基于涡动力学分析的离心泵偏小流量下叶轮内非定常流动特性研究

The hydraulic performance, operation stability and reliability of centrifugal pump are mostly determined by unsteady flow structures at the lower flow rate conditions. It is one of critical issues need to be solved in pump area. Although the unsteady flow structures in centrifugal pump impeller are to be more intense by decreasing the flow rate, the unsteady flow characteristics at lower flow rate conditions and the correlations between operation parameters and the unsteady flow characteristics are still not fully revealed.. The project is to investigate the characteristics of unsteady flow in centrifugal pump impeller at lower flow rate conditions by using the theoretical analysis, numerical simulation and experiments. A new dynamic nonlinear SGS model based on the effect of vortex characteristics and system rotation is presented. The large eddy simulation is applied to simulate the flow fields in centrifugal pump by the new SGS model. The parametric characterization of unsteady flow based on vorticity dynamics is constructed. Also the correlations of operation parameters and unsteady flow characteristics are established. Therefore, the unsteady flow mechanism of centrifugal pump at lower flow rate conditions is investigated. It can provide a technical support for optimizing centrifugal pump in theoretically. And it is a theoretical foundation for the control strategy that ensures pump work in stabilization.

偏小流量下的非定常流动在很大程度上决定了离心泵的水力性能，严重制约了离心泵的运行稳定性和可靠性，是泵领域亟待解决的关键问题之一。虽然目前已知离心泵叶轮内的非定常流动现象会随着流量的减小而越强烈，但国内外还未能很好地揭示偏小流量下离心泵叶轮内的非定常流动特征以及运行参数与非定常流动的关联机理。. 本项目拟通过理论分析、数值计算和内外特性实验研究，深入研究离心泵偏小流量下叶轮内非定常流动机理。建立基于旋涡特性和系统旋转效应修正的非线性动态亚格子应力模式，开展离心泵全流场大涡模拟计算，建立基于涡动力学的内部非定常流动参数化表征，确定运行参数与内部非定常流动之间的映射关系，从而揭示离心泵偏小流量下叶轮内部非定常流动机理，为离心泵优化设计理论提供技术支撑，为离心泵稳定运行的控制策略奠定理论基础。

本项目从偏小流量工况下离心泵叶轮内部不稳定流动的角度出发，采用试验、数值模拟和理论相结合的方法开展了以下几个方面的工作。首先，采用PIV技术探索了叶轮流道内不稳定流动涡的发生、发展规律；其次，针对叶轮流道内摩擦损失大、逆压梯度高和叶片曲率大等特点，提出了考虑旋转和曲率修正的数值模型，开展了模型泵内流场的瞬态计算，定性和定量的分析了叶轮内不稳定流动涡运动规律及对水力性能的影响机制；再次，引入边界涡量流动力学理论进行内流诊断，分析了叶片表面的边界涡量流（BVF）、摩擦力线、近壁面处的相对速度矢量以及无量纲压力系数的分布规律，确定了叶轮内产生回流区的位置及其动力学根源，给出了设计准则；最后，采用熵产理论和Q准则，定量分析了不同运行参数下的离心泵内部各个部件的流动损失特性，揭示了离心泵内部流动的损失机理，项目研究成果对泵内不稳定流动结构的时空特性及其损失机理作出了新的诠释，丰富了泵内流的基础理论，为离心泵的优化设计提供了理论支撑。