Study on cavitation damage characteristics around a hollow-jet valve

In this paper, to make clear the mechanism of cavitation damage around a ho llow-jet valve, cavitation damage test was conducted in a hollow-jet model valve. The eroded surfaces of specimens were observed by Scanning Electron Microscope (SEM) at different times of the test. Cavitation aspects were al so observed photographically by a high-speed camera. It was found that the damage occurs in cavitating flows around a hollow-jet valve with two patter ns. One is characterized by a big plastic crater, which seems to be generat ed by one blow event of cavitating vortex collapse near a specimen surface. Another is due to a small brittle irregular pit formed by the cumulative e ffects of many weaker blows, The former is the main cause to lead serious d amage. The high-speed photographic observations of the cavitation aspects s howed that more cavitating vortices in middle cavitation number state occur than these in other states. The damage tests also illustrated that the mid dle state is the most dangerous for cavitation damage around a hollow-jet v alve.