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Old   November 22, 2012, 06:39
Question Premixed combustion model - help!
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Hesham Khalil
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Hye guys,

I am trying to simulate flame-vortex interaction in a swirl stabilized dump plane combustor, basically the effect of vortex shedding on the flame, using the premixed combustion model of fluent. I also try to deduce the frequency of the instabilities, which is equal to the acoustic longitudinal quarter wave mode of the combustor, to compare with the experiments.
The problem is that the wall temperature is not known to me, but both the mean temperature inside the combustor and the inlet velocity are known.
I have done two trials:
1- using the adiabatic premixed model, in which i don't need the wall temperature, and set the velocity inlet and pressure outlet boundary conditions at both combustor inlet and exit respectively, along with periodic boundary conditions in the span wise direction where only a quarter section of the combustor was used. I used DES with RKE model as submodel. The continuity equation doesnot converge easily, although i started from a RANS steady state solution.(pressure based with SIMPLE algorithm used).
2- using the non-adiabatic model, with the same set-up, but applying massflow inlet at the inlet, and idealgas for density, while applying no heat transfer at the walls, i note that the solution converge so easy without the need to start from steady state solution but the temperature keeps rising in the combustor and exceeds the adiabatic flame temperature and keeps going up!!

could you please advice which is the best combustion model to use? and if periodic boundary conditions are appropriate with DES or i shall solve the complete combustor? and what type of pressure i need to monitor if i want to capture the acoustics? is it the static pressure or the dynamic one?

Thanks for your help. it is greatly appreciated.
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