Patent Publication Number: US-11022072-B2

Title: Gas turbine engine convergent/divergent exhaust nozzle divergent seal with preloaded dovetail interface background

Description:
This application claims priority to and is a divisional of U.S. patent application Ser. No. 14/249,774 filed Apr. 10, 2014, which claims priority to U.S. Provisional Patent Appln. No. 61/811,522 filed Apr. 12, 2013, U.S. Provisional Patent Appln. No. 61/811,544 filed Apr. 12, 2013 and U.S. Provisional Patent Appln. No. 61/811,551 filed Apr. 12, 2013. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present disclosure relates to a gas turbine engine and, more particularly, to a nozzle system therefor. 
     2. Background Information 
     Gas turbine engines, such as those which power modem military aircraft, include a compressor section to pressurize a supply of air, a combustor section to burn a hydrocarbon fuel in the presence of the pressurized air, and a turbine section to extract energy from the resultant combustion gases and generate thrust. Downstream of the turbine section, an augmentor section, or “afterburner”, is operable to selectively increase thrust. The increase in thrust is produced when fuel is injected into the core exhaust gases downstream of the turbine section and burned with the oxygen contained therein to generate a second combustion and passed through a variable area exhaust nozzle system. 
     A variable area exhaust nozzle such as a convergent/divergent (C/D) nozzle optimizes the thrust produced within the gas turbine engine by provision of a multitude of nozzle positions. The term “convergent-divergent” describes an exhaust nozzle having a convergent section upstream of a divergent section. Exhaust gases from the turbine section pass through the decreasing diameter convergent section before passing through the increasing diameter divergent section. Convergent/Divergent (C/D) exhaust nozzles may be configured for an augmented or non-augmented engine in a two or three dimensional configuration with or without the capability to vector. 
     The nozzle defines a throat or jet area and an exit area. The jet area is the minimum cross sectional area of the nozzle and is defined by the interface between an aft end of the convergent section and a forward end of the divergent section. The exit area is the cross sectional area measured at the aft most section of the nozzle. The area ratio of a nozzle is the exit area divided by the jet area. The area ratio range provides a general indicator of engine performance and an increase in the area ratio range results in more efficient engine performance with increased engine thrust, fuel efficiency and a decrease in actuator loads required to articulate the nozzle as the engine power setting increases. 
     The convergent and divergent sections generally include circumferentially disposed flaps and flap seals. The alternately disposed flaps and flap seals accommodate changes injet area and nozzle axis skew (if the nozzle is vectorable). 
     SUMMARY 
     A divergent flap seal according to one disclosed non-limiting embodiment of the present disclosure includes a flap seal body with a spine, the flap seal body manufactured of a non-metallic material; a mount engaged with the spine at a dovetail interface; and a resilient member at the dovetail interface. 
     In a further embodiment of the present disclosure, the mount is manufactured of a metallic alloy. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the flap seal body is manufactured of a monolithic ceramic material. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the monolithic ceramic material is a SN240 monolithic ceramic. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the resilient member is a leaf spring. 
     A divergent flap seal according to another disclosed non-limiting embodiment of the present disclosure includes a flap seal body with a spine, the flap seal body manufactured of a non-metallic material; a forward mount engaged with the spine at a forward dovetail interface; a first resilient member at the forward dovetail interface; an aft mount engaged with the spine at an aft dovetail interface; and a second resilient member at the aft dovetail interface. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the first resilient member and the second resilient member are located between the spine and a tail of the respective forward mount and aft mount. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the spine has a male dove tail geometry and the tail of the respective forward mount and aft mount has a female dove tail geometry to radially lock onto the dovetail spine. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the spine forms a flared pin in cross-section. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the first resilient member and the second resilient member is a leaf spring. 
     A further embodiment of any of the foregoing embodiments of the present disclosure includes a clamp plate mounted to the forward mount and the aft mount to sandwich the first resilient member and the second resilient member at least partially within the spine. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the first resilient member and the second resilient member are at least partially within a forward dovetail socket and an aft dovetail socket in the spine. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the first resilient member and the second resilient member is a leaf spring. 
     A method of mounting a divergent flap seal of a convergent/divergent nozzle system according to another disclosed non-limiting embodiment of the present disclosure includes preloading a mount manufactured of a metal alloy with respect to a flap seal body manufactured of a non-metallic material. 
     A further embodiment of any of the foregoing embodiments of the present disclosure includes attaching the mount to the flap seal body at a dovetail socket within a spine of the flap seal body. 
     A further embodiment of any of the foregoing embodiments of the present disclosure includes attaching the mount to the flap seal body at a spine of the flap seal body, the spine and mount defining a dovetail interface in cross section. 
     A further embodiment of any of the foregoing embodiments of the present disclosure includes clamping the mount to the spine without thru fasteners. 
     A convergent/divergent nozzle system according to another disclosed non-limiting embodiment of the present disclosure includes a convergent section and a divergent section. The divergent section is downstream of the convergent section. The divergent section includes a flap seal body manufactured of a non-metallic material. 
     A further embodiment of any of the foregoing embodiments of the present disclosure includes a forward mount manufactured of a metallic alloy, wherein the forward mount is attached to a spine of said flap seal body. 
     A further embodiment of any of the foregoing embodiments of the present disclosure includes a flap seal joint structure mounted to the forward mount. 
     A further embodiment of any of the foregoing embodiments of the present disclosure includes an aft mount manufactured of a metallic alloy, which aft mount is engaged with the spine. 
     A further embodiment of any of the foregoing embodiments of the present disclosure includes a flap seal position guide mounted to the forward mount and the aft mount. 
     A further embodiment of any of the foregoing embodiments of the present disclosure includes an axial stop mounted to the aft mount to axially interface with an end of the spine. 
     A method of mounting a divergent flap seal of a convergent/divergent nozzle system according to another disclosed non-limiting embodiment of the present disclosure includes the step of attaching a mount manufactured of a metal alloy to a flap seal body manufactured of a non-metallic material at a dovetail socket within a spine of the flap seal body. 
     A further embodiment of any of the foregoing embodiments of the present disclosure includes the step of clamping the metal alloy mount to the spine without thru fasteners. 
     A further embodiment of any of the foregoing embodiments of the present disclosure includes the step of sandwiching a tail of the mount within the spine. 
     A further embodiment of any of the foregoing embodiments of the present disclosure includes the step of sandwiching a tail of the mount within a dovetail socket of the spine. 
     The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, the following description and drawings are intended to be exemplary in nature and non-limiting. 
    
    
     
       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 view of an exemplary gas turbine engine with a nozzle section according to one disclosed non-limiting embodiment. 
         FIG. 2  is a lateral cross-section of a convergent divergent nozzle in a first Position. 
         FIG. 3  is a perspective partial cross-section of the convergent divergent nozzle in the first position. 
         FIG. 4  is a lateral cross-section of a convergent divergent nozzle in a second Position. 
         FIG. 5  is a perspective view of the convergent divergent nozzle in the second position. 
         FIG. 6  is an outer perspective view of a portion of the divergent section from a cold side. 
         FIG. 7  is a perspective view of a divergent flap seal from a cold side according to one non-limiting embodiment. 
         FIG. 8  is a lateral sectional view of a dovetail interface of the divergent flap seal of  FIG. 7 . 
         FIG. 9  is a longitudinal sectional view of the divergent flap seal of  FIG. 9 . 
         FIG. 10  is a perspective view of a divergent flap seal from a cold side according to another non-limiting embodiment. 
         FIG. 11  is a longitudinal sectional view of a dovetail interface of the divergent flap seal of  FIG. 10 . 
         FIG. 12  is a lateral sectional view of the divergent flap seal of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  is disclosed herein as a two-spool low-bypass augmented turbofan that generally  10  incorporates a fan section  22 , a compressor section  24 , a combustor section  26 , a turbine section  28 , an augmenter section  30 , an exhaust duct section  32 , and a nozzle system  34  along a central longitudinal engine axis “A”. Although depicted as an augmented low bypass turbofan in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are applicable to other gas turbine engines including non-augmented engines, geared architecture engines, direct drive turbofans, turbojet, turboshaft, multi-stream variable cycle and other engine architectures with a nozzle system. 
     An outer structure  36  and an inner structure  38  define a generally annular secondary airflow path  40  around a core primary airflow path  42 . Various structure and modules may define the outer structure  36  and the inner structure  38  which essentially define an exoskeleton to support the rotational hardware therein. 
     Air that enters the fan section  22  is divided between a core primary airflow through the core primary airflow path  42  and a secondary airflow through a secondary airflow path  40 . The core primary airflow passes through the combustor section  26 , the turbine section  28 , then the augmentor section  30  where fuel may be selectively injected and burned to generate additional thrust through the nozzle system  34 . It should be appreciated that additional airflow streams such as third stream airflow typical of variable cycle engine architectures may additionally be sourced from the fan section  22 . 
     The secondary airflow may be utilized for a multiple of purposes to include, for example, cooling and pressurization. The secondary airflow as defined herein is any airflow different from the core primary airflow. The secondary airflow may ultimately be at least partially injected into the core primary airflow path  42  adjacent to the exhaust duct section  32  and the nozzle system  34 . 
     With reference to  FIG. 2 , the exhaust duct section  32  may be circular in cross-section as typical of an axisymmetric augmented low bypass turbofan that terminates in a Convergent/Divergent (C/D) nozzle system  34 . The Convergent/Divergent (C/D) nozzle system  34  generally includes a convergent section  44  and a divergent section  46 . The convergent section  44  includes a multiple of circumferentially distributed convergent flaps  50  (only one  15  shown in section), each pivotably connected to a stationary frame  52  with a cooling liner panel  54  of the exhaust duct section  32  upstream thereof. The divergent section  46  includes a multiple of circumferentially distributed divergent flaps  56  (only one shown in section) pivotally connected at a joint  58  to an aft section of the convergent flaps  50 . 
     A plurality of divergent flap seals  60  ( FIG. 3 ) are distributed circumferentially between and to at least partially overlap the adjacent divergent flaps  56 . Taken collectively, the convergent and divergent flaps and the flap seals circumscribe the nozzle centerline “A” to define a variable radial outer boundary for the core primary airflow. A control system (illustrated schematically) varies the angular orientations of the convergent flaps  50  and divergent flaps  56  to adjust a nozzle throat A 8  and exit A 9  about a nozzle centerline “A” between example minimum position ( FIGS. 2 and 3 ) and a maximum position ( FIGS. 4 and 5 ). 
     The liner panels  54 , taken collectively, form a liner that cooperates with the convergent flaps  50  to define an annular cooling airflow passageway that guides the secondary  5  airflow (illustrated schematically be arrows S) along an annular inner surface of the convergent flaps  50  and at least partially into the divergent flaps  56 . The secondary airflow “S” is typically sourced from the fan section  22 , the compressor section  24 , a third stream airflow, ambient airflow and/or other airflow that is different from the core primary airflow (illustrated schematically by arrow “C”). 
     With reference to  FIG. 6 , the divergent section  46  includes alternate divergent flap seals  60  and divergent flaps  56 —illustrated from a side opposite the hot-side which is directly exposed to engine exhaust gases of the core primary airflow C. It should be understood that the divergent section  46  portion as illustrated herein is for descriptive purposes only and applies to each adjacent flap  56  and flap seal  60  defined about the circumference of the nozzle system  34 . Each divergent flap  56  includes a divergent flap hot-side panel and a coldside panel  64 . The divergent flap hot-side panel and the coldside panel  64  may form an at least partially hollow interior to receive the secondary airflow “S” there through. Each divergent flap  56  may be described as having a length between a forward section  66  and an aft section  68 , and a width between a first longitudinal side  70  and a second longitudinal side  72 . The forward section  66  of each divergent flap  56  includes joint structure that forms a portion of the joint  58  along the hinge axis H. 
     The aft section  68  of each divergent flap  56  may include a plow tip  74 . It should be understood that separate or integral tip sections of various shapes and configurations will benefit here from. The plow tip  74  may be chiseled and includes a hinge point  76  for attachment of an external flap  78  ( FIGS. 2 and 4 ). 
     With reference to  FIG. 7 , each divergent flap seal  60  includes a flap seal body  82 , a spine  84 , a flap seal joint  86  and a flap seal position guide  88 . The flap seal joint  86  forms a portion of the joint  58  about hinge axis H that surrounds the engine centerline “A”. Each flap seal body  82  may be described as having a length between a forward section  90  and an aft section  92 , and a width between a first longitudinal side  94  and a second longitudinal side  96 . The flap seal body  82  is a relatively planar member manufactured of a non-metallic material such as a SN240 monolithic ceramic. The aft section  92  may be of a chevron shape. 
     The spine  84  extends from the flap seal body  82  of each divergent flap seal  60  along a central axis F between the forward section  90  and the aft section  92  transverse to the hinge axis H and parallel to the first longitudinal side  94  and the second longitudinal side  96 . The spine  84  defines a backbone that has a flared dovetail shape in cross-section with a head  98  and a rib  100 . The head  98  is thicker than the rib  100 . 
     A forward mount  102  and an aft mount  104  interfaces with the spine  84 . The forward mount  102  and the aft mount  104  each includes a respective tail  106 ,  108  that receives the head  98  of the spine  84 . That is, the spine  84  forms a male dove tail geometry and the respective tail  106 ,  108  form a female dove tail geometry to radially lock onto the spine  84  ( FIG. 8 ). 
     The forward mount  102  and the aft mount  104  each includes a respective threaded post  110 ,  112  to support a respective bridge clamp  114 ,  116  that provide a slidable interface with a respective bridge support  118 ,  120  of the adjacent divergent flap  56  ( FIG. 6 ). That is, the bridge clamps  114 ,  116  are transverse to the central axis F to bridge the overlap interface with the adjacent divergent flaps  56  that flank each divergent flap seal  60  to at least partially radially support each divergent flap seal  60 . 
     The flap seal position guide  88  is mounted between the forward mount  102  and the aft mount  136 . The flap seal position guide  88  supports a slider  122  with link arms  123  that attach to the respective adjacent divergent flap  56  to further guide movement of the divergent flap seal  60  ( FIG. 6 ). As the flap seal position guide  88 , the forward mount  102  and the aft mount  104  are manufactured of metal alloys, the components may be readily fastened together with fasteners  124  such as rivets or bolts ( FIG. 9 ). 
     The forward mount  102  is also attached to the flap seal joint  86  with a fastener  126  such as rivets or bolts. The forward mount  102  is thereby axially fixed relative to the spine  84  by the flap seal joint  86 . The aft mount  104  is attached to an axial stop  128  with a fastener  130  such as rivets or bolts. The aft mount  104  is attached to the forward mount  102  through the flap seal position guide  88  such that the axial stop  128  provides aftward axial retention of the divergent flap sea  160 . That is, the axial stop  128  interfaces with an edge  132  of the spine  84  to  15  prevent the flap seal body  82  from axially sliding out of the mounts  102 ,  104  ( FIG. 9 ). That is, the ceramic divergent flap seal  60  is effectively retained to the metal alloy mounts  102 ,  104  yet differential thermal expansion is readily accommodated without thru-fasteners. 
     In operation, as the metal alloy of the mounts  102 ,  104  thermally expand from engine operation, the tail  106 ,  108  may expand in any direction away from the ceramic material spine  84  to provide a thermally free design. The spine  84  is also loaded in compression that is advantageous in monolithic ceramic materials. As there is a relatively large shear area provided by the spine  84 , the shear stress is relatively low which is also advantageous in monolithic ceramic materials. The dovetail interface also removes the need for thru-fasteners which need otherwise penetrate the monolithic ceramic materials. 
     With reference to  FIG. 9 , a resilient member  138  (also shown in  FIG. 8 ) may alternatively or additionally be utilized to provide a frictional damper at the dovetail interface. The resilient member  138  may be a leaf spring, resilient material other bias member. The resilient member  138  may be manufactured of a flat piece of metal alloy that is formed in a partially arcuate shape. When the resilient member  138  is deformed, a preload is provided between the spine  84  and the respective tail  106 ,  108  of the forward mount  102  and the aft mount  104 . 
     The resilient member  138  maintains surface contact between the spine  84  and the respective tail  106 ,  108  as, under some operational conditions, the ceramic divergent flap seal  60  divergent seal can experience a zero (0) external load in, for example, an under expanded condition. The resilient member  138  provides a specified output load within a given space between the spine  84  and the respective tail  106 ,  108 . 
     With reference to  FIG. 10 , each divergent flap seal  60 ′ according to another disclosed non-limiting embodiment includes a flap seal body  140 , a spine  142 , a flap seal joint  144  and a flap seal position guide  146 . The flap seal joint  144  forms a portion of the joint  58  about hinge axis H that surrounds the engine centerline A. Each flap seal body  140  may be described as having a length between a forward section  148  and an aft section  150  with a width between a first longitudinal side  152  and a second longitudinal side  154 . The flap seal body  140  is a relatively planar member manufactured of a non-metallic material such as a SN240 monolithic ceramic. The aft section  150  may be of a chevron shape. 
     The spine  142  extends from the flap seal body  140  of each divergent flap seal  60  along a central axis F between the forward section  148  and the aft section  150  transverse to the hinge axis H and parallel to the first longitudinal side  152  and the second longitudinal side  154 . The spine  142  defines a backbone that has a forward dovetail socket  156  and an aft dovetail socket  158 . 
     A forward mount  160  and an aft mount  162  (also shown in  FIGS. 11 and 12 ) interfaces with the spine  142  at the respective forward and aft dovetail sockets  156 ,  158 . The forward mount  160  and the aft mount  162  each includes a respective tail  164 ,  166  that is received within the respective forward and aft dovetail sockets  156 ,  158 . 
     The forward mount  160  and the aft mount  162  each includes a respective threaded post  168 ,  170  to support a respective bridge clamp  114 ,  116  that provide a slidable interface with a respective bridge support  118 ,  120  of the adjacent divergent flap  56  ( FIG. 6 ). That is, the bridge clamps  114 ,  116  are transverse to the central axis F to bridge the overlap interface with the adjacent divergent flaps  56  that flank each divergent flap seal  60  to at least partially radially support each divergent flap seal  60 . 
     The flap seal position guide  146  is attached to a clamp plate  172  that is mounted between the forward mount  160  and the aft mount  136 . The flap seal position guide  146  supports a slider  122  with link arms  123  ( FIG. 6 ) that attach to the respective adjacent divergent flap  56  to further guide movement of the divergent flap seal  60 . As the flap seal position guide  146  and the clamp plate  172  are manufactured of metal alloys, the components may be readily fastened together with fasteners  17   4  such as rivets or bolts. 
     The clamp plate  172  includes a forward circular aperture  176  and an aft slot aperture  178 . The forward circular aperture  176  and the aft slot aperture  178  are aligned with the respective forward and aft mount  160 ,  162 . 
     The forward circular aperture  176  receives a fastener  180  such as a rivet or 5 bolt that extends through the clamp plate  172 , the forward mount  160  and the flap seal joint  144 . The tail  164  of the forward mount  160  is thereby sandwiched within the forward dovetail socket  156  between the clamp plate  172  and a back plate  182  of the forward mount  160 . 
     The aft slot aperture  178  receives a fastener  184  such as a rivet or bolt that extends through the clamp plate  172  and the aft mount  162 . The tail  166  of the aft mount  162  is 10 thereby sandwiched within the aft dovetail sockets  158  between the clamp plate  172  and a back plate  186  of the aft mount  162 . The aft slot aperture  178  permits axial thermal expansion and contraction of the flap seal position guide  146  is attached to a clamp plate  172 . That is, the ceramic divergent flap seal  60  is effectively retained to the metal alloy mounts  160 ,  162  yet differential thermal expansion is readily accommodated without thru-fasteners. 
     In operation, as the metal alloy mounts  160 ,  162  thermally expand from engine operation, the aft slot aperture  178  provides a thermally free design. The spine  142  is also loaded in compression that is advantageous in monolithic ceramic materials. The dovetail interface also removes the need for thru-fasteners which need otherwise penetrate the monolithic ceramic materials. A preload mechanism may alternatively or additionally be utilized to provide a frictional damper at the dovetail interface. 
     With reference to  FIG. 11 , a resilient member  190  (also shown in  FIG. 12 ) may alternatively or additionally be utilized to provide a frictional damper at the dovetail interface. 
     The resilient member  190  is located between the respective tail  164 ,  166  of the forward mount  160  and an aft mount  162  and the aft dovetail sockets  156 ,  158 . The resilient member  190  is also sandwiched and thereby retained within the aft dovetail sockets  158  between the clamp plate  172  and a back plate  186  of the aft mount  162 . When the resilient member  190   5  is deformed, a preload is provided. 
     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 here from. 
     Although the different non-limiting embodiments have specific illustrated components, the embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments. 
     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.