A novel method for lubrication oil consumption measurement for wholistic tribological assessments of internal combustion engines

The research and development of combustion engines will face multiple challenges during the next years. Increasing reliability while further reducing emissions and life cycle costs are just a few of them. The reduction of the lubrication oil consumption (LOC) addresses all the aforementioned challenges. Reducing the oil consumption of an engine, reduces emissions like particle emissions, hydrocarbon emissions and combustion anomalies. However, the biggest incitement for optimizing the oil consumption would be to lower the life cycle cost through extending the durability of the exhaust gas aftertreatment system, as contaminants coming from the oil are considered to lead to poisoning of catalytic materials. In addition, it is also important to take the cost of the lubrication oil itself into account as well. Thus, especially for manufacturers of large stationary gas engines, reducing – or rather, optimizing – the lube oil consumption is becoming more and more of a focus. However, a further reduction of the LOC causes state-of-the-art measurement methods to reach their limitations regarding resolution and lower detection limit (LDL). Hence, new methods need to be developed. Most currently available systems are based on the tracer technology, where a naturally abundant or synthetically added substance of the oil is traced down in the exhaust gas. By quantifying the amount of tracer in the exhaust gas, the LOC can be calculated. The newly developed and patented (Rossegger and Engelmayer, 2018) [1] method presented in this article is based on the use of the stable hydrogen isotope deuterium (2H) as a tracer. It is added to the oil by conducting a hydrogen/deuterium (1H/2H) exchange process with synthetic oil, which is then blended into the oil. When operating the engine, the deuterium can be detected in the exhaust gas water vapor using an isotopic water analyzer based on the cavity ring-down spectroscopy (CRDS). The present article will first focus on the synthesis of the tracer, then on the design of a prototype and finally present measurement results collected on a passenger car engine.