Influence of the upper-rotor device with axial and inclined grooves on the axial-flow pump cavitation characteristics

The paper presents results of the experimental study of an axial-flow pump with the upper-rotor device in the form of axial and inclined grooves. It demonstrates influence of their number, length and angle of inclination on the cavitation characteristics. In the overwhelming majority of cases, pressure characteristics of the pumps with axial impellers have the non-monotonic curves complicating their design and regulation processes. This problem is of theoretical and practical interest, since ensuring the monotonically decreasing pressure characteristic of an axial-flow pump is one of the most important goals in designing and optimizing the unit. Upper-rotor devices with the axial or inclined grooves positioned relative to the pump rotor rotation axis could be introduced to create the monotonically decreasing pressure characteristics. However, the upper-rotor device influence on the cavitation characteristics was not sufficiently studied. Cavitation characteristics of an axial-flow pump with an upper-rotor device were experimentally obtained, and the obtained results were analyzed. Using an upper-rotor device with the axial or inclined grooves improves the pump anti-cavitation quality at low flow rates, but worsens it at the high flow rates. For certain designs in length, number and slope of the grooves, no influence on the anti-cavitation qualities was identified.
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