The transport sector is responsible for about one third of the global CO2
emissions. To align to the net zero emission scenario, the transportation sector
needs the implementation of policies aimed to reduce as much as possible the
highly emitting transport options and, at the same time, the use of new
technologies to reduce the environmental impact of transport methods whose
emissions cannot be entirely eliminated.
An exploitable solution for the internal combustion engine (ICE), even in the
nearest future, would be to use hydrogen as a fuel in these engines. This is
supported by the fact that H2-ICE is the only ICE technology currently capable
of meeting the standards imposed by the European Union for 2035. Due to the
possibility of different injection strategies as well as the variation of
in-cylinder back pressure, the comprehensive knowledge of hydrogen injection jet
behavior and characteristics is fundamental for improving the combustion process
in direct injection H2-ICE.
In this context, current study focuses on the characterization of experimental
hydrogen jets in terms of mass flow rate and jet morphology under a wide range
of engine-like conditions by the use of an injector appropriate for direct
injection applications. A measuring system, suitable for gaseous fuels, was used
for measuring instantaneous and total flow rates as well as the dynamic behavior
of the entire injection system. The spatial and temporal evolution of a highly
under-expanded H2 jet was studied by a Z-type schlieren optical setup. H2 fuel
was injected into a constant-volume combustion vessel (CVCV) at different
injection pressures (up to 50 bar) and ambient back pressures simulating typical
engine conditions. Measurements of jet penetrations, jet width, and total areas
of the injected gas showed a strong dependence on those parameters.