GB2552469A

GB2552469A - Fan

Info

Publication number: GB2552469A
Application number: GB1612556.9A
Authority: GB
Inventors: Benson Christopher
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2016-07-20
Filing date: 2016-07-20
Publication date: 2018-01-31
Anticipated expiration: 2036-07-20
Also published as: GB201612556D0; GB2552469B

Abstract

A fan for a gas turbine engine comprising a plurality of blades 40, and each blade has a blade root 52. The fan also comprises a disc 58 having a plurality of slots 60, wherein each slot 60 receives a blade root 52. A sensor arrangement 66, 68, 20, 72 is provided and configured for sensing movement of the blade root 52 relative to the slot 60. The sensor arrangement may comprise a sensor element provided adjacent to or integrated into the slot 60, provided in or on the base of the slot 60 or between and/or adjacent to the blade root 52 and a portion of the slot 60. The sensing arrangement may comprise a first sensor element 66 positioned proximal the leading edge of the blade and a second root sensor element 68 provided at the trailing edge of said blade. The blades may be made of a composite material.

Description

(54) Title of the Invention: Fan

Abstract Title: A fan for a gas turbine engine having a sensor arrangement for detecting blade root movement (57) A fan for a gas turbine engine comprising a plurality of blades 40, and each blade has a blade root 52. The fan also comprises a disc 58 having a plurality of slots 60, wherein each slot 60 receives a blade root 52. A sensor arrangement 66, 68, 20, 72 is provided and configured for sensing movement of the blade root 52 relative to the slot 60. The sensor arrangement may comprise a sensor element provided adjacent to or integrated into the slot 60, provided in or on the base of the slot 60 or between and/or adjacent to the blade root 52 and a portion of the slot 60. The sensing arrangement may comprise a first sensor element 66 positioned proximal the leading edge of the blade and a second root sensor element 68 provided at the trailing edge of said blade. The blades may be made of a composite material.

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FAN

TECHNICAL FIELD

The present disclosure concerns a fan for a gas turbine engine and/or a gas turbine engine.

BACKGROUND

Gas turbine engines are typically employed to power aircraft. Typically a gas turbine engine will comprise an axial fan driven by an engine core. The engine core is generally made up of one or more turbines which drive respective compressors via coaxial shafts. The fan is usually driven off an additional lower pressure turbine in the engine core.

The fan generally has a plurality of blades extending from a hub and, in a turbofan arrangement the fan is circumscribed by a casing. During flight of an aircraft, the blades of the fan can be impacted by foreign objects such as birds or ice. Impact by foreign objects can cause damage to the blades and/or damage to a liner of the casing as a result of movement of the blade during a impact. In very rare occasions the impacts can result in a blade being released from the fan, however in the majority of cases the damage is not as extreme.

When the blades are metallic, impact damage can be easily detected because the blades are ductile so they often deform on impact, which is visible when the aircraft is on the ground and the gas turbine engine is at rest, and which will also cause increased vibration and/or aero effects that can be detected in flight. When a metallic casing is used, impact damage can often be detected. The fan casing generally includes a fan track liner which has an abradable layer and a compressible layer (such as a layer having a honeycomb structure). When there is a high impact to the blades, the blades can rub heavily against the fan track liner, and this heavy rubbing will be visible upon inspection.

Composite blades, i.e. blades having a fibre reinforced resin matrix structure defining an aerofoil body of the blade, are typically of a laminate nature and generally stiffer than metallic blades. This means, that composite blades can incur impact damage internally that is not visible on the exterior surface, for example through delamination and/or matrix cracking. This type of damage is often referred to as barely visible impact damage (BVID). Composite blades generally also have a higher level of damping than metallic blades due to their viscoelastic nature, so there is less likely to be any major aeromechanical changes following an impact.

Composite casings often have a fan track liner arrangement that is more robust than a liner of a metallic casing because the liner of the composite casing is arranged to prevent a blade fully engaging with the casing. The liner of a composite casing is often deeper than a metallic casing liner and it includes multiple layers. The arrangement of the composite casing means that, in the event of an impact to the blade or as a result of multiple impacts, there is a possibility of sub-surface damage to internal layers of the casing liner that is not visible on the surface, nor indicated by typical rubbing of the abradable layer. Such damage to the casing is also often referred to as barely visible damage.

As described above, when a gas turbine engine has a composite fan blade and/or a composite fan casing, there is a risk that the composite blades and or the composite casing and liner arrangement can incur damage that goes undetected.

SUMMARY

The present disclosure seeks to provide an arrangement that enables barely visible impact damage to a composite blade and/or a case assembly to be detected. The present disclosure further seeks to provide an arrangement that can improve the characterisation of damage to metallic and/or composite blades.

According to an aspect there is provided a fan for a gas turbine engine. The fan comprises a plurality of blades each having a blade root. A disc is provided and has a plurality of slots, wherein each slot receives a blade root. A sensor arrangement is provided and configured for sensing movement of the blade root relative to the slot.

Sensed movement of the blade root relative to the disc slot can be used to indicate that an impact has occurred and/or to provide characterising information in relation to the impact.

The sensor arrangement may comprise a sensor element provided adjacent to or integrated into the slot.

The sensor arrangement may comprise a sensor element provided in or on a base of the slot.

The slot of the disc and/or the root of the blade may be dovetail shaped.

The sensor element may be in or on a surface that defines the base of the slot (e.g. when the slot is dovetail shaped, the surface defining the widest portion of the slot). The slot may comprise flanks. The sensor element may be positioned in or on the flanks.

The sensor element may be provided in or on a member positioned between and/or adjacent to the blade root and a portion of the slot. For example, the sensor element may be provided in or on an axial retention system. An axial retention system is an arrangement that restricts axial movement of a blade with respect to the disc. In arrangements where a slider mechanism is used to secure the blade root in slot, the sensor element may be provided in or on the slider mechanism. In arrangements where thrust rings or shear plates are provided at a leading and a trailing edge of the blade, the sensors may be provided in or on the thrust rings or shear plates.

The sensing arrangement may comprise a first slot sensor element positioned proximal to leading edge of the blade, and a second slot sensor element positioned proximal to a trailing edge of the blade.

The first sensor element and the second slot sensor element may be a hall effect sensor.

The sensing arrangement may comprise a sensor element in or on the blade root.

A first root sensor element may be provided proximal to a leading edge of the blade and a second root sensor element is provided proximal to a trailing edge of the blade.

The first root sensor element and the second root sensor element may be a magnet.

The sensing arrangement may comprise a hall effect sensor.

The sensor arrangement may comprise alternative sensors, for example an optical sensor, an inductive sensor, a capacitive sensor, an ultrasonic sensor, and/or an accelerometer.

The sensing arrangement may comprise a magnet and hall effect sensor set proximal to the leading edge of the blade, and a magnet and hall effect sensor set proximal to the trailing edge of the blade.

The magnet or hall effect sensor of each of the magnet and hall effect sensor set may be provided in or on the root of the blade or in, on or adjacent to the slot of the disc.

For example, the first and/or second root sensor element may be a magnet and the first and/or second slot sensor element may be a sensor that detects the change in position of the magnet. Alternatively, the first and/or second slot sensor element may be a magnet and the first and/or second root sensor element may be a sensor that detects the change in position of the magnet. The change in position of the magnet may be detected based on the hall effect.

The sensing arrangement may be wired or maybe wireless.

The sensing arrangement may comprise multiple sensor elements in the region of the leading edge and/or the trailing edge. For example, two sensor elements may be provided in a thickness direction at the leading edge and/or the trailing edge, on, in or adjacent to the blade root or the slot. In this way, detection of lateral movement of the blade can be more easily detected.

The blades may be composite blades.

In the present application, a composite blade is defined by a blade that comprises a fibre reinforced resin matrix. For example, a body defining an aerofoil may be made from fibre reinforced resin matrix. The blade may comprise additional components such as a metallic leading edge and a metallic trailing edge. The body may have various constructions, including a woven structure, interleaved plies, or laminated plies which may be reinforced in a thickness direction using reinforcement members such as pins, tufts and/or stiches.

Alternatively, the blades may be a metallic blades.

In a further aspect there is provided a gas turbine engine comprising the fan according to the previous aspect.

The gas turbine engine may comprise a fan casing circumscribing the fan.

The fan casing may be made from a composite material. Alternatively, the fan casing may be a metallic fan casing.

The gas turbine engine may comprise a controller configured for receiving a signal indicative of the position of the blade root relative to the blade slot from the sensor arrangement.

The controller may be configured to compare the sensed input to a predefined data set, and decide whether or not an impact has occurred based on the comparison.

The controller may be arranged to cause a display to indicate whether a blade impact has occurred.

The display may be a display provided in a cockpit of an aircraft to which the gas turbine engine is connected and/or the display may be a display of a computer remote to an aircraft, for example a display that is part of a structural health monitoring system.

The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore except where mutually exclusive any feature described herein may be applied to any aspect and/or combined with any other feature described herein.

DESCRIPTION OF THE DRAWINGS

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

Figure 1 is a sectional side view of a gas turbine engine;

Figure 2 is a perspective view of a fan blade;

Figure 3 is a sectional end view of a blade root in a disc slot;

Figure 4 is a sectional side view of a blade root in a disc slot;

Figure 5 is a schematic of a control system associated with sensors of the blade root and disc slot arrangements of Figures 3 and 4;

Figure 6 is a schematic illustration of blade root movement in a disc slot in the event of an impact;

Figure 7 is an illustrative plot of sensor output versus time for a selected period of time during an example impact;

Figure 8 is a sectional side view of blade root and disc slot with a slider arrangement;

Figure 9 is an end view of a blade root and disc slot with sensors provided on the flanks of the blade root and disc slot; and

Figures 10 and 11 are sectional end views of multiple sensors provided in a thickness direction of the blade root and disc slot.

DETAILED DESCRIPTION

With reference to Figure 1, a gas turbine engine is generally indicated at 10, having a principal and rotational axis 11. The engine 10 comprises, in axial flow series, an air intake 12, a propulsive fan 13, an intermediate pressure compressor 14, a high-pressure compressor 15, combustion equipment 16, a high-pressure turbine 17, an intermediate pressure turbine 18, a low-pressure turbine 19 and an exhaust nozzle 20. A nacelle 21 generally surrounds the engine 10 and defines both the intake 12 and the exhaust nozzle 20.

The gas turbine engine 10 works in the conventional manner so that air entering the intake 12 is accelerated by the fan 13 to produce two air flows: a first air flow into the intermediate pressure compressor 14 and a second air flow which passes through a bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 14 compresses the airflow directed into it before delivering that air to 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 combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 17, 18, 19 before being exhausted through the nozzle 20 to provide additional propulsive thrust. The high 17, intermediate 18 and low 19 pressure turbines drive respectively the high pressure compressor 15, intermediate pressure compressor 14 and fan 13, each by suitable interconnecting shaft.

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.

The fan 13 includes a plurality of fan blades 40 mounted to a disc. The fan 13 is surrounded by a fan casing 38. In the present example, both the fan blades 40 and the fan casing 38 are made from composite material.

Referring now to Figure 2, the fan blades 40 each comprise an aerofoil body 42 having a leading edge 44, a trailing edge 46, a concave pressure surface wall 48 extending from the leading edge to the trailing edge and a convex suction surface wall extending from the leading edge to the trailing edge. The fan blade has a root 52 via which the blade can be connected to the disc. The fan blade has a tip 56 at an opposing end to the root. The fan blade may also have an integral platform 54 which may be hollow or ribbed for out of plane bending stiffness. The fan blade includes a metallic leading edge and a metallic trailing edge. The remainder of the blade (e.g. the body of the blade) is made from composite material. In this example, the body is made from a laminate of plies of reinforcement fibres embedded in a resin matrix, and reinforced using pins. However, in alternative embodiments the body may have an alternative construction, for example it may be woven or interleaved, and/or it may be stitched or tufted.

Referring now to Figure 3 and 4, in the present example, the root 52 of the blade is dovetailed. The disc 58 to which the blade 40 is mounted includes a plurality of slots 60 in which the root of the blades are received. The slots 60 are shaped and dimensioned so as to be complimentary to the blade root. In this example, the slots are dovetail shaped.

The fan 13 is provided with a sensing arrangement. In the present example, the sensing arrangement includes hall effect sensors and magnets. The blade root 52 includes a magnet 62, 64 provided at the leading edge and the trailing edge. The magnets 62, 64 are mounted in a recess of the blade root and affixed to the blade root using a suitable adhesive, so that the root profile of the blade is unchanged by the presence of the magnets. However, in alternative embodiments the magnets may be connected in an alternative manner and/or may be formed integrally with the blade root.

Each magnet 62, 64 of the blade root is associated with a hall effect sensor 66, 68 provided in the slot of the blade disc. In the present example, a recess is provided in the slot and the sensor is mounted in the recess to limit any change in profile of the blade slot. However, it will be appreciated that the sensor can be mounted in any suitable manner and/or may be embedded in the disc.

As will now be described, the sensors 66, 68 are connected to a controller, and in this example the sensors are connected via a wire 70.

Referring to Figure 5, the sensors 66, 68 are connected to a controller 72. The controller 72 is part of a system that includes an output device 80. The controller, the sensors, and the output device may be coupled to one another via a wireless link and may consequently comprise transceiver circuitry and one or more antennas. Additionally or alternatively, the controller, the sensors and the output device may be coupled to one another via a wired link and may consequently comprise interface circuitry (such as a Universal Serial Bus (USB) socket). It should be appreciated that the controller, the sensors and the output device may be coupled to one another via any combination of wired and wireless links. For example, the sensors may be connected to a transmitter by a wired connection, and the transmitter may wirelessly output a signal indicative of a signal received from the sensors.

The controller may comprise: control circuitry; and/or processor circuitry; and/or at least one application specific integrated circuit (ASIC); and/or at least one field programmable gate array (FPGA); and/or single or multi-processor architectures; and/or sequential/parallel architectures; and/or at least one programmable logic controllers (PLCs); and/or at least one microprocessor; and/or at least one microcontroller; and/or a central processing unit (CPU); and/or a graphics processing unit (GPU).

In various examples, the controller may comprise at least one processor 74 and at least one memory 76. The memory stores a computer program 78 comprising computer readable instructions that, when read by the processor, causes performance of the methods described herein. The computer program may be software or firmware, or may be a combination of software and firmware.

The processor may be located on the gas turbine engine 10, or may be located remote from the gas turbine engine 10, or may be distributed between the gas turbine engine 10 and a location remote from the gas turbine engine 10. The processor may include at least one microprocessor and may comprise a single core processor, may comprise multiple processor cores (such as a dual core processor or a quad core processor), or may comprise a plurality of processors (at least one of which may comprise multiple processor cores).

The memory may be located on the gas turbine engine, or may be located remote from the gas turbine engine, or may be distributed between the gas turbine engine and a location remote from the gas turbine engine. The memory may be any suitable non-transitory computer readable storage medium, data storage device or devices, and may comprise a hard disk and/or solid state memory (such as flash memory). The memory may be permanent nonremovable memory, or may be removable memory (such as a universal serial bus (USB) flash drive or a secure digital card). The memory may include: local memory employed during actual execution of the computer program; bulk storage; and cache memories which provide temporary storage of at least some computer readable or computer usable program code to reduce the number of times code may be retrieved from bulk storage during execution of the code.

The computer program may be stored on a non-transitory computer readable storage medium. The computer program may be transferred from the nontransitory computer readable storage medium to the memory. The nontransitory computer readable storage medium may be, for example, a USB flash drive, a secure digital (SD) card, an optical disc (such as a compact disc (CD), a digital versatile disc (DVD) or a Blu-ray disc). In some examples, the computer program may be transferred to the memory via a wireless signal or via a wired signal.

The sensors and/or output device may be coupled to the system either directly or through intervening input/output controllers. Various communication adaptors may also be coupled to the controller to enable the apparatus to become coupled to other apparatus or remote printers or storage devices through intervening private or public networks. Non-limiting examples include modems and network adaptors of such communication adaptors.

The output device may be any suitable device for conveying information to a user. For example, the output device may be a display (such as a liquid crystal display, or a light emitting diode display, or an active matrix organic light emitting diode display, or a thin film transistor display, or a cathode ray tube display), and/or a loudspeaker, and/or a printer (such as an inkjet printer or a laser printer). The controller is arranged to provide a signal to the output device to cause the output device to convey information to the user.

Referring to Figures 6 and 7, during operation of the gas turbine engine, if a blade 40 is impacted by a foreign object, such as a bird, the blade and blade root 52 will move, for example it will rock and pivot in the slot 60 of the disc 58, as illustrated in the solid and dotted line of Figure 6. As the blade rocks in the slot, the magnets 62, 64 vary position with respect to the hall effect sensors 66, 68. This variation in position varies a voltage (or alternative signal) output by the sensors, as is illustrated in Figure 7. As can be seen in Figure 7, there is a transient signal spike over time, which indicates that the blade is rocking and therefore it is likely that an impact has taken place.

The signal is sent to the controller, where it can be displayed directly or information relating to the sensors can be displayed, e.g. “normal operation” or “impact detected” messages may be displayed. The output device may be in the cockpit of an aircraft to indicate to the pilot that an impact has occurred. Additionally, or alternatively, the output device may output the signal to inform an engine health monitoring system or specialists, and/or a maintenance scheduling system. Since a sensor is associated with only one blade, it is possible to easily locate which blade or blades have been impacted without removal or inspection of the entire set of fan blades.

Provision of the sensing arrangement means that a blade impact event can be detected even when there is no visible damage to the blade or casing assembly (the assembly including the casing and the casing liner). The blade and/or casing assembly components can then be replaced or repaired if required. Whether replacement is required can be determined using a non-destructive examination (NDE) technique.

The sensors and magnets can be easily embedded in or bonded to the disc, blade, or intermediary component and have negligible effects on the operation of the fan.

Monitoring of impacts on a blade and casing can improve the planned maintenance of a blade and/or casing, which could reduce the frequency of inspections.

Further, the impact can be better characterised because data is collected during an impact event. This means that this arrangement can also be useful for metallic blades, to better characterise an impact and therefore better inform how the blade should be treated post-impact.

Referring now to Figure 8, the sensors have been described as being provided in the slot 60 of the disc 58. However, in alternative embodiments they may be provided on a tertiary component, e.g. an intermediary component. For example, some designs of fans use a slider 72 with a chocking spring 74 to locate and secure the root of the blade in the slot. In such examples, the sensors 66, 68 may be provided in the slider. Alternatively, in examples where thrust rings or shear plates are used at the leading and trailing ends of the disc to maintain the axial position of the blade with respect to the disc, sensors may be provided in the thrust rings or shear plates. In such examples, magnets may be provided at a position spaced from the root of the blade. As will be appreciated by the person skilled in the art, the sensors or magnets may be appropriately arranged to detect movement of the blade, and in fan systems having alternative axial retention systems the sensors or magnets may be provided on or integrated into these alternative axial retention systems.

Referring now to Figure 9, the sensors 66, 68 have been described as being positioned at the base of the slot 60 of the disc 58, but in alternative embodiments, the sensor may be in any suitable position, for example the sensors may be provided on flanks 76 of the slot, and magnets 62, 64 may be provided on flanks 78 of the blade root 52.

Referring now to Figures 10 and 11, instead of only a single sensor being provided at the leading edge and the trailing edge of the disc slot, as previously described, more than one sensor, e.g. two sensors 66A, 66B may be provided. In this way, rocking of the blade in a suction surface to pressure surface direction can be detected, and pitching couples can be detected.

The blade roots and slots have been described as dovetailed but in alternative embodiments the roots and slots may have any suitable shape, for example a fir tree shape.

The magnets have been described as being mounted to the blade root, but in alternative examples the magnets may be provided in or on the disc slot and the sensors may be provided in or on the blade root. However, arrangements where the sensors are in the region of the disc slot rather than the blade root are more easily manufactured.

The sensors have been described as hall effect sensors and magnets, but in alternative embodiments any suitable sensors may be used, for example an optical sensor, an inductive sensor, a capacitive sensor, an ultrasonic sensor, and/or an accelerometer.

It will be understood that the invention is not limited to the embodiments abovedescribed 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.

Claims

1. A fan for a gas turbine engine, the fan comprising: a plurality of blades each having a blade root;

a disc having a plurality of slots, wherein each slot receives a blade root; and a sensor arrangement configured for sensing movement of the blade root relative to the slot.

2. The fan according to claim 1, wherein the sensor arrangement comprises a sensor element provided adjacent to or integrated into the slot.

3. The fan according to claim 2, wherein the sensor arrangement comprises a sensor element provided in or on a base of the slot.

4. The fan according to claim 2, wherein the sensor element is provided in or on a member positioned between and/or adjacent to the blade root and a portion of the slot.

5. The fan according to any one of claims 2 to 4, wherein the sensing arrangement comprises a first slot sensor element positioned proximal to leading edge of the blade, and a second slot sensor element positioned proximal to a trailing edge of the blade.

6. The fan according to any one of the previous claims, wherein the sensing arrangement comprises a sensor element in or on the blade root.

7. The fan according to claim 6, wherein a first root sensor element is provided proximal to a leading edge of the blade and a second root sensor element is provided proximal to a trailing edge of the blade.

8. The fan according to any one of the previous claims, wherein the sensing arrangement comprises a hall effect sensor.

9. The fan according to claim 8, wherein the sensing arrangement comprises a magnet and hall effect sensor set proximal to the leading edge of the blade, and a magnet and hall effect sensor set proximal to the trailing edge of the blade.

10. The fan according to claim 9, wherein the magnet or hall effect sensor of each of the magnet and hall effect sensor set is provided in or on the root of the blade or in, on or adjacent to the slot of the disc.

11. The fan according to any one of the previous claims, wherein the blades are composite blades.

12. A gas turbine engine comprising the fan according to any one of the previous claims.

13. The gas turbine engine according to claim 12 comprising a fan casing circumscribing the fan, and wherein the fan casing is made from a composite material.

14. The gas turbine engine according to claim 12 or 13 comprising a controller configured for receiving a signal indicative of the position of the blade root relative to the blade slot from the sensor arrangement.

15. The gas turbine engine according to claim 14, wherein the controller is configured to compare the sensed input to a predefined data set, and decide whether or not an impact has occurred based on the comparison.

16. The gas turbine engine according to claim 14 or 15, wherein the controller is arranged to cause a display to indicate whether a blade impact has occurred.

Intellectual

Property

Office

Application No: Claims searched:

GB1612556.9

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