DESIGN AND ANALYSIS OF A TWO-STAGE POPPET VALVE FOR FLOW CONTROL

Abstract

This paper explores dynamic modelling and design of a typical two stage metering poppet valve system. In particular, nonlinear and linear models of a spring force feedback configuration are developed and parameters tuned through the use of root locus techniques. Typical steady state conditions as well as extreme high and low pressure drops are simulated in attempts to uncover instabilities and other possible undesirable performance characteristics of the valve. Finally the nonlinear model is used to produce Bode magnitude plots at various pressure drops in order to estimate the system bandwidth. Results indicate that increasing the size of the orifice at the inlet of the pilot stage of the valve increases performance in terms of rise time at the cost of a more oscillatory response. High pressure differences between the inlet and outlet of the valve were found to cause performance to increase significantly as well as move poles into a region indicated less damping. A scheme for controlling the inlet orifice area to the pilot stage is presented and shown to improve performance capability (bandwidth) of the valve while maintain a damped response.