Detection of cavitation threshold on standard orifice plate and control valves

Kavitacija se pojavlja v tokovnih razmerah, pri katerih lokalni tlak pade pod nasičeni parni tlak kapljevine. Standardna metoda za določanje prehoda iz nekavitirajočega v kavitirajoče področje uporablja analizo ravni zvočnega tlaka, ki izvira z mesta nastanka kavitacije. Zaradi njenih številnih omejitev smo razvili alternativno metodo, s katero lahko na preprost način preučujemo prag kavitacije. Nov postopek omogoča enostavnejše zaznavanje kavitacije brez uporabe posebnih digitalnih frekvenčnih filtrov in aproksimacije signala, ki se sicer uporabljajo kot pripomoček standardne metode. Poleg tega na predstavljeno metodo ne vpliva hrup industrijskega okolja, odstranjen je subjektivni vpliv preizkuševalca in omogočena natančnejša analiza pojava kavitacije. To metodo smo razvili, preizkusili in primerjali z referenčno standardno metodo na standardni zaslonki in izbranem regulacijskem ventilu.Cavitation occurs in the regions of flow where the local pressure declines below the saturated vapor pressure of the liquid. A standardized way to detect the transition from a non-cavitation to a cavitation regime is to employ microphone detection of the sound emitted near the area of cavitation appearance. We have developed an alternative and simple piezoelectric detection method to observe the cavitation threshold. The new method allows easier and faster cavitation detection without the need for special digital filters or signal approximation curves, which are usually used with the detection method prescribed by the standard. New technique eliminates the effect of an industrial environment’s noise, removes the subjectivity of the operator and enables a more detailed observation of the cavitation phenomenon. We have developed and tested this method, also including comparison with the existing standardized technique, on the reference test orifice plate and on a chosen control valve