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-   -   about reaction of oxygen and CH4 (http://www.cfd-online.com/Forums/fluent/28695-about-reaction-oxygen-ch4.html)

Devy July 8, 2001 05:38

about reaction of oxygen and CH4
 
Hi,

Now I am studying TUT 8.in fluent mannul, "Chemical Mixing and Gas Combustion". I don't consider the reaction of air and CH4.I just consider the reaction of oxygen and CH4.So I remove the N2 from material pannel.And I change the air as to oxygen in the boundary of air-inlet,and I don't change the other model.

When the solution is converged,I found the temperature rised to 10000K.And this is not true.

I've tried everything I can imagine!!!

Would you give me some advice?

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

Devy 2001.7.7

John C. Chien July 8, 2001 12:38

Re: about reaction of oxygen and CH4
 
(1). I am not using the code and I am not familiar with this part of your problem. (2). But, I have two suggestions: (a). Follow only the tutorial examples and make sure that you are getting good solutions. Then if you are satisfied, you can change parameters within the sample cases. This will make sure that you are still doing the "same thing". (b). "trial-and-error" approach is not going to work, unless you are familiar with the program source codes. (for a black box, this is difficult, I guess) And even if you can obtain a solution by trial-and-error, it is likely that the solution is just a solution and it is not the correct one, unless it is validated. (3). If you can call your support engineer, I think, that's the best solution.

Kay July 10, 2001 22:47

Re: about reaction of oxygen and CH4
 
Hi,Devy: Have you solved your problem? I encountered the same problem. Kay

Christian July 11, 2001 02:32

Re: about reaction of oxygen and CH4
 
Hi Devy

As I understand your case, you have taken away the N2 and added O2 instead and then added the needed CH4 for the combustion to be stoichiometric. If you substituted the N2 with O2 in the air, I would expect a higher temperature due to the higher O2 content and due to that you don't have to heat up any inert N2.

Christian

Devy July 11, 2001 03:30

Re: about reaction of oxygen and CH4
 
But the temperature should not be so high.

John C. Chien July 11, 2001 04:49

Re: about reaction of oxygen and CH4
 
(1). You may want to repeat the same process for other known chemical reactions. (2). In this way, you should know whether it is due to input error or code error.

J July 13, 2001 08:07

Re: about reaction of oxygen and CH4
 
Use the pdf model. It is more valid for this type of problem anyway. You shouldn't be getting peak temperatures much above ~3500K depending on your problem. Use Cp calcualated by mixing law and put the polynomials in for each species if using f.rate /eddy model. This tends to reduce temps.


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