Study of High-Pressure Hydrogen direct injection for Internal Combustion Engines

Hydrogen-fueled internal combustion engines (H2-ICEs) are gaining increasing interest for both light and heavy-duty applications since no carbon emissions are produced from its combustion process. The current development of hydrogen-based ICEs focuses on the direct injection (DI) strategy as it allows better engine efficiency than the port fuel injection one. The fuel spray behaviour is a fundamental aspect of the in-cylinder air-fuel mixing ratio, affecting the combustion process, the engine performances, and the pollutants emissions. It is then important and necessary to observe and understand the behaviour of the fuel jet. The present work aims to deal the hydrogen jet behaviour in terms of mass flow rate measurements and morphology investigation under a wide range of engine-like conditions by a Compressed Hydrogen Gas (CHG) injector used for typical direct injection applications. A measuring system, suitable for the gaseous fuels, was used for measuring the instantaneous flow rate as well the dynamic behaviour of the injection system. High-speed z-type schlieren imaging was used to investigate the evolution and shockwave structures of highly under-expanded H2 jets by injecting in a constant volume combustion vessel. Macroscopic jet parameters were measured to study the H2 jet morphology as function of injection and ambient pressure.