Soot yield in FDS

[Derek]

I was reading a post from 2008, to confirm, is soot yield still assumed to be .01 automatically in FDS (propane)?

 

Example:

Taking the PVC.fds example species code below (slightly modified); does FDS automatically recalculate soot yield to reflect this defined fuel? or does it need to be specified?

If it does automatically recalculate the soot yield, what formula does it use?

 

&SPEC ID = 'PVC', FORMULA = 'C2H3Cl', ENTHALPY_OF_FORMATION = 297.492 /
&SPEC ID = 'OXYGEN',            LUMPED_COMPONENT_ONLY = .TRUE. /
&SPEC ID = 'NITROGEN',          LUMPED_COMPONENT_ONLY = .TRUE. /
&SPEC ID = 'HYDROGEN CHLORIDE', LUMPED_COMPONENT_ONLY = .TRUE. /
&SPEC ID = 'WATER VAPOR',       LUMPED_COMPONENT_ONLY = .TRUE. /
&SPEC ID = 'CARBON MONOXIDE',   LUMPED_COMPONENT_ONLY = .TRUE. /
&SPEC ID = 'CARBON DIOXIDE',    LUMPED_COMPONENT_ONLY = .TRUE. /
&SPEC ID = 'SOOT',              LUMPED_COMPONENT_ONLY = .TRUE. /

&SPEC ID = 'AIR', SPEC_ID = 'OXYGEN','NITROGEN', VOLUME_FRACTION =1.53,5.76, BACKGROUND=.TRUE. /
&SPEC ID = 'PRODUCTS', SPEC_ID ='HYDROGEN CHLORIDE','WATER VAPOR','CARBON MONOXIDE','CARBON DIOXIDE','SOOT','NITROGEN',
           VOLUME_FRACTION = 1.0,1.0,0.14,0.96,0.90,5.76 /

&REAC FUEL='PVC', HEAT_OF_COMBUSTION=24000, SPEC_ID_NU='PVC','AIR','PRODUCTS',
NU=-1,-1,1 /

 

 

 

 

 

Thanks!

[dr_jfloyd]

Have you tried reading the User's Guide and Technical Reference?

[Derek]

The user guide does state .01 is still the default. I know you can define soot yield by placing something like "SOOT_YIELD=0.01 " in the reaction line. Other than the default or specifying it (which I did find in the user guide), can FDS calculate the soot yield based on the species setup below? I didn't find more detail that part of my question unfortunately.

On Wednesday, October 22, 2014 2:45:29 PM UTC-4, Derek wrote:

[Derek]

I did see a reference to soot yield being specified only if the 'simple chemistry' approach is being used, which I am pretty sure this method of defining species below is not the 'simple chemistry' approach. I'd appreciate confirmation if possible. Thanks.

[Kevin]

Which User's Guide are you looking at? What date, FDS version?

SOOT_YIELD is only meaningful for simple chemistry. When all the species and reaction stoichiometry are explicitly defined, it is not simple chemistry.

[Derek]

Version 6.1.1.

Thanks, I was just confirming that since the example below was not a simple chemistry setup, that FDS does indeed calculated the soot yield (rather than use the default .01). Also, does the userguide break down how the soot yield is specifically calculated formula wise (for the non simple chemistry setup), or would that be in the Technical Reference? I went through the userguide quickly, but didn't find what I was looking for.

[Craig Weinschenk]

FDS does not calculate the soot yield. For simple chemistry it needs to be specified by the user and in the example you posted, the user needs to determine the soot yield from experiments or literature and then balance the chemical reaction.

[dr_jfloyd]

Where in the guide does it say the default soot yield is 0.01? I don't see anywhere we state this (if we do we need to fix it).  The descriptions for soot yield in the are:

12.1.1

SOOT_YIELD The fraction of fuel mass converted into smoke particulate, ys. Note that this parameter is only appropriate when the simple chemistry model is applied. (Default 0.)

Table 17.23 REAC (Reaction Parameters)

SOOT_YIELD Real Section 12.1.1 kg/kg 0.0

On Wednesday, October 22, 2014 4:01:57 PM UTC-4, Derek wrote: