Condition determination of a gas turbine engine

Abstract

Disclosed herein is a method of automatically determining an operating condition of at least part of a gas turbine engine 10 for an aircraft, the method comprising: measuring one or more gas pressure waves by a gas pressure detector 401, wherein the gas pressure detector 401 is located in the gas turbine engine 10; and automatically determining, by a computing system, an operating condition of at least part of a gas turbine engine 10 in dependence on an output signal of the gas pressure detector 401.

Claims

1. A method of automatically determining an operating condition of at least part of a gas turbine engine for an aircraft, the method comprising: measuring one or more gas pressure waves by a gas pressure detector, wherein the gas pressure detector is located in the gas turbine engine and comprises an acoustic element, and the acoustic element has a directional sensitivity; and automatically determining, by a computing system, an operating condition of the at least part of the gas turbine engine in dependence on an output signal of the gas pressure detector, wherein: the gas pressure detector comprises a plurality of acoustic elements; each acoustic element has directional sensitivity; and all of the acoustic elements have different orientations such that the gas pressure detector is able to detect gas pressure waves with substantially the same sensitivity in all of the directions that a respective acoustic element is orientated in.

2. The method according to claim 1, further comprising measuring one or more gas pressure waves by one or more further gas pressure detectors, wherein: the one or more further gas pressure detectors are located in the gas turbine engine; and said automatically determining of the operating condition is also dependent on the output signal from each of the one or more further gas pressure detectors.

3. The method according to claim 1, wherein the computing system performs a Fourier Transform on the output signal of the gas pressure detector to generate a frequency domain version of the output signal.

4. The method according to claim 1, wherein said automatically determining of the operating condition comprises comparing, by the computing system, the output signal of the gas pressure detector with one or more predetermined signals.

5. The method according to claim 4, wherein: the computing system performs a Fourier Transform on the output signal of the gas pressure detector to generate a frequency domain version of the output signal; and said comparing of the output signal of the gas pressure detector with the one or more predetermined signals is a comparison of the frequency domain version of the output signal with the one or more predetermined signals.

6. The method according to claim 1, further comprising filtering, by the computing system, the output signal of the gas pressure detector.

7. The method according to claim 1, further comprising: monitoring, by the computing system, the operating condition of the at least part of the gas turbine engine; and detecting, by the computing system, a change in the operating condition.

8. The method according to claim 7, further comprising determining, by the computing system, a type of the change in the operating condition of the at least part of the gas turbine engine in dependence on comparison of the output signal of the gas pressure detector with one or more predetermined signals.

9. The method according to claim 8, wherein: the determined type of the change includes a pipe cracking, bursting and/or leaking; and/or the determined type of the change comprises a type of pipe that a change has occurred in, including at least one of a cabin air pipe, anti-ice air pipe or handling bleed pipe.

10. The method according to claim 7, further comprising determining a location of the change.

11. The method according to claim 10, further comprising measuring one or more gas pressure waves by one or more further gas pressure detectors, wherein: the one or more further gas pressure detectors are located in the gas turbine engine; said automatically determining of the operating condition is also dependent on the output signal from each of the one or more further gas pressure detectors; and the location of the change is determined in dependence on a difference in time of arrival of gas pressure waves received at two or more of the gas pressure detectors.

12. The method according to claim 1, wherein the acoustic elements are arranged to form a substantially spherical shape such that the sensitivity of the gas pressure detector is substantially the same in all directions around the gas pressure detector.

13. The method according to claim 1, wherein: each acoustic element comprises an acoustic sensor and a housing; and the housing is a horn wave guide.

14. The method according to claim 1, wherein the gas pressure detector is located in a fire zone of the gas turbine engine.

15. The method according to claim 1, further comprising impacting the gas turbine engine, wherein the automatically determining of the operating condition of the at least part of the gas turbine engine is dependent on one or more gas pressure waves caused by the impact.

16. A system comprising a gas turbine engine for an aircraft and a computing system, wherein: the gas turbine engine comprises one or more gas pressure wave detectors; and the computing system is arranged to automatically detect the operating condition of the at least part of the gas turbine engine according to the method of claim 1.

17. The system according to claim 16, wherein the gas turbine engine further comprises: an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan comprising a plurality of fan blades; and a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft.

18. The system according to claim 17, wherein: the turbine is a first turbine, the compressor is a first compressor, and the core shaft is a first core shaft; the engine core further comprises a second turbine, a second compressor, and a second core shaft connecting the second turbine to the second compressor; and the second turbine, second compressor, and second core shaft are arranged to rotate at a higher rotational speed than the first core shaft.

19. A gas pressure detector comprising: a plurality of acoustic elements, wherein sensitivity of detection of a gas pressure wave by each acoustic element is dependent on a direction that the acoustic element is aligned in relative to a direction of propagation of the gas pressure wave, wherein: all of the acoustic elements have different orientations such that the gas pressure detector is able to detect gas pressure waves with substantially the same sensitivity in all of the directions that an acoustic element is orientated in; and the acoustic elements are arranged to form a substantially spherical shape such that the sensitivity of the gas pressure detector is substantially the same in all directions around the gas pressure detector.

20. The gas pressure detector according to claim 19, wherein: each acoustic element comprises an acoustic sensor and a horn wave guide; the acoustic element is arranged at a first end of the horn wave guide; and a second end of the horn wave guide, that is opposite the first end of the horn wave guide, is shaped as a polygon in a cross-section that is orthogonal to a longitudinal axis of the horn wave guide.

21. The gas pressure detector according to claim 19, wherein the acoustic elements are arranged such that a shape of the gas pressure detector is a dodecahedron.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments will now be described by way of example only, with reference to the Figures, in which:

(2) FIG. 1 is a sectional side view of a gas turbine engine;

(3) FIG. 2 is a close up sectional side view of an upstream portion of a gas turbine engine;

(4) FIG. 3 is a partially cut-away view of a gearbox for a gas turbine engine;

(5) FIG. 4 is a cross-section along the longitudinal axis of a gas turbine engine according to an embodiment;

(6) FIG. 5 is a cross-section of a gas turbine engine according to an embodiment, wherein the cross-section is orthogonal to the longitudinal axis of the gas turbine engine;

(7) FIG. 6 is an acoustic element according to an embodiment;

(8) FIG. 7 shows an arrangement of a plurality of acoustic elements according to an embodiment; and

(9) FIG. 8 is a flowchart of a method according to an embodiment.

DETAILED DESCRIPTION

(10) FIG. 1 illustrates a gas turbine engine 10 having a principal rotational axis 9. The engine 10 comprises an air intake 12 and a propulsive fan 23 that generates two airflows: a core airflow A and a bypass airflow B. The gas turbine engine 10 comprises a core 11 that receives the core airflow A. The engine core 11 comprises, in axial flow series, a low pressure compressor 14, a high-pressure compressor 15, combustion equipment 16, a high-pressure turbine 17, a low pressure turbine 19 and a core exhaust nozzle 20. A nacelle 21 surrounds the gas turbine engine 10 and defines a bypass duct 22 and a bypass exhaust nozzle 18. The bypass airflow B flows through the bypass duct 22. The fan 23 is attached to and driven by the low pressure turbine 19 via a shaft 26 and an epicyclic gearbox 30.

(11) In use, the core airflow A is accelerated and compressed by the low pressure compressor 14 and directed into the high pressure compressor 15 where further compression takes place. The compressed air exhausted from the high pressure compressor 15 is directed into the combustion equipment 16 where it is mixed with fuel and the mixture is combusted. The resultant hot combustion products then expand through, and thereby drive, the high pressure and low pressure turbines 17, 19 before being exhausted through the nozzle 20 to provide some propulsive thrust. The high pressure turbine 17 drives the high pressure compressor 15 by a suitable interconnecting shaft 27. The fan 23 generally provides the majority of the propulsive thrust. The epicyclic gearbox 30 is a reduction gearbox.

(12) An exemplary arrangement for a geared fan gas turbine engine 10 is shown in FIG. 2. The low pressure turbine 19 (see FIG. 1) drives the shaft 26, which is coupled to a sun wheel, or sun gear, 28 of the epicyclic gear arrangement 30. Radially outwardly of the sun gear 28 and intermeshing therewith is a plurality of planet gears 32 that are coupled together by a planet carrier 34. The planet carrier 34 constrains the planet gears 32 to precess around the sun gear 28 in synchronicity whilst enabling each planet gear 32 to rotate about its own axis. The planet carrier 34 is coupled via linkages 36 to the fan 23 in order to drive its rotation about the engine axis 9. Radially outwardly of the planet gears 32 and intermeshing therewith is an annulus or ring gear 38 that is coupled, via linkages 40, to a stationary supporting structure 24.

(13) Note that the terms “low pressure turbine” and “low pressure compressor” as used herein may be taken to mean the lowest pressure turbine stages and lowest pressure compressor stages (i.e. not including the fan 23) respectively and/or the turbine and compressor stages that are connected together by the interconnecting shaft 26 with the lowest rotational speed in the engine (i.e. not including the gearbox output shaft that drives the fan 23). In some literature, the “low pressure turbine” and “low pressure compressor” referred to herein may alternatively be known as the “intermediate pressure turbine” and “intermediate pressure compressor”. Where such alternative nomenclature is used, the fan 23 may be referred to as a first, or lowest pressure, compression stage.

(14) The epicyclic gearbox 30 is shown by way of example in greater detail in FIG. 3. Each of the sun gear 28, planet gears 32 and ring gear 38 comprise teeth about their periphery to intermesh with the other gears. However, for clarity only exemplary portions of the teeth are illustrated in FIG. 3. There are four planet gears 32 illustrated, although it will be apparent to the skilled reader that more or fewer planet gears 32 may be provided within the scope of the claimed invention. Practical applications of a planetary epicyclic gearbox 30 generally comprise at least three planet gears 32.

(15) The epicyclic gearbox 30 illustrated by way of example in FIGS. 2 and 3 is of the planetary type, in that the planet carrier 34 is coupled to an output shaft via linkages 36, with the ring gear 38 fixed. However, any other suitable type of epicyclic gearbox 30 may be used. By way of further example, the epicyclic gearbox 30 may be a star arrangement, in which the planet carrier 34 is held fixed, with the ring (or annulus) gear 38 allowed to rotate. In such an arrangement the fan 23 is driven by the ring gear 38. By way of further alternative example, the gearbox 30 may be a differential gearbox in which the ring gear 38 and the planet carrier 34 are both allowed to rotate.

(16) It will be appreciated that the arrangement shown in FIGS. 2 and 3 is by way of example only, and various alternatives are within the scope of the present disclosure. Purely by way of example, any suitable arrangement may be used for locating the gearbox 30 in the engine 10 and/or for connecting the gearbox 30 to the engine 10. By way of further example, the connections (such as the linkages 36, 40 in the FIG. 2 example) between the gearbox 30 and other parts of the engine 10 (such as the input shaft 26, the output shaft and the fixed structure 24) may have any desired degree of stiffness or flexibility. By way of further example, any suitable arrangement of the bearings between rotating and stationary parts of the engine (for example between the input and output shafts from the gearbox and the fixed structures, such as the gearbox casing) may be used, and the disclosure is not limited to the exemplary arrangement of FIG. 2. For example, where the gearbox 30 has a star arrangement (described above), the skilled person would readily understand that the arrangement of output and support linkages and bearing locations would typically be different to that shown by way of example in FIG. 2.

(17) Accordingly, the present disclosure extends to a gas turbine engine having any arrangement of gearbox styles (for example star or planetary), support structures, input and output shaft arrangement, and bearing locations.

(18) Optionally, the gearbox may drive additional and/or alternative components (e.g. the intermediate pressure compressor and/or a booster compressor).

(19) Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. For example, such engines may have an alternative number of compressors and/or turbines and/or an alternative number of interconnecting shafts. By way of further example, the gas turbine engine shown in FIG. 1 has a split flow nozzle 20, 22 meaning that the flow through the bypass duct 22 has its own nozzle that is separate to and radially outside the core engine nozzle 20. However, this is not limiting, and any aspect of the present disclosure may also apply to engines in which the flow through the bypass duct 22 and the flow through the core 11 are mixed, or combined, before (or upstream of) a single nozzle, which may be referred to as a mixed flow nozzle. One or both nozzles (whether mixed or split flow) may have a fixed or variable area. Whilst the described example relates to a turbofan engine, the disclosure may apply, for example, to any type of gas turbine engine, such as an open rotor (in which the fan stage is not surrounded by a nacelle) or turboprop engine, for example. In some arrangements, the gas turbine engine 10 may not comprise a gearbox 30.

(20) The geometry of the gas turbine engine 10, and components thereof, is defined by a conventional axis system, comprising an axial direction (which is aligned with the rotational axis 9), a radial direction (in the bottom-to-top direction in FIG. 1), and a circumferential direction (perpendicular to the page in the FIG. 1 view). The axial, radial and circumferential directions are mutually perpendicular.

(21) A gas turbine engine 10 may comprise a large number of fluid carrying pipes/ducts. The fluids in the pipes can be at high temperatures and/or high pressures.

(22) It is necessary to monitor the operating condition of a gas turbine engine 10 in order to determine if a change in operating condition, in particular a fault condition, has occurred. A fault condition may be, for example, a pipe failure such as a leak occurring or a pipe bursting. If a fault condition occurs then the fault condition should be quickly detected so that appropriate action can be taken.

(23) It is known to detect pipe failures by monitoring the temperature within a gas turbine engine 10. A large burst in a pipe can alter the temperature of the bulk of the gas turbine engine 10. A fault condition can therefore be detected by detecting the temperature change of the bulk. For example, thermometers arranged in the fire zone of the gas turbine engine 10 can detect a fault condition whenever there is an unexpected change of the measured temperatures. However, this known technique is not able to detect a small burst in a pipe that may only cause local effects and does not significantly change the bulk temperature. In addition, a fault cannot be detected until the fault causes a temperature change and this can be a slow process.

(24) Embodiments improve on known techniques by using the acoustics of a gas turbine engine 10 to determine its operating condition. The acoustics, i.e. sound, that the gas turbine engine 10 makes is measured and monitored. Any change of the sound can be used to determine that there has been a change in the operating condition of the gas turbine engine 10.

(25) Embodiments may also include techniques for recognising a type of fault condition that has occurred in dependence on the sound of the gas turbine engine 10.

(26) Embodiments may also include applying techniques for determining the location of a specific sound source. This may be used to determine the location of a fault, such as a burst pipe.

(27) Embodiments are described below with reference to a microphone used to detect sound. However, the techniques of embodiments are not restricted to the sound being a human audible sound and the sound can more generally can be any type of gas pressure wave. The gas may be air and the detected waves air pressure waves. The gas pressure wave may be audible to a human or it may be, for example, ultra-sonic, super-sonic or sub-sonic.

(28) The microphone is also not restricted to being capable of only measuring/recording human audible sounds and may more generally be a gas pressure detector/transducer for detecting the gas pressure waves.

(29) When a gas turbine engine 10 is operating, a failure of a pipe within the gas turbine engine 10 will have an acoustic effect. The acoustic effect may be the direct sound of the pipe wall rupturing and/or fluid passing out of, or into, the pipe through the hole in the pipe wall caused by the rupture.

(30) The acoustic effects can also be used to determine the operating condition of other parts of the system and changes other than burst pipes. For example, the monitored acoustics may include any components of the power plant noise signature such as fan noise, combustor rumble and/or compressor acoustics. Any changes in the measured sound and/or differences to expected values of the measured sound can be used to detect a failure.

(31) The techniques for measuring and monitoring sounds in a gas turbine engine 10 according to embodiments are not restricted to being performed when the gas turbine engine 10 is operating. For example, a sound may be induced in the gas turbine engine 10 by, for example, impacting a part of the gas turbine engine 10. The condition of the gas turbine engine 10 may be determined in dependence on the sound generated in response to the impact.

(32) FIG. 4 is a cross-section along the longitudinal axis of a gas turbine engine 10 according to an embodiment.

(33) As shown in FIG. 4, the gas turbine engine 10 comprises a bulk 406 that is surrounded by a bypass duct 407. Within the bulk 406 is a fire zone 405 that surrounds a core engine. The core engine is also referred to herein as a core 11 or engine core 11. There are one or more inlets 402 to the fire zone 405 and a plurality of outlets 403 from the fire zone 405. Within the bulk 406 are pipes 404 and microphones 401.

(34) FIG. 5 is a cross-section of a gas turbine engine 10 according to an embodiment. The cross-section is orthogonal to the longitudinal axis of the gas turbine engine 10.

(35) As shown in FIG. 5, there are splitters/pylons 501 between the bulk 406 and the outer surface of the gas turbine engine 10. Two microphones 401 are positioned in the fire zone 405. The microphones 401 are located on opposite sides of the core engine to each other.

(36) One of the pipes 404 shown in FIG. 5 has burst and this has generated pressure waves 502 that propagate through the gas in the fire zone 405.

(37) Each microphone 401 measures the sound of its environment and outputs an electric signal that is generated in dependence on the measured sound. Each microphone 401 is in communication with a computing system. The output signal from each microphone 401 is transmitted to the computing system.

(38) The computing system may record each signal received from a microphone 401. The computing system can detect changes to the operating condition of a part of the gas turbine engine 10 and/or the entire gas turbine engine 10 by, for each microphone 401, comparing the most recently received signal to previously received signals.

(39) The computing system may analyse each signal that it receives from a microphone 401 by performing a Fourier transform on the signal. The Fourier transform may be, for example, a fast Fourier transform and/or a discrete Fourier transform. The Fourier transform generates a frequency domain representation of the signal. This can be used to determine if the sound comprises components within specific frequency ranges that may be an indication of an incorrect operating condition. For example, a burst pipe may cause super-sonic screech noise to be generated. The burst pipe can then be detected by the computing system whenever frequency components corresponding to super-sonic screech noise are present in a received signal from a microphone 401.

(40) The computing system may determine the operating condition of a part of the gas turbine engine 10 and/or the entire gas turbine engine 10 by comparing the received signal from each microphone 401 to predetermined values/waveforms of signals.

(41) The computing system may store, or have access over a network to, a library of predetermined sound profiles with each sound profile corresponding to one of a plurality of types of fault condition. The fault conditions may include cracked, burst and/or leaking pipes as well as other events that may occur. The computing system may therefore be able to determine, from a comparison of a signal received from a microphone 401 and the sound profiles, the type of fault condition that has occurred. If there are predetermined sound profiles for different types of pipe, the computing system may be able to determine the type of pipe that has failed. For example, cabin air, anti-ice air and handling bleed pipes may all have different sound profiles when they burst and the type of pipe that has burst can therefore be automatically determined by the computing system. The sound profiles may be generated, for example, empirically or through modelling.

(42) The comparison of a signal received by the computing system from a microphone 401 and sound profile may be performed in either the time domain or the frequency domain. If it is performed in the frequency domain then this will allow events that are characterised by the components of their frequency spectrum to be easily compared. Each signal received by the computing system from a microphone 401 may also have other process performed on it, such as filtering operations to prevent aliasing.

(43) The computing system may be able to determine the location and/or direction of a sound source caused by an event occurring, such as a hole occurring in a pipe. If there is only one microphone 401, the location of the sound source may be determined if the microphone 401 is directional and/or if the sound profile is dependent on the distance between the microphone 401 and the sound source.

(44) When more than one microphone 401 is used, as shown in FIG. 5, in addition to the above techniques for a single microphone 401 being used, the difference in phase, i.e. time of arrival, of the sound signal received by each microphone 401 can be used to determine the location of the sound source. This can also assist the determination of the type of event that has occurred.

(45) In the example shown in FIG. 5, the burst pipe is a sound source. A first microphone 401 above the core engine is closer to the burst pipe than a second microphone 401 below the core engine. The first microphone 401 will therefore detect the sound from the sound source before the second microphone 401. The time difference between when the first and second microphones 401 detect the same sound from the sound source can be used to determine the location of the sound source.

(46) Embodiments are not restricted to the microphones 401 being provided in the locations, and with the relative orientations, shown in FIGS. 4 and 5. Embodiments include microphones 401 being provided in other locations and with different relative orientations. For example, in FIG. 5 there may alternatively be three or more microphones 401 in the fire zone 405 around the circumference of the core engine. The number of microphones 401 is also not restricted. For example, there may be nine or more microphones 401. The microphones 401 may also be provided in other parts of the gas turbine engine 10 than the fire zone 405.

(47) Each microphone 401 may comprise one or more acoustic elements 600. As shown in FIG. 6, each acoustic element 600 may comprise an acoustic sensor 601 and a housing 602 of the acoustic sensor 601. The housing 602 both protects the acoustic sensor 601 and provides the acoustic sensor 601 with directional sensitivity. The housing 602 may be a horn waveguide. Each acoustic element 600 has a directional sensitivity to sound that is dependent on the orientation of the horn waveguide. The shape of the cross-section of the end of the horn waveguide may be a regular polygon. A plurality of acoustic elements 600 may be arranged together in a tessellated manner as shown in FIG. 7. The shape formed by combining the acoustic elements 600 may be, for example, be a dodecahedron. The microphone 401 therefore has a substantially spherical shape. The microphone 401 comprises a plurality of acoustic elements 600 with orientations that allow the microphone 401 to detect sounds with substantially the same sensitivity in all directions.

(48) When a microphone 401 comprises a plurality of acoustic elements 600, each acoustic element 600 generates and outputs an electric signal that is generated in dependence on the measured sound. The signal output from the microphone 401 that is transmitted to the computing system may comprise a plurality of signals, with each of the plurality of signals being an output signal from one of the acoustic elements 600 comprised by the microphone 401. Alternatively, the plurality of electric signals from the acoustic elements 600 may be combined with each other at the microphone 401 to generate a single electric signal that is transmitted to the computing system.

(49) Embodiments improve the determination of the operating condition of a gas turbine engine 10 over known techniques based on thermal detection. In particular, a one microphone 401 can detect sound changes over a large region that would require a plurality of thermal detectors, a change of condition can be detected instantly (there is no thermal lag), the location and/or direction of a sound source can be determined, microphones 401 are not expensive and the microphones 401 can detect changes in other parts of the overall system that contribute to the sound profile of the system.

(50) In an alternative to the above-described techniques, one or more of the microphones 401 may be a single horn, or other shape, so that a directional signal is measured.

(51) Embodiments include detecting any type of fault event and well as the general engine health, such as engine degradation and deterioration.

(52) Embodiments may also be integrated with an engine vibration monitoring system and/or thermal detection system.

(53) FIG. 8 is a flowchart of a process for automatically determining an operating condition of at least part of a gas turbine engine 10 for an aircraft according to an embodiment.

(54) In step 801, the process begins.

(55) In step 803, one or more gas pressure waves are measured by a gas pressure detector 401, wherein the gas pressure detector 401 is located in the gas turbine engine 10.

(56) In step 805, a computing system automatically determines an operating condition of at least part of a gas turbine engine 10 in dependence on an output signal of the gas pressure detector 401.

(57) In step 807, the process ends.

(58) Embodiments are not restricted to all of the microphones 401 being located within the gas turbine engine 10. Embodiments also include one or more microphones 401 being located outside of the gas turbine engine 10. There may be microphones located both inside and outside of the gas turbine engine 10 or all of the microphones may be located outside of the gas turbine engine 10.

(59) Embodiments may be used for detecting burst ducts in an automatic thrust pull back system. Other applications that embodiments may be used for include determining if operations are being correctly performed during a pilot shutdown operation and determining if ventilation systems, cooling systems and/or pressure relief panels are operating correctly.

(60) When incorrect operation is detected, embodiments include automatically generating messages to maintenance teams and dispatch notes for reporting the incorrect operation.

(61) 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.