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December 1, 2023, 13:35 |
combustion does not occur with reactingFoam
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#1 |
New Member
Edoardo
Join Date: Apr 2023
Location: Italy
Posts: 27
Rep Power: 3 |
Hello,
I am trying to simulate a flammable gas flow in atmosphere with reactingFoam. You can find the whole case directory attached at the end. If I do not ignite the gas (/constant/combustionProperties --> active off and /constant/chemistryProperties --> chemistry off) the gas leak is totally diffusive and results are good. However, if I try to ignite the flammable gas (/constant/combustionProperties --> active on and /constant/chemistryProperties --> chemistry on) the reaction does not occur. Therefore the results are exactly the same as withouth ignition. The reaction is a single-step reaction, implemented in /constant/reactionGRI. reactionGRI Code:
elements ( ) ; species 4 ( H2 O2 H2O N2 ) ; reactions { un-named-reaction-2 { type irreversibleinfiniteReaction; reaction "2H2 + O2 + 3.79N2 = 2H2O + 3.79N2"; } } Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: v2012 | | \\ / A nd | Website: www.openfoam.com | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; location "constant"; object chemistryProperties; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // chemistryType { chemistrySolver ode; chemistryThermo psi; TDAC off; } initialChemicalTimeStep 1e-07; chemistry on; odeCoeffs { solver seulex; // Rosenbrock34, seulex or rodas23 absTol 1e-12; relTol 1e-7; } // ************************************************************************* // Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: v2012 | | \\ / A nd | Website: www.openfoam.com | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; location "constant"; object combustionProperties; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // combustionModel EDC; active on; EDCCoeffs { version v2005; } // ************************************************************************* // Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: v2012 | | \\ / A nd | Website: www.openfoam.com | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; location "constant"; object thermophysicalProperties; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // thermoType { type hePsiThermo; mixture reactingMixture; //singleStepReactingMixture; transport sutherland; thermo janaf; energy sensibleEnthalpy; equationOfState perfectGas; specie specie; } inertSpecie N2; chemistryReader foamChemistryReader; foamChemistryFile "<constant>/reactionsGRI"; foamChemistryThermoFile "<constant>/thermo.compressibleGasGRI"; dpdt false; // ************************************************************************* // 1) Why does the reaction not occur? 2) Is irreversibleinfiniteReaction in /constant/reactionGRI correct? Maybe is it not fast enough to show something in a short time? 3) In /constant/thermophysicalProperties should be selected mixture reactingMixture or singleStepReactingMixture? 4) Could be the problem the lack of ignition? Really thank for your help. |
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December 4, 2023, 15:33 |
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#2 |
Senior Member
abdikerim kurbanaliev
Join Date: Jun 2010
Location: Kyrgyzstan, Osh
Posts: 121
Rep Power: 16 |
Try to use another turbulence model. For example RNG instead of standard k-e-model.
Please see this post reactingFoam SandiaD_LTS tutorial error. May be it will help you. Good luck! |
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December 4, 2023, 21:11 |
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#3 | |
New Member
Edoardo
Join Date: Apr 2023
Location: Italy
Posts: 27
Rep Power: 3 |
Quote:
@kerim thank you for your answer. I followed your tips and switched standard k-eps model to RNG k-eps model in turbulenceProperties... but the results do not show any combustion, only diffusion. Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: v2012 | | \\ / A nd | Website: www.openfoam.com | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; location "constant"; object turbulenceProperties; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // simulationType RAS; RAS { RASModel RNGkEpsilon; kEpsilonCoeffs { Prt 1; } turbulence on; printCoeffs on; } // ************************************************************************* // |
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December 5, 2023, 14:59 |
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#4 |
Senior Member
Troy Snyder
Join Date: Jul 2009
Location: Akron, OH
Posts: 220
Rep Power: 19 |
Edoardo1993,
Per your original post, I would suggest changing the reaction in reactionsGRI from irreversibleinfiniteReaction to irreversibleArrheniusReaction. You can then adjust the Arrhenius rate constants and activation temperature until you get a reaction. If ignition/combustion still does not occur, re-running with alternative RAS models per Kerim is also advised. Notably, irreversibleArrheniusReaction is only used in conjunction with LES turbulence in the combustion tutorials. |
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December 5, 2023, 16:39 |
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#5 | |
New Member
Edoardo
Join Date: Apr 2023
Location: Italy
Posts: 27
Rep Power: 3 |
Quote:
Thank you tas38. I did not know about LES and irreversibleinfiniteReaction. Now, my reaction file is: Code:
reactions { un-named-reaction-2 { type irreversibleArrheniusReaction; reaction "2H2 + O2 + 3.79N2 = 2H2O + 3.79N2"; A 5.2e16; beta 0; Ta 14906; } } |
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December 6, 2023, 10:13 |
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#6 |
Senior Member
Troy Snyder
Join Date: Jul 2009
Location: Akron, OH
Posts: 220
Rep Power: 19 |
Edoardo1993,
Yes, you could try adding an ignition source (small box with high temperature) using setFieldsDict containing a boxToCell region as in DLR_A_LTS. However, if I recall, the EDC model should not require a direct ignition source. Combustion is initiated simply due the presence of turbulence, i.e. and . I just noticed in your combustionProperties file you have active on;, however, I believe this should be active true;. Not sure if no vs. true makes a difference, but I would try this first. |
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December 7, 2023, 18:42 |
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#7 |
New Member
Edoardo
Join Date: Apr 2023
Location: Italy
Posts: 27
Rep Power: 3 |
Quote:
tas38, thank you for your kind help. I knew that active true and on are the same keyword. Regarding ignition with EDC model, I created another directory for test and the combustion starts only when the flammable flow touches an hot spot, in my case a wall with T=1000K (probably you can get similar result with setFieldDict). I don't see any reaction to occur when this wall is cold. What do you mean with "Combustion is initiated simply due the presence of turbulence, i.e. and "? The greater k and epsilon, the faster the reaction? |
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December 16, 2023, 10:48 |
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#8 |
New Member
Edoardo
Join Date: Apr 2023
Location: Italy
Posts: 27
Rep Power: 3 |
Hello. I hope someone can help me because I am still stucked with this issue.
I finally managed to ignite the gas with fvOptions setting some cells at 1200K. The problem is the simulation is running only when using CH4. As soon as I switch the gas to H2 (changing the reaction with "H2 + 2O2 = 2H2O" and the thermo.compressibleGas ), the simulation starts but it stops because of several errors.. Code:
elements ( O C H N ); species ( O2 H2O CH4 CO2 N2 ); reactions { methaneReaction { type irreversibleArrheniusReaction; reaction "CH4 + 2O2 = CO2 + 2H2O"; A 5.2e16; beta 0; Ta 14906; } } Furthermore, I have another question. I attempted to integrate the GRI reactions, which I found in the SANDIAD_LTS tutorial, into the working model with CH4. Why does the reaction occur with the single-step reaction but not with the GRIMECH file?" |
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January 3, 2024, 01:47 |
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#9 |
New Member
Han Yu
Join Date: Nov 2023
Posts: 8
Rep Power: 2 |
Hello. I want to simulate a combustion model through EDC model based on reactingFoam. Could you please show me a tutorial about EDC implementation? Thank you very much!
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Tags |
combustion, hydrogen, ignition, reactingfoam, reaction |
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