SPRAY CHARACTERISTICS IN A DIRECT-INJECTION DIESEL ENGINE

Abstract

In this study the numerical calculations of the spray characteristics in a direct-injection diesel engine are performed. Calculation parameters are injection pressure, swirl ratio, and breakup model. The breakup models used are the Reitz and Diwakar model and the Taylor analogy breakup (TAB) model. A modified k-e turbulence model which considered the compressibility effect due to the compression and expansion of piston is used. In the quiescent condition, spray tip penetration and spray tip velocity are predicted and compared with the experimental results. There is good agreement between the results of calculation and the experimental data. In the motoring condition, although the evaporation rate is not affected by the swirl ratio variation, it is greatly influenced by the injection pressure variation. Using the TAB model, the evaporation rate is substantially increased at the early stage of spray and the Sauter mean diameter is considerably decreased.