Characteristics Of Lead Bismuth Fluid Medium Fluid Solid Coupling

Accelerator driven subcritical system(ADS)is one of the most promising evolution technology.ADS use lead bismuth eutectic alloy(LBE)as a spallation target and coolant.For lead bismuth fluid,Turbulent buffeting to be extremely easy to cause the heat exchanger tube wear or break.According to foreign reports,About 40%nuclear power plants exist tube rupture accident.For the lead bismuth loop,there are not so many countries do experiment on it.But because the denser of lead bismuth fluid is larger,if Fluid solid coupling occurs,it result in heat transfer pipeline breakage,leakage,fluctuation and Seriously affect the safety of the whole loop.So the study and calculation of the lead bismuth fluid solid coupling phenomenon is very necessary for the design of the heat exchanger and the safety of whole reactor.The study of lead bismuth fluid solid coupling characteristics can be divided into three aspects:the vortex shedding,turbulent buffeting,elastic vibration.U sing Sweden TALL lead bismuth loop,and our team independently design natu ral circulation loop as the research object,to calculated and analyzed three kin ds of vibration mode.Vortex shedding:along with the pipeline diameter is larger,the vortex shedding frequency is smaller,it also far from the natural frequency of the pipe,the occurrence probability of flow induced vibration phenomenon is smaller.The probability of damage to the pipeline is smaller.Flow velocity increases,the vortex shedding frequency is larger,the more similar with the natural frequency of the pipe,the probability of occurrence of flow induced vibration phenomenon larger.strouhal ha number increases,the vortex shedding frequency is larger,the more similar with the natural frequency of the pipe,the occurrence probability of flow induced vibration phenomenon is more larger.Turbulent buffeting:When the pipeline structure and lead bismuth flow is ce rtain,the heat exchange tube cross number increases,the greater the buffeting coefficients pipeline,less probability to occur turbulent buffeting phenomenon.Lead bismuth fluid velocity increases,the more prone to turbulent buffeting ph enomenon.With the longitudinal heat tube center distance increases,the buffeti ng coefficients decreased first and then increased,When buffeting coefficients i n the bottom of the curve,the most intense turbulent buffeting phenomenon oc cur.Horizontal heat pipe center distance is greater,the turbulent buffeting phen omenon is not clear.Elastic excitation:When the lead bismuth fluid velocity is close to the critical velocity,elastic vibration phenomenon will occur.Because lead bismuth fluid design maximum velocity is 3m/s,the critical velocity of elastic vibration is far from it,so it does not appear elastic excitation condition.Lead bismuth flow coupling mechanics:when the lead bismuth fluid speed is low,the main reason induced vibration is the vortex shedding phenomenon;when the Reynolds number is larger than 300,the tail appears turbulent vortex vortex,turbulent vibration began to influence the amplitude of the pipeline;when the speed is reached the vortex shedding frequency and the natural frequency of the pipeline is consistent,then resonance,pipeline amplitude reached the maximum,the vortex shedding phenomena influence the amplitude of the pipeline to achieve the maximum.As the speed increases,the vortex shedding phenomenon of pipeline amplitude reduced turbulence buffeting into shadow,the main factors influencing the amplitude of the pipeline.When the flow rate reaches the critical velocity,fluid elastic instability,pipe vibration,amplitude straight up.The research results show that Influence factors on the vortex shedding frequency,the percentage contribution of flow velocity is largest,Value is 40.74%;Second is the impact of Strouhal ha number,account for 26.70%;The third is the pipe diameter,the percentage contribution rate is 10.9%;The interaction of the two factors accounted for the percentage contribution rate of 20.67%,The interaction of the three factors of the percentage of the contribution rate is only0.99%,can be negligible.Because lead bismuth density is almost 10 ten times than water,therefore the vibration energy is higher,the amplitude is larger.Finally,designed a lead bismuth natural circulation loop and described the experimental steps and fluid solid coupling experiment of lead and bismuth.