Combustion Instability in Lab-Scale HREs with Swirl Injectors: Pre- and Post-Chamber Effects

Abstract Combustion instability in hybrid rocket engines (HREs) remains a significant challenge, leading to pressure oscillations, vibrations, and potential engine failure. This study aims to mitigate instability while optimizing performance and safety by investigating the effects of oxidizers swirl injector, pre-combustion chamber, and post-combustion chamber lengths. Using paraffin-based fuels and oxygen, the methodology is based on experimental lab-scale firing tests to analyze the impact of these parameters on combustion dynamics. The research integrates combustion theory, fluid dynamics, and chamber design to identify optimal configurations that reduce instability and enhance fuel regression rates. The study culminates in a proposed engine design that achieves stable combustion and improved performance, offering a pathway to safer and more efficient HREs.