Attachment assembly and gas turbine engine with attachment assembly

An attachment assembly for attaching a center structure to an outer structure at least partially circumscribing the center structure, the attachment assembly having a bushing provided within the center structure or the outer structure, the bushing defining a first through passage, a bushing adapter slidably mounted within the first through passage and defining a second through passage, a threaded passage provided on the other of the center structure or the outer structure and a bolt passing through the first through passage and the second through passage and threaded into the threaded passage.

BACKGROUND OF THE INVENTION

Turbine engines, and particularly gas or combustion turbine engines, are rotary engines that extract energy from a flow of combusted gases passing through the engine onto a multitude of turbine blades. Exhaust from combustion flows through a high pressure turbine and a low pressure turbine prior to leaving the turbine engine through an exhaust nozzle. Exhaust within and leaving the exhaust nozzle is at extremely high temperatures. The exhaust transfers heat to the components of the turbine engine, including the exhaust nozzle. As the components of the turbine engine absorb heat from the exhaust, the heat signature of the turbine engine is increased. It is beneficial to use components that can withstand such heat.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, an embodiment of the invention relates to an attachment assembly for attaching a center structure to an outer structure at least partially circumscribing the center structure, the attachment assembly having a bushing provided within the center structure or the outer structure, the bushing defining a first through passage, a bushing adapter slidably mounted within the first through passage and defining a second through passage, a threaded passage provided on the other of the center structure or the outer structure and a bolt having a head and a shank with a threaded portion wherein the bolt passes through the first through passage and the second through passage, with the head abutting the bushing adapter and the threaded portion threaded into the threaded passage.

In another aspect, an embodiment of the invention relates to a gas turbine engine, having a centerbody a support structure circumscribing the centerbody and an attachment assembly for operably coupling the centerbody to the support structure and configured to allow a cooling air flow to the centerbody where the attachment assembly includes a bushing provided on the centerbody or the support structure, the bushing defining a first through passage, a bushing adapter slidably mounted within the first through passage and defining a second through passage, a threaded passage provided on the other of the centerbody or the support structure and a bolt having a head and a shank with a threaded portion wherein the bolt passes through the first through passage and the second through passage, with the head abutting the bushing adapter and the threaded portion threaded into the threaded passage.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Embodiments of the invention relate to an attachment assembly for use in a gas turbine engine. For purposes of explaining the environment of embodiments of the invention,FIG. 1illustrates an exemplary gas turbine engine10for an aircraft forming an environment for the attachment assembly. It will be understood that the principles described herein are equally applicable to turboprop, turbojet, and turbofan engines, as well as turbine engines used for other vehicles or in stationary applications. The engine10has a generally longitudinally extending axis or centerline12extending forward14to aft16. The engine10includes, in downstream serial flow relationship, a fan section18including a fan20, a compressor section22including a booster or low pressure (LP) compressor24and a high pressure (HP) compressor26, a combustion section28including a combustor30, a turbine section32including a HP turbine34, and a LP turbine36, and an exhaust section38.

The fan section18includes a fan casing40surrounding the fan20. The fan20includes a plurality of fan blades42disposed radially about the centerline12.

The HP compressor26, the combustor30, and the HP turbine34form a core44of the engine10which generates combustion gases. The core44is surrounded by a core casing46, which can be coupled with the fan casing40. A HP shaft or spool48disposed coaxially about the centerline12of the engine10drivingly connects the HP turbine34to the HP compressor26. A LP shaft or spool50, which is disposed coaxially about the centerline12of the engine10within the larger diameter annular HP spool48, drivingly connects the LP turbine36to the LP compressor24and fan20.

The LP compressor24and the HP compressor26respectively include a plurality of compressor stages52,54, in which a set of compressor blades56,58rotate relative to a corresponding set of static compressor vanes60,62(also called a nozzle) to compress or pressurize the stream of fluid passing through the stage. In a single compressor stage52,54, multiple compressor blades56,58can be provided in a ring and can extend radially outwardly relative to the centerline12, from a blade platform to a blade tip, while the corresponding static compressor vanes60,62are positioned downstream of and adjacent to the rotating blades56,58. It is noted that the number of blades, vanes, and compressor stages shown inFIG. 1were selected for illustrative purposes only, and that other numbers are possible.

The HP turbine34and the LP turbine36respectively include a plurality of turbine stages64,66, in which a set of turbine blades68,70are rotated relative to a corresponding set of static turbine vanes72,74(also called a nozzle) to extract energy from the stream of fluid passing through the stage. In a single turbine stage64,66, multiple turbine blades68,70can be provided in a ring and can extend radially outwardly relative to the centerline12, from a blade platform to a blade tip, while the corresponding static turbine vanes72,74are positioned upstream of and adjacent to the rotating blades68,70.

A center structure in the form of a centerbody80is mounted to the low pressure turbine section. The centerbody80is included in the exhaust section38and is utilized to minimize the turbulence produced in the exhaust gas within the exhaust sections38.

In operation, the rotating fan20supplies ambient air to the LP compressor24, which then supplies pressurized ambient air to the HP compressor26, which further pressurizes the ambient air. The pressurized air from the HP compressor26is mixed with fuel in combustor30and ignited, thereby generating combustion gases. The combustion gases are discharged into the HP turbine34, which extracts work from these gases to drive the HP compressor26. The combustion gases are then discharged into the LP turbine36, which extracts additional work to drive the LP compressor24, and the exhaust gas is ultimately discharged from the engine10via the exhaust section38. The driving of the LP turbine36drives the LP spool50to rotate the fan20and the LP compressor24.

Some of the ambient air supplied by the fan20can bypass the engine core44and be used for cooling of portions, especially hot portions, of the engine10, and/or used to cool or power other aspects of the aircraft. In the context of a turbine engine, the hot portions of the engine are normally downstream of the combustor30, especially the turbine section32, with the HP turbine34being the hottest portion as it is directly downstream of the combustion section28. Other sources of cooling fluid can be, but is not limited to, fluid discharged from the LP compressor24or the HP compressor26.

FIG. 2illustrates details of the mounting of the centerbody80to a support structure82of the turbine section32. The centerbody80can be formed from any suitable material including, but not limited to, a ceramic matrix composite. As the centerbody80faces high temperatures within the exhaust section the material should be suitable for such high temperatures.

The support structure82can be any suitable structure for operably coupling the centerbody80to the remainder of the gas turbine engine10including, but not limited to, the core casing46. In the illustrated example, ofFIG. 2, the support structure can include a turbine exhaust frame of the gas turbine engine10that supports the HP turbine vanes74ofFIG. 1. In the illustrated example, the centerbody80is attached to a bracket84of the support structure82via an attachment assembly86.

As better illustrated inFIG. 3, the support structure82can circumscribe the centerbody80and a plurality of attachment assemblies86can be utilized to mount the centerbody80to the support structure82. The plurality of attachment assemblies86can be circumferentially spaced about the centerbody80and support structure82.

FIG. 4shows an enlarged view of the attachment assembly86and how it operably couples the centerbody80to the bracket84attached to the support structure82. The bracket84can be integrally formed with a portion of the support structure82or can be bolted onto a portion of the support structure as illustrated. Regardless, the bracket84can be formed from a stiff material to limit deflection.

A bushing88is illustrated as being provided within an opening90in the center body80. The bushing88can include a cylindrical body87that terminates in a shoulder89, which forms a stop, and an internal portion91that can define a first through passage92. In the illustrated example, washer(s)94and a fastener96are utilized to clamp the bushing88against the centerbody80. The washer(s)94can be any suitable washer(s) including belleville washers. The washer(s)94can control the clamp load on the centerbody80at a minimum design intent value that takes into account dimensional stack-up and thermal growth of the clamping and clamped elements. While any suitable fastener96can be utilized, the fastener has been illustrated as including a wire98and wire collar100. Alternatively, the fastener96can include a threaded nut. In such an instance, the bushing88would include a threaded portion and the threaded nut would thread on the bushing88until it hit a mechanical stop on bushing88in order to control compression of the washer(s)94.

A bushing adapter102can be slidably mounted within the first through passage92defined by the bushing88. The bushing adapter102can define a second through passage104.

A threaded passage112is illustrated as being provided on the support structure82and can be included in the attachment assembly86. More specifically, a nut110is illustrated as being mounted on the bracket84and the nut110includes a threaded opening forming the threaded passage112. The nut110can be mounted to the bracket84in any suitable manner including, but not limited to, the nut110riveted to the bracket84.

A bolt120having a head122and a shank124with a threaded portion126can also be included in the attachment assembly86. The bolt120can pass through both the first through passage92and the second through passage104. The head122of the bolt120abuts the bushing adapter102and the threaded portion126threads into the threaded opening112of the nut110to constrain or secure the centerbody80to the support structure82. As illustrated, the bolt120can also include a third through passage128extending through its length. The third through passage128defines a fluid path from an interior of the center structure80to an exterior of the center body80including to the support structure82.

It will be understood that the attachment assembly86can be formed in any manner of suitable ways to operably couple the centerbody80to the support structure82. In one embodiment, the internal portion91of the bushing88can be cylindrical and the bushing adapter102can have an annular shoulder130with at least a partially rounded cross section that enables a swivel joint between the bushing88and the bushing adapter102. This enables a swivel joint between the bushing88and the bushing adapter102. As the attachment assembly86can be utilized on a gas turbine engine10with a variable exhaust nozzle that can cause a high plug load in the AFT direction during a failed open nozzle condition, the attachment assembly can transfer this plug load to the support structure82, without imparting overturning moments at each bushing88, due to the swivel joint between the bushing88and bushing adapter102.

In one embodiment, an upper diameter132of the bushing adapter102can be eccentric, with a radial eccentricity of 0.025 inches.FIG. 5is a top view of the attachment assembly86, which better shows the eccentricity of the bushing adapter102. The bolt120has been removed to better illustrate that the upper diameter132of the bushing adapter is eccentric.

Referring back toFIG. 4, other features of the bushing adapter102, including for example all other features of the bushing adapter102can be concentric to an axis134of the bolt120. The clearance between the upper diameter132of the bushing adapter102and the diameter of the internal portion91of the bushing88can be very small. By way of non-limiting example, the clearance can be about 0.003 inches. The clearance between a protrusion136of the bushing adapter102and a circumferential slot138of the bracket84can be of the same magnitude. The bushing adapter eccentricity can be used to enable adjustment of the axial position of the centerbody80, while accommodating the position tolerances of the various features of the attachment assembly86. This can include that shims (not shown) of a known thickness can be used to set the axial distance between the forward end of the centerbody80and the aft end of the support structure82. After the centerbody80is positioned axially, the bushing adapters102can be inserted into position. If all the openings are in their theoretical position, no adjustment is needed. If some openings are out of position within their manufacturing tolerances, then the bushing adapter102can be turned about its bolt centerline such that it is translated circumferentially in the circumferential slot138of the bracket84. These adjustments enable the bushing adapter102to engage with both the internal portion91of the bushing88and with the circumferential slot138of the bracket84.

Alternatively, the bushing adapter102can have an upper diameter132that is concentric with the other features of the bushing adapter102. In such an instance, the slot138of the bracket84can be modified to have a small clearance opening while some of the other brackets of the multiple attachment assemblies86have large clearance holes. This alternative, does not allow any adjustment of the axial position of the centerbody80, but assembly becomes easier because an installer only has to drop the bushing adapters102in place with no additional adjustments. In such an instance, the bushing adapter102and the bolt122may be formed as a single part.

As illustrated more clearly inFIG. 6, a controlled gap140is located between the centerbody80and a portion of the support structure82. Airflows that provide cooling flow, such as compressor bleed air, for the attachment assembly86have been illustrated with arrows. One airflow150flows through the gap140between the support structure82and the centerbody80. Another airflow152flows along the third through passage within the bolt120.

The above described embodiments provide for a variety of benefits including the attachment assembly allows differential thermal growth between the support structure and the centerbody. A further benefit provided is that the attachment assembly meters cooling flow by allowing a controlled gap between the forward end of the centerbody and the mating features of the support structure and the bolts of the assemblies include a cylindrical cooling passage along their length. This allows for cooling of the attachment assembly itself as well as allows for cooling of the centerbody. This results in advantages such as the ability to operate in higher temperature environments than typical metal designs while minimizing necessary cooling flows and weight.

Prior centerbody designs used flexible brackets bolted on bushings on the centerbody and would not be capable of being utilized in environments that operate in high temperatures that require hardware cooling. The above-described embodiments can also withstand high plug loads as opposed to conventional flexible bracket attachments that either fail themselves or transfer high overturning moments to bushings attached to the centerbody. The above described embodiments can also include a swivel joint between the bushing adapters and the bushings. Further still, conventional centerbody designs are traditionally metal designs and the above described embodiments allow for a ceramic matrix composite material to be utilized, which allows for the advantages that come along with that material system including weight reductions.

To the extent not already described, the different features and structures of the various embodiments may be used in combination with each other as desired. That one feature may not be illustrated in all of the embodiments is not meant to be construed that it may not be, but is done for brevity of description. Thus, the various features of the different embodiments may be mixed and matched as desired to form new embodiments, whether or not the new embodiments are expressly described. All combinations or permutations of features described herein are covered by this disclosure. Further still, while embodiments of the invention have been described as being in an environment of the gas turbine engine10it will be understood that the attachment assembly may be utilized for attaching any suitable center structure to an outer structure at least partially circumscribing the center structure.