中文摘要：

根据无过载离心泵最大轴功率与额定轴功率比值（功率备用系数K）公式，通过推导，将K表示成仅与比转数、叶片出口角和叶片数相关的函数，以此函数给出了K的三维曲面以及在不同叶片数下K关于叶片出口角和泵比转数的等高线。K和叶片数关系不大，叶片出口角、泵比转数对K影响较大；在相同的K下，比转数越高，可取的最大叶片出口角越大。由等高线图可以根据比转数、K选择合理的叶片出口角。实例证明，该方法能够快捷实现无过载离心泵设计，避免了传统方法叶片出口角选择的盲目性。

英文摘要：

According to the formula of the ratio K of the maximal axle power to the rated axle power of the nonoverload centrifugal pumps, K was expressed as the function of specific speed, impeller outlet angle and number of blades by calculating the formula. The three-dimensional image of K and contours about specific speed and impeller outlet angle of K under different numbers of blades were drawn based on the function. K is not close to the number of blades; while the impeller outlet angle and specific speed have a greater effect on K. Under the same K, the higher the specific speed was, the bigger the impeller outlet angle would be. Reasonable impeller outlet angle can be chosen according to the specific speed and K from the contours. The example showed that the method can make the design of non-overload centrifugal pumps successfully and quickly, and can avoid the blindness in choosing the impeller outlet angle with the traditional method.