Patent Publication Number: US-11028729-B2

Title: Heat shield, systems and methods

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of, and claims priority to, and the benefit of U.S. patent application Ser. No. 14/682,767, filed on Apr. 9, 2015, and entitled “HEAT SHIELD, SYSTEMS AND METHODS” which is incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This disclosure relates to a gas turbine engine, and more particularly to heat shields for oil tube fittings. 
     BACKGROUND 
     Engine oil tubes and fittings may be subjected to relatively high temperatures. Once subjected to excessive heating, oil may undergo coking. Oil coking may cause solid oil deposits to form within oil tubes, causing undesirable effects such as blocked passageways and filters. 
     SUMMARY 
     A heat shield is described herein, in accordance with various embodiments. A heat shield may comprise a base portion, a top portion, and a tapered portion extending between the top portion and the bottom portion. The base portion may comprise a sheet metal bounding a triangular void. The top portion may comprise a sheet metal bounding an ovular void. 
     A lubricating assembly is described herein, in accordance with various embodiments. A lubricating assembly may include an oil tube, a fitting, and a heat shield. The fitting may be configured to be attached to the oil tube. The heat shield may be configured to be attached to the oil tube. In various embodiments, the oil tube may be dual wall oil tube comprising an inner wall and an outer wall. 
     A method of cooling an oil tube fitting is disclosed herein, in accordance with various embodiments. The method of cooling an oil tube fitting may include disposing a heat shield about an oil tube. When in the installed position, the heat shield may at least partially encase an oil tube fitting. When in the installed position and during operation, the heat shield may be configured to prevent heat transfer between the oil tube fitting and surrounding hot air. When in the installed position, the heat shield may be configured to be separated from the oil tube fitting by a gap. 
     Introducing a heat shield may prevent oil tube fittings from excessively heating, preventing oil coking. 
     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 
         FIG. 1  illustrates an example gas turbine engine, in accordance with various embodiments; 
         FIG. 2A  illustrates a schematic view of an example mid-turbine frame assembly, in accordance with various embodiments; 
         FIG. 2B  illustrates a schematic view of an oil tube fitting heat shield assembly, in accordance with various embodiments; 
         FIG. 3A  illustrates a side view of an oil tube fittings heat shield assembly, in accordance with various embodiments; and 
         FIG. 3B  illustrates a top view of an oil tube fitting heat shield, 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. 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 changes and adaptations in design and construction may be made in accordance with this invention and the teachings herein. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. The scope of the invention is defined by the appended claims. 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. Surface shading lines may be used throughout the figures to denote different parts but not necessarily to denote the same or different materials. In some cases, reference coordinates may be specific to each figure. 
     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. 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 used herein, “distal” refers to the direction radially outward, or generally, away from the axis of rotation of a turbine engine. As used herein, “proximal” refers to a direction radially inward, or generally, towards the axis of rotation of a turbine engine. 
     In various embodiments and with reference to  FIG. 1 , a gas turbine engine  20  is provided. Gas turbine engine  20  may be a two-spool turbofan that generally incorporates a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines may include, for example, an augmenter section among other systems or features. In operation, fan section  22  can drive air along a bypass flow-path B while compressor section  24  can drive air for compression and communication into combustor section  26  then expansion through turbine section  28 . Although depicted as a turbofan gas turbine engine  20  herein, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of gas turbine engines including three-spool architectures. 
     Gas turbine engine  20  may generally comprise a low speed spool  30  and a high speed spool  32  mounted for rotation about an engine central longitudinal axis A-A′ relative to an engine static structure  36  via one or more bearing systems  38  (shown as bearing system  38 - 1  and bearing system  38 - 2 ). It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided, including for example, bearing system  38 , bearing system  38 - 1 , and bearing system  38 - 2 . 
     Low speed spool  30  may generally comprise an inner shaft  40  that interconnects a fan  42 , a low pressure (or first) compressor section  44  (also referred to a low pressure compressor) and a low pressure (or first) turbine section  46 . Inner shaft  40  may be connected to fan  42  through a geared architecture  48  that can drive fan  42  at a lower speed than low speed spool  30 . Geared architecture  48  may comprise a gear assembly  60  enclosed within a gear housing  62 . Gear assembly  60  couples inner shaft  40  to a rotating fan structure. High speed spool  32  may comprise an outer shaft  50  that interconnects a high pressure compressor  52  (e.g., a second compressor section) and high pressure (or second) turbine section (“HPT”)  54 . A combustor  56  may be located between high pressure compressor  52  and HPT  54 . A mid-turbine frame  57  of engine static structure  36  may be located generally between HPT  54  and low pressure turbine  46 . Mid-turbine frame  57  may support one or more bearing systems  38  in turbine section  28 . Inner shaft  40  and outer shaft  50  may be concentric and rotate via bearing systems  38  about the engine central longitudinal axis A-A′, which is collinear with their longitudinal axes. As used herein, a “high pressure” compressor or turbine experiences a higher pressure than a corresponding “low pressure” compressor or turbine. 
     The core airflow may be compressed by low pressure compressor  44  then high pressure compressor  52 , mixed and burned with fuel in combustor  56 , then expanded over HPT  54  and low pressure turbine  46 . Mid-turbine frame  57  includes airfoils  59  which are in the core airflow path. Low pressure turbine  46  and HPT  54  rotationally drive the respective low speed spool  30  and high speed spool  32  in response to the expansion. 
     Gas turbine engine  20  may be, for example, a high-bypass geared aircraft engine. In various embodiments, the bypass ratio of gas turbine engine  20  may be greater than about six (6). In various embodiments, the bypass ratio of gas turbine engine  20  may be greater than ten (10). In various embodiments, geared architecture  48  may be an epicyclic gear train, such as a star gear system (sun gear in meshing engagement with a plurality of star gears supported by a carrier and in meshing engagement with a ring gear) or other gear system. Geared architecture  48  may have a gear reduction ratio of greater than about 2.3 and low pressure turbine  46  may have a pressure ratio that is greater than about 5. In various embodiments, the bypass ratio of gas turbine engine  20  is greater than about ten (10:1). In various embodiments, the diameter of fan  42  may be significantly larger than that of the low pressure compressor  44 , and the low pressure turbine  46  may have a pressure ratio that is greater than about (5:1). Low pressure turbine  46  pressure ratio may be measured prior to inlet of low pressure turbine  46  as related to the pressure at the outlet of low pressure turbine  46  prior to an exhaust nozzle. It should be understood, however, that the above parameters are exemplary of various embodiments of a suitable geared architecture engine and that the present disclosure contemplates other gas turbine engines including direct drive turbofans. 
     In various embodiments, with reference to  FIG. 2A , a mid-turbine frame (MTF) assembly is illustrated. MTF assembly  257  may include bearing compartment  238 , outer case  266 , and inner case  268 . MTF vane  259  may be located between inner case  268  and outer case  266 . Oil tube fitting  212  may be attached to a portion of bearing compartment  238 . Oil tube  206  may extend between outer case  266  and oil tube fitting  212 . Oil  214  may be located within oil tube  206 . Oil  214  may be used to lubricate at least a portion of bearing compartment  238 . Oil tube  206  may be located at least partially within MTF vane  259 . Sleeve  210  may encase at least a portion of oil tube  206 . Oil tube fitting heat shield (also referred to herein as heat shield)  202  may be located between MTF vane  259  and oil tube fitting  212 . 
     Extremely hot exhaust may impinge on MTF vane  259  which may cause MTF vane  259  to increase in temperature due to convective heat transfer from the hot exhaust. Heat waves  218  may radiate from MTF vane  259 . In various embodiments, heat waves may radiate to other nearby components which may cause the nearby components to increase in temperature. In return, the nearby components may transfer heat conductively to other adjacent components and/or fluids. For example, heat waves may radiate from MTF vane  259  to oil tube  206  which may convectively transfer heat from MTF vane  259  to oil tube  206 . Heat may be conductively transferred to oil located inside oil tube  206 . Furthermore, when oil exceeds various threshold temperatures, it may undergo severe oxidative and thermal breakdown which may cause solid deposits to form. These deposits may be undesirable as they may impede the flow of fluid through various components including, for example, tubes and filters. Heat shield  202  may be configured to block heat waves  218  radiating from MTF vane  259  from directly impinging on oil tube fitting  212 . Furthermore, heat shield  202  may help minimize convective heat transfer from hot air surrounding oil tube fitting  212 . Accordingly, heat shield  202  may help block heat from being transferred to oil tube fitting  212 . In various embodiments, heat shield  202  may help prevent oil from coking within oil tube fitting  212 . Sleeve  210  may be configured to block radiating heat waves from MTF vane  259  from impinging on oil tube  206 . 
     In various embodiments, with reference to  FIG. 2B , oil tube  206  may comprise an inner tube  207  and an outer tube  208 . Accordingly, oil tube  206  may be referred to as a dual wall tube. Inner tube  207  may be enclosed by outer tube  208 . There may be a space between inner tube  207  and outer tube  208  which may be occupied by air. The outer tube  208  may be configured to contain oil within outer tube  208  in the event that there is an oil leak from inner tube  207 . Outer tube  208  may be configured to prevent heat transfer from surrounding hot air to inner tube  207 . Oil tube  206  may be configured to attach to oil tube fitting  212 . Oil tube  206  may be attached to oil tube fitting  212  via weld, solder, braze, or any other suitable method. Heat shield  202  may comprise a base portion  204  and a top portion  203 . Top portion  203  of heat shield  202  may be configured to attach to oil tube  206 . Top portion  203  of heat shield  202  may be configured to attach to oil tube  206  via weld, solder, braze, or any other suitable method. Top portion  203  of heat shield  202  may be configured to attach to oil tube  206  in close proximity to an end of oil tube  206 . Top portion  203  of heat shield  202  may be configured to attach to oil tube  206  in close proximity to a proximal end of oil tube  206 . Top portion  203  of heat shield  202  may be configured to attach to oil tube  206  such that there is a small gap between heat shield  202  and sleeve  210 . Base portion  204  of heat shield  202  may be configured to at least partially encase oil tube fitting  212 . 
     In various embodiments, various components of MTF assemblies may comprise various materials. Various components, including heat shield  202 , may comprise a high temperature metal (e.g., an austenitic nickel-chromium-based alloy such as INCONEL), a high temperature composite, and/or the like. In further embodiments, heat shield  202  may comprise a high temperature stainless steel. 
     In various embodiments, heat shield  202  may comprise a wall thickness “T.” In various embodiments, heat shield  202  may be manufactured via a hydro-forming process. Wall thickness “T” may be chosen according to various design considerations. In various embodiments, wall thickness “T” may be between 0.010 in (0.25 mm) and 0.030 in (0.76 mm) in thick. During manufacturing, sheet metal of a preferred wall thickness may be chosen to be hydro-formed to the desired heat shield geometry. For example, if a heat shield comprising a wall thickness of 0.5 mm is desired, a piece of sheet metal comprising a wall thickness of 0.5 mm may be used and formed into the desired geometry using high pressure hydraulic fluid to press the sheet metal into a die in a process known as hydro-forming. In various embodiments, a single piece of sheet metal may be hydro-formed into heat shield  202 . In various embodiments, two or more pieces of sheet metal may be hydro-formed into different geometries and welded together to form heat shield  202 . 
     With reference to  FIG. 3A  and  FIG. 3B , elements with like element numbering as depicted in  FIG. 2A  and  FIG. 2B , are intended to be the same and certain properties, including material properties, will not be repeated for the sake of clarity. 
     In various embodiments, with reference to  FIG. 3A  and  FIG. 3B , oil tube fitting  312  may be separated from heat shield  302  by a gap “G”. Heat shield  302  may be configured to be separated from oil tube fitting  312  by gap “G” such that a conductive thermal path does not exist between heat shield  302  and oil tube fitting  312 . Gap “G” may be configured to be minimal while allowing thermal expansion of heat shield  302  and oil tube fitting  312  without creating a thermal conduction path between heat shield  302  and oil tube fitting  312 . Minimizing gap “G” may allow heat shield  302  to more effectively minimize convective heat transfer between oil tube fitting  312  and surrounding hot air. Minimizing gap “G” may allow heat shield  302  to more effectively minimize convective heat transfer between oil tube fitting  312  and radiated heat from an adjacent MTF vane. 
     In various embodiments, the base portion  304  of heat shield  302  may comprise a triangular geometry. For example,  FIG. 3B  illustrates the base portion  304  of heat shield  302 , wherein the base portion bounds a triangular void. In various embodiments, the base portion  304  of heat shield  302  may comprise one of a square, rectangular, oblong, round, elliptical, or any other geometry. The geometry of the base portion  304  of heat shield  302  may be driven by the geometry of oil tube fitting  312 . Accordingly, the geometry of oil tube fitting  312  and base portion  304  may be complementary. In various embodiments, the top portion  303  of heat shield  302  may comprise an ovular geometry. For example,  FIG. 3B  illustrates the top portion  303  of heat shield  302 , wherein the top portion  303  bounds an ovular void. In various embodiments, the top portion  303  of heat shield  302  may comprise a square, rectangular, oblong, round, elliptical, or any other geometry. The geometry of the top portion  303  of heat shield  302  may be driven by the geometry of oil tube  306 . Accordingly, the geometry of oil tube  306  and top portion  303  may be complementary. In various embodiments, the geometry of top portion  303  and base portion  304  may be complementary. In various embodiments, the geometry of top portion  303  and base portion  304  may be different. In various embodiments, top portion  303  may be connected to base portion  304  by a tapered portion  305 . 
     In various embodiments, top portion  303  may comprise a cross-sectional area. The cross-sectional area of top portion  303  may be the area of a slice of top portion  303  taken along line B-B in the x-z plane according to the coordinates provided in  FIG. 3A . The cross-sectional area of top portion  303  may be best visualized by viewing top portion  303  from the top view as shown in  FIG. 3B . In various embodiments, base portion  304  may comprise a cross-sectional area. The cross-sectional area of base portion  304  may be the area of a slice of base portion  304  taken along line C-C in the x-z plane according to the coordinates provided in  FIG. 3A . The cross-sectional area of base portion  304  may be best visualized by viewing base portion  304  from the top view as shown in  FIG. 3B . 
     A method of cooling an oil tube fitting is disclosed herein, in accordance with various embodiments. The method of cooling an oil tube fitting may include disposing a heat shield about an oil tube. When in the installed position, the heat shield may at least partially encase an oil tube fitting. When in the installed position and during operation, the heat shield may be configured to prevent heat transfer between the oil tube fitting and surrounding hot air. When in the installed position, the heat shield may be configured to be separated from the oil tube fitting by a gap. 
     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 inventions 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. 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 intended to invoke 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.