三峡工程地下电站前流速流态和泥沙淤积对电站运行的影响分析

Analysis on influence of flow velocity-flow regime and sedimentation on operation of underground hydropower station of Three Gorges Project

依据三峡工程地下电站河工模型试验结果,分析了三峡枢纽运用70年间,地下电站前及引水渠的流速流态和泥沙淤积状况。分析认为,造成地下电站前流态复杂的主要原因是由于与大坝相连的偏岩子山体被部分挖除,使地下电站和右电厂之间形成连通道,从地下电站引水渠和连通道进入地下电站的两股水流在电站前交汇并相互作用的结果,随着枢纽运用年限的增加,坝前泥沙淤积量增大,通过连通道的水流流量逐渐加大,使电站引水渠内水流的回流强度和表面行近流速进一步增强,因而增大发电水头损失。因此,建议在枢纽运用初期,修建连通道隔流堤,使汛期地下电站引水由正向和侧向混合进流变为单一、平顺的正向进流,以减少电站水头损失,提高机组发电效益。

Based on the result model test for the underground hydropower station of Three Gorges Project, the flow velocity, flow regime and sedimentation in front of the station and its diversion canal within an operation period of 70 years are analyzed herein. The analysis shows that the complicated flow regime therein is mainly caused by the confluence and interaction of two flows created by both the diversion canal and the connecting canal between the underground hydropower station and the right bank powerhouse excavated out by cutting of a part of Pianyanzi-mountion adjacent to dam. The head lose of power generation is to be increased due to the increase of the operation years of the project, as the sedimentation in front of the dam is to be increased along with the gradual enlargement of the discharge through the connecting canal, which will lead the intensity of reflow and surface approach velocity to be further enhanced. Therefore, it is suggested to construct a dividing dike for the connecting canal during the early operation period of the project, so as to make the mixed flow composed of normal direction approach flow and lateral approach flow become a single and smooth normal direction flow during flood season, and then to reduce the head lose of the power station and enhance the power generation benefit of the generating units as well.