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-   -   Methane+air temperature too high (http://www.cfd-online.com/Forums/fluent/33858-methane-air-temperature-too-high.html)

Stanislav Kraev June 1, 2004 16:07

Methane+air temperature too high
 
Could anybody tell me, why resulting temperature of methane combustion is too high (>2000K). I used several turbulent models (results are quite similar), Species Transport model and standard chemical models form fluent library. Radiation doesn't change the temperature a lot.

Arun June 1, 2004 21:30

Re: Methane+air temperature too high
 
Hi Stanislav,

Try doing the 2-step reaction. One step reaction might give an over prediction of temperature. All the best.

Arun

Stanislav Kraev June 2, 2004 01:43

Re: Methane+air temperature too high
 
Yeah. I tried 2-step reaction. Temperature still >2000K.

Arun June 2, 2004 02:36

Re: Methane+air temperature too high
 
Did you try changing the grid? Sometimes grid resolution can also show variations in the solution. Also look at the time step of your reaction carefully. Sometimes the code might be stable for large time steps but will not give you the right solution. All the best.

Arun

Stanislav Kraev June 2, 2004 02:50

Re: Methane+air temperature too high
 
Thanks. I think I found where the problem was. I used velocity inlets (don't know why :)). Tested pressure inlets and it's ok now (~1300K). Grid resolution was quite good and I used stationary case. If somebody want to tell something about my problem, it would be cool! See you.

zxaar June 3, 2004 10:54

Re: Methane+air temperature too high
 
follow the tutorial , in that they mention if they modify the CP to polynomial fit rather than constant , the temperature it predicts is less that what u otherwise get


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