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Experimental Study on Effects of Vortex-Prevention Devices for Suppressing Air Entrainment Inside Surface Intake Facility

Author(s): Kohsei Takehara; Nobuyuki Hisasue; Yasuhide Takano

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Keywords: Intake facility; Air-entrainment; Vortex-prevention device; PTV; MLS

Abstract: In the hydro-electrical power station, water in the reservoir is taken into the electrical power generator through an intake facility. In the common intake facilities, the free surface flow merges into the closed pipe flow, which leads to the electrical power generator. Air entrapment by the intake vortices inside the surface intake facilities causes the deterioration of power generation, the destruction of blade in a turbine, and so on. It is very important for the hydro-electrical power station to suppress the air entrapment by the intake vortices. To suppress the air entrapment by the vortices, vortexprevention devices have been proposed and some of them have been used in hydro-electrical power stations. Those vortex-prevention devices are effectively suppress the air entrapments in a certain hydraulic condition. However, the hydraulic properties of flow structure by those vortex-prevention devices are still unclear. In this research, the effects of the vortex-prevention devices in the surface intake facilities are investigated experimentally by using the particle tracking velocimetry (PTV) .The vorticity distribution is evaluated by the Moving Least Square (MLS) method, which can accurately evaluate the vorticity from the randomly distributed velocity vectors obtained by the PTV. Three types of the surface intake facilities were tested to evaluate the effects of the vortex-prevention devices. The average velocity distribution, the turbulent properties distribution, the average vorticity distribution and statistics property distribution of vorticity are calculated from the obtained velocity distributions. The results show that the vortex-preventing devices effectively stabilize the flow in the dead water region. As a result, air-entrapment by surface vortex is suppressed by the vortex-preventing devices.


Year: 2015

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