Determination Of Values For Flow Coefficients Of First Stage Orifices In Two-Stage Electrohydraulic Servovalves

Abstract

The first stage of hydraulic amplification of two-stage electrohydraulic servovalve is usually a flapper-nozzle valve with two nozzles. This is the combination of four orifices (two with constant and two with variable areas) that form a hydraulic bridge. It is usual to add a constant orifice in the return line of the first stage in order to reduce volumetric losses and eliminate cavitation. Usually, it is assumed that flow coefficients of these orifices take constant values in equations for volumetric flows calculation regardless working fluid flow regimes. Variations of Reynolds numbers and for these values calculated flow coefficients of analyzed orifices in transient regimes of a servovalve for step input current are analyzed.