Thermal Management of Pre-Chamber Spark Plugs for the Mitigation of Abnormal Ignition in Hydrogen-Fueled Engines – An Experimental and Numerical Study

The internal combustion engine will continue to contribute to global mobility, particularly when operated with CO₂-neutral or low-carbon fuels. Pre-chamber ignition systems are increasingly investigated to meet future requirements regarding efficiency, emissions, and combustion stability. In combination with hydrogen as a carbon-free fuel, pre-chamber spark plugs enable a significant extension of the lean operating limit while ensuring reliable ignition under demanding boundary conditions. A key development challenge is the thermal management of the pre-chamber spark plug. While the thermal behaviour of conventional production spark plugs is well established, limited knowledge exists for pre-chamber systems. The interaction of chamber geometry, material selection, manufacturing and joining processes, and installation position in the cylinder head strongly influences thermal loading and operational behaviour. Excessive local temperatures may promote knock, pre-ignition, or material degradation and must therefore be systematically addressed. The objective of this study is to establish a comprehensive system-level understanding of the thermal behaviour of pre-chamber spark plugs. Experimental investigations are conducted on a single-cylinder research engine test bench using hydrogen and RON 95 for reference. The pre-chamber material is varied systematically, and the components are equipped with dedicated temperature measurement instrumentation to capture local temperature distributions under representative operating conditions. Thermal hotspots are identified, parameter sensitivities are analysed, and design recommendations are derived. Furthermore, the knocking behaviour of hydrogen combustion was studied using both pre-chamber and standard spark plugs. The experimental data are further used to validate a fully coupled transient conjugate heat transfer (CHT) model integrated into a dynamic engine CFD simulation with moving boundaries. The model accounts for realistic wall thicknesses, temperature-dependent material properties, cyclic thermal loading, and calibrated convective boundary conditions. The combined experimental–numerical approach enables cycle-resolved assessment of local heat fluxes and critical temperature levels, providing a robust basis for targeted pre-chamber design optimization.