The study demonstrates that the dump plane is not merely a geometric boundary but can actively trigger and amplify thermoacoustic oscillations through near-field counter-rotating vortex interactions. Under certain forcing conditions, this creates rapid heat release events synchronized with pressure oscillations, leading to strong positive feedback and instability growth. The paper extends previous work on vortex–wall and vortex–nozzle interactions by identifying the dump plane itself as an active participant in thermoacoustic instability generation.The work contributes: (1) a new experimentally supported instability mechanism, (2) detailed phase-resolved flow/flame diagnostics, (3) insight into vortex-driven heat release modulation, and (4) implications for passive and active instability control in practical combustors. The most important contribution of the work is the proposed mechanism for dump-plane-mediated instability.The study shows that: A vortex near the dump plane induces strong inward flow because of a ground-effect-like interaction. This inward motion drags the flame and heat release zone into the inlet region. A second counter-rotating vortex forms near the dump corner. The interaction between the two vortices rapidly burns entrained reactants. The resulting pressure rise reinforces the vortex motion, closing a positive thermoacoustic feedback loop.This produces a characteristic tri-lobed or “clover-shaped” flame observed experimentally at 500 Hz forcing. The schematic on page 10 summarizes this process visually. Simultaneous pressure and heat-release measurements showed that, for the 500 Hz case, heat release oscillations were in phase with pressure oscillations, producing a positive local Rayleigh index. This confirms that the dump-plane-mediated vortex interactions actively reinforce thermoacoustic oscillations. In contrast, the 200 Hz case showed negligible Rayleigh reinforcement near the dump plane.
154 0 0 0
Vortex Driven Heat Release Modulation Premixed Combustors
Amardip Ghosh #Advanced Propulsion Systems (APSYS) Lab
The study demonstrates that the dump plane is not merely a geometric boundary but can actively trigger and amplify thermoacoustic oscillations through near-field counter-rotating vortex interactions. Under certain forcing conditions, this creates rapid heat release events synchronized with pressure oscillations, leading to strong positive feedback and instability growth. The paper extends previous work on vortex–wall and vortex–nozzle interactions by identifying the dump plane itself as an active participant in thermoacoustic instability generation.The work contributes: (1) a new experimentally supported instability mechanism, (2) detailed phase-resolved flow/flame diagnostics, (3) insight into vortex-driven heat release modulation, and (4) implications for passive and active instability control in practical combustors. The most important contribution of the work is the proposed mechanism for dump-plane-mediated instability.The study shows that: A vortex near the dump plane induces strong inward flow because of a ground-effect-like interaction. This inward motion drags the flame and heat release zone into the inlet region. A second counter-rotating vortex forms near the dump corner. The interaction between the two vortices rapidly burns entrained reactants. The resulting pressure rise reinforces the vortex motion, closing a positive thermoacoustic feedback loop.This produces a characteristic tri-lobed or “clover-shaped” flame observed experimentally at 500 Hz forcing. The schematic on page 10 summarizes this process visually. Simultaneous pressure and heat-release measurements showed that, for the 500 Hz case, heat release oscillations were in phase with pressure oscillations, producing a positive local Rayleigh index. This confirms that the dump-plane-mediated vortex interactions actively reinforce thermoacoustic oscillations. In contrast, the 200 Hz case showed negligible Rayleigh reinforcement near the dump plane.