Aircraft drag reduction system and internally cooled electric motor system, and aircraft using same

Abstract

To provide an aircraft propulsion system adapted to reduce surface friction on at least one portion of an outer surface.SOLUTION: An aircraft may also have an internally cooled electric motor adapted for use within the aircraft. The motor may have a stator toward the center and an external rotor. A rotor structure can be a composite structure that is air-cooled and has an internal grid adapted for airflow. The stator structure may be a composite structure that is liquid-cooled and has an internal grid adapted to allow liquid to flow through. A fluid pump may pump liquid coolant through a non-rotating portion of the motor stator and then pass it through a heat exchanger, and the heat exchanger is partially cooled by air flowing through a rotating portion of the motor rotor. A drag reduction section and a cooled electric motor section can share the same inlet.SELECTED DRAWING: Figure 1B

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 62 / 643,763, Bevirt et al., filed March 16, 2018, which is incorporated herein by reference in its entirety. This application claims priority to U.S. Provisional Patent Application No. 62 / 694,910, Bevirt et al., filed July 6, 2018, which is incorporated herein by reference in its entirety.

[0002] The present invention relates to the field of aviation, namely aircraft propulsion systems used in air vehicles. Summary of the Invention

[0003] The aircraft propulsion system having a drag reduction portion is adapted to reduce surface friction on at least a portion of an exterior surface of the aircraft. The drag reduction portion can include an inlet for intake of airflow. The aircraft can also have an internally cooled electric motor adapted for use in an air vehicle. The motor can have a stator towards the center and an external rotor. The rotor structure can be a composite structure with an internal grid adapted for airflow and air cooling. The stator structure can be a composite structure with an internal grid adapted for liquid cooling and liquid flowing therethrough. A fluid pump can pump liquid coolant through a non-rotating portion of the motor stator and then through a heat exchanger, which is partially cooled by air flowing through a rotating portion of the motor rotor. The drag reduction portion and the cooled electric motor portion can share the same inlet. [Brief description of the drawings]

[0004] [Figure 1A] 1 is a schematic diagram of a propulsion system according to some embodiments of the present invention. [Figure 1B] 1 is a schematic diagram of a propulsion system according to some embodiments of the present invention. [Figure 2A]FIG. 1 is a diagram of a vertical take-off and landing aircraft in a take-off configuration according to some embodiments of the present invention. [Figure 2B] FIG. 1 is a diagram of a vertical take-off and landing aircraft in a forward flight configuration in accordance with some embodiments of the present invention. [Figure 3A] 1 is a partial cutaway view of a nacelle and rotor according to some embodiments of the present invention. [Figure 3B] 1 is a partial cutaway view of a nacelle and rotor according to some embodiments of the present invention. [Figure 3C] FIG. 2 is a partial rear view of a nacelle according to some embodiments of the present invention. [Figure 4A] FIG. 2 is a shaded partial view of a nacelle and rotor according to some embodiments of the present invention. [Figure 4B] 1 is a diagram of a nacelle and rotor according to some embodiments of the present invention. [Figure 4C] FIG. 2 is a view of a nacelle interior according to some embodiments of the present invention. [Figure 5A] FIG. 2 is a shaded view of a nacelle and rotor according to some embodiments of the present invention. [Figure 5B] FIG. 2 is a shaded view of a nacelle and rotor according to some embodiments of the present invention. [Figure 6A] FIG. 2 is a shaded view of a rotor and nacelle having a bypass according to some embodiments of the present invention. [Figure 6B] FIG. 2 is a diagram of a rotor and nacelle having a bypass according to some embodiments of the present invention. [Figure 6C] FIG. 2 is a partial cutaway view of a rotor and nacelle having a bypass according to some embodiments of the present invention. [Figure 7A] FIG. 2 is a shaded view of a rotor and nacelle having a bypass according to some embodiments of the present invention. [Figure 7B] FIG. 2 is a diagram of a rotor and nacelle having a bypass according to some embodiments of the present invention. [Figure 8] FIG. 2 is a diagram of a rotor and propeller hub according to some embodiments of the present invention. [Figure 9A]1 is a partial cutaway view of a motor having liquid cooling according to some embodiments of the present invention. [Figure 9B] 1 is a partial cutaway view of a motor having liquid cooling according to some embodiments of the present invention. [Figure 9C] 1 is a partial cutaway view of a motor having liquid cooling and an associated heat exchanger according to some embodiments of the present invention. [Figure 10A] 1 is a photograph of a rotor structure adapted for internal cooling according to some embodiments of the present invention. [Figure 10B] 1 is a photograph of a rotor structure adapted for internal cooling according to some embodiments of the present invention. [Figure 10C] 1 is a side cutaway view of a rotor structure adapted for internal cooling according to some embodiments of the present invention. [Figure 10D] FIG. 2 is a partial top view of a rotor structure adapted for internal cooling according to some embodiments of the present invention. [Figure 11] FIG. 2 is a diagram of a cooling subsystem flow path according to some embodiments of the present invention. [Figure 12] FIG. 1 is a representation of a bypass mechanism according to some embodiments of the present invention. [Figure 13] 2 is a partial cross-sectional side view of a diffuser according to some embodiments of the present invention. [Figure 14] 1 is a representation of a flow path according to some embodiments of the present invention. [Figure 15A] FIG. 2 is a representation of a flow path using a sectional fan according to some embodiments of the present invention. [Figure 15B] FIG. 1 is a representation of a flow path using a split diffuser feeding a sectional fan according to some embodiments of the present invention. [Figure 15C] FIG. 2 is a representation of a flow path using a split diffuser according to some embodiments of the present invention. [Figure 16A] FIG. 4 illustrates a velocity distribution through a split diffuser according to some embodiments of the present invention. [Figure 16B] FIG. 4 illustrates pressure distribution through a split diffuser according to some embodiments of the present invention. [Figure 17A] FIG. 13 is an inhalation velocity diagram at 0% inhalation velocity ratio. [Figure 17B] FIG. 13 is a turbulence intensity diagram at 0% inlet velocity ratio. [Figure 18A] FIG. 1 is an inhalation velocity diagram at 10% inhalation velocity ratio. [Figure 18B] FIG. 11 is a diagram showing turbulence intensity at 10% inlet velocity ratio. [Figure 19A] FIG. 1 is an inhalation velocity diagram at 20% inhalation velocity ratio. [Figure 19B] FIG. 13 is a diagram showing turbulence intensity at 20% inlet velocity ratio. [Figure 20] 1 is a graph of energy loss versus volumetric flow ratio according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] An aircraft propulsion system can reduce drag on the rotor nacelle and on the aircraft as a whole. The drag reduction portion can include inducted air in the nacelle aft of the rotor. The inducted air can weaken or eliminate the turbulent boundary layer aft of the inducted air inlet. The inducted air can also be used in a thermal management subsystem that assists in cooling the electric motors used to power the aircraft. The thermal management subsystem can include a heat exchange from a cooling liquid inside the motor to the flowing air inducted from the air inlet. In some aspects, the inducted air is used exclusively for drag reduction. In some aspects, the inducted air is used for both drag reduction and cooling the aircraft motors.

[0006] In some aspects, the intake air is used to reduce drag on the aircraft, and the drag airflow is used to drive a fan coupled to a liquid pump that drives coolant through the motor, thereby eliminating or reducing the need for power to drive the thermal management subsystem of the motor. In some aspects, the intake air can be separated into separate airflow paths, with a portion of the intake air being routed through a thermal management subsystem and then through a heat exchanger to cool the liquid used to cool the motor. This same air routed through the heat exchanger can then also drive a fan coupled to the liquid pump, thus providing both convective cooling and driving the liquid flow in the motor cooling system. Another portion of the intake air can bypass the motor cooling system. The use of a bypass allows for an increased intake air volume, which allows for tuning the intake air volume to reduce drag on the aircraft.

[0007] As shown in FIGS. 1A-1B, 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 that is in thermal communication with the drive mechanism and air surrounding the system. The rotor includes a set of vanes 105 coupled to a hub 106 and defines a cowl 107. The nacelle 102 defines an outer surface 108 and a bore 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, a heat exchanger 121 (e.g., a radiator), and may include a flow actuator 113.

[0008] System 100 may optionally include a tilt mechanism 120 housed at least partially within the lumen of the nacelle, a power source 114, and any other suitable components. System 100 may function to reduce surface friction on at least a portion of an exterior surface of the aircraft. The system may manipulate airflow (e.g., external airflow, internal airflow, etc.) and convectively cool system components. The system may also or alternatively function to aspirate a boundary layer formed on the aircraft surface (e.g., at a location between a rotor and a nacelle of an aircraft propulsion system) and perform any other suitable function.

[0009] The aircraft propulsion system may be used with rotorcraft. The rotorcraft is preferably a tilt rotor aircraft having multiple aircraft propulsion systems (e.g., rotor assemblies, rotor systems, etc.) operable between forward and hovering configurations. However, the rotorcraft may alternatively be a fixed wing aircraft having one or more rotor assemblies, a helicopter having one or more rotor assemblies (e.g., at least one rotor assembly or aircraft propulsion system is substantially axially oriented to provide horizontal thrust), and / or any other suitable rotorcraft or rotor-propelled vehicle. The rotorcraft preferably includes an all-electric drivetrain (e.g., battery-powered electric motors) driving one or more rotor assemblies, but may additionally or alternatively include a hybrid drivetrain (e.g., electric-gasoline hybrid including an internal combustion generator), an internal combustion drivetrain (e.g., including a gas turbine engine, a turboprop engine, etc.), and any other suitable drivetrain.

[0010] The term "rotor" as used herein in connection with aircraft propulsion systems or otherwise may refer to a rotor, a propeller, and / or any other suitable rotary aerodynamic actuator. While a rotor may refer to a rotary aerodynamic actuator using an articulated or semi-rigid hub (e.g., the blades and the hub may be articulated, flexibly, rigidly, and / or otherwise), and a propeller may refer to a rotary aerodynamic actuator using a rigid hub (e.g., the blades and the hub may be articulated, flexibly, rigidly, and / or otherwise), as used herein, no such distinction is made or implied, and the use of "rotor" may refer to both configurations, and any other suitable configurations of articulated or rigid blades, and / or any other suitable configurations of blades and a central member or hub. Similarly, the use of "propeller" may refer to both configurations, and any other suitable configurations of articulated or rigid blades, and / or any other suitable configurations of blades and a central member or hub. Accordingly, a tiltrotor aircraft may be referred to as a tiltpropeller aircraft, a tiltprop aircraft, and / or otherwise referred to or described as appropriate.

[0011] As shown in Figures 1A and 1B, an 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 air surrounding the system. The rotor includes a set of vanes coupled to a hub. The nacelle defines an outer surface, a cavity, an inlet, a diffuser, and an outlet. In some aspects, the nacelle can have a first outlet for air traveling 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 subsystem can include a liquid cooling mechanism, a heat exchanger (e.g., a radiator), and can include a flow actuator.

[0012] System 100 may optionally include a tilt mechanism at least partially contained within the bore of the nacelle, a power source, and any other suitable components. The rotor functions to rotate within the fluid under power from the drive mechanism to provide thrust (e.g., to an aircraft to which the rotor is attached). The rotor includes a set of blades coupled to a hub and a cowl or spinner that at least partially surrounds the hub. The rotor may optionally include any suitable components that support and / or control the rotor surface (e.g., linkages and / or actuators that change the pitch of the blades, structural elements that hold the set of blades and / or hub, etc.).

[0013] The set of blades functions to transfer the rotational momentum of the rotor to the fluid, thereby providing axial momentum (e.g., providing thrust) to at least a portion of the fluid. The rotor can have any suitable number of blades, and the rotor preferably has five blades, but can alternatively have three blades, four blades, six blades, and any other suitable number of blades. The blades may be rigidly fixed to the hub, include variable pitch functionality (e.g., by suitable variable pitch linkages, cyclic pitch control, etc.), and / or connect to the hub or rotor head by one or more hinges (e.g., drag hinges, flap hinges, etc.) to allow the blades to lead, lag, and / or flap relative to the hub or rotor head under aerodynamic loads during rotation of the rotor. However, the blades may be otherwise suitably coupled to one another and / or otherwise suitably mechanically coupled to form at least a portion of the rotor. In a particular example, the rotor includes five variable pitch blades, but in alternative examples, the rotor may have any suitable number of blades having variable or fixed pitch.

[0014] The rotor blades are preferably unconstrained (e.g., by any kind of physical structure) at their blade tips, although the rotor may additionally or alternatively include a fairing surrounding the blade tips (e.g., a duct in a ducted fan, etc.). In such variations, the fairing may function to attenuate acoustic signature components (e.g., sound waves) emanating from the blade tips during rotation. However, the rotor blades may additionally or alternatively be constrained or unconstrained in any suitable manner.

[0015] The hub functions to interconnect the sets of blades and provide an area where the rotor couples to the drive mechanism and receives rotational force (e.g., shaft power) from the drive mechanism. In variations, the hub may define at least a portion of a rotating portion of the drive mechanism (e.g., a rotor of an electric motor including a rotor and a stator, a portion of a rotor of an electric motor, etc.). In further variations, the hub may be directly or indirectly coupled to an output shaft of the drive mechanism.

[0016] The cowl functions to define the forwardmost contact point between the rotor and the external fluid (e.g., ambient air), the surfaces that form the boundary layer during aircraft operation, and the wetted surfaces of the rotor separate from the wetted surfaces of the blade sets. The cowl also functions to define a bore that houses all or a portion of the propulsion system elements (e.g., drive mechanisms, thermal management subsystems, hubs, etc.).

[0017] The cowl is preferably shaped to minimize drag. In a variation, the cowl rotates with the rotor relative to the nacelle and is separated from the nacelle by a gap. The gap may define at least a portion of the inlet to the nacelle (e.g., an annular inlet, a segmented partial annulus, etc.). In an alternative variation, the cowl and / or a portion of the cowl may remain stationary relative to the nacelle during rotor operation (e.g., the cowl defines a slot through which the vane set rotates). The diameter of the cowl in the forward-projecting direction is preferably smaller than the diameter of the forward-most point of the nacelle in the forward-projecting direction (e.g., the point of the nacelle closest to the cowl). However, in an aircraft propulsion system variation, the diameter of the cowl may alternatively be larger than, substantially equal to, or otherwise appropriately sized to the diameter of the forward-most point of the nacelle in the forward-projecting direction.

[0018] The nacelle serves to house the aircraft propulsion system components and define the outer surface (e.g., wetted surface, exterior surface) of the portion of the aircraft propulsion system downstream from the rotor. The nacelle may also serve to intake external flow and decelerate the flow internally (e.g., via a diffuser) before exhausting the flow (e.g., via an outlet). The nacelle defines an outer surface and a bore and may include a drag reduction portion, which may define an inlet, diffuser, and / or outlet. The nacelle should be understood to include any structural portion of the airframe (e.g., nose, wings, tail, etc.) that is located near and structurally supports the drive mechanism and rotor, and any other suitable components of the aircraft propulsion system.

[0019] In a variant, the nacelle is a structural member distinct from the wing and / or tail to which it is attached (e.g., rigidly mounted, rotatably coupled via a tilting mechanism, etc.). In such a variant, the nacelle is preferably not configured as a lifting body, but may additionally or alternatively be configured to provide at least some lift to the aircraft during flight. In an alternative variant, the nacelle may be integral with the wing and / or tail to which it is attached. In such a variant, the nacelle may define lifting and / or control surfaces (e.g., act as part of the wing and / or tail). However, the nacelle may be otherwise suitably configured and / or positioned in relation to the aircraft.

[0020] The outer surface serves to separate the internal features and components of the nacelle from the external airflow. The outer surface may also serve to define at least a portion of the inlet and / or outlet. The outer surface may also serve to define the wetted surface of the aircraft propulsion system near the rotor (e.g., substantially all of the wetted surface, a majority of the wetted surface, etc.). The outer surface may also serve to define a shape 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, which may include defining a cross-section that minimizes static pressure recovery along the surface in the axial direction that may cause undesirable flow separation, accelerating the flow along a maximized downstream portion of the outer surface to promote stability of the laminar boundary layer (e.g., maintaining a negative pressure gradient directed along the outer surface direction), and / or any other suitable shape features configured to promote laminar flow along a maximum portion of the nacelle outer surface.

[0021] The lumen serves to define a volume that holds components of the aircraft propulsion system and / or other aircraft subsystems, which may include, in variants, at least a portion of the tilt mechanism, a power source, a power supply subsystem (e.g., power distribution cables, conduits, etc.), all or a portion of a mechanical actuator (e.g., that actuates a control surface of the aircraft), all or a portion of a drive mechanism, and any other suitable components.

[0022] The drag reduction portion functions to reduce drag on the aircraft propulsion system, and thus on the aircraft as a whole, during operation. The drag reduction portion is preferably configured to reduce drag during forward flight (e.g., operation of the aircraft in a forward configuration, operation of the aircraft propulsion system in a forward configuration, etc.), but may additionally or alternatively reduce drag during any suitable operational mode of the aircraft (e.g., hovering, vertical takeoff and / or landing, forward operation of the aircraft having at least a subset of the aircraft propulsion system of the aircraft between forward and hovering configurations, etc.). The drag reduction portion may include an inlet and an outlet. The drag reduction mechanism may optionally include a diffuser and / or a bypass.

[0023] In some aspects, the air vehicle can use a bladed propeller powered 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 air vehicle can rotate with the leading edge facing up, with the propeller providing vertical thrust for takeoff and landing. In some aspects, the motor-driven propeller unit on the wing can itself rotate relative to the fixed wing, with the propeller providing vertical thrust for takeoff and landing. Rotation of the motor-driven propeller unit can allow for thrust direction changes by rotating both the propeller and the electric motor, thus eliminating the need for gimbals or other methods for torque drive around or through the rotary coupling.

[0024] In some aspects, an air vehicle according to an embodiment of the present invention takes off from the ground with vertical thrust from the rotor assemblies deployed in a vertical configuration. As the air vehicle begins to gain altitude, the rotor assemblies can begin to tilt forward to begin forward acceleration. As the air vehicle gains forward speed, the airflow over the wings provides lift and the rotors are no longer needed to maintain altitude using vertical thrust. Once the air vehicle reaches sufficient forward speed, some or all of the blades used to provide vertical thrust during takeoff can be retracted along with the nacelle. In some aspects, all of the rotor assemblies used for vertical takeoff and landing are also used during forward flight. The nacelle supporting the rotor assemblies can have recesses that allow the blades to be stored in the recesses, significantly reducing drag on rotor assemblies that are not in use.

[0025] After takeoff, the air vehicle begins to transition to forward flight by tethering the rotors from a vertical thrust orientation to a position that includes a horizontal thrust element. As the air vehicle begins to move forward at high speeds, lift is generated by the wings, and therefore less vertical thrust from the rotors is needed. As the rotors are tethered further toward a forward flight, horizontal thrust configuration, the air vehicle gains greater speed.

[0026] The electric motor / propeller combination is outboard of the articulated joint, allowing the propeller to be rigidly mounted to the motor, which remains even as the propeller moves at various altitudes relative to the aft nacelle section. In such a configuration, the rotational force from the motor does not need to be gimbals or transmitted across the rotary joint. In some aspects, the deployment is entirely of the motor-driven rotor.

[0027] In a first vertical configuration according to some embodiments of the invention, as shown in the vertical takeoff configuration of FIG. 2A, an air vehicle 200 uses fixed wings 200, 203, which may be forward swept wings, with the same or different types of rotors adapted for both vertical takeoff and landing and forward flight. An aircraft body 201 supports a left wing 202 and a right wing 203. Motor-driven rotor assemblies 206, 207 on the wings include propellers, which may be retracted and stowed in the nacelle body. The aircraft body 201 is also attached to a rearward extending, raised aft stabilizer 204. The aft stabilizer has an aft rotor assembly 205 attached to the aft stabilizer. Although passenger seating for two is contemplated, different embodiments of the invention may accommodate other numbers of passengers.

[0028] In some aspects, all or a portion of the wing mounted rotors can be adapted for use in a forward flight configuration, while other wing mounted rotors can be adapted to be fully retracted during normal forward flight. The air vehicle 200 can have four rotors on the right wing 203 and four rotors on the left wing 202. The inner rotor assembly on each wing can have a wing mounted rotor 206 adapted to flip up to a deployed position for vertical takeoff and landing, return towards a retracted position during transition to forward flight, and then retract and stow the blades during forward flight. The outer rotor assembly 207 can pivot in unison from a horizontal thrust configuration to a vertical thrust configuration.

[0029] Similarly, each aft stabilizer 204 can have a rotor unit mounted thereto, both of which are adapted to be used during vertical takeoff and landing and transition modes. In some aspects, all of the rotor designs are the same, and a subset having forward flight main blades is used. In some aspects, all of the rotor designs are the same, and all rotors are used for forward flight. In some aspects, a different number of rotor units can be mounted on the aft stabilizer 204.

[0030] In some embodiments, the electric motors of the air vehicle are powered by rechargeable batteries. Using multiple batteries to drive one or more power buses improves reliability in the event of a single battery failure. In some embodiments, the batteries can be spread along the rotating section, with one battery for each of the motor / duct fan assemblies. In some embodiments, the battery or batteries can be partially or completely within the aircraft body, with power being sent to the motors through the rotating coupling. In some embodiments, the batteries are within the vehicle body, on a platform with an adjustable position, allowing the balance of the vehicle to be adjusted according to the weight of the pilot.

[0031] FIG. 2B shows air vehicle 200 in a forward flight configuration.

[0032] 3A shows in partial view a nacelle 303, which provides an aerodynamic cover for the support structure of a motor-driven rotor assembly according to some embodiments of the invention. A spinner or cowl 301 is mounted forward of rotor 302 (propeller not shown in this view). 3B is a view of the nacelle 303 showing the rotor and some other parts omitted for clarity. In some aspects, the nacelle can be a multi-route nacelle adapted to enable the forward portion of the nacelle to transition from a forward-facing horizontal configuration to a vertical take-off and landing configuration using an internally mounted deployment mechanism. In some aspects, the nacelle can be a wingtip-mounted nacelle adapted to transition between horizontal and vertical flight configurations by rotating about a central pivot hub.

[0033] The rotor 302 rotates around the inner stator. An air gap 304 between the outer surface of the rotor 302 and the nacelle 303 allows air to be taken inside the nacelle. In some embodiments, the outer periphery of the nacelle 302 also has air inlets that allow air to be delivered to the inner region of the rotor structure. In some embodiments, the outer rotor structure has an outer surface with a lattice-work inner support between the surfaces, allowing air to flow and to be used to cool the structure. Air flowing through the rotor structure exits the structure in a region adjacent to the incoming air through the air gap 304. These air flows are then available to flow to a heat exchanger that cools the liquid passing through the inner stator of the motor. In some embodiments, the outer rotor structure does not allow air to flow within the outer rotor structure. The air flow taken through the air gap 304 can act to reduce the drag of the air vehicle.

[0034] FIG. 3C is a view of the rear portion of the nacelle 303. The rear airflow outlet 305 allows incoming air that entered the nacelle through the gap 304 and the rotor structure to exit. In some aspects, the nacelle 303 can be a split nacelle with an internal deployment mechanism, which can split as the nacelle and motor-driven assembly transition from a forward flight configuration to a vertical take-off and landing configuration. After splitting the nacelle, the air exiting the motor area can exit through the gap that caused the split in the nacelle. In some aspects, the nacelle can be a solid nacelle, and the transition from a forward flight configuration to a vertical take-off and landing configuration involves the rotation of the entire nacelle about a fixed pivot. In some aspects, the air vehicle can have a combination of motor-driven rotor assemblies, some of which have split nacelles and some of which rotate about a fixed pivot. In some aspects, there may be one or more additional outlets, as described below.

[0035] 4A, 4B, 4C, 5A and 5B show rotor assembly 205 according to some embodiments of the present invention. In this exemplary embodiment, the propeller and cowl are coupled to rotating structure 302 and are forward of nacelle 303. Air can enter heat exchanger 319 at the forward region of nacelle 303 and the aft region of the rotor. In some aspects, the leading edge of nacelle 303 defines 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 heat exchanger 319 before exiting through airflow outlet 305. Blocking structure 402 at the aft end of the heat exchanger airflow openings prevents air from flowing further aft and past the heat exchanger into the nacelle. The blocking structure is shown in FIG. 4C with some elliptical openings, for example, these openings are expected to provide access for items such as electrical wires and are otherwise not open to airflow during use. Air enters the heat exchanger 319 and then inside the internal structure 404 in the nacelle. The airflow then exits from inside the internal structure 404 through ventilation holes 405 and then into the nacelle 303 and out the airflow outlet 305. The deployment mechanism 403 is adapted to pivot the rotor assembly from a forward flight configuration to a vertical take-off and landing configuration. A support structure 411 supports the heat exchanger and allows the airflow flowing through the heat exchanger to then enter the internal structure 404 of the nacelle.

[0036] 6A, 6B, 7A and 7B show an embodiment of rotor assembly 207 where airflow can flow through the heat exchanger and then out through main airflow outlet 501, or the flow can bypass and flow past the inlet of heat exchanger 319 and out through bypass outlet 505. FIG. 6C shows the rotor assembly without the outer nacelle surface for clarity. In this exemplary embodiment, airflow enters ring gap 304. A portion of the airflow can pass through the inlet to the heat exchanger and into the area behind the heat exchanger, where flow aft is blocked by bypass blocking structure 507. Bypass duct 506 fluidly couples to the area aft of the heat exchanger and forward of bypass blocking structure 507. The bypass duct allows the bypass flow to continue out bypass outlet 505.

[0037] The nacelle may be pivotable about pivot body 502 from a forward flight configuration to a vertical take-off and landing configuration.

[0038] The addition of bypass flow allows for more air to be ingested through the ring gap than may be used or required by the thermal management subsystem. This ability to allow for more airflow may allow users to tune the drag reduction portion to lower energy losses of the aircraft. As described below, in some aspects, the ratio of the volumetric flow rate of the ingested airflow to the volumetric flow rate of the boundary layer ahead of the inlet can be set to reduce drag. In some aspects, a bypass flow is utilized to allow for more airflow to be ingested.

[0039] Another portion of the airflow in the ring gap 304 can enter the heat exchanger 319 and exit from the interior of the inner nacelle structure 504. The inner nacelle structure 504 can have an air flow passage 508 adapted to allow air within the inner nacelle structure to exit from the interior of the inner nacelle structure and proceed inside the nacelle 503. In this case, the air within this region of the nacelle can continue to exit the nacelle through the main airflow outlet 501.

[0040] 8 is a diagram of the motor and propeller hub with some parts removed for clarity. Propeller hub 310 is mounted to rotor 302 and rotates simultaneously with the rotor. The propeller hub has propeller interface surfaces 311 spaced around the circumference of the propeller hub.

[0041] In some embodiments of the invention, aspects of a motor cooling system are shown as shown in the cutaway views of Figures 9A, 9B, and 9C. In some aspects, the cooling system can have an air cooling system through the rotor structure and a liquid cooling system in the stator structure. The liquid cooling system can use a heat exchanger that facilitates heat transfer from a liquid flowing through the vanes of the heat exchanger to an airflow. The airflow through the rotor structure can also partially cool the liquid after it exits the rotor structure and then enters the heat exchanger. Additionally, the cooling system can utilize a fan to facilitate additional airflow. In some aspects, there is no airflow through the rotor structure.

[0042] 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 magnets 312. In an exemplary embodiment, the rotor support structure 315 can have metal surfaces 360, 361 with an inner grid structure 364 adapted to structurally support mechanical loads applied to the rotor support structure while allowing air to flow through the structure to cool the structure. Air can enter the rotor support structure through gaps 362 in the surface 360. In some aspects, the air entry gap can be around the front of the periphery of the rotor support structure. Air flow through the rotor support structure can exit through the rear 363 of the structure.

[0043] The stator 342 may have structures adapted for internal flow, such as a section 314 under the stator winding rods 313. A fluid trapping cover 341, such as a fiberglass cylindrical section, may be around the outer periphery of the stator winding rods. The fluid trapping cover allows fluid to flow between the stator winding rods, allowing convection cooling of the stator winding rods and windings. Within the stator, fluid flow structures 316 pump and pump fluid from a fluid pump 317 to the stator winding rods. fluid flow It passes through structure 316 , forward through stator support structure 314 , back around stator winding rods 313 , under the fluid capture cover, and through heat exchanger 319 .

[0044] The airflow through the heat exchanger can be a combination of air exiting the rear of the rotor support structure 315 and other air taken in through the gap 304 between the exterior surface of the rotor 302 and the nacelle 303. In some aspects there is a solid rotor support structure and the airflow entering the heat exchanger does not travel through the rotor structure. After the fluid flows through the heat exchanger 319 it is pumped back through the fluid flow structure 316 to the fluid pump 317. An air fan 318 also facilitates the airflow through the heat exchanger 319. The air fan 318 can be coupled to the fan 318, as shown in an expanded view in FIG. 9A. 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 pull the air through the heat exchanger. In some aspects the same motor can drive both the air fan and the fluid pump. In some aspects, the captured air flowing through the heat exchanger can then drive a fan, which in turn drives a fluid pump.

[0045] 10A and 10B are photographs of an example portion of a rotor support structure according to some embodiments of the present invention. As shown in the side view of FIG. 12 and in FIGS. 10C and 10D, the rotor support structure has a top solid surface and a bottom solid surface with a latticework support structure therebetween. In some aspects, the rotor support structure can be a single piece constructed using metal 3D printing. As shown in FIG. 10D, a series of gaps in the periphery of the top solid surface allow airflow to enter the internal latticework. The airflow can then exit the rotor support structure's internal latticework via the rotor support structure's outer surface.

[0046] FIG. 11 illustrates the air and fluid flow through a liquid-cooled electric motor according to some embodiments of the present invention. FIG. 11 is a cutaway view with pump 317 and fan 318 in an exploded view position for clarity. In an exemplary embodiment, the fluid resides in the fluid flow structure 316, flows from the pump 317, and flows radially outward 334 in an outlet passage in the fluid flow structure 316, which may be part of or coupled to the stator support structure. Heat generating electrical components may be mounted on the forward side of the fluid flow structure, and the fluid in the fluid flow structure may cool these components. The fluid then flows 332 within the stator support structure 314 in an area adjacent to and radially inward from the winding rods and windings. The fluid then exits the interior of the stator support structure 314 at the front of the stator support structure, and is then routed radially through the winding rods 313 and windings to the rear 336 within the fluid capture cover. The fluid then flows 337 through a heat exchanger 319 where it is cooled by air flowing through the heat exchanger. Finally, the fluid flows 338 through a return passage in the fluid flow structure and into the pump 317.

[0047] Airflow through the motor enters through a path 331 through the rotor support structure 315. Some or all of the airflow exiting the rotor support structure may then enter the heat exchanger 319. Airflow also flows 330 around the exterior of the rotor and down 333 through the heat exchanger 319. Both the exterior airflow 330 and the interior airflow 331 may enter through the airflow gap 304. In the case of a solid rotor, the air does not flow through the rotor support structure. The air fan 318 may also draw air into and through the airflow system described above. In some aspects, the air fan may be used to draw in a significant amount of air and have a beneficial impact on aircraft aerodynamics. In some aspects, such as hover mode, the air fan may be the primary driver for the airflow through the heat exchanger. A relatively narrow gap between the motor and the nacelle is used to capture the boundary layer formed on the motor, which helps clean the boundary layer flow on the nacelle itself and promotes laminar flow on the nacelle, thus reducing drag. In some aspects, the nacelle is shaped to take advantage of this beneficial effect. In some embodiments, there is no airflow through the rotor structure. In such embodiments, all airflow entering the heat exchanger or bypass duct is the external airflow 330.

[0048] In one exemplary embodiment, the coolant pump can pump coolant in the range of 10-15 liters per minute, and the coolant can be a polyolefin coolant. The coolant temperature entering the heat exchanger can be about 85°C and leaving the heat exchanger at 70°C. This can be done by running the motor at 700 rpm while operating at 75.5 kW continuous steady power and 1030 Nm torque. The motor can reject 6.3 kW of heat in this scenario. The fan airflow can vary between 800-1500 cfm.

[0049] The flow conditioner 181 can be positioned at various locations relative to the bypass duct 183 and can be used to adjust or direct the flow or volume of the intake air. The intake air can enter the inlet 180 and a portion of the airflow can bypass the heat exchanger 184 and enter the bypass duct 183. The fan 182 can be used to increase the volume of airflow. In some embodiments, the flow conditioner can be used to change the ratio of the volume of flow entering the bypass duct. In some embodiments, the actuation system can move a mechanical flow director, such as a louver, which can change the volume of flow entering the bypass duct 183. In some embodiments, the flow conditioner can also change the total volume of air intake through the air inlet 180.

[0050] In some embodiments of the invention, as shown in FIG. 13, a multi-way diffuser 196 is used to slow the intake air 191 as it enters a bypass duct 195 in the system and the rotor rotates about axis 197. The multi-way diffuser 196 can be in the nacelle 194 in the forward region of the bypass duct 195, adjacent to the air inlet or behind the air inlet. In this exemplary embodiment, all of the intake air 191 from the flowing air 190 flows through the diffuser and enters the duct. In some aspects, a multi-way diffuser can be used in the intake air stream, which then splits between what enters the thermal control system and what enters the bypass. In some aspects, a multi-way diffuser can be used in the intake air stream, which is generally through the thermal control system.

[0051] Figure 14 shows the advantage of a multi-way diffuser over a single passage. In a single passage, the entrained air 260 can separate 261 from the inner surfaces of the passages as the passages expand in volume. In a multi-way diffuser, the air flows 270a, 270b, 270c pass through passages separated by diffuser layers 271a, 271b. The air 271a, 271b, 271c exiting the passages in a multi-way diffuser does not separate from the inner surfaces of the passages.

[0052] In one variant, the air flow path may flow into a sectional fan 180, as shown in FIG. 15A. The sectional fan 180 is preferably configured to correspond to a sectional diffuser of the nacelle, as shown in FIG. 15B, but may be configured otherwise as appropriate. In this variant, the sectional fan 180 may function to extract momentum from the flow in a first section 181 (e.g., an outer section of the concentric section) and to provide momentum to the flow in a second section 183 (e.g., an inner section of the concentric section). The sectional fan 180 may include a separator 182, such as a cylindrical separator. In an exemplary case, the ingested air 185a, 185b may proceed on different sides of a diffuser plate 189. The diffuser plate 189 may start outboard of the heat exchanger 188, in the forward region of the nacelle 186. The diffuser plate concentrically separates the flow into two air flow paths 185a, 185b. The diffuser plate provides a channelized airflow that continues through the heat exchanger and may enter the interior of the nacelle.

[0053] In some embodiments of the invention, as shown in FIG. 15C, the multi-way diffuser has multiple diffuser plates 189a, 189b, 189c, 189d, 189e, 189f, 189g. The diffuser plates can start in the forward region of the nacelle 186, outboard of the heat exchanger 188. The diffuser plates concentrically separate the flow into different air flow paths. The diffuser plates provide a channelized airflow that can continue through the heat exchanger and enter the interior of the nacelle. In some aspects, the diffuser plate structure also acts as a turning vane for the airflow. It is noted that the function of the channelized diffuser is to separate airflow regions with different total pressures. The function of the diffuser is to slow the flow inside the nacelle and increase the pressure of the flow.

[0054] The drag reduction portion preferably functions to reduce drag by promoting laminar flow over at least a portion of the outer surface of the nacelle, which is physically promoted by aspirating a boundary layer (e.g., a turbulent boundary layer) at a location between the rotor and the nacelle (e.g., where the boundary layer is most likely to be entirely turbulent downstream of the rotor due to physical structural separation between the rotor and the nacelle). After aspirating the internal airflow (e.g., via an inlet / gap), it is preferably expanded and decelerated (e.g., via a diffuser) such that skin friction between the internal airflow and the drag reduction features is reduced (e.g., proportional to the reduction in flow velocity). This can result in a net drag reduction along with the maintenance of laminar flow along the outer surface downstream of the inlet (and, e.g., a concomitant reduction in skin friction compared to turbulent flow). The drag reduction portion preferably also minimizes internal pressure losses (e.g., in a diffuser, in an associated heat exchanger, etc.). However, the drag reduction portion can additionally or alternatively reduce drag in any other suitable manner.

[0055] In variations, the drag reduction portion can operate between various modes including a full bypass mode, a partial bypass mode, and a non-bypass mode. In a full bypass mode, flow through the drag reduction portion is not driven through a heat exchanger of the thermal management subsystem (e.g., the flow bypasses the heat exchanger). In a non-bypass mode, the entirety of the flow through the drag reduction portion is driven through a heat exchanger of the thermal management subsystem. In a partial bypass mode, the bypass ratio (e.g., the percentage of flow through the drag reduction mechanism that bypasses the heat exchanger) is adjusted. The partial bypass mode can function to manage the possibility of pressure loss in the heat exchanger. This pressure loss can result from operating in a non-bypass mode at certain aircraft speeds, and in such cases, a partial bypass mode can be utilized to direct a fraction of the intake air between the inlet and outlet to prevent the air from passing through the heat exchanger and to prevent too much airflow from being fed to the heat exchanger (and, for example, to prevent pressure loss or other drag-inducing and / or efficiency-reducing losses). The bypass ratio can be adjusted passively (e.g., actuated by the flow field itself in response to flow velocity) and / or actively (e.g., adjusting the flow by adjustable flow actuators such as variable size openings, valves, etc.). The drag reduction portion preferably operates between operational modes such as bypass mechanisms such as louvers driven by electromechanical actuators that can redirect airflow through the drag reduction portion and / or away from the drag reduction mechanism as shown by example in FIG. 12. However, the drag reduction portion can also or alternatively be otherwise suitably transitioned between various operational modes and any other suitable operational modes.

[0056] In a variation, the drag reduction portion may be passively operated. In one example of this variation, the components of the drag reduction portion are preferably static (e.g., inlet size is fixed, diffuser shape and size is fixed, outlet size is fixed, etc.), and the airflow through the drag reduction portion may be determined by the speed of the system (e.g., the airspeed of the aircraft). In another example of this variation, the components of the drag reduction portion may be dynamically actuated by a flow field (e.g., the pressure of the flow field exerts a force on the outlet, increasing or decreasing the size of the outlet depending on the airspeed). However, the drag reduction portion may also or alternatively be passively actuated in any suitable manner and / or actively actuated (e.g., by an actuatable variable size outlet, etc.).

[0057] The inlet of the drag reduction section functions to intake airflow moving past the trailing edge of the rotor cowl. The inlet is preferably shaped to minimize and / or prevent flow separation to promote laminar flow on the nacelle outer surface downstream of the inlet. However, the inlet may be otherwise suitably shaped. The drag reduction section may be designed to tune the amount of intake air at the designed airspeed, thereby minimizing drag.

[0058] The inlet is preferably located proximate a separation region (e.g., a gap) between a rotating outer surface of the rotor system (e.g., the rotor) and a static outer surface of the rotor system (e.g., the outer surface of the nacelle). In particular, the inlet is preferably located proximate a location on the rotor system where the flow downstream of the rotor would stagnate in the absence of the inlet, and leverages a high pressure area resulting from the stagnation to drive airflow into the inlet (e.g., additionally or alternatively activating flow actuation, such as via a flow actuator, or a large negative pressure gradient between the outlet and 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 configuration.

[0059] The outlets function to reintroduce the internal airflow (e.g., from the diffuser) into the external free stream. The outlets can also function to restrict the flow rate through drag reduction mechanisms (e.g., passively via outlet shape, actively via actuation of outlet size, etc.). The outlets can be located at various locations relative to the outer surface of the nacelle. The outlets can be located on the outer surface, near the inlet, and upstream of the trailing edge or aft region of the nacelle. In an alternative variation, the outlets can be located at the trailing edge or aft region of the nacelle (e.g., immediately following the nacelle). The outlets can be an annular region (e.g., similar to the inlet), a segmented annular region, a region located proximal to the inlet, and / or have any other suitable geometric distribution or configuration relative to the shape of the nacelle to minimize the effect of spill through the outlet on the airflow downstream.

[0060] The outlet may be of fixed or variable geometry (e.g., cross-sectional size, diameter, shape, etc.). In variations in which the outlet is of variable size, the size may be varied manually (e.g., via a control linkage, via a manually adjustable mechanical aperture such as a throttle opening or other opening, via a fly-by-wire actuator, etc.) or automatically (e.g., via a closed loop controller, via a speed dependent variable throttle, etc.).

[0061] FIG. 16A is the velocity magnitude modeling output for the airflow velocity through the diffuser 289 as it enters the interior of the nacelle 286. The airflow flows past the outer surface of the rotor 291 and enters the gap between the rotor 291 and the nacelle 286. The diffuser 289 is a multi-way diffuser with multiple diffuser plates. As shown in FIG. 16A, the airflow velocity slows down in the diffuser through the nacelle. As can be seen from the pressure distribution modeling output in FIG. 16B, there is an increase in pressure just outside the diffuser, as well as throughout the diffuser and nacelle. As shown in FIG. 16B, the use of a multi-way diffuser with multiple diffuser plates separates the higher pressure into the axially aft passage, preventing air from recirculating in the overall flow path. At the aft end of the diffuser plate, the fan acts to equalize the pressure behind the fan by momentum transport as explained above. The pressure difference in the diffuser passage is a fraction of the external flow pressure. In some embodiments, the pressure difference in the diffuser passage is in the range of 5% to 100% of the external dynamic pressure. In some embodiments, the pressure difference in the diffuser passage is in the range of 10% to 50% of the external dynamic pressure.

[0062] A design parameter for designing and tuning the drag reduction portion of the system according to some embodiments of the invention is the volumetric flow ratio. The volumetric flow ratio is defined as the ratio of the volumetric flow rate of the entrained air to the volumetric flow rate of the boundary layer at the rear of the rotor and in front of the inlet. FIG. 20 shows energy loss 270 versus volumetric flow ratio 271. The horizontal axis 271 is set at the energy loss level seen in a baseline system with no entrained air intake. As shown, as air is entrained, the energy loss rises due to internal losses 272. As more air is entrained, a point is reached where the energy loss drops 273. This is due to the restoration of laminar flow on the outer surface of the nacelle as shown in FIG. 19A. A low energy loss point 274 is reached, which may represent less energy loss than the baseline system without entrained air intake. With even more air intake, the internal losses rise and the overall energy loss increases 275. In some aspects, the volumetric flow ratio is greater than 0.1. In some embodiments, the volumetric flow ratio is greater than 0.2. In some embodiments, the volumetric flow ratio is greater than 0.5. In some embodiments, the volumetric flow ratio is greater than 1.0. In some embodiments, the volumetric flow ratio is greater than 2.0.

[0063] A method for reducing energy losses in an aircraft may include inducting air into an aft region of a rotor, directing the air to a diffuser, and exhausting the air. The diffuser may direct all or a portion of the inlet air to a thermal management system. A bypass duct may be utilized to increase the volumetric flow rate of the inlet air.

[0064] 17A, 18A, and 19A show the turbulence intensity at 0%, 10%, and 20% inlet velocity ratios, respectively. Turbulence intensity is the ratio of the energy density of the flow to the turbulent energy fluctuations in the free stream. Lighter areas indicate more turbulence. The inlet velocity ratio represents the inlet velocity ratio of the free stream. At 0% inlet velocity ratio, as shown in FIG. 17A, there is not much of a turbulent boundary layer at the spinner 401. As the flow approaches the air gap entrance 402, turbulence begins. In this example, there is no inlet velocity at the air gap entrance 402. The turbulent layer 403 is only seen along the nacelle 404. At 10% inlet velocity ratio, as shown in FIG. 18A, there is not much of a turbulent boundary layer at the spinner 401. As the flow approaches the air gap entrance 402, turbulence begins. In this example, the inlet velocity ratio at the air gap entrance 402 is 10%. A thinning of the turbulent layer 405 is seen just after the air gap entrance 402, but along the nacelle 404. Later, the turbulent layer thickens downstream 406. At an inlet velocity ratio of 20%, as shown in FIG. 19A, there is not much of a turbulent boundary layer at the spinner 401. As the flow approaches the air gap entrance 402, turbulence begins. In this example, the inlet velocity ratio at the air gap entrance 402 is 20%. Although the turbulent layer 405 does not disappear, a significant thinning 407 is seen just after the air gap entrance 402, but along the nacelle 404. Then, the turbulent layer begins 408 and then thickens downstream 406.

[0065] Figures 17B, 18B and 19B show the velocities at inlet velocity ratios of 0%, 10% and 20%, respectively. These results show that the flow picture outside the nacelle does not change significantly with changing inlet velocity ratio.

[0066] In some embodiments, the aircraft may actively draw in air to increase the intake velocity at the air gap inlet. In some aspects, air may be actively drawn in to cool the electric motors, as described above. In some aspects, air may be actively drawn in regardless of whether the air is used specifically for motor cooling.

[0067] As shown, the flow quality over the nacelle changes dramatically between 10% intake and 20% intake. In some embodiments, the intake velocity ratio is greater than 10%. In some embodiments, the intake velocity ratio is greater than 15%. In some embodiments, the intake velocity ratio is greater than 20%.

[0068] As is apparent from the above description, a wide variety of embodiments can be constructed from the description set forth herein, and further advantages and modifications will readily occur to those skilled in the art. Thus, the invention in its broader aspects is not limited to the specific details illustrated and described by way of example. Accordingly, departures may be made from such details without departing from the spirit or scope of Applicant's general invention.

Claims

1. 1. A fluid cooled electric motor assembly, the motor assembly comprising: An outer rotor, the outer rotor comprising: a rotor support structure coupled to an outer race of the main bearing; a plurality of magnets coupled to an interior surface of the rotor support structure; an outer rotor comprising: An inner stator, the inner stator comprising: a stator support structure including a fluid flow passage radially inward relative to the plurality of winding bars; a plurality of winding bars coupled to the stator support structure; a fluid capture cover around an outer peripheral surface of the plurality of wire rods; an inner stator comprising: A cooling fluid; one or more heat exchangers fluidly coupled to the fluid flow path; Fluid pump and 1. A fluid cooled electric motor assembly comprising:

2. The rotor support structure includes: an outer solid surface; an inner solid surface; a support grid between said outer solid surface and said inner solid surface; 10. The fluid cooled electric motor assembly of claim 1 comprising:

3. The fluid-cooled electric motor assembly of claim 1 , wherein the one or more heat exchangers comprise one or more annular ring heat exchangers.

4. 4. The fluid-cooled electric motor assembly of claim 3, further comprising an air intake fan, said air intake fan adapted to draw air into said one or more annular ring heat exchangers from a radially outer region of said one or more annular ring heat exchangers to a radially inner region of said one or more annular ring heat exchangers.

5. 5. The fluid cooled electric motor assembly of claim 4, wherein said fluid pump is rotationally coupled to said air intake fan.

6. The fluid-cooled electric motor assembly of claim 1 further comprising a drive motor for said fluid pump.

7. The fluid cooled electric motor assembly of claim 3 further comprising a drive motor for said fluid pump.

8. 5. The fluid cooled electric motor assembly of claim 4, further comprising a drive motor rotatably coupled to said air intake fan.

9. 6. The fluid cooled electric motor assembly of claim 5, further comprising a drive motor rotatably coupled to said air intake fan.

10. 1. An aircraft vehicle comprising a plurality of electric motor driven rotor assemblies, the electric motor driven rotor assemblies comprising: An outer rotor, the outer rotor comprising: a rotor support structure coupled to an outer race of the main bearing; a plurality of magnets coupled to an interior surface of the rotor support structure; an outer rotor comprising: An inner stator, the inner stator comprising: a stator support structure radially inward from the plurality of winding bars and including a fluid flow passage; a plurality of winding bars coupled to the stator support structure; a fluid capture cover around an outer peripheral surface of the plurality of wire rods; an inner stator comprising: A cooling fluid; one or more heat exchangers fluidly coupled to the fluid flow path; Fluid pump and An aircraft vehicle comprising:

11. 11. The air vehicle of claim 10, further comprising a nacelle structure coupled to the electric motor driven rotor assembly, the nacelle structure defining an outer surface, a forward edge of the outer surface defining an air gap behind the outer rotor.

12. 11. The air vehicle of claim 10, wherein the one or more heat exchangers comprise one or more annular ring heat exchangers.

13. 12. The air vehicle of claim 11, wherein the one or more heat exchangers comprise one or more annular ring heat exchangers.

14. The air vehicle of claim 11 , wherein an outer surface of the one or more annular ring heat exchangers is fluidly coupled to the air gap.

15. The air vehicle of claim 13 , wherein an outer surface of the one or more annular ring heat exchangers is fluidly coupled to the air gap.

16. 15. The air vehicle of claim 14, further comprising an air intake fan, the air intake fan adapted to draw air into the one or more annular ring heat exchangers from a radially outer region of the one or more annular ring heat exchangers to a radially inner region of the one or more annular ring heat exchangers.

17. The rotor support structure includes: an outer solid surface; an inner solid surface; a support grid between said outer solid surface and said inner solid surface; The aviation vehicle of claim 10 .

18. The rotor support structure includes: an outer solid surface; an inner solid surface; a support grid between said outer solid surface and said inner solid surface; 17. The aviation vehicle of claim 16, comprising:

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