Study On Aeration Mitigation Of Cavitation For The Flood Discharge Tunnel Of XIAOWAN Hydropower Station

For a long time, the cavitation phenomenon is considered being a problem hard to be solved by humanbeing. Cavitation and the research on it, no matter we analyse it from international or domestic, it has being taken seriously attention and has a gradually thorough trend on it.Not only the academic exchange is more and more, but also there are many engineering problem on it, study content of the problem is broadening, expanding, it has also becoming one of the problem that many relating industry pay attention to.The domestic and international research circumstances indicate that, study on cavitation and cavitation errosion mechanism and their influencing factors have got a great progress already. But we must point out that, since cavitation and the cavitation errosion is a complicated phenomenon such as microcosmic, instant, random and heterogeneous,by now, theory and many research result about cavitation and cavitation errosion can not all be desired , a lot of problem remains to further study and probed in a deepgoing way.The engineering experience indicates that, aerator is an important measure to provent cavitation errosion for flood spillway tunel, according to the research and test taken by domestic institute on some in building or already building large-scale flood spillway tunnel, the reasonable setting of aerator can get a perfect aeration effect. At present, aeration facilities are set up to almost all the in building or already building large-scale flood discharging bulding, however, basically the practice of aerator is prior, the corresponding research and model tests of aeration facilities are relative lagging. Accordingly, the design of hydraulic characteristic and calculation of aeration facilities is mainly dependent on experience and qualitative research, the research in theory aspect is comparatively few.Based on former study of others, this paper is basically aim at the problem of cavitation and cavitation erosion and aeration facilities for proventing cavitation erosion. Associate with the project example of the flood spillway tunnel of Xiaowan hydropower station, carried on a research mainly to the cavitation and cavitation errosion and aeration mitigation and their application in the flood spillway tunnel with high head and huge discharge.the shape of the aerator which was change the slope partly under the aerator was carried out. Such kind of aerator reduced the intensity of the flow of backwater in the air chamber,avoid the accumulation of the backwater in the air chamber,and shaped a whole air chamber under the aerator.As far as the straight barely flow part of the spillway tunnel is concerned, an outstanding advantage of partly changing the slope under the aerator is there needn't to set up a small ridge or"U"type slot on the aerator, this kind of design is convenient to project construction , ensure the construction quality, reduced the cavitation erosion and increase the safety degree of flood spillway tunnel.