Mounting assembly for the aft end of a ceramic matrix composite liner in a gas turbine engine combustor

A mounting assembly for an aft end of a liner of a gas turbine engine combustor including a support member, wherein a longitudinal centerline axis extends through the gas turbine engine. The mounting assembly includes a pin member extending through each one of a plurality of circumferentially spaced openings in a portion of the support member for the combustor and into a plurality of partial openings formed in the aft end of the liner, with each pin member including a head portion at one end thereof, and a device positioned within each opening in the support member so as to retain the pin members therein. The pin members and the support member are able to slide radially and/or axially with respect to the liner aft end as the support member experiences thermal growth greater than the liner.

BACKGROUND OF THE INVENTION

The present invention relates generally to the use of Ceramic Matrix Composite liners in a gas turbine engine combustor and, in particular, to the mounting of such CMC liners to a support member of the combustor at an aft end so as to accommodate differences in radial and axial growth.

It will be appreciated that the use of non-traditional high temperature materials, such as Ceramic Matrix Composites (CMC), are being studied and utilized as structural components in gas turbine engines. There is particular interest, for example, in making combustor components which are exposed to extreme temperatures from such material in order to improve the operational capability and durability of the engine. As explained in U.S. Pat. No. 6,397,603 to Edmondson et al., substitution of materials having higher temperature capabilities than metals has been difficult in light of the widely disparate coefficients of thermal expansion when different materials are used in adjacent components of the combustor. This can result in a shortening of the life cycle of the components due to thermally induced stresses, particularly when there are rapid temperature fluctuations which can also result in thermal shock.

Accordingly, various schemes have been employed to address problems that are associated with mating parts having differing thermal expansion properties. As seen in U.S. Pat. No. 5,291,732 to Halila, U.S. Pat. No. 5,291,733 to Halila, and U.S. Pat. No. 5,285,632 to Halila, an arrangement is disclosed which permits a metal heat shield to be mounted to a liner made of CMC so that radial expansion therebetween is accommodated. This involves positioning a plurality of circumferentially spaced mount pins through openings in the heat shield and liner so that the liner is able to move relative to the heat shield.

U.S. Pat. No. 6,397,603 to Edmondson et al. also discloses a combustor having a liner made of Ceramic Matrix Composite materials, where the liner is mated with an intermediate liner dome support member in order to accommodate differential thermal expansion without undue stress on the liner. The Edmondson et al. patent further includes the ability to regulate part of the cooling air flow through the interface joint.

Accordingly, it would be desirable for a mounting assembly to be developed for a CMC liner which is able to accommodate differences in axial and radial growth between such liner at an aft end and a support member of the combustor while maintaining the circumferential position of such liner with respect thereto.

BRIEF SUMMARY OF THE INVENTION

In a first exemplary embodiment of the invention, a mounting assembly for an aft end of a liner of a gas turbine engine combustor including a support member is disclosed, wherein a longitudinal centerline axis extends through the gas turbine engine. The mounting assembly includes a pin member extending through each one of a plurality of circumferentially spaced openings in a portion of the support member for the combustor and into a plurality of partial openings formed in the aft end of the liner, with each pin member including a head portion at one end thereof, and a device positioned within each opening in the support member so as to retain the pin members therein. The pin members and the support member are able to slide radially and/or axially with respect to the liner aft end as the support member experiences thermal growth greater than the liner.

In a second exemplary embodiment of the invention, a combustor for a gas turbine engine having a longitudinal centerline axis extending therethrough is disclosed as including: an outer liner having a forward end and an aft end, with the outer liner being made of a ceramic matrix composite material; an outer casing located substantially parallel to the outer liner so as to form an outer passage therebetween, the outer casing being made of a metal; an outer support member associated with the outer casing and located adjacent the outer liner aft end, the outer support member being made of a metal; and, an assembly for mounting the outer liner to the outer support member. In this way, the outer support member is movably connected to the outer liner aft end in a radial and/or axial direction as the outer casing and the outer support member experience thermal growth greater than the outer liner.

In accordance with a third embodiment of the invention, a combustor for a gas turbine engine having a longitudinal centerline axis extending therethrough is disclosed as including: an inner liner having a forward end and an aft end, the inner liner being made of a ceramic matrix composite material; an inner support cone located substantially parallel to the inner liner so as to form an inner passage therebetween, the inner support cone being made of a metal; and, an assembly for mounting the inner liner aft end to the inner support cone. In this way, the inner support cone is movably connected to the inner liner aft end in a radial and/or axial direction as the inner support cone experiences thermal growth greater than the inner liner.

In accordance with a fourth embodiment of the invention, a method of mounting an aft end of a liner to a support member of a combustor in a gas turbine engine having a longitudinal centerline axis is disclosed, wherein the liner is made of a material having a lower coefficient of thermal expansion than the support member. The method includes the steps of fixedly connecting the support member to a stationary portion of the gas turbine engine and connecting the liner aft end to the support member in a manner so as to permit radial movement of the support member with respect to the liner aft end. Additional steps may include connecting the liner aft end to the support member in a manner so as to permit axial movement of the support member with respect to the liner aft end and preventing circumferential movement of the support member with respect to the liner aft end.

In accordance with a fifth embodiment of the invention, a mounting assembly for an aft end of a liner of a gas turbine engine combustor including a support member is disclosed, wherein a longitudinal centerline axis extends through the gas turbine engine. The mounting assembly includes a pin member extending through each one of a plurality of circumferentially spaced openings in a first portion of the support member for the combustor, a plurality of openings formed in the aft end of the liner and into a plurality of partial openings formed in a second portion of the support member oriented substantially parallel to the support member first portion, each pin member including a head portion at one end thereof, and a device positioned within each opening in the support member first portion so as to retain the pin members therein. The pin members and the support member are able to slide radially and/or axially with respect to the liner aft end as the support member experiences thermal growth greater than the liner. The support member also includes a third portion connecting the first and second support member portions, wherein a gap for receiving the liner aft end is defined between the first and second support member portions.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings in detail, wherein identical numerals indicate the same elements throughout the figures,FIG. 1depicts an exemplary gas turbine engine combustor10which conventionally generates combustion gases that are discharged therefrom and channeled to one or more pressure turbines. Such turbine(s) drive one or more pressure compressors upstream of combustor10through suitable shaft(s). A longitudinal or axial centerline axis12is provided through the gas turbine engine for reference purposes.

It will be seen that combustor10further includes a combustion chamber14defined by an outer liner16, an inner liner18and a dome20. Combustor dome20is shown as being single annular in design so that a single circumferential row of fuel/air mixers22are provided within openings formed in such dome20, although a multiple annular dome may be utilized. A fuel nozzle (not shown) provides fuel to fuel/air mixers22in accordance with desired performance of combustor10at various engine operating states. It will also be noted that an outer annular cowl24and an inner annular cowl26are located upstream of combustion chamber14so as to direct air flow into fuel/air mixers22, as well as an outer passage28between outer liner16and a casing30and an inner passage32between inner liner18and an inner casing31. An inner annular support member34, also known herein as an inner support cone, is further shown as being connected to a nozzle support33by means of a plurality of bolts37and nuts39. In this way, convective cooling air is provided to the outer surfaces of outer and inner liners16and18, respectively, and air for film cooling is provided to the inner surfaces of such liners. A diffuser (not shown) receives the air flow from the compressor(s) and provides it to combustor10.

It will be appreciated that outer and inner liners16and18are preferably made of a Ceramic Matrix Composite (CMC), which is a non-metallic material having high temperature capability and low ductility. Exemplary composite materials utilized for such liners include silicon carbide, silicon, silica or alumina matrix materials and combinations thereof. Typically, ceramic fibers are embedded within the matrix such as oxidation stable reinforcing fibers including monofilaments like sapphire and silicon carbide (e.g., Textron's SCS-6), as well as rovings and yarn including silicon carbide (e.g., Nippon Carbon's NICALON®, Ube Industries' TYRANNO®, and Dow Corning's SYLRAMIC®), alumina silicates (e.g., Nextel's 440 and 480), and chopped whiskers and fibers (e.g., Nextel's 440 and SAFFIL®), and optionally ceramic particles (e.g., oxides of Si, Al, Zr, Y and combinations thereof) and inorganic fillers (e.g., pyrophyllite, wollastonite, mica, talc, kyanite and montmorillonite). CMC materials typically have coefficients of thermal expansion in the range of about 1.3×10−6in/in/° F. to about 3.5×10−6in/in/° F. in a temperature of approximately 1000-1200° F.

By contrast, outer casing30, nozzle support33, inner support cone34and an outer support member40are typically made of a metal, such as a nickel-based superalloy (having a coefficient of thermal expansion of about 8.3-8.6×10−6in/in/° F. in a temperature range of approximately 1000-1200° F.). Thus, liners16and18are better able to handle the extreme temperature environment presented in combustion chamber14due to the materials utilized therefor, but attaching them to the different materials utilized for outer casing30, nozzle support33, inner support cone34and outer support member40presents a separate challenge. Among other limitations, components cannot be welded to the CMC material of outer and inner liners16and18.

Accordingly, it will be seen inFIG. 2that a mounting assembly36is provided for an aft end38of outer liner16and an outer support member40so as to accommodate varying thermal growth experienced by such components. It will be appreciated that mounting assembly36shown inFIG. 2is prior to any thermal growth experienced by outer liner16, outer casing30and outer support member40. As seen inFIG. 3, however, outer liner16, outer casing30and outer support member40have each experienced thermal growth, with outer casing30and outer support member40having experienced greater thermal growth than outer liner16due to their higher coefficients of thermal expansion. Accordingly, outer casing30and outer support member40are depicted as being permitted to slide or move in a radial direction with respect to longitudinal centerline axis12away from outer liner aft end38.

More specifically, it will be understood that outer support member40includes a plurality of circumferentially spaced openings42formed in a portion thereof and outer liner aft end38, which has an increased thickness, preferably includes a plurality of circumferentially spaced partial openings or holes44(i.e., which do not extend completely through liner aft end38) formed therein which are positioned so as to be in alignment therewith. A pin member46preferably extends through each opening42and is received in a corresponding partial opening44in outer liner aft end38. Pin members46each include a head portion48at one end thereof. Openings42may include a portion43which is either chamfered or otherwise has an enlarged radius so as to better receive head portion48of pin members46. The location and/or depth of such portion43may also be utilized to verify that pin members46are properly positioned within partial openings44of outer liner aft end38.

A device50is provided within a groove portion52formed in a sidewall53defining opening42in outer support member40. Device50, which preferably is a ring-shaped member and is commonly known as a snap ring, is positioned within opening42of outer support member40in order to retain pin member46therein. In such case, ring member50is compressed against an outwardly expanding force until adjacent groove portion52and then released therein. It will then be appreciated that a diameter54of pin head portion48is greater than an inner diameter56of ring member50to provide a mechanical stop.

Of course, partial openings44in outer liner aft end38are preferably sized so that pin members46, and therefore outer support member40and outer casing30, are able to slide radially with respect to outer liner aft end38as outer support member40and/or outer casing30experience thermal growth greater than outer liner16. Accordingly, outer support member40and outer casing30are able to move between a first radial position (seeFIG. 2) and a second radial position (see FIG.3). Partial openings44may be substantially circular (when viewed from a top radial perspective) so as to permit only radial movement of pin members46, outer support member40and outer casing30, but preferably are ovular in shape (seeFIG. 4) so that a major axis45thereof is aligned substantially parallel to longitudinal centerline axis12. In this way, pin members46, outer support member40and outer casing30are able to slide axially with respect to outer liner aft end38when thermal growth of outer support member40and/or outer casing30is greater than outer liner aft end38. This design of partial openings44also serves as a stack-up tolerance during assembly of combustor10. It will be appreciated that outer support member40and/or outer casing30are also able to move between a first axial position (seeFIG. 2) and a second axial position (see FIG.3). Partial openings44will also preferably have a circumferential length41along a minor axis47which is substantially the same as a diameter49for openings42so that circumferential movement of outer support member40and outer casing30is discouraged. It will be understood that a length57of pin members46, a depth60of partial openings44, and an axial length51along major axis45of partial openings44will be sized so as to permit a desirable amount of thermal growth for outer support member40and outer casing30.

It will further be noted that each pin member46preferably includes a partial opening58formed therein which includes threads59along a sidewall61thereof. This is provided so that there will be an easy way of retrieving pin member46once ring member50is removed. More specifically, a tool or other device may be threadably mated with threads59of partial opening58so that pin member46may be lifted out of opening42and partial opening44.

Similarly, it will be see inFIG. 5that a mounting assembly62is provided for an aft end64of inner liner18and inner support cone34. It will be appreciated that mounting assembly62shown inFIG. 5is prior to any thermal growth experienced by inner liner18, inner support cone34and possibly nozzle support33. As seen inFIG. 6, however, inner liner18, nozzle support33and inner support cone34have each experienced thermal growth, with inner support cone34and nozzle support33having experienced greater thermal growth than inner liner18due to their higher coefficients of thermal expansion. Accordingly, inner support cone34is depicted as being permitted to slide or move in a radial direction with respect to longitudinal centerline axis12toward inner liner18.

More specifically, it will be understood that inner support cone34has a plurality of circumferentially spaced openings68formed in a portion66thereof and inner liner aft end64, which has an increased thickness, preferably includes a plurality of circumferentially spaced partial openings or holes70formed therein which are positioned so as to be in alignment with openings68. A pin member72preferably extends through each opening68and is received in a corresponding partial opening70in inner liner aft end64. Pin members72may each include a head portion at one end thereof as described with respect to pin head portion48herein. In such case, openings68may include a portion which is either chamfered or otherwise has an enlarged diameter so as to better receive such head portion of pin members72. Further, the location and/or depth of such portion may also be utilized to verify that pin members72are properly positioned within partial openings70of inner liner aft end64.

As seen inFIGS. 5 and 6, however, an alternate device74is utilized to retain pin members72in openings68and partial openings70. In particular, it will be understood that a flexible metal band76is preferably inserted within an annular groove portion77formed in inner support cone34which intersects each opening68in inner support cone34to provide a mechanical stop. It will be noted that band76is preferably continuous within annular groove portion77and is of sufficient length so as to overlap for at least a portion of the circumference therein. Band76also preferably has a width80which is sized to be retained within annular groove portion77of inner support cone34.

Of course, partial openings70in inner liner aft end64are preferably sized so that pin members72, and therefore inner support cone34and nozzle support33, are able to slide radially with respect to inner liner aft end64as inner support cone34and nozzle support33experience thermal growth greater than inner liner18. Accordingly, inner support cone34is able to move between a first radial position (seeFIG. 5) and a second radial position (see FIG.6). Partial openings70may be substantially circular (when viewed from a bottom radial perspective) so as to permit only radial movement of pin members72and inner support cone34, but preferably are ovular in shape (seeFIG. 7) so that a major axis71thereof is aligned substantially parallel to longitudinal centerline axis12. In this way, pin members72, nozzle support33and inner support cone34are able to slide axially with respect to inner liner aft end64when thermal growth of nozzle support33and inner support cone34are greater than inner liner aft end64. It will be appreciated that nozzle support33and inner support cone34are also able to move between a first axial position (seeFIG. 5) and a second axial position (see FIG.6). Partial openings70will also preferably have a circumferential length65along a minor axis73which is substantially the same as a diameter75for openings68so that circumferential movement of inner support cone34and support nozzle33are discouraged. It will be understood that a length81of pin members72, a depth84of partial openings70, and an axial length67along major axis71of partial openings70will be sized so as to permit a desirable amount of thermal growth for nozzle support33and inner support cone34.

It will further be noted that each pin member72may include a partial opening formed therein which includes threads along a sidewall thereof (not shown) like that described above with respect to pin member46. This is provided so that there will be an easy way of retrieving pin member72once device74is removed. More specifically, a tool or other device may be threadably mated with such threads of the partial opening so that pin member72may be lifted out of opening68and partial opening70.

It will further be seen that a plurality of circumferentially spaced support members86(known as a drag link) are connected to inner support cone34and extend axially forward to be movably connected with a forward end87of inner liner18via a mounting assembly88. In particular,FIG. 8shows that each drag link86has a wishbone-type shape and includes first and second portions90and92which extend from a common junction portion93. First and second drag link portions90and92each include an opening97and99formed in a forward portion101and103, respectively, thereof which are in alignment with openings in inner liner forward end87, and aft portion of inner cowl26and an inner portion of dome20. Forward portions101and103are spaced so that a mounting assembly88is positioned therebetween. An aft portion91of each drag link86includes an opening95therein so that it may be connected to inner support cone34via a bolt94and nut96. It will be appreciated that drag links86are provided to assist in minimizing vibrations by providing a measure of stiffness to combustor10.

An alternative mounting assembly98for an aft end102of an inner liner100is depicted inFIGS. 9 and 10. As seen therein, an inner support cone104includes a first portion106located radially inside inner liner aft end102, a second portion108located radially outside inner liner aft end102, and a third portion110connecting first and second portions106and108located axially downstream of inner liner aft end102. It will be noted that an annular gap or opening112exists between first and second portions106and108and that inner liner aft end102is positioned therein. In order to movably connect inner liner aft end102and inner support cone104, a plurality of circumferentially spaced openings114are formed in first inner support cone portion106, a plurality of circumferentially spaced openings116are formed in inner liner aft end102, and a plurality of circumferentially spaced partial openings118are formed in second inner support cone portion108, where openings114, openings116and partial openings118are in substantial alignment.

It will be noted that a pin member120is positioned to extend through each of openings114and116and be received in a corresponding partial opening118. Pin members120may include a head portion at one end thereof as described above with respect to pin head portion48. In such case, openings114may include a portion which is either chamfered or otherwise has an enlarged diameter so as to better receive such head portion of pin members120. The location and/or depth of such chamfered portion may also be utilized to verify that pin members120are properly positioned within partial openings118of inner liner aft end102.

As seen inFIGS. 9 and 10, pin member120does not include a head portion since a device126like that described for device74above is utilized to retain pin members120. In particular, it will be understood that a flexible metal band128is preferably inserted within an annular groove portion130formed in inner support cone104which intersects each opening114in inner support cone104to provide a mechanical stop. It will be noted that band128is preferably continuous within annular groove portion130and is of sufficient length so as to overlap for at least a portion of the circumference therein. Band128also preferably has a width132which is sized to be retained within annular groove portion130of inner support cone104.

Of course, partial openings118in second inner support cone portion108are preferably sized so that pin members120, and therefore inner support cone104and nozzle support33, are able to slide radially with respect to inner liner aft end102as nozzle support33and inner support cone104experience thermal growth greater than inner liner100. Accordingly, inner support cone104is able to move between a first radial position (seeFIG. 9) and a second radial position (see FIG.10). Openings116may be substantially circular (when viewed from a bottom radial perspective) so as to permit only radial movement of pin members120, nozzle support33and inner support cone104, but preferably are ovular in shape (seeFIG. 11) so that a major axis136thereof is aligned substantially parallel to longitudinal centerline axis12. In this way, pin members120, nozzle support33and inner support cone104are able to slide axially with respect to inner liner aft end102when thermal growth of nozzle support33and inner support cone104are greater than inner liner aft end102. It will be appreciated that nozzle support33and inner support cone104are also able to move between a first axial position (seeFIG. 9) and a second axial position (see FIG.10). Openings118will also preferably have a circumferential length137along a minor axis138which is substantially the same as a diameter140for openings114and a diameter142for partial openings118so that circumferential movement of nozzle support33and inner support cone104are discouraged. It will be understood that a length144of pin members120, a depth146of partial openings118, and an axial length135along major axis136of openings116will be sized so as to permit a desirable amount of thermal growth for nozzle support33and inner support cone104.

It will further be noted that pin members120may include a partial opening formed therein which includes threads along a sidewall thereof (not shown) like that described above with respect to pin member46. This is provided so that there will be an easy way of retrieving pin member120once device126is removed. More specifically, a tool or other device may be threadably mated with such threads of the partial opening so that pin member120may be lifted out of openings114and116and partial openings118.

Having shown and described the preferred embodiment of the present invention, further adaptations of the mounting assemblies for an aft end of a combustor liner can be accomplished by appropriate modifications by one of ordinary skill in the art without departing from the scope of the invention. In particular, it will be appreciated that mounting assemblies62and98may also be utilized with an outer liner when the outer support member has a configuration similar to the aft end of inner support cone portion34and104. Further, devices other than ring-shaped member50and bands76and126may be utilized to retain the pin members within their respective areas.