Abstract: It is common in the engineering practice that the working flow of the centrifugal pump is higher than that required by the water delivery system. The translation of the shroud to reduce the width of the impeller outlet can reduce the working flow to achieve the purpose of energy saving in the pumping station. Numerical simulation method is used to study the effect of axially shifting impeller shroud on the performance of centrifugal pump. Combined with the theory, the conversion formula of the front cover plate changing the head of the centrifugal pump is deduced. The results show that cutting the outer diameter of the impeller and translating the shroud of the impeller will reduce the working head of the centrifugal pump. The difference is that the former moves the head curve downward and the decline is greater, while the latter's head curve becomes steeper, but maintain a higher head in small flow conditions. Compared with cutting the outer diameter of the impeller, the hydraulic performance of the centrifugal pump is deteriorated. The translation of the shroud of the impeller suppress the development of the continuous vortex in the impeller under low flow conditions, and the efficiency of the centrifugal pump is increased, which is more suitable for the occasions where multiple pumps work in parallel. According to the basic equation of the pump, the conversion formula of shifting shroud to change centrifugal pump head is derived, and the error of the conversion formula is corrected by using multiple regression analysis. After the test of different centrifugal pump models, the results show that the conversion formula can relatively accurately predict the change of H-Q curve in the range of 0.8~1.0 times working conditions of the centrifugal pump when the moving amount of the shroud of the impeller is small.

Key words: double-suction centrifugal pump, impeller trim, impeller outlet width, Conversion formula