Combustion of walls that facing each other

Update: January 18, 2018
OpenFOAM 4.x

Case directory

$FOAM_TUTORIALS/combustion/fireFoam/les/oppositeBurningPanels

Summary

Propane flows in from the region "burner" that is a part of the floor of the air-filled domain, and burns. A part of the walls (transparent part) facing the burner is made of combustible material. All surfaces other than the floor and combustible walls are assumed to be open, and calculations are made for 5 seconds after ignition.

Model geometry Model geometry

The combustible walls and the empty space are calculated separately, and the whole phenomenon is calculated by mapping the solutions.

The combustion reactions of the chemical species, propane and air, in the empty space are defined in the file "reactions" in the directory "constant" as follows. The properties of each chemical species are defined in the file "thermo.compressibleGas" in the same directory.

species
(
    O2
    H2O
    C3H8
    CO2
    N2
);
reactions
{
    propaneReaction
    {
        type         irreversibleinfiniteReaction;
        reaction     "C3H8 + 5O2 + 18.8N2 = 3CO2 + 4H2O + 18.8N2";
    }
}

These two files, "reactions" and "thermo.compressibleGas", are imported in the file "thermophysicalProperties" in the directory "constant" to do the configuration.

The material of the walls and the combustion reactions are defined in the file "reactions" in the directory "constant/panelRegion" as follows. We can see that the wall material (wood) is burning and turning into charcoal (char) and gas.

species
(
    wood
    char
);
gaseousSpecies
(
    gas
);
reactions
{
    charReaction
    {
        type        irreversibleArrheniusSolidReaction;
        reaction    "wood^4.86 = char + gas";
        A           7.83e10;
        Ta          15274.57;
        Tcrit       400;
    }
}

The meshes are as follows.

Mesh Meshes
Meshes of combustible walls Meshes of combustible walls

The calculation result is as follows. Volume rendering is used to draw the distribution of CO2.

CO2 at 1 sec (CO2) CO2 at 1 sec (CO2)
CO2 at 2 sec (CO2) CO2 at 2 sec (CO2)
CO2 at 3 sec (CO2) CO2 at 3 sec (CO2)
CO2 at 4 sec (CO2) CO2 at 4 sec (CO2)
CO2 at 5 sec (CO2) CO2 at 5 sec (CO2)

The temperature of the combustible wall (maximum X-coordinate side) is shown below.

Temperature of the combustible wall (maximum X-coordinate side) (T)

The volume fraction of the material "wood" in the combustible wall (maximum X-coordinate side) at the final time is shown below. It can be seen that the volume fraction is decreasing in the intense combustion part at the bottom center of the region.

5秒での体積率(wood) Volume fraction of combustible wall (maximum X-coordinate side) in 5 sec (wood)

Commands

cp -r $FOAM_TUTORIALS/combustion/fireFoam/les/oppositeBurningPanels oppositeBurningPanels
cd oppositeBurningPanels

# Make base meshes
blockMesh

# Refine a part of the meshes
topoSet -dict system/cRefine.topoSetDict
refineMesh -overwrite -dict system/refineMeshDict

# Make combustible walls
topoSet -dict system/f.topoSetDict
extrudeToRegionMesh -overwrite

# Make burner
topoSet -dict system/fBurner.topoSetDict
createPatch -overwrite

cp 0/ph_rgh.orig 0/ph_rgh

decomposePar -force
decomposePar -region panelRegion
decomposePar -fields

mpirun -np 6 fireFoam -parallel

reconstructPar
reconstructPar -region panelRegion

paraFoam -touch
paraFoam -touch -region panelRegion

paraFoam
paraFoam -region panelRegion

Calculation time

2 hours 25 minutes 12.78 seconds *6 parallel, Inter(R) Core(TM) i7-2600 CPU @ 3.40GHz 3.40GHz