Experimental Investigation into Port Water Injection on the Transient Behavior of a Heavy-Duty Hydrogen Engine

Hydrogen-fuelled internal combustion engines are a potential carbon-free propulsion solution for high-power applications such as construction machinery and heavy-duty commercial vehicles. However, compared to conventional diesel engines, hydrogen engines exhibit limitations in transient operation and at full load, primarily due to the high reactivity of hydrogen. In spark-ignited hydrogen engines, combustion anomalies represent the main constraint during performance-oriented operation, particularly during transient phases that require mixture enrichment to meet dynamic torque demands. Water injection is investigated in this study as a means to mitigate these limitations. The paper describes the implementation of a port water injection system on a heavy-duty commercial hydrogen engine and evaluates its influence on engine performance with a focus on transient operating conditions. A combustion anomaly evaluation method developed in-house is applied to quantify the effect of water injection on abnormal combustion behaviour. The results show that water injection shifts the combustion anomaly limit toward richer air–fuel ratios, thereby enabling mixture enrichment up to stoichiometric conditions during transient load changes. Water is injected cyclically into each intake port to achieve a defined water-to-hydrogen ratio during load steps. Even at low water injection rates, a significant reduction in engine response time is observed, leading to transient torque response comparable to that of a diesel reference engine. Improved torque demand tracking is demonstrated in dynamic test cycles. In steady-state operation, the application of water injection also extends the achievable full-load operating range. Overall, the results indicate that port water injection is an effective measure for suppressing abnormal combustion in heavy-duty hydrogen engines and enables more aggressive yet stable engine calibration with minimal water consumption, contributing to diesel-like performance characteristics.