Shaft shear detection through shaft oscillation

• US 10,228,305 B2
• Filed: 09/20/2017
• Issued: 03/12/2019
• Est. Priority Date: 01/18/2016
• Status: Active Grant

• Current Assignee: Pratt & Whitney Canada Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Pratt & Whitney Canada Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Shenouda, Antwan
• Primary Examiner(s): Tankersley, Blake A
• Assistant Examiner(s): Hinze, Leo T
• Application Number:
  US15/710,584
• Publication Number:
  US 20180010980A1
• Time in Patent Office: 538 Days
• CPC Class Codes: F01D 21/003 Arrangements for testing or measuring for measuring vibrations G01H
• CPC Class Codes: F01D 21/04 responsive to undesired position of rotor relative to stator or to breaking-off of a part of the rotor, e.g. indicating such position
• CPC Class Codes: F01D 21/045 special arrangements in stators or in rotors dealing with breaking-off of part of rotor
• CPC Class Codes: F01D 21/06 Shutting-down
• CPC Class Codes: F02C 3/04 having a turbine driving a compressor power transmission arrangements F02C7/36; control of working fluid flow F02C9/16
• CPC Class Codes: F02C 9/46 Emergency fuel control
• CPC Class Codes: F02K 3/06 with front fan
• CPC Class Codes: F05D 2220/323 for aircraft propulsion, e.g. jet engines
• CPC Class Codes: F05D 2240/60 Shafts
• CPC Class Codes: F05D 2270/091 in particular sudden load loss
• CPC Class Codes: F05D 2270/334 Vibration measurements
• CPC Class Codes: F05D 2270/80 Devices generating input signals, e.g. transducers, sensors, cameras or strain gauges
• CPC Class Codes: F05D 2270/81 Microphones
• CPC Class Codes: G01L 5/00 Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
• CPC Class Codes: G01M 13/028 Acoustic or vibration analysis
• CPC Class Codes: G01M 15/14 Testing gas-turbine engines or jet-propulsion engines

Abstract

There is described a shaft shear event detection method. The method comprises obtaining a demodulated waveform of a shaft oscillation wave superimposed on a shaft rotational speed signal, comparing the amplitude to an amplitude threshold, detecting oscillation when the amplitude threshold is exceeded for a plurality of samples, and detecting a shaft shear when oscillation continues for a predetermined time limit.

Claims

1. A method for detecting a shear of a rotating shaft of a gas turbine engine, the shaft positioned between a source and a load, the method comprising:

receiving a speed sensor signal from a speed sensing device;

determining, from the speed sensor signal, a demodulated waveform of a shaft oscillation wave superimposed on a shaft rotational speed signal, the waveform having an amplitude and a frequency;

comparing the amplitude of the waveform to an amplitude threshold;

detecting an oscillation of the shaft when the amplitude threshold is exceeded for a plurality of samples;

detecting a shear of the rotating shaft when oscillation continues for a predetermined time limit; and

in response to detecting the shear of the rotating shaft, commanding a fuel shutoff of the gas turbine engine.

2. The method of claim 1, wherein the amplitude threshold comprises a lower amplitude threshold and an upper amplitude threshold.

3. The method of claim 1, wherein the demodulated waveform is obtained through amplitude demodulation.

4. The method of claim 1, wherein the demodulated waveform is obtained through frequency demodulation.

5. The method of claim 1, wherein the speed sensing device comprises a phonic wheel sensing assembly;

and wherein the speed sensor signal is received from the phonic wheel sensing assembly.

6. The method of claim 1, wherein the predetermined time limit is measured as a function of a period of the waveform.

7. A system for detecting a shear of a rotating shaft of a gas turbine engine, the shaft positioned between a source and a load, the system comprising:

a processing unit; and

a non-transitory computer-readable memory having stored thereon program instructions executable by the processing unit for;

receiving a speed sensor signal from a speed sensing device;

determining, from the speed sensor signal, a demodulated waveform of a shaft oscillation wave superimposed on a shaft rotational speed signal, the waveform having an amplitude and a frequency;

comparing the amplitude of the waveform to an amplitude threshold;

detecting an oscillation of the shaft when the amplitude threshold is exceeded for a plurality of samples;

detecting a shear of the rotating shaft when oscillation continues for a predetermined time limit; and

in response to detecting the shear of the rotating shaft, commanding a fuel shutoff of the gas turbine engine.

8. The system of claim 7, wherein the amplitude threshold comprises a lower amplitude threshold and an upper amplitude threshold.

9. The system of claim 7, wherein the demodulated waveform is obtained through amplitude demodulation.

10. The system of claim 7, wherein the demodulated waveform is obtained through frequency demodulation.

11. The system of claim 7, wherein the speed sensing device comprises a phonic wheel sensing assembly;

and wherein the speed sensor signal is received from the phonic wheel sensing assembly.

12. The system of claim 7, wherein the predetermined time limit is measured as a function of a period of the waveform.

13. A non-transitory computer-readable medium having stored thereon program instructions for detecting a shear of a rotating shaft of a gas turbine engine, the shaft positioned between a source and a load, the program instructions executable by a processing unit for:

receiving a speed sensor signal from a speed sensing device;

determining, from the speed sensor signal, a demodulated waveform of a shaft oscillation wave superimposed on a shaft rotational speed signal, the waveform having an amplitude and a frequency;

comparing the amplitude of the waveform to an amplitude threshold;

detecting an oscillation of the shaft when the amplitude threshold is exceeded for a plurality of samples;

detecting a shear of the rotating shaft when oscillation continues for a predetermined time limit; and

in response to detecting the shear of the rotating shaft, commanding a fuel shutoff of the gas turbine engine.