Low-Frequency Feed-System-Coupled Combustion Instability in Hybrid Rocket Motors

The low-frequency unstable combustion of hybrid rocket motors was investigated using the transfer function of the full thermal-combustion-gasdynamic coupled system that was coupled with a liquid oxidizer feed system. This transfer function was obtained based on the method developed by Karabeyoglu et al. The transfer function is applicable to the motors that have a long fuel port length. The linear stability limits and the frequencies of pressure oscillations in hybrid rocket motors were obtained theoretically using the transfer function. In addition, we compared these results with the results obtained under the assumption that various physical quantities change in bulk mode.