基于气体动理学方法的航空压气机锯齿尾缘叶片降噪优化研究

The structure of serrated trailing edge can improve the wake flow characteristic and reduce the trailing edge noise. When hybrid methods for computation of flow/ acoustic fields are used to study the noise reduction of serrated trailing edge, one would face a difficult problem about how to accurately calculate and measure the small-scale turbulence in the microstructure of serrated trailing edge. Because the gas-kinetic scheme holds distinct numerical advantages in capturing the multi-scale and small-scale turbulence in complicated structures, it will be used to investigate the noise reduction of air compressor serrated trailing edge blade from the perspective of flow mechanism in the present project. The following contents are included: (1) A model will be constructed for computation and analysis of unsteady turbulence around serrated trailing edge based on gas-kinetic scheme; (2) The flow fields characteristics near the wall of blade and in the wake zone will be investigated numerically, based on which the mechanism of flow loss will be analyzed; (3) Based on the gas-kinetic scheme coupled with linearized Euler equations, a prediction model will be constructed for turbulent noise, and the noise reduction mechanism of serrated trailing edge will be revealed; (4) Based on the relationship between the structure parameter of serrated trailing edge and trailing edge noise as well as wake flow loss, the optimal structure of serrated trailing edge to obtain the minimal noise and flow loss will be investigated. And then, the results will be validated by experiments. Some theoretical guidance and data supports will be provided for the design of high performance and low noise air compressors by the present project.

尾缘锯齿结构可以改善叶片尾迹流动特性，是降低压气机叶片尾缘噪声的有效手段。针对采用流场/声场混合计算方法进行锯齿尾缘降噪研究中面临的锯齿细观结构附近小尺度湍流难以精确计算及测量的问题，项目拟利用气体动理学方法在多尺度湍流及复杂结构内小尺度湍流精细刻画方面的数值优势，从流动本质出发开展航空压气机叶片尾缘锯齿降噪优化研究，具体的：(1)基于气体动理学方法，建立锯齿尾缘非定常湍流计算分析模型；(2)模拟研究不同条件下，不同形状锯齿尾缘叶片近壁区及尾迹区域流场特性，分析流动损失机理；(3)基于气体动理学方法和线化欧拉方程耦合求解建立湍流噪声预测模型，揭示锯齿尾缘降噪机理；（4）在建立锯齿尾缘结构参数与尾缘噪声、尾迹流动损失之间联系的基础上，对尾缘锯齿结构进行优化研究，获得噪声最小、流动损失最少的最优锯齿构型，对计算结果进行试验验证与分析。项目研究可为高性能、低噪声压气机的设计提供理论基础和参考依据

针对飞机起降阶段发动机叶轮机的重要噪声源——叶片尾缘自噪声和湍流干涉噪声，项目开展了基于仿生结构的噪声控制研究。主要研究工作可概括为：1)掌握了非定常湍流分析建模方法和气动噪声预测建模方法。基于气体动理学方法和大涡模拟方法，建立了叶片三维非定常湍流计算分析模型及程序；基于大涡模拟和FW-H方程耦合方法，建立了气动噪声预测模型及程序。2)揭示了各类气动噪声和流场特性之间的关联。基于局部精细化流场测量和数值模拟，分析了孤立叶片尾迹流场特性和叶片尾缘自噪声之间的关系，建立了叶片间湍流流场特性与湍流干涉噪声之间的联系，揭示了各类噪声产生机理。3)设计了有效的叶片尾缘自噪声控制策略。基于不同参数下的噪声源分布规律及贡献度特性，对湍流流经孤立叶片主要声源进行了识别和定位，确定了上游叶片采用锯齿尾缘、下游叶片采用波浪前缘的噪声控制方案。4)研究了不同仿生结构在抑制湍流宽频噪声方面的作用机制和能力。剖析了尾缘锯齿结构、波浪前缘结构对流场内各种涡结构特性、流场相关性和相干性、叶片表面压力脉动等特性的影响规律。5)提出了通过改善上游尾迹来降低湍流干涉噪声的方案。研究发现，上游尾迹流场中各种尺度的非定常、非线性和不稳定涡结构是湍流干涉噪声的主要来源，因此，探索了多孔介质和小肋凸起结构对上游尾迹的影响规律和降噪效果。6)构建了锯齿尾缘叶片多目标优化计算方法及程序。以气动性能和气动噪声为目标，对锯齿尾缘叶片进行了单目标和多目标优化，获得了气动性能最佳、降噪效果最好的最优锯齿构型。项目研究可为航空叶轮机气动噪声控制提供理论参考和数据支持。