螺旋形蜗壳型式对高比转数离心泵性能的影响

Effects of spiral volute type on performance of high specific speed centrifugal pump

为了研究2种不同螺旋形蜗壳型式下高比转数离心泵的水力特性,以某一螺旋形单蜗壳为原型,设计了一台各截面面积相等、主要几何参数相同且带有对数螺旋形隔板的双蜗壳.选用SST k-ω湍流模型,应用ANSYS 14.5软件,对单、双蜗壳高比转数离心泵进行了不同工况的三维湍流数值计算,并利用原型泵的外特性试验,验证了数值计算方法的准确性.结果表明:在大流量工况下,双蜗壳泵具有更高的水力效率和扬程;额定工况及小流量工况下,隔板的存在影响不大.此外,双蜗壳内的压力脉动整体小于单蜗壳内的,尤其在靠近蜗壳出口处,双蜗壳内的监测点压力脉动幅值显著降低,这表明隔板能有效地抑制压力脉动;从扩散管段的截面流线图可以看出其流动比单蜗壳的更顺畅;不同工况下,双蜗壳匹配作用下的叶轮所受径向力均小于单蜗壳作用下的,尤其在大流量工况下,差值最大,说明隔板也能更好地平衡叶轮所受径向力.这对高比转数离心泵水力设计具有一定的参考价值.

In order to study the internal flow field in two high specific speed centrifugal pumps with different volutes, a pump with logarithmic spiral splitter is designed based on a pump with single logarithmic spiral volute. The cross-sectional area and the main parameters of two pumps are identical. A series of numerical simulations are conducted by making use of the SST k - to turbulence model and ANSYS 14.5 software to obtain the unsteady, three-dimensional and turbulent flows in the centrifugal pumps with single and double volutes under different operational conditions. The performance of the pump with single volute are tested to validate the accuracy of simulations. It is found that the pump with double volute is subject to a better hydraulic efficiency and higher head at high flow rates. Howe- ver, the effect of the splitter on the performance is minor under design and part-load conditions. In ad- dition, the pressure fluctuations in the double volute pump are less than those in the single volute pump, especially at the outlet, suggesting the splitter can damp pressure fluctuations effectively. It can be seen that the flow in the double volute is smoother than that in the single volute based on the streamline patterns in the diffuser. Compared with the single volute pump, the double volute centrifugal pump can undergo a reduced radial thrust, especially at high flow rates. The results are valuable for the hy- draulic design of high specific speed centrifugal pumps in some degree.