A study on hydrogen concentration in the crankcase of a hydrogen internal combustion engine

Hydrogen internal combustion engines (ICE) are considered as a potential countermeasure against global warming, especially for heavy-duty vehicles, where electrification (EV conversion) is challenging. In a hydrogen ICE, a part of hydrogen in the combustion chamber is carried into the crankcase with blow-by gas. If the hydrogen concentration in the crankcase exceeds its ignition limit of 4%, combined with hot spots ( e.g. , bearing seizure), it can lead to an explosion. Therefore, it is crucial to maintain the hydrogen concentration in the crankcase below 4%. Previous engine tests conducted by the authors have shown that engine type and piston ring design influence the hydrogen concentration in the crankcase. In this study, the pressure and hydrogen concentration in each piston land, as well as the hydrogen concentration in the crankcase, were calculated to identify the specifications that affect hydrogen levels in the crankcase. As a result of these calculations, it was found that factors such as the top and oil control ring gap widths, the type of oil control ring, hydrogen injection timing, ignition timing, and the number of rings play a significant role in reducing hydrogen concentration in the crankcase. These findings offer insights for the practical application of hydrogen engines and are presented in this paper. • Calculation method for hydrogen concentration developed considering piston ring behavior. • Optimizing injection timing helps reducing hydrogen concentration in the crankcase. • Earlier ignition timing results in lower hydrogen concentration in the crankcase. • A 3-piece oil control ring might reduce hydrogen concentration in the crankcase. • There is an optimal combination of gap widths for the top and oil control rings.