Combustion and performance characteristics of a hydrogen-fueled engine converted from a 0.8-L gasoline engine for the range-extender generator applications in 5-ton electric forklifts

The global push toward carbon neutrality is driving the adoption of alternative power sources, with hydrogen engines emerging as a promising power solution in this transition. Unlike other carbon-neutral technologies, hydrogen engines offer the unique advantage of being retrofittable to existing engines. However, retrofitted hydrogen engines often suffer from significantly reduced power output compared to their original gasoline counterparts, primarily because of their inability to operate at rich air–fuel ratios without abnormal combustion. In this study, the combustion, performance, and emission characteristics of a hydrogen-fueled engine converted from a 0.8-L gasoline port fuel injection engine for use as a 15-kWe generator in the range-extender system of a 5-ton electric forklift were investigated. Hardware changes were minimized by replacing only the injectors and recalibrating the ECU to enable stable stoichiometric operation. Real-duty power demands were identified through a modified VDI 2198 cycle, which informed the target engine operating conditions. Under stoichiometry, the converted engine achieved a maximum power output equal to 76% of the original gasoline engine, while carbon dioxide emissions were reduced by 99%. The influence of excess-air ratio variation on combustion characteristics and emissions was further analyzed to maintain power output. The results demonstrate that the converted hydrogen engine with optimized control strategies can provide both acceptable power density and substantially lower emissions, confirming the feasibility of hydrogen engine retrofits for range-extender applications.