Determination of the elastic-damping characteristics of the vent-relief valve

Valve devices are the main elements determining the reliability of pneumatic and gas systems. One of the main disadvantages of valve devices is their operation in an oscillatory mode, which occurs due to the instability of the system with the valve. To evaluate stability, linearized mathematical models with constant coefficients are used. In this paper, it is shown that for a relief valve maintaining pressure in the tank, the values of these coefficients are not constant and depend on the operating mode of the valve - the height of its lift. For these purposes, a mathematical model in lumped parameters of the "valve - tank" system is developed. The model takes into account that when leaving through the valve shatter, part of the gas follows the poppet. Mathematical modeling shows that such hydrodynamic interaction of the valve shatter and gas flow leads to additional negative components of general damping and elasticity in the equilibrium equation of the poppet, the values of which are proportional to the valve lift. This indicates that the coefficients of the poppet equilibrium equation during valve lift can become negative when the valve moves away from the sealing element, which ensures its instability and operation in an oscillatory mode. The obtained dependencies for the elastic-damping properties of the valve are confirmed experimentally.