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 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 of either 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 herein by reference 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 during both the VTOL and hovering phases, as well as during cruise. Because the propulsion system must maintain a low percentage of total weight to maximize payload and fuel reserve, the challenge is to employ a system that generates approximately four to six times more thrust during takeoff (lift-by-thrust-only mode) or hovering than during wing-borne and cruise. In the first case, thrust is balanced against the aircraft's weight, requiring much larger engines and power or thrust. However, during cruise, the aircraft's wings counterbalance the weight, necessitating much smaller engine size to counterbalance drag.

[0004]

[0004] Traditionally, VTOL has been achieved either with separate systems (lift / cruise, which separates thrust at the expense of weight) or with pure rotorcraft like helicopters (which compromise fixed-wing capabilities). The most successful aircraft employing VTOL capabilities use the same system for both the vertical and fixed-wing stages. Examples include vertical takeoff and landing jets like the Harrier Hawker, which orients turbofan jets (but ultimately oversizes the engines for fixed-wing stage missions), and the V-22 Osprey, which utilizes a turboprop with tilt capability. The tiltrotor approach is not without risks, such as vibration, vortex ring conditions (VRS), and a large footprint and complex architecture.

[0005]

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

[0007] [Figure 1]

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

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

[0009] FIG. 1 illustrates a perspective view of variable vanes 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 the FPS system elements extended for air braking, according to one embodiment. [Figure 5]

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

[0012] FIG. 1 illustrates a perspective view of system elements in a cruise configuration according to one embodiment. [Figure 7]

[0013] 10 illustrates an alternative embodiment of the present invention that uses wing-integrated FPS system elements that allow for concealment of the thrust augmenter during forward flight. [Figure 8] 10 illustrates an alternative embodiment of the present invention that uses wing-integrated FPS system elements that allow for concealment of the thrust augmenter 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. As such, embodiments 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 that allows for the tilting of rotorless thrusters to transition from hover to cruise. Pressurized fluid can be used as a source to provide thrust augmentation during VTOL and hover. One or more embodiments may include a system used in all phases of flight (vertical and fixed-wing) while still providing forward thrust augmentation.

[0010]

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

[0011]

[0018] More descriptively, a fan or compressor or similar machine receives mechanical work and compresses ambient air to a pressure ratio of 1.5 to 2.5. This component may have one or several stages and may be driven without the need for reduction gearing, preferably by a gas turbine stage such as the free turbine of a turboshaft engine. This element is optionally advantageous because it can employ a lighter, simpler structure due to the reduced 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 that power to fan 21, which compresses the air to the pressure ratios described above. Air is pumped into plenum 12, immediately downstream of fan 21, from which it can be directed to side ports 13 and 14 or axially downstream through a nozzle with variable vanes 16. Vanes 16 can be fully closed or fully open by mechanisms known in the art. For example, one such mechanism could be variable guide vanes, as employed in typical compressors. Another mechanism could be a machine screw that rotates the hub of vane 16, forcing the vanes closed. When closed, as seen in FIGS. 1 and 3 , all flow from fan 21 is forced to flow through side ports 13 and 14 of plenum 12 and, via valve 15, to FPS system elements 17 and 18 fluidly connected to plenum 12.

[0013]

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

[0014]

[0021] The fan 21 itself can be made 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 flow rate of 15 kg / s, a total pressure of 180-200 kPa, and an air temperature of 353 Kelvin, flow 22 is split and delivered to FPS elements 17, 18 embedded within the aircraft fuselage. FPS elements 17, 18 are described in more detail as ejectors, for example, in U.S. Patent Application Nos. 15 / 221,389, filed July 27, 2016, and 15 / 256,178, filed September 2, 2016, which are incorporated by reference as if fully set forth herein, and can augment thrust that would otherwise be generated simply by accelerating and expanding the flow relative to atmospheric pressure to a ratio of at least 2:1, and up to a ratio of 3:1. In this example, the thrust achieved by ejector augmentation is given by Equation 1 below:

[0023]

number

[0024] This contrasts with the 5.65 kN thrust achieved using a simple nozzle. In this case, 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 supplied to the fan 21.

[0017]

[0026] FIG. 9 illustrates a cross section of the upper half of ejector 200, the structure and function of which are similar or identical to those of elements 17 and 18. Plenum 211 is supplied with air (i.e., a pressurized motive gas stream) hotter than ambient, for example, from a combustion-based engine that may be employed by the vehicle. This pressurized motive gas stream, indicated by arrow 600, is introduced into the interior of ejector 200 via at least one conduit, such as primary nozzle 203. More specifically, primary nozzle 203 is configured to accelerate motive fluid stream 600 as a wall jet directly onto convex Coanda surface 204 to a variable, predetermined, desired velocity. Additionally, primary nozzle 203 provides an adjustable volume of fluid stream 600. This wall jet then serves to entrain a secondary fluid, such as ambient air, indicated by arrow 1, through intake structure 206, which may be approaching ejector 200 at a non-zero velocity from the direction indicated by arrow 1 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 entirely 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) profiles in the axial direction of the ejector 200 no longer have the highs and lows present at the throat section 225, but become more uniform at the terminal end 100 of the diffuser 210. As the mixture of flow 600 and air 1 approaches the exit face of the terminal end 100, the temperature and velocity profiles become more uniform. In particular, the mixture is at a temperature low enough to be directed toward an airfoil such as a wing or control surface.

[0019]

[0028] When vanes 16 are closed and fan 21 provides this power, sufficient thrust can be obtained from such a system to lift an aircraft weighing, for example, 1,100 to 1,400 kg. This type of aircraft can direct the thrust provided by fan 21 through ports 13 and 14 upward via pivoting FPS elements 17, 18, which can also rotate about their primary axis via pivot joint 23. The pivoting or orientation of FPS elements 17, 18 can change the aircraft's attitude, first during vertical takeoff, then during hovering by small angle changes, and finally during transition to fixed-wing operation by pivoting the FPS elements, directing 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 swivel joint 23, which also allows flow passage to the elements 17, 18, can be gradually changed to allow perfect balance of the aircraft from a hover state to increasing speed, e.g., increasing the aircraft's wing lift at a forward speed 10% greater than the aircraft's stall speed. For example, one embodiment of a VTOL aircraft can reach a speed of 50 miles per hour within tens of seconds of hovering at a fixed point, while still balancing a portion of its weight with the FPS 17, 18 pointing 45 degrees upward relative to the direction of flight, and while still accelerating forward as the wings begin to support, e.g., 50% of the forward-flying aircraft's weight. At this point, while the aircraft is still rapidly accelerating to 100 miles per hour, the FPS elements 17, 18 have moved to a fully horizontal position (90 degrees or more perpendicular to the initial VTOL position), and the balance between drag and thrust is achieved solely using the FPS system (i.e., all air 22 is routed through ports 13 and 14 to provide motive fluid to the FPS elements). As the forward airspeed 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 this 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 terminal thrust available in fixed-wing operation can be increased by switching the vanes 16 to their fully open position, closing the valve 15 to block the air supply to ports 13 and 14, and forcing all of the air 22 out of the plenum 12 through the vanes 16 to generate an accelerating flow 25, propelling the aircraft in fixed-wing mode and in a forward direction at a speed adjustable by the RPM of the fan 21.

[0021]

[0030] Thus, embodiments solve the problem of mismatch between separate takeoff and cruise powerplants by using the same powerplant to provide mechanical work to the fan 21 via the shaft 11. In addition, reducing fuel flow to the main gas turbine, which provides the mechanical power, slows the fan 21, similar to turbofan operation. By shutting off air to the FPS elements 17, 18 at the end of the transition and during full fixed-wing high-speed flight, slowing the fan due to reduced mechanical work will result in fuel savings and allow a much wider flight envelope in altitude, speed, and maneuverability, since the aircraft requires significantly less thrust for forward movement. For example, 30% of the thrust required for a VTOL using the FPS elements 17, 18 could be provided by using the nozzle vanes 16 for high-speed cruise, while operating the fan 21 at less than maximum speed. This means adjusting for the thrust calculated with an augmentation 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 easily accelerate to high altitudes and speeds in excess of 400 miles per hour. Conversely, a cruise-to-hover transition, as illustrated in FIG. 6, can be achieved by closing vanes 16, forcing air through ports 13 and 14 to initiate FPS operation (open), and reversing the rotational motion of FPS elements 17 and 18 from a nearly horizontal, recessed position in the aircraft fuselage to a nearly vertical position for hovering or landing. Rotating FPS elements 17 and 18 also allow them to be used as air brakes, gradually reducing the lift generated by the wings and slowing the aircraft to a point where elements 17 and 18 provide the majority of the aircraft's weight balance. Once the aircraft has sufficiently slowed and is nearly stationary in hover mode, modulation of fan 21 (here operating with vane system 16 fully closed and ports 13 and 14 fully open) can reduce thrust until the aircraft is ready to land.

[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, which has a mode 1.8 pressure ratio, allows for the use of low temperature, lightweight materials for the FPS elements 17, 18, such as high temperature plastic composites.

[0037] Maintenance becomes much easier to achieve.

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

[0039] The gas turbine can be replaced with an electric motor for use with high energy density batteries.

[0040] Using a high efficiency system and the same size turboshaft turbine minimizes cost and weight.

[0023]

[0041] One embodiment of the aircraft 40 can be further improved by incorporating an FPS system into aerodynamic control surfaces, such as airfoils, to reduce drag during high-speed flight. Such an embodiment is illustrated in FIGS. 7 and 8. In FIG. 7, propulsion elements 30 and 31, similar in functionality to elements 17 and 18, rotate to 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 FIG. 8, the FPS propulsion elements 30 and 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) within the devices 30, 31. These wall jets entrain ambient air at a high bypass ratio through slot-shaped peripheries across the aft faces 32, 33. The faces 32 and 33 are partially surrounded by sidewalls 34a, 34b, 35a, 35b. These sidewalls taper toward the trailing edges 36 and 37 of the airfoils.

[0025]

[0043] In Figure 7, surfaces 32 and 33 serve to generate more lift (lift augmentation) at angles shallower than 45 degrees relative to the horizontal (direction of flight). In this case, at the target speed, the suction sides of surfaces 32 and 33, seeing the flow emerging from elements 30 and 31, will experience a greater local velocity compared to the speed of aircraft 40. In this case, the additional lift generated by the pressure difference between the suction and pressure sides of surfaces 32 and 33 just prior to switching to the turbofan nozzle jet method will produce greater lift, as determined by Bernoulli, as is known in the art. The moment of switching from using elements 30 and 31 for propulsion during vehicle VTOL, acceleration, and climb to guiding compressed air through nozzle vanes 16 is expected to coincide with the best conditions for the aircraft to travel at the fastest safe speed, with good coordination between switching valve 15 and the attitude of 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 due to expansion through the nozzle vanes 16 at high speeds would coincide with elements 30 and 31 generating excessively large ram drag due to the entrained air in order to potentially produce sufficient net force to further accelerate the aircraft 40. For example, a vehicle employing this system may be able to accelerate to a speed in the range of 150-200 miles per hour and 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 fuel consumption because elements 30 and 31 are no longer employed and no longer produce sufficient net force for acceleration. At this point, the air mass entrainment by these elements, and therefore thrust augmentation, may fall below an acceptable level, and switching to using compressed air flow due to 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 the drag and ram drag present during operation, which in turn is useful for slowing down and economically flying at lower speeds but with greater efficiency in the low speed regime.Such a system would provide the fastest possible commercial or military application 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 approximately 125 mph, high thermal and better propulsive efficiency are achieved using entrained fluid (thrust augmentation) from ambient air, even though entrainment increases ram drag. The entrainment ratio can exceed 10, for example, and the velocity experienced by the mixture of compressed air and entrained air can reach 105 m / s (235 mph). Because 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, thermal efficiency increases at different rates, and the overall high total efficiency is obtained as the product of propulsive efficiency and thermal efficiency.

[0027]

[0045] One or more embodiments of the invention 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 that can be fully opened or closed, and having at least one other opening that can 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 produces 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 pivoted 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 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 pivots to minimize drag and becomes inactive while the fan air is directed entirely through a single propulsion nozzle.

[0028]

[0056] While the foregoing text sets forth detailed descriptions of many different embodiments, it should be understood that the scope of protection is defined by the language of the claims that follow. The detailed description should be construed as exemplary only and does not describe every possible embodiment, as doing so 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. The following is a summary of the claims as originally filed: [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 only through 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 according to [1], wherein the ejector is rotatable at least 90 degrees relative to the plenum. [3] The one or more ejectors are: Convex surface and 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 into 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 end configured to provide an outlet from the system for the introduced primary and secondary fluids. The system according to [1], comprising:

Claims

1. A propulsion system for an aircraft having a fuselage, 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; first and second ejectors fluidly coupled to the plenum via one or more valves; a nozzle disposed within the output port, the nozzle comprising a set of nozzle 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 first and second 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; the system operates in a third configuration in which the nozzle vanes are partially closed and the compressed ambient air exits the plenum partially through the one or more valves to the first and second ejectors; 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 first and second ejectors include: Convex surface and 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 into 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 end configured to provide an outlet from the system for the introduced primary and secondary fluids. The system of claim 1 , comprising:

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