Patent Application
20160186657
The present disclosure relates generally to turbine engines and, more specifically, to a turbofan having a reduced fan tip speed, which enables an improved fan assembly architecture to be utilized.
At least some known gas turbine engines, such as turbofans, include a fan, a core engine, and a power turbine. The core engine includes at least one compressor, a combustor, and a high-pressure turbine coupled together in a serial flow relationship. More specifically, the compressor and high-pressure turbine are coupled through a shaft to form a high-pressure rotor assembly. Air entering the core engine is mixed with fuel and ignited to form a high energy gas stream. The high energy gas stream flows through the high-pressure turbine to rotatably drive the high-pressure turbine such that the shaft rotatably drives the compressor. The gas stream expands as it flows through a power or low-pressure turbine positioned aft of the high-pressure turbine. The low-pressure turbine includes a rotor assembly having a fan coupled to a drive shaft. The low-pressure turbine rotatably drives the fan through the drive shaft.
Many modern commercial turbofans are manufactured with increasingly large bypass ratios to facilitate improving engine efficiency. However, increasing the bypass ratio of the turbofan results in an increased fan size and fan tip speed. Fan blades in turbofans having relatively large bypass ratios are generally manufactured from a metallic material to ensure the fan blades have sufficient strength to withstand foreign object impacts at the increased fan tip speeds, for example. Fan blades manufactured from metallic material are generally heavy and increase the weight of a turbine engine. At least some known fan blades are manufactured from composite material, such as carbon fiber reinforced polymer. However, fan blades manufactured from composite material generally have reduced strength and impact resistance when compared to metallic counterparts. Therefore, it is desired to have a turbofan architecture than can accommodate non-metallic fan blades.
In one aspect, a turbine engine assembly is provided. The assembly includes a low-pressure turbine configured to rotate at a first rotational speed, and a fan assembly coupled to the low-pressure turbine and configured to rotate at a second rotational speed lower than the first rotational speed. The fan assembly includes a fan blade fabricated from a composite material and having a configuration selected based on the second rotational speed of the fan assembly.
In another aspect, a turbine engine assembly is provided. The assembly includes a low-pressure turbine configured to rotate at a first rotational speed, and a drive shaft including a first portion and a second portion. The first portion is coupled to the low-pressure turbine. The assembly also includes a fan assembly coupled to a second portion of the drive shaft, and a gearbox coupled along the drive shaft between the first and second portions such that the fan assembly is configured to rotate at a second rotational speed lower than the first rotational speed. The fan assembly includes a fan blade having a configuration selected based on the second rotational speed of the fan assembly.
In yet another aspect, a method of manufacturing a turbine engine assembly is provided. The method includes coupling a low-pressure turbine to a first portion of a drive shaft, wherein the low-pressure turbine is configured to rotate at a first rotational speed. The method also includes coupling a fan assembly including a fan blade to a second portion of the drive shaft, coupling a gearbox along the drive shaft between the first and second portions such that the fan assembly is configured to rotate at a second rotational speed lower than the first rotational speed, and selecting a configuration of the fan blade based on the second rotational speed of the fan assembly.
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:
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.
Embodiments of the present disclosure relate to turbine engines, such as turbofans, and methods of manufacturing thereof. More specifically, the turbine engines described herein include a low-pressure turbine operating at a first rotational speed and a gearbox coupled to a drive shaft extending from the low-pressure turbine. The drive shaft is coupled between the low-pressure turbine and a fan assembly, and the gearbox decouples the rotational speed of the fan assembly from the low-pressure turbine such that the fan assembly rotates at a second rotational speed lower than the first rotational speed. Reducing the rotational speed of the fan assembly enables a configuration of the fan assembly to be modified to enhance performance of the turbine engine. For example, reducing the rotational speed of the fan assembly enables fan blades of the turbofan to be manufactured from composite material, which facilitates reducing the weight of the turbofan and facilitates reducing centrifugal loading at connections between the fan blades and a fan hub during operation. As such, further modifications to the fan assembly, such as utilizing variable pitch fan blades, can be implemented to enhance turbine engine performance and increase component architecture options for the turbine engine.
As used herein, the terms “axial” and “axially” refer to directions and orientations that extend substantially parallel to a centerline of the turbine engine. Moreover, the terms “radial” and “radially” refer to directions and orientations that extend substantially perpendicular to the centerline of the turbine engine. In addition, as used herein, the terms “circumferential” and “circumferentially” refer to directions and orientations that extend arcuately about the centerline of the turbine engine. It should also be appreciated that the term “fluid” as used herein includes any medium or material that flows, including, but not limited to, air, gas, liquid and steam.
In operation, air entering turbine engine assembly 100 through intake 122 is channeled through fan assembly 102 towards booster compressor 104. Compressed air is discharged from booster compressor 104 towards high-pressure compressor 106. Highly compressed air is channeled from high-pressure compressor 106 towards combustor 108, mixed with fuel, and the mixture is combusted within combustor 108. High temperature combustion gas generated by combustor 108 is channeled towards turbine assemblies 110 and 112. Low-pressure turbine 112 rotates at a first rotational speed, and gearbox 128 operates such that fan assembly 102 operates at a second rotational speed lower than the first rotational speed. In one embodiment, the second rotational speed is such that a fan tip speed of fan blades 114 is less than about 1,200 feet per second. Combustion gas is subsequently discharged from turbine engine assembly 100 via exhaust 124. In an alternative embodiment, the rotational speeds of low-pressure turbine 112 and fan assembly 102 are decoupled by any mechanism or arrangement of components that enables turbine engine assembly 100 to function as described herein.
In one embodiment, fan blades 114 are fabricated at least partially from composite material. As used herein, the term “composite” refers to a material including a reinforcement material, such as fibers or particles, supported in a binder or matrix material. Exemplary composite material includes a carbonaceous (e.g. graphite) fiber embedded in a resin material such as epoxy. At least some composite materials are commercially available and include fibers unidirectionally aligned in a sheet impregnated with a resin, forming a pre-impregnated material (i.e. “prepreg”). Prepreg material can be formed into a part shape, and cured via an autoclaving process or press molding process to form a lightweight, rigid, and relatively homogeneous article.
Fan blade 114 includes a foam core structure 132 and at least one layer 134 of composite material applied to foam core structure 132. Foam core structure 132 has a cambered airfoil shape generally corresponding to the shape of fan blade 114. Foam core structure 132 is fabricated from a polymeric foam material having a lower density than the composite material. An exemplary polymeric foam material includes, but is not limited to, an elastomeric polyurethane foam having a density of about 40% of the density of the composite material. As such, fabricating fan blades 114 from the composite material and polymeric foam material facilitates reducing a weight of fan assembly 102 by up to about 20%. Moreover, operating fan assembly 102 at the slower second rotational speed enables fan blades 114 having reduced strength and impact resistance, when compared to metallic fan blades, to be utilized. In an alternative embodiment, fan blades 114 are fabricated from a metallic material having a reduced size when compared to fan blades utilized if fan assembly 102 operated at the first rotational speed.
Referring to
As described above, operating fan assembly 102 at the slower second rotational speed enables lighter weight fan blades 114 to be utilized than if fan assembly 102 operated at the first rotational speed. Utilizing lighter weight fan blades 114 reduces an amount of centrifugal loading induced on fan hub 142 by fan blades 114 during operation of turbine engine assembly 100. As such, an actuatable and more complex coupling arrangement between fan hub 142 and fan blades 114, such as coupling arrangement 140, may be used when compared to a standard dovetail coupling mechanism for use with a fixed pitch blade, for example.
The turbine engine assembly and methods described herein relate to turbine engines, such as turbofans, that leverage a low-speed fan assembly to enable the use of fan blades with characteristics that facilitate improving engine performance. For example, the fan assembly is configured to rotate at a lower rotational speed than a low-pressure turbine. Reducing the rotational speed of the fan assembly reduces strength and impact resistance requirements of the fan blades, which enables the fan blades to be manufactured from light-weight materials, for example. Moreover, a configuration of the fan assembly can be enhanced to improve engine performance.
Although specific features of various embodiments of the present disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of embodiments of the present disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.
This written description uses examples to disclose the embodiments of the present disclosure, including the best mode, and also to enable any person skilled in the art to practice embodiments of the present disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the embodiments described herein 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.
This non-provisional application claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 62/082,634, entitled “TURBINE ENGINE ASSEMBLY AND METHOD OF MANUFACTURING THEREOF”, filed Nov. 21, 2014, which is herein incorporated in its entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62082634 | Nov 2014 | US |
