SOOT molar mass

[Antony]

Hi,

I have 2 test files for the same reaction, C4.5H6.4O1. One of it defined the chemical balance equation, for the another one defined the CO yield and SOOT yield. However, from the .out file, I found that the soot molar mass is set at 12g/mol in the chemical balance equation file; while define the CO and soot yield file, the soot molar mass is set at 10g/mol. Could you explain please?

Attachment Test3b: define chemical balance equation; Test3d: set the CO and soot yield

Thanks,
Antony

[dr_jfloyd]

See  SOOT_H_FRACTION in 12.1.1 Simple Chemistry Parameters in the User's Guide

[Antony]

Thanks, but why assuming 10% of soot are hydrogen? Will this hydrogen burn again and release heat?

In addition, I am simulating a reaction process which combine of 2 materials with 2 chemical equations. Could I simplify the 2 equations into one by using simple chemistry parameters? How do obtain the combined heat of combustion, CO yield soot yield, etc.

Thanks,
Antony

[Antony]

I read the technical guide 5.1.2 example for methane air reaction. The chemical balance equation will as follows: (taken y_CO=0.1, y_SOOT=0.01)
CH4 + 1.9581(O2+3.76N2) --> 2H2O + 0.0571CO + 0.9295CO2 + 0.0133C + 7.3624N2
If include the Y_CO_INFTY and 40% humidity in the background air species, how would the above equation be changed to?
The matrix shown in the example is mass fraction or mole fraction?
Could you tell me which source code shall I look into details? fire.f90?

[dr_jfloyd]

Soot is not pure carbon: http://fire.nist.gov/bfrlpubs/fire93/PDF/f93056.pdf

At this time, simple chemistry does not include a soot oxidation reaction.  Whatever mass becomes soot, will remain as soot.

With more than one fuel you could pick the fuel representing the most mass or you could do a mass or molar average of the fuel chemistry and CO/Soot yields to create a new fuel.

The Example table in 5.1.2 is mass fraction.

Reactions are processed in read.f90

With Y_CO2_INFTY and HUMIDITY you are simply adding terms for CO2 and H2O to air.  So instead of 1.9581(O2+3.76N2)  you would have 1.9581(O2+aN2+bCO2+cH2O) where a,b,c give you the correct mass fractions for your selected CO2 and H2O inputs