JP6184036B2 - Friction resistant fan case - Google Patents

Description

  The present invention relates generally to gas turbine engines, and more specifically to a structure for housing a fan of a gas turbine engine.

  A turbofan engine typically includes a fan, a booster, a high pressure compressor, a combustor, a high pressure turbine, and a low pressure turbine in a series axial relationship about the longitudinal central axis of the engine. The high pressure turbine is drivingly connected to a high pressure compressor via a first rotor shaft, and the low pressure turbine is drivingly connected to both a fan and a booster via a second rotor shaft. The fan includes an annular disk and a plurality of radially extending blades attached to the disk, the disk and blades being able to rotate about the longitudinal central axis of the engine. Such fans are surrounded by a fan case. The fan case is specifically designed so that, during operation, the fan blade can be stored if the fan blade comes off its disk. This will cause structural damage to the engine or aircraft if one or more fan blades are removed from the disk in the unlikely event of a sudden failure of one or more blades, debris ingestion or other causes That can be prevented or minimized.

  The fan case also serves as an outer flow path boundary through the fan rotor and approaches and surrounds the fan blade tips to minimize leakage through the fan blades. Yes. Prior art fan cases are typically made of sacrificial abradable material to protect the fan blades when they come into contact (referred to as “friction”). The inside is covered. The sacrificial wear of the abradable material prevents damage to expensive fan blades, but this increases the radial clearance of the blade tips, resulting in loss of engine thrust.

  In some engines, during operation, for example during aircraft maneuvers, the fan blades are subject to unavoidable friction or temporarily become unbalanced. In these cases, simply using an abradable material can result in unacceptable loss of thrust.

  Accordingly, there is a need for a fan casing that can withstand fan blade friction while maintaining the desired clearance.

European Patent No. 2290199

  This need is addressed by the present invention which provides a fan case incorporating an easily breakable friction resistant bumper.

  According to one aspect of the present invention, a case device for a gas turbine engine includes an annular case having an inner surface in which an annular recess is formed, and an annular having a low friction contact surface made of an easily breakable material disposed in the recess. Including bumpers. The bumper is configured to be able to flex elastically when the applied force falls below a predetermined threshold.

  According to another aspect of the present invention, a fan device includes an annular fan case having an inner surface in which an annular recess is formed, an annular bumper having a low-friction contact surface made of an easily breakable material disposed in the recess, The bumper includes a rotor carrying an array of blades mounted for rotation within the case such that the bumper is axially aligned with the blade tips. The bumper is configured such that when the blade and the bumper come into contact with each other, when the applied force falls below a predetermined threshold, the bumper can elastically bend in the radial direction.

  The invention can best be understood by reference to the following description taken in conjunction with the accompanying drawings.

1 is a schematic half-sectional view of a fan section of a gas turbine engine incorporating a fan case constructed in accordance with an aspect of the present invention. FIG. 2 is an enlarged view of a part of the fan case shown in FIG. 1.

  Referring to the drawings in which like elements are numbered with like reference numerals throughout the Figures, FIG. 1 illustrates an exemplary turbofan gas turbine engine used to power an aircraft in flight. A portion of the fan section 10 is shown. Fan section 10 includes a fan 12 that rotates about a longitudinal central axis “A” by a conventional fan shaft 14 that is powered by a conventional low pressure turbine (not shown). The fan 12 includes a rotor disk 16 from which an array of airfoil-shaped (only one shown in FIG. 1) fan blades 18 extend radially outward therefrom. The rotor disk 16 and the fan blade 18 may be separable from each other or may be part of a rotor or “blisk” with blades attached together. Each fan blade 18 includes a leading edge 20, a trailing edge 22, a root 24 and a tip 26. Arranged downstream of the fan 12 is an array of airfoil-shaped outlet guide vanes (“OGV”) 27. Although the invention will be described in the context of a fan and fan case, it will be understood that the principles of the invention are equally applicable to casings surrounding other types of rotating components.

  The annular fan case 28 surrounds the fan 12. The term “annular” as used herein refers to a closed ring structure that is generally ring-shaped and includes not only circular but also non-circular shapes. The fan case 28 has a front end 30 and a rear end 32. The front flange 34 mates with the nacelle (not shown) and the rear flange 36 mates with the flange 38 of the downstream engine casing component 40. The fan case 28 has an outer surface 42 and an opposite inner surface 44. Inner surface 44 cooperates with other components described in more detail below to define a flow path surface “F” that is configured to approach and surround the tip 26 of fan blade 18.

  According to known implementations, the fan case 28 is sized and shaped to withstand anticipated operational loads such as gas pressure loads, body loads, and steering loads. The fan case 28 further functions to function as a storage member, in other words, configured to withstand penetration even when the fan blade 18 detached from the rotor disk 16 collides. In general, the blade may come off due to foreign matter sucked in by the fan 12 during engine operation. This is commonly referred to as a “blade out” event. In the illustrated example, the fan case 28 has a monolithic structure and is made of an alloy such as aluminum, titanium, or steel. The fan case may be made of a composite material as well. The term “axial alignment” as used herein means a common or overlapping position of two components measured along a longitudinal central axis A.

  As best seen in FIG. 2, an annular recess 46 is formed in a portion of the inner surface 44, and a bumper 48 is disposed in the recess. The bumper 48 may be an annular component having a contact surface 50 that is positioned in axial alignment with the fan blade 18. As will be described in more detail below, the bumper 48 can be elastically deflected radially due to linear stress-strain behavior while in contact with the blade at a relatively low load, resulting in a relatively high load. Thus, the friction of the contact surface 50 is configured to be low so as to be easily broken while in contact with the blade. The term “low friction”, as used herein, corresponds to and refers to a generally stiff and smooth condition rather than a rough finish. In the illustrated example, the bumper 48 has a generally axially aligned web 52, a pair of spaced apart radially extending legs 54, and optionally, a leg 54. And a pair of flanges 56 extending axially forward and rearward from both distal ends of the two. The flange 56 is shaped to conform to the interior of the recess 46. The web 52 of the bumper 48 defines a contact surface 50 and has a slightly convex or curved surface with respect to the fan blade 18. The bumper 48 is sized and shaped so that no changes are required to the indentation 46 or the fan case 28 compared to conventional fan case designs. Therefore, even if the bumper is used, the storage function of the fan case 28 is not significantly affected.

  The bumper 48 is constructed so as to easily break when the blade collides. The term “easy to break”, as used herein, is a material that breaks down, that is, breaks that break apart rather than stretched, essentially disintegrating into very small, low-mass pieces. Point to. In the illustrated example, the bumper 48 is made of a composite system, for example, an intermediate-modulus graphite fiber in a reinforced epoxy matrix. The surface near the center of the bumper 48 in the radial direction can incorporate a glass fiber layer so as to minimize damage to the blade tip 26 upon contact. The bumper 48 can be fixed in place in the recess 46 using a known adhesive.

  Optional filler 58 is disposed in an annular channel defined by the shape of bumper 48. The purpose of the filler 58 is to make the bumper 48 rigid and / or brake it so that the harmonic vibrations of the bumper can be controlled. Materials such as composite honeycombs or elastomers (eg incorporating aramid fibers such as NOMEX®) can be used for this purpose. Filler 58 may be provided as a single piece or multiple pieces and may be bonded to bumper 48 and / or indentation 46 using known adhesives.

  A known type of abradable material 60 may be placed in the space of the recess 46 in front of and behind the bumper 48. In the illustrated example, the abradable material 60 is made of a phenol resin in which glass microspheres are embedded. The exposed surface of the abradable material 60 cooperates with the bumper 48 and the inner surface 44 of the fan case 28 to define the flow path surface F. During the manufacturing process, some or all of the inner surface 44, abradable material 60 and bumper 48 are machined with one or more processing steps to form the contour of the flow path surface F.

  During operation, the bumper 48 and the fan blade 18 are not normally in contact. Occasionally, the fan 12 may become slightly unstable, thereby causing it to deflect radially from its nominal position (ie, rotate in a spiral or spiral rather than simply rotating). As a result, the front end portion 26 of the fan blade 18 is deflected in the radial direction and may contact the bumper 48, specifically, the web 52. Because the contact surface 50 of the web 52 is low friction, the fan blade 18 can move or slide smoothly along that surface. On the other hand, when the applied force falls below a predetermined threshold, the bumper 48 can be elastically bent linearly in the radial direction by the leg portion 54. Thus, the bumper 48 can be considered a “friction resistant” structure. The bumper 48 prevents the fan blade tip 26 from contacting the abradable material 60. Contact with the abradable material 60 increases the radial clearance between the flow path surface F and the fan blade 18 and may lead to unacceptable loss of engine thrust, so it is desirable not to contact.

  In contrast, the bumper 48 acts as a frangible fuse when a fan blade out event occurs, which is an event that generates a force significantly greater than blade friction. The bumper 48, when brought into contact with the blade, is substantially crushed or broken into very small low mass pieces. This avoids the effects of fan blade outload or the occurrence of secondary damage. As an example, the load when the bumper 48 is fused may be as much as 40-50% greater than the load expected during occasional friction. The features of the bumper 48 can be tailored to a particular application by selecting the dimensions of the web 52 and legs 54, as well as the type of composite, and the number, dimensions and orientation of the plies.

  In testing fan cases constructed as described above, the bumper can exhibit the required linear elastic behavior when subjected to frictional loads, while avoiding the effects of fan blade-out loads. It was proved that the higher the load, the more it collapses as needed. In tests, it was further demonstrated that the bumper 48 did not crush or delaminate after the action of a friction load, preventing loss of thrust.

  In the above description, a fan case with a friction-resistant bumper has been described. While particular embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications can be made to the present invention without departing from the spirit and scope of the invention. Accordingly, the foregoing description of the preferred embodiment of the invention and the best mode for practicing the invention are provided for purposes of illustration only and are not intended to be limiting. The invention is defined by the claims.

DESCRIPTION OF SYMBOLS 10 Fan section 12 Fan 14 Fan shaft 16 Rotor disk 18 Fan blade 20 Front edge 22 Rear edge 24 Root part 26 Tip part 27 Outlet guide vane 28 Fan case 30 Front end 32 Rear end 34 Front flange 36 Rear flange 38 Flange 40 Downstream engine casing structure Element 42 Outer surface 44 Inner surface 46 Recess 48 Bumper 50 Contact surface 52 Web 54 Leg 56 Flange 58 Filler 60 Abradable material

Claims (20)

A casing device for a gas turbine engine,
An annular case having an inner surface in which an annular recess is formed;
A bumper disposed in the indentation, made of an easily breakable material, having a low friction contact surface, and configured to bend elastically when the applied force falls below a predetermined threshold; A case device. The bumper includes a web defining the contact surface and a pair of parallel legs spaced from the web, the web and the legs cooperating with the channel. The apparatus of claim 1, wherein the apparatus is defined. The apparatus of claim 2, wherein the web is convexly curved inward in the radial direction .
The apparatus of claim 2, wherein the bumper includes a pair of flanges extending in opposite directions from a distal end of the leg. The apparatus of claim 1, wherein the bumper comprises a carbon-epoxy composite. The apparatus of claim 5, wherein the composite includes at least one layer of glass fibers on the contact surface. The apparatus of claim 2, further comprising a filler disposed in the channel of the bumper. The apparatus of claim 7, wherein the filler comprises a honeycomb structure. Further comprising an abradable material disposed in the recess adjacent to the bumper, whereby the abradable material, the contact surface and the inner surface cooperate to provide a radial direction of fluid flowing inside the case; The apparatus of claim 1, wherein the apparatus defines an outer flow path surface.
The apparatus of claim 9, wherein the abradable material comprises a phenolic resin. A fan device for a gas turbine engine,
An annular fan case having an inner surface formed with an annular recess;
An annular bumper disposed in the indentation, made of an easily breakable material and having a low friction contact surface;
A rotor carrying blades array mounted for rotation within the previous SL case, the bumper is configured to match the tip and the axial direction of the blade, said bumper, wherein said blade When the applied force falls below a predetermined threshold by contacting the bumper, it can be elastically bent in the radial direction.
Fan device.
The bumper includes a web defining the contact surface and a pair of parallel legs spaced from the web, the web and the legs cooperating to define a channel. The apparatus of claim 11, comprising: The apparatus of claim 12, wherein the web is convexly curved radially inward .
The apparatus of claim 12, wherein the bumper includes a pair of flanges extending in opposite directions from a distal end of the leg. The apparatus of claim 11, wherein the bumper comprises a carbon-epoxy composite. The apparatus of claim 15, wherein the composite comprises at least one layer of glass fibers. The apparatus of claim 12, further comprising a filler disposed in the channel of the bumper. The apparatus of claim 17, wherein the filler comprises a honeycomb structure. Further comprising an abradable material disposed in the recess adjacent to the bumper, whereby the abradable material, the contact surface and the inner surface cooperate to provide a radial direction of fluid flowing inside the case; The apparatus of claim 11, wherein the apparatus defines an outer flow path surface.
The apparatus of claim 19, wherein the abradable material comprises a phenolic resin.