Approaches for Mechanical Development and Validation of Hydrogen Internal Combustion Engines

Hydrogen Internal Combustion Engines (H2 ICEs) are seen as a viable zero-emission technology that can be implemented relatively quickly and cost-effectively by automotive manufacturers. The changed boundary conditions of a hydrogen-fueled engine in terms of mechanical and thermal aspects require a review and potential refinement of the design especially for the 'piston bore interface' (liner honing, ring and piston design) but also for other engine sub-systems, e.g. the crankcase ventilation system. The influence of oil entry into the combustion chamber is even more important in hydrogen engines due to the risk of oil-induced pre-ignition. Therefore, investigations of the interaction between friction, blowby and oil transfer into the combustion chamber were performed and are presented in this paper. During the investigations experimental tests were carried out on a single cylinder engine ('floating liner') and on a multi-cylinder engine. The 'floating liner' concept allows the crank angle resolved measurement of friction force between piston, rings and liner. A baseline and three different liner honing variants were measured during hydrogen operation and were compared to a baseline measurement during gasoline operation. In parallel the oil consumption was determined by balancing all carbon-containing components in the intake air and exhaust gas. This is only possible when using a carbon-free fuel like hydrogen. The measured influences on the single cylinder engine were validated in addition on the multi cylinder engine. The aim is to find solutions that are advantageous for hydrogen propulsion both in tribological terms and in terms of the tendency for oil-induced combustion anomalies. The measurement results are a very good base to identify further potentials for optimization and can be used as input for simulation models. The overall approach also supports the implementation of digital twins for a targeted and effective mechanical development and validation of future hydrogen engines.