Experimental studies on challenges in hydrogen heavy-duty and marine engines

This dissertation addresses two critical challenges in developing hydrogen-powered heavy-duty and marine engines: (1) hydrogen jet dynamics and mixing and (2) hydrogen pre-ignition induced by engine lubricating oils. Experiments on hydrogen jet dynamics are conducted using high-speed z-type schlieren imaging in a constant- volume chamber under varying pressure ratios, needle lifts, nozzle geometries, injection angles, and injection durations. Results show that higher pressure ratios and increased needle lift enhance jet penetration and cross-sectional area, improving air-fuel mixing due to the greater mass of injected fuel and momentum. Nozzle geometry also significantly affects jet behavior. Single-hole nozzles produce faster penetration and multi-hole nozzles produce larger cross-sectional areas that improve air-fuel mixing. However, variations in the injection angle lead to jet-piston impingement near the periphery, resulting in uneven air-fuel mixtures, while injection duration has minimal impact on jet dynamics. These findings offer valuable insights for optimizing injection parameters to improve air-fuel mixing, especially in direct-injection hydrogen engines. The dissertation also investigates pre-ignition phenomenon in hydrogen engines induced by engine lubricating oils. Using a rapid compression expansion machine (RCEM) with optical access, this study evaluates lubricating oils from different API (American Petroleum Institute) categories. These lubricants, with varying levels of calcium and magnesium detergents, are studied under a range of air-to-fuel and compression ratios. The results reveal that API Group V base oils with lower calcium content exhibit greater resistance to pre-ignition, while the role of calcium in increasing reactivity in API Group II oils is minimal. These findings highlight the critical role of engine lubricating oil composition in influencing flame propagation, pre-ignition limits, and overall combustion dynamics. By integrating experimental and computational approaches, this dissertation provides practical solutions for optimizing jet dynamics and mixing, as well as for selecting lubricating oils for hydrogen engines. These advancements support the adoption of hydrogen as a zero-carbon fuel for heavy-duty and marine applications.