SELF-EXCITED VIBRATION OF A CONTROL VALVE DUE TO FLUID–STRUCTURE INTERACTION

Abstract

In this paper, the mechanism causing self-excited vibration of a piping system is determined using a dynamic model which couples the hydraulics of a piping system with the structural motion of an air-operated, plug-type automatic control valve. In the dynamic model developed, the structural system consists of a valve spring–mass system, while the fluid system consists of a pump, upstream piping, control valve and downstream piping. The coupling between the structural and the fluid systems at the control valve is obtained by making the fluid flow coefficient at the control valve to be a function of valve plug displacement, and by making the valve plug displacement to be a function of fluid pressure and velocity. The dynamic model presented in this paper, for the first time, considers compressibility of the fluid in both the upstream and downstream piping. The dynamic model presented was benchmarked against in situ measurements. The data used for the benchmarking are provided in the paper. A review of the numerical results obtained indicates that the self-excited vibration occurs due to the coincidence of water hammer, acoustic feedback in the downstream piping, high acoustic resistance at the control valve, and negative hydraulic stiffness at the control valve.