Role of Precombustion Chamber Design in Feed-System Coupled Instabilities of Hybrid Rockets

Abstract

Oxidizer feed-system coupled instabilities have been observed in several liquid and hybrid propellant rocket engines, though, not likely to be catastrophic for the latter. However, severe pressure oscillation in hybrid rocket may result in a significant reduction in the performance of the propulsion system restricting the application of the technology. In this research, it was studied, theoretically and experimentally, feed-system coupled instabilities for hybrid rocket engines. Two test campaigns were performed to investigate the effects of the pre-combustion chamber and oxidizer injector configurations on engine pressure oscillation. Then, an extended mathematical formulation, including the injector pressure drop, the pre-combustion chamber residence time, the gas residence time, and the combustion time lag, has been proposed. The investigation was based on a transfer function using the stability limit analysis and the root locus method. It has been found that the configuration of pre-combustion chamber plays an important role in the nature of the feed