Application of a One-Dimensional Dilution and Evaporation Lubricant Oil Model to Predict Oil Evaporation under Different Engine Operative Conditions Considering a Large Hydrogen-Fuelled Engine 2023-24-0009

The increasing environmental concern is leading to the need for innovation in the field of internal combustion engines, in order to reduce the carbon footprint. In this context, hydrogen is a possible mid-term solution to be used both in conventional-like internal combustion engines and in fuel cells (for hybridization purposes), thus, hydrogen combustion characteristics must be considered. In particular, the flame of a hydrogen combustion is less subjected to the quenching effect caused by the engine walls in the combustion chamber. Thus, the significant heating up of the thin lubricant layer upon the cylinder liner may lead to its evaporation, possibly and negatively affecting the combustion process, soot production. The authors propose an analysis which aims to address the behavior of different typical engine oils, (SAE0W30, SAE5W30, SAE5W40) under engine thermo-physical conditions considering a large hydrogen-fuelled engine. The operative conditions are obtained by means of simulations through a zero-dimensional engine model in OpenWAM environment. The lubricant oils composition and properties are defined by means of a statistical interference-based optimization approach which identifies the most proper mixture of heavy hydrocarbons as a surrogate of real oils. Then, the mixture is implemented in an in-house developed heat and mass transfer one-dimensional model which accounts for the lubricant oil evaporation and the mutual diffusion between the oil surrogate components. This work aims to test and analyze the response of different lubricant oils to heating and evaporation processes during the compression and combustion stroke of a hydrogen-fuelled internal combustion engine. The behaviour and the properties evolution during the compression and part of the expansion strokes of different lubricant oils in two different engine operative conditions are captured and discussed.