Study on Fundamental Mechanical Problems in Fluidelastic Instability of Steam Generator Heat Transfer Tube Bundles

In order to explore the mechanism of the fluidelastic instability of the tube bundle and the influence mechanism of the support mode and the internal flow load on the fluidelastic instability of the tube bundle, a theoretical model of the flow induced vibration of the heat transfer tube under complex fluid excitation is established by comprehensively considering the effects of the steady flow elasticity, internal flow excitation and unsteady flow force on the flow induced vibration of the heat transfer tube. Based on the eigenvalue stability theory, the fluidelastic instability mechanism of heat transfer tube under the action of two-phase cross-flow is obtained, and the effects of internal flow excitation and unsteady flow force on the fluidelastic instability mechanism of heat transfer tube are analyzed systematically. The research shows that the support mode will affect the critical velocity of instability, but will not affect the fluidelastic instability mechanism; the internal flow in the tube will couple the modes of the tube bundle, and the high-speed internal flow will change the instability mechanism of the tube bundle; As a kind of forced force, the unsteady flow force may cause the "beating vibration" of the tube bundle before the fluidelastic instability, which shall be avoided in the engineering design.