Radial Thrust of Single-Blade Centrifugal Pump

Abstract

A single-blade centrifugal pump is widely used as a sewage pump. However, a single-blade is acted on by a large radial thrust during the pump operation because of the geometrical axial asymmetry of the impeller. Therefore to secure the pump reliability, it is necessary to grasp the radial thrust quantitatively and elucidate a behavior and a generation mechanism. This study investigated the radial thrust acting on a single-blade centrifugal impeller by an experiment and a CFD analysis, and the results clearly indicated the following facts. The fluctuating component of the radial thrust increased as the flow rate changed from the design flow rate to a partial or excessive flow rate. Furthermore, the radial thrust was modeled by a combination of three components, inertia, momentum and pressure components by applying unsteady conservation of momentum to this impeller. The grand total of these components was in agreement with the radial thrust calculated by integrating the pressure and the shearing stress on the impeller surface. In addition the behavior of each component was shown and the effects of those components that gave to the radial thrust were clarified. The pressure component had the greatest effect on a time-averaged value and a fluctuating component of the radial thrust. The time-averaged value of the inertia component was approximately 0 even if the flow rate changed. But its fluctuating component had a magnitude nearly comparable to the pressure component at a partial flow rate and slightly decreased with increase of the flow rate.