Measurement of Flow Induced Rotor Oscillations in a Single-Blade Centrifugal Pump

The composition of sewage water with partially large portions of fibers and solids requires a special impeller geometry, in order to avoid operational disturbances of the pump by clogging. Therefore the almost exclusively used single stage machines particularly are equipped with single-blade impellers. The rotation of the impeller in the pump casing produces a strongly uneven pressure field along the perimeter of the casing. The resulting periodically unsteady flow forces affect the impeller and produce radial deflections of the pump shaft which can be recognized as vibrations at the bearing blocks or at the pump casing [1]. In this contribution the experimental investigation of the dynamic behavior of a pump rotor under the influence of the flow forces is described. To verify calculated results performed earlier a lot of measurements have been carried out at several speeds of rotation and at different volume flow rates. The pump which before was investigated numerical had been equipped with several sensors. The deflections of the pump rotor were measured with two proximity sensors and compared to the computed amounts. Measurements of the static pressure in the casing gave the connection between the rotor oscillations and the pressure fluctuations produced by the single-blade impeller. The simultaneous measurements of the vibration velocities and accelerations at the pump casing showed the effects of the transient hydrodynamic stimulation forces.