Learning Forum

[singh.112]

HI all,

I am working on modelling self-excited thermoacoustic instability in gas turbine combustor. I am using FGM combustion model with LES. However I am unable to capture any periodic behavious from the simulations as shown in experiments. With the same boundary conditions when I tried of using EDC with URANS, I was able to get periodic behaviour of the flame. Running EDC is computationaly very expensive I wanted to run FGM. Any help will be higly apprecited. 

Thanks in advance. 

 

[Ren]

Hello,

Did you activate the "Compressibility Effects" PDF option in the Species model dialog box?

Are you using the "Turbulent Flame Speed" turbulence-chemistry interaction method?

 

[singh.112]

Hello Ren, 

Thanks for your response. 

I did try the compressibility effects but it was giving periodic signal for even stable case. After seing the results, I went through the suerguide where it was mentioned that for significant pressure changes only we should use compressibility effects. I am not sure what should be considered significant pressure variation. Yes I did try turbulent flame speed approach but without compressibility effects. Without compressibility effects, I did not get any periodic signals. 

 

 

 

[Ren]

For thermoacoustics, the pressure-density coupling is important. So, the compressibility effects option is necessary.

The user guide is referring to combustion applications involving compressible flows (higher Mach number values). 

 

[singh.112]

Okay I will just give a try one more time with turbulent flame speed. 

Should I use ZIMONT or PETERS approach ? 

 

[Ren]

You can use either. One may be better than the other depending on the fuels and flow configuration. Sometimes, it may also be necessary to tweak the model parameters.