Study On Flow Pattern And Vibration Characteristics Of Penstock In Forebay Of Pumping Station Based On Numerical Simulation

Large scale pumping station plays a very important role in water conservancy and transmission in China.The Yanhuanding Yellow River Project(later called "Yanhuanding project")in Ningxia is a livelihood project built to solve the problem of drinking water for local people and animals,develop irrigation agriculture and improve the ecological environment.However,limited by the early technical means and construction funds,and most of the pumping stations were built in the last century,the long-term operation makes the salt environmental engineering unable to reach the designed water supply capacity,and the project benefits cannot be brought into full play.In view of this,this paper focuses on three problems: the disorder of the flow pattern in the forebay of the pump station,the deviation of the pump from the high efficiency area caused by frequency converter and the flow induced vibration of the pressure pipeline of the pump station.In view of the disorder of the flow pattern in the forebay of the pump station,this paper based on the realizable K-? turbulence model is used to calculate the flow pattern of the water inlet pool of the pump station,and it is compared with the prototype monitoring results of hxh03-1s ultrasonic Doppler velocity and direction meter in the water inlet pool of the pump station,to verify the accuracy of the numerical simulation results and to put forward the efficient optimization scheme of different startup combinations.In view of the problem that the pump deviates from the efficient operation area,this paper obtains the results under different rotational speeds through experimental research According to the corresponding flow rate and device efficiency,the empirical formula for sfwp80-800 water pump is fitted based on the least square method.Aiming at the problem of flow induced vibration of pressure pipeline in pump station,the fluid structure coupling finite element numerical model based on algor software is established,and the hydrodynamic response of pipeline vibration is analyzed by pipeline flow state analysis and modal identification The influence of water flow on the vibration mode of penstock is verified by the vibration signal obtained by DASP vibration test system.The conclusion is as follows:(1)According to the simulation results of a typical pump station's forward inlet forebay,the opposite direction eddy current appears on both sides of the suction bell mouth and the flow of the suction bell mouth forms a new vortex belt,which causes a secondary impact on the side wall of the forebay without the inlet pipe,forms a new irregular eddy current at the bottom of the water intake,and then affects the internal flow pattern of the bell mouth pipe.Most of the previous studies This study shows that when the size of intake structure is not designed properly,the damage of vortex caused by side wall impact can not be ignored;(2)According to the simulation results of the lateral forebay of a typical pump station,the flow direction of the lateral forebay is at a certain angle with the center line of the suction pipe.The main flow deviates seriously to one side of the suction pipe,and a strip-shaped return area is formed at the right side wall of the forebay,and the flow pattern is greatly affected by the unit startup combination.A large range of static water area is formed at the end of the forebay where the unit is not started,and most of the sediment is along the right side The side wall is distributed or deposited at the end of the forebay,which greatly reduces the operation efficiency of the pump station.(3)Through the numerical simulation of the flow pattern of the forebay under 10 different startup combination schemes,it can be seen that the unit at the end of the forebay can be opened as much as possible to improve the flow pattern of the forebay effectively,reduce the static water area in the forebay,increase the flow velocity in the forebay and reduce the sediment deposition;(4)Through the experimental study,the corresponding flow and comprehensive efficiency under different rotating speeds are obtained,and the data obtained are fitted and analyzed based on the least square method.The relationship between the flow ratio,efficiency ratio and frequency ratio applicable to the sfwp80-800 water pump is derived,and the optimal frequency modulation range of efficiency is proposed to be 46 hz ~ 50 Hz,which can provide useful information for the calculation of the frequency modulation range of the frequency control water pump in the actual project Draw lessons from;(5)The fluid structure coupling finite element model of pressure pipeline based on algor is established to simulate the flow excited vibration characteristics of pressure pipeline of pump station.The numerical simulation results are consistent with the measured conditions,which shows that the numerical model is reasonable and reliable;(6)Through the analysis of the hydrodynamic characteristics and vibration modes under different working conditions,it is found that the vibration of the water inlet pipe,the joint of the main pipe and the branch pipe and the main water outlet pipe is even and strong,and the vibration of the water inlet pipe is stronger than that of the water outlet pipe,which needs to be paid attention to.