Learning Forum

[up201705193]

Hello, I am a fairly new to Fluent and I am trying to simulate a combustion in a furnace with 4 inlets (fuel and air enter both already mixed) and flue gas entering in one wall (this is a section of a bigger furnace). I am using the eddy dissipation model, and the boundary conditions I am using are mass-flow inlets and an outflow. The fuel (ch4) enters with air in the 4 inlets mixing with the flue gas and everything goes out through a single outlet. . I am using k-e model for turbulance and DO model for radiation. My mesh size is 289486 nodes and 200357 elements. My quesgtion is why is my flame temperature so low (only 1000K)? My system converged as you can see by the residuals represented below. Another question I have is how can I improve my mesh? I recently had only the Ansys student version so I had a max cell limit of 500000.
The system converged this way:

Flame Temperature:

Mesh:

[Rob]

The flame also looks very short, and that may be a lack of mesh resolution. Use domain decomposition and/or bodies of influence to refine the mesh local to the inlets. Use a poly mesh too, tets can be very diffusive in combustion cases.  What did you set the inlet/outlet radiation temperature as? I'm wondering if you're losing too much heat in that way. Try with the radiation model off and compare the results.