Numerical Simulation of Effects of Swirl Ratio on Flow and Emissions of Diesel Engine

Abstract

With the increase of EGR, soot emission increases firstly (because of the lower oxidation rate of soot) and then decreases (because of the lower formation rate of soot), that is the so‐called soot‐bump. Previous papers mainly attempted to reduce soot emission at low temperature combustion condition by optimizing and altering some parameters, few papers clarified the effects of these parameters on the shape, peak value and the corresponding EGR rate of soot‐bump as well as CO emissions. The effects of swirl ratio on flow and emissions of a direct injection diesel engine were studied by numerical simulation method in this paper. The results indicate that with the increase of swirl ratio, the soot‐bump peak value decreases, and the corresponding EGR rate of peak value increases, the soot‐bump curve will decline rapidly after the peak value. In the same EGR rate, soot emission decreases with the increase of swirl ratio. The CO emission decreases firstly and then increases with the increase of swirl ratio, the corresponding EGR rate of soot‐bump peak value is almost the same as the EGR rate when CO emission increases drastically.