Flow Characteristics around a Valve Plate Installed in a Duct : 1st Report, Swing type Valve Plate Installed at a Duct Exit

Abstract

The steady flow characteristics around a swing-type valve plate installed in a rectangular duct are studied theoretically and experimentally in order to determine the fluid force acting on a swing-type check valve and the side-gap-leakage effects. The results show that the side-gap leakage has dominant influence upon the fluid force characteristics, which can be well predicted by a small modification of the conventional two-dimensional potential flow theory. For the case of a large side gap, the pressure over the valve plate becomes nearly uniform and is equal to the upstream one. And that the fluid force is expressed as a function of only the velocity ratio of the jet to the upstream, if the side-gap-leakage is less than the mainflow volume. It is pointed out that the separation zone at the back of a valve plate is recovered very rapidly due to momentum transfer effects of side-gap-leakage, and that the outlet flow from a valve plate is not contracted with its width nearly equal to the valve opening one. The experimental formulae of moment coefficient are also presented.