| Tubes are constantly scoured by transverse flow in tubular heat exchangers，which makes them easily destroyed by flow induced vibration. Fluid-elastic instabilityis the most important excitation mechanism among all. Research on this mechanism issignificant for both rational design and safety operation of heat exchangers.Vibration responses of a tube array with S/d=1.28at different flow velocities aretested in this paper. Change patterns of tube array with velocity are obtained.Fluid-structure coupling model of tube array is established using CFD. Influenceof turbulence model and axial size is considered in research and proper numericalmodel is established afterwards. Results show that a computation model with an axialsize of d and LES is applicable for the research of fluid-elastic instability. Resultsagree well with experiment in general trends of amplitude and frequency responses oftubes, but large errors exist in prediction of RMS amplitudes.Researches on the tubes’ vibration performance of fluid-elastic have been doneaccording to the computation and experiment results. Results indicate that thedominant vibration direction is varied according to flow velocity and tube position.Adjacent tubes have a phase lag of180°after critical velocity. Methods for criticalvelocity prediction are also discussed. According the analyses, the onset offluid-elastic can be estimated by sensor observation, but this lacks accuracy and needsa fair amount of engineer experience. Amplitude-velocity diagram method is intuitiveand easy to get the critical velocity, but it is not very accurate and a prejudging ofdominant vibration is needed for a better prediction. Spectrum data analysis methodcan precisely predict critical velocity in heavy fluid, but it isn’t acceptable in lightfluid cases.Cases for square and rotated square array with S/d=1.28and1.5are simulated inthis paper. Results indicate that square array have a higher critical velocity, and alarger S/d means a higher critical velocity in square cases. |
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