| The combination of water and shipping in the Nansi Lake-Dongping Lake section of the first phase of the South-North Water Transfer Project is a typical river-lake-pump station complex system in the East Route of the South-to-North Water Transfer Project.Through the practice of water diversion from the two lake sections from 2013 to 2017,it is found that there are many hydraulic problems affecting safe operation in the dispatching operation.Aiming at this kind of problem,this paper takes the two-lake section of the South-North Water Transfer Project(Nansihu to Dongping Lake)as the research object,and establishes a scheduling simulation model of the one-dimensional hydraulic model coupled with the pumping station node,and its water-transport hydraulic characteristics and cascades.The operating efficiency of the pumping station's water delivery system was analyzed.The obtained research results can provide reference for the project operation of the two lakes section of the East Route of South-to-North Water Transfer Project,which has theoretical and practical significance.The results achieved include the following:(1)Taking the water conveyance system of the cascade pumping station in the two lakes of the East Route of the South-to-North Water Transfer Project as the research object,based on the St.Venan equations,the discrete method is determined,and the scheduling simulation model of the one-dimensional hydraulic model coupled with the pumping station node is established.The measured data of many years have been determined for the normal water delivery conditions and the roughness of the water and grass blocking conditions.The rationality and reliability of the model have been verified by the measured data,which provides a model basis for the hydraulic characteristics analysis.Under the normal water delivery conditions,the simulated water level of the pumping station node is not much different from the measured water level.The overall error is within 0.05 m.The difference between the simulated water level and the measured value is within 0.1m,and the Denglou pumping station under the condition of water and grass blockage The overall error between the simulated and measured values of the water level change at the station and the station is within 0.2,and the model reliability is high.(2)Based on the simulation model of water delivery scheduling of cascade pumping stations in the two lakes,different water delivery conditions and emergency conditions were simulated.The parameters such as water level and flow rate under different operating conditions were calculated,and different water conveyers were studied.The main conclusions are as follows:(1)The greater the flow between channels,the greater the hydraulic loss.Take the Changgou-Donglou section as an example,under three different flow conditions,that is,under increasing flow conditions,the hydraulic losses are 0.21 m and 0.69 m,respectively.1.11m;hydraulic loss is positively correlated with mileage;The hydraulic loss is positively correlated with the mileage;when the water flow between the channels is the same,the hydraulic loss between the channels decreases with the increase of the upstream water level;(2)In view of the blocked conditions of water and grass,taking the Changgou-Donglou section as an example,the hydraulic loss and local hydraulic loss along the course caused by the different coverage of the water grass were simulated.It can be seen from the results that under the condition of water grass clogging,the hydraulic loss is positively correlated with the degree of flooding.Combined with the conclusions obtained under normal water delivery conditions and the growth characteristics of aquatic plants,it is suggested that during the flooding period,the Hukou to Denglou sections should maintain high water level operation to inhibit the growth of aquatic plants and reduce their impact on water transport in the channels.(3)According to the water loss in the two lakes,the inter-stage storage under different water level and flow conditions is calculated.Based on this,the concept and calculation formula of water loss based on total balance are proposed.Comparing with the results obtained from the statistical data and the empirical formula method,it is found that the results obtained are not much different from the 2016 water loss results calculated by the measured data.The difference between the results of the empirical formula method and the empirical formula method is within 2%.feasible.(4)Aiming at the fault conditions of a certain pumping station in the water conveyance system of the two lakes,the accident conditions of the single-stage pumping station were simulated.When the single-stage pumping station is shut down,the system will be threatened to operate safely within a certain period of time.Due to the wide water surface between the two lake sections,the water level changes slowly,and the reaction time of the system control is about 2 hours for the single-stage pumping station to stop.Based on the accident conditions,the control measures for the accident conditions were put forward.After the accident,the lower and lower pumping stations took measures to gradually shut down,so that the water level of the inlet pool and the water level of the outlet pool were smaller in the later stage.Stabilization was achieved after about 2 hours,and the inlet and outlet of the pumping station did not exceed their restricted water level.(5)The water pumping system is divided into two systems: pumping station and water delivery.Based on this,the efficiency of the pumping station at each level of the two lakes,the efficiency of the water delivery system and the operating efficiency of the water pumping system of the cascade pumping station are calculated and analyzed.The operating efficiency of the two-stage pumping station operating conditions in the water pumping system of the cascade pumping station lays the foundation for the optimal operation of the cascade pumping station.Through the comparison between the operating efficiency of the three-stage pumping station water delivery system and the operating efficiency of the two-stage pumping station water delivery system,it is found that the efficiency of the water delivery system,the efficiency of the pumping station system and the total system efficiency under the operating conditions of the two-stage pumping station are higher than the third-level.The total efficiency can be increased by 4% to 9% on average. |
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