US20180347585A1

US20180347585A1 - Fan track liner assembly

Info

Publication number: US20180347585A1
Application number: US15/611,034
Authority: US
Inventors: Timothy Unton
Original assignee: Rolls Royce Corp
Current assignee: Rolls Royce Corp
Priority date: 2017-06-01
Filing date: 2017-06-01
Publication date: 2018-12-06

Abstract

A fan track liner assembly for a gas turbine engine. The assembly may comprise an annular attrition liner, outer member, containment core, and containment liner. The containment core may be embedded between the attrition liner and the outer member. The containment liner may be bonded to a radially outer surface of the outer member. The fan track liner assembly is disposed between a plurality of rotatable fan blades and an engine casing that encases the fan blades. The containment core and/or containment liner may comprise aerogel.

Description

FIELD OF THE DISCLOSURE

The present disclosure relates generally to a fan containment system for a gas turbine engine, and more specifically to a fan track liner having a containment core or containment liner comprising aerogel.

BACKGROUND

Turbofan gas turbine engines (which may be referred to simply as ‘turbofans’) are typically employed to power aircraft. Turbofans are particularly useful on commercial aircraft where fuel consumption is a primary concern. Typically a turbofan 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 that drive respective compressors' via coaxial shafts. The fan is usually driven directly off an additional lower pressure turbine in the engine core.
The fan comprises an array of radially extending fan blades mounted on a rotor and will usually provide, in current high bypass gas turbine engines, around seventy-five percent of the overall thrust generated by the gas turbine engine. The remaining portion of air from the fan is ingested by the engine core and is further compressed, combusted, accelerated and exhausted through a nozzle. The engine core exhaust mixes with the remaining portion of relatively high-volume, low-velocity air bypassing the engine core through a bypass duct.
To satisfy regulatory requirements, such engines are required to demonstrate that if part or all of a fan blade were to become detached from the remainder of the fan (known as a Fan Blade Off Event, or FBOE), that the detached parts are suitably captured within the engine containment system.
The fan is radially surrounded by a fan casing. It is known to provide the fan casing with a fan track liner and a containment system designed to contain any released blades or associated debris. Often, the fan track liner can form part of the fan containment system. The challenge to designing an effective fan track liner—and fan containment system in general—is to provide a system that is strong enough to absorb and spread the energy of a FBOE while minimizing the weight penalty incurred by the system.
A conventional fan containment system or arrangement 100 is illustrated in FIG. 1 and surrounds a fan comprising an array of radially extending fan blades 40. Each fan blade 40 has a leading edge 44, a trailing edge 45 and fan blade tip 42. The fan containment arrangement 100 comprises a fan case 150. The fan case 150 has a generally frustoconical or cylindrical annular casing element 152 and a hook 154. The hook 154 is positioned axially forward of an array of radially extending fan blades 40. A fan track liner 156 is typically directly bonded to the fan case 150 using adhesive. The fan track liner 156 is provided as a structural filler to bridge a deliberate gap provided between the fan case 150 and the fan blade tip 42.
The fan track liner 156 has, in circumferential layers, an attrition liner 158 (also referred to as an abradable liner or an abradable layer), a septum 162, and an intermediate layer that in this embodiment is a honeycomb layer 160. The septum layer 162 acts as a bonding, separation, and load spreading layer between the attrition liner 158 and the honeycomb layer 160. The honeycomb layer 160 may be an aluminium honeycomb. The tips 42 of the fan blades 40 are intended to pass as close as possible to the attrition liner 158 when rotating. The attrition liner 158 is therefore designed to be abraded away by the fan blade tips 42 during abnormal operational movements of the fan blade 40 and to just touch during the extreme of normal operation to ensure the gap between the rotating fan blade tips 42 and the fan track liner 156 is as small as possible without wearing a trench in the attrition liner 158. During normal operations of the gas turbine engine, ordinary and expected movements of the fan blade 40 rotational envelope cause abrasion of the attrition liner 158. This allows the best possible seal between the fan blades 40 and the fan track liner 156 and so improves the effectiveness of the fan in driving air through the engine.
The purpose of the hook 154 is to ensure that, in the event that a fan blade 40 detaches from the rotor of the fan 12, the fan blade 40 will not be ejected through the front, or intake, of the gas turbine engine. During such a fan-blade-off event, the fan blade 40 travels tangentially to the curve of rotation defined by the attached fan blades. Impact with the containment system (including the fan track liner 156) of the fan case 150 prevents the fan blade 40 from travelling any further outside of the curve of rotation defined by the attached fan blades. The fan blade 40 will also move forwards in an axial direction, and the leading edge 44 of the fan blade 40 collides with the hook 154. Thus the fan blade 40 is held by the hook 154 and further axially forward movement is prevented. A trailing blade (not shown) then forces the held released blade rearwards where the released blade is contained. Thus the fan blade 40 is unable to cause damage to structures outside of the gas turbine engine casings.
Improvements are desired to the conventional fan track liner described with reference to FIG. 1 that would allow equal or improved fan blade containment capability while incurring a decreased weight penalty.

SUMMARY

The present application discloses one or more of the features recited in the appended claims and/or the following features that, alone or in any combination, may comprise patentable subject matter.
According to an aspect of the present invention, a fan track liner assembly for a gas turbine engine comprises an annular attrition liner forming a radially inner member of the assembly; a composite septum bonded to a radially outer surface of the attrition liner; and a containment core bonded to a radially outer surface of the septum, the containment core comprising aerogel.
In some embodiments the containment core comprises aerogel encased in a sheath. In some embodiments the sheath comprises composite. In some embodiments the radially outer surface of the containment core is adapted to be bonded to a fan casing in the gas turbine engine. In some embodiments the containment core comprises a plurality of arcuate segments that collectively form an annulus. In some embodiments the containment core is axially segmented. In some embodiments the containment core comprises aerogel produced from one of a silica, alumina, chromia, carbon, organic, metal oxide, or metal-based gel.
According to another aspect of the present disclosure, a fan track liner assembly for a gas turbine engine comprises an annular attrition liner forming a radially inner member of the assembly; an annular outer member positioned radially outward from the annular attrition liner; a containment core embedded between the attrition liner and the outer member; and an outer containment liner bonded to a radially outer surface of the outer member, the outer containment liner comprising aerogel.
In some embodiments the containment core comprises aerogel. In some embodiments the assembly is adapted to be carried by a fan casing in the gas turbine engine with the outer containment liner being positioned between the outer member and the fan casing. In some embodiments the assembly is coupled to a fan casing with fasteners.
In some embodiments the containment core comprises a metal honeycomb. In some embodiments the metal is aluminum. In some embodiments the outer containment liner is axially segmented. In some embodiments the outer containment liner comprises a plurality of arcuate segments that collectively form an annulus. In some embodiments the outer containment liner wherein comprises aerogel produced from one of a silica, alumina, chromia, or carbon, gel.
According to yet another aspect of the present disclosure, a method of making a fan containment system comprises assembling a fan track liner assembly comprising an attrition liner, a septum, a containment core, and an outer member. The step of assembling comprises bonding the septum to a radially outer surface of the attrition liner; bonding the containment core to a radially outer surface of the attrition liner; and coupling the outer member to the attrition liner such that the containment core is encased between the outer member and the attrition liner; bonding a containment liner comprising aerogel to a radially outer surface of the outer member; and coupling the fan track liner assembly to an engine casing such that the fan track liner assembly is disposed radially outward from a plurality of rotatable fan blades.
In some embodiments the coupling is accomplished with fasteners. In some embodiments the containment liner is encased in a composite sheath prior to bonding to the outer member. In some embodiments the containment core comprises aerogel.

BRIEF DESCRIPTION OF THE DRAWINGS

The following will be apparent from elements of the figures, that are provided for illustrative purposes and are not necessarily to scale.

FIG. 1 is a partial view of a cross-section through a typical fan case arrangement.

FIG. 2 is a cross-section through the rotational axis of a gas turbine engine.

FIG. 3 is a partial view of a cross-section through a fan containment system in accordance with some embodiments of the present disclosure.

FIG. 4 is a partial view of a cross-section through a fan containment system in accordance with some embodiments of the present disclosure.

While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the present disclosure is not intended to be limited to the particular forms disclosed. Rather, the present disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to a number of illustrative embodiments illustrated in the drawings and specific language will be used to describe the same.
With reference to FIG. 2 a bypass gas turbine engine is indicated at 10. The engine 10 comprises, in axial flow series, an air intake duct 11, fan 12, a bypass duct 13, an intermediate pressure compressor 14, a high pressure compressor 16, a combustor 18, a high pressure turbine 20, an intermediate pressure turbine 22, a low pressure turbine 24 and an exhaust nozzle 25. The fan 12, compressors 14, 16 and turbines 20, 22, 24 all rotate about the major axis of the gas turbine engine 10 and so define the axial direction of the gas turbine engine.
Air is drawn through the air intake duct 11 by the fan 12 where it is accelerated. A significant portion of the airflow is discharged through the bypass duct 13 generating a corresponding portion of the engine thrust. The remainder is drawn through the intermediate pressure compressor 14 into what is termed the core of the engine 10 where the air is compressed. A further stage of compression takes place in the high pressure compressor 16 before the air is mixed with fuel and burned in the combustor 18. The resulting hot working fluid is discharged through the high pressure turbine 20, the intermediate pressure turbine 22 and the low pressure turbine 24 in series where work is extracted from the working fluid. The work extracted drives the intake fan 12, the intermediate pressure compressor 14 and the high pressure compressor 16 via shafts 26, 28, 30. The working fluid, that has reduced in pressure and temperature, is then expelled through the exhaust nozzle 25 generating the remainder of the engine thrust.
The intake fan 12 comprises an array of radially extending fan blades 40 that are mounted to the shaft 26. The shaft 26 may be considered a hub at the position where the fan blades 40 are mounted. FIG. 2 shows that the fan 12 is surrounded by a fan containment system 300 that also forms one wall or a part of the bypass duct 13.
In the present application a forward direction (indicated by arrow F in FIG. 2) and a rearward direction (indicated by arrow R in FIG. 2) are defined in terms of axial airflow through the engine 10.
Fan track liners in a gas turbine engine have several functions. A fan track liner defines the outer annulus line of the fan flowpath. A fan track liner must be tolerant of fan blade impingement or rub; these rubs may be light if caused by routine operational excursions of the fan blades or may be heavy if caused by a more severe event such as a bird strike. The fan track liner must also be able to withstand substantial impacts from ice and other debris. Finally, the fan track liner must work in conjunction with the fan casing to contain a fan blade during a FBOE.
The fan track liner 156 described above with reference to FIG. 1 is a typical fan track liner used in the art. During a FBOE, the honeycomb layer 160 of fan track liner 156 undergoes plastic deformation to absorb some energy of the detached fan blade. However, the honeycomb layer 160 may not provide good load spreading to the fan casing 152, sometimes rendering the fan track liner 156 of FIG. 1 inadequate.
Fan track liner 156 may also be difficult, time-consuming, and expensive to repair. As blade rubs and debris impacts degrade the attrition liner 158, this liner must occasionally be replaced. In current versions, replacing the attrition liner typically requires removal of the old liner and bonding a new liner in place with adhesive. This process can be time-consuming and expensive, and can result in long down-times for the affected engine. Bonding of the new liner is typically required to be performed in a controlled environment, requiring removal of the engine and/or aircraft from operation.
The present disclosure is directed to a fan blade containment assembly and fan track liner that improve fan blade containment capability and/or reduce the weight penalty attributed to fan containment. More specifically, the present disclosure is directed to an embodiment of fan containment assembly comprising a containment core and outer containment liner. One or both of the containment core and outer containment liner may comprise aerogel. The present disclosure is additionally directed to an embodiment of a fan containment assembly comprising a containment core of aerogel bonded to an ending casing. By using aerogel to form one or both of the containment core and the containment liner, the present disclosure provides systems and methods of improving the containment capability of a fan containment assembly with a marginal weight penalty. In some embodiments the weight of the fan containment assembly is decreased by replacing metallic components with aerogel components.
An aerogel is an ultralight material derived from a gel. The liquid of the gel (typically water) is dried and replaced with gas (typically air). Aerogels tend to have strong structural and insulating properties.
FIG. 3 is a partial view of a cross-section through a fan containment system 300 in accordance with some embodiments of the present disclosure. Fan containment system 300 comprises fan track liner assembly 301 and fan case 350.
The fan case 350 has a generally frustoconical or cylindrical annular casing element 352 and a hook 354. The hook 354 is positioned axially forward of an array of radially extending fan blades 40.
Fan track liner assembly 301 comprises attrition liner 358, septum 362, containment core 361, outer member 359, and containment liner 365.
Attrition liner 358 comprises an annular, abradable material and is designed to be abraded away by the fan blade tips 42 during abnormal operational movements of the fan blade 40. Attrition liner 358 forms fan flowpath boundary 303 that is the radially outer surface of the fan flowpath. Attrition liner 358 additionally forms the radially inner member of the fan containment system 300.
Septum 362 is bonded to a radially outer surface of the attrition liner 358. Septum 362 acts as a bonding, separation, and load spreading layer between the attrition liner 358 and the containment core 361. Septum 362 distributes any applied load between the attrition liner 358 and the containment core 361. In some embodiments septum 362 may comprise composite material, for example ceramic matrix composite. In other embodiments septum 362 may comprise an organic matrix composite, and that organic matrix composite may include carbon fiber or fiberglass.
A containment core 361 is defined between an outer member 359 and attrition liner 358. Outer member 359 is an annular member that may comprise metal or composite material. Outer member 359 is coupled to casing element 352 by one or more fasteners 366, that may be used in conjunction with washers (not shown) to affix outer member 359 to casing element 352. Outer member 359 is disposed radially inward and offset from casing element 352 such that one or more voids 369 may be defined between the outer member 359 and casing element 352.
In some embodiments an outer containment liner 365 may be disposed in void 369 between outer member 359 and casing element 352. Containment liner 365 may be bonded to a radially outer surface of outer member 359, bonded to a radially inner surface of casing element 352, or both. In the illustrated embodiment, containment liner 365 is bonded to a radially outer surface of outer member 359.
In embodiments where the structure of the outer member 359 and casing element 352 are such that multiple voids 369 are formed, an outer containment liner 365 may be disposed in one or more of the voids 369. For example, a portion of containment liner 365 may be disposed in a forward void 369 while a portion of containment liner 365 may also be disposed in an aft void 369.
In some embodiments the containment liner 365 of the illustrated embodiment may be axially segmented. For example, in the embodiment illustrated in FIG. 3, the containment liner 365 is formed in two portions, one axially forward of the other. In some embodiments a gap is provided between axially segmented portions, while in other embodiments the axially adjacent portions abut one another.
Containment core 361 and/or containment liner 365 may comprise aerogel. In some embodiments the aerogel of the containment core 361 and/or containment liner 365 is encased in a respective composite sheath 371. A composite sheath prevents moisture migration into the aerogel. Moisture migration would undesirably add weight to the fan track liner assembly 301 and potentially degrade performance of the aerogel. In some embodiments the aerogel of the containment core 361 and/or containment liner 365 may be encased in a plastic, metal, or similar sheath.
Each of outer member 359, containment core 361, and containment liner 365 may be axially or circumferentially segmented. An axially segmented component comprises more than one axially adjacent annular containment cores. A circumferentially segmented component comprises a plurality of arcuate segment that collectively form a component annulus. The component may be axially and circumferentially segmented. Alternatively, the component may be integrally formed.
The aerogel used to form containment core 361 and/or containment liner 365 may be made from silica, alumina, chromia, or carbon gel. The aerogel may be optimized to achieve maximum strength, maximum insulation, or a combination of the two.
Containment core 361 may comprise a metal honeycomb structure, for example a honeycomb structure made of aluminum or aluminum-based material.
During a FBOE, the aerogel of the containment core 361 and/or containment liner 365 functions to absorb and spread the energy of a released fan blade. The aerogel absorbs energy through brittle fracture of the material and through frictional forces generated by the entrained gas passing through the voidal structure of the aerogel. The brittle fracture of the aerogel minimizes the secondary damage caused by the FBOE, and the aerogel does not impede the released blade from nesting in the fan track liner assembly 301 to prevent ricochet damage. The aerogel's structure will provide for spreading the fan blade load over a greater area of the fan case 350, reducing stresses on the fan case 350 and thus allowing for a thinner and/or lighter fan case 350.
The fan containment system 300 of FIG. 3 provides numerous advantages. The addition of a containment liner 365 comprising aerogel incurs only a marginal weight penalty that substantially improves the absorption capability of the fan track liner assembly 301. In embodiments having a containment core 361 comprising aerogel, the replacement of a metallic structure with an aerogel structure results in a weight savings. Aerogel in contact with structural elements such as the fan case 350 may provide vibrational damping.
The present disclosure of a containment liner and/or a containment core comprising aerogel is amenable to use with a variety of existing fan containment systems. For example, the present disclosure may be combined with existing hard wall (e.g. steel, aluminum, titanium, carbon composite) or soft wall (e.g. woven aramid fiber) systems.
In another embodiment of the present disclosure, the typical honeycomb layer disclosed with reference to FIG. 1 above is replaced with aerogel. FIG. 4 is a partial view of a cross-section through a fan containment system 400 in accordance with some embodiments of the present disclosure. Fan containment system 400 comprises fan track liner assembly 401 and fan case 450.
The fan case 450 has a generally frustoconical or cylindrical annular casing element 452 and a hook 454. The hook 454 is positioned axially forward of an array of radially extending fan blades 40.
Fan track liner assembly 401 comprises attrition liner 458, septum 462, and containment core 461. Attrition liner 458 comprises an abradable material and is designed to be abraded away by the fan blade tips 42 during abnormal operational movements of the fan blade 40. Attrition liner 458 forms fan flowpath boundary 403 that is the radially outer surface of the fan flowpath. Attrition liner 458 additionally forms the radially inner member of the fan track liner assembly 401.
Septum 462 is bonded to a radially outer surface of the attrition liner 458. Septum 462 acts as a bonding, separation, and load spreading layer between the attrition liner 458 and the containment core 461. Septum 462 distributes any applied load between the attrition liner 458 and the containment core 461. In some embodiments septum 462 may comprise composite material, for example ceramic matrix composite. In other embodiments septum 462 may comprise an organic matrix composite, and that organic matrix composite may include carbon fiber or fiberglass.
Containment core 461 may comprise aerogel. In some embodiments the aerogel of the containment core 461 is encased in a composite sheath 471. A composite sheath prevents moisture migration into the aerogel. Moisture migration would undesirably add weight to the fan track liner assembly 401 and potentially degrade performance of the aerogel. In some embodiments the aerogel of the containment core 461 may be encased in a plastic, metal, or similar sheath.
Containment core 461 may be bonded to a radially outer surface of septum 462 and may be bonded to fan casing element 452. In some embodiments a radially outer surface of the containment core 461 is adapted to be bonded to fan casing element 452.
Containment core 461 may be axially or circumferentially segmented. An axially segmented containment core 461 comprises more than one axially adjacent annular containment cores. A circumferentially segmented containment core 461 comprises a plurality of arcuate segment that collectively form a containment core annulus. Containment core 461 may be axially and circumferentially segmented. Alternatively, containment core 461 may be integrally formed.
The aerogel used to form containment core 461 may be made from silica, alumina, chromia, carbon, organic, metal oxide, or metal-based gels. The aerogel may be crosslinked, doped, or re-enforced. The aerogel may be optimized to achieve maximum strength, maximum insulation, or a combination of the two.
The embodiment of FIG. 4 provides numerous advantages over the prior art described above with reference to FIG. 1. First and foremost, the fan track liner assembly 401 of FIG. 4 achieves a substantial weight savings over the design in FIG. 1 by replacing honeycomb layer 160—typically made of aluminum or other metal honeycomb—with a containment core 461 formed from aerogel.
The present disclosure additionally provides a method of making a fan containment system. The method comprises coupling a fan track liner assembly to a fan casing, such that the fan track liner assembly is disposed radially outward from a fan. The fan track liner assembly may be coupled to the fan casing using fasteners.
The fan track liner assembly is assembled by bonding a septum to a radially outer surface of an attrition liner, bonding a containment core to a radially outer surface of the septum, and coupling an outer member to the attrition layer such that the containment core is encased between the outer member and the attrition layer. In some embodiments the outer member may be bonded to one or both of the attrition layer and the containment core. In some embodiments the containment core comprises a metallic honeycomb, while in other embodiments the containment core comprises aerogel. A containment liner may be bonded to outer member, such that upon installation of the fan track liner assembly the containment liner is disposed between the outer member and the fan casing. The containment core and/or containment liner may be encased in a sheath prior to or during assembly.
Although examples are illustrated and described herein, embodiments are nevertheless not limited to the details shown, since various modifications and structural changes may be made therein by those of ordinary skill within the scope and range of equivalents of the claims.

Claims

What is claimed is:

1. A fan track liner assembly for a gas turbine engine comprising:

an annular attrition liner forming a radially inner member of said assembly;

a composite septum bonded to a radially outer surface of said attrition liner; and

a containment core bonded to a radially outer surface of said septum, said containment core comprising aerogel.

2. The fan track liner assembly of claim 1 wherein said containment core comprises aerogel encased in a sheath.

3. The fan track liner assembly of claim 2 wherein said sheath comprises composite.

4. The fan track liner assembly of claim 1 wherein the radially outer surface of said containment core is adapted to be bonded to a fan casing in the gas turbine engine.

5. The fan track liner assembly of claim 1 wherein said containment core comprises a plurality of arcuate segments that collectively form an annulus.

6. The fan track liner assembly of claim 1 wherein said containment core is axially segmented.

7. The fan track liner assembly of claim 1 wherein said containment core comprises aerogel produced from one of a silica, alumina, chromia, carbon, organic, metal oxide, or metal-based gel.

8. A fan track liner assembly for a gas turbine engine, said assembly comprising:

an annular attrition liner forming a radially inner member of said assembly;

an annular outer member positioned radially outward from said annular attrition liner;

a containment core embedded between said attrition liner and said outer member; and

an outer containment liner bonded to a radially outer surface of said outer member, said outer containment liner comprising aerogel.

9. The fan track liner assembly of claim 8 wherein said containment core comprises aerogel.

10. The fan track liner assembly of claim 8 wherein said assembly is adapted to be carried by a fan casing in the gas turbine engine with said outer containment liner being positioned between said outer member and the fan casing.

11. The fan track liner assembly of claim 8 wherein said assembly is coupled to a fan casing with fasteners.

12. The fan track liner assembly of claim 8 wherein said containment core comprises a metal honeycomb.

13. The fan track liner assembly of claim 12 wherein said metal is aluminum.

14. The fan track liner assembly of claim 8 wherein said outer containment liner is axially segmented.

15. The fan track liner assembly of claim 8 wherein said outer containment liner comprises a plurality of arcuate segments that collectively form an annulus.

16. The fan track liner assembly of claim 8 said outer containment liner wherein comprises aerogel produced from one of a silica, alumina, chromia, or carbon gel.

17. A method of making a fan containment system comprising:

assembling a fan track liner assembly comprising an attrition liner, a septum, a containment core, and an outer member, said step of assembling comprising:

bonding said septum to a radially outer surface of said attrition liner;

bonding said containment core to a radially outer surface of said attrition liner; and

coupling said outer member to said attrition liner such that said containment core is encased between said outer member and said attrition liner;

bonding a containment liner comprising aerogel to a radially outer surface of said outer member; and

coupling said fan track liner assembly to an engine casing such that said fan track liner assembly is disposed radially outward from a plurality of rotatable fan blades.

18. The method of claim 17 wherein said coupling is accomplished with fasteners.

19. The method of claim 17 wherein the containment liner is encased in a composite sheath prior to bonding to said outer member.

20. The method of claim 17 wherein said containment core comprises aerogel.