非均匀入流对双吸离心泵内部流动影响的研究

发布时间：2018-06-25 01:07

本文选题：双吸离心泵 + 非均匀入流　；参考：《西安理工大学》2017年硕士论文

【摘要】：对离心泵而言,良好的入流是保证整泵水力性能的重要因素,然而在离心泵的实际运行中,往往存在由于安装空间受限而导致的入口管路弯曲、进口回流及预旋等非均匀入流,从而造成了离心泵“设计过程中的均匀入流”和“实际运行中的非均匀入流”之间的矛盾。本文基于双吸离心泵的实际工程应用,分析在入口管路弯曲所引起的入流非均匀情况下的泵内部流动特性,为提高双吸离心泵的实际运行效率与安全稳定性提供借鉴,为促进离心泵工程应用领域的节能降耗开拓新思路。首先,搭建了双吸离心泵压力脉动试验台,对均匀入流条件下的双吸离心泵进行外特性试验,并采用高频动态压力传感器对蜗壳各测点及进、出口管处的压力脉动进行测量与分析;对均匀入流条件下双吸离心泵模型进行数值模拟,内容与试验中保持一致,对比分析模拟计算结果与试验结果发现:(1)该双吸离心泵试验与数值模拟得到的外特性趋势一致;(2)蜗壳内压力脉动主频为叶频,且在隔舌处的压力脉动最为强烈;(3)在小流量工况下,试验中出现了主频为2.6倍叶频的压力脉动。模拟计算结果与试验结果基本一致,在此基础上,对双吸离心泵进行非均匀入流下内部流动的数值模拟研究。其次,对水平及竖直弯管两种非均匀入流管路进行建模,对非均匀入流下的双吸离心泵进行定常计算,主要对进口法兰处的流动非均匀性、外特性、叶轮内部及进出口截面的流动进行分析,研究结果表明:(1)双吸离心泵在非均匀入流管路下运行时,泵扬程及效率均下降,水平弯管对泵性能的影响高于竖直弯管;(2)双吸离心泵非均匀入流对叶轮进、出口截面的流速、静压和湍动能分布产生了较大影响;(3)水平弯管入流下,扬程及效率最大下降幅值分别为0.48m和1.02%; (4)在水平弯管入流时,双吸离心泵两侧叶轮入流流量存在差异,这种差异在叶轮内部只出现在部分流道;在设计工况下,双吸叶轮两侧流量的不均匀性使叶轮产生了大小为50. 2N的轴向力。最后,对非均匀入流条件下的双吸离心泵进行非定常计算,分别对蜗壳内压力脉动及轴向力进行分析,研究结果表明:(1)泵非均匀入流主要引起轴频压力脉动的大幅上升,并伴随叶频压力脉动的小幅上升,在隔舌位置的压力脉动幅值上升最大;(2)叶轮两侧入流的流量差异并不会引起叶轮两侧压力脉动的较大变化。(3)非均匀入流会严重改变叶轮轴向力的分布规律,并导致轴向力脉动幅值大幅增加。
[Abstract]:For centrifugal pumps, good inlet flow is an important factor to ensure the hydraulic performance of the whole pump. However, in the actual operation of centrifugal pumps, there are often inhomogeneous inflow flows, such as inlet pipe bending, inlet reflux and pre-rotation, which are caused by limited installation space, etc. Thus, the contradiction between "uniform inflow in the design process" and "non-uniform inflow in actual operation" of centrifugal pump is caused. Based on the practical engineering application of double suction centrifugal pump, this paper analyzes the internal flow characteristics of the pump under the condition of non-uniform inlet flow caused by the bending of the inlet pipe, which provides a reference for improving the practical operation efficiency and safety and stability of the double suction centrifugal pump. In order to promote the application of centrifugal pump engineering energy saving and consumption reduction new ideas. First of all, a double suction centrifugal pump pressure pulsation test bench is set up to test the external characteristics of double suction centrifugal pump under the condition of uniform inflow, and the high frequency dynamic pressure sensor is used to measure and enter the volute. The pressure pulsation at the outlet pipe is measured and analyzed, and the numerical simulation of the double suction centrifugal pump model under the condition of uniform inlet flow is carried out, which is consistent with the experimental results. The results of comparison and analysis show that: (1) the external characteristic of the double suction centrifugal pump is the same as that of the numerical simulation; (2) the main frequency of pressure pulsation in the volute is the frequency of the blade. The pressure pulsation is the strongest in the tongue septum. (3) under the condition of small flow rate, the pressure pulsation of the main frequency is 2.6 times of the blade frequency. The simulation results are in good agreement with the experimental results. On this basis, the numerical simulation of the internal flow of the double suction centrifugal pump under non-uniform inflow is carried out. Secondly, two kinds of non-uniform inlet pipes, horizontal and vertical, are modeled, and the steady calculation of double suction centrifugal pump under non-uniform flow is carried out, mainly for the flow non-uniformity and external characteristics of the inlet flange. The flow inside the impeller and the inlet and outlet section is analyzed. The results show that: (1) when the double suction centrifugal pump operates under the non-uniform inlet line, the pump head and efficiency are decreased. The influence of horizontal elbow on pump performance is higher than that of vertical bend; (2) the non-uniform inflow of double suction centrifugal pump has a great effect on the velocity of flow, static pressure and turbulent kinetic energy distribution of impeller inlet and outlet section; (3) the distribution of turbulent kinetic energy and static pressure in the inlet and outlet sections of the double suction centrifugal pump. The maximum drop amplitudes of lift and efficiency are 0.48m and 1.02m respectively. (4) the inlet flow rate of impeller on both sides of double suction centrifugal pump is different when the horizontal bend pipe flows in, and the difference only occurs in some channels inside the impeller. The inhomogeneity of the flow on both sides of the double suction impeller causes the impeller to produce a size of 50. The axial force of 2N. Finally, the unsteady calculation of double suction centrifugal pump under the condition of non-uniform inflow is carried out, and the pressure pulsation and axial force in the volute are analyzed respectively. The results show that: (1) the non-uniform inflow of the pump mainly causes the increase of axial frequency pressure pulsation. Accompanied by a small increase in the pressure pulsation of the leaf frequency, The amplitude of pressure pulsation in the position of tongue separation is the biggest, (2) the difference of inlet flow on both sides of impeller does not cause the great change of pressure fluctuation on both sides of impeller. (3) the distribution of axial force of impeller will be changed seriously by non-uniform inflow. The amplitude of axial force pulsation is greatly increased.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH311

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