Numerical Analysis of Cavitation Phenomenon in a Vaned Ring-Type Needle Valve

Cavitation is a destructive phenomenon in industrial needle-type control valves. In order to reduce the damaging effects of cavitation, a circular row of vanes is used at the end section of the needle valve. By changing the path of flow at the end section of the valve and generating a spiral movement in fluid, these vanes increase the near-wall pressure; thus, cavitation intensity is reduced and the bubbles move away from the walls. In this study, the effect of vane camber angle on cavitation intensity and formation location has been investigated. The results show that by increasing the vane camber angle from 10 degrees to 70 degrees, the spiral movement of flow increases and cavitation intensity diminishes mildly; however, as the camber angle increases beyond 70 degrees, the spiral flow movement increases considerably and there is a significant reduction in cavitation intensity. It should be mentioned that at camber angles less than 70 degrees, the flow coefficient remains almost constant; but at angles greater than 70 degrees, the flow coefficient diminishes, resulting in an increase of energy supply cost. (C) 2014 American Society of Civil Engineers.