平面转弯有压输水隧洞对进/出水口水力特性影响研究

Study on Influence of Planar Turning Pressurized Water Tunnel on Hydraulic Characteristics of Inlet/Outlet Water

受地形、地质等条件的限制,与抽水蓄能电站侧式进/出水口衔接的输水隧洞会存在平面转弯段.当输水隧洞的平面转弯段距进/出水口较近时,转弯角度、转弯半径R以及转弯后直隧洞长度L等参数对出流工况下进/出水口水力特性有着重要影响.平面转弯输水隧洞转弯段若布置不当,出流工况水流进入进/出水口时可能会出现偏流现象,直接影响进/出水口流量分配,然而目前缺乏平面转弯输水隧洞各参数的设计建议值.以抚宁抽水蓄能电站侧式进/出水口为研究对象,通过数值模拟的方法研究了平面转弯有压输水隧洞对进/出水口出流水力特性的影响并进行了偏流成因分析.结果表明:对于设计合理的进/出水口体型,平面转弯有压输水隧洞转弯段若布置不当,水流在进入转弯段后会形成二次流,导致转弯段后隧洞横断面流速分布不均匀,转弯段外侧流速大于内侧,进/出水口会产生偏流现象,直接影响各孔口流量分配;转弯角度的增加会使各孔口流量分配越不均匀;R和L的增加能有效改善进入进/出水口时的水流条件;当R≥30.0D(D为输水隧洞洞径)同时保证L≥10D时,或L≥40D时,水流进入进/出水口时的偏流现象可以得到有效改善.研究成果可为抽水蓄能电站侧式进/出水口连接隧洞的平面转弯布置提供设计依据.

Due to the constraints of topographical and geological conditions,there is a planar turning section in the water tunnel which is connected to the side inlet/outlet of a pumped storage power plant.When the planar turning sec-tion is close to the inlet/outlet,the parameters such as the turning angle,turning radius(R)and the straight tunnel length after turning(L)will obviously affect the hydraulic characteristics of the inlet/outlet water under outflow con-ditions.If the turning section of the planar turning water tunnel is not properly arranged,then a bias flow phenomenon may occur when water flows into the inlet/outlet under outflow conditions,directly affecting the inlet/outlet flow dis-tribution.However,there is a lack of design recommendations for each parameter of the planar turning water tunnel at present.In this paper,the side inlet/outlet of Funing Pumped Storage Power Plant is as the research object,the influ-ence of the planar turning pressurized water tunnel on the hydraulic characteristics of inlet/outlet water is studied through numerical simulations,and the causes of bias flow are also analyzed.Results show that for a reasonably de-signed inlet/outlet body,if the turning section of the planar turing pressurized water tunnel is not properly arranged,then water will form a secondary flow after entering the turning section,resulting in an uneven distribution of flow velocity in the cross-section of the tunnel after the turning section.In addition,the flow velocity on the outside of the turning section is higher than that on the inside,resulting in the bias flow phenomenon at the inlet/outlet,which directly affects the flow distribution at each orifice.The increase in turning angle will make the flow distribution at each orifice more uneven,while the increases in R and L can effectively improve the flow conditions when water enters the inlet/outlet.When R is more than or equal to 30.0D(where D is the diameter of water tunnel)and L is more than or equal to 10D,or L is more than or equal to 40D,the bias flow phenomenon when water enters the inlet/outlet can be effectively improved.The research results can provide a design basis for the planar turning arrangement of a water tunnel connected to the side inlet/outlet of a pumped storage power plant.