Experimental Study of Entrainment by Hydrogen-Like Impinging Jets of Various Types in a Confined Compartment

<div>Recent literature has highlighted significant heat transfer losses and elevated particle formation in direct-injection hydrogen engines, particularly when compared to hydrocarbon fuels such as methane. These challenges are attributed to hydrogen’s unique physicochemical properties, notably its short flame quenching distance and high diffusivity, as well as the interaction between the hydrogen jet and lubricated cylinder surfaces, which promotes lubricant entrainment into the combustion chamber. Consequently, a fundamental understanding of these entrainment mechanisms is a prerequisite for developing engineering strategies to enhance thermal efficiency and mitigate particle formation.</div> <div>The reported study investigates gaseous jet–air interaction in a confined volume to elucidate the influence of injector geometry on jet propagation and air entrainment. Three distinct jet configurations were examined: the wide hollow-cone, the narrow hollow-cone, and the round jets. The jet evolution and propagation were recorded using the Schlieren optical imaging technique for various pressure ratio values.</div> <div>The results indicate that for the wide hollow-cone jet, impingement on the vertical wall of the confined space is decoupled from horizontal surface impingement. Furthermore, this configuration yields a higher total entrained mass compared to narrow hollow-cone and round jets, under identical injected mass and pressure ratios. A notable finding is the inverse correlation between injection pressure and entrained volume for a fixed injected mass. Consequently, this study proposes new quantitative metrics for evaluating mixture preparation in direct-injection internal combustion engines.</div>