ESTIMATION OF THE FLUIDELASTIC INSTABILITY BOUNDARY FOR STEAM-GENERATOR TUBES SUBJECTED TO TWO-PHASE FLOWS

摘要

The estimation of tube wear due to vibration-induced tube-support impacting remains an important problem for operating steam generators. For fluidelastic excitation this requires a realistic model for the excitation fluid forces.Recently the authors (Mureithi et al, 2008) have presented detailed force measurements in a rotated triangular tube bundle subjected to air-water two-phase flow. The data provides new potential to designers to estimate expected fluid dynamic loads for two-phase flow conditions. In particular, the data may be used for quantitative estimation of critical velocities for fluidelastic instability - the most important excitation mechanism for steam generator tube bundles.In the work reported here the fluid force field is employed along with the quasi-steady vibration stability model, adapted to two-phase flows, to model the two-phase flow problem and predict the critical instability velocity for a steam-generator U-tube subjected to non-uniform two-phase flow. The implication of the present model, with respect to improved estimation of tube wear is discussed in the paper.