Patent Grant
7600967
This invention relates to axial flow rotary machines of the type having a flowpath for working medium gases and a stator structure extending circumferentially with respect to the working medium flow path. More particularly, this invention relates to a stator assembly having an array of wall segments that extend circumferentially for bounding the working medium flow path, such as an outer air seal or the platforms of an array of stator vanes. While this invention was conceived during work in the field of axial flow gas turbine engines, this invention has application to other fields which employ rotary machines.
An axial flow, gas turbine engine typically has a compression section, a combustion section and a turbine section. An annular flowpath for working medium gases extends axially through the sections of the engine. A stator assembly extends inwardly and outwardly of and about the annular flowpath for confining the working medium gases to the flowpath and for directing the working medium gases along the flowpath.
As the gases are passed along the flowpath, the gases are pressurized in the compression section and burned with fuel in the combustion section to add energy to the gases. The hot, pressurized gases are expanded in the turbine section to produce useful work. A major portion of this work is used as output power, such as for driving a free turbine or developing thrust for aircraft.
A remaining portion of the work generated by the turbine section is not used for output power. Instead, this portion of the work is used in the compression section of the engine to pressurize the working medium gases for the combustion section and for providing cooling air to selected locations in the engine. A rotor assembly extends through the engine for transferring this work from the turbine section to the compression section. The rotor assembly has arrays of rotor blades in the compression section for doing work on the working medium gases and arrays of rotor blades in the turbine section for receiving work from the working medium gases. The rotor blades in the turbine section have airfoils that extend outwardly across the working medium flowpath. The turbine airfoils are angled to the approaching flow to receive the work from the gases and to drive the rotor assembly about the axis of rotation.
The stator assembly in both sections has an inner case and an outer case for bounding the working medium flowpath. Arrays of stator vanes extend across the working medium flowpath between the cases. The arrays of stator vanes are disposed in interdigitated fashion with the arrays of rotor blades. Each stator vane includes an outer wall segment or platform which bound the flow path, forming an array of outer wall segments. Each stator vane has one or more airfoils that extend inwardly from the outer platform. The airfoils direct the approaching flow to the adjacent row of rotor blades at the desired angle.
The stator assembly further includes a second array of wall segments which are disposed between the arrays of stator vanes and outwardly of the rotor blades. The second array of wall segments, commonly referred to as an outer air seal, are supported from the outer case and extend circumferentially about the working medium flowpath. The segments are circumferentially spaced leaving a clearance gap therebetween. The clearance gap is provided to accommodate changes in diameter of the array of wall segments in response to operative conditions of the engine as the outer case is heated and expands or is cooled and contracts.
The stator assembly includes a support structure, such as upstream support and a downstream support, for supporting the seal segments of the outer air seal from the outer case. The seal segments are adapted by flanges to engage the supports. These flanges are typically called “hooks.” The outer case and the support structure position the seal segments in close proximity to the blades and provide a seal surface which radially faces the working medium gases. The seal surface blocks the leakage of working medium gases past the tips of the rotor blades.
The inwardly facing surfaces of the seal segments are commonly formed with abradable material to enable the seal segments to accept rubbing contact with the tips of the rotor blades under operative conditions. As a result, the rotor blades exert a circumferential force and moment on the seal segments urging the seal segments in the circumferential direction about the axis of the engine. The forces and the moment are resisted by the support structure.
The outer air seal assembly typically includes pins that extend between one of the supports and the outer air seal segment to restrain the segments against the circumferentially directed forces. An example of such pins is shown in U.S. Pat. 4,247,248 issued to Chaplin, DeTolla and Griffin entitled “Outer Air Seal Support Structure For Gas Turbine Engine.” In addition to resisting the forces and moments arising from rubbing contact between the rotor blades and the surface of the outer air seal segment, these pins locate the outer air seal segments. These pins require the machining of appropriate openings to receive the pins, require installation in a location that is difficult to reach and to inspect, and, require the manufacture and maintenance of additional parts for the engine.
As a result of being disposed adjacent to the flowpath, the surfaces of the segments and the segments themselves are in intimate contact with the hot working medium gases. The segments receive heat from the gases and the segments are cooled to keep the temperature of the segments within acceptable limits. Pressurized cooling air is flowed from supply chambers on the interior of the outer air seal assembly through cooling air holes to the exterior surface of the segments. The cooling air provides transpiration cooling as the air passes through walls of the seal segments and, after the air is discharged from the segments, provides film cooling with a film of air on the exterior of the segments. The film of cooling air provides a barrier between the segments and the hot, working medium gases.
Leak paths exist from the supply chambers of cooling air to the working medium flowpath because of the segmented nature of the outer air seal segments and the supports. These leak paths divert cooling air away from locations where the cooling air provides helpful cooling. These leak paths decrease the aerodynamic efficiency of the engine because the engine expended work to compress the cooling air. Any reduction in cooling air consumption reduces the performance penalty caused by the work of pressurization. As a result, seal chambers are provided to intercept the leak paths at critical locations in the engine to decrease the loss of cooling air.
One example of such a seal chamber in another part of the turbine section is shown in U.S. Pat. No. 4,336,943 issued to Chaplin entitled “Wedge-Shaped Seal for Flanged Joints.” In Chaplin, the seal chamber is provided with a seal member or ring. The ring has arms which open toward a region of higher pressure. The arms are each urged against a surface bounding the seal chamber to block the loss of cooling air from the engine.
This type of seal member is also employed adjacent to outer air seal assemblies in conjunction with the support for the adjacent array of stator vanes. The vane support and the outer air seal assembly form the seal chamber for the seal member to locate, position, and retain the seal member. Inspection of the disposition of the seal member after installation requires disassembly of the adjacent vane support.
The above art notwithstanding, scientists and engineers working under the direction of Applicants' Assignee have sought to develop structure for blocking a leak path through a seal chamber that uses a resilient seal member disposed between two circumferentially extending structures bounding the flow path and which facilitates assembly, disassembly and inspection of the disposition of the resilient seal member and locating and retaining the resilient seal member under non-operative and operative conditions of the engine.
According to the present invention, a stator assembly has two circumferentially extending structures that are spaced apart leaving an annular seal chamber therebetween for intercepting a leak path for cooling air, the stator assembly including a resilient seal member that extends across the space between the structures to divide the seal chamber into a high pressure region and a low pressure region and that has arms opening toward the high pressure region to engage the structures and further including a retainer member extending across the space in the low pressure region that is removably attached to a portion of the stator assembly for locating and retaining the resilient seal member and for providing access to the chamber during assembly and disassembly of the resilient seal member.
In accordance with the present invention, a stator assembly for a rotary machine having a resilient seal member which extends circumferentially in an annular seal chamber and axially between a first structure and a second structure further includes a retainer member that is removably attached to one of the structures and that extends axially and faces radially to bound the seal chamber, the resilient seal member being urged radially against the retainer member and urged axially against the first structure and the second structure by pressurized cooling air of the leak path to block the flow of cooling air through the seal chamber, the retainer member providing access to the seal chamber for installing, locating and enclosing the seal member under non-operative conditions of the engine and for retaining the seal member radially against cooling air pressure under operative conditions.
In accordance with one embodiment of the present invention, the rotary machine has a flow path for working medium gases, the second structure is an array of circumferentially extending wall segments each having a surface that bounds the flow path for working medium gases and the first structure extends circumferentially about and outwardly of the wall segments to provide a support for both the retainer member and the stator members.
This invention in one embodiment is in part predicated on the recognition that the seal chamber may be formed for use with a coolable outer air seal assembly which includes an outer air seal support for the outer air seal and that the retainer member may provide access to the chamber for disposing a resilient seal member in the chamber and, in a detailed embodiment, retain the outer air seal against circumferential movement.
In accordance with one particular embodiment, the wall segments of the second structure are an array of outer air seal segments that slidably engage the circumferentially extending support and the seal chamber is bounded axially on one side by the support and bounded axially on the other side by a seal wall extending from the hooks of at least two outer air seal segments. The seal wall extends about the support and is spaced axially from the support.
In accordance with one embodiment of the present invention, the retainer member is formed of an array of retainer segments which are engaged by the array of outer air seal segments, with at least one segment of one of the arrays having a radially extending anti-rotation projection which extends into an associated opening in a segment of the other array of segments such that the retainer member both prevents circumferential movement of the array of outer air seal segments and fixes the location of the resilient seal member.
In accordance with one embodiment of the present attention, the retainer member is a cast member formed with the opening and the outer air seal is a cast member formed with the projection.
In accordance with one detailed embodiment, the retainer member has a first wall or support arm which extends axially and circumferentially to bound the seal chamber and a second wall which extends circumferentially and radially from the first wall to form a corner with the first wall, the second wall extending radially inwardly into close proximity with the portion of the outer air seal member axially bounding the seal chamber leaving a radial gap R therebetween which is spaced from the top and bottom of the seal chamber, the second wall extending radially adjacent to the opening in the retainer member to reduce bearing stresses resulting from engagement between retainer member and the anti-rotation projection on the outer air seal by increasing the area of engagement with the second wall of the retainer member and reducing the turning moment on the retainer member by having the anti rotation projection on the outer air seal member extend outwardly to engage the first wall of the retainer member at a diameter which is greater than the diameter of the remainder of the outer air seal segment.
In accordance with another detailed embodiment, the axial thickness of the radial wall on the retainer member is less than the axial thickness of the inwardly extending wall of the outer air seal member to promote engagement between the base of the resilient seal member and the wall of the outer air seal segment.
In accordance with one embodiment, the axial gap between the support and the support arm of the retainer member is smaller than the axial gap between the wall of the resilient seal member at the tip or outer diameter of the resilient seal member.
In one detailed embodiment, the axial length of the resilient seal member in the uninstalled condition is greater than the axial length of the seal chamber such that the resilient seal member in the uninstalled condition has an axial length which is greater in the uninstalled condition and than in the installed condition.
In accordance with one detailed embodiment, the resilient seal member is an accordion shaped resilient seal member having an uninstalled axial length between the sealing surfaces of the seal member that is greater than the installed axial length between the sealing surfaces.
In accordance with one detailed embodiment, the orientation of the accordion seal member under operative conditions causes the pressure of the cooling air from the outer air seal to urge the sealing surfaces of the accordion seal member against the outer air seal member and the support.
According to the present invention, a method of forming the outer air seal assembly includes forming a cartridge-like module of an outer air seal assembly which includes an outer air seal support, a plurality of outer air seal segments and a retainer member with a radially extending seal member extending between the structures and trapped with the retainer member. The method includes forming a module by disposing the outer air seal assembly in a first fixture having grooves for receiving the rearward side of the outer air seal assembly, the fixture extending outwardly of the outer diameter of the outer air seal assembly; forming a second module by disposing the outer air seal assembly in a second fixture having a diameter that is smaller than the outer diameter of the outer air seal assembly; inserting the second module in the rotary machine; securing the outer air seal assembly to the rotary machine and removing second fixture from the engine.
A primary feature of the present invention is a first structure and a second structure which form a seal chamber for a seal member. Another primary feature is a retainer member for the seal member which is disposed in the seal chamber. In one particular embodiment, the retainer member extends between the structures and is supported by being attached to one of the structures that form the seal chamber. In one embodiment, a feature is the modular nature of a subassembly formed by a fixture and an outer air seal assembly. In one detailed embodiment, the modular outer air seal assembly includes an outer air seal support, a plurality of outer air seal segments and the retainer member with a radially extending seal member extending between the structures and trapped with the retainer member. In one detailed embodiment, a feature is an anti rotation projection extending radially between an outer air seal segment and the retainer member that is attached to one member and extends into a slot in the other. In one detailed embodiment, a feature is a hook on an outer air seal segment having a seal wall extending radially from the outer air seal segment to bound the seal chamber and a lug extending radially from the wall to form the radially extending anti-rotation projection.
A principal advantage of the present invention is the engine efficiency which results from blocking the loss of cooling air from a coolable stator assembly of a rotary machine which results from forming a seal chamber and disposing a resilient seal member in the chamber. In one embodiment another advantage is the life-cycle cost of an assembly having a seal chamber and a resilient seal member associated with the ease of manufacture, repair and inspection of the assembly that results from use of a modular type subassembly containing the seal member. In particular, ease of manufacture is promoted by supporting the second structure from the first structure, disposing the seal member in the seal chamber and attaching the retainer member from the first structure to form the modular subassembly. In one detailed embodiment, an advantage is the durability of the seal retainer associated with the level of force it uses to resist the anti-rotation moment acting on the seal segment during a rub of a rotor blade. The force is lower with the anti-rotation projection or lug extending outwardly from the hook of the outer air seal segment to a larger diameter as compared to the moment arm that results from having the lug extend inwardly from the seal retainer to engage the outer air seal segment at a smaller diameter.
The resilient seal member is disposed in the seal chamber and urged axially by cooling air pressure against the support and the outer air seal members under operative conditions, the outer air seal assembly further including a circumferentially extending retainer member which is removably attached to the support for providing access to the seal chamber and which extends axially to bound the seal chamber for enclosing the seal member in the seal chamber, for locating the seal member under non-operative conditions, and for retaining the seal member radially against cooling air pressure under operative conditions.
The foregoing features and advantages of the present invention will become more apparent in light of the following detailed description of the invention and the accompanying drawings.
The stator assembly 16 includes an outer case 26 and arrays of stator vanes 28, 32. The first array of stator vanes 28 extends inwardly from the outer case across the working medium flowpath 12. The first array of stator vanes are upstream of the array of rotor blades 24. The second array of stator vanes 32 is similarly disposed downstream of the array of rotor blades. An outer air seal assembly 34 having an outer air seal 36 is disposed between the first and second arrays of stator vanes. The outer air seal assembly has a first structure, as represented by an outer air seal support 38, which extends inwardly from the outer case to support and position the outer air seal. The outer air seal is coolable and forms a second structure of the outer air seal assembly.
The outer air seal 36 is formed of a plurality of outer air seal segments, as represented by the wall segments 36a, 36b. The outer air seal has a seal section 48 having a seal surface 52, as represented by this seal surfaces 52a, 52b. The seal surface 52 extends circumferentially about the axis A and axially outwardly of the array the rotor blades 24 shown in
The outer air seal support 38 extends circumferentially about and outwardly of the outer air seal 36 to support the segments 36a, 36b of the outer air seal. In this particular embodiment, the outer air seal support is formed of a plurality of segments, as represented by the segments 38a, 38b. Each support segment engages two associated outer air seal segments 36a, 36b. Each support segment has a first side 56, as represented by the sides 56a, 56b, which face circumferentially. A second side 58, as represented by the side 58a, faces circumferentially and is spaced circumferentially from the first side of the adjacent segment by a circumferential gap G.
The rearward wall 64 is spaced axially from the forward wall 62 leaving a portion of a supply region 76 for cooling air therebetween. The rearward wall has a rearward outer rail 78 which engages the outer case. A rearward inner 82 rail is spaced radially from the rearward outer rail. The rearward inner rail 82 extends axially in the rearward direction. The rearward inner rail 82 has an outwardly facing surface which extends circumferentially about an axis As which is coincident with the axis A in the installed condition.
As shown in
Each outer air seal segment 36a also has a rearward hook 92 which extends axially rearward from the seal section 48. The rear ward hook extends over the rearward inner rail 82 of the support segment 38a, which is the first structure of the outer air seal assembly. The rearward hook has an inwardly facing surface 94 which slidably engages the outwardly facing surface 84 of the rearward rail 82 of the associated segment of the outer air seal support.
A radially extending seal wall 96 extends inwardly from the rearward hook 92. The seal wall extends circumferentially and is spaced from the rearward wall 64 of the outer air seal support segment 38a leaving the annular seal chamber 98 therebetween. An anti-rotation projection 102 extends radially from the seal wall. The anti-rotation projection 102 is adapted to extend into an associated opening of the stator assembly, such as the opening 104 in the retainer member 42. As mentioned above, the retainer member is attached to the first structure, that is, the outer air seal support segment 38a.
The resilient seal member 44b extends across the axial length Ls of the seal chamber 98 between the rearward wall 64 of the first structure and the seal wall 96 of a the second structure (outer air seal segment 38). The resilient seal member divides the seal chamber into a high pressure region 106 and a low pressure region 108.
The retainer member 42 is disposed in the low pressure region 108. The retainer member faces radially and extends axially across the axial length Ls of the seal chamber 98 to bound the seal chamber. The retainer member is removably attached to the outer air seal support 38 (that is, the first structure of the stator assembly) by a pair of circumferentially spaced bolts 112.
A third bolt hole 114 is provided for receiving an attachment bolt 116. The attachment bolt is provided for attaching the outer air seal assembly 34 to the outer case 26. As shown in
The retainer member 42 has the radially extending opening 104 for receiving the anti-rotation projection 102. Accordingly, the retainer member both: locates and retains the resilient seal member 44b against the pressure forces of the high and low pressure regions 106,108; and, locates and retains the outer air seal segment 36a against circumferential displacement. The retainer member 42 also provides access to the seal chamber 98 during assembly and disassembly of the resilient seal member,
As shown in
As shown in
As shown in
As shown in
In particular, the first side 56a of the outer air seal support segment 38a has a first slot 162 which extends radially between the rearward inner rail 82 to the rearward outer rail 78 to receive radial portions 152r, 154r of the pair of feather seals 152, 154. The second slot 164 extends axially between the forward inner rail 68 and the rearward inner rail 82. A third slot 166 extends radially outwardly of the second slot, the third slot extending axially between the forward wall 62 and the rearward wall 64. The second and third slots each adapt the side to receive the associated axially extending portions 152a, 154a of the pair of feather seals 152, 154.
The first feather seal 152 has the radially extending portion 152r disposed in the first radial slot 162. The first feather seal has its axially extending portion disposed in the third axial slot 166. The radial and axial portions block the leakage of cooling air from the outer cooling air chamber 132 in between adjacent support segments in both the radial and rearward directions, but some small leakage of cooling air does occur.
The second feather seal 154 has the radially extending portion 154r which is also disposed in the first radial slot to block leakage in the rearward direction from the outer cooling air chamber and, the inner cooling air chamber 134 in structures that do not have continuous bulkheads that seal off the inner chamber. The second feather seal has an axially extending portion 154a disposed in the third axial slot 166 to radially block the leakage of cooling air from the region between adjacent bulkheads bounding the inner cooling air chamber of adjacent support segments 38a, 38c. The second feather seal 154 also blocks leakage in the rearward direction from the outer cooling air chamber by the radial portion 154r of the second feather seal overlapping the first feather seal 152r.
As noted above,
The seal chamber 98 is bounded axially on one side by the support segment 38 (rearward wall 64) and bounded axially on the other side by the outer air seal segments (seal wall 96 of the rearward hooks 92 of at least two outer air seal segments 36a, 36b). These hooks extend about the support and are spaced axially from the support. In particular, the seal chamber is bounded axially on the upstream side by the rearward walls 64 and is bounded axially on the downstream side by the seal wall 96. The seal wall extends radially from the remaining portion of the rearward hook 92 and is spaced by an axial length Ls from the rearward wall 64 of the outer air seal segment. The rearward hook 92 also has an outwardly facing surface 95 which radially bounds a portion of an annular seal chamber 98.
As shown, the retainer member 42 is disposed in the low pressure region 108 of the seal chamber 98. The retainer member 42 has a first retainer wall 43a which extends axially and circumferentially to radially bound the seal chamber. The retainer member 42 has a second retainer wall 43r which extends circumferentially and radially from the first retainer wall to form a corner with the first retainer wall. The second retainer wall extends radially inwardly into close proximity with the seal wall 96 of the outer air seal member. The second retainer wall axially bounds the seal chamber leaving a radial gap R between the retainer member and the outer air seal segment. The radial gap R is spaced radially from the top and bottom of the seal chamber.
The second retainer wall 43r extends radially adjacent to the opening 104 in the retainer member 42. The second retainer wall is adapted to engage the anti-rotation projection 102 on the associated seal segment in case of an interference rub between the rotor blades and the outer air seal segment. This reduces bearing stresses resulting from engagement between retainer member 42 and the anti-rotation projection on the outer air seal by increasing the area of engagement with the second wall and by reducing the turning moment on the retainer member by having the anti rotation projection on the outer air seal member extend outwardly to engage the first wall of the retainer member at a diameter which is greater than the diameter of the remainder of the outer air seal segment.
The resilient seal member 44b has an axial length Lu in the uninstalled condition which is greater than the axial length Ls of the seal chamber. As a result, the resilient seal member in the uninstalled condition has an axial length Lu which is greater than the length Ls in the installed condition. The resilient seal member 44b further includes a first arm 45 for engaging the rearward wall 64 of the first structure and a second arm 46 for engaging the seal wall 96 of the second structure. The arms open toward the high pressure region 106 such that high pressure cooling air urges the arms apart into engagement with the walls. In this particular embodiment, the resilient seal member 44 is formed of a series of U-shaped members each having a pair of axially spaced arms diverging to form a U-shaped opening therebetween. Each arm is joined to an arm of the adjacent U-shaped member and disposed in the seal chamber such that the openings in the resilient seal member 44b adjacent the first and second arms 45, 46 face the region of higher pressure under operative conditions. Other configurations might be used, such as the alternate embodiment 44a, that are provided with arms that are urged by the high pressure cooling air into engagement with the adjacent structure.
As mentioned above, the outer air seal 36 is spaced radially inwardly from the second partition 128 of the outer air seal support to leave the outer air seal cooling air chamber 144 therebetween. The seal section of the outer air seal includes a feather seal slot 168 which faces an associated feather seal slot in the circumferentially adjacent outer air seal segment. The feather seal slot has an axially extending portion 168a, a forwardly extending radial portion 168fr and a rearwardly extending radial portion 168rr which adapt the segment to receive the third feather seal 156 and the fourth feather seal 158.
The third feather seal 156 has an axial portion 156a which is disposed in the feather seal slot of the outer air seal segment. The third feather seal extends for substantially the entire length of the axial portion of the feather seal slot in the outer air seal segment. The third feather seal has a radially extending portion 156r disposed in the forwardly extending radial portion of the feather seal slot.
Similarly, the fourth feather seal 158 has an axial portion 158a which is disposed in the feather seal slot of the outer air seal segment. The fourth feather seal, like the third feather seal, extends for substantially the entire length of the axial portion of the feather seal slot in the outer air seal segment. The fourth feather seal has a radially extending portion 158r disposed in the rearwardly extending radial portion of the feather seal slot. The overlapping axial portions of the third and fourth feather seals act to provide a double seal to radially block the leakage of cooling air from the cooling air chamber 144.
The outer air seal assembly 34 shown in
The fixture 174 extends circumferentially about an axis Af which is coincident with the axis As of the outer air seal assembly 34. The fixture includes an annular support section 175 disposed about the axis As. The fixture in the support section has a first groove 176 which extends circumferentially and which receives the outer air seal with its plurality of outer air seal segments 36a, 36b. A second groove 178 is radially outwardly of the first groove and extends circumferentially about the support section. The second groove receives the axial projection 74 on the forward wall 62 of the outer air seal support 38. A third groove 182 is radially outwardly of the second groove and extends circumferentially about the support section. The third groove receives the forward inner rail 68 of the outer air seal support.
During buildup, the fixture is disposed horizontally on a surface, such as a flat plate, with the axis Af extending in the vertical direction. As mentioned the module 172 is built-up of segments including the support segments, such as the support segments 38a, 38b (shown in
The method of installing the built-up outer air seal assembly in the second fixture 186 is simplified by the formation of the module 172. The method includes disposing a restraining member, such as a flat plate, on top of the module 172 with the axis of the fixture Af extending in the vertical direction. This causes the flat plate to rest on the module 172, with the flat plate engaging the rearward portion of the outer air seal assembly 34. The horizontally disposed fixture 174 and the outer air seal assembly are clamped together with the flat plate. The unit of the module and the flat plate is simply turned upside down such that the outer air seal assembly now rests on the flat plate. In other words, the flat plate is turned from being on top of the out air seal assembly to being underneath the outer air seal assembly. The fixture 174 is lifted off and the fixture 186 is mounted to the outer air assembly with tying members, as was done with fixture 174. This permits inserting in the module 184 into the engine, removing the tying members, and installing attachment bolts 116 through the holes 114 to secure the outer air seal assembly to the engine.
This design permits the ready insertion and bolting-up of a complete outer air seal assembly in the engine decreasing the time needed to complete installation of the outer air seal assembly and decreasing the chance for parts to be lost in the engine. The modular nature of the outer air assembly enables installation of critical parts, such as the outer air seal, the feather seals, and the resilient seal member 44 and inspection of these parts and the resilient seal member for correct orientation after installation. In turn, this reduces the amount of time needed to overhaul an engine or to build up a new engine. In particular, during an engine overhaul, having the outer air seal assembly in stock as an independent, interchangeable unit for later insertion into the engine allows for the replacement or interchanging of damaged parts without having to take time to tear down individual parts from the engine to repair the damaged assembly by repairing or replacing individual parts. Removing the parts as one unit decreases the cost of overhauling an engine and reduces the downtime for damaged engines, permitting the return of the overhauled engine to active service.
During operation of the engine 10 shown in
Interference contact between the rotor blades and the circumferentially extending outer air seal 36 urges the outer air seal segments in the circumferential direction. The retainer member 42, which is formed of an array of retainer segments, is engaged by the array of outer air seal segments, at least one of which has the radially extending anti-rotation projection 102. The anti-rotation projection extends into the associated opening 104 in the retainer segment to prevent circumferential movement of the array of outer air seal segments. In the embodiment shown, each retainer segment engages a pair of seal segments 36a, 36b.
Circumferential engagement between the anti-rotation member or lug 102 on the outer air seal 36 and the retainer member 42 blocks circumferential movement of the outer air seal 36 in response to the force exerted by the rotor blades 24. This circumferentially directed force creates a turning moment that must be resisted by the retainer member. An advantage is the durability of the outer air seal assembly, which is a subassembly for the engine 10, for a given weight and axial thickness of the seal retainer. This results from the level of force exerted by the seal retainer that is required to provide the anti-rotation moment needed to resist the turning moment acting on the seal segment during a rub of a rotor blade. By having the anti-rotation element or lug extend outwardly from the hook of the outer air seal segment to a larger diameter, the moment arm acted on by the resisting force is larger than the moment arm for an assembly having the same construction except for having the lug extend inwardly from the seal retainer to engage the outer air seal segment at a smaller diameter.
Cooling air is flowed from the interior of the outer air seal assembly 34 through the outer chamber 132 and the inner chamber 134 of the support segment 38. The cooling air is flowed thence through the second partition 128 to impinge on the outer air seal segment 36a and through the cooling holes 148 in the outer air seal to provide film cooling to the exterior of the seal section 48 over the seal surface 52. The leak path extends from the cooling air chamber 144 of the outer air seal between segments at the feather seals and elsewhere due to slight mismatches in structure because of tolerances.
For example, the leak path extends between the inwardly facing surface 94 (of the rearward hook 92) and the outwardly facing surface 84 (of the rearward inner rail 82). The leak path is intercepted by the seal chamber 98. The high-pressure cooling air enters the high-pressure region 106 of the seal chamber and exerts axially directed forces on the arms 45, 46 of the resilient seal member 44a (
A particular advantage of the present invention is the many functions performed by the retainer member 42. For example, the retainer member in cooperation with the anti-rotation member on the outer air seal, positively locates the outer air seal segment in the circumferential direction at build up, installation, and under operative conditions. In addition, the retainer member provides access to the seal chamber 98 for installing, locating and enclosing the resilient seal member 44 under non-operative conditions of the engine and for retaining the resilient seal member radially against cooling air pressure under operative conditions.
As shown in
As shown in
Although the invention has been shown and described with respect to detailed embodiments thereof, it should be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the claimed invention.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3966356 | Irwin | Jun 1976 | A |
| 5145316 | Birch | Sep 1992 | A |
| 5188506 | Creevy et al. | Feb 1993 | A |
| 5423659 | Thompson | Jun 1995 | A |
| 5971703 | Bouchard | Oct 1999 | A |
| 5993150 | Liotta et al. | Nov 1999 | A |
| 6435820 | Overberg | Aug 2002 | B1 |
| Number | Date | Country | |
|---|---|---|---|
| 20070025837 A1 | Feb 2007 | US |
