Optimizing Hydrogen Direct Injection to Overcome Design Challenges in Jet Ignition Systems

ABSTRACT Hydrogen direct injection (DI) is a critical technology for advancing internal combustion engines (ICEs) as efficient, low‐emission alternatives in a sustainable energy future. While high‐pressure direct injection (HPDI) offers significant advantages in efficiency and power density—particularly when paired with jet ignition systems—it remains underdeveloped compared to port fuel injection (PFI) and low‐pressure DI (LPDI) systems. This study identifies the limitations of existing HPDI injector designs, including insufficient injection pressures and mass flow rates, and emphasizes the need for single‐fuel HPDI systems. A novel method utilizing cryogenic hydrogen warmed to ambient temperature in a constant‐volume chamber is proposed to achieve higher injection pressures without added complexity. When integrated with jet ignition, this approach delivers brake thermal efficiencies of up to 50% across diverse operating conditions, far surpassing PFI and LPDI. The findings underscore the urgent need for investment in HPDI technology to unlock the full potential of hydrogen ICEs, enhancing efficiency, power density, and sustainability.