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United States Patent 3,826,088
Nash ,   et al. July 30, 1974

GAS TURBINE ENGINE AUGMENTER COOLING LINER STABILIZERS AND SUPPORTS

Abstract

A stabilizing and support system for an augmenter cooling liner of a gas turbine engine is shown to include a plurality of stabilizers circumferentially spaced around, and mounted to, the liner. Each of the stabilizers is captured on its outer end by a stabilizer guide which permits relative thermal expansion to take place between the cooling liner and the exhaust duct to which the liner is mounted. The stabilizer guides are mounted to a positioning band which, in turn, mounts to the inside of the exhaust duct. The positioning band is provided with a gap which permits the band and stabilizer guides to flex to a diameter smaller than the internal diameter of the exhaust duct to permit easy assembly of the liner into the exhaust duct.


Inventors: Nash; Dudley O. (Forest Park, OH), Lyons; Charles S. (West Chester, OH)
Assignee: General Electric Company (Cincinnati, OH)
Appl. No.: 05/328,769
Filed: February 1, 1973


Current U.S. Class: 60/766 ; 285/123.1; 285/123.15; 285/47; 60/799
Current International Class: C07D 277/20 (20060101); C07D 277/00 (20060101); F23R 3/00 (20060101); F23R 3/60 (20060101); F02K 1/00 (20060101); F02K 1/82 (20060101); F02K 1/80 (20060101); F02k 003/10 (); F16l 021/00 ()
Field of Search: 60/261,39.32,39.65,39.69,39.31,270 285/47,133R,138

References Cited

U.S. Patent Documents
2544538 March 1951 Mahnken et al.
2581999 January 1952 Blatz
2801520 August 1957 Highberg
2851854 September 1958 Doll
3138930 June 1964 Waters et al.
Foreign Patent Documents
1,183,143 Mar., 1970 GB
Primary Examiner: Croyle; Carlton R.
Assistant Examiner: Garrett; Robert E.
Attorney, Agent or Firm: Bird, Jr.; Thomas J. Lawrence; Derek P.

Claims



What is claimed is:

1. In a gas turbine engine of the type including a compressor, a turbine, a combustion system, an augmenter, an exhaust duct surrounding said augmenter, and a cooling liner positioned within said duct, at least a portion of which liner extends downstream from said augmenter and is adapted to protect said exhaust duct from the high temperature gas generated by said augmenter, the improvement comprising:

a mounting and stabilizing system for said cooling liner including a plurality of stabilizers, means for connecting said stabilizers to said liner, a positioning band adapted to surround a circumferential row of said stabilizers, a plurality of stabilizer guides connected to said positioning band, each of said guides being adapted to capture one of said stabilizers in at least a first direction but to permit relative movement of said stabilizer with respect to said stabilizer guide along said first direction, and means for connecting said band to said exhaust duct.

2. The improved gas turbine engine of claim 1 wherein said band includes at least one gap therein so as to be capable of contraction to a diameter smaller than the internal diameter of said duct for ease of assembly to said exhaust duct.

3. The improved gas turbine engine of claim 1 wherein each of said stabilizer guides is connected to said band, and said stabilizers are circumferentially spaced around said band so as to substantially preclude buckling of said cooling liner during normal operation of said engine.

4. The improved gas turbine engine of claim 3 wherein said band includes at least one gap such that said band may be contracted to a smaller diameter so as to permit easy insertion of said liner and band into said duct.

5. The improved gas turbine engine of claim 3 wherein said stabilizer guide includes means for capturing said stabilizer in a direction perpendicular to said first direction.

6. The improved gas turbine engine of claim 3 wherein said stabilizer guide and said band include aligned openings, said duct includes a plurality of holes, and said openings are adapted to mate with said holes in said exhaust duct.

7. The improved gas turbine engine of claim 5 wherein said stabilizer includes a mounting plate adapted to be connected to said liner, a top plate adapted to be captured by said stabilizer guide, and a link member adapted to interconnect said mounting plate and said top plate.

8. The improved gas turbine engine of claim 6 wherein said stabilizer guide includes a generally U-shaped channel member having a bight portion and a pair of overhanging lip members extending from said bight portion adapted to capture said top plate, said lip members being spaced from the bight portion of said channel member so as to accommodate relative movement between said channel member and said stabilizer.

9. The improved gas turbine engine of claim 8 wherein said band includes a gap permitting contraction of said band to a diameter smaller than that of said exhaust duct.
Description



BACKGROUND OF THE INVENTION

This invention relates generally to augmented gas turbine engines and, more particularly, to means for supporting and stabilizing cooling liners associated with an augmented turbofan engine.

The invention herein described was made in the course of or under a contract, or a subcontract thereunder, with the United States Department of the Air Force.

Gas turbine engines generally comprise a compressor for compressing air flowing through the engine, a combustion system in which high energy fuel is mixed with the compressed air and ignited to form a high energy gas stream, and a turbine which includes a rotor portion operatively connected to the compressor to drive the same. Many modern-day gas turbine engines are of the turbofan type in which a second or low pressure compressor is mounted forwardly of the high pressure compressor and is driven by a second turbine mounted downstream of the first turbine. The low pressure compressor or fan presents an additional stage of compression and, in addition, is normally of a greater diameter than the high pressure compressor. The turbofan engine is therefore capable of flowing a much larger mass of air, thereby greatly increasing the thrust output of the engine.

An additional known method of increasing the thrust output of the engine is to provide the engine with an augmentation system. In such an engine, additional fuel is injected into an exhaust duct formed downstream of the second turbine and is ignited to provide an additional high energy gas stream which, in certain circumstances, is mixed with fan airflow and then ejected through an exhaust nozzle system to provide high energy thrust output from the engine. The augmentation system is normally located within the exhaust duct of the engine, and, in most cases, some means must be provided for protecting the exhaust duct from the extremely high temperatures associated with the augmenter. One common means of providing this protection is to position a cooling liner within the exhaust duct and to pass cooling air between the liner and the exhaust duct.

A number of basic problems confront the designer of such augmenter cooling liners. The first such problem is concerned with the structural stabilizing of the lightweight, cylindrical member which forms the cooling liner. The cooling liner is spaced radially inwardly from the exhaust duct and is subjected to external pressure loading. In order to assure a relatively constant flow of cooling air, it is necessary that the coolant pressure outside of the liner be greater than the pressure of the combustion gases inside the liner. In such a case, the coolant will flow through slots or openings provided in the liner and will form a film of coolant on the inside of the liner, thereby protecting the same from the high gas temperatures within the liner. Because the pressure is greater on the outside of the liner than on the inside, the necessarily thin liner shells must be stabilized against buckling or collapsing inwardly.

One such manner of stabilizing previous liners was to convolute the liner and hang the same from the exhaust duct by a series of hangers which are mounted to the inside of the duct and connected to various points or similar hangers mounted along the convoluted liner. This type of liner has proven relatively successful in turbojet applications. In the case of augmented turbofan engines, however, air from the fan flow path is utilized to cool the liners. This fan air is of much lower temperature than the turbine discharge air which is used as a coolant in turbojet applications and, thus, a much more effective coolant. In such a case, however, the convolutions provide too great a coolant flow area for efficient use of the low temperature, fan air as a coolant. In other words, in turbofan applications the cooling liner must be maintained as close as possible to a pure cylindrical member in order to minimize the flow area between the liner and the exhaust duct. The primary reason convoluted liners are not used on turbofan augmenters, however, is due to the alternate hot and cold streaks imposed on the liner by the mixed flow augmenter. Convoluted liners are susceptible to thermal fatigue failure or severe heat distortion as a result of these hot and cold streaks.

An additional method of stabilizing the cooling liners, which has proven relatively successful, is to provide a series of reinforcing rings around the liner which provide the stabilizing feature and, in certain designs, also act as mounting brackets. Such reinforcing rings, however, tend to be extremely heavy and in many cases are incapable of accommodating the relative thermal expansion between the cooling liner and the surrounding exhaust duct.

An additional problem confronting the gas turbine engine designer is concerned with the assembly of the liner with its surrounding mounting system into the exhaust duct. As previously mentioned, the gap between the cooling liner and the exhaust duct defines a cooling flow path, and, in the case of turbofan engines, must be maintained at a minimum flow area for efficient use of low temperature fan air as a coolant. All known prior art mounting systems have proven very difficult to assemble into the exhaust duct because of the cumulative friction between the multiplicity of hangers and tracks and because of the time involved in attempting to line up all of the many mounting members.

SUMMARY OF THE INVENTION

It is an object of this invention, therefore, to provide an augmenter cooling liner mounting system which will stabilize the relatively thin, cylindrical liner against buckling or collapsing inwardly and will permit easy assembly of the liner into the exhaust duct. It is an additional object of this invention to provide such a mounting system which will be lightweight and will provide minimum flow areas between the liner and the surrounding exhaust duct such that the liner is capable of use with relatively low temperature, low pressure fan air as a coolant.

Briefly stated, the above and similarly related objects are attained in the present instance by providing a cooling liner mounting system which constrains the liner round at a number of stations along its axial length by the use of stabilizers attached to the liner and stabilizer guides attached to the duct. The stabilizers are equally spaced circumferentially around the liner with a sufficient number being used such that buckling cannot take place between them. The stabilizers are fitted to the stabilizer guides with sufficient clearances to accommodate relative thermal expansion between the cooling liner and the exhaust duct. The stabilizers and guides are then attached to a positioning band which surrounds the required number of stabilizers for each axial location. Each positioning band is provided with a gap which permits the band and the stabilizer guides to flex to a smaller diameter during assembly, thereby providing large clearances between the exhaust duct and the liner. Suitable connecting means are associated with the positioning bands such that the bands may be connected directly to the exhaust duct when the liner is properly positioned within the duct.

DESCRIPTION OF THE DRAWINGS

While the specification concludes with a series of claims which particularly point out and distinctly claim the subject matter which Applicants regard as their invention, a clear understanding of the invention will be obtained from the following detailed description, which is given in connection with the accompanying drawings, in which:

FIG. 1 is a schematic, axial cross-sectional view of a gas turbine engine incorporating the present inventive liner;

FIG. 2 is an enlarged, partial view of the cooling liner of FIG. 1;

FIG. 3 is a sectional view, taken generally along line 3--3 of FIG. 2;

FIG. 4 is a partial sectional view, taken generally along line 4--4 of FIG. 2;

FIG. 5 is a partial perspective view of the liner support assembly with portions deleted for clarity; and

FIG. 6 is a view, similar to FIG. 3, showing the liner during the assembly step.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to the drawings wherein like numerals correspond to like elements throughout, attention is directed initially to FIG. 1 wherein a gas turbine engine 10 of the mixed flow turbofan type is shown to include a core engine 12 which includes a fan turbine 14 which drives a plurality of fan blades 15 mounted on a shaft 16. The fan blades 15 are located within an inlet 17 formed by an outer or fan casing 18 which surrounds the entire gas turbine engine 10. The fan casing 18 cooperates with a core engine casing 20 to define parallel flow paths 22 and 23.

Air entering the flow path 23 is compressed by means of a compressor 24 and is mixed with fuel in combustor 26. Fuel is delivered to the combustor 26 by means of a plurality of fuel injection points 27 from fuel tubes 28 which extend through the flow path 22. The resultant high energy gas stream exits the combustor 26 and drives a turbine 30 which, in turn, drives the compressor 24 by means of a shaft 31.

As further shown in FIG. 1, air flowing through the outer or fan flow path 22 and air exiting the core engine 12 flow through a mixer 32, which operates to mix the two separate flow paths. The mixed flow path is then acted upon by an augmenter 34, which consists of a plurality of fuel injectors 38. The resultant fuel/air mixture in the augmenter 34 is ignited by means of a suitable igniter (not shown), flows through an exhaust duct 40, and thereafter provides an additional propulsive force by exiting through an exhaust nozzle 42.

The exhaust duct 40 is located at the downstream end of the fan casing 18 and is shown in FIG. 1 to include an outer cylindrical casing 44 and a cooling air liner which is generally designated by the numeral 46. The cooling liner 46 is spaced radially inwardly from the exhaust duct casing 44 and defines an annular coolant flow path 48 having an inlet 50 formed by a forward lip 52 at the upstream end of the cooling liner 46.

As is well known in the art, the cooling liner 46 includes a plurality of openings or slots 54 adapted to deliver cooling air from the passageway 48 to the inside of the liner 46. The coolant flowing through the openings 54 provides a film of cool air on the inside of the liner 46 thereby protecting both the liner 46 and the surrounding cylindrical casing member 44 from the high temperatures associated with the operation of the augmenter 34.

The operation of the engine 10 is well known and will be discussed only briefly. Air flows through the inlet 17 and is acted upon by the fan blades 15. A first portion of this pressurized air flows through the fan flow path 22, while a second portion flows through the core engine flow path 23 and is acted upon by the compressor 24. A high energy gas stream is generated by the combustor 26 and drives the high pressure turbine 30 and low pressure turbine 14, which, in turn, drive the core engine compressor 24 and the fan 15. Air exiting the low pressure turbine 14 and air flowing through the fan flow path 22 are mixed within the mixer 32 and the mixed flow is delivered to the region of the augmenter 34, and a resultant fuel/air mixture generated by the augmenter 34 is ignited to provide an additional propulsive force by exiting through the exhaust nozzle 42.

A portion of the air flowing through the fan flow path 22 flows through the inlet 50 and, thus, through the coolant passageway 48. This cooling air thereafter flows through the openings 54 and forms a film on the inside of the cooling liner 46 thereby protecting the liner 46 and the surrounding casing member 44 from the high gas temperatures associated with operation of the augmenter 34.

The gas turbine engine 10 described above is typical of many present-day augmented turbofan engines and has been described solely to place the present invention in proper perspective. As will become clear to those skilled in the art, the present invention will be applicable to other types of gas turbine engines and, therefore, the engine 10 is merely meant to be illustrative.

Referring now to FIGS. 2 through 6, the gas turbine engine augmenter cooling liner 46 and its associated mounting and stabilizing system is shown in greater detail. Referring initially to FIG. 2, the exhaust duct casing 44 is mounted to the downstream end of the fan casing 18 by means of flange sections 56 and 58, which form the downstream and upstream ends of the fan casing 18 and the exhaust duct casing 44, respectively. The flange sections 56 and 58 are interconnected in any suitable manner, such as by means of bolts 60.

The cooling liner 46 is mounted to the fan casing 18 and the exhaust duct casing 44 by means of a plurality of stabilizer assemblies 62, the details of which are shown in FIGS. 2 through 6. The stabilizer assemblies 62 are located at one or more positions along the axial length of the cooling liner 46, depending on the length of the liner. The stabilizer assemblies 62 include a plurality of stabilizers 64 which are equally spaced around the circumference of the liner 46. Each of the stabilizers 64 includes a mounting plate 66 which attaches directly to the cooling liner 46, a top plate 68 and an interconnecting link 70, which preferably is formed integrally with the mounting plate 66 and top plate 68.

The mounting plates 66 are connected to the liner 46 in any suitable manner, such as by means of rivets 72, and the stabilizers 64 are equally spaced around the perimeter of the cooling liner 46 in a circumferential row. The stabilizers act to hold the liner round within the exhaust duct 44. A sufficient number of the stabilizers 64 are provided circumferentially to preclude buckling of the liner 46 between the stabilizers. The stabilizers also act to maintain the proper passage height between the exhaust duct 44 and the liner 46.

The top plate 68 of each of the stabilizers 64 is captured within a stabilizer guide 74, which comprises a generally U-shaped channel member as shown in FIG. 2 having a bight portion 75 and a pair of overhanging lip members 76 extending inwardly from opposite sides thereof. The lip members 76 may extend over only a portion of the length of the stabilizer guide 74 as best shown in FIG. 5 in order to reduce the weight thereof. As clearly shown in FIGS. 2 and 5, the overhanging lips 76 and the bight portion 75 of the stabilizer guide 74 act to capture the stabilizer 64 in a radial direction (R--R) and an axial direction (A--A) with respect to the centerline of the engine 10. The stabilizers 64 are captured in the circumferential direction (C--C) by means of a pair of capture nuts 78 located on opposite ends of the U-shaped channel portion of the stabilizer guide 74. Thus, as described above, each of the stabilizers 64 has associated therewith a stabilizer guide 74, and each of the stabilizers 64 is captured in all three directions by the stabilizer guides 74.

The stabilizer guides 74 are equally spaced around, and permanently connected to, a positioning band 80, which comprises a U-shaped ring sized to fit within the exhaust duct casing 44. While the stabilizer guide 74 may be connected to the positioning band 80 in any desired manner, in the present case, a pair of studs 82 associated with each of the capture nuts 78 are used to connect the stabilizer guides 74 to the positioning band 80. The capture nuts 78 also provide a threaded opening 84 which is adapted to align with a hole 86 provided in the positioning band 80. The threaded openings 84 and holes 86 in the stabilizer guide 74 and the positioning band 80 are, in turn, adapted to be aligned with a plurality of holes 88 located in the exhaust duct casing 44 when the liner 46 is positioned within the duct 44. In this manner, the positioning band 80 may be connected to the cylindrical casing 44 by means of a plurality of bolts 90, when the positioning band 80 is properly positioned within the cylindrical casing 44.

As best shown in FIGS. 3 and 6, the positioning band 80 is formed to include a gap 92 to aid in the assembly of the combustion liner 46 to the exhaust duct casing 44. As shown in both FIGS. 2 and 3, the stabilizer guides 74 are designed so as to provide a gap 94 between the top plate 68 and the bight portion 75 of the stabilizer guide 74. The gap 94 is designed to accommodate the differential thermal growth between the cooling liner 46 and the duct casing 44 during operation of the augmenter. That is, the gap 94 permits the cooling liner 46 to grow at a faster rate than the surrounding casing 44. In addition, the gap 94 formed between each of the top plates 68 of the stabilizers 64 and the bight portion 75 of the stabilizer guides 74, and the gap 92 formed in the positioning band 80 permits the positioning band 80 to be contracted to a smaller diameter with the amount of contraction depending on the size of the gap 94. The ability to contract the positioning band 80 greatly enhances the assembly of the cooling liner 46 into the cylindrical casing 44.

As most clearly shown in FIG. 6, assembly of the cooling liner 46 is accomplished as follows. The positioning band 80 is contracted to its smallest possible diameter thereby providing a gap G between the positioning band 80 and the exhaust duct casing 44. The cooling liner is then slid into the cylindrical casing 44 and one of the threaded openings 84 within the positioning band 80 is aligned with one of the corresponding holes 88 in the cylindrical casing 44 thereby aligning one of the threaded openings 84 with the hole 88 in the casing. A bolt 90 is then positioned within the opening 84 thereby partially securing the positioning band 80 to the inside of the casing 44 and also aligning each of the remaining holes 86 and 88 around the circumference of the positioning band 80 and the casing 44, respectively. The remaining bolts 90 are positioned within the threaded openings 84 and the positioning band 80 is thus secured to the casing 44. In this manner, the stabilizer guides 74, the stabilizer 64, and, thus, the cooling liner 46 are connected to the casing 44. The stabilizers 64 act to hold the liner 46 round within the casing 44, to define the proper dimension for the coolant passageway 48, permit relative thermal expansion to occur between the liner 46 and the casing 44, are lightweight, and easily aligned during assembly.

It should be readily apparent that a number of the mounting assemblies 62 could be axially spaced, as required, along the liner 46 to mount the liner at various points. In addition, the mounting assemblies 62 could be used in conjunction with other mounting schemes or could be used as the sole type of mount, depending upon the application. In addition, changes could be made in the shape of the individual components, such as the stabilizers 64, without departing from the broad concept disclosed herein. The appended claims are intended to cover these and similar variations in the inventors' concepts disclosed herein.

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