Fluidic pressure ratio sensing for jet engine controls

Abstract

The reasons are outlined for the introduction of fluidics into jet engine controls, for example, their high resistance to extremes of environment, and then two alternative basic methods of applying fluidics are compared. These methods are: (I) a “black box” approach in which a fluidic circuit performs the computational function and is provided with a stabilised pressure supply and output power amplification, and (II) fluidic element integration into a hydro/mechanical and/or electrical system. It is shown that the latter solution maximizes the advantage of high resistance to environmental conditions, provided that fluidic elements, which can meet required operating pressure and pressure ratio range, are available. Various pressure ratio sensors are considered and a unit based upon the jet pipe valve is found to possess the required characteristics. The requirement for high pressure proportional amplifiers and bistable switches is met by combining conventional elements with vortex valves. The design of the fluidic elements is described and performance is illustrated by test data. The application of the elements to compressor bleed valve, turbine pressure ratio and compressor range pressure ratio control is described. Unit performance is illustrated by test data.