Study On Two Key Problems Of Large-scale Two-way Passage Pumping Station

Our country has a vast territory and there is a time and space imbalance of the rainfall in most areas.In order to solve the problem of drought(or lack of water)irrigation and self-diversion,flood water drainage and self-drainage,a large number of large-scale bidirectional flow path pump stations for irrigation and drainage combined have been built along the Yangtze River and Taihu Basin.Bidirectional flow path pump stations for irrigation and drainage combined is characterized by its outstanding features of diversity and comprehensive,It is could lifting,irrigation and self-diversion and many other functions.However,in engineering practice,most bidirectional flow path pump stations only use their functions of lifting and pumping,and the self-diversion functions have not yet been effectively utilized.In order to give full play to the benefits of irrigation and drainage combined bidirectional flow path pump stations in our country of self-diversion comprehensive,it is necessary to carry out research on many key technical issues which restrict the use of self-diversion functions of pump stations.This paper combines the large-scale irrigation and drainage combined bidirectional flow path pump station—JianBi pump station.We take the method of numerical simulation and experimental to research of the overcurrent characteristics of bidirectional flow path in self-diversion conditions,feasibility of self-diversion applications for pump stations and entire hub and the pumping unit startup transition process and other issues,The main contents of the study are as follows:1.Research on bidirectional flow path overcurrent characteristics with different gate opening under self-diversion conditions.For the inlet and outlet flow channels,forward and reverse flows are taken in 25 gate opening combinations respectively,a total of 75 kinds of gate opening combinations are calculated,the over-current characteristics of two-way flow passages with different gate opening combinations under different over-current modes were obtained.2.Under the same overcurrent condition,the optimal gate control scheme is studied.Assuming a specific condition,such as a specific flow demand at a certain water level,The flow characteristics of the two-way flow channel are analyzed to find out all the combinations of gate opening degrees that meet the conditions.Comparing and analyzing the flow patterns inside the flow passage,comprehensively consider the impact and determine the best gate control solution.Through analysis,it can be concluded that,when a specific flow is required at a certain water level,the inlet side gate is fully opened and control the outlet side gate opening is the optimal gate control scheme for the forward and reverse flow of the inlet and outlet channels.At this point,the flow pattern inside the flow channel is the best.3.Research on flow characteristics and safety of pumps under the condition of self-diversion.The axial force acting on the rotor of the pump unit and the torque around the shaft were analyzed when the pump unit was stopped and the two-way flow path flowed under the check water level.Through the study,it can be seen that under the condition of self-diversion,the force of the water on the rotor and the torque around the shaft are all small enough,it can not to make the pump unit generate impulse or lift.4.Research on the turbulent characteristics,erosion and riverbank safety of the channel(discharge)at the pump station under self-diversion conditions.Research on self-diversion overflow of pump station hub,research the distribution of flow velocity of the river channel(discharge)under different flow patterns and different flow rates and verify whether the maximum flow rate meets the condition of not flushing the river.5.Starting transition process of bidirectional flow path pump station research.Calculate when time change the variation of flow,efficiency,lift and other parameters and internal flow state of the flow channel during start-up of the bidirectional flow path pump station.Through the study,it is found that when the water level difference between the upstream and downstream sides of the two-way flow channel is large,during the opening and closing process of the gate,there will be a backflow on the outlet side of the outlet flow channel.The reverse flow increases first with the increase of time,then decreases until it reaches zero,and then finally flows out positively.The point where the reverse flow is the largest occurs at the relative opening of the gate of 0.35,and the reverse flow is zero at the gate.The relative opening is 0.65,which is independent of the opening and closing speed of the gate.