Low Cost Electronically Controlled Fuel Metering System for Small Gas Turbine Engines

The cost of fuel control systems for small gas turbine engines is quite high and could be significantly reduced by simplifying the fuel metering system and bringing it under electronic control. Such an attempt has been made regarding the popular Bendix DP-F2 fuel control unit (FCU).

Presently, the DP-F2 FCU is using a metering valve with a complex profile head, being moved in a calibrated orifice using double bellows operated by the compressor pressure. The differential pressure across the metering valve is controlled by a bypass valve fitted with a diaphragm which moves a shaped plunger inside a multi-orifice barrel.

It is proposed to use a pressure balanced metering valve with a plunger moved in a slitted barrel by a stepper motor, which is changing the valve flow area according to the engine compressor pressure signal. The proposed new differential pressure bypass valve uses a diaphragm with an attached plate as a simple flat-seat restrictor controlling the fuel bypass back to the tank. The proposed design could be adapted to the DP-F2 FCU either partly (only the new bypass valve), or fully (including the new metering valve under electronic control). The new system was computer simulated, tested and optimized and showed a satisfactory behavior during steady state and transient processes.