Apparatus and method for detecting a damaged rotary machine aerofoil

• US 6,659,712 B2
• Filed: 06/18/2002
• Issued: 12/09/2003
• Est. Priority Date: 07/03/2001
• Status: Expired due to Term

• Current Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Inventors: Rowe, Arthur L, Horswill, Michael A, Brooks, Richard V
• Primary Examiner(s): Nguyen, Ninh H.
• Application Number:
  US10/173,116
• Publication Number:
  US 20030007861A1
• Time in Patent Office: 539 Days
• Field of Search: 415/1, 415/30, 415/118, 416/38, 416/42, 416/61, 731/16
• US Class Current: 415/1
• CPC Class Codes: F01D 17/04 responsive to load
• CPC Class Codes: F01D 17/06 responsive to speed
• 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 21/14 responsive to other specific conditions
• CPC Class Codes: F05D 2270/301 Pressure
• CPC Class Codes: F05D 2270/304 Spool rotational speed
• CPC Class Codes: F05D 2270/52 by electrical means, e.g. relays or switches
• CPC Class Codes: G01M 15/12 by monitoring vibrations
• CPC Class Codes: G01M 15/14 Testing gas-turbine engines or jet-propulsion engines
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

A gas turbine engine (10) comprises a fan rotor (26) having a plurality of fan blades (24) and an apparatus (34) for detecting damage to the fan blades (24). The apparatus (34) comprises a transducer (36) arranged to detect the pressure in the gas flow around the fan blades (34) and to produce a pressure signal. A speed sensor (48) is arranged to measure the speed of rotation of the fan rotor (26) and to produce a speed signal. A processor unit (40) analyses the pressure signal and the speed signal to detect changes in the amplitude of the pressure signal, which occur at multiples of the rotational frequency of the fan rotor (24). The changes indicate differences in pressure between the gas flow around a damaged fan blade (24) and the gas flow around the remainder of the fan blades (24). The processor unit (40) sends a signal indicative of damage to a fan blade (24), if the difference in pressure is above the predetermined level, to an indicator device (44, 46).

Claims

1. A rotary machine comprising a plurality of aerofoils arranged in a set, an apparatus for detecting damage to at least one of the aerofoils in the set, the apparatus for detecting damage to at least one of the aerofoils in the set comprising at least one pressure transducer arranged to detect the pressure in the fluid flow around the aerofoils in the set and to produce a pressure signal corresponding to said pressure, a processor unit arranged to analyse the pressure signal to determine if the difference in pressure between the fluid flow around at least one of the aerofoils in the set and the fluid flow around the remainder of the aerofoils in the set is above a predetermined level, the processor unit is arranged to produce a signal indicative of damage to at least one of the aerofoils in the set if the difference in pressure is above the predetermined level and to send the signal to an indicator device.

2. A rotary machine as claimed in claim 1 wherein the machine comprises a rotor and a stator, the aerofoils are rotor blades mounted on the rotor and the at least one pressure transducer is mounted on the stator.

3. A rotary machine as claimed in claim 2 wherein the rotor blades are gas turbine engine fan blades or gas turbine engine compressor blades.

4. A rotary machine as claimed in claim 2 wherein a speed sensor is arranged to detect the speed of rotation of the rotor and to produce a speed signal corresponding to said speed, the processor unit being arranged to analyse the speed signal to determine the rotational frequency of the rotor, the processor unit being arranged to analyse the pressure signals and the rotational frequency of the rotor to detect changes in the amplitude of the pressure which occur at the same frequency as, or at multiples of the rotational frequency of, the rotational frequency of the rotor.

5. A rotary machine as claimed in claim 2 wherein a casing is arranged around the rotor blades and the casing partially defines a duct in which the rotor blades rotate.

6. A rotary machine as claimed in claim 5 wherein the at least one pressure transducer is arranged in the casing.

7. A rotary machine as claimed in claim 5 wherein the at least one pressure transducer is arranged in the duct.

8. A rotary machine as claimed in claim 1 wherein the machine comprises a rotor and a stator, the aerofoils are stator vanes mounted on the stator and the at least one pressure transducer is mounted on the rotor.

9. A rotary machine as claimed in claim 8 wherein the stator vanes are gas turbine engine fan outlet guide vanes or gas turbine engine compressor vanes.

10. A rotary machine as claimed in claim 1 wherein the pressure transducer has a low pass mechanical sensitivity to detect low frequency fluctuations in pressure.

11. A rotary machine as claimed in claim 1 comprising a low pass electrical filter arranged to filter the pressure signal before it is analysed by the processor unit.

12. A rotary machine as claimed in claim 1 comprising a low pass acoustic filter arranged to filter the pressure in the gas flow around the aerofoils before it is detected by the pressure transducer.

13. A rotary machine as claimed in claim 1 wherein the processor unit has means to sample the pressure signal at high frequency and means to perform a Fourier transformation.

14. A rotary machine as claimed in claim 1 wherein the at least one pressure transducer is arranged upstream of the aerofoils or downstream of the aerofoils.

15. A method of detecting damage to a rotary machine aerofoil, the machine comprising a plurality of aerofoils arranged in a set, the method comprising detecting the pressure in the fluid flow around the aerofoils in the set and producing a pressure signal corresponding to said pressure, analysing the pressure signal to determine if the difference in pressure between the fluid flow around at least one of the aerofoils in the set and the gas flow around the remainder of the aerofoils in the set is above a predetermined level, producing a signal indicative of damage to at least one of the aerofoils in the set if the difference in pressure is above the predetermined level and sending the signal to an indicator device.

16. A method as claimed in claim 15 wherein the machine comprises a rotor and a stator, the aerofoils are rotor blades mounted on the rotor and the at least one pressure transducer is mounted on the stator.

17. A method as claimed in claim 16 wherein the rotor blades are gas turbine engine fan blades or gas turbine engine compressor blades, the method comprising detecting the pressure in the fluid flow around the fan blades or detecting the pressure in the fluid flow around the compressor blades.

18. A method as claimed in claim 16 comprising measuring the speed of rotation of the rotor, analysing the speed of rotation of the rotor to determine the rotational frequency of the rotor, analysing the pressure signals and the rotational frequency to detect changes in the amplitude of the static pressure which occur at the same frequency as, or at multiples of the rotational frequency of, the rotational frequency of the rotor.

19. A method as claimed in claim 16 wherein a casing is arranged around the rotor blades and the casing partially defines a duct in which the rotor blades rotate.

20. A method as claimed in claim 19 comprising detecting the pressure using at least one pressure transducer arranged in the casing.

21. A method as claimed in claim 19 comprising detecting the pressure using at least one pressure transducer arranged in the duct.

22. A method as claimed in claim 15 wherein the machine comprises a rotor and a stator, the aerofoils are stator vanes mounted on the stator and the at least one pressure transducer is mounted on the rotor.

23. A method as claimed in claim 22 wherein the stator vanes are gas turbine engine fan outlet guide vanes or gas turbine engine compressor vanes, the method comprising detecting the pressure in the fluid flow around the fan outlet guide vanes or detecting the pressure in the fluid flow around the compressor vanes.

24. A method as claimed in claim 15 comprising detecting low frequency fluctuations in pressure.

25. A method as claimed in claim 15 comprising filtering the pressure signal before it is analysed using a low pass electrical filter.

26. A method as claimed in claim 15 comprising filtering the pressure in the gas flow around the rotor blades before it is detected using a low pass acoustic filter.

27. A method as claimed in claim 15 comprising sampling the pressure signal at high frequency and performing a Fourier transformation.

28. A method as claimed in claim 15 comprising detecting the pressure upstream of the aerofoils or downstream of the aerofoils.