Engine exhaust nozzle seal

Abstract: A divergent flap seal (20) for a gas turbine engine exhaust nozzle having a longitudinal axis is provided, having a body (26), a spine member (28), and a flap position guide (31). The flap position guide (31) separates adjacent divergent flaps (18) regardless of the angle the flaps are skewed relative to the longitudinal axis of the nozzle, thereby more evenly distributing the flaps about the circumference of the nozzle.

Description: This invention pertains to engine nozzles in general, and to seals for sealing between flaps within the engine nozzle in particular. In certain gas turbine driven aircraft, it is advantageous to equip the engine with a convergent-divergent (c\d) exhaust nozzle. The term "convergent-divergent" describes an exhaust nozzle having a convergent section upstream of a divergent section. Exhaust gases exiting the turbine(s) pass through the decreasing diameter convergent section before passing through the increasing diameter divergent section. In engines having conventional c\d nozzles, both the convergent and divergent sections are symmetric about the longitudinal axis of the engine. The divergent section includes a plurality of flaps, hinged at the interface between the convergent and divergent sections, which can be rotated radially outward to change the angle at which the divergent section diverges from the longitudinal axis. Flap seals are positioned between the flaps of the divergent section to prevent exhaust gas from escaping between the flaps. In gas turbine engines featuring vectorable c\d exhaust nozzles, the axis of the divergent section may be skewed from the longitudinal axis to create pitch and yaw thrust vectoring. Skewing the divergent flaps causes the position of the flaps relative to one another to vary depending upon the direction and magnitude of the skew and the position of the particular flap relative to the skew. In some circumferential segments of the skewed nozzle, spacing between flaps decreases and flaps may overlap and mechanically damage one another during vectoring maneuvers. In other segments, spacing between flaps increases and forces the seals to assume a complicated geometry to accommodate what would otherwise have been a circumferential space between adjacent flaps. In either case, the cross-sectional area of the nozzle may be different than anticipated, and/or inconsistent. A person of skill in the art will recognize that performance characteristics of the nozzle depend on the ratio of nozzle and throat cross-sectional areas. Inconsistent nozzle cross-sectional area, therefore, is an undesirable attribute. Prior art flap seals are disclosed in W094/02732 (which forms the basis of the preamble of claim 1) US-A-4,690,330 and US-A-5,269,467. Hence, what is needed is a exhaust nozzle flap seal that can accommodate complex geometries, one that prevents mechanical damage between adjacent flaps, and one that helps provide a consistent nozzle cross-sectional area. According to the invention, there is provided a divergent flap seal for a gas turbine engine exhaust nozzle having a longitudinal axis, comprising: a body having a plurality of corrugations formed therein and extending across its width; and a spine member, attached to a first side of said body, extending along the length of said body; characterised in that said body further comprises: a first and a second channel, each channel having walls extending lengthwise along said body, and one of said channels being disposed on each side of said width; and a flap position guide, positioned on said first side of said body, adjacent an aft end of said body, said flap position guide extending out from said body a distance sufficient, in use, to separate adjacent flaps regardless of the vectored position of the nozzle and being attached to said spine member. An advantage of the present invention is that the flap position guide of each flap seal prevents adjacent flaps from overlapping one another. As a result, flaps are prevented from mechanically damaging one another. In addition, separating adjacent flaps distributes the flaps more evenly about the circumference of the nozzle. Even flap distribution helps provide a consistent nozzle cross-sectional area in a vectorable exhaust nozzle, and therefore a more consistently performing exhaust nozzle. A further advantage of the present invention is that it helps to maximize the kinematic envelope of the vectorable nozzle. Distributing the flaps more evenly about the circumference of the nozzle reduces the interferences between adjacent flaps and thereby increase the envelope within which the nozzle may diverge. Some preferred embodiments of the invention will now be described, by way of example only with reference to the accompanying drawings, in which: FIG. 1 shows a partial perspective view of an exhaust nozzle for a gas turbine engine. FIG. 2 is a diagrammatic illustration showing an exhaust nozzle. FIG. 3 is an hot-side view of a flap seal. FIG. 4 is a cold-side view of the flap seal shown in FIG. 3. FIG. 5 is a side view of the flap seal, partially cut-away, showing one embodiment of a flap position guide. FIG. 6 is a side view of the flap seal, partially cut-away, showing another embodiment of a flap position guide. FIG. 7 is a sectional view of the flap seal shown in FIG. 3. FIG. 8 is a sectional view of the flap seal shown in FIG. 3. FIG.9 is a diagrammatic partial view of the hot side of the seal showing a particular face segment embodiment. FIG. 10 is a diagrammatic partial view of the hot side of the seal showing another face segment embodiment. Referring to FIG.1, a gas turbine engine includes an exhaust nozzle 10 comprising a convergent section 12 upstream of a divergent section 14. Both the convergent 12 and the divergent 14 sections are symmetrically arranged about the longitudinal axis 16 of the engine, although the divergent section 14 may be selectively skewed from the axis 16. FIG.2 shows a diagrammatic representation of a divergent section skewed an angle  from the longitudinal axis 16 of the engine. The divergent section 14 includes a plurality of flaps 18 and flap seals 20 pivotly attached to the convergent section 12 on one end. Mechanical linkage 22 links the flaps 18 and the flap seals 20 together, such that actuating the flaps causes the seals to actuate in like manner. A second mechanical linkage 24, attached to each of the flaps 18, actuates the flaps 18 and flap seals 20 about the longitudinal axis 16, or about an axis skewed relative to the longitudinal axis 16, or both. Referring to FIGS. 3 and 4, each flap seal 20 includes a body 26, a spine member 28, a plurality of face segments 30, and a flap position guide 31 (see also FIGS. 5 and 6). FIG.3 shows a "hot-side" view of a flap seal 20. The hot-side of the flap seal 20 is defined as that side which is directly exposed to exhaust gases exiting the engine. The cold-side of the flap seal 20 is defined as the side of the flap seal 20 opposite that which is directly exposed to exhaust gases. The body 26 may be described as having a length 32, defined as extending between a forward end 33 and an aft end 35, and a width 34. The body 26 further includes a plurality of corrugations 36 formed in the body 26, extending across the body width 34, and a first 38 and a second 40 channel (see FIG.7 also). Corrugation geometries other than that shown in FIGS. 5,6, and 8 may be used alternatively. Referring to FIG.7, the first 38 and second 40 channel are formed along the width edges 42,44 of the body 26 by folding the edges of the body 26 sheet metal back over into a "U" shape. The walls of the "U" extend lengthwise along the body 26. In one embodiment, a spacer 48 having a predetermined thickness is inserted into each channel 38,40 and spot welded into place. Referring to FIGS. 8 and 9, each face segment 30 includes a midsection 50, having an inner 52 and an outer 54 surface, a first edge 56, a second edge 58, a first end 60, and a second end 62 (see FIG.9). The edges 56,58 are parallel with each other and substantially perpendicular with the ends 60,62. Each face segment 30 further includes a first flange 64 and a second flange 66. The first flange 64 is attached to the first edge 56 of the midsection 50. The second flange 66 is attached to the second edge 58 of the midsection 50. In the preferred embodiment, the first 64 and second 66 flanges are formed by bending sections of the face segment 30 away from the midsection 50. Hence, the face segments 30 may be formed from a sheet metal blank. The first 64 and second 66 flanges comprise mating geometries such that when face segments 30 are positioned adjacent each other, the first flange 64 of one face segment 30 couples with the second flange 66 of the adjacent face segment 30. FIG.8 shows the preferred embodiment of the first 64 and second 66 flanges. The first flange 64 is perpendicular to the midsection 50. The second flange 66 is "L" shaped; i.e., it includes a first section 68 perpendicular to the midsection 50 and a second section 70 parallel to the midsection 50. Referring to FIG.3, the end face segment 72 includes only one of the first 64 or second 66 flanges (see FIG.8) and is extended in the midsection 50. When assembled with the body 26, the end face segment 72 and body 26 create a pocket 74 (shown in phantom) for receiving a hinge means 76 for pivotly attaching the seal 20. United States Patent No. 5,238,189, hereby incorporated by reference, discloses such a hinge means 76. Referring to FIGS. 9 and 10, in one embodiment the face segments 30 further comprise a scallop 78 extending along either the first 56 or second 58 edge, or both. The scallops 78 decrease the distance between the first 56 and second 58 edges in a particular face segment 30 and increase the distance between edges 56,58 of adjacent face segments 30 to permit greater thermal growth in a particular area of the seal 20. The scallops 78, for example, may be placed in the center region of all face segments 30 if the seal 20 is to experience a steep thermal gradient in the center region along the entire length of the seal 20. Alternatively, if the thermal gradient is significantly higher in a particular area of the seal 20, then the face segments 30 in that particular area may include scallops 78 to allow for greater thermal expansion in that particular area; i.e., hot spots at one end of the seal 20 or along the width edges 42,44, etc. FIG.8 shows scallops 78 near the ends 60,62 of the face segments 30 to allow for thermal expansion near the ends 60,62 and to facilitate translation within the channels 38,40. Referring to FIGS. 5 and 6, the spine member 28 is a rigid member attached to the cold-side of the body 26, attached by conventional means to the corrugations 36 of the body 26. The spine member 28 includes means 80 for attaching the flap seal 20 to the linkage 24 (see FIG.1) which connects the flaps 18 and flap seals 20 together. In one embodiment, shown in FIG.5, the flap position guide 31 is attached to the spine member 28 at a position between the flap seal attachment means 80 and the aft end 35. The flap position guide 31 extends out from the body 26 a distance sufficient to separate adjacent flaps 18 regardless of the vectored position of the nozzle. FIG. 6 shows an alternative embodiment of the flap position guide 37, where the guide 31 is integrally formed within the spine member 28 in the region between the flap seal attachment means 80 and the aft end 35 of the seal 20. Referring to FIG. 8, during assembly the face segments 30 are attached to the corrugations 36 of the body 26 by spot welds 90 (see FIG. 3 also). The face segments 30 are sized and positioned such that the first flange 64 and second flange 66 of adjacent face segments 30 nest together, separated by a predetermined gap 82. The gap 82 is sized to allow the expected thermal expansion of adjacent face segments 30. The mating geometries of the first 64 and second 66 flanges substantially prevent gases passing along the outer surface 54 of the face segments 30 from passing between the face Segments 30. Referring to FIGS. 7 and 9, the ends 60,62 of the segments 30 are free to translate within the channels 38,40 (FIG.7). The spacers 48 positioned in the channels 38,40, inboard of the ends 60,62, help to maintain a channel gap 84 sufficient to prevent binding of the face segments 30. The spacers 48 also help position the face segments 30 during assembly. It will be seen from the above description that the present invention in its preferred embodiments at least provides a divergent flap seal that prevents mechanical damage between adjacent divergent flaps in a vectorable exhaust nozzle, an exhaust nozzle flap seal that can accommodate complex nozzle geometries in a vectorable exhaust nozzle, and a divergent flap seal that helps provide a consistent nozzle cross-sectional area in a vectorable exhaust nozzle. Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the scope of the claimed invention.

Claims: A divergent flap seal (20) for a gas turbine engine exhaust nozzle having a longitudinal axis, comprising: a body (26) having a plurality of corrugations (36) formed therein and extending across its width; and a spine member (28), attached to a first side of said body, extending along the length of said body; characterised in that said body further comprises: a first and a second channel (38,40), each channel having walls extending lengthwise along said body, and one of said channels being disposed on each side of said width; and a flap position guide (31), positioned on said first side of said body, adjacent an aft end of said body, said flap position guide extending out from said body a distance sufficient, in use, to separate adjacent flaps regardless of the vectored position of the nozzle and being attached to said spine member. A divergent flap seal according to claim 1, wherein said flap position guide (31) is integrally formed with said spine member (28). A divergent flap seal according to claim 1 or 2, wherein said flap seal further comprises: a plurality of face segments (30), each attached to said body (26) on the side of said body opposite said side to which said spine member (28) is attached, wherein the ends (60,62) of said face segments (30) are freely received within said first and second channels (38,40) such that said ends may translate within said channels. A divergent flap seal according to claim 3, wherein each said face segment (30) comprises: a midsection (50), having an inner (52) and an outer (54) surface, and a first edge (56) and a second edge (58), said edges parallel with each other and substantially perpendicular with said ends (60,62); a first flange (64), attached to said first edge (56) of said midsection; a second flange (66), attached to said second edge (58) of said midsection, wherein said first and second flanges comprise mating geometries such that when face segments are positioned adjacent each other, said first flange of one face segment couples with said second flange of the adjacent face segment, said flanges separated by a predetermined gap (82) along their geometries; wherein said mating geometries of said first and second flanges substantially prevent gases passing along said outer surface of said face segments from passing between said face segments, and allow thermal growth of adjacent face segments. A divergent flap seal according to claim 4, wherein: said first flange (64) extends out from said inner surface (52) of said midsection (50) in a substantially perpendicular direction; and said second flange (66) comprises an "L" shaped geometry extending out from said inner surface (52) of said midsection (50). A divergent flap sea! according to claim 4 or 5, wherein said face segments (30) further comprise a scallop (78) extending along one of said first or second edge (56,58), thereby decreasing the distance between said first and second edges in a particular face segment, and increasing the distance between edges of adjacent face segments to permit greater thermal growth in a particular area of said seal. A divergent flap seal according to claim 6, wherein the distance between the first and second edges (56,58) of said face segments (30) is less at each end than the maximum distance between the first and second edges otherwise within said face segments. A divergent flap seal according to any of claims 3 to 7, further comprising spacers (48) having a thickness equal to or greater than the thickness of the ends of said face segments (30); wherein said spacers are received within said channels (38,40), inboard of said ends, and fixed in place, thereby spacing said channel walls a distance apart sufficient to prevent said ends of said face segments from binding in said channels. A divergent flap seal according to any preceding claim, wherein said channels (38,40) extend continuously along the entire length of said body. An exhaust nozzle (10) for a gas turbine engine, comprising: a convergent section (12); and a divergent section (14), wherein said convergent and divergent sections are disposed about a longitudinal axis and pivotally attached to one another, wherein said divergent section includes: a plurality of flaps (18), pivotally attached to said convergent section (12); a plurality of seals (20), wherein each of said seals is as claimed in any preceding claim; means (22) for mechanically linking said flaps (18) and said seals (20) together; and means (24) for actuating said flaps and seals about said longitudinal axis of said nozzle and/or for actuating said seals about an axis skewed from the longitudinal axis.

Inventors: BERGER CURTIS W, JOHNSON BRADLEY C, JOHNSON STEVEN B, MILLER WILLIAM J, BERGER, CURTIS W., JOHNSON, BRADLEY C., JOHNSON, STEVEN B., MILLER, WILLIAM J.
Applicants: UNITED TECHNOLOGIES CORP, UNITED TECHNOLOGIES CORPORATION
Application year: 1996
Main classification: F02K1
IPC codes: F02K1