Experimental investigation of the heat flux characteristic of the active prechamber for hydrogen engine in a constant volume bomb calorimeter

Hydrogen internal combustion engines are increasingly recognized as promising solutions for carbon-free power; however, the short flame quenching distance of hydrogen leads to heat transfer losses typically three times higher than those of conventional fuels. In this study, the combustion and heat flux characteristics of a hydrogen-air mixture ignited by a 6-orifice active prechamber designed for 230 mm large bore marine engine are measured and analyzed in a constant volume bomb calorimeter system by schlieren. The variation of ignition delay, pressure rise, and heat flux peak values with equivalence ratio ranging from the ultra-lean of 0.2 to rich mixture of 1.2 is examined under initial pressures of 1 and 3 bar. The influence of the spark plug offset in the prechamber on the initial flame velocity of different orifices is analyzed, holding certain guiding significance for the spatial arrangement of the prechamber in the cylinder. Furthermore, the variation of the ignition delay time, the pressure, and the heat flux in the main chamber with respect to the equivalence ratio under different initial pressure are analyzed. In addition, the trends of the peak pressure and peak heat flux within the different range of equivalence ratio are also examined. These findings provide valuable experimental data on thermal characteristics of hydrogen-air flame, contributing to the development of heat transfer models for hydrogen internal combustion engines.