Overspeed limiter for gas turbine fuel control

摘要

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.