Mechanism of self-excited vibration and dynamic stability for pneumatic valves

Based on the disturbance response characteristics of spring oscillator, the mechanism of pneumatic valves' self-excited vibration due to fluid-structure interaction was developed. Moreover, adopted small signal stability analysis theory, the dynamic mathematics model and stability analysis model for a check valve were constructed, and the critical stable curve and the parameter impact rule of the check valve were obtained by solving the characteristics root of the linear equations. The validation of stability analysis model was preformed by the pneumatic experiment of a check valve. The results indicate that there is a critical stability curve of pressure and mass flow, and the critical mass flow is one-to-one corresponding to the working pressure. If the mass flow is less than the critical mass flow at a constant working pressure, the check valve become unstable which causes the cyclical motion of the spool excited by a very small distribution; otherwise, the check valve is stable and keeping a fixed opening. Moreover, increasing the damp coefficient and the inlet diameter or decreasing the spring stiffness partly enlarge the stable region, which can be used for the optimum design of check valve.