| Under the background of vigorous development in hydropower industry,the capacity of hydroelectric generating unit grows higher and the structure becomes more complicated,as a consequence,the vibration and stability problem of the hydroelectric generating sets becomes increasingly prominent.In any power machinery,structure vibration is a serious problem,which may cause the fatigue damage of key parts,induce the generation of crack,leading to the damage,bend,crack of structure even causing disastrous safety issue.Therefore,structure vibration is a focus problem in both theory and engineering research for a long time.While,it is more complicated when the hydroelectric generating units are under the condition of hydraulic-electric-mechanical multi-field coupling,except the vibration caused by mechanical factor,the electromagnetic exciting vibration of dynamo and hydraulic exciting vibration of hydro turbine also exist,which will couple and impact each other,the universality and complexity of this phenomenon make it be a scientific and engineering problem waiting to be solved in hydropower industry.The vibration analysis model of hydroelectric generating units' structure is the key point and base for the vibration mechanical study.Traditionally,the dynamics modelling based on numerical analysis uses the simplified and equivalent method,which couldn't describe the true response characteristic of the sets accurately and engineering value is not very high,restricting the key technology study and development of vibration fault diagnosis,structure optimization,structure stress analysis and life calculation etc.So,in this study,the mechanism of hydraulic-electric-mechanical multi-field coupling is taken as the point cut for this vibration research,the fluid-solid coupled vibration characteristics analysis model based on CFD and finite element method(FEM),the magnetic-solid coupled vibration characteristic analysis model based on Two-dimension electromagnetism and Three-dimension structure as well as the transient process flow field simulation model of pumped storage unit are built.By combining theoretic model analysis with actual engineer cases,a deep research on the vibration of the stay vane in hydroelectric generating unit,generator stator stand and the key parts in pump turbine is conducted,analyzing the cause of vibration,study the distribution regularity and the evolution mechanism of flow field and electromagnetic field,besides,the related optimized methods are proposed,which obtains some theoretical achievements and method innovation,these achievements are applied successfully in Jiangxi Hongping Pump Storage Power Station.The achievements and innovation in this study are as follows:(1)The simulation analysis model of double row cascade flow field of hydraulic turbine is built,an orthogonal test taking flow edge thickness,fillet radius,angle of inclination and trailing edge shape as the controlled variables is designed,finding out the flow pattern characteristics and evolution regularity of Karman Vortex Street influenced by vane's shape parameters.Furthermore,the exciting vibration analysis model of stay vane based on CFD and fluid-solid coupled method is worked out,obtaining the vibration responding characteristic,stress distribution of vane and the fatigue life of the stay vane under the perturbation of Karman Vortex Street.On this basis,the intelligent optimization system of hydro turbine's stay vane is put forward innovatively combined neural network and intelligence algorithm,this system uses the shedding frequency,energy loss,the length of the trail and fatigue life as the performance index,which could realize the multi-objective intelligent optimization of the stay vane's shape and it is applied in engineering practice successfully.(2)This study focuses on the abnormal vibration of dynamo stator frame which is a common phenomenon and whose reason is unclear till now,in this study,the failure hydroelectric generating unit in a domestic hydropower station is taken as the object,the weak magnetic-solid coupled vibration characteristic analysis FEM model based on Two-dimension electromagnetism and Three-dimension structure is established,the result shows that simulation test data is highly consistent with hat in the site experimental test.According to this model,the generation mechanism of electromagnetic vibration is analyzed,the impacts on electromagnetic exciting vibration caused by factors such as eccentric rotor & stator,the rotor which is out of round and the rib structure etc.are deeply explored,in addition,the diagnostic results and optimization suggestions are given to this hydroelectric generating unit based on the actual data,that means the simulation result is applied in the engineering project successfully,which has significant value in both theoretical research and engineering in a certain extent.(3)In order to study the flow field evolution mechanism of the pumped storage hydro unit's hydraulic transient process,Jiangxi Hongping Pumped Storage Power Station is taken as the research object,One-dimension simulation based on characteristic method and Three-dimension simulation based on the computational fluid dynamics are considered,then,the simulation model of the pumped storage hydro unit's hydraulic transient process with full flow path and refinement,and the model's effectiveness and accuracy are proved by comparing turbine's and pump's operating condition in simulation with that in site experiment.In addition,this study works out the hydraulic characteristic parameters and fluid field distribution condition of the transient process when the pump is deenergized,elaborates the complicated fluid field's evolution regularity of the transient process,which lays good theoretical foundation for the study on the key equipment's vibration in the future.(4)Aimed at the problem that the hydraulic transient process is not stable when the pump is in outage operating condition,the Three-dimension FEM structure analysis method is adopted,combining the fluid-solid coupling and magnetic-solid coupling theory,the unbalanced magnetic pull and hydrodynamic pressure are loaded in the model,realizing the transient response analysis on pump unit's main shafting and runner of the pump turbine.On this basis,the pump's parameters effects on spindle's vibration characteristic is studied as well as the runner's deformation and stress distribution under different operating condition,which offers scientific instruction for the safe operation of pumped storage hydro set. |
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