A question about soot yield and CO yield

[Haiyuan Piao]

Hi everyone,

I wish to put a fire in a compartment. The fire is t square at first stage, soot yield is 0.07, CO yield is 0.04 before ventilation limit. Once the fire reach the ventilation limit, I need the soot yield = 0.14 and CO yield = 0.4. Because both products are proportion with HRR, I guess I couldn't use as User Guide with constant mass flux as follows,

&SPEC ID='MY SMOKE', MW=29., MASS_EXTINCTION_COEFFICIENT=8700. /

&SURF ID='SMOLDER', TMP_FRONT=1000., MASS_FLUX(1)=0.0001, SPEC_ID='MY SMOKE',

COLOR='RED' /

&VENT XB=0.6,1.0,0.3,0.7,0.0,0.0, SURF_ID='SMOLDER' /

How to do this kind of problem? Many many thanks!

Haiyuan

[Kevin McGrattan]

The simple chemistry model does not allow this. You could try the two step option, but it will be difficult to control the yields. The chemistry of under-ventilated combustion or smoldering is complex, and for a large-scale fire scenario, you probably have to just control the generation rate of smoke and CO using RAMPs.