Gas turbine engine combustor surge retention

A combustor assembly for a gas turbine engine includes a static structure and an annular combustor extending around a central axis and located radially inwards of the static structure. The annular combustor includes an annular outer shell and an annular inner shell that define an annular combustion chamber there between. The annular combustor is free of any rigid attachments directly between the static structure and the annular outer shell. The annular outer shell includes a radially-outwardly extending flange. A stop member is rigidly connected with the static structure and is located adjacent the radially-outwardly extending flange such that axial-forward movement of the annular combustor is limited.

BACKGROUND

This disclosure relates to a combustor and, more particularly, to controlling position of a combustor.

Combustors, such as those used in gas turbine engines, typically include radially spaced inner and outer liners that define an annular combustion chamber in between. A bulkhead panel is provided at a forward end of the chamber to shield a forward section of the combustor from the relatively high temperatures in the chamber. A plurality of fuel nozzles extend into the combustor through the forward end and into the bulkhead panel to provide fuel to the combustor.

SUMMARY

A combustor assembly for a gas turbine engine according to an aspect of the present disclosure includes a static structure and an annular combustor extending around a central axis and being located radially inwards of the static structure. The annular combustor includes an annular outer shell and an annular inner shell that define an annular combustion chamber there between. The annular combustor is free of any rigid attachments directly between the static structure and the annular outer shell. The annular outer shell includes a radially-outwardly extending flange. A stop member is rigidly connected with the static structure and is located adjacent the radially-outwardly extending flange such that axial-forward movement of the annular combustor is limited.

In a further non-limiting embodiment of the any of the foregoing embodiments, the stop member is axially-forwardly spaced apart by a distance D from the radially-outwardly extending flange such that movement of the annular combustor is limited to an amount equal to the distance D.

In a further non-limiting embodiment of the any of the foregoing embodiments, the annular combustor includes a forward end and an aft end, and the radially-outwardly extending flange is located at the aft end.

In a further non-limiting embodiment of the any of the foregoing embodiments, the annular combustor includes at least one opening at the forward end through which at least one corresponding fuel nozzle is received with a clearance gap distance G between the fuel nozzle and the opening, and D is less than G.

In a further non-limiting embodiment of the any of the foregoing embodiments, the stop member is affixed to a vane support ring.

In a further non-limiting embodiment of the any of the foregoing embodiments, the stop member is affixed with a fastener and the stop member includes an anti-rotation feature.

In a further non-limiting embodiment of the any of the foregoing embodiments, the anti-rotation feature includes an aft-projecting rail.

In a further non-limiting embodiment of the any of the foregoing embodiments, the aft-projecting rail includes a rounded end.

In a further non-limiting embodiment of the any of the foregoing embodiments, the radially-outwardly extending flange includes a radial slot that is slidingly engaged with a bushing that has a stop member located at an axially forward end thereof.

In a further non-limiting embodiment of the any of the foregoing embodiments, the bushing has a polygonal cross-section.

In a further non-limiting embodiment of the any of the foregoing embodiments, the stop member is integral with the static structure.

In a further non-limiting embodiment of the any of the foregoing embodiments, the stop member includes a circumferentially-extending arm that defines a circumferential slot in which the radially-outwardly extending flange is received.

In a further non-limiting embodiment of the any of the foregoing embodiments, the stop member is affixed to a turbine vane platform.

In a further non-limiting embodiment of the any of the foregoing embodiments, the stop member includes a ring structure, a tab extending radially inwardly from the ring structure and a circumferential flange extending opposite the tab, the circumferential flange being attached to the static structure.

A gas turbine engine according to an aspect of the present disclosure includes a static structure, a compressor section and an annular combustor in fluid communication with the compressor section. The annular combustor extends around a central axis and is located radially inwards of the static structure. The annular combustor includes an annular outer shell and an annular inner shell that define an annular combustion chamber there between. The annular combustor is free of any rigid attachments directly between the static structure and the annular outer shell. The annular outer shell includes a radially-outwardly extending flange. A turbine section is in fluid communication with the annular combustor. A stop member is rigidly connected with the static structure and is located adjacent the radially-outwardly extending flange such that axial-forward movement of the annular combustor is limited.

In a further non-limiting embodiment of the any of the foregoing embodiments, the stop member is axially-forwardly spaced apart by a distance D from the radially-outwardly extending flange such that movement of the annular combustor is limited to an amount equal to the distance D.

In a further non-limiting embodiment of the any of the foregoing embodiments, the annular combustor includes a forward end and an aft end, and the radially-outwardly extending flange is located at the aft end.

In a further non-limiting embodiment of the any of the foregoing embodiments, the annular combustor includes at least one opening at the forward end through which at least one corresponding fuel nozzle is received with a clearance gap distance G between the fuel nozzle and the opening, and D is less than G.

In a further non-limiting embodiment of the any of the foregoing embodiments, the stop member is affixed with a fastener and the stop member includes an anti-rotation feature.

A method for controlling movement of a combustor in a gas turbine engine, according to an aspect of this disclosure includes limiting axial-forward movement of an annular combustor in a gas turbine engine using a stop member that is axially-forwardly spaced apart by a distance D from a radially-outwardly extending flange on an annular outer shell of the annular combustor such that axial-forward movement of the annular combustor is limited to an amount equal to the distance D.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1illustrates an example gas turbine engine20. The gas turbine engine20is disclosed herein as a high bypass, two-spool turbofan that generally incorporates a fan section22, a compressor section24, a combustor section26and a turbine section28. Alternative engines might include an augmentor section (not shown) among other systems or features. The fan section22drives air along a bypass flowpath while the compressor section24receives air along a core flowpath for compression and presentation into the combustor section26then expansion through the turbine section28. Although depicted as a turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with turbofans and the teachings may be applied to other types of turbine engines, including three-spool architectures and ground-based turbines that do not include the fan section22.

The gas turbine engine20generally includes a low spool30and a high spool32mounted for rotation about an engine central longitudinal axis A relative to an engine static structure36via several bearing systems38. It should be understood that various bearing systems38at various locations may alternatively or additionally be provided.

The low spool30generally includes an inner shaft40that interconnects a fan42, a low pressure compressor44and a low pressure turbine46. The inner shaft40is connected to the fan42through a geared architecture48to drive the fan42at a lower speed than the low spool30. The high spool32includes an outer shaft50that interconnects a high pressure compressor52and high pressure turbine54. It is to be understood that “low pressure” and “high pressure” as used herein are relative terms indicating that the high pressure is greater than the low pressure. An annular combustor56is arranged between the high pressure compressor52and the high pressure turbine54. The inner shaft40and the outer shaft50are concentric and rotate via bearing systems38about the engine central longitudinal axis A which is collinear with their longitudinal axes.

The core airflow is compressed by the low pressure compressor44then the high pressure compressor52, mixed and burned with fuel in the annular combustor56, then expanded over the high pressure turbine54and low pressure turbine46. The turbines46and54rotationally drive the respective low spool30and high spool32in response to the expansion.

FIG. 2Ashows a perspective, isolated view of the annular combustor56, andFIG. 2Bshows an exploded perspective view of the annular combustor56. In this example, the annular combustor56is a 4-piece construction that includes an annular outer shell60, an annular inner shell62that is radially inwardly spaced from the annular outer shell60to define an annular combustion chamber64there between, an annular hood66and a bulkhead68that is secured to the annular outer shell60, annular inner shell62and annular hood66. The annular outer shell60, the annular inner shell62, the annular hood66and the bulkhead68each extend circumferentially around the engine central longitudinal axis A.

FIG. 3Ashows a cross-section of the annular combustor56, andFIG. 3Bshows a sectioned, perspective view of the annular combustor56. The annular inner shell62includes a plurality of radially-inwardly extending flanges62a(one shown) that rigidly affix the annular combustor56within the gas turbine engine20. A plurality of fuel nozzles70(one shown) extend from an outer static structure72through corresponding openings74in the annular hood66that is located at the forward end of the annular combustor56. It is to be understood that relative positional terms, such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are relative to the normal operational attitude of the gas turbine engine20and should not be considered otherwise limiting.

The annular outer shell60is free of any free of any rigid attachments directly between the static structure72and the annular outer shell60. In this regard, the annular combustor56is “free floating” within the gas turbine engine20such that the flanges62aprovide the exclusive rigid support. The term “rigid” and variations thereof as used herein refer to a support that resists deformation under the weight of the annular combustor56and under the loads generated in operation of the gas turbine engine20. Rigid supports, such as the flanges62a, thus support the weight of the annular combustor56under the loads generated in operation, while a flexible or non-rigid support could not bear the weight of the annular combustor56under such loads.

Certain events in the operation of the gas turbine engine20can cause the annular combustor56to move axially forward. As an example, a surge event in the gas turbine engine20can cause a back pressure that tends to urge the annular combustor56forward in a pivot motion about the flanges62a. At least a component of the pivot motion is in an axially forward direction. If the axially-forward component of the motion is substantial, the fuel nozzle70can come into contact with the sides of the openings74. A plurality of stop members76are therefore used in combination with a radially-outwardly extending flange60aof the annular outer shell60to limit axial-forward motion of the annular combustor56. Because the stop members76are used to limit movement, the annular combustor56does not need to be made more structurally robust, such as with thicker walls, to resist movement.

FIG. 4shows an expanded cross-section of the stop member76and the radially-outwardly extending flange60a. The radially-outwardly extending flange60extends completely around the annular outer shell60. The stop member76is rigidly connected with the static structure72and is axially-forwardly spaced apart by a distance D, such as 0.010-0.050 inches (0.254-1.27 millimeters), from the radially-outwardly extending flange60a. Thus, the stop member76limits the axial-forward movement of the annular combustor56by an amount that is equal to the distance D. The annular outer shell60of the annular combustor56is still free-floating in that it is not rigidly affixed to any other structure, but the stop member76limits movement in excess of the distance D to thereby ensure that the sides of the openings74do not contact the fuel nozzles70.

As an example, the distance D between the radially-outwardly extending flange60aand the stop member76is selected such that the distance D is less than a gap distance, represented as distance G inFIG. 3A, between the fuel nozzle70and corresponding sides of the opening74. Thus, the annular combustor56is permitted to move, but only by an amount that avoids contact between the fuel nozzles70and the sides of the openings74.

Referring also toFIG. 5, the stop member76in this example is a distinct piece that is secured onto a vane support ring80of the static structure72in the gas turbine engine20. In one example, six stop members76are uniformly circumferentially secured around the vane support ring80, although the number of stop members76will vary depending on the weight of the annular combustor56and loads generated during operation. Because the stop members76are distinct pieces that are secured onto the vane support ring80, the annular combustor56can first be assembled to the vane support ring80prior to securing the stop members76. Thus, the stop members76do not hinder assembly of the annular combustor56to the vane support ring80.

The stop member76includes an opening76athrough which a fastener81is received to secure the stop member76and the vane support ring80together. In a further example, the fastener81is a bolt that is received through the opening76aand a corresponding opening82ain a boss82of the vane support ring80. The fastener81is secured using a nut84such that the stop member76is rigidly affixed.

The stop member76includes a radially-extending flange90that extends from a boss92, which includes the opening76afor securing the stop member76as described above. The boss92extends between a radially outer side94, a radially inner side96, a forward side98and an aft side100. Optionally, the aft side100of the stop member76includes anti-rotation features102that ensure proper orientation of the stop member76when it is secured to the boss82of the vane support ring80.

In this example, the anti-rotation features102include aft-projecting rails102aand102bthat flank the opening76a. The rails102aand102bextend from the radially inner side96of the boss92toward the radially outer side94, but in this example do not extend all the way to the radially outer side94. The rails102aand102binclude respective rounded ends102cthat act as sliding surfaces when the stop member76is assembled onto the boss82. That is, the rounded ends102creceive and guide the boss82there between as the stop member76is slid onto the boss82. The rails102aand102bthus flank the boss82and thereby limit rotation of the stop member76about the central axis of the opening76aas the fastener81is tightened to secure the stop member76.

In a further example, the radially-outwardly extending flange60a, the stop member76, the fastener81, the nut84and the boss82are designed such that, given the expected thermal expansions of each of these components, which are made of a metal alloy or alloys, during engine20operation, there is the distance D between the radially-outwardly extending flange60aand the stop member76. Further, the radially-outwardly extending flange60a, the stop member76, the fastener81, the nut84and the boss82may be designed with expansion gaps, such as gap83, to maintain clearance between moving parts and thus reduce wear.

FIG. 6shows another embodiment of a stop member176. In this disclosure, like reference numerals designate like elements where appropriate and reference numerals with the addition of one-hundred, or multiples thereof, designate modified elements that are understood to incorporate the same features and benefits of the corresponding elements. In this embodiment, the annular outer shell60includes a plurality radially-outwardly extending flanges160athat are discreet tabs. The flanges160aare uniformly circumferentially spaced about the annular outer shell60, for example.

The stop member176is axially-forwardly spaced apart from the radially-outwardly extending flange160aand extends from a static structure172, such as a case, that surrounds or partially surrounds the annular combustor56. In one example, the static structure172is a diffuser case. The stop member176is integrally formed with the static structure172. Alternatively, the stop member176is a separate and distinct piece that is affixed to the static structure172.

FIG. 7Ashows a cross-section of another example stop member276, andFIG. 7Bshows a perspective view of the stop member276. In this example, the annular outer shell60includes a plurality of radially-outwardly extending flanges260athat have radial slots260b. The radial slots260bof the flanges260afit over corresponding bushings210that are rigidly affixed to a turbine vane platform212. Each of the bushings210includes a forward end210a, which includes a corresponding stop member276. The bushings210are secured to the turbine vane platform212of static structure272using a fastener282to provide the axial distance D between the stop member276and the flange260a. Optionally, a clamp member214and spring washer216(FIG. 7A) are provided between the turbine vane platform212and the flange260a.

The bushing210has a polygonal cross-section210b. In this example, the polygonal cross-section is rectangular or square such that the sides of the bushing210function as a bearing surface for sliding contact with the sides of the radial slots260bof the flanges260a. Thus, the sides of the bushing210guide axial movement of the annular combustor56. The stop member276has an enlarged cross-section relative to the polygonal cross-section of the bushing210. Thus, forward movement of the annular combustor causes the flange260ato butt against the stop member276and prevent further axial-forward movement of the annular combustor56.

FIG. 8Aillustrates a cross-section of another stop member376, andFIG. 8Billustrates a perspective view of the stop member376. In this example, the stop member376is a circumferential arm376aof static structure372that defines a circumferential slot376b. A radially-outwardly extending flange360aof the annular outer shell60is received into the circumferential slot376b. As an example, the radial size of the circumferential slot376bis larger than the axial thickness of the flange360asuch that there is a distance D between the forward side defining the circumferential slot376band the flange360a. Thus, the stop member376limits axial-forward movement of the annular combustor56, as described above.

FIG. 9Aillustrates a perspective, cutaway view of another stop member476, andFIG. 9Billustrates a cross-section of the stop member476. In this example, the stop member476includes tabs476a(one shown) that extends radially inwardly from the outer static structure472such that there is a distance D between the forward side of the flange460aand the aft side of the tab476a. Thus, the stop member476limits axial-forward movement of the annular combustor56, as described above.

The stop member476includes a ring structure477from which the tabs476aextend. The ring structure477extends around the engine central axis A and includes a circumferential flange479that extends radially in a direction opposite of the tabs476a. The circumferential flange479is secured between a first flange472aand a second flange472bof the outer static structure472. The circumferential flange479, first flange472aand second flange472binclude openings481that align to receive a fastener483(FIG. 9A), such as a bolt, there through to secure the circumferential flange479between the first flange472aand the second flange472b.