Towards Robust Hydrogen Combustion: Precise Lube Oil Consumption Measurement as an Enabler for Tackling Pre-ignition

The use of carbon-free fuels, such as ammonia or hydrogen, or at least carbon neutral fuels, such as green methane or methanol is one of the most important paths in the development of clean internal combustion engines (ICE). Especially for large, heavy-duty engines, this seems to be the most promising route, as replacing them with battery electric or fuel cell drives poses even greater challenges, at least for the time being. But for some applications or areas of the world, even small ICEs for trucks, passenger cars or off-road vehicles, operated with alternative fuels will still remain the mean of choice. One of the biggest challenges in the development of hydrogen combustion engines is achieving high compression ratios and mean effective pressures due to combustion anomalies, caused by the low ignition delay and broad flammability limit of hydrogen. Oil droplets are considered to be one of the main triggers for pre-ignition and knocking. Therefore, this paper will first give a brief introduction showing the results of studies on the contribution of oil droplets to combustion anomalies. As the correlation between these two phenomena was clearly seen, the second part of the paper will focus on the measurement of oil consumption, which is an important way to combat combustion anomalies. To this end, three innovative measurement technologies were compared. The first method is based on the balance of carbon entering and leaving the combustion chamber. The second method is based on the use of deuterium, which is added to the engine oil as a tracer. The third method is based on measuring the unburnt portion of hydrocarbons with a time-of-flight mass spectrometer (TOF-MS). All methods provide very similar results and are therefore considered to be very precise and sensitive. The respective advantages and disadvantages are shown in the discussion chapter.