Feedback directions governing self-sustained thermoacoustic instability in rocket engine combustors.

This article focuses on investigating the feedback interactions among acoustic pressure, heat release rate, vorticity, flow velocity, and temperature fluctuations during high-frequency thermoacoustic instability (TAI) in a single-element liquid rocket engine combustor known as HAMSTER. Using symbolic transfer entropy (STE) applied to high-fidelity large eddy simulation (LES) data validated by experiments, the study identifies the direction and strength of mutual influences between these variables on spatiotemporal scales, revealing that vorticity near the fuel collar acts as a primary driver amplifying acoustic pressure oscillations. The analysis quantifies seven distinct stages of feedback interactions within one TAI cycle, showing dynamic switching in the dominant driving variables and highlighting the complex nonlinear coupling sustaining TAI. These findings provide insights into the epicenter and mechanisms of TAI, offering potential pathways for combustor redesign and instability mitigation in rocket engines.