This project was initiated as part of a new research and development focus to
improve hydropower generation. One aspect of the problem is severe cavitation
erosion which is experienced when hydroturbines are operated at best power and in
spinning reserve. Air injection has been used successfully to minimize or eliminate
cavitation erosion in other applications. Thus, an investigation was initiated to
determine whether or not air injection would be an effective solution for turbine
erosion problems. A specially instrumented hydrofoil of elliptic planform ·and a
NACA 0015 cross section was tested at flow velocities up to 20 m s·I, at various
values of cavitation index. Pitting rate was not measured directly but was inferred
from direct measurement of impulsive pressures on the surface of the hydrofoil and
by monitoring accelerometers mounted at the base of the hydrofoil. Cavitation noise
was also measured by a hydrophone positioned in the water tunnel test section. Air
was injected through small holes in the leading edge of the foil. Air injection was
found to be very effective in minimizing erosion as inferred from all three cavitation
erosion detection techniques.
Arndt, Roger E. A.; Paul, Saurav; Ellis, Christopher R..
Investigation of the Use of Air Injection to Mitigate Cavitation Erosion.
St. Anthony Falls Laboratory.
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