# Patent

## Title
Support assembly for a gas turbine engine

## Abstract

A support assembly for a gas turbine engine includes an outer support that extends about a circumferential axis and includes at least one engagement member. An inner support forms a cavity. A control ring is located within the cavity and includes at least one tab for engaging at least one engagement member on the outer support.

## Background
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
This invention was made with government support under Contract No FA8650-09-D-2923-0021 awarded by the United States Air Force (AETD Contract). The Government has certain rights in this invention.


BACKGROUND
Gas turbine engines typically include a fan delivering air into a compressor. The air is compressed in the compressor and delivered into a combustion section where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine blades, driving them to rotate. Turbine rotors, in turn, drive the compressor and fan rotors.
The efficiency of the engine is impacted by ensuring that the products of combustion pass in as high a percentage as possible across the turbine blades. Leakage around the blades reduces efficiency.
Thus, a blade outer air seal is provided radially outward of the blades to prevent leakage radially outwardly of the blades. The blade outer air seal may be held radially outboard from the rotating blade via connections on the case or a blade outer air seal support structure. The clearance between the blade outer air seal and a radially outer part of the blade is referred to as a tip clearance.
Since the rotating blade and blade outer air seal may respond radially at different rates due to loads, the tip clearance may be reduced and the blade may rub on the blade air outer seal, which is undesirable. Therefore, there is a need to control the clearance between the blade and the blade outer air seal in order to increase the efficiency of the gas turbine engine.
SUMMARY
In one exemplary embodiment, a support assembly for a gas turbine engine includes an outer support that extends about a circumferential axis and includes at least one engagement member. An inner support forms a cavity. A control ring is located within the cavity and includes at least one tab for engaging at least one engagement member on the outer support.
In a further embodiment of the above, at least one cover plate encloses the cavity defined by the inner support.
In a further embodiment of any of the above, at least one cover plate and the inner support are made of the same material.
In a further embodiment of any of the above, the inner support includes at least one slot for accepting at least one tab on the control ring.
In a further embodiment of any of the above, at least one engagement member includes a protrusion that extends radially inward from the outer support.
In a further embodiment of any of the above, at least one engagement member includes a pair of protrusions that engage the circumferential sides of one of at least one tab on the control ring.
In a further embodiment of any of the above, the control ring and the outer support are unitary hoops.
In another exemplary embodiment, a gas turbine engine includes an outer support that extends about a circumferential axis and includes at least one engagement member. An inner support forms a cavity. A control ring is located within the cavity and includes at least one tab for engaging at least one engagement member on the outer support. A blade outer air seal is attached to the inner support.
In a further embodiment of any of the above, at least one cover plate encloses the cavity defined by the inner support.
In a further embodiment of any of the above, at least one cover plate and the inner support are made of the same material.
In a further embodiment of any of the above, the inner support includes at least one slot for accepting at least one tab on the control ring.
In a further embodiment of any of the above, at least one engagement member includes a protrusion that extends radially inward from the outer support.
In a further embodiment of any of the above, at least one engagement member includes a pair of protrusions that engage circumferential sides of one of at least one tab on the control ring.
In a further embodiment of any of the above, the outer support engages an engine static structure.
In another exemplary embodiment, a method of controlling radial growth in a gas turbine engine includes locating a unitary control ring within a cavity defined by an inner support. Circumferential movement of the control ring is restricted relative to an outer support with at least one engagement member.
In a further embodiment of any of the above, the inner support includes at least one slot for accepting at least one tab on the control ring.
In a further embodiment of any of the above, at least one engagement member includes a protrusion that extends radially inward from the outer support.
In a further embodiment of any of the above, at least one engagement member includes a pair of protrusions that engage circumferential sides of one of at least one tab on the control ring.
In a further embodiment of any of the above, the method includes engaging the outer support with an engine static structure.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of an example gas turbine engine.
FIG. 2 is a cross-sectional view of a turbine section of the example gas turbine engine of FIG. 1.
FIG. 3 is a cross-sectional view of an example support assembly for a blade outer air seal.
FIG. 4 is an end view of the example support assembly of FIG. 3.
FIG. 5 is a perspective view of an example control ring.



DETAILED DESCRIPTION
FIG. 1 schematically illustrates a gas turbine engine 20. The gas turbine engine 20 is disclosed herein as a two-spool turbofan that generally incorporates a fan section 22, a compressor section 24, a combustor section 26 and a turbine section 28. Alternative engines might include an augmentor section (not shown) among other systems or features. The fan section 22 drives air along a bypass flow path B in a bypass duct defined within a nacelle 15, while the compressor section 24 drives air along a core flow path C for compression and communication into the combustor section 26 then expansion through the turbine section 28. Although depicted as a two-spool 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 two-spool turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures.
The exemplary engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis A relative to an engine static structure 36 via several bearing systems 38. It should be understood that various bearing systems 38 at various locations may alternatively or additionally be provided, and the location of bearing systems 38 may be varied as appropriate to the application.
The low speed spool 30 generally includes an inner shaft 40 that interconnects a fan 42, a first (or low) pressure compressor 44 and a first (or low) pressure turbine 46. The inner shaft 40 is connected to the fan 42 through a speed change mechanism, which in exemplary gas turbine engine 20 is illustrated as a geared architecture 48 to drive the fan 42 at a lower speed than the low speed spool 30. The high speed spool 32 includes an outer shaft 50 that interconnects a second (or high) pressure compressor 52 and a second (or high) pressure turbine 54. A combustor 56 is arranged in exemplary gas turbine 20 between the high pressure compressor 52 and the high pressure turbine 54. A mid-turbine frame 57 of the engine static structure 36 is arranged generally between the high pressure turbine 54 and the low pressure turbine 46. The mid-turbine frame 57 further supports bearing systems 38 in the turbine section 28. The inner shaft 40 and the outer shaft 50 are concentric and rotate via bearing systems 38 about the engine central longitudinal axis A which is collinear with their longitudinal axes.
The core airflow is compressed by the low pressure compressor 44 then the high pressure compressor 52, mixed and burned with fuel in the combustor 56, then expanded over the high pressure turbine 54 and low pressure turbine 46. The mid-turbine frame 57 includes airfoils 59 which are in the core airflow path C. The turbines 46, 54 rotationally drive the respective low speed spool 30 and high speed spool 32 in response to the expansion. It will be appreciated that each of the positions of the fan section 22, compressor section 24, combustor section 26, turbine section 28, and fan drive gear system 48 may be varied. For example, gear system 48 may be located aft of combustor section 26 or even aft of turbine section 28, and fan section 22 may be positioned forward or aft of the location of gear system 48.
The engine 20 in one example is a high-bypass geared aircraft engine. In a further example, the engine 20 bypass ratio is greater than about six (6), with an example embodiment being greater than about ten (10), the geared architecture 48 is an epicyclic gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3 and the low pressure turbine 46 has a pressure ratio that is greater than about five. In one disclosed embodiment, the engine 20 bypass ratio is greater than about ten (10:1), the fan diameter is significantly larger than that of the low pressure compressor 44, and the low pressure turbine 46 has a pressure ratio that is greater than about five 5:1. Low pressure turbine 46 pressure ratio is pressure measured prior to inlet of low pressure turbine 46 as related to the pressure at the outlet of the low pressure turbine 46 prior to an exhaust nozzle. The geared architecture 48 may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3:1. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including direct drive turbofans.
A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section 22 of the engine 20 is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft (10,668 meters), with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption (‘TSFC’)”—is the industry standard parameter of lbm of fuel being burned divided by lbf of thrust the engine produces at that minimum point. “Low fan pressure ratio” is the pressure ratio across the fan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.45. “Low corrected fan tip speed” is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram° R)/(518.7° R)]0.5. The “Low corrected fan tip speed” as disclosed herein according to one non-limiting embodiment is less than about 1150 ft/second (350.5 meters/second).
The example gas turbine engine includes fan 42 that comprises in one non-limiting embodiment less than about twenty-six (26) fan blades. In another non-limiting embodiment, fan section 22 includes less than about twenty (20) fan blades. Moreover, in one disclosed embodiment low pressure turbine 46 includes no more than about six (6) turbine rotors schematically indicated at 34. In another non-limiting example embodiment low pressure turbine 46 includes about three (3) turbine rotors. A ratio between number of fan blades 42 and the number of low pressure turbine rotors is between about 3.3 and about 8.6. The example low pressure turbine 46 provides the driving power to rotate fan section 22 and therefore the relationship between the number of turbine rotors 34 in low pressure turbine 46 and number of blades 42 in fan section 22 disclose an example gas turbine engine 20 with increased power transfer efficiency.
Although the gas turbine engine 20 shown is a high bypass gas turbine engine, other types of gas turbine engines could be used, such as a turbojet engine.
FIG. 2 illustrates an enlarged schematic view of the high pressure turbine 54, however, other sections of the gas turbine engine 20 could benefit from this disclosure, such as the compressor section 24 or low pressure turbine 46. In the illustrated example, the high pressure turbine 54 includes a one-stage turbine section with a first rotor assembly 60. In another example, the high pressure turbine 54 could include a two or more stage high pressure turbine section.
The first rotor assembly 60 includes a first array of rotor blades 62 circumferentially spaced around a first disk 64. Each of the first array of rotor blades 62 includes a first root portion 72, a first platform 76, and a first airfoil 80. Each of the first root portions 72 is received within a respective first rim 68 of the first disk 64. The first airfoil 80 extends radially outward toward a first blade outer air seal (BOAS) assembly 84. The BOAS 84 is supported by a support assembly 100.
The first array of rotor blades 62 are disposed in the core flow path that is pressurized in the compressor section 24 then heated to a working temperature in the combustor section 26. The first platform 76 separates a gas path side inclusive of the first airfoils 80 and a non-gas path side inclusive of the first root portion 72.
An array of vanes 90 are located axially upstream of the first array of rotor blades 62. Each of the array of vanes 90 include at least one airfoil 92 that extend between a respective vane inner platform 94 and an vane outer platform 96. In another example, each of the array of vanes 90 include at least two airfoils 92 forming a vane double. The vane outer platform 96 of the vane 90 may at least partially engage the BOAS 84.
As shown in FIGS. 2 and 3, the support assembly 100 includes an outer support 102, an inner support 104, a control ring 106, and a cover plate 108. The outer support 102 forms a complete unitary hoop and includes an axially extending flange 110 and a radially extending flange 112. The axially extending flange 110 engages a case or a portion of the engine static structure 36 when installed in the gas turbine engine 20. The radially extending portion of the outer support 102 extends radially inward from the axially extending flange 110. In this disclosure, radially or radially extending is in relation to the engine axis A of the gas turbine engine 20 unless stated otherwise.
In the illustrated example, the inner support 104 includes a C-shaped cross section with an opening of the C-shaped cross section facing an axially upstream or forward direction. In another example, the opening of the C-shaped cross section faces in an axially downstream or rearward direction. The C-shaped cross section is formed by a radially inner flange 114 connected to a radially outer flange 116 by a radially extending flange 118. The radially extending flange 118 includes an axial surface 120 that engages or abuts an axial surface 122 on the radially extending flange 112 on the outer support 102 to prevent the inner support 104 from moving axially downstream past the radially extending flange 112.
The radially outer flange 116 is spaced radially inward from the axially extending flange 110 on the outer support 102 such that a clearance between the axially extending flange 110 and the radially outer flange 116 is maintained during operation of the gas turbine engine 20. By maintaining the clearance between the axially extending flange 110 and the radially outer flange 116, the inner support 104 is allowed to grow radially outward when exposed to elevated operating temperatures during operation of the gas turbine engine 20 without transferring a load to the outer support 102.
In the illustrated example, the radially inner flange 114 includes attachment members 124 that extend radially inward from a radially inner surface of the radially inner flange 114 to support the BOAS 84 as shown in FIGS. 1 and 2. Although the attachment members 124 are shown as a pair of hooks with distal ends pointing axially downstream in the illustrated example, the attachment members 124 could include hooks pointing in opposite directions or more than or less than two hooks.
In the illustrated example, the cover plate 108 is attached to an axially forward end of the inner support 104 to from a cavity 126 that surrounds the control ring 106. Both the inner support 104 and the cover plate 108 are made of corresponding segments that fit together to form a circumferential ring.
In one example, the cover plate 108 and the inner support 104 are made of the same material. By making the cover plate 108 and the inner support 104 of the same material, the thermal growth of the cover plate 108 will closely match the thermal growth of the inner support 104 to ensure that the axial ends of the inner support 104 grow at a similar rate in the radial direction. In another example, the cover plate 108 and the inner support 104 are made of dissimilar material to control positioning of the support assembly 100.
As shown in FIGS. 2-4, the control ring 106 includes a plurality of tabs 130 that extend radially outward from a radially outer side of the control ring 106. In the illustrated example, the tabs 130 extend from an axial forward end of the control ring 106 radially outward and an axially forward face 132 of the control ring 106 is flush with an axially forward face 134 of the control ring 106.
The plurality of tabs 130 extend radially outward from the control ring 106 and pass through a slot 136 in the radially outer flange 116 on the inner support 118. Each of the tabs 130 extend through the slots 136 and include circumferential sides 138 that engage protrusions 140 located on the outer support 102. In the illustrated example, the protrusions 140 are arranged in pairs in order to engage the opposing circumferential sides 138 of each of the tabs 130. The protrusions 140 prevent circumferential movement of the control ring 106 relative to the outer support 102, but the protrusions 140 do not restrict axial and radial movement of the control ring 106 relative to the outer support 102.
During assembly of the support assembly 100, the plurality of inner supports 104 are arranged in a circumferential ring surrounding the control ring 106 with the control ring 106 located in the cavity 126. Each of the corresponding plurality of cover plates 108 is placed on the inner support 104
The inner supports 104, the control ring 106, and the plurality of cover plates 108 are then placed within the outer support 102 such that the axial surface 120 on the inner support 104 contacts or is in close proximity to the axial surface 122 on the outer support 102. The plurality of tabs 130 extend between corresponding pairs of protrusions 140 to prevent the control ring 106 from rotating circumferentially relative to the engine axis A. The tabs 130 are sized such that as the control ring 106 grows in the circumferential direction from heat during operation of the gas turbine engine 20, the tabs 130 do not contact and transfer a load from the control ring 106 to the outer support 102.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.

## Claims

1. A support assembly for a gas turbine engine comprising:
an outer support extending about a circumferential axis including at least one engagement member;
an inner support forming a cavity; and
a control ring located within the cavity including at least one tab for engaging the at least one engagement member on the outer support, wherein the inner support includes at least one slot for accepting the at least one tab on the control ring.

2. The assembly of claim 1, further comprising at least one cover plate enclosing the cavity defined by the inner support.

3. The assembly of claim 2, wherein the at least one cover plate and the inner support are made of the same material.

4. The assembly of claim 1, wherein the at least one engagement member includes a protrusion extending radially inward from the outer support.

5. The assembly of claim 4, wherein the at least one engagement member includes a pair of protrusions that engage circumferential sides of one of the at least one tab on the control ring.

6. The assembly of claim 1, wherein the control ring and the outer support are unitary hoops.

7. A gas turbine engine comprising:
an outer support extending about a circumferential axis including at least one engagement member;
an inner support forming a cavity;
a control ring located within the cavity including at least one tab for engaging the at least one engagement member on the outer support, wherein the inner support includes at least one slot for accepting the at least one tab on the control ring; and
a blade outer air seal attached to the inner support.

8. The gas turbine engine of claim 7, further comprising at least one cover plate enclosing the cavity defined by the inner support.

9. The gas turbine engine of claim 8, wherein the at least one cover plate and the inner support are made of the same material.

10. The gas turbine engine of claim 7, wherein the at least one engagement member includes a protrusion extending radially inward from the outer support.

11. The gas turbine engine of claim 10, wherein the at least one engagement member includes a pair of protrusions that engage circumferential sides of one of the at least one tab on the control ring.

12. The gas turbine engine of claim 7, wherein the outer support engages an engine static structure.

13. A method of controlling radial growth in a gas turbine engine comprising:
locating a unitary control ring within a cavity defined by an inner support, wherein the inner support includes at least one slot for accepting at least one tab on the control ring; and
restricting circumferential movement of the control ring relative to an outer support with at least one engagement member.

14. The method of claim 13, wherein the at least one engagement member includes a protrusion extending radially inward from the outer support.

15. The method of claim 14, wherein the at least one engagement member includes a pair of protrusions that engage circumferential sides of one of the at least one tab on the control ring.

16. The method of claim 13, further comprising engaging the outer support with an engine static structure.