CO and soot yield

[AmirrezaHBSH]

Hello, I have a lumped fuel that defined as C0.77 H0.96 O0.79. I am trying to use the Default Hydrocarbon Combustion Chemistry section 5.1.2 reference guide to calculate the stoichiometric coefficients, however, I can not define the yield of soot and CO. Any suggestion on how I should proceed would be highly appreciated.

[mcgratta]

Soot yield is not an intrinsic property of the molecular formula. It generally comes from doing an experiment and measuring the amount of particulate matter that is generated by the fire.

[drjfloyd]

&SPEC ID='CARBON DIOXIDE',LUMPED_COMPONENT_ONLY = .TRUE./

What does the user's guide say the input LUMPED_COMPONENT_ONLY=.TRUE. means?

[AmirrezaHBSH]

&SPEC ID='CARBON DIOXIDE',LUMPED_COMPONENT_ONLY = .TRUE./

What does the user's guide say the input LUMPED_COMPONENT_ONLY=.TRUE. means?

The logical parameter LUMPED_COMPONENT_ONLY indicates that the species is only present as part of a
lumped species. When T, FDS will not allocate space to track that species individually.

[drjfloyd]

Do you see why you have gotten the error message?

[AmirrezaHBSH]

Do you see why you have gotten the error message?

Yes thank you I completely understand the problem, however, I defined the input file for the first case by defining primitive species, and the second case using lumped species approach, the HRR for these two cases with identical conditions is different. Am I missing something related to this issue?

Two inputs are as follows:

1:
&SPEC ID='NITROGEN', BACKGROUND=.TRUE./
&SPEC ID='METHANE', LUMPED_COMPONENT_ONLY = .TRUE./
&SPEC ID='CARBON MONOXIDE', LUMPED_COMPONENT_ONLY = .TRUE./
&SPEC ID='CARBON DIOXIDE'/
&SPEC ID='HYDROGEN', LUMPED_COMPONENT_ONLY = .TRUE./
&SPEC ID='OXYGEN'/
&SPEC ID='WATER VAPOR'/

&SPEC ID = 'FUEL',SPEC_ID='METHANE','CARBON MONOXIDE','CARBON DIOXIDE','HYDROGEN', VOLUME_FRACTION=0.13,0.5,0.15,0.22 /

&INIT XB = 0.0,0.1,0.0,0.1,0.0,0.1,
SPEC_ID(1)='FUEL', MASS_FRACTION(1) = 0.7,
SPEC_ID(2)='OXYGEN', MASS_FRACTION(2)= 0.3/

&COMB FIXED_MIX_TIME=0.1 /

&REAC FUEL='FUEL'
SPEC_ID_NU='FUEL','OXYGEN','CARBON DIOXIDE','WATER VAPOR'
NU=-1,-0.62,0.78,0.48/

[AmirrezaHBSH]

2:
&SPEC ID='NITROGEN', BACKGROUND=.TRUE./
&SPEC ID='METHANE'/
&SPEC ID='CARBON MONOXIDE' /
&SPEC ID='CARBON DIOXIDE' /
&SPEC ID='HYDROGEN'/
&SPEC ID='OXYGEN' /
&SPEC ID='WATER VAPOR' /

&INIT XB = 0.0,0.1,0.0,0.1,0.0,0.1,
SPEC_ID(1)='METHANE', MASS_FRACTION(1) = 0.0692,
SPEC_ID(2)='CARBON MONOXIDE', MASS_FRACTION(2) = 0.4615,
SPEC_ID(3)='CARBON DIOXIDE', MASS_FRACTION(3)= 0.2231,
SPEC_ID(4)='HYDROGEN', MASS_FRACTION(4)=0.0154,
SPEC_ID(5)='OXYGEN', MASS_FRACTION(5)=0.2308 /

&COMB FIXED_MIX_TIME=0.1 /

&REAC FUEL='METHANE'
SPEC_ID_NU='METHANE','OXYGEN','CARBON DIOXIDE','WATER VAPOR'
NU=-1,-2,1,2 /

&REAC FUEL='CARBON MONOXIDE'
SPEC_ID_NU='CARBON MONOXIDE','OXYGEN','CARBON DIOXIDE'
NU=-1,-0.5,1 /

&REAC FUEL='CARBON DIOXIDE'
SPEC_ID_NU='CARBON DIOXIDE','CARBON MONOXIDE','OXYGEN'
NU=-1,1,0.5 /

&REAC FUEL='HYDROGEN'
SPEC_ID_NU='HYDROGEN','OXYGEN','WATER VAPOR'
NU=-1,-0.5,1 /

[drjfloyd]

Double check your math. When I do a quick calc with integer values for molecular weight:
In the first case, CH4 is 9 % mass fraction of FUEL. So your INIT of 70 % FUEL means a mass fraction of 6.3 %. In your second case you have 6.9 %

[AmirrezaHBSH]

Double check your math. When I do a quick calc with integer values for molecular weight: In the first case, CH4 is 9 % mass fraction of FUEL. So your INIT of 70 % FUEL means a mass fraction of 6.3 %. In your second case you have 6.9 %

Thank you so much. All calculations were checked and the mass fractions are now correct. Although the difference is not significant like previous case, there is still a small deviation between two HRR plots versus time in both cases. Calculated heat of combustion by FDS in Lumped species approach is larger than the heat of combustion that I can calculate manually based on EPUMO2 for lumped fuel.

Inputs are as follows:

Lumped:
&SPEC ID='NITROGEN', BACKGROUND=.TRUE./
&SPEC ID='METHANE', LUMPED_COMPONENT_ONLY = .TRUE./
&SPEC ID='CARBON MONOXIDE', LUMPED_COMPONENT_ONLY = .TRUE./
&SPEC ID='CARBON DIOXIDE'/
&SPEC ID='HYDROGEN', LUMPED_COMPONENT_ONLY = .TRUE./
&SPEC ID='OXYGEN'/
&SPEC ID='WATER VAPOR'/

&SPEC ID = 'FUEL',SPEC_ID='METHANE','CARBON MONOXIDE','CARBON DIOXIDE','HYDROGEN', VOLUME_FRACTION=0.13,0.5,0.15,0.22 /

&INIT XB = 0.0,0.1,0.0,0.1,0.0,0.1,
SPEC_ID(1)='FUEL', MASS_FRACTION(1) = 0.7,
SPEC_ID(2)='OXYGEN', MASS_FRACTION(2)= 0.3/

&COMB FIXED_MIX_TIME=0.1 /

&REAC FUEL='FUEL'
SPEC_ID_NU='FUEL','OXYGEN','CARBON DIOXIDE','WATER VAPOR'
NU=-1,-0.62,0.78,0.48/

Primitive:
&SPEC ID='NITROGEN', BACKGROUND=.TRUE./
&SPEC ID='METHANE'/
&SPEC ID='CARBON MONOXIDE' /
&SPEC ID='CARBON DIOXIDE' /
&SPEC ID='HYDROGEN'/
&SPEC ID='OXYGEN'/
&SPEC ID='WATER VAPOR'/

&INIT XB = 0.0,0.1,0.0,0.1,0.0,0.1,
SPEC_ID(1)='METHANE', MASS_FRACTION(1) = 0.063,
SPEC_ID(2)='CARBON MONOXIDE', MASS_FRACTION(2) = 0.42,
SPEC_ID(3)='CARBON DIOXIDE', MASS_FRACTION(3)= 0.203,
SPEC_ID(4)='HYDROGEN', MASS_FRACTION(4)=0.014,
SPEC_ID(5)='OXYGEN', MASS_FRACTION(5)=0.3 /

&COMB FIXED_MIX_TIME=0.1 /

&REAC FUEL='METHANE'
SPEC_ID_NU='METHANE','OXYGEN','CARBON DIOXIDE','WATER VAPOR'
NU=-1,-2,1,2 /

&REAC FUEL='CARBON MONOXIDE'
SPEC_ID_NU='CARBON MONOXIDE','OXYGEN','CARBON DIOXIDE'
NU=-1,-0.5,1 /

&REAC FUEL='CARBON DIOXIDE'
SPEC_ID_NU='CARBON DIOXIDE','CARBON MONOXIDE','OXYGEN'
NU=-1,1,0.5 /

&REAC FUEL='HYDROGEN'
SPEC_ID_NU='HYDROGEN','OXYGEN','WATER VAPOR'
NU=-1,-0.5,1 /

[drjfloyd]

See 13.1.2 in the User's Guide.