MODIFIED START SEQUENCE OF A GAS TURBINE ENGINE

• US 20170233103A1
• Filed: 02/12/2016
• Published: 08/17/2017
• Est. Priority Date: 02/12/2016
• Status: Active Grant

• Current Assignee: Rtx Corporation
• Original Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Sutliff, Jeffrey W., Greene, JR., William H., White, Kenneth J., Virtue, JR., John P., Glahn, Jorn A., Hoover, Philip D., Pinedo, Victor M., Solomonides, Jason B., Feulner, Matthew R., Teicholz, Matthew D.
• Granted Patent: US 10,040,577 B2
• Time in Patent Office: Days
• CPC Class Codes: B64D 27/16 of jet type
• CPC Class Codes: B64F 1/34 for starting propulsion plant
• CPC Class Codes: F02C 7/27 Fluid drives turbine starters F02C7/277
• CPC Class Codes: F02C 7/277 the starter being a separate turbine
• CPC Class Codes: F05D 2220/323 for aircraft propulsion, e.g. jet engines
• CPC Class Codes: F05D 2260/85 Starting
• CPC Class Codes: F05D 2270/303 Temperature
• CPC Class Codes: F05D 2270/71 synthesized, i.e. parameter computed by a mathematical model

Abstract

A system for starting a gas turbine engine of an aircraft is provided. The system includes a pneumatic starter motor, a discrete starter valve switchable between an on-state and an off-state, and a controller operable to perform a starting sequence for the gas turbine engine. The starting sequence includes alternating on and off commands to an electromechanical device coupled to the discrete starter valve to achieve a partially open position of the discrete starter valve to control a flow from a starter air supply to the pneumatic starter motor to drive rotation of a starting spool of the gas turbine engine below an engine idle speed.

Claims

1. A system for starting a gas turbine engine of an aircraft, the system comprising:

a pneumatic starter motor;

a discrete starter valve switchable between an on-state and an off-state; and

a controller operable to perform a starting sequence for the gas turbine engine, the starting sequence comprising alternating on and off commands to an electromechanical device coupled to the discrete starter valve to achieve a partially open position of the discrete starter valve to control a flow from a starter air supply to the pneumatic starter motor to drive rotation of a starting spool of the gas turbine engine below an engine idle speed.

2. The system as in claim 1, wherein the electromechanical device has a cycle time defined between an off-command to an on-command to the off-command that is at most half of a movement time for the discrete starter valve to transition from fully closed to fully open.

3. The system as in claim 1, wherein the electromechanical device is a solenoid that positions the discrete starter valve based on intermittently supplied electric power.

4. The system as in claim 1, wherein the electromechanical device is an electric valve controlling muscle air to adjust the position of the discrete starter valve.

5. The system as in claim 1, wherein the controller modulates the on and off commands to the electromechanical device to further open the discrete starter valve and increase a rotational speed of the starting spool.

6. The system as is claim 1, further comprising:

an electronic engine control system comprising;

a memory for recording a current heat state of the gas turbine engine at shutdown and for recording a shutdown time of the gas turbine engine; and

a risk model for determining a time period (t_motoring) for motoring the gas turbine engine at a predetermined speed N_target wherein the predetermined speed is less than a speed used to start the gas turbine engine and wherein t_motoring is a function of the heat state recorded at engine shutdown and an elapsed time of an engine start request relative to the previous shutdown time.

7. The system as in claim 6, wherein the time period (t_motoring) is calculated automatically during a start of the gas turbine engine.

8. The system as in claim 6, wherein the controller modulates a duty cycle of the discrete starter valve via pulse width modulation.

9. The system as in claim 6, wherein the predetermined speed N_target is within a predetermined speed range N_targetMin to N_targetMax that is used regardless of the calculated time period t_motoring.

10. A gas turbine engine and a system for controlling a start sequence of the gas turbine engine, comprising:

an electronic engine control system;

a thermal model resident upon the electronic engine control system and configured to synthesize a heat state of the gas turbine engine;

a memory for recording the current heat state of the gas turbine engine at shutdown and for recording a shutdown time of the gas turbine engine;

a model for determining a time period (t_motoring) for motoring the gas turbine engine at a predetermined speed N_target wherein the predetermined speed is less than a speed used to start the gas turbine engine and wherein t_motoring is a function of the heat state recorded at engine shutdown and an elapsed time of an engine start request relative to a previous shutdown time; and

a controller for modulating a starter valve of a starter of the gas turbine engine in order to maintain the gas turbine engine within a predetermined speed range of N_targetMin to N_targetMax for homogenizing engine temperatures.

11. The gas turbine engine and system of claim 10, wherein the time period (t_motoring) is calculated automatically during a start of the gas turbine engine.

12. The gas turbine engine and system of claim 10, wherein the controller modulates a duty cycle of the starter valve via pulse width modulation.

13. The gas turbine engine and system of claim 10, wherein the starter valve controls the flow of an air supply into the starter of the gas turbine engine.

14. A method for providing a start sequence of a gas turbine engine, comprising:

determining a heat state of the gas turbine engine via an engine thermal model;

storing the heat state of the gas turbine engine at shutdown;

recording a time of the engine shutdown; and

using a risk model to determine a motoring time period t_motoring for a start sequence of the gas turbine engine, wherein the risk model uses the recorded time of the engine shutdown and the stored heat state of the gas turbine engine at shut down to determine the motoring time period t_motoring.

15. The method as in claim 14, wherein the gas turbine engine is motored at a predetermined speed range of N_targetMin to N_targetMax during the motoring time period, which is less than a normal idle start speed N2.

16. The method as in claim 15, further comprising dynamically varying a position of a starter valve during the motoring time period in order to motor the gas turbine engine at the predetermined speed range of N_targetMin to N_targetMax.

17. The method as in claim 14, wherein the risk model is located on an electronic control of a system programmed to automatically implement the motoring time period.

18. The method as in claim 17, wherein the heat state is determined by a first thermal model and a second thermal model each being resident upon the electronic engine control system.

19. The method as in claim 14, further comprising providing a time of an engine start request and an inlet air temperature to the risk model when the risk model determines the motoring time period.

20. The method as in claim 14, wherein the motoring time period determines the duration of a modified start sequence of the gas turbine engine and the modified start sequence requires motoring of the gas turbine engine at a predetermined speed N_target during the motoring time period without introduction of fuel and an ignition source to the gas turbine engine, wherein the predetermined speed N_target is less than a normal idle start speed N2.