13th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
Loads seen by a pump impeller over a wide range of operating flowrates are critical in designing its drive train. In the recirculation zones at lower flowrates (0.3Qn), loads can deviate significantly from empirical laws. To investigate these phenomena, a comparison between numerical simulations and experiments are carried out on a single volute horizontal Ns 70 (SI) pump. The experimental tests are carried out using an array of strain gauges with on-board conditioners on a modified pump shaft. Torque, axial and radial forces are measured after static calibration.The numerical simulations are performed using CFX with an unsteady RANS model, using the transient rotor-stator approach during a minimum of 8 revolutions. A Two-equation k-ε turbulence model combined to a 7 650 000 hexahedral elements model are used to compute the flow from 0.2 to 1.4Qn. The measurements and the simulations exhibit a similar drop in traction forces around 0.3Qn, at the pre-rotation onset. A complete analysis of hydraulics instabilities leading to an inversion of the volute flow pattern explains the force drop.