基于两相流的多级离心泵汽蚀性能分析

发布时间：2018-01-08 09:17

本文关键词：基于两相流的多级离心泵汽蚀性能分析　出处：《华南理工大学》2011年硕士论文　论文类型：学位论文

【摘要】：多级离心泵在运转过程中,有时会出现水力机械特有的汽蚀现象。汽蚀现象改变了流道内的速度分布,使离心泵的效率下降、扬程降低,引起机器振动,同时也会使叶轮遭受破坏,严重影响工作性能,并妨碍其正常运行。所以如何准确地预测泵的汽蚀性能,防止汽蚀的发生是一个重要的研究方向。由于汽蚀现象本身的复杂性以及测量的困难性,要对汽蚀现象准确的定量分析还很难。随着计算流体动力学(CFD)技术在水力机械内部流场计算中应用日益广泛,CFD成为优化设计的重要工具。所以使用数值模拟研究多级离心泵内部的汽蚀流动,预测泵的汽蚀性能,对汽蚀现象进行准确地定量分析已经成为可能。本文利用CFX软件的RNG k-ε湍流模型和SIMPLEC算法,采用Rayleigh-Plesset汽蚀模型对多级离心泵的首级叶轮进行了汽蚀模拟。分析了压力场和速度场,得到了不同压力、不同流量下的气泡分布和速度矢量分布。还对9个流量工况下的叶轮进行了完整的汽蚀模拟计算,从汽蚀未发生、汽蚀初生到汽蚀发展,找到了临界汽蚀余量点,得到了NPSH-Q曲线,并和实验曲线进行了比对。本文得到的结论如下： 1、为了验证模拟软件和模型的准确性,先对多级离心泵的两级叶轮和导叶进行无汽蚀模型的单相流动数值模拟,把模拟结果和实验结果进行了对比,模拟曲线和实验曲线的趋势一致,误差较小,证明了模拟的有效性和可行性。从模拟结果发现泵压力最低的地方在多级离心泵首级叶轮叶片进口处,为下面的工作打下了基础。 2、对多级离心泵的首级叶轮进行了汽蚀模拟。得到了压力分布图和速度矢量分布图,知道了汽蚀初生的位置在叶片背面进口稍后处。调节出口压力和流量,得到了汽蚀随压力和流量变化图。利用模拟计算可以观察到汽蚀初生,找到汽蚀初生点,这对防止离心泵的汽蚀有重要的意义。 3、对9个流量工况下的叶轮进行了汽蚀模拟,找到临界汽蚀余量得到NPSH-Q曲线并与实验曲线进行对比,两条曲线的趋势基本一致,在大流量工况下误差较大,在小流量工况,特别是额定工况下模拟结果和实验结果较为接近。说明该模拟方法可以准确预测离心泵的汽蚀性能,也说明数值模拟预测可以代替繁琐而又复杂的泵汽蚀实验。
[Abstract]:During the operation of multi - stage centrifugal pump , cavitation phenomenon which is peculiar to the hydraulic machinery can sometimes occur . The cavitation phenomenon changes the velocity distribution in the flow channel , so that the efficiency of the centrifugal pump is reduced , the lift is reduced , the machine vibration is caused , meanwhile , the impeller is damaged , the working performance is seriously affected , and the normal operation of the pump is hindered . As the computational fluid dynamics ( CFD ) technology is widely used in the calculation of the flow field in the hydraulic machinery , the computational fluid dynamics ( CFD ) technology has been widely used in the calculation of the internal flow field of the hydraulic machinery , and the CFD has become an important tool for the optimization design . In this paper , the first - stage impeller of multi - stage centrifugal pump is simulated by using the rng k - 蔚 turbulence model and SIMPLEC algorithm of CFX software . The pressure field and velocity field are analyzed . The conclusions are as follows : 1 . In order to verify the accuracy of the simulation software and the model , the single - phase flow numerical simulation of the non - cavitation model is carried out on the two - stage impeller and the guide vane of the multistage centrifugal pump . The simulation results and the experimental results are compared , the simulation curves and the experimental curves are consistent , the errors are small , the simulation results are proved to be valid and feasible . 2 . The cavitation simulation of the first impeller of the multistage centrifugal pump is carried out . The pressure distribution map and velocity vector distribution map are obtained . It is known that the position of the cavitation is at a later stage at the back of the blade . The pressure and flow rate of the cavitation are adjusted . The cavitation inception can be observed by using the simulated calculation , and the cavitation inception point can be found , which is of great significance to prevent cavitation erosion of the centrifugal pump . 3 . The cavitation simulation of the impeller under 9 flow conditions is carried out , the critical cavitation margin is found to be compared with the experimental curve , the trend of the two curves is basically consistent , and the simulation results and the experimental results are close to the experimental results under the condition of large flow conditions . The simulation method can accurately predict the cavitation performance of the centrifugal pump , but also the numerical simulation prediction can replace the tedious and complicated pump cavitation experiment .

【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH311

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