Aircraft Drag Reduction System and Internal Cooling Electric Motor System and Aircraft Using the Same

Abstract

An aircraft propulsion system having a drag reduction portion adapted to reduce surface friction on at least a portion of the external surface of the aircraft. The drag reduction portion may include an inlet for sucking in an air flow. The aircraft may also have an internally cooled electric motor adapted for use in an aircraft. The motor may have its stator oriented towards the center and have an external rotor. The rotor structure may be air-cooled and may be a complex structure having an internal lattice adapted for an air flow. The stator structure may be liquid-cooled and may be a complex structure having an internal lattice adapted for liquid to flow through. A fluid pump may pump a liquid coolant through a non-rotating portion of the motor stator and then through a heat exchanger, which is partially cooled by air that has flowed through a rotating portion of the motor rotor. The drag reduction portion and the cooled electric motor portion may share the same inlet.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority of U.S. Provisional Patent Application No. 62 / 643,763, filed on March 16, 2018, by Bevirt et al., the entire content of which is incorporated herein by reference. This application claims the priority of U.S. Provisional Patent Application No. 62 / 694,910, filed on July 6, 2018, by Bevirt et al., the entire content of which is incorporated herein by reference. Field of the invention

[0003] The present invention relates to the field of aviation, namely an aircraft propulsion system used on an aircraft. Brief description of the drawings

[0004] Figure 1A is a schematic diagram of a propulsion system according to some embodiments of the present invention.

[0005] FIG. 1 is a schematic diagram of a propulsion system according to some embodiments of the present invention.

[0006] Figure 2A is a vertical take - off and landing aircraft in a take - off configuration according to some embodiments of the present invention.

[0007] Figure 2B is a vertical take - off and landing aircraft in a forward - flight configuration according to some embodiments of the present invention.

[0008] Figure 3A is a partial cross - sectional view of a cabin and a rotor according to some embodiments of the present invention.

[0009] Figure 3B is a partial cross - sectional view of a cabin and a rotor according to some embodiments of the present invention.

[0010] Figure 3C is a partial rear view of a cabin according to some embodiments of the present invention.

[0011] Figure 4A is a shaded view of a cabin and a rotor according to some embodiments of the present invention.

[0012] Figure 4B is a view of a cabin and a rotor according to some embodiments of the present invention.

[0013] Figure 4C is a view of the interior of a cabin according to some embodiments of the present invention.

[0014] Figure 5A is a shaded drawing of a cabin and a rotor according to some embodiments of the present invention.

[0015] Figure 5BIs a shaded view of a nacelle and a rotor according to some embodiments of the present invention.

[0016] Figure 6A Is a shaded view of a rotor and a nacelle with a bypass according to some embodiments of the present invention.

[0017] Figure 6B Is a view of a rotor and a nacelle with a bypass according to some embodiments of the present invention.

[0018] Figure 6C Is a partial cross-sectional view of a rotor and a nacelle with a bypass according to some embodiments of the present invention.

[0019] Figure 7A Is a shaded view of a rotor and a nacelle with a bypass according to some embodiments of the present invention.

[0020] Figure 7B Is a view of a rotor and a nacelle with a bypass according to some embodiments of the present invention.

[0021] Figure 8 Is a view of a rotor and a propeller hub according to some embodiments of the present invention.

[0022] Figure 9A Is a partial cross-sectional view of a motor with liquid cooling according to some embodiments of the present invention.

[0023] Figure 9B Is a partial cross-sectional view of a motor with liquid cooling according to some embodiments of the present invention.

[0024] Figure 9C Is a partial cross-sectional view of a motor with liquid cooling and an associated heat exchanger according to some embodiments of the present invention.

[0025] Figure 10A Is a photograph of a rotor structure suitable for internal cooling according to some embodiments of the present invention.

[0026] Figure 10B Is a photograph of a rotor structure suitable for internal cooling according to some embodiments of the present invention.

[0027] Figure 10C Is a side cross-sectional view of a rotor structure suitable for internal cooling according to some embodiments of the present invention.

[0028] Figure 10D Is a top partial view of a rotor structure suitable for internal cooling according to some embodiments of the present invention.

[0029] Figure 11 Is a view of a cooling subsystem flow path according to some embodiments of the present invention.

[0030] Figure 12Schematic diagram of a bypass mechanism according to some embodiments of the present invention.

[0031] Figure 13 Partial cross-sectional side view of a diffuser according to some embodiments of the present invention.

[0032] Figure 14 Presents a representative view of a flow path according to some embodiments of the present invention.

[0033] Figure 15A Schematic diagram of a flow path using a segmented fan according to some embodiments of the present invention.

[0034] Figure 15B Schematic diagram of a flow path of a diffuser using zones assigned to a segmented fan according to some embodiments of the present invention.

[0035] Figure 15C Schematic diagram of a flow path using a zoned diffuser according to some embodiments of the present invention.

[0036] Figure 16A Shows the velocity distribution through a zoned diffuser according to some embodiments of the present invention.

[0037] Figure 16B Shows the pressure distribution through a zoned diffuser according to some embodiments of the present invention.

[0038] Figure 17A View of the suction velocity at a suction velocity fraction of 0%.

[0039] Figure 17B View of the turbulence intensity at a suction velocity fraction of 0%.

[0040] Figure 18A View of the suction velocity at a suction velocity fraction of 10%.

[0041] Figure 18B Turbulence intensity graph at a suction velocity fraction of 10%.

[0042] Figure 19A View of the suction velocity at a suction velocity fraction of 20%.

[0043] Figure 19B Turbulence intensity graph at a suction velocity fraction of 20%.

[0044] Figure 20 Graph of the ratio of energy loss to volume flow fraction according to some embodiments of the present invention. Summary of the Invention

[0045] An aircraft propulsion system having a drag reduction portion adapted to reduce skin friction on at least a portion of the exterior surface of the aircraft. The drag reduction portion may include an inlet for sucking in an air stream. The aircraft may also have an internally cooled electric motor adapted for use in an aircraft. The motor may have its stator oriented towards the center and have an external rotor. The rotor structure may be air cooled and may be a complex structure having an internal lattice adapted for an air flow. The stator structure may be liquid cooled and may be a complex structure having an internal lattice adapted for liquid flow therethrough. A fluid pump may pump a liquid coolant through a non-rotating portion of the motor stator and then through a heat exchanger that is partially cooled by air that has flowed through a rotating portion of the motor rotor. The drag reduction portion and the cooled electric motor portion may share the same inlet. Detailed Description

[0046] An aircraft propulsion system that can reduce drag on the rotor nacelle and the entire aircraft. The drag reduction portion may include sucking air into the nacelle behind the rotor. The sucking of air may thin or eliminate a turbulent boundary layer behind the inlet where the air is sucked in. The sucked-in air may also be used in a thermal management subsystem to assist in cooling an electric motor that powers the aircraft. The thermal management subsystem may include heat exchange from a coolant inside the motor to the flowing air sucked in from the air inlet. In some aspects, the sucked-in air is only used to reduce drag. In some aspects, the sucked-in air is used both to reduce drag and to cool the motor of the aircraft.

[0047] In some aspects, the sucked-in air is used to reduce drag on the aircraft, and the sucked-in air stream is used to drive a fan coupled to a liquid pump that pumps coolant through the motor, thereby eliminating or reducing the electrical power requirement for thermal management of the motor. In some aspects, the sucked-in air may be split into separate air flow paths, with a portion of the intake air being directed through the thermal management subsystem and then through a heat exchanger to cool the liquid used to cool the motor. Then, the same air flowing through the heat exchanger may also drive a fan coupled to the liquid pump, thereby providing convective cooling and driving the liquid flow in the cooling system of the motor. Another portion of the sucked-in air may bypass the motor cooling system. The use of the bypass allows an increase in the intake air volume, which may allow adjustment of the intake air volume to reduce drag on the aircraft.

[0048] As Figure 1A - 1BAs shown, the aircraft propulsion system 100 includes: a rotor 101, a nacelle 102 including a drag reduction portion, a drive mechanism 103 coupled to the rotor and the nacelle, and a thermal management subsystem 104 in thermal communication with the drive mechanism and the air around the system. The rotor includes a set of blades 105 coupled to a hub 106 and defines a fairing 107. The nacelle 102 defines an outer surface 108 and an inner cavity 109, and the drag reduction portion includes an inlet 110 and an outlet 111 and may include a diffuser 112. The drive mechanism includes a rotating portion 122 rigidly coupled to the hub and a stationary portion coupled to the nacelle. The thermal management subsystem 104 includes a liquid cooling mechanism 123 and a heat exchanger 121 (such as a radiator) and may include a flow actuator 113.

[0049] The system 100 may optionally include: an inclination mechanism 120 at least partially housed in the inner cavity of the nacelle, a power supply 114, and any other suitable components. The system 100 may serve to reduce surface friction on at least a portion of the outer surface of the aircraft. The system may manipulate the airflow (e.g., external airflow, internal airflow, etc.) to convectively cool system components. The system may additionally or alternatively serve to: ingest the boundary layer formed on the aircraft surface (e.g., at a location between the rotor and the nacelle of the aircraft propulsion system); and perform any other suitable functions.

[0050] The aircraft propulsion system can be used with a rotorcraft. The rotorcraft is preferably a tiltrotor aircraft having a plurality of aircraft propulsion systems (e.g., rotor assemblies, rotor systems, etc.) that can operate between a forward configuration and a hover configuration. However, the rotorcraft can alternatively be a fixed-wing aircraft having one or more rotor assemblies, a helicopter having one or more rotor assemblies (e.g., where at least one rotor assembly or aircraft propulsion system is substantially axially oriented to provide horizontal thrust), and / or any other suitable rotorcraft or vehicle propelled by a rotor. The rotorcraft preferably includes an all-electric powertrain (e.g., a battery-powered electric motor) to drive one or more rotor assemblies, but may additionally or alternatively include a hybrid powertrain (e.g., a gas-electric hybrid including an internal combustion engine), an internal combustion powertrain (e.g., including a gas turbine engine, a turboprop engine, etc.), and any other suitable powertrain.

[0051] As used herein, the term "rotor" related to an aircraft propulsion system or other aspects may refer to a rotor, a propeller, and / or any other suitable rotating aerodynamic actuator. Although a rotor may refer to a rotating aerodynamic actuator that utilizes a hinged or semi-rigid hub (e.g., where the blade-to-hub connection may be hinged, flexible, rigid, and / or connected in other ways), and a propeller may refer to a rotating aerodynamic actuator that utilizes a rigid hub (e.g., where the blade-to-hub connection may be hinged, flexible, rigid, and / or connected in other ways), when used herein, there is no such explicit or implicit distinction, and the use of "rotor" may refer to any configuration of hinged or rigid blades, and any other suitable configuration, and / or any other suitable configuration in which the blades are connected to a central member or hub. Similarly, the use of the term "propeller" may refer to any configuration of hinged or rigid blades and any other suitable configuration, and / or any other suitable configuration of the blade connection to the central member or hub. Thus, a tiltrotor aircraft may be referred to as a tiltprop aircraft and / or an aircraft appropriately referred to or described in other ways.

[0052] As Figure 1A and 1B As shown, the aircraft propulsion system 100 includes: a rotor, a nacelle, a drive mechanism coupled to the rotor and the nacelle, and a thermal management subsystem in thermal communication with the drive mechanism and the air surrounding the system. The rotor includes a set of blades coupled to a hub. The nacelle defines an outer surface, an inner cavity, an inlet, a diffuser, and an outlet. In some aspects, the nacelle may have a first outlet for air passing through the thermal management subsystem and a second outlet for air bypassing the thermal management subsystem. The drive mechanism includes a rotating portion rigidly coupled to the hub and a stationary portion coupled to the nacelle. The thermal management system includes a liquid cooling mechanism and a heat exchanger (e.g., a radiator), and may include a fluid actuator.

[0053] The system 100 may optionally include: a tilt mechanism at least partially housed in the inner cavity of the nacelle, a power source, and any other suitable components. The rotor functions to rotate in a fluid under the action of the drive mechanism to provide thrust (e.g., provided to an attached aircraft). The rotor includes a set of blades coupled to a hub and a fairing or spinner at least partially surrounding the hub. The rotor may optionally include any suitable components for supporting and / or controlling the rotor surface (e.g., linkages and / or actuators for changing the blade pitch, structural elements for holding the blade set and / or hub, etc.).

[0054] The function of the blade assembly is to transfer the rotational momentum of the rotor to the fluid, so that at least a part of the fluid has axial momentum (e.g., to provide thrust). The rotor can have any suitable number of blades. The rotor preferably has five blades, but alternatively can have three blades, four blades, six blades, and any other suitable number of blades. The blades can be rigidly fixed to the hub, fixed to the hub and include variable pitch capabilities (e.g., through appropriate variable pitch linkages, cyclic pitch control, etc.), and / or connected to the hub or rotor head by one or more hinges (e.g., drag hinges, flap hinges, etc.) so that the blades can lead, lag, and / or flap relative to the hub or rotor head during the rotation of the rotor under aerodynamic loads. However, the blades can additionally be suitably interconnected with each other and / or additionally be suitably mechanically connected to form at least a part of the rotor. In a specific example, the rotor includes five variable pitch blades; in an alternative example, the rotor can have any suitable number of blades with variable or fixed pitch.

[0055] The rotor blades are preferably unconstrained at the blade tips (e.g., constrained by any kind of physical structure), but the rotor can additionally or alternatively include a shroud that surrounds the blade tips (e.g., a duct such as a ducted fan). In such a variant, the shroud can serve to dampen the acoustic characteristic components (e.g., sound waves) originating from the blade tips during rotation. However, the rotor blades can additionally or alternatively be constrained or unconstrained in any suitable manner.

[0056] The function of the hub is to interconnect the blade assembly and provide the area where the rotor is connected to the drive mechanism and receives rotational power (e.g., shaft power) from it. In various variants, the hub can define at least a part of the rotating part of the drive mechanism (e.g., the rotor of an electric motor including the rotor and stator, a part of the rotor of an electric motor, etc.). In additional variants, the hub can be directly or indirectly connected to the output shaft of the drive mechanism.

[0057] The function of the shroud is to define the foremost contact points of the rotor with the external fluid (e.g., the surrounding air), the surface that forms the boundary layer during the movement of the aircraft, and the wetted surface of the rotor except for a set of blades. The shroud also serves to define an internal cavity to accommodate all or part of the elements of the propulsion system (e.g., the drive mechanism, the thermal management subsystem, the hub, etc.).

[0058] The shape of the fairing is preferably such that the drag is minimized. In a variant, the fairing rotates relative to the nacelle together with the rotor and is separated from the nacelle by a gap. The gap can define at least a part of the inlet of the nacelle (e.g., an annular inlet, a segmented partial annulus, etc.). In an alternative variant, during rotor operation, the fairing and / or parts thereof can remain static relative to the nacelle (e.g., where the fairing defines a slot through which the blade set rotates). The diameter of the fairing in the forward projection direction is preferably smaller than the diameter of the most forward point of the nacelle in the forward projection direction (e.g., the point of the nacelle closest to the fairing); however, the diameter of the fairing can alternatively be larger than the diameter of the most forward end of the nacelle in the forward projection direction, substantially equal to the diameter of the most forward end of the nacelle in the forward projection direction, or have different dimensions depending on the variation of the aircraft propulsion system.

[0059] The function of the nacelle is to house the components of the aircraft propulsion system and to define the outer surface (e.g., the wetted surface, the external surface) of the various parts of the aircraft propulsion system downstream of the rotor. The nacelle can also serve to absorb the external flow and decelerate it internally (e.g., through a diffuser) before the discharged flow (e.g., through an outlet). The nacelle defines an outer surface and an inner cavity and can include a drag reduction portion, where the drag reduction portion can define an inlet, a diffuser, and / or an outlet. The nacelle should be understood to include any structural part of the fuselage (e.g., the nose, the wing, the tail section, etc.) arranged behind the drive mechanism and the rotor and structurally supporting the drive mechanism and the rotor, as well as any other suitable components of the aircraft propulsion system.

[0060] In a variant, the nacelle is a structural member distinct from the wing and / or tail to which the nacelle is connected (e.g., rigidly mounted, rotatably coupled through a tilting mechanism, etc.). In such a variant, the nacelle is preferably not configured as a lifting body but can additionally or alternatively be configured to provide at least some lift to the aircraft during flight. In an alternative variant, the nacelle can be integral with the wing and / or tail portion to which the nacelle is connected. In such a variant, the nacelle can define lift and / or control surfaces (e.g., serving as part of the wing and / or tail portion). However, the nacelle can be appropriately constructed and / or arranged relative to the aircraft.

[0061] The function of the outer surface is to separate the internal features and components of the nacelle from the external airflow. The outer surface can also serve to define at least a portion of the inlet and / or outlet. The outer surface can also serve to define the wetted surface of the aircraft propulsion system behind the rotor (e.g., substantially all of the wetted surface, a majority of the wetted surface, etc.). The outer surface can also serve to define a geometry that minimizes drag (e.g., promotes the formation and maintenance of a laminar boundary layer, prevents flow separation, etc.). The outer surface is preferably shaped to promote laminar flow, and the outer surface can include: defining a cross-section that minimizes the static pressure recovery along the axial surface, which can lead to undesirable flow separation; accelerating the flow along the maximum downstream portion of the outer surface (e.g., maintaining a negative pressure gradient oriented along the direction of the outer surface) to promote the stability of the laminar boundary layer; and / or any other suitable geometric features configured to promote laminar flow along the majority of the outer surface of the nacelle.

[0062] The function of the inner cavity is to define a volume for holding components of the aircraft propulsion system and / or other aircraft subsystems. In variants, these held components can include at least a portion of the tilting mechanism, all or a portion of the power source, an electrical power delivery subsystem (e.g., distribution cables, conduits, etc.), a mechanical actuator (e.g., for actuating control surfaces of the aircraft), all or a portion of the drive mechanism, and any other suitable components.

[0063] The function of the drag reduction portion is to reduce the drag on the aircraft propulsion system during flight operation, thereby reducing the drag of the entire aircraft. The drag reduction portion is preferably configured to reduce drag during forward flight (e.g., operation of the aircraft in a forward arrangement, operation of the aircraft propulsion system in a forward configuration, etc.), but can additionally or alternatively reduce drag in any suitable operating mode of the aircraft (e.g., hovering, vertical takeoff and / or landing, forward movement of the aircraft between forward and hovering configurations with a subset of the aircraft propulsion system of at least a portion of the aircraft). The drag reduction portion includes an inlet and an outlet; the drag reduction mechanism optionally includes a diffuser and / or a bypass.

[0064] In some aspects, an aircraft can use a blade-type propeller driven by an electric motor to provide thrust during takeoff. The propeller / motor unit can be referred to as a rotor assembly. In some aspects, the wings of the aircraft can rotate with the leading edge facing upward such that the propeller provides vertical thrust for takeoff and landing. In some aspects, the motor-driven propeller unit on the wing itself can rotate relative to the fixed wing such that the propeller provides vertical thrust for takeoff and landing. The rotation of the motor-driven propeller unit can allow the direction of thrust to be changed by rotating both the propeller and the electric motor, and thus no gimbal or other means around or through a rotating joint is required for torque drive.

[0065] In some aspects, an aircraft according to an embodiment of the present invention takes off from the ground using vertical thrust from a rotor assembly that has been deployed in a vertical configuration. As the aircraft begins to gain altitude, the rotor assembly can begin to tilt forward in order to begin accelerating forward. As the aircraft acquires forward speed, the airflow over the wings generates lift, such that the rotors are no longer required to use vertical thrust to maintain altitude. Once the aircraft has reached sufficient forward speed, some or all of the blades used to provide vertical thrust during takeoff can be retracted along its nacelle. In some aspects, all of the rotor assemblies used for vertical takeoff and landing are also used during vertical flight. The nacelle that supports the rotor assembly can have a recess such that the blades can be nested in the recess, thereby greatly reducing the drag of the retracted rotor assembly.

[0066] After takeoff, the aircraft will begin to transition to forward flight by hinging the rotors from the vertical thrust direction to a position that includes a horizontal thrust element. As the aircraft begins to move forward at a certain speed, the wings will generate lift, and thus less vertical thrust from the rotors is required. As the rotors are further hinged towards the forward flight, horizontal thrust configuration, the aircraft attains a higher speed.

[0067] An electric motor / propeller combination located outside of the hinge joint can rigidly mount the propeller to the motor such that this rigidity can be maintained even as the propeller moves in various orientations relative to the rear nacelle portion. With this configuration, the rotational power from the motor does not need to be balanced or otherwise transferred to the rotational joint. In some aspects, this deployment is the deployment of an entire motor-driven rotor.

[0068] In a first vertical configuration according to some embodiments of the present invention, as Figure 2A shown in the vertical takeoff configuration of, aircraft 200 uses fixed wings 202, 203, which can be forward-swept wings, with the same or different types of rotors suitable for vertical takeoff and landing and forward flight. The aircraft body 201 supports the left wing 202 and the right wing 203. The motor-driven rotor assemblies 206, 207 on the wings include propellers that can be retracted and nested within the nacelle body. The aircraft fuselage 201 that extends rearward is also attached to an elevated rear stabilizer 204. The rear stabilizer has a rear rotor assembly 205 attached thereto. Although two passenger seats are anticipated, other numbers of passengers can be accommodated in different embodiments of the present invention.

[0069] In some aspects, the rotors mounted on all or part of the wings may be adapted for use in a forward flight configuration, while the rotors mounted on other wings may be adapted to be fully retracted during normal forward flight. The aircraft 200 may have four rotors on the right wing 203 and four rotors on the left wing 202. The inner rotor assemblies on each wing may have a rotor 206 mounted on the wing, which is adapted to flip up to a deployed position for vertical takeoff and landing, retract back to a stowed position during the transition to forward flight, and then have its blades stowed and nested during forward flight. The outer rotor assemblies 207 may pivot uniformly from a horizontal thrust configuration to a vertical thrust configuration.

[0070] Similarly, each rear stabilizer 204 may have a rotor unit mounted thereon, and both rotor units are adapted for use during vertical takeoff and landing and during the transition mode. In some aspects, all rotor designs are the same, with some being used for forward flight together with the main blades. In some aspects, all rotor designs are the same, and all rotors are used for forward flight. In some aspects, different numbers of rotor units may be mounted to the rear stabilizer 204.

[0071] In some embodiments, the electric motors of the aircraft are powered by rechargeable batteries. In the event of a single battery failure, using multiple batteries to drive one or more power buses can improve reliability. In some embodiments, the batteries may be spread along the rotating part, and each motor / ducted fan assembly may have a battery. In some embodiments, one or more batteries may reside partially or entirely within the aircraft fuselage, and the power is led to the motors through a rotary coupling. In some embodiments, the batteries reside in the aircraft fuselage on shelves with adjustable positions such that the aircraft balance can be adjusted according to the pilot's weight.

[0072] Figure 2B The aircraft 200 in a forward flight configuration is shown.

[0073] Figure 3A The cabin 303 is shown in a partial view, which provides an aerodynamic cover for the support structure of the motor-driven rotor assembly according to some embodiments of the present invention. A spinner or fairing 301 is mounted in front of the rotor 302 (the propeller is not shown in this view). Figure 3B is a view of the cabin 303, which shows the rotor, and some other parts are omitted for clarity. In some aspects, the cabin may be a multi-piece cabin, which is adapted to transition the front part of the cabin from a forward-facing horizontal configuration to a vertical takeoff and landing configuration by using an internally mounted deployment mechanism. In some aspects, the cabin may be a cabin mounted on the wing tip, which is adapted to transition between horizontal and vertical flight configurations by rotating around a central pivot hub.

[0074] The rotor 302 rotates around the internal stator. The air gap 304 between the outer surface of the rotor 302 and the nacelle 303 allows air to enter the interior of the nacelle. In some aspects, the outer circumferential surface of the nacelle 302 will also have air inlets that allow air to enter the interior region of the rotor structure. In some aspects, the outer rotor structure has an outer skin surface with internally supported lattice members therebetween that allow air flow and use of the air flow to cool the structure. The air flowing through the rotor structure exits the structure in regions adjacent to the incoming air passing through the air gap 304. These airflows can then flow through a heat exchanger that cools the liquid flowing through the internal stator of the motor. In some aspects, the outer rotor structure will not allow air flow within the outer rotor structure. The air flow entering through the air gap 304 can serve to reduce the drag of the aircraft.

[0075] Figure 3C It is a view of the rear of the nacelle 303. The rear air outlet 305 allows the incoming air that has passed through the air gap 304 and into the nacelle through the rotor structure to exit. In some aspects, the nacelle 303 can be a split nacelle with an internal deployment mechanism that can separate when the nacelle and motor-driven components transition from a forward flight configuration to a vertical takeoff and landing configuration. Once the nacelle is separated, the air discharged from the motor area can exit through the gap created when the nacelle is separated. In some aspects, the nacelle can be a solid nacelle, and the transition from the forward flight configuration to the vertical takeoff and landing configuration includes rotating the entire nacelle around a fixed pivot. In some aspects, the aircraft can have a combination of motor-driven rotor assemblies, some of which have separate nacelles and some of which rotate around fixed pivots. In some aspects, as described below, there may be one or more other outlets.

[0076] Figure 4A 、 4B Figures 4C, 5A, and 5B illustrate a rotor assembly 205 according to some embodiments of the present invention. In this illustrative embodiment, the propeller and fairing are coupled to the rotating structure 302 and are located in front of the nacelle 303. Air can enter the heat exchanger 319 in front of the nacelle 303 and behind the rotor. In some aspects, the front edge of the nacelle 303 defines an air gap 304 that allows air to flow into the nacelle. In this embodiment, all of the air flowing into the interior of the nacelle flows through the heat exchanger 319 before exiting via the air outlet 305. A blocking structure 402 at the rear end of the air flow opening of the heat exchanger blocks air from flowing further rearward into the nacelle from behind the heat exchanger. Although, for example, in Figure 4CA blocking structure with some oval openings is shown, but it is expected that these openings will provide an entrance for items such as electrical wires and will be airtight during use. Air flows into the heat exchanger 319 and then into the interior of the internal structure 404 within the cabin. The air flow can then leave the interior of the internal structure 404 through the ventilation holes 405, then flow within the cabin 303 and out through the air flow outlet 305. The deployment mechanism 403 is adapted to pivot the rotor assembly from a forward flight configuration to a vertical takeoff and landing configuration. The support structure 411 supports the heat exchanger and also allows the air flow that has passed through the heat exchanger to subsequently enter the internal structure 404 of the cabin.

[0077] Figure 6A , 6B , Figures 7A and 7B show embodiments of the rotor assembly 207, in which the air flow can pass through the heat exchanger and then flow out through the main air flow outlet 501, but it is also allowed that a bypass flow passes through the inlet of the heat exchanger 319 and flows out through the bypass outlet 505. Figure 6C The rotor assembly with the outer cabin surface removed for clarity of view is shown. In this illustrative embodiment, the air flow enters through the annular gap 304. A portion of the air flow can pass through the inlet of the heat exchanger and enter the area behind the heat exchanger, in which the air flow flowing backward is blocked by the bypass blocking structure 507. The bypass duct 506 is fluidly connected to the area behind the heat exchanger and in front of the bypass blocking structure 507. The bypass duct allows the bypass flow to continue flowing out to the bypass outlet 505. The cabin can pivot about the pivot 502 to transition from a forward flight configuration to a vertical takeoff and landing configuration.

[0078] The increase in the bypass flow causes the amount of air entering through the annular gap to be greater than the amount of air that may be used or required by the thermal management subsystem. This ability to allow a greater flow of air can allow the user to adjust the drag reduction portion to reduce the energy loss of the aircraft. As described below, in some aspects, the ratio of the volumetric flow rate of the inlet air flow to the volumetric flow rate of the boundary layer in front of the inlet can be set to reduce drag. In some aspects, the bypass flow is utilized to allow more inlet air flow.

[0079] Another portion of the air flow entering the annular gap 304 can enter the heat exchanger 319 and leave inside the internal cabin structure 504. The internal cabin structure 504 can have an air flow channel 508 that is adapted to allow the air inside the internal cabin structure to leave the interior of the internal cabin structure and travel inside the cabin 503. Then, the air in this area of the cabin can continue to exit the cabin through the main air flow outlet 501.

[0080] Figure 8It is a diagram of a motor and a propeller hub. For clarity, some of the components are omitted. The propeller hub 310 is mounted to the rotor 302 and rotates in unison with the rotor. The propeller hub has propeller interfaces 311 spaced around its periphery.

[0081] In some embodiments of the present invention, as Figure 9A , 9B and the cross-sectional views in 9C show, various aspects of the motor cooling system are shown. In some aspects, the cooling system can cool the air passing through the rotor structure and cool the liquid within the stator structure. The liquid cooling system can use a heat exchanger that promotes heat transfer from the liquid to the air flow passing through the heat exchanger. The air flow passing through the rotor structure can also partially cool the fluid after leaving the rotor structure and then entering the heat exchanger. Additionally, the cooling system can utilize a fan to promote further air flow. In some aspects, no air flows through the rotor structure.

[0082] The stator 342 is coupled to the inner race of the bearing. The rotor 343 is coupled to the outer race. The rotor 343 has a rotor support structure 315 adapted to support various components including the magnet 312. In an exemplary embodiment, the rotor support structure 315 can have metal surface skins 360, 361 that have an internal lattice structure 364 which can both structurally support the mechanical loads placed on the rotor support structure and allow air to flow through the structure to cool the structure. Air may enter the rotor support structure through the voids 362 in the surface skin 360. In some aspects, the air entry voids can be located around the front portion of the outer periphery of the rotor support structure. The air flow passing through the rotor support structure can exit through the rear portion 363 of the structure.

[0083] The stator 342 can have a structure adapted for internal flow, such as the portion 314 below the stator winding bar 313. There may be a fluid capture cover, such as a fiberglass cylindrical portion, around the outer circumference of the stator winding bar. The fluid capture cover allows fluid to flow between the stator winding bars to allow convective cooling of the stator winding bars and the windings. Inside the stator is a fluid flow structure 316 that draws fluid from the fluid pump 317, passes through the fluid flow structure 316, forward through the stator support structure 314, then around the stator winding bar 313 back under the fluid capture cover, and through the heat exchanger 319.

[0084] The airflow through the heat exchanger can be a combination of air exiting from the rear of the rotor support structure 315 and other air entering through the air gap 304 between the outer surface of the rotor 302 and the nacelle 303. In some aspects, there is a solid rotor support structure where the airflow entering the heat exchanger does not pass through the rotor structure. After flowing through the heat exchanger 319, the fluid returns to the fluid pump 317 through the fluid flow structure 316. The air fan 318 also facilitates the airflow through the heat exchanger 319. Although shown in an enlarged view in Figure 9A , the air fan 318 can be coupled to the fan 318. In some aspects, the fluid pump 317 can be driven by a motor to drive the fluid through the fluid system. In some aspects, the air fan 318 can be driven by a motor to draw air through the heat exchanger. In some aspects, the same motor can drive the fan and the fluid pump. In some aspects, the intake air flowing through the heat exchanger can then drive the fan, which in turn drives the fluid pump.

[0085] Figure 10A and 10B are photographs of exemplary portions of a rotor support structure according to some embodiments of the present invention. As seen in the side view of Figure 12 , and as seen in Figure 10C and Figure 10D , the rotor support structure has a top solid surface and a bottom solid surface, with a lattice member support structure therebetween. In some aspects, the rotor support structure can be a monolithic piece constructed using metal 3D printing. As shown in Figure 10D , a series of voids on the outer circumference of the top solid surface allow airflow to enter the internal lattice members. Then, the airflow can exit the internal lattice members of the rotor support structure via the outer surface of the rotor support structure.

[0086] Figure 11 shows the air and fluid flowing through a liquid-cooled electric motor according to some embodiments of the present invention. Figure 11It is a cross-sectional view. For clarity, the pump 317 and the fan 318 are in a disassembled view position. In an exemplary embodiment, the fluid resides within the fluid flow structure 316, exits the pump 317, and flows radially outward 334 within the outflow channel in the fluid flow structure 316, which can be part of or coupled to the stator support structure. The heat-generating electrical components can be mounted on the front side of the fluid flow structure, and the fluid within the fluid flow structure can cool those components. Then, the fluid flows 332 within the stator support structure 314 in a region adjacent to and radially inward from the wire bars and windings. Then, the fluid exits the interior of the stator support structure 314 at the front of the stator support structure and then flows backward 336 through the wire bars 313 and windings and extends radially within the fluid capture cover. Then, the fluid 337 passes through the heat exchanger 319, where it is cooled by the air flow passing through the heat exchanger. Finally, the fluid 338 flows through the return channel within the fluid flow structure and enters the pump 317.

[0087] The air flow through the motor enters the path 331 through the rotor support structure 315. Then, some or all of the air flow leaving the rotor support structure can also enter the heat exchanger 319. The air flow also flows around the outside of the rotor 330 and downward 333 through the heat exchanger 319. Both the external air flow 330 and the internal air flow 331 can enter through the air flow gap 304. In the case of a solid rotor, no air flows through the rotor support structure. The air fan 318 can also draw air in and through the above air flow system. In some aspects, the fan can be used to draw in a large amount of air to have a beneficial effect on the aerodynamics of the aircraft. In some aspects, for example, in the hover mode, the fan can be the main driver for the air flow through the heat exchanger. The relatively narrow gap between the motor and the nacelle is used to absorb the boundary layer formed on the motor, which helps to clean the boundary layer flow on the nacelle itself, thereby promoting laminar flow on the nacelle and reducing drag. In some aspects, the nacelle is shaped to utilize this beneficial effect. In some embodiments, no air flow passes through the rotor structure. In such embodiments, all of the air flow entering the heat exchanger or the bypass duct is the external air flow 330.

[0088] In an exemplary embodiment, the coolant pump can pump 10 - 15 liters of coolant per minute, and the coolant can be a polyalphaolefin coolant. The temperature of the coolant entering the heat exchanger may be approximately 85 degrees Celsius, and when exiting, it may be 70 degrees Celsius. This can occur when the motor is operating at a speed of 700 rpm and has a continuous hover power of 75.5 kW and a torque of 1030 Nm. In this case, the motor may dissipate 6.3 kW of heat. The fan air flow may vary between 800 - 1500 cfm.

[0089] The flow regulator 181 can be arranged at various positions relative to the bypass duct 183 and can be used to regulate or direct the flow or the amount of intake air. The inhaled air can enter through the inlet 180, and a portion of the air stream can bypass the heat exchanger 184 and enter the bypass duct 183. The fan 182 can be used to increase the air flow rate. In some aspects, the flow regulator is used to vary the proportion of the flow entering the bypass duct. In some aspects, an actuation system can engage a mechanical deflector, such as a louver, which can vary the flow entering the bypass duct 183. In some aspects, the flow regulator can also vary the total amount of air entering through the air inlet 180.

[0090] In some embodiments of the present invention, as Figure 13 shown, in a system where the rotor rotates about the axis 197, when the intake air 191 enters the bypass duct 195, the multi-channel diffuser 196 is used to slow down the intake air 191. The multi-channel diffuser 196 can be located within the nacelle 194, adjacent to or behind the air inlet, and in the front region of the bypass duct 195. In this exemplary embodiment, all of the incoming air 191 from the flowing air 190 flows through the diffuser and into the duct. In some aspects, the multi-channel diffuser can be used in the incoming air stream and then distributed between entering the thermal control system and the bypass duct. In some aspects, the multi-channel diffuser can be used in the entire incoming air stream passing through the thermal control system.

[0091] Figure 14 The advantages of the multi-channel diffuser relative to a single-channel flow path are shown. In a single-channel flow path, as the volume of the channel expands, the intake air 260 can separate from the inner surface of the channel 261. In the multi-channel diffuser, the air streams 270a, 270b, 270c flow through channels separated by diffuser layers 271a, 271b. The air 271a, 271b, 271c discharged from the channels within the multi-channel diffuser does not separate from the inner surface of the channel.

[0092] In a variant, as Figure 15A shown, the air flow path can flow into a segmented fan 180. As Figure 15BAs shown, the segmented fan 180 is preferably configured to correspond to the segmented diffuser of the nacelle, but can be configured appropriately in other ways. In this variant, the segmented fan 180 can serve to extract momentum from the flow at the first segment 181 (e.g., the outer segment of the concentric segments) and supply the momentum to the flow at the second segment 183 (e.g., the inner segment of the concentric segments). The segmented fan 180 can include a separator 182, such as a cylindrical separator. In an exemplary case, the inlets 185a, 185b can travel on different sides of the diffuser plate 189. The diffuser plate 189 can start from the outer side of the heat exchanger 188 in the front region of the nacelle 186. The diffuser plate concentrically divides the flow into two airflow paths 185a, 185b. The channeled airflow provided by the diffuser plate can continue through the heat exchanger and enter the interior of the nacelle.

[0093] In some embodiments of the present invention, as Figure 15C shown, the multi-channel diffuser has a plurality of diffuser plates 189a, 189b, 189c, 189d, 189e, 189f, 189g. The diffuser plates can start from the outer side of the heat exchanger 188 in the front region of the nacelle 186. The diffuser plates concentrically divide the airflow into different flow paths. The channeled airflow provided by the diffuser plates can continue through the heat exchanger and enter the interior of the nacelle. In some aspects, the diffuser plate structure also serves as turning vanes for the airflow. It should be noted that the function of the channel diffuser is to separate regions of airflow with different total pressures. The function of the diffuser is to slow down the airflow and increase the pressure inside the nacelle.

[0094] The drag reduction section preferably serves to reduce drag by promoting laminar flow on at least a portion of the outer surface of the nacelle, which is physically promoted by ingesting the boundary layer (e.g., turbulent boundary layer) at a location between the rotor and the nacelle (where the boundary layer is most likely to be fully turbulent downstream of the rotor due to the physical structural separation between the rotor and the nacelle). After ingestion (e.g., through an inlet / air gap), the internal airflow is preferably expanded (e.g., through a diffuser) and decelerated so as to reduce the surface friction between the internal airflow and the drag reduction mechanism (e.g., proportional to the flow rate). This can result in a net reduction in drag while maintaining laminar flow along the outer surface downstream of the inlet (e.g., surface friction is also reduced compared to turbulence). The drag reduction section also preferably minimizes the internal pressure loss (e.g., in the diffuser, in the connected heat exchanger, etc.). However, the drag reduction section can additionally or alternatively reduce drag in any other suitable way.

[0095] In a variant, the drag reduction section can operate between various modes, including full bypass mode, partial bypass mode, and no bypass mode. In full bypass mode, the flow through the drag reduction section is not driven through the heat exchanger of the thermal management subsystem (e.g., the flow bypasses the heat exchanger). In no bypass mode, the entire flow through the drag reduction section is driven through the heat exchanger of the thermal management subsystem. In partial bypass mode, the bypass fraction (e.g., the percentage of the flow rate through the drag reduction mechanism that bypasses the heat exchanger) is adjusted. The partial bypass mode can manage the possible pressure loss in the heat exchanger, which may be caused by operating in no bypass mode at certain aircraft speeds; in such cases, the partial bypass mode can be used to direct a portion of the inhaled air between the inlet and outlet without passing the air through the heat exchanger to prevent an excessive air flow supply to the heat exchanger (e.g., and cause pressure losses or other losses that result in drag and / or efficiency reduction). The bypass portion can be adjusted passively (e.g., actuated by the flow field itself, as a function of the flow velocity) and / or actively (e.g., throttled by a controllable flow actuator such as a variable-sized orifice, valve, etc.). The drag reduction section preferably operates between operating modes using a bypass mechanism such as louvers, which is driven by an electromechanical actuator that can redirect the air flow through and / or away from the drag reduction section mechanism, e.g., Figure 12 as an example in. However, the drag reduction section can additionally or alternatively transition appropriately between various operating modes and any other suitable operating modes.

[0096] In a variant, the drag reduction section can operate passively. In an example of this variant, the components of the drag reduction section are preferably static (e.g., the inlet size is fixed, the diffuser shape and size are fixed, the outlet size is fixed, etc.), and the air flow through the drag reduction section can scale with the system speed (e.g., the airspeed of the aircraft). In another example of this variant, the components of the drag reduction section can be actuated dynamically by the flow field (e.g., where the pressure of the flow field applies a force to the outlet and increases or decreases the size of the outlet according to the airspeed). However, the drag reduction section can additionally or alternatively operate passively and / or actively in any suitable manner (e.g., through an actuatable variable-sized outlet, etc.).

[0097] The inlet of the drag reduction section is used to absorb the air flow moving through the trailing edge of the cowling of the rotor. The inlet is preferably shaped to minimize and / or prevent flow separation to promote laminar flow on the outer surface of the nacelle downstream of the inlet. However, the inlet can be shaped appropriately in other ways. The drag reduction section can be designed such that the amount of air inhaled at the designed airspeed has been adjusted to minimize drag.

[0098] The inlet is preferably arranged near a separation zone (e.g., a gap) between the rotating outer surface (e.g., a rotor) of the rotor system and the static outer surface (e.g., the outer surface of the nacelle) of the rotor system. In particular, the air inlet is preferably arranged proximal to the position where the downstream flow of the rotor stagnates on the rotor system in the absence of an air inlet, in order to utilize the high-pressure zone generated by the stagnation to drive the air flow into the air inlet (e.g., in addition to or instead of active flow actuation, e.g., via a flow actuator or a large negative pressure gradient between the outlet and the inlet). The inlet is preferably an annular region, but may additionally or alternatively be a partial annulus, a segmented annulus, and / or have any other suitable geometric configuration.

[0099] The function of the outlet is to re-introduce the internal air flow (e.g., from the diffuser) into the external free air flow. The outlet can also serve to limit the flow velocity through the drag reduction mechanism (e.g., passively through the outlet geometry, actively through actuation of the outlet size, etc.). The outlet can be arranged at various positions relative to the outer surface of the nacelle. The outlet can be arranged at the outer surface at the rear of the inlet and upstream of the trailing edge or region of the nacelle. In an alternative variant, the outlet can be arranged at the trailing edge or region of the nacelle (e.g., at the tail of the nacelle). The outlet can be an annular region (e.g., in a manner similar to the inlet), a segmented annular region, a region located near the inlet to minimize the influence of the outflow through the outlet on the downstream air flow, and / or have any other suitable geometric distribution or arrangement relative to the nacelle geometry.

[0100] The outlet can be a fixed or variable geometry (e.g., cross-sectional dimensions, diameter, shape, etc.). In variants where the outlet has a variable size, the size can be changed manually (e.g., via a control linkage, via a manually adjustable mechanical restrictor (e.g., an iris or other orifice), via a fly-by-wire controller, etc.), or automatically (e.g., via a closed-loop controller, via a speed-dependent variable throttle, etc.).

[0101] Figure 16A is the modeled output of the velocity magnitude of the air flow when the air flow enters the interior of the nacelle 286 through the diffuser 289. The air flow flows over the outer surface of the rotor 291 and enters the air gap between the rotor 291 and the nacelle 286. The diffuser 289 is a multi-channel diffuser having a plurality of diffuser plates. As Figure 16A shown, the air flow velocity in the diffuser and through the nacelle has slowed down. As seen in the modeled output of the Figure 16B pressure distribution, an increased pressure is seen on the outer side of the diffuser and throughout the diffuser and the nacelle. As Figure 16BAs shown, the use of a multi-channel diffuser with multiple diffuser plates separates the higher pressure axially rearward into the channels, thereby preventing air from recirculating throughout the flow channel. As described above, at the rear end of the diffuser plate, the fan equalizes the pressure behind the fan through momentum transfer. The pressure difference within the diffuser channel is part of the external flow dynamic pressure. In some aspects, the pressure difference within the diffuser channel is in the range of 5% to 100% of the external dynamic pressure. In some aspects, the pressure difference within the diffuser channel is in the range of 10% to 50% of the external dynamic pressure.

[0102] A design parameter for the design and adjustment of a drag reduction section for a system according to some embodiments of the present invention is the volume flow fraction. The volume flow fraction is defined as the ratio of the volume flow rate of the inlet air to the volume flow rate of the boundary layer behind the rotor and in front of the inlet. Figure 20 Illustrates the relationship between the energy loss 270 and the volume flow ratio 271. The horizontal axis 271 is set to the energy loss level seen in the baseline system without intake air being drawn in. As shown, as air enters, the energy loss rises 272 due to internal losses. As more air enters, the energy loss drops to point 273. This is due to the laminar flow recovery on the outer surface of the nacelle, as Figure 19A shown. A low energy loss point 274 can be reached, and the energy loss represented by this energy loss point 274 is less than that of the baseline system without intake air being drawn in. As more intake air enters, the internal losses increase and the total energy loss increases 275. In some aspects, the volume flow fraction is greater than 0.1. In some aspects, the volume flow fraction is greater than 0.2. In some aspects, the volume flow fraction is greater than 0.5. In some aspects, the volume flow fraction is greater than 1.0. In some aspects, the volume flow fraction is greater than 2.0.

[0103] A method for reducing the energy loss of an aircraft may include the following steps: drawing air into the area behind the rotor; guiding the air into a diffuser; and discharging the air. The diffuser may guide all or part of the drawn-in air through a thermal management system. A bypass channel may be utilized to increase the volume flow rate of the drawn-in air.

[0104] Figure 17A 、 18A and 19A respectively show the turbulence intensity at 0%, 10%, and 20% intake velocity fractions. The turbulence intensity is the fraction of the turbulent energy fluctuations in the free stream relative to the flow energy density. The brighter regions indicate more turbulence. The intake velocity fraction represents the intake velocity fraction of the free stream. As Figure 17A shown, at an intake velocity fraction of 0%, the spinner 401 relatively has no turbulent boundary layer. As the flow approaches the air gap inlet 402, turbulence begins. In this example, the air gap inlet 402 has no intake velocity. The turbulent layer 403 can be seen along the entire nacelle 404. AsFigure 18A As shown, at an inhalation velocity fraction of 10%, the spinner 401 has relatively no turbulent boundary layer. As the flow approaches the air gap inlet 402, turbulence begins. In this example, there is a 10% inhalation velocity fraction at the air gap inlet 402. Immediately after the air gap inlet 402, the entire nacelle 404 sees the turbulent layer 405 thinning. The turbulent layer then thickens downstream 406. As Figure 19A shown, at an inhalation velocity fraction of 20%, the spinner 401 has relatively no turbulent boundary layer. As the flow approaches the air gap inlet 402, turbulence begins. In this example, there is a 20% inhalation velocity fraction at the air gap inlet 402. A significant thinning 407 (if not elimination) of the turbulent layer 405 is seen across the entire nacelle 404 just after the air gap inlet 402. Then, the turbulent layer begins 408 and then thickens downstream 406.

[0105] Figure 17B , 18B Figures 19A, 19B, and 19C respectively show the velocities at inhalation velocity fractions of 0%, 10%, and 20%. These results indicate that as the inhalation velocity fraction changes, the flow pattern outside the nacelle does not show much.

[0106] In some embodiments, the aircraft can actively inhale air to cause or increase the suction velocity at the air gap inlet. In some aspects, as described above, air can be actively inhaled to cool the electric motor. In some aspects, air can be actively inhaled regardless of whether the air is specifically for motor cooling.

[0107] As shown, the airflow quality across the nacelle changes sharply between 10% and 20% of the suction. In some aspects, the inhalation velocity fraction is greater than 10%. In some aspects, the inhalation velocity fraction is greater than 15%. In some aspects, the inhalation velocity fraction is greater than 20%.

[0108] It is obvious from the above description that various embodiments can be configured according to the description given herein, and additional advantages and modifications will be readily apparent to those skilled in the art. Therefore, the present invention in its broader aspects is not limited to the specific details and illustrative examples shown and described. Accordingly, departures may be made from these details without departing from the spirit or scope of the applicant's general invention.

Claims

1. An aircraft having a drag reduction system, the aircraft comprising: A rotor assembly driven by an electric motor, the rotor assembly driven by an electric motor comprising: An electric motor, the electric motor comprising: A motor rotor; and A motor stator, the motor rotor being rotatably coupled to the motor stator; A propeller hub coupled to the front end of the motor rotor; A propeller coupled to the propeller hub; An intake fan structurally coupled to the stator; and A cabin, the cabin comprising a cabin structure coupled to the rotor assembly driven by an electric motor, the cabin defining an outer surface, the motor rotor being entirely in front of the front edge of the cabin, the front edge of the outer surface of the cabin defining an air inlet gap behind the motor rotor of the electric motor, the intake fan being adapted to draw air into the air inlet gap, the air inlet gap being fluidly coupled to the interior of the cabin, wherein the air inlet gap includes an annular gap behind the outer circumference of the motor rotor, the rotor assembly driven by an electric motor being adapted to draw air into the air inlet gap during flight at a volume flow fraction greater than 0.

2.

2. The aircraft according to claim 1, wherein, The rotor assembly driven by the motor further includes a diffuser fluidly coupled to the air inlet gap and fluidly coupled to the interior of the cabin.

3. The aircraft according to claim 1, wherein, The cabin includes an air flow outlet fluidly coupled to the interior of the cabin.

4. The aircraft according to claim 2, wherein, The cabin includes an air flow outlet fluidly coupled to the interior of the cabin.

5. The aircraft according to claim 1, wherein, The rotor assembly driven by the motor further includes one or more annular heat exchangers fluidly coupled to the air inlet gap on a first side and fluidly coupled to the interior of the cabin on a second side.

6. The aircraft according to claim 1, wherein, The rotor assembly driven by the motor further includes an intake fan adapted to draw air into the air inlet gap and structurally coupled to the stator.

7. The aircraft according to claim 1, wherein, The rotor assembly driven by the motor is adapted to draw air into the air inlet gap during flight at a volume flow fraction greater than 0.

5.

8. The aircraft according to claim 2, wherein The rotor assembly driven by the motor is adapted to draw air into the air inlet gap during flight at a volume flow fraction greater than 0.

5.

9. The aircraft according to claim 1, wherein, The intake fan is a segmented fan segmented in the radial direction, the segmented fan being adapted to transfer the momentum of a first portion of the air flow passing through the fan to a second portion of the air flow passing through the fan; Wherein the diffuser includes an air flow channel structure adapted to radially direct the air flow passing through the diffuser to different intake regions of the segmented fan.

10. The aircraft according to claim 1, wherein, The rotor assembly driven by the motor further includes: A bypass duct fluidly coupled to the air inlet gap; and A bypass air flow outlet.

11. The aircraft according to claim 10, wherein, The rotor assembly driven by the motor is adapted to draw air into the air inlet gap during flight at a volume flow fraction greater than 0.

5.

12. The aircraft according to claim 10, wherein, The rotor assembly driven by the motor is adapted to draw air into the air inlet gap during flight at a volume flow fraction greater than 1.0.

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