Fluidmechanics Characteristics of Butterfly Valve

There are several stages of Cavitation phenomena in the flow around butterfly valves. The cavitation stage such as cavitation inception, supercavitation inception, cavitation damage inception, choking (or flashing) cavitation occurs for the various valve opening angles. In this paper, these cavitation stages were theoretically predicted for valve loss coefficient. The cavitation prediction was performed by applying the free streamline theory, where the relation between the loss coefficient and the critical cavitation factor were formulated. As for the experiment, the cavitation inception and critical supercavition were obtained from the vibration intensity rising and the noise level rising, and the flashing cavitation was observed by means of flow visuarization. The theoretical predicted characteristic curves and these experimental results were compared, and agreed very well with each other.