ABSTRACT
Regenerative cooling technology is a critical solution to ensure the reliable operation of scramjet combustion chambers under extreme thermal environments. However, drastic variations in fuel properties can trigger flow instability, risking local cooling failure and flight safety. The interaction and propagation mechanisms of such instabilities in multi-channel systems remain poorly understood. In this study, the regenerative cooling system is simplified into a multi-channel configuration, and a three-dimensional numerical simulation is conducted using supercritical RP-3 as the coolant. The results reveal that, under the gravity, flow instability initiates in low-flow channels, followed by delayed instability in high-flow channels, eventually forming density wave oscillations. The initial instability stems from strong density gradients in low-flow regions, which induce downstream turbulence. This increases resistance in adjacent channels, triggering a positive feedback loop involving flow rate, fluid density, and pressure drop. Consequently, instability spreads, evolving into a self-excited, sustained oscillation across the system.
