A comprehensive review of hydrogen production technology and the performance, combustion, and emissions of hydrogen-fueled internal combustion engines

With the intensification of global climate change and the depletion of fossil fuel reserves, the energy transition has become an urgent and significant global challenge. Hydrogen fuel, valued for its carbon-free emissions and high energy density, is regarded as a cornerstone of future clean energy systems. This study first establishes prerequisite hydrogen production technologies, emphasizing renewable pathways as the most sustainable approach. Existing research has seldom provided systematic explanations of fundamental hydrogen combustion theories, such as laminar burning velocity. Therefore, this paper offers a detailed analysis of these fundamental theories and emphasizes their critical role in optimizing internal combustion engine performance. Given the direct influence of hydrogen injection strategies on combustion stability and efficiency—thereby dictating power output, fuel economy, and emissions—we comprehensively evaluate the effects of injection parameters (angle, timing, injector geometry, and injection mode) on engine behavior. Furthermore, recent advancements in mitigating abnormal combustion (e.g., backfire and knocking) and reducing nitrogen oxide emissions are critically reviewed, highlighting complex triggering mechanisms involving in-cylinder hotspots and injection dynamics, as well as cross-triggering effects between phenomena. Finally, based on the existing literature, this paper summarizes current research trends and suggests potential future research directions.