DICOM V6.3 USER MANUAL March 26th, 2015
Contents
1. Default value is 1 DICOM V6 3 USER MANUAL March 26th 2015 UNIVERSITAT Ilo POLIT CNICA dla slo a DE VAL NCIA motores t rmicos e Angle options In this field the spray cone angle to define the spray radial boundary in terms of the axial velocity profile has to be introduced There are two options for selecting the spray cone angle Single angle Figure 5 One angle to define the whole spray radial boundary Double angle Figure 6 Two angles to define the spray radial boundary The Transition x m is the axial distance from the nozzle where the spray angle change from the Spray angle to the Far angle e Radial profile This section makes it possible to select one of the four mathematical functions Exponential Spalding Hinze and Schlichting that have been considered for the radial distribution of the conserved properties in terms of r R which is a normalized radial coordinate with r radial coordinate R spray outer radius as derived from cone angle d o Exponential Gaussian PN exp Log 100 o Spalding PN 14 k 7 o Hinze PN E 1 k o Schlichting Abramovich PN 1 k 3 1 4 INJECTION RATE To introduce injection information two approaches can be considered namely direct input Figure 7 where both momentum and mass fluxes are given by the user and derived input Figure 8 where mass flow is given by th2. Flow type C Isothermal Spray Gas Jet inert reactive MAIN NUMERICS MORPHOLOGY INJECTION RATE MIXING LAW C Spray inert reactive motores t rmicos Air Density kg m3 22 8 Pressure Pa 16210000 Yn2inf 10 767 Yo2inf 10 233 Yco2inf 0 Yh2o0inf 10 Fuel Temperature Tfo K 363 Reactivity Parameter 0 inert 1 reactive fLOL fo Fuel properties nC12H26 Figure 10 User input interface MIXING LAW tab option for steady cases Gas jet is selected although a similar layout occurs for Spray cases 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 DICOM V6 3 USER MANUAL March 26th 2015 10 UNIVERSITAT POLIT CNICA dla slo a DE VALENCIA motores t rmicos 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 61
3. e Start starts the calculation a ES bIcom v6 3 eo LS File Language MAIN NUMERICS MORPHOLOGY INJECTION RATE MIXING LAW CANYT motores t rmicos Case name CASE Open Directory of output files C Browse Time approach O Steady C Transient Figure 2 User input interface MAIN tab for Steady case DICOM V6 3 USER MANUAL March 26th 2015 3 UNIVERSITAT A POLIT CNICA E PS DE VALENCIA motores t rmicos The working procedure with the user interface 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 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 MAIN 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 momentum fluxes and time constant fuel and ambient gas thermodynamic variables and composition All input parameters are therefore scalar values e TRANSIENT
4. LATY A O A motores t rmicos Saxe UNIVERSITAT POLIT CNICA DE VALENCIA DICOM V6 3 USER MANUAL March 26 2015 Jos M Garc a Oliver jgarciao mot upv es Walter Vera Tudela walvetu mot upv es CMT MOTORES T RMICOS Camino de Vera s n e 46022 Valencia Espa a Tel 34 963 877 650 Fax 34 963 877 659 E mail cmt mot upv es e Web http www cmt upv es UNIVERSITAT POS POLIT CNICA ETEF DE VAL NCIA motores t rmicos CONTENTS E INTRODUCTION EE 3 SEENEN 3 3 INPUT DATA vicnwesiencnseeancsnnasnsnenecsmeskaensnijakienensiebesenneebhsinensebexenensbanicznecbnelemsekertbwssknesbewsknentei 4 3 1 STEADY CALCULATION serrat 4 T MAIN coi 4 ee NUMERIC o eree E EEN 5 3 1 3 MObPHOL OGN 6 3AA INJEC TON RATE sea id adeda 7 As cee eee eee ee ee eee ee 8 3 2 TRANSIENT CAICULATION 10 SSC NN E 11 322 NUMERIC ern atacan eee 12 SSC TE RE coman eee 13 3 2 4 MObPHOL OGN 14 SE SE BIS ene CAR 15 20 WIXING E 16 a OUTPOT Een 19 NR En E 19 d2 o o e 19 A o 20 a une EE 20 db C021 K O ee cee 22 o REFERENCES sust eee eee ee ee 24 DICOM V6 3 USER MANUAL March 26th 2015 2 UNIVERSITAT A POLIT CNICA dia olo a DE VAL NCIA 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 t
5. pw Yp Ser dr 0 kg s Radially integrated total mass flux R M p w 2nr dr 0 m s Cross sectional average velocity from the ratio of momentum and mass fluxes I Umed 7 M fmed Cross sectional average velocity from the ratio of fuel and total mass fluxes e fmea wt 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 e med ye E A C MN La of the intact zone in terms of axial velocity Rini_u Rini_ f ie mixture fraction Rini_f Ro nm Radius where a certain equivalence ratio b is found Revap no Radius where a mixture fraction for full evaporation fevap is found only for liquid spray calculations DICOM V6 3 USER MANUAL March 26th 2015 22 UNIVERSITAT 1 POLIT CNICA E Pn DE VALENCIA motores t rmicos kg m Radial integral of total fuel mass i e total fuel mass per unit length R my p f 2nr dr 0 mfmix_o kg m Radial integral of fuel mass from R_ to R Le total fuel mass per unit length below a characteristic equivalence ratio 9 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 3 3 lt Mfmixevap p f 2rr dr kg m Radial integral of total air mass i e total air mass per unit length R ma p f 2ar dr 0 Radial
6. which are summarized in two parameters o Spatial increase m Spatial discretization in the axial direction Ax which defines the cell size and corresponding spatial resolution 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 CFLA CFL and the local flow velocity by means of At E DICOM 6 3 elos File Language MAIN NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING Law Fla olp e Mode selection Automatic Discretization A eee Open C Free Discretization Spatial increase constant 1 Start Figure 14 DISCRETIZATION tab for transient cases Automatic option ES picom 3 eck File Language MAIN NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING Law ite 3 motores t rmicos Mode selection C Automatic Discretization Discretization Courant Number 50 Spatial increase 5E 5 SI Hu oO Q Hu CH oO Et N w p o un o Du OH 2 Spatial increase constant 1 Start Figure 15 DISCRETIZATION tab for transient cases Free discretization option DICOM V6 3 USER MANUAL March 26th 2015 13 UNIVERSITAT POLIT CNICA Jaeabe DE VALENCIA motores t rmicos ES DICOM v6 3 File Language co II
7. 0 Fuel properties nC12H26 Figure 21 MIXING LAW tab option for transient cases Spray is selected although a similar layout occurs for Gas Jet cases DICOM V6 3 USER MANUAL March 26th 2015 18 UNIVERSITAT A POLIT CNICA dia olo a DE VAL NCIA 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 fraction 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 considers the amount of species that can be found in either liquid or vapour phase Furthermore the characteristic evaporation mixture fraction value fevap is given at the end of the first row This file is written once for the steady calculation while it ca
8. Ex MAIN NUMERICS MORPHOLOGY INJECTION RATE MIXING LAW E Y A AAA motores t rmicos Velocity fraction for spray boundary 0 01 Open Schmidt Number 1 Angle options Single angle Spray angle D I Save C Double angle Start Radial Profile Exponential Spalding C Hinze C Schlichting Figure 16 MORPHOLOGY tab for transient cases single angle selection ES picom v6 3 o E File Language MAIN NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING Law ole pl Y A el motores t rmicos Velocity fraction for spray boundary 0 01 Open Schmidt Number 1 Angle options Single angle Spray angle 17 75 Save Double angle Transition x m az Far angle 24 5 Start Radial Profile Exponential C Spalding C Hinze C Schlichting epale Figure 17 MORPHOLOGY tab for transient cases double angle selection 3 2 4 MORPHOLOGY The parameters introduced in this part are the same as in the steady case Figure 17 Velocity fraction for 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 Schmidt number The Schmidt number is in the ratio of momentum and mass diffusivities Default value is 1 Angle options In this field the spray cone angle to define the spray radial boundary in te
9. Mass fraction increase for integral tables Increase in mixture fraction on the axis for the radial integral tables which are performed to solve conservation equations Default is 0 01 Note that mixture fraction values are between 0 and 1 Some additional parameters are specific for transient cases e Maximum calculation time s Final instant of calculation of the model e Convergence boundary for main equations Condition for calculation end in conservation equations lf the difference between results of two successive computations is less than this limit value calculation stops Default value is 10 e Cell velocity value to define 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 DICOM V6 3 USER MANUAL March 26th 2015 12 ER UNIVERSITAT 1 POLIT CNICA dla olo a DE VAL NCIA motores t rmicos 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 14 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 fully modify the details of the discretization method Figure 15
10. 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 Ss m Maximum jet tip penetration Maximum penetration of a surface with a characteristic equivalence ratio d DICOM V6 3 USER MANUAL March 26th 2015 20 UNIVERSITAT POLIT CNICA dla olo a DE VALENCIA motores t rmicos Maximum liquid length as calculated from the spray tip towards the 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 Integral of the mixture fraction all over the spray It should be equal to the injected fuel mass until the corresponding time SR may 2 f sera as Q mfmix_o kg Integral of fuel mass below a characteristic equivalence ratio dh Mf mixg M of Ar dr di mf_mixevap Kg Integral of fuel mass outside of the iso surface of evaporation mixture fraction fevap SR Mf mixevap 7 I p f 2mr dr dx 0 Revap Integral of the mixture fraction all over the spray S R Ma J PAP Berar a Q FOR fm Lift Off Length based upon input fLOL fLOL 0 for inert spray mfsq Integral of the fuel mass all over the spray It should be equal to the injected fuel mass for inert cases For reacting ones it corresponds to the unburned fuel mass SR M
11. 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 9 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 3 1 5 2 Gas jet Spray The next two cases Figure 10 require the same input data and the difference between both cases is the state of injected fuel gas or liquid respectively e Air density kg m3 Density in the chamber into which injection is performed e Pressure Pa Pressure in the chamber into which injection is performed Chamber temperature is calculated from pressure and density e Yn2inf Yo2inf Yco2inf Yh2oinf Mass fraction values of nitrogen oxygen carbon dioxide and water respectively in ambient air e Fuel temperature Tfo K Fuel temperature when injected into the combustion chamber e Reactivity Parameter 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 fl
12. integral of unburned fuel mass e unburned fuel mass per unit length Mpsa ert Beer dr o 0 mfl kg m Radial integral of fuel mass in liquid mfl or vapour mfv phase R Ms o Ya 2rer de 0 R Mery oo Zero Q kg m Radial integral of a certain species e g 02 CO2 H20 R Mi pY Ser dr Temperature on the centerline Tcl Tmed K Cross 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 MAIN 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 V6 3 USER MANUAL March 26th 2015 23 UNIVERSITAT DCH POLIT CNICA dla olo a DE VAL NCIA motores t rmicos 5 REFERENCES 1 Pastor J V L pez 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
13. 0456 2012 4 Pastor J Garcia Oliver J Pastor J M and Vera Tudela W One Dimensional Diesel Spray Modeling of Multicomponent Fuels Atomization and Sprays in press 2015 DOI 10 1615 AtomizSpr 2014010370 DICOM V6 3 USER MANUAL March 26th 2015 24
14. 42E 005 0 0020556 3 8542E 005 0 0020851 4 0942E 005 0 0021128 A 33427 005 0 0021387 4 5742E 005 0 0021628 4 8142E 005 0 0021851 5 0542E 005 0 0022056 Figure 11 Example of input text files for injection mass flux in a transient case A similar structure can be used for other input files ES DICOM v6 3 le ks File Language MAIN NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING LAW ole pl Y A motores t rmicos Case name CASE Open Directory of output files C Browse Time approach fake C Steady Transient Start epale Time interval for saving results s 0 0001 Figure 12 User input interface MAIN tab for Transient case To enable such transient conditions input files have to be provided for injection mass momentum 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 11 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 Sl units 3 2 1 MAIN The interface is similar to the steady case The following fields can be selected Figure 12 e Case name Heading name given to all the output files e Di
15. 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 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 MAIN The first tab allows selecting if the model is transient or steady When selecting Steady case the two fields on this screen are e Case name Heading name given to all the output files e Directory of output files Folder in which the program will write the output files There is a button which is labeled as Browse to select the folder DICOM V6 3 USER MANUAL March 26th 2015 4 UNIVERSITAT POLIT CNICA dla olo a DE VAL NCIA motores t rmicos ES DICOM w63 Fil
16. active 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 under inert conditions TOL should be 0 t_soc should be bigger than the final calculation time o Ifa calculation is performed under reacting conditions Ambient has to contain oxygen fLOL should be bigger than 0 t soc should be smaller than the final calculation time e Fuel properties Name of the species that will be used as fuel This field has to be the same as It appear in a database file with the name props DICOM_DB dat This file includes fuel properties such as molecular weight critical temperature critical pressure standard enthalpy of formation etc has to be included compulsorily at the following path C DICOM props DICOM_DB dat z E DICOM v6 3 jh e Je File Language la pip a MAIN NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING LAW motores t rmicos Flow type C Isothermal Spray C Gas Jet inert reactive Spray inert reactive Air Density File kg m3 s CA Browse Pressure File Pa s Ca Browse Yn2in J f0 767 Yo2inf J 0 233 Yco2inf J o Yh2oinf o Fuel Temperature Tfo K 363 Reactivity Parameter O inert 1 reactive fLOL 0 Start of Combustion Time t_soc s
17. ame 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 lt fLOL The user has to check incompatibility among different inputs o Ifa calculation is performed under inert conditions fLOL should be 0 o Ifa calculation is performed under reacting conditions Ambient has to contain oxygen fLOL should be bigger than 0 e Fuel properties Name of the species that will be used as fuel This field has to be the same as it appear in a database file with the name props _DICOM_DB dat This file includes fuel properties such as molecular weight critical temperature critical pressure standard enthalpy of formation etc has to be included compulsorily at the following path C DICOM props DICOM_DB dat DICOM V6 3 USER MANUAL March 26th 2015 9 UNIVERSITAT POLIT CNICA DE VALENCIA LATY AAA AAA motores t rmicos ES bicom v6 3 o IS Ex File Language MAIN NUMERICS MORPHOLOGY INJECTION RATE MIXING Law CATY Flow type motores t rmicos C Gas Jet inert reactive C Spray inert reactive e m Open Air Density kg m3 22 8 Fuel Density kg m3 750 Save Stoichiometric Mass Fraction fst 0 06 Start ele Figure 9 User input interface MIXING LAW tab option for steady cases Isothermal spray fs DICOM v6 3 File Language
18. e Language Maximum calculation length m 0 1 Increase in x of the discretization dx m 0 0001 Mass Fraction increase for State Relationships 0 001 Mass Fraction increase for integral tables 0 01 Convergence limit for iteration 1E 6 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 Maximum calculation length m Define the maximum size of the calculation domain in terms of spray axial distance Increase in x of the discretization dx m Spatial discretization in the axial direction Ax which defines the cell size and corresponding spatial resolution Mass Fraction increase 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 Mass Fraction increase for integral tables Increase in mixture fraction on the axis for the radial integral tables which are performed to solve conservation equations Default is 0 01 Note that mixture fraction values are between 0 and 1 Convergence limit for iteration Numerical value for calculation end in conservation equations lf the difference between results of 2 Successive computations is less than this limit value calculation stops Default value is 10 DICOM V6 3 USER MANUAL March 26th 2015 5 UNIVERSITAT POLIT CNICA DE VALENCIA LATY AAA AAA mot
19. e 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 ES DICOM v6 3 ez File Language MAIN NUMERICS MORPHOLOGY INJECTION RATE MIXING Law ESP motores t rmicos Selection of the inyeccion rate Derived input Open Momentum N vam Mass Flow kg s mos SCOTS Nozzle Diameter m Ss Start eles Figure 7 INJECTION RATE tab and DIRECT INPUT option for steady cases DICOM V6 3 USER MANUAL March 26th 2015 7 UNIVERSITAT MA POLIT CNICA E P A DE VALENCIA motores t rmicos f ES DICOM v6 3 ce C fem File Language MAIN NUMERICS MORPHOLOGY INJECTION RATE MIXING LAW rC Y motores t rmicos Selection of the inyeccion rate C Direct input E Open o ae Mass Flow kg s 0 00261 Save Inyection Pressure increase Pa 143790000 Velocity Ratio Cv H Nozzle Diameter m Duef Start II E Figure 8 INJECTION RATE tab and DERIVED INPUT option for steady cases 3 1 4 1 Direct input e Momentum N Injection orifice momentum flux e Mass flow 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 f
20. f sq UE 00 m Integral of the burned fuel mass all over the spray Mat Msg Integral of a characteristic species O2 CO2 H20 all over the spray SR mi aner dro 00 mfl kg Integral of the fuel mass all over the liquid I or vapour v part of the mfv spray respectively S R Mr I oke 2nr dr dx 00 S R Mf y I o bro Z r dr dx 00 Maximal velocity along the axis at every time step only for transient cases Axial location where uclmax is found only for transient cases fclmax Maximal mixture fraction along the axis at every time step only for transient cases x_fclmax Axial location where fclmax is found only for transient cases DICOM V6 3 USER MANUAL March 26th 2015 21 UNIVERSITAT HI POLIT CNICA ETEF DE VALENCIA 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 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 Axial component of the velocity vector on the centerline Mixture fraction on the centerline T N Radially integrated momentum flux only for transient cases le Ia Gerd Radially integrated fuel mass flux only for transient cases R My
21. ion rate Direct input SE Open o ae EA Browse Save Inyection Pressure increase Pa 143790000 Velocity Ratio Cv H Nozzle Diameter m Duef Start II E Figure 19 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 flow file kg s 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 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 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 densit
22. low together with fuel density MIXING LAW tab 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 flow kg s Injection orifice mass flux e Injection Pressure increase Pa Pressure difference between injection system and ambient into which injection occurs e Velocity Ratio Cv Velocity loss coefficient through injection hole 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 3 1 5 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 DICOM V6 3 USER MANUAL March 26th 2015 8 UNIVERSITAT 6 POLIT CNICA dia olo a DE VAL NCIA motores t rmicos e Gas jet Local density is calculated by means of an incompressible ideal gas law where local temperature and composition
23. n 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 fey G 0 p PNG E EdE where r R is a normalized radial coordinate with r radial coordinate R spray outer radius as derived from cone angle PN is the mathematical function that describes the radial evolution of conservative variables as described in the Morphology Tab 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 6 0 et ag min where Emin Smin IS a minimum and maximum normalized radial coordinate DICOM V6 3 USER MANUAL March 26th 2015 19 UNIVERSITAT 1 POLIT CNICA E Pn DE VALENCIA 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 ca
24. n 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 wf wf Effective injection velocity at the nozzle exit Injection momentum flux at the nozzle exit kg s Injection mass flux at the nozzle exit kg m3 Ambient air density inside the chamber where the spray is injected kg m3 Injected fuel density injected fuel density Mixture fraction of stoichiometric conditons Mixture fraction atthe itoi ocaton OC o Fully evaporation mixture fraction only for liquid spray cases 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
25. n value for stoichiometric conditions 3 2 6 2 Gas jet inert reactive Spray inert reactive The next two cases Figure 21 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 Air Density File kg m3 Density in the chamber into which injection is performed It s given in terms of the location of a text file with the time evolution of density Pressure File 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 Yn2inf Yo2inf Yco2inf Yh2oinf Mass fraction values of nitrogen oxygen carbon dioxide and water respectively in ambient air Fuel temperature Tfo K Fuel temperature when injected into the combustion chamber Reactivity Parameter 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 DICOM V6 3 USER MANUAL March 26th 2015 17 UNIVERSITAT POLIT CNICA dla olo a DE VAL NCIA motores t rmicos mixture fraction on the axis fcl x is such that fcl x gt fLOL and the flow is totally re
26. o perform a calculation The general flow of information is described in Figure 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 text files which can be later processed and analyzed with additional not provided software wee A A Ke KK zs 3 OUTPUT FILES INTERFACE 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
27. ores t rmicos ES DICOM v6 3 File Language Ra Velocity fraction for spray boundary 0 01 Schmidt Number 1 Angle options Single angle Spray angle D I C Double angle Radial Profile Exponential C Spalding C Hinze Schlichting H H ll 4 motores t rmicos Open Save Start epale Figure 5 User input interface MORPHOLOGY tab for steady cases single angle selection ES bicom v6 3 File Language MAIN NUMERICS MORPHOLOGY INJECTION RATE MIXING LAW Velocity fraction for spray boundary 0 01 Schmidt Number 1 Angle options Single angle Spray angle 17 75 Double angle Transition x m 0 15 Far angle BE Radial Profile Exponential C Spalding Hinze Schlichting H H ll 4 motores t rmicos Open Save Start epale Figure 6 User input interface MORPHOLOGY tab for steady cases double angle selection 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 Velocity fraction for 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
28. rectory of output files Folder in which the program will write the output files There is a button which is labeled as Browse to select the folder DICOM V6 3 USER MANUAL March 26th 2015 11 UNIVERSITAT I P POLIT CNICA ETEF DE VAL NCIA motores t rmicos ES Dicom w63 coll File Language MAIN NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING Law Jeska motores t rmicos Maximum calculation length m Maximum calculation time s 0 002 Open Mass Fraction increase for State Relationships 0 001 Mass Fraction increase for integral tables 0 01 Save Convergence boundary for main equations 1E 8 Cell velocity value to define penetration m s 0 001 Start H H Figure 13 User input interface NUMERICS tab for transient cases Default values e Time interval for saving results s This input defines the time interval where the software will create a new result file xdata dat section 4 5 3 2 2 NUMERICS In this tab Figure 13 parameters for discretization of the problem have to be introduced Some of the parameters are the same as for steady cases e Maximum calculation length m Define the maximum size of the calculation domain in terms of spray axial distance e Mass Fraction increase 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
29. rms of the axial velocity profile has to be introduced There are two options for selecting the spray cone angle Single angle Figure 16 One angle to define the whole spray radial boundary Double angle Figure 17 Two angles to define the spray radial boundary DICOM V6 3 USER MANUAL March 26th 2015 14 UNIVERSITAT A POLIT CNICA dia olo a DE VAL NCIA motores t rmicos The Transition x m is the axial distance from the nozzle where the spray angle change from the Spray angle to the Far angle e Radial profile This section makes it possible to select one of the four mathematical functions Exponential Spalding Hinze and Schlichting that have been considered for the radial distribution of the conserved properties in terms of r R which is a normalized radial coordinate with r radial coordinate R spray outer radius as derived from cone angle d o Exponential Gaussian PN exp Log 100 o Spalding PN 14 k 7 o Hinze PN E 1 k o Schlichting Abramovich PN 1 k t 3 2 5 INJECTION RATE To introduce injection information two approaches have been considered namely direct input Figure 18 where both momentum and mass fluxes are given by the user and derived input Figure 19Figure 19 INJECTION RATE tab and DERIVED INPUT option for transient cases where mass flow is given by the user and moment
30. um 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 file N s Location of the file containing the time evolution of injection orifice momentum flux e Mass flow file kg s 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 ES bicom v6 3 e Il GI as File Language MAIN NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING Law EE A motores t rmicos Selection of the inyeccion rate C Derived input Momentum File N s em o a a 3 Ca Browse Mass Flow File kg s s Ca Browse Nozzle Diameter m E5 Start Figure 18 INJECTION RATE tab and DIRECT INPUT option for transient cases DICOM V6 3 USER MANUAL March 26th 2015 15 UNIVERSITAT MA POLIT CNICA E P ET DE VALENCIA motores t rmicos ES DICOM v6 3 ce C fem File Language MAIN NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING Law e plo a motores t rmicos Selection of the inyecc
31. y 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 DICOM V6 3 USER MANUAL March 26th 2015 16 A POLIT CNICA dia olo a UNIVERSITAT DE VAL NCIA motores t rmicos ES DICOM v6 3 oe File Language MAIN NUMERICS DISCRETIZATION MORPHOLOGY INJECTION RATE MIXING LAW ji motores t rmicos Flow type N Isothermal Spray Gas Jet inert reactive C Spray inert reactive Air Density File kg m3 s Open Cs Browse Fuel Density kg m3 750 Save Stoichiometric Mass Fraction fst 0 06 Start Figure 20 MIXING LAW tab option for transient cases Isothermal spray 3 2 6 1 Isothermal jet spray This is the simplest case Figure 20 which only requires the following inputs Air Density File kg m3 s 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 Fuel density kg m3 Density of injected fuel Stoichiometric mass fraction Mixture fractio
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