EP2449216A1

EP2449216A1 - Rotor blade and method for reducing tip rub loading

Info

Publication number: EP2449216A1
Application number: EP10727571A
Authority: EP
Inventors: Nicholas Joseph Kray; David W. Crall; Daniel E. Mollmann; Donald Lee Gardner; Marcia Boyle Johnson; Howard P. Weaver; Max Robert Farson
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2009-06-30
Filing date: 2010-06-02
Publication date: 2012-05-09
Also published as: CA2766534C; JP5628307B2; JP2012532268A; WO2011002570A1; CA2766534A1

Abstract

An air foil (42) for use in a rotor assembly is disclosed, the airfoil having a tip- cutter (100) located on a sidewall (44) near a tip portion (60). Wherein the tip-cutter (100) ιs capable of removing a portion of an abradable material (32) during a tip rub. In another embodiment an airfoil (42) has a tip-grinder (120) located on the tip portion (60) wherein the tip-grinder (120) capable of removing a portion of an abradable material (32) during a tip rub in another embodiment an airfoil (42) has a tip-rake (110) that facilitates reducing loading induced to said airfoil (42) during tip rubs. A method (300) for reducing tip rub loads in a rotor blade (15) is described comprising the steps of incorporating a tip-cutter (100) having a selected a cutter-profile (102) on a selected location on the blade (15) such that tip-cutter (100) is capable of removing a portion of a static structure (32) during a tip rub such that tip rub loads are facilitated to be reduced.

Description

ROTOR BLADE AND METHOD FOR REDUCING

TFP RUB LOADING

BACKGROUND OP THE INVEN TION

{000! I This invention relates generally to gas turbine engines, and more specifically to methods and apparatus to reduce lip rub loads induced in rotor blades j⁽i⁽iO2j At least some known gas turbine engines typieaik include a casing, a fan rotor assembh . low and high pressure compressors, a eombυstor, and at least one turbine. ^'The compressors compress air which is channeled to the eombustor where it is mixed with fuel The mixture is then ityiited for generation hot combustion eases The combustion gases are channeled to the turbme{s) which extracts energy from the combustion gases for powering the compressor(s). as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator

[0003] Some known fan and compressor assemblies include a casing that encloses a rotor having a plural Uy of rotor blades Under certain engine operating conditions, the rotor blades may be subject to blade tip rub ev ents that induce radial and tangential loads sn the Made airfoils. Excessne rub loads nmv facilitate damage in the blade due to vibrator} and fatigue conditions. Excessn e rub loads from the blade tubs may also facilitate secondary damage that includes damage to non-adjacent blades and the casing. Excess: \ e fan blade rubs max' exert large aib loads on the rotating disks and bearings if the blade plows through the fan case abradable system.

10004] Accordingly, it would be desirable to have a rotor and casing system comprising rotor blades hauπg features to reduce the rub loads that are induced during blade lip rubs. H is desirable to have a rotor blade haung an airfoil that machines away the casing abradabie material during tip nibs ϊt is desirable to e a method of forming rotor assemblies having reduced blade tip rub loads.

BRIEF DESCRIPTION OF THE INVENTION

{00051 The abo\ e-mentιoned need or needs may be met b> exemplar} embodiments which provide an airfoil comprising a first sidewalk a second sidewall coupled to said first sidewall at a leading edge and at a {Tailing edge, a tip portion extending between said first and second sidewalls and a tip-cutter located on the first sidewall near the tip portion, said lip-cutler capable of removing a portion of an abradable material during a tip rub.

[0006] in another embodiment, an airfoil comprises a tip-grinder located on a tip portion, said tip-grinder capable of removing a portion of an abradable material during a tip rub foots? I in another embodiment an airfoil comprises a tip-rake located on at least a part of the tip portion extending between satd first and second sidewalls, said tip-rake having a rake-profile that facilitates reducing loading induced to said airfoil during tip rubs.

[0008] In another embodiment, a blade assembly comprises an airfoil and a metal leading edge (MLE) coupled to at least a portion of said airfbiL said MLE having a tip-cutter capable of removing a portion of an abradable material during a tip rub. j 00091 In another embodiment, a falisk comprises a plurality of airfoils extending from a hub and a tip-colter .located on at least one airfoil, said tip-cutler capable of removing a portion of an abradable materia! during a tip rub.

100101 In another embodiment, a biisk comprises a plurality of airfoils extending from a hub and a tip-grinder located on at least one airfoil, said tip-grinder capable of removing a portion of an abradable material during a tip rub.

[001 1 ] in another aspect of the present invention a method is provided for reducing tip rub loads in an airfoil comprising the steps of selecting a location of contact between the airfoil and a static structure; selecting a location on the airfoil for incorporating a tip-cutter; selecting a cutter-profile for the tip-cutter; and incorporating lhe tip-cutler on the selected location on lhe airfoil such thai tip-cutter is capable of removing a portion of lhe static structure during a tip rub such thai tip rub loads are facilitated to be reduced. 10012 ] In another aspect of the present invention, a method for reducing tip rub loads in an airfoil comprises providing a tip-grinder located on a lip portion, said tip-grinder capable of removing a portion of an abradable material during a tip rub,

[0013] In another aspect of the present invention, a method for reducing tip rub loads in an airfoil comprises providing a lip-rake located on at least a part of the tip portion, said tip-rake having a rake-profϊle that facilitates reducing loading induced to said airfoil during tip rubs,

[0014| In another aspect of the present .invention, a method for assembling a rotor assembly comprises the steps of providing a blade assembly including an airfoil and a metal leading edge (MLE); removing material from a portion of the MLE to form a tip-cutter; and coupling the blade assembly to a rotor hub such that during tip rubs lhe tip-cutter machines an abradable material to facilitate reducing radial loading induced to the blade during tip rubs.

BMEF DESCRIPTION OF THE DRAWINGS

100151 The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding part of the specification. The invention, however, may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures .in which: j00! 6| FfG. ϊ is a diagrammatic view of an exemplary gas turbine engine comprising an airfoil according to an exemplar)_' embodiment of the present invention.

[001 7] FlO. 2 is a perspective view¹ of a rotor blade comprising an airfoil according to an exemplary embodiment of the present invention.

[0018] FlG. 3 is a perspective view of the tip portion of the airfoil shown in FlG. 2.

[0019] FlG, 4 is a cross-sectional illustration of the tip portion of the airfoil shown in FIG. 2 positioned within lhe casing of lhe gas turbine engine shown in FlG. JOOZUj FiG 5 js a schematic \ sen of an exemplary rotor blade according to an ailernatjx e embodiment of the psesent m\ en Ii on

1002 I j FIG 6 is a Ikw cbaii showing the steps of a method of i educing tip aib loading

DFT AILED DFSC RIP TlON Oi- THh INVFNTION

|0022| Figure 1 is a schematic initiation of an exemplars engine assenibh 10 haung an exemplars embodiment of the present im ention of a rotoi blade 15 hav ing a tip portion 60 that facilitates reducing rub loads induced to the iotor blade 15 when a tip rub occurs betw een the blade tip and the casing 1 ? Engine asscmbh 10, haung a longitudinal axis 12. comprises a fan asscmbh 13, a booster compressoi 14, a core gas turbine engine 16, and a low-pressure tυibme 26 that is coupled with fan assembK 13 and booster compiessoi 14 Coie gas tiwbme engine 16 includes a high-pressure compiessoi 22. a combυstor 24, and a high-pressure turbine 18 Booster compressor 14 includes a pluralm of rotor blades 40 that extend substantially tadialh outw ard from a iotor dtsl 20 coupled to a first dm e shaft 31 fcngme assemble 10 has an intake side 28 and an exhaust side 30 Compressor 22 and high-pressure turbine IH are coupled together b\ a second dm e shaft 29

|00231 During operation, atr enters engine IO through intake side 2H and Oows through fan assembh 13 and compressed air is supplied fsom fan assembh 13 to booster compressor 14 and high pressure compressor 22 The pluraht) of rotoi blades 40 compress the air and deln er the compressed mr to core gas turbine engine 16 ΛnOow is further compressed b> the high-pressure compressor 22 and is deliv ered to combustor 24 HoI gases Horn combustor 24 dme rotating tuibmes 18 and 26 and exit Kas turbine entune IO thiouah exhaust side 30

100241 The present imention ιdes an exemplars apparatus and method for reducing rub loads induced in an airfoil, such as, for example, in a rotor blade I ⁴ _* and rotor assembh 13 used m a gas turbine engine 10 Figure 2 is a perspective \sew of a iotor blade 15 used m the fan or cornpressot section of the engine J O In FIG 1 the rotor blade shown as numeral item 1 ^ is a fan rotor blade and rotor Made show n a.s numeial item 40 is a cυπipressoi section rotoi blade Although the present invention is described herein with respect to fan and compressor rotor blades, the present invention is not limited Io such components, and applies to integrally bladed disks {"BUSKS'^") that have integral airfoils, and turbine rotors 18. 26. In the exemplars- embodiment shown in FlG, 2, a rotor blade 15 is provided that includes an airfoil 42 having a first sidewall 44 (alternatively referred to herein as "Pressure Side" and "Concave Side"), a second sidewall 46 (alternatively referred to herein as "Suction Side^"' and "Convex Side"), a root portion 54 and a tip portion 60. Rotor blade 15 includes an airfoil 42, a platform portion 55. and an integral dovetail portion 43 that is used for mounting rotor blade 15 to rotor hub 21. Airfoil portion 42 includes a first sidewall 44 and a second sidewall 46. ϊn the exemplar)¹ embodiment, first sidewall 44 is substantially concave and defines a pressure side of rotor blade 15, and second sidewall 46 is substantially convex and defines a suction side of rotor blade 15. Sidewaϊls 44 and 4(S are joined together at a leading edge 48 and at an axi ally-spaced trailing edge 50. Trailing edge 50 is spaced chord-wise and downstream from leading edge 48. First and second sidewalls 44 and 46. respectively, each extend longitudinally or radially outward in a span 5.2 from the blade root portion 54 to a blade lip portion 60. Tip portion 60 is defined between sidewalls 44 and 46 and includes a lip surface 62, a concave edge 64. and a convex edge 66. Dovetail portion 43 includes a platform 55 positioned at root portion 54 and extending circumferential!} outward from first aid second sidewalis 44 aid 46, respectively. In the exemplars^' embodiment, dovetail 43 is positioned substantially axially adjacent root portion 54, In an alternative embodiment, dovetail 43 may be positioned substantially citcuniferentially adjacent root portion 54 Rotor blades 15, 40 may have any conventional form, with or without dovetail 43 or platform 55. For example, the airfoil 42 of rotor blades 1.5, 40 may be formed integrally with a rotor hub 21 or disk (alternatively referred to herein as a blisk). In a bhsk-type configuration, the rotor blades 15. 40 do not include dovetail 43 and platform 55.

[0025 j In the exemplary embodiment shown in FIG. 1 and FIG. 4. an abradable material 32 is coupled to a casing 1.7 thai extends circuniferentially around a longitudinal axis 12. Platforms 55 of rotor blades 40 define an inner boundary of a flow-path 35 extending through booster compressor 14. In an alternative embodiment. such as. for example, a blisk I SO, the inner boundary may be defined by a rotor disk 2 S (shown in Figure I )- ^'^e casing 17 and abradable material 32 define a radially outer boundary of the (low-path 35 As shown in FIG. 4, abradable material 32 is spaced a distance Di and D2 from each rolor blade tip portion 60 such that a clearance gap 33 is defined between materia! 32 and airfoil 42. Specifically abradable material 32 is spaced a distance D2 from convex edge 66 and a distance Dl from concave edge 64. Distances Dl and D2 are selected to facilitate preventing tip rubs between rotor blades J 5. 40 and abradable material 32 during engine operation. In the exemplar)_' embodiment, the inner and outer boundaries of fiow-path are nol parallel and stacking axis 80 is not required to be perpendicular to outer flow path boundary.

[0026] During normal engine operations, rotor disk 20 (and rotor bub 21 ) rotates within an orbiting diameter that is substantially centered about longitudinal axis 12. Accordingly, rotor blades 15. 40 rotate about longitudinal axis 12 such thai clearance gap 33 (see FIG. 4) is substantially maintained and. more specifically, such that tip portion 60 remains a distance Dl from abradable material 32. with the exception of minor variations due to small engine 10 imbalances Clearance gap 33 is also sized to facilitate reducing an amount of air i.e., tip spillage. that may be channeled past tip portion 60 during engine operation.

10027 ) Under some transient engine operating conditions, blades 15 may deflect such that tip portion 60 may rub abradable material 32. During such tip rubs, in conventional blades, some portions of the airfoil tip may be jammed into abradable material 32. such that radial and axial loads axe induced to rotor blades. Frequent tip rubs of this kind may increase the radial loads and blade vibrations. Such loading and vibratory stresses may increase and perpetuate the dynamic stresses of conventional airfoils, which may subject the conventional blades to material fatigue. Over time, continued operation with material fatigue may cause blade cracking and/or shorten the useful life of the rotor blades.

[0028] FlO. 2 illustrates an exemplary fan rotor blade 15 according to one embodiment of the present invention, FiG. 3 is a perspective view of the tip portion of the airfoil 42 of the rotor blade 15. FiG. 4 is a cross-sectional illustration of the tip portion of the airfoil 42 of the rotor blade shown in FiG. 2 positioned within the casing 1 7 of the gas turbine engine 10 shown in FIG. 1. Specifically, in the exemplary embodiment shown in FlOS. 2-4, rotor blade 15 has a tip portion 60 that facilitates reducing radial loading induced to blade 15 if lip rubs occur during engine operation.

[0029] In the exemplary embodiments of the present invention shown in FlOS. 1-5 herein, certain features are provided near the airfoil tip 61 aid leading edge 48 regions that facilitate reducing the rub loads that are generated when airfoil tip rubs against the abradable material 32 under certain operating conditions. Specifically, these features reduce the rub loads by re.niovi.ng a portion of the abradable materia! 32 by machining. One such feature, shown in the exemplary embodiments herein (See FIG. 2). is a lip-cutter K)O that is located near the lip portion 60. In the exemplars- embodiment shown in FlO. 2. the tip-cutter 100 is located near the leading edge 48 near the tip 6 L on the ^"pressure Side^'' (first sidewail 44) of the airfoil 42. The tip-cutter 1.00 has a cutter-profile 102 having geometric features (See FiG. 4) that are capable of removing a portion of the abradable material 32 by machining during a tip rub. The exemplar}' cutter-profile 102. shown in FlG 4. comprises a cutter-angle 104 located at the leading edge 48 at the airfoil tip 61 The cutter-angle 104 is an angle between the leading edge 48 and a flat portion 108 at the blade tip 6 L as shown in FlO. 4. The cutter-angle 104 is selected such that it promotes the machining and removal of the abradable material 32 during a lip rub event. The cutter-angle 104 may have a value between about 1 degree and 10 degrees. hi a preferred embodiment, the cutter-angle 104 has a value between about 2 degrees and about 5 degrees. The cutter-profile 102 shown in FIG. 4 further comprises an arcuate recess 106 that extends into the airfoil to a certain depth "B ^* (See FTG. 4). In a preferred embodiment, lhe depth ^£"B^" has a value of about 0.005 inches. In other embodiments, the depth "B" may have a value of up to about (1050 inches. The cutler profile 102 near the tip M extends in a span- wise direction along a portion of the leading edge 48, as shown in FlG. 2. The cutter profile 102 also extends in a chordwise direction along a portion of the airfoil 42 from the leading edge 48 towards the trailing edge 50 such that the depth "B^"' and the cutter-angle 108 gradually reduce to zero so as to blend smoothly with the airfoil concave side 44 to promote smooth airflow in the airfoil 42. 100301 In another exemplar)¹ embodiment of the present invention, the airfoil 42 has a tip-grinder S 20 located on the tip portion 60. such as. for example, near the leading edge 48. as shown in FlG. 2. The tip-grinder J 20 comprises an abrasiv e material applied to the airfoil tip that serves as a cutting agent for an abradable material 32 located in the casing i 7. The tip-gπnder abradable material may be regular or irregular in shape and may have sharp edges that are less than .010 inches in radius. The tip-grinder 120 is made from a suitable material that is capable of removing a portion of an abradable materia! 32 during a tip nib. The tip-grinder 120 is made from a ceramic, metallic or intermetallic material having a composition comprising of embedded abrasive materia!. In the case of metallic and intermetaliic particles the hardness of the material would be in excess of Vickers 750 (g/mra^Λ2). Known abrasive materials may be used in the tip-grinder 120. Preferred known abrasive materials used for the tip-grinder 120 include Aluminum Oxide, Silicon Carbide, CBN or Diamond, The iip-grinderl20 may be bonded to the airfoil 42 using known methods such as brazing and welding. In a preferred embodiment, the tip- grinder 1.20 is banded to the airfoil 42 by brazing. In alternative embodiments of the blade 15, the tip-grinder 120 may be bonded or applied to the airfoil 42 by thermal spray or using a known bonding adhesive. Although the lip-grinder 120 is shown in FlO. 4 as being located near the leading edge 48 tip. in alternative embodiments, the tip-grinder 120 may be located at the blade tip near trailing edge 50, or other suitable locations on the tip 61.

|UU311 In another aspect, the present invention comprises a tip-rake 1 10 (See FlG. 4) extending between the first and second sidewalls 44, 46, located on at least a part of the tip portion 60. The tip-rake il O has a rake-profile 1 12 that facilitates reducing loading induced to the airfoil 42 during lip tubs, ϊn the exemplary embodiment shown in FiO. 4, the rake-profile 1 1.2 has a rake angle 1 14 ("A^""} with respect to a plane 82 that is substantially perpendicular to a stacking axis 80 of the airfoil 42. The stacking axis 80 is an axis that extends through blade 15 in a span-wise direction from root portion 54 to tip portion 60. The tip-rake 1 10 may have a rake angle 1 14 between about 2 degrees and about 15 degrees. In a preferred embodiment, the tip-rake I I O has a rake angle 114 between about 3 degrees and about 5 degrees. [0032 j In the exemplary embodiments shown in FlOS. 2-5, tip surface 62 extends obliquely between airfoil sidewaSls 44 and 46. More specifically, tip surface 62 is oriented at a rake angle A. Rake angle A of tip surface 62 is measured with respect to a plane 82 extending through rotor blade 15 substantially perpendicular to stacking axis 80. Plane 82 facilitates the fabrication and orientation of tip surface 162. In one embodiment, durmg a fabrication process, plane 82 is established using a plurality of datura points defined on an external surface of blade 15. Alternatively, blade tip surface 62 may be oriented at any rake angle A that enables blade 15 to function as described herein.

[0033] In the exemplary embodiment, the tip surface 62 has a rake- profile 1 12 defined by rake angle A. The orientation of the rake tip surface 62 as defined by the rake-profile 1 12 causes the clearance gap 33 to be non-uniform across blade tip portion 60. Specifically, in the exemplary embodiment, because tip surface 62 is oriented at rake angle A, a height D2 of clearance gap 33 at convex edge 66 (see FIGS. 2 and 4) is greater than a height Dl of clearance gap 33 at concave edge 64 (see FJCJS. 2 and 4). hi the exemplary embodiment, surface 62 having a rake-profile 1 12 is formed via a raking process. Alternatively, surface 62 may be flat having a substantially constant rake angle A using any other known fabricating process, including but not limited to. a machining process.

[0034] In another exemplary- embodiment of the present invention, a conventional blade may be modified to create the blade 15 to include tip portion 60 as described herein. Specifically, a tip-cutter 100 is formed by machining, or other known methods, near the tip of a blade as described herein. Further, optionally, a tip- grinder 120 is coupled to an existing blade as described herein and shown in FΪGS. 2- 5. Additionally and optionally, excess blade material from an existing blade tip portion 60 is removed via a raking process to form tip portion 60 with a corresponding rale-profile 1 12 and rake angle A that facilitates prevention of convex edge 66 contact with abradabie materia! 32 during a tip rub. The rake angle A may have a value between about 5 degrees and about 15 degrees. More specifically, in a preferred embodiment, the rake angle A has a value between about 3 degrees and about 5 degrees, ϊn alternative embodiments, blade 15 $x formed with tφ portion 60 having rake-profile 1 12 and rake angle A, and lip-cutter 100 via a known processes. such lhat tip portion 60 is formed with a desired rake-profile 1 12, and cutler-profile 102. and optionally, tip-grinder i 12 is added at the lip 6i .

10035 j During normal engine operations, the rotor disk 20 rotates within an orbiting diameter that is substantially centered about longitudinal axis 12. Accordingly, rotor blades 15, 40 rotate about longitudinal axis 12. and a sufficient clearance gap 33 is maintained between rotor blade tip portion 60 and abradabie material 32. In the event blade 15 or 40 is deflected, tip portion 60 may inadvertently Rib abradabie material 32. As shown in FIGS. 2 and 4, because tip portion 60 is oriented at rake angie A, during a tip rub, concave edge 64 is closer to the abradabie materia! 32, rather than convex edge 66. ^'The tip-gπnder 120, if present, first contacts the abradable material 32 and machines away a portion of the abradabie material 32. The tip-cutter i00 is at the leading end of the biade 15 in the rotational direction 125 and machines away a portion of the abradabfe material 32 during a tip rub event. The cutter-profile 102 is such that the cutter-angle J 04 makes contact with the abradabie material 32 at an angie to machine it, and arcuate recess 106 removes the machined abradabie material 32 away from the tip 61. As a result, during tip rubs, radiai and axial ioads induced to rotor blade 15 are facilitated to be reduced in comparison to conventional rotor blades. Moreover, dynamic stresses induced to biade 15, which may result in biade cracking in conventional biades due to material fatigue, are also facilitated to be reduced. Specifically, loading and vibrators' stresses induced to blade 15 are reduced because die abradabie material 32 is machined away during tip rubs, rather than being jammed against the casing 17 as conventional blades do.

[0036] FΪG. 5 shows a schematic view of an alternative exemplary embodiment of the present invention of a blade 170 having features to reduce tip rub loads as described before. The exemplars' blade 170 shown in FIG 5 is a fan blade that may be used with gas turbine engine 10 (shown in FlG. 1 ). The fan blade 170 includes an airfoii 154, a blade tip cap 150 that cooperates vvith a radially innermost surface (not shown) of casing J 7 to form clearance 33 (shown in FlG. 1 ) therebetween. In the alternative exemplary embodiment shown in FlG. 5, cap 150 is formed from titamum sheet metal. Alternatively, cap 150 is formed from any material that facilitates operation of blade 170 as described herein. Blade 170 also includes a dovetail root portion 152 that facilitates coupling to a rotor hub 21 The airfoil 154 of blade 170 is formed from materials via processes that are both known in the art. Such materials include, but are not limited to, composites. Blade 170 also includes a trailing edge guard 156. In the exemplary embodiment guard 156 is formed from titanium sheet metal. Alternatively, guard 156 is formed from airs- material that facilitates operation of blade 170 in the engine H⁾. Airfoil 154 has a first radial length 157.

[0037] Blade 170 further includes a metal leading edge (MLE) 158. MLE 158 is formed from any metallic material that facilitates operation of fan rotor assembly 13 in the engine 10. including, but not being limited to, titanium alloys aid inconei alloys. MLF 158. as well as cap 150 and guard 156, are coupled to airfoil 154 via methods known in the art. wherein such methods include, but are not limited to. brazing, welding, and adhesive bonding. MLE 158 includes a solid nose region 160 and a plurality of sidewalks 162 (only one facing sidevvail .162 shown in FIG 5) MLE 158 extends along substantially ail of airfoil radial length 157. Moreover, a radial!}' innermost portion of MLE 158 extends radially inward Io root portion 152 and a radially outermost portion of MLE 158 extends radially outward such that MLE 158 is substantially Hush with cap 150. Therefore, in the exemplary embodiment, MLE 158 is configured with a second radial length 163 that is greater than first radial length 157 Alternatively, length 163 is any value that facilitates operation of blade 170 during tip rub events as described previously herein.

[0038] When assembled in engine 10, the blade 1 70 and casing 37 cooperate to form clearance 33 therebetween. As described previously herein, under certain engine operating conditions, rotor blade 170 tip 61 may contact the abradable material 32 that surrounds the blade tips (See FIGS 1 and 4). For example, unbalanced conditions within engine 10 (shown in FIG. 1) may facilitate a decrease in a radial distance between lip cap 150 and casing 17 thereby increasing a probability of contact, or rub, between cap 150 and the abradable material 32 in the casing 1 7. Such rubbing will induce radial and tangential forces, wherein a least a portion of such loads will be transferred into casing 1 7 and a portion into airfoil 154. The alternative exemplary embodiment of blade 170 shown in FlG. 5 has features located in the blade tip portion 60 that reduce the tip rub loads as described previously herein. The blade 170 has a tip-cutter 100 (described previously herein) located at the tip portion 60 of the blade leading edge solid nose region 160. The tip-cutter 100 has a culler-profile 102 having a flat portion 108. cutter-angle 104 and an arcuate recess 106 as described previously herein. The tip-culler 100 is configured such thai, during up rub events, it makes contact with the abradable material 32 at an angle and machines away the abradable material 32 resulting in reduced rub loads. The cutter-profile 102 recess 106 is such that the abradable material 32 that is machined is removed away from the contact region. The cutter-angle 104 may have a value between about 1 degree and about 10 degrees, hi a preferred embodiment, the cutter-angle 104 has a value between about 2 degrees and about 5 degrees.

|00391 The blade 1 70 may further comprise a tip-grinder 120 located at the blade tip portion 60, as described previously In FlG. 5, the tip-grinder 120 is shown located at the tip portion 60 of the blade leading edge solid nose region 160 Alternatively, the tip-grinder 120 may be located at other suitable locations in the tip portion 60 of blade tip cap 150. The lip-grinder 120 is made from a suitable material that is capable of removing a portion of an abradable material 32 during a tip rub. The tip-grinder 120 comprises an abrasive material that serves as a cutting agent for an abradable material 32 located in the casing 17. The tip-grinder abradable material may be regular or irregtxlar in shape and may have sharp edges that are less than .010 inches in radius. The tip-grinder 120 is made from a ceramic, metallic or intermεtallic material having a composition comprising of embedded abrasive material, ϊn the case of metallic and intermetailic particles the hardness of the material would be in excess of Vickers 750 (g/mm^Λ2). Known abrasive materials may be used in the tip-grinder 120, Preferred known abrasive materials used for the tip-grinder 120 include Aluminum Oxide, Silicon Carbide, CBN or Diamond. The tip-grinderl 20 may be bonded to the MLE 158 or tip cap 150 using known methods such as brazing and welding In a preferred embodiment, the tip-grinder 120 is bonded to the MLE 158 by brazing. In alternative embodiments of the blade 15, the tip-grinder 120 may be bonded or applied to the MLE 158 and/or tip cap 150 by thermal spray or using a known bonding adhesive. [(.HMOj In another aspect, blade 170 shewn in FiO. 5 may further comprise a tip-rake 1 10 (See FIG. 4 for example) extending between the first and second sidewalls 44, 46. located on at least a part of {he tip portion 60 of the tip cap 150. The tip-rake I U) has a rake-profile S 12 that facilitates reducing loading induced to the airfoil 42 during tip rubs, As described previously herein (see FlO. 4 for example), the rake-profile 1 12 has a rake angle 1 14 OW) such that during tip rub event, contact between the blade tip 61 and abradable material 32 occurs at the concave edge of the blade tip to reduce rub loads. The tip-rake 1 H⁾ may have a rake angle i 14 between about 2 degrees and about 15 degrees. Tn a preferred embodiment, the tip-rale 1 10 has a rake angle J J 4 between about 3 degrees and about 5 degrees

10041 ] FIG. 6 is a flow chart showing the steps of a method 300 of reducing tip rub loading. The method 300 comprises the step 305 of selecting a location of contact during a tip aib event between the tip of the blade and a static structure, such as lhe abradable material 32 This is illustrated in FIG. 4, for example, wherein the location of contact is chosen as the pressure side 44 leading edge tip. Step 31(s comprises selecting cutter-profile 102 (described previously herein) for the tip- cutter 100. Step 315 comprises the optional step of selecting a lip-grinder 120, Suitable materials capable of machining the abradable 32 can be chosen, as described previously. Step 320 comprises the optional step of selecting a tip rake-proftSe. also described previously herein. Step 325 comprises incorporating the tip-cutter 100 on the blade tip. Preferably, this is done by machining, although other known methods may be used. Step 330 comprises the optional step of bonding the tip-grinder 120 (if opted in step 315) as described previously. Step 335 comprises the optional step of incorporating the tip-rake 110 rake-profile 1 12 on the blade (if opted in step 320).

[0042 J Exemplary embodiments of rotor blades are described above in detail. The rotor blades are not .limited to the specific embodiments described herein, but rather, components of each assembly may be utilized independently and separately from other components described herein. For example, each rotor blade component can also be used in combination with other blade system components, including, but not limited to. blisks, and with other gas and non-gas turbine engines. Although the present invention described herein is described in connection with the turbine engine shown in FlG. 1 , it should be apparent to those skilled in the art and guided by the teachings herein provided that with appropriate modification, the apparatus and method of the present invention can also he suitable for any engine with compressors capable of operating as described herein.

[0043] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

WH AT IS CLAIMED IS:

1. An airfoil 42 comprising: a first sidewail 44; a second sidewail 46 coupled to said first sidewail 44 at a leading edge 48 and at a trailing edge 50; a tip portion 60 extending between said first and second sidewalls 44, 46; and a tip-cutter 100 located on the first sidewail 44 near the tip portion 60. said tip-cutter U)O capable of removing a portion of an abradable material 32 during a tip rub.

2. An airfoil 42 according to claim .1 wherein the tip-cutter 100 has a cutter- profile 102 that facilitates reducing loading induced to said airfoil 42 during tip a rub.

3. An airfoil 42 according to claim 2 wherein the cutter-prof lie 102 comprises a cutter-angle 104 located at the leading edge 48 at the airfoil tφ.

4. An airfoil 42 according to claim 3 wherein said cutter-angle 104 has a value between about two degrees and about five degrees.

5. An airfoil 42 according to claim I wherein said tip-cutter 100 extends along a portion of the leading edge 48.

6. An airfoil 42 according to claim 1 wherein said tip-cutter 100 extends in a chordwise direction along a portion of the airfoil 42.

7. Art airfoil 42 according to claim 1 further comprising a tip-grinder 120 located on the tip portion 60. said lip-grinder 120 capable of removing a portion of an abradable material 32 during a tip rub.

S An airfoil 4.2 according to claim 1 further comprising a tip-rake 1 10 located on at least a part of the tip portion 60, extending between said first and second sidewalls 44, 46. said tip-rake having a rake-profile 1 12 that facilitates reducing loading induced to said airfoil 42 during tip rubs y. An airfoil 42 comprising: a first sidewall 44; a second sidewall 46 coupled Io said first sidewali 44 at a leading edge 48 and at a trailing edge 50; a tip portion 60 extending between said first and second sidewails 44. 46; and a tip-grinder 120 located on at least a pail of the tip portion 60, said tip-grinder 120 capable of removing a portion of an abradable material 32 during a tip rub.

10. An airfoil 42 according to claim 9 wherein the tip-grinder is located near the leading edge 48.

1 1. An airfoil 42 according to claim 9 wherein the tip-grinder 120 is located near the trailing edge 50.

12. An airfoil 42 according to claim 9 wherein the tip-grinder 120 comprises a ceramic material.

13. An airfoil 42 according to claim 9 wherein the tip-gπnder 120 is bonded to the airfoil 42 by brazing.

14. An airfoil 42 according to claim 9 wherein the tip-grinder 120 is applied to the airfoil 42 by thermaϊ-spraying.

15. An airfoil 42 according to claim 9 further comprising a tip-rake 1 10 located on at least a part of the tip portion 60, extending between said first and second sidewalls 44. 46, said tip-rake 1 H) having a rake-profile 1 12 that facilitates reducing loading induced to said airfoil 42 during tip rubs. 16 An airfoil 42 in accordance with Claim 1 s further comprising a stacking axis HO and a plane H2 substantially pei pendsculai to sasd slacking axis KO, wherein said tsp-sake 1 10 has a iakc angle H 4 between about 5° and about J ^⁰ with respect Io said plane K2

17 An aπfoϊl 42 πi accordance with Claim 15 located within a casmg 17 wherein a first distance 131 measured between the casmg 1 ? and said first SJ dew all 44 is smaller than a second distance 132 measured betw een the casmg 17 and said second sidcw all 46

18 Λn airfoil 42 m accordance with Claim 15 forming a potlion of a iotot assembh 13 wherein an abiadable 32 extends circumfeientiaJh around a longitudinal axis 12 of the rotor assembh H. and said tip-rake profile 1 12 facilitates causing said tjp-gnnder 120 near the first ssdew all 44 to contact the abradable matena! >2 while said second sidewall 46 av oids contacting the abradable matena! 32 during Up aibs

IV Λ rotor assembh 13 compiising a rotor hub 21. and a pluralits of joior blades 15 coupled io said joior hub 2! such that each said ioior blade 15 composes an anfoiϊ portion 42 comprising a first sidewalϊ 44, a second ^aid first 44 at a leadmg edge 48 and at a trailing edge 50. a root portion 54, a tip portion ^o extending between said first and second Sidewalls 44, 46, and a tip-cutter 100 located on the first sidew all 44 near the tip portion 60, said up-cutter 100 capable of removing a portion ol an abiadable matena! 32 diaing a tip rub

20 Λ rotoi assembh 13 ui accordance with Claim 19 w herein an abradabie casing 17 extends circumferennalh about the rotor assembh 13. and said tip-cutter Wu has a cutter-profile it>2 that facilitates reducing loading induced to said aufoil 42 during a ttp tub

21 Λ iotor as^erahh 13 composing a rotor hub 21 , and a plurality of rotor blades 15 coupled to said rotor hub 2 ! such that each said rotor blade 15 comprises an airfoil portion 42 comprising a first sidewall 44. a second sidewall 46 coupled to said first sidewall 44 at a leading edge 48 and at a trailing edge 50, a root portion 54, a tip portion 60 extending between said first and second sidewalis 44, 46, and a tip-grinder 120 located on the tip portion 60, said ttp- grmder 120 capable of removing a portion of an abradable materia! 32 during a tip rub.

22. A rotor assembly 13 hi accordance with Claim 21 wherein an abradable easing 1 7 extends circumferentiaily about the rotor assembly 13. and said tip-grinder 120 facilitates reducing loading induced to said airfoil during a tip rub.

23. A blade assembly 170 comprising: an airfoil 154; and a metal leading edge (MLE) 158 coupled to at least a portion of said airfoil 154, said MLE having a lip-cutter 100 capable of removing a portion of an abradable material 32 during a tip rub,

24. A blade assembly 170 according to claim 23 further comprising a tip-grinder 120 located on a tip portion 60 of the blade assembly 1 70, said tip-grinder 120 capable of removing a portion of an abradable materia! 32 during a tip rub.

25 A blade assembly 170 according to claim 23 further comprising a tip-rake 1 10 located on at least a part of a tip portion 60 of the blade assembly 170, said tip-rake having a rake-profile 112 that facilitates reducing loading induced in the blade assembly 170 during a tip rub.

26. A busk ^"180 comprising a plurality of airfoils 42 extending from a hub 21 , each airfoil 42 comprising a first sidewall 44, a second sidewall 46 coupled to said first sidewall 44 at a leading edge 48 and at a trailing edge 50, a root portion 54. a tip portion 60 extending between said first and second sidewalis 44, 46, aid a tip-cutter 100 located on the first sidewall 44 of at least one airfoil 42 near the tip portion GO, said tip-cutter 100 capable of removing a portion of an abradable material 32 during a tip rub.

27. A blisk 180 comprising a plurality of airfoils 42 extending from a hub 21, each airfoil 42 comprising a first sidewaJl 44, a second sidewali 46 coupled to said first sidewall 44 at a leading edge 48 and at a {railing edge 50, a root portion 54. a tip portion 60 extending between said first and second sidewalls 44. 46. and a tip-grinder 120 located on the tip portion 60 of at least one airfoil 42, said tip-grinder 120 capable of removing a portion of an abradable material 32 during a tip rub.

28. A method 300 for reducing tip nib loads m an airfoil 42 comprising the steps of: selecting a location of contact^" between the airfoil 42 and a static structure 32; selecting a location on the airfoil 42 for incorporating a tip-cutter 100; selecting a cutter-profile 102 for the tip-cutter 100; and incorporating the lip-cutter 100 on the selected location on the airfoil 42 such thai tip-cutter 100 is capable of removing a portion of the static structure 32 during a tip rub such that tip rub loads are facilitated to be reduced.

29. A method 300 according to claim 28 wherein the static structure is an abradable material 32

30. A method 300 according to claim 28 wherein the step of selecting a tip-cutter profile 102 comprises selecting a cutter-angle 104.

31. A method 300 according to claim 28 wherein the tip-cutter 100 extends along a portion of a leading edge S.8 of the airfoil 42

31. A method 300 according to claim 28 wherein the tip-cutter 100 extends in a chordwise direction along a portion of the airfoil 42. 13 A method 300 according to claim 28 wherein Ae step of incorporating the Up- cutter 100 comprises machining the tip-cutler profile J 02 on the selected location on the an foil 42

34 Λ method 300 accoiding to claim 28 further compiising the step of selecting a tφ-grmder 120

35 A method 300 aeeotding to claim 34 further compiismg lhc step of bonding the up-gnnder 120 to the airfoil 42

36 Λ method 300 accotdmg Io claim 34 whet em the step of bonding comprises

37 A method 300 accotdmg to claim 28 fuither eompttsmg the .step of selecting a tip πike l it* ha\ mg a tip-rake profile 1 12 that facilitates reducing loading induced to the an foil 42 dimng tip nibs

38 4 method 300 according to claim 37 wherein the tip-rake I IO is incorporated on the airfoil 42 b> machining

3^> Λ method (oi assembling a rotoi assembK 13, said method compiling the steps of proΛ iώng a rotor blade 15 including a first sidewall 44. a second sidewall 46. where the first and second sidew alLs 44 46 ate connected at a leading edge 48 and a uasling edge 50 and extend in :>pan from a loot portion 54 to a tip portion 60, reraoung blade mateiia! from a portion of the tip portion 60 to form a Up- cutter H)O hax ifig a cutter-profile 102, and coupling the rolot blade 15 to a rolot hub 21 such that duπng tip tubs the tip- ctittet 100 machines an abradable inateiial 32 to facilitate reducing radial loading induced to the blade dunng tip rubs

40 A method according to claim 39 wherein the tip-cutter 100 is formed near the leading edsje 48 of the rotor blade 15 4! . A method according to claim 39 wherein cutter-profile 102 comprises a cuiter- angle 104

42. A method according to claim 39 further comprising the step of bonding a tip- grinder 120 to the rotor blade 15.

43. A method according to claim 42 wherein the step of bonding comprises brazing.

44. A method according to claim 39 further comprising the step of incorporating a tip-rake 1 10 having a rake-profile 1 12 that facilitates reducing ϊoadmg induced to the blade 15 during tip rubs.

45 A method according to claim 44 wherein the tip-rake 1. 1.0 is incorporated on the rotor blade 15 bv machinum.

46. A method for assembling a rotor assembly 13. said method comprising the steps of: providing a blade assembly 170 including an airfoil .154 and a metal leading edge (MLE) 158 coupled to at least a portion of said airfoil 154; removing material from a portion of the MLE to form a tip-cutter 100 having a cutter-profile 102; and coupling the bϊade assembly 170 to a rotor hub 21 such that during tip rubs the tip-cutter 100 machines an abradable material 32 to facilitate reducing radial loading induced to the blade durmg tip rubs.

47. A method according to claim 46 further comprising the step of providing a tip- grinder 120 located on a tip portion 60 of the blade assembly 170, said tip-grinder .120 capable of removing a portion of an abradable material 32 during a tip aib.

48. A method according fo claim 46 further comprising the step of providing a tip- rake 1 10 located on at least a part of a tip portion 60 of the blade assembly 170, said tip-rake having a rake-profile 1 12 that facilitates reducing loading induced in the blade assembly 170 during a lip rub.