Experimental and Numerical Investigation of Spark Plug and Passive Pre-Chamber Ignition on a Single-Cylinder Engine with Hydrogen Port Fuel Injection for Lean Operations

The race towards zero carbon emissions is ongoing with the need to reduce the consumption of fossil energy resources. This demands immediate and reliable developments regarding technical environmentally friendly solutions for the power and transportation sectors. An alternative way to achieve a carbon-free powertrain is the use of green hydrogen for internal combustion engines. In this work the self-designed Fraunhofer single-cylinder engine with a displacement volume of 430 mm3 developed for extreme lean combustion and passive pre-chamber ignition was adapted for hydrogen engine operation. With hydrogen combustion, the customized cooling system resulting in low metal temperatures is simulated and optimized to avoid hot spots in the combustion chamber. The investigated single-cylinder engine is characterized by a compression ratio of 12.2, port fuel injection and a conventional spark plug. Based on the results, the engine is operated with a passive pre-chamber to investigate its influence on the ignition of hydrogen mixture. The advantages of pre-chamber combustion for short burning duration and high knock resistance have been demonstrated, especially at full load. This work points out the possibility to reach 23 bar indicated mean effective pressure with optimization of the port fuel injection strategies, operating the engine at lambda 2 and achieving an indicated efficiency above 43 %. The further increase in performance is restricted by the mechanical load limit of 180 bar peak cylinder pressure. Since the engine was still not knock-limited, virtual optimisation showed the possibility to increase the indicated mean effective pressure up to 28 bar at lambda 1.5, with 4 bar boost pressure.