A Numerical Study on Turbocharging System for PFI-SI Type Hydrogen Combustion Engine

The hydrogen internal combustion engine (H2ICE) has received increasing attention in various industry sectors as it produces nearly zero carbon emissions. However, it has been reported that the power output is lower than the gasoline engine especially for port fuel injection (PFI) type hydrogen engines. It is mainly due to low density of the hydrogen which reduces volumetric efficiency. A turbocharging system can improve the power output by pushing more air into the combustion chamber. However, it was observed that incorrect matching hampers the increment of the power output which results in low specific power (<30kW/L). To achieve the equivalent performance of a turbocharged PFI gasoline engine, the required boosting system for the PFI H2ICE has been numerically investigated using 1D engine simulation. As a base engine, a 1.6L turbocharged PFI gasoline engine was used. The validated base engine model was modified for the hydrogen operation and the simulation was carried out at wide open throttle (WOT) from 1000 to 4000 RPM under the equivalence ratio (ϕ) of 0.55. It was identified that the PFI H2ICE requires 50% higher mass flow and 90% higher boost pressure against the turbocharged gasoline engine. A single-stage charging system is not able to supply the required boost and mass flow over the wide range of operation. Instead, a two-stage boosting system with VGT at high pressure stage could deliver such a high boost and mass flow. The boost and mass flow demand are mainly influenced by the operational lambda (λ) and target performance which should be considered in designing the boosting system for the PFI SI type H2ICE.