# Patent

## Title
Inner diameter shroud assembly for variable inlet guide vane structure in a gas turbine engine

## Abstract

An inner shroud assembly includes an aft core segment mountable to a forward core segment to support a multiple of vanes for rotational movement relative thereto. A shroud backing plate segment engageable with the aft core segment and at least one fastener which passes through the shroud backing plate, the aft core segment and the forward core segment.

## Background
BACKGROUND
The present disclosure relates to a gas turbine engine and more particularly to an inner diameter shroud assembly for a variable inlet guide vane structure.
Gas turbine engines generally include a high pressure compressor, a combustor, and a high pressure turbine. The high pressure compressor, combustor, and high pressure turbine may be collectively referred to as the core of an engine. Such gas turbine engines also may include a low pressure compressor for supplying compressed air, for further compression, to the high pressure compressor.
The low pressure compressor typically includes a rotor surrounded by a casing. The casing is typically fabricated to be removable, such as by forming the casing into portions that are removably joined together. The low pressure compressor includes a plurality of stages and each stage includes a row of rotor blades and a row of stator vanes. The casing supports the stator vanes, and the rotor supports the rotor blades. The stator vane rows typically direct air flow toward a downstream rotor blade row.
Several compressor stator vanes may be rotatively mounted to allow each vane to rotate around a longitudinal axis which extends in a radial direction from the centerline of the engine to adjust the angular orientation of the vane relative to the airflow. These variable stator vane assemblies facilitate control of air flow through the compressor to enhance performance of the compressor.
Integration of the variable stator vane assemblies into the casing may be relatively complicated. Furthermore, assembly modularity of various case design philosophies such as ring-case and split-case arrangements may need to be accommodated.
SUMMARY
An inner shroud assembly according to an exemplary aspect of the present disclosure includes an aft core segment mountable to a forward core segment to support a multiple of vanes for rotational movement. A shroud backing plate segment engageable with the aft core segment and at least one fastener which passes through the shroud backing plate to retain the aft core segment to the forward core segment.
An inner shroud assembly according to an exemplary aspect of the present disclosure includes an aft core segment mountable to a forward core segment to support a multiple of vanes for rotational movement. A shroud backing plate segment engageable with the aft core segment. A fastener retainer mountable to the shroud backing plate segment. At least one fastener receipt member mountable within the aft core segment and the forward core segment, the at least one fastener receipt member spans the aft core segment and the forward core segment. A fastener which passes through the fastener retainer and the shroud backing plate to retain the aft core segment to the forward core segment.
An inner shroud assembly according to an exemplary aspect of the present disclosure includes an aft core segment mountable to a forward core segment to support a multiple of vanes for rotational movement. A shroud backing plate segment engageable with the aft core segment, the shroud backing plate defines an aft segment perpendicular to a base segment, the base segment at least partially spans the aft core segment and the forward core segment. At least one alignment member mountable within the aft core segment and the forward core segment. At least one fastener receipt member mountable within the shroud backing plate and a fastener which passes through said fastener receipt member to retain the aft core segment to the forward core segment.



BRIEF DESCRIPTION OF THE DRAWINGS
Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows:
FIG. 1 is a general schematic sectional view through a gas turbine engine along the engine longitudinal axis;
FIG. 2 is a expanded schematic sectional view through a low pressure compressor section of the gas turbine engine illustrating one embodiment of an inner shroud assembly;
FIG. 3 is an exploded view of the inner shroud assembly viewed from an aft perspective thereof;
FIG. 4 is an exploded view of a forward core segment and an aft core segment from an aft perspective thereof;
FIG. 5 is an exploded view of the forward core segment and the aft core segment from a top perspective thereof;
FIG. 6 is a perspective sectional view of the inner shroud assembly viewed from an aft perspective thereof attached to a forward center body engine casing;
FIG. 7 is a longitudinal sectional view of the inner shroud assembly attached to the forward center body engine casing;
FIG. 8 is a perspective view of a shroud backing plate segment;
FIG. 9 is a perspective view of a fastener retainer segment;
FIG. 10 is an expanded sectional view of the inner shroud assembly of FIG. 10;
FIG. 11 is an exploded view of the inner shroud assembly of FIG. 10 viewed from an outer perspective thereof;
FIG. 12 is a sectional view of the inner shroud assembly of FIG. 10;
FIG. 13 is a perspective sectional view of the inner shroud assembly of FIG. 10 attached to the Number-2 Bearing Support Housing;
FIG. 14 is a perspective view of the inner shroud assembly of FIG. 10 which illustrates an anti-rotation pad;
FIG. 15 is a perspective view of a fastener retainer which includes tabs in an unengaged position to receive a tool to tighten/loosen the fastener;
FIG. 16 is a perspective view of a fastener retainer which includes tabs in an engaged position;
FIG. 17 is a perspective partial sectional view of the inner shroud assembly of FIG. 10; and
FIG. 18 is a partially assembled view of the inner shroud assembly of FIG. 10 viewed from a rearward perspective thereof.



DETAILED DESCRIPTION
FIG. 1 illustrates a general schematic view of a gas turbine engine 10 such as a gas turbine engine for propulsion. While a two spool high bypass turbofan engine is schematically illustrated in the disclosed non-limiting embodiment, it should be understood that the disclosure is applicable to other gas turbine engine configurations, including, for example, gas turbines for power generation, turbojet engines, low bypass turbofan engines, turboshaft engines, etc.
The engine 10 includes a core engine section that houses a low spool 14 and high spool 24. The low spool 14 includes a low pressure compressor 16 and a low pressure turbine 18. The core engine section drives a fan section 20 connected to the low spool 14 either directly or through a gear train. The high spool 24 includes a high pressure compressor 26 and high pressure turbine 28. A combustor 30 is arranged between the high pressure compressor 26 and high pressure turbine 28. The low and high spools 14, 24 rotate about an engine axis of rotation A.
Air compressed in the compressor 16, 26 is mixed with fuel, burned in the combustor 30, and expanded in turbines 18, 28. The air compressed in the compressors 16, 26 and the fuel mixture expanded in the turbines 18, 28 may be referred to as a hot gas stream along a core gas path. The turbines 18, 28, in response to the expansion, drive the compressors 16, 26 and fan section 20.
Referring to FIG. 2, the low pressure compressor 16 includes alternate rows of low pressure compressor rotor blades 40 mountable to disks 42 which at least partially define a rotor stage. A multiple of variable inlet guide vanes 44 facilitate direction of the airflow from a front center body 32 into the low pressure compressor rotor blades 40.
An outer shroud 46, which may also be referred to as a ring case, secures an outer trunion 48 of each variable vane 44. The outer trunion 48 is driven to pivot by a linkage 50 connected to an actuator 52.
An inner shroud assembly 60 secures an inner trunion 62 of each variable vane 44 for pivotal movement. It should be understood that although the front center body 32 is disclosed as the static structure to which the inner shroud assembly 60 is attached in the disclosed, non-limiting embodiment, the inner shroud assembly 60 may be mounted to other static structures.
The variable vane 44 can be caused to pivot through operation of the actuator 52 and linkage 50 in response to operational conditions to control the direction of air delivered from one compressor stage to the downstream compressor stage. The times when such pivotal movement is desirable are within the level or ordinary skill in the art. This disclosure relates to an inner shroud assembly 60, and not the movement of the vane 44 itself. Although a particular variable inlet guide vane 44 stage is illustrated in the disclosed non-limiting embodiment, it should be understood that any variable vane structure may benefit herefrom.
Referring to FIG. 3, the inner shroud assembly 60 generally includes a multiple of forward core segments 64, a multiple of aft core segments 66, a multiple of shroud backing plate segments 68, a multiple of fastener retainers 70, a multiple of fasteners 72 and a multiple of fastener receipt members 74.
The forward core segments 64 and the aft core segments 66 in the disclosed, non-limiting embodiment are manufactured of a composite material and define an arcuate segment of approximately sixty degrees. Each of the forward core segments 64 and the aft core segments 66 have corresponding outer support surfaces 76A, 76B which are part-cylindrical to receive a platform 44P of the vane 44 (FIGS. 4 and 5). Respective corresponding part-cylindrical inner support surfaces 80A, 80B support an extended diameter portion 44D of the inner trunion 62 with a reduced diameter part-cylindrical center portion 78A, 78B located between the outer support surfaces 76A, 76B and the inner support surfaces 80A, 80B to capture an intermediate portion 44T of the inner trunion 62. It should be understood that the forward core segments 64 and the aft core segments 66 may define alternative support structures to support an inner trunion of other configurations and designs.
The forward core segments 64 and the aft core segments 66 include alignment apertures 84A (FIG. 4 from 84B to 84A), 84B each of which receive a fastener receipt member 74 therein. As the forward core segments 64 and the aft core segments 66 may be manufactured of a composite material, the fastener receipt members 74 may be manufactured of a metallic material to protect the forward core segments 64 and the aft core segments 66 from the fasteners 72 which pass therethrough to engage the front center body 32 (FIG. 6). The fastener receipt members 74 facilitate alignment and prevent relative rotation between the forward core segments 64 and the aft core segments 66. The fastener receipt members 74 also operate as standoffs to prevent compression of the forward core segments 64 and the aft core segments 66 when the fasteners 72 are tightened into the front center body 32.
The forward core segments 64 also define a circumferentially intermittent interface surface 86 (FIG. 5) which locks the forward core segments 64 into the front center body 32 which includes a corresponding intermittent interface surface (FIG. 7).
Each of the multiple of shroud backing plate segments 68 in the disclosed, non-limiting embodiment are manufactured of a metallic material such as aluminum and define an arcuate segment of approximately one hundred and eighty degrees. (also illustrated in FIG. 8) Each of the multiple of shroud backing plate segments 68 supports the forward core segments 64 and the aft core segments 66 and include apertures 88 which align with apertures 84.
Each of the multiple of fastener retainers 70 in the disclosed, non-limiting embodiment are manufactured of a metallic material such as Inconel 625 or Nickel Alloy and define an arcuate segment of approximately one hundred and eighty degrees for receipt into the shroud backing plate segments 68 (also illustrated in FIG. 9). Each of the multiple of fastener retainers 70 are keyed to the adjacent shroud backing plate segments and include apertures 90 which align with apertures 88 and 84 (FIGS. 6 and 7). The multiple of fastener retainers 70 prevent gas impingement onto the heads of the fasteners 72 to provide protection therefrom. The multiple of fastener retainers 70 also lock the fasteners 72 to prevent rotation thereof and thereby provide tertiary retention, fastener abrasion protection and galvanic protection.
Referring to FIG. 10, another non-limiting embodiment of an inner shroud assembly 100 generally includes a multiple of forward core segments 102, a multiple of aft core segments 104, a multiple of shroud backing plate segments 106A, 106B, a multiple of alignment members 108, a multiple of fasteners 110 a multiple of fastener retainers 112, a multiple of fastener receivers 114, and a multiple of fastener receipt members 116.
The forward core segments 102 and the aft core segments 104 in the disclosed, non-limiting embodiment are manufactured of a composite material and define an arcuate segment of approximately sixty degrees generally as described above.
The forward core segments 102 and the aft core segments 104 define alignment apertures 118A, 118B which receive the alignment members 108 therein (FIG. 11). The alignment members 108 include a central increased diameter section 108A controlling the depth to which the pin is installed and circumferentially aligns 76A and 76B of leading and trailing composite segments 102 and 104 respectively. Alignment member 108 provides structural circumferential and radial alignment of core segments 102 and 104 and additionally enhances production assembly. In this non-limiting embodiment, the multiple of fasteners 110 are separate from the multiple of alignment members 108.
Each of the multiple of shroud backing plate segments 106A, 106B in this non-limiting embodiment are manufactured of a metallic material such as aluminum and define an arcuate segment of approximately one hundred and eighty degrees (also illustrated in FIG. 12). Each of the multiple of shroud backing plate segments 106A, 106B supports the respective forward core segments 102 and the aft core segments 104 and includes apertures 120 which receive the fastener receivers 114.
Referring to FIG. 12, the shroud backing plate segments 106A abut the front center body 32 to capture and protect the forward core segments 102. The shroud backing plate segments 106B operates to capture and protect the aft core segments 104. The shroud backing plate segments 106A, 106B may include a respective lip 106C, 106D which captures an upper surface of the forward core segments 102 and the aft core segments 104. Additionally, 106C and 106D minimize non-metallic surfaces of composite segments 102 and 104 Exposed to the ID-Flow Path 51.
Referring to FIG. 13, an anti-rotation pad 132 extends radially inward from the forward core segments 102 to engage with an anti-rotation recessed area 134 within the shroud backing plate segment 106A (also illustrated in FIG. 5). The anti-rotation pad 132 and the anti-rotation recessed area 134 operates as an anti-rotation feature as the fasteners 110 extend through the multiple of fastener receipt members 116 which do not pass through the forward core segments 102 and the aft core segment 104 as in the above discussed non-limiting embodiment (FIG. 14).
The aft shroud backing plate segment 106B includes a recessed area 128 about each aperture 120 to receive the fastener retainer 112 therein. The recessed area 128 essentially follows the outer profile of the fastener retainer 112.
The fastener retainer 112 includes tabs 130 which engage the flange, hex or double hex fastener 110 to prevent rotation thereof and thereby provide a fastener rotation prevention mechanism which uniquely accommodates the flanges of double hex head configured bolt fasteners. A loose fastener 110 will essentially rotate the fastener retainer 112 into the recessed area 128 which operates as a rotation stop to prevent further loosening of the fastener 110.
The tabs 130 initially provide space to receive a fastener tool which engages the fastener 110 (FIG. 15). Once the fastener 110 is properly tightened, the tabs 30 may be bent into engagement with the fastener head 110H (FIG. 16).
The tabs 30 also serve to retain the bolt head 110H if unforeseen fractures occur from either fatigue or assembly, achieve tertiary retention. The fastener retainer 112 further provides fastener abrasion protection and galvanic protection (FIGS. 17 and 18).
It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting.
It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.
Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.
The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.

## Claims

1. An inner shroud assembly comprising:
forward core segment;
an aft core segment mountable to said forward core segment to support a multiple of vanes for rotational movement;
a shroud backing plate segment engageable with said aft core segment;
a fastener retainer mountable to said shroud backing plate segment wherein said fastener receipt member limits compression upon said forward core segment and said aft core segment if said one fastener is tightened;
at least one alignment members mountable within said aft core segment and said forward core segment; and
a fastener which passes through said fastener retainer and said shroud backing plate to retain said aft core segment to said forward core segment.

2. The assembly as recited in claim 1, wherein said aft core segment and said forward core segment each define an arcuate segment of approximately sixty degrees.

3. The assembly as recited in claim 2, wherein said shroud backing plate and said fastener retainer each define an arcuate segment of approximately one hundred and eighty degrees.

4. An inner shroud assembly comprising:
a forward core segment;
an aft core segment mountable to said forward core segment to support a multiple of vanes for rotational movement;
a shroud backing plate segment engageable with said aft core segment, said shroud backing plate defines an aft segment perpendicular to a base segment, said base segment at least partially spans said aft core segment and said forward core segment;
at least one alignment members mountable within said aft core segment and said forward core segment;
at least one fastener receipt member mountable within said shroud backing plate wherein said fastener receipt member limits compression upon said forward core segment and said aft core segment if said one fastener is tightened; and
a fastener which passes through said fastener receipt member to retain said aft core segment to said forward core segment.

5. The assembly as recited in claim 4, further comprising a fastener retainer adjacent to said shroud backing plate segment, said fastener retainer includes tabs operable to lock said fastener.

6. The assembly as recited in claim 5, wherein said fastener retainer includes an arcuate surface opposite said tabs.

7. The assembly as recited in claim 6, wherein an outer surface of an aft segment of said shroud backing plate segment defines a recessed area which follows an outer profile of said fastener retainer.

8. An inner shroud assembly comprising:
a forward core segment;
an aft core segment mountable to said forward core segment to support a multiple of vanes for rotational movement;
a first shroud backing plate segment engageable with said aft core segment;
a second shroud backing plate segment engageable with said forward core segment; and,
at least one fastener which passes through said first shroud backing plate and said second shroud backing plate to retain said aft core segment to said forward core segment wherein said first shroud backing plate segment engages said second shroud backing plate segment.

9. The inner shroud assembly of claim 8 wherein said first shroud backing plate segment engages said second shroud backing plate segment between said fastener and said forward and aft core segments.