Numerical Investigation of Flow-Induced Vibration and Fretting Wear Potential of Multi-Span U-Tubes with Clearance Supports

Abstract

In this paper, a numerical model is developed to predict the non-linear dynamic response of a steam generator mutli-span U-tubes with Anti-Vibration Bar (AVB) supports and the associated fretting wear due to fluid excitations. Both the crossflow turbulence and fluidelastic instability forces are considered in the model. The finite element method is utilized to model the vibrations and impact dynamics. The tube bundle geometry is similar to the geometry used in CANDU® steam generators. Eight sets of flat bar supports are considered. Moreover, the effect of clearances between the tubes and their supports, and axial offset between the supports are investigated. The results are presented and comparisons are made for the parameters influencing the fretting-wear damage such as contact ratio, impact forces and normal work rate. It is clear that the tubes in loose flat-bar supports have complex dynamics due to the possible combinations of geometry, tube-to-support clearance, offset, and misalignment. However, the results of the numerical simulation along with the developed model provide new insight into the flow-induced vibration mechanism and fretting wear of multi-span U-tubes that can be incorporated in future design guidelines of steam generators and large heat exchangers.