The Influence of the Notch Shape and Number on Proportional Directional Control Valve Metering Characteristics

The paper investigates, by means of a 3D, steady-state, incompressible and isothermal CFD analysis, the influence of the notch shape and number on proportional directional control valves metering edge characteristics. The numerical activity is firstly performed for a sharp metering edge, considered as reference case. Then, different configurations of notched metering edges are considered, coming from the adoption of two notch geometrical shapes largely used in proportional directional control valves actual design, and from asymmetrical displacement of two, three and four notches on the spool periphery. For all the cases considered, the qualitative analysis of the internal flow field is performed in order to highlight the fluid efflux main characteristics. After, a quantitative analysis of the metering characteristics is introduced, with the aim of determining the influence of the metering configuration, of the spool position and of the operating conditions on the efflux characteristics (the discharge coefficient and the jet angle).