As the force output of an electromagnetic actuator is limited, achieving reliable operation of a direct-acting solenoid valve at high pressures and flow rates can be challenging. The major performance obstacle is the hydrodynamic flow force acting on the spool as it moves between energized and de-energized states. With trends in the fluid power industry requiring valves to operate at higher pressures and volumetric flow rates, while minimizing electrical power consumption, methods to reduce hydrodynamic flow forces become critical in developing functional products. This paper presents CFD simulation and correlating experimental results in using back angles to reduce the hydrodynamic flow forces in a direct-acting, solenoid operated, cartridge-style, directional control valve. Traditional methods of calculating flow forces are discussed and a brief summary of prior research is presented. A commercially available CFD package, Fluent, was used to numerically estimate the flow forces using a realizable k-ε turbulence closure model. A parametric analysis of flow, pressure, and spool stroke showed sensitivity to the metering edge geometry. A special fixture was created to isolate and directly measure the forces acting on the spool. The addition of a +60° back-angle showed the largest flow force reduction of 36% compared to a spool with no back angle.
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