Research on stability and control strategies for a spring-loaded valve with bypass outlet

Abstract

The stability and control strategies of a spring-loaded valve with bypass outlet have been studied by combining numerical and theoretical analysis. First, a nonlinear dynamical model and a CFD model of a spring-loaded valve with bypass outlet are developed. The theoretical analysis requires parameters such as discharge coefficients and fluid forces obtained from CFD simulations. The equivalent area of the fluid forces and discharge coefficients are similar at different pressure differences, leading to a reduced-order formulation that serves the theoretical analysis of nonlinear dynamics. Second, the valve disc oscillates at small constant flow rates by nonlinear dynamical analysis. The oscillation frequency is a superposition of the Helmholtz cavity and the mass spring system, which increases as the valve disc impacts the seat or the upper limiter. More importantly, there is a frequency lock-in phenomenon at small fluctuating flow rates, which vanishes at large flow rates. The oscillations are not symmetric during the opening and closing processes, and the oscillations are more severe during the opening processes. Finally, the bypass outlet has a great effect on the stability of valve disc, which can appropriately kill the nonlinear component in the dynamic equation. A reasonable bypass sleeve design can reduce the unstable flow range and oscillation amplitude. This paper provides a reference for the design of spring-loaded valves.