Patent Application
20170191498
This invention relates generally to turbofan engines, and more particularly, to methods and apparatus for operating turbofan engines.
Turbofan engines typically include high and low pressure compressors, a combustor, and at least one turbine. The compressors compress air which is mixed with fuel and channeled to the combustor. The mixture is then ignited for generating hot combustion gases, and the combustion gases are channeled to the turbine which extracts energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator.
When turbofan engines operate in various conditions, foreign objects may be ingested into the engines. More specifically, various types of foreign objects may be entrained in the inlet of a turbofan engine, ranging from large birds, such as sea gulls, to hailstones, sand and rain. The foreign objects may impact a blade resulting in a portion of the impacted blade being torn loose from a rotor. Such a condition, known as foreign object damage, may cause the rotor blade to pierce an engine casing resulting in cracks along an exterior surface of the engine casing, and possible injury to nearby personnel. Additionally, the foreign object damage may cause a portion of the engine to bulge or deflect resulting in increased stresses along the entire engine casing.
To facilitate preventing the increased engine stresses and the possible injury to personnel, at least some known engines include a metallic casing shell to facilitate increasing a radial and an axial stiffness of the engine, and to facilitate reducing stresses near the engine casing penetration. However, casing shells are typically fabricated from a metallic material which results in an increased weight of the engine and therefore the airframe.
In addition, thermal conduction and the resulting localized thermal expansion and contraction of elements of the engine casing induce local thermal stresses that may deform the engine casing, thereby degrading engine performance. For example, local thermal stresses may deform a compressor casing out of round, impacting compressor clearance and further hampering the ability to control compressor clearance. Existing casing reinforcement materials, such as Kevlar, are insulating, and further exacerbate the local thermal stresses within the engine casing.
In one embodiment, a wrap configured to cover a surface of a casing surrounding a rotating member includes one or more graphene sheets and a matrix configured to stabilize said one or more graphene sheets. The matrix is further configured to receive an adhesive or mechanical fastener. The matrix is further configured to bond to a surface of the casing using the adhesive or mechanical fastener. The wrap is further configured to facilitate heat transfer over the casing, to structurally reinforce the casing, and to enhance containment resilience.
In another embodiment, a method of assembling a turbofan engine with a casing surrounding a rotating member includes providing one or more graphene sheets. The graphene sheets contain graphene and a matrix configured to stabilize the graphene. The method also includes bonding the matrix of the one or more graphene sheets to a surface of the casing using an adhesive or using mechanical fasteners inserted through a plurality of connecting rings formed within the matrix and into the surface of the casing to form a wrap. The wrap includes the one or more graphene sheets and the matrix. The wrap is configured to facilitate heat transfer over the casing, to structurally reinforce the casing, and to enhance containment resilience.
In an additional embodiment, a turbofan engine includes a core engine comprising a rotating member surrounded by a casing and a wrap covering at least a portion of a surface of the casing. The wrap includes one or more graphene sheets, and a matrix configured to stabilize the one or more graphene sheets. The matrix is further configured to receive an adhesive and bond to the surface of the casing using the adhesive. The wrap is further configured to facilitate heat transfer over the casing, to structurally reinforce the casing, and to enhance containment resilience.
These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Although specific features of various embodiments may be shown in some drawings and not in others, this is for convenience only. Any feature of any drawing may be referenced and/or claimed in combination with any feature of any other drawing.
Unless otherwise indicated, the drawings provided herein are meant to illustrate features of embodiments of the disclosure. These features are believed to be applicable in a wide variety of systems comprising one or more embodiments of the disclosure. As such, the drawings are not meant to include all conventional features known by those of ordinary skill in the art to be required for the practice of the embodiments disclosed herein.
In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings.
The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.
“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, “approximately”, and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.
The following detailed description illustrates embodiments of the disclosure by way of example and not by way of limitation. It is contemplated that the disclosure has general application to a wrap and a method of using the wrap to facilitate heat transfer over a casing of a turbofan engine and to structurally reinforce the casing. Although various embodiments of the wrap and method of using the wrap are described in terms of this exemplary embodiment, it is to be understood that the wrap and method are suitable for facilitating heat transfer and structurally reinforcing a body as defined herein without limitation.
In various embodiments, a wrap comprising one or more graphene sheets is bonded to a casing of a turbofan engine, thereby enhancing heat transfer over the casing and providing structural reinforcement to the casing. The graphene within the graphene sheets is an advanced material known for being about 200 times stiffer than steel and for conducting heat 10 times faster than copper, as well as for light weight. Wrapping the casing with graphene enhances the containment characteristics of the casing in the event of an intake of a foreign object into the turbofan engine and/or a blade failure. In addition, the graphene casing wrap facilitates uniform heat conduction around the casing allowing for better tip clearance control. The high strength of graphene enables a reduction of the thickness relative to existing designs that make use of materials such as Kevlar, and an associated reduction in weight of the turbofan engine.
During operation, air flows through fan assembly 12, along a central axis 34, and compressed air is supplied to high pressure compressor 14. The highly compressed air is delivered to combustor 16. Airflow (not shown in
In this exemplary embodiment, wrap 50 further includes a gap 90 between abutted graphene sheets 52, 54. In various aspects, gap 90 may be included in wrap 50 to enable easy access to certain components of casing 35. By way of non-limiting example, gap 90 may be situated over a joint 40 between elements 36, 38 of casing 35 to facilitate maintenance of casing 35. In various other embodiments, gap 90 may be included in wrap 50 to accommodate deformation of casing 35 due to thermal stresses experienced during operation of turbofan engine 10. In these embodiments, gap 90 may be sized to accommodate the expected range of deformation due to thermal stresses. In other embodiments, gap 90 may be sized to control heat transfer by defining a discontinuity in thermally conductive graphene sheets 52, 54 of wrap 50.
In various embodiments, wrap 50 is bonded to at least a portion of surface 44 of casing 35. In some embodiments, wrap 50 is bonded to a region of surface 44 to ameliorate deformation due to thermal stresses. By way of non-limiting example, wrap 50 is bonded to surface 44 of casing 35 in segments of high pressure compressor 14. In this example, wrap 50 enables enhanced thermal transfer from casing 35, thereby facilitating control of compressor clearance by reducing thermal expansion and/or contraction during operation of turbofan engine 10. By way of another non-limiting example, wrap 50 is bonded to surface 44 of casing 35 in segments of fan assembly 12. In this example, wrap 50 may be bonded to surface 44 of casing 35 in regions corresponding to a prime containment zone (not illustrated), corresponding to a zone that extends both axially and circumferentially around fan assembly 12 and represents an area wherein a fan blade (not shown) is most likely to be radially flung or ejected from fan assembly 12 in the event of a blade failure.
In various embodiments, wrap 50 includes at least 10 graphene sheets arranged in layers. In various other embodiments, wrap 50 includes at least 20 graphene sheets, at least 30 graphene sheets, at least 40 graphene sheets, at least 50 graphene sheets, at least 60 graphene sheets, at least 70 graphene sheets, at least 80 graphene sheets, at least 90 graphene sheets, or at least 100 graphene sheets, arranged in layers. In another embodiment, wrap 50 includes a plurality of graphene sheets ranging from about 10 to about 100 graphene sheets arranged in layers. In these embodiments, the number of graphene sheets arranged in layers may be selected to enable a desired level of structural reinforcement and/or to enable a desired enhancement in heat conduction for casing 35.
Referring again to
In another embodiment, wrap 50 further includes one or more flexible graphene sheets 94 situated over one or more protrusions 42 projecting from surface 44 of casing 35. One or more flexible graphene sheets 94 may be situated over local regions that contain protrusions 42 to accommodate protrusions 42 and enable a close fit and bonding of wrap 50 to casing 35. By way of non-limiting example, one or more flexible graphene sheets 94 are situated over protrusion 42 associated with a joint 40 of casing elements 36, 38.
In one embodiment, wrap 50 is bonded to surface 44 of casing 35 using adhesive 56. Any suitable adhesive 56 may be used to bond wrap 50 to surface 44 without limitation. Non-limiting examples of suitable adhesives include high temperature epoxy resins capable of withstanding temperatures of up to about 650° F., representative of ambient temperatures during engine operation. In one embodiment, wrap 50 may be bonded to surface 44 at innermost graphene sheet 58. In another embodiment, matrix 88 is configured to receive adhesive 56 to facilitate bonding of wrap 50 to surface 44. In an additional embodiment, individual graphene sheets 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78 may be bonded to one another using adhesive (not illustrated) between adjacent graphene sheets 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78. In this embodiment, the bonding of graphene sheets 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78 may enhance the thermal conductivity and structural integrity of wrap 50.
In one embodiment, wrap 50 is bonded to surface 44 of casing 35 using a plurality of mechanical fasteners 97. In this embodiment, each mechanical fastener 97 is inserted through a connecting ring 98 formed within matrix 88 of wrap 50. Any suitable fastener 97 may be used to bond wrap 50 to surface 44 including, but not limited to, screws, rivets, staples, and any other suitable mechanical fastener 97 without limitation. Wrap 50 is provided with a plurality of connecting rings 98 formed within matrix 88 to receive plurality of fasteners 97 to enhance the bonding of wrap 50 to surface 44 of casing 35. In another embodiment, individual graphene sheets 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78 may be bonded to one another using adhesive (not illustrated) between adjacent graphene sheets 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78 as described herein previously, and wrap 50 is bonded to surface 44 of casing 35 using plurality of mechanical fasteners 97. In another embodiment, both adhesive 56 and plurality of mechanical fasteners 97 are used to bond wrap 50 to surface 44 of casing 35.
In one embodiment, a turbofan engine 10 may incorporate wrap 50 to enhance heat conduction and structural integrity of casing 35. In this embodiment, wrap 50 covers surface 44 of casing 35 surrounding rotating member (not illustrated) of core engine 13. Wrap 50 comprises at least one graphene sheet 52, 54 and matrix 88 bonded to surface 44 of casing 35 using adhesive 56, as described herein previously.
Exemplary embodiments of wrap, methods of using a wrap to facilitate the heat conduction and structural integrity of a casing of a turbofan engine are described above in detail. The wrap, and methods of using such wrap are not limited to the specific embodiments described herein, but rather, components of systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, the methods may also be used in combination with other systems requiring selective heat transfer and/or structural reinforcement, and are not limited to practice with only the systems and methods as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other machinery applications that are currently configured to receive and accept heat transfer and structural reinforcement elements.
Example methods and apparatus for facilitating heat transfer and enhancing structural integrity of a casing of a turbofan engine are described above in detail. The apparatus illustrated is not limited to the specific embodiments described herein, but rather, components of each may be utilized independently and separately from other components described herein. Each system component can also be used in combination with other system components.
This written description uses examples to describe the disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
