The Influence of Guidevane on Flow Field in Bend

• Main Authors: Su, Zhi-Yuan, 蘇致遠
• Other Authors: Yen Ruey-Hor
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/71909034352547984234

碩士 === 國立臺灣大學 === 機械工程學系研究所 === 86 === For turbulent flow in a bend it was known that the pressure gradients in the axial direction take positive values in the neighborhood of both the inlet on the outer wall and the outlet on the inner wall.Therefore, it is expected that the separation phenomena can be seen in this region. IF a region of adverse pressure gradient exists in the flow,the pressure gradient will exert itself along the wall near which the fluid velocity is small.The momentum contained in the fluid layers that are adjacent to the wall will be insufficient to overcome the force exerted by the pressu- re gradient,so that a region of reverse flow will exist.The separation ph- enomena in a bend are significan-t.The process of separation is associate- d with large rates of dissipation of energy. Guidevane can be installed in bend to reduce the pressure loss and Pro- vide more uniform flow at the exit of the bends.They also can reduce the maximum velocity at the exit from bend.Guidevane act to reduce the the pr- essure loss in turbulent flow in bends(1)by directing the flow about the inner radius of the bend,thereby preventing flow separation and the forma- tion of eddies,and(2)by subdividing the flow into separate channel,each of which has a radius of curvature to width ratio considerably greater than the bend without vanes. The purpose of this article is to analyze the flow field that have gui- devane or not and compute pressure loss coefficient by CFX.The results of simulations will provide better design of guidevanes with constant thickn- ess applicable for bend.