Chandler Evans Inc.

Colt Industries Inc.

Robert E Peck

Albert H White

Gene Meyer

Raymond D Zagranski

Raymond H Devanney

A manual backup system (10) for a fuel control incorporating a metering valve (108) controlled by an electronic computer has a power piston (34) and a loading piston (60) in confronting relationship adapted to engage each other upon power being withdrawn from a solenoid operated valve (72). The loading piston acts to maintain an arm (28) in engagement with the power piston so that it follows the power piston's movements as controlled by a servo valve (48), incorporating a fuel flow to compressor discharge pressure schedule (54), operated by a PLA lever (74). The position of the arm represents a requested fuel flow to discharge pressure ratio. The arm is mechanically connected to the metering valve through a multiplier linkage (96) which is also connected to a compressor discharge pressure transducer (98) so that the metering valve is positioned in accordance with the requested fuel flow to discharge pressure ratio as multiplied by the sensed compressor discharge pressure. Fuel flow is metered on the basis of an adjustable manual fuel flow to compressor discharge pressure schedule with the PLA lever operating in its normal quadrant. The PLA lever is not susceptible to being back driven during changeover or manual operation.

Manual backup for electronic fuel control

A fuel control for a gas turbine engine has an actuator (24) for a fuel metering valve (22) which includes two stepper motors (46 and 48) which selectively drive a differential mechanism operatively connected to the valve. The differential mechanism includes two identical gear assemblies (60, 64) which are mounted for rotation upon a shaft (26) connected to the valve. The gear assemblies include worm gears (58, 62) in engagement with worms (54, 56) driven by the stepper motors and bevel gears (68, 70). A spider bevel gear (66), carried by the shaft, is in meshing engagement with the bevel gears of the gear assemblies such that rotation of one of the gear assemblies with the other at rest causes a circumferential movement of the spider bevel gear which rotates the shaft and positions the valve. Two identical electronic control units (A, B), which each sense selected engine parameters are respectively connected to the stepper motors for controlling their operation. Only one of the electronic control units functions to control its stepper motor during normal operation while the positions worm and gear assembly associated with the other stepper motor remain frozen without any backdriving. Changeover to the other electronic control unit because of a malfunction or other reason may be effected by switching logic or operation of a selector switch (100).

Dual stepper motor actuator for fuel metering valve

A fuel control for a gas turbine engine has a positive displacement pump (28) for supplying fuel to the engine. Fuel flow from the pump is metered by a metering valve (30) which has a constant pressure head held across it by a metering head regulator valve (48) adapted to bypass flow around the pump in a conduit (50). An overspeed valve and solenoid assembly (42) is positioned in the control downstream of the metering valve for shutting off fuel flow to the engine in the event of an overspeed of a turbine of the engine. The metering head regulator valve is referenced to a pressure downstream of the overspeed valve and solenoid assembly by a pressure sense line (68). The solenoid (96) is controlled by a dual channel overspeed valve control circuit (102) having proportional plus derivative gains (108, 110). When the overspeed valve (76) of the assembly is operated, the pump is not deadheaded because the metering head regulator valve is referenced to a lower pressure downstream of the overspeed valve. By not deadheading the pump, faster fuel shutoff can be achieved and leakage across the overspeed valve minimized.

Overspeed limiter for gas turbine fuel control

A fuel metering system for a gas turbine engine with a low pressure drop fuel vaporizing system includes an engine driven centrifugal pump (10) supplied with fuel at a given absolute pressure (Pi) from a tank. The pump discharges fuel to a rapidly pulsed, solenoid operated ball valve (20) which functions as a metering valve in controlling flow to the engine. The solenoid (38) of the metering valve receives periodic voltage pulses of appropriate width from an electronic control which senses selected engine parameters and computes the required fuel flow and the pressure differential (Pr-P.sub.D) across the metering valve. Since the pressure differential across the metering valve increases with engine speed, favorable flow turndown ratios may be achieved without operating the metering valve at high or low values of duty cycle.

Pulse width modulated fuel metering system

A fuel control for a gas turbine engine has a positive displacement pump (10) which directs fuel to a constant flow regulator (14) which generates a constant or fixed rate flow of fuel. A flow diverter (16) includes a dividing device which divides the constant flow of fuel between a discharge conduit (18) connected to the burner nozzles of the engine and a bypass conduit (20) connected to the inlet side of the pump. A computer (22) which is adapted to sense various engine parameters; and calculate fuel flow controls the flow dividing device in order to apportion the flow so that the calculated fuel flow is delivered to the engine.

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Prospect, CT, United States of America

Robert E Peck