摘 要

离心泵作为在工农业各个领域中被广泛使用的一类泵产品，对电能的消耗巨大且其效率不高，所以提高离心泵产品的设计技术水平对经济发展、节约能耗、保护环境有着重要的意义；随着计算机技术的快速发展，计算流体动力学（CFD）已经与离心泵性能的研究得以结合，有着耗时短、成本低、观察直接的优点。本文对离心泵整机流场进行数值模拟研究，探索并揭示叶片数变化对离心泵内流动及外特性的影响。

本文利用大型三维造型软件UG建立了M129-50型清水泵计算域模型，包括进口管段、出口管段、蜗壳及叶片数分别为5、6、7的叶轮流体域模型，然后分别装配成整体流道模型导入ICEM进行网格划分，最后运用运用CFD软件FLUENT分别对叶片数为5、6、7的离心泵在不同工况下进行了数值模拟研究。

本文分析了以上数值模拟的计算结果。分别对设计工况下的整机流场，各种工况下的靠近叶轮前后盖面侧、蜗壳内部流场和不同叶片数下的整机流场进行了速度矢量和压力分布的分析，分析发现：整机流场内的速度压力变化与离心泵的实际工作特性规律基本一致；叶轮区域的速度压力分布呈现了非轴对称性的特点；在小流量工况下，前后盖板侧旋涡比较严重，在靠近叶片进口边处存在负压区域，其中叶片吸力面较为严重，更容易发生气蚀现象；蜗壳内压力速度分布比较均匀，扩压效果明显，只是在隔舌区域存在冲击、回流等现象和局部的高压区；六、七叶片的离心泵整机流场的流动稳定性远好于五叶片的离心泵，七叶片离心泵流动稳定性略好于六叶片离心泵。计算了不同叶片数、不同工况下的扬程和效率等外特性参数值，并绘制了特性曲线与试验值进行对比。对比发现：各特性参数随着流量的变化趋势与所给的试验曲线基本一致，扬程计算值之间差别较大，随着叶片数增多，计算扬程值依次变大；效率的预测曲线与试验曲线十分接近，较小的叶片数变化对离心泵效率的影响很小。

关键词：离心泵；数值模拟；叶片数；内流场；外特性

Abstract

Centrifugal pumps are the most comprehensive products among pumps. They are widely used in various fields of industry and agriculture. They consume huge amounts of electrical energy but their efficiency is not high. Therefore, improving the design and technical level of centrifugal pump products is of great significance to economic development, energy saving, and environmental protection. With the rapid development of computer technology, computational fluid dynamics (CFD) has been used to study the performance of centrifugal pump because of its advantages of short time, low cost and direct observation. In this paper, the flow field of the whole centrifugal pump is studied by numerical simulation, and the influence of the number of blades on the internal and external characteristics of the centrifugal pump is explored.

In this paper, the large-scale three-dimensional modeling software UG is used to establish the calculation domain model of M129-50 clean water pump, including the inlet pipe section, outlet pipe section, volute and the number of impeller with blade of 5, 6, 7 fluid domain models respectively. Then assemble the whole flow channel model into ICEM for meshing. Finally, the CFD software FLUENT was used to numerically study the centrifugal pumps with 5, 6 and 7 blades under different working conditions.

This paper analyzes the calculation results of the above numerical simulation. The flow field of the whole machine under the design conditions, the flow field near the front and back cover surfaces of the impeller, the internal flow field of the volute, and the flow field of the whole machine under different blade numbers under various conditions were analyzed. The analysis found: The speed and pressure changes in the flow field of the whole machine are basically consistent with the actual working characteristics of the centrifugal pump; The velocity and pressure distribution in the impeller area exhibits non-axisymmetric characteristics; Under low flow conditions, the vortexes on the front and rear cover sides are more serious, and there is a negative pressure area near the blade inlet, where the suction surface of the blade is more serious and cavitation is more likely to occur; The pressure and velocity distribution in the volute is relatively uniform, and the effect of pressure expansion is obvious, but there are phenomena such as impact and backflow and local high-pressure areas in the area of the diaphragm; The flow stability of the flow field of the six- and seven-blade centrifugal pump is much better than that of the five-blade centrifugal pump, and the flow stability of the seven-blade centrifugal pump is slightly better than that of the six-blade centrifugal pump. The characteristic parameters such as head and efficiency under different blade Numbers and different working conditions were calculated, and the characteristic curves were compared with the experimental values. Comparison found: The change trend of each characteristic parameter with flow rate is basically consistent with the given test curve, There is a big difference between the calculated values of head, As the number of blades increases, the calculated head value becomes larger in sequence; The efficiency prediction curve is very close to the test curve, and the small change in the number of blades has little effect on the efficiency of the centrifugal pump.

Key Words：Centrifugal pumps；Numerical Simulation；Number of blades；internal flow field；External characteristics

目录

摘 要 I

Abstract II

第1章 绪论 1

1.1 研究背景 1

1.2 离心泵内部流动数值模拟研究的发展现状 1

1.2.1 数值模拟的基本思想 1

1.2.2 离心泵内部流场数值模拟研究现状 2

1.3 研究的目的和意义 3

1.4 本文的研究方法和主要内容 4

第2章 CFD基本理论 5

2.1 计算流体力学简介 5

2.2 计算流体力学控制方程 6

2.2.1 连续性方程 6

2.2.2 动量方程 6

2.3 湍流模型 7

2.3.1 湍流概述 7

2.3.2 雷诺时均方程法 8

2.3.3 两方程模型 9

2.4 基于有限体积法的控制方程离散 10

2.5 FLUENT中流场数值计算的主要方法 10

2.6 本章小结 11

第3章 离心泵建模及网格划分 12

3.1 离心泵的设计参数 12

3.2 流体域模型建模 14

3.2.1 叶轮流体域三维实体建模 14

3.2.2 蜗壳流体域三维实体建模 16

3.3 离心泵整机流道三维模型 17

3.4 网格划分 17

3.5 本章小结 19

第4章 离心泵整机流场模拟计算及结果分析 20

4.1 旋转叶轮与静止泵体耦合模型 20

4.2 边界条件 20

4.2.1 进口边界条件 20

4.2.2 出口边界条件 21

4.2.3 壁面边界条件 21

4.3 数值模拟方案确定 22

4.4 离心泵数值模拟结果分析 23

4.4.1 整机流场数值模拟分析 23

4.4.2 叶轮流场数值模拟分析 25

4.4.3 蜗壳流场数值模拟分析 28

4.5 扬程和效率计算 29

4.5.1 扬程 29

4.5.2 效率 30

4.6 本章小结 31

第5章 不同叶片数对泵性能影响 33

5.1 引言 33

5.2 不同叶片数离心泵内流场模拟结果分析 33

5.2.1 不同叶片数下的速度场分析 33

5.2.2 不同叶片数下的压力场分析 36

5.3 不同叶片数离心泵参数计算 38

5.4 本章小结 42

第6章 总结 43

参考文献 44

致谢 45

绪论

研究背景

泵作为一种机械装置，在输送流体的过程中可以实现将其他动力机的能量转化为流体的动能和势能。泵的种类有许多种，通常情况下将其分为叶轮式泵、容积式泵和喷射式泵等，这种分类的原则是根据其工作原理不同划分的，我们常见的离心泵、轴流泵、和旋涡泵都是叶轮式泵的一种，但是他们的叶轮和流道结构是有着不同程度的区别的。

离心泵在农业日常作业中是比较常见的，同时在工业的大多数领域同样有其身影，据相关统计，离心泵在所有的泵类产品应用的总数中所占的比例达70%以上。离心泵能有如此广泛的适用范围，也归结于其有着简单的结构、使用可靠和维护方便等优点。但是泵对电能的损耗巨大，据统计我国各种泵每年的的耗电量约占全国总耗电量的20%,其中离心泵的耗电量就占总发电量的10%以上。^[1][2]然而我国的离心泵效率仅有50%～60%一,其效率平均比国外低10%～30%,^[1][2]节电潜力非常之大。因此研究离心泵内流场的流动和外特性参数，优化其各个零部件，最后得到稳定均匀的离心泵流场和具高性能、高效率的离心泵。泵行业整体的发展也会随着离心泵结构的改进朝好的方向更进一步。