论文总字数：29479字

摘 要

离心泵是一种应用十分广泛的通用型机械，随着经济的不断发展，各行各业开始对离心泵的性能提出了更高的要求。传统的设计方法已经不能完全满足人们的需要，所以研究安全、经济、高效的离心泵尤为重要。而研究离心泵内定常气蚀及内部流动对提高离心泵的气蚀性能、增强运行的可靠性、降低运行时的噪声和振动均具有十分重要的意义。本文将运用Pro/E软件对离心泵建立三维模型，保存后导入IECM中进行网格划分，再将划分好的网格导入到CFX中进行定常数值模拟。分析离心泵的气蚀性能及其内部的流动规律，为离心泵的优化设计以及高性能离心泵的开发提供参考，本文主要研究内容和结论如下：

1. 采用CFX对1.0Q流量工况下的离心泵内部流动进行数值模拟，通过不断降低离心泵进口压力使离心泵发生空化，并对后处理得到的压力、速度、气体体积分数以及叶片压力进行分析。结果表明：在扬程下降3%(发生空化)时，压力、速度、气体体积分数和叶片压力均会发生突变。
2. 采用CFX进一步模拟了5种不同流量工况下离心泵内部流动，对空化时的压力、速度、气体体积分数以及叶片压力进行分析。结果表明：随着流量的增大，压力逐渐减小；气体体积分数有先增大再减小的趋势，但这些变化并不明显；速度和叶片压力均无明显变化。
3. 根据CFX模拟结果，计算出5种流量工况下空化时的离心泵进出口压力以及叶轮转矩，对离心泵的扬程、轴功率、效率、有效气蚀余量(NPSH)等定常性能进行了分析。结果表明：数值模拟得到的离心泵外特性曲线和理论的外特性曲线走向基本一致。

关键词：离心泵 数值模拟 外特性 定常流动

Study on Steady Cavitation Performance and Internal Flow of Centrifugal Pumps

Abstract

Centrifugal pump is a general machine with a wide range of applications. With the continuous development of the economy, all walks of life begin to place higher requirements on the performance of centrifugal pumps. Traditional design methods can no longer fully meet people's needs. Therefore, it is particularly important to study safe, economic, and efficient centrifugal pumps. Studying the normal cavitation erosion and internal flow of the centrifugal pump is of great significance to improve the cavitation performance of the centrifugal pump, enhance the reliability of operation, and reduce the noise and vibration during operation. In this dissertation, the Pro/E software was used to establish a three-dimensional model of the centrifugal pump. The model was meshed in the IECM, and then was imported into CFX for steady simulation. The cavitation performance of the centrifugal pump and its internal flow law were analyzed. The results can provide a reference for the optimal design of the centrifugal pump and the development of the high performance centrifugal pump. The main research contents and conclusions of this dissertation are as follows:

1. The inlet pressure of the centrifugal pump was continuously reduced, and the internal flow of the centrifugal pump under a 1.0Q flow condition was numerically simulated using the CFX. The pressure, velocity, volume fraction of the gas, and pressure of the blade after the post-treatment were analyzed. The results show that when the head drops by 3% (cavitation occurs), the pressure, velocity, gas volume fraction and blade pressure will change dramatically.
2. The internal flow of the centrifugal pump under five different flow conditions was further simulated by CFX, and the pressure, velocity, gas volume fraction, and blade pressure during cavitation were analyzed. The results show that
3. with the increase of flow rate, the pressure gradually decreases; the gas volume fraction has the tendency of increasing first and then decreasing, but these changes are not obvious; the speed and the blade pressure have no obvious changes.
4. According to the CFX simulation results, the inlet and outlet pressures of the centrifugal pump and the impeller torque under cavitation under five flow conditions were calculated. The steady performance including real head, shaft power, efficiency, and NPSH of the centrifugal pump was analyzed. The results show that the external characteristic curve of the centrifugal pump obtained by numerical simulation is basically consistent with the theoretical external characteristic curve.

Keywords: centrifugal pump; numerical simulation; external characteristics; steady flow

目 录

摘 要 I

Abstract II

目 录 IV

第一章 绪论 1

1.1 离心泵工作原理及背景介绍 1

1.1.1 离心泵的介绍 1

1.1.2 离心泵的工作原理 1

1.1.3 离心泵气蚀的介绍 2

1.2 离心泵汽蚀的相关研究 3

1.2.1 离心泵研究的现状 3

1.2.2 离心泵内流动性研究 3

1.2.3 离心泵数值模拟研究方法 3

1.3 本课题研究的内容 4

1.3.1 几何模型建立与网格划分 4

1.3.2 离心泵内定常汽蚀性能的数值模拟 4

1.3.3 模拟结果分析 4

1.4 采用的研究方法 5

1.4.1 建立几何模型 5

1.4.2 数值模拟研究 5

1.4.3 理论分析研究 5

1.5 本章小结 5

第二章 离心泵的实体建模及网格划分 6

2.1 离心泵的实体建模 6

2.1.1 叶轮的实体建模 6

2.1.2 蜗壳的三维实体建模 8

2.1.3 离心泵的实体建模 9

2.2 离心泵三维模型的网格划分 9

2.2.1 离心泵网格种类 10

2.2.2 离心泵模型的网格划分 10

2.3 数值模拟介绍 10

2.3.1 CFX软件简介 10

2.3.2 三维湍流模型 11

2.3.3 控制方程介绍 11

2.4 本章小结 12

第三章 离心泵的内部流动及外特性分析 13

3.1 数值模拟步骤 13

3.1.1 定常数值模拟步骤 13

3.1.2 气蚀数值模拟步骤 15

3.1.3 数值模拟结果分析 15

3.2 离心泵定常流动研究 16

3.2.1 残差曲线图 16

3.2.2 离心泵内压力分布图 16

3.2.3 离心泵内速度分布云图 18

3.2.4 离心泵内气体体积分数云图 19

3.2.5 离心泵内叶片压力云图 22

3.3 外特性分析 23

3.3.1 离心泵扬程分析 23

3.3.2 离心泵的功率分析 24

3.3.3 离心泵的效率分析 25

3.4 本章小结 27

第四章 空化条件下的内部流动分析 28

4.1 不同流量下离心泵内扬程和有效气蚀余量关系分析 28

4.2 离心泵汽蚀余量(NPSH)分析 29

4.3 空化条件下内部流动云图分析 30

4.3.1 空化条件下压力云图分析 30

4.3.2 空化条件下速度云图分析 32

4.3.3 空化条件下气体体积分数云图分析 33

4.3.4 空化条件下叶片压力云图分析 35

4.4 本章小结 36

第五章 总结与展望 37

5.1 总结 37

5.2 展望 38

符号说明 39

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