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-   -   Species transport model problem (http://www.cfd-online.com/Forums/fluent/74649-species-transport-model-problem.html)

argeus April 5, 2010 20:31

Species transport model problem
 
Hi,
I ve got a problem with species transport model reaction simulation. I have to simulate a supersonic combustion 2H2+O2->2H2O in a nozzle. Because of supersonic flow I use a coupled solver and standard k-eps and thats why I use species transport. Problem is, that when I try to use eddy-dissip. interaction model there was no reaction at all. Initializing of solution with high temperature and non zero fuel content does not help. And when I adjust the high temperature condition at pressure inlet (in some cases I need 1800K and maybe more) the solution has a convergence problem (courant number set to 0.5 and no solution). Some ideas why the reaction mechanism does not work? For instance, how the fluent knows an activation energy of the reaction by using eddy-dissip? Its good idea to use a eddy-dissip?
Thank you very much in advance...

hello2ap August 28, 2010 21:15

Quote:

Originally Posted by argeus (Post 253257)
Hi,
I ve got a problem with species transport model reaction simulation. I have to simulate a supersonic combustion 2H2+O2->2H2O in a nozzle. Because of supersonic flow I use a coupled solver and standard k-eps and thats why I use species transport. Problem is, that when I try to use eddy-dissip. interaction model there was no reaction at all. Initializing of solution with high temperature and non zero fuel content does not help. And when I adjust the high temperature condition at pressure inlet (in some cases I need 1800K and maybe more) the solution has a convergence problem (courant number set to 0.5 and no solution). Some ideas why the reaction mechanism does not work? For instance, how the fluent knows an activation energy of the reaction by using eddy-dissip? Its good idea to use a eddy-dissip?
Thank you very much in advance...

i also have the same problem

Marta October 19, 2010 08:08

Hi All, I am experiencing the same problem, but i cannot use the coupled solver, because my laptop can't afford occupying all that memory.
Now I am trying using lower relaxation factors for species conservation equations. Up to now, i did not manage to make my simulation converge.

Have you found a solution?

Thanks in advance,

Marta

Jenny_W March 11, 2013 12:16

Hi Everyone,
I am modelling compressible non-combustion reacting flow in FLUENT and facing the same problem. I tried all species transport models and increasing inlet temperature but they didn't work.
If anyone knows what may have gone wrong, please give me some suggestions.
Thank you,
Jenny

epc1 March 11, 2013 13:17

Quote:

Originally Posted by Jenny_W (Post 413161)
Hi Everyone,
I am modelling compressible non-combustion reacting flow in FLUENT and facing the same problem. I tried all species transport models and increasing inlet temperature but they didn't work.
If anyone knows what may have gone wrong, please give me some suggestions.
Thank you,
Jenny


Hello Jenny, can you be more specific on what is happening? Are reactions not happening at all?

Jenny_W March 11, 2013 17:50

Hi,
Thank you for your reply.
I am modelling atmospheric reactions which are not available in FLUENT library.

I have to fill in the reaction mechanism (including kinetic parameters) in the reaction panel.

I use k-e model. I choose species transport and turbulence-chemistry interactions (laminar finite rate, EDC etc).

After setting BCs, I initialise and patch a region of high temperature. The simulation runs for a few thousand iterations but there was no reaction - no products formed and the kinetic rate of reaction is zero.

Would you advise what could have gone wrong?
Thank you,
Jenny

epc1 March 11, 2013 19:02

Quote:

Originally Posted by Jenny_W (Post 413243)
Hi,
Thank you for your reply.
I am modelling atmospheric reactions which are not available in FLUENT library.

I have to fill in the reaction mechanism (including kinetic parameters) in the reaction panel.

I use k-e model. I choose species transport and turbulence-chemistry interactions (laminar finite rate, EDC etc).

After setting BCs, I initialise and patch a region of high temperature. The simulation runs for a few thousand iterations but there was no reaction - no products formed and the kinetic rate of reaction is zero.

Would you advise what could have gone wrong?
Thank you,
Jenny

Ok Jenny,

You also have to patch in the products of the chemical reaction in order for it to procede.

Hope this helps

Jenny_W March 12, 2013 04:50

Hi Ernesto,
I will do that. Thank you very much for your help.
Regards,
Jenny


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