• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.9
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• pp.863-871
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• 2013

Flow characteristics of velocity-control trim in a valve is investigated numerically with high pressure drop. A basic trim widely used for a valve in domestic powerplants is selected and designed for a baseline of velocity-control trim. The numerical analysis is focused on flow rate and cavitation with the basic trim. For a condition of high-pressure drop, pressure drop between inlet and outlet and fluid temperature are selected to be 18.1 MPa and $160^{\circ}C$, respectively, which are typical ones considering operating conditions adopted in powerplants. With this baseline model and condition, design changes are made for improvement of flow rate and cavitation phenomenon. For re-design, trim is divided into three zones in radial direction and design parameters of flow area, stage, and flow direction are considered in each zone. With these combined parameters applied to each zone, 4 models with design changes are proposed and their flow rates and cavitation areas are investigated. From comparison with those in the baseline model of a basic trim, proposed models show better performance in both flow rate and cavitation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.245-253
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• 2011

We investigate the flow characteristics of elementary-flow paths with $90^{\circ}$ bends; a velocity-control trim consists of such paths. For geometric similarity, the width and length of each path are selected, and the number of bends is 0, 4, or 8. The flow tests are conducted with the same flow-path elements. The numerical results are in good agreement with the experimental data. In elements without bends, the volume flow rate decreases with the length of the flow path, with a constant pressure drop between the inlet and the outlet. However, in flow paths with $90^{\circ}$ bends, it increases and then decreases with the length of the flow path. For a fixed number of $90^{\circ}$ bends, better pressure-drop characteristics are observed as the length of the flow path increases. For a fixed flow-path length, a flow-path element with more bends has a smoother pressure drop along the path.