Fuel control system for a gas turbine

Claim 2

In a gas turbine comprising at least one combustion chamber and a rotor structure, said rotor structure being rotatable at a low speed during a cranking period, at an intermediate speed during an ignition period, and at a high speed during an operating period, and a system for controlling fuel supplied to said combustion chamber, said control system comprising: valve means for regulating the flow of fuel to said combustion chamber during said ignition and operating periods; means responsive to at least one parameter of turbine operation for continuously determining the fuel flow required by said combustion chamber and for providing a signal representative of said fuel flow; means for applying said signal to said valve means to effectuate operation of said valve means to regulate the flow of fuel therethrough; said signal applying means including two alternative paths for said signal, the first of said paths being operative during said ignition period; means responsive to the level of said signal for effecting transfer of said signal to the second path when said signal reaches a predetermined level; and means associated with said second path for maintaining a minimum signal level corresponding to the minimum fuel flow required to maintain combustion during said operating period.

Claim 3

The system recited in claim 1 wherein the second alternative path carries the control signal during the operating period.

Claim 4

The system recited in claim 1 wherein the alternative paths have a common portion and the means responsive to the signal level is connected to said common portion.

Claim 5

The system recited in claim 1 wherein the means to effect transfer of the signal to the second path comprises a signal diverting device; and the signal level responsive means activates the diverting device to divert the control signal to the second path, when the level of the signal corresponds to the operating period of the turbine.

Claim 6

The system recited in claim 1 wherein a plurality of turbine parameters are detected and converted into signals, and furthermore, means are provided to process the information in the signals and generate an output signal which is a continuous function of the fuel demanded.

Claim 7

The system recited in claim 5 wherein the signals fed into the signal processing means are electrical and the fuel demand signal exiting therefroM is electrical, means for converting said demand signal from an electrical demand signal to a pneumatic demand signal, said pneumatic signal in communication with first and second alternative signal paths.

Claim 8

The system recited in claim 1 wherein the minimum signal maintaining means comprises: a signal regulating device providing a minimum low level signal to maintain combustion; a low limit signal path; a first one way signal blocking device secured to said low limit path; a second one way signal blocking device secured to the second alternate path; said first blocking device preventing the low level signal in said low limit path from entering the second path, when the magnitude of the signal in the second path is greater than the magnitude of said low limit signal; said second blocking device preventing the signal in the second alternate path from continuing therethrough, when the magnitude of the low limit signal is greater than the signal in the second path.

Claim 9

The system recited in claim 1 wherein the fuel control signal is an electrical signal, means for converting said electrical signal to a pneumatic signal, said signal level responding means electrically activating a signal diverting device when the pressure level of the pneumatic signal reaches a level corresponding to the operating period, to switch the pneumatic flow in the signal paths therein, from the first path to the second path.

Claim 10

In a gas turbine comprising at least one combustion chamber and a rotor structure, said rotor structure being rotatable at a low speed during a cranking period, at an intermediate speed during an ignition period, and at a high speed during an operating period, a system for controlling fuel supplied to said combustion chamber, said control system comprising: valve means for regulating the flow of fuel to said combustion chamber during said ignition and operating periods; means to detect the value of at least one turbine parameter and convert it into a fuel control signal which is a continuous function of the fuel demand of the turbine; first and second alternate signal paths, having a common portion, said paths being adapted to carry said control signal to said valve means; means for diverting said signal from said first path to said second path; means for sensing the magnitude of said signal in said common portion, said sensing means activating said diverting mans; means for maintaining a minimum control signal to the valve to insure that the valve structure remains open to supply fuel to the combustion chamber at least at the minimum quantity needed to sustain combustion during the operating period; said minimum control signal maintaining means being associated with the second signal path.

Claim 11

In a gas turbine comprising at least one combustion chamber and a rotor structure, said rotor structure being rotatable at a low speed during a cranking period, at an intermediate speed during an ignition period, and at a high speed during an operating period, a system for controlling fuel supplied to said combustion chamber, said control system comprising: valve means for regulating the flow of fuel to said combustion chamber during said ignition and operating periods; means to detect the value of at least one turbine parameter and convert it into a fuel control signal which is a continuous function of the fuel demand of the turbine; first and second alternate signal paths, having a common portion, said paths being adapted to carry said control signal to said valve means; means for diverting said signal from said first path to said second path; means for sensing the magnitude of said signal in said common portion, said sensing means activating said diverting mans; means for maintaining a minimum control signal to the valve to insure that the valve structure remains open to supply fuel to the combustion chamber at least at the minimum quantity needed to sustain combustion during the operating period; said minimum control signal maintaining means being associated with the second signal path.

Claim 12

The system recited in claim 9 wherein the sensing means activates the diverting means, when the magnitude of the demand signal reaches a level corresponding to the operating period, to switch the signal from the first path to the second path, so that the first path carries the control signal during the ignition period and the second path carries the control signal during the operating period.

Claim 13

The system recited in claim 9 wherein the minimum control signal means provides a predetermined minimum signal into the second path when the control signal falls below the value of the minimum signal.

Claim 14

The system recited in claim 9 wherein the minimum control signal means comprises: a signal regulating device providing a minimum low level signal to prevent turbine flameout; a low limit path connecting said device to the second alternate path; a first one way signal blocking device secured to said low limit path; a second one way signal blocking device secured to the second alternate path; said first blocking device preventing the low level signal in said low limit path from entering the second path, when the magnitude of the signal in the second path is greater than the maGnitude of said low limit signal, said second blocking device preventing the signal in the second alternate path from continuing therethrough, when the magnitude of the low limit signal is greater than the signal in the second path.

Claim 15

The system recited in claim 12 wherein the minimum control signal means comprises a pneumatic system, wherein the signal regulating device provides a predetermined pneumatic signal, the low limit path carries the pneumatic signal to the second alternate path, the second alternate path carries a pneumatic signal, and said first and second blocking devices are one-way check valves which block the respective signals when the pressure from the signal in the respective path is less than the pressure in the corresponding path.