Abstract: Poppet valves are basic components of many manufacturing operations and industrial processes. The valve plug will withstand unbalanced pressure during the switching process due to the complex fluid-structure interaction (FSI) in the local flow condition, especially with the occurrence of cavitation, which results in a convoluted generation and propagation of mechanical and fluid-dynamic vibrations. In the present work, computational fluid dynamics (CFD) approaches are proposed to model the flow-driven movement of the disc, in consideration of the valve stem rigidity, for a cryogenic poppet valve with liquid nitrogen as the working fluid. Cavitation effects are included in the CFD simulations. The relationship between the displacement of the disc and the resistance of the stem is obtained in advance using the finite element method (FEM), and implemented in CFD calculations based on the user-defined functions (UDFs). The disc vibration is realized using the dynamic mesh technology according to the resultant flow field force and resistance of the stem determined in the UDF. The vibration characteristics of the valve disc, including velocity and vibration frequency, are presented. The temporal evolutions of cavitation behavior due to the vibration are also captured. Comparisons of results between cavitation and non-cavitation conditions are made, and spectral analysis of the transient pressure fluctuations reveals that the presence of cavitation induces transient unbalanced loads on the valve disc and generates instantaneous tremendous pressure fluctuations in the flow field. Various pressure differences between the inlet and outlet as well as valve openings are modeled to probe the influences of FSI on valve disc vibration mechanisms. The consequent analysis gives deeper insights and improves understanding of the mechanism of the complicated interaction between the cavitating flow and the vibration of the valve disc.

Key words: Poppet valve; Computational fluid dynamics (CFD); Cavitation; Flow-induced Vibration; Fluid-structure interaction (FSI)

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