发表机构
Department of Aerospace Engineering, Indian Institute of Science（印度科学研究所航空工程系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过实验与降阶模型揭示双腔超声速燃烧室低频呼吸振荡由空腔与自由流周期性质量交换及压力-剪切层反馈驱动，并发现乙烯点火热释放可永久抑制该振荡。
AI 中文摘要
低频空腔呼吸振荡会强烈影响空腔稳定超声速燃烧室中的火焰稳定性和可操作性，然而在相对布置的双腔构型中，其水动力学起源和抑制机制仍未被充分理解。我们利用同步高速纹影成像、壁面压力测量、数值模拟、非线性相空间重构、希尔伯特变换分析和降阶建模，研究了低焓和高焓条件下相对布置双腔超声速燃烧室的呼吸动力学。在低焓条件下，观察到自持呼吸模态，主频约为156 Hz，空腔底部与斜坡压力之间存在较大相位差。测量和模拟表明，空腔与自由流之间的周期性质量交换驱动了空腔的周期性降压和再增压，建立了压力-剪切层反馈回路，从而维持振荡。一个与剪切层位移坐标耦合的双压力态降阶模型再现了测量到的频率、压力相位关系和稳定性特征，证明要捕捉该动力学过程，体腔压力和再附着/激波脚压力状态两者缺一不可。上游氮气注入仅产生瞬态衰减，随着注入气体向下游对流，振荡得以恢复。相比之下，乙烯注入后点火可永久抑制振荡，非线性吸引子坍缩至稳定平衡态。热释放重新组织了空腔压力场，并改变了密度、可压缩性和压力响应时间尺度，从而削弱了维持呼吸模态的反馈机制。
英文摘要
Low-frequency cavity breathing oscillations can strongly affect flame stabilization and operability in cavity-stabilized supersonic combustors, yet their hydrodynamic origin and suppression remain insufficiently understood in opposed twin-cavity configurations. We investigate the breathing dynamics of an opposed twin-cavity supersonic combustor under low- and high-enthalpy conditions using synchronized high-speed Schlieren imaging, wall-pressure measurements, numerical simulations, nonlinear phase-space reconstruction, Hilbert-transform analysis, and reduced-order modelling. Under low-enthalpy conditions, a self-sustained breathing mode is observed at a dominant frequency of approximately 156 Hz, with large phase differences between cavity-floor and ramp pressures. Measurements and simulations show that periodic mass exchange between the cavity and freestream drives cyclic cavity depressurization and repressurization, establishing a pressure-shear-layer feedback loop that sustains the oscillation. A two-pressure-state reduced-order model, coupled with a shear-layer displacement coordinate, reproduces the measured frequency, pressure phase relationship, and stability characteristics, demonstrating that both bulk-cavity and reattachment/shock-foot pressure states are required to capture the dynamics. Upstream nitrogen injection produces only transient attenuation, with the oscillation recovering as the injected gas convects downstream. In contrast, ethylene injection followed by ignition permanently suppresses the oscillation, with the nonlinear attractor collapsing to a stable equilibrium. Heat release reorganizes the cavity pressure field and alters density, compressibility, and pressure-response timescales, thereby weakening the feedback mechanism responsible for sustaining the breathing mode.
