Patent Publication Number: US-10760529-B2

Title: Composite wear pad for exhaust nozzle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of, claims priority to and the benefit of, U.S. Ser. No. 14/709,072 filed May 11, 2015 entitled “COMPOSITE WEAR PAD FOR EXHAUST NOZZLE,” which is hereby incorporated herein in its entirety for all purposes. 
    
    
     GOVERNMENT LICENSE RIGHTS 
     This disclosure was made with government support under FA 8650-09-D-2923 0021 awarded by The United States Air Force. The government has certain rights in the disclosure. 
    
    
     FIELD 
     The present disclosure relates generally to convergent nozzles of aircraft and, more particularly, to wear pads positioned between a slider block and a slider track of a convergent nozzle system. 
     BACKGROUND 
     Exhaust from turbine sections of gas turbine engines may include uncombusted oxygen. Similarly, if the gas turbine engine is a bypass engine, the bypass air also contains oxygen. Some gas turbine engines may include an augmentor section capable of providing afterburning capabilities. In these gas turbine engines, the exhaust from the turbine section and/or the bypass air may be mixed with additional fuel and combusted in the augmentor section. This secondary combustion further increases the thrust of the gas turbine engine by increasing velocity of the fluid exiting the gas turbine engine. Due to the significant variance in velocity of the exhaust, some of these gas turbine engines may include a variable, or convergent, nozzle capable of changing in dimension based on the velocity of the exhaust fluid. This allows the nozzle to have an optimal shape during afterburning and non-afterburning portions of a flight. 
     SUMMARY 
     What is described is a composite wear pad for being coupled to a slider block of a convergent nozzle of a gas turbine engine. The composite wear pad includes a high heat capacity composite having a resin and a plurality of carbon fibers bonded together by the resin. The composite wear pad also includes a first rod coupled to the high heat capacity composite at a first axial end of the composite wear pad such that a first end thickness. The composite wear pad also includes a second rod coupled to the high heat capacity composite at a second axial end of the composite wear pad such that the first axial end and the second axial end of the composite wear pad each have an end thickness that is greater than a middle thickness of the composite wear pad. 
     Also described is a system. The system includes a slider block configured to slide along a slide track of a convergent nozzle and defining a first slot having a first outer distance and a first inner distance that is greater than the first outer distance. The system also includes a composite wear pad having a first axial end having a first end thickness that is greater than the first outer distance of the slider block such that the composite wear pad resists axial separation in response to the first axial end being positioned within the first slot. 
     Also described is a system. The system includes a slider block configured to slide along a slide track of a convergent nozzle and defining a first slot and a second slot. The system also includes a composite wear pad that includes a high heat capacity composite having a resin and a plurality of carbon fibers bonded together by the resin. The composite wear pad also includes a first rod coupled to the high heat capacity composite at a first axial end of the composite wear pad such that the first axial end of the composite wear pad can be received by the first slot. The composite wear pad also includes a second rod coupled to the high heat capacity composite at a second axial end of the composite wear pad such that the second axial end of the composite wear pad can be received by the second slot. 
     The foregoing features and elements are to 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 
       The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, is best be obtained by referring to the detailed description and claims when considered in connection with the drawing figures, wherein like numerals denote like elements. 
         FIG. 1  is a cross-sectional view of an exemplary gas turbine engine having afterburning capabilities, in accordance with various embodiments; 
         FIG. 2  illustrates a portion of a convergent nozzle of the gas turbine engine of  FIG. 1 , in accordance with various embodiments; 
         FIG. 3  illustrates a convergent flap coupled to a static structure via a slider block and a slider track, in accordance with various embodiments; 
         FIG. 4  illustrates the slider block of  FIG. 3  coupled to a composite wear pad, in accordance with various embodiments; 
         FIG. 5  illustrates a slider block coupled to a composite wear pad, in accordance with various embodiments; and 
         FIG. 6  illustrates a cross-sectional view of the composite wear pad of  FIG. 4 , in accordance with various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration and their best mode. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the inventions, it should be understood that other embodiments may be realized and that logical, chemical and mechanical changes may be made without departing from the spirit and scope of the inventions. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. 
     With reference now to  FIG. 1 , a gas turbine engine  100  is provided. An A-R-C axis is shown throughout the drawings to illustrate the axial (A), radial (R) and circumferential (C) directions. As used herein, “aft” refers to the direction associated with the tail (e.g., the back end) of an aircraft, or generally, to the direction of exhaust of the gas turbine engine. As used herein, “forward” refers to the direction associated with the nose (e.g., the front end) of an aircraft, or generally, to the direction of flight or motion. As utilized herein, radially inward refers to the negative R direction and radially outward refers to the R direction. 
     Gas turbine engine  100  may have afterburning capabilities. In that regard, gas turbine engine  100  may include a nose cone  102 , a fan section  104 , a compressor section  106 , a combustor section  108 , a turbine section  110 , a tail cone  112 , bypass ducts  114 , an augmentor section  132 , an augmentor liner  116  and a nozzle section  118 . Nose cone  102  may improve the aerodynamics of gas turbine engine  100 . Nose cone  102  may also provide vibration control functions. Fan section  104  may include a plurality of fan blades that rotate about an axis A-A′ of gas turbine engine  100  and propel fluid (such as air) aft. In that regard, a portion of the air is received by compressor section  106  and a portion of the air is received by bypass ducts  114 . 
     The airflow received by compressor section  106  is compressed using a plurality of stages of rotors and stators. The compressed air is then received by combustor section  108  which receives fuel and includes an ignition source. The air and fuel are mixed in combustor section  108  and ignited, creating a flow of exhaust in the aft direction. The exhaust may include compounds created during the ignition and some remaining oxygen that did not react during the combustion. 
     Turbine section  110  may include multiple stages of blades and vanes. The exhaust created by combustor section  108  is received by turbine section  110 . In response to receiving the exhaust, the turbine blades rotate, creating torque. The torque created in turbine section  110  may then be mechanically transferred to fan section  104  in order to cause rotation of the plurality of fan blades and/or compressor section  106  in order to cause rotation of the rotors. 
     Augmentor liner  116  may include a material defining a plurality of holes such that fluid may pass from one side of augmentor liner  116  to the other side of augmentor liner. In that regard, augmentor section  132  may receive the air flowing through bypass ducts  114 . Similarly, the exhaust from turbine section  110  may be received by augmentor section  132 . 
     The exhaust received by augmentor section  132  may have a velocity. In that regard and in various embodiments, the airflow through bypass ducts  114  and the exhaust from turbine section  110  may flow through augmentor section  132  and provide thrust. Augmentor section  132  may include an ignition source and be capable of receiving additional fuel. In response to augmentor section  132  receiving fuel and initiating combustion, the oxygen from the exhaust and the air received via bypass ducts  114  may mix with the fuel and be combusted. This creates a second exhaust having a higher velocity than the velocity of the received exhaust, thus generating more thrust than when combustion is not occurring in augmentor section  132 . 
     Nozzle section  118  may receive air and/or exhaust from augmentor section  132  and may further increase the velocity of the air and/or exhaust. Nozzle section  118  may be a convergent nozzle such that it includes a convergent section  120  and a divergent section  122  that meet at throat  124 . 
     The velocity of exhaust flowing through nozzle section  118  may vary based on whether combustion is occurring in augmentor section  132  or not such that the velocity may be greater if combustion is occurring in augmentor section  132 . Accordingly and with reference to  FIGS. 1 and 2 , a diameter  130  of nozzle section  118  may be selectively altered by changing position of a convergent flap  202  relative to a static structure  200 . The diameter  130  may be selectively altered based on the velocity of exhaust flowing through nozzle section  118 . This further alters an angle  126  between convergent section  120  and throat  124  as well as an angle  128  between divergent section  122  and throat  124 . Nozzle section  118  may thus be changed to provide optimal acceleration of the exhaust based on the velocity of the exhaust. 
     Static structure  200  may define and/or include a slider track  206 . A slider block  204  may be coupled to convergent flap  202  and slider track  206 . Slider block  204  may be capable of being received by and slide along slider track  206  and be capable of changing position axially and radially relative to static structure  200 . In response to slider block  204  changing position, diameter  130  of throat  124  is increased or decreased. In response to slider block  204  moving aft relative to static structure  200  from a forward position, a forward end of inner surface  210  of divergent section  122  may move radially inward, increasing diameter  130 . Similarly, in response to slider block  204  moving forward relative to static structure  200  from an aft positon, the forward end of inner surface  210  of divergent section  122  may move radially outward, reducing diameter  130 . 
     With reference now to  FIG. 3 , a composite wear pad  300  may be coupled to slider block  204  and positioned between an outer surface  304  of slider block  204  and an outer surface  302  of slider track  206 . Similarly, a second composite wear pad  306  may be coupled to slider block  204  and positioned between an outer surface  308  of slider block  204  and an inner surface  310  of slider block  204 . 
     As mentioned above and in various situations, slider block  204  may change position relative to slider track  206 . During this motion, friction may occur between outer surface  304  of slider block  204  and outer surface  302  of slider track  206 . In a similar manner, convergent flap  202  may change position relative to slider block  204 , creating friction between outer surface  308  of convergent flap  202  and inner surface  310  of slider block  204 . In that regard, composite wear pad  300  and second composite wear pad  306  may be positioned at these friction points and may resist the friction. 
     With reference now to  FIGS. 3 and 6 , composite wear pad  300  may include a high heat capacity composite  301  having plurality of carbon fibers  600  bonded using a resin at  602 . In various embodiments, plurality of carbon fibers  600  may have some fibers aligned in a first direction and other fibers aligned in a second direction, creating a woven pattern from plurality of carbon fibers  600 . In various embodiments, plurality of carbon fibers may all be aligned in the axial direction such that a longitudinal axis of each fiber is parallel to slider track  206  in the axial direction. In various embodiments, resin  602  may include a high temperature thermosetting polyimide resin such as AFR-PE-4™, available from Maverick Corporation of 11359 Grooms Road, Blue Ash, Ohio. Plurality of carbon fibers  600  and resin  602  may be resistant to heat. In various embodiments, the plurality of carbon fibers  600  and resin  602  may be resistant to temperatures up to 250 degrees Celsius (250° C., 482° F.), up to 300° C. (572° F.) or up to 350° C. (662° F.). Second composite wear pad  306  may also include a high heat capacity composite having a plurality of carbon fibers  600  bonded using a resin. In various embodiments, the resin may include a high temperature thermosetting polyimide resin and the plurality of carbon fibers and the resin may be resistant to heat. 
     Because slider block  204  changes position relative to slider track  206 , friction can occur between the two. Thus, composite wear pad  300  may be subjected to friction between the two. The carbon used in plurality of carbon fibers  600  includes friction-based wear resistance, thus, composite wear pad  300  resists wear during use. This results in a longer lifespan of composite wear pad  300  than if it comprised different materials having less wear-resistant properties. 
     Temperatures near slider block  204  can be relatively high, as hot exhaust flows in close proximity to slider block  204 . Because of this, it is undesirable to use grease between slider block  204  and slider track  206 . However, the properties of the carbon of plurality of carbon fibers  600  provide a low-friction interface, reducing the need for lubrication. This property reduces an amount of friction between outer surface  304  of slider block  204  and outer surface  302  of slider track  206 . This also provides advantages such as reducing or eliminating a requirement for changing grease in this location. Another benefit is the reduction of debris, as grease may attract debris. 
     With reference now to  FIG. 4 , slider block  204  may define a first slot  402  and a second slot  403 . In various embodiments, high heat capacity composite  301  may circumferentially surround a first rod  404  on a first side of composite wear pad  300  and circumferentially surround a second rod  405  on a second side of composite wear pad  300 . In various embodiments, first rod  404  and second rod  405  may have a cylindrical shape such that high heat capacity composite  301  may enclose the curved surface of cylindrical first rod  404  and cylindrical second rod  405 . In various embodiments, first rod  404  and second rod  405  may include a metal such as steel, steel alloy, titanium or the like. 
     During manufacture and after first rod  404  and second rod  405  are circumferentially surrounded by composite wear pad  300 , high heat capacity composite  301 , first rod  404  and second rod  405  may be co-cured together, for example, using an Autoclave. In various embodiments, the curing may be performed in a high pressure and high temperature environment. In various embodiments, high heat capacity composite  301 , first rod  404 , second rod  405  and slider block  204  may be cured together. Because first rod  404  and second rod  405  are cured together and used in a relatively high-temperature environment, first rod  404  and second rod  405  may include titanium, as a coefficient of thermal expansion of titanium closely matches that of the material of composite wear pad  300 . 
     High heat capacity composite  301  may have a middle thickness  456  and first axial end  460  and second axial end  463  of composite wear pad  300  may have an end thickness  452 . End thickness  452  may be measured as the largest thickness of the portion of composite wear pad  300  including first rod  404  or second rod  405  and may be greater than middle thickness  456 . First slot  402  and second slot  403  may have an inner distance  453  and an outer distance  454 . Inner distance  453  may be greater than outer distance  454  and positioned axially aft relative to a first axial end  460  of composite wear pad  300 . Inner distance  453  may be the same as or slightly greater than end thickness  452  of composite wear pad  300  (i.e., within five percent (5%) or within 10% of end thickness  452 ). Similarly, outer distance  454  may be the same as or slightly greater than middle thickness  456  (i.e., within 5% or within 10% of middle thickness  456 ). 
     Outer distance  454  may be positioned on first axial end  460  above an axial arm  462  of slider block  204 . In that regard, first axial end  460  of composite wear pad  300  may be circumferentially aligned with first slot  402  and force may be applied to composite wear pad  300  in the circumferential direction, causing first axial end  460  to slide into first slot  402 . Because end thickness  452  is greater than outer distance  454 , first axial end  460  may resist separation from slider block  204  in the axial direction. Second axial end  463  of composite wear pad  300  may resist axial separation in the same manner. 
     Because first rod  404  and second rod  405  are cured with high heat capacity composite  301 , the rods resist separation from high heat capacity composite  301 . With reference to  FIGS. 3 and 4  and based on the shape of annular cavity of first slot  402  and second slot  403 , in response to the portions of composite wear pad  300  containing first rod  404  and second rod  405  being inserted into first slot  402  and second slot  403 , composite wear pad  300  will resist separation from slider block  204 . This is particularly true in response to axial movement of slider block  204  relative to static structure  200 . As an additional benefit of coupling composite wear pad  300  to slider block  204  in this manner and returning reference to  FIG. 4 , in response to replacement of composite wear pad  300  being desired, a new composite wear pad may be coupled to slider block  204  without replacing slider block  204 . This is achieved by applying a circumferential force to composite wear pad  300  such that first axial end  460  and second axial end  463  of composite wear pad  300  slide out from first slot  402  and second slot  403 . 
     In various embodiments and with reference to  FIG. 5 , a slider block  510  may define a first triangular slot  500  and a second triangular slot  501 , each defining a cavity having a triangular prism shape. Similarly, a composite wear pad  520  may include a high heat capacity composite  505  having a first end  512  coupled to a first triangular rod  502  and a second end  518  coupled to a second triangular rod  503 . First end  512  may include a first flap  514  positioned on a base of first triangular rod  502  and another flap  516  positioned on another base of first triangular rod  502 . High heat capacity composite  505 , first triangular rod  502  and second triangular rod  503  may be co-cured together in order to couple composite wear pad  520  to first triangular rod  502  and second triangular rod  503 , such that high heat capacity composite  505 , first triangular rod  502  and second triangular rod  503  resist separation. Due to the triangular cavity of first triangular slot  500  and second triangular slot  501 , composite wear pad  520  will resist separation from slider block  510 . 
     In various embodiments and with reference to  FIGS. 3 and 4 , second composite wear pad  306  may include a high heat capacity composite similar to high heat capacity composite  301  and rods similar to first rod  404  and second rod  405  and slider block  204  may include slots similar to first slot  402  and second slot  403 . In that regard, second composite wear pad  306  may be coupled to slider block  204  in a similar manner as composite wear pad  300  is coupled to slider block  204 . 
     In various embodiments, the slots of the slider block may have any shape so long as an inner distance of the slot is larger than an outer distance of the slot. A composite wear pad may include a rod having a shape similar to the slots such that in response to a high heat capacity composite being coupled to the rod, the combination of the high heat capacity composite and the rod form a shape that substantially fills a volume defined by the slots (i.e., the volume of the high heat capacity composite coupled to the rod is within 5% or within 10% of the volume defined by a slot) and may not separate from the slots in response to axial movement of the slider block relative to a static structure, due to the end thickness of the rods being larger than the outer distance of the slots. 
     Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the inventions. The scope of the invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” Moreover, where a phrase similar to “at least one of A, B, or C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C. Different cross-hatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials. 
     Systems, methods and apparatus are provided herein. In the detailed description herein, references to “one embodiment”, “an embodiment”, “various embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments. 
     Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112(f), unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.