Abstract: A variable area inline valve receives a pressurized fluid and regulates the amount of pressurized fluid flowing through the valve. The valve includes a piston assembly which slides longitudinally along a center line of the valve to control a variable flow area through which the fluid passes to the outlet of the housing. To stabilize the valve, the valve includes an axial feedback passage through which outlet fluid enters and is fed back to a first cavity to provide a retarding force to the piston movement. This fluid feedback assembly allows a proportional amount of the outlet fluid pressure to act on the piston assembly and stabilize the valve by providing a positive spring rate to the valve (i.e., negative feedback). The size of both the feedback orifice and a vent orifice which vents the first cavity to ambient sets the gain of the feedback.

Abstract: A gas turbine engine bleed air system in which air flow from a high pressure and a low pressure compressor stage of a gas turbine engine are mixed together by controlling the pressure at the outlet of a proportional valve. The pressure is controlled by modulating the flow area of the proportional valve through which the high pressure air flows in order to achieve a scheduled pressure value. The scheduled pressure value is determined as a function of a temperature error at a location downstream of the proportional valve in the bleed air system.

Abstract: Bleed air flow from each engine of a multi-engine gas turbine powered aircraft is determined by using venturi flow probe sensors (50,100) which each include a venturi (52,102). The pressure differential associated with the pressure within the throat of the venturis (52,102) and the pressure immediately upstream of the venturi is partially indicative of the bleed air flow associated with the respective engine. The appropriate sensed pressure and temperature values are provided to a controller (18) which calculates the bleed air flow from each engine. The controller (18) also calculates a trim signal (224) which is used to partially control the position of pressure regulating valves (14,64) in order to substantially equalize the flow of bleed air from each of the gas turbine engines.