Enhanced combustion of ammonia engine based on novel air-assisted pre-chamber turbulent jet ignition

Abstract

Ammonia has demonstrated great potential for achieving zero carbon emissions from internal combustion engines. However, the application of ammonia in engines faces the risks of ignition failure, low burning rate, and high nitrogen oxides emissions. Pre-chamber turbulent jet ignition (TJI) can provide multi-point ignition and fast combustion. Thus, in this study, a novel self-designed air-assisted pre-chamber apparatus is proposed to optimize the engine performance and combustion in a spark-ignition ammonia engine. The effects of high-reactivity pre-chamber fuels, including hydrogen, gasoline, and methane, on the performance of a TJI engine are investigated for the first time. The results show that, in the TJI mode considering the pre-chamber fueled with high-reactivity fuels, both the indicated mean effective pressure and indicated specific fuel consumption are improved compared with those in the spark-ignition mode. The enhanced combustion process involving shortened ignition delay and combustion duration is achieved by using the TJI mode. Double-peak phenomena are observed in both the pressure and heat release rate curves. In the TJI mode with the pre-chamber fueled with hydrogen, an optimal engine performance involving a high indicated mean effective pressure, low fuel consumption, and low coefficient of indicated mean effective pressure variation is obtained. Moreover, both peaks of the heat release rate are higher, and the ignition delay and combustion duration are further shortened owing to the jet effect produced by hydrogen combustion in the pre-chamber. Low NOx and NH3 emissions are observed in the TJI mode, particularly when the pre-chamber is fueled with hydrogen.