GAS TURBINE STARTING WITH STEPPING SPEED CONTROL

• US 20100293961A1
• Filed: 05/19/2009
• Published: 11/25/2010
• Est. Priority Date: 05/19/2009
• Status: Active Grant

• Current Assignee: Hamilton Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Hamilton Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Sullivan, Timothy J., Tong, Bing, Hilgeman, Paul E., Mack, Tarrence L.
• Granted Patent: US 8,245,517 B2
• Time in Patent Office: Days
• US Class Current: 60/778
• CPC Class Codes: F01D 19/00 Starting of machines or engines; Regulating, controlling, or safety means in connection therewith warming-up before starting F01D25/10; turning or inching gear F01D25/34
• CPC Class Codes: F02C 7/26 Starting; Ignition
• CPC Class Codes: F05D 2260/85 Starting

Abstract

The system and method of the present invention provides stepping speed control of a gas turbine engine to reliably light-off a gas turbine engine. During starting, the speed of the gas turbine engine is incremented by stepped amounts through the light-off window from a minimum speed value to a maximum speed value, with the speed of the gas turbine dwelling at each stepped value for a period of time before incrementing the speed of the engine to the next stepped level. If the gas turbine engine is stepped through the entire light-off window without success, the controller decreases the speed of the gas turbine engine to the minimum value and begins the process again. The process continues until successful light-off is initiated or until the light-off window is traversed a certain number of times, after which the start process is aborted.

Claims

1. A system for starting a gas turbine engine, the system including:

a starter-motor connected to rotate the gas turbine engine at a speed defined by a speed command value; and

a controller for generating speed command values provided to the starter-motor to control the speed of the gas turbine engine, the controller providing speed command values that result in stepped increases in the speed of the gas turbine engine through a light-off window from a minimum speed value to a maximum speed value, with the speed of the gas turbine dwelling at each stepped speed command value for a period of time before the controller increments the speed command value to the next stepped level, wherein if the gas turbine engine is stepped through the entire light-off window without success, the controller decreases the speed of the gas turbine engine to the minimum speed value and repeats the stepped traversal of the light-off window.

2. The system of claim 1, wherein the controller provides a deceleration delay following each traversal of the light-off window to allow the gas turbine engine to decelerate to the minimum speed value before initiating repeating the stepped traversal of the light-off window.

3. The system of claim 2, wherein light-off of the gas turbine engine is continually attempted at each stage of the start-up process, including during the stepped increases in speed of the gas turbine engine and during the deceleration delay associated with the gas turbine engine following an unsuccessful traversal of the light-off window.

4. The system of claim 1, wherein the control selects an amount of time to dwell at each stepped speed interval based on one or more factors, including but not limited to ambient temperature, altitude, aircraft speed, and/or humidity.

5. The system of claim 1, wherein increments to the speed command value are selected from a group consisting of percentage increments over a current speed command value, constant increment over a current speed command value, variable increment based on factors sensed by the controller, and variable, pre-programmed increment values.

6. The system of claim 1, wherein the controller provides speed command values that result in stepped increases in the speed of the gas turbine engine through the light-off window while an air inlet door is moving from a closed state to an opened state.

7. A method of starting a gas turbine engine, the method comprising:

(a) incrementing a speed command value of the gas turbine engine by stepped amounts through the light-off window from a minimum speed value to a maximum speed value;

(b) dwelling for a period of time at each stepped speed command value before incrementing the speed command value;

(c) decreasing the speed command value of the gas turbine engine to the minimum speed value following traversal of the light-off window without successful light-off; and

repeating steps (a) through (c) until light-off of the gas turbine engine is successful or the light-off window is traversed a number of times without successful light-off.

8. The method of claim 7, wherein incrementing the speed of the gas turbine engine includes:

incrementing the speed command value based on one of the following methods, a percentage-based increment of the speed command value, a constant value increment of the speed command value, a variable value increment based on factors sensed by the controller, and a variable value increment based on pre-programmed values.

9. The method of claim 7, wherein dwelling for a period of time at each stepped speed command value before incrementing the speed command value includes:

maintaining a first timer indicating time spent at the selected speed command value; and

comparing the first timer to an acceleration-delay value, wherein when the first timer exceeds the acceleration-delay value the speed command value is incremented at step (a) or decreased to the minimum speed value if the light-off window has been traversed at step (c).

10. The method of claim 9, further including

selecting the acceleration delay value based on one or more sensed conditions, including but not limited to ambient temperature, altitude, aircraft speed and/or humidity.

11. The method of claim 7, wherein decreasing the speed command value of the gas turbine engine to the minimum speed value following traversal of the light-off window without successful light-off further includes:

introducing a deceleration delay to allow the gas turbine engine to decelerate to the minimum speed command value.

12. The method of claim 10, wherein introducing the deceleration delay includes:

maintaining a second timer indicating time spent decelerating; and

comparing the second timer to a deceleration-delay value, wherein when the second timer exceeds the deceleration-delay value the gas turbine engine dwells at the minimum speed at step (b).

13. The method of claim 12, wherein the deceleration-delay value is selected based on a difference between the maximum speed value and the minimum speed value.

14. The method of claim 7, further including:

performing steps (a) through (c) contemporaneous with opening of an inlet air door.

15. A gas turbine engine starter system that supports starting and light-off of a gas turbine engine, the starter system comprising:

a first input connected to receive signals provided by one or more temperature sensors monitoring exhaust temperature of the gas turbine engine;

an output connected to provide a speed command signal to a starter-generator that dictates an engine speed during starting; and

a controller connected to the first input and the output, the controller maintaining a minimum speed command value, a maximum speed command value, and a counter, wherein the controller generates speed command values during start-up provided at the output to control the speed of the gas turbine engine during start-up based on the following algorithm implemented by the controller, the algorithm comprising;

(a) setting the speed command value equal to the minimum speed command value, the minimum speed command value representing a minimum speed associated with the light-off window;

(b) maintaining the speed command value at the selected speed for a dwell time, during which time light-off of the engine is attempted;

(c) continually monitoring the temperature signals provided at the first input to determine whether light-off has been successful, wherein if light-off is successful at any stage then proceeding to step (j);

(d) following unsuccessful light-off during the dwell time, comparing the speed command value to the maximum speed value representing a maximum speed associated with the light-off window, wherein if the speed command value exceeds the threshold value then proceed to step (g);

(e) incrementing the speed command value;

(f) repeating steps (b) through (e);

(g) incrementing the counter, wherein the counter represents a number of traversals through the light-off window;

(h) comparing the first counter to a threshold value, wherein if the counter exceeds the threshold value then starting of the gas turbine engine start is aborted;

(i) repeating steps (a) through (h); and

(j) setting the speed command value to a self-sustaining speed value to accelerate the gas turbine engine to a self-sustaining speed if light-off is successful, at which time the starter motor is disengaged.

16. The system of claim 15, wherein the controller further maintains an acceleration-delay value and a first timer, wherein the step of maintaining the speed command value at the selected value for the dwell time further includes:

maintaining the first timer indicating time spent at the selected speed command value;

comparing the first timer to the acceleration-delay value; and

proceeding to step (d) when the first timer exceeds the acceleration delay value.

17. The system of claim 16, wherein the step of maintaining the speed command value further includes:

selecting the acceleration delay value based on one or more sensed conditions, including but not limited to ambient temperature, altitude, aircraft speed, and/or humidity.

18. The system of claim 15, wherein the controller further maintains a deceleration delay value and a second timer, wherein following the step of setting the speed command value to the minimum speed after unsuccessfully traversing the light-off window, the method further includes:

maintaining the second timer indicating time spent decelerating; and

comparing the second timer to the deceleration-delay value and proceeding to step (b) when the second timer exceeds the deceleration-delay value.

19. The system of claim 18, wherein the deceleration-delay value is selected based on a difference between the maximum speed value and the minimum speed value.

20. The system of claim 15, wherein the step of incrementing the speed command value includes:

incrementing the speed command value based on one of the following methods, a percentage-based increment of the speed command value, a constant value increment of the speed command value, a variable value increment based on factors sensed by the controller, and a variable value increment based on pre-programmed values.

21. The system of claim 15, further including:

a second input connected to receive signals provided by an inlet air door controller that is responsible for opening an inlet air door, wherein the controller is further connected to the second input and initiates start-up in response to notification from the inlet air door controller that the inlet air door is opening.