Calculation of the In-Cylinder Flow and Heat Transfer in DI and IDI Diesel Engines

Two computer models were used for simulation of the local flow, wall temperature, and heat transfer in combustion chambers of diesel engines. A multidimensional model linked with the conventional k-e turbulence model was employed for the calculation of in-cylinder phenomena. A finite difference procedure with an expanding/contracting grid in axisymmetric and curvilinear representation was used. Fuel injection, accommodated by an empirical formula of spray, was modeled in the form of gaseous jet. Combustion was treated using experimental data of the heat release rate. The temperature distributions of the walls were calculated by another model of thermal analysis, a finite element method, for the cylinder head, cylinder, comet chamber, and piston. Both models were coupled with boundary conditions, namely, wall functions. In DI engine, the flow and temperature fields of cylinder and piston cavity were calculated. In IDI engine, only the comet chamber was considered for the flow and temperature computations. These calculations were utilized to estimate heat transfer performance of combustion chambers and to investigate the thermal effects of hardware design.