lb C 1597 8 Fx R 640 08 ar Pt l p 14 7 psia 34 791 in T 70 F 530 R lt il P1V mRT pV 14 7 34 791 ap 3 m 640 08 530 x10 lbm KT l U C T m 1597 8 530 1 5076x1077 1276 6 in 1b PEZ Y Y 128 v 1 4 VN 34 791 Po P v3 14 7 4 791 318 57 psia T parar _ 318 57 3 866 530 14 7 34 791 p 1276 31 R 1 1 192 C m T T 2 4088 1276 3 530 1797 7 in 1b 1 2 0 0 1797 7 14 14 1797 7 in 1b U U 192 1276 7 1797 7 3074 4 in lb Pt 3 U 4588 4 in lb from combustion of octene U U 204 3074 4 4588 4 7662 8 in 1b 3 U C mT _ U3 _ 7662 76 _ qe T3 o T 2 3 mRT 1 50756x10 640 08 3181 5 794 P4 ve a eae T S e 94 0 psia Pt pts 129 14 V 3 866 P 794 02 255 36 639 psia mo Pata _ 36 639 34 791 USUS 4 mR 1 508x10 O U C m
27. 1390 11400 11410 11420 11430 11440 11450 11460 11470 11480 11490 11500 11510 11520 11530 87 Subroutine Adj angle SUB Adj_angle Dat Th Per Idcl Idc2 Idc3 IThis subroutine adjusts the crank angle Idata to account for the phase error in Ipressure and encoder input due to the Iflexible coupling and misalignment lof crankshaft and encoder shaft The Icalibration equation is based on Imotoring data IVariables and constants used Dat Array holding data Th Crank angle at which the shaft encoder output goes high when engine not running 1n degrees Per Period of engine cycle Tdc1 Idc2 Idc3 Points where piston at inner dead center Rom Rev min of engine Offset Angular offset phase error of pressure and crank angle data in degrees Frac angle proportion of crank shaft revolution in error Adj_idc Number of data points by which the IDC data points must be shifted due to phase error Angle Adjusted crank angle degrees Subprograms used Calc_rpm Calculates rev min of engine Rom FNCalc_rpm Per IF Th gt 180 THEN Th Th 360 END IF Offset 0095680 Rpm 1 Frac_angle 0ffset 360 Adj_idc INT Frac_angle Idc 1idcl1 IF Frac_angle lt 0 THEN Adj_idc Adj_idc END IF 2 98 ih 88 1154 Idel Idel Adj_ide 11550 Idc2 Idc2 Adj_ide 11560 Idc IdcZtAdj idc 11570 FOR I Idel TO Idc3 11580 Angle Dat I 3 Offset 11530 IF Angle
28. 150 END IF 3170 IF FNMax ch2 5 lt 63 THEN 3180 OUTPUT 712 CH2 VOLTS 05 3190 WAIT Interval 3200 Volts ch2 05 3210 ELSE 3220 SUBEXIT 3230 END IF 3240 IF FNMax_ch2 5 lt 5 THEN 3250 OUTPUT VIZ Cre VOLTS i 202 3260 WAIT Interval 3270 Volts_ch2 02 3280 END IF 3290 SUBEND Like Scale hor Scale ch2 v maximizes the resolution of the data Scale ch2 v sets the vertical volts div scale of channel 2 so that the pressure data occupies as much of the scope screen vertically as possible This subroutine performs the scale adjustment differently than the horizontal scale was adjusted however Here the vertical scale is changed if the conditions of the IF statement are met if the waveform runs off the screen or if the waveform could be expanded further and then the maximum value is checked again to see if further adjustment is needed It is done this way for the vertical scale because if the waveform runs off the screen it must obviously be scaled and then checked that it is all on the screen If the waveform must be expanded it may have a maximum value so small that the resolution of 1 126 returned by Max ch2 would not be sufficient to select the correct vertical scale directly as was done in Scale hor Now this subprogram will be explained step by step 78 First the time Interval is calculated that the program must pause for the scope to adjust the volts div of Channel 2 and acquire a new waveform before the maximum v
29. 6 17 7 23 81 253 16 337 18 7 23 6 253 438 838 18 5 23 38 254 79 339 19 3 23 17 255 6 340 19 5 22 96 256 43 341 18 5 22 74 257 24 842 18 7 22 53 258 06 343 19 9 22 31 258 97 344 19 5 22 1 259 69 845 19 9 21 88 260 51 846 19 3 21 66 261 32 0 XD UN 03 10 UN YY CO Y y 600 UN CO UN LU UM CO Y Y O CO CO WON CO UN N SU CO 00 Y RUIN ON Y ee e de y ee y de o e o e dh e y e dy e ILIA ld ao Il o ld dl de y a A ARAS e dd O PcORAIPOSPRAOPOCOCO C C CO gt I gt gt DI 071 UN NA LA YA 00 gn 00 O0 X y N CO 0009 09 LO CO LD LO 155 n3 J fad ry CO NNS CO JUN PO J OD NO n3 no N NS NND M D NDN O eO Y U1 uo NO J ib J DC 09 II a SEH SHEL SONNEI G19 ANDAN MG 0 0104 04 0 SI 00 00 00 00 00 00 CO LO 10 19 CO UD 3 156 324 16 UN UN ON SP P p 6000 CO COO NNN NOOO OO c4U160 O yin CO MU CO WA Y NS Y 1 CO UN 0 YN YN CO J C2 2 CO CO CO Q2 CO CO CO Lo P 9 p D lo gt gt gt 157 245 4 346 22 347 04 347 25 348 67 349 49 35 2 351 12 351 94 352 75 Jod 5f 354 38 358 47 359 28 158 Results Taken at 25 Degrees Spark Advance Pis Cn E 188 38 F p 1a vi WX Vin 3l RESULTS Enaine speed 1380 9 Compression ratio 9 work Gross work output 170 68 Valve loss 16 46 Net work 154 21 Indica
30. A DIGITAL INDICATOR DIAGRAM GENERATION SYSTEM FOR THE RICARDO E6 ENGINE by Peggy A Faber A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE in Mechanical Engineering Approved by Prof Name lllegible Thesis Advisor Prof Robert A Ellison Prof Name lllegible Prof Name lllegible Department Head DEPARTMENT OF MECHANICAL ENGINEERING COLLEGE OF ENGINEERING ROCHESTER INSTITUTE OF TECHNOLOGY ROCHESTER NEW YORK MAY 1987 Title of Thesis A Digital Indicator Diagram Generation System for the Ricardo E6 Engine L Peggy A Faber hereby grant permission to the Wallace Memorial Library of R I T to reproduce my thesis in whole or in part Any reproduction will not be for commetcial use or profit ABSTRACT This paper explains and evaluates an indicator diagram generation system for a single cylinder internal combustion research engine The apparatus is digital and consists of a piezo electric pressure transducer with charge amplifier a shaft encoder a digital oscilloscope and a computer with printer Motoring data provides valuable information on the performance of the system which is used in the computer software to produce results accurate to 5 4 percent Results include the indicator diagram itself the work produced the horsepower and the indicated mean effective pressure Included are an overview of indicator diagram theory discussion of the apparatu
31. ASEC 5 Time_div 5 SUBEXIT END IF IF Per lt 3 8 AND Per gt 1 9 THEN DUTPUT 712 HDR ASEC 2 Time_div 2 SUBEXIT END IF IF Per lt 1 9 AND Per gt 395 THEN DUTPUT 712 HOR ASEC 1 Time divz l SUBEXIT ENO IF IF Per lt 95 AND Per gt 38 THEN DUTPUT 712 HOR ASEC 5 Time_div 05 SUBEXIT END IF IF Per lt 38 AND Per gt 19 THEN OUTPUT 712 HDR ASEC 2 Time_div 2 SUBEXIT 0850 2070 2080 2030 2100 2110 2120 2130 2140 2150 2160 2170 2180 2190 2200 2210 73 END IF IF Per lt 19 AND Per gt 095 THEN OUTPUT 712 HOR ASEC 1 Time_div 01 SUBEXIT END IF IF Per lt 095 AND Per gt 038 THEN OUTPUT 712 HOR ASEC 005 Time_div 005 SUBEXIT END IF IF Per lt 038 THEN OUTPUT 712 HOR ASEC 002 Time_div 002 END IF SUBEND Scale hor sets the horizontal seconds division scale so that two cycles of the waveform takes up as much of the scope screen as possible to provide maximum horizontal resolution of the waveform It does this by a series of IF statements which set the horizontal scale according to the period of two encoder output periods or one engine cycle The HOR ASEC output statements sends the sec div value to the oscilloscope and the Time div variable is returned to the rest of the subprograms through the parameter list The subroutine is then exited by the SUBEXIT statement 74 Subroutine Turn on ch2 118 SUB Turn_on_ch2 1190 This subrouti
32. EN GRAPHICS OFF GCLEAR FOR I 1 TO 18 PRINT NEXT I END IF IF Resp P OR Resp p THEN DUMP GRAPHICS 701 GOTO Choice Can make multiple copies END IF SUBEND Subroutine Graph ind plots the indicator diagram itself on the computer Screen and produces a hard copy if desired by the user The axes are scaled to 96 the data for maximum resolution of the plot The more important commands and logic of this subroutine will now be explained GINIT establishes a set of default values for the graphics operations and GRAPHICS ON turns the computer graphics display on The screen is then cleared of all printed messages by the first FOR NEXT loop The next section finds the maximum and minimum volume values and the maximum pressure value in the data and the extrema of the axes are set in the WINDOW statement The AXES statement sets the axis locations and the tic spacing LORG and LABEL are used to label the axis increments and the diagram itself see BASIC Language Reference for HP Series 200 Computers for details on these and other commands The MOVE statement moves the pen without drawing a line on the path moved while DRAW causes a line to be left in the pen path The last 12 lines of the subroutine prompt the user as to whether a hard copy of the plot is desired and produces the printout Multiple copies can be made by responding with P more than once at the prompt The smoothness of this plot is limited by the resolution
33. FF KEY 1 OFF KEY 2 OFF KEY 3 OFF KEY 4 FOR I 1 TO 18 PRINT NEXT I PRINT To stop data scroll use PAUSE key PRINT To resume scroll use CONTINUE key FOR I TO 5 PRINT NEXT I WAIT 10 PRINT Pt P psia Utin 3 Angle deg FOR IsFirst pt TO Last pt A I 1 INT A I 1 100 5 100 A 1 2 INT AC1I 2 100 5 100 A 1 3 INT A 1 3 100 5 100 PRINT 1 4t1 1 gt A4 1 2 A11 3 NEXT I PRINT HARD COPY INPUT Respon IF Respon Y OR Respon y THEN PRINTER IS 701 PRINT Pt P psia U in 3 Angle deg 110 38380 FOR IsFirst pt TO Last pt 8330 PRINT I A I 1 ACI 2 ACI 3 8400 NEXT I 8410 PRINTER IS 8420 ELSE 8430 SUBEXIT 38440 END IF 8450 SUBEND Print data produces a hard copy of the modified data as follows Datapoint Pt Pressure P psia Volume V in3 Crank angle Angle deg All data points in one engine cycle are listed 111 APPENDIX D SETTING UP THE INDICATOR DIAGRAM GENERATION EQUIPMENT The following instructions deal with the setting up of the equipment for generating indicator diagrams The instructions consist of selections for setting up the three major sub systems digital computer oscilloscope etc oscilloscope etc pressure measurement volume measurement shaft encoder DIGITAL SYSTEM The digital components of the system are as follows Digitizing oscilloscope Tektronix model 2430 Desktop computer Hewlett Packard model 982G Thermal printer
34. L CALL FOR PRI NEXT PRIN CALL CALL CALL CALL CALL CALL IF CALL CALL CALL CALL CALL CALL CALL FOR PRI NEXT PRIN 61 Ch2 nv_degs Calculates crank angle degs j_angle Adjusts crank angle to account for phase error between pressure and crank angle data nv_volume Calculates cylinder volume from crank angle ess Calculates cylinder pressure Chi 1 24 Abort_prog 5 KEY KEY KEY KEY KEY t_prog FALSE I 1 TO 18 NT I tialize array T TO 1024 t 1 1 0 t 1 2 0 t 1 3 0 T I Get_comp_ratioltr Get ca FanQ e R Get num_avQ N IST TO NB NT I T GATHERING OATA Init _setup S_div V_chi V_che Read avg4_chi Chi 5 div Period Chi 5 div Per I 1I2 13 Scale hor Per 5 div Turn on chn Scale ch2 v U ch2 Rbort prog 5 div Abort_prog TRUE THEN SUBEXIT Read avg4 cht Cht 5 div Period Chi 5 div Per I I2 I3 Aca ch2 Dat I1 I2 5 div Ph N Conv degs DatC I1 I2 15 Adj angle Dat Th Per I I2 I3 Conv volume Dat Cr I1 13 Press Dat 11 12 13 V_ch2 R Ph I TO 18 NI CU I T DATA GATHERING COMPLETE Q Ph D SUBEND 62 Subroutine New performs the entire data acquisition for each run and converts the raw data to units of pressure volume and crank angle It is important to understand the sequence of events in this subroutine to evaluate the significance of the results obtained New utilizes 13 subprograms to obtain the final data mentione
35. O POP 108 E y 3 ee ld NIN DAD oS ND 09 DO DECO Sd CC MU BS 9 142 Q3 I CO PO U1 U1 CO DW UI Y 74 Y 74 CO Y U1 02 02 U1 Y 00 N UT NA DON Y YA Y YN SY a YN s Y RU Y YN GO A ITOPIRSS CAD OUS NM NN ER wr Q LO S P7 SITU POT LJ CO CO U LO W Gu LON CH O J 1 Soe Nm 14 149 149 o ab LA Un UP ot AY Un PO 249 MN 0 2 20 0 YD DN LA J NHADNO Ti Ln Un Ninn LD OO IND DINO PU gt co NO 143 312 UJ O G2 G9 UU GY 2 CO Us mea O 01 00 Y MU W QJ DO pa Co Lu OO n3 Po n3 I G3 PO J Y DN Jc ta CJ CO CO OD C2 CO WwW O UT gt O MN O 10 CO Y A 33b CRU UT NICO UD UO LD 9 LOO UV UD SS KD SJ WWW NUTO J UO UO UT C3 WW UT OUTS WOON 164 165 165 lbE 157 1 CO 169 1569 170 171 E 34 L6 173 174 175 176 Fela 178 178 a m 180 181 182 132 183 184 185 172 18 187 187 188 129 190 191 191 192 193 194 195 196 196 197 198 199 200 200 201 202 203 204 205 18 31 ne 16 144 ES PO Pa n3 n 20 COD oO oo OO OO
36. T 2 4088 1321 0 3182 0 in 1b 3U4 U Ua 3182 02 7662 76 4480 74 in lb 32 34 3 0 0 4480 74 3 4 34 4480 74 in lb 4 1 22 1905 4 in lb 401 z C nCT T 2 4088 530 1321 in 491 4 1 AS 1905 4 0 0 1905 4 in lb 130 Calculations for Comparison of Actual and Air Standard Cycle Results Shown in Table III Actual Cycle W 171 59 ft lb 505 COSNESTTCIPC 48 from eq n 3 based on power loop only BMEP _ bhp _ 2 06 7 7 TMEP int 3227 63 12 from eq n 12 Air Standard Cycle 1 1 puts pu exu Iesu from eq n 5 BEW W Uy QW 4 1797 7 0 0 4480 7 0 0 2683 0 in 1b 223 6 ft 1b 5 W 2683 0 B IMEP 7 7 3277391 3 8 86 76 psia from eq n 6 131 APPENDIX H ERROR ANALYSIS OF ACTUAL RESULTS The percent error in X with a relation of the following form A Bm cn X where A B and C are independent variables can be written as 13 E EE ESP po where AA AB and AC are errors in A B and C see ref 9 pg 270 Work is calculated in the computer software using the Trapezoid rule or p V 14 WO int hoje where V is the width of the volume interval In order n to calculate the percent error in work therefore the percent errors in pressure and volume measurements must be determined These determinations will be shown in the following sections 132 Error in Volum
37. T and ENTER statements it contains Besides controlling the information flow between the computer and the oscilloscope the program must also acquire information from the user handle and store the data mathematically manipulate the data and present the results of the run The program was written to perform these tasks in an efficient and user friendly manner Highlights of the program will now be presented with a brief overview of its structure When the program runs the first task it performs is to print some basic equipment setup messages on the screen to remind the user to connect the transducers to the correct oscilloscope channels apply an excitation voltage to the shaft encoder etc Then the user is prompted to input the change amplifier range setting the number of engine cycles to be averaged over and the angular offset between the crank angle at which the shaft encoder output goes high and zero degrees inner dead center These quantitites are then used to calculate cylinder pressure determine an averaged and therefore more accurate result and to correct for shaft encoder misalignment respectively The scope settings are then initialized to their power up state by a single output statement so that they are known at the beginning of each run 27 Since the maximum resolution of the scope is 256 increments vertically and 1024 increments horizontally the volts div and seconds div settings must be adjusted so that a
38. The actual indicator diagram could then be further analyzed as explained in the Theory section Analysis of the fuel air cycle would also provide a much more sophisticated exercise in thermodynamics than does the air standard cycle 3 Adapting the software to allow for the production of an indicator diagram for compression ignition diesel running of the engine could be accomplished with a modest effort Changes would have to be made to 47 subroutines that deal with cylinder volume assignment because of the different piston geometries used for the two types of operation The suggestions above would increase the accuracy and depth of the analysis possible from a Ricardo engine indicator diagram The present results however are sufficient for many purposes in engine analysis including determination of thermal efficiency mechanical efficiency and evaluation of the effects of variation of engine operating conditions It is hoped that the work represented in this report will serve to increase the value of the Ricardo engine as a research and educational tool 48 REFERENCES Taylor C F The Internal Combustion Engine in Theory and Practice Vol I The MIT Press Second Edition 1985 Karlekar B V Thermodynamics for Engineers Prentice Hall 1983 Pish R H A New Generation Cylinder Performance Indicator Mechanical Engineering Dec 1984 Nagao F M Ikegami Errors of an Indicator Due to a Connecting Pa
39. This expression is concise but the temperature in an engine cylinder is very difficult to measure The efficiency of the air standard cycle in terms of the Pressure Pressure Y Positive Work Negative Work NNN Su CX SLY DEER KKK LY 3 2 XXN AAA AX J 2 2941 RR V o 1 1 o0 SACS OX Vine Volume Yopc Fig 3 Work Areas for Air Standard Otto Cycle Volume V Fig 4 Non Flow Model of Air Standard Otto Cycle Air Standard Cycle Actual Cycle Pressure p Volume Y Fig 5 Schematic of Actual and Air Standard Otto Cycles from ref 2 pg 308 compression ratio a known quantity for an engine is see Appendix A for derivation 5 The above expression can be compared to the thermal efficiency found experimentally for an actual Otto cycle Another quantity that can be calculated with the information gained from an indicator diagram is the indicated mean effective pressure IMEP The IMEP represents the ratio of the net work output based on the power loop of the indicator diagram to the volume swept by the piston Thus IMEP 16 1 2 The IMEP represents the theoretical pressure at which a constant pressure expansion from IDC to ODC would produce the work indicated in the diagram Comparing engines using the IMEP instead of the net work only is a way to compensate for the size differences between engines The mechanical efficiency of the engine is det
40. alue of the waveform is looked at by function Max ch2 see section below In the lines after the Reduce line label the program increases the Volts div value if needed based on the value returned by Max ch2 Function Max ch2 returns the maximum value of twenty waveforms on Channel 2 read the section on FNMax ch2 now which is between 127 and 126 If the waveform does not need to be reduced the program goes to the line labeled Enlarge to check the fit of the waveform to the screen Fatal error is set to TRUE if after the vertical scale has been set to its maximum value of 50 Volts div the waveform still goes off the screen The segment after the line labeled Enlarge decrease the Volts div value in a minimum of 20 mV div The new Volts div setting for Channel 2 it sent back through the parameter list in the Volts ch2 variable The time taken to execute this subprogram is worthwhile since there is a maximum vertical resolution of the waveform of only 1 256 which must be exploited as fully as possible 3320 2530 5340 3550 3360 3370 3380 3390 3400 3410 3420 3430 3440 3450 3460 3470 3480 3490 3500 3510 5520 3530 3540 3550 3560 3570 3580 3590 3500 3610 79 Function FNMax ch2 DEF FNMax_ch2 5 This function finds the maximum value of waveform on Ch2 on a scale of 127 to 125 Twenty waveforms are sampled IUariahles and constants used S Horizontal scale setting of scope Max Ma
41. aptured by recording the pressure in the cylinder for two revolutions after triggering off the shaft encoder signal The critical factors considered in choosing a shaft encoder for engine applications are the maximum slew speed maximum rpm the rise time of the signal and the construction of the device The 25GN has a maximum slew speed of 3 000 rpm which is the maximum recommended rpm of the Ricardo engine The rise time of the signal is 0 15 msec for a maximum output of about 5 Volts was measured This means that the trigger lags zero degrees of crank angle by 0 86 degrees at 3 000 rpm and by 0 34 degrees at 1 200 rpm see Appendix B for calculations The lag results from the oscilloscope trigger level being set at 1 6 Volts for the shaft encoder The trigger level was set at this level by empirically trying various levels that would consistently trigger the scope from the rising edge of the encoder signal It was found that lower trigger levels did not trigger the scope reliably The variation of trigger lag with rpm should be compensated for by the computer software The 25GN is designed for use in dirty environments since it has a sealed shaft It is made for use in industrial applications and subjected to vibration as it would be when mounted in an engine 25 The shaft encoder signal is fed directly to Channel 1 of the oscilloscope where it is used to trigger the scope and measure engine rpm Data Acquisition Device A Tektroni
42. ark advance are in good agreement with those obtained by Taylor The complete results from firing the engine with the spark advance at 20 degrees are contained in Appendix I 45 CONCLUSIONS AND RECOMMENDATIONS As a result of this project it is now possible to produce an indicator diagram and generate related data for the Recardo E6 Research Engine run in the spark ignition mode The basic equipment used is a water cooled piezoelectric pressure transducer and peripherals a shaft encoder digital oscilloscope and a desktop computer Computer software developed for this system 1s interactive and user friendly It is designed to achieve maximum resolution of the data and it produces work results accurate to about 5 4 Preliminary evaluation of motoring data revealed that there was a phasing problem between pressure and volume data The phase changed linearly in direct proportion to the engine speed and the problem was corrected to within one degree of crank angle by correcting it in the computer software Further investigation of motoring data the log log plot of p V data and analysis of the pumping loop indicates that there may be a problem with assignment of a reference pressure This aspect is not considered important here since it does not affect the results obtained from the indicator diagram work power etc Obtaining the correct reference pressure is suggested for future project work on this system The results obtained while
43. ation system that has been assembled for use with the Ricardo E6 variable compression ratio research engine An indicator diagram the plot of cylinder pressure versus volume for an engine cycle is a valuable tool in observation and evaluation of engine performance The project involved the specification of movement parameters the selection of the system components and the interfacing and writing of computer software to control the data acquisition and produce the final results The Ricardo E6 research engine is a versatile educational tool It is a single cylinder engine that can be run in spark or compression ignition modes using a variety of fuels Its compression ratio can be changed while the engine is running as can the carburetor settings and the spark timing An indicator diagram of accuracy to at least two digits was needed to provide engine data for use in thermodynamics and other college level courses A computer controlled instrumentation system was specified and assembled It consists of a flush mounted water cooled piezo electric pressure transducer a shaft encoder a digital oscilloscope and the computer The components were selected for their accuracy versatility the oscilloscope for instance will have many applications and their ease of use The software allows multiple indicator diagrams to be generated in a session and produces in addition an analysis of work output The theory behind engine evaluation will be discus
44. ays ld1 and Id2 store the cumulative data for phase 1 and phase 2 type waveforms respectively after sorting The first two OUTPUT statements turn on the Exp Exh Intake Compr Y y l A f 1 3 1 j 3 i j j i IDC1 ODC1 IDC2 ODC2 time IDC3 a Phase 1 Intake Compr _ Exp Exh o e i dj i 3 gt 1 j I y gt IDC1 ODC1 IDC2 ODC2 time IDC3 b Phase 2 Encoder Output ax Pressure Output Fig Al Locations of Piston Strokes in Phases 1 amp 2 83 84 Channel 2 display set the data encoding and specify the data source of the acquisition The interval Interval to be waited for acquisition and downloading of data is then calculated and the phase counters are set to zero The line label Rch2 for read channel 2 marks the beginning of the program segment to be repeated until N waveforms of either phase type have been acquired The acquire mode is set to Normal the curve requested and the waveform downloaded into array A The first IF THEN ELSE sorts the waveforms by phase loads the arrays and increments the counters The IF checks the counters to determine if N waveforms of either phase have been acquired and returns control to line Rch2 if both counters are less than N The second IF THEN ELSE loads the averaged waveform into the data array B to be passed through the parameter list and assigns a value t
45. bprograms used None DEG IThe following are parameters set by the Igeometry of the Ricardo engine inches 924 3575 IPiston stroke Dz3 000 Cylinder bore L 9 500 IRod length Vo 25 PI D D S R 1 Further values to save computation time Epsi 5 2 L Eps1 Epsi Epsi A Vox R 1 2 C A Epsi Const Vo0 A C ICompute volumes FDR IsIdc TD 1dc3 X B 1 5 ow i Ei dd As rmm B I z 8eConst A COS OO C SQRCEITEpS1 sQ i SINCAO 127 NEXT I SUBEND 90 Conv volume converts the values in column 2 of the data array array B from degrees of crank angle to cylinder volume The subroutine implements the following formula ref 8 pg 172 for cylinder volume 1 1 V Vi 1 7 1 0050 1 1 e sin 11 where V cylinder volume Vo clearance volume r compression ratio crank angle and where S stroke length L connecting rod length 5560 5570 5580 5580 5500 5510 5520 5630 5640 5650 5550 5670 5580 5590 5700 5710 5720 5730 5740 5750 5750 5770 5780 5790 5800 5810 5820 5830 5840 5850 5850 5870 5880 5830 5300 5810 5920 5930 5940 5850 5960 91 Subroutine Press SUB Press C 1I1 12 13 V_div R Ph IThis subroutine converts the input from Ithe pressure transducer to pressure units l psia It takes the pressure when the Iniston is at ODC at the end of the Isuction stroke as equaling the pressure lin the intake manifold approximating lthat to b
46. d above These subprograms will now be explained except for those that are sufficiently explained by their comments 63 Subroutines Get comp ratio Get ca range Get num avg 4250 4260 4270 4280 4280 4300 4310 4320 43350 43540 4550 4350 4370 4380 4390 4400 4410 4420 4430 4440 4450 4450 4470 4480 4430 4500 4510 4520 5280 5290 5300 5310 5320 5330 5340 5350 5360 SUB Get_comp_ratio Cr IThis subroutine acquires the compression lratio for this run by prompting the user to enter it through the keyboard 1Uariahles and constants used 1 Cr Compression ratio Confirm Allows user to confirm response Subprograms used None DIM Confirm 1 Resp PRINT Enter the COMPRESSION RATIO PRINT for this run PRINT Then press CONTINUE key INPUT Cr PRINT PRINT Are you sure Y N then CONTINUE INPUT Confirm IF Confirm Y OR Confirm y THEN FOR I i TO 18 PRINT NEXT I ELSE PRINT GOTO Resp END IF SUBEND SUB Get_ca_range Range IThis subroutine prompts the user to enter ithe charge amplifier range Variables and constants used Range Charge ampl range setting psi Volt i Confirm Allows user to confirm entry 5370 64 DIM Confirm i1 5380 Resp PRINT Enter the charge amplifier RANGE 5390 5400 5410 5420 5430 5440 5450 5460 5470 5480 5490 5500 5510 5520 5530 10500 10510 10520 10530 10540 10550 10560
47. during combustion Pressure Fuel Air Cycle Actual Cycle Volume Fig 6 Comparison of Actual and Fuel Air Otto Cycles from ref 1 pg 108 12 13 5 Heat losses 6 Blowdown and pumping losses The contribution from leakage around the piston rings is usually insignificant except at every low engine speeds Incomplete combustion occurs because of quenching of the flame at the cool cylinder walls It is also known that the mixture does not reach chemical equilibrium by the time the exhaust valve opens thus the heat of combustion of the fuel based on calorimeter data is higher than the heat actually supplied by the charge in the cylinder Progressive burning is the time for the travel of the flame from the spark position through the cylinder As mentioned above this occurs between a and bin Fig 6 The combustion time varies inversely with engine speed because of increased turbulence with speed ref 1 pg 109 so that the crank angle occupied by combustion tends to remain constant as the piston speed varies and the relative position of a and b does not change Time loss occurs because the piston is moving during combustion and the heat loss is due primarily to conduction through the cylinder wall during expansion as stated earlier Blowdown and pumping losses occur when the valves are open Figure 7 shows a detailed view of this portion of a typical indicator diagram The momentum of the escaping gas causes the curve to fa
48. e Cylinder volume can be written as see Fig A3 for defini tions of variables so that AY 28D j an V iD h tis Measurements D L and T are assumed to be accurate to 0 001 in and are as follows 3 000 0 001 in 9 500 0 001 in 2 188 0 001 in J il i i The quantities above effect the value of h as does the value of the crank angle 8 The error in 8 arises from the following sources t 0 5 degrees from reading the flywheel i 2 901 degrees from three standard deviations of the angle correction formula discussed in the Evaluation of Motoring Data section i 5 degrees from possible error in the theory behind above mentioned angle correction formula The total error in can therefore be taken as 3 901 deg 133 e Cylinder volume Cylinder inner diameter Cleared height Hieght of clearance volume Rod length Throw length Length as shown Crank angle a Angles as shown Fig A3 Schematic of Engine Geometry 134 In order to determine hg the compression ratio r must be known Here the compression ratio will be taken as 9 00 since this is the ratio used when gathering data in this report The stroke S of the Ricardo engine is 4 375 inches The value of ho can now be calculated Lr S 77 4 375 0 547 in The error in h due to the error in 8 will be evaluated here since the percent error in L and T is relativel
49. e operating conditions were compression ratio of 9 0 and the shaft encoder output going high at 358 degrees as measured on the flywheel The engine speed was varied between 202 and 2 703 rpm with data taken while the engine speed was being increased and then decreased Figure 13 shows the results The vertical axis represents the difference between the theoretically correct angle of maximum pressure 359 degrees or 1 degree before IDC and 1n p Fig 12 Compression Stroke Motoring Data O Q O O O e a Q e oO a Comp Ratio a 220 2 rpm o O a ga oO 0 5 1 1 5 la V V ax 9 35 36 005Z 39 dut1IOo1OM WOJJ HAY Yate eaeq aunssa ug Lad jo 195SjJjO IBTTdUV jo UOT JeTICA El stg Ndd OSZ2Z 000Z OSZI OO0GI OGcI 0001 0S4 OOS a D p P sS1uTod 8urdde 1a4Q0 A udi urpuaosad y g a a uda Surpueosy g ODO yA B amp 57 Om a s a s pB EE a a osz OL s33p 338330 1e n3uy Dz C 37 the measured angle of maximum pressure It can be seen that the pressure output lags the shaft encoder output increasingly with rpm The data taken while increasing the rpm is interspersed with that taken while decreasing rpm and the plot is fairly linear A least square fitted line through the results yields an equation relating crank angle to rpm to correct the phase change as follows A0 0 001 rpm 0 761 2 727 10 where the error is based on three standard deviations The raw data is conta
50. e 14 7 psia lUariables and constants used C Array holding data 11 12 13 Points at inner dead center Y div Uolts div setting of Ch2 R Range setting of charge amplifier in psi Volt Ph Phase of pressure waveform Ph if I1 at end of compression Ph 2 1f 11 at end of exhaust OQdel OdeZ Point at ODC after suction stroke Ref Reference point in cycle end of suction stroke Conv factor Conversion factor from vertical value to ps1 Subprograms used None IDetermine ODC after suction stroke IF Ph 1 THEN Ode2Z INI 1latl2 2 Ref C Odc2 1 END IF IF Ph 2 THEN Odc1 INT 11 12 2 Ref C 0dc1 1 END IF Conv_factor R V_div 25 FOR I I1 TO 3 C I 1 14 7 Conv_factors C I 1 Ref NEXT I SUBEND 92 Subroutine Press calculates the pressure of each data point in the cycle and substitutes the pressure value in psia for the previous value in vertical increments in column 1 of the data array The assumption that this subroutine is based on as is mentioned in the comment is that the pressure in the cylinder at the end of the suction stroke is approximately atmospheric pressure about 14 7 psia Taylor ref 1 states that this approximation can be made for many engines because at this point in the cycle the piston has been moving very slowly and the intake valve is fully open Because of the encoding of the data RPB from the pressure transducer the vertical values lie betwe
51. e pump to the upper reservoir and it is gravity fed through the pressure transducer to the lower reservoir Two reservoirs are used in order to isolate the pump from the transducer so that any pump vibration will not interfere with the transducer readings The pump is a Tuthill gear pump model B9421 which has a low flowrate of about 18 gallons hour which is higher than the flowrate through the transducer of about 8 gallons hour The overflow line is therefore necessary so that the upper reservoir does not overflow and also to maintain constant pressure head level at the level of the intake to the overflow line The ball valve is used to prevent the upper reservoir from draining causing the lower reservoir to overflow The system is thus self regulating and does not need to be monitored once it is set up and running The specifications of the Kistler 7061 pressure transducer are given in Table 1 The 7061 has a sensitivity of 5 27 pC psi in the 0 20 bar range This is high compared to many such transducers which is very desirable For instance the piezoelectric transducer previously used with the Ricardo engine 20 Upper Reservoir Overflow Line J Pressure IE Transducer E ILL Lower Reservoir Fig 9 Cooling Water System for Pressure Transducer 21 Table 1 Technical Data for Kistler Model 7061 Pressure Transducer Range bar Calibrated
52. e so that the output signal stays with the input level without dying out but it must not be so large that drifting occurs As mentioned above the time constant can be regulated using the charge amplifier and should be checked and adjusted at the beginning of each run as explained in the manual accompanying the charge amplifier and the appendix on setting up the system Volume Measurement Cylinder volume measurement is done with the use of a shaft encoder which tracks the crank angle of the engine power shaft If the dimensions of the cylinder and rod linkage are known then the cylinder volume can be calculated from the crank angle In many modern indicator diagram generating systems the shaft encoder delivers a pulse at each degree of crank angle and a zero pulse when the piston is at IDC zero degrees crank angle The Ricardo engine has a massive flywheel on the drive shaft so that the angular velocity of the drive shaft can be assumed to be constant when the engine is operated at steady 24 state Thus a shaft encoder signal at zero degrees of crank angle is sufficient for calculating piston position The shaft encoder used here Sequential Information Systems Inc model 25GN delivers a square wave with an amplitude of about 5 Volts once per revolution The wave is first used to determine the rate of rotation of the revolutions per second of the drive shaft The entire cycle which takes place in two revolutions can then be c
53. en 0 and 256 These units must be converted to pressure The IF THEN ELSE section of the subroutine determines which data point corresponds approximately with the end of the suction stroke based on the phase of the averaged waveform The value of this data point Ref is assigned the known reference pressure as explained above The conversion factor Conv factor converts from vertical increment value to psi as follows Con factor Rx V div 25 12 where R the charge amplifier range setting in psi Volt V div the Ch 2 vertical setting of the scope in Volts div 25 the number of vertical increments per scope division 93 The resulting units of Conv factor are psi vertical increment The FOR NEXT loop does the actual conversion for each data point using the conversion factor and the reference point value 5990 5000 5010 5020 5030 5040 6050 6060 5070 5080 6098 6100 6110 6120 5 t30 6140 6150 6160 6170 6180 6190 5200 6210 6220 6230 6240 6250 6260 6270 6280 6290 6300 5310 5320 5330 5340 6350 6360 6370 6380 6390 5400 6410 94 Subroutine Graph ind SUB Graph_ind C Idc1 Idc3 This subprogram plots the indicator i diagram and produces a hard copy if desired Variables and constants used io Es Array holding data Idcl Idc3 Beginning and end points of data Resp String holding user s response to whether hard copy of plot desired Maxp Maximum pressure
54. en bevel under SETUP Now the setup menu is on the screen Press the button under TERM stands for terminator to get to the next menu level Now press the button 113 under LF EOI so that this selection is underlined You have now set the scope to look for linefeed and end of line characters as line terminators in commands from the computer 3 Press the OUTPUT button again on the front of the scope This returns you to the first level of the output menu Now press the button under SETUP and then the button under MODE on the menu display Select T L Talk Listen from the MODE menu o Press the OUTPUT button once more then SETUP and select ADDR address from the setup menu to set the address of the scope with respect to the computer Set the address displayed on the screen to 12 by pressing the buttons under the arrows Pressing the button under the arrow pointing up increases the address number and pressing the arrow under the arrow pointing down decreases it The scope can be turned off now if desired since it will store the settings just made until they are changed by the user PRESSURE MEASUREMENT SYSTEM The pressure measurement system consists of the following components Piezo electric pressure transducer Kistler model 7061 Charge amplifier Kistler model 504A 36 Cooling water apparatus for pressure transducer 114 Output lead for pressure transducer Buel and Kjaer No A00038 Output lead for charge am
55. ent is therefore Se 7 s 0 004 or 0 42 Now to determine the percent error in equation 14 is put in the form of equation 13 so that W Aw on 0 004 0 050 0 054 or 5 4 It should be noted that the percent error in work calculated above would also be the error in the indicated horsepower since the period of the engine cycle is measured very accurately by the system In order to determine the error in IMEP we must start with the following relation ref 9 pg 269 f af f ad Af T SA 88 4B lac ac 16 where f is a function of the independent variables A B C etc Equation t6 determining IMEP is IMEP e 9 137 If Vi and V5 are considered independent variables the error in IMEP can be written according to equation 16 as AIMEP jaw hM lav 9 IMEP lav IMEP W W Av A Av Gv v way W has been substituted in the above relation for SSW Dividing both sides by equation 6 we obtain an equation for the percent error in IMEP or ia ly Y 17 We now must find V4 and V5 as follows Ty V 4 D h and V TY 2 an 4 V TT Sp lt PR The error in V using equation 16 is D An 2 Y pnap T T p DAh 2hZD 18 a AV 4 138 Vi and V are the cylinder volumes at 8 180 and 98 180 respectively Therefore the previously determined values of h and h can be used By equation Qs AV
56. eratures of comparison ignition running is necessary Also note the low acceleration sensitivity of the transducer that prevents interference from engine vibration Thus the Kistler 7061 transducer was chosen for its high sensitivity flush mounted configuration and because it is designed specifically for service in engines The pressure transducer itself is only part of the pressure measurement system The signal from the transducer must be input to a charge amplifier which converts the current output by the piezo electric crystals into voltage The charge amplifier is set to the transducer sensitivity pC psi and the desired range Volts psi The time constant of the pressure measurement system can be controlled using the charge amplifier storage time constant The storage time constant is actually the RC time constant of the feedback circuit in the charge amplifier The TIME CONSTANT switch selects the 23 feedback resistance and the RANGE selects the feedback capacitance It is important to select an appropriate pressure system time constant so that the output of the system tracks the input correctly The electrical leads make up the remainder of the pressure measurement system The entire system must be considered when evaluating the output The signal from the system dies out according to a time constant which results from the effective resistance and capacitance of the circuit The time constant must be adjusted to be as large as possibl
57. ermined from the ratio of the brake mean effective pressure BMEP to the IMEP The BMEP is defined by W 7 Vi 7 Vo BMEP Here the work Wg is the work output to the engine shaft usually measured by a dynamometer The mechanical efficiency nm is then calculated by 10 B BMEP 8 ln IMEP A theoretical cycle that resembles an actual engine more closely than the air standard cycle is the fuel air cycle This cycle is used as a direct basis of comparison between a real cycle and an ideal one since the working medium used is a mixture of gases closely resembling those that would be in a real engine In the fuel air cycle the ratio of specific heats and the specific heats of the gases change as they do in reality Like the air standard cycle heat is added at constant volume but unlike the air standard heat is taken as coming from the combustion of fuel in the cylinder This combustion is idealized however The assumptions that the process is based on are as follows ref 1 pg 68 l There is no chemical change in the fuel or air before combustion 2 Thereischemical equilibrium after combustion 3 The gases go through adiabatic processes during compression and expansion strokes 4 Velocities of gases are negligible in the cylinder When leaded gasoline is used as fuel octene CgHig is used to approximate the variable mixture that actually makes up gasoline The heat of combustion 11 of octene
58. etween 1 05 and 1 4 thus causing the real process curve to fall below that of the air standard curve Another factor that contributes to the relative position of the compression curves is the assumption of the air standard cycle that compression and expansion are constant entropy This of course is not so and the real compression curve would be expected to fall below the constant entropy curve even for a cylinder charge consisting entirely of air Because of the relative displacement of the measured and air standard curves in Fig 14 itis necessary to analyze the actual and air standard results to compare the work outputs Table 2 shows that the real work output is 23 lower than that of the air standard cycle Many factors contribute to this lower work output including the air standard cycle assumptions of constant entropy in compression and expansion strokes and complete combustion of fuel at constant volume As expected the IMEP and thermal efficiency values are also lower for the real cycle The following portion presents results obtained while varying an engine operating condition The operating condition that was varied was the spark advance angle since it has a very noticeable effect on the shape of the indicator diagram the ihp and the IMEP refer to Fig 8 Figure 15 a and b the indicator diagrams produced at 20 degrees and 40 degrees spark advance respectively show the general shape changes that result The maximum pressure occur
59. follow 1250 1260 1270 1280 1290 1300 1310 1320 15350 1540 1550 1360 1370 1330 1390 1400 1410 1420 1430 1440 1450 1450 1470 1480 1490 1500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600 1610 70 Subroutine Period SUB Period A Sec div Per Idci Idc2 dc3 IThis subroutine finds the period of two lcycles of the square wave one engine cycle Variables and constants used A Array containing waveform Sec div Horizontal scope setting Per Period of engine cycle secs 1 Idc Idc2 Idc3 Points in cycle where shaft encoder signal goes high Level Vertical value that waveform must cross to be considered high Subprograms used None Level 148 Find idc FOR I 1 TO 1024 IF A I gt gt Level ANO ACI 1 Level THEN Idci I GOTO Find idcZ ENO IF NEXT I Find idcZ FOR I Idc TO 1024 IF A I gt Level ANO ACI 1 sLevel THEN IdcZel GOTO Find idcj3 ENO IF NEXT I Find idc3 FOR I Idc2 1 TO 1024 IF ACI gt Level ANO A I 1 lt Level THEN Idc32I GOTO Perio ENO IF NEXT I Perio Pers Idc3 Idc 5ec div 50 Idc22INT CIdc Idc2 2 SUBENO 71 Period determines the period of one engine cycle two shaft rotations and records the data points at which the shaft encoder output goes high It does this by looking at the binary values of the waveforms and finding the first and third points where the curve crosses the threshold value of 148 vertically These point
60. g water should be allowed to circulate through the pressure transducer for as 123 long as possible so unplug the circulation pump and turn off the valve for this system last The pressure transducer can be left in place in the sparkplug hole of the engine if the system will be used again soon If the transducer will not be used again soon however it is best to remove the transducer and replace with the plug provided The pressure transducer has a finite lifetime and it is best to remove it after use so that no one runs the engine with the transducer in place and its cooling water system off The shaft encoder can be left in place 124 APPENDIX F MOTORING DATA USED TO INVESTIGATE PRESSURE CRANK ANGLE PHASING Ascending rpm Angle of Max Press Descending rpm Angle of Max Press WN Y 00 00 di Un EU On O COONAN E W CO bh 125 APPENDIX G CALCULATIONS FOR COMPARISON OF AIR STANDARD OTTO CYCLE AND ACTUAL RESULTS TAKEN AT 20 DEGREES SPARK ADVANCE Determination of Energy Ideally Added by Fuel per Cycle Table Al Volumetric Flowrate of Fuel Data Fuel Level mi Time Flowrate Point ES DEE 1 2 3 4 5 6 7 8 9 0 mn O ON wm bw CO mean 189 cc sec Above data taken at 1360 rpm spark advance of 20 degrees etc under same conditions and directly after generating results at 20 degrees spark advance in Appendix F 126 Heat of Combustion of octene 19
61. gle Idel Idc2 Idc3 First second and third points where shaft encoder output goes high or three IDC s in cycle Cr Compression ratio Per Period of engine cycle Ph Phase of waveform 1e if IDC at end of compression stroke or end of exhaust stroke N Number of waveforms to be averaged Th Crank angle at which shaft encoder output goes high when engine not running ISubprograms used Start up Prints brief equipment setup instructions on screen Get offset Inputs crank angle at which shaft encoder output goes high New Acquires data for new indicator diagram and modifies it Graph ind Produces plot of indicator diagram Print data Produces hard copy of modified data points 450 460 470 480 490 500 510 520 530 540 550 560 570 580 590 600 b1 620 630 640 650 DIM Dat 1024 3 CALL Start_up CALL Get_offset Th Label soft keys ON KEY LABEL GET DATA GOTO Uat ON KEY LABEL PLOT P V 6010 Plot pv ON KEY 2 LABEL ANALYZE GOTO Al ON KEY 3 LABEL HC DATA GOTO Hc data ON KEY 4 LABEL END GOTO The end Spin DISP Press key k for a neu run GOTO Spin Dat CALL NeutDat 2 11 I2 I3 Cr Per Ph N Th GOTO Spin Plot pv CALL Graph_ind Dat 11 15 GOTO Spin Al CALL An Dat 2 11 12 13 Per Cr Ph N GOTO Spin Hc data CALL Print data Dat 11 15 GOTO Spin The end END o7 The main program first calls subroutine Start up see section below which prints a set of brief e
62. gle error at 3000 rpm 3000 rpm 50 rev sec 18 000 degrees sec 18000 degrees sec 0 048 msec 0 864 degrees error 53 APPENDIX C COMPUTER SOFTWARE The software package for the Ricardo engine indicator diagram is original and specifically tailored to the engine geometry HP Basic Version 1 0 is the programming language with Tektronix interfacing commands sent to the oscilloscope in the OUTPUT statements The software was written to incorporate some desirable features including flexibility straight forward directions optional hardcopies of results and confirmation of user input The aim of these features is to make the software as easy flexible and efficient to use as possible The input demanded from the user by the software includes the engine compression ratio the range setting of the charge amplifier and the number of engine cycles to be averaged The results consist of the following Plot of indicator diagram itself Analysis of data including Gross and net indicated work output of cycle Work lost to pumping or valve losses Indicated mean effective pressure IMEP Indicated horsepower output List of user input compression ratio number of cycles averaged Listing of modified data Pressure Volume Crank angle 54 The software consists of the main program and subprograms both subroutines and functions The convention of using functions when one value is to be returned and where the subprogram does not
63. haust valve opens at 1 and piston pushes gas out of cylinders The work associated with the indicator diagram is b T pev for each process Here W refers to the work done by the gas on the piston The net work is the integral around the cycle or 5W pdV 2 The area under the curve for each process is thus the work done during that process These areas and the net work are shown in Figure 3 It can be seen that the negative work done from 1 to 0 is cancelled out by the positive work from 0 to 1 This leaves the closed cycle 1 2 3 4 1 which can be modeled as a control mass The ideal processes for the air standard cycle are shown in Figure 4 Processes 1 2 and 3 4 are constant entropy adiabatic and reversible and 2 3 and 4 1 are constant volume Figure 5 shows an actual Otto cycle superimposed on an air standard cycle The area of the power loop of the real cycle is smaller than that of the air standard and area of the lower loop of the real cycle represents negative work or pumping losses As a result we can expect the air standard cycle to have a greater net work output than can be achieved in practice One of the quantities that a designer is most concerned with is the thermal efficiency nt of an engine the efficiency with which the engine uses the power supplied to it The definition of efficiency nt in general is _ benefit 96W 3 a cost 2Q It can be shown ref 2 pg 298 that a A 4 n 71 3
64. his paper diagrams produced at various degrees of spark advance using the equipment assembled for the project are compared m a y a Ve Measured Motoring SA Comb u Curve degrees O bmep imep f m mo imep ni 0 40 72 99 0 0 252 0 73 103 0261 13 40 82 109 0 278 0 82 l3 0 287 26 38 84 109 0 278 0 82 115 0 293 9 39 39 72 99 5 0 253 0 74 103 0 263 CFR engine 314 x 41 in r 6 Fp 113 ny 034 p 143 psia p 14 55 psia T 130 F 1200 rpm Sloan Automotive Laboratories 11 13 47 Fig 8 Effect of Spark Advance on Indicator Diagram ref 1 pg 128 16 17 COMPONENTS OF THE MEASUREMENT SYSTEM In order to create an indicator diagram the instrumentation system must be able to simultaneously detect cylinder pressure and piston position Piston position can then be converted to cylinder volume The data must then be presented graphically Indicator diagrams have been generated in a variety of ways in the past and the systems used to generate diagrams vary considerably The constraints imposed by the system and the skill of the user determine the accuracy reliability and therefore the usefulness of the diagram Historically the first apparatus capable of generating an indicator diagram of sufficient accuracy to be useful was the MIT Performance Analyzer ref 3 pg 81 82 The MIT Performance Analyzer similar to the Farnborough Apparatus used up to now at RIT is a mechanical mechan
65. ined in Appendix F It should be noted that if the flexible coupling alone were responsible for phase change with rpm the pressure output would be expected to lead the encoder output increasingly with rpm However the results are opposite to this expectation The results point to a constant time lag between pressure and encoder output Compression of the coupling spider with rpm would counteract this effect but the relation would also be linear within a certain range The net affect of these two phenomena would be a linear relationship between phase shift and engine speed which is reflected in the data In conclusion the proper phasing of pressure and crank angle data was an important result of the analysis of motoring data The relation between phase offset and rpm resulting from the data was used in the computer software to correct for the phenomenon 38 FIRING RESULTS The firing results are presented here in two contexts so that they may be considered with respect to expected results First a typical set of results is compared to those calculated for an air standard cycle Secondly firing results taken while the spark advance was varied from 20 degrees to 45 degrees are presented During that data gathering runs the main engine operating variables were held constant While obtaining all results the compression ratio was maintained at 9 and the carburetor settings were fixed The dynamometer settings were also held constant with
66. ing these strokes ft lbs Subprograms used FNTrap Returns integral under curve between two points using the Trapezoid method of numerical integration IFind points at ODC Dde1 INT 11 12 2 DGG2 INT 12Z Z Use the trapezoid rule to calculate work done during four engine strokes IF P 1 THEN Power_stroke FNTrap A 11 0dcl 12 Exhaust strokes FNTrap A C 0dcl I2 14 Intake strokes FNTrap AC6 2 12 0dc2 12 Compr_stroke FNTrap t gt 0dc2 13 12 END IF IF P 2 THEN Power_stroke FNTrap A 12 0dc2 12 Exhaust_stroke FNTraptA 0dc2 13 12 Intake_stroke FNTrap A 11 0dc1 12 101 7520 Compr strokesFNTrapiA C 0dcl 122 12 7530 END IF 7540 IFind net uorks 7550 Pu Pouer stroketCompr stroke 7560 Nw Intake_stroke Exhaust_stroke 7570 Ntw Pw Nw 7580 SUBEND Subroutine Work calculates three types of work that can be determined from the indicator diagram These works are defined as follows refer to Fig A2 1 Positive Work Area of the upper loop of the indicator diagram 2 Negative Work Area of the lower loop of the indicator diagram valve losses 3 NetWork The sum of the above two It should be noted that these works are named according to the signs that they have when the engine is firing Positive Work will be a positive number when the engine is firing and the Net Work will be positive When the engine is being motored drive
67. ired does not fit on the scope screen vertically the data points are digitized to a value of 0 Volts instead of their true values This of course plays havoc with the results and the program attempts to avoid this situation by scaling vertically based on the maximum pressure of twenty cycles Now that the horizontal time scale and the vertical scale of Channel 2 have been adjusted the waveforms that will be used for the indicator diagram can be acquired 3640 3650 3660 3670 3680 3690 3700 3710 3720 5730 3740 3750 5760 37710 3780 3190 3800 3810 5820 3830 3840 3850 5850 3870 5880 5830 3300 3910 3920 Subroutine Acq ch2 SUB Acq ch2 8C I1 I2 S div Phase N This subroutine acquires the output curve Ibased on the average of N cycles lUariables and constants used 8 2 D array to store data 11 12 Points where shaft encoder i output goes high S div Horizontal scale scope setting Phase Indicates if I occurs at end of compression stroke Phase or at end of exhaust stroke Phase 2 N Number of waveforms to be averaged A Temporary array to receive down loaded waveform Idi ld2 Arrays to collect waveform data for each phase I Counti Count2 Counters for number of waveforms kept in Idi and ld respectively i Interval Time to wait for scope to acquire waveform Subprograms used None DIM 10Z4 Idi 1024 Id2 i 24 Interval 20 5_d1v 1
68. is taken to be 19 035 Btu lbm see ref 1 Chs 3 and 4 for a more complete explanation and gas tables for the fuel air cycle The actual Otto cycle will now be discussed comparing it to the fuel air cycle The fuel air cycle represents the performance limit which can be approached by spark ignition engines Figure 6 shows how a typical engine cycle differs from the fuel air cycle For the comparison the cycles are assumed to coincide as to temperature pressure and composition at a point such as point x in the approximate center of the compression stroke A fundamental difference between the two cycles is that in the actual cycle no process occurs at constant volume The curves in Fig 6 correspond very closely up to point a since the actual compression is nearly isentropic Ignition of the fuel occurs at point a with the accompanying increase in pressure and the fuel continues to burn until point b where the charge is completely burned Points a and b are at the same piston position in a well adjusted engine The line y z represents an isentrope through b The true process drops below this line because of heat loss At point c the exhaust valve starts to open and the pressure loss between c and 1 is due to exhaust blowdown Probable causes for the differences between the actual and the air fuel cycles include the following ref 1 pg 108 Leakage Incomplete combustion Progressive burning oa Se NE Time losses piston moving
69. ism activated by pressure that causes a stylus to mark a card attached to a rotating cylinder The diagram produced was actually of pressure vs time making the apparatus of limited value when working with many engines and mechanical problems due to temperature effects on the hardware required frequent maintenance Electronic cylinder performance indicators came into use in the early 1960 s These could calculate horsepower directly but the circuit components were dedicated and had to be changed for each different transducer used The advent of the digital computer and attendant data acquisition devices multiple channeled A D converters has allowed the generation of indicator diagrams to become much more simple flexible and accurate Interactive software allows the user to input parameters specific to 18 a run such as the compression ratio used and to select the output desired A digital system is used in the present indicator diagram generation In order to produce an indicator diagram four basic functional components are used These are as follows Pressure measuring device Means of tracking the cylinder volume Data acquisition device P m A Data manipulation and control device The components will be discussed separately in the following sections Pressure Measurement The device used to measure engine pressure must be able to operate in the desired pressure range and to withstand severe temperature and pressu
70. it takes the engine to reach equilibrium but it is not necessary to use it Turn on Power Switches 1 and 2 of the Dynamometer Control Unit Turn the Oil Heater Switch on the Control Unit to the ON position Use the Armature Supply Volts Knob to set the Supply Volts the left most gage on the Control Unit to 60 Volts Use the Field Control Knob to set the Field Volts the right most gage on the Control Unit to the maximum possible You are now ready to motor the engine Make sure that the alligator clip is grounded clipped onto the screw provided and that its wire will not interfere with the flywheel Now turn the Master Switch on the Control Unit to the Motor position The dynamometer will now act as a motor to turn the engine over Open the Fuel Line Valve Disconnect the Alligator Clip from the screw making sure that it does not touch any other parts Put the lever on the Starting Carburetor Valve to the OPEN position towards you Now comes the tricky part After a short while the engine will begin to fire When you hear it begin to fire fairly regularly turn the Master Switch of the Dynamometer to the OFF position Quickly go back to the carburetor and close the Starting Carburetor Valve and turn the main fuel valve open about 1 revolution to the 4 00 position The engine will run for a while and then probably begin to die out When it begins to die open the Starting Carburetor Valve until it catches again 169 This
71. itches outside the testcell door The suggestions above would increase the accuracy and depth of the analysis possible from a Ricardo engine indicator diagram The present diagram however is sufficient for many purposes in engine analysis including determination of thermal efficiency mechanical efficiency and evaluation of the effects of variation of engine operating conditions It is hoped that the work represented in this report will serve to increase the value of the Ricardo engine as a research and educational tool
72. l Volts ch2 25 ELSE GOTO Enlarge END IF IF FNMax ch2 5 gt 125 THEN OUTPUT 712 CH2 VOLTS 14 WAIT Interval Volts ch2 10 ELSE SUBEXIT END IF IF FNMax_ch2 5 gt 125 THEN OUTPUT 712 CH2 VOLTS 20 WAIT Interval Volts _ch2 20 ELSE 76 BB SUBEXIT 2670 END IF 2680 IF FNMax_ch2 5 gt 125 THEN 690 OUTPUT 712 CH2 VOLTS 50 2700 WAIT Interval 2710 Volts_ch2 50 2720 ELSE 2730 SUBEA LE 2740 END IF 750 IF FNMax_ch2 S5 gt 125 THEN 2760 The input to Ch2 is too great in 2770 lamplitude to handle 2780 PRINT FATAL PROBLEM 2790 PRINT The amplitude of the input from 2800 PRINT Ch2 is too great for the program 2810 PRINT to handle 2820 PRINT Adjust and begin again 2830 Fatal_error TRUE 2840 SUBEXIT 2850 END IF 2800 Enlarge tEnlarge the vertical scale so that 2870 the waveform covers as much of the 2880 scale as possible 2830 IF Max lt 63 THEN 300 OUTPUT 712 CH2 VOLTS 1 2310 WAIT Interval 2320 Volts ch2 1 2930 ELSE 2940 SUBEXIT 2950 END IF 2360 IF FNMax_ch2 S5 iB3 THEN 910 OUTPUT Tl2 Che VOLTS 2980 WAIT Interval 2990 Volts_ch2 5 3000 ELSE 3010 SUBEXIT 3020 END IF 3030 IF FNMax ch2 5450 THEN 3040 OUTPUT FIZI 6 VOLTS 27 3050 WAIT Interval 3060 Volts_ch2 2 3070 ELSE 3080 SUBEXIT 3090 END IF 3100 IF FNMax_ch2 5 lt 63 THEN 3110 OUTPUT 7127 CH2 VOLTS 1 3120 WAIT Interval 3130 Volts ch27 1 3140 ELSE 3150 SUBEXIT 77 3
73. ll below ambient pressure to point b The increase in pressure from Vi to V2 over the exit manifold pressure Pe represents the pressure differential needed to push the gas from the cylinder as the piston moves from V1 to Vg The pressure is lower than that in the inlet manifold Pe to bring a new charge into the chamber The shape of the curve in the region of IDC depends on the timing of the 25 3 Pressure psia Fig Schematic of Pumping Loop of Typical Indicator Diagram from ref 1 pg 159 14 15 closing of the exhaust valve and the opening of the inlet valve which occur in that area As mentioned above the low pressure during intake is the result of the throttling effect of the valves The work lose due to pumping is indicated on Fig 7 by the area of the lower loop Figure 8 shows the effect of variation of the spark advance on an actual indicator diagram taken from Taylor ref 1 pg 128 Spark advance is the number of crank angle degrees before inner dead center that the sparkplug fires in a sparkignition engine The general shape of the diagrams change with the peak pressure decreasing as the spark advance decreases The spark advance also effects the mean effective pressures both BMEP and IMEP Other engine operating variables such as compression ratio fuel air ratio and engine speed can also be manipulated with characteristic effects on indicator diagrams see ref 1 pgs 127 133 In the Results section of t
74. lowed to exceed 400 Volts Regulating the Engine Running The Main Throttle on the carburetor should be used to regulate the rpm of the engine Advancing the throttle increases the rpm and the fuel flow screw may have to be adjusted to accommodate the new throttle setting The spark time may also have to be adjusted when the throttle setting is changed Turn up the Field voltage to increase the load applied by the dynamometer Increasing the load decreases the rpm of the engine STOPPING THE ENGINE 1 2 3 Turn the Fuel Line Valve to the OFF position Short out the engine ignition by clipping the Alligator Clip to the screw When the engine flywheel is completely at rest turn the Master Switch of the Dynamometer Control Unit to the OFF position Turn off the oil heater and the air heater if they were used Turn off Power Switches 1 and 2 of the Control Unit Close the fuel valve under the fuel tank Put the open end of the tubing at the X intersection under the Calibrated Cylinder in an appropriate can to receive the excess fuel Open the bottom and side valves to let the fuel drain from the Calibrated Cylinder 172 5 If the exit temperature of the cooling water is 70 F or less unplug the Water Pump and turn the line water off with the Line Water Valve 6 When you are ready to leave the room turn off the Exhaust Fan switch near the Dynamometer Control Unit and the lights fan and vents sw
75. lt THEN 11600 Angle 360 Angle 11610 END IF 11620 IF Angle gt 360 THEN 1163 Angle Angle 360 11640 END IF 115650 Dat 1 3 Angle 11650 NEXT 1 11670 SUBEND The Adj angle subroutine makes use of motoring data analysis to correct the phasing between pressure and crank angle data The correction is based on the engine rpm and the alignment between the shaft of the shaft encoder and the drive shaft as expressed in equation 10 The subroutine performs two tasks adjusting the angle value and adjusting the data points assigned to be IDC s The value of the phase error Offset is calculated from the relation obtained between rpm and phase error from motoring data The IDC s are then adjusted accordingly Then the angle values are adjusted in the FOR NEXT loop 4860 4870 4880 4890 4300 4310 4920 4330 4940 4350 43650 4970 4980 4990 5000 5010 5020 5030 5040 5050 5050 5070 5080 5030 5100 5110 5120 5130 5140 5150 5160 5170 5180 5190 9200 5210 5220 5230 5240 5250 89 Subroutine Conv volume SUB Conv volume 8 R Idcl 1dc3 This subroutine converts the crankangle values from radians to cylinder volume ini ASAS Variables and constants used B Array holding data R Compression ratio Idel Ide3 Beginning and end pooints of cycle waveform S D L Defined below Vo Clearance volume Epsi Epsi sq A C Const Used to save computation time X Crank angle for data point ISu
76. n by the dynamometer however the Positive Work will be a negative number and the Net Work will be negative The Negative Work valve losses is always a negative quantity The area under the curve must be determined for each of the four engine strokes Subroutine Work uses function FNTrap see below to return the numerical integration under each stroke process line Processes that occur Pressur a Pressure Volume Volume Engine Firing b Engine Motored Jere positive work Wav negative work Fig A2 Work Areas of Indicator Diagram Firing and Motoring Modes 102 103 while the piston is traveling toward ODC in an indicator diagram are positive in sign and those that occur when the piston is moving toward IDC are negative This simplifies the determination of the sign of the work for each process since FNTrap returns values of the correct sign automatically according to the sign convention used here The first two lines of code in Work find the two data points in the waveform data which correspond to points where the piston is at approximately ODC The segments of data which correspond to the various strokes must then be determined based on the phase of the waveform This is done by the IF THEN ELSE section of the subroutine which can be understood by referring to Fig Al 104 Function FNTrap 7610 DEF FNTrap A Start Finish 7620 This function returns the value of the 7630 larea under the da
77. n engine cycle occupies as much of the available resolution as possible without running off the scale The program adjusts the scope settings as follows The trigger source for the scope is the positive slope of the zero pulse of the shaft encoder and the horizontal scope setting is adjusted so that three of these leading edges are captured on the screen One complete engine cycle is thus captured and occupies as much of the screen as possible The vertical settings Volts div is then adjusted in a similar manner but by looking at the input from the pressure transducer The scope is now ready to acquire data averaging over the desired number of waveforms After the waveform has been acquired and averaged the computer converts the raw data to units of pressure volume and crank angle The phasing between pressure and crank angle and volume adjustment is made based on the shaft encoder alignment input by the user and motoring results see Motoring section for explanation Calculations use the trapezoid method of numerical integration to determine the engine work The results for the run appear on the computer screen and hard copies can be produced if desired The results include the following Plot of cylinder pressure vs volume Listing of modified data pressure volume crank angle List of analytical results including Gross work output 28 Valve losses Net work output Indicated horsepower Indicated mean effective press
78. ndicated horsepower delivered by the engine 3870 3880 38930 3900 3810 9920 3930 3940 9950 9960 9970 3980 3390 10000 10010 10020 10030 106 Function FNInd mep DEF FNInd_mep C Work 11 12 1Calculates the indicated mean effective Ipressure IMEP Work is 1nput n ft lbs land and volumes are input in 1n 43 IMEP returned in psi Variables and constants used C Array holding data Work Work of power loop 11 12 First tuo data points where piston at IDC Subprograms used None ImepeWork 12 CCCIIT I2 0 2 2 CC I4 2 RETURN Imep FNEND Function FNInd mep returns the indicated mean effective pressure IMEP in psi using equation 6 10060 10070 10080 10030 10100 10110 10120 10130 10140 10150 10160 10170 10180 10130 10200 10210 102 0 10230 10240 10250 10260 16270 10280 102390 18300 10310 10520 10330 10340 10350 10360 10570 10380 10390 10400 10410 10420 10450 10440 10450 10460 10470 107 Subroutine Prnt SUB Prnt Cr N Rpm Pu Nu Netw Hp Imep IPrints out the results of the analysis of I the data hardcopy is optional Variables and constants used Gr Compression ratio N Number of cycles averaged Rpm Pw Nw Hp Imep Resp Rev min Work of power loop Valve losses Netw Net work of cycle Indicated horsepower output Indicated mean effective pressure Input by user for hardcopy Subprog
79. ne Get offset 10300 SUB Get offset Theta 10910 This subroutine prompts the user to enter 10920 the crank angle at which the shaft encoder 10850 output goes high and returns that value 10940 10350 Variables and constants used 10950 Theta Angle at which the shaft encoder 10970 output goes high degrees 10980 10990 Subprograms used None 11000 11010 PRINT Enter angle degrees on flvwheel 11020 PRINT at which shaft encoder output 11030 PRINT goes high then CONTINUE key 11040 PRINT 11050 PRINT If preferred input then CONTINUE key 11050 INPUT Theta 11070 FOR I 1 TO 18 11080 PRINT gt 11090 NEXT I 11100 SUBEND This subroutine acquires the crank angle degree read from the engine flywheel at which the shaft encoder output goes high This value is later used for correction of pressure volume phasing 8480 8490 8500 8510 8520 8530 8540 8550 8560 8570 8580 8590 8600 8610 8620 8630 8640 8650 8660 8670 8680 8690 8700 8710 8720 8730 8740 9750 8760 8770 8780 8790 8800 8810 8820 8830 8840 8850 8860 8870 8880 8890 8900 8910 60 Subroutine New SUB New Dat I1 I2 I3 Cr Per Ph N Th IThis subroutine runs the data gathering land calls subroutines that communicate lwith the oscilloscope Variables and constants used Dat Array holding data I1 I2 I3 Data points corresponding to IDC or points where the shaft encoder output goes high Cr C
80. ne turns on ChZ 1200 OUTPUT 712 VMODE CHZ ION 121 WAIT 1 1220 SUBEND This subroutine simply causes Channel 2 to be displayed on the oscilloscope screen by outputting the VMODE CH2 0N statement The program then waits for 1 second to allow the Channel 2 trace to appear on the Screen since it will not be displayed unless the scope is triggered form Channel 1 UI FJ 6 Y Qo 3 0 g1 SS SS C C CJ Cy CJ C Cy Ps pI Fr h po PI F3 po PF pr FJ GI OY OF C4 OF P PF Po Fa Po P Ol OI m Ul C Cy 23570 2380 2390 2400 2410 2420 2430 2440 2450 2450 2470 2480 2490 2500 2510 2520 2550 2540 2550 2550 2570 2580 2590 2500 2610 2620 2630 2540 2650 Pl 19 Subroutine Scale ch2 v SUB Scale_ch2_v Volts_ch2 Fatal error 5 This subroutine scales the Volts div on ICh2 so thew waveform fits the screen lvertically as closely as possible Variables and constants used Volts ch2 Volts div setting of Ch2 on the scope i Fatai error String to hold boolean value for abortion of data acqui S Horizontal scale setting of scope Max Maximum value of waveform Interval Time in sec to wait for i scope to digitize input ISubprograms used 1 FNMax_ch2 Returns maximum vertical value of 2 waveforms Intervalz20 S l Reduce Reduce height of waveform if it Iruns off the screen Max FNMax_ch2 S IF Max gt 125 THEN OUTPUT 712 CH2 VOLTS lt s WAIT interva
81. o Phase for use later in the program 85 Subroutine Conv degs 4550 SUB Conv degs B Idcl Idc2 1dc3 4580 IThis subroutine converts from horizontal 4570 lindex points to degrees and stores these 4580 lin column 3 of array B 4530 Constant angular velocity is assumed 4500 4610 Variables and constants used 4620 1 B Array holding data 4630 Idcl Idc2 l1dc3 Points where shaft 4540 encoder output goes high 46550 Increment Increment in degrees between 4560 data points 4670 4580 ISubprograms used None 4630 4700 Increment 720 Idc3 lIdcl 4710 BLE T 4720 BiIdoe2 3 0 4730 SEAE ala 9 4740 J 4750 POR ISrpDger rp TO T SIEF 4760 8 1 3 360 Increment J 4770 J J 1 4780 NEXT 1 47390 FOR i ldci 1 TO Ide2 1 4800 B I 3 B 1 1 3 Increment 4810 NEXT 1 4820 FOR I ldc2 1 TO 1024 4830 B I 3 BCI 1 3 Increment 4840 NEXT I 4850 SUBEND Conv degs fills the second column of the data array here called array R with the crank angle in degrees The critical assumption used is that the angular velocity of the drive shaft is constant The formula for calculating the 86 increment is therefore simply 2x360 two shaft rotations in degrees divided by the number of data points in one engine cycle 11130 11140 11150 11160 11170 11180 11190 11200 11210 11220 11230 11240 11250 11260 11270 11280 11290 11300 11310 11320 11330 11540 11350 11360 11370 11380 1
82. oke plot can be curved if the time constant of the pressure system is too low allowing decay of the response The value of n from the slope of the log log plot should fall between 1 24 and 1 35 depending on the engine speed and other factors ref 7 pg 7 Deviations from this range can be caused by an error in scaling or in the calibration or performance of the transducer system Phasing of Pressure With Respect to Volume The phasing of pressure with respect to volume can be checked by looking at the data points taken near the region of peak pressure When these data points are plotted on pressure vs crank angle the maximum pressure should occur just before IDC The maximum would occur before rather than at IDC because of irreversibilities due primarily to heat transfer Peak pressure after IDC indicates that the pressure is retarded with respect to volume and peak pressure more than two degrees before IDC means that the pressure is probably advanced The results obtained while motoring the engine were evaluated according to the criteria above The pumping loop pressure is considered first The exhaust stroke pressure was consistently higher than the assigned reference pressure of 14 7 psia The intake stroke pressures were lower than the reference pressure at ODC after the intake stroke only after about 90 degrees crank angle see Fig 11 It would be expected that the intake pressure would fall below 14 7 psia before 90 but the
83. ompression ratio Per Period of engine cycle Ph Phase of data N Number of cycles averaged Th Crank angle at which shaft encoder output goes high Chi Array holding waveform from Chi of scope shaft encoder Abort_prog String holding boolean value for abortion of data acqui 5 div Time scale setting on scope VU chi V_ch2 Volts div setting on scope for Chl amp Ch2 respetively R Range setting on charge amplifier Get comp ratio Inputs compression ratio Get ca range Inputs range setting of charge amplifier Get num avg Inputs number of uave forms to be averaged Init setup Sets initial state of scope Read avg4 chl Acquires waveform from Chl averaged over 4 Period Calculates period of engine cycle Scale hor Fits one engine cycle to screen horizontally Turn on ch2 Displ Ch2 on scope screen Scale chZ v Scales Ch2 Volts div to scope screen Subprograms used Acg_ch2 Acquires averaged waveform from 8920 8930 8940 8950 8360 8970 8980 8990 9000 9010 9020 9030 9040 9050 9060 9070 9080 3090 9100 3110 3120 3130 3140 3150 9150 9170 9180 9190 9200 9210 9220 9230 9240 9250 9260 9270 9280 9290 9300 9310 9320 9330 9340 9350 3350 9370 9380 3330 3400 3410 3420 Co Ad Co Pr DIM OFF OFF OFF OFF OFF Abor FOR PRI NEXT Ini FOR Da Da Da NEX CALL CAL
84. output Tighten the setscrews until snug 3 Gently insert the encoder shaft fitting and key into the flexible coupling and replace the four mounting flange screws 4 Test the encoder alignment again using the scope display 5 Repeat the above four steps until the encoder alignment is within acceptable limits When alignment is attained tighten the setscrew on the flexible coupling until just snug 120 APPENDIX E RUNNING THE INDICATOR DIAGRAM GENERATION EQUIPMENT After the indicator diagram generation system has been set up as described in the section Setting up the Indicator Diagram Equipment you are ready to run the equipment and generate diagrams The procedure for running the system while the engine isin spark ignition mode follows 1 Turn on the indicator diagram generation equipment computer printer oscilloscope cooling water pump for pressure transducer charge amplifier and power supply Be especially careful to turn on the cooling water pump for the pressure transducer and open the valve in that system since the transducer must be cooled constantly while the engine is running When turned on a message will appear on the computer asking which language B or H is desired Do not respond and the system will default to Basic B 2 Start the Ricardo engine following the Starting the Engine and Running the Engine sections of Ricardo Operating Instructions Spark Ignition running Adjus
85. p cyclas V in 3 Angle deg 16 02 mL 16 86 Ia ur 162 Restlts Taken at 45 Degrees Spark Advance Po ftpsial wi Y Trees RESULTS Engine speed 1376 15 Compression ratio 9 Hork Gross work output 166 67 Valve loss 15 38 Net work 151 3 Indicated horsepower TMEP 64 68 psi Averaged over 20 Pt P psia 511 340 3 4 33 512 340 7 4 39 513 339 3 4 45 rpm ee ft lb ft 1b So hp cycles V in 3 Angle deg 14 15 14 97 I5 163 APPENDIX J RICARDO ENGINE OPERATING INSTRUCTIONS Spark Ignition Running The following instructions lead the user through the steps in running the Ricardo Research engine in the spark ignition mode Three figures should be referred to when using these instructions the Schematic of the Ricardo Cell Fig A4 the Dynamometer Control Unit Fig A5 and the Ricardo Carburetor Fig A6 Do NOT smoke in the test cell STARTING THE ENGINE 1 Turn on the exhaust fan switch on the wall in front of the dynamometer control unit and the lights fan and vents switches outside the testcell door These should remain on whenever the engine is running or has been run recently Keep the testcell doors wide open while running the engine 2 Check the cooling water level in the Coolant Water Column The level should be within 8 inches of the top of the column If it has fallen below this add distilled water to the proper level before continuing Plug in the water p
86. partial range bar bar Overioad bar Sensitivity pC bar Natural frequency kHz Linearity for all ranges FSO Hysteresis for all ranges FSO Acceleration sensitivity without cooling bar g with cooling bar g Operating temperature range without cooling Therma sensitivity shift 20 100 C 20 350 C 200 50 C Transient temperature error Propane flame intermittent on front 10 Hz insulation at 20 C Shock resistance Tightening torque Cooling water pressure Capacitance Mass Plug ceramic insulator 10 32 UN 22 which had a sensitivity of 1 03 pC psi The natural frequency of the transducer must be considered for the application The rule of thumb used for relating the instrument s natural frequency to the frequency of the input is that the natural frequency should be at least twice the frequency of the input This typically guarantees a constant relationship between input and output The 7061 has a natural frequency of more than 45 kHz This is well above the natural frequency required by this application since the maximum freqeuncy of the input is only 25 Hz at 3 000 rpm The Kistler 7061 is specifically designed for use in engine testing in both spark and compression ignition modes and can withstand the temperatures and pressures tpyically encountered The Ricardo engine can be run in either mode while varying other operation parameters so a transducer that can handle even the high pressures and temp
87. plifier RNC to alligator cable type RG58 A U Torque wrench Micro torque recommended with 9 16 in deep socket The first part of this system to check is the transducer cooling water circulation apparatus This apparatus should be set up as shown in Fig 9 Components section Both reservoirs must be more than half full of distilled water to allow for maximum heat transfer without significant increase of the water temperature Check the water level in both reservoirs If either reservoir is less than half full add more distilled water to the lower reservoir Then pump the water to the upper if that reservoir is low by running the circulation pump If the cooling water appears dirty or the lids have been left off the reservoirs empty the water from the apparatus rinse reassemble the system and then add fresh distilled water to the lower reservoirs while the pump is running until the proper levels are reached in both reservoirs ONLY distilled water should be used so that mineral deposits do not develop in the pressure transducer Make sure that the reservoir lids are always firmly in place so that the water is not contaminated Check the water lines for the transducer cooling carefully making sure that they do not touch surfaces of the engine such as the exhaust pipe that will become hot Also check that the lines are not positioned near moving parts of the engine such as the flywheel or the magnito coupling Once the transducer cooling wa
88. quipment setup messages on the computer screen The computer soft keys are then labeled The soft keys are the set of keys on the computer keyboard which are labeled k0 through k9 When they are pressed the program executes the GOTO s appearing at the end of the ON KEY statements The program returns to the line labeled Spin after each subroutine called is completed and the softkey display is activated so that the user can select the subroutine New Graph ind An or Print data to be called 6830 6840 6850 6860 6870 6880 6890 59300 5810 6920 6330 6940 6350 5950 6370 5380 6390 7000 7010 7020 7030 7040 7050 7060 1070 7080 58 Subroutine Start up SUB Start_up This subroutine prints basic equipment tset up messages PRINT SHAFT ENCODER PRINT Apply 5 Volts DC excitation PRINT to shaft encoder PRINT Attach output leads to Chl of PRINT TEK 2530 oscilloscope PRINT PRINT PRESSURE TRANSDUCER PRINT Attach output from charge PRINT amplifier to Ch2 of PRINT TEK 2430 oscilloscope PRINT PRINT MAKE SURE THAT THE OSCILLOSCOPE PRINT OUTPUT SETUP 15 AS DESCRIBED PRINT IN USER S MANUAL PRINT ADDRESS 12 PRINT MODE T L PRINT TERMINATOR LF EOI PRINT Press CONTINUE key to procede PAUSE FOR I 1 TD 18 PRINT NEXT I SUBEND Subroutine Start up prints out some basic equipment setup message on the computer screen 99 Subrouti
89. rams used None DIM Resp i FOR 1 1 PRINT NEXT 1 PRINT PRINT PRINT PRINT PRINT PRINT PRINT PRINT PRINT PRINT PRINT PRINT TO 18 i RESULTS Engine speed INT Rpm 100 5 2 100 rpm Compression ratio Ur Mork Gross work output INTCPu 100 52 100 tt ib5 Valve loss INT Nw 100 5 100 rt 1b Net work INT Netw 100 5 100 ft 1o Indicated horsepower INT Hp 100 5 100 hp TIMEP INT Imep 100 5 100 psi Averaged over N cycles ICheck if a hardcopy is desired INPUT DO YOU WANT A HARDCOPY Y N Resp IF Resp Y OR Resp y THEN DUMP ALPHA 4701 FND IF FOR I PRINT NEXT I SUBEND TO 18 108 Subroutine Prnt Printout causes the analyzed results to be printed on the computer screen One copy of the results is available each time this subroutine is called 8000 8010 8020 8030 8040 8050 8060 8070 8080 80390 8100 8110 8120 8130 8140 8150 8160 8170 8180 8190 8200 8 10 8220 8230 8240 8250 8 60 8270 8280 8290 8300 8310 8320 8330 8340 8350 8360 8570 109 Subroutine Print data SUB Print_data A First_pt Last_pt This subroutine prints a hard copy of the pressure volume and crank angle data Variables and constants used A Array holding data First_pt Last_pt First and alst points to be printed Respon User response to whether hard copy of data desired DIM Resnon 1 OFF KEY O
90. re variations in the engine cylinder while giving reliable output with acceptable sensitivity The pressure transducer used in the system here is a flush mounted water cooled piezo electric pressure transducer made by Kistler Instrument Co This type of piezo electric transducer design is considered to be the most satisfactory for measuring pressure in an internal combustion engine ref 3 Being flush mounted there is no connecting passage between the pressure to be measured in the engine cylinder and the transducer diaphragm Previous designs for mounting the transducer used a connecting passage in the transducer fitting between the transducer itself and the opening to the cylinder to isolate the transducer from the severe conditions in the engine cylinder The new generation flush mounted pressure transducers 19 are cooled by water flowing around the piezo electric crystals This configuration avoids the problems of damping phase shift and possible ringing and attenuation of pressure input due to a connecting passage refs 4 5 6 Temperature variation causes changes in the transducer output called thermal drift due to thermal strain of the transducer diaphragm and other components Thermal drift is kept to a minimum in the Kistler model 7061 by water cooling it Fig 9 shows the water cooling system designed for the pressure transducer in this application The system circulates distilled water from the lower reservoir via th
91. running the engine compare well with those expected from the air standard cycle The work output from the real cycle is 23 less than that of the air standard When the spark advance angle is varied while holding other operating variables constant the results and indicator diagrams produced are as expected and in line with those presented in the literature 46 Further work with the indicator diagram generation system and the Ricardo engine itself could result in a more accurate diagram as well as enabling a more sophisticated analysis of the engine performance Some recommendations for further work are as follows 1 Determination of the pressure at the inlet port when the piston is at ODC at the end of the intake stroke would enable a correct reference pressure to be assigned As previously mentioned at this point the piston is moving slowly and the intake valve is fully open The pressure in the cylinder can therefore be taken as that in the intake manifold Correct reference pressure assignment allows accurate absolute pressure determination which would be checked by the log log p V plot and the pumping loop of motoring data 2 Determination of the mass flow rate of air into the engine would make the fuel air ratio known since the fuel flow rate is presently measurable This would enable a fuel air cycle indicator diagram to be generated which is a much closer theoretical model of the real cycle than is the air standard cycle
92. s evaluation of the motoring data and a thorough explanation of the computer software Sample results taken while varying the spark advance of the engine compare well with those expected Actual results are compared with those of the air standard Otto cycle with the work of the actual cycle being 23 percent lower than that of the air standard The paper also includes complete instructions for operating the apparatus providing directions for setting up and running the indicator diagram generation equipment and instructions for running the engine in spark ignition mode Suggestions are made for further work so that the results may be compared to the fuel air cycle ll TABLE OF CONTENTS Page ABSIRACT saca isaac RS eo ii PIS POP TABLES np ai se EUM D da V LIST OF FIGURES sorene ia d eaters qua ES red ob oe vi INTRODUCTION Suisse I EAR tages x deed oh ad ext 1 INDICATOR DIAGRAM THEORY seen 3 COMPONENTS OF THE MEASUREMENT SYSTEM 17 EVALUATION OF MOTORING DATA eese 30 PIRING RESULTS versionado a dan 38 CONCLUSIONS AND RECOMMENDATIONS 45 REFERENCES x22 o2 s RE UR cease 48 BIBLIOGRAPHY NRN 49 APPENDICES Appendix A Derivation of Thermal Efficiency of Air Standard Otto Cycle in Terms of Compression Kallo detesta A 50 Appendix B Calculations of Error in Crank Angle Due to Rise Time of Shaft Encoder Output 51 Appendix C Computer Soft
93. s closer to IDC as spark advance increases and the power loop is more squat in shape at the smaller spark advance angle 20 degrees Table 3 presents the results of varying the spark 41 Table 2 Comparison of Actual and Air Standard Cycle Results Cycle Work Output imep Thermal ft 1b psia Efficiency 7 Actual Air Standard xpower loop only 42 250 p psia vs V Cin 32 a 20 Degree Spark Advance 30a P psia vs V inx 3 b 40 Degree Spark Advance Fig 15 Indicator Diagrams Taken at Two Spark Advance Settings Actual Results 43 Table 3 Firing Results Varying Spark Advance Max Pressure IMax Pres psia 44 advance The indicated results IMEP and ihp are good to about 5 7 and 5 4 respectively see Appendix H which are except for the results at 45 degrees in line with those presented in Fig 8 From Table 3 the IMEP is highest at 20 degrees while it is highest between 13 and 26 degrees according to Taylor s results The two results are compatible considering the differences in operating conditions compression ratio rpm etc The ihp results from Table 2 show a maximum at 30 degrees due to the higher engine speed at which that data was taken The maximum pressure is higher at greater spark advance and the angle of maximum pressure is smaller at larger spark advance which are also results to be expected Generally the results obtained with varying the sp
94. s correspond approximately to the first and third times the piston reaches inner dead center or the first and last points of the engine cycle The period is then calculated using the sec div value and the second IDC point is assigned to a data point midway between the first and third IDC s since constant angular velocity is assumed The period and the three IDC s are returned to the calling program Subroutine Period is called twice by New the first time to get an initial value of the cycle period and again after the horizontal setting of the scope has been scaled for maximum resolution see Scale hor This is done so that slight variations of rpm with time have a minimal effect in the diagram 1640 1650 1660 1670 1680 1690 1700 1710 1720 1730 1740 1750 1760 1770 1780 1790 1800 1810 1820 1830 1840 1850 1860 1870 1880 1890 1300 13910 1 320 1930 13940 1950 1360 1370 1 380 1990 2000 2010 2020 2030 2040 2050 72 Subroutine Scale hor SUB Scale_hor Per Time_div lAdjusts the horizontal time scale so Ithat two periods of the square wave are lin as much of the 20 time scale divisions las possible IUariables and constants used Per Period of engine cycle secs Time div Horizontal scale scope setting sec div ISubprograms used None IF Per lt 19 AND Per gt 39 5 THEN DUTPUT 7121 HDR ASEC 1 0 Time divz1 0 SUBEXIT END IF IF Per lt 9 5 AND Per gt 3 8 THEN DUTPUT 7121 HDR
95. s the button under AUTO on the screen display to select that trigger mode from the menu Now turn on the power supply and adjust its output by using the 6 Volt knob until the vertical display on the scope shows 5 Volts 25 V Turn the power source off and then detach the scope probe from the source leads Attach the scope and power source leads to the shaft encoder leads as follows 6 6 V lead from power source to red wire from shaft encoder labeled EXCITATION e Common lead from power source to black wire from shaft encoder labeled GROUND EXCITATION AND INDEX e Main probe lead grey from Chl of the scope to white wire from shaft encoder labeled ZERO INDEX OUTPUT e Reference scope probe lead black from Chl of the scope to black wire mentioned above from shaft encoder Now turn on the power source The shaft encoder system is now set up so that the encoder output is displayed on the scope screen and you are 118 ready to go to the next section to check the alignment of the encoder with the engine crank angle Checking the Alignment of the Shaft Encoder In order to determine the alignment of the encoder with the crank angle of the engine shaft the system must first be set up as described in the section above The encoder output is compared with the crank angle that is marked on the large flywheel on the drive shaft The degrees marked on the flywheel are referenced by the metal pointer tha
96. sed in the next section beginning with the air standard Otto cycle The air standard cycle is a very simplified approximation of an actual cycle The fuel air cycle a much more sophisticated and closer approximation to an actual engine cycle is also presented theoretically so that it may be used for comparison with experimental results after further development of the apparatus INDICATOR DIAGRAM THEORY An indicator diagram is a plot of pressure versus volume of the cylinder or crank angle of an engine From it the work output and efficiency of an engine may be determined These diagrams vary with the type of engine cycle Otto diesel etc and the operating parameters such as compression ratio richness of the mixture etc As such they are used to evaluate engine performance and to investigate the effects of varying the operating parameters In this discussion the indicator diagram for the Otto cycle spark ignition four stroke will be addressed For the thermodynamic analysis of the cycle a control volume must be defined Figure 1 shows the control volume for the engine cylinder V p and T are the volume pressure and temperature of the gas in the cylinder W the power delivered to the driveshaft and Q the power delievered by fuel combustion are shown in the positive sense The velocity vectors Vi and Va represent the velocity of the gas entering and leaving the manifolds The air standard Otto cycle also called the con
97. ssage Bulletin of JSME Vol 8 No 29 1965 pp 98 108 Iberall D S Attentuation of Oscillatory Pressures in Instrument Lines Trans of ASME Vol 2 1970 Benedict R P Fundamentals of Temperature Pressure and Flow Measurements 2nd Edition John Wiley and Sons 1977 Lancaster D R R B Kreiger J H Liensch Measurement and Analysis of Engine Pressure Data SAE Publication 750026 Feb 1975 Furgeson C R Internal Combustion Engines Applied Thermosciences John Wiley and Sons 1986 Beckwith T G N L Buck R D Marangoni Mechanical Measurements Third Edition Addison Wesley 1982 10 11 12 13 14 49 BIBLIOGRAPHY Benedict R P The Response of a Pressure Sensing System Trans of ASME June 1960 pp 482 488 Benedict R P Fundamentals of Temperature Pressure and Flow Measurements 2nd Edition John Wiley and Sons 1977 Brown W L Methods for Evaluating Requirements and Errors in Cylinder Pressure Measurement SAE Publication 670008 Doeblin E O Measurement Systems Application and Design McGraw Hill 1983 Furgeson C R Internal Combustion Engines Applied Thermosciences John Wiley and Sons 1986 Holman J P Experimental Methods for Engineers McGraw Hill 1971 Iberall A S Attenuation of Oscillatory Pressures in Instrument Lines Trans of ASME Vol 2 1970 James M L G M Smith J C Wolford Applied Numerical Methods for Digital
98. stant volume air cycle is an idealized standard to which a real Otto cycle can be compared see Fig 2 The idealization is based on the following assumptions ref 1 pg 23 The gas in the cylinder is air and it behaves as an ideal gas All processes are reversible The Ideal Gas Law is valid for all processes e OF N m Heat is added and withdrawn from the gas through the walls of the cylinder during both of the constant volume processes Pressure Piston Control Volume 7 Fig l Control Volume for Engine Cycle Definition of Positive Quantities V Volume V Fig 2 Indicator Diagram for Air Standard Otto Cycle 9 No throttling of gas at the valves i e gas enters and exits the control volume at ambient pressure and velocities can be ignored The endpoints of the cycle on the horizontal axis of the indicator diagram in Figure 2 correspond to the cylinder volume at inner dead center IDC and outer dead center ODC the extreme points of the piston stroke The cycle shown involves six ideal processes four of which take place during piston strokes These processes are as follows with the processes involving piston movement marked by xx XxX 0 1 Intake stroke Intake valve opens at 0 the piston moves out the intake valve closes at 1 1 2 Piston compresses the gas 2 3 Constant volume heat addition 3 4 Powerstroke Gas expands 4 1 Constant volume heat removal 1 0 Exhaust stroke Ex
99. t is mounted above the wheel on the engine so that the piston is at top dead center when 0 deg is positioned under the pointer Check the alignment of the encoder as follows 1 Setup the encoder system as described in the section above 2 Rotate the flywheel in the direction of increasing degrees clockwise when looking at the wheel from the dynamometer end of the shaft until the encoder signal goes from low to high as observed on the scope screen This should take place less than 3 deg from 0 deg on the flywheel 3 Ifthe encoder is not aligned properly with the crank angle adjustment is necessary as described in the next section Adjusting Shaft Encoder Alignment This section details the procedure used to align the shaft encoder properly with the crank angle Before proceeding you should keep in mind 119 that the encoder is rated for maximum loadings of 40 lbs axially and 35 lbs radially Any forces applied to the encoder shaft should be well below these values or the inner mechanism of the encoder will be damaged 1 Remove the four screws on the mounting flange of the encoder Loosen the setscrew on the flexible coupling Gently withdraw the encoder shaft and fitting from the flexible coupling being careful not to lose the key between the fitting and the coupling 2 Loosen the two setscrews in the fitting and rotate the fitting on the encoder shaft to a position where it would likely produce a correctly aligned
100. t the carburetor valves and the spark angle until the engine is running smoothly The engine should be running at an almost constant rpm 121 Insert the disc containing the program IND in the disc drive of the computer Type GET IND and then the EXECUTE key The program will be loaded and while this is happening the LED next to the drive door will flash When the LED stops flashing press the RUN key on the computer A set of basic equipment set up instructions will appear on the computer screen After checking that these have been complied with press the CONTINUE key Enter the crank angle degree at which the shaft encoder output goes high as instructed in the next prompt Value can be read from the degrees marked on the engine flywheel The blocks at the bottom of the screen correspond to the soft keys labeled k0 through k9 located above the character keyboard on the computer Pressing the soft keys causes the following to be performed by the program GET DATA Data is acquired and modified to units of pressure volume and crank angle Requires input by user of compression ratio charge amplifier Range setting and number of cycles to be averaged PLOT P V Plots indicator diagram User inputs P from keyboard for hardcopy of plot and Q to exit program segment ANALYZE Calculates and displays indicated work indicated horsepower and IMEP User inputs Y from keyboard for hardcopy of results and
101. ta points from point 764 START to point FINISH The TRAPEZIOD 7650 Imethod is used to evaluate th area 7660 I numerically 767 768 Variables and constants used 7690 A Array holding data points with 7700 vertical coord 1n first column and 7710 horizontal coord in second column 7720 Start Finish Row of first data point 7730 and last data point in interval 7740 Integral Value of area under curve 7750 between Start and Finish 7760 710 Integral 778 FOR I Start TO Finish 1 7790 Integral A 1 1 A 1 1 1 Ac1I 1 2 At1 2 2 Inteoral 7800 NEXT I 7810 RETURN Integral 7820 FNEND Function FNTrap uses the trapezoid method to do a numerical integration on the data passed in array A between point Start and point Finish It should be noted that if Start is a higher number than Finish as it would be when the piston is traveling from a large volume at ODC to a smaller one at IDC the value of the integral returned will be negative 7850 7860 7870 7880 7890 7300 7810 7820 7930 7340 7850 73960 7970 105 Function FN Horsepower DEF FNHorsepower Work Per IThis function returns the horsepower for Ithe cycle based on the work entered The work must be entered in ft lbs Variables and constants used Work Work output of cycle ft lbs gt Per Period of engine cycle Hp Horsepower Hp Work 550 Per RETURN Hp FNEND This function returns the i
102. ted horsepower IMEP 66 24 psi Averaged over 20 Pt P psia 115 2818 116 259 9 4 96 117 259 3 5 04 cpm ft lh ft lb ft lh 3 23 ho cycles MO 21 65 22 48 159 Results Taken at 30 degrees Spark Advance P esias vs V L1NAAS UI 1 RESULTS Engine speed 1406 8 com Compression ratio 9 Work Gross work output 171 02 h Valve loss 1 45 ft lb Net work 153 52 ft lb Indicated horsepower Judd hp IMEP 66 37 psi Averaged over 20 cycles D sia V in 3 Angle deg 117 Pp Sues 118 268 5 4 68 18 7 119 268 1 4 6 19 54 120 268 3 4 83 20 39 121 268 5 4 31 21 23 Results Taken at 35 Degrees Spark Advance RESULTS Fnaine speed 1398 6 rom Compression ratio 9 Work Gross work output 162 36 PPh Valve loss 18 48 tt 1b Net work 143 88 eb Indicated horsepower 345 MER 63 01 psi Averaged over 20 cyelas Pt P psia V in 3 Angle deg 507 291 7 4 53 16 91 508 292 5 4 6 17 75 509 292 3 4 67 18 58 P psia vs Y LINXR J 160 161 Results Taken at 40 Degrees Spark Advance i F ipzia cun 150 100 10 15 28 RESULTS Engine speed 1395 35 Compression ratio 9 Work Gross work output 156 69 Valve loss 18 99 Net work 137 71 Indicated horsepower IMEP 60 31 psi Averaged over 20 Pt P psia 507 305 9 4 47 508 306 3 4 53 509 305 1 4 6 wm Y Lp rites es Pd 3k e ft lb ft lb ft ib 2 91 h
103. ter apparatus has been set up and checked as explained above the rest of the pressure measurement system can be assembled as outlined below 115 Use the torque wrench set to 221 in lb with the 9 16 in deep socket to torque the pressure transducer into the port opposite the sparkplug in the engine cylinder The transducer sensitivity should be set on the front of the charge amplifier to 5 27 pC psi Set the charge amplifier sensitivity to 50 psi Volt and the time constant to LONG Attach one end of the B and K No A00038 cable to the output of the pressure transducer Attach the other end of the cable to the INPUT port on the back of the charge amplifier In order to minimize electrical noise in the transducer output make sure that this cable does not rest on any other live electrical wires Connect up the cooling water lines to the pressure transducer by attaching the 1 8 in sections of Tygon tubing to the two barbed fittings on the transducer Attach the BNC end of the RG58 A U cable to the output port on the back of the charge amplifier The alligator clips at the other end of the cable should be connected to the Ch2 probe of the oscilloscope making sure that the polarity is correct SHAFT ENCODER SYSTEM The shaft encoder and peripherals are listed below 116 Optical Incremental Encoder and connector Sequential Information Systems Inc model 25GN 21Z 5V H1 D1 B3 T1 Power Supply HP model 6236B Banana to Alliga
104. ties oooooo o 4 Indicator Diagram for Air Standard Otto Cycle 4 Work Areas for Air Standard Otto Cycle 7 Non Flow Model of Air Standard Otto Cycle 7 Schematic of Actual and Air Standard Cycles 8 Comparison of Actual and Fuel Air Otto Cycles 12 Schematic of Pumping Loop of Typical Indicator Diagram oooooocmocmomoomo 14 Effect of Spark Advance on Indicator Diagram 16 Cooling Water System for Pressure Transducer 20 Schematic of Engine and Indicator Diagram Generating Equipment Actual Results 29 Indicator Diagram Engine Motored at 230 rpm 33 Compression Stroke Motoring Data 35 Variation of Angular Offset of Peak Pressure Data with rpm 36 Comparison of Actual and Air Standard Power Loops 39 Indicator Diagrams Taken at Two Spark Advance Settings 0 cc cece ee cee ee eee e eens 42 Locations of Piston Strokes in Phasesland2 83 Work Areas of Indicator Diagram Firing and Motoring Modes oi i I CR RE 102 Schematic of Engine Geometry Laan 133 Schematic of Ricardo Cell 0 cee eee ee eee 164 V1 Fig A5 Dynamometer Control Unit Fig A6 Ricardo Carburetor vii INTRODUCTION This report describes and evaluates an indicator diagram gener
105. tor leads 2 The basic setup of the shaft encoder system will now be given followed by instructions for checking the alignment of the output of the encoder with the crank angle If the alignment is found to be incorrect the directions for correcting the alignment are included These directions for correcting the alignment of the encoder would also be of use when installing the encoder after removing it from the shaft for any reason Setup of Basic Shaft Encoder System Following is a description of the setup of the shaft encoder system It involves applying the excitation voltage to the encoder and connecting the output leads from the encoder to the oscilloscope 1 Insert the banana ends of the banana to alligator leads into the 6V and COMMON ports of the power supply Set the METER knob to 6V then turn the VOLTAGE 6V knob under the METER knob to its extreme counter clockwise position 2 Five 5 25V Volts excitation must be applied to the shaft encoder The level of the power supply output can be checked by using a voltmeter of sufficient accuracy or by using the horizontal scale of the oscilloscope 117 to use the oscilloscope attach the leads from the power supply to the Chl scope probe Set Chl Volts Div to 2 Volts div and the Sec Div to 5 ns div Select the AUDIO trigger mode by pressing the trigger MODE button positioned toward the left on the face of the scope The MODE menu will now be displayed on the screen Pres
106. ump to the extension cord 3 Open the Cooling Water Valve and the Cooling Water H E heat exchanger valves these valves are open when the handles are parallel to the lines Close the Engine Oil H E valve Fig A4 164 SCHEMATIC OF THE RICARDO CELL Line water valve Shaft encoder Engine oil H E valve Oil H E bypass Engine coo ant valve H E valve Oil Cooling water thermometer valve Carburetor and air filter Cooling water and heater thermometers Fuel line Alligator bern En clip Lenee OCT Coolant water column Dynamometer Pump Dynamometer control unit Calibrated V cylinder i Waste water Exhaust fan E switch drain f Fuel Resistor tank bank Lights fan vents switches E milium 165 Power Supply Armature Armature Field Air Heater Control Field Control off Field Control Motor 9 6 e Load Knob off Master Switch Arm Supply Volts Water Pump Armature O Oil Heater Supply Volts O R Knob Power Switch 2 Fig A5 DYNAMOMETER CONTROL UNIT 166 Air Heater en ee p Valve e a Main Fuel Y Valve gt Starting Carburetor Valve Les E ES yo Fuel Flow Screw Idle Ad justment Screw Fig A6 RICARDO CARBURETOR 167 Open the Line Water Valve at the wall This valve does not need to be fully open but should be adjusted so that it runs quietly You should now see water running down the Waste Water Drain Next go to the
107. ure For a detailed description of the computer program and a thorough discussion of the rationale behind it see Computer Software Appendix C Figure 10 shows the basic setup of the equipment schematically Instructions for setting up and running the indicator diagram generation system are contained in Appendices D and E respectively 29 Flywheel Pressure engine Transducer Cylinder Charge i Amplifier Shaft Encoder Power Supply MA Digital Oscilloscope Computer Printer Fig 10 Schematic of Engine and Indicator Diagram Generating Equipment 30 EVALUATION OF MOTORING DATA Before generating data while the engine is firing the motoring data taken while the dynamometer is turning the engine over should be evaluated to check some key system variables ref 7 pp 5 7 Motoring data is useful for several reasons First there is little variation between cycles in motoring data and so this data can yield information about the accuracy and reliability of the test setup Motoring data is also not affected by various combustion introduced phenomena such as inhomogeneities and high rates of heat transfer The motoring data can be used to check the following system variables Qualitative check of pumping loop pressure Phasing scaling and transducer performance from logarithmic p V diagram Phasing of pressure with respect to volume Some methods of investigating the motoring data to check these quantities is disc
108. ussed below see Lancaster et al ref 7 for further information 31 Qualitative Check of Pumping Loop Pressure The pumping loop of the motoring data can serve as a check of the reference pressure value The reference pressure is usually the value assigned to the pressure in the engine manifolds and is equal to the pressure in the cylinder at a specific point in the cycle The exhaust stroke of the pumping loop should contain pressures that are mainly above the reference pressure and the intake stroke should take place below the reference pressure If the pressures in the pumping loop do not meet these criteria the reference pressure assignment is incorrect Checks from the Logarithmic p V Diagram The logarithmic p V diagram from motoring data for the compression stroke can yield a wealth of insight into the validity of the system variable assignments The portion of the indicator diagram data between the closing of the intake valve and just prior to the IDC can be approximated by a polytropic process where pV constant 9 The above function when plotted on a logP logV diagram is a straight line with a slope of n Lancaster et al ref 7 pg 6 state that when an erroneous reference pressure is assigned the initial portion of the log log plot shows a curvature and the latter portion of the plot becomes curved when an incorrect clearance volume is assigned The central portion of the log p V compression 32 str
109. ware sse 53 Appendix D Setting Up the Indicator Diagram Generation Equipment lesse 111 Appendix E Running the Indicator Diagram Generation Equipment Ln 120 Appendix F Motoring Data Used to Investigate Pressure Crank Angle Phasing 124 iil Appendix G Appendix H Appendix I Appendix J Calculations for Comparison of Air Standard Otto Cycle and Actual Results Taken at 20 Degrees Spark Advance 125 Error Analysis of Actual Results 131 Sample Results cuida 139 Ricardo Engine Operating Instructions Spark Ignition Running eee 163 1V Table 1 Table 2 Table 3 Table Al Table A2 Table A3 LIST OF TABLES Page Technical Data for Kistler Model 7061 Pressure Transducer 21 Comparison of Actual and Air Standard Cycle Results ooooooooo o 41 Firing Results Varying Spark Advance 43 Volumetric Flowrate of Fuel 125 State Values of Air Standard Cycle 126 First Law Chart for Air Standard Cycle 127 Fig 1 Fig 2 Fig 3 Fig 4 Fig 5 Fig 6 Fig 7 Fig 8 Fig 9 Fig 10 Fig 11 Fig 12 Fig 13 Fig 14 Fig 15 Fig Al Fig A2 Fig A3 Fig A4 LIST OF FIGURES Page Control Volume for Engine Cycle Definition of Positive Quanti
110. x Digital Oscilloscope model 2430 is used to acquire and digitize the data in this system The two channel oscilloscope can be programmed by a computer through the interface bus and all the front panel settings sec div Volts div trigger settings etc can be controlled by the computer The data can be downloaded to a computer for processing The sampling rate number of readings acquired per second of the oscilloscope is an important parameter to be considered The sampling rate necessary to acquire one data point per crank angle degree is 18 kHz at 3 000 rpm The scope acquires 1024 data points of 8 bits each per waveform at a maximum sampling rate of 100 MHz This means that the sampling rate is more than adequate for the application and the data is good to three significant digits The oscilloscope can average the data over a preset number of waveforms which is important in engine applications since there is pressure variation between cycles ref 7 pg 3 The waveform can also be viewed on the scope screen which is useful during initial setup of the system and for monitoring the progress of the data acquisition 26 Computer The data manipulation and control device consists of a Hewlett Packard 9826 Desktop computer and the program IND As mentioned above the computer is designed to communicate with other devices through its interface bus The program contains these communications in high level commands in the OUTPU
111. ximum vertical value of waveforms so far Greatest Max vertical value for individual waveform Interval Time to wait for scope to acquire curve OUTPUT ZIS START TL 9TOP 10245 OUTPUT 7123 UMODE CH2Zt0N OUTPUT Tiz DATA S0BUL60H2 Interval 290 5 1 Max 500 FOR I 1 10 20 OUTPUT 712 ACQ MOD NOR WAIT Interval OUTPUT 712 MAXIMUM ENTER 7izs 6reatest IF Breatest gt Max THEN Max Greatest END IF NEXT 1 RETURN Max FNEND Max ch2 returns the maximum vertical value of twenty waveforms sampled on Channel 2 This maximum value lies between 127 and 126 the full scale range of the scope screen The datapoints of the waveform from the 80 START 1 to STOP 1024 the entire curve are considered Channel 2 is turned on VMODE statement and the data source is specified as Channel 2 DATA SOU statement In the FOR NEXT loop the waveform is acquired while the program is pausing due to the WAIT statement The scope sends the maximum vertical value of the curve in response to the MAXIMUM request which is entered into the variable Greatest The IF statement assigns the value in Greatest to Max if it is the highest so far This is repeated for twenty waveform acquisitions and the value of Max is returned by the function Twenty waveforms are checked by this function because if the engine is running roughly there is a large fluctuation in peak pressure between cycles If part of the curve acqu
112. y small less than 001 for L and T compared to 011 for 8 The error inh at three different values of 9 will now be determined 9 0 h 2h 0 547 in 9 0 40 0 3 901 3 901 Using the Law of Sines T L sine sin so that a ean sin a sim sin 3 901 0 898 B 180 0 180 3 901 0 898 175 201 E RERO UR sing sin so that Z L Sin _ 9 500 Sin 175 201 _ 11 682 in sin6 sin 3 901 135 h hg L T Z 0 547 9 500 2 188 11 682 0 553 in Ah 0 553 0 547 0 006 in Therefore the percent error at 0 0 is Ah 0 006 n OR Similarly o Ah 0 148 6 90 h 737900 0 049 9 180 4h _ 0 002 T 71 992 99999 As can be seen from above the effect of the error in on the percent error inh is greatest at 90 This is to be expected since the piston travels farther at 9 90 and 8 270 for each increment in shaft rotation than at any other value of 8 The percent error inh at 8 90 will therefore be used below Using equation 15 oy S MITTEN 0 049 0 001 0 049 0 050 or 5 02 Error in Pressure The error in the pressure measurement is due to the limits in the digitizing of the oscilloscope since 136 the error due to the pressure transducer itself is very small when the transducer is water cooled The scope digitizes using 8 bits or a 1 in 256 resolution The percent error in pressure measurem

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