涡声相互作用诱导的压气机声共振机理及抑制方法研究

Acoustic resonance in compressors is a complicated vortex sound interaction phenomenon, which cannot only cause high intensity sound pressure fluctuation over 160dB(2000Pa) to reduce the compressor efficiency severely, but also lead to blade failure issues and pose a serious threat to the structural integrity. Most of the previous theoretical models, based on the linear theory, fail to depict the inner link between the flow and sound field. In this project we aim to establish a rapid and effective model, which can give the details of the vortex structure and sound field distribution simultaneously to study the non-linear vortex sound interaction, and the control strategy of acoustic resonance will also be evaluated based on some experimental measurements. To be specific, a discrete vortex model together with the vortex sound theory and the time-domain boundary element method will be introduced to simulate the sound radiation and propagation of the vortex shedding from the blade trailing edge. After the coupling calculation between the flow and sound field completed by imposing the feedback sound to the vortex shedding, an enclosure acoustic resonance prediction model can be obtained. Then, the influence of inside acoustic liner on the suppression of acoustic resonance will be measured in a flow duct to validate and improve the theoretical model. And finally, some previous experimental data measured on a real aeroengine will be used to explore the mechanism of acoustic resonance in compressors, and the engineering feasibility of the suppression method will also be assessed. Through this investigation, we can obtain more insight into the underlying mechanism of vortex sound interaction, and get a better understanding of the acoustic resonance problem in compressors.

压气机声共振是一种复杂的涡声相互作用现象，能够产生超过160dB（2000Pa）的声压波动，不仅极大影响压气机工作效率，还可导致叶片疲劳破坏，严重威胁结构可靠性。现有研究普遍采用线性理论模型，不能真正体现涡声之间的内在联系。本申请旨在发展一种快速、有效的声共振模型预测方法，细致刻画声共振状态下的流场和声场特征，分析涡声非线性相互作用，并结合实验研究探讨声共振的产生机理及其控制策略。拟采取的研究措施是基于离散涡方法、涡声理论和时域边界元方法模拟叶片尾迹涡发声及声传播，借助声反馈，实现流场与声场的实时耦合求解，建立完整的声共振预测模型。然后，利用流管实验研究壁面声处理对声共振的抑制效果，验证并完善理论模型。最后，结合已有的真实压气机实验数据，探讨声共振的产生机理，并评估其抑制方法的工程可行性。该研究可加深我们对涡声相互作用机制的理解，同时为认识压气机声共振问题提供新的理论指导。

压气机内部声共振是分离涡与声波相互作用的结果，其不仅恶化压气机工作效率，还可诱发叶片疲劳失效，威胁结构安全。本项目瞄准复杂声共振现象背后的物理机制，开展考虑涡声非线性相互作用的叶片槽道间声共振快速预测模型开发，研究基于壁面声处理的声共振抑制方法，最后结合真实压气机试验数据探讨声共振的产生机理及其控制策略。本项目取得的具体研究成果包括：1）基于无网格方法发展了叶片尾迹涡与槽道间声场的自发非线性相互作用的物理模型，在保证计算精度和效率的前提下，实现了对声共振频率和幅值的同步预测，获得了反馈声波对流场尾迹涡的涡量、频率及其时空演化过程的调制规律，揭示了叶片尾迹涡模态与槽道内声模态之间的频率竞争和锁定机制。2）基于壁面声处理的方法，有效切断了声波与脱落涡之间的反馈路径，获得了利用吸声系数较低的声衬便可大幅降低声共振声压和脱落涡幅值的实验结果，从而实现了对叶片声波激励与尾迹涡激励源的双重控制。3）对某型航空发动机压气机内部的异常噪声、流场和叶片振动规律进行了深入分析，证实了该压气机在特定转速区内出现了声共振现象，在真实结构和复杂流动条件下验证了涡声相互作用导致声共振理论的合理性，深化了对实际工程中声共振现象及其抑制策略的理解。