Abstract
Single-blade centrifugal impellers for sewage systems undergo both unsteady radial and axial thrusts. Therefore, it is extremely important for the improvement of pump reliability to quantitatively grasp these fluctuating hydrodynamic forces and determine the generation mechanism behind them. In this study, we conducted component analyses of radial and axial thrusts of closed, single-blade centrifugal pumps with different blade outlet angles by numerical analysis while considering leakage flow. The results revealed the effect of the blade outlet angle on the components of radial and axial thrusts. For increased flow rates, the time-averaged values of the pressure component were similar for all impellers, although its fluctuating components were higher for impellers with larger blade outlet angles. Moreover, the fluctuating inertia component of the impeller with a blade outlet angle of 8° decreased as the flow rate increased, whereas those with 16° and 24° angles increased. Therefore, the radial thrust on the hydraulic part was significantly higher for impellers with high blade outlet angles.
Highlights
Sewage pumps for transporting fluids with solid and fibrous foreign bodies are required to have a high foreign body passage diameter; a centrifugal pump with a single wide blade is often used
The time-averaged values of the pressure component were similar for all impellers, the fluctuating component was larger for impellers with larger blade outlet angles
Higher flow rates, more than half of the momentum components were counteracted by the pressure components
Summary
Sewage pumps for transporting fluids with solid and fibrous foreign bodies are required to have a high foreign body passage diameter; a centrifugal pump with a single wide blade is often used. The single-blade centrifugal pumps in current usage are equipped with an axially nonsymmetric volute casing around an axially nonsymmetric impeller For this reason, the static pressure distribution surrounding the impeller is extremely nonuniform, and an excessively fluctuating radial thrust acts on the impeller [3, 4]. The hydrodynamic forces acting on the rear and front shroud parts were neglected in the numerical analyses For this purpose, we carried out numerical analyses with consideration for leakage flows behind the rear and front shrouds and revealed the behaviors of radial and axial thrusts [14]. As a continuation of a previous report [15], we conducted numerical analyses with consideration of leakage flows behind the rear and front shrouds for closed, single-blade centrifugal pumps with different blade outlet angles. We conducted component analyses of radial and axial thrusts and revealed the effect of the blade outlet angle on the thrust components
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