Shaft shear detection through shaft oscillation

Patent metadata

Field	Value
Publication number	US-10228305-B2
Application number	US-201715710584-A
Country	US
Kind code	B2
Filing date	Sep 20, 2017
Priority date	Jan 18, 2016
Publication date	Mar 12, 2019
Grant date	Mar 12, 2019

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.

First claim

The invention claimed is:

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.

Assignees

• Pratt & Whitney Canada

Inventors

• Shenouda Antwan

Classifications

• F02C9/46

  Emergency fuel control · CPC title

• F05D2240/60

  Shafts · CPC title

• F05D2270/80

  Devices generating input signals, e.g. transducers, sensors, cameras or strain gauges · CPC title

• G01L5/00

  Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes · CPC title

• F05D2270/334

  Vibration measurements · CPC title