环形燃烧室周向燃烧不稳定性模态转变机理研究

Lean premixed combustion is commonly adopted in civil aero-engine and industrial gas turbine combustors in order to reduce pollutant emissions. However, these lean premixed combustors often suffer from combustion instability which lower combustor performance and reduce mechanical durability. Azimuthal instability is usually found in annular combustions where azimuthal mode switches between standing and spinning mode randomly. Experiments and large-eddy simulation are conducted to investigate mode switching mechanisms of azimuthal combustion instability. Simultaneous pressure fluctuation, velocity oscillation and unsteady heat release measurements are conducted to reveal thermo-acoustic coupling mechanisms of azimuthal instabilities. Effects of nozzle space and swirling array on thermo-acoustic coupling and mode switching are analyzed. Standing and spinning forcing are carried out to investigate multi-nozzle flame response respectively. Mode switching mechanisms are revealed with the thermo-acoustic coupling mechanisms and multi-nozzle flame response, which offers basic models for theory analysis and prediction of azimuthal combustion instability. The results of this project will support the design of future high-performance aero-engine and gas turbine combustors.

民用航空发动机及燃气轮机燃烧室通常采用贫预混燃烧降低污染物排放，这带来燃烧不稳定性问题。燃烧不稳定性导致燃烧室性能下降，结构部件寿命缩短。环形燃烧室通常发生周向驻波模态和旋转模态燃烧不稳定性，且会在驻波模态和旋转模态之间发生随机转变。本项目拟采用实验测量和大涡模拟相结合的手段对环形燃烧室周向模态转变机理开展研究。通过压力脉动、喷嘴出口速度脉动和火焰非稳态热释放同步测量，分析周向燃烧不稳定性热声耦合规律，讨论喷嘴间距和旋向组合对多喷嘴火焰热声耦合及模态转变的影响。采用横向驻波声激励和旋转声激励探讨不同声模态下环形燃烧室多喷嘴火焰动态响应特性。通过多喷嘴火焰热声耦合规律及火焰响应特性揭示周向模态转变机理，为环形燃烧室周向燃烧不稳定性的理论分析及预测提供模型基础和实验参考，支撑未来高性能航空发动机及燃气轮机燃烧室的研制与性能的进一步提高。

民用航空发动机及燃气轮机燃烧室通常采用贫预混燃烧降低污染物排放，这将带来燃烧不稳定性问题。燃烧不稳定性通常会导致燃烧室性能下降，结构部件寿命缩短。环形燃烧室通常发生周向驻波模态和旋转模态燃烧不稳定性，且会在驻波模态和旋转模态之间发生随机转变。.本项目首先以环形燃烧室单喷嘴火焰为研究对象，开展纵向声激励下单喷嘴火焰响应特性研究，获取小幅值激励下单喷嘴火焰动态响应过程，提取单喷嘴火焰传递函数。此外，开展入口大幅值扰动下单喷嘴火焰非线性响应特性研究，提取火焰描述函数，揭示火焰动态响应火焰/旋涡脱落耦合机理。在此基础上，采用实验测量和大涡模拟相结合的手段对环形燃烧室周向模态转变机理开展研究。通过压力脉动、喷嘴出口速度脉动和火焰非稳态热释放同步测量，分析周向燃烧不稳定性热声耦合规律，讨论当量比和周向火焰个数对多喷嘴火焰热声耦合及模态转变的影响，探讨横向驻波声激励和旋转声激励下环形燃烧室多喷嘴火焰动态响应特性。.通过本项目研究，揭示了环形燃烧室周向燃烧不稳定性热声耦合规律，构建了不同声模态激励下环形燃烧室多喷嘴火焰响应模型，建立了环形燃烧室周向燃烧不稳定性大涡模拟预测方法，阐明了环形燃烧室模态转变机制。突破了环形燃烧室周向模态识别技术，多喷嘴火焰热释放、动态压力和喷嘴出口速度脉动同步测量技术和环形燃烧室燃烧不稳定性大涡模拟技术，为环形燃烧室周向燃烧不稳定性的理论分析及预测提供模型基础和实验参考。