Research On Vibration Characteristics Of Turbine Head Cover And Correlative Hydropower House

Hydropower house is a complex coupling system composed of water flow,unit and plant structure,the vibration safety problem of which is one of the important research contents of the reliable operation of hydropower stations.In recent years,with the increase of turbine head and capacity,the excitation load on the unit has increased sharply,and the vibration problem of the turbine head cover has become increasingly prominent.With the problem of vibration of the turbine head cover and the dynamic response safety of the plant structure and based on the related principles of dynamics and fatigue analysis,the vibration safety characteristics of turbine head cover is studied by means of prototype observation analysis and numerical simulation,which emphasized on the stress analysis and fatigue analysis of the head cover bolts.And vibration safety of underground powerhouse is studied.Main work and achievements of this paper are as follows:(1)The finite element model of turbine head cover was established,and based on the prototype measured data,the water pressure pulsation load of which under different working conditions was inversed.The vibration of head cover mainly reflected in the vertical direction.Vibration of head cover in various steady,unit startup and shutdown,load-rejection conditions of prototype tests was analyzed and combined with finite element dynamic analysis,water pressure pulsation of turbine head cover was carried out.When the unit is in steady conditions of 100MW～600MW,the water pressure pulsation load of head cover reaches the largest double amplitude value in 100MW condition,which is 19.3m water head and 5.6 times of the unit rated output(600MW).(2)Based on the inversion result of the water pressure pulsation and from the two aspects of stress analysis and fatigue analysis,the safety of the turbine head cover bolts was studied.With the method of numerical dimulation,the influence law of the stress of head cover bolts was studied.Results show that the number and the distribution pattern of the bolts have a significant impact on its stress.The maximum stress reaches 809.9 MPa when the bolts are extremely distributed,far exceeding the yield stress of the material.According to the results of fatigue analysis,fatigue life of bolts decreases sharply under the transient load conditions.When survival rate is 99%,the fatigue life of head cover bolts is 7.494*10~5 in load-rejection condition,which accounts for only 3%～5%of those in various steady conditions.(3)The finite element model of the underground hydropower house structure was established.Based on the prototype test data analysis and numerical simulation,the vibration safety of the plant structure was studied.The first-order mode shape of the plant structure is represented by the vertical vibration of the floor near the suspension hole of the generator layer,and the natural vibration frequency is 20.475 Hz.Through analysis of the vibration source of the plant structure,it shows the volute uneven flow field(41.675Hz)belonging to hydraulic vibration source is more likely to cause resonance,so effective methods should be taken to ensure that the source frequency and the high-order natural frequency of the plant structure are staggered.Finally,the dynamic response under water pressure pulsation load of the plant structure was analyzed through the method of harmonic response and time history analysis.The analysis results show that the vibration of the concrete near volute is the most obvious,which is within the allowable range of the specification.