Effects of lateral swirl combustion chamber geometries on the combustion and emission characteristics of DI diesel engines and a matching method for the combustion chamber geometry

摘要

Previous experimental results show that a lateral swirl combustion system (LSCS) significantly improves the fuel consumption and the soot emission in direct injection (DI) diesel engines. To further improve LSCS performance and effectiveness, this study undertook numerical simulation to analyze the effects of the LSCS chamber geometries on combustion and emission characteristics under the condition of 2500 r/min and full load, revealing the relevant influence mechanisms. Based on a sensitivity analysis on the indicated power, the chamber geometry optimization was accomplished. The performance improvement of the optimized LSCS was verified using a single-cylinder DI engine. However, due to the interplay between fuel spray jets and wall surfaces, the optimized results are different for various fuel supply systems. To apply the LSCS effectively in different fuel supply systems, a matching method for LSCS chamber geometry is proposed in this paper.The results show that the combustion performance of the LSCS is primarily affected by the geometries of the split-flow creation, in which theta (the deviation angle of flow-guide) plays a dominant role. When. was in the range of 15-27 degrees, the combustion chamber created favorable flow guidance for spray and promoted the fuel/air mixture formation. After the geometrical optimization of the LSCS, fuel consumption decreased by 2.8-4.1 g/(kW.h) and soot emission decreased by 69-75% under various engine speeds as compared with the double swirl combustion system (DSCS).