Hydraulic Transients Research Of Diversion System In Cascade Hydropower Stations Connected By Open Channel

The cascade hydropower stations connected by open channel are one new method of river basins development. The open channel that connects two hydropower stations is very important to maintain the operation stability of units in cascade hydropower stations. The hydraulic transients research of the diversion and power system will not only supply the scientific basis for the design of cascade hydropower stations, but also be very important to ensure the safety and stability of units operation in cascade hydropower stations.Based on open-channel flow transients, pressure flow transients and other basis theory of hydraulic transients, this paper adopts the research methods that combine numerical calculation with physical model test to analyze hydraulic transients in the diversion and power system of cascade hydropower stations connected by open channel, which is combined with the actual project of Tianlonghu-Jinlongtan cascade hydropower stations.Firstly, the numerical calculation of hydraulic transients is made. The multiple time increment method that is applied to deal with the conjunction boundary of open-channel flow and pressure flow is given. The mathematical model of the whole diversion and power system is made to analyze the variation process of the open-channel flow depth, the surge chamber oscillation and the units' operation parameter in all control working conditions. The minor oscillation stability of cascade hydropower stations is studied. The numerical calculation results verify preliminarily the feasibility of such design, at the same time show that it is aneffective measure to set up overflow section in the open channel in order to ensure the stability operation of units and it is necessary to monitor the open-channel flow depth in order to ensure the diversion discharge of the lower station is less than the outflow discharge of the upper station.Lastly, hydraulic model test of diversion system is carried out. The model scale selection of hydraulic model which includes open channel, long diversion tunnel and surge chamber is discussed. The model test results of the open-channel flow depth and the surge chamber oscillation verify the numerical calculation is correct. Some useful suggestion is given to optimize the connection form of open channel and diversion tunnel.