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seaspace May 26, 2003 22:51

Help on premixed combustion heat
 
I try to simulate 2-d premixed combustion of methane and air in porous media burner with a laminar flame. Overall reaction model(ch4+2o2--->co2+2h2o) based on Arrhenius reaction laws was employed.

When using the reaction model, one should have the exact velues of some related parameters,eg. the pre-exponential factor,heat of reaction per unit mass reactant and activation energy. After refering to some publications, I was confuseded completely because no any two papers have the same values.

What are the exact velues of the parameters on earth?

What should i do?

Thanks to any response!

Seaspace

Volker May 27, 2003 04:38

Re: Help on premixed combustion heat
 
Hi, The heat of reaction shouldn't be a problem, but I don't think there is such a thing as 'exact' pre-exponential factors and activation energy if you are looking at the overall reaction. As you are describing several hundred elementary reactions in one step, your two parameters can only cover a narrow range of conditions (if they manage that) depending on your application. I would recommend starting with a set of parameters from literature and see if the results make sense. Look for articles by Zhou, Pereira, Bouma, De Goey, Hsu, Ellzey, Viskanta or Echigo. Hope that helps.

Volker

matej May 27, 2003 05:28

Re: Help on premixed combustion heat
 
HI,

as Volker said, the 'Activation energy' is always the same,preexponential changes. To check it, bets would be to start with literature values and check the flame velocity S_L under normal condition if you get about the right velocity. Generally most of the codes takes the values for global reactions from Westbrook:

@Article{Westbrook, author = "Westbrook, Ch.K., Dryer,F.L.,", title = "Chemical Kinetic Modeling of Hydrocarbon Combustion", journal = "Prog. Energy Combustion Science", year = 1984, volume = 10, pages = {1--57} }

or:

"On Simplified Reaction Mechanisms for the Oxidation of Hydrocarbon Fuels in Flames by C. K. Westbrook and F. T. Dryer", Combustion Science and Technology, 1985, Vol.43, pp. 333-339.

Are you sure, that single step global methane will do in porus burner? no catalysis?

matej


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