Experimental investigation on the influence of gasoline injection pressure on the hydrogen knock limit and performance of a hydrogen–gasoline dual fuel engine

This study experimentally investigated the influence of gasoline injection pressure (GIP) on the performance and hydrogen knock limit of a gasoline direct-injection hydrogen–gasoline dual-fuel engine. The GIP was varied from 50 to 140 bar, and hydrogen was introduced at a step size of 2 LPM until knock onset at spark timings of 4° and 12° CA before top dead center (BTDC). The hydrogen knock limit was extended at a higher GIP, with maximum hydrogen flow rates of 10 and 16 LPM at 12° CA and 4° CA BTDC, respectively. Increasing the GIP and retarding the spark timing negatively affected brake thermal efficiency, brake mean effective pressure, and in-cylinder pressure. The CO₂ and NO_x emissions decreased, and the CO emissions increased with an increase in the GIP. The cyclic variation increased considerably with GIP. However, hydrogen blending exhibited a completely opposite trend to that of GIP.