Power plants – Combustion products used as motive fluid – Combined with regulation of power output feature
Reexamination Certificate
1999-01-27
2001-06-26
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
Combined with regulation of power output feature
Reexamination Certificate
active
06250067
ABSTRACT:
TECHNICAL FIELD
This invention relates to fuel delivery systems and more particularly to fuel delivery systems for aircraft gas turbine systems.
BACKGROUND ART
It is well known in the art of fuel delivery systems for aircraft gas turbine engines to use a primary electronic fuel control system with a mechanical secondary or backup system for monitoring and scheduling fuel delivery to the engine. The fuel control has two operating modes. In the first or primary mode the electronic engine control (EEC) schedules fuel flow to the engine in conjunction with the hydromechanical unit (HMU). In the backup or secondary mode the fuel delivery to the engine is scheduled by the HMU only.
The problem arises in that the EEC and HMU schedule a different fuel flow in response to pilot input. This is due to the fact that the EEC monitors different parameters than the HMU and can set an optimum engine speed (fuel flow) to achieve a desired thrust level. The HMU sets an engine speed for a given power lever setting. The differences in commanded engine speed are especially critical during takeoff. If the fuel control should switch from the primary to the secondary control the change in commanded engine speed could result in an excessive increase or decrease in engine thrust.
There exists a need, therefore, for a fuel delivery system which minimizes changes in engine thrust when switching from a primary control to a backup or secondary control.
DISCLOSURE OF INVENTION
The object of the subject invention is to provide an improved fuel delivery system which minimizes changes in engine thrust when switching from a primary control to a backup or secondary control. The object of the subject invention is achieved by the fuel delivery system described herein.
The fuel delivery system comprises a primary control means for commanding a first flow of fuel to the engine wherein the primary control is responsive to a first set of parameters indicative of an engine condition.
The fuel delivery system further comprises a secondary control means for commanding a second flow of fuel to the engine wherein said secondary control is responsive to a second set of parameters indicative of said engine condition, and wherein said second flow of fuel commanded by said secondary control may differ from said first flow of fuel commanded by said primary control for said engine condition. The fuel delivery system also includes a means for selecting either said primary control or said secondary control and a tracking means for minimizing the difference between said second flow of fuel commanded by the secondary controller and said first flow of fuel commanded by the primary controller.
REFERENCES:
patent: 4137707 (1979-02-01), Wanger
patent: 4794755 (1989-01-01), Hutto et al.
patent: 5088278 (1992-02-01), Smith et al.
patent: 5709079 (1998-01-01), Smith
patent: 3542273 (1987-06-01), None
patent: 2300451 (1996-06-01), None
Chapski David L.
Dyer Gerald P.
Tardif Mark R.
Casaregola Louis J.
United Technologies Corporation
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