An experimental and computational analysis of backfire initiation and propagation in a single-cylinder hydrogen port-fuel-injection engine

Abstract The global push for defossilization necessitates the advancement of hydrogen internal combustion engines as a key solution for the heavy-duty transport sector. However, the distinct combustion properties of hydrogen, particularly its high reactivity, introduce operational challenges for port-fuel-injected (PFI) engines, most critically the risk of backfire—the uncontrolled ignition in the intake system. This phenomenon not only makes the engine potentially unsafe for operation but also severely limits the achievable power density and combustion stability. Addressing this barrier requires a comprehensive understanding of the complex interactions between various engine control parameters. This study presents a coordinated experimental and computational fluid dynamics (CFD) investigation focusing on strategies to mitigate backfire in a single-cylinder, heavy-duty hydrogen PFI engine. The influence of engine parameters such as injector location, start of injection (SOI) timing, backpressure, engine valve timing and injection pressure and duration on mixture formation, and backfire onset were also analyzed. The findings establish critical guidelines for defining the stable operating window, demonstrating how the tuning of key control variables can effectively promote mixture preparation, reduce backfire instances and potentially increase engine efficiency. This research provides an essential framework for the reliable, safe and efficient deployment of hydrogen PFI technology in future low-carbon transportation applications.