[Touqeer]

Hi Everyone,

I have been trying to setup a steady state non premixed gaseous fuel(natural gas) gas turbine combustor simulation in CONVERGE CFD(v2.3), using SAGE detailed chemistry model.
Each and everytime I run this case, the temperature in the Combustor goes beyond 3500K and stays close to that value indicating that fuel is burning at that temperature, while the Adiabatic flame temperature for natural gas is less than 2500k.

I have tried multiple combinations, chaning the location of source, mapping general flow cases, but nothing seems to work

Is there any specific property in SAGE that I should change ?

[Gaurav_Kumar]

Dear Touqeer,

We suspect that the effects of the heat addition provided by the source still remains in the domain which is why you are seeing a temperature above the ADFT. If you run the case longer, you should see the effects of the source heat addition wash out of the model and the flame temperature drops to something close to the ADFT.

Since some of the accuracy of detailed chemistry is lost (specifically NOx) at large time-steps that are used in steady-state, we recommend the FGM model any time steady-state combustion is used for gas turbines. Another point is that RANS models with SAGE detailed chemistry do not account properly for the effects of fluctuations on turbulence and chemistry regardless of how resolved the mesh is. Time-accurate LES models with the SAGE detailed chemistry solver do account for the fluctuations with proper mesh size. Please see our white paper on this topic at https://convergecfd.com/resources/re...nt-science.pdf. The FGM model incorporates those fluctuations in RANS models.

We are happy to review your setup/results if you send them to support@convergecfd.com