Studies of the flow of air in a model mixed-flow pump by laser Doppler anemometry. Part 2: Velocity measurements within the impeller

The behavior of air in the rotor of a model mixed-flow bowl pump was investigated using a laser Doppler anemometer. The model was operated at 4 different flowrates at the same rotational speed (1200 rpm); the best efficiency point, and 3 off-design points in an unstable region of the performance characteristic. For each flowrate, the blade-to-blade distributions of three-dimensional velocities were mapped within the rotor, and at inlet and outlet. The results of the flow surveys show complex flow phenomena occurring within the model, and the way the structure of the flow changes as the flowrate is reduced. The velocity distributions observed at the best efficiency point, and the predictions of a through-flow calculation used in the computer-aided design process for this machine are compared.