掺气坎后水流掺气浓度分布及掺气保护长度试验研究

Experimental Study on Air Concentration in Flow along Chute and Length of Protective Segment

在掺气减蚀研究中,掺气设施的掺气保护长度是检验掺气减蚀效果的重要指标,而水流掺气浓度及其分布将决定掺气保护长度。通过反弧段泄槽模型试验,研究了不同流量、不同挑坎高度时掺气浓度与掺气保护长度的变化规律。结果表明,掺气坎后水流掺气浓度沿程分布规律为先增大后减小,而在断面上的分布规律为由水流表面到水流底部逐渐减小;泄槽反弧段与泄槽直段及不同水深处掺气浓度的沿程衰减率不同;在其他条件不变时,掺气浓度与流量大小成反比,与挑坎高度成正比;掺气有效保护长度随流量增大而减小,随掺气坎高的增大而增大。

In the study of cavitation reduction by aeration,the length of protective segment of the aeration facility is an important index and it is determined by the aeration density and the air concentration distribution in the flow.Based on the model test of the chute with an anti-arc section,the air concentration and its distribution in the flow along the chute and the length of protective segment were investigated for different flow discharges and the aerators with different heights.The experimental results show that in the areas downstream the aerator,the aeration density of the flow increases first and reach its maximum values and then decreases along the chute.Along the flow depth,the aeration density of the flow decreases from the flow surface to the bottom.For the areas near the flow surface and near the flow bottom and for the segments of anti-arc and straight part of the chute,the attenuation rates of the air concentration in the flow are different.Under the conditions of other factors remain unchangeable,the air concentration in the flow and the length of protective segment increases with the decrease of flow discharge and with the increase of aerator＇s height.