[openfoammaofnepo]

Hi All,

I tried to use PaSR to calculate a simple jet flame, firstly used infinitelyFastChemistry model to obtain an fully burning jet flame field, which seem reasonable. Then I changed the combustion model to PaSR, and if course changed other PaSR related parameter. When the simulation goes, the flame is convected downstream and finally it become just cold. What is the problem for the simulation? Anybody also has this experince?

I put my combustionProperties, chemistryProperties and reactions below:

combustionModel    PaSR<rhoChemistryCombustion>;
active  true;
infinitelyFastChemistryCoeffs
{
    semiImplicit    no;
    C               10;
}
laminarCoeffs
{
}
noCombustionCoeffs
{
}
PaSRCoeffs
{
    Cmix                1.0;
    turbulentReaction   yes;
//  useReactionRate     true;
}

chemistryType
{
    chemistrySolver   ode;  //EulerImplicit;
    chemistryThermo   rho;
}

chemistry           on;

initialChemicalTimeStep 1e-07;

EulerImplicitCoeffs
{
    cTauChem        1;
    equilibriumRateLimiter off;
}

odeCoeffs
{
    solver          Rosenbrock34;
    absTol          1e-12;
    relTol          0.01;
}

species
(
    CH4
    CO
    CO2
    H2
    H2O
    O2
    N2
);

reactions
{
//- for infinite fast reaction model
//  methaneReaction
//  {
//      type         irreversibleinfiniteReaction;
//      reaction      "CH4 + 2O2 + 7.5N2 = CO2 + 2H2O + 7.5N2";
//  }

//- for PaSR combustion model
    methaneReaction
    {
        type     irreversibleArrheniusReaction;
        reaction "CH4 + 2O2^1.0 = CO2 + 2H2O^1.0";
        A        7e+06;
        beta     0;
        Ta       10063.8;
    }
    hydrogenReaction
    {
        type     irreversibleArrheniusReaction;
        reaction "H2 + 0.5O2^1.0 = H2O";
        A        4.74342e+12;
        beta     0;
        Ta       10063.8;
    }
}

[openfoammaofnepo]

Problem solved. The activation energy is too small, so that the reaction is so weak.

Originally Posted by openfoammaofnepo

Hi All,

I tried to use PaSR to calculate a simple jet flame, firstly used infinitelyFastChemistry model to obtain an fully burning jet flame field, which seem reasonable. Then I changed the combustion model to PaSR, and if course changed other PaSR related parameter. When the simulation goes, the flame is convected downstream and finally it become just cold. What is the problem for the simulation? Anybody also has this experince?

I put my combustionProperties, chemistryProperties and reactions below:

combustionModel    PaSR<rhoChemistryCombustion>;
active  true;
infinitelyFastChemistryCoeffs
{
    semiImplicit    no;
    C               10;
}
laminarCoeffs
{
}
noCombustionCoeffs
{
}
PaSRCoeffs
{
    Cmix                1.0;
    turbulentReaction   yes;
//  useReactionRate     true;
}

chemistryType
{
    chemistrySolver   ode;  //EulerImplicit;
    chemistryThermo   rho;
}

chemistry           on;

initialChemicalTimeStep 1e-07;

EulerImplicitCoeffs
{
    cTauChem        1;
    equilibriumRateLimiter off;
}

odeCoeffs
{
    solver          Rosenbrock34;
    absTol          1e-12;
    relTol          0.01;
}

species
(
    CH4
    CO
    CO2
    H2
    H2O
    O2
    N2
);

reactions
{
//- for infinite fast reaction model
//  methaneReaction
//  {
//      type         irreversibleinfiniteReaction;
//      reaction      "CH4 + 2O2 + 7.5N2 = CO2 + 2H2O + 7.5N2";
//  }

//- for PaSR combustion model
    methaneReaction
    {
        type     irreversibleArrheniusReaction;
        reaction "CH4 + 2O2^1.0 = CO2 + 2H2O^1.0";
        A        7e+06;
        beta     0;
        Ta       10063.8;
    }
    hydrogenReaction
    {
        type     irreversibleArrheniusReaction;
        reaction "H2 + 0.5O2^1.0 = H2O";
        A        4.74342e+12;
        beta     0;
        Ta       10063.8;
    }
}

[Zhiheng Wang]

Use c= 0 to minimize the turbulent and laminar reaction time scale it must be low reynolds no case try c = in combustion PaSR directory.