[cunconbkhp]

Hi foamers!

I'm learning to use the fireFoam solver.

While running the "oppositeBurningPanels" tutorial, i've had this problem : i can view the total mass loss rate of the solid panel (solid region) but when i've tried to estimate the heat release rate of the fluid region (volintegrate of Qdot in region0), i have only the heat realease rate of the burner (always 60 kW). The pyrolysis gas was not burned??? i've verified all the boundary conditions at the solid/fluid interfaces: nothing wrong :

for U :
"(region0_to.*)"
{
type mappedFlowRate;
nbrPhi phiGas;
value uniform (0 0 0);
}

for T :

for C3H8
"(region0_to.*)"
{
type totalFlowRateAdvectiveDiffusive;
value $internalField;
}

"(region0_to.*)"
{
type compressible::turbulentTemperatureRadCoupledMixed;
Tnbr T;
kappaMethod fluidThermo;
qrNbr none;
qr qr;
value $internalField;
}

the function for the total HRR is like below :

HRR_vol
{
type volFieldValue;
//functionObjectLibs ("libfieldFunctionObjects.so");
libs ("libfieldFunctionObjects.so");
log true;
writeControl adjustableRunTime;
writeInterval 5e-2;
writeFields false;
regionType all;
operation volIntegrate;
enabled true;
fields
(
Qdot
);
}

So please help me to resolve this problem?.

Thanks in advance!

[Kummi]

Hi,
The pyrolysis has occurred burning solid fuel and using coupled boundary conditions, the volatile gases relased during pyrolysis (phigas) is transferred into fluid zone.

In OpenFoam, Pyrolysis model is solved based on regionmodel. Region model in the sense of 1D, that is the phiGas is transferred (normal) perpendicular to fluid zone.
Thank you

[cunconbkhp]

Hi Kummi, thank you for your reply.

if the pyrolysis gas is transfer to the fluide zone and is converted to the fuel gas (C3H8), they will burn when mix with air in the region0. Is that right?. I want to output the total HRR of the region0 but with my function, i can only output the HRR of the burner but not the HRR from the wood's pyrolysis. Can we do it with fireFoam?

[Kummi]

Hi,
I have worked only with solid region not with fluid, so no idea about HRR unless I look into it. I have searched regarding HRR and found some useful information for you.
Heat Release Rate in fireFoam
HRR in fireFoam

https://hal.archives-ouvertes.fr/hal...almon_2020.pdf
https://www.diva-portal.org/smash/ge...FULLTEXT01.pdf
https://www.researchgate.net/publica..._Configuration
Hope it helps.
Thank you

[cunconbkhp]

Hi Kummi!

Thanks for the references. My problem is solved.

I have others question about the pyrolysis in fireFoam.

Q1 : do you know how the solver accounts for the real heat of combustion of the solid combustible.

By example : the heat of combustion of wood is abour 16000 kJ/kg but the heat of combustion of propane ("oppositeBurningPanels" tutorial) is about 45000 kJ/kg. If all the pyrolysis gas is converted to propane, will we over estimate the heat realese rate of wood?

Q2 : the pyrolysis reaction for solid is wood^4.86 = char + gas. Does this mean 50% of mass will become char and 50% of mass will become gas? By example if i want to have 20% of mass for char and 80 % of mass for gas, can i write the reaction like this : wood^4.86 = 0.2*char + 0.8*gas

Thanks

[cunconbkhp]

For whom might be interested in my questions. I've found the answer for the Q2 : the mass fraction of char and gas are calculated from the density of condensed phase like below :

+ % to gas = 1-rho_char/rho_wood
+ % to char = rho_char/rhowood.

You can find more informations in this file : solidChemistryModel.C .