Dynamic laser ignition characteristics of solid fuel and oxygen for hybrid rocket system

The transient laser ignition process in a slab burner that is similar to hybrid rocket motors is investigated in this study. The coupling characteristics between solid fuel properties, pyrolysis rate, and laser power were analysed. The results show that the laser ignition process can be divided into four stages: preheating, pyrolysis, ignition, and combustion, with the preheating and pyrolysis stages primarily controlled by the solid heating rate and the mixing characteristics in the fuel-rich combustion zone. Meanwhile, the ignition and combustion stages were characterized by ignition kernel growth and flame front propagation. The ignition delay time and the establishment of steady-state combustion were significantly affected by the ignition energy and fuel properties, i.e., The ignition delay time increases exponentially with decreasing laser energy. An increase in oxidizer flow flux reduces the demand for mixing during ignition, but the corresponding increase in combustion pressure poses challenges to the ignition process. A two-dimensional transient numerical model was established based on optical-thermal coupling theory to further understand the dynamic pyrolysis process of solid fuel particles. The model was validated through fire experiments under different laser ignition energy conditions. The results indicate that the deviation of the maximum penetration depth and ignition delay time between the experiment and the simulation is within 7 %.