Study on Vibration Response Mechanism of Tube Bundle for Helical Coil Steam Generator

The helical tube bundle vibrates under the action of fluid impact. If this phenomenon occurs for a long time, the helical tube will gradually fail due to fretting wear, while excessive vibration in a short time will cause damage. Therefore, it is important to reveal the vibration response mechanism of helical tube bundles. In this paper, a flow excitation model with regard to the tube bundle was established, and the robustness of the numerical method was verified by comparing the experimental results with the simulation results. The core component of the shock vibration test system is a simplified three-layer helical tube bundle. The inlet is located below the shell and in the middle of the two supporting parts, that is, the middle and lower part of the span. The outlet is located at the top, opposite the entrance. The winding direction of the tube changes alternately, from inside to outside are left, right and left. The structural parameters of the pitch diameter ratio between adjacent tube layer (a=1.5), the pitch diameter ratio in the same layer (b=2.6) and the helix angle (α=15°) are used for the experimental bundle. The helical tube is stuck in the groove of the support, and then a support is constrained in the outer layer of the helical tube, and the two supports are matched with each other to fix the winding tube. The sensor is attached to the middle position of the test tube to monitor the vibration response of the helical tube in the in-plane and out-of-plane directions respectively. The wire of the sensor is fixed along the wall of the tube and extended to the supporting positions at both ends respectively. The wire is led out of the inside of the housing by using preset perforated bolts. Based on the time-domain data of the helical tube vibration, the influence of the relative position of the tube and the structural parameters of the tube bundle on the tube vibration response was studied by wavelet analysis method. The results show that along the fluid flow direction, the more backward the helical tube is, the more intense the vibration response in the out-of-plane direction is. The smaller the pitch diameter ratio between adjacent tube layers, the larger the amplitude and the more violent the fluctuation. The effects of pitch diameter ratio in the same layer and helix angle on the amplitude in both directions are not obvious. The research results provide a theoretical basis for the analysis of turbulent buffeting and fluid elastic instability for the helical tube bundles.