| 陈为升,黎耀军,刘竹青.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[J].水利学报,2022,53(5):586-597 |
| 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 |
| 投稿时间：2021-10-22 |
| DOI：10.13243/j.cnki.slxb.20210948 |
| 中文关键词: 离心叶轮 平均流动动能 湍动能 能量损失 超大涡模拟 |
| 英文关键词: centrifugal impeller mean flow kinetic energy turbulent kinetic energy energy loss very large eddy simulation |
| 基金项目:国家自然科学基金项目(51679240) |
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| 摘要点击次数: 769 |
| 全文下载次数: 336 |
| 中文摘要: |
| 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(Pθθ) 和径向-周向分量(Prθ) 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(Prr) 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, Prθ和 Prr是产生湍流脉动的主导因素, Pθθ则对平均流动动能损失起抑制作用。 |
| 英文摘要: |
| 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 (1.0Qd, 0.6Qd and 0.25Qd), 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 vis- cous dissipation term and the turbulent kinetic energy production term of the mean flow kinetic energy transport e- quation, 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 Pθθ and Prθ, promoting energy transport from the mean flow to the turbulent structure, increasing the circumferential and radial components of turbulent kinetic energy, while Prr reduces the radial component of turbulent kinetic energy and sup- presses the mean kinetic energy losses. For the shear flow caused by blade suction side separation flows and in the impeller outlet backflow, Prθ and Prr are the dominant factors for turbulent kinetic energy production, and Pθθ sup- presses the generation of turbulent kinetic energy. |
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