Quantitative Visualization of the Flow Within the Volute of a Centrifugal Pump. Part B: Results and Analysis

Abstract

PDV is used for measuring the velocity within the volute of a centrifugal pump at different impeller blade orientations, on and off design conditions. It is demonstrated that the flow is “pulsating” and depends on the location of the blade relative to the tongue. The leakage also depends on blade orientation and increases with decreasing flow rate. The velocity near the impeller is dominated by the jet/wake phenomenon. Differences in the outflux from the impeller, resulting from changes inflow rate, occur primarily near the exit. Away from the tongue the distributions of vθ mostly agrees with the assumption that vθ ∝ 1/r. Sites prone to high velocity fluctuations include the blade wake, interface between the jet and the wake and near the tongue. Angular momentum and kinetic energy fluxes, turbulent stresses and tubulence production are also computed. It is shown that at the same θ the momentum flux can increase near the impeller and decrease at the perimeter. Consequently, the mean flux cannot be used for estimating conditions near the impeller. Torques caused by τrθ and τθθ can be as high as 2 and 5 percent of the change in angular momentum flux, respectively.