An experimental study of using coal to liquid (CTL) and diesel as pilot fuels for gasoline dual-fuel combustion

Abstract

Compared to conventional spark-ignition (SI) and compression-ignition (CI) combustion modes, the dual-fuel combustion mode could achieve higher thermal efficiency of internal combustion engine. In this study, the experiment of using directly injected coal to liquid (CTL) and conventional diesel as pilot fuel was carried out on a modified gasoline dual-fuel engine. The potential of using CTL as pilot fuel to improve the thermal efficiency and emissions performance of the engine is revealed. The results show that the dual-fuel mode can significantly reduce the combustion duration (CD) while maintaining a low peak of heat release rate (PHRR) as well as a low peak of pressure rise rate (PPRR), thereby improving the indicated thermal efficiency (ITE). Compared with conventional diesel, using CTL as pilot fuel on the dual-fuel engine can further improve the ITE, decrease the premixed gasoline ratio (Rp), reduce the PPRR and cycle variations (COV). The dual-fuel mode also helps to reduce the particle emissions, especially for gasoline/CTL mode. After the optimization of injection strategy, compared with gasoline/diesel mode, the ITE of gasoline/CTL mode can be increased by 2%, with the PPRR and the NOx emissions being reduced by 46.1%, and 20.1%, respectively.