大型混流泵Alford效应下的稳定性研究

Stability of large high-speed mixed-flow pump under the Alford effects is one of the important problems in the defense equipment and the large-scale hydraulic projects. The clearance fluid excitation mechanism is the basic study to solve such fluid excitation issues. In this project, the physical characteristics of the non-uniform tip clearance flow field inside the mixed-flow pump will be explored to study the clearance fluid excitation mechanism and the rotor dynamics response. PIV test, pressure measurements and numerical methods are used to study the distribution of the vorticity, pressure and velocity field. The state characteristics of the non-uniform tip leakage flow and the leakage vortex flow entrainment effect will be explored to reveal the nature of the disturbance in the whirl flow field. The impact of tip clearance, speed, eccentricity and whirl frequency on the physical structure of the flow field and the impeller blade loads will be investigated using the parallel vector method and vorticity moment theory. The calculation model of Alford force will be established and corrected in accordance with the experimental results. The effect of fluid force on the modal frequency, amplitude and axis trajectory will be discussed, the time domain response and frequency domain response of different whirl parameters will be studied to establish the criteria to determine whether the Alford force has a self-excited effect. This project aims to reveal the clearance fluid excitation mechanism, master the self-excited vibration response mechanism of impeller rotor caused by the fluid excitation force, and provide a theoretical basis for suppress and weaken the adverse effect of the Alford effects.

大型混流泵Alford效应下的稳定性问题已成为国防装备和大型水利工程急需解决的难题之一，研究间隙流体激振机理是解决这类流体激振问题的基础研究。本项目从探索混流泵非均匀叶顶间隙流场的物理特性出发，研究间隙流体激振机理及其引发的转子动力学响应。基于PIV、压力测量和数值方法研究流场的涡量、压力和速度场分布，探索非均匀叶顶间隙泄漏流的流态特征和泄漏涡的卷吸效应，揭示涡动流场的扰动本质；采用平行矢量法和涡量矩理论研究叶顶间隙、转速、偏心距和涡动频率对瞬态流场物理结构和叶片载荷的影响规律，建立Alford力的计算模型，并根据实验结果予以修正；探讨流体力对转子系统模态频率、振幅和轴心轨迹的影响，研究不同涡动参数下的时域和频域响应，建立Alford力是否具有自激效应的判断准则。本项目研究旨在揭示间隙流体激振机理，掌握流体激振力诱导转子自激振动响应机制，为抑制或消弱Alford效应的不良影响提供理论依据。

大型混流泵Alford效应下的稳定性问题已成为国防装备和大型水利工程急需解决的难题之一，研究间隙流体激振机理是解决这类流体激振问题的基础研究。. 本项目从探索混流泵非均匀叶顶间隙流场的物理特性出发，研究了间隙流体激振机理及其引发的转子动力学响应。项目创建了涡动流场的“多区域动态滑移方法”，并综合利用先进PIV试验手段和精细数值计算，研究了非均匀轮缘间隙下叶片表面静压、湍动能分布以及轮缘泄漏流的流态特征和泄漏涡的卷吸效应，建立了非均匀间隙流动与不稳定特征结构的关系，从非均匀轮缘间隙对内部流场的扰动揭示能量损失的产生机理，阐明了能量性能下降的本质原因。采用涡核提取方法和涡量矩理论研究了流量工况和偏心距对非均匀轮缘间隙流场物理结构和叶片载荷的影响规律，分析了非均匀轮缘间隙流场的非定常特征，探讨了不同流量工况、偏心距、涡动频率比对瞬态Alford力的影响规律，揭示了间隙流体激振的产生机理，构建了混流泵Alford力的数学模型。建立了考虑Alford力作用的耦合动力学模型，分析了流体力对转子系统模态频率、临界转速的影响，研究了不同因素下非均匀间隙流体激振力引发的动力学效应，测量绘制了表征转子运动特性的轴心轨迹图，为抑制或消弱Alford效应的不良影响、提高和改善混流泵的水力性能和运行稳定性提供理论依据。. 项目研究成果不仅可以加深和丰富人们对水力机械中Alford效应的理解，而且可以为相关水力机械的动力学稳定性设计提供参考。同时，间隙流体激振机理的研究对于控制或消弱核电、火电和国防装备等大型机组的振动失稳具有重要的战略意义。. 项目研制了系列高性能导叶式混流泵水力模型，特种混流泵产品振动噪声低，水力损失小，高效范围宽，应用范围广，取得了显著的经济和社会效益，推动了我国泵行业减振降噪技术的进步，荣获了2016年首届中国军民两用技术创新应用大赛银奖。