Method of engine starting in a gas turbine engine

• US 6,810,676 B2
• Filed: 12/14/2001
• Issued: 11/02/2004
• Est. Priority Date: 12/14/2001
• Status: Expired due to Term

• Current Assignee: Pratt & Whitney Canada Corporation (Rtx Corporation)
• Original Assignee: Pratt & Whitney Canada Corporation (Rtx Corporation)
• Inventors: OʼConnor, Richard John
• Primary Examiner(s): FREAY, CHARLES GRANT
• Application Number:
  US10/016,869
• Publication Number:
  US 20030110777A1
• Time in Patent Office: 1,054 Days
• Field of Search: 607/72, 607/78, 607/86, 607/90, 60/391.83, 60/393.4, 60/396.4, 607/73, 607/76, 607/84, 607/88, 607/93
• US Class Current: 60/778
• CPC Class Codes: F02C 7/26 Starting; Ignition
• CPC Class Codes: F02C 9/28 Regulating systems responsive to plant or ambient parameters, e.g. temperature, pressure, rotor speed F02C9/30 - F02C9/38, F02C9/44 take precedence
• CPC Class Codes: F05D 2270/301 Pressure
• CPC Class Codes: F05D 2270/303 Temperature
• CPC Class Codes: F05D 2270/304 Spool rotational speed

Abstract

A method of engine starting in a gas turbine engine comprises rotating the engine to provide an air flow into a combustor of the engine and injecting fuel into the combustor at a varying rate until the engine is lighted-off. The varying rate of the fuel flow is a function of time and is represented by a curve having at least one high frequency with respect to a light-off time, representing instant changes of the rate for intersecting a light-off zone while reducing a quantity of fuel injected into the combustor. After the light-off occurrence fuel is continuously injected into the combustor to accelerate the engine to a self-sustaining operation condition. This method of the present invention is adapted to find light-off points under various temperature and altitude conditions, thereby advantageously providing a rapid light-off, particularly under cold weather conditions.

Claims

1. A method of engine starting in a gas turbine engine comprising:

rotating the engine at an increasing speed as a function of time to accelerate the engine and provide an air flow into a combustor of the engine;

injecting fuel into the combustor at a varying rate during the acceleration of the engine until the engine is lighted-off, the varying rate being a function of time and represented by a curve having at least one high frequency with respect to a light-off time, representing instant changes of the rate for intersecting a light-off zone while reducing a quantity of fuel injected into the combustor; and

then,

continuously injecting fuel into the combustor to accelerate the engine to a self-sustaining operation condition.

2. A method as claimed in claim 1 wherein the curve comprises a low frequency with respect to the light-off time, representing a change trend of the varying rate.

3. A method as claimed in claim 1 wherein the curve has an increasing trend and comprises an oscillatory profile.

4. A method as claimed in claim 1 wherein the curve has an increasing trend and comprises a series of spikes.

5. A method as claimed in claim 1 wherein the curve has an increasing trend and comprises a squared-off wave profile.

6. A method as claimed in claim 1 wherein the curve has an increasing trend and comprises a step profile.

7. A method as claimed in claim 1 further comprising introduction of a predetermined first fuel flow level into the combustor prior to fuel injection at the varying rate.

8. A method as claimed in claim 7 further comprising:

selecting a minimum engine speed to begin the introduction of the predetermined first fuel flow level for starting the engine under a variety of altitude and temperature conditions.

9. A method as claimed in claim 8 further comprising:

sensing a temperature of the fuel to be injected into the combustor;

sensing a temperature of the air flow to be provided into the combustor;

sensing a forward flight velocity ram quantity;

sensing an ambient air pressure;

sensing the varying speed of the engine; and

processing the sensed data to determine the minimum engine speed for the introduction of the predetermined first fuel flow level.

10. A method as claimed in claim 9 further comprising:

measuring a light-off time taken from the beginning of the introduction of the predetermined first fuel flow level, to the occurrence of the light-off; and

storing the measured light-Off time and the sensed data in a database for reference in a future engine starting process when a search shows no data associated with an altitude and temperature condition, similar to a current altitude and temperature condition generated in a previous light-Off process and stored in the database.

11. A method as claimed in claim 10 further comprising:

changing a criterion of the minimum engine speed and the predetermined first fuel flow level to reduce the light-off time according to the stored data associated with the similar altitude and temperature condition, when such data is located in the database; and

storing data regarding the changes and the light-off time currently measured, and deleting the previously stored data of the minimum engine speed and the predetermined first fuel flow level and the previously stored light-off time associated with thin similar altitude and temperature condition, when the current light-off time is shorter than the previously stored light-off time.

12. A method as claimed in claim 1 further comprising:

sensing a temperature of an exhaust gas flow to determine if the light-off occurs.

13. A method as claimed in claim 1 further comprising:

biasing a profile of the curve representing the varying fuel injection rate according to changes in the altitude and temperature conditions.

14. A method as claimed in claim 1 further comprising:

changing the predetermined first fuel flow level according to changes in the altitude and temperature conditions.