DICOM V5.3 USER MANUAL - CMT
Contents
1. o Courant Number CFL This constant defines the relation between spray propagation velocity and temporal and spatial discretization through the definition Once the spatial resolution Ax is given time step At can be calculated by means of CFL and the local flow velocity by means of At pu DICOM v5 30 File Language Hel GENERAL NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING LAW os motores t rmicos Mode selection Spatial increase constant Figure 13 User input interface DISCRETIZATION tab for transient cases Automatic option DICOM V5 3 USER MANUAL Sept 5th 2013 12 S UNIVERSITAT 1 POLITECNICA DE VALENCIA Aa olo a motores t rmicos File Language Help Er AA motores t rmicos GENERAL NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING Law Mode selection Automatic Discretization Discretization Courant Number 50 Spatial increase 5E 5 Spatial increase constant Figure 14 User input interface DISCRETIZATION tab for transient cases Free discretization option File Language Help Fa ele a GENERAL NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING LAW motores t rmicos u ucl at spray boundary Schmidt Number 1 Spray angle 34 46 Figure 15 User input interface MORPHOLOGY tab for transient cases 3 2 4 MORPHOLOGY The parameters introduced in this p2. gas jets can be considered DICOM V5 3 USER MANUAL Sept 5th 2013 15 UNIVERSITAT SF POLIT CNICA DE VAL NCIA EPT motores t rmicos DICOM v5 3 0 File Language He GENERAL NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING LAW Selection of Mixture Law isothermal Spray Gas Jet inert reactive Spray inert reactive AA motores t rmicos Air Density File kg m3 s e chorros 2005 200642006 Proves temp Browse Fuel Density kg m3 Stoichiometric mass fraction Figure 18 User input interface MIXING LAW tab option for transient cases Isothermal spray 3 2 6 1 Isothermal jet spray This is the simplest case Figure 18 which only requires the following inputs e Air density kg m3 Pure air density i e chamber density before de injection This parameter can change with time so input is given in terms of the location of a text file with the time evolution of density e Fuel density kg m3 Density of injected fuel e Stoichiometric mass fraction Mixture fraction value for stoichiometric conditions 3 2 6 2 Gas jet inert reactive Spray inert reactive The next two cases Figure 19 require the same input data but the difference between both cases resides in the state of injected fuel gas or liquid respectively In this case particular fuel properties are considered depending on the compilation e Air density kg m3 Density in the chamber into which
3. DICOM V5 3 USER MANUAL Sept 5th 2013 10 UNIVERSITAT POLITECNICA DE VALENCIA File Language Help GENERAL NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING LAW Output folder s chorros2005 2006 2006 Proves temp Browse Treatment choice Time interval for xdata files s 5E 5 DICOM v5 3 0 File Language Help GENERAL NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING Law Domain x size m ME Maximum time of calculation s 0 002 df for state relationships 0 01 dfcl for integral tables 0 01 Convergence boundary for main equations 1E 8 Velocity limit for penetration m s 0 001 ETT M G motores t rmicos AE motores t rmicos Er motores t rmicos Figure 12 User input interface NUMERICS tab for transient cases Default values 3 2 2 NUMERICS In this tab Figure 12 parameters for discretization of the problem have to be introduced Some of the parameters are the same as for steady cases e Domain x size m Define the maximum size of the calculation domain in terms of spray axial distance e Df for state relationships Increase in mixture fraction for the calculations of state relationships Default is 0 01 Note that mixture fraction values are between 0 and 1 e Dfa for integral tables Increase in mixture fraction on the axis for the radial integral tables which are performed to solve c
4. at the nozzle exit 10 N Injection momentum flux at the nozzle exit MO kg s Injection mass flux at the nozzle exit rho a kg m3 Ambient air density inside the chamber where the spray is injected rho f kg m3 Injected fuel density do m Effective nozzle diameter as calculated from momentum mass flux and injected fuel density Ta K Air temperature Tst K Temperature of stoichiometric surface fLOL Mixture fraction at the lift off location fevap_CxHy Fully evaporation mixture fraction One row is written per calculation time step in transient cases For steady ones boundary conditions do not change and the file has only one row where time column is omitted 4 4 temp2 dat This file records the time evolution of the main results from the model in terms of global parameters The format of the file is exactly the same for both the steady and the transient model formulations The file has exactly the same structure as temp1 dat i e a time column followed by a number of columns with different variables depending on the mixing law case and according to the following list VARIABLE UNITS DEFINITION S m Maximum jet tip penetration S 6 m Maximum penetration of a surface with a characteristic equivalence ratio DICOM V5 3 USER MANUAL Sept 5th 2013 19 LETT motores t rmicos S_evap m Maximum liquid length as calculated from the spray tip towards th
5. every time step only for transient cases x_fclimax m Axial location where fclmax is found only for transient cases DICOM V5 3 USER MANUAL Sept 5th 2013 20 LETT motores t rmicos 4 5 xdata dat This file includes for a certain time instant the evolution along the spray axis of the following variables VARIABLE UNITS DEFINITION xeje m Axial coordinate For transient cases this variable ranges from zero to the spray tip penetration at the corresponding time step For steady cases this variables ranges from zero to the user defined Domain x size in the Numerics Tab ucl m s Axial component of the velocity vector on the centerline fel Mixture fraction on the centerline I N Radially integrated momentum flux only for transient cases R 1 pru 2nr dr 0 Mf kg s Radially integrated fuel mass flux only for transient cases R My pu Y 2ar dr 0 M kg s Radially integrated total mass flux R M p w 2nr dr 0 umed m s Cross sectional average velocity from the ratio of momentum and mass fluxes I Umea M fmed Cross sectional average velocity from the ratio of fuel and total mass fluxes Mr mea M rho cl kg m3 Density on the centerline rho med kg m3 Cross sectional average density from the average mixture rho med flow fraction rho med or from the ratio of mass and volume fluxes rho med flow R m Spray radius Rini u
6. injection is performed It s given in terms of the location of a text file with the time evolution of density e Pressure Pa Pressure in the chamber into which injection is performed Input is given in terms of the location of a text file with the time evolution Ambient temperature is obtained from that of density and pressure e YN2 inf YO2 inf kg kg Mass fraction values of nitrogen and oxygen respectively in ambient air If the addition of both of them is smaller than unity the remaining mass fraction is calculated as composed of CO2 and H20 obtained from a stoichiometric reaction of fuel and air depending on fuel composition e Fuel temperature K Fuel temperature when injected into the combustion chamber e fLOL Mixture fraction on the axis at the lift off location fLOL is O for an inert flow 1 for a non lifted flame and has a value between 0 and 1 for the simulation of a lifted flame In the latter case the flow is considered as totally inert for locations where mixture fraction on the DICOM V5 3 USER MANUAL Sept 5th 2013 16 UNIVERSITAT POLITECNICA DE VALENCIA EP Y A motores t rmicos axis fcl x is such that fcl x gt fLOL and the flow is totally reactive for axial locations such that fcl x lt fLOL e Start of combustion time t_soc s This parameter indicates the time instant at which combustion begins The user has to check incompatibility among different inputs o Ifa calculation is performed unde
7. momentum fluxes and time constant injection and ambient thermodynamic variables and composition All input parameters are therefore scalar values e TRANSIENT In this case all or some of the above mentioned boundary conditions may change with time Accordingly input data is made up of text files containing the time evolution of these variables Even though there are few differences between both approaches namely if some of the variables are time constant or change with time the present section will describe the input form in two subsections the first one for the steady case the second one for the transient case One important issue is that fuel properties are compiled into the corresponding executable file Accordingly different versions of the code have to be used to change fuel type 3 1 STEADY CALCULATION As previously described steady calculations apply for sprays where injection conditions and chamber properties are constant with time Therefore there will not be need for input data in text file format for injection density or pressure in function of the time All necessary input information will be fed directly from the input user interface The execution of the code will be much faster than the transient case where time evolution has to be tracked 3 1 1 GENERAL The first tab allows selecting if the model is transient or steady When selecting Steady case the only field on this screen is e Output folder Folder in which t
8. A UNIVERSITAT w POLIT CNICA ole olp al DE VAL NCIA motores t rmicos DICOM V5 3 USER MANUAL September 5 2013 CMT MOTORES T RMICOS Camino de Vera s n 46022 Valencia Espafia Tel 34 963 877 650 Fax 34 963 877 659 E mail cnt mot upv es e Web http www cmt upv es LETT Q motores t rmicos CONTENTS E INN cnt sas 3 2 INPUT DAT Asis nnBw M iError Marcador no definido 2 1 STEADY CALCULATION eee nnne nnne nnns 4 DN CEN cscs NULLE UM eee eee ete 4 A A 5 23 MORPHOLOGY sosa aU eae Ve A rT REPRE 6 ED A RU eT Ren ER LLL NE 6 215 MIX NG LAW Rm 8 2 2 TRANSIENT CALCULATION cc csccceceesseseeseeeeeeneees 10 A 10 253 NUMEROS io 11 22 am O 72 0 ee Roe aE ie operose st 12 293 MORDIDO 13 2 2 5 INJECTION ENTE oe cee mum IM UEM EM EDD 14 2 2 6 MINE 15 MESRINE 18 A A eC n 18 A A A PE nnana 18 co E 19 A RR 19 3 5 ROMA Al oidos ioicbica 21 A A 23 DICOM V5 3 USER MANUAL Sept 5th 2013 2 8 UNIVERSITAT POLITECNICA DE VALENCIA Ae pl a motores t rmicos 1 INTRODUCTION DICOM is a one dimensional 1D spray model that predicts the evolution of a turbulent jet under some simplifying hypotheses Scientific basis for the model can be found in 1 3 This document summarizes the main steps for a user to perform a calculation The general flow of information is described in F
9. PN G 0 exp G Log 100 tan 8 2 and G is a parameter that depends on the term of the conservation equation where the integral is performed in particular G can be equal to 1 2 Sc 1 Sc or 0 Species integrals which are related to the radial accumulation of a certain species i according to the definition Emax INT fa G 0 p Y Edi Emin where Emin amp min is a minimum and maximum normalized radial coordinate DICOM V5 3 USER MANUAL Sept 5th 2013 18 LETT motores t rmicos Density integrals are always recorded while species integrals depend on the mixing law This file is written once for the steady calculation while it can be calculated at different time instants in the transient case In that situation each time the file is saved the timestamp in us is added to the file name For example integ_000100 dat is the result of radial integrals at 100us after start of calculation The file is always calculated whenever news state relationships are calculated 4 3 temp1 dat DICOM calculates with a small time step depending on previously discussed discretization considerations File temp1 dat records the time evolution of boundary conditions for the spray problem The first column for this file is time and the rest of the columns include the following variables VARIABLE UNITS DEFINITION u0 m s Effective injection velocity
10. art are the same as in the steady case Figure 15 The only difference between both approaches is that for the transient model no possibility is given to choose among different radial distribution mathematical functions Only the Gaussian one is used e u ucl at spray boundary Numerical value that defines the spray radial limit in terms of a fraction of the on axis velocity Default value is 0 01 This value is directly linked to the spray cone angle input value e Schmidt number The turbulent Schmidt number is in the ratio of momentum and mass diffusivities Default value is 1 DICOM V5 3 USER MANUAL Sept 5th 2013 13 e UNIVERSITAT 2 POLIT CNICA DE VALENCIA EPT motores t rmicos e Spray angle In this field the spray cone angle to define the spray radial boundary in terms of the axial velocity profile has to be introduced This is one of the fundamental parameters for any 1D spray calculation 3 2 5 INJECTION RATE To introduce injection information two approaches have been considered namely direct input Figure 16 where both momentum and mass fluxes are given by the user and derived input Figure 17 where mass flow is given by the user and momentum flux is calculated from the mass flow and an effective velocity derived from user inputs of velocity coefficient and injection pressure drop Effective velocity is constant with time 3 2 5 1 Direct input e Momentum flux N Location of the file containing the tim
11. ate Direct input Mass flux kg s 0 00751 Inyection Pressure increase Pa 70000000 Velocity coefficient Cv 1 Nozzle Diameter m 240e 6 AAA motores t rmicos Figure 7 User input interface INJECTION RATE tab and DERIVED INPUT option for steady cases 3 1 4 1 Direct input e Momentum flux N Injection orifice momentum flux e Mass flux kg s Injection orifice mass flux e Nozzle diameter m Nominal injection orifice diameter Although this parameter is given as an input in real practice model output does not depend on this parameter but on the effective diameter that can be obtained from given momentum and mass flow together with fuel density MIXING LAW tab DICOM V5 3 USER MANUAL Sept 5th 2013 UNIVERSITAT 1 POLIT CNICA DE VALENCIA LET Q motores t rmicos 3 1 4 2 Derived input In this case mass flux is given as input parameter and momentum flux is calculated from injection pressure drop and velocity coefficient considering Bernouilli Law e Mass flux kg s Injection orifice mass flux e Injection Pressure increase Pa Pressure difference between injection system and ambient into which injection occurs e Velocity coefficient Cv Velocity loss coefficient through injection hole e Nozzle diameter m Diameter of injector hole 3 1 5 MIXING LAW Finally the last tab contains parameters that define the local dens
12. e S evap o nozzle S evap or from the nozzle to the tip of the spray S evap o Only one of them is provided in steady cases miny kg Integral of the mixture fraction all over the spray It should be equal to the injected fuel mass until the Torresponang time Miny I f 2nr dr dx mfmix_o kg Integral of fuel mass below a sharactorisiic equivalence ratio q SR Mf mixg J of 2mr ar ax 0 R mf mixevap kg Integral of fuel mass outside of the iso surface of evaporation mixture fraction fevap SR Mf mixevap pf 2nr dr dx 0 Revap ma kg Integral of the mixture machon all over the spray ZI 1 f 2nr dr dx LOL m Lift Off Length based pen am fLOL 0 for inert spray mfsq kg Integral of the fuel mass all over the spray lt should be equal to the injected fuel mass for inert cases For reacting ones it corresponds to the unburned fuel mass SR Mp sq Per amr ar ax 00 mf_q kg Integral of the burned fuel mass all over the spray Mea Miny Esq mO2 kg Integral of a characteristic species O2 CO2 H20 all over the spray mCcO2 mH20 m ff p Yi 2nrsdr dx mfi kg Integral of the fuel mass alli BUS the liquid I or vapour v part of the mfv Spray respectively SR my Por 2rr ar ae SR Mey J os amr dr dx 00 uclmax m s Maximal velocity along the axis at every time step only for transient cases x uclmax m Axial location where uclmax is found only for transient cases fclmax Maximal mixture fraction along the axis at
13. e calculation DICOM v5 3 0 File Language Help GENERAL NUMERICS MORPHOLOGY INJECTION RATE MIXING LAW motores t rmicos Output folder le chorros 2005 2006 2006 Proves temp Browse Treatment choice Steady Transient Figure 2 User input interface GENERAL tab for Steady case DICOM V5 3 USER MANUAL Sept 5th 2013 3 UNIVERSITAT 56 POLIT CNICA DE VALENCIA dasa motores t rmicos The general working flow is as follows e The user fills the input information directly or by uploading a case file e After clicking upon Start The following events occur o The user is asked to save the input configuration in a file This is a security just in case this information has not been saved yet o For reacting cases a value of the cone angle for the reacting part of the spray i e downstream of lift off is asked for This value is not saved in the input file o Finally the solver is launched and calculation proceeds until it is finished e The code output information can be analyzed 3 INPUT DATA Different tabs are available in the user interface that allow for the configuration of one case The main one is the GENERAL tab where one can choose between the two main approaches for DICOM calculation e STEADY In this case boundary conditions for spray development are constant with time This means time constant nozzle injection parameters injection mass and
14. e conservation equations Default is 0 01 Note that mixture fraction values are between 0 and 1 Convergence criteria for iterative computation Numerical value for calculation end in conservation equations If the difference between results of 2 successive computations is less than this limit value calculation stops Default value is 10 DICOM V5 3 USER MANUAL Sept 5th 2013 5 UNIVERSITAT Ill POLIT CNICA J DE VALENCIA KEY motores t rmicos B DICOM 530 Ele Language Er motores t rmicos GENERAL NUMERICS MORPHOLOGY INJECTION RATE MOONG LAW u ucl at spray boundary p Schmidt Number 1 Spray angle 3446 Radial Profile 5 Gaussian Spalding Hinze Schlichting Figure 5 User input interface MORPHOLOGY tab for steady cases 3 1 3 MORPHOLOGY In the next tab Figure 5 there are some parameters that define the spray morphology namely geometry speed profile and distribution of mass fraction e u ucl at spray boundary Numerical value that defines the spray radial limit in terms of a fraction of the on axis velocity Default value is 0 01 This value is directly linked to the spray cone angle input value e Schmidt number The Schmidt number is in the ratio of momentum and mass diffusivities Default value is 1 e Spray angle In this field the spray cone angle to define the spray radial boundary in terms of the axial velocity profile has to be introduced This is on
15. e evolution of injection orifice momentum flux e Mass flux kg s Location of the file containing the time evolution of injection orifice mass flux e Nozzle diameter m Nominal injection orifice diameter Although this parameter is given as an input in real practice model output does not depend on this parameter but on the effective diameter that can be obtained from given momentum and mass flow together with fuel density MIXING LAW tab DICOM v5 3 0 File Language Help GENERAL NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING Law Selection of the inyeccion rate 6 Direct input Derived input Momentum File N s c chorros 2005 2006 2006 Proves temp Browse Mass Flow File kg s s c chorros 2005 2006 2006 Proves temp Browse Nozzle Diameter m 240e 6 Figure 16 User input interface INJECTION RATE tab and DIRECT INPUT option for transient cases DICOM V5 3 USER MANUAL Sept 5th 2013 14 e UNIVERSITAT 2 POLIT CNICA DE VALENCIA Ae ol a motores t rmicos DICOM v5 3 0 File Language Help GENERAL NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING LAW motores t rmicos Selection of the inyeccion rate Direct input Derived input e chorros 2005 2006 2006 Proves temp Browse Inyection Pressure increase Pa 70000000 Velocity coefficient Cv 1 Nozzle Diameter m 240e 6 Figure 17 Use
16. e of the fundamental parameters for any 1D spray calculation e Radial profile This part makes it possible to select one of the four mathematical functions Gaussian Spalding Hinze and Schlichting that have been considered for the radial distribution of the conserved properties The Gaussian profile is the one that is most often used and as such some parts of the code only work with this function 3 1 4 INJECTION RATE To introduce injection information two approaches can be considered namely direct input Figure 6 where both momentum and mass fluxes are given by the user and derived input Figure 7 where mass flow is given by the user and momentum flux is calculated from the mass flow and an effective velocity derived from user inputs of velocity coefficient and injection pressure drop DICOM V5 3 USER MANUAL Sept 5th 2013 6 so UNIVERSITAT J POLITECNICA DE VALENCIA DICOM v5 3 0 File Language Help GENERAL NUMERICS MORPHOLOGY INJECTION RATE MIXING LAW Selection of the inyeccion rate Derived input Momentum flux N 1 50180 Mass flux kg s I Nozzle Diameter m Zmes LETT M G motores t rmicos Er AA motores t rmicos Figure 6 User input interface INJECTION RATE tab and DIRECT INPUT option for steady cases File Language Help GENERAL NUMERICS MORPHOLOGY INJECTION RATE MIXING Law Selection of the inyeccion r
17. he program will write the output files There is a button which is labeled as Browse to select the folder DICOM V5 3 USER MANUAL Sept 5th 2013 4 UNIVERSITAT POLITECNICA DE VALENCIA EP T motores t rmicos DICOM v5 3 0 lh Er AE motores t rmicos File Language Help GENERAL NUMERICS MORPHOLOGY INJECTION RATE MIXING LAW Domain x size m ME dx m 8 0001 Open df for state relationships 0 01 dfcl for integral tables 0 01 Save Convergence criteria for iterative computation 1E 6 Start Figure 3 User input interface NUMERICS tab for steady cases Default values ey Spe u s r 0 a 1 iu D la gt x 0 1 lux ux 3 i X X X AX Xia X 7S X Figure 4 Schematic of the model approach 3 1 2 NUMERICS In this tab Figure 4 parameters for discretization of the problem have to be introduced Domain x size m Define the maximum size of the calculation domain in terms of spray axial distance dx m Spatial discretization in the axial direction Ax which defines the cell size and corresponding spatial resolution df for state relationships Increase in mixture fraction for the calculations of state relationships Default is 0 01 Note that mixture fraction values are between 0 and 1 df for integral tables Increase in mixture fraction on the axis for the radial integral tables which are performed to solv
18. igure 1 The user interface is the only graphic interface of the program It allows the introduction of both the model needed input data and also the location of the output data This user interface makes it possible to edit manage save an input file which stores the configuration for one case and launches the solver which performs the calculations After the calculation output information is written into ASCII text files This type of file allows the utilization of different software for further processing and plotting the data USER CASE FILE DICOM OUTPUT INTERFACE input sd solver gt es AAN Figure 1 General flow of information in DICOM In Section 2 a brief description is given of the general User Interface In Section 3 the parameters needed to create a calculation case will be explained as well as how to feed them into the program Finally Section 4 contains the description of output files 2 USER INTERFACE The user interface allows the introduction of input data the management of input files and the execution of the solver A series of tabs have been arranged in the program main window to provide the program with the necessary info to set up a case On the other hand there are three buttons on the right hand side of the user interface to manage input data files Figure 2 e Open loads input data of a previous test from a text file e Save saves the current case configuration case in a text file e Start starts th
19. ity and therefore the type of jet spray flow that is calculated Three cases are considered e Isothermal spray jet Local density is the result of isothermal mixing of pure fuel and pure air No combustion can be considered in this case Fuel properties are neglected except for the pure fuel density and the stoichiometric mixture fraction e Gas jet Local density is calculated by means of an incompressible ideal gas law where local temperature and composition change locally but pressure is constant Both inert and reacting i e combusting gas jets can be considered e Spray Local density is calculated by means of a mixture of a liquid and gas phase by means of real gas equation of state Both inert and reacting i e combusting gas jets can be considered 3 1 5 1 Isothermal jet spray This is the simplest case Figure 8 which only requires the following inputs e Air density kg m3 Pure air density i e chamber density before de injection e Fuel density kg m3 Density of injected fuel e Stoichiometric mass fraction Mixture fraction value for stoichiometric conditions DICOM v5 3 0 File Language Help GENERAL NUMERICS MORPHOLOGY INJECTION RATE MIXING LAW IA Selection of Mixture Law motores t rmicos isothel ray Gas Jet inert reactive Spray inert reactive Air Density kg m3 Fuel Density kg m3 Stoichiometric mass fraction Figure 8 User input interface MIXING LAW tab option f
20. m Radius of the intact zone in terms of axial velocity Rini u Rini f or mixture fraction Rini f R 6 m Radius where a certain equivalence ratio is found Revap m Radius where a mixture fraction for full evaporation fevap is found If a gas jet or an isothermal spray is calculated Revap has no meaning and this variable is replaced by the R 3 DICOM V5 3 USER MANUAL Sept 5th 2013 21 y UNIVERSITAT POLIT CNICA DE VALENCIA CATY motores t rmicos mf kg m Radial integral of total fuel mass i e total fuel mass per unit length R my p f 2ar dr 0 mfmix kg m Radial integral of fuel mass from R_ to R i e total fuel mass per unit length below a characteristic equivalence ratio R Memixd efiam R mfmixevap kg m Radial integral of fuel mass from R_evap to R i e total fuel mass per unit length outside of fevap iso surface R Mfmixevap p f 2urur Revap ma kg m Radial integral of total air mass i e total air mass per unit length R ma e Q D 2nr dr 0 mf sq kg m Radial integral of unburned fuel mass i e unburned fuel mass per unit length R Mesq p 1 2nr ar 0 mfi kg m Radial integral of fuel mass in liquid mfl or vapour mfv mfv phase R mri oom dr 0 R Mev o Ypo 2 dr 0 mO2 kg m Radial integral of a certain species e g O2 CO2 H20 mCO2 R mH20 mi p Yi 2ar dr 0 Tcl K Temperature on the centerline Tmed K Cros
21. n fuel composition e Fuel temperature K Fuel temperature when injected into the combustion chamber e fLOL Mixture fraction on the axis at the lift off location fLOL is O for an inert flow 1 for a non lifted flame and has a value between 0 and 1 for the simulation of a lifted flame In the latter case the flow is considered as totally inert for locations where mixture fraction on the axis fcl x is such that fcl x gt fLOL and the flow is totally reactive for axial locations such that fcl x fLOL The user has to check incompatibility among different inputs o Ifa calculation is performed under inert conditions fLOL should be O o lfacalculation is performed under reacting conditions Ambient has to contain oxygen fLOL should be bigger than 0 DICOM V5 3 USER MANUAL Sept 5th 2013 9 er UNIVERSITAT J POLITECNICA el DE VALENCIA ETT motores t rmicos 3 2 TRANSIENT CALCULATION The transient approach makes it possible to introduce a time variable boundary condition out of the following e Injection mass momentum flux to model variable injection cases e In cylinder thermodynamic conditions pressure and density which also may entail a time evolution of temperature to simulate engine changing conditions e Flow chemical state i e a transition from inert to reacting conditions at a defined time instant mixture ignition To enable such transient conditions input files have to be provided for injection mass nome
22. ntum flux as well as in cylinder thermodynamic variables The structure of any of such files is fairly simple a two column ascii text file where the first column is time with zero equal to start of injection and the second one is the input variable Separation character is a space An example of an input file for injection rate is shown in Figure 10 The first text row with the column headers is not taken into account by the program All input file variables are expressed in terms of SI units 3 2 1 GENERAL The interface is similar to the steady case The following fields can be selected Figure 11 e Output folder Folder in which the program will write the output files There is a button which is labeled as Browse to select the folder e Time interval for xdata files s This input defines the time interval where the software will create a new result file xdata dat section 4 5 t s M kg s 0 0 00020848 1 2142E 005 0 0013587 1 4542E 005 0 0017001 1 6942E 005 0 0017504 1 9342E 005 0 0017952 2 1742E 005 0 0018382 2 4142E 005 0 0018792 2 6542E 005 0 0019183 2 8942E 005 0 0019555 3 1342E 005 0 0019908 3 3742E 005 0 0020241 3 6142E 005 0 0020556 3 8542E 005 0 0020851 4 0942E 005 0 0021128 4 3342E 005 0 0021387 4 5742E 005 0 0021628 4 8142E 005 0 0021851 5 0542E 005 0 0022056 Figure 10 Example of input text file for injection mass flux in a transient case A similar structure can be used for other input files
23. onservation equations Default is 0 01 Note that mixture fraction values are between 0 and 1 DICOM V5 3 USER MANUAL Sept 5th 2013 11 UNIVERSITAT 1 POLIT CNICA DE VALENCIA Emm motores t rmicos Some additional parameters are specific for transient cases e Maximum time of calculation s Final instant of calculation of the model e Convergence boundary for main equations Condition for calculation end in conservation equations If the difference between results of two successive computations is less than this limit value calculation stops Default value is 10 e Velocity limit for penetration m s Boundary value velocity such that if the cell outlet velocity is below it the cell is assumed to be the last cell in the jet spray and it defines the tip penetration Default value is 0 001 m s 3 2 3 DISCRETIZATION This tab contains the information for both the temporal and spatial discretization of the model Two approaches can be selected e Automatic discretization makes use of default values Figure 13 The user is only allowed to modify a Spatial increase factor which modifies the default spatial discretization Ax by a constant factor e Free discretization This method allows the user to full modify the details of the discretization method Figure 14 which are summarized in two parameters o dx m Spatial discretization in the axial direction Ax which defines the cell size and corresponding spatial resolution
24. or steady cases Isothermal spray DICOM V5 3 USER MANUAL Sept 5th 2013 8 UNIVERSITAT SF POLIT CNICA DE VAL NCIA EPTT motores t rmicos DICOM v5 3 0 Ele Language Help GENERAL NUMERICS MORPHOLOGY INJECTION RATE MIXING LAW Selection of Mixture Law Isothermal Spray Gas Jet inert reactive Spray inert reactive AE motores t rmicos Air Density kg m3 30 Pressure Pa 8100000 fLOL a s YN2 inf kg kg 0 77 YO2 inf kg kg 0 23 Fuel Temperature K 350 Figure 9 User input interface MIXING LAW tab option for steady cases Gas jet is selected although a similar layout occurs for Spray cases 3 1 5 2 Gas jet Spray The next two cases Figure 9 require the same input data and the difference between both cases is the state of injected fuel gas or liquid respectively In this case particular fuel properties are considered depending on the compilation e Air density kg m3 Density in the chamber into which injection is performed e Pressure Pa Density in the chamber into which injection is performed Chamber temperature is calculated from pressure and density e YN2 inf YO2 inf kg kg Mass fraction values of nitrogen and oxygen respectively in ambient air If the addition of both of them is smaller than unity the remaining mass fraction is calculated as composed of CO2 and H20 obtained from a stoichiometric reaction of fuel and air depending o
25. r inert conditions fLOL should be 0 t1 soc should be bigger than the final calculation time o Ifa calculation is performed under reacting conditions Ambient has to contain oxygen LOL should be bigger than 0 t1 soc should be smaller than the final calculation time DICOM v5 3 0 File Language Help GENERAL NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING LAW Selection of Mixture Law sothermal Spray Gas Jet inert reactive TAE motores t rmicos Air Density File kg m3 s c chorros 2005 2006 2006 Proves temp Browse Pressure File Pa s e chorros 2005 2006 2006 Proves temp Browse fLOL 0 14 Start of combustion time t_soc s YO2 inf kg kg 0 23 YN2 inf kg kg 077 Fuel Temperature K 350 Figure 19 User input interface MIXING LAW tab option for transient cases Gas jet is selected although a similar layout occurs for Spray cases DICOM V5 3 USER MANUAL Sept 5th 2013 17 X UNIVERSITAT POLIT CNICA DE VALENCIA Ae pl a motores t rmicos 4 OUTPUT FILES All output files are written in the address introduced in the interface Five types of files are calculated 4 1 Relst dat This file contains the calculation of state relationships for the spray model The first column includes the mixture fraction and the others include thermodynamic variables density and temperature together with local composition in terms of mass frac
26. r input interface INJECTION RATE tab and DERIVED INPUT option for transient cases 3 2 5 2 Derived input In this case mass flux is given as input parameter and momentum flux is calculated from injection pressure drop and velocity coefficient considering Bernouilli s Law e Mass flux kg s Location of the file containing the time evolution of injection orifice mass flux e Injection Pressure increase Pa Pressure difference between injection system and ambient into which injection occurs e Velocity coefficient Cv Velocity loss coefficient through injection hole e Nozzle diameter m Diameter of injector hole 3 2 6 MIXING LAW Finally the last tab contains parameters that define the local density and therefore the type of jet spray flow that is calculated Three cases are considered e Isothermal spray jet Local density is the result of isothermal mixing of pure fuel and pure air No combustion can be considered in this case Fuel properties are neglected except for the pure fuel density and the stoichiometric mixture fraction e Gas jet Local density is calculated by means of an incompressible ideal gas law where local temperature and composition change locally but pressure is constant Both inert and reacting i e combusting gas jets can be considered e Spray Local density is calculated by means of a mixture of a liquid and gas phase by means of real gas equation of state Both inert and reacting i e combusting
27. s sectional average temperature from the average mixture fraction Yi cl Mass fraction of species on the centerline For transient cases the program creates one file after a characteristic time has elapsed This time interval is selected by the user in the GENERAL tab The filename includes the timestamp in us For steady cases only one file is recorded with the same information and no time stamp DICOM V5 3 USER MANUAL Sept 5th 2013 22 i UNIVERSITAT POLIT CNICA DE VALENCIA EP Y HET motores t rmicos 5 REFERENCES 1 Pastor J V Lopez J J Garcia Oliver J M Pastor J M A 1D model for the description of mixing controlled inert diesel sprays Fuel 87 2008 2871 2885 2 Desantes J M Pastor J V Garcia Oliver J M Pastor J M A 1D model for the description of mixing controlled reacting diesel sprays Combustion and Flame 156 2009 234 249 3 Pastor J Payri R Garcia Oliver J and Nerva J Schlieren Measurements of the ECN Spray A Penetration under Inert and Reacting Conditions SAE Technical Paper 2012 01 0456 2012 DICOM V5 3 USER MANUAL Sept 5th 2013 23
28. tion According to the selected mixing law different versions can be found Isothermal Only mixture fraction and density are calculated Gas jet For an inert case mixture fraction density temperature and mass fractions for the gas mixture are tabulated For the reacting case state relationships include both the same values as for the inert case together with the same variables under reacting conditions Spray The structure of the file is exactly the same as for gas jet cases but composition consider the amount of species that can be found in either liquid or vapour phase Furthermore the evaporation mixture fraction value is given at the end of the first row This file is written once for the steady calculation while it can be calculated at different time instants in the transient case In that situation each time the file is saved the timestamp in us is added to the file name For example relst_000100 dat is the result of calculating state relationships at 100us after start of calculation 4 2 Integ dat This file includes the results of the calculation of radial integrals as a function of mixture fraction on the spray centerline fcl Two types of integrals are recorded Density integrals according to the definition INT fa G 0 p PNG G d where r x is a normalized radial coordinate PN is the mathematical function that describes the radial evolution of conservative variables e g for the Gaussian case
Download Pdf Manuals
Related Search