Ignition of a large stationary natural gas engine by high-peak power passively Q-switched Nd:YAG/Cr4+:YAG laser spark plugs

A high-power large stationary natural gas engine was operated with the help of compact laser ignitors. The laser devices, employing high-peak power passively Q-switched composite Nd:YAG/Cr4+:YAG ceramic media with monolithic resonators, were designed for both pre-chamber and direct ignition configurations. The maximum cylinder pressures and their cycle-to-cycle variability (expressed as the coefficient of variation of the maximum pressure) were evaluated at nominal engine operating powers of 200 kW and 250 kW, as well as at a higher output of 275 kW. Under nominal operating conditions, including lean fuel-air mixtures near the misfire limit, the laser spark plug with pre-chamber achieved higher maximum pressures and showed either improved combustion stability at 200 kW or comparable to that at 250 kW relative to the pre-chambered electric spark plug. Furthermore, long-term endurance testing over several hours yielded encouraging results, supporting the viability of laser ignition technology for high-power natural gas engines.