GAS TURBINE ENGINE TEMPERATURE MEASUREMENT SYSTEM

Abstract

A temperature measurement system for a gas turbine engine, the gas turbine engine including, in axial flow sequence, a compressor section, a combustor section having plural fuel spray nozzles, and a turbine section. The temperature measurement system includes one or more optical thermometers, each optical thermometer configured to measure the temperature of a component washed by the working gas of the engine, the or each component being in the combustor section or the turbine section at a first position along the axis of the engine.

Claims

1-15. (canceled)

16. A temperature measurement system for a gas turbine engine, the gas turbine engine comprising, in axial flow sequence, a compressor section, a combustor section having plural fuel spray nozzles, and a turbine section; the temperature measurement system comprising one or more optical thermometers, each optical thermometer configured to measure the temperature of a component washed by the working gas of the engine, the or each component being in the combustor section or the turbine section at a first position along the axis of the engine.

17. The temperature measurement system according to claim 16, comprising a plurality of the optical thermometers in an optical thermometer array, the optical thermometer array configured to measure a circumferential temperature profile of the engine at the first position.

18. The temperature measurement system according to claim 17, wherein the number of optical thermometers within the optical thermometer array is equal to the number of fuel spray nozzles.

19. The temperature measurement system according to claim 16, wherein: the turbine section comprises a circumferential row of nozzle guide vanes at the entrance into the turbine section from the combustor section; and the or each optical thermometer is configured to measure the temperature of a respective nozzle guide vane.

20. The temperature measurement system according to claim 16, further comprising: one or more test bodies configured to be disposed in the combustor section or turbine section such that the or each test body is a component washed by the working gas of the engine.

21. The temperature measurement system according to claim 16, wherein: the or each optical thermometer comprises an optical fibre and a respective photodiode, the optical fibre comprising a first end configured to collect electromagnetic radiation emitted from the respective component, and a second end connected to the respective photodiode.

22. The temperature measurement according to claim 21, wherein the second end of the or each optical fibre is connected to the respective photodiode by coupling optics comprising one or more lenses.

23. The temperature measurement system according to claim 21, wherein the or each optical fibre comprises a sapphire optical fibre section.

24. The temperature measurement system according to claim 16, further comprising one or more thermocouples configured to measure working gas temperatures in the turbine section at a second position along the axis of the engine.

25. The temperature measurement system according to claim 24, wherein the or each thermocouple is a single immersion thermocouple.

26. The temperature measurement system according to claim 24, wherein the first position is upstream of the second position.

27. The temperature measurement system according to claim 24, comprising a plurality of the thermocouples in a thermocouple array configured to measure a circumferential temperature profile in the working gas.

28. The temperature measurement system according to claim 27, wherein the number of thermocouples in the thermocouple array is less than the number of fuel spray nozzles.

29. The temperature measurement system according to claim 27, further comprising one or more further thermocouples in a further thermocouple array and configured to measure a circumferential temperature profile in the working gas at a third position along the axis of the engine, the third position being downstream of the second position.

30. A gas turbine engine comprising, in axial flow sequence, a compressor section, a combustor section having plural fuel spray nozzles, and a turbine section; and wherein the gas turbine engine further comprises the temperature measurement system according to claim 16.

Description

SUMMARY OF THE FIGURES

[0034] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0035] FIG. 1 shows a longitudinal cross-section through a ducted fan gas turbine engine;

[0036] FIG. 2 shows schematically part of a longitudinal cross-section through the turbine section of a gas turbine engine;

[0037] FIGS. 3A-3C are schematics showing the positions of fuel spray nozzles, optical thermometers and thermocouples at an axial position along the engine in the turbine section, a first axial position in the turbine section, and second axial position in the turbine section, respectively; and

[0038] FIGS. 4A-4C show schematics of couplings between an optical fibre and a photodiode.

DETAILED DESCRIPTION OF THE INVENTION

[0039] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art.

[0040] With reference to FIG. 1, a ducted fan gas turbine engine is generally indicated at 10 and has a principal and rotational axis X-X. The engine comprises, in axial flow series, an air intake 11, a propulsive fan 12, an intermediate pressure compressor 13, a high-pressure compressor 14, combustor section 15, a high-pressure (HP) turbine 16, an intermediate pressure (IP) turbine 17, a low-pressure (LP) turbine 18 and a core engine exhaust nozzle 19. A nacelle generally surrounds the engine 10 and defines the intake 11, a bypass duct 22 and a bypass exhaust nozzle 23.

[0041] During operation, air entering the intake 11 is accelerated by the fan 12 to produce two air flows: a first air flow A into the intermediate-pressure compressor 13 and a second air flow B which passes through the bypass duct 22 to provide propulsive thrust. The intermediate-pressure compressor 13 compresses the air flow A directed into it before delivering that air to the high-pressure compressor 14 where further compression takes place.

[0042] The compressed air exhausted from the high-pressure compressor 14 is directed into the combustor section 15 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 16, 17, 18 that together form the turbine section 100, before being exhausted through the nozzle 19 to provide additional propulsive thrust. The high, intermediate and low-pressure turbines respectively drive the high and intermediate-pressure compressors 14, 13 and the fan 12 by suitable interconnecting shafts.

[0043] Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. By way of example such engines may have an alternative number of interconnecting shafts (e.g. two) and/or an alternative number of compressors and/or turbines. Further the engine may comprise a gearbox provided in the drive train from a turbine to a compressor and/or fan.

[0044] FIG. 2 shows schematically part of a longitudinal cross-section through the turbine section 100 of the gas turbine engine 10. The turbine section 100 of FIG. 2 contains the three turbines: the HP turbine 16, the IP turbine 17, and the LP turbine 18. Each turbine 16, 17, 18 connects to a respective interconnecting shaft, with the HP turbine 16 attached at one end of the HP compressor drive shaft 46, the IP turbine 17 connected to the IP drive shaft 47, and the LP turbine 18 connected to the LP shaft 48. The shafts are arranged concentrically, with the HP compressor drive shaft 46 outermost, followed by the IP drive shaft 47 and then the LP shaft 48 at the centre. In FIG. 2, the HP and IP turbines 16, 17 in the turbine section 100 of FIG. 2 are shown each having just a single circumferential row of turbine blades 36, 37, whereas the LP turbine 18 is shown having two circumferential rows of turbine blades 38, but other numbers of rows in each turbine are possible. Immediately upstream of each row of turbine blades 36, 37, 38 is positioned a corresponding circumferential row of nozzle guide vanes (NGVs) 26, 27, 28. The NGVs 26, 27, 28 are washed by the working gas of the engine and the rows of NGVs 26, 27, 28 deflect the working gas flow passing through the turbine section 100 so that each row of turbine blades 36, 37, 38 can extract energy the gas flow more efficiently. In the example of FIG. 2, there is shown one row of HP NGVs 26, one row of IP NGVs 27 and two rows of LP NGVs 28 corresponding to the respective rows of blades 36, 37, 38. Surrounding the turbines is the turbine casing 21. In FIG. 2, the temperature measurement system comprises both optical thermometers 30 and thermocouples 40, The optical thermometers 30 are provided in a circumferential optical thermometer array around the engine 10 and the thermocouples 40 are provided in a circumferential thermocouple array around the engine 10. The optical thermometers 30 are configured to measure the temperature of the HP NGVs 26 and the thermocouples 40 are configured to measure the working gas temperatures in the turbine section 100. The optical thermometers' measurement points are upstream of those of the thermocouples 40.

[0045] The optical thermometers 30 each comprise an optical fibre 32 and a photodiode 31, the optical fibre comprising a first end that is disposed in a thermo well within a respective HP NGV 26 and a second end connected to the photodiode 31. Since the optical thermometers 30 are configured to measure the temperature of respective HP NGVs 26, the first end of the optical fibre 32 of each optical thermometer 30 is disposed at a first position along the axis X-X of the engine at which the HP NGV 26 is positioned. Electromagnetic radiation is radiated from the surface of the thermo well in each HP NGV 26 and a portion of this radiation is collected by the first end of the respective optical fibre 32. The radiation collected by the first end of the optical fibre 32 is transmitted along the fibre to the photodiode 32, which converts the radiation into an electrical signal. The photodiodes 32 are located within an electronic photodiode sensing unit (EPSU) 33, with the EPSU 33 configured to determine the temperature of each of the HP NGVs 26 provided with an optical thermometer 30 from the signal generated by the respective photodiode 31. The thermo wells provided in the HP NGVs 26 have a geometry that produces a black body cavity i.e. a cavity having an emissivity equal to about one. Thermo wells approximate a black body cavity when the depth exceeds their diameter by a factor of at least five; by way of example, a thermo well in the HP NGV 26 may be cylindrical, having a diameter of 1.25 mm and a depth of 15 mm. By conducting calibration tests for the optical thermometers and thermo wells at known temperatures, the electrical signal generated by the photodiodes 31 in response to the radiation transmitted to them via their respective optical fibres 32 from the surface of the respective thermo wells can be converted into a temperature value.

[0046] The optical fibres 32 each comprise a sapphire optical fibre section and, optionally, a silica glass optical fibre section, the sapphire optical fibre section being used where the optical fibre 32 is exposed to harsh working conditions (primarily high temperatures) of turbine section 100 that a silica glass optical fibre section would not withstand (the same applies to optical thermometers configured to measure the temperature of a component in the combustor section 15). Sapphire is used for a section of the optical fibre 32 because it is highly inert and therefore able to withstand the high temperature environment of the turbine section 100. Transmitting the radiation from the thermo wells to the respective photodiodes 31 using optical fibres 32 allows the photodiodes 31 and the EPSU 33 to be located in a suitable environment where their electronic components will not be damaged by exposure to very high temperatures. The optical thermometers 30 have a measurement range from approximately 500? C. to 1800? C., with the highest measurement accuracy generally being provided for temperatures above 800? C. As the temperature of the component in which the thermo well is provided (i.e. the HP NGVs 26 in the case of FIG. 2) increases, the emissivity of the thermo well increases (typically non-linearly with temperature) and hence the signal strength and the accuracy of the temperature measurement improves at higher temperatures, which coincides with when it is most important to have an accurate measure of temperature, because it is at high temperatures that materials and cooling systems in the combustor section 15 and/or turbine section 100 experience the most exacting conditions.

[0047] The thermocouples 40 shown in FIG. 2 are single immersion thermocouples and are positioned downstream of the optical thermometers 30, being disposed at a second position along the axis X-X of the engine between the final row of LP NGVs 28 and the penultimate row of LP turbine blades 38. The thermocouples 40 have a temperature measurement range that covers the entire temperature range of the working gas at the second position, including at light-up and flame out. Accordingly, although the optical thermometers 30 may be unsuited to determining if the engine is lit, whether flame out has occurred, and what the temperature distribution is at low temperatures, the thermocouples 40 can be used for these tasks.

[0048] FIGS. 3A-3C show transverse cross-sections through the combustor section 15 and turbine section 100 of the gas turbine engine 10 in FIG. 2, and provide more detail on the circumferential distribution of components of the temperature measurement system.

[0049] FIG. 3A is a transverse cross-section through the combustor section 15 of the gas turbine engine 10. A plurality of fuel spray nozzles 50 are arranged circumferentially around the combustor, each fuel spray nozzle 50 generating a spray of fuel from fuel injected by a respective fuel injector 55. The combustor section 15 may take the form of a multi-chamber combustor, an annular-chamber combustor or a turbo-annular-chamber combustor. The combustor in FIG. 3A comprises twelve fuel spray nozzles 50 and respective fuel injectors 55, equiangularly spaced about the axis X-X of the engine. An engine electronic controller (EEC) 60 within a control system (i.e. a Full Authority Digital Electronic Controller (FADEC)) is able to exert control over fuel valves via a fuel metering unit (FMU) 65.

[0050] It is desirable to maintain a circumferential temperature profile within the combustor section 15 and turbine section 100 of the engine 10 that is as uniform as possible and as close to the set point temperature in the FADEC, so that the rate of wear of engine components is uniform (i.e. avoiding different angular sectors being exposed to substantially different temperatures over extended periods of time) and as low as possible.

[0051] Typically, as shown in the transverse cross-section of FIG. 3B through the turbine section 15 at the aforementioned first position, the temperature measurement system comprises a plurality of optical thermometers 30 (each in the form of an optical fibre 32 having a first end disposed in a thermo well and a second end connected to a respective photodiode (not shown in FIG. 3B) within the EPSU 33) equally spaced circumferentially around the turbine casing 21 in an array. The first position is in the HP turbine 16 (see FIG. 2), with the first end of each optical fibre 32 disposed in a thermo well provided in a respective HP NGV 26 (the HP NGVs 26 are not shown in FIG. 3B). In FIG. 3B, the positions of the fuel spray nozzles 50 are projected onto the cross section to indicate their positions relative the first ends of the optical fibres 32. Although in FIG. 3B the first end of each optical fibre 32 is circumferentially aligned with a respective fuel spray nozzle 50, in practice, the swirl of the gas flow through the engine, the mixing of gas from adjacent sectors down the engine and the fuel spray nozzles 50 spraying fuel into adjacent sectors means that there is not a simple correspondence between a single fuel spray nozzle 50 and a respective optical thermometer 30. Nevertheless, by positioning the optical thermometer array further upstream in the engine than a conventional thermocouple-based array and accounting for the above factors, the temperature measurement system can correlate the temperature at a certain circumferential position to the performance of one or more fuel spray nozzles 50.

[0052] FIG. 3C is a transverse cross section through the turbine section 100 at the aforementioned second position that is upstream of the final row of LP NGVs 38, but downstream of the penultimate row of turbine blades 28 in the LP turbine 18 (see FIG. 2). The temperature measurement system further comprises the four thermocouples 40 disposed such as to measure the temperatures of the working gas at this second position. The four thermocouples 40 are connected to the EEC 60 such that the temperatures they measure can inform control of the engine 10, and in particular the FMU 65. Similarly to FIG. 3B, the positions of the fuel spray nozzles 50 are projected onto the cross section to indicate their positions relative the thermocouples 40. The four thermocouples 40 form a thermocouple array configured to measure a circumferential temperature profile in the working gas, with the thermocouples 40 approximately equiangularly spaced around the turbine casing 21. There are fewer thermocouples 40 in the thermocouple array than there are optical thermometers 30 in the optical thermometer array and thus also fewer thermocouples 40 in the thermocouple array than there are fuel spray nozzles 50 in the combustor section 15. There is no one-to-one correspondence of thermocouples 40 to fuel spray nozzles 50 and in FIG. 3C the thermocouples 40 are shown not circumferentially aligned with a respective fuel spray nozzle 50.

[0053] A conventional working gas temperature measurement system for use in the turbine section of a gas turbine engine 10 typically comprises a greater number of thermocouples 40 than are shown in FIG. 3C. A common arrangement, for example, would be 14 dual immersion thermocouples 40 set up in two networks at different positions along the axis of the engine. However, due to the optical thermometer array disposed upstream of the thermocouple array in the present arrangement shown in FIGS. 2 and 3A-3C, it is possible to reduce the number of thermocouples 40 needed to accurately measure the temperature profile of the working gas at the second position in the turbine section 100. In particular, because the thermocouple array is positioned further downstream than the optical thermometer array, it is unnecessary to have as large a number of thermocouple measurement points, since the working gas should be well mixed and therefore closer to a homogenous temperature by the time it reaches this second position.

[0054] As discussed above, the thermocouples 40 generally have a different measurement range to the measurement range of the optical thermometers 30. In particular, the low temperature sensitivity of the thermocouples 40 allows them to detect events such as light-up and flame-out. However, because there are relatively few thermocouples 40 in the temperature measurement system, there may be a concern that the accuracy of the circumferential temperature profiles provided by the thermocouples 40 at low temperatures outside the measurement range of the optical thermometers 30 may be reduced. However, in practice this is not a significant problem because at such low temperatures the rate of wear on engine components is substantially lower than at normal operating temperatures, and consequently variations in the circumferential temperature profile at these low temperatures are unlikely to lead to major damage to the components of the turbine section 100.

[0055] Although not illustrated in FIGS. 2 and 3A-3C, the temperature measurement system may include a further thermocouple array configured to measure a circumferential temperature profile in the working gas at a third position along the axis of the engine, the third position being downstream of the second position. The further thermocouple array is typically configured in a similar manner to the thermocouple array illustrated in FIG. 3C. However, the further thermocouple array may contain fewer thermocouples than the thermocouple array configured to measure working gas temperatures at the second position. This may be based on the third position being even further downstream along the axis of the engine than the second position (and therefore the temperature profile is expected to be more uniform than at the second position), and/or space constraints within the engine.

[0056] In the forgoing description of FIGS. 3A-3C, the thermo wells into which the first end of the optical fibres 32 of the optical thermometers 30 are disposed are provided in the HP NGVs 26. However, a thermo well for an optical thermometer 30 can also be provided in other components of the gas turbine engine. By way of example, a thermo well can be provided in the lining of the combustor in order to measure the combustor liner temperature. Alternatively, a test body may be disposed in the combustor section 15 or the turbine section 100 such that it is washed by the working gas of the engine and a thermo well can be provided in the test body for the first end of an optical fibre 32 to be inserted into.

[0057] FIGS. 4A-4C provide schematics of possible couplings between the optical fibre 32 and the photodiode 31 within an optical thermometer 30. In both FIG. 4A and FIG. 4B, coupling optics are interposed between the optical fibre 32 and the photodiode 31 to focus the radiation exiting the second end of the optical fibre onto the photodiode 31. In FIG. 4C coupling optics are omitted.

[0058] In FIG. 4A, the second end of the optical fibre 32 is placed up to the photodiode 31 with two lenses 34a and 34b interposed therebetween. Lens 34a is a collimating lens and lens 34b then focusses the collimated radiation on to the photodiode 31. This arrangement ensures that any minor misalignment in any of the three axes will not result in signal reduction or loss. Likewise, any vibrations should not cause the radiation transmitted by the optical fibre 32 to fall outside detection region of the photodiode 31. The arrangement in FIG. 4A is versatile in that it allows the photodiode 31 to be changed to a different configuration without needing the coupling optics to be modified.

[0059] In FIG. 4B, the second end of the optical fibre 32 is placed up to the photodiode 31 with a single lens 34 interposed therebetween, which both collects the radiation transmitted by the optical fibre and focusses this onto the photodiode 31. The coupling optics illustrated in FIG. 4B allow the coupling between the optical fibre 32 and the photodiode 31 to be made much more compact than the arrangement in FIG. 4A. However, this is at the expense of versatility-changes to the fibre 32 and/or the detector 32 would likely require modification of the coupling optics.

[0060] In FIG. 4C, the second end of the optical fibre 32 is placed up to the photodiode directly 31, without any lenses interposed therebetween. In order to facilitate this arrangement, the fibre width, photodiode window and their relative positions are arranged such that the rays of light from the fibre are contained within the window of the photodiode. The arrangement in FIG. 4C allows the space occupied by the coupling to be reduced in comparison to the arrangements of FIGS. 4A and 4B.

[0061] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0062] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0063] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0064] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0065] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word comprise and include, and variations such as comprises, comprising, and including will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0066] It must be noted that, as used in the specification and the appended claims, the singular forms a, an, and the include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent about, it will be understood that the particular value forms another embodiment. The terms about and approximately in relation to a numerical value is optional and means for example +/?10%.

LIST OF FEATURES

[0067] Gas turbine engine 10 [0068] Air intake 11 [0069] Propulsive fan 12 [0070] Intermediate-pressure compressor 13 [0071] High-pressure compressor 14 [0072] Combustor section 15 [0073] High-pressure turbine 16 [0074] Intermediate-pressure turbine 17 [0075] Low-pressure turbine 18 [0076] Core engine exhaust nozzle 19 [0077] Turbine casing 21 [0078] Bypass duct 22 [0079] Bypass exhaust nozzle 23 [0080] High-pressure nozzle guide vane 26 [0081] Intermediate-pressure nozzle guide vane 27 [0082] Low-pressure nozzle guide vane 28 [0083] Optical thermometer 30 [0084] Photodiode 31 [0085] Optical Fibre 32 [0086] Electronic photodiode sensing unit 33 [0087] Lens 34, 34a, 34b [0088] High-pressure turbine blade row 36 [0089] Intermediate-pressure turbine blade row 37 [0090] Low-pressure turbine blade row 38 [0091] Thermocouple 40 [0092] High-pressure compressor drive cone 46 [0093] Intermediate-pressure drive shaft 47 [0094] Low-pressure shaft 48 [0095] Fuel spray nozzle 50 [0096] Fuel injector 55 [0097] Engine electronic controller 60 [0098] Fuel metering unit 65 [0099] Turbine section 100