Air entrainment phenomena in hydraulic structures of Electric Power Plants and the related problems

Air entrainment phenomena often occur in hydraulic structures of electric power plants, possibly causing some operational problems. For example, air-entraining vortices in pump sumps could induce vibration and noise, while foam is generated in weirs of cooling water channel systems and is discharged into sea. As a result, seascape gets worse and foam often adheres to fishing net. Air-entraining vortices produce bubbles at inlets of a hydro power plant. These bubbles can be accumulated at some places, which could increase loss of channel and induce air hammer phenomena and vibration of pump. A large amount of air entrained in spillway of a hydro power plant can also induce self-priming phenomena or air hammer phenomena. This paper introduces these air entrainment phenomena and the related problems, with showing the related future subjects. (author)