Convergence problem for P1 & Energy

HP

Hi! I am modelling the combustion in a pf boiler and I confront convergence problems.

For my case I use unstructured grid (440K cells), k-e (standard) for turbulence, EBU for combustion interaction with turbulence, 1 chemical reaction and P1 model for radiation. I also inject in the continuous phase 19,000 particles every 25 iterations.

The problem is that it is impossible to meet the convergence criteria for energy and P1 (set at 1e-6), as the residuals decrease at about 5e-5 and then become flat. I also notice that the temperatures in the combustion chamber are about 200K greater than the correct. Notice that all the other residuals are below their corresponding criteria of convergence.

I have already tested the following with no result: --number of continuous phase solution before calculate the discrete phase --alteration of the relaxation factors --1ord and 2ord discretisation schemes

I confronted the same problem (with the same residuals) in another case I had dealed with, where the chemical equillibrium (pdf) model was selected for combustion modelling.

Does anybody have any suggestions?

Thanks in advance for your help.

Ilias