Vibration evaluation of water guide bearing of bulb tubular unit
[Objective]For the water guide bearing with fan-shaped support structure,the horizontal structural stiffness is insuffi-cient,resulting in a large vibration value.It is necessary to evaluate the vibration of the water guide bearing and determine a rea-sonable vibration limit to ensure the safety and stability of the unit.[Methods]The vibration of the water guide bearing of the same type of bulb tubular unit is statistically analyzed.The finite element calculation of the water guide bearing is carried out.The field test of vibration and dynamic stress is carried out.The correlation between dynamic stress and vibration is analyzed.The fatigue characteristics of the water guide bearing structure are evaluated to determine the reasonable vibration limit.[Results]The result show that the median of the horizontal vibration statistical sample of the water guide bearing is 131.6 μm,according to the standard requirements,1.6 times the median value of 200.0 µm is taken as the reference value of the vibration limit.Based on the finite element analysis and actual measurement of the water guide bearing in Lingjintan Power Plant,the max-imum static stress of the water guide bearing is 33.8 MPa,which is far less than the allowable stress requirement,the maximum horizontal vibration peak value of the water guide bearing under test conditions is 91.0 µm,and the maximum dynamic stress peak value of the sector plate is 1.4 MPa.[Conclusion]The result show that:The horizontal vibration of water guide bearing of bulb tubular units increases with the increase of the active power of the unit,the main frequencies of vibration and dynamic stress are the rotation frequency of the unit and the frequency doubling of blade blades,the vibration amplitude has a good linear rela-tionship with the dynamic stress amplitude,and the dynamic stress at a vibration amplitude of 200.0 µm can be predicted by lin-ear fitting.According to the ultimate dynamic stress and static stress obtained by finite element analysis,the fatigue life and damage coefficient of water guide bearing support structure can be obtained by S-N curve,and the result show that it can meet the requirements of service life cycle.
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