Numerical Simulation and Experiments for Flows in Control Valve

• Main Authors: Chin-Cheng WANG, 王謹誠
• Other Authors: Ming-Jyh CHERN
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/57837844542848396237

碩士 === 國立臺灣科技大學 === 機械工程系 === 91 === Computational and experimental methods were used to investi-gate the performance and flow patterns of a ball valve. The re-sults obtained in this study would be helpful to predict the performance coefficients including loss coefficient, K, flow coefficient, Cv, and cavitation number, Ccs. Various patterns of flows in ball valves, i.e., recirculation region and cavita-tion phenomena, were visualized using a particle tracking flow visualization method (PTFV). In addition, Computational Fluid Dynamics (CFD) could verify the characteristics of flows in ball valves. It could be useful to design and exclude operational problems from ball valves. The control of volumetric flow rate in a ball valve was very important when a ball valve was utilized in piping sys-tem. It was difficult to linearly control the flow rate in a ball valve without external devices. V-ports and R-ports are employed to reach this purpose. In order to investigate the effects of V-ports and R-ports on the volumetric flow rate and flow features, experiments were conducted at various valve opens and Reynolds numbers. The experimental results presented that V-ports with angle 60 and 30 degree make the flow rate proportional to the valve open. R-ports of diameters 4 mm, 3 mm and 2 mm have the same tendencies, too. Meanwhile, the ball valves may pay more pressure drop between the inlet and the out-let of the valve. In other words, more energy was lost. In additions, V-ports of angle 30 degree, R-ports of diameters 4 mm, 3 mm and 2 mm increased the possibility of cavitation comparing with flows without external devices in terms of cavitation number. The computational results were compared with the experimental ones. It turns out that numerical results underpredict the energy loss in such turbulent flows, but the tendencies obtained by numerical and experimental methods are very close. The numerical results of cavitation coefficient agree with experiments.