Understanding Lubricant Induced Pre-Ignition in Hydrogen Internal Combustion Engines

H2–ICEs present a promising option for reducing exhaust emissions including CO2 in challenging transportation sectors, such as long-haul and off-highway applications. Compared to petroleum-based fuels, hydrogen offers benefits such as high laminar flame speed, high overall flame speed, and a wide flammability range. However, with low minimum ignition energy hydrogen presents challenges in maintaining stable combustion under high loads, and its low minimum quenching distance causes flames to burn closer to the combustion chamber walls, leading to energy losses through thermal transport.
While hardware design and configuration significantly affect the premature ignition of hydrogen in H2–ICEs, the role of lubricants is under investigation. In this study, the authors introduce a novel methodology to isolate the lubricant's impact on preignition by precisely metering oil into one cylinder of a six-cylinder heavy-duty hydrogen engine and measuring the frequency and magnitude of cylinder pressure spikes and compare it with per-ignition measurement in normal engine operation without external oil dosing. Using this external oil dosing method the authors examined the influence of different lubricant additives on pre-ignition in H2–ICEs. The findings deviate from those related to low-speed pre-ignition (LSPI) in spark-ignited gasoline engines, suggesting that pre-ignition phenomena in H2–ICEs differ substantially from LSPI in gasoline direct injection engines. Understanding these differences in lubricant formulation is crucial for developing lubricants that not only limit but also reduce the severity of pre-ignition events in H2–ICEs.