Sweep 2 User Manual. - Computational Modelling Group
Contents
1. R 11 8 Mechanism Input File XML 11 10 11 12 13 8 1 mechanism element 4 2 422 4428 eee eier ande 11 5 2 Modelelement cir sea A 4 11 8 2 1 Accepted model elements 3 222 8 Se ee RS RO HO 12 A 6 ade Row RS CHE EEE EEE REEMA 12 4 comp nentelement ie AAR EAR EE RE R 12 Sa Gena Clem a aE ES ERD REE EER ERAS 12 S0 Molwtelement ces Sood Boa Bee Ba Be ES REE Sw SS 13 Do TIEREN o sos pass a SR aaa aT eae aia a a Tala eee es 13 e element o Goa Ss Sor dee Bi ae a Be we OS OS 13 8 9 reactionelement soss toets etd ase bot bg we aoa ne a h a i 14 891 SUMADOS type Barton en ea besis e Se eS 15 8 9 2 condensation type reactions 2 zes Hs cous 15 5 10 formula element 2 0 08 0 8 8 8 2 eM sra ae a ae kan ann 16 Bl reactant element i s pom s oo eh mg e h ahnt et er 16 9 12 prod ct element scos soc OS AOS ROM ROS KERR EHR ERK ER 16 9 13 parti lein element shido a OR SRR ERR Yee 16 8 14 particleout element ioc 808 rs Er RR GR RE Re ken 17 8 15 A nand E elements a ssaa cautau ia ana are 17 8 16 particleterm element 22 4244 34 de easredevas 17 8 17 coagulation element code 17 Chemistry Profile File 18 Output Files 19 Example Settings File 20 Example Chemistry Profile 20 Example Mechanism File 20 1 Introduction SWEEP is a population balance solver for particulate systems which exist dispersed in a gas phase It is based on a Monte Carlo method and includes various algorithm2. 4 Coagulation two particle event 5 1 Inception reactions Inception reactions in SWEEP are modelled as two body species collisions The collision is modelled using the transition kernel of Patterson er al 2006b The rate per unit volume takes the form 1 cion 2 kir NiCa Cp 1 Where k is the transition regime coagulation kernel constant N4 is Avodgadro s num ber C a is the gas phase concentration of the first incepting species and Cpg is the gas phase concentration of the second incepting species The constants for the free molecular kernel kfm the slip flow kernel ksp and the transition kernel k are defined as keT 1 1 2 he SOO da dg 2 2 Ma MB IT Te 14 1057 re 2 RE 22 da do 3 3u dA dp kms hip 4 Km kes kp is the Boltzmann constant T is the temperature and ju is the viscosity of the gas phase m and d are the mass and collision diameter of species i respectively The Knudsen number of a sphere of diameter d is given by T Kn 4 74 x 10 5 Where P is the pressure 5 2 Surface Reactions Surface reactions rates per particle in SWEEP have the general form E 2 2 Rutas AT exp Fs 1107 Tc 6 j l i l Where A n and E are the Arrhenius pre exponential factor temperature exponent and activation energy respectively R is the gas constant and T is the temperature 0 is a property of the particle which is raised to some power p and J is the numbe
3. Norris J 2006a The Linear Process Deferment Algorithm A new technique for solving population balance equations SIAM Journal on Scientific Computing 28 303 320 Patterson R Singh J Balthasar M Kraft M amp Wagner W 2006b Extending stochastic soot simulation to higher pressures Combust Flame 145 638 642 23
4. the Intel fortran compiler ifort 4 Running the Program SWEEP is provided with a driver program which reads the gas phase chemistry profile from a text file tab separated or CSV and solves the population balance without coupling to the gas phase As SWEEP was developed as a library of routines there is no obligation to use this program though it should be a useful starting point for writing customised driver programs Three input files are required to run SWEEP with this driver program 1 A settings input file sweep inp 2 The chemistry profile file 3 The particle mechanism file in XML format The names of the chemistry profile file and the mechanism file are given in the settings file see section 7 for more details The structure of these input files is detailed in subsequent sections To run the program collect all the input files together with the executable in a single directory and execute 5 Physical Model SWEEP solves the Smoluchowski population balance equation using a Monte Carlo par ticle technique with the Linear Process Deferment Algorithm LPDA enhancement Pat terson ef al 2006a The particle population is modelled in a gas phase environment and soot processes can also include gas phase species interactions The processes which can be modelled by SWEEP are 1 Particle inception zero particle events 2 Surface reactions single particle events 3 Surface condensations single particle events
5. 0 Routines for calculating the rates of particle coagulation swpcoag_model f90 Definition of the coagulation model including kernels for different flow regimes swpensemble f90 Definition of the particle ensemble type and routines which act upon it swperr f90 List of error codes produced by SWEEP and their descrip tions swpmech f90 Routines which set and read the mechanism type swpmech_reader f90 Routines which read a mechanism from an XML file swpmech_types f90 Definitions of the mechanism type and its dependent types swparams f90 List of control parameters and some constants used by SWEEP swppart f90 Definition of the particle type and routines which act upon it swpprocess f90 Routines which calculate process rates and perform both DSA and LPDA processes on the particle ensemble swprng f90 Wrapper for the random number generator currently in use mt19937 f swpsoln f90 Definition of the solution type and routines which act upon it swpstats f90 Routines for extracting useful statistics from a particle en semble and compiling particle lists for export swpstep f90 The stochastic stepping algorithm routines 3 Compiling the Code The code was compiled on Win32 systems using the Compaq Visual Fortran CVF 6 6 IDE Workspace and project files are supplied for this purpose For Linux systems a 4 Makefile is provided which compiles the program using
6. Cambridge Centre for Computational Chemical Engineering University of Cambridge Department of Chemical Engineering User Manual for SWEEP 2 Population Balance Software Matthew Celnik submitted May 18 2006 c4e Edited by Cambridge Centre for Computational Chemical Engineering Department of Chemical Engineering University of Cambridge Cambridge CB2 3RA United Kingdom Fax 44 0 1223 334796 E Mail c4e cheng cam ac uk World Wide Web http www cheng cam ac uk c4e Contents 1 Introduction 3 2 File List 4 3 Compiling the Code 4 4 Running the Program 5 5 Physical Model 5 3 1 Inception reactions is oe ERE enter ORES RE er 6 de US ASUS ra ES EAD ER A AAA 6 5 3 Condensation reactions 5 ro RR 7 JE Rone res on road AAA EES EES 7 SEIS RES ns eh a AAA Ben en A 8 6 Particle Models 8 7 Settings Input File 8 ol CHENETIER KeyWord sg soe om Ze wh nn Bra 8 72 MECHFILE keyword e ke eh Pek ooh Sok 4 eke is 9 Ta RUNS REVWO copar KES ARES KERR ER REDRESS 9 TA STARTT keyword aaa OR EHR OR eGR 9 T TIME keyWord a ega sora Ae se A oe kpa ee KE HR RH eRe eS 9 T O PCOUNT keyword ps sid phang nk s tome BR ORS ORE Rs 9 7 7 MAXMO keyword 414 44 4 ira aa et 10 7 8 ACTSURFMODEL keyword 10 7 9 OUTPUTEILE keyword a 24 4 4 44 HR RR bo eee we 10 7 10 PMODEL Keyword o cc esr 2 REM Oa eee OR a ia 10 7 11 LOWSTAT keyword 244442444 e bt 4h en 11 7 12 HIGHSTAT keyword 2053 a ior sack nk one
7. action element of type condensation may contain any number of product elements A reaction element of type condensation must contain one and only one particlein element which defines the type of particle to which the process occurs A reaction element of type condensation may contain a maximum of one particleout element which defines the type of particle output from the process If no particleout element is given then the output particle is the same type as the input particle If the output particle is of a different type from the input particle then the process may not be deferred and the defer attribute is ignored A reaction element of type condensation may contain an A element to define a rate constant which is interpreted as a reaction efficiency No other Arrhenius rate elements are required A reaction element of type condensation may not contain a particleterm element A reaction element of type condensation may contain any number of component and track elements Any components or tracker variables not explicitly given will be assigned a value of zero when the program is run 15 8 10 formula element The formula element is used inside an inception or reaction element and is provided only as a reference for the user It is not used by SWEEP It takes the form lt formula gt rxn_form lt formula gt rxn_form The reaction formula string 8 11 reactant element The reactant element is
8. clein id X gt lt particleout id X gt lt A gt 8 0E7 lt A gt lt n gt 1 56 lt n gt lt E units cal gt 3 8E0 lt E gt lt particleterm id as power 1 0 gt lt component id C dx 2 gt lt track id H dx 1 gt lt reaction gt lt reaction type surface name 02 oxidation defer true gt lt formula gt X 02 to X 2 2C0 lt formula gt lt reactant id 02 stoich 1 gt lt product id CO stoich 2 gt lt A gt 2 2e12 lt A gt lt n gt 0 0 lt n gt lt E units cal gt 7 5 lt E gt lt particleterm id as power 1 0 gt lt component id C dx 2 gt lt reaction gt lt Condensation reactions single particle events gt lt reaction type condensation name A4 condensation defer true gt lt formula gt X A4 to X 16 lt formula gt lt reactant id A4 stoich 1 m 3 19e 22 d 0 79e 7 gt lt component id C dx 16 gt lt track id H dx 10 gt lt reaction gt lt Coagulation rules gt lt coagulation name default gt lt formula gt X X to X lt formula gt lt particlein id X gt lt particlein id X gt lt particleout id X gt lt coagulation gt lt mechanism gt 22 References Frenklach M amp Wang H 1994 Detailed Mechanism and Modeling of Soot Particle Formation pp 162 192 Springer Verlag New York Patterson R Singh J Balthasar M Kraft M amp
9. d by lt track id gt id Symbol used to represent the tracking variable When the track element is used inside an inception or reaction element then it defines the change in that variable due to the process and takes the form lt track id dx gt id Symbol representing the tracking variable to change dx The real amount by which to change the variable 8 8 inception element The inception element contains all the information required to define a particle inception process Typically an inception element will take the form lt inception name gt lt formula gt icn_form lt formula gt lt reactant id stoich m q gt lt reactant id stoich m q gt lt product id stoich gt lt particleout id gt lt component id dx gt lt track id dx gt lt inception gt name Name of the inception reaction 13 icn_form Formula of the inception This is optional and provided as a reference tool for the user An inception element can contain a maximum of two reactants and in any case the stoichiometry of the reactants must sum to two because they are modelled as two body processes An error is produced if the stoichiometry does not sum to two Reactant masses and collision diameters must also be provided See the reactant element description for more details An inception element may contain any number of product elements including zero A
10. e That is particles become rounder due to surface growth and removal 7 Settings Input File The settings input file defines the settings of the solver at run time which are not set elsewhere It must have the filename sweep inp and be a plain text file Settings are set in the input file by writing a keyword listed below followed by the values Only one settings may be written per line 7 1 CHEMFILE keyword Use this keyword to set the file name of the chemistry profile input CHEMFILE filename filename File name of chemistry profile 7 2 MECHFILE keyword Use this keyword to set the file name of the mechanism file MECHFILE filename filename File name of mechanism input 7 3 RUNS keyword Use this keyword to define how many runs to perform in order to get an averaged result RUNS num num Number of runs to perform Positive integer 7 4 STARTT keyword Sets the start time of the simulation This value must lie in the range given in the chemistry profile input STARTT time time Start time of the simulation Real 7 5 TIME keyword Sets a stop time point for the simulation and gives the number of output steps to produce up to that time At each time point the particle size list is output from SWEEP Up to ten time points may be specified in the input file one per line and they must be given in chronological order TIME tim steps tim Stop time Real steps Number of ou
11. ements and the reactant masses and collision diameters are not required See the reactant element description for more details A reaction element of type surface may contain any number of product elements A reaction element of type surface must contain one and only one particlein element which defines the type of particle to which the process occurs A reaction element of type surface may contain a maximum of one particleout ele ment which defines the type of particle output from the process If no particleout ele ment is given then the output particle is the same type as the input particle If the output particle is of a different type from the input particle then the process may not be deferred and the defer attribute is ignored A reaction element of type surface may contain elements which define the Arrhenius rate coefficients A n E If these elements are omitted then the default values are used See the definitions of these elements for more details A reaction element of type surface must contain a particleterm element which de fines how the rate expression depends on the particle properties See the definition of the particleterm element for more details 8 9 2 condensation type reactions A reaction element of type condensation must contain only one reactant element and the reactant masses and collision diameters must be given See the reactant element description for more details A re
12. ic en hancements This manual briefly outlines the functionality of the software and provides all information required for a user to run the program The internals of the population balance simulation are a subject of current research and are not described here reference should be made to the original papers which are listed at http como cheng cam ac uk Please cite this software as SWEEP2 Cambridge Soot Simulator Cambridge 2006 http como cheng cam ac uk Sweep is the name of a dog from a childrens TV show in which the main character a bear is called Sooty 2 File List sweep f90 Main source file of SWEEP library used by calling code mt19937 f An implementation of the Mersenne twister random number generator profile_driver_input f90 Input routines for driver program profile_driver_output f90 Output routines for driver program profile_driver_program f90 The driver program for profiled chemistry data swpchem_point f90 Chemistry module for variable chemistry expressed as a sin gle array of gas phase variables swpchem_point_dppt f90 Same as swpchem_point f90 except the chemistry is stored in double precision and accessed via a pointer swpchem_profile f90 Chemistry routines for fixed chemistry expressed as a pro file of gas phase variables at different time points swpchem_shared f90 Routines and data shared by all flavours of swpchem_ f90 swpcoag f9
13. ile const or abf value If the const active surface model is used then this value is used to supply the constant fraction If it is omitted then the fraction is assumed to be one 7 9 OUTPUTFILE keyword Provides the name of the output files for the simulation OUTPUTFILE filename filename Name of the output files 7 10 PMODEL keyword Selects the particle model used for the simulation If this keyword is omitted from the file then SWEEP assumes the spherical particle model PMODEL model model Name of the particle model to use Accepted values are spherical for the spher ical particle model and surfvol for the surface volume model 10 7 11 LOWSTAT keyword Sets the smallest diameter of particle that is summed for ensemble statistics LOWSTAT value value Smallest diameter particle in cm to be summed for ensemble statistics 7 12 HIGHSTAT keyword Sets the largest diameter of particle that is summed for ensemble statistics HIGHSTAT value value Largest diameter particle in cm to be summed for ensemble statistics 8 Mechanism Input File XML The particle mechanism for SWEEP is provided as an XML file If you are unfamiliar with XML then it is advised you read up about it before reading this section There are plenty of internet references and books on the subject for example http www w3schools com xml Following is a description of all the valid XML e
14. ism File lt xml version 1 0 encoding ISO 8859 1 gt 20 lt mechanism name abf soot gt lt Choose which models to use gt lt model id haca gt lt model id actsurf type abf gt lt Define particle types and components gt lt particle id X gt lt component id C gt lt density gt 1 8 lt density gt lt molwt gt 12 011 lt molwt gt lt component gt lt Tracker variables gt lt track id H gt lt Inceptions gt lt inception name Pyrene inception gt lt formula gt A4 A4 to X32 lt formula gt lt reactant id A4 stoich 2 m 3 19e 22 d 0 79e 7 gt lt particleout id X gt lt component id C dx 32 gt lt track id H dx 20 gt lt inception gt lt Surface reactions single particle events gt lt reaction type surface name 0H oxidation defer true gt lt formula gt X OH to X 1 CO H lt formula gt lt reactant id 0H stoich 1 gt lt product id CO stoich 1 gt lt product id H stoich 1 gt lt A gt 2 1693357e26 lt A gt lt n gt 0 5 lt n gt lt E gt 0 0 lt E gt lt particleterm id d power 2 0 gt lt component id C dx 1 gt lt reaction gt lt reaction type surface name C2H2 addition defer true gt 21 lt formula gt X C2H2 to X 2 H lt formula gt lt reactant id C2H2 stoich 1 gt lt product id H stoich 1 gt lt parti
15. lements that can be used in a mechanism file and their contexts An example mechanism file is provided in the appendix 8 1 mechanism element The root element in a mechanism file is the mechanism element and it has the following form lt mechanism name gt lt mechanism gt name The name of the mechanism This attribute is optional All other elements are written inside the mechanism element 8 2 model element The model element tells SWEEP to use a particular model when solving An example of a model is how active surface is treated The model element has the following form lt model id type gt id Unique identifier for the model to activate type Additional information about the model if more than one option is available 11 8 2 1 Accepted model elements Use the HACA model for calculation of radical site fraction Frenklach and Wang 1994 lt model id haca gt Use the ABF correlation for active site fraction alpha lt model id actsurf type abf gt 8 3 particle element The particle element defines a symbol used to represent a particle type in the XML file To define more than one particle type include this element multiple times The particle element has the following form lt particle id gt id Symbol used to define the particle type 8 4 component element The component element takes two forms in a mechanism file If it stands alone from an inception or reaction eleme
16. lume cm 9 10 11 12 13 14 15 16 17 18 19 Average particle mass g Average particle surface area cm Active surface fraction Average particle diameter nm Sample volume cm Ensemble scaling factor Second size moment atoms cm Third size moment atoms cm Fourth size moment atoms cm 3 Fifth size moment atoms cm Sixth size moment atoms cm7 Additionally the particle size list PSL is output at the end of each time interval as defined in the settings file These are also written to binary file for each run and then post processed on completion of the program to provide a single CSV file with a list of all particles for all runs The PSL contains the following information for each particle 19 1 Relative weighting 2 Volume cm 3 Surface area cm 4 Diameter nm 5 Particle type number 6 Number of each particle component 7 Values for all tracking variables 11 Example Settings File CHEMFILE jwl 69 dat MECHFILE abfmech xml RUNS 10 STARTT 0 0DO TIME 4 0D 4 400 TIME 1 4D 3 200 PCOUNT 2048 MAXMO 6 0e8 ACTSURFMODEL profile OUTPUTFILE test 12 Example Chemistry Profile This is an example chemistry profile with the gas phase species concentrations omitted for clarity Byll Time T P Alpha C2H2 H2 H 02 0H H20 C0 A4 0 00 500 60 8 sisi 0 05 500 0 0287 25 4 0 10 500 0 038 5 is os 13 Example Mechan
17. n inception element must contain one and only one particleout element which defines the type of particle produced by the process An inception element must contain at least one component element and any number of track elements Any components or tracker variables not explicitly given will be assigned a value of zero when the program is run 8 9 reaction element The reaction element contains all the information required to define a particle process other than inception Typically a reaction element will take the form lt reaction type name defer gt lt formula gt rxn_form lt formula gt lt reactant id stoich m d gt lt product id stoich gt lt particlein id gt lt particleout id gt lt A gt arrn_A lt A gt lt n gt arrn_n lt n gt lt E gt arrn_E lt E gt lt particleterm id power gt lt component id dx gt lt track id dx gt lt reaction gt type The type of single particle process Accepted types are surface and condensa tion These are explained later on name Name of the reaction defer true false flag telling SWEEP whether this process should be simulated using LPDA true or DSA C false rxn form Formula of the reaction This is optional and provided as a reference tool for the user 14 8 9 1 surface type reactions A reaction element of type surface can contain any number reactant el
18. ngs three of which must be included in the file These are 1 Time Denotes the column of time coordinates 2 T Denotes the column of gas phase temperature 3 P Denotes the column of gas phase pressure 4 Alpha Denotes the column of soot active site fraction This column is optional The other columns should be headed by the names of the pertinent gas phase species These names should match those used in the mechanism XML file otherwise the program fail The units of the chemistry file are seconds for time Kelvin for temperature bar for pressure and mol cm for species concentrations Alpha is a dimensionless quantity with a value between zero and one 18 10 Output Files Data for each run is stored in a numbered binary file with the name supplied in the settings file These file are given the dat extension Once all runs have been completed these binary files are processed and the averaged data is output to CSV file along with the 99 confidence intervals The output file contains statistics and information about the particle population along with the process rates at each output point The statistics output in order are NY Dn A A W N Stochastic particle count Number density cm First size moment atoms cm Particle volume fraction Particle mass concentration g cm Total particle surface area cm cm Average first size moment per particle 8 Average particle vo
19. nt then it defines a component used to build particles In this case it must contain a density and a molwt element also and takes the form lt component id gt lt density gt dens_val lt density gt lt molwt gt molwt_val lt molwt gt lt component gt id Symbol used to identify the particle component dens_val The component density in mol cm molwt_val The component molecular weight in g mol The second form of the component element is as part of an inception or reaction definition and is used to define the change in that component s value due to the process In this case it takes the form lt component id dx gt id Symbol of component to change for process dx The integer amount by which to change the component 8 5 density element The density element is only used inside the component element and takes the form 12 lt density gt dens_val lt density gt dens_val The component density in mol cm 8 6 molwt element The molwt element is only used inside the component element and takes the form lt molwt gt molwt_val lt molwt gt molwt_val The component molecular weight in g mol 8 7 track element The track element comes in two flavours First it is used to define a tracking variable which is summed per particle Tracking variables are different from components because they are not used to calculate particle properties A tracking variable is areal quantity and is define
20. programmed then this will have a significant effect of computation time 8 17 coagulation element The coagulation element is used to define the resultant particle type of a coagulation if more than one particle type has been defined It will take the form 17 lt coagulation name gt lt formula gt coag_form lt formula gt lt particlein id gt lt particlein id gt lt particleout id gt lt coagulation gt name Reference name of the coagulation coag form The formula of the coagulation This is provided for user reference only and is not used by SWEEP The coagulation element must contain two particlein elements to define the types of particles which are coagulating The coagulation element must contain only one particleout element to define the resul tant particle type of the coagulation If a possible coagulation exists for which no coagulation element has been defined then the resultant particle type is the first type defined in the mechanism not that defined in the coagulation 9 Chemistry Profile File The chemistry profile file is a text file with tab or comma separated data The first line of the file should contain two values The first is the number of number of points in the chemistry profile and the second is the number of columns in the file excluding the time column The second line in the file contains the header row for the subsequent profile There are four reserved column headi
21. r of soot particle properties used in the rate expression C is the concentration of gas phase species 1 Vi is the forward stoichiometric coefficient of species 2 and J is the number of reactant species for the reaction SWEEP has pre programmed variables for 0 these are 6 1 Volume cm Mass g Inverse mass to the power one half g Collision diameter cm Collision diameter squared cm Inverse collision diameter squared cm 2 3 4 5 6 Inverse collision diameter cm 7 8 Surface area cm 9 Active surface area cm 10 Collision diameter squared times inverse mass to the power one half cm g 9 SWEEP is optimised to use these properties reactions defined in the mechanism which do not use these properties will take substantially longer to solve This is not recommended 5 3 Condensation reactions Condensation reactions in SWEEP are modelled as a free molecular collision between a single gas phase species and a soot particle The rate per particle takes the form Reond 12 2 TkgT m d 2dd d 7 Where C m and d are the gas phase concentration mol cm mass g and collision diameter cm of the condensing species respectively d is the collision diameter of the particle 7 is the efficiency of collision 5 4 Coagulation Coagulation is modelled in SWEEP using the Smoluchowski coagulation equation This takes the form nfs Y Ble y
22. t The particleout element is used inside the inception and reaction elements to define the product particle type It takes the form lt particleout id gt id The symbol representing the product particle type 8 15 A n and E elements The A n and E elements are used inside the inception and reaction elements to define the Arrhenius rate parameters for expressions of the form AT exp E RT They take the form lt A gt arrn_A lt A gt lt n gt arrn_n lt n gt lt E units gt arrn_E lt E gt arrn_A Arrhenius pre exponential coefficient arrn_n Arrhenius temperature exponent arrn_E Arrhenius activation energy units Units of the activation energy Permitted values are s1 for energies in Joules and cal for energies in kilo calories 8 16 particleterm element The particleterm element is used inside the inception and reaction elements to define how the rate expression depends on the particle properties It takes the form lt particleterm id power gt id 1D of the particle property used to calculate the rate expression Permitted values are d collision diameter cm s surface area cm as active surface area cm and v volume cm power The exponent to which to raise the particle property Only certain combinations of properties and powers are included in SWEEP and if a property and power combi nation is chosen which is not pre
23. tput points up to the given time Positive integer 7 6 PCOUNT keyword Sets the maximum stochastic particle count PCOUNT num num Maximum particle count Positive integer power of 2 7 7 MAXMO keyword Used to set the internal scaling of SWEEP For best results it should be set to the maximum expected number density of the simulation If it is set too low then SWEEP has to remove particles from the ensemble which leads to potential errors in volume fraction and can increase computation time If it is set too high more than one third above the maximum expected value then the particle doubling algorithm will not work and there will probably be insufficient particles to get a statistically meaningful solution In order to estimate this parameter it is suggested to select a value larger than expected 1012 might be a good initial estimate and run the simulation noting the largest actual Mo value observed Then edit the input file with a value slightly higher about 5 than the true value MAXMO num num The maximum expected number density Real 7 8 ACTSURFMODEL keyword Used to tell SWEEP how the active surface model should be used The options are profile for the active surface fraction defined in the chemistry profile const for a constant active surface and abf to use the ABF correlation for active surface fraction ACTSURFMODEL model value 39 66 model Name of the model to use One of prof
24. used inside the inception and reaction elements to define a reactant chemical species in the gas phase It takes the form lt reactant id stoich m d gt id The symbol of the reactant species This must match the symbols provided to SWEEP via the input file stoich The integer stoichiometric coefficient of the reactant species There may be some restrictions on this value depending on the context See definitions of the inception and reaction elements for more details m The mass of the reactant species in g This is required for inceptions and condensation type reactions otherwise it can be omitted d The collision diameter of the reactant species in cm This is required for inceptions and condensation type reactions otherwise it can be omitted 8 12 product element The product element is used inside the inception and reaction elements to define a prod uct chemical species to the gas phase It takes the form lt product id stoich gt id The symbol of the product species This must match the symbols provided to SWEEP via the input file stoich The integer stoichiometric coefficient of the product species 8 13 particlein element The particlein element is used inside the inception and reaction elements to define the reactant particle type It takes the form lt particlein id gt id The symbol representing the reactant particle type 16 8 14 particleout elemen
25. y n e uml D Bla valen 8 n x is the number density of particles of type x and B x y is the coagulation kernel of particles of types x and y A discussion of the coagulation kernel in SWEEP is given by Patterson ef al 2006b The forms of the free molecular and slip flow kernels have already been presented in the discussion of inception reactions 7 5 5 Ensemble Rates The total rates for the entire soot ensemble can be found by summing the per particle rates for each particle For the stochastic simulation this will give you the rate per sample volume that is the volume which would contain the number of particles in the ensemble To get the rates per unit volume these rates must be divided by Vsmp in where Vimp 18 the sample volume N is the number of particles in the ensemble and Mp is the particle number density 6 Particle Models SWEEP has two particle models programmed the spherical particle model and the surface volume model The spherical particle model assumptions are 1 Particles are perfect spheres and can be described by one size coordinate volume 2 Coagulation by total coalescence and does not conserve surface area The surface volume model assumptions are 1 Particles form aggregate structures and are described by two size coordinates vol ume and surface area 2 Coagulation by point contact and therefore conserves surface area 3 All surface processes act to increase the sphericity of a particl
Download Pdf Manuals
Related Search