Linking lubricant oil contamination to pre-ignition events in hydrogen engines–The HyLube mechanism

The practical use of hydrogen as a fuel for Internal Combustion Engines (ICEs) poses unresolved challenges. However, many issues concerning combustion control and emissions do not originate from the fuel itself but rather from the inevitable interference of lubricant oil in the combustion process. This study investigates the catalytic action of lubricant oil to elucidate certain pre-ignition events in hydrogen ICEs that are not yet fully understood. In pursuit of this goal, a numerical tool is developed, which can also contribute to improving the design of future powertrains. In the first part of the work, a reduced chemical model named the “HyLube” reaction mechanism was developed for investigating hydrogen-lubricant interactions. A single surrogate species, i.e., n-hexadecane (n-C16H34), was selected to mimic the chemical properties of lubricant oil, based on prior research. Extensive validation using experimental data from the literature demonstrated the accuracy and reliability of the model. With 133 species and 2074 reactions, the kinetic mechanism is well-suited for integration into CFD simulations of engines. In the second part, using the “HyLube” mechanism, predictions were made to determine if lubricant oil contamination affects hydrogen ICE operation. Zero-dimensional simulations quantified the impact of adding the lubricant oil surrogate to H2/air mixtures on charge reactivity across a range of engine-like thermodynamic conditions, encompassing compression ratio and equivalence ratio variations. The findings indicated significant effects, especially at lower temperatures, suggesting potential hazards before combustion initiation.