The present invention generally relates to turbofan engines, and more particularly relates to a turbofan engine having an improved nacelle inlet and engine fan housing assembly and method for making same.
Aircraft engine competitiveness is typically determined by attributes such as performance, cost, reliability, and weight. Performance generally includes aerodynamic efficiency and acoustics, and the acoustics are continually driven to be quieter by regulatory requirements and the market. Therefore, in order to improve aircraft engine competiveness, architectural design changes may be required.
The aerodynamically streamlined inlet section of an aircraft engine is generally referred to as the nacelle inlet and is typically comprised of multiple components coupled to an engine fan housing and bypass structure that surrounds the bulk of the aircraft engine block. Much of the noise in an aircraft engine comes from a fan assembly that is housed within an engine fan housing structure. The fan assembly includes a fan rotor hub centered on and rotatable about an axially extending centerline of the engine. A plurality of fan blades extends radially out from the fan rotor hub. These blades may be detachable or a part of a singular, machined or molded, fan (such as an integrally bladed rotor “IBR” or blisk fan). The opening of the nacelle inlet assembly typically has an aerodynamic shape that is narrow near the inlet of the turbofan engine and widens internally near the fan.
The noise generated by the fan and emitted from the front of the aircraft engine may be reduced through acoustic treatment of the engine inlet (nacelle). The employment of materials to dampen one or more noise frequencies is referred to as acoustic treatment, and the effectiveness of acoustic treatment that can be incorporated into the nacelle and surrounding parts is limited by the assembly and design constraints associated with an aircraft engine. Generally, these constraints require that each part of the aircraft engine be assembled in sequence with adequate clearance and access to perform all necessary assembly steps and processes. When the blades of the fan are not detachable (e.g. such as in the case of a blisk fan), making provisions for adequate structural integrity, clearance, access, and removal of the fan restricts the amount of acoustic treatment that may be employed in the nacelle inlet.
In addition, gaining access for maintenance, repair or replacement on a blisk fan blade in an aircraft engine generally requires removal of the entire fan assembly, which increases labor time, the number of assembly interfaces that must be interacted with, and the number of parts that must be manipulated. Additionally, blisk fan usage may influence the distribution of parts and weight throughout the nacelle inlet assembly and engine fan housing structure. The number of parts that go into the engine, the number of assembly interfaces in the engine, and the way in which loads are carried by the engine each contribute to the total engine weight. Therefore, the engine architectural decision to utilize a blisk fan may decrease overall engine weight.
Accordingly, it would be desirable to provide a nacelle inlet assembly for use in an engine fan housing structure that provides adequate clearance for accessing and removing a blisk fan from a turbofan engine. It would also be desirable to provide a nacelle inlet assembly that may be slidably coupled to the engine fan housing structure, thus minimizing assembly interfaces and overall aircraft engine weight. It would be further desirable to provide a nacelle inlet assembly and engine fan housing structure that enables efficient distribution of load and increased acoustic treatment.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
In view of the foregoing, there is provided a nacelle inlet assembly for use in a turbofan engine, the nacelle inlet assembly comprising a substantially cylindrical acoustic liner having a circular inlet edge and a D-lip inseparably coupled to the circular inlet edge.
There is also provided a nacelle inlet assembly for use in a turbofan engine that includes an engine fan housing structure with a substantially circular opening of a first diameter surrounding an integrally bladed rotor fan. The nacelle inlet assembly comprises a substantially cylindrical housing configured to slidably couple to the substantially circular opening of the engine fan housing structure. The cylindrical housing has a second diameter smaller than the first diameter. The nacelle inlet assembly also comprises an acoustic liner forming an inner surface of the cylindrical housing, and a D-lip inseparably coupled to the acoustic liner. The bladed rotor fan is removable through the circular opening only when the cylindrical housing is removed.
A method is also provided for integrally bladed rotor fan access in a turbofan engine having an engine fan housing structure with a substantially circular opening. The method comprises forming a substantially cylindrical nacelle inlet assembly of a first length, having a first diameter larger than a diameter of the integrally bladed rotor fan and smaller than a diameter of the circular opening of the engine fan housing structure. A circular inlet edge of the acoustic liner is inseparably coupled to a D-lip to form an acoustic liner/D-lip assembly.
Other desirable features and advantages will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.
A more complete understanding of the subject matter may be derived by referring to the following Detailed Description and Claims when considered in conjunction with the following figures, wherein like reference numerals refer to similar elements throughout the figures, and wherein:
The following Detailed Description is merely exemplary in nature and is not intended to limit the embodiments of the subject matter or the application and uses of such embodiments. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Any implementation described herein as exemplary is not necessarily to be construed as preferred or advantageous over any other implementations. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding Technical Field, Background, Brief Summary or the following Detailed Description.
For the sake of brevity, functional aspects of various turbofan engine systems and subsystems (and the individual operating components thereof) may not be described in detail herein. 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 an embodiment of the subject matter.
The following descriptions may refer to elements or features being “coupled” together. As used herein, unless expressly stated otherwise, “coupled” means that one element/node/feature is directly or indirectly joined to (or directly or indirectly communicates with) another element/node/feature, and not necessarily mechanically. Thus, although the drawings may depict one exemplary arrangement of elements, additional intervening elements, devices, features, or components may be present in an embodiment of the depicted subject matter. In addition, certain terminology may also be used in the following description for the purpose of reference only, and thus are not intended to be limiting.
In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Numerical ordinals such as “first,” “second,” “third,” etc. simply denote different singles of a plurality and do not imply any order or sequence unless specifically defined by the claim language. The sequence of the text in any of the claims does not imply that process steps must be performed in a temporal or logical order according to such sequence unless it is specifically defined by the language of the claim. The process steps may be interchanged in any order without departing from the scope of the invention as long as such an interchange does not contradict the claim language and is not logically nonsensical.
Various embodiments are directed to a combined nacelle inlet assembly and engine fan housing structures in gas turbine engines, and methods for producing the same. The embodiments described herein are merely an example and serve as a guide for implementing the novel systems and method herein on any industrial, commercial, or consumer turbofan application. As such, the examples presented herein are intended as non-limiting.
Engine fan assembly 104, including fan rotor hub 110 and a plurality of fan blades 108 (only one of which is shown), is positioned for rotation such that the tips of fan blades 108 are accommodated within a fan containment structure 310 that is positioned circumferentially around fan rotor hub 110 to protect the aircraft from damage by the fan blades 108.
An exposed contoured surface 312 is formed along at least a section of the of nacelle inlet assembly 204 including at least along a section of the exposed surface of acoustic liner 304 in accordance with well-known design considerations. Acoustic liner 304 is also permanently coupled to the inside aft region and nacelle inlet forward bulkhead 305, at D-lip 106. In the acoustic treatment of a traditional nacelle inlet, the dimensions and contours of acoustic liner 304 are dictated by the aerodynamic shape of the inlet end 200 and tunability is limited to the selection of a single noise frequency centered in a limited noise frequency range emitted by the fan assembly that most needs dampening. Therefore, the acoustic treatment in a traditional nacelle inlet typically has a constant cross sectional thickness and a uniform internal pattern that results in a narrow predetermined frequency range dampening effectiveness.
With continued reference to
The inside exposed contoured surface 412 of the exemplary acoustic liner 400 has an acoustically determined contour (i.e., an aerodynamic profile of variable thickness) that may now be longer than the acoustic liner 304 depicted in
The increased length of the engine fan housing structure 206 in the exemplary embodiment also provides an improvement in overall weight and weight distribution. To begin with, nacelle inlet forward bulkhead 406 (which includes a plurality of fasteners 408) is closer to the inlet end 200 of the turbofan engine than the aft bulkhead 306 plus fasteners 308 shown in the nacelle inlet assembly 204 of
Engine fan housing structure 600 is shown having a forward extending substantially cylindrical opening 601 that terminates at fan containment structure 404. The forward edge of the substantially cylindrical opening 601 is provided with one or more exemplary fasteners 408. Exemplary fasteners 408 may be spaced along the opening of the engine fan housing structure 600. The cylindrical housing 606 of nacelle inlet assembly 418 has a diameter slightly smaller than that of the circular opening of engine fan housing structure 600 so as to permit nacelle inlet assembly 418 to be slidably received within, and coupled to, engine fan housing structure 600 and coupled thereto via fasteners 408. As the acoustic liner (obscured in this view) may be coupled to, or comprise, the inner surface of the cylindrical housing 606, the acoustic liner may be coupled via fasteners to the engine fan housing structure 600.
Thus, there has been provided a system and method for coupling a nacelle inlet assembly to an engine fan housing structure that provides adequate clearance and access for removing a blisk fan from a turbofan engine. This is accomplished by utilizing a nacelle inlet forward compartment D-lip and an acoustic liner that are inseparable and removable as an integral unit thus providing sufficient clearance for removable of the blisk fan. The nacelle inlet assembly may be slidably coupled to the engine fan housing structure, minimizing assembly interfaces and overall aircraft engine weight.
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or embodiments described herein are not intended to limit the scope, applicability, or configuration of the claimed subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope defined by the claims, which includes known equivalents and foreseeable equivalents at the time of filing this patent application.