Numerical Study on Cavitation Reduction in Velocity-Control Trim of Valve with High Pressure Drop

Key Words: Cavitation(공동현상), Velocity Control(속도제어형), Valve Trim(밸브트림), High PressureDrop(고차압)초록: 본수치적연구에서는국내의발전소에서사용되는일반적인고차압트림의형상중대표적으로사용되는형상의트림을기본형트림으로정하여, 이를설계한후캐비테이션과유량의관점에서유동특성을살펴보았다. 실제로운전되는발전소계통의운전조건을참고하여고차압조건으로서입·출구차압을18.7 MPa로, 온도를160 로설정하였다. 트림의주요설계인자로서유로의면적, 유로의단(stage)과유로의방향을채택하여, 유량과케비테이션발생특성을개선하기위해기본형트림을재설계하였다. 개선을위해트림을반경방향으로세영역으로나눈후각영역에서재설계인자를이용하여형상을변경하였다. 4가지의재설계모델을제안하였으며, 각모델형상에대한수치해석을수행하였다.유량및캐비테이션발생량의관점에서기본형트림과설계개선트림들을비교하여재설계모델의성능이개선되었음을확인하였다.Abstract: Flow characteristics of velocity-control trim in a valve is investigated numerically with high pressuredrop. A basic trim widely used for a valve in domestic powerplants is selected and designed for a baselineof 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 areselected to be 18.1 MPa and 160℃, respectively, which are typical ones considering operating conditionsadopted in powerplants. With this baseline model and condition, design changes are made for improvement offlow rate and cavitation phenomenon. For re-design, trim is divided into three zones in radial direction anddesign parameters of flow area, stage, and flow direction are considered in each zone. With these combinedparameters applied to each zone, 4 models with design changes are proposed and their flow rates andcavitation areas are investigated. From comparison with those in the baseline model of a basic trim, proposedmodels show better performance in both flow rate and cavitation.