Experimental Investigation on Laser Ignition and Flame Stabilization in an Oxygen/Methane CO2-Diluted Combustor at Elevated Pressures

Direct-fired oxy-fuel supercritical carbon dioxide (sCO2) combustors present a novel approach for near-total carbon capture. However, maintaining a stable flame under extreme pressure and temperatures, characteristic of these combustors, poses significant challenges. Re-ignition failure could necessitate depressurization to atmospheric levels, leading to substantial time and energy losses. This study experimentally investigates laser ignition and flame stabilization in a simplified oxygen/methane-fired, CO2-diluted combustor across various thermodynamic conditions. The test rig comprised a seven-hole showerhead nozzle installed in a pressure vessel, producing a jet flame at pressures up to 5 bar. Non-reactive laser-induced plasma kernel generation experiments were also performed to assess the effect of pressure on kernel dimensions up to 25 bar. The optical access of the combustor enabled plasma kernel generation and laser ignition by focusing a 532-nm laser beam, produced by a 10 Hz Nd:YAG laser, approximately 5 mm from the nozzle tip. The optical access also allowed the collection of images of the flame’s CH* chemiluminescence to assess flame stabilization and plasma kernel dimensions. The results indicate that pressure and CO2 dilution have a considerable impact on flame stabilization. Furthermore, the diameter of the plasma kernel was observed to decrease with increasing pressure, highlighting the importance of laser ignition testing at elevated pressures.