Gas turbine fuel control

Claim 2

A fuel control system for a gas turbine engine, said engine having at least one fluid compressor means, a combustor means, at least one turbine means and a surge valve for bleeding air from the output of said compressor means, said control system comprising: means for measuring a plurality of engine operating parameters and generating signals representative thereof; a first plurality of schedule means for receiving selected engine parameter signals from said measuring means and providing an output signal according to a predetermined schedule, said output signal varying according to variations in said engine parameter signals; first selection means for selecting the lowest value of the outputs of said first schedule means and providing an output signal representative thereof; a second plurality of schedule means including surge schedule means for receiving selected engine parameter signals and providing an output signal according to a predetermined schedule, said output varying according to variations in said parameter signals; second selection means for selecting the highest value of the output of said second schedule means and first selection means and providing a fuel flow signal representative thereof; fuel regulator means for receiving the fuel flow signal from said second selection means for regulating fuel flow to said engine; surge valve control means for sensing the fuel flow signal from said second selection means and the position of said surge valve for adjusting said surge valve position to increase the rate of compressor bleed if the fuel flow signal is limited by the engine surge schedule and for decreasing the rate of compressor bleed if the fuel flow is less than the surge schedule by a predetermined amount.

Claim 3

The fuel control system of claim 1 wherein said plurality of engine parameters comprises engine rotational speed, power lever position, turbine inlet temperature, and compressor discharge pressure.

Claim 4

The fuel control system of claim 2 wherein said first plurality of schedule means comprises an engine acceleration schedule, surge schedule, start schedule and power lever position signal and said second plurality of schedules comprises a minimum fuel schedule and a deceleration schedule.

Claim 5

The fuel control system of claim 3 wherein the input signals to said surge valve control means include, surge schedule signal, power lever position signal and fuel flow signal from said second selection means; the output of said surge control means is connected at an input to said deceleration schedule, said surge schedule and to a surge valve actuator.

Claim 6

The fuel control system of claim 4 wherein said engine is a two-spool engine having first and second compressor means and first and second turbine means, said first compressor means and said first turbine means comprising a first spool at said second compressor and said second turbine means comprising a second spool and said engine rotational speed parameter comprises first spool speed signal and a second spool speed signal and the input to said surge schedule comprises first spool speed signal second spool speed signal and the output of said surge valve control means.

Claim 7

A fuel control system for a gas turbine engine wherein the control parameter is W f /P c where W f equals fuel flow in pounds per hour and P c equals compressor discharge pressure in pounds per square inch, said system comprising a plurality of scheduled signals having output signals proportional to W f /P c versus engine speed according to a predetermined schedule, said system comprising: a first signal selector means whose output is the lowest of its input signals; a power lever position signal generator connected to the first signal selector means for generating a control parameter signal proportional to the power lever position; an acceleration schedule signal generator connected to said first signal selection means for generating a control parameter signal for limiting engine acceleration; a surge schedule signal generator means connected to said first signal selector means for generating a control parameter signal for limiting fuel flow according to surge valve position and engine speed; a second signal selector means having as one of its signal inputs the output of said first signal selector means, the output of said second signal selector means being the highest value of its signal inputs, said output being connected to a fuel flow regulator for regulating fuel flow to said engine; a minimum fuel schedule signal generator connected to the input of said second signal selector for generating control parameter signal for limiting the minimum fuel flow to said engine; a deceleration schedule signal generator connected to the input of said second signal selector means for generating a control parameter signal to limit engine deceleration; and a surge valve control means connected to the output of said second signal selector means and to the output of said surge schedule signal generating means and said power lever position signal generator said surge valve control means generating output signal for varying the output of said surge schedule generating means and said deceleration schedule signal generating means.

Claim 8

A fuel control system for a gas turbine engine wherein the control parameter is W f /P c where W f equals fuel flow in pounds per hour and P c equals compressor discharge pressure in pounds per square inch, said system comprising a plurality of scheduled signals having output signals proportional to W f /P c versus engine speed according to a predetermined schedule, said system comprising: a first signal selector means whose output is the lowest of its input signals; a power lever position signal generator connected to the first signal selector means for generating a control parameter signal proportional to the power lever position; an acceleration schedule signal generator connected to said first signal selection means for generating a control parameter signal for limiting engine acceleration; a surge schedule signal generator means connected to said first signal selector means for generating a control parameter signal for limiting fuel flow according to surge valve position and engine speed; a second signal selector means having as one of its signal inputs the output of said first signal selector means, the output of said second signal selector means being the highest value of its signal inputs, said output being connected to a fuel flow regulator for regulating fuel flow to said engine; a minimum fuel schedule signal generator connected to the input of said second signal selector for generating control parameter signal for limiting the minimum fuel flow to said engine; a deceleration schedule signal generator connected to the input of said second signal selector means for generating a control parameter signal to limit engine deceleration; and a surge valve control means connected to the output of said second signal selector means and to the output of said surge schedule signal generating means and said power lever position signal generator said surge valve control means generating output signal for varying the output of said surge schedule generating means and said deceleration schedule signal generating means.

Claim 9

Fuel control system of claim 6 wherein the output of the power lever position signal generator is limited by a turbine inlet temperature or engine speed.

Claim 10

A fuel control system for a gas turbine engine, having a control parameter of W f /P c wherein W f equals fuel flow in pounds per hour and P c equals compressor discharge pressure, said system comprising: first signal generator means for selecting desired engine power output level; second signal generator means for generating a first plurality of control parameter signals representative of selected engine performance limits; first selection means having as its output the lowest of said first and second signal generating means; third signal generator means for generating a second plurality of control parameter signals representative of other selected engine performance limits; second selection means having as its output the higher control parameter signal of said first selection means and third signal generating means; compressor bleed valve control means; means for modifying the output of said second selector means in response to the output of said compressor bleed valve control means.

Claim 11

A fuel control system for a gas turbine engine, having a control parameter of W f /P c wherein W f equals fuel flow in pounds per hour and P c equals compressor discharge pressure, said system comprising: first signal generator means for selecting desired engine power output level; second signal generator means for generating a first plurality of control parameter signals representative of selected engine performance limits; first selection means having as its output the lowest of said first and second signal generating means; third signal generator means for generating a second plurality of control parameter signals representative of other selected engine performance limits; second selection means having as its output the higher control parameter signal of said first selection means and third signal generating means; compressor bleed valve control means; means for modifying the output of said second selector means in response to the output of said compressor bleed valve control means.

Claim 12

The fuel control system of claim 8 wherein the means for modifying the output of said selector means comprises: means for comparing the output of said second selector means with a predetermined bleed valve schedule; means for increasing the output of said second selector means when said bleed valve schedule exceeds the output of said second selector means by a predetermined amount, and means for increasing the bleed valve open area for increasing compressor bleed when the output of said second selector means is limited by the bleed valve open area.

Claim 13

A control system for a gas turbine engine for controlling fuel flow and bleed valve position said system comprising: means for generating a fuel flow signal representative of desired fuel flow; means for generating a surge valve position schedule signal, said schedule signal indicating a predetermined relationship between engine speed and allowable fuel flow; means for selecting the higher of the fuel flow signal or said surge valve position signal, said selected signal being representative of the fuel flow supplied to the engine; servo means for adjusting the surge valve position to increase engine bleed if the surge schedule is limiting the selected signal and increasing the fuel flow signal accordingly; means for adjusting the surge valve position to reduce engine bleed if the surge valve position signal is above the selected signal by the amount of the fuel flow increase.

Claim 14

A control system for a gas turbine engine for controlling fuel flow and bleed valve position said system comprising: means for generating a fuel flow signal representative of desired fuel flow; means for generating a surge valve position schedule signal, said schedule signal indicating a predetermined relationship between engine speed and allowable fuel flow; means for selecting the higher of the fuel flow signal or said surge valve position signal, said selected signal being representative of the fuel flow supplied to the engine; servo means for adjusting the surge valve position to increase engine bleed if the surge schedule is limiting the selected signal and increasing the fuel flow signal accordingly; means for adjusting the surge valve position to reduce engine bleed if the surge valve position signal is above the selected signal by the amount of the fuel flow increase.