Conversion of a Small Size Passenger Car to Hydrogen Fueling: 0D/1D Simulation of Port- vs Direct-Injection and Boosting Requirements

Hydrogen is an energy vector with low environmental impact and will play a significant role in the future of transportation. Converting a spark ignition (SI) engine powered vehicle to H₂ fueling has several challenges, but was overall found to be feasible with contained cost. Fuel delivery directly to the cylinder features numerous advantages and can successfully mitigate backfire, a major issue for H₂ SI engines. Within this context, the present work investigated the specific fuel system requirements in port- (PFI) and direct-injection (DI) configurations. A 0D/1D model was used to simulate engine operating characteristics in several working conditions. As expected, the model predicted significant improvement of volumetric efficiency for DI compared to the PFI configuration. Boosting requirements were predicted to be at levels quite close to those for gasoline fueling. Apart from tougher requirements with respect to the fact that the injector would have to withstand much higher pressure and temperature, the DI solution would also need to feature higher flow rate. Increased injection pressure was another requirement that was identified as essential for ensuring correct fuel delivery during the compression stroke. The contradicting effects of injection rate and required pressure were investigated in two different hypotheses: low pressure DI (LPDI) and high pressure DI (HPDI).