Extending the knock limits of hydrogen DI ICE using water injection

Abstract

This paper presents an experimental and numerical study of a directly-injected, spark ignited, heavy-duty, hydrogen-fuelled engine with boost. Consistent with prior works, engine operation with compression ratios of 12:1 and 14:1 but without water injection are found to be knock-limited at richer conditions, more advanced spark timings, and particularly at the higher compression ratio. Water injection into the intake manifold is then used to suppress autoignition and knock, and thus enable diesel-like power via richer operation at more optimal operating conditions.The dependence of these observed trends on key physical processes is then examined numerically. This includes considering water injection to potentially impact autoignition via three potential routes - a charge cooling effect, a thermophysical effect and a kinetic effect. The impact of charge cooling is found to be dominant, with the thermophysical effect also significant but the kinetic effect weak.