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

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Kohsei Takehara, Nobuyuki Hisasue, Yasuhide Takano

Friday 3 july 2015

11:45 - 12:00h at Asia (level 0)

Themes: (T) Water engineering, (ST) Hydraulic machinery and industrial flows, (ST) River and coastal engineering

Parallel session: 15C. Engineering - Industrial

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In the hydro-electrical power station, water in the reservoir is conducted into the electrical power generator through an intake facility. In the common intake facilities, the free surface flow merges into the closed pipe flow. Air entrapment by surface vortices inside the surface intake facilities causes the deterioration of power generation, destruction of blade in a turbine, and so on. It is important for the hydro-electrical power station to suppress the air entrapment by the surface vortices. To suppress the air entrapment by the vortices, some vortex-prevention devices have been proposed and have been used in some hydro-electrical power stations. Some vortex-prevention devices are effectively working in a certain condition. However, the hydraulic properties of flow structure by the 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 PTV used in this research is consists of the Kalman filtering theory and the Chai-square test and has been developed by Takehara et al. The vorticity distribution is evaluated by the Moving Least Square (MLS) method, which has been also developed by Takehara et al. The MLS method 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.