Power plants – Combustion products used as motive fluid – Combined with regulation of power output feature
Reexamination Certificate
1998-07-10
2001-02-20
Freay, Charles G. (Department: 3746)
Power plants
Combustion products used as motive fluid
Combined with regulation of power output feature
C137S599010, C137S110000, C137S115090
Reexamination Certificate
active
06189312
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a fuel metering arrangement for a gas turbine engine, such as a jet engine, primarily for use in aircraft.
It is conventional practice to meter the fuel flow to a gas turbine engine by the use of a metering valve having a metering orifice of which the area is variable according to fuel demand, usually under the control of a closed loop servo-system. It is important to maintain the pressure drop across the metering valve substantially constant and this is commonly achieved by connecting a pressure drop regulator valve between the inlet and outlet sides of the metering valve.
SUMMARY OF THE INVENTION
An object of the invention is to provide a fuel metering arrangement employing a metering valve controlled by a pressure drop regulator valve, in which protection is provided against at least downward failure of the pressure drop regulator valve.
According to the invention, a fuel metering arrangement comprises a fuel flow metering valve, a pressure drop regulator valve arranged and operable to maintain the pressure drop across the metering valve substantially constant, and a throttle device arranged and operable to regulate fuel flow upon failure of the regulator valve in an insufficiently closed or fully open position.
In one convenient arrangement, main and emergency pressure drop regulator valves are provided arranged in parallel, the emergency regulator valve operating to regulate fuel flow upon failure of the main regulator valve in an insufficiently open or fully closed position, the throttle device operating to regulate fuel flow upon failure of the main regulator valve in an insufficiently closed or fully open position.
The throttle device is preferably arranged in series with the main pressure drop regulator.
Preferably, the emergency pressure drop regulator is a spill valve arranged to respond to a pressure drop across the metering valve higher than that normally permitted by the main pressure drop regulator, and the throttle device is a throttle valve arranged to respond to a pressure drop across the metering valve lower than that normally permitted by the main regulator valve.
Typically, the spill valve is housed within the throttle valve and normally urged to a position in which it closes off an emergency spill orifice and the throttle valve is normally urged towards a fully open position.
In another convenient arrangement, two fuel flow metering valves are arranged in series and the main and emergency pressure drop regulators are arranged respectively upstream of the metering valves, the throttle device being connected between the main regulator valve and the upstream side of the first metering valve.
REFERENCES:
patent: 4175383 (1979-11-01), Smith
patent: 4716723 (1988-01-01), Ralston et al.
patent: 5513493 (1996-05-01), Severn et al.
patent: 5709079 (1998-01-01), Smith
patent: 5896737 (1999-04-01), Dyer
patent: 0 436 513 A1 (1991-07-01), None
patent: 0 481 620 A1 (1992-04-01), None
patent: 0 761 948 A2 (1997-03-01), None
patent: 2 300 451 (1996-11-01), None
Andrus Sceales, Starke & Sawall
Freay Charles G.
Lucas Industries PLC
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