Turbomachinery system fiberoptic multi-parameter sensing system and method

• US 20090320609A1
• Filed: 06/25/2008
• Published: 12/31/2009
• Est. Priority Date: 06/25/2008
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Pietrykowski, Matthew Damian, Chan, David So Keung, Li, Yun, Xia, Hua, McCarthy, Kevin Thomas, Wu, Juntao, Zheng, Danian, Ross, Alexander Seth, Gawrelski, Richard Joseph, Turnquist, Norman Arnold
• Granted Patent: US 8,042,412 B2
• Time in Patent Office: Days
• US Class Current: 73/862.08
• CPC Class Codes: G01H 9/004 using fibre optic sensors light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125
• CPC Class Codes: G01L 3/109 involving measuring phase difference of two signals or pulse trains
• CPC Class Codes: G01L 3/12 involving photoelectric means
• CPC Class Codes: G01M 11/081 by using a contact-less detection method, i.e. with a camera

Abstract

A fiberoptic multi-parameter sensing system for monitoring turbomachinery system shaft static and dynamic torques, vibration modes and associated operation status includes a multi-furcated fiber bundle based optical splitter configured to transmit light to a surface of at least one turbomachinery system shaft through a plurality of optical fiber bundles disposed at a plurality of locations in proximity to the surface of the at least one shaft, in which the plurality of locations together are arranged in a substantially axial direction between the ends of the at least one shaft. The system further includes an array of high-temperature bifurcated fiber bundle based reflectance probes to receive reflectance signals from the shaft surface and send to an array of photosensitive detectors, configured to detect dynamic light reflected from the at least one turbomachinery system shaft surface in response to the transmitted light during rotation of at least one turbomachinery system shaft and generate dynamic reflected light signals there from. A sensing mechanism is configured to determine a torque or vibration on at least one turbomachinery system shaft in response to the dynamic reflected light signal signatures based on time-domain and frequency-domain signal processes.

Claims

1. A method of sensing turbomachinery system shaft static and dynamic torques, vibration modes and associated operation status, the method comprising:

transmitting light to a plurality of shaft surface locations on a turbomachinery system via a plurality of optical fiber bundles, the plurality of shaft surface locations arranged in a substantially axial direction between the ends of at least one shaft, such that a plurality of dynamic reflected light signals are received from the plurality of shaft surface locations while at least one shaft is rotating; and

determining at least one turbomachinery system shaft torque or vibration characteristic based on at least one characteristic of the dynamic reflected light signals received from the shaft surface.

2. The method according to claim 1, wherein each optical fiber is multi-furcated such that light is transmitted to each turbomachinery shaft surface location via one leg of a multi-furcated optic fiber splitter and further such that light received from each shaft surface location in response to the transmitted light is received via a bi-furcated optic fiber reflectance probe.

3. The method according to claim 1, wherein transmitting light to a plurality of shaft surface locations on a turbomachinery system comprises transmitting light to an optical encoded turbomachine shaft surface.

4. The method according to claim 3, wherein determining at least one turbomachinery system shaft torque or vibration characteristic based on at least one characteristic of the reflected signals comprises:

determining a shaft twist angle value based on the plurality of reflected signal signatures; and

determining a turbomachinery system shaft torque based on a shaft twist angle value corresponding time delay or phase shift by differentiating any two reflectance signatures.

5. The method according to claim 4, wherein determining a shaft twist value based on the plurality of reflected signals comprises:

measuring when a difference between reflectance pattern signatures of reflected light signals detected via a plurality of reflectance probes at a desired wavelength of interest exceeds a desired threshold via a photodetecting mechanism;

determining differential time delays associated with the reflected signal signature; and

determining a shaft twist angle value based on the reflected signal differential time delays from their reflectance pattern recognition.

6. The method according to claim 4, wherein determining a turbomachinery system shaft torque based on the shaft twist angle value comprises calibrating an industry accepted gold standard torque sensor for use with the respective turbomachinery system shaft such that the twist angle value corresponds to an absolute value of torque retrieved from a look-up table or from a formulas, or from a calibration transfer function.

7. The method according to claim 4, wherein determining a turbomachinery system shaft torque based on the shaft twist angle value comprises calculating a torque value based on the twist angle value.

8. The method according to claim 7, wherein determining a turbomachinery system shaft torque based on the shaft twist angle value further comprises calibrating out any differences between reflectance signals received from different locations along the at least one turbomachinery system shaft such that no measurable differences exist between measured signals associated with the optic fibers while the at least one shaft is stationary and prior to calculating the torque value.

9. The method according to claim 3, wherein determining a turbomachinery system shaft torque or vibration characteristic based on at least one characteristic of the reflected signals comprises:

determining a turbomachinery system shaft fundamental vibration frequency and a desired number of higher order harmonic turbomachinery system shaft vibration frequencies based on the plurality of received reflectance signals; and

determining a turbomachinery system shaft torsional vibration based on the shaft fundamental vibration frequency and shaft higher order harmonic shaft vibration mode frequencies.

10. The method according to claim 3, wherein transmitting light to an optical encoded turbomachinery system shaft comprises transmitting light to a shaft having a texture defined by altering the surface depth of desired shaft surface areas relative to other shaft surface areas to alter the texture of the surface of the shaft.

11. The method according to claim 3, wherein transmitting light to an optical encoded turbomachinery system shaft comprises transmitting light to a shaft having a short length v-groove through the surface of the shaft at desired locations such that the corresponding time delay can be detected from any two v-groove locations to determine the shaft twist angle value by differentiating their reflectance pattern signatures during each rotating cycle.

12. The method according to claim 3, wherein transmitting light to an optical encoded turbomachinery system shaft comprises transmitting light to a shaft having a periodic pattern or aperiodic chirped straight line pattern on or through the surface of the shaft at desired locations such that the corresponding time delay can be detected from any of two pattern locations to determine the shaft twist angle value by differentiating their reflectance pattern signatures during each rotating cycle.

13. The method according to claim 1, wherein determining a turbomachinery system shaft torque or vibration characteristic based on at least one characteristic of the reflected signals comprises:

determining a turbomachinery system shaft fundamental vibration frequency and a desired number of higher order harmonic turbomachinery system shaft vibration mode frequencies based on the plurality of received reflectance signals; and

determining a turbomachinery system shaft flexural vibration based on the shaft fundamental vibration frequency and shaft higher order harmonic shaft vibration frequencies.

14. The method according to claim 1, wherein transmitting light to a plurality of shaft surface locations on a turbomachinery system via a plurality of optic fiber bundles, the plurality of shaft surface locations together arranged in a substantially axial direction between the ends of at least one turbomachinery system shaft, such that a plurality of light signals are reflected from the plurality of locations while at least one shaft is rotating, comprises transmitting light via a multifurcated fiber bundle element and, receiving reflected light via a bifurcated fiber bundle element, and further wherein each optic fiber bundle associated with a shaft location is coupled to a respective reflectance probe placed in close proximity to the surface of the at least one turbomachinery shaft.

15. The method according to claim 1, wherein transmitting light to a plurality of shaft surface locations on a turbomachinery system via a plurality of optic fiber bundles, the plurality of shaft surface locations together arranged in a substantially axial direction between the ends of at least one turbomachinery shaft, such that a plurality of light signals are received from the plurality of locations while the at least one shaft is rotating, comprises transmitting light from a light source selected from a single wavelength light source, a LED light source, a broadband light source, and a multi-chromatic light source, operating either in continuous mode or in frequency modulated pulsed mode.

16. A system for sensing turbomachinery system shaft static and dynamic torques, vibration modes and associated operation status, the sensing system comprising:

a light source configured to transmit light to a surface of at least one turbomachinery system shaft through a plurality of optical fiber bundles disposed at a plurality of locations in proximity to the surface of the at least one shaft, the plurality of locations together arranged in a substantially axial direction between the ends of the at least one shaft;

an array of photodetectors, CCD or CMOS detectors configured to detect dynamic light reflected from the at least one turbomachinery system shaft surface in response to the transmitted light during rotation of the at least one turbomachinery system shaft and generate dynamic reflected light signals there from; and

a sensing mechanism configured to determine a torque or vibration on the at least one turbomachinery system shaft in response to the dynamic reflected light signal signatures or pattern recognition based on time-domain and frequency-domain signal processes.

17. The system according to claim 16, wherein the at least one turbomachinery system shaft is optical encoded.

18. The system according to claim 17, wherein the vibration is a torsional vibration.

19. The system according to claim 17, wherein the optical encoded shaft comprises an optical encoding mechanism attached onto or embedded into the surface of the shaft either by directly laser micromachining, laser marking or welding.

20. The system according to claim 17, wherein the optical encoded shaft comprises an encoding mechanism implemented via altering the surface depth of desired shaft surface areas relative to other shaft surface areas to alter the texture of the surface of the shaft such that the optical encoding mitigates fault signal detection from rusted or dirty contaminated shaft surface areas.

21. The system according to claim 17, wherein the optical encoded shaft comprises an encoding mechanism selected from a v-groove disposed through the shaft surface at desired locations, a periodic or aperiodic chirped pattern disposed onto the shaft surface at desired locations, and a single straight line pattern disposed onto the shaft surface at desired locations, surrounding the shaft circumference in certain angles.

22. The system according to claim 21, wherein the optical encoding marks are symmetrically distributed around a shaft circumference.

23. The system according to claim 16, wherein the vibration is a flexural vibration.

24. The system according to claim 16, wherein the light source is selected from a single wavelength light source, a LED light source, a broadband superluminescent light source, and a multi-chromatic light source.

25. The system according to claim 16, wherein each optical fiber transmission line comprises a multi-furcated fiber bundle selected from plastic fibers, silica fibers, and sapphire fibers.

26. The system according to claim 16, wherein the photodetecting mechanism comprises a silicon-based photosensor array for visible signal detection.

27. The system according to claim 16, wherein the photodetecting mechanism comprises a silicon-based charge-couple detector (CCD) or CMOS for visible signal detection.

28. The system according to claim 16, wherein the photodetecting mechanism comprises a InGaAs or InGaNP based PIN diode or avalanch detector or arrays for near infrared signal detection.

29. The system according to claim 16, further comprising a 1×

2 or 1×

N reflectance probe corresponding to each optical fiber, each reflectance probe configured to transmit light received from the light source along its corresponding optical fiber bundle to the surface of the at least one shaft via a transmission leg of the reflectance probe and further configured to receive light reflected from the surface of the at least one shaft via a measurement leg of the reflectance probe.

30. The system according to claim 16, wherein the sensing mechanism comprises an industry accepted gold standard torque sensor for use with the respective at least one turbomachinery system shaft such that a measured shaft twist angle value corresponds to an absolute value of torque retrieved from a look-up table or from a formulas, or from a calibration transfer function.

31. The system according to claim 16, wherein the sensing mechanism comprises a signal processor configured to determine when the reflectance signatures of received light at a desired wavelength of interest exceeds a desired threshold, determine differential time delays associated with the reflected signal signatures, determine a shaft twist angle value based on the reflected signal differential time delays, and determine a shaft torque based on the shaft twist angle.

32. The system according to claim 31, wherein the signal processor with reflectance signal pattern recognition is further configured to calibrate out any differences between desired reflected signals to mitigate undesired measurable differences between the desired reflected signals.