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karthick August 2, 2001 14:18

reaction rate
i am modelling a diffusion flame. I am using methane as fuel and oxygen as oxidizer.I am using finite rate chemistry model. I want to know the production rates of the products and the consumption rates of reactants. can anyone help me in this regard? thanks. karthik

Jin-Wook LEE August 2, 2001 20:37

Re: reaction rate
FLuent has the database for the reaction rate coefficients of methane-air reacton. I think that you can use the coefficients for methane-oxygen reaction if you do not have any alternative.

One comment : I recommend 'finite rate / eddy dissipation' rather than 'finite rate only' for the diffusion flame, if your system belong to the turbulent flow regime.

Sincerely, Jinwook

karthick August 3, 2001 00:03

Re: reaction rate
thank very much for the reply. my flow conditions lie within laminar regim. i think i must use finite rate chemistry and i am using the database values as inputs to the finite rate chemistry calculation in the fluent. but after some iterations i want to know the 'consumption rates of reactants and produstion rates of products'. can u please suggest me how to get it.

thank you once again.


Jin-Wook LEE August 3, 2001 04:54

Re: reaction rate
I hope that following procedures would be helpfull to you.

Display --> Contour --> Contours of Reactions --> Rate of Reaction-1(or 2, 3...)

Report --> Volume Integral(or Surface Integral) --> Rate of Reaction-1(or 2, 3...)

Sincerely, Jinwook

karthik August 3, 2001 13:23

Re: reaction rate
Once again i thank u for ur reply. I actually want to have production rates of each and every product species and consumption rates of each and every reactants. I don't want to have overall reaction rates. take the case of methane reacting with oxygen.

CH4 + 2O2 --> CO2 + 2H2O

i want to have rate at which methane is being consumed. not the reaction rate of above reaction.

THANKS karthik

Devy August 4, 2001 11:04

Re: reaction rate
Now I am studying TUT fluent mannul, "Chemical Mixing and Gas Combustion". I don't consider the reaction of air and CH4.I just consider the reaction of pure oxygen and CH4.So I remove the N2 from material pannel.I change the air as to oxygen in the boundary of air-inlet.And I use Cp calcualated by mixing law and put the piecewise-polynomials in for each species. I don't change the other model.

When the solution is converged,I found the temperature rised to 4800K.And this is not true.Theoretical values of combustion temperature can be obtained from industry standard thermochemical codes for pure oxygen and CH4.And the temperature is about 2800K.

I've tried everything I can imagine!!!

Would you give me some advice?

Thanks a lot, in advance......

Devy 2001.8.5

Ugur August 5, 2001 17:54

Re: reaction rate
I don't know where you get the temperature of 2800 K as maximum flame temperature, but if you consider a constant volume adiabatic combustion, it can be upto 6000 K, for stoichiometric combustion.


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