Study on characteristics of nozzle flapper system considering flow force

Abstract

A pneumatic nozzle flapper is an important displacement pressure converting element in pneumatic control systems. Recently, the drive current applied to a nozzle flapper tends to be smaller for saving the electric power and the drive force of the flapper is considered to be on the order of the flow force. As a result, the flow force influences the flapper displacement. So it is necessary to predict accurately the characteristics of the nozzle flapper. In this paper, the pneumatic nozzle flapper model including flow force of air jet through nozzle is proposed and the characteristics of the flow force are experimentally analyzed by the frequency response tests. There are 2 kind of the flow forces, that is, the flow force of static pressure and dynamic pressure, however the flow force of dynamic pressure is a negligible quantity, when the pneumatic nozzle flapper is designed.