Effects of the Spark Location and Timing in a Heavy-Duty Hydrogen-Fueled Engine

The use of hydrogen in internal combustion engines offers a promising route to low-carbon propulsion in heavy-duty transportation. However, its distinct combustion characteristics as high flame speed, wide flammability limits, and susceptibility to abnormal combustion, necessitate careful engine and ignition system design. This study investigates the combined influence of spark plug location and ignition timing on the performance of a heavy-duty Volvo Diesel engine modified to operate in a spark-ignited mode with hydrogen fuel at low compression ratio under different load conditions. Three-dimensional computational fluid dynamics simulations with detailed hydrogen chemistry, including diffusive-thermal effects, were conducted to evaluate flame development, combustion efficiency, and heat release under different loads. Model validation against combustion behavior and jet characteristics from a low-pressure, high-mass-flow direct injector is also presented. The results demonstrate that spark plug placement is pivotal to control for combustion stability and efficiency due to the complex in-cylinder mixing associated with direct hydrogen injection. For each load, optimal ignition timings were identified, highlighting the critical interplay between ignition strategy and plug location. This study enhances the understanding of both the challenges and opportunities in converting conventional diesel engines to hydrogen-fueled internal combustion engines, thereby supporting the transition toward cleaner alternatives for heavy-duty transportation.