The Analysis On Pressure Pulsation Characteristics Of Hydro-turbine And Its Causing Vibration Of Power House

With the development of China's hydropower industry,has been built in the planning and construction of a large number of large capacity,high head hydropower station powerhouse structure size increasing,structure stiffness and strength is relatively low,vibration problems have become increasingly prominent,especially with the increase of the unit capacity and the head of the giant hydropower station,the vibration problem is particularly prominent.The exciting force generated by the operation of the unit will affect the whole or partial vibration of the powerhouse structure.In order to adapt to the development direction of hydropower station with higher water head and large capacity,it is valuable and necessary to further study and discuss hydraulic vibration.Hydraulic vibration of hydraulic turbine is one of the main vibration sources of hydropower plant.The amplitude,frequency and phase of pressure fluctuation in the volute are different under different working conditions.It belongs to the unstable fluctuating load,including the complex forms of traveling wave and standing wave.In order to study the distribution of pressure pulsation in the volute and the tail pipe and the sensitivity of the method to the vibration of the plant,the most unfavorable condition is determined.The pressure pulsation method is described in accordance with the traveling wave and the standing wave.The amplitude and phase distribution characteristics of the pressure pulsation in different forms are studied,and the load is applied reasonably.The action mechanism and the vibration response rule of the pressure pulsation excitation source are defined,and the vibration calculation results of the plant structure are finally obtained.The main research work is as follows:(1)Based on the ANSYS software,the model of the actual hydropower plant unit section is established.According to the traveling wave form load and the standing wave form load,the pressure pulsation mode in the volute is simplified.The input of the load amplitude and phase is realized by the surf154 element,and the effect of the pressure pulsation at different frequencies is calculated by the harmonic response analysis and the transient dynamic analysis.Based on the vibration response,the amplitude and phase distribution of concrete enveloped by spiral case are obtained.The low frequency range machine pier,the wind shield and the vertical column traveling wave scheme are the most unfavorable,the floor layout scheme is the most unfavorable,the high frequency traveling wave or the standing wave scheme is the most unfavorable load scheme.(2)According to the distribution of pressure pulsating vortex bands that may occur under the working condition of the draft tube,the pressure pulsation load in the draft tube is simulated according to the load and the uniform load of the traveling wave.Different types of pulsating pressure loads are applied to the straight cone section,the curved elbow section and the diffusion section,and the vibration response results of the hydropower plant structure under the action of different frequency and different pressure pulsation schemes are obtained by the harmonic response analysis.The difference between the displacement and stress of the traveling wave scheme and the uniform distribution scheme is compared.It is suggested that the uniform load form with the same amplitude and the same phase should be used as the most unfavorable solution.(3)In the powerhouse model of hydropower station,the pressure fluctuating load scheme of uniform flow,traveling wave and standing wave is applied to the whole flow passage of hydraulic turbine.The displacement and stress responses of typical locations of factory buildings under different plans are calculated by harmonic response analysis,and the results are compared.It is found that under the times of rotating frequency of the runner blades,the uniform distribution scheme is the most unfavorable for the pier,the wind cover and the hydraulic turbine column.The most disadvantageous scheme is the traveling wave and the standing wave scheme of the generator floor slab,and the most disadvantageous scheme is the selection of the electric sandwich floor and the vertical column.