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

Abstract

<div class="section abstract"><div class="htmlview paragraph">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 low-carbon internal combustion engines (ICE). Especially for large, heavy-duty engines, this is a promising route, as replacing them with battery electric or fuel cell drives poses even greater challenges, at least for the time being. For some applications or areas of the world, small ICEs for trucks, passenger cars or off-road vehicles, operated with alternative fuels will still remain the means 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. This paper will give a brief introduction, showing the results of studies on the contribution of oil droplets to combustion anomalies. In this study, oil droplets were artificially injected into the intake manifold in order to trigger pre-ignition. 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 qualitative results. The deuterium and the carbon method show very good quantitative congruence as well and are therefore considered to be very precise and. The respective advantages and disadvantages are shown in the discussion chapter.</div><div class="htmlview paragraph">Additionally, measurement data will show the influence of the hydrogen production (green vs. grey) on its isotopic ratio. This can be a measure for classifying hydrogen without knowing the exact source.</div></div>