| Fernando Lopez Parra
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September 8, 2003 12:55 |
Temperature fields
Hi to all. Let's see if you guys can give some help to this clumpsy student. The main objective of my work is the detailed analysis of diesel combustion. More specifically, I am looking at the soot and NOx generation in heavy duty diesel engines. But that is still a bit far. Now I am trying to state the accuracy of the solver, for which I am simulating simple diffusion flames. I have tried different methods, models and parameters (always trying to make some sense) but my temperature fields are (I believe) too high. For acetylene combustion I get peak temperatures of over 2200K, when probably the maximum should be around 1600 to 1800K. This obviously upsets the soot concentration levels and everything else. Does anybody have a feel for what could I be doing wrong. The convergence of the cases is normal, I used default values for the most relevant parameters. I tried the species transport model with piece-wise polynomial Cp and then the non-adiabatic equilibrium PDF. At the moment I am working on flamelets. I realise that soot and NOx formation are very much non-equilibrium processes, but, is there any way of achieving an acceptable accuracy for soot and NOx levels with FLUENT? I also know that some people tweaked the 5 coefficients of the piece-wise polyn Cp and found that the default ones led to and overpredicton of the temperature fields, but I do not know who they are and cannot find the paper. Has any of you guys come across this problem before? Thanks very much for your help, and soory for the wordy message. Regards Fernando
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