Cavitation Damage Mechanisms: Experimental Study of Cavitation in a Spool Valve

摘要

Cavitation has been investigated in directional control valves in order to identify damage mechanisms characteristic of components of aircraft hydraulic systems. Extensive tests were conducted in a representative metal spool valve and in a model three times larger. Both valves are well instrumented for the purpose of accurately measuring mean quantities as well as detecting the onset and extent of cavitation once it developed. Non-cavitating data taken with both valves showed that the position of the high-velocity annular jet issuing from the orifice shifted orientation depending upon valve opening and Reynolds number. By means of high-frequency response pressure transducers strategically placed in the valve chamber of each test valve cavitation could be sensed by the correlation of noise with a cavitation index. Cavitation inception could be detected by comparing energy spectra for a fixed valve opening and a constant discharge. Another sensitive indicator of cavitation inception is the ratio of cavitating to non-cavitating spectral densities. The incipient cavitation index as defined in this investigation correlates well with the Reynolds number for both valves. Once cavitation develops, an accelerometer properly located on the cavitating component can be as sensitive to cavitation noise as a pressure transducer. Energy levels under developed cavitation were affected to some extent by temperature differences.