Abstract: The dynamic coupling effect of medium pressure pulsation and valve plate opening in vacuum systems seriously threatens the vacuum sealing integrity of the system, exacerbates the uneven stress distribution and deformation of the valve body, and thereby affects the instability load of the valve body. Therefore, the critical load of dynamic instability of the newly made three eccentric vacuum butterfly valve body is analyzed under the action of fluid medium. Based on the ANSYS Workbench platform, a three-dimensional parametric model is established to perform bidirectional fluid structure coupling (FSI) calculations between the unsteady flow of vacuum/low-pressure fluid medium (150℃ water vapor, Knudsen number 0.003-0.1, slip flow zone) and the valve body structure. In the fluid domain, the k-ω SST turbulence model is used to accurately simulate complex flow characteristics and calculate the distribution of fluid forces. In the structural domain, geometric nonlinear buckling analysis is performed based on the arc length method to accurately capture the instability behavior of the valve body under fluid forces, draw displacement load curves, and determine the critical load of instability under the dynamic coupling of medium pressure pulsation and valve plate opening. The results show that, under the dynamic coupling condition of 300 Hz medium pressure pulsation and valve plate 90° opening, the critical load for dynamic instability of the valve body is the worst, only 3×10³ Pa, and the risk of instability is the highest, which can easily lead to seal failure and vacuum degree damage.

Key words: vacuum sealing, triple eccentric vacuum butterfly valve, maximum unstable load, k-ω SST turbulence model, arc-length method