Effects of different prechamber spark plug geometries on combustion anomalies in an internal combustion engine

Operating an Otto-Engine with hydrogen as fuel the probability of combustion anomalies like knocking, pre-ignition and backfiring increases significantly. Knocking is strongly dependent on the operating point, while the cause for preignition is still investigated. Literature as well as preliminary investigations to this work suggest that especially the spark plug has a significant influence on the occurrence of preignition and backfiring. Hence, the scope of this paper is to identify and understand the influence of the spark plug on preignition in order to reduce their occurrence and receive more mechanical power from the engine. In the first step, the operating conditions leading to preignition and backfiring are determined experimentally using a naturally aspirated single cylinder gas engine and a state-of-the-art prechamber spark plug. Afterwards, different prechamber designs of the spark plug, including a variation of the cap volume, thickness and the orifices diameter, are investigated with respect to their tendency to cause preignition. Additionally, measurements are done with a spark plug in which the electrode material has been changed. 3D-CFD simulations with the aim of visualizing the flow processes in the prechamber support the analysis of the experimental results and are the base for new prechamber designs.