离心泵叶轮内失速涡的触发机理及动力学特性研究

Stall often occurs in the centrifugal pump impeller at part load condition. Under the stall condition, the periodic generation and shedding of stall vortex always induces the low frequency pressure fluctuation, and makes the noise stronger and intensifies the vibration, which has severe influence on the safety and stability of pumps. We intends to study stall vortex systematically by using theoretical analysis, experiments and numerical simulation. Firstly, the model combined SST k-w and DMNM is builted for predicting stall phenomenon in pumps with high accuracy and it is verified by PIV test results, which establishes the foundation for predicting the stall flow in the pump accurately. Secondly, based on the Omega vortex identify method, the characteristic parameters of the stall vortex in the impeller are established, and the stall vortex criterion is proposed. The topological structures of the stall vortex in the impeller are identified based on numerical and experimental research. Then the dynamic evolution history and the dominant factors dominance are revealed. Finally, based on the spectral characteristics of the velocity fluctuations and the Lyapunov index, the correlation mechanism between the inlet swirl and the stall vortices is revealed, and the quantitative relationship between the characteristic parameters of the inlet swirl and the characteristic parameters of the stall vortex is established, which could provide theoretical support for the stable operation of centrifugal pumps.

离心泵在小流量工况下运行时，叶轮中容易出现失速现象。失速涡不断地产生和脱落会诱发低频的压力脉动，使得水泵噪音增强，振动加剧，严重影响机组安全运行。本项目拟采用理论分析、数值模拟及实验相结合的方法对失速涡进行深入研究。首先构建动态混合非线性SGS模型与SST k-w 和耦合求解失速流场的计算策略，与试验结果进行对比验证，为准确预测失速涡奠定了基础；其次，基于Omega涡识别方法，提出失速涡判据并建立叶轮内失速涡的特征参数，通过数值和实验研究识别叶轮内失速涡的拓扑结构，揭示失速涡的相关物理量的动力学演化历程和主导因素；最后，以获得的速度脉动的频谱特征以及李雅普诺夫指数为依据，揭示入口旋流与失速涡的关联机理，建立入口旋流的特征参数与失速涡特征参数之间的定量关系，从而为进一步提高离心泵机组稳定运行提供理论支撑。

离心泵在小流量工况下运行时，叶轮中容易出现失速现象。失速涡不断地产生和脱落会诱发低频的压力脉动，使得水泵噪音增强，振动加剧，严重影响机组安全运行，然而失速涡的演变机理仍尚未被揭示。本项目采用实验与数值模拟相结合的方法对失速涡产生机理和时频特性进行深入研究。课题发展了可以较为准确预测失速涡SST k-w 与DMNM(动态混合非线性)的混合RANS/LES求解模型，该方法可以在网格数有限的条件下保证预测精度，为深入开展失速涡演变机理研究奠定了基础；基于不变参量的涡动力学方法，提出失速涡判据，将Liutex-Omega涡识别方法应用于失速涡拓扑结构分析，建立了叶轮内失速涡的特征参数；通过所识别叶轮内失速涡的拓扑结构并结合压力脉动的时频分析，揭示了不同入口旋流与失速涡的关联机理，从而为进一步提高离心泵机组稳定运行提供理论支撑。最后，基于被动流动控制技术和失速涡触发机理，提出了一种能有效抑制失速涡的机构并进行了结构设计。