# Patent

## Title
Gas turbine engine geared architecture axial retention arrangement

## Abstract

A gas turbine engine includes a fan, an engine static structure, a geared architecture to drive the fan and supported relative to the static structure, a fan drive turbine to drive the geared architecture, a first member secured to the geared architecture, and a second member secured to the engine static structure and configured to cooperate with the first member to limit movement of the geared architecture relative to the static structure. A fan drive gear system and method are also disclosed.

## Background
This application is a continuation application of U.S. patent application Ser. No. 13/435,353, which was filed on Mar. 30, 2012.


BACKGROUND
This disclosure relates to limiting axial movement of a geared architecture within a turbomachine during an extreme event.
Turbomachines, such as gas turbine engines, typically include a fan section, a turbine section, a compressor section, and a combustor section. Turbomachines may employ a geared architecture connecting the fan section and the turbine section.
Support structures are used to hold the geared architecture within the turbomachine. The support structures may be relatively compliant to accommodate some movement of the geared architecture relative to other portions of the turbomachine. Extreme engine events such as fan blade loss or failure of fan shaft bearing supports may encourage significant axial movement of the geared architecture and the fan, relative to other portions of the turbomachine. These movements are undesirable as is known. The relatively compliant support structures may not provide desired axial retention of the geared architecture during extreme engine events.
SUMMARY
A gas turbine engine according to an exemplary embodiment of this disclosure, among other possible things includes a fan, an engine static structure, a geared architecture to drive the fan and supported relative to the static structure, a fan drive turbine to drive the geared architecture, a first member secured to the geared architecture, and a second member secured to the engine static structure and configured to cooperate with the first member to limit movement of the geared architecture relative to the static structure.
In a further embodiment of any of the foregoing gas turbine engines, the first and second members are circumferentially aligned with one another and spaced apart from one another during a normal operating condition.
In a further embodiment of any of the foregoing gas turbine engines, the first and second members limit axial movement of the geared architecture relative to the engine static structure.
In a further embodiment of any of the foregoing gas turbine engines, includes a flex support supporting the geared architecture relative to the engine static structure.
In a further embodiment of any of the foregoing gas turbine engines, includes a support structure secured to the geared architecture and the flex support. The support structure includes at least one of a torque frame, a carrier, and a lubrication manifold, and the second member is removably secured to at least one of the torque frame, the carrier, and the lubrication manifold.
In a further embodiment of any of the foregoing gas turbine engines, the gas turbine engine has a bypass ratio greater than about six (6).
In a further embodiment of any of the foregoing gas turbine engines, the geared architecture has a gear reduction ratio greater than about 2.3.
In a further embodiment of any of the foregoing gas turbine engines, the geared architecture is a planetary gear train.
In a further embodiment of any of the foregoing gas turbine engines, the planetary gear train includes a plurality of gears supported within the carrier. The carrier is fixed against rotation by the torque frame. A central sun gear is operatively connected to the fan drive turbine. A ring gear is configured to drive the fan.
In a further embodiment of any of the foregoing gas turbine engines, the fan is operatively coupled to the geared architecture via a fan shaft, and the fan shaft is supported relative to the engine static structure by at least two bearings.
In a further embodiment of any of the foregoing gas turbine engines, the fan drive turbine has a pressure ratio greater than about five (5).
In a further embodiment of any of the foregoing gas turbine engines, the flex support includes a bellow, an annular mounting flange opposite the bellow and the first member is removably secured to the annular mounting flange.
In a further embodiment of any of the foregoing gas turbine engines, the first member and the second member are U-shaped brackets oriented in opposite radial positions.
In a further embodiment of any of the foregoing gas turbine engines, further includes a brace to strengthen the axial retention of the first member.
In a further embodiment of any of the foregoing gas turbine engines, at least one of the torque frame and the flex support includes at least one feature configured to limit annular rotation of at least one of the first and second members.
In a further embodiment of any of the foregoing gas turbine engines, the first and second members engage one another by axial movement in opposite directions.
A method of assembling a gas turbine engine in which a fan is driven by a speed reduction device according to an exemplary embodiment of this disclosure, among other possible things includes providing attachment features in a first structure and a second structure, securing first and second members respectively to the first and second structures, and installing the first structure onto an engine static structure and the speed reduction device onto the second structure such that the first and second members are engageable with one another during an extreme event.
In a further embodiment of any of the foregoing methods, the first structure is a flex support having a bellow and an annular mounting flange opposite the bellow, and the securing step includes mounting a lubrication manifold onto the second structure, and securing the second members over the lubrication manifold.
In a further embodiment of any of the foregoing methods, further includes the step of positioning the first and second members in a first angular position relative to one another, and rotating the first and second members from the first angular position to a second angular position against a brace.
In a further embodiment of any of the foregoing methods, the first and second members are arranged in an axially spaced relation to one another in an installed condition, and are configured to engage one another by moving axially in opposite directions.
A fan drive gear system for a gas turbine engine according to an exemplary embodiment of this disclosure, among other possible things includes a geared architecture configured to drive a fan, a first member secured to the geared architecture, and a second member configured for securing to a static structure and configured to cooperate with the first member to limit movement of the geared architecture relative to the static structure.
In a further embodiment of any of the foregoing fan drive gear systems, the first and second members are circumferentially aligned with one another and spaced apart from one another during a normal operating condition.
In a further embodiment of any of the foregoing fan drive gear systems, includes a flex support supporting the geared architecture relative to the static structure.
In a further embodiment of any of the foregoing fan drive gear systems, includes a support structure secured to the geared architecture and the flex support. The support structure includes at least one of a torque frame, a carrier, and a lubrication manifold, and the second member is removably secured to at least one of the torque frame, the carrier, and the lubrication manifold.
In a further embodiment of any of the foregoing fan drive gear systems, the geared architecture includes a plurality of gears supported within the carrier. The carrier is fixed against rotation by the torque frame. A central sun gear is operatively connected to the fan drive turbine, and a ring gear configured to drive the fan.
In a further embodiment of any of the foregoing fan drive gear systems, the geared architecture has a speed reduction ratio greater than about 2.3.
A method of designing a gas turbine engine in which a fan is driven by a speed reduction device according to an exemplary embodiment of this disclosure, among other possible things includes defining attachment features in a first structure and a second structure, configuring first and second members for securement respectively to the first and second structures, and defining the first structure for attachment to an engine static structure and the second structure for attachment to the speed reduction device such that the first and second members are engageable with one another during an extreme event.
In a further embodiment of any of the foregoing methods, the first structure is defined as a flex support having a bellow and an annular mounting flange opposite the bellow, the second structure is configured for securement to a lubrication manifold and the second member is configured for securement over the lubrication manifold.
In a further embodiment of any of the foregoing methods, further includes configuring the first and second members to be positioned in a first angular position relative to one another and that rotating the first and second members from the first angular position to a second angular position abuts against a brace.
In a further embodiment of any of the foregoing methods, includes defining the first and second members to be arranged in an axially spaced relation to one another in an installed condition and to engage one another by moving axially in opposite directions during the extreme event.



BRIEF DESCRIPTION OF THE DRAWINGS
The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
FIG. 1 shows a partial section view of an example gas turbine engine.
FIG. 2A depicts a highly schematic view of an example geared architecture support assembly of the FIG. 1 gas turbine engine during normal operation.
FIG. 2B depicts a highly schematic view of the FIG. 2A geared architecture support during an extreme event.
FIG. 3 is a cross-sectional view of a geared architecture and an example support assembly during normal operation.
FIG. 4 is a rear view of an example oil manifold of the support assembly.
FIG. 5 is a front view of an example flex support of the support assembly.
FIG. 6A is a front view of the oil manifold and flex support in a first angular position during assembly.
FIG. 6B is a top elevational view of the support assembly in the first angular position.
FIG. 7 is a front view of the oil manifold and flex support in a second angular position after assembly.



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 flowpath B while the compressor section 24 drives air along a core flowpath C for compression and communication into the combustor section 26 then expansion through the turbine section 28. 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 as the teachings may be applied to other types of turbine engines including three-spool architectures.
The 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.
The low speed spool 30 generally includes an inner shaft 40 that interconnects a fan 42, a low pressure (or first) compressor section 44 and a low pressure (or first) turbine section 46. The inner shaft 40 is connected to the fan 42 through 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 high pressure (or second) compressor section 52 and high pressure (or second) turbine section 54. A combustor 56 is arranged 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 supports one or more 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. As used herein, a “high pressure” compressor or turbine experiences a higher pressure than a corresponding “low pressure” compressor or turbine.
The core airflow C 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. The turbines 46, 54 rotationally drive the respective low speed spool 30 and high speed spool 32 in response to the expansion.
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 ten (10), the geared architecture 48 is an epicyclic gear train, such as a star 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 5. 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 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. 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, 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 per hour divided by lbf of thrust the engine produces at that minimum point. “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 [(Tambient deg R)/518.7)^0.5]. The “Low corrected fan tip speed” as disclosed herein according to one non-limiting embodiment is less than about 1150 ft/second.
A fan shaft 60 interconnects the geared architecture 48 to the fan 42. The fan shaft 60 is supported by a pair of bearings 38, which are tapered roller bearings in one example. The bearings normally limit the axial travel of the fan shaft 60 and fan 42. During operation, the engine 20 may experience extreme events such as a fan blade loss or a failure of a fan shaft bearing support 62 supporting the bearings 38, which is part of the engine static structure 36. In such events, the fan 42 may undesirably tend to move axially forward relative to the other portions of the engine 20, such that the fan 42 and associated components could become disengaged from the engine 20.
Referring to FIGS. 2A and 2B with continuing reference to FIG. 1, the example engine 20 includes other features that limit movement of the fan 42 during an extreme event, particularly if the bearings 38 or bearing support 62 are ineffective. For example, the example engine 20 includes a geared architecture support assembly 64 that limits forward movement of the fan 42 and the geared architecture 48 during an extreme event.
The example support assembly 64 includes at least a first member 66 and a second member 68. The first member 66 and the second member 68 are respectively operatively connected to the geared architecture 48 and the engine static structure 36, which functions as a mechanical ground. A compliant flex support 70 mounts the geared architecture 48 to the engine static structure 36. In the example, the first member 66 and the second member 68 are both arranged axially aft the geared architecture 48 relative to a direction of flow through the engine 20.
During normal engine operation, the first and second members 66, 68 are spaced apart from one another providing a gap 72, as shown in FIG. 2A. During an extreme event, such as a blade loss, the geared architecture 48 may experience an extreme load in the direction F due to the fan 42 rotating and attempting to move axially forward relative to other portions of the engine 20, as shown in FIG. 2B. In such an event, extreme movements of the geared architecture 48 are limited by the cooperation of the first and second members 66, 68 such that the loading in the direction F causes the first and second members 66, 68 to engage one another at area 74. This contact blocks movement of the geared architecture 48 axially forward. Since the geared architecture 48 is connected to the fan 42, limiting movement of the geared architecture 48 may prevent the fan 42 from moving axially forward the remaining attached portions of the engine 20.
One example support assembly 64 is illustrated schematically in FIG. 3. The flex support 70 is secured to a carrier 81 by a torque frame 82. A lubrication manifold 78 is arranged axially between the carrier 81 and the flex support 70. A geartrain 84 of the geared architecture 48 is supported by the torque frame 82. In one example, the geartrain 84 is a planetary gear arrangement in which planetary gears are supported by the carrier 81 and fixed against rotation by torque frame 82. A central sun gear receives rotational drive from the inner shaft 40 (FIG. 1) and a ring gear rotationally drives the fan 42 through the fan shaft 60 (FIG. 1).
The flex support 70 includes a bellow 89, which is provided by a wall that doubles back on itself to provide an undulation. The bellow 89 accommodates a relative movement of the geared architecture 48 relative to the engine static structure 36. An annular mounting flange 91 at an end opposite the bellow 89 is rotationally fixed relative to the engine static structure 36 by fasteners, splines and/or other means.
In the example illustrated, the support assembly 64 is provided by sets of first and second members 66, 68, which are removably secured respectively to the flex support 70 and the lubrication manifold 78. The first and second members 66, 68 are provided by U-shaped brackets oriented in opposite radial positions from one another to facilitate assembly. In the example, each set of members include five circumferentially spaced brackets.
The support assembly 64 may be retrofitted to existing gas turbine engines with geared architectures. In one example, first and second machined surfaces 86, 88 are respectively provided on the flex support 70 and a back side 87 of the lubrication manifold 78. If these machined surfaces are not provided on existing parts, the manufacturer can mill these surfaces, for example, as part of the retrofitting process. First fasteners 90 secure the first member 66 to the end 91. Second fasteners 92 secure the second member 68 to the lubrication manifold 78 and carrier 81. Existing geared architectures may be retrofitted by replacing the pre-existing fasteners that secure the lubrication manifold 78 to the carrier 81 with longer fasteners while reusing existing holes in the carrier 81 and the lubrication manifold 78. The first and second fasteners 90, 92 are threaded fasteners in one example.
Each first member 66 is provided by spaced apart legs 94 joined by a bend 96. Similarly, each second member 68 is provided by spaced apart legs 98 joined by a bend 100. The legs 94, 98 are axially spaced from one another to provide the gap 72 during normal operation.
Referring to FIG. 4, the lubrication manifold 78 may include integrally formed lubrication passages 79 that are cast into the lubrication manifold 78 to provide a unitary structure. The second members 68 include a second flange 104 supporting a leg 98 and secured to an outer periphery of the lubrication manifold. Alternately, the second member 68 could be secured directly to the carrier 81 through windows or scallops 76 in the lubrication manifold 78. Referring to FIG. 5, the first member 66 includes a first flange 102 supporting a leg 94 and secured to the annular mounting flange 91 of the flex support 70.
Referring to FIGS. 6A-7, with the first and second members 66, 68 respectively are secured to the flex support 70 and the lubrication manifold 78. The lubrication manifold 78 is arranged in a first angular position 106, illustrated in FIGS. 6A and 6B, such that the first and second members 66, 68 are circumferentially adjacent to one another but misaligned. The lubrication manifold 78 is rotated relative to the flex support 70 to circumferentially align the first and second members 66, 68 relative to one another in a second angular position 108. In this example, the first member 66 includes a brace 110 to strengthen the axial retention of the member. The annular rotation is limited by existing features, which are machined into the torque frame 82 and the flex support 70.
Features of the disclosed examples include a support structure that permits some movement of a geared architecture relative to other portions of an engine during normal operation of the engine, but limits movements during extreme events, particularly axially forward movements of the geared architecture.
Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.

## Claims

1. A method of assembling a gas turbine engine in which a fan is driven by a speed reduction device, the method comprising the steps of:
providing attachment features in a flex support having a bellow and an annular mounting flange opposite the bellow and a carrier, the carrier supporting a portion of the speed reduction device;
securing first and second members respectively to the flex support and the carrier including positioning the first and second members in a first angular position relative to one another, and rotating the first and second members from the first angular position to a second angular position against a brace; and
installing the flex support onto an engine static structure and the carrier onto a torque frame secured to the flex support such that the first and second members are engageable with one another during an extreme event.

2. The method according to claim 1, wherein the securing step includes mounting a lubrication manifold onto the carrier, and securing the second members over the lubrication manifold.

3. The method according to claim 1, wherein the first and second members are arranged in an axially spaced relation to one another in an installed condition, and are configured to engage one another by moving axially in opposite directions.

4. A method of designing a gas turbine engine in which a fan is driven by a speed reduction device, the method, comprising the steps of:
defining attachment features in a flex support having a bellow and an annular mounting flange opposite the bellow and a carrier, the carrier supporting a portion of the speed reduction device;
configuring first and second members for securement respectively to the flex support and the carrier; and
defining the flex support for attachment to an engine static structure and the carrier for attachment to a torque frame secured to the flex support such that the first and second members are engageable with one another during an extreme event, wherein the first and second members are arranged in an axially spaced relation to one another in an installed condition to engage one another by moving axially in opposite directions during the extreme event.

5. The method according to claim 4, wherein the carrier is configured for securement to a lubrication manifold and the second member is configured for securement over the lubrication manifold.

6. The method according to claim 4, further including configuring the first and second members to be positioned in a first angular position relative to one another and that rotating the first and second members from the first angular position to a second angular position abuts against a brace.