【作者】 许文静；

【导师】 朱祖超；

【作者基本信息】 浙江理工大学 ， 流体机械及工程， 2012， 硕士

【摘要】 离心叶轮是低比转速离心泵的主要过流部件之一，其作用是将原动机的机械能直接传给流体，以提高液体的静压能和动压能，因此叶轮的结构对离心泵内部流场及性能有着至关重要的作用。对此，本文基于三维N-S方程和RNG k-ε湍流模型对具有4叶片普通叶轮、8叶片和12叶片复合叶轮的三台低比转速离心泵进行了非定常数值模拟，并进行了外特性性能试验测试。主要研究内容如下：采用PRO/E三维造型软件对4叶片、8叶片和12叶片叶轮低比转速离心泵进行三维整机全流场造型，并用CFD软件FLUENT对其内部流动进行了数值模拟，分析了不同时刻3台离心泵内部的速度场和压力场；此外，在蜗壳具有代表性的四个断面的壁面附近以及蜗舌部位设置了监测点，对蜗壳壁面附近的压力脉动进行了分析；最后，对三台低比转速离心泵的外特性性能进行了数值预测和试验测试，并将数值结果和试验结果进行了对比。经过分析，得出了以下结论：(1)针对数值模拟得到的3个叶轮内部不同时刻的速度场进行了分析，发现由于普通叶轮中没有布置分流叶片，相邻长叶片间流道比较宽阔，流体的流动不可能完全被叶片所夹持，使得长叶片压力面较厚边界层内的液体不能顺利排出，因此在4叶片普通叶轮的流道中存在大面积的低速回流区，这种现象在8叶片复合叶轮中有所改善，而在12叶片叶轮中改善最为明显。在12叶片叶轮中液流基本沿叶片的曲率流动，可见分流叶片在一定程度上可以改善叶轮内部的速度分布；(2)对数值模拟得到的3个叶轮内部不同时刻的压力场进行了分析，发现12叶片叶轮内部的静压分布较为均匀，静压曲线基本上沿圆周方向分布，且静压系数明显大于4叶片叶轮相同半径上叶片的静压系数。此外，蜗壳腔体以及出口的静压系数也较大，说明分流叶片不仅可以改善泵内部的压力分布，同时也可以提高相同位置的压力值；(3)对数值模拟得到蜗壳壁面附近的压力脉动进行了分析，表明复合叶轮可以改善蜗壳内部的压力脉动，值得注意的是，复合叶轮产生的压力脉动的频率成分相比普通叶轮复杂，在复合叶轮中，除了基频及其倍频外，长叶片产生的频率在低频区上也会占主导地位；(4)针对3台低比转速离心泵进行了外特性性能试验研究，试验结果表明，12叶片叶轮离心泵扬程较高，但随着叶片数的增大，轴功率会变大，在一定程度上会影响泵的效率。更多还原

【Abstract】 As the one of main flowparts in low-specific-speed centrifugal pump, impeller is totranform the mechanical energy of original motive into the pressure and kinetic energy of liquid,so the structure of the centrifugal impeller has a crucial role on flow condition and performanceof pump. Based on Reynolds-averaged Navier-Stokes equations and the RNG k-ε turbulencemodel, the whole flow field in low-specific-speed centrifugal pump with four-blade, eight-blade and twelve–blade impeller was simulated respectively in this thesis. And the experimentalinvestigation was also carried out on three low-specific-speed centrifugal pumps. The maincontents were as follows:The whole flow field in low-specific-speed centrifugal pump with four-blade, eight-bladeand twelve–blade impeller were completed by three-dimensional modeling software Pro/e, thevelocity and pressure distribution inside pump flow field were simulated by using FLUENT atthree different time. In addition,the pressure fluctuations were analyzed by setting upmonitoring points near the wall of volute and tongue.Finally,the pump external characteristicsreached by numerical prediction and experimental results were compared.After analysis,conclusions are as follows:(1) From the velocity analysis, it can be seen that the channel between the two long bladesis relatively wide and the fluid cannot be clamped well for ordinary impeller without splitterblades. As the result, fluid coming from the thick boundary layer on blade pressure side can notbe successfully discharged. So there exists a large area of low speed recirculation zone betweentwo blades inside four blades impeller, which is improved inside the other two impellers withsplitter blades. To some extent splitter blade can improve velocity distribution in the channel ofimpeller;(2) As can be seen in the static pressure analysis, static pressure distribution inside twelveblades impeller is more uniform and static pressure coefficient is significantly greater than fourblades impeller blades in the same radius, the same change rules can been also seen insidevolute chamber and the exit.All is indicating that splitter blades can not only improve thepressure distribution inside the pump, but also increase the pressure at same location;(3) From pressure fluctuation analysis, numerical results show that the complex impeller can significantly improve the pressure fluctuation inside volute chamber. Compared withordinary impeller, it is worth noting that frequency components generated by the compleximpeller is more complex. In addition to fundamental frequency and its harmonic, pressurefluctuation generated by the long blades play the dominant role in low frequency region forcomplex impeller;(4) The experimental results show the higher head is obtained by the pump with twelveblades. The pump shaft power becomes larger with the increase of the number of blades, whichwill affect pump efficiency to a certain extent.更多还原