Optimum Vane Number and Angle of Centrifugal Pumps With Logarithmic Vanes

Abstract

The optimum number of vanes for a given centrifugal pump or blower cannot be estimated by Pfleiderer’s equation because of its limitations. In the present investigation, Stodola’s effect is analysed for logarithmic shape vanes and theoretical equations have been obtained to estimate the vane number for optimum efficiency of the unit. The experiments conducted on six impellers whose blade number varied from 2 to 10, resulted in a maximum efficiency of 62.4 percent for the impeller having seven vanes of blade angle 30 deg, which is also the same blade number predicted by the theoretical equation. The experimental results of Varley, and Bommes regarding the optimum number of vanes are in agreement with the theoretical predictions, whereas the empirical equations of Pfleiderer and others suggested either low or high values. Optimum blade angle for maximum efficiency has been worked out for an impeller having logarithmic vanes. In the present investigations an optimum blade angle of 27.3 deg has been obtained for a seven bladed impeller. The results obtained from the present theory agree very well with the results of Varley and Kasai.