AN EXPERIMENTAL INVESTIGATION OF FLOW-INDUCED VIBRATION OF A 43-ELEMENT SIMULATION CANDU FUEL BUNDLE UNDER CONFINED AXIAL FLOW

摘要

This paper presents some recent experimental studies of the flow-induced vibration of a 43-element simulation CANDU fuel bundle under confined axial flow of fresh water. The side-to-side lateral acceleration of a fuel rod near the entrance region is measured using MEMS-based accelerometers and analyzed to evaluate bundle vibrations for different volume flow rates. The power spectrum densities (PSDs) of the recorded acceleration data show: (ⅰ) the presence of the shaft synchronous frequencies due to mechanical unbalance, (ⅱ) fundamental and higher orders of acoustic waves associated with a 7-vane pump, and (ⅲ) the presence of dominant frequencies due to flow through the porous fuel bundle structure. The dominating frequencies of the flow-induced vibration vary almost proportionally with the mass flow rates or mean pipe flow velocities, giving a direct indication of the presence of a shedding-like phenomenon. This outcome, regarding occurrence of shedding, indicates that the flow entering the fuel bundle acts more like a cross-flow instead of the traditionally perceived axial flow.