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.
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.
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.
