非对称导叶布局及其减振机理研究

In this project, a transient analytical method of blade forced response under stator-rotor wake influence is proposed in dealing with asymmetric aerodynamic load. After investigating the vibration characteristics of the blades under the wake excitation of the asymmetric vane spacing from upstream, the fluid-structure interaction mechanism of transmission and resonance is analyzed in the flow induced vibration mode of the blades. The effect of asymmetric spacing in the turbomachinery is studied as well as the method of integrated optimization under the interaction of fluid-structure. It is significant both in method and engineering application to improve the numerical prediction method of aeroelastic stability suitable for engineering design. The work can be summarized as follows. .The reduction effect on the vibratory stress due to the asymmetric vane spacing is examined. It is possible to optimize the structure of flow field resulting from the stator vane by shifting the circumferential position of some or all of the vanes. Then the asymmetric vane spacing can result in decreasing the levels of the excitation force at specific frequencies to control the blade forced response downstream. .The vibratory response of the blades is calculated by the transient response analysis for different asymmetric vane spacing. The results are obtained by comparing the response characteristics of frequency and amplitude for the asymmetric vane spacing with those for the symmetric vane spacing. The mechanism of the vribation reduction due to the asymmetric vane spacing is investigated so as to the method of transient fluid-structure coupled aeroelastic numerical prediction.This project focuses on the foundamential research to improve aerodynamic performance and structural reliability in the turbomachinery.

本项目的研究目标是通过开展上游气流激振力在非对称布局下对叶片振动特性影响的物理机理分析，探索叶片系统在流动诱发振动过程中的流固耦合传递机制和共振响应机制，研究到其一般规律，获得高性能叶轮机非对称布局优化设计技术、流固耦合一体化预测方法，促进叶轮机械新型设计技术的发展。研究的主要内容包括研究叶轮机静子叶片非对称布局降低振动应力的气动设计准则，通过设计不同形式的叶片布局以优化流场的时空结构，在一定频率范围内降低气流激振力进而控制叶片的强迫响应水平；考虑叶片振动、气体动力学的耦合系统，探讨转子叶片在不同非对称导叶布局下振动响应的频率及幅值特性的变化，并获得转子叶片振动应力的一般性高精度数值预测方法。本项目将深入研究非对称导叶布局设计技术与减振机理，为提升叶轮机气动性能和结构可靠性做基础研究。

针对上游尾迹引起的流动诱发叶片振动问题，对导叶进行非对称布局设计，在一定频率范围内控制叶片振动响应。针对非对称导叶布局设计技术与减振机理中的关键问题，本项目探索流动诱发振动过程中的流固耦合传递机制，研究导叶非对称布局降低振动应力的气动优化设计准则，并探讨非对称流场的气动稳定性及不稳定流动的数学辨识方法。主要研究进展如下：. 针对全周多排多叶片的复杂计算域，采用动网格技术，建立了具有多个移动边界的叶片振动流固耦合数值模型。开展不同非对称布局形式下叶片振动特性的数值解析，结果表明适当的非均匀导叶布局可以在一定频率范围内分散气流激振力的能量，有效降低下游转子叶片的激振力水平，从而达到减振的效果。. 通过分析流场参数、叶片气动力与振动响应之间的关系，揭示了流动诱发叶片振动的流固耦合传递机理，气流激振力起到了传递上游流场信息的作用；提出了导叶非对称布局降低振动应力的气动优化设计准则，非对称导叶布局的调整要依据叶片变形方向和所受气动力方向的相位关系来确定。. 针对不同研究对象采用非对称导叶布局技术对叶片振动响应进行减振处理，结果显示其明显改善优化了流场，在一定频率范围内降低气流激振力进而控制叶片的强迫响应水平，减振效果存在一个最佳栅距非均匀度范围（4%-6%），叶片疲劳寿命提升了20.3%。. 项目分析了压气机在非对称流场下的气动稳定性，非对称周期干扰形成的周向模态波会诱使压气机发生气动不稳定流动。在不同干扰下，压气机空间模态幅值及其灵敏度在接近不稳定边界时均出现明显波动。通过监测一阶模态幅值灵敏度，能够提前辨识出气动不稳定流动的失速先兆。. 项目围绕关键科学问题进行攻关，基本达到了预期目标, 取得了明显进展，为进一步的理论研究提供了的基础性工作。研究成果用于某型高压转子叶片振动响应优化，取得显著减振效果，提高了叶片疲劳寿命。在项目执行期间已发表论文8篇，其中国际期刊论文SCI收录1篇，国内期刊及国际会议论文EI收录7篇。