离心泵压力脉动的特性分析和测试(硕士)

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离心泵压力脉动的特性分析和测试(硕士)(论文35000字)
摘要
离心泵在产生静态压力分量的同时还产生动态压力分量,也就是压力脉动,压力脉动象交流信号一样叠加在静态压力分量上。离心泵大多采用螺旋型蜗壳 ,蜗壳与隔舌的不对称性造成叶轮出口流动的环形畸变,尤其是在非设计工况点时,畸变更为剧烈,因此在设计主轴时,必须考虑由于压力分布不平衡引起的脉动特性。离心泵内的压力脉动是极其复杂的,对同一台泵,不同工况呈现不同性质的压力脉动。泵内部流场非定常的湍流特性、叶轮与进水管的动静干扰、涡流及回流等都可能引起压力脉动,该压力脉动激发泵体和管道的机械振动,影响泵的正常运转,降低了泵的使用寿命;如果这种激励振动的频率接近泵的主频,还会发生共振,振动会在相邻的环境介质内产生声压波动,产生很大的噪声。可见,泵内压力脉动是影响水泵运行稳定性的重要因素,也是导致噪声污染的重要原因。因而,对泵内部压力脉动进行研究,降低泵的振动噪声成为当前研究的重要任务之一。
本文首先应用CFD(Computational Fluid Dynamics)技术Fluent软件 ,在多工况下同时监测叶轮流道与蜗壳内压力脉动的情况,以揭示压力脉动与离心泵性能之间的关系,为进一步预测离心泵非定常流动诱发压力脉动提供依据。为了研究离心泵在不同工况下以及不同位置间压力脉动的变化规律及其关系,基于标准 k-ε湍流模型和滑移网格模型,应用Fluent软件对离心泵内部流场先后进行定常与非定常三维模拟,得到大致的内部流场特性及监测点的压力脉动情况。计算结果表明:在小流量工况下,由于内部流场的不稳定运行各监测点处的压力脉动都比较大且不均匀;在叶轮流道中,接近叶轮出口处的压力脉动明显高于叶轮流道其他区域压力脉动。大流量工况下在蜗壳隔舌和出口处会产生一定回流导致蜗壳该处附近压力脉动表现不稳定。蜗壳隔舌处由于该位置流域比较复杂压力脉动较大;蜗壳出口处的波动情况非常平缓,这主要是因为蜗壳出口段的缓冲与稳流作用。
其次进行测量系统的方案设计,先对压力变送器和数据采集模块的参数进行充分的了解,完成二者的硬件选型以及电路接线图的构造。再利用Labview软件编写上位机界面,通过设置采样频率、采样数据点、采集量程等操作完成8条通道数据的采集和曲线的显示,且保存数据。

关键词:离心泵,压力脉动,定常模拟,非定常模拟,上位机界面
Abstract
Centrifugal pump produces static pressure components and produces dynamic pressure components,that is,pressure pulsation. Pressure pulsation is superimposed on static pressure components just like AC signals. Most of the spiral volute centrifugal pump,volute ring distortion and asymmetry of the tongue caused by impeller exit flow,especially in the non design condition,the distortion is more violent,so in the design of the spindle,the pressure must be due to the unbalanced distribution of fluctuation caused by considering. The pressure pulsation in the centrifugal pump is extremely complex,and the pressure pulsation of the same pump is different in different working conditions. Pump internal flow field and unsteady turbulent characteristics,the impeller and the water inlet pipe of the rotor stator interaction,eddy current and reflux may cause pressure pulsation,mechanical vibration of the pressure pulsation excitation pump and pipeline,affect the normal operation of the pump,reduce the service life of the pump; if the excitation frequency is close to the frequency of the pump. The resonance vibration will occur,will produce pressure fluctuations in the ambient medium adjacent,have a great noise. It can be seen that the pressure pulsation in the pump is an important factor affecting the stability of the pump operation,and is also an important cause of noise pollution. Therefore,it is one of the important tasks to study the pressure pulsation in the pump and reduce the vibration noise of the pump.
This paper first applies CFD technology FLUENT software to monitor the pressure pulsation in impeller and volute simultaneously under multiple conditions,so as to reveal the relationship between pressure pulsation and centrifugal pump performance,and provide a basis for further prediction of unsteady flow induced pressure pulsation in centrifugal pumps. In order to study the centrifugal pump under different working conditions and the variation of pressure fluctuation between different locations and their relationship,standard k- turbulence model and sliding mesh model based on the application of FLUENT software on the internal flow field of centrifugal pump has steady and unsteady three-dimensional simulation,get the pressure pulsation of internal flow characteristics and monitoring points of the roughly. The calculation results show that under the condition of small flow rate,the pressure pulsation at each monitoring point is large and uneven due to the unstable internal flow field,and the pressure pulsation near the impeller outlet is significantly higher than that in other regions of impeller passage. Under the large flow condition,there will be a certain reflux in the tongue and outlet of the volute,which results in the instability of the pressure fluctuation near the worm shell. Because of the complex pressure pulsation at the location of the basin,the fluctuation of the outlet of the volute is very gentle,which is mainly due to the buffering and steady flow of the outlet section of the volute.
On the other hand,on the design of the measurement system,we fully understand the parameters of the pressure transmitter and data acquisition module,and complete the hardware selection of the two parts and the construction of the wiring diagram. Then we use LabVIEW software to write the upper machine interface. We set up sampling frequency,sampling data points and collecting ranges to complete the 8 channel data collection and curve display,and save data.

Keywords:centrifugal pump, pressure fluctuation, Constant simulation, Unsteady simulation, Unsteady simulation

目录
摘要    I
Abstract    II
第1章 绪论    1
1.1 课题的研究背景及意义    1
1.2 国内外研究现状    2
1.2.1 国外研究现状    2
1.2.2 国内研究现状    3
1.3 论文工作的主要内容    4
第2章 泵内流动数值计算方法及压力脉动的相关理论    5
2.1 离心泵的三维建模    5
2.1.1 叶轮实体模型的建立    5
2.1.2 蜗壳实体模型的建立    6
2.1.3 进水管实体模型的建立    7
2.1.4 元件的装配    8
2.2 数值计算方法概述    9
2.2.1 流动控制方程    10
2.2.2 旋转区域中流动问题的建模    12
2.2.3 湍流模型    13
2.2.4 求解控制    14
2.3 离心泵的网格划分    15
2.3.1 网格相关问题的概述    15
2.3.2 网格划分    16
2.4 离心泵压力脉动的分类    18
2.5 离心泵压力脉动的产生    19
2.5.1 动静干扰引起的压力脉动    19
2.5.2 二次流引起的压力脉动    20
2.5.3 汽蚀引起的压力脉动    21
2.6 压力脉动的分析方法    21
2.6.1 时域法    21
2.6.2 频域法    22
2.7 本章小结    23
第3章 离心泵内三维数值特性分析    24
3.1 定常数值模拟    24
3.1.1 网格检查    24
3.1.2 设置求解器与计算模型    25
3.1.3 设置边界条件    25
3.1.4 设置检测器与计算    26
3.1.5 定常数值模拟结果分析    27
3.2 非定常数值模拟    31
3.2.1 计算方法    31
3.2.2 压力脉动特征参数的确定    32
3.2.3 压力脉动监测点位置的设定    32
3.2.4 时间步长及采样频率的确定    33
3.2.5 非定常数值模拟结果分析    34
3.3本章小结    43
第4章 测量系统的方案设计    44
4.1 系统要求    44
4.1.1 总体要求    44
4.1.2 系统功能要求    45
4.1.3 系统技术指标    45
4.1.3 系统方案结构    45
4.2 硬件设计    46
4.2.1 变送器    46
4.2.2 信号调理模块    47
4.2.3 数据采集卡    48
4.2.4 电路接线图    49
4.3 软件设计    50
4.3.1 程序面板的设计    51
4.3.2 前面板的设计和程序打包    54
4.4本章小结    55
第5章 结论与展望    56
5.1 结论    56
5.2 展望    57
参考文献    58
在学研究成果    61
致谢    62