Ducted fan assembly with a movable leading edge

The present disclosure relates generally to rotor-driven aircraft and more particularly, but not by way of limitation, to a ducted fan assembly with a movable leading edge.

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.

Rapid commercial growth and expansion of urban areas often increases the distance from one side of a metropolitan area to another. This rapid commercial growth and expansion often results in an increase in the population, further resulting in more congestion and emissions due to an increased number of vehicles on the current highway infrastructure. As technology further increases, such metropolitan areas will continue to grow, placing serious burden on the current highway infrastructure to handle the increased traffic and furthering the need for improved travel across a metropolitan area that reduces emissions while allowing faster, more convenient, and more efficient travel throughout a metropolitan area and/or between bordering states. One approach is to utilize tiltrotor aircraft to carry people across metropolitan areas. Tiltrotor aircraft are configured to fly in helicopter mode for vertical takeoff and landing (VTOL) and in airplane mode for high-speed flight. These aircraft are preferably compact and light-weight vehicles. As with all commercial aircraft, safety is a primary concern. One safety aspect in consideration is the durability of components of the aircraft, such as the rotor ducts. For example, aircraft sometimes encounter foreign objects (e.g., birds or debris) that may strike a rotor or a rotor duct. To ensure the safety of the occupants of the aircraft, components of the aircraft (e.g., the rotor duct) are designed to withstand strikes from foreign objects.

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 to be used as an aid in limiting the scope of the claimed subject matter.

In an embodiment, a ducted fan assembly includes a housing that further includes a rotor. The ducted fan assembly also includes a rim that defines an opening surrounding at least a portion of the housing. The ducted fan assembly also includes a movable leading edge that is attached to the rim and extends around at least a portion of a perimeter of the ducted fan assembly, where the movable leading edge is adjustable between at least a first position and a second position.

In an embodiment, a method is performed on an aircraft that includes a ducted fan assembly. The method includes, during a first mode of operation of the aircraft, adjusting a movable leading edge of the ducted fan assembly to a first position in which the movable leading edge extends outward from a rim of the ducted fan assembly.

In an embodiment, a rotorcraft includes a plurality of fan assemblies. Each fan assembly includes a housing that further includes a rotor. Each fan assembly also includes a rim that defines an opening surrounding at least a portion of the housing. Each fan assembly also includes a movable leading edge that is attached to the rim and extends around at least a portion of a perimeter of the fan assembly, where the movable leading edge is adjustable between at least a first position and a second position.

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.

FIG. 1 is a perspective view of an aircraft oriented in a helicopter mode according to aspects of the disclosure;

FIG. 2 is a perspective view of an aircraft oriented in an airplane mode according to aspects of the disclosure;

FIG. 3 is a perspective view of a ducted fan assembly according to aspects of the disclosure;

FIG. 4 is a sectioned view of a ducted fan assembly according to aspects of the disclosure;

FIGS. 5A-C illustrate a ducted fan assembly with an adjustable bladder in a first position for helicopter mode; and

FIGS. 6A-C illustrate a ducted fan assembly with an adjustable bladder in a second position for airplane mode.

Various aspects will now be described more fully with reference to the accompanying drawings. The disclosure may, however, be embodied in many different forms and should not be construed as limited to the aspects set forth herein.

Referring now to FIGS. 1 and 2 , perspective views of a rotorcraft 101 operating in helicopter and airplane modes, respectively, are shown according to aspects of the disclosure. Rotorcraft 101 is generally configured as a vertical takeoff and landing (VTOL) aircraft, more specifically a tiltrotor, that is operable in an airplane mode associated with forward flight and a helicopter mode associated with vertical takeoff from and landing to a landing zone. Rotorcraft 101 comprises a fuselage 103 comprising a cockpit and/or passenger compartment, wings 105 extending from the fuselage 103 , a pair of ducted fan assemblies 107 a , 107 b carried by, supported by and/or otherwise coupled to fuselage 103 , a pair of ducted fan assemblies 107 c , 107 d carried by, supported by, and/or otherwise coupled to wings 105 . Ducted fan assemblies 107 a - 107 d are arranged about fuselage 103 to be generally coplanar when rotorcraft 101 is in helicopter and airplane modes.

Each ducted fan assembly 107 a , 107 b is supported by a rotatable shaft or spindle 113 extending at least partially through fuselage 103 and coupled to the pair of ducted fan assemblies 107 a , 107 b . The pair of ducted fan assemblies 107 a , 107 b may be selectively rotated with respect to fuselage 103 by at least one actuator (e.g. electric, electro-mechanical, magnetic, and/or hydraulic) in order to transition rotorcraft 101 between the airplane and helicopter modes. Each ducted fan assembly 107 a - 107 d comprises a duct 108 a - 108 d , respectively, with each duct 108 a - 108 d having a plurality of structural supports and/or struts 110 a - 110 d . In some aspects, outer surfaces of the ducts 108 may be shaped to provide optimal and/or preferred flight characteristics in at least one of the airplane mode and the helicopter mode.

Ducted fan assemblies 107 a , 107 b each include a fan 112 a , 112 b , respectively. It will be appreciated that fans 112 a , 112 b rotate in opposing directions with respect to one another to balance the torque generated by each fan 112 a , 112 b . Each fan 112 a , 112 b includes plurality of rotor blades. Fans 112 a , 112 b are disposed within their respective duct 108 and are configured to generate thrust when selectively rotated. As illustrated in FIGS. 1 and 2 , each fan 112 a , 112 b comprises five rotor blades. However, in other aspects, each fan 112 a , 112 b may comprise two, three, five, six, seven, eight, and/or more rotor blades.

Each wing 105 carries a single ducted fan assembly of the pair of ducted fan assemblies 107 c , 107 d . The pair of ducted fan assemblies 107 c , 107 d are supported by a rotatable shaft or spindle (e.g., similar to spindle 113 ) that extends at least partially through wings 105 and is coupled to the pair of ducted fan assemblies 107 c , 107 d . The pair of ducted fan assemblies 107 c , 107 d may be selectively rotated with respect to fuselage 103 by at least one actuator (e.g. electric, electro-mechanical, magnetic, and/or hydraulic) in order to transition rotorcraft 101 between the airplane and helicopter modes. The pair of ducted fan assemblies 107 c , 107 d are structurally similar to the pair of ducted fan assemblies 107 a , 107 b and each includes its own duct 108 c , 108 d , struts 110 c , 110 d , fans 112 c , 112 d . Compared to the pair of ducted fan assemblies 107 a , 107 b , the pair of ducted fan assemblies 107 c , 107 d are disposed further outboard of fuselage 103 .

Rotorcraft 101 is controlled via flight control system 150 . Flight control system 150 includes flight control computer 152 that connected to and in communication with propulsion system 154 . Propulsion system 154 is controlled by flight control computer 152 and includes components that assist with the flight of rotorcraft 101 . Propulsion system 154 may generally include a hybrid electrical system, a hybrid hydraulic system and/or combinations thereof. Flight control computer 152 is configured to selectively control the components of propulsion system 154 to operate rotorcraft 101 . Flight control system 150 may include flight control input hardware (e.g. flight controls) configured to receive inputs and/or commands from a pilot to control operation of the rotorcraft 101 and/or a plurality of sensors and/or gauges configured to provide feedback regarding operational characteristics of rotorcraft 101 to the flight control computer 152 . Additionally, flight control computer 152 may be configured to selectively control the operation, orientation, rotation, position, and/or rotational speed of the pairs of ducted fan assemblies 107 a , 107 b and 107 c , 107 d . In some aspects, flight control system 150 may comprise fly-by-wire architecture for controlling rotorcraft 101 . Additionally, in some aspects, flight control system 150 may be capable of optionally-piloted operation. Furthermore, in some aspects, flight control system 150 may comprise collective pitch control for adjusting the pitch of rotor blades 124 and rotational speed control for individually adjusting a rotational speed of rotor systems 122 of each of the ducted fan assemblies 107 a - 107 d , without the need for cyclic control for controlling operation of rotorcraft 101 .

FIG. 3 illustrates ducted fan assembly 107 a according to aspects of the disclosure. Ducted fan assembly 107 a will be discussed with the understanding that the discussion thereof applies to ducted fan assemblies 107 b - 107 d . Ducted fan assembly 107 a is depicted in FIG. 3 without fan 112 a . Ducted fan assembly 107 a includes duct 108 a and a central housing 119 that is configured to support and house components such as a rotor, a gearbox, and/or other components to which fan 112 a may be positioned over and attached. Ducted fan assembly 107 a further includes a plurality of stators 121 that extend outward from housing 119 . In this embodiment, ducted fan assembly 107 a includes four stators 121 that extend radially outward from housing 119 . More specifically, ducted fan assembly 107 a has two primary stators that include an inboard primary stator 121 a and an outboard primary stator 121 b . Inboard primary stator 121 a is configured to be coupled to a corresponding spindle, such as spindle 113 . Ducted fan assembly 107 a is rotatable about a spindle axis 123 that is defined by spindle 113 . Ducted fan assembly 107 a includes two secondary stators 121 c . Primary inboard and outboard stators 121 a , 121 b respectively are configured to carry a larger proportion of the load of ducted fan assembly 107 a back to fuselage 103 than are secondary stators 121 c . Inboard primary stator 121 a and outboard primary stator 121 b are longitudinally aligned relative to each other on opposed sides of housing 119 and secondary stators 121 c are longitudinally aligned relative to each other on opposed sides of housing 119 and aligned perpendicularly to inboard primary stator 121 a and outboard primary stator 121 b . In this regard, stators 121 are equally spaced about housing 119 . It should be appreciated that ducted fan assembly 107 may be alternatively configured with more or fewer stators 121 . It should further be appreciated that ducted fan assembly 107 a may be alternatively configured with different spacing of stators 121 about housing 119 .

Ducted fan assembly 107 a further includes an inboard control vane 125 a and an outboard control vane 125 b , which are pivotally attached to inboard primary stator 121 a and outboard primary stator 121 b , respectively. Inboard control vane 125 a and outboard control vane 125 b are pivotable about a vane axis 127 that extends parallel to spindle axis 123 . In this embodiment, inboard control vane 125 a and outboard control vane 125 b are configured to rotate together to facilitate yaw control, changes of direction, turning, etc. during flight of rotorcraft 101 . It should be appreciated, however, that inboard control vane 125 a and outboard control vane 125 b may alternatively be configured to rotate independently from one another. It should further be appreciated that ducted fan assembly 107 a is not limited to the illustrated configuration of inboard control vane 125 a and outboard control vane 125 b . For example, ducted fan assembly 107 a may alternatively be configured with more or fewer control vanes, such as a single control vane that defines a continuous control surface. Ducted fan assembly 107 a includes a movable leading edge 129 that forms an outer covering of ducted fan assembly 107 a , and that defines an opening that extends through ducted fan assembly 107 a . As shown, housing 119 is located primarily aft of the opening. An outer surface of movable leading edge 129 can include, for example, one or more sections of skin.

Movable leading edge 129 is configured to change shape, or adjust between various positions, to alter the flow path of air around duct 108 a . For example, movable leading edge 129 can adjust between a first position for helicopter mode and a second position for airplane mode. For example, in the first position for helicopter mode, movable leading edge 129 can extend to form a lip, or bulge, that maximizes the amount of lift produced by ducted fan assembly 107 a . Continuing this example, in the second position for airplane mode, movable leading edge 129 can be retracted relative to the first position so as to reduce drag for more efficient aerodynamics. In some embodiments, movable leading edge 129 can be, for example, a rigid structure that is mechanically actuated to extend and retract. In other embodiments, movable leading edge 129 can be formed from a multiple-chamber bladder that extends and retracts through changes in air pressure. An example structure of movable leading edge 129 will be discussed in more detail relative to FIGS. 4, 5A -C and 6 A-C.

FIG. 4 is a sectioned view of ducted fan assembly 107 a according to aspects of the disclosure. Ducted fan assembly 107 a includes a rim 128 that extends around the perimeter of duct 108 a and is supported by the plurality of stators 121 and the control vanes 125 . Rim 128 provides structure and support for ducted fan assembly 107 a . As shown in FIG. 4 , rim 128 defines an opening surrounding at least a portion of central housing 119 .

An adjustable bladder 130 sits on, or is attached to, rim 128 to form movable leading edge 129 . In some aspects, rim 128 includes a frame 132 that in cross-section forms a hat-like shape. Frame 132 reinforces rim 128 and provides additional structure to which adjustable bladder 130 may be secured. Rim 128 is positioned within duct 108 a to be adjacent to fan 112 a . In certain embodiments, rim 128 is made from metals or composites that are more rigid than adjustable bladder 130 , such that the rim 128 has greater rigidity than adjustable bladder 130 . In some embodiments, in order to maintain proper spacing between fan 112 a and duct 108 a , it is advantageous for at least the portion of duct 108 a that is adjacent to the tips of fan 112 a (e.g., its blade tips) be rigid. In a typical aspect, a space between the tips of fan 112 a and duct 108 a (e.g., a space between the tips of blades of fan 112 a and rim 128 ) is, for example, less than or equal to 0.25 inches.

Adjustable bladder 130 is formed from a pliable material that can deform in the event a foreign object impacts adjustable bladder 130 during flight. Allowing adjustable bladder 130 to deform attenuates the energy of the strike to minimize or eliminate damage to duct 108 a . Adjustable bladder 130 is rigid enough to provide a desired aerodynamic shape to improve the performance of duct 108 a (i.e., maintains shape for the efficient flow of air over duct 108 a to improve the amount of thrust generated by ducted fan assembly 107 a ), but is also pliable enough to absorb and withstand impacts from foreign objects. For example, adjustable bladder 130 may be made from various polymers. In some aspects, the polymer is a rubber material and may be reinforced with fibers (e.g., polymers and the like).

Adjustable bladder 130 includes multiple chambers configured to be filled with a gas. In some aspects, each chamber of adjustable bladder 130 is separately filled with a gas (e.g., nitrogen as nitrogen is less sensitive to changes in temperature) and sealed. In an example, a first chamber of adjustable bladder 130 can remain at a constant pressure while a second chamber of adjustable bladder 130 can have a variable pressure. The pressure within the second chamber can be controlled, or varied, so as to cause the adjustable bladder 130 , and the movable leadable edge 129 formed thereby, to adjust between the first position for helicopter mode and the second position for airplane mode. In various embodiments, in the first position for helicopter mode, the second chamber has its pressure increased so as to cause adjustable bladder 130 to extend outward from rim 128 to form a lip or bulge that maximizes the amount of lift produced by ducted fan assembly 107 a . Conversely, in the second position for airplane mode, the second chamber can have its pressure decreased (e.g., complete deflation in some embodiments) so as to cause adjustable bladder 130 to retract inward, toward rim 128 , to form a more aerodynamic shape suitable for airplane mode. In the example of FIG. 4 , adjustable bladder 130 is in the second position for airplane mode. Although adjustable bladder 130 is described as having two chambers and configurability to adjust between two positions, in various embodiments, adjustable bladder 130 can have any number of chambers and configurability to adjust between or among any number of positions.

The rigidity of adjustable bladder 130 is determined in part by the material it is made from and in part by the pressure provided by the gas with which its chambers are filled. In some aspects, adjustable bladder 130 may include a feature 138 , such as a blow-off valve, a weakened section, and the like, to bleed off pressure that results from a foreign object impacting adjustable bladder 130 during flight. In the event of a failure of adjustable bladder 130 or as a part of maintenance, adjustable bladder 130 may be removed from rim 128 for inspection, repair, or replacement.

Compared to traditional ducts, which are formed from metal or composites, adjustable bladder 130 offers improved performance regarding impacts by foreign objects. For example, compared to metals and composites, adjustable bladder 130 can more easily retain its shape after an impact event. Retaining shape after an impact event can prevent the loss in performance that occurs when a metal or composite duct is deformed or destroyed by an impact event. Adjustable bladder 130 also provides weight savings compared to conventional duct designs. A further benefit is the ease and low cost with which adjustable bladder 130 can be manufactured.

FIGS. 5A-C illustrate ducted fan assembly 107 a with adjustable bladder 130 in the first position for helicopter mode. More particularly, FIG. 5A is a sectioned view in which adjustable bladder 130 is shown to have two chambers, namely, a first chamber 131 and a second chamber 133 . In a typical embodiment, the first chamber 131 has approximately the same pressure in both the first position for helicopter mode and the second position for airplane mode. In the illustrated embodiment, the second chamber 133 has been inflated, or had its pressure increased, such that movable leading edge 129 extends outward to form a lip or bulge. As described previously, the lip or bulge of the movable leading edge 129 serves to maximize the amount of lift produced by ducted fan assembly 107 a . FIG. 5B is a zoomed-in view of the sectioned view of FIG. 5A . FIG. 5C is a perspective view of adjustable bladder 130 in the first position for helicopter mode and illustrates the lip or bulge of the movable leading edge 129 extending around the entire perimeter of ducted fan assembly 107 a.

FIGS. 6A-C illustrate ducted fan assembly 107 a with adjustable bladder 130 in the second position for airplane mode. More particularly, FIG. 6A is a sectioned view showing the first chamber 131 at approximately the same pressure described relative FIGS. 5A-C . In the illustrated embodiment, the second chamber 133 has been deflated, or had its pressure decreased, such that movable leading edge 129 retracts inward and the lip or bulge described relative to FIGS. 5A-C is no longer visible. In that way, the adjustable bladder 130 has retracted to form a more aerodynamic shape suitable for airplane mode. FIG. 6B is a zoomed-in view of the sectioned view of FIG. 6A . FIG. 6C is a perspective view of adjustable bladder 130 in the second position for airplane mode.

Depending on the aspect, 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 aspects, 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 aspects 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 aspects include, while other aspects 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 aspects or that one or more aspects 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 aspect.

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 aspect, 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 aspects, 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.