GB2449709A - Method and apparatus for determining a clearance between relatively movable components - Google Patents

Method and apparatus for determining a clearance between relatively movable components Download PDF

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Publication number
GB2449709A
GB2449709A GB0710560A GB0710560A GB2449709A GB 2449709 A GB2449709 A GB 2449709A GB 0710560 A GB0710560 A GB 0710560A GB 0710560 A GB0710560 A GB 0710560A GB 2449709 A GB2449709 A GB 2449709A
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GB
United Kingdom
Prior art keywords
relatively movable
movable components
abradable material
optical
distance
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
GB0710560A
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GB0710560D0 (en
Inventor
Harold Heyworth
John David Black
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Rolls Royce PLC
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Rolls Royce PLC
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Filing date
Publication date
Application filed by Rolls Royce PLC filed Critical Rolls Royce PLC
Priority to GB0710560A priority Critical patent/GB2449709A/en
Publication of GB0710560D0 publication Critical patent/GB0710560D0/en
Publication of GB2449709A publication Critical patent/GB2449709A/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D11/00—Preventing or minimising internal leakage of working-fluid, e.g. between stages
    • F01D11/08—Preventing or minimising internal leakage of working-fluid, e.g. between stages for sealing space between rotor blade tips and stator
    • F01D11/12—Preventing or minimising internal leakage of working-fluid, e.g. between stages for sealing space between rotor blade tips and stator using a rubstrip, e.g. erodible. deformable or resiliently-biased part
    • F01D11/122—Preventing or minimising internal leakage of working-fluid, e.g. between stages for sealing space between rotor blade tips and stator using a rubstrip, e.g. erodible. deformable or resiliently-biased part with erodable or abradable material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D21/00—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for
    • F01D21/003—Arrangements for testing or measuring
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D21/00—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for
    • F01D21/04—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for responsive to undesired position of rotor relative to stator or to breaking-off of a part of the rotor, e.g. indicating such position
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D66/00—Arrangements for monitoring working conditions, e.g. wear, temperature
    • F16D66/02—Apparatus for indicating wear
    • F16D66/021—Apparatus for indicating wear using electrical detection or indication means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D66/00—Arrangements for monitoring working conditions, e.g. wear, temperature
    • F16D66/02—Apparatus for indicating wear
    • F16D66/021—Apparatus for indicating wear using electrical detection or indication means
    • F16D66/026—Apparatus for indicating wear using electrical detection or indication means indicating different degrees of lining wear
    • F16D66/027—Sensors therefor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D66/00—Arrangements for monitoring working conditions, e.g. wear, temperature
    • F16D66/02—Apparatus for indicating wear
    • F16D66/021—Apparatus for indicating wear using electrical detection or indication means
    • F16D66/028—Apparatus for indicating wear using electrical detection or indication means with non-electrical sensors or signal transmission, e.g. magnetic, optical
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/14—Measuring arrangements characterised by the use of optical techniques for measuring distance or clearance between spaced objects or spaced apertures
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
    • G01B21/02—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness
    • G01B21/08—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness for measuring thickness
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
    • G01B21/16—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring distance of clearance between spaced objects
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
    • G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/14—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring distance or clearance between spaced objects or spaced apertures

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)

Abstract

An apparatus 60 for determining a clearance between relatively movable components 30,46, such as a stator and the rotor blades of a gas turbine engine, in which an abradable material 48 is arranged on a first one 46 of the components 30,46. A first probe 51 measures a first distance D1 from a datum position 49 to a second one 30 of the components 30,46. A second probe 52 measures a second distance D2 from the datum position 49 to the surface 47 of the abradable material 48 on the first one 46 of the components 30,46. An analyser 56 subtracts the second distance D2 from the first distance D1 to determine the clearance 50 between the components 30,46. The second probe 52 may comprise at least one optical member 55 arranged to extend to different depths within the abradable material 48. At least one radiation detector 54 is arranged to detect radiation in the at least one optical member 55 and the analyser 56 is arranged to detect a difference in the radiation collected in the optical member 55 at different depths in the abradable material 48 and hence the amount of wear of the abradable material 48 produced by the components 30,46.

Description

A METHOD AND AN APPARATUS FOR DETERMINING A CLEARANCE
BETWEEN RELATIVELY MOVABLE COMPONENTS
The present invention relates to a method and an apparatus for determining a clearance between relatively movable components, in particular to a method and an apparatus for determining a clearance between a rotor and a stator, more particularly to a method and an apparatus for determining a clearance between rotor blades and a stator casing.
The clearance between turbine rotor blades and a turbine casing and the clearance between compressor rotor blades and a compressor casing in a gas turbine engine is critical in obtaining good fuel consumption, i.e. good efficiency.
In conventional designs of gas turbine engines, the rotor blades may interact with the stator casing and the stator casings are provided with an abradable lining.
During operation of the gas turbine engine the clearance between the tips of the rotor blades and the stator casing gradually becomes greater, leading to reduction in efficiency and increase in fuel consumption.
Without a knowledge of the amount of wear of the abradable lining of the stator casing it is impossible to estimate the clearance and hence actively change the clearance.
Accordingly the present invention seeks to provide a novel apparatus for determining a clearance between relatively movable components, which reduces or overcomes, the above-mentioned problem.
Accordingly the present invention provides an apparatus for determining a clearance between relatively movable components, an abradable material arranged on a first one of the relatively movable components, the apparatus comprising a first probe to measure a first distance from a datum position to a second one of the relatively movable components, a second probe to measure a second distance from the datum position to the surface of the abradable material on the first one of the relatively movable components and an analyser to subtract the second distance from the first distance to determine the clearance between the relatively movable components.
Preferably the first probe comprises a capacitance probe.
Preferably the second probe comprises at least one optical member arranged within the abradable material, the at least one optical member extending to different depths within the abradable material such that different portions of the at least one optical member are at different distances from the second one of the relatively movable components, at least one radiation detector being arranged to detect radiation in the at least one optical member, an analyser being arranged to analyse the radiation collected by the at least one optical member, the analyser being arranged to detect a difference in the radiation collected in the optical member at different depths in the abradable material and hence the amount of wear of the abradable material produced by the relatively movable components.
Preferably the at least one optical element comprises a plurality of optical fibres.
Preferably the optical fibres extend to different depths within the abradable material such that a first end of each optical fibre is at a different distance from the second one of the relatively movable components, the second end of each optical fibre is arranged to supply radiation to the at least one radiation detector.
Preferably the ends of the optical fibre are arranged on the surface of a cone.
Alternatively the ends of the optical fibres are arranged on the surface of an ellipse.
Alternatively the optical fibres extend to different depths within the abradable material such that a portion of each optical fibre is at a different distance from the second one of the relatively movable components, both ends of each optical fibre are arranged to supply radiation to the at least one radiation detector.
Alternatively the optical element has a conical surface or an elliptical surface.
Preferably the optical member comprises sapphire.
Preferably the analyser being arranged to detect a difference in the peak wavelengths or a difference in the maximum intensity at the peak wavelength.
Alternatively the second probe comprises a plurality of electrical circuits arranged within the abradable material, the electrical circuits extending to different depths within the abradable material such that different electrical circuits are at different distances from the second one of the relatively movable components, the analyser being arranged to detect which electrical circuits have been broken and which electrical circuits are intact and hence the amount of wear of the abradable material produced by the relatively movable components.
Preferably the first relatively movable member is a stator casing and the second relatively movable member is a rotor.
Preferably the rotor includes a plurality of rotor blades.
Preferably the rotor blades are turbine rotor blades.
Alternatively the rotor blades are compressor rotor blades.
The present invention also provides a method of determining a clearance between relatively movable components, arranging an abradable material on a first one of the relatively movable components, measuring a first distance from a datum position to a second one of the relatively movable components, measuring a second distance from the datum position to the surface of the abradable material on the first one of the relatively movable components and subtracting the second distance from the first distance to determine the clearance between the relatively movable components.
Preferably using a capacitance probe to measure the first distance.
Preferably arranging at least one optical member within the abradable material to measure the second distance, arranging the at least one optical member to extend to different depths within the abradable material such that different portions of the at least one optical member are at different distances from the second one of the relatively movable components, detecting radiation in the at least one optical member, analysing the radiation collected by the at least one optical member, detecting a difference in the radiation collected in the optical member at different depths in the abradable material and hence the amount of wear of the abradable material produced by the relatively movable components.
Preferably a plurality of optical fibres are arranged in the abradable material.
Preferably the optical fibres are arranged to extend to different depths within the abradable material such that a first end of each optical fibre is at a different distance from the second one of the relatively movable components, detecting radiation at the second end of each optical fibre.
The ends of the optical fibres may be arranged on the surface of a cone.
The ends of the optical fibres may be arranged on the surface of an ellipse.
The optical fibres may be arranged to extend to different depths within the abradable material such that a portion of each optical fibre is at a different distance from the second one of the relatively movable components, detecting radiation at both ends of each optical fibre.
An optical element may be provided with a conical surface or an elliptical surface.
A sapphire optical member may be provided.
A difference in the peak wavelengths or a difference in the maximum intensity at the peak wavelength may be detected.
Alternatively arranging a plurality of electrical circuits within the abradable material to measure the second distance, arranging the electrical circuits to extend to different depths within the abradable material such that different electrical circuits are at different distances from the second one of the relatively movable components, detecting which electrical circuits have been broken and which electrical circuits are intact and hence the amount of wear of the abradable material produced by the relatively movable components.
Preferably the first relatively movable member is a stator casing and the second relatively movable member is a rotor.
Preferably the rotor includes a plurality of rotor blades.
Preferably the rotor blades are turbine rotor blades.
Alternatively the rotor blades are compressor rotor blades.
The present invention will be more fully described by way of example with reference to the accompanying drawings in which:-Figure 1 shows a turbofan gas turbine engine having an apparatus for determining a clearance between relatively movable components according to the present invention.
Figure 2 shows an enlarged view of an apparatus for determining a clearance between a rotor blade and a stator casing according to the present invention.
Figure 3 shows an enlarged view of another apparatus for determining a clearance between a rotor blade and a stator casing according to the present invention.
Figure 4 shows an enlarged view of a further apparatus for determining a clearance between a rotor blade and a stator casing according to the present invention.
Figure 5 shows an enlarged view of an alternative apparatus for determining a clearance between a rotor blade and a stator casing according to the present invention.
Figure 6 is a graph of intensity against wavelength for radiation in a turbine at temperatures at two different temperatures.
A turbofan gas turbine engine 10, as shown in figure 1, comprises in axial flow series an intake 12, a fan section 14, a compressor section, 16, a combustion section 18, a turbine section 20 and a core exhaust 22. The turbine section 20 comprises a high-pressure turbine 24 arranged to drive a high-pressure compressor (not shown) in the compressor section 16, an intermediate pressure turbine 26 arranged to drive an intermediate pressure compressor (not shown) in the compressor section 16 and a low pressure turbine 28 arranged to drive a fan (not shown) in the fan section 14.
The high-pressure turbine 24 of the turbine section 20 is shown more clearly in figure 2. The high-pressure turbine 24 comprises one or more stages of turbine rotor blades 30 arranged alternately with one or more stages of turbine stator vanes 32. Each of the turbine rotor blades comprises a root 34, a shank 36, a platform 38 and an aerofoil 40. The turbine rotor blades 30 are arranged circumferentially around a turbine rotor 42 and the turbine rotor blades 30 extend generally radially from the turbine rotor 42. The roots 34 of the turbine rotor blades 30 are located in circumferentially, or axially, extending slots 44 in the periphery of the turbine rotor 42. The platforms 36 of the turbine rotor blades 30 together define the inner boundary of a portion of the flow path through the high-pressure turbine 24. The aerofoils 40 of the turbine rotor blades 30 have tips 44 at their radially outer extremities.
The turbine rotor blades 30 are enclosed by a generally cylindrical, or conical, stator casing 46, which is provided with an abradable material 48 on its inner surface. The tips 44 of the turbine rotor blades 30 are spaced from the abradable material 48 by a clearance 50.
The abradable material 48 forms a lining on the inner surface of the stator casing 46.
An apparatus 60 for determining the clearance 50, distance C, between the tips 44 of the turbine rotor blades and the abradable material 48 on the stator casing 46 is provided, as shown in figures 2, 2A and 2B. The apparatus comprises a first probe 51 to measure a first distance Dl from a datum position 49 to the tips 44 of the turbine rotor blades 30 and a second probe 52 to measure a second distance D2 from the datum position 49 to the surface 47 of the abradable material 48 on the stator casing 46 and an analyser 56 to subtract the second distance D2 from the first distance Dl to determine the clearance 50, distance C, between the tips 44 of the turbine zotor blades 30 and the surface 47 of the abradable material 48. The datum position 49 is any suitable position and in this example is the outer surface 49 of the stator casing 46. The surface 47 is the inner surface of the abradable material 48. Thus the true clearance between the tips 44 of the turbine rotor blades 30 and the surface 47 of the abradable material 48 is calculated from the thickness of the abradable material 48 as measured by the second probe 52 and the distance measured by the first probe 51.
The first probe 51 comprises a capacitance probe, although other suitable probes may be used.
The second probe 52 comprises a plurality of optical members, optical fibres, 55 arranged within the abradable material 48. The optical members, optical fibres, 55 extend to different depths from the stator casing 46 within the abradable material 48 such that a first end 55A of each of the optical members, optical fibres, 55 is at a different distance from the tips 44 of the turbine rotor blades 30 to the first ends 55A of the some of the other optical members, optical fibres, 55. At least one radiation detector 54 is arranged to detect radiation in the optical members, optical fibres, 55. The second ends 55B of the optical members, optical fibres, 55 are optically connected to the radiation detector 54. An analyser 56 is arranged to analyse the radiation collected by the optical members, optical fibres, 55. The analyser 56 is arranged to detect a difference in the radiation collected in the optical members, optical fibres, 55 at different depths in the abradable material 48 and hence the amount of wear of the abradable material 48 produced by the turbine rotor blades 30 moving relative to the stator casing 46. The analyser 56 senses radiation when the first end 55A of an optical member, optical fibre, 55 is uncovered, e.g. when the abradable material 48 is worn away to uncover the first end 55A of the optical member, optical fibre, 55. The analyser 56 senses black body radiation from the high-pressure turbine 24 when the first end 55A of an optical member, optical fibre, 55 is uncovered and in particular the analyser 56 detects a difference in the peak wavelengths of the radiation between the uncovered and covered first ends 55A of the optical members 55, i.e. it detects a reduction in the peak wavelength of the radiation in an uncovered first end 55A of an optical fibre 55 relative to a covered first end 55A of an optical fibre 55.
Alternatively the analyser 56 detects a difference in the maximum intensity at the peak wavelength between the uncovered and covered first ends 55A of the optical members 55, i.e. it detects an increase in the intensity of the radiation in an uncovered end 55A of an optical fibre 55 relative to a covered first end 55A of an optical fibre 55.
It is to be noted that after an optical fibre 55 has been uncovered by the passage of a turbine rotor blade 30, it is possible for the optical fibre 55 to be recovered by pollutants, worn abradable material when the turbine rotor blade 30 has passed the optical fibre 55.
Figure 6 shows the intensity against wavelength for radiation emitted at temperatures of 1000K and 1500K. A temperature of 1000K is a typical temperature of a stator casing 46 and a temperature of 1500K is a typical temperature of a turbine rotor blade 30. Thus, it is seen that at a temperature of 1500K the intensity of the radiation emitted at the peak wavelength is much greater than the intensity of the radiation emitted at the peak wavelength at a temperature of 1000K. It is also seen that at a temperature of 1500K the peak wavelength of the radiation emitted is at a lower wavelength than the peak wavelength at a temperature of 1000K.
An alternative apparatus 60B for determining the clearance 50 between the tips 44 of the turbine rotor blades 30 and the abradable material 48 on the stator casing 46 is shown in figure 3. The apparatus 60B is substantially the same as that shown in figure 2 and like parts are denoted by like numerals. This differs in that the first ends 55A of the optical members 55 are arranged substantially on the surface of a cone.
Another apparatus 60C for determining the clearance 50 between the tips 44 of the turbine rotor blades 30 and the abradable material 48 on the stator casing 46 is shown in figure 4. The apparatus 60C is substantially the same as that shown in figure 1 and like parts are denoted by like numerals. This differs in that the optical members, the optical fibres, 55 extend to different depths within the abradable material 48 such that a portion 55C of each optical member, optical fibre, 55 is at a different distance from the tips 44 of the turbine rotor blades 30.
In this example both ends of each optical member, optical fibre, 55 are arranged to supply radiation to the at least one radiation detector 54. In this case the optical members 55 have portions 55D extending to the portions 55C and portions 55E returning from the portions 55C. The analyser 56 senses radiation when the portion 55C of an optical member, optical fibre, 55 is cut/broken, e.g. when the abradable material 48 is worn away to cut/break the portion 55C of the optical member, optical fibre 55. The portions 55C of different optical members 55 are arranged at different distances from the tips 44 of the turbine rotor blades 30, e.g. at different depths within the abradable material 48.
Another apparatus 60D for determining the clearance 50 between the tips 44 of the turbine rotor blades 30 and the abradable material 48 on the stator casing 46 is shown in figure 5. The apparatus 60D is substantially the same as that shown in figure 2 and like parts are denoted by like numerals. This differs in that a single optical member 55 is provided and it is arranged to have a substantially conical surface 55F. Alternatively, the single member 55 may have an elliptical surface or a parabolic surface.
Although the present invention has been described with reference to a second probe comprising a plurality of optical elements extending to different depths in the abradable material it is equally possible to use a second probe comprising a plurality of electrical circuits arranged within the abradable material, the electrical circuits extending to different depths within the abradable material such that different electrical circuits are at different distances from the second one of the relatively movable components, the analyser being arranged to detect which electrical circuits have been broken and which electrical circuits are intact and hence the amount of wear of the abradable material produced by the relatively movable components.
Other second probes suitable for use in the present invention are a plurality of thermocouples or a Fabry-Perot etalon, whose thickness may be measured optically from radially outside the stator casing.
The present invention allows correction for the worn nature of the abradable material and hence a more accurate determination of the clearance between the turbine rotor blades and the turbine casing may be made. The present invention provides a passive apparatus and requires no external power supply. The present invention is optical in nature and hence is not susceptible to electromagnetic interference. The apparatus does not require a cooling flow of coolant, e.g. air, if the optical member comprises sapphire. The apparatus is dormant and does not require cleaning. The apparatus is installed in the turbine casing from one side only. The apparatus may comprise for example twenty optical fibres, each optical fibre is 0.2mm in diameter and the apparatus has a final diameter of 4mm, however it may be possible to make the apparatus smaller in diameter. The apparatus may be capable of use to temperatures in excess of 2000K if the optical fibres comprise sapphire.
It is possible to provide a plurality of the apparatus aligned and spaced apart axially in the turbine casing to monitor wear in the axial extent and to monitor relative axial movement of the turbine rotor blades.
Although the present invention has been described with reference to unshrouded turbine rotor blades it is equally applicable to shrouded turbine rotor blades.
The optical fibres may be solid optical fibres or hollow optical fibres e.g. photonic crystal optical fibres.
Although the present invention has been described with reference to the measurement of a clearance between relatively rotating components, rotor blades and a stator casing, of a gas turbine engine it is equally applicable to the measurement of a clearance between stator vanes and a rotor of a gas turbine engine or between other rotor and stator components of a gas turbine engine. The present invention is also applicable to measurement of clearance between brake disc and a brake pad by determining brake disc wear, refractory lining wear, bearing wear, internal combustion engine cylinder wear etc.

Claims (40)

  1. Claims: - 1. An apparatus for determining a clearance between
    relatively movable components, an abradable material arranged on a first one of the relatively movable components, the apparatus comprising a first probe to measure a first distance from a datum position to a second one of the relatively movable components, a second probe to measure second distance from the datum position to the surface of the abradable material on the first one of the relatively movable components and an analyser to subtract the second distance from the first distance to determine the clearance between the relatively movable components.
  2. 2. An apparatus as claimed in claim 1 wherein the first probe comprises a capacitance probe.
  3. 3. An apparatus as claimed in claim 1 or claim 2 wherein the second probe comprising at least one optical member arranged within the abradable material, the at least one optical member extending to different depths within the abradable material such that different portions of the at least one optical member are at different distances from the second one of the relatively movable components, at least one radiation detector being arranged to detect radiation in the at least one optical member, an analyser being arranged to analyse the radiation collected by the at least one optical member, the analyser being arranged to detect a difference in the radiation collected in the optical member at different depths in the abradable material and hence the amount of wear of the abradable material produced by the relatively movable components.
  4. 4. An apparatus as claimed in claim 3 wherein the at least one optical element comprises a plurality of optical fibres.
  5. 5. An apparatus as claimed in claim 4 wherein the optical fibres extend to different depths within the abradable material such that a first end of each optical fibre is at a different distance from the second one of the relatively movable components, the second end of each optical fibre is arranged to supply radiation to the at least one radiation detector.
  6. 6. An apparatus as claimed in claim 5 wherein the ends of S the optical fibre are arranged on the surface of a cone.
    1. An apparatus as claimed in claim 5 wherein the ends of the optical fibres are arranged on the surface of an ellipse.
  7. 7. An apparatus as claimed in claim 3 or claim 4 wherein the optical fibres extend to different depths within the abradable material such that a portion of each optical fibre is at a different distance from the second one of the relatively movable components, both ends of each optical fibre are arranged to supply radiation to the at least one radiation detector.
  8. 8. An apparatus as claimed in claim 3 wherein the optical element has a conical surface or an elliptical surface.
  9. 9. An apparatus as claimed in any of claims 3 to 9 wherein the optical member comprises sapphire.
  10. 10. An apparatus as claimed in any of claims 3 to 10 wherein the analyser being arranged to detect a difference in the peak wavelengths or a difference in the maximum intensity at the peak wavelength.
  11. 11. An apparatus as claimed in claim 1 or claim 2 wherein the second probe comprising a plurality of electrical circuits arranged within the abradable material, the electrical circuits extending to different depths within the abradable material such that different electrical circuits are at different distances from the second one of the relatively movable components, the analyser being arranged to detect which electrical circuits have been broken and which electrical circuits are intact and hence the amount of wear of the abradable material produced by the relatively movable components.
  12. 12. An apparatus as claimed in any of claims 1 to 12 wherein the first relatively movable member is a stator casing and the second relatively movable member is a rotor.
  13. 13. An apparatus as claimed in claim 13 wherein the rotor includes a plurality of rotor blades.
  14. 14. An apparatus as claimed in claim 14 wherein the rotor blades are turbine rotor blades.
  15. 15. An apparatus as claimed in claim 14 wherein the rotor blades are compressor rotor blades.
  16. 16. An apparatus as claimed in any of claims 1 to 16 wherein the relatively movable components are components of a gas turbine engine.
  17. 17. An apparatus for determining a clearance between relatively movable components substantially as hereinbefore described with reference to and as shown in figures 1 and 2 of the accompanying drawings.
  18. 18. An apparatus for determining a clearance between relatively movable components substantially as hereinbefore described with reference to and as shown in figures 1 and 3 of the accompanying drawings.
  19. 19. An apparatus for determining a clearance between relatively movable components substantially as hereinbefore described with reference to and as shown in figures 1 and 4 of the accompanying drawings.
  20. 20. An apparatus for determining a clearance between relatively movable components substantially as hereinbefore described with reference to and as shown in figures 1 and 5 of the accompanying drawings.
  21. 21. A method of determining a clearance between relatively movable components, arranging an abradable material on a first one of the relatively movable components, measuring a first distance from a datum position to a second one of the relatively movable components, measuring a second distance from the datum position to the surface of the abradable material on the first one of the relatively movable components and subtracting the second distance from the first distance to determine the clearance between the relatively movable components.
  22. 22. A method as claimed in claim 22 comprising measuring the first distance using a capacitance probe.
  23. 23. A method as claimed in claim 22 or claim 23 comprising arranging at least one optical member within the abradable material to measure the second distance, arranging the at least one optical member to extend to different depths within the abradabj.e material such that different portions of the at least one optical member are at different distances from the second one of the relatively movable components, detecting radiation in the at least one optical member, analysing the radiation collected by the at least one optical member, detecting a difference in the radiation collected in the optical member at different depths in the abradable material and hence the amount of wear of the abradable material produced by the relatively movable components.
  24. 24. A method as claimed in claim 24 comprising arranging a plurality of optical fibres in the abradable material.
  25. 25. A method as claimed in claim 24 comprising arranging the optical fibres to extend to different depths within the abradable material such that a first end of each optical fibre is at a different distance from the second one of the relatively movable components, detecting radiation at the second end of each optical fibre.
  26. 26. A method as claimed in claim 26 comprising arranging the first ends of the optical fibres on the surface of a cone.
  27. 27. A method as claimed in claim 26 comprising arranging the first ends of the optical fibres on the surface of an ellipse.
  28. 28. A method as claimed in claim 24 comprising arranging the optical fibres to extend to different depths within the abradable material such that a portion of each optical fibre is at a different distance from the second one of the relatively movable components, detecting radiation at both ends of each optical fibre.
  29. 29. A method as claimed in claim 29 comprising providing an optical element with a conical surface or an elliptical surface.
  30. 30. A method as claimed in any of claims 24 to 30 comprising providing a sapphire optical member.
  31. 31. A method as claimed in any of claims 24 to 31 comprising detecting a difference in the peak wavelengths or a difference in the maximum intensity at the peak wavelength.
  32. 32. A method as claimed in claim 22 or claim 23 comprising arranging a plurality of electrical circuits within the abradab].e material to measure the second distance, is arranging the electrical circuits to extend to different depths within the abradable material such that different electrical circuits are at different distances from the second one of the relatively movable components, detecting which electrical circuits have been broken and which electrical circuits are intact and hence the amount of wear of the abradable material produced by the relatively movable components.
  33. 33. A method as claimed in any of claims 22 to 33 wherein the first relatively movable member is a stator casing and the second relatively movable member is a rotor.
  34. 34. A method as claimed in claim 34 wherein the rotor includes a plurality of rotor blades.
  35. 35. A method as claimed in claim 35 wherein the rotor blades are turbine rotor blades.
  36. 36. A method as claimed in claim 35 wherein the rotor blades are compressor rotor blades.
  37. 37. A method of determining a clearance between relatively movable components substantially as hereinbefore described with reference to and as shown in figures 1 and 2 of the accompanying drawings.
  38. 38. A method of determining a clearance between relatively movable components substantially as hereinbefore described with reference to and as shown in figures 1 and 3 of the accompanying drawings.
  39. 39. A method of determining a clearance between relatively movable components substantially as hereinbefore described with reference to and as shown in figures 1 and 4 of the accompanying drawings.
  40. 40. A method of determining a clearance between relatively movable components substantially as hereinbefore described with reference to and as shown in figures 1 and 5 of the accompanying drawings.
GB0710560A 2007-06-02 2007-06-02 Method and apparatus for determining a clearance between relatively movable components Withdrawn GB2449709A (en)

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