Experimental Study On Flow-induced Vibration Of Heat Transfer Tubes In Steam Generator Of PWR Under Steam-liquid Two-phase Flow Condition

In the Pressurized Water Reactor(PWR),Steam Generator(SG)heat transfer tube is responsible for transferringheat fromthe reactor primary circuit to the secondary loop,and also an important component of the primary circuit pressure boundary,its structural integrity is veryimportant tothe safety of reactor.The heat transfer tube may vibrate under the complex steam-liquid two-phase flow on the secondary side of the steam generator,which is an important influence factor of the heat transfer tube damage.Therefore,whendesigning the reactor steam generator,the nuclear engineering community attach great importance to the heat transfer tube flow-induced vibration study under steam-liquid two-phase flow.Because the actual working condition is very complex,simulating it is very difficult,at present,air is used instead of steam to carry on the experiment,but it is different from the real situation.Therefore,the flow-induced vibration experiment of steam generator heat transfer tube under under steam-liquid two-phase flowis carried out in this paper.Under high temperature and high pressure conditions,the visualization of the experiment is very poor,and the measurement is also very difficult.Therefore,the visualization experiment platform of low temperature and low pressure is established by modeling analysis.The experimental platform uses a single row of non-uniform heat flux electric heating rods to provide a two-phase flow field,during the experiment,the heating power was controlled to simulate different working conditions.The flow pattern of the flow field is observed through the visualization window,and the phenomenon of annular flow at the top of the experimental bench was found——steam-liquid two-phase flow "swept" from the hotside to the cold side.In this paper,the amplitude of the heat transfer tube under different conditions is measured,and the Fast Fourier Transform(FFT)of the measured vibration time-domain is performedto obtain the distribution of excitation energy of the steam-liquid two-phase flow in the frequency domain.In the steam generator tube flow-induced vibration experiment,it is always questionable whether air can be used instead of steam.In this paper,the experimental data under steam-liquid two-phase flow are compared with those under air-water condition for this question.In order to weaken the severity oflateral flowin the elbow region,also to reduce the intensity of flow-induced vibration,the design of the central baffle is proposed,that is,installing a baffle in the middle of the elbow region to obstruct the lateral flow.The effect of the central baffle on weakening the flow-induced vibration was evaluated through experiments by comparing the vibration before and after installing the center baffle.In this paper,the vibration characteristics of the heat transfer tube are obtained,The amplitude of vibration in the elbow area of the heat transfer tube is small,which is in the order of?m,and the vibration is a random vibration with no obvious regularity.In this paper,the amplitude of the heat transfer tubes under the steam-liquid two-phase flow condition is generally larger than that under the air-water condition in the cited literature,which indicates that under the experimental conditions in this paper and the cited literature,the flow-induced vibration experiment under the steam-liquid two-phase flow condition is more conservative.This conclusion provides some reference for the flow-induced vibration experiment of the heat transfer tube under two-phase flow condition.The central baffleweakened the "sweep" flow from the hot side to the cold side,reduced the amplitude of the heat transfer tube,and effectively weakened the flow-induced vibration.