Schwingungs- und Festigkeitsprobleme von Axialpumpenschaufeln im kavitierenden Off-design Betrieb -

The series of measurements concerns itself with the mechanical load of four different
axial-flow pump bladings with different operating and cavitation conditions (cavitation-
free to total cavitation). Firmness problems at the blades of partial load operated
pumps offered cause and basis for these attempts. In particular with impellers of
axial-flow pumps, which torques higher in partial load exhibit than in the design point,
the demands become on the blades more largely. An additional dynamic blade load
is added by rotating stall. With hydraulic pumps cavitation appears as the further
effect with nearly all pumps in practice. Operators of pumps accept cavitation so long,
as the increase of pumping head is lower then 3% of the cavitation free one. In such
a cavitation stage of axial pumps the steam zone is marked very good and leads to
substantial auxiliary loads of the blade. Axial-flow pump impellers do not have a
material connection under the blades, these at the outside diameter can freely
vibrate. Consequently damages at the blade root are to be registered due to
aforementioned loads. The most evident views supplied the range of the bending
strain and the characteristic frequencies over the flow rate. Clearly evidently a rise is
starting from occurrence rotating stall (with all blades starting from approximately
78% of the operation flow) after the outline. This dynamic load is strengthened to a
large extent by the cavitation