Abstract
Numerical calculations and experimental measurements were carried out in a closed hydraulic test rig to investigate the vibration characteristics and instabilities induced by the development of cavitation in a centrifugal pump. The internal flow characteristics in the impeller and vibration signals at four different positions of the pump system were analyzed during the cavitation process. The results revealed that the occurrence and development of cavitation could be effectively detected by the sudden increase in the intensity of vibration at the testing points. Corresponding relationships were formulated between the occurrence and the development of cavitation and the intensification of the vibration at the measuring locations. It was found out that the virtual incipient for cavitation was much smaller than the traditional “critical” point.
Highlights
Vibration signals were produced by the shock waves and high-speed jets, which were induced by the collapse and shedding of cavitation bubbles near the solid wall
It is obvious that the intensifications of the vibration signals in different positions are resulted from the generation and development of cavitation
Because the accelerometer 1 is closer than other accelerometers to the region of cavitation bubbles and the running impeller and shaft, the vibration signals measured by accelerometer 1 is greater than that of the other three accelerometers
Summary
Cavitation and its related effects are complicated phenomenon and exist in most hydraulic machineries which include pumps, turbines, turbo-pump inducers, hydrofoils, and propellers.[1,2,3,4,5] Primary problems produced by cavitation in pumps include inducing the flow instabilities, reducing the longevity of centrifugal pumps, being responsible for the vibration and noise generation, for the loss of efficiency in pumps, and for the erosive damage on surface of flow channels.[6,7,8,9,10,11,12] it is significant to know the inception and development of cavitation in a pump in a bid to prevent the pump operate at the cavitation condition For this purpose, various kinds of methods are selected to research the development of cavitation. The best efficiency point (BEP) and the occurrence of cavitation in a centrifugal pump have been detected using the AE technique in Alfayez and Mba[24]
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