Injection strategy for simultaneous reduction of NOx and soot emissions using two-stage injection in DME fueled engine

The ultimate purpose of this study is the reduction of exhaust emissions from a dimethyl ether (DME) fueled diesel engine without deterioration of engine performance, such as indicated mean effective pressure (IMEP) and indicated specific fuel consumption (ISFC). In this study, we applied multiple injection strategies to achieve the research goal. In a comparison between diesel and DME single injection combustion, the IMEP in both fuels was similar around the top dead center (TDC) injection condition (this is the typical injection timing). However, the nitrogen oxide (NOx) emission in DME was higher than that in diesel. The single injection combustion in DME and diesel was compared on the basis of the same energy input condition. When the injection timing was advanced in order to reduce the DME NOx emission, the IMEP in DME decreased below the diesel level. Therefore, multiple injection strategies, including pilot injection, split injection, and advanced + post injection, were applied in this study. In the experimental results, the pilot injection strategy with advanced main injection (2nd injection) resulted in the lowest NOx, HC, and CO emissions. In the case of soot emission, DME itself has soot free combustion, and emitted an ignorable amount of soot. Moreover, the pilot injection strategy showed the highest IMEP level and the lowest ISFC level in the test conditions.