Numerical Analysis of Hydrogen Injection and Mixing in Wankel Rotary Engines

The Wankel rotary engine has been an attractive alternative for transportation due to its unique features of lightweight construction, small size, high power density, and adaptability to various fuels. This paper aims to investigate the performance of air-fuel mixing in a hydrogen-fuelled Wankel rotary engine using different fuelling strategies. To achieve this, 3D computational fluid dynamics (CFD) simulations were conducted using CONVERGE software on a prototype engine with a displacement of 225 cc, manufactured by Advanced Innovative Engineering UK. Initially, the simulations were validated by comparing the results with experimental data obtained from the engine fuelled with conventional gasoline under both motored and fired conditions. After validating the model, simulations were conducted on the premixed hydrogen engine combustion, followed by more detailed simulations of port fuel injection (PFI) and direct injection (DI) of hydrogen in the engine. The results indicate that hydrogen is a promising substitute for conventional carbon-based fuels in Wankel engines, as it can reduce carbon dioxide (CO₂) emissions. The DI strategy has the potential to increase engine performance by improving volumetric efficiency and better controlling the fuel mass trapped in the combustion chamber. Injecting the fuel into the chamber guarantees mixture enrichment for combustion and generates charge stratification that reduces heat release rate and improves power generation. The reduced heat release rate also lowers heat transfer losses from flame-to-wall interaction, which greatly impacts Wankel engine efficiency. Lean mixtures have the potential to reduce nitrogen oxides (NO_x) emissions in combustion. In summary, this study demonstrates the compatibility of hydrogen direct injection fuelling with the Wankel engine. The study provides important insights to improve the understanding of hydrogen application in this engine concept for future design and optimization of hydrogen injection configuration and strategy.