Effect of In-Cylinder Flow Motion on Fuel-Air Mixture Formation in a Medium-Duty DI-SI H2 Engine: An Experimentally Supported CFD Study

The increased utilization of batteries and fuel-cells for powering electric applications, as well as bio- and e-fuels into internal combustion engines are seen as options to lower the carbon footprint of industry and transportation sectors. When high power outputs and fast refueling are requisites, H₂ ICEs may be a relevant choice. Applications include electricity conversion within a genset or mechanical energy in a vehicle. Within this framework, a John Deere 4045 Diesel engine converted to a H₂ single-cylinder is studied at relevant operating conditions for the mentioned use cases, which pose high torque and power output requirements. The modified engine integrates a Phinia DI-CHG 10 outward-opening H₂ injector instead of the Diesel unit, as well as a spark-plug rather than the glow-plug. To explore the effects of in-cylinder air flow on the H₂-air mixing, two piston designs are employed: one conserves the intake generated swirl; the other contains deflectors promoting a more complex flow and resulting in a lower swirl ratio. Tests concerning this work are performed at 1500 rpm, suitable for electricity generation at a frequency of 50 Hz, start of injection timing at -120 °CA aTDC, injection pressure of 41 bar and air-fuel equivalence ratio of 2.0. The in-cylinder mixing study is supported by 3D-CFD non-reactive simulations, performed with CONVERGE. The computational setup relies on a validation for the injection event within a constant volume chamber, as well as the agreement between experimental and numerical quantities of air and H₂ into the cylinder. In-cylinder flow pattern and H₂-air mixing are shown to be affected according to piston design. The trends of mixture distribution are consistent for different engine load cases, providing understanding for experimental results such as NOx emissions and combustion indicators.