The main aim in this study was to investigate the effect of soot radiation on the maximum flame temperature, the total heat flux to wall and the NOx-emission levels in a medium speed diesel engine. Also the effect of turbulence models (STD or RNG k-epsilon) the combustion and emission results were investigated. The RNG k-epsilon model was modified as part of the velocity dilatation term by using an analysis of rapid spherical distortion. In the modified KIVA2-CFD code the Magnussen EDC (Eddy Dissipation Concept) model was used for the fuel vapor combustion, the Tesner & Magnussen model for the soot formation, the combined Magnussen EDC/Nagle & Strickland-Constable for the soot combustion, the extended Zeldovich model for the NO-formation and the chi-squared model for the spray. Radiative heat transfer was dealt with in two ways, in the first the simplified method was used (pure soot emission) and in the second the radiative transport equation was solved with the discrete ordinate method (DOM). The soot absortion coefficient was calculated with the correlation of Kent & Honnery. The computations were done with and without radiant heat loss in order to observe the effect of soot radiation in the results. The predicted cylinder pressures and the heat release rates in both cases were compared with the corresponding measured data. The soot, NOx and heat flux results were compared to the results obtained from literature, due to the non-availability of measured data. The predicted results are reasonable and behaved correctly. The simulation results show that the effect of soot radiation in the combustion process is remarkable and therefore it has to be taken into consideration when modelling diesel engine processes. Also the modified RNG k-epsilon model yields slightly more realistic combustion results than the STD k-epsilon model.

This content is only available via PDF.
You do not currently have access to this content.