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A hydraucone is a form of draft tube used with a hydro turbine. It has a bell-mouth shape and its salient feature is a flat plate deflector near the mouth. The term ''hydraucone'' was introduced by William M. White, who obtained a U.S. patent for it in 1917.〔 Apparatus for utilizing the hydraucone action of water〕〔 DISCHARGE-CHAMBER For WATER-WHEELS〕〔 Return-Regainer〕〔 Diffuser for Hydraulic Machines〕 ==Background== White observed that the simplest method of changing the direction of a jet of water was to direct it at a flat plate. The shape of the water jet as it hits the plate was the inspiration for the hydraucone profile. The main purpose of a draft tube is to recover the residual kinetic energy of the water that exits over the turbine. It does this by distributing the water that exits from the turbine uniformly over the larger area of the draft tube exit. This reduces the water velocity and water pressure at the turbine exit. The kinetic energy of the water, which is proportional to the square of the water velocity, is thus transformed into effectively a higher head across the turbine. The hydraucone draft tube is very efficient at recovering energy from the rotational motion of the water (swirl) as well as the linear motion (flow) of the water. It has fallen into disuse due to the difficulty of supporting a very wide opening under a large turbine. It only requires a shallow excavation, however, which is an advantage in rocky terrain. Its compact shape makes it suitable for small hydro projects where the excavation is much less than that required for the more conventional elbow shaped draft tube. An elbow-shaped draft tube is less efficient than a bell-mouth tube due to the fluid losses in the turn of the elbow. The difference in efficiency is more pronounced when there is swirl present as the gyroscopic effect of the rotation hinders the deflection at the elbow. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hydraucone」の詳細全文を読む スポンサード リンク
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