Preliminary Assessment of Hydrogen Direct Injection Potentials and Challenges through a Joint Experimental and Numerical Characterization of High-Pressure Gas Jets

The interest towards hydrogen fueling in internal combustion engines (ICEs) is rapidly growing, due to its potential impact on the reduction of the carbon footprint of the road transportation sector in a short-term scenario. While the conversion of the existing fleet to a battery-electric counterpart is highly debated in terms of both technical feasibility and life-cycle-based environmental impact, automotive researchers and technicians are exploring other solutions to reduce, if not to nullify, the carbon footprint of the existing ICE fleet. Indeed, ICE conversion to "green"fuels is seen as a promising short-term solution which does not require massive changes in powertrain production and end-of-life waste management. To better evaluate potentials and challenges of hydrogen fueling, a clear understanding of fuel injection and mixture formation prior to combustion is mandatory. The paper reports a preliminary experimental and numerical characterization of high-pressure gas jets exiting from a single-hole injector derived from a GDI unit and purposely re-designed for gaseous fuel operations. A wide range of operating conditions is explored to perform a sensitivity analysis to key-factors such as injection pressure and temperature and ambient backpressure. Multiple state-of-the-art experimental techniques are adopted to characterize the gas jets and to support the numerical sensitivity analyses to key modelling aspects such as grid density and turbulence modelling.