New alternative (partially homogeneous) combustion process as a method for reduction of concentrations of nitric oxides and soot in combustion products of diesel

A new alternative (partially homogeneous) combustion process in diesel engines is proposed that provides changes in local values of the excess air coefficient and the temperature of the working substance in ranges lying beyond the area of the formation of nitric oxides and soot. It is important that the process is realized without significant changes in the serial construction. Modeling of the alternative process and the traditional diesel engine process is carried out on the basis of fundamental equations of three-dimensional nonstationary transfer in combination with models of combustion and formation of harmful substances: nitric oxides and soot. The set of equations for the model of the diesel cylinder with moving boundaries (valves, piston) is used in the Reynolds form and is closed by means of the k-xi-f turbulence model considering the near-wall anisotropy of turbulence. The developed 3D models of the diesel engine work process are realized in the CFD code of the AVL-FIRE software complex. It is found that transition from the classic diesel engine process to partially homogeneous combustion makes it possible to block practically completely the formation of nitric oxides and to decrease soot emission substantially.