In the future, the hydrogen engine will undoubtedly play an important role in the mobility of goods and people as well as in the field of mobile machinery. In addition to issues such as transient, lean operation, exhaust gas aftertreatment and components durability, engine oil-induced combustion anomalies play a key role in development. In the course of several projects on hydrogen engines for passenger cars and commercial vehicles, the institute has developed a method to evaluate different oil formulations for their tendency to combustion anomalies (mainly pre-ignition) as simply and efficiently as possible. The aim was to minimise both the amount of oil required and the test time. The test was carried out by externally dosing the test oil into the intake port of one cylinder. This means that a direct online comparison with the other cylinders (without oil dosing) already provides an indication of the tendency towards abnormal combustion. The amount of oil added is varied in the range corresponding to a real oil input into the combustion chamber (e.g. influence of higher oil consumption due to ageing).

The following diagram shows the complete measurement setup. In addition to varying the amount of oil, it is also possible to preheat the oil. The oil should then be introduced relatively close to the intake valve to minimise wall wetting. Pre-ignition is detected by fuel conversion (10 % and 50 % mass fraction burnt) and maximum cylinder pressure (PMAX).

The following figure shows a comparison of two oil samples. In principle, each measurement starts with preconditioning (no dosing), followed by the dosing phase and a final post-conditioning phase (no dosing). As can be clearly seen in the example shown, the exact oil formulation has a significant effect on the number of pre-ignitions during the dosing phase. This method can therefore be used to compare and evaluate a wide variety of oil formulations quickly and efficiently.