有压泄洪隧洞出口渐变段设计与研究

Research and design for the transition section of the flood discharge tunnel with pressure

在水利枢纽工程中,有压隧洞出口一般采用收缩出口断面的方法,以确保出口渐变段顶板具有一定的压力水头,避免发生空蚀破坏。然而出口断面面积的收缩对泄流能力有着显著的影响,选择合理的渐变段体型能起到调整水流的作用,使之在出口不发生水流的分离、旋流、空蚀的前提下达到最大泄流量。如果断面收缩率取得过大,会使隧洞出口顶板产生空蚀破坏,而断面收缩率取得过小,又会减小隧洞泄流能力。本文通过汾河水库泄洪隧洞出口渐变段体型设计结合水工模型试验,对合理选择隧洞出口渐变段体型进行了研究,使其出口断面收缩率大于国内同类隧洞,其研究结果可供工程设计人员借鉴。

In water-control projects, the outlets of tunnel with pressure always adopt contraction section in order to ensure the roof of the transition section has a pressure head to avoid cavitation damage. However, the contraction cross-section of the outlet has a significant impact on the discharge capacity of the transition section, to choose a reasonable size can be adjusted to the action of water, to arrive at the maximum discharge under no separation, swirl and cavitation occurred. If the cross-section shrinkage is too large, outlet tunnel roof will generate cavitation damage, otherwise it is too small, and the discharge capacity of the tunnel will be reduced. In this paper, a reasonable choice of the tunnel outlet size of the transition section were studied through the design of the transition section of the tunnel outlet or Fenhe Reservoir combined with hydraulic structure model test, its outlet section shrinkage rate is bigger than the familiar national tunnels, which result can provide the reference for the same kind of projects.