finite rate chemistry for methane

[aditya14172]

facing issue with finite rate chemistry of methane, the increase in temperature is not enough and also ignition is not sustaining

methane.txt

[drjfloyd]

How much OXYGEN have you defined as being present in your domain?

[aditya14172]

21%, same as the amount of oxygen present in atmosphere.

[drjfloyd]

Where in your input file did you define that the SPEC of OXYGEN has an initial volume fraction of 21 %?

[aditya14172]

Sir by default for air it is defined: &SPEC ID='AIR', BACKGROUND=T,
SPEC_ID(1)='OXYGEN', VOLUME_FRACTION(1)=0.2076,
SPEC_ID(2)='NITROGEN', VOLUME_FRACTION(2)=0.7825,
SPEC_ID(3)='WATER VAPOR', VOLUME_FRACTION(3)=0.0095,
SPEC_ID(4)='CARBON DIOXIDE', VOLUME_FRACTION(4)=0.0004 / like for the above case if i see in slice file for oxygen i can see the variation of oxygen volume fraction
please suggest any other error i might be making

[drjfloyd]

"The array SPEC_ID_NU contains the list of tracked species participating in the reaction as a product or
reactant."

Your REAC uses the tracked species OXYGEN. Not the lumped background species AIR.

[aditya14172]

Sir, i have tried that case too , even that is not working, So referring the User Guide i have tried this format of defining SPEC_ID_NU

[mcgratta]

Take a look at the Smyth Slot Burner validation cases. Run them, and then use this input file for your own case.

[aditya14172]

Sir, Smyth Slot Burner has infinite rate chemistry for R1. I need to learn what should I do for single step finite rate chemistry.

[mcgratta]

What case have you tried that you say is not working? What were the results of your effort?

[aditya14172]

Sir,here is the case, getting the similar results:
methane.txt

[mcgratta]

The case Smyth_AM_fine.fds has a three step reaction, one fast, two finite-rate.

[aditya14172]

Yes sir, but here i am trying for a single step finite rate in case of methane.

[mcgratta]

Well, I've never tried to run a single step finite rate simulation of methane combustion. I cannot say whether your kinetic parameters are appropriate or not. I cannot say whether your grid is resolved enough.

[drjfloyd]

Please carefully read the User's Guide and look at the examples that use Arrhenius chemsitry and also review how species are handeled in FDS.

As stated in the User's Guide and as I posted here earlier: "The array SPEC_ID_NU contains the list of tracked species participating in the reaction as a product or reactant."

&REAC ID = 'R1'
FUEL = 'METHANE'
A = 5.012e16
E = 151080
SPEC_ID_NU = 'METHANE','OXYGEN','CARBON DIOXIDE','WATER VAPOR'
NU = -1,-2,1,2
SPEC_ID_N_S = 'METHANE','OXYGEN'
N_S = 0.1,1.65 /

R1 is not using AIR. R1 is using OXYGEN.

Here is your input for the tracked species of oxygen:
&SPEC ID='OXYGEN' /

You have not given an initial concentration.