Effect of Relative Impeller-to-Volute Position on Hydraulic Efficiency and Static Radial Force Distribution in a Circular Volute Centrifugal Pump

Abstract

The hydraulic performance and radial hydraulic force characteristics of a circular volute centrifugal pump are strongly affected by the impeller to volute relative position. For a typical design configuration the geometric center of the impeller will be coincident with the volute geometric center. However, assembling a circular volute pump with the impeller center eccentric from the volute center can radically alter both the hydraulic performance and the radial hydraulic force characteristics. In particular, at the design flow coefficient an optimum impeller to volute relative position exists where the efficiency is maximized and the resultant radial force is minimized. At the optimal relative position a 5 percent and a 3.5 percent increase in the efficiency was realized compared to the centered positions for the circular and spiral volutes, respectively. In addition the nondimensional resultant radial force at the design flow coefficient was reduced from 0.045 at the centered position to 0.005 at the optimal position for the circular casing. This value of radial thrust is similar in magnitude to the radial thrust for the spiral volute operating at the design flow coefficient. By assembling a circular volute pump with the appropriate relative impeller to volute position the design simplicity of a circular volute can be utilized without compromising pump hydraulic performance or radial force characteristics as compared to a typical spiral volute. [S0098-2202(00)02303-8]