Modelling medium speed diesel engine combustion, soot and NO{sub}x-emission formations

摘要

The purpose of the present study was to model combustion, soot and NO{sub}x- emissions of a medium speed diesel engine using the modified KIVA-2 code. Assesment of the droplet vaporization, the soot formation and its oxidation models were also done regarding the medium speed diesel engine. Heavy fuel spray was modeled with the standard KIVA-2 chi-squared model including drag modification during droplet vaporization (the droplet distribution model), droplet vaporization with the high pressure Spalding and Abramzon & Sirignano models, combustion with the Magnussen EDC-model including a two step reaction mechanism, NO{sub}x formation with the extended Zeldovich model, soot formation with the modified Tesner & Magnussen model and soot oxidation with the EDC-model and Nagle and Strickland-Constable model (NSC). The RNG k-epsilon turbulence model was also implemented into the code. The Redlich-Kwong real gas equation of state and the formulation of Peng-Robinson fugacity coefficient equation were used. The predicted cylinder pressures and heat-release rates in different cases were compared to that measured. Predicted NO{sub}x and soot values were compared with typical corresponding medium speed diesel engine values, this was due to the non-availability of NO{sub}x and soot measured values. In certain cases the predicted cylinder pressures and heat-release rates are quite well in agreement with those measured. The NO{sub}x and soot results are reasonable and behaved correctly. The developed engine CFD-modelling tool is at such a level now that it can aid the design of medium speed diesel engines.