叶轮机湍流噪声的管道模态相干原理及物理机制研究

After the obviously reduction of the rotor-stator interaction tone noise, turbomachinery turbulence broadband noise is now a major contributor to the noise emission of modern high-bypass-ratio turbofan engines in use on civil aircraft. Turbulence broadband noise is scattered while passing through the various rotor-stator stages present in turbomachinery components. Since these scattering processes depend on the modal content of the sound field, it is reasonable to decompose the acoustic field into modes to investigate the mechanism of turbulence broadband noise and to identify and separate the different broadband noise sources. Due to the complexity as well as the lack of investigation of the turbulence noise, the mechanisms responsible for turbulence noise and the statistical relation between radiation modes and turbulence source are still not perfectly understood and further studies are required.This study concerns the mode propagation and mode coherence functions of the turbulence broadband noise in the flow duct of turbomachinery. The turbulence and radiated noise will numerically simulated using the LES as well as the Goldaterin flow-duct aeroacoustic equation to obtain the modes of turbulence broadband noise. The turbulence flow-filed around rotor-stator and radiated sound in the inlet duct will be measured using 3D hot-wire and the microphone array on a high-loaded single-stage axial-flow fan. The turbulence broadband noise data from simulation and experiment will be compared, and the turbulence broadband noise modes will be statistical analyzed based on the random process theory. The technique that enables the separation of different stochastic noise sources in turbomachinery with respect to modal decomposition will be investigated. At last, the mechanism behind the turbomachiner turbulence broadband noise will be understood using the turbulence structure around blade as well as the modes decomposition in the inlet duct.

湍流宽频噪声既是未来航空发动机降噪设计的关键，也是目前自然科学领域研究的热点和难点。该申请项目以揭示航空叶轮机湍流噪声管道声模态随机特性和传播规律、构建湍流噪声源与管道声模态时空特征的数学关系为主要研究目的，研究航空叶轮机湍流噪声源识别理论和湍流噪声物理机制。应用湍流流场和声场数值模拟所获得的海量叶轮机湍流/噪声数据，辅助于轴流风扇流场/声场实验测量结果，以湍流噪声管道声模态统计分析理论为指导，以湍流噪声管道模态分解和识别为主要技术突破口，进行叶轮机湍流噪声理论和数值模拟的"正问题"研究和湍流噪声源分离识别的"反问题"研究，提高对叶轮机湍流噪声认识水平，发展完善叶轮机湍流噪声分析模型等，是本项目的研究特色和创新之处。本项目研究内容包括有关湍流噪声物理机制、随机噪声模态干涉理论、噪声源分离识别理论等流体力学和航空科学领域重要基础理论问题，其研究成果将为未来安静航空发动机设计奠定理论基础。

“从源头上减少噪声排放，加快绿色技术在飞机和航空发动机上的应用”是目前世界范围内绿色航空概念的主要目标，本项目以低噪声航空发动机研制为背景，进行了航空叶轮机湍流噪声管道声模态统计特征、传播规律以及湍流噪声源识别等研究。.本项目系统地研究了发动机管道内宽频噪声模态统计相干特性，弄清了管道声模态相干系数的分布规律，揭示了航空叶轮机湍流噪声管道声模态随机特性和传播规律、研究结果表明，湍流宽频随机噪声的管道模态之间是统计不相干的，在湍流宽频噪声的实验分析过程中，模态之间的交叉项在统计平均后可以忽略不计，这一研究结果为降低宽频噪声测试难度提供了理论依据，为宽频噪声模态识别建立了理论基础，也得到实验分析结果的证实。.本项目建立并发展了管道声模态识别误差分析理论和实验测试方法，构建了湍流噪声源和管道声模态时空特征的数学关系，建立了发动机管道声模态识别的传声器阵列设计准则，发展了高效高精度的基于管道声压互谱信号空间关系解耦出管道声模态的实验测试方法，开发了叶轮机械管道声模态识别测量的数据处理软件和数值计算软件，系统分析了湍流宽频噪声管道声模态分布特征与传播方向、声波频率以及模态阶数的相互关系，深刻揭示了叶轮机宽频噪声管道声模态的频谱特性以及变化规律，分析研究了叶轮机宽频噪声管道内不同声模态之间的相关性。本项目研究结果为准确捕获风扇宽频噪声管道声强度的实验测量和数值模拟奠定了坚实理论基础。.本项目的实验和数值模拟研究工作，深化了对叶轮机噪声管道声场结构的认识，弄清了叶轮机管道声模态的分布特征，掌握了管道声模态的分布特征与声波频率、传播方向以及管道几何形状的相互关系，并深刻揭示风扇噪声源分布规律。本项目获得的实验测试和数值模拟新技术，对于航空发动机低噪声设计的突破性创新具有重要的潜在价值。