CFD Flow Analysis of Steady-State Flow Forces on Valves

The analysis and evaluation of the steady-state flow forces acting on the spool of hydraulic valves is a keyaspect in many working conditions. Flow forces are generated by the pressure flow fields caused by the high fluid velocity across the metering edges. During the years different piston shapes had been tested in order to reduce or cancel the effect of flow forces, and some of these resulted partially successful. The flow-forces ac;ting on a conventionally shaped spool are compared in the paper with those acting on a "specially shaped" spool, and the flow field in the latter case is investigated at different pressure and opening of the valve. To this purpose a Computational Fluid Dynamics (CFD) analysis based on the finite element method has been carried out. The computer codes used are FLOTRAN, with ANSYS 5.0 used as pre- and post-processor for data preparation and visualization [1][2], and FIDAP 7.07 [8]. The comparison between the classical theoretical assumptions and the results from the CFD analysis provided precious information about the feasibility of the analysis techniques.