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在新设计叶轮时,往往会产生所需要的作功能力与希望得到最佳的气动效率、宽阔平坦的性能曲线之间的矛盾。这时,除了改善叶轮的其它几何参数之外,往往采用双列叶栅(即长、短叶片)。双列叶栅的优点在于不显著降低叶轮的作功能力的同时,可以使较小直径叶轮进口处的叶片不致过于稠密,减小阻塞,降低叶道进口处的马赫数M_(w1),改善进口流场。由于长、短叶片结构有可能采用较多的叶片数,这对减少叶轮流道中二次涡流的影响、提高叶轮的动强度都是有利的。
In the new design of the impeller, often produce the required work ability and hope to get the best aerodynamic efficiency, wide and flat conflict between the performance curve. At this time, in addition to improving the other geometric parameters of the impeller, double row cascades (ie long and short blades) are often used. The double row cascade has the advantage of not reducing the working ability of the impeller remarkably and at the same time, the blades at the inlet of the smaller diameter impeller can not be too dense, reducing the obstruction, reducing the Mach number M_ (w1) at the inlet of the impeller, improving Import flow field. As long and short blade structure may use more blades, which reduce the secondary vortex flow in the impeller and improve the dynamic strength of the impeller are beneficial.