US20200398978A1 - Low-drag rotor blade extension - Google Patents
Low-drag rotor blade extension Download PDFInfo
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- US20200398978A1 US20200398978A1 US16/447,421 US201916447421A US2020398978A1 US 20200398978 A1 US20200398978 A1 US 20200398978A1 US 201916447421 A US201916447421 A US 201916447421A US 2020398978 A1 US2020398978 A1 US 2020398978A1
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- A61K31/33—Heterocyclic compounds
- A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
- A61K31/435—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with one nitrogen as the only ring hetero atom
- A61K31/44—Non condensed pyridines; Hydrogenated derivatives thereof
- A61K31/4427—Non condensed pyridines; Hydrogenated derivatives thereof containing further heterocyclic ring systems
- A61K31/4439—Non condensed pyridines; Hydrogenated derivatives thereof containing further heterocyclic ring systems containing a five-membered ring with nitrogen as a ring hetero atom, e.g. omeprazole
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- A61K31/40—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having five-membered rings with one nitrogen as the only ring hetero atom, e.g. sulpiride, succinimide, tolmetin, buflomedil
- A61K31/407—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having five-membered rings with one nitrogen as the only ring hetero atom, e.g. sulpiride, succinimide, tolmetin, buflomedil condensed with other heterocyclic ring systems, e.g. ketorolac, physostigmine
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- A61K31/4164—1,3-Diazoles
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- A61K31/5365—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with at least one nitrogen and one oxygen as the ring hetero atoms, e.g. 1,2-oxazines ortho- or peri-condensed with heterocyclic ring systems
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- B64C—AEROPLANES; HELICOPTERS
- B64C11/00—Propellers, e.g. of ducted type; Features common to propellers and rotors for rotorcraft
- B64C11/02—Hub construction
- B64C11/04—Blade mountings
- B64C11/08—Blade mountings for non-adjustable blades
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- B64C11/02—Hub construction
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- B64C11/08—Blade mountings for non-adjustable blades
- B64C11/10—Blade mountings for non-adjustable blades rigid
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- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C27/00—Rotorcraft; Rotors peculiar thereto
- B64C27/32—Rotors
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Abstract
Description
- This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
- Drag is a key factor that limits the performance of a helicopter, particularly its top speed. Drag opposes the motion of a helicopter as the helicopter moves through the air. The total amount of drag acting upon a helicopter results from the summation of profile drag, induced drag, and parasitic drag. Profile drag is caused by the frictional resistance of the rotor blades passing through air. Induced drag is caused by the circulation of air around the rotor blade as lift is generated by the rotor blade. Parasitic drag is caused by the movement of non-lift generating components through air. Parasitic drag varies with the square of the velocity of the helicopter, making it a large component of the total amount of drag acting on a high-speed helicopter (e.g., helicopters that achieve speeds of 180 knots or more).
- An example of a low-drag rotor extension for a rotorcraft includes a first connector configured to attach the rotor extension to a rotor blade, a second connector configured to attach the rotor extension to a rotor hub of the rotorcraft, a shaft disposed between the first and second connectors, and a damper mount attached to the second connector.
- An example of a low-drag rotorcraft includes a rotor hub coupled to a mast and a plurality of rotor extensions. Each rotor extension is configured to secure a rotor blade to the rotor hub and includes a first connector configured to attach the rotor extension to a rotor blade, a second connector configured to attach the rotor extension to the rotor hub; a shaft disposed between the first and second connectors, and a damper mount attached to the second connector. The rotorcraft also includes a fairing enclosing the damper and at least a portion of the rotor hub.
- This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of claimed subject matter.
- The disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.
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FIG. 1 illustrates a rotorcraft in accordance with aspects of the disclosure; -
FIGS. 2A and 2B illustrate top and side views, respectively, of a faired rotor system in accordance with aspects of the disclosure; -
FIGS. 3A and 3B illustrate a rotor extension in accordance with aspects of the disclosure; -
FIG. 4 is a comparative view of a traditional rotor blade and a rotor blade that includes the rotor extension ofFIGS. 3A and 3B in accordance with aspects of the disclosure; -
FIGS. 5A and 5B illustrate a rotor extension in accordance with aspects of the disclosure; and -
FIG. 6 is a comparative view of a traditional rotor blade and a rotor blade that includes the rotor extension ofFIGS. 5A and B in accordance with aspects of the disclosure. - It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
- In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present disclosure, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction.
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FIG. 1 illustrates an example of arotorcraft 100. Rotorcraft 100 includes afuselage 102, amain rotor system 110 withrotor blades 120, and atail rotor system 112 withtail rotor blades 122. An engine withinfuselage 102 suppliesmain rotor system 110 andtail rotor system 112 with torque to rotaterotor blades 120 andtail rotor blades 122. Afairing 130 covers a rotor hub 134 (seeFIG. 2 ) that couplesrotor blades 120 to amast 132. Fairing 130 improves the aerodynamic efficiency ofrotorcraft 100 by reducing drag ofrotor hub 134. As illustrated inFIG. 1 ,rotorcraft 100 includes fourrotor blades 120. In other aspects,rotorcraft 100 could include as few as two or threerotor blades 120 or more than four rotor blades 120 (e.g., five, six, etc.).Landing gear 104 extend fromfuselage 102 and supportrotorcraft 100 when rotorcraft 100 is landing or whenrotorcraft 100 is at rest on the ground. Rotorcraft 100 is not meant to be limiting. Aspects of the disclosure apply to other rotorcraft as well. - Generally speaking, the faster a rotor blade moves through the air and the greater an angle of attack of the rotor blade, the more lift that is generated. It will be appreciated that the speed of a rotor blade increases along a length of the rotor blade (known as the asymmetry of lift). In practical terms, the portion of a rotor blade proximal to the rotor hub tends to produce less lift (absent changes to the angle of attack resulting from specific rotor blade geometries) than the distal portion of a rotor blade due to the disparity in speed between the proximal and distal portions. This disclosure recognizes that a portion of the rotor blade proximal to the yoke/rotor hub can be replaced with a rotor extension that produces little to no lift without having a detrimental effect upon the amount of lift produced by the rotor blade. Replacing some of the proximal portion of the rotor blade with a rotor extension reduces drag to improve the aerodynamic efficiency of the aircraft, which is particularly desirable for high-speed helicopters.
- In some aspects, utilizing rotor extensions can also reduce a cost of each rotor blade as some high-performance rotorcrafts utilize rotor blades made of expensive materials (e.g., composites). Costs are reduced because less material is needed to manufacture the rotor blade due to its shortened length and/or because the proximal portions of a rotor blade often comprise more complex shapes that are more costly to manufacture. Utilizing rotor extensions also allows for the fairing covering the rotor hub to be packaged more tightly and with smaller openings or cut-outs for the rotor blades as the cross-section of the rotor extension can be made smaller than the cross-section of a conventional rotor blade that attaches to the rotor hub without a rotor extension. Utilizing a rotor extension also creates a pivot point for blade fold that is positioned farther from the rotor hub, which allows the rotor blade to fully clear the rotor hub assembly for a compact blade fold. In some aspects,
rotor blade 120 can be folded by removing one or more fasteners at an end of the rotor extension and pivotingrotor blade 120 about a remaining fastener. -
FIGS. 2A and 2B are top and side views, respectively, ofmain rotor system 110 according to aspects of the disclosure.Main rotor system 110 includes afairing 130 that enclosesrotor hub 134 to reduce the drag ofmain rotor system 110. Eachrotor blade 120 is coupled torotor hub 134 via arotor extension 124. In various aspects,rotor extension 124 may be coupled to the yoke, mast, or other rotating component. Fairing 130 includes cut-outs 126 that permitrotor extensions 124 to pass through. Each cut-out 126 is dimensioned to accommodate a range of motion of therotor extension 124 that passes therethrough. For example, during flight,rotor blades 120 pivot about their coupling torotor hub 134 as a result of various dynamic forces such as flapping, coning, lead/lag, pitch, and the like. Cut-outs 126 are dimensioned to be just large enough to allow for the various movements ofrotor blades 120 while minimizing the size of cut-outs 126 to improve the aerodynamic efficiency offairing 130. -
FIGS. 3A and 3B are perspective views ofrotor extension 124.FIG. 3A illustrates an uninstalledrotor extension 124 andFIG. 3B illustratesrotor extension 124 attached torotor blade 120. Eachrotor extension 124 includes afirst connector 136, ashaft 138, and asecond connector 140. As illustrated inFIGS. 3A and 3B ,first connector 136 is atongue 136 andsecond connector 140 is aclevis 140. In other aspects, first and second connectors may comprise other connector types. In some aspects,rotor extension 124 may include adamper mount 142 attached toshaft 138 orclevis 140 for attaching a damper torotor extension 124. In some aspects,shaft 138 orclevis 140 may include a pitch horn that couples to a pitch link to control a pitch ofrotor blade 120.Rotor extension 124 may be made of various materials, including titanium, steel, aluminum, metal matrix composite, composites, and the like. -
Tongue 136 includes one or more mountingholes 144 that receive fasteners (e.g., a pin, a screw, a bolt, and the like) to securerotor extension 124 torotor blade 120. As illustrated inFIGS. 3A and 3B ,tongue 136 is configured to fit inside of an opening in an end ofrotor blade 120. As illustrated inFIG. 3B , the opening in the end ofrotor extension 124 is formed so that an outer profile ofrotor blade 120 is not altered and an outer surface ofrotor blade 120 remains smooth and unobstructed by connection ofrotor extension 124 torotor blade 120.Rotor blade 120 includes corresponding mountingholes 146 that align with the one or more mounting holes 144. In other aspects,tongue 136 may instead attached to an exterior portion ofrotor blade 120. -
Rotor blade 120 may be folded abouttongue 136 by removing a fastener from the connection betweenrotor blade 120 andtongue 136.Rotor extension 124 allows for a compact blade fold as the pivot point abouttongue 136 is sufficiently far away fromrotor hub 134 to allow therotor blades 120 toclear fairing 130. -
Shaft 138 joinstongue 136 withclevis 140. In some aspects,shaft 138 is a hollow tube to reduce a weight ofrotor extension 124.Clevis 140 is disposed on an end ofshaft 138opposite tongue 136 and couples torotor hub 134. In a typical aspect,rotor extension 124 couples torotor hub 134 via a bearing assembly that includes an inboard beam and a centrifugal force bearing. As illustrated inFIGS. 3A and 3B ,clevis 140 is arranged generally vertically. It will be appreciated thatclevis 140 could be arranged horizontally or at an angle between horizontal and vertical as needed to allow forrotor extension 124 to attach to a particular rotor hub. In some aspects,clevis 140 could be replaced with an alternative connection suited to a particular rotor hub. -
Shaft 138 may have a variety of cross-sections, including circular, elliptical, rectangular, polygonal, and the like. As illustrated inFIGS. 3A and 3B ,shaft 138 has a circular cross-section.Shaft 138 has a cross-section that is notably smaller than that of a conventional rotor blade (e.g., seeFIG. 4 ), which allows the size of cut-outs 126 to be minimized. Having a circular cross-section enablesrotor extension 124 to maintain its projected frontal area regardless of the pitch of therotor blade 120, resulting in a consistent amount of drag generated byshaft 138 regardless of pitch angle. It has been determined that the benefits of minimizing the size of the opening of cut-out 126 outweighs the benefits of using a moreaerodynamic shaft 138. For example, using an elliptical cross-section onshaft 138 improves the aerodynamics of the portion ofshaft 138 that isoutside fairing 130. However, an elliptical cross-section increases the size of cut-out 126. The increase in drag resulting from the larger cut-out 126 results in a net increase in the drag acting onrotorcraft 100. - In some aspects,
shaft 138 comprises more than one cross-section to overcome the potential drawbacks of using an elliptical cross-section. For example, a portion ofshaft 138 that passes through cut-out 126 may comprise a first cross-section (e.g., circular) and a portion ofshaft 138 disposed outside of fairing 130 may comprise a second cross-section (e.g., elliptical). Using a circular cross-section for the first cross-section minimizes a size of cut-out 126 and using an elliptical cross-section for the second cross-section optimizes aerodynamics of the portion ofshaft 138 disposed outside of fairing 130. - In some aspects,
shaft 138 comprises a first cross-section (e.g., circular) and a portion ofshaft 138 located outside of fairing 130 includes an extension fairing 178 fitted toshaft 138 to improve the aerodynamics of the portion ofshaft 138 located outside fairing 130. Extension fearing 178 may comprise an elliptical shape, a blade-like shape, or other aerodynamic shape to minimize the drag created by the portion ofshaft 138 located outside fairing 130. Extension fairing 178 can be a removable piece that attaches torotor extension 124 via fasteners, adhesives, and the like, or can be integrally formed as a part ofrotor extension 124. - In various aspects,
tongue 136 andclevis 140 are set at an angle relative to each other to add an amount of blade twist torotor extension 124. Blade twist describes a geometric twist along a length of the rotor blade to change the rotor blade's pitch along the length of the rotor blade to combat asymmetry of lift. Pitch is decreased as the distance from the hub increases to even out the amount of thrust generated along the length of the rotor blade.FIGS. 3A and 3B illustrate that aface 137 oftongue 136 and aface 141 ofclevis 140 are arranged at an angle relative to one another (e.g., not parallel to one another) to introduce an amount of blade twist torotor blade 120. In some aspects, approximately 10 degrees of blade twist as added viaextension 124. In other aspects, more than 10 degrees or less than 10 degrees of blade twist may be added byrotor extension 124. Introducing blade twist viarotor extension 124 may be desirable as the amount of blade twist added byrotor extension 124 does not need to be added torotor blade 120, which is typically made from expensive composite materials. To incorporate blade twist into the design ofrotor blade 120 adds complexity to the structure ofrotor blade 120, adding to its cost. In some aspects,rotor extension 124 may be designed without any blade twist, withfaces -
FIG. 4 is a top view of aconventional rotor blade 121 overlaid on top of a combination ofrotor extension 124 attached torotor blade 120.FIG. 4 illustrates the reduction in surface area, and thus the reduction in drag, afforded by usingrotor extension 124. -
FIGS. 5A-5B illustrate arotor extension 200 according to aspects of the disclosure. In various aspects,rotor extension 200 may be used in place ofrotor extension 124. Compared torotor extension 124,rotor extension 200 has a flat, blade-like shape.Rotor extension 200 reduces drag compared to a conventional rotor blade by having a lower profile shape (e.g., seeFIG. 6 ). Eachrotor extension 200 includes atongue 202 and atongue 204 that are disposed on opposite ends of anextension portion 206.Rotor extension 200 may be made of various materials, including titanium, steel, aluminum, metal matrix composite, composites, and the like. In some aspects,rotor extension 200 is made from carbon fiber, fiberglass, or a combination of the two. -
Tongue 202 includes one or more mounting holes that receive fasteners to securerotor extension 200 torotor blade 120 andtongue 204 includes one or more mounting holes that receive fasteners to securerotor extension 200 to ayoke attachment 208. Fasteners can be pins, screws, bolts, and the like.Yoke attachment 208 includes corresponding mounting holes that align with the one or more mounting holes oftongue 204. As illustrated inFIGS. 5A and 5B ,yoke attachment 208 comprises abody portion 210 that couples to rotor hub to securerotor blade 120 thereto. In a typical aspect,yoke attachment 208 couples to the rotor hub via a bearing assembly, such as a centrifugal bearing assembly. - In various aspects,
tongue 202 andtongue 204 are set at an angle relative to each other to add an amount of blade twist to rotor extension 200 (best seen inFIG. 5B ). Introducing blade twist viarotor extension 200 may be desirable as the amount of blade twist added byrotor extension 200 does not need to be added torotor blade 120, simplifying the shape ofrotor blade 120, which is typically made from expensive composite materials. To incorporate blade twist into the design ofrotor blade 120 adds complexity to the structure ofrotor blade 120, adding to its cost. In some aspects,rotor extension 200 may be designed without any blade twist. -
FIG. 6 is a perspective view of aconventional rotor blade 121 overlaid on top of a combination ofrotor extension 200 attached torotor blade 120.FIG. 6 illustrates the reduction in surface area/size, and thus the reduction in drag, afforded by usingrotor extension 200. - Depending on the embodiment, certain acts, events, or functions of any of the algorithms, methods, or processes described herein can be performed in a different sequence, can be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the algorithms, methods, or processes). Moreover, in certain embodiments, acts or events can be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially. Although certain computer-implemented tasks are described as being performed by a particular entity, other embodiments are possible in which these tasks are performed by a different entity.
- Conditional language used herein, such as, among others, “can,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment.
- The term “substantially” is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. In any disclosed embodiment, the terms “substantially,” “approximately,” “generally,” “generally in the range of,” and “about” may be substituted with “within [a percentage] of” what is specified, as understood by a person of ordinary skill in the art. For example, within 1%, 2%, 3%, 5%, and 10% of what is specified herein.
- While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the devices or algorithms illustrated can be made without departing from the spirit of the disclosure. As will be recognized, the processes described herein can be embodied within a form that does not provide all of the features and benefits set forth herein, as some features can be used or practiced separately from others. The scope of protection is defined by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.
Claims (20)
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US16/447,421 US20200398978A1 (en) | 2019-06-20 | 2019-06-20 | Low-drag rotor blade extension |
US17/025,371 US11358711B2 (en) | 2019-06-20 | 2020-09-18 | Tetracyclic heterocycle compounds useful as HIV integrase inhibitors |
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