[mohsen0488]

Hello guys

Im working on a part of Industrial cracking furnace which it has been shown in attached figure,

My problem is that at outlet B.C I have some back flows and I can not eliminate it, which it causes bad convergency in energy and compositions equations during the iterations.

Models:
Combustion: Species Transport
Two steps reaction for methane
Radiation: Do
Turbulence: K-e RNG

Mesh number: 12M tetrahedra
I have back flows from 250 meshes at Pressure outlet BC

Outlet temperature of Industrial furnace is 1300 k, but my simulation is over-predict and it has predicted 1700 k. I tried to increase air mass flow but it didn’t solve my problem, anyway I have a limitation for excess air (up to 10-20 %).

I plot facet averaged temperature on outlet surface as well as for all mole fraction species. And after about 5000 iterations results get constant but my results for outlet temperature is over-predict.

Does anyone know what is the problem in my simulation?

Many thanks in advance