GB2441782A - Apparatus for measurement of temperature - Google Patents

Apparatus for measurement of temperature Download PDF

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Publication number
GB2441782A
GB2441782A GB0618254A GB0618254A GB2441782A GB 2441782 A GB2441782 A GB 2441782A GB 0618254 A GB0618254 A GB 0618254A GB 0618254 A GB0618254 A GB 0618254A GB 2441782 A GB2441782 A GB 2441782A
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GB
United Kingdom
Prior art keywords
optical fibre
length
connector
temperature
etalon
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.)
Withdrawn
Application number
GB0618254A
Other versions
GB0618254D0 (en
Inventor
John David Black
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rolls Royce PLC
Original Assignee
Rolls Royce PLC
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Rolls Royce PLC filed Critical Rolls Royce PLC
Priority to GB0618254A priority Critical patent/GB2441782A/en
Publication of GB0618254D0 publication Critical patent/GB0618254D0/en
Publication of GB2441782A publication Critical patent/GB2441782A/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
    • G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
    • G01K11/3206—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres at discrete locations in the fibre, e.g. using Bragg scattering

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Temperature Or Quantity Of Heat (AREA)

Abstract

An apparatus 10 for measuring temperature comprises at least three lengths of optical fibre 14, 16, 18 and at least two connectors 20, 22. A first length 14 of optical fibre is connected to a second length 16 of optical fibre by a first connector 20 and the first length is spaced from the second length by a gap or an etalon 28. The second length of optical fibre is connected to a third length 18 of optical fibre by a second connector 22 and the second length is spaced from the third length by a gap or an etalon 28. A light source 12 transmits light into the optical fibre and a light detector 24 detects light in the optical fibre. An analyser 26 analyses the detected light to determine the dimensions of the gaps or the thicknesses of the etalons and hence the temperatures at the connectors.

Description

2441782
1
AN APPARATUS FOR MEASUREMENT OF TEMPERATURE
The present invention relates to an apparatus for measuring temperature, in particular to an apparatus for 5 measuring the temperature in high temperature environments, for example in a gas turbine engine or a solid oxide fuel cell stack.
Accordingly the present invention seeks to provide a novel apparatus for measuring temperature. 10 Accordingly the present invention provides an apparatus for measuring temperature comprising at least three lengths of optical fibre and at least two connectors, a first length of optical fibre being connected to a second length of optical fibre by a first connector, the first 15 length of optical fibre being spaced from the second length of optical fibre by a gap or by an etalon, the second length of optical fibre being connected to a third length of optical fibre by a second connector, the second length of optical fibre being spaced from the third length of 20 optical fibre by a gap or by an etalon, a light source to transmit light into the optical fibre,, a light detector to detect light in the optical fibre and an analyser to analyse the detected light to determine the distance between the first optical fibre and the second optical 25 fibre and hence the temperature at the first connector and to determine the distance between the second optical fibre and the third optical fibre and hence the temperature at the second connector.
Preferably the optical fibre is a sapphire optical 30 fibre.
Preferably the etalon is a sapphire etalon.
Preferably the first connector comprises a hollow connector body, the hollow connector body has a first tapering surface and a second tapering surface, a first 35 collett abutting the first tapering surface to hold the first optical fibre, a second collett abutting the second tapering surface to hold the second optical fibre, a first biasing means to bias the first collet against the first
tapering surface and a second biasing means to bias the second collett against the second tapering surface.
Preferably the first biasing means and the second biasing means comprise screws.
5 Preferably the first connector comprises a ceramic hollow connector body. Preferably the ceramic hollow connector body comprises alumina. Preferably the screws comprise a ceramic. Preferably the screws comprise alumina.
10 Preferably the apparatus comprises more than three lengths of optical fibre and more than two connectors to measure the temperature at more than two connectors.
Preferably the apparatus is arranged in a solid oxide fuel cell stack to measure the temperature at two or more 15 connectors corresponding to two or more positions in the solid oxide fuel cell stack.
Preferably the gap or the thickness of the etalon in the first connector is different to the gap or the thickness in the second connector.
20 Alternatively the apparatus is arranged in a gas turbine engine to measure the temperature at two or more connectors corresponding to two or more positions in the gas turbine engine.
The present invention will be more fully described by 25 way of example with reference to the accompanying drawings in which:-
Figure 1 shows an apparatus for measuring temperature according to the present invention.
Figure 2 shows an enlarged cross-sectional view of a 30 connector and first and second lengths of optical fibre forming an apparatus for measuring temperature according to the present invention.
Figure 3 shows an enlarged cross-sectional view of an alternative connector and first and second lengths of 35 optical fibre forming an apparatus for measuring temperature according to the present invention.
An apparatus 10 for measuring temperature according to the present invention is shown in figures 1 and 2. The apparatus 10 for measuring temperature comprises a light
source 12, a plurality of lengths of optical fibre 14, 16 and 18, a plurality of connectors 20 and 22, a light detector 24 and an analyser 26. The light source 12 may be a laser. The lengths of optical fibre 14, 16 and 18 may be 5 lengths of quartz fibre, lengths of sapphire fibre or lengths of other suitable optical fibre, quartz fibre is suitable for use up to a temperature of about 750°C and sapphire fibre is suitable for use up to a temperature of about 1800°C. Note, sapphire optical fibre is capable of 10 withstanding very high temperatures, but it is difficult to manufacture in long lengths.
The lengths of optical fibre 14, 16 and 18 are joined using the connectors 20 and 22. In particular a first length of optical fibre 14 is connected to a second length 15 of optical fibre 16 by a first connector 20 and the first length of optical fibre 14 is spaced from the second length of optical fibre 16 by a gap 28. The second length of optical fibre 16 is connected to a third length of optical fibre 18 by a second connector 22 and the second length of 20 optical fibre 16 is spaced from the third length of optical fibre 18 by a gap 28.
The light source 12 transmits light into the first length of optical fibre 14 and the light detector 24 detects light in the first length of optical fibre 14. The 25 analyser 26 analyses the detected light to determine the distance, the length of the gap 28, between the first length of optical fibre 14 and the second length of optical fibre 16 in the first connector 20 and hence the temperature at the first connector 20. The analyser 26 30 analyses the detected light to determine the distance, the length of the gap 28, between the second length of optical fibre 16 and the third length of optical fibre 18 in the second connector 22 and hence the temperature at the second connector 22.
35 The connector 20, shown more clearly in figure 2,
comprises a hollow cylindrical connector body 40 and the hollow connector body 40 has a first end 42 and a second end 44. The hollow connector body 40 has an internal surface 46, which is has a first cylindrical surface 48 at
4
the first end 42 and has a second cylindrical surface 50 at the second end 44. The first cylindrical surface 48 is connected to the second cylindrical surface 50 by a first tapering surface, a first conical surface, 52, a third 5 cylindrical surface 56 and a second tapering surface, a second conical surface, 54. The first and second cylindrical surfaces 48 and 50 have the same diameter and the third cylindrical surface 56 has a smaller diameter than the first and second cylindrical surfaces 48 and 50 10 such that the first tapering surface 52 increases in diameter from the third cylindrical surface 56 to the first cylindrical surface 48 and the second tapering surface 54 increases in diameter from the third cylindrical surface 56 to the second cylindrical surface 54.
15 A first end 60 of the first length of optical fibre 14
is positioned coaxially in the first end 42 of the hollow cylindrical connector body 40 of the connector 20 and a first end 62 of the second length of optical fibre 16 is positioned coaxially in the second end 46 of the hollow 20 cylindrical connector body 40 of the connector 20. A first collett 64 abuts the first tapering surface 52 to hold the first length of optical fibre 14 and a second collett 66 abuts the second tapering surface 54 to hold the second length of optical fibre 16. The first cylindrical surface 25 48 and the second cylindrical surface 50 are provided with screw threads 68 and 70 respectively.
A first biasing means, a first screw, 72 is positioned in the first end 42 of the hollow cylindrical connector body 40 of the connector 20 to bias the first collet 64 30 against the first tapering surface 52 and a second biasing means, a second screw, 74 is positioned in the second end 44 of the hollow cylindrical connector body 40 of the connector 20 to bias the second collett 66 against the second tapering surface 54. The first and second biasing 35 means, first and second screws, 72 and 74 are threaded into screw threads 68 and 70 respectively to bias the first and second colletts 64 and 66 against the first and second tapering surfaces 52 and 54 respectively such that the first and second colletts 64 and 66 are pushed radially
inwardly against the first and second lengths of optical fibre 14 and 16. The first and second screws 72 and 74 preferably comprise grub screws.
In figure 2 an air gap 28 is provided between the 5 first length of optical fibre 14 and the second length of optical fibre 16 to form a Fabry-Perot cavity.
An alternative connector 120, is shown in figure 3, and is substantially the same as the connector 20 shown in figure 2. The connector 120 differs in that an etalon 128 10 is positioned between the first length of optical fibre 14 and the second length of optical fibre 16 to form a Fabry-Perot etalon and in figure 3 the distance, thickness, of the Fabry-Perot etalon is measured.
The connectors 20 and 22 comprise a ceramic hollow 15 connector body, for example the ceramic hollow connector body comprise alumina. The screws comprise a ceramic, for example alumina.
When light is transmitted into the length of optical fibre some of the light is reflected from the optical 20 fibre/air gap interface or optical fibre/etalon interface in each connector. The reflected light is subject to interference effects due to multiple reflections within the Fabry-Perot cavity producing periodic modulation of the reflected light intensity with wavelength. If a
25 monochromatic light, e.g. laser light, is used it may be scanned in wavelength, or if a broadband light source is used reflected light may be analysed using a scanning filter to give a trace of light intensity versus wavelength, from which the modulation period is determined. 30 The modulation period is dependent on the distance between the ends of the lengths of optical fibre, e.g. the distance of the Fabry-Perot cavity gap or the thickness of the Fabry-Perot etalon.
As the connector expands due to temperature, the 35 Fabry-Perot cavity gap/Fabry-Perot etalon thickness increases, decreasing the modulation period and giving a measure of the temperature. When a number of connectors are used in series the initial gap between the lengths of optical fibre, or the thickness of the etalons may be
6
different in each connector, so that reflected light signals from individual connectors may be identified.
Either two lengths of optical fibre may be held in each connector so that their polished ends form a Fabry-5 Perot cavity with a gap, an air gap, between them or a solid Fabry-Perot etalon, a solid sapphire Fabry-Perot etalon or a solid quartz Fabry-Perot etalon, may be placed between and abutted against the polished ends of the lengths of optical fibre. The ends of the lengths of 10 optical fibre may have reflective coatings if required.
The apparatus for measuring temperatures is applicable for use on gas turbine engines, on solid oxide fuel cell stacks, on other types of internal combustion engines, on other types of fuel cell stacks and also for other 15 applications.
The apparatus for measuring temperature allows the temperature to be measured at a plurality of positions through one optical fibre lead out compared to thermocouples which require one lead out per sensor. The 20 apparatus for measuring temperature is not electrically conducting, which is advantageous in solid oxide fuel cell stacks.
It may be possible to use a metallic connector, e.g. the connector body and metallic screws, if there is no 25 requirement for a non-conducting connector. It may be possible to hold the lengths of optical fibre in the connector using other devices rather than a collet and screw.
30
7

Claims (1)

  1. Claims:-
    1. An apparatus for measuring temperature comprising at least three lengths of optical fibre and at least two connectors, a first length of optical fibre being connected 5 to a second length of optical fibre by a first connector, the first length of optical fibre being spaced from the second length of optical fibre by a gap or by an etalon, the second length of optical fibre being connected to a third length of optical fibre by a second connector, the 10 second length of optical fibre being spaced from the third length of optical fibre by a gap or by an etalon, a light source to transmit light into the optical fibre, a light detector to detect light in the optical fibre and an analyser to analyse the detected light to determine the 15 distance between the first optical fibre and the second optical fibre and hence the temperature at the first connector and to determine the distance between the second optical fibre and the third optical fibre and hence the temperature at the second connector.
    20 2. An apparatus as claimed in claim 1 wherein the lengths of optical fibre comprise sapphire optical fibre.
    3. An apparatus as claimed in claim 1 or claim 2 wherein the etalon is a sapphire etalon.
    4. An apparatus as claimed in any of claims 1 to 3 25 wherein the first connector comprises a hollow connector body, the hollow connector body has a first tapering surface and a second tapering surface, a first collett abutting the first tapering surface to hold the first optical fibre, a second collett abutting the second 30 tapering surface to hold the second optical fibre, a first biasing means to bias the first collet against the first tapering surface and a second biasing means to bias the second collett against the second tapering surface.
    5. An apparatus as claimed in claim 4 wherein the first 35 connector comprises a ceramic hollow connector body.
    6. An apparatus as claimed in claim 5 wherein the ceramic hollow connector body comprises alumina.
    8
    7. An apparatus as claimed in claim 4, claim 5 or claim 6 wherein the first biasing means and the second biasing means comprise screws.
    8. An apparatus as claimed in claim 7 wherein the screws 5 comprise a ceramic.
    9. An apparatus as claimed in claim 8 wherein the screws comprise alumina.
    10. An apparatus as claimed in any of claims 1 to 9 wherein the gap or the thickness of the etalon in the first
    10 connector is different to the gap or the thickness in the second connector.
    11. An apparatus as claimed in any of claims 1 to 10 wherein the apparatus comprises more than three lengths of optical fibre and more than two connectors to measure the
    15 temperature at more than two connectors.
    12. An apparatus as claimed in any of claims 1 to 11 wherein the apparatus is arranged in a solid oxide fuel cell stack to measure the temperature at two or more connectors corresponding to two or more positions in the
    20 solid oxide fuel cell stack.
    13. An apparatus as claimed in any of claims 1 to 11 wherein the apparatus is arranged in a gas turbine engine to measure the temperature at two or more connectors corresponding to two or more positions in the gas turbine
    25 engine.
    14. An apparatus for measuring temperature substantially as hereinbefore described with reference to and as shown in figures 1 and 2 of the accompanying drawings.
    15. An apparatus for measuring temperature substantially 30 as hereinbefore described with reference to and as shown in figures 1 and 3 of the accompanying drawings.
GB0618254A 2006-09-16 2006-09-16 Apparatus for measurement of temperature Withdrawn GB2441782A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB0618254A GB2441782A (en) 2006-09-16 2006-09-16 Apparatus for measurement of temperature

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0618254A GB2441782A (en) 2006-09-16 2006-09-16 Apparatus for measurement of temperature

Publications (2)

Publication Number Publication Date
GB0618254D0 GB0618254D0 (en) 2006-10-25
GB2441782A true GB2441782A (en) 2008-03-19

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GB (1) GB2441782A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR3087008A1 (en) * 2018-10-08 2020-04-10 Commissariat A L'energie Atomique Et Aux Energies Alternatives TEMPERATURE SENSOR WITH DEFORMATION-INSENSITIVE BRAGG ARRAY

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62257034A (en) * 1986-04-30 1987-11-09 Sumitomo Electric Ind Ltd Temperature sensor
US4861979A (en) * 1986-05-30 1989-08-29 Societe Anonyme Dite Compagnie Generale D'electricite Optical fiber multipoint measuring device with time multiplexing
US4950886A (en) * 1989-06-30 1990-08-21 Claus Richard O Partially reflecting optical fiber splice for temperature and strain measurement
US5301001A (en) * 1992-02-12 1994-04-05 Center For Innovative Technology Extrinsic fiber optic displacement sensors and displacement sensing systems
US5698848A (en) * 1995-06-07 1997-12-16 Mcdonnell Douglas Corporation Fiber optic sensing systems and methods including contiguous optical cavities
US5869835A (en) * 1995-12-22 1999-02-09 Udd; Eric Asymmetric fiber optic grating sensor
GB2347209A (en) * 1999-02-22 2000-08-30 Univ Cranfield Fibre optic sensing

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62257034A (en) * 1986-04-30 1987-11-09 Sumitomo Electric Ind Ltd Temperature sensor
US4861979A (en) * 1986-05-30 1989-08-29 Societe Anonyme Dite Compagnie Generale D'electricite Optical fiber multipoint measuring device with time multiplexing
US4950886A (en) * 1989-06-30 1990-08-21 Claus Richard O Partially reflecting optical fiber splice for temperature and strain measurement
US5301001A (en) * 1992-02-12 1994-04-05 Center For Innovative Technology Extrinsic fiber optic displacement sensors and displacement sensing systems
US5698848A (en) * 1995-06-07 1997-12-16 Mcdonnell Douglas Corporation Fiber optic sensing systems and methods including contiguous optical cavities
US5869835A (en) * 1995-12-22 1999-02-09 Udd; Eric Asymmetric fiber optic grating sensor
GB2347209A (en) * 1999-02-22 2000-08-30 Univ Cranfield Fibre optic sensing

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR3087008A1 (en) * 2018-10-08 2020-04-10 Commissariat A L'energie Atomique Et Aux Energies Alternatives TEMPERATURE SENSOR WITH DEFORMATION-INSENSITIVE BRAGG ARRAY
WO2020074808A1 (en) * 2018-10-08 2020-04-16 Commissariat A L'energie Atomique Et Aux Energies Alternatives Deformation-insensitive bragg grating temperature sensor

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Publication number Publication date
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