Patent Application
20130302168
Present embodiments relate generally to gas turbine engines. More particularly, but not by way of limitation, present embodiments relate to apparatuses and methods for varying the shape of composite airfoils either actively or both actively and passively.
In turbine engines, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases which flow downstream through turbine stages. These turbine stages extract energy from the combustion gases. A high pressure turbine includes a first stage nozzle and a rotor assembly including a disk and a plurality of turbine blades. The high pressure turbine first receives the hot combustion gases from the combustor and includes a first stage stator nozzle that directs the combustion gases downstream through a row of high pressure turbine rotor blades extending radially outwardly from a first rotor disk. In a two stage turbine, a second stage stator nozzle is positioned downstream of the first stage blades followed in turn by a row of second stage turbine blades extending radially outwardly from a second rotor disk. The stator nozzles direct the hot combustion gas in a manner to maximize extraction at the adjacent downstream turbine blades.
The first and second rotor disks are joined to the compressor by a corresponding rotor shaft for powering the compressor during operation. These are typically referred to as the high pressure turbine. The turbine engine may include a number of stages of static airfoils, commonly referred to as vanes, interspaced in the engine axial direction between rotating airfoils commonly referred to as blades. A multi-stage low pressure turbine follows the two stage high pressure turbine and is typically joined by a second shaft to a fan disposed upstream from the compressor in a typical turbo fan aircraft engine configuration for powering an aircraft in flight.
As the combustion gasses flow downstream through the turbine stages, energy is extracted therefrom and the pressure of the combustion gas is reduced. The combustion gas is used to power the compressor as well as a turbine output shaft for power and marine use or provide thrust in aviation usage. In this manner, fuel energy is converted to mechanical energy of the rotating shaft to power the compressor and supply compressed air needed to continue the process.
One desirable characteristic for design of gas turbine engines is to always improve efficiency and enhance performance. Due to varying operating condition during operation of the turbine engine, and the fact that changes in turbine blade shape result in different characteristics in performance and efficiency, it would be desirable to design airfoil blades for enhanced operating performance at differing operating instances. For example, one desirable instance to maximize operating efficiency is during takeoff. Another instance to maximize operating efficiency is during cruising condition at flight altitude.
Since known blades are formed of materials which are rigid, design work to maximizing efficiency is typically only available at a single operating instance.
As may be seen by the foregoing, there is a need to optimize performance at multiple operating conditions. Additionally, there is a need to optimize blade designs for multiple operating characteristics which improves performance of the gas turbine engine at various operating conditions.
Some embodiments of the present disclosure involves an airfoil or blade which is morphable into at least two shapes by way of input from at least an active actuator. Additionally, passive actuation may also be utilized. The airfoil or blade includes a root and an airfoil portion connected to the root. The airfoil has a leading edge, a trailing edge and an outer edge opposite the root. The airfoil is formed of a composite material which is layered and includes at least one morphable area which may change shape through the active actuation.
Some embodiments of the blade include a passive actuation such as, by way of non-limiting example, a shape memory alloy which may be utilized in addition to the active actuation. Other passive actuation may include asymmetric layering of material.
According to certain embodiments of the instant disclosure, the blade may change camber by active actuation, passive actuation or a combination.
All of the above outlined features are to be understood as exemplary only and many more features and objectives of the shape changing airfoil may be gleaned from the disclosure herein. Therefore, no limiting interpretation of this summary is to be understood without further reading of the entire specification, claims, and drawings included herewith.
The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the shape changing airfoil will be better understood by reference to the following description of embodiments taken in conjunction with the accompanying drawings, wherein:
Reference now will be made in detail to embodiments provided, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation, not limitation of the disclosed embodiments. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present embodiments without departing from the scope or spirit of the disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to still yield further embodiments. Thus it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Present embodiments provide an airfoil which may be formed of various layers of material which has at least one morphable area or portion. For example, one material may be a polymeric matrix composite (PMC). This allows for optimization of the blade shape for more than one operating condition. According to a second embodiment, the material may be a ceramic matrix composite. Other materials may used, such as carbon based materials for example, as well and therefore the description should not be considered limiting. The morphable portion may change shape by way of active actuation, passive actuation or a combination.
The terms fore and aft are used with respect to the engine axis and generally mean toward the front of the turbine engine or the rear of the turbine engine in the direction of the engine axis, respectively.
Referring now to
Referring initially to
The axis-symmetrical shaft 24 extends through the through the turbine engine 10, from the forward end to an aft end. The shaft 24 is supported by bearings along its length. The shaft 24 may be hollow to allow rotation of a low pressure turbine shaft 28 therein. Both shafts 24, 28 may rotate about a centerline 26 of the engine. During operation the shafts 24, 28 rotate along with other structures connected to the shafts such as the rotor assemblies of the turbine 20 and compressor 14 in order to create power or thrust depending on the area of use, for example power, industrial or aviation.
Referring still to
Referring now to
Referring now to
The blade 30 of
Additionally, referring still to
The instant description applies to the exemplary blades as well as other blades which may be within the scope of the present disclosure. Referring again to
The blade 30 is formed of a composite material and may be solid, hollow, partially hollow or may be filled in whole or part with some low density material. The material of the airfoil 34 may be the same or different material from that of the root 32.
Referring to
The active actuation may occur by way of a piezoelectric actuator which is embedded in the composite laminate material defining the blade 30. The piezoelectric actuator 62 is an active actuator which receives a voltage input and changes shape due to the driving force created by application of voltage to the piezoelectric actuator 62. The actuator 62 is positioned closer to the outer surface of the morphable area to create maximum bending of the airfoil surface. With use of this active actuator 62, more compliant composite materials may be utilized which are more capable of handling strain and require less driving force to deflect. One exemplary material which may be utilized may be S-glass in the morph region 50 and carbon for the remaining region of the airfoil 34. Thus it may be desirable that the morphable portion 50 be formed of at least partially different materials than the remainder of the airfoil portion 34 or the same materials.
Active actuator leads 64 may be embedded in the composite material and terminated outside the structure to provide electrical voltage to the piezoelectric actuator 62, for example. With the actuator 62 embedded the actuator is protected from erosion and other damaging effects which may limit operation of the actuator 62. The leads 64 may exit at any location which does not interfere with performance and which does not damage the lead. Coatings for example may be used to cover the leads and protect such from damage.
Alternate forms of actuation may be utilized. Referring to
Still a further form of passive actuation may come from asymmetric composite layout where according to such embodiment the asymmetric composite layout may change shape of the airfoil 34 due to for example centrifugal force on the turbine blade 30 during high speed rotation.
Actuation of the active and passive actuator results in a camber change or stagger change of the airfoil 34 through shape change of the morphable portions 50, 52. Camber is generally recognized as the amount of cupping of the blades and stagger is the relative angle of the airfoil to the axial direction of flow. The initial shape of an airfoil 30 prior to changing shape may be optimized such that the bending loads (or moments) are favorable to aid morphing of a fan blade or that the shape at least does not hinder the actuation of the actuator 62. Multi-material systems and varying weight distributions may be optimized such that in-plane load from centrifugal forces due to blade rotation and the induced bending moments aid actuation of the airfoil shape change. In a chordwise cross-section, an initial shape of a blade may be singly curved with a relatively high curvature while the morphed shape is singly curved with a relatively low curvature. Additionally, materials of differing densities or rigidities may be used to aid the morphing of the blade 30.
Laminated structures using composite materials may be used to construct the fan blades 30. These composite materials exhibit various coupling behaviors such as bending and twisting deflections in the direction perpendicular to loading in the presence in plane and bending loads. Such coupling properties of the laminate composite structures may be used to change the airfoil shape of the blade 30. By tailoring the ply or layer layup of the composite material, in both asymmetric and/or multi-material ply orientations, and the region where the ply orientations occur, the airfoil shape can be morphed as a function of rotational speed of fan blade. The airfoil shape for this type of passive actuation may be changed by tailoring the ply or laminate layers in the morphable portion 50 and in one of several manners. First, the layers may be asymmetric through the thickness of the laminated structure. Second, the layup may use two or more distinct materials such as multi-material laminate structure. Third, the weight distribution at various locations of the fan blade may be intentionally changed causing varying force loading due to the centrifugal force during rotation of the turbine blade. Again, this passive actuation may be utilized in addition to the active actuation and may be at one or more various regions of the blade 30 to achieve the airfoil 34 shape change.
While multiple inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the invent of embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.
Examples are used to disclose the embodiments, including the best mode, and also to enable any person skilled in the art to practice the apparatus and/or method, including making and using any devices or systems and performing any incorporated methods. These examples are not intended to be exhaustive or to limit the disclosure to the precise steps and/or forms disclosed, and many modifications and variations are possible in light of the above teaching. Features described herein may be combined in any combination. Steps of a method described herein may be performed in any sequence that is physically possible.
All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases.
It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.
In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.
