Visualization of Flow in a Control Valve with a Three-stage Perforated Cage via Computational Fluid Dynamics

The purpose of this study was to confirm, through experiments and computational fluid dynamics (CFD) analysis, the flow characteristics of a control valve with a three-stage perforated cage and to evaluate the flow state from the CFD visualization results. The control valve evaluated in this study was a size 2-inch perforated cage valve. We used a 3D metal printer to create two types of cages with different resistances in the first or second stage. The flow coefficient Cv was calculated from three differential pressure conditions, and the liquid pressure recovery factor FL was calculated from the maximum differential pressure. We calculated and compared the flow characteristics, Cv and FL, obtained from experiments and CFD analysis to confirm the validity of the CFD analysis model used in this study. We visualized the pressure distribution, velocity distribution, and void fraction obtained from the CFD analysis. The visualization results showed that the perforations in the first and second stages had non-choked turbulent flows with no cavitation, whereas perforations in the third stage had cavitation at the inlet of the perforations. We found that cavitation in the third stage could be suppressed by increasing the resistance of the first stage rather than increasing the resistance of the second stage.