The focus of the present study has been directed towards the development and optimisation of a new high-energy loss / severe service control valve cage. From this, an advanced design methodology has been created which is able to relate the effects of strong three-dimensionality in the flow to the specific geometrical features of the flow path design through the valve cage, thus allowing the design of the cage to be optimised and aid the prediction of troublesome phenomena such as cavitation. The chosen cage design, which consisted of a number of flow paths in which were located a series of densely packed, low aspect ratio, staggered cylinder arrays, was evaluated against existing cage designs of this type. From this point the critical geometrical features of the flow path though the cage were identified and used to define the basis for a parametric study. This study was carried out using computational fluid dynamics (CFD) to simulate the flow through 140 different cylinder array configurations. The results from this were used to develop a series of analytical expressions able to represent the effect of each geometrical feature on the properties of the fluid flow. These were then compiled into a design methodology which could be used to size the valve cage. To validate the computational predictions, a senes of experimental measurements of the velocity distributions within five representative models of the cylinder arrays, considered in the parametric study, were taken using particle image velocimetry (PIV). This required the use of a specially built flow rig and the selection of a line fluid able to provide a near refractive index match with the Perspex cylinders. The chosen line fluid was liquid paraffin BP. A prototype cage was installed into a real process environment to test the performance of the new design methodology and its ability to predict the onset of cavitation. The performance of the prototype cage showed a good agreement with the computational predictions. As a consequence of this study, the author has developed a new approach to the design of a control valve cage which allows the cage to be sized and optimised against a given set of process conditions. It is envisaged that this new method will be of benefit in the future design of control valves, leading to an improved level of performance across the Industry
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:603418 |
| Date | January 2003 |
| Creators | Morton, Karen M. |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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