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Research Papers: Flows in Complex Systems

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

[+] Author and Article Information
Guillermo Palau-Salvador

Department of Rural Engineering, Polytechnic Hydraulic Division, University of Valencia, Camino de Vera s/n, 46022 Valencia, Spainguipasal@agf.upv.es

Pablo González-Altozano, Jaime Arviza-Valverde

Department of Rural Engineering, Polytechnic Hydraulic Division, University of Valencia, Camino de Vera s/n, 46022 Valencia, Spain

J. Fluids Eng 130(1), 011102 (Dec 19, 2007) (9 pages) doi:10.1115/1.2813131 History: Received December 04, 2006; Revised July 16, 2007; Published December 19, 2007

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 Cv 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 Cv with higher velocity magnitude within the valve, whereas after smoothing Cv increased and served to delay cavitation inception.

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Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Section of the original control valve studied by CFD

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Figure 2

Experimental loop and schematic position of the pressure sensors used in the experimental test

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Figure 3

Valve upstream and downstream pressure. Percentage of piston stroke in the five regulation rehearsals with one pump and with two pumps in sequence.

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Figure 4

Schematic protocol used to model the valve

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Figure 5

Comparison of the pressure values between the experimental test and the CFD results for openings of 100%, 35%, and 15% and flow rates of 0.0123m3∕h, 0.00472m3∕h, and 0.00726m3∕h, respectively

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Figure 6

Effect of the piston shape on the hydraulic behavior of the valve when it was completely open and the flow rate equal to 0.0123m3∕h. (a) Original geometry, (b) modified geometry, (c) velocity vectors around the piston of the original shape, and (d) velocity vectors around the modified piston shape.

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Figure 7

Effect of the downstream chamber geometry on the hydraulic behavior of the valve when it was 15% open and a flow rate of 0.00726m3∕h. (a) Original geometry, (b) modified geometry, (c) velocity vectors around the piston of the original shape, (d) velocity vectors around the modified piston shape, (e) velocity contours in the original chamber geometry, and (f) velocity contours in the modified chamber geometry.

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Figure 8

Comparison of the x velocity in three sections located 0cm, 12.5cm, and 25cm from the exit of the valve, on the original and modified geometries, with an opening of 100% and 15% and a flow rate of 0.0123m3∕h and 0.00726m3∕h, respectively. The origin of the coordinate system was placed at the exit of the valve in the center of the pipe, and x, y, and z represent the streamwise, spanwise, and vertical directions, respectively.

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Figure 9

Cv values from the experimental CFD model with the original geometry and the CFD model with the modified geometry for different opening values

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Figure 10

Vapor fraction around the piston path for both piston shape and downstream chamber (original and modified geometries) with an opening of 15% for four different flow rates, from 7.26l∕s (experimental flow rate without any observed cavitation process) to 9.61l∕s

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