Experimental investigation for enhancing the performance of hydrogen direct injection compared to gasoline in spark ignition engine through valve timings and overlap optimization

Abstract

Recent advances in hydrogen internal combustion technologies highlight its potential for high efficiency and zero carbon emissions, offering a promising alternative to fossil fuels. This paper investigates the effects of valve timings and overlaps on engine performance, combustion characteristics, and emissions in a boosted direct-injection single-cylinder spark ignition engine using both gasoline and hydrogen. Optimized direct hydrogen injection effectively eliminates backfires and hydrogen slip during positive cam overlaps, significantly reducing the pumping mean effective pressure. The study’s primary finding demonstrates the potential of hydrogen to operate as a direct substitute for a gasoline engine without necessitating changes to the cam profiles at the high load operation. Furthermore, the study demonstrates that hydrogen leads to much higher thermal efficiencies across a wider range of engine loads when operated at a lean, air-to-fuel ratio of 2.75. The engine operating with such a lean-burn hydrogen mixture keeps the engine-out NOx emission at ultra-low levels. Compared to gasoline, hydrogen exhibits greater stability and a reduced reliance on camshaft timing during engine operation.