FLOW VISUALIZATION OF REATTACHING JET FLOW FOR INSTANTANEOUS SPOOL-VALVE OPENING

Abstract

The jet flow, when the valves are immediately opened, issuing from the metering orifice of the spool valves commonly used for hydraulic power applications is investigated by flow visualization test. A two-dimensional model of the spool valve is designed to visualize the jet flow by a hydrogen-bubble method. The images of flow fields taken by a CCD monochrome camera are fed into a microcomputer, and a digital image processing technique is employed to investigate the process of reattaching jet formation. The influence of the Reynolds number and the spool speed on the time required of the jet from the orifice to the wall is described.