Study On Coupling Vibration Characteristics Of High Hydraulic Head Hydropower House Structure

With the development of China's hydropower industry,the capacity and rated head of hydraulic generator units has gradually increased,and the effects of hydraulic loads,electromagnetic loads and mechanical loads in the hydropower house have correspondingly enhanced.The structural vibration problems have become increasingly prominent.A number of different degrees vibration safety problems occurred in some large scale hydropower stations at home and abroad.Based on the coupling relationship between unit and powerhouse structure,the contribution of different vibration source loads to the vibration of the powerhouse structure,and the influence on structural vibration among muliti units,this paper systematically studies the coupling vibration characteristics of the high hydraulic head hydropower house structure through prototype observation,theoretical derivation and numerical simulation.The main work and achievements are as follows:(1)The coupled vibration analysis model of unit and powerhouse structure was established,and the coupling vibration characteristics of a high hydraulic head hydropower station unit and powerhouse structure were systematically studied.The rationality and accuracy of the coupled vibration analysis model were verified by the comparison of model response and the measured vibration results.Based on the coupling modal analysis and response calculation,the first-order mode shape of the unit and powerhouse structure is represented as the combined horizontal vibration of the generator rotor,the upper frame,the stator frame and the wind tunnel wall;the natural frequency is 8.4Hz.The mutual coupling of the nodes in the unit and the powerhouse structure is significant in the horizontal direction,with the characteristics of layered coupling.Based on the sensitivity analysis of load and structural stiffness,the sensitivity difference of the vertical vibration of the unit shaft structure and the powerhouse structure to the different frequency components in the measured hydraulic load was found;the different effects of bearing stiffness and magnetic pull stiffness on the vibration of unit and powerhouse structure were obtained.(2)Based on the prototype observation and analysis,combined with the information entropy and numerical simulation method,the vibration characteristics of the powerhouse structure of a high hydraulic head hydropower station were further studied.Through the vibration test of the hydropower station structure,the vibration rules of different structure measuring point were analyzed.Based on the information entropy characteristics of long term and low frequency monitoring data,correlation between powerhouse structure and unit was studied.The contribution of different loads to the vibration of the powerhouse structure was quantitatively analyzed;it is found that the hydraulic load plays the most important role in the low load condition with relatively strong structural vibration;the contribution ratio of hydraulic load alone reaches 76.7%.Finally,based on the finite element model,the vibration of powerhouse structure under the hydraulic load in extreme conditions was studied;the distribution rule of vibration intensity of different structures was obtained.(3)Based on the field structural vibration test,theoretical derivation and numerical simulation,the propagation of powerhouse structure vibration among units in hydropower stations was studied systematically.Through the theoretical derivation,the propagation formula of structural vibration among units was established,and the propagation rules of vibration in different directions and different frequencies among multiple units were revealed.The results show that the transmission ratio between adjacent units of lateral-river vibration is about 17% to 25%,which is significantly larger than those of longitude-river vibration and vertical vibration.The propagation ratios of vibration caused by the low frequency tail fluctuation and the rotation of hydraulic generator respectively are basically equal.Finally the finite element model was used for verification.