Model for predicting air-fuel mixing, combustion and emissions in DI diesel engines over whole operating range

Abstract

A multi-zone model of diesel sprays evolution and combustion named as RK-model has been developed. The model with submodels of NO and soot formation has been implemented into ICE thermodynamic analysis software (DIESEL-RK). The RK-model takes into account: the shape of injection profile, including split injection; drop sizes; direction of each spray in the combustion chamber; the swirl intensity; the piston bowl shape. Evolution of wall surface flows generated by each spray depends on the spray and wall impingement angle and the swirl intensity. Interaction between nearwall flows (further named wall surface flows) generated by the adjacent sprays is taken into account. The method considers hitting of fuel on the cylinder head and liner surfaces. The evaporation rate in each zone is determined by Nusselt number for the diffusion process, the pressure and the temperature, including temperatures of different walls where a fuel spray gets. A parametric study of the swirl intensity effect has been performed and a good agreement with experimental data was obtained. The calculations results allow describing the phenomenon of increased fuel consumption with increase of swirl ratio over the optimum value. The model has been used for simulation of different engines performances. The calculated results obtained for high-speed, truck and mediumspeed diesels have shown a good agreement of SFC, power, smoke and NO emissions with the experimental data over the whole operating range, including modes of idling and 7...10% capacity. The model does not require recalibration for different operating modes of a diesel engine.