Three-Dimensional Modeling and Geometrical Influence on the Hydraulic Performance of a Control Valve

The ability to understand and manage the performance of hydraulic control valves is important in many automatic and manual industrial processes. The use of computational fluid dynamics (CFD) aids in the design of such valves by inexpensively providing insight into flow patterns, potential noise sources, and cavitation. Applications of CFD to study the performance of complex three-dimensional (3D) valves, such as poppet, spool, and butterfly valves, are becoming more common. Still, validation and accuracy remain an issue. The Reynolds-averaged Navier-Stokes equations were solved numerically using the commercial CFD package FLUENT V6.2 to assess the effect of geometry on the performance of a 3D control valve. The influence of the turbulence model and of a cavitation model was also investigated. Comparisons were made to experimental data when available. The 3D model of the valve was constructed by decomposing the valve into several subdomains. Agreement between the numerical predictions and measurements of flow pressure was less than 6% for all cases studied. Passive flow control, designed to minimize vortical structures at the piston exit and reduce potential cavitation, noise, and vibrations, was achieved by geometric smoothing. In addition, these changes helped to increase C υ and reduce the area affected by cavitation as it is related to the jet shape originated at the valve throat. The importance of accounting for full 3D geometry effects in modeling and optimizing control valve performance was demonstrated via CFD. This is particularly important in the vicinity of the piston. It is worth noting that the original geometry resulted in a lower C υ with higher velocity magnitude within the valve, whereas after smoothing C υ increased and served to delay cavitation inception.