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-   -   WGS as equilibrium reaction? (http://www.cfd-online.com/Forums/fluent/45356-wgs-equilibrium-reaction.html)

Jackie July 11, 2007 15:39

WGS as equilibrium reaction?
 
Hi,Greg Perkins,

Recently, I read your paper (ANZIAM J.45(E) ppC817-830,2004) which is very interesting. And in this paper,you mentioned that 'the water-gas-shift reaction,R6 is modelled as equilibrium reaction'.

According to the definition of Volumetric reaction rate (DEFINE_VR_RATE), it seems that the reaction rate is always requested, instead of the equilibrium relation. So, could you please clarify how to implement the equilibirum reaction in FLUENT?

Hope to get help from you and thanks in advance.

Phil July 11, 2007 21:48

Re: WGS as equilibrium reaction?
 
The non-premixed, premixed and partially premixed models can be run using the equilibrium assumption. Or you can add a flamelet library or replace it with a flamelet library.

You should read these sections in the user guide.

Phil

Jackie July 12, 2007 09:50

Re: WGS as equilibrium reaction? (..Greg Perkins)
 
Thanks,Phil,

I am interested in using the finite-rate approach to define my rate expressions(4 reactions),in which WGS is also included. Then, under this framwork, how to treat WGS reaction specially as equilibrum reaction is what I am concerning.

It seems that Greg Perkins has solved this problem. I am not sure how he achieved this. Please give the comments on it if anyone has some ideas.

Phil July 15, 2007 09:26

Re: WGS as equilibrium reaction? (..Greg Perkins)
 
As far as I know an equilibrium reaction means that there is exactly enough air to turn all the fuel to products, and leave no excess air or fuel.

Bearing this in mind I expect that you need to calculate the air fuel ratio to get a stoichiometric mixture.

You may need to write a UDF to calculate the equivalence ratio and you will then be aiming for an equivalence ratio of 1 in the main mean bulk of your model, with mixing only.

This is my understanding of the equilibrium reaction but I could be wrong. Some input from Greg Perkins would be helpful.

Phil

Kim July 23, 2007 04:38

Re: WGS as equilibrium reaction?
 
Hi, Jackie!

I am working at fuel cell modeling and have same problem with writing the water-gas-shift reaction as equilibrium reaction in my UDF. I'm wondering if you solved this problem meanwhile.

Regards Kim


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