Comparative investigations of flame kernel development in a laser ignited hydrogen-air mixture and methane-air mixture

In this research, experimental investigations are carried out to study the laser ignition of hydrogen-air mixtures, which are compared with the baseline data of laser ignited methane-air mixtures. Experiments were carried out in a high pressure constant volume combustion chamber (CVCC) to investigate the flame kernel development and visualization, and flame speeds. The initial operating conditions of the experiments were set to 373 K chamber temperature and 10 bar chamber filling pressure. The flame kernel growth was investigated for different hydrogen-air mixture strengths ranging from λ = 2.0-5.0 and compared with the baseline of methane-air mixtures of λ = 1.2. A Q-switched Nd: YAG laser at 1064 nm wavelength with pulse duration of 6-9 ns was used for ignition by generating laser plasma inside the CVCC. The results indicate that the phenomenon of micro-explosions in the wave-front of hydrogen-air mixtures lead to significantly different flame front evolution and higher flame speeds compared to methane-air mixtures.