The present disclosure relates generally to gas turbine engines and, more particularly, to gas turbine engines and tandem fans configured for boundary layer ingestion.
Conventional aircraft typically employ pylons to space one or more gas turbine engines away from boundary layers that form on the surfaces of the aircraft, such as, for example, the wings or fuselage. Recent advances in airframe and engine technologies have led to positioning the engines directly adjacent to or partially integrated within the wings or fuselage. While these design features may increase energy efficiencies and decrease adverse environmental impacts—e.g., noise—the design features have led to technical difficulties related to boundary layer ingestion. For example, in embodiments where the engines are positioned within the boundary layer that forms around the wings or fuselage, the engines may be subjected to distortion associated with boundary layer ingestion. Engines mounted directly adjacent the fuselage or wings are known in the art as boundary layer ingestion (BLI) engines. There are different design considerations for a BLI engine compared to a conventional engine due to the impact of the boundary layer on engine operation.
A tandem fan for a boundary layer ingestion engine is disclosed. In various embodiments, the tandem fan includes a fan disk configured for rotation about a longitudinal axis; a primary fan blade extending radially from the fan disk, the primary fan blade having a primary fan blade span; and a secondary fan blade extending radially from the fan disk, the secondary fan blade having a secondary fan blade span within about ninety percent to about one-hundred percent of the primary fan blade span.
In various embodiments, the secondary fan blade span is about equal to the primary fan blade span. In various embodiments, the primary fan blade includes a primary fan blade tip configured for disposition a primary tip distance away from a radially inner surface of a fan case within about one percent to about five percent of the primary fan blade span. In various embodiments, the secondary fan blade includes a secondary fan blade tip configured for disposition a secondary tip distance away from the radially inner surface of the fan case within about one percent to about five percent of the secondary fan blade span. In various embodiments, both the primary tip distance and the secondary tip distance are equal.
In various embodiments, the primary fan blade includes a primary fan blade trailing edge and the secondary fan blade includes a secondary fan blade leading edge and the secondary fan blade leading edge is positioned axially forward of the primary fan blade trailing edge by a first distance. In various embodiments, the first distance is within about zero percent to about thirty percent of the primary fan blade chord.
In various embodiments, the primary fan blade includes a primary fan blade leading edge and the secondary fan blade includes a secondary fan blade trailing edge and the secondary fan blade trailing edge is positioned axially aft of the primary fan blade leading edge by a second distance. In various embodiments, the second distance is within about one-hundred percent to about two-hundred fifty percent of the primary blade chord. In various embodiments, at least one of the primary fan blade tip and the secondary fan blade tip is connected to a shroud.
A boundary layer ingestion engine is disclosed. In various embodiments, the engine includes a fan case; a spool operably coupled to at least one of an electric motor and a gas turbine engine; and a tandem fan operably coupled to the spool, the tandem fan comprising a fan disk configured for rotation about a longitudinal axis, a primary fan blade extending radially from the fan disk, the primary fan blade having a primary fan blade span, and a secondary fan blade extending radially from the fan disk, the secondary fan blade having a secondary fan blade span within about ninety percent to about one-hundred percent of the primary fan blade span.
In various embodiments, the secondary fan blade span is about equal to the primary fan blade span. In various embodiments, the primary fan blade includes a primary fan blade tip configured for disposition a primary tip distance away from a radially inner surface of the fan case within about one percent to about five percent of the primary fan blade span. In various embodiments, the secondary fan blade includes a secondary fan blade tip configured for disposition a secondary tip distance away from the radially inner surface of the fan case within about one percent to about five percent of the secondary fan blade span. In various embodiments, the primary tip distance and the secondary tip distance are equal.
In various embodiments, the primary fan blade includes a primary fan blade trailing edge and the secondary fan blade includes a secondary fan blade leading edge and the secondary fan blade leading edge is positioned axially forward of the primary fan blade trailing edge by a first distance. In various embodiments, the first distance is within about zero percent to about thirty percent of the primary fan blade chord.
In various embodiments, the primary fan blade includes a primary fan blade leading edge and the secondary fan blade includes a secondary fan blade trailing edge and the secondary fan blade trailing edge is positioned axially aft of the primary fan blade leading edge by a second distance. In various embodiments, the second distance is within about one-hundred percent to about two-hundred fifty percent of the primary blade chord.
In various embodiments, the fan disk comprises a forward fan disk and an aft fan disk and both the forward fan disk and the aft fan disk are configured for rotation by the spool.
A boundary layer ingestion system configured for mounting to or downstream of a fuselage of an aircraft is disclosed. In various embodiments, the boundary layer ingestion system includes a fan case configured for attachment to or downstream of the fuselage; a tandem fan rotationally disposed within the fan case, the tandem fan including: a fan disk configured for rotation about a longitudinal axis, a primary fan blade extending radially from the fan disk, the primary fan blade having a primary fan blade span, and a secondary fan blade extending radially from the fan disk, the secondary fan blade having a secondary fan blade span, wherein the secondary fan blade span is within about ninety percent to about one-hundred percent of the primary fan blade span; and a power source configured to rotate the tandem fan.
The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, may best be obtained by referring to the following detailed description and claims in connection with the following drawings. While the drawings illustrate various embodiments employing the principles described herein, the drawings do not limit the scope of the claims.
The following detailed description of various embodiments herein makes reference to the accompanying drawings, which show various embodiments by way of illustration. While these various embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that changes may be made without departing from the scope of the disclosure. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. 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 or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. It should also be understood that unless specifically stated otherwise, references to “a,” “an” or “the” may include one or more than one and that reference to an item in the singular may also include the item in the plural. Further, all ranges may include upper and lower values and all ranges and ratio limits disclosed herein may be combined.
Referring now to
Referring now to
With reference now to
In various embodiments, the boundary layer thickness δ (see 226 in
where Ux/v is the Reynolds number. For typical airliners flying at cruising speed and altitude—e.g., within ranges of about 30,000-40,000 feet (≅9,000-12,000 meters) and about 400-600 mph (≅600-1,000 kph)—the boundary layer thickness δ near the inlet 214 to the boundary layer ingestion engine 202 may be on the order of one to two feet (or 30 to 60 cm) or greater, depending on the length of the aircraft or the applicable surface of the aircraft. Accordingly, as indicated in
Referring now to
In various embodiments, the secondary fan blade leading edge 372 of each of the plurality of secondary fan blades 370 is positioned a first distance 380 from the primary fan blade trailing edge 364 of each of the plurality of primary fan blades 360. In various embodiments, the first distance 380 may be a positive value, where the secondary fan blade leading edge 372 is positioned axially forward of the primary fan blade trailing edge 364 (as indicated in
In various embodiments, each of the plurality of primary fan blades 360 includes a primary fan blade tip 384 that is disposed a primary tip distance from the radially inner surface of the fan case 330. In various embodiments, the primary tip distance is between about one percent (1%) to about five percent (5%) of the primary fan blade span 366. In various embodiments, each of the plurality of secondary fan blades 370 includes a secondary fan blade tip 386 that is disposed a secondary tip distance from the radially inner surface of the fan case 330. In various embodiments, the secondary tip distance is between about one percent (1%) to about five percent (5%) of the secondary fan blade span 376. In various embodiments, both the primary tip distance and the secondary tip distance are equal. In various embodiments, the secondary fan blade span 376 is equal in value to about ninety percent (90%) to about one-hundred percent (100%) of the primary fan blade span 366. In various embodiments, the primary fan blade span 366 is about equal to the secondary fan blade span 376.
In various embodiments, each of the primary fan blades 360 exhibits a primary pitch angle 383 and each of the plurality of secondary fan blades 370 exhibits a secondary pitch angle 385. In various embodiments, the secondary pitch angle 385 is equal to about ten percent (10%) to about one-hundred percent (100%) of the primary pitch angle 383. In various embodiments, the primary fan blade trailing edge 364 of each of the plurality of primary fan blades 360 is offset a circumferential distance 387 from the secondary fan blade leading edge 372 of each of the plurality of secondary fan blades 370. In various embodiments, the circumferential distance 387 is equal to about zero percent (0%) to about one-hundred percent (100%) of a primary fan circumferential blade spacing 389.
In various embodiments, the term “about” as used in this disclosure contemplates±five percent (5%) of the indicated percentage value. In addition, the disclosure contemplates the pluralities of primary and secondary blades will exhibit blade dimensions and orientations—e.g., the various chord lengths, pitch angles and relative axial and circumferential spacings—that vary along the respective span of each of the blades. Thus, the various dimensions and orientations identified above may be considered, in various embodiments, average values taken along the length of the spans. In various embodiments, the various dimensions and orientations identified above may also be considered, for example, values exhibited at the mid span of each of the respective pluralities of blades.
In various embodiments, the fan disk 352 comprises a single disk to witch each of the plurality of primary fan blades 360 and each of the plurality of secondary fan blades 370 are attached. In various embodiments, the fan disk 352 comprises a forward fan disk 351 to which each of the plurality of primary fan blades 360 is attached and an aft fan disk 353 to which each of the plurality of secondary fan blades 370 is attached. In various embodiments, the fan disk 352 is attached to and rotated by a spool 355 (or shaft). In various embodiments, both the forward fan disk 351 and the aft fan disk 353 are attached to and rotated at the same velocity by the spool 355.
Referring now to
A tandem fan for use in a boundary layer ingestion engine has been described. The pluralities of primary and secondary airfoils of the tandem fan permit decoupling of Mach number effects—e.g., variations of Mach number at different locations throughout the inlet due to the presence of the boundary layer—and the turning of the mass flow through the tandem fan. The configuration achieves diffusion of shock waves and deceleration of the inlet mass flow through the primary blades having marginal camber and then turning of the mass flow via the secondary blades. The configuration thus provides for a larger work factor than a single fan since it permits greater loading of the tandem system. Hence, for a given work input, the rotational velocity of the tandem fan may be reduced, resulting in a reduction of the relative Mach number of the flow entering the tandem fan. This reduces shock-induced losses that occur in the undistorted portion of the mass flow at the inlet. Further, since the primary fan is less sensitive to incidence variations, the losses in the distorted portion of the flow may also be reduced. In addition, because the work produced by fans typically increases with the radius of the fan blades, the use of full-length (or radius) blades for both the primary stage and the secondary stage enables the tandem fan disclosed herein to more effectively realize the full amount of work achievable by the tandem fan, as opposed to tandem fans where one set of blades (typically the upstream set of blades) has a length (or radius) less than the downstream set of blades. Such embodiments having an upstream set of blades with lengths (or spans) less than the downstream set of blades are typically not intended to deliver additional work or realize the full work potential, but are intended to reduce the fundamental natural frequency of the blades within the tandem fan system for purposes of structural integrity, particularly where the upstream set of blades employs relatively thin blades relative to the thickness of the downstream set of blades.
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 disclosure. The scope of the disclosure 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. Different cross-hatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials.
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 to be construed under the provisions of 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.
Finally, it should be understood that any of the above described concepts can be used alone or in combination with any or all of the other above described concepts. Although various embodiments have been disclosed and described, one of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. Accordingly, the description is not intended to be exhaustive or to limit the principles described or illustrated herein to any precise form. Many modifications and variations are possible in light of the above teaching.
This application claims priority to U.S. Prov. Appl. 62/801,291, entitled “Tandem Fan for Boundary Layer Ingestion Systems,” filed Feb. 5, 2019, the entirety of each of which is incorporated herein by reference for all purposes.
Number | Date | Country | |
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62801291 | Feb 2019 | US |