Numerical investigation of the effect of swirl number on performance, combustion, and emissions characteristics in a converted heavy-duty natural gas engine

In this research, the performance, combustion characteristics, and emission behaviour of a diesel engine converted to a spark ignition engine running on natural gas were investigated. The studies were performed at full load, 2,300 rpm, constant spark ignition time, and seven different swirl ratios. As a result, the homogeneous-air fuel mixture formed in the cylinder due to the swirl ratio rising, and the increased combustion performance dominated the heat loss because of the rise in the swirl number, thereby improving the performance. However, with the increase of in-cylinder temperatures, NOX emissions increased. As the swirl ratio increased from 1.2 to 2.4, the gross indicated power (GIP), indicated mean effective pressure (IMEP), indicated thermal efficiency (ITE), and maximum pressure rise rate (MPRR) values increased by 4.1, 4.13, 3.98, 102.2%, while the gross indicated specific fuel consumption (GISFC) value improved by 3.97%.