Patent Publication Number: US-2016237950-A1

Title: Backside coating cooling passage

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Patent Application No. 61/887,683 filed Oct. 7, 2013, which is hereby incorporated herein by reference in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This disclosure was made with Government support under N00019-02-C-3003 awarded by the United States Air Force. The Government may have certain rights in this disclosure. 
    
    
     BACKGROUND 
     The present disclosure relates to gas turbine engines, and more particularly to cooling arrangements therefor. 
     Gas turbine engines, such as those which power modern military and commercial 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 to generate thrust. Downstream of the turbine section, military aircraft engines often include an augmentor section, or “afterburner” 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. 
     The augmentor section and downstream exhaust duct and nozzle sections may be exposed to high temperature exhaust gases. The exhaust gas temperatures may in some instances exceed the metal alloy capabilities in these sections such that a cooling flow is provided therefor. The cooling flow is provided though numerous cooling holes typically machined via a laser drill to sheath the hardware from the exhaust gases. 
     SUMMARY 
     A component for a gas turbine engine, according to one disclosed non-limiting embodiment of the present disclosure, includes a substrate with an aperture. The gas turbine engine component also includes a backside coating on a backside of the substrate to form a shaped passage with the aperture. 
     In a further embodiment of the present disclosure, the shaped passage includes a convergent section, a divergent section and a throat therebetween. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the divergent section is at least partially defined within the aperture. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the backside coating is about as thick as the substrate. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the backside coating forms a thickness between about 20%-100% of the inner boundary of the aperture. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the inner boundary of the aperture is about 0.050-0.10 inches (1.27-2.54 mm) in characteristic diameter.   
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the shaped passage includes a convergent section, a divergent section and a throat therebetween. The coating reduces the throat to about 10%-70% of the inner boundary of the aperture. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the shaped passage includes a convergent section, a divergent section and a throat therebetween. The coating reduces the throat to about 50% of the inner boundary of the aperture. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the shaped passage includes a convergent section, a divergent section and a throat therebetween. The throat is about 0.060 inches (1.5 mm) in characteristic diameter, the divergent section is about 0.090 inches (2.3 mm) in characteristic diameter. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the backside coating is applied to the backside of the substrate as a spot. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the component is a hot sheet of an exhaust duct. 
     A liner assembly for a gas turbine engine, according to another disclosed non-limiting embodiment of the present disclosure, includes a hot sheet with a multiple of apertures. The liner assembly also includes a backside coating on a backside of the hot sheet and at least partially onto an inner boundary of each of the multiple of apertures. The backside coating forms a passage with each of the multiple of apertures including a convergent section, a divergent section and a throat therebetween. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, a cold sheet is includes and spaced from the hot sheet, the backside coating faces the cold sheet. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the backside coating defines a spot for each of the multiple of apertures. 
     A method of forming a shaped aperture in a component of a gas turbine engine, according to another disclosed non-limiting embodiment of the present disclosure, includes applying a backside coating on a backside of a substrate and at least partially onto an inner boundary of an aperture. The backside coating forms a passage with the aperture including a convergent section, a divergent section and a throat therebetween. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the method includes locally applying the backside coating as a spot for each aperture. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the method includes applying the backside coating to the entirety of the backside. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the method includes reducing the throat to about 10%-70% of the inner boundary of the aperture. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the method includes forming the aperture through the substrate prior to application of the backside coating. 
     In a further embodiment of any of the foregoing embodiments of the present disclosure, the method includes applying a coating on the front side of the substrate. The aperture is then formed through the substrate and the front side coating prior to application of the backside coating. 
     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 embodiments. The drawings that accompany the detailed description can be briefly described as follows: 
         FIG. 1  is a general schematic view of an example gas turbine engine; 
         FIG. 2  is a perspective cross section of an example exhaust duct section of the engine; 
         FIG. 3  is a cross section through a passage according to one disclosed non-limiting embodiment; 
         FIG. 4  is a backside view showing a coating applied as a spot for each passage; 
         FIG. 5  is a flow chart of a coating application process; 
         FIG. 6  is a cross section through a substrate aperture prior to a coating application according to one non-limiting embodiment; and 
         FIG. 7  is a cross section through a substrate aperture prior to a coating application according to another non-limiting embodiment. 
     
    
    
     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 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 section  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. 
     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 static structure and case 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 primary airflow through the primary airflow path  42  and a secondary airflow through the secondary airflow path  40 . The 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 section  34 . It should be appreciated that additional airflow streams such as a third stream airflow typical of variable cycle engine architectures may additionally be provided. 
     The secondary airflow may be utilized for a multiple of purposes to include, for example, cooling and pressurization. The secondary airflow as defined herein as any airflow different from the primary airflow. The secondary airflow may ultimately be at least partially injected into the primary airflow path  42  adjacent to the exhaust duct section  32  and the nozzle section  34 . 
     With reference to  FIG. 2 , the exhaust duct section  32  generally includes an outer exhaust duct case  44  (illustrated schematically) of the outer structure  36  and a liner assembly  46  spaced inward therefrom. The exhaust duct section  32  may be circular in cross-section as typical of an axis-symmetric augmented low bypass turbofan, non-axisymmetric in cross-section or combinations thereof. In addition to the various cross-sections, the exhaust duct section  32  may be non-linear with respect to the central longitudinal engine axis A to form, for example, a serpentine shape to block direct view to the turbine section  28 . Furthermore, in addition to the various cross-sections and the various longitudinal shapes, the exhaust duct section  32  may terminate in the nozzle section  34  which may be a convergent divergent nozzle, a non-axisymmetric two-dimensional (2D) vectorable nozzle section, a flattened slot convergent nozzle of high aspect ratio or other exhaust duct arrangement. 
     The liner assembly  46  operates as a heat shield to protect the outer exhaust duct case  44  from the extremely hot combustion gases in the primary airflow path  42 . Air discharged from, for example, the fan section  22  is communicated through the annular passageway  40  defined between the outer exhaust duct case  44  and the inner liner assembly  46 . Since fan air and is relatively cool compared to the hot gases in the primary airflow path  42 , the fan air cools the liner assembly  46  to enhance the life and reliability thereof. 
     The liner assembly  46  is mounted to the outer exhaust duct case via a multiple of hanger brackets  48 . The liner assembly  46  generally includes a cold sheet  50  separated from a hot sheet  52  by a plurality of structural supports  54  which attach the cold sheet  50  to the hot sheet  52 . During engine operation, the cold sheet  50  receives relatively large pressure loads and deflections, while the hot sheet  52  receives relatively small pressure loads and deflections and thereby better retains a heat resistant coating. It should be appreciated that various types of structural supports as well as locations therefor may be used herewith and that the illustrated structural supports  54  are but non-limiting examples. 
     The cold sheet  50  may be corrugated with various rippled or non-planar surfaces and include a multiple of metering passages  56  to receive secondary airflow from between the outer exhaust duct case  44  and the liner assembly  46 . The secondary airflow is communicated through passages  58  in the hot sheet  52 . The passages  58  provide effusion cooling and are generally more prevalent than the metering passages  56  which provide impingement cooling to the hot sheet  52 . The secondary airflow thereby provides impingement and effusion cooling to sheath the liner assembly  46  from the relatively high temperature combustion products. 
     A backside  62  of the hot sheet  52  includes a backside coating  60  such as a thermal backside coating. A front side  64  of the hot sheet  52 , opposite the backside  62 , is a gas path side of the hot sheet  52  adjacent the relatively high temperature combustion products which, for example, may be generated by the secondary combustion of the augmenter section  30 . Although the hot sheet  52  is illustrated herein as representative of a substrate  66  with the backside coating  60 , it should be appreciated that various backside coated components will benefit herefrom to include, but not be limited to, airfoil components. 
     With reference to  FIG. 3 , each passage  58  in this disclosed non-limiting embodiment is a shaped cooling passage which is often alternatively referred to as a “diffusion”, “fanned” or “laid back” cooling passage. The passage  58  generally defines a convergent section  70 , a divergent section  72  and a throat  74  therebetween. That is, the passage  58  is a “shaped” passage. 
     The passage  58  generally includes an aperture  80  formed into the substrate  66  which is with the backside coating  60  applied the backside  62  thereof. The aperture  80  may be, for example, drilled, cut, punched or otherwise formed through the substrate  66 . Then the backside coating  60  is applied to the backside  62  of the substrate  66 . The backside coating  60  may be applied via, for example, an air-plasma spray that partially passes through the aperture  80  to at least partially form the convergent section  70 , the divergent section  72  and the throat  74 . That is, as the backside coating  60  is applied on the backside  62  of the substrate  66 , the backside coating  60  accumulates around the inner boundary  81  of the aperture  80 . 
     In one example, the substrate  66  may be about equal in thickness to the backside coating  60  which may be about 0.2 inches (5 mm) thick. More specifically, the backside coating  60  may be 50%-200% the thickness of the substrate  66 , and/or about 20%-100% of a characteristic diameter of the aperture  80 . The aperture  80  in one disclosed non-limiting embodiment is about 0.050-0.10 inches (1.27-2.54 mm) in characteristic diameter. The term “characteristic diameter” as defined herein is applicable to circular and non-circular apertures such as an oval or racetrack shaped aperture  70 . That is, the aperture  70  includes, but is not limited to, a circular cross section. 
     In one example, the throat  74  may be about 0.060 inches (1.5 mm) in characteristic diameter and the divergent section  72  may be about 0.090 inches (2.3 mm) in characteristic diameter. In another example, the backside coating  60  reduces the throat  74  to about 10%-70% and more particularly to about 50% of the inner boundary of the aperture  80 . 
     The backside coating  60  may be applied to the entire backside  62 , or, alternatively, the backside coating  60  need only be applied locally to the backside  62  at each aperture  80  to essentially form spots  82  of backside coating  60  on the backside  62  ( FIG. 4 ). The application as spots  82  locally to each aperture  80  facilitates, for example, weight reduction. 
     The convergent section  70  forms an entrance  84  to the passage  58  and the throat  74  controls the cooling airflow through the passage  58 . The divergent section  72  forms an exit  86  from the passage  58  to diffuse or fan the cooling air to facilitate airflow cooling of the substrate  66 . 
     With reference to  FIG. 5 , a flow chart illustrates one disclosed non-limiting embodiment of a method  200  for fabricating the passage  58 . The method  200  initially includes forming the aperture  80  in the substrate  66  (step  202 ;  FIG. 6 ). The aperture  80  may be, for example, drilled, cut, punched or otherwise formed through the substrate  66 . Optionally, the substrate  66  already includes a front side coating  60 A on the front side  64  of the substrate  66  prior to fomiation of the aperture  80  (step  201 ;  FIG. 7 ). 
     Next, the backside coating  60  is applied to the backside  62  of the substrate  66  (step  204 ). As the thickness of the backside coating increases through application, the backside coating  60  progressively reduces the through area of the aperture  80  to form the throat  74 . The convergent section  70  to the passage  58  is thereby defined by the backside coating  60 , which also defines the throat  74  and the divergent section  72 . The size of the throat  74  is a function of, for example, the backside coating type, backside coating thickness, backside coating spray angle and shape of aperture  80 . In general, the thickness accumulation of the backside coating  60  forms the throat  74 , to readily form the hourglass type passage  58 . 
     As application of the backside coating  60  forms the passage  58 , manufacture thereof is relatively efficient and inexpensive compared to conventional passages. 
     The use of the teens “a” and “an” and “the” and similar references in the context of description (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or specifically contradicted by context. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. It should be appreciated that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting. 
     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. 
     It should be appreciated that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be appreciated that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. 
     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 features 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 appreciated 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.