VISUAL DETERMINATION OF CAVITATION DEGREES IN HIGH ENERGY CENTRIFUGAL PUMPS

الملخص

In the present paper an experimental investigation using high speed digital camera was carried out in order to find out the cavitation degrees in high energy centrifugal pumps. The used centrifugal pumps were of 10 hp, 20 hp and 30 hp. A special water tunnel was designed and constructed in order to obtain adequate information about incipient, developed and breakdown cavitation in a closed flow system, and hence using it as criteria of cavitation degrees. The experiments were carried in fluid mechanics laboratory at College of Engineering Technology Hoon, Libya.. A special test section of 20mm × 40mm dimension with transparent perspex face was conducted in order represent the represent the point corresponding to 3% drop in head. The photography results showed that the cavity length increases with increasing the flow rate ratio. Using a 30 hp centrifugal pump,  a snow-white color cavities were appeared,  while a misty white color appears when using 10 and 20 hp centrifugal pumps. Also it was obtained that at B. E. P. the cavity length was varied between 40 mm and 50 mm, while the B.E.P. range was found to be varied between cavity lengths 25 mm to 60 mm. For cavitation performance experiments it was obtained that that incipient cavitation for the test pumps varied between cavity lengths 58 mm to 63 mm. The developed cavitation was obtained at cavity lengths varied between cavity lengths 64 mm to 73 mm. The breakdown cavitation was obtained at cavity lengths varied between cavity lengths 67 mm to 84 mm.

Key worlds: Cavitation, centrifugal pumps, cavity length, cavitation inception, developed cavitation, breakdown cavitation.