Effects of ammonia addition on knock suppression and performance optimization of kerosene engine with a passive pre-chamber

Abstract

The spark-ignition (SI) engine fueled kerosene faces the significant risk of knocking. Ammonia can be considered as a knock inhibitor to suppress the knock and optimize the performance of the kerosene engine, which also has excellent potential for reducing carbon emissions from internal combustion engines (ICE). In this paper, the effects of ammonia addition on the combustion characteristics, knock intensity, and performance of the kerosene engine with pre-chamber turbulent jet ignition (PTJI) were investigated experimentally. The results show that the knock intensity of the PTJI kerosene engine is reduced after adding ammonia and the knock tolerance is significantly broadened. The PTJI kerosene engine achieves full load operation at the compression ratio (CR) of 9 without knocking occurrence after blending ammonia, and the maximum increase of the indicated mean effective pressure (IMEP) and thermal efficiency is 2.95 bar and 12.6%, respectively. An advanced spark timing (ST) is obtained under ammonia addition conditions, resulting in higher in-cylinder pressure and superior combustion performance. The ignition delay ST-CA10 and combustion duration CA10-CA90 are prolonged as the ammonia ratio (ENH3) increases. An optimization operating strategy for the kerosene engine was proposed based on the CR, engine speed, supercharging, and ammonia addition. The best thermal efficiency of 26.88% with an IMEP of 8.25 bar is obtained at 1500 rpm, CR = 9, ENH3 = 20%, and a further improvement of engine power (IMEP > 12.0 bar) is achieved by supercharging.