Control of opening duration in a pneumatically operated valve with two-fluid combination and quadratic damping

Abstract

In this paper, opening characteristics of a pneumatically operated valve and methodology for controlling the valve opening duration have been investigated through numerical simulation. The valve has a poppet mounted with spring which is actuated by a pneumatic command pressure to provide a displacement of 30 mm in fully open condition. The spring housing comprises of columns of two fluids, namely air and oil, and an orifice which communicates with an adjacent auxiliary chamber. As the poppet is actuated, air initially passes through the orifice leading to a fast opening of the valve. Subsequently, opening rate of the valve is reduced as oil column encounters the orifice. The governing differential equations of motion for the valve poppet were solved using a fourth-order Runge–Kutta method, and the resistance offered by the orifice to oil flow was considered using a quadratic damping model. Simulations were carried out for two different orifice sizes, and results were validated with experiments. It was noted that for the same valve assembly, the opening duration can be controlled by varying the length of oil column and/or the orifice diameter, with no change in command pressure.