Physical bases for the design of highly efficient rotors in centrifugal pumps

Abstract

1. Existing notions concerning optimum (less than 40°) angles of blade inclination in the rotors of centrifugal pumps at the outlet from the rotor are based on experimental results. Analysis of the theory and experimental data indicated that the shapes of blades of one-sided curvature, which bend gradually rearward, are not optimal. A new blade profile featuring double curvature is being developed. 2. The problem of optimizing the performance of centrifugal pumps can be resolved, if in a rotor with rearward-curving blades, which has long and evenly tapered interblade channels, only the trailing edge of the blades is curved forward over a segment 15–35% (including the transitional segment) of their overall length and up to an ultimate value of 80–135°, and supplementary short blades, which repeat the shape of the forward-curving ends of the basic blades and have the same length, are mounted between the forward-curving ends of the basic blades. 3. Tests conducted on a 2K-6 pump indicated that a rotor having blades of this shape provides for a 30–95% increase in pump head, a 3–5% increase in efficiency, an increase of 50% and more in allowable suction height, and a 20–47% increase in delivery. The noise level is reduced. The data obtained must be defined more precisely for pumps with large blades. 4. The increase in head and delivery due to a change in blade shape makes it possible to cover a larger area on the combined Q-H diagram with a pump of the same make, as a result of which 20–30% fewer type pumps are required to completely cover the area of the combined curve of the fields.