EP2894298A1

EP2894298A1 - Fan assembly with fan blade under-root spacer

Info

Publication number: EP2894298A1
Application number: EP15150185.5A
Authority: EP
Inventors: James R. Murdock; Mark Quinn
Original assignee: United Technologies Corp
Current assignee: RTX Corp
Priority date: 2014-01-08
Filing date: 2015-01-06
Publication date: 2015-07-15
Also published as: US20150192144A1

Abstract

A fan assembly (12) includes a rotor (31) having an outer periphery (32) and a slot (32) extending radially inwardly through the outer periphery (32). The slot (33) terminates at a base surface (34) disposed at a radial depth (R₁) from the outer periphery (32) of the rotor (31). The fan assembly (12) also includes a fan blade (30) that includes an airfoil (39) connected to a root (38) that is received in the slot (32). The root (38) terminates at an inner face (44) and has a radial length (R₂) that is less than the radial depth (R₁) of the slot (32) to define a gap (50) between the inner face (44) of the root (38) and the base surface (34) of the slot (33) when the root (38) is biased away from the base surface (34). A spacer (51) is disposed within the gap (50) and is fabricated from a polymer, which may be a composite material such as a polymer embedded with reinforcing materials such as carbon fibers and glass fibers.

Description

BACKGROUND

Technical Field:

This disclosure relates to turbomachinery and, more particularly, to various means for holding a turbomachinery fan blade in a radially tight fashion within a supporting rotor slot.

Description of the Related Art:

Turbomachinery fan blades may be secured to a supporting rotor by providing shaped slots in the rotor that mateably receive correspondingly shaped roots of the fan blades. For example, the rotors may include dovetail or fir tree shaped slots that receive correspondingly shaped roots disposed at the radially inwardly ends of the fan blades. The slots of the rotor and the roots of the fan blades are adapted to lock the fan blades against radial movement as the rotor spins about its axis.
However, for large fan blades, such as high bypass ratio fan blades, interlocking blade shrouds may also be used to prevent excessive blade deflection and to dampen vibration. The combination of interlocking blade shrouds and a root/slot locking system for the fan blades and rotor can make it difficult or impossible to insert the fan blades in the slots of the rotor and/or to remove the fans blades from the rotor for service and/or replacement purposes. To facilitate removal and replacement of a shrouded and locked fan blade from a fully assembled rotor, the slots may be oversized so that a fan blade may be moved radially inwardly a sufficient distance to permit the distal tip of the fan blade to clear the interlocking blade shrouds.
Where such radially oversized slots are utilized, spacers may be used to hold each blade radially tight within its respective slot. Such spacers may also facilitate balancing of the rotor and may prevent hammering and/or relative motion between abutting blade root and rotor surfaces, which may increase wear and therefore increase maintenance costs.
Typically, such spacers may be formed from a metallic material, which may cause galling during operation as the fan blade root and the rotor slot engage the metallic spacer. Further, metallic spacers may cause damage to the fan blade roots and/or the rotor slots during installation or removal of the fan blades from the rotor. Moreover, metallic spacers may be suitable for use only in closely toleranced rotor slots, thereby limiting their applicability.

SUMMARY OF THE DISCLOSURE

In one aspect, a fan assembly for turbomachinery is disclosed. The disclosed fan assembly may include a rotor having an outer periphery and at least one slot extending radially inwardly through the outer periphery of the rotor. The slot may terminate at a base surface disposed at a radial depth from the outer periphery of the rotor. The fan assembly may further include at least one fan blade including an airfoil connected to a root. The root maybe received in the slot. The root may terminate at an inner face. The root has a radial length that is less than the radial depth of the rotor slot to define a gap between the inner face of the root and the base surface of the slot when the root is biased away from the base surface of the slot. The fan assembly may further include a spacer disposed in the gap. The spacer may be fabricated from a polymer.
In another aspect, a method of coupling a fan blade to a rotor is disclosed. The method may include providing a rotor that includes an outer periphery and at least one slot extending radially through the outer periphery before terminating at a base surface disposed at a radial depth from the outer periphery of the rotor. The method may further include providing at least one fan blade including an airfoil connected to a root. The root may terminate at an inner face and may have a radial length that is less than the radial depth of the slot. The method may further include providing a spacer fabricated from a polymer. The method may further include inserting the root of the fan blade into the slot of the rotor and moving the root and fan blade radially away from the base surface of the slot to expose a gap between the inner face of the root and the base surface of the slot. The method may further include inserting the spacer into the gap.
In another aspect, a method of removing a fan blade from a rotor of a fan assembly is disclosed. The method may include providing a fan assembly that includes a rotor including an outer periphery and at least one slot extending radially through the outer periphery before terminating at a base surface disposed at a radial depth from the outer periphery of the rotor. The fan assembly may further include at least one fan blade including an airfoil connected to a root. The root maybe received in the slot of the rotor. The root may terminate at an inner face and the root may have a radial length that is less than the radial depth of the slot. The fan assembly may further include a spacer fabricated from a polymer and that is disposed between the base surface of the slot and the inner face of the root. The method may further include biasing the root radially outwardly away from the base surface of the slot, removing the spacer from between the inner face of the root and the base surface of the slot and removing the root from the slot.
In any one or more of the embodiments described above, the polymer of the spacer may further include at least one reinforcing material.
In any one or more of the embodiments described above, the reinforcing material may be selected from a group consisting of carbon fibers and glass fibers.
In any one or more of the embodiments described above, the spacer may be injection-molded.
In any one or more of the embodiments described above, the polymer may be selected from a group consisting of: polyetherimide (PEI), polyimide, polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polysulfone, nylon, polyphenylsulfide, polyester, and combinations thereof.
In any one or more of the embodiments described above, the slot may have a dovetail-shaped cross-sectional profile.
In any one or more of the embodiments described above, the base surface of the rotor slot may be disposed between a pair of sidewalls that may extend from the base surface to the outer periphery of the rotor. The sidewalls may extend towards each other to form a throat disposed between the base surface and the outer periphery of the rotor. The base surface may have a width and the throat may also have a width. Further, the inner face of the root may be disposed between two pressure faces. The inner face of the root may have a width that is smaller than the width of the base surface of the rotor slot and that is larger than the width of the throat of the rotor slot.
In any one or more of the embodiments described above, the root of the fan blade and the slot of the rotor may be shaped so that the root is mateably received in the slot.
Other advantages and features will be apparent from the following detailed description when read in conjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the disclosed methods and apparatuses, reference should be made to the embodiment illustrated in greater detail on the accompanying drawings, wherein:

FIG. 1 is a sectional view of a gas turbine engine;
FIG. 2 is a perspective view of a rotor and fan blade that forms one part of the fan assembly of the gas turbine engine illustrated in FIG. 1.
FIG. 3 is a partial perspective view of the rotor and fan blade shown in FIG. 2 and with a disclosed spacer that maybe received in the gap between the root of the fan blade and the base surface of the slot of the rotor.
FIG. 4 is a perspective view of the spacer illustrated in FIG. 3.
FIG. 5 is another partial perspective view of the rotor and fan blade but with the spacer disposed in the gap between the inner face of the root of the fan blade and the base surface of the slot of the rotor.
FIG. 6 is an enlarged partial perspective view of the fan blade, rotor and spacer as illustrated in FIG. 5.

It should be understood that the drawings are not necessarily to scale and that the disclosed embodiments are sometimes illustrated diagrammatically and in partial views. In certain instances, details which are not necessary for an understanding of the disclosed methods and apparatuses or which render other details difficult to perceive may have been omitted. It should be understood, of course, that this disclosure is not limited to the particular embodiments illustrated herein.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1 is a sectional view of a gas turbine engine 10. The gas turbine engine 10 may include a fan section 11 that, in turn, may include a fan blade assembly 12. The fan blade assembly 12 may be mounted immediately aft of a nose cone 13 and immediately fore of a low pressure compressor (LPC) 14. The LPC 14 may be part of a compressor section 15 and may be disposed between the fan blade assembly 12 and a high pressure compressor (HPC) 16. The LPC 14 and HPC 16 may be disposed fore of a combustor 17, which may be disposed between the HPC 16 and a high pressure turbine (HPT) 18 that is part of a turbine section 19. The HPT 18 is typically disposed between the combustor 17 and a low pressure turbine (LPT) 21. The LPT 21 may be disposed immediately fore of a nozzle 22. The LPC 14 may be coupled to the LPT 21 via a shaft 23, which may extend through an annular shaft 24 that may couple the HPC 16 to the HPT 18. An engine case 25 may be disposed within an outer nacelle 26 that surrounds the fan section 11.
Turning to FIG. 2, the fan blade assembly 12 may include a plurality of fan blades 30 mounted to a rotor 31. More specifically, the rotor 31 may include an outer periphery 32 through which a plurality of dovetail shaped slots 33 extend. The slots 33 may include inner base surfaces 34. The base surfaces 34 may each be disposed between inwardly slanted sidewalls 36, 37 that extend inwardly towards each other as they extend radially outwardly from their respective base surfaces 34. As also shown in FIG. 2, the slots 33 may each accommodate a correspondingly shaped root 38 of a fan blade 30. The dovetail shaped root 38 may be connected to a blade 39 that includes a leading edge 41 and a trailing edge 42. The leading and trailing edges 41, 42 are disposed on either side of the blade tip 43.
As shown in FIGS. 2-3 and 5-6, the root 38 may include an inner face 44 that may be disposed between and connected to inwardly slanted pressure faces 45, 46. The pressure faces 45, 46 may each engage the inwardly slanted sidewalls 36, 37 respectively of their respective slot 33 in the rotor 31.
While dovetail shaped slots 33 and roots 38 are shown herein, the reader will note that other types of slots and roots, including but not limited to fir tree shaped slots and correspondingly shaped roots are also clearly applicable to this disclosure and are considered within the scope of this disclosure.
Turning to FIG. 3, as described above, each slot 33 extends radially inwardly through the outer periphery 32 of the rotor 31. Each slot 33 terminates at a base surface 34 that is disposed at a radial depth R₁ from the outer periphery 32. The base surface 34 is disposed between and is connected to a pair of sidewalls 36, 37. The sidewall 36, 37 extend from the base surface 34 to the outer periphery 32 and extend towards each other to form a throat at or below the outer periphery 32. The throat has a width W₁ as illustrated in FIG. 3. The width W₁ is less than the width W₂ of the base surface 34 as illustrated in FIG. 3. In other words, the slot 33 may have a dovetail-shaped cross-sectional profile. As indicated above, other profiles, such as fir tree, T-shaped, etc. may be employed.
Turning to FIG. 5, the root 38 of the fan blade 30 also has a dovetail-shaped cross-sectional profile. Specifically, the root 38 extends radially inwardly before terminating at an inner face 44 that has a radial distance R₂. The radial distance R₂ (FIG. 5) is less than the radial depth R₁ of each slot 33 (FIG. 3). Further, referring back to FIG. 5, the inner face 44 of the root 38 has a width W₃ that is less than the width W₁ of the throat of each slot. In other words, the root 38 may have a complementary dovetail-shaped cross-sectional profile that matches the profile of the slots 33. Specifically, the inner face 44 of the root 38 is disposed between and connected to the pair of inwardly slanted pressure faces 45, 46. When the fan blade 30 is biased in a radially outwardly direction, the pressure faces 45, 46 engage the throat of the slot 33, which prevents the fan blade 30 from disengaging from rotor 31. Once the fan blade 30 is biased in a radially outwardly direction, a gap 50 exists between the inner face 44 of the root 38 and the base surface 34 of the slot 33 as illustrated in FIG.3. To hold the fan blade 30 tight within the slot 33, a spacer 51 may be inserted into the gap 50 as illustrated in FIGS. 5 and 6. The spacer 51, in addition to holding the blade 30 radially tight within the slot 33 may also facilitate balancing of the rotor 31 and may further prevent hammering and/or relative motion between the pressure faces 45, 46 of the root 38 and the side walls 36, 37 of the slot 33.
A perspective view of the spacer 51 is illustrated in FIG. 4. The spacer 51 may have a thickness that is slightly less than or about equal to the thickness of the gap 50 illustrated in FIG. 3. Tapered side walls 52, 53 surround the inner face 44 of the root 38 and enhance the ability of spacer 51 to prevent hammering and relative motion of the fan blade 30 within the slot 33. The upper surface 54 engages the inner face 44 of the root 38 while the bottom surface 55 engages the base surface 34 of the slot 33. Because the spacer 51 is fabricated from a polymeric material, it has a lower coefficient of friction than typical metallic materials used to fabricate such spacers and may be easier to insert into the gap 50 than conventional metal spacers. Further, by using a polymeric material, weight savings and cost savings are also achieved.
An exemplary substrate for use in fabricating the spacer 51 is an injection-molded, compression-molded, blow-molded, additively manufactured or a composite-layup piece formed of at least one of the following: polyamide, polyetherimide (PEI), polyimide, polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polysulfone, nylon, polyphenylsulfide, polyester, or any of the foregoing with fiber reinforcement e.g., carbon fiber or glass-fiber.
Because the spacer 51 may be fabricated from a polymer, it may provide a substantial reduction in cost versus a metallic spacer. For example, typical metallic spacers must be machined and, depending upon the specific material used, can cost several hundred dollars. In contrast, an injection molded polymeric spacer may cost substantially less than a hundred dollars. The disclosed spacers 51 also are substantially lighter than metallic spacers. For example, the composite materials listed above have a density of about 1/3 of the density of titanium and about 1/2 of the density of aluminum, which are both common metal spacer materials.
While only certain embodiments have been set forth, alternative embodiments and various modifications will be apparent from the above description to those skilled on the art. These and other alternatives are considered equivalents in within the scope of this disclosure.

Claims

A fan assembly (12) comprising:
a rotor (31) having an outer periphery (32) and at least one slot (33) extending radially inwardly through the outer periphery (32) and terminating at a base surface (34) disposed at a radial depth (R₁) from the outer periphery (32) of the rotor (31);

at least one fan blade (30) including an airfoil (39) connected to a root (38), the root (38) being received in the slot (33), the root (38) terminating at an inner face (44) and having a radial length (R₂) that is less than the radial depth (R₁) of the slot (33) to define a gap (50) between the inner face (44) of the root (38) and the base surface (34) of the slot (33); and

a spacer (51) disposed in the gap (50), the spacer (51) being fabricated from a polymer.
The fan assembly (12) of claim 1, wherein the polymer is embedded with at least one reinforcing material.
The fan assembly (12) of claim 2, wherein the reinforcing material comprises carbon fibers and/or glass fibers.
The fan assembly (12) of any of claims 1 to 3, wherein the spacer (51) is injection-molded.
The fan assembly (12) of any preceding claim, wherein the polymer comprises polyamide, polyetherimide (PEI), polyimide, polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polysulfone, nylon, polyphenylsulfide, polyester, or combinations thereof.
The fan assembly (12) of any preceding claim, wherein the slot (33) has a dovetail-shaped cross-sectional profile.
The fan assembly (12) of any preceding claim, wherein the base surface (34) is disposed between a pair of sidewalls (36,37) that extend from the base surface (34) to the outer periphery (32) of the rotor (31), the sidewalls (36,37) extending towards each other to form a throat disposed between the base surface (33) and the outer periphery (32) of the rotor (31), the base surface (33) having a width (W₂) and the throat having a width (W₁) and the inner face (44) of the root (38) being disposed between two pressure faces (45,46), the inner face (44) having a width (W₃) that is smaller than the width (W₂) of the base surface (33) and that is larger than the width (W₁) of the throat.
The fan assembly (12) of any preceding claim, wherein the root (38) and slot (33) are shaped so that the root (38) is mateably received in the slot (33).
A method of coupling a fan blade (30) to a rotor (31), the method comprising:
providing a rotor (31) including an outer periphery (32) and at least one slot (33) extending radially through the outer periphery (32) before terminating at a base surface (34) disposed at a radial depth (R₁) from the outer periphery (32);

providing at least one fan blade (30) including an airfoil (39) connected to a root (38), the root (38) terminating at an inner face (44) and having a radial length (R₂) that is less than the radial depth (R₁) of the slot (33);

providing a spacer (51) fabricated from a polymer;

inserting the root (38) of the fan blade (30) into the slot (33) of the rotor (31);

moving the root (38) radially outwardly away from the base surface (34) of the slot (33) to expose a gap (50) between the inner face (44) of the root (38) and the base surface (34) of the slot (33); and

inserting the spacer (51) into the gap (50).
The method of claim 9, wherein the polymer is embedded with at least one reinforcing material, and optionally wherein the reinforcing material is selected from the group consisting of carbon fibers and glass fibers.
The method of claim 9 or 10, wherein the spacer (51) is injection-molded.
The method of any of claims 9 to 11, wherein the polymer comprises polyamide, polyetherimide (PEI), polyimide, polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polysulfone, nylon, polyphenylsulfide, polyester, and/or combinations thereof.
The method of any of claims 9 to 12, wherein the slot (33) has a dovetail-shaped cross-sectional profile.
The method of any of claims 9 to 13, wherein the base surface (34) of the slot (33) is disposed between a pair of sidewalls (36,37) that extend from the base surface (34) to the outer periphery (32), the sidewalls (36,37) extending towards each other to form a throat disposed between the base surface (34) and the outer periphery (32), the base surface (34) having a width (W₂) and the throat having a width (W₁), the inner face (44) of the root (38) is disposed between two pressure faces (45,46), the inner face (44) having a width (W₃) that is smaller than the width (W₂) of the base surface (34) and that is larger than the width (W₁) of the throat, and the moving of the fan blade (30) radially outward away from the base surface (34) includes moving of the fan blade (30) radially outward away from the base surface (34) until the two pressure faces (45,46) of the root (38) engage the throat of the slot (33).
The fan assembly of any of claims 1 to 8, wherein the gap (50) is defined between the inner face (44) of the root (38) and the base surface (34) of the slot (33) when the root (38) is biased away from the base surface (34) of the slot (33).