Dynamic Analysis And Identification Of Powerhouse Structure Of Two-row Placed Units

The capacity and size of modern hydrogenerator units become larger with the rapid development of the hydroelectric enterprise. The vibration of powerhouse structure has increasingly become a major problem. At present, the study on dynamic characteristic of the powerhouse structure, vibration-source identification and vibration response prediction in the problem is still inadequate. Especially, because of the complexity and particularity of load and structure, the dynamic research on the powerhouse of two-row placed units is more insufficient and the study on characteristics of unit joint operation is close to zero. Therefore, it is significant to discuss these problems further. Based on prototype observation data of a series of large hydropower stations such as Lijiaxia Hydropower Station, the vibration problem is studied in this dissertation according to the theoretical analysis and the test analysis. The principal contents and achievement of this dissertation are as follows:(1) The characteristics of mechanical, electromagnetic and hydraulic loads are analyzed and their reasonable acting modes are discussed. Especially, the distribution rule of trailing vortex is mainly studied. According to the test results of point pressure fluctuation of tail pipe, pressure fluctuation distribution of the whole conical tube surface is gained and reasonable simulation method of vortex acting is put forward.(2) According to field test of powerhouse of two-row placed units, the vibration sources are identified. The most main dynamic loads that induce vibration of powerhouse structure are found out. The acting effects of various dynamic loads are evaluated from magnitude.(3) Based on principle of dynamics, the structural vibration and the variability of loads during machine halting process are analyzed by combining the units test results with structural test results. Furthermore, a new method to identify dynamic characteristics of powerhouse supporting structure using halting process is put forward. The method makes full use of the advantage of wavelet analysis.(4) Stability rule and powerhouse structure vibration of upstream and downstream units are analyzed and differences between upstream and downstream units are gained while units are operating by themselves. Further, characteristics and vibration response of powerhouse structure are studied during combined operation of two-row placed units under various loading conditions. Some conclusions favorable to guide the operation of the relevant project are drawn.(5) A thorough analysis of relations between a series of fluctuation and vibration during normal operation of hydropower station is provided, including pressure fluctuation, verticalvibration of unit and vertical vibration of powerhouse. From relations between displacement and frequency of vibration, source of vertical vibration is found out. Based on the observed data, feedback analysis of 3-D FEM is used to analyze powerhouse structure and a new method of calculating vertical dynamic displacement is advanced. The study on vibration response of several large power stations shows that the calculating results of new method are more close to test values than standard method.(6) The alterations of major forces such as axial force, torque and unbalanced force are thoroughly analyzed and a new method to calculate dynamic response of plant structure in starting up process is put forward.