Adaptive vertical take-off and landing propulsion system

Abstract

To provide a propulsion system which is efficient in both vertical take-off and landing (VTOL) and hover phases of a VTOL aircraft as well as cruise conditions.SOLUTION: A propulsion system for an aircraft includes a plenum having an intake port and an output port. A fan is coupled to a motor configured to power the fan, and the powered fan is configured to compress ambient air entering the intake port. One or more ejectors are fluidically coupled to the plenum via one or more valves. A nozzle is disposed within the output port and includes a set of vanes. The system operates in a first configuration in which the nozzle vanes are closed and the compressed ambient air exits the plenum only through the one or more valves into the one or more ejectors. The system operates in a second configuration in which the one or more valves are closed; the nozzle vanes are open; and the compressed ambient air exits the plenum only through the output port.SELECTED DRAWING: Figure 1

Description

Copyright Notice

[0001]

[0001] This disclosure is protected under U.S. and international copyright laws. (c) 2019 Jetoptera. All rights reserved. ((c) denotes a copyright symbol). A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the exact facsimile reproduction by any party of the patent document or the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. Priority Claim

[0002]

[0002] This application claims priority to U.S. Provisional Application No. 62 / 758,441, filed November 9, 2018, U.S. Provisional Application No. 62 / 817,448, filed March 12, 2019, and U.S. Provisional Application No. 62 / 839,541, filed April 26, 2019, the entire disclosures of which are incorporated by reference herein as if fully set forth herein. [Background technology]

[0003]

[0003] One of the main challenges in designing a vertical take-off and landing (VTOL) aircraft is sizing the propulsion system to be efficient in both VTOL and hovering phases as well as in cruise. Since the propulsion system must be kept as a low percentage of the total weight to maximize payload and fuel reserve, the challenge is how to employ a system that produces approximately 4 to 6 times more thrust during take-off (lift-by-thrust-only mode) or hovering compared to wing-borne and cruise conditions. In the first case, thrust is balanced against the weight of the aircraft, and much larger engines and power or thrust are required, while in cruise conditions, the aircraft's wings are balanced against the weight, and the engines must be sized much smaller to balance the drag.

[0004]

[0004] Traditionally, VTOL has been achieved with either separate systems (lift / cruise, which separates thrust at the expense of weight) or pure rotorcraft such as helicopters (which compromise fixed-wing capabilities). Most successful aircraft employing VTOL capabilities use the same systems for both the vertical and fixed-wing stages. Examples include vertical takeoff and landing jets such as the Harrier Hawker, which orients turbofan jets (but ultimately oversizes the engines for the fixed-wing stage mission), and the V22 Osprey, which utilizes turboprops with tilt capabilities. The tiltrotor approach is not without risks such as vibration, vortex ring conditions (VRS), and large footprints, as well as complex architectures.

[0005]

[0005] For smaller systems (i.e., 2-4 passenger aircraft), large lift+cruise aircraft are the dominant design, especially in the growing urban air mobility market. Especially for electric VTOLs, efficiency reasons lead to 8-16 large inter-rotor moving parts and a very large footprint. A wingspan to carry 4-6 passengers can be as large as that of a small regional aircraft. The weight of today's aircraft with low energy density batteries also imposes complex maneuvers with large wings and multi-rotors, increasing risk.

[0006]

[0006] Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings: [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 shows an oblique perspective view of an embodiment of a VTOL configuration. [Diagram 2]

[0008] FIG. 1 is a perspective view of a cruise configuration with FPS system elements used as air brakes for transition to VTOL, according to one embodiment. [Diagram 3]

[0009] FIG. 1 illustrates a perspective view of a variable vane in a VTOL configuration according to one embodiment. [Figure 4]

[0010] FIG. 1 illustrates a perspective view of a variable vane in a full cruise configuration with FPS system elements extended for air braking, according to one embodiment. [Diagram 5]

[0011] 1 illustrates a perspective view of the FPS system elements at 45 degrees and an intermediate transition from a VTOL configuration to a fixed-wing configuration while the aircraft is accelerating solely through the FPS system elements, according to one embodiment. [Figure 6]

[0012] FIG. 2 illustrates a perspective view of system elements in a cruise configuration according to one embodiment. [Figure 7]

[0013] 13 illustrates an alternative embodiment of the present invention that uses wing-integrated FPS system elements that allow for concealment of the augmentation device during forward flight. [Figure 8] 13 illustrates an alternative embodiment of the present invention that uses wing-integrated FPS system elements that allow for concealment of the augmentation device during forward flight. [Figure 9]

[0014] 1 is a cross-sectional view of an ejector according to an embodiment of the present invention, illustrating the top half of the ejector and the velocity and temperature profiles within the internal flow. Detailed Description

[0008]

[0015] This patent application is intended to describe one or more embodiments of the present invention. It is understood that the use of absolute terms such as "must" and "will" and specific quantities should be interpreted as applicable to one or more of such embodiments, but not necessarily to all such embodiments. Thus, an embodiment of the present invention may omit or include modifications of one or more features or functionality described in the context of such absolute terms.

[0009]

[0016] A Fluid Propulsion System (FPS) according to one embodiment introduces an alternative approach whereby rotorless thrusters can be tilted to transition from hover to cruise. Pressurized fluid can be used as a source to obtain thrust augmentation during VTOL and hover. One or more embodiments may include a system used in all phases of flight (vertical and fixed wing phases) while still obtaining forward thrust augmentation.

[0010]

[0017] One embodiment includes a lift+cruise solution with a source of compression of air-bearing fluid, such as a fan or compressor, and dual capability to switch from augmented thrust in vertical flight (VTOL+hover) to a separate turbofan configuration in cruise. Such a configuration and operation removes speed limitations, allowing VTOL vehicles to move forward at very high speeds, have higher altitude capabilities, and operate very efficiently with significantly reduced fuel burn (specific fuel consumption).

[0011]

[0018] More descriptively, a fan or compressor or similar machine receives mechanical work and compresses the ambient air to a pressure ratio of 1.5 to 2.5. This component may have one or several stages and may be driven by a gas turbine stage, preferably a free turbine of a turboshaft engine, without the need for reduction gears. This element is optionally advantageous because it may employ a lighter and simpler construction due to the reduction in weight and moving parts.

[0012]

[0019] Referring to FIG. 1, shaft 11 receives mechanical power from an electric motor or turboshaft free turbine and transmits the power to fan 21 to compress the air to the pressure ratios mentioned above. Air is pumped to plenum 12 immediately downstream of fan 21, from where it can be directed to side ports 13 and 14 or axially downstream through a nozzle having variable vanes 16. Vanes 16 can be fully closed or fully open by mechanisms known in the art. For example, one such mechanism can be variable guide vanes employed in typical compressors. Another mechanism can be a machine screw that rotates the hub of vane 16 to force the vane closed. When closed as seen in FIG. 1 and FIG. 3, all flow from fan 21 is forced to flow to side ports 13 and 14 of plenum 12 and through valve 15 to FPS system elements 17, 18 fluidly connected to plenum 12.

[0013]

[0020] In one embodiment, the fan 21 receives power, for example 1000 kW, from the free turbine of a turboshaft type gas turbine rotating at, for example, 25,000 RPM, which is typical of a machine of a typical turboprop architecture, before reduction gearing, at full speed. Such power and speed can produce a compressed air flow of, for example, 1.8 atmospheres (pressure ratio 1.8 or about 180 kPa) and a flow rate of about 15 kg / s, assuming an efficiency of 80% on the part of the fan.

[0014]

[0021] The fan 21 itself may be manufactured from ultra-lightweight materials such as titanium or composites, the former using wide-chord composite swept fan blades for greater efficiency and manufactured in one piece as a blisk, including designs with low noise characteristics.

[0015]

[0022] Assuming a total pressure of 15 kg / sec, 180-200 kPa, and an air temperature of 353 Kelvin, the flow 22 is split and delivered to FPS elements 17, 18 embedded within the aircraft fuselage. The FPS elements 17, 18 are described in more detail as ejectors in, for example, U.S. Patent Application No. 15 / 221,389, filed July 27, 2016, and U.S. Patent Application No. 15 / 256,178, filed September 2, 2016, which are incorporated by reference as if fully set forth herein, and which can augment thrust that would otherwise be produced by simply accelerating and expanding the flow relative to atmospheric pressure to at least a 2:1 ratio, and up to a 3:1 ratio. In this example, the thrust achieved by ejector augmentation is given by Equation 1 below:

[0023]

number

[0024] This is in contrast to 5.65 kN thrust when using a simple nozzle, where 287 J / kg-K is the air constant, 1.4 is the air exponent factor, 353 K is the discharge temperature from the fan 21 compression, 2 is the boost ratio, and 15 kg / s is the total mass flow rate.

[0016]

[0025] With further optimization of the FPS elements 17, 18, the total thrust can reach a boost ratio of 2.5, i.e. 14.122 kN, for the same amount of mechanical input power of 1000 kW provided to the fan 21.

[0017]

[0026] FIG. 9 illustrates a cross-section of the upper half of the ejector 200, the structure and function of which are similar or identical to those of elements 17, 18. The plenum 211 is supplied with air (i.e., pressurized motive gas flow) hotter than the ambient, for example, from a combustion-based engine that may be employed by the vehicle. This pressurized motive gas flow is indicated by arrow 600 and is introduced into the interior of the ejector 200 through at least one conduit, such as the primary nozzle 203. More specifically, the primary nozzle 203 is configured to accelerate the motive fluid flow 600 as a wall jet directly on the convex Coanda surface 204 to a variable predetermined desired velocity. Additionally, the primary nozzle 203 provides an adjustable volume of the fluid flow 600. This wall jet then serves to entrain a secondary fluid, such as ambient air, indicated by arrow 1, through the intake structure 206, which may be approaching the ejector 200 from the direction indicated by arrow 1 with a non-zero velocity or may be stationary. In various embodiments, the nozzles 203 may be arranged in an array, as well as in a curved, spiral, and / or zigzag orientation.

[0018]

[0027] The mixture of flow 600 and air 1 may move completely axially at the throat section 225 of the ejector 200. As the mixing and smoothing process continues due to diffusion in a diffusing structure such as the diffuser 210, the temperature (800) and velocity (700) profile in the axial direction of the ejector 200 no longer has the highs and lows present at the throat section 225, but becomes more uniform at the end 100 of the diffuser 210. As the mixture of flow 600 and air 1 approaches the exit face of the end 100, the temperature and velocity profile becomes nearly uniform. In particular, the mixture is at a low enough temperature to be directed towards an airfoil such as a wing or control surface.

[0019]

[0028] When the vanes 16 are closed and the fan 21 provides this power, sufficient thrust can be obtained from such a system to be able to lift an aircraft weighing, for example, 1100-1400 kg. This type of aircraft can direct the thrust provided by the fan 21 through the ports 13 and 14 upwards via the pivoting FPS elements 17, 18, which can also rotate about their main axis through the pivoting joint 23. The pivoting or orientation of the FPS elements 17, 18 can change the attitude of the aircraft, firstly during vertical takeoff, then during hovering by small angle changes, and finally during the transition to fixed wing operation by pivoting the FPS elements, to direct the thrust from 45 degrees (as shown in FIG. 5) up to 90 degrees perpendicular to the initial VTOL position shown in FIG. 1.

[0020]

[0029] The angle of the pivot joint 23, which also allows the flow to pass to the elements 17, 18, can be gradually changed to allow perfect balance of the aircraft from a hovering state to increasing the lift of the aircraft's wings at a forward speed, for example 10% greater than the aircraft's stall speed. For example, an aircraft according to one embodiment of a VTOL aircraft can reach a speed of 50 miles per hour within a few tens of seconds of hovering at a fixed point while still balancing part of its weight with the FPS 17, 18 pointing 45 degrees upwards relative to the flight direction, and still accelerating in a forward direction as the wings begin to support, for example, 50% of the weight of the aircraft flying forward. At this point, while the aircraft is still accelerating rapidly to 100 miles per hour, the FPS elements 17, 18 have moved to a completely horizontal position (90 degrees or more perpendicular to the initial VTOL position) and the balance between drag and thrust is achieved simply using the FPS system (i.e., all the air 22 is sent through ports 13 and 14 to supply the motive fluid to the FPS elements). As the forward air speed approaches, for example, 150 miles per hour, the vanes 16 begin to open, forcing the airflow 22 past the vanes, propelling the aircraft forward faster. During the transition to full fixed-wing operation, the FPS boost ratio decreases due to the increased ram drag imposed by the air entering the FPS elements 17, 18. The final thrust available in fixed-wing operation can be increased by switching the vanes 16 to a fully open state, closing the valve 15 to block the air supply to ports 13 and 14, and forcing the entirety of the air 22 out of the plenum 12 through the vanes 16 to generate an accelerating flow 25, propelling the aircraft in a fixed-wing mode and in a forward direction, at a speed adjustable by the RPM of the fan 21.

[0021]

[0030] Thus, the embodiment solves the problem of mismatch between separate takeoff and cruise power plants by using the same power plant to provide mechanical work to the fan 21 via the shaft 11. In addition, the reduction in fuel flow to the main gas turbine providing the mechanical power slows the fan 21, similar to turbofan operation. At the end of the transition and during full fixed wing high speed flight, by cutting off the air to the FPS elements 17, 18, the slowing of the fan due to the reduction in mechanical work will lead to fuel savings and allow a much wider flight envelope in altitude, speed, and maneuverability since the aircraft will require significantly less thrust for forward movement. For example, 30% of the thrust required for a VTOL using the FPS elements 17, 18 can be provided by using the nozzle vanes 16 for high speed cruise while operating the fan 21 at a speed lower than the maximum speed. This means adjusting the thrust calculated with a boost ratio of 1.0 according to Equation 2:

[0031]

number

[0032] The above is when the aircraft is in full fixed wing mode. A typical general aviation aircraft achieving such thrust will have no problem accelerating to high altitudes and speeds in excess of 400 miles per hour. Conversely, the transition from cruise to hovering as illustrated in FIG. 6 can be accomplished by closing vanes 16, forcing air through ports 13 and 14 to initiate FPS operation (open) and reversing the pivoting motion of FPS elements 17, 18 from a nearly horizontal, recessed position in the aircraft fuselage to a nearly vertical position for hovering or landing. By rotating FPS elements 17, 18, they can also be used as air brakes to gradually reduce the lift generated by the wings and slow the aircraft to a point where elements 17, 18 provide the majority of the balance for the aircraft's weight. Once the aircraft has sufficiently slowed down and is nearly stationary in hovering mode, the thrust can be reduced by modulating fan 21 (now operating with vane system 16 fully closed and ports 13 and 14 fully open) until the aircraft lands.

[0022]

[0033] Such a system has the following advantages:

[0034] There are no moving parts for the FPS elements 17, 18 other than the pivoting of the elements to aid in a smooth transition from vertical to cruise (fixed wing) operation.

[0035] Complexity is minimized.

[0036] The low discharge temperature of the air from the fan 21 having a mode 1.8 pressure ratio allows the use of cooler, lighter weight materials for the FPS elements 17,18, such as high temperature plastic composites.

[0037] Maintenance becomes much easier to accomplish.

[0038] Higher speeds can be achieved during cruise by switching to fan-type operation.

[0039] Gas turbines can be replaced with electric motors for use with high energy density batteries.

[0040] By using a highly efficient system and the same size turboshaft turbine, costs and weight can be minimized.

[0023]

[0041] One embodiment of the aircraft 40 may be further improved by incorporating the FPS system into aerodynamic control surfaces such as airfoils to reduce drag during high speed flight. Such an embodiment is illustrated in Figures 7 and 8. In Figure 7, propulsion elements 30, 31, similar in functionality to those of elements 17, 18, rotate into a horizontal configuration to match the profile of the aircraft's main wing 41. In this configuration, thrust is generated only through the turbofan nozzle 16, and valve 15 is closed to prevent airflow through the FPS elements 30 and 31. As illustrated in Figure 8, the FPS propulsion elements 30, 31 and associated surfaces 32-37 rotate relative to the wing 41 to generate thrust upward for hovering and VTOL. In this configuration, the variable nozzle vanes 16 are closed and all airflow is directed through the FPS elements 30 and 31.

[0024]

[0042] Figure 7 illustrates the geometry of this alternative embodiment. Compressed air is directed from the main plenum 12 to wall jets (not shown) in the devices 30, 31. These wall jets entrain ambient air at a high bypass ratio through slot-shaped peripheries across the trailing faces 32, 33. The faces 32 and 33 are partially bounded by side walls 34a, 34b, 35a, 35b. The side walls taper toward the trailing edges 36 and 37 of the airfoils.

[0025]

[0043] In FIG. 7, the surfaces 32, 33 serve to generate more lift (lift augmentation) at angles shallower than 45 degrees to the horizontal (flight direction). In this case, at the speed of interest, the suction side of the surfaces 32, 33 looking at the flow coming out of the elements 30 and 31 will experience a greater local velocity compared to the speed of the aircraft 40. In this case, the additional lift generated by the pressure difference between the suction side and the pressure side of the surfaces 32, 33 just before switching to the turbofan nozzle jet method will generate more lift, according to the conditions determined by Bernoulli, as known in the art. The moment of switching from using the elements 30 and 31 for propulsion during VTOL, acceleration, and ascent of the vehicle to guiding compressed air through the nozzle vanes 16 is expected to coincide with the best conditions for the aircraft to move at the fastest safe speed, with good coordination between the valve 15 that switches and the attitude of the aircraft 40. Switching to using compressed air as the motive / primary air for the thrusters (elements 30 and 31) with entrainment into the direct jet by expansion through the nozzle vanes 16 at high speeds would coincide with the point at which elements 30 and 31 would generate excessively large ram drag from the entrained air in order to produce as much net force as possible to further accelerate the aircraft 40. For example, a vehicle employing this system may accelerate to a speed in the range of 150-200 miles per hour to reach steady state flight, but this switch is necessary for the vehicle to accelerate to 400 miles per hour. Thus, the vehicle may experience an increase in speed and increased fuel consumption because elements 30 and 31 are no longer employed and no longer produce sufficient net force for acceleration. At this point, the entrainment of air mass by these elements, and therefore the thrust augmentation, may be below an acceptable level, and switching to using compressed air flow from expansion through the nozzle vanes 16 would allow further acceleration. At this point, the thrusters 30, 31 can be aligned with a streamlined profile that reduces drag and ram drag present during operation, which in turn is useful for slowing down and flying economically at lower speeds but with greater efficiency in the low speed regime.Such a system would provide the fastest possible commercial or military applications with VTOL capability.

[0026]

[0044] Switching from thruster (fluid) entrainment mode to fan mode results in optimized thermal and propulsive efficiencies between the two regimes. In regimes below about 125 mph, high thermal and better propulsive efficiency are obtained using fluid (thrust augmentation) entrained with ambient air, even though the entrainment increases ram drag. The entrainment rate can be, for example, greater than 10, and the velocity appearing in the mixture of compressed air and entrained air can reach 105 m / s (235 mph). Since entrainment decreases and ram increases with speed, above 125 mph, a switch is made to use the entire primary air as a direct jet. Thus, the thermal efficiencies increase at different rates, and the overall high total efficiency is obtained as the product of the propulsive efficiency and the thermal efficiency.

[0027]

[0045] One or more embodiments of the invention may include the following features:

[0046] A propulsion system suitable for VTOL capable of transferring aircraft thrust from vertical flight to fixed wing flight, comprising a fan or compressor and a plenum communicating with a set of vanes which may be fully opened or closed, and having at least one other opening which may be fully opened or closed to channel said fan discharge air from the fan to a secondary thrust augmentation system.

[0047] A secondary thrust augmentation system producing an augmentation of 1.25 to 3.

[0048] A system in which a fan creates a pressure ratio of 1.1 to 3.0 within the plenum.

[0049] A system that allows additional opening ports to be opened or closed.

[0050] A system in which the secondary thrust system can be rotated from a fully vertical position to a fully horizontal position and, in addition, can be stored or embedded in the fuselage in a simplified manner.

[0051] A system with a movable vane system that can rotate, accelerate the air up to forward cruising speed, or close completely and feed into an augmentation system.

[0052] An aircraft using a system that can employ a gas turbine as mechanical work input to the fan.

[0053] An aircraft using a system in which an electric motor can be employed as the drive for the fan.

[0054] An aircraft using a system that can employ a hybrid system as a fan drive.

[0055] An aircraft employing multiple systems in which the secondary thrust system swivels to minimize drag and becomes inactive while the fan air is directed entirely through a single propulsive nozzle.

[0028]

[0056] Although the preceding text describes detailed descriptions of many different embodiments, it should be understood that the scope of protection is defined by the language of the following claims. The detailed description should be construed as exemplary only and does not describe all possible embodiments, as describing all possible embodiments would be impractical, if not impossible. Many alternative embodiments could be implemented using either current technology or technology developed after the filing date of this patent, and still fall within the scope of the claims.

[0029]

[0057] Thus, many modifications and variations may be made to the techniques and structures described and illustrated herein without departing from the spirit and scope of the claims. Accordingly, it is to be understood that the methods and apparatus described herein are illustrative only and are not limiting on the scope of the claims.

Claims

1. 1. A propulsion system for an aircraft, comprising: a plenum having an intake port and an output port; a fan coupled to a motor configured to power the fan, wherein the powered fan is configured to compress ambient air entering the intake port; one or more ejectors fluidly coupled to the plenum via one or more valves; a nozzle disposed within the output port, the nozzle comprising a set of vanes; Equipped with the system operates in a first configuration in which nozzle vanes are closed and the compressed ambient air exits the plenum through only the one or more valves to the one or more ejectors; the system operates in a second configuration in which the one or more valves are closed, the nozzle vanes are open, and the compressed ambient air exits the plenum only through the output port. system.

2. The system of claim 1 , wherein the ejector is rotatable relative to the plenum through an angle of at least 90 degrees.

3. The one or more ejectors include: A convex surface, a diffusing structure coupled to the convex surface; at least one conduit coupled to the convex surface and configured to introduce a primary fluid produced by the vehicle to the convex surface; an intake structure coupled to the convex surface and configured to introduce a secondary fluid accessible to the vehicle into the diffusing structure, wherein the diffusing structure includes a terminal portion configured to provide an exit from the system for the introduced primary and secondary fluids. The system of claim 1 , comprising:

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