基于平均流动动能输运的离心叶轮内能量损失及其机理分析  

Analysis of energy losses and its mechanisms in a centrifugal impeller based on mean flow kinetic energy transport

作　　者：陈为升 黎耀军[1,2] 刘竹青 CHEN Weisheng;LI Yaojun;LIU Zhuqing(Collge of Water Rsoures and Cinl Engineering.China Agriaultural hinveriy,Beajng 100083,China;Beijing Kngineering Research Center of Safety and Knegy Sasing Technology for Water Supply Netuork System,Beging 100083,China)

机构地区：[1]中国农业大学水利与土木工程学院,北京100083 [2]北京市供水管网系统安全与节能工程技术研究中心,北京100083

出　　处：《水利学报》2022年第5期586-597,共12页Journal of Hydraulic Engineering

基　　金：国家自然科学基金项目(51679240)。

摘　　要：叶轮内能量损失是影响离心泵水力性能的关键因素,为探明离心式叶轮内的能量损失特性,本文采用可直接求解大尺度湍流结构的超大涡模拟方法对某低比转速离心叶轮三种流量(分别为1.0,0.6和0.25倍设计流量)下的内部流动进行数值模拟,基于平均流动动能输运研究叶轮内的流动特征、能量损失特性及其机理。通过积分平均流动动能输运方程的直接黏性耗散项和湍动能生成项,分别计算直接黏性损失和湍动能生成对应的平均流动动能损失,建立流场特征与能量损失的关联,获得流场中能量损失的空间分布特征。结果表明,叶轮内直接黏性损失集中在近壁区,且随流量降低而显著减小;湍动能生成是平均流动动能损失的主要形式,其与叶轮内流动的剪切效应直接相关,在叶片压力面,脱流和分离涡形成强剪切流动,湍动能生成项周向-周向分量(P_(θθ))和径向-周向分量(P_(rθ))将增加周向和径向速度脉动而使湍动能增加,径向-径向分量(P_(rr))则减小速度脉动的径向分量,从而抑制平均流动动能转换为湍动能;对于叶片吸力面分离流动及叶轮出口回流所形成的强剪切流动,P_(rθ)和P_(rr)是产生湍流脉动的主导因素,P_(θθ)则对平均流动动能损失起抑制作用。Energy losses in the impeller are the key factors affecting the hydraulic performance of centrifugal pump. In this paper, the Very Large Eddy Simulation (VLES) turbulence model which directly resolves the large-scale turbulence structure is used to numerically simulate the internal flow of a low specific speed centrifugal impeller at three flow rates (1.0Q_(d), 0.6Q_(d) and 0.25Q_(d)), aim to reveal the mean flow kinetic energy loss characteristics in the impeller. A power loss analysis method based on the transport of mean flow kinetic energy is proposed and applied to study the internal flow features, energy losses and its mechanism of the impeller. The newly proposed power loss analysis model calculates the direct viscous losses and the turbulent energy production by integrating the direct viscous dissipation term and the turbulent kinetic energy production term of the mean flow kinetic energy transport equation, establishes the correlation between flow characteristics with mean flow kinetic energy loss, and obtains the spatial distribution of mean flow kinetic energy losses in the flow. The results show that the direct viscous losses of the impeller are concentrated in the near-wall region and decreases significantly with the decrease of flow rate. The strong shear effect resulted by the complex flow structure in the turbulent core region of the impeller is the direct cause for transfer of energy from the mean flow to the turbulent structures. However, differences are found in the mechanism of turbulent kinetic energy production for different flow structures. In the strong shear flow region formed by the blade pressure side separation flow, the turbulent kinetic energy production term components P_(θθ) and P_(rθ), promoting energy transport from the mean flow to the turbulent structure, increasing the circumferential and radial components of turbulent kinetic energy, while P_(rr) reduces the radial component of turbulent kinetic energy and suppresses the mean kinetic energy losses. For the shear flow cause

关 键 词：离心叶轮 平均流动动能 湍动能 能量损失 超大涡模拟 

分 类 号：TH31[机械工程—机械制造及自动化]