Measuring the impact of flow force on the spool of a servo valve by means of computational fluid dynamics

The development and design of servo valve spools with high performance requirements require accurately calculating the impacts on the spool. During the operation of the servo valve, the most significant impact on the spool is exerted by the flow force, which is determined by the flow rate of the liquid and the angle of deflection of the jet. Existing methods for calculating the magnitude of the flow force do not take into account the actual shape of the sleeve and spool collars, which negatively affects the accuracy of the calculations. This article develops a method for calculating the impact of the flow force on a servo valve spool using computational fluid dynamics, taking into account the shape of the sleeve and spool collars. The article presents a simulation of the fluid flow through the spool sleeve of a servo valve in various positions of the spool at a pressure drop across the valve of 7 MPa under no load conditions. Based on the simulation results, for each of the spool position under consideration, the actual flow rate through the servo valve and the jet deflection angles are determined, taking into account the actual structure of the spool sleeve. Based on the actual flow rates, the flow rate coefficients of the servo valve are defined and the flow characteristics are built. Using the data on the jet deflection angles and the obtained flow characteristic, the dependence of the resulting impact of the flow force on the spool of the servo valve on the spool position is calculated. As the result of the study, a step-by-step method for calculating the resulting impact of the flow force on the spool is developed, which is applicable for various operating modes of the servo valve, determined by the supply pressure and the load values.