A Study of the Behaviour of a Single-Bladed Waste-Water Pump

Abstract

A single-vaned centrifugal pump, typical of the kind employed in waste-water applications (e.g. sewage treatment), has been investigated numerically. The primary objective was to identify a modelling approach that was accurate, but at an acceptable computational cost. A test program has been executed to provide data to validate the numerical models. The global performance of the pump was assessed in terms of the pressure head, the mass flowrate, the power consumption, and the pump efficiency. In addition, time-resolved surface-pressure measurements were made at the volute wall. Five combinations of three modelling approximations (two or 3D; k-ε or Reynolds stress model turbulence model; unsteady or quasi-steady) were investigated and compared with the experimental results. It was found that the choice of turbulence model did not have a significant effect on the predictions. In all cases, the head-discharge curve was well predicted. However, it was found that only the quasi-steady models could capture the trend of the power consumption curve, and hence that of the efficiency. Discrepancies in the magnitude of the power consumption can be accounted for by the lack of losses such as leakage in the numerical models. Qualitative analysis of the numerical results identifies the trailing edge of the impeller as the primary source of power loss, with the flow in the region of the cut water also contributing significantly to the poor overall efficiency of the design.