Spatiotemporal distribution of mixture homogeneity: Mechanism analysis of injection pulse width on combustion characteristics in hydrogen engines

Injection pulse width (IPW) is a critical parameter governing the mixture formation and combustion characteristics of port fuel injection (PFI) hydrogen internal combustion engines (HICEs). Based on a heavy-duty six-cylinder PFI HICE, this study investigates the effects of five IPW conditions (56 °CA to 68 °CA) on mixture distribution via 3D simulation. By introducing the hydrogen mass spatial mixing deficiency (HSMD) and spatial angular distribution, the regulatory mechanism of IPW on the temporal and spatial distribution of the air-fuel mixture in the intake port and cylinder is quantitatively revealed. The results show that with the reduction of IPW, the peak in-cylinder pressure and peak heat release rate decrease by 24.69% and 33.93%, respectively, accompanied by an extended combustion duration. The late combustion phase is the most significantly affected by the IPW. Under long IPW conditions (≥62 °CA), the maximum pressure oscillation amplitude of partial monitoring points exceeds 0.1 MPa, indicating a prominent knock tendency. In the intake port, hydrogen mainly flows through the single-side manifold. A shorter IPW advances the peak HSMD with a higher peak value, and simultaneously restricts the circumferential diffusion of hydrogen. The maximum in-cylinder turbulent kinetic energy increases by 7.5% with the reduction of IPW, while the mean HSMD rises and the phase of the peak value advances. The hydrogen-rich region before ignition gradually shrinks with the shortening of IPW.