Prediction of Soot emissions from Direct Injection Diesel Engine

Abstract

A modeling of the combustion process inside D. I. compression ignition engines has become extremely important for both improving combustion efficiency and describing the conditions in which pollutant emission formation occurs. In this investigation an axisymmetric turbulent combustion flow with heat transfer has been considered for a four-stroke diesel engine. The flow field and combustion in axisymmetric engine cylinder is expressed by unsteady compressible conservation equation for mass, axial and radial momentum, energy, and species concentration and k-ε model to account for Reynolds's stress. The expanding and contracting feature of piston is introduced through an appropriate coordinate transformation and conservation equations modified accordingly. A model for the prediction of combustion and exhaust emissions has been formulated and developed. Combustion is assumed to be instantaneous and depends on the availability of fuel vapor mixture and air. The emission model use the soot formation model and kinetics of soot oxidation reaction to calculate the global soot emission as a major pollutant from diesel engine. The capabilities of the model in predicting soot formation, oxidation and emission have been demonstrated. Detailed prediction results at various engine loads are presented and discussed.