Reasonable methods for determining the optimum number of blades in a low specific speed centrifugal pump with closed-type impeller with splitters, i.e. compound impeller have been rather rare in the literature so far. In the article, a new analytical method was put forward to determine such an optimum number of blades by including the effect of turbulent boundary layer over impeller blades. Three conventional impellers with different numbers of full-length blades and two compound impellers with different numbers of splitters were designed and manufactured. The corresponding performance tests were then conducted. Results showed that the optimum numbers of blades exist for two kinds of impeller in terms of head at design point, pump efficiencies at design point and best efficiency point, and slope of head-flow rate curve at shut-off point. The estimated optimum numbers of blades are in good agreement with the numbers based on the experiments. The conventional impellers with full-length blades are more prone to the hump phenomenon than the compound impellers at the optimum numbers of blades. For the compound impellers, however, the hump effect is negligible at the optimum number of blades, and their head and efficiency are higher than those for the impellers with full-length blades. The method is applicable to compound impeller design in low specific speed centrifugal pumps.

中文翻译：

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一种确定低比转速离心泵复合叶轮最佳叶片数的分析方法

迄今为止，在文献中很少有合理的方法来确定具有分流器的闭式叶轮即复合叶轮的低比转速离心泵中最佳叶片数。本文提出了一种新的分析方法，通过考虑湍流边界层对叶轮叶片的影响来确定最佳叶片数量。设计制造了三种不同全长叶片数量的常规叶轮和两种不同分流器数量的复合叶轮。然后进行了相应的性能测试。结果表明，两种叶轮在设计点扬程、设计点和最佳效率点的泵效率、关断点扬程-流量曲线斜率等方面均存在最佳叶片数。估计的最佳叶片数量与基于实验的数量非常吻合。在最佳叶片数下，具有全长叶片的传统叶轮比复合叶轮更容易出现驼峰现象。然而，对于复合叶轮，在最佳叶片数下驼峰效应可以忽略不计，其扬程和效率高于全长叶片叶轮。该方法适用于低比转速离心泵的复合叶轮设计。在最佳叶片数下，驼峰效应可以忽略不计，扬程和效率高于全长叶片叶轮。该方法适用于低比转速离心泵的复合叶轮设计。在最佳叶片数下，驼峰效应可以忽略不计，扬程和效率高于全长叶片叶轮。该方法适用于低比转速离心泵的复合叶轮设计。