Patent ID: 7836676
Filing Date: 2010-11-23
Classification: F02C,F23K

Abstract:
1. A fuel metering unit, comprising: a fuel metering valve coupled to receive a flow of fuel from a fuel source and having a variable area flow orifice through which fuel from the fuel source flows, the fuel metering valve coupled to receive hydraulic fluid and operable, upon receipt of the hydraulic fluid, to adjust the area of the variable area flow orifice based in part on the pressure of the hydraulic fluid; a metering valve actuator coupled to receive fuel flow command signals and hydraulic fluid from one or more hydraulic fluid sources, the metering valve actuator operable, upon receipt of the fuel flow command signals and the hydraulic fluid, to supply variable pressure hydraulic fluid to the fuel metering valve; a fail-fixed valve disposed in fluid communication between the metering valve actuator and the fuel metering valve, the fail-fixed valve movable between a first position, in which the fuel metering valve receives the variable pressure hydraulic fluid from the metering valve actuator, and a second position, in which fuel metering valve does not receive the variable pressure hydraulic fluid from the metering valve actuator; a flow increase valve in fluid communication with the fuel metering valve, the flow increase valve adapted to (i) receive hydraulic fluid at a first pressure from a first hydraulic fluid source and (ii) selectively couple the fuel metering valve to the first hydraulic fluid source to thereby increase the area of the variable area flow orifice; and a flow decrease valve in fluid communication with the fuel metering valve, the flow decrease valve adapted to (i) receive hydraulic fluid at a second pressure from a second hydraulic fluid source and (ii) selectively couple the fuel metering valve to the second hydraulic fluid source to thereby decrease the area of the variable area flow orifice.