离心泵内三维尾迹涡的瞬态演化及激励特性研究

Unsteady wake vortex shedding from the blade of centrifugal pumps and its excitation characteristics are crucial ways to clarify rotor-stator interaction mechanism and low noise control of centrifugal pumps. Wake flow of a low specific speed centrifugal pump is investigated in the present project. Advanced flow measuring techniques and LES numerical simulation method are together combined to illustrate the unsteady evolution characteristics of wake vortex. Structures of three-dimensional vortexes are extracted and captured based on multiple vortex identification methods. Besides, dynamic mode decomposition method DMD is applied to separate vortexes of different frequencies and to discuss their temporal and spatial evolutions. The evolution of vortex and its interaction with the volute tongue and volute casing wall are deeply depicted. The turbulent fluctuation signals excited by wake flow interaction are processed with time/frequency methods to obtain the typical frequencies. Furthermore, the correlations of wake flow and the induced turbulent fluctuation signals are established. Based on the pressure wave interaction effect, the potential and wake interactions and their coupling mechanisms are carried out. Finally, the intrinsic mechanism of rotor-stator interaction would be revealed and explained. Project research would provide a new explanatory on rotor-stator interaction from the aspect of unsteady wake vortex evolution and its interaction effect. Besides, the obtained results would provide support on the effective internal flow control and design theory of low noise centrifugal pumps.

离心泵内三维尾迹涡的瞬态演化及激励特性是探明动静干涉作用的内在流动机理，实现泵低噪声内流控制的关键问题。项目以离心泵叶片尾迹流为研究对象，结合先进的流动测量技术与高精度LES数值计算方法，研究叶片出口尾迹涡的非稳态演化特征。基于涡识别技术对三维尾迹涡结构进行提取，并采用动态模态分解技术DMD探讨不同频率涡团结构的时空分布特征，深入剖析尾迹涡演化及其与隔舌、壳体的相互作用过程。同时对尾迹涡干涉诱发的压力、速度脉动信号进行采集，采用时/频域分析技术对特征频率进行提取，构建尾迹涡演化与水力激励特征的关联。结合压力信号的干涉效应，探索势、尾流耦合干涉作用的分解模式，揭示动静干涉作用的内在流动机制。项目研究成果将从尾迹涡演化、干涉角度对动静干涉作出新诠释，可为低噪声离心泵内流控制及水力设计方法的研究提供理论支撑。

本研究以动静干涉作用下的离心泵叶片尾迹流及复杂激励特征为研究对象，结合数值计算、光学试验、压力脉动试验，探明叶片尾迹流的复杂时空演化过程及激励特性，最终揭示动静干涉的内流作用机制。以研究叶轮出口复杂流动的时空演化过程为核心内容，探明了叶轮出口的射流-尾迹结构及其非稳态发展过程，揭示了叶轮内部典型涡结构分布规律，刻画了叶片尾迹涡与隔舌的撞击、干涉、运动、变形、耗散过程，提出了多工况下离心泵内三种尾迹干涉模式。开展了泵内不同工况下激励特性的研究，获得了压力脉动信号的时/频特征，通过压力脉动和涡结构演变特性的关联分析认为离心泵不同测点处的压力脉动能量由该区域旋涡强度所决定，提出基于叶片尾缘修整的低噪声控制方法，并基于实验证明了其有效性。本研究从离心泵内尾迹演化及干涉角度出发，探索泵内非定常流场脉动与尾迹演化、输运过程的关联，从尾迹干涉角度揭示动静干涉作用的内流机制。研究将从基础内流角度分析动静干涉诱发的复杂流动及激励现象，研究成果可以为离心泵动静干涉激励的调控及低噪声水力优化设计奠定理论基础。