Adaptive Vertical Takeoff and Landing Propulsion System

Abstract

The invention provides a propulsion system sized to be efficient in both VTOL and hovering phases, as well as in cruising mode. [Solution] The 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 located in the output port and includes a set of vanes. The system operates in a first configuration where the nozzle vanes are closed and the compressed ambient air exits the plenum to one or more ejectors through only one or more valves. The system operates in a second configuration where one or more valves are closed and the nozzle vanes are open, and the compressed ambient air exits the plenum through only the output port.

Description

Copyright Notice

[0001]

[0001] This disclosure is protected under U.S. and international copyright laws. (c) 2019 Jetoptera. All rights reserved. ((c) indicates a copyright mark). Portions of the disclosure of this patent document contain material subject to copyright protection. The copyright owner does not object to the reproduction in patent documents or patent disclosures as any patent document or patent disclosure may appear in the Patent and Trademark Office's patent file or records, but reserves all other copyrights. Priority Claim

[0002]

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

Background Art

[0003]

[0003] One of the main challenges in designing a vertical takeoff and landing (VTOL) aircraft is determining the size of the propulsion system to be efficient during both the VTOL and hovering phases as well as in cruise. To maximize the payload and fuel reserve, it is necessary to keep the proportion of the total weight occupied by the propulsion system low. Thus, during takeoff (lift-by-thrust-only mode) or hovering, compared to the wing-borne and cruise states, the challenge is how to adopt a system that produces approximately 4 to 6 times greater thrust. In the first case, the thrust balances the weight of the aircraft and much larger engines and power or thrust are required. However, in cruise, since the wings of the aircraft balance the weight, it is necessary to make the engine size much smaller to balance the drag.

[0004]

[0004] Traditionally, VTOL has been achieved either with separate systems (lift / cruise, which separates thrust but compromises weight) or with pure rotary-wing aircraft such as helicopters (which compromises fixed-wing capabilities). The most successful aircraft employing VTOL capabilities use the same system for both the vertical and fixed-wing phases. Examples include vertical take-off and landing jets such as the Harrier Hawker, which directs turbofan jets (but eventually uses larger engines for missions in the fixed-wing phase), and the V22 Osprey, which utilizes turboprops with tilting capabilities. The tiltrotor approach is not without its risks, including vibration, vortex ring conditions (VRS), a large footprint, and a complex architecture.

[0005]

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

[0006]

[0006] Preferred and alternative embodiments of the present invention will be described in detail below with reference to the following drawings. [Brief explanation of the drawing]

[0007] [Figure 1]

[0007] An oblique view of an embodiment of the VTOL configuration is shown. [Figure 2]

[0008] This is a perspective view of a cruising configuration having an FPS system element used as an air brake for transitioning to VTOL, according to one embodiment. [Figure 3]

[0009] A perspective view of a variable vane in a VTOL configuration according to one embodiment is shown. [Figure 4]

[0010] A perspective view of a variable vane in a complete cruising configuration having an extended FPS system element for applying air brakes, according to one embodiment, is shown. [Figure 5]

[0011] This shows an intermediate transition from a VTOL configuration to a fixed-wing configuration and a perspective view of the 45-degree FPS system element, according to one embodiment, while the aircraft is accelerating solely by the FPS system element. [Figure 6]

[0012] A perspective view of the system elements in a cruising configuration according to one embodiment is shown. [Figure 7]

[0013] An alternative embodiment of the present invention is shown, which uses a wing-integrated FPS system element that can conceal the thrust booster during forward flight. [Figure 8] An alternative embodiment of the present invention is shown, which uses a wing-integrated FPS system element that can conceal the thrust booster during forward flight. [Figure 9]

[0014] This is a cross-sectional view of an ejector according to an embodiment of the present invention, showing the upper half of the ejector and the velocity and temperature profiles of the internal flow. Detailed explanation

[0008]

[0015] This patent application is intended to describe one or more embodiments of the present invention. The use of absolute terms such as "must" and "will," and specific quantities, should be interpreted as applicable to one or more such embodiments, but not necessarily to all such embodiments. Therefore, embodiments of the present invention may omit or modify one or more features or functionalities described in the context of such absolute terms.

[0009]

[0016] One embodiment of a fluid propulsion system (FPS) introduces an alternative method that allows a non-rotating thruster to be tilted to transition from hovering to cruising. During VTOL and hovering, thrust enhancement can be obtained using pressurized fluid as a supply source. One or more embodiments may include a system used in all stages of flight (vertical and fixed-wing stages) while still obtaining thrust enhancement in the forward direction.

[0010]

[0017] One embodiment includes a lift-and-cruise solution with a compression source for an air-containing fluid, such as a fan or compressor, and a dual capability to switch from enhanced thrust in vertical flight (VTOL + hovering) to a separate turbofan configuration for cruising. Such a configuration and operation eliminates speed limitations, allowing the VTOL vehicle to move forward at very high speeds, achieve higher altitude capabilities, and operate very efficiently with a significant reduction in fuel combustion (fuel consumption rate).

[0011]

[0018] More descriptively, a fan or compressor or similar machine performs the mechanical work, compressing the ambient air to a pressure ratio of 1.5 to 2.5. This component may have one or more stages and may be driven by a gas turbine stage, preferably such as a free turbine in a turboshaft engine, without requiring reduction gears. This component is optionally advantageous because it can employ a lighter and simpler structure due to the reduction of weight and moving parts.

[0012]

[0019] Referring to Figure 1, shaft 11 receives mechanical power from an electric motor or a turboshaft free turbine, and transmits this power to fan 21 to compress air to the aforementioned pressure ratio. The air is pumped to plenum 12 located immediately downstream of fan 21, from where it can be directed to side ports 13 and 14 or axially downstream through a nozzle having a variable vane 16. The vane 16 can be completely closed or completely opened by mechanisms known in the art. For example, one such mechanism may be a variable guide vane employed in a typical compressor. Another mechanism may be a mechanical screw that rotates the hub of the vane 16 to force the vane closed. When closed, as seen in Figures 1 and 3, all flow from fan 21 is forced to flow to side ports 13 and 14 of plenum 12 and, via valve 15, to FPS system elements 17, 18 fluidically connected to plenum 12.

[0013]

[0020] In one embodiment, the fan 21 receives, for example, 1,000 kW of power from a free turbine of a turboshaft-type gas turbine rotating at, for example, 25,000 RPM. This value is typical for a machine such as a typical turboprop architecture at full speed, before the reduction gear. 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 80% efficiency in the fan section.

[0014]

[0021] The fan 21 itself can be manufactured from an ultralight material such as titanium or composite material, the former using wide-cord composite sweep fan blades for higher efficiency and manufactured as a single unit as a blisk. A design with low noise characteristics is included.

[0015]

[0022] Assuming a flow rate of 15 kg / second, a total pressure of 180-200 kPa, and an air temperature of 353 Kelvin, the flow 22 is divided and delivered to FPS elements 17,18 embedded within the aircraft's fuselage. The FPS elements 17,18 are described in more detail as ejectors, for example, in 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 herein by reference as fully described herein. These can enhance the thrust produced by accelerating and expanding the flow relative to atmospheric pressure to a ratio of at least 2:1, and up to 3:1, without which it would simply be amplified. In this example, the thrust achieved by the ejector augmentation is given by Equation 1 below:

[0023]

number

[0024] The above is in contrast to the thrust of 5.65 kN when a simple nozzle is used. In this case, 287 J / kg-K is the air constant, 1.4 is the air exponential coefficient, 353 K is the discharge temperature from fan 21 compression, 2 is the enhancement ratio, and 15 kg / s is the total mass flow rate.

[0016]

[0025] Further optimization of FPS elements 17 and 18 allows the total thrust to reach an augmentation ratio of 2.5, or 14.122 kN, when the amount of mechanical input power supplied to fan 21 is the same as the amount of 1000 kW supplied.

[0017]

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

[0018]

[0027] The mixture of stream 600 and air 1 may move completely axially in the throat section 225 of ejector 200. Due to diffusion in a diffusion structure such as diffuser 210, the mixing and smoothing process continues, so the temperature (800) and velocity (700) profiles in the axial direction of ejector 200 no longer have the high and low values present in throat section 225 but become more uniform at the end portion 100 of diffuser 210. As the mixture of stream 600 and air 1 approaches the exit surface of end portion 100, the temperature and velocity profiles become substantially uniform. In particular, the mixture is at a temperature low enough to be directed towards an airfoil such as a wing or a control surface.

[0019]

[0028] When the vane 16 is closed and the fan 21 supplies this power, sufficient thrust can be obtained from such a system to lift an aircraft weighing, for example, 1100 to 1400 kg. An aircraft of this type can direct the thrust supplied from the fan 21 through ports 13 and 14 upward through the swiveling FPS elements 17, 18, and the swiveling FPS elements 17, 18 can also rotate about their main axes via the swivel joints 23. The swiveling or orientation of the FPS elements 17, 18 can change the attitude of the aircraft first during vertical takeoff, further during hovering with small angle changes, and finally during the transition to fixed-wing operation by swiveling the FPS elements, so that the thrust can be directed from 45 degrees (as shown in FIG. 5) to a maximum of 90 degrees perpendicular to the initial VTOL position shown in FIG. 1.

[0020]

[0029] By gradually changing the angle of the swivel joint 23, which also allows the flow to pass through elements 17 and 18, perfect balance of the aircraft is possible from a hovering state to increasing speed, and the lift of the aircraft's wings can be increased 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 mph within tens of seconds of hovering at a fixed point, while still balancing a portion of its weight with the FPS elements 17 and 18, which are oriented 45 degrees upward with respect to the direction of flight, and while still accelerating forward 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 rapidly accelerating to 100 mph, the FPS elements 17 and 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 simply using the FPS system (i.e., all the air 22 is sent through ports 13 and 14 to supply the driving fluid to the FPS elements). For example, as the forward air velocity approaches 150 miles per hour, the vanes 16 begin to open, allowing the airflow 22 to pass through the vanes, thus propelling the aircraft forward more quickly. During the above transition to full fixed-wing operation, the FPS augmentation ratio decreases due to the increased ram drag caused by the air flowing into the FPS elements 17,18. The final thrust obtained in fixed-wing operation can be increased by switching the vanes 16 to a fully open position, closing the valves 15 to cut off the air supply to ports 13 and 14, and allowing the entire air 22 to exit the plenum 12 through the vanes 16 to generate an accelerated flow 25, propelling the aircraft in fixed-wing mode and forward at a speed adjustable by the RPM of the fan 21.

[0021]

[0030] Thus, the embodiment solves the mismatch between separate takeoff and cruising power plants by using the same power plant to supply mechanical work to the fan 21 via shaft 11. In addition, a reduction in fuel flow to the main gas turbine providing mechanical power slows down the fan 21, as well as turbofan operation. At the end of the transition and during full fixed-wing high-speed flight, the reduction in mechanical work by cutting off air to the FPS elements 17,18 slows down the fan, resulting in fuel savings and a much wider flight envelope in terms of altitude, speed, and maneuverability, as the thrust required for the aircraft to move forward is significantly reduced. For example, 30% of the thrust required for VTOL using FPS elements 17,18 can be supplied by using nozzle vanes 16 for high-speed cruising while operating the fan 21 at a speed lower than its maximum speed. This means adjusting the thrust to an augmentation ratio of 1.0 calculated by Equation 2:

[0031]

number

[0032] The above applies when the aircraft is in all-fixed-wing mode. A typical general-purpose aircraft that achieves such thrust can accelerate without problems to high altitudes and speeds exceeding 400 miles per hour. Conversely, by closing vane 16 and 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, embedded position in the aircraft's fuselage to a nearly vertical position for hovering or landing, a transition from cruising to hovering, as illustrated in Figure 6, can be achieved. Due to the rotation of FPS elements 17 and 18, they can also be used as air brakes to gradually reduce the lift generated by the wings and decelerate the aircraft until elements 17 and 18 provide most of the balance for the aircraft's weight. Once the aircraft has decelerated sufficiently and is nearly stationary in hovering mode, the thrust can be reduced to the point where the aircraft is ready to land by modulating fan 21 (which operates with vane system 16 fully closed and ports 13 and 14 fully open).

[0022]

[0033] Such a system has the following advantages:

[0034] Aside from the rotation of elements to facilitate a smooth transition from vertical to cruising (fixed-wing) flight, there are no movable parts for FPS elements 17 and 18.

[0035] Complexity is minimized.

[0036] Because the air discharge temperature from fan 21, which has a mode 1.8 pressure ratio, is low, low-temperature and lightweight materials such as heat-resistant plastic composites can be used for FPS elements 17 and 18.

[0037] Maintenance becomes much easier to achieve.

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

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

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

[0023]

[0041] One embodiment of the aircraft 40 can be further improved by incorporating the FPS system into an aerodynamic control surface such as an aerofoil to reduce drag during high-speed flight. Such embodiments are illustrated in Figures 7 and 8. In Figure 7, propulsion elements 30, 31, which are functionally similar to those of elements 17, 18, are rotated 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 the 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 are rotated relative to the wing 41 to generate upward thrust for hovering and VTOL. In this configuration, the variable nozzle vane 16 is closed, and all airflow is directed through the FPS elements 30 and 31.

[0024]

[0042] Figure 7 illustrates the geometric shape 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 with a high bypass ratio through slot-shaped peripheries that cross the rear surfaces 32, 33. Surfaces 32 and 33 are partially enclosed by side walls 34a, 34b, 35a, 35b. These side walls are tapered toward the trailing edges 36 and 37 of the aerofoil.

[0025]

[0043] In Figure 7, surfaces 32 and 33 play a role in generating more lift (lift enhancement) at angles shallower than 45 degrees with respect to the horizontal (direction of flight). In this case, at the target speed, the suction side of surfaces 32 and 33, which observe the flow coming out of 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 and pressurized sides of surfaces 32 and 33 just before switching to the turbofan nozzle jet method will produce greater lift, as is known in the industry, under the conditions determined by Bernoulli. The moment of switching from using elements 30 and 31 for propulsion during the vehicle's VTOL, acceleration, and climb to guiding compressed air through the nozzle vane 16 is expected to coincide with the best conditions for the aircraft to move at the fastest and safest speed, in conjunction with good coordination between the switching valve 15 and the attitude of the aircraft 40. Switching to a state where compressed air is used as the primary air driving the thrusters (elements 30 and 31) with entrainment into the direct jet due to expansion through the nozzle vane 16 at high speed would coincide with elements 30 and 31 generating excessively large ram drag due to the entrained air in order to produce as much net force as possible sufficient to further accelerate the aircraft 40. For example, a vehicle employing this system can accelerate to speeds in the range of 150-200 mph and reach steady-state flight, but this switch is necessary for the vehicle to accelerate to 400 mph. Consequently, the vehicle may experience increased speed and fuel consumption because elements 30 and 31 are no longer employed and no longer produce enough net force for acceleration. At this point, the entrainment of air mass by these elements, and thus the increase in thrust, may fall below an acceptable level, and further acceleration is enabled by switching to the use of compressed air flow rate due to expansion in the nozzle vane 16. At this point, thrusters 30 and 31 can be aligned with a streamlined profile that reduces the drag and ram drag present during operation. The reverse is effective for deceleration, allowing for more economical flight at lower speeds but with greater efficiency in low-speed regimes.Such systems would lead to the fastest possible commercial or military applications with VTOL capabilities.

[0026]

[0044] Switching from thruster (fluid) entrainment mode to fan mode results in optimized thermal and propulsion efficiency between the two regimes. In regimes below approximately 125 mph, even though entrainment increases ram drag, using the fluid (thrust enhancement) from entrained ambient air yields high thermal and better propulsion efficiency. The entrainment rate can exceed, for example, 10, and the velocity appearing in the mixture of compressed air and entrained air can reach 105 m / s (235 mph). As entrainment decreases and ram increases with speed, above 125 mph, the system switches to using 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 propulsion efficiency and thermal efficiency.

[0027]

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

[0046] A propulsion system suitable for VTOL that can transmit the thrust of an aircraft from vertical flight to fixed-wing flight, comprising a fan or compressor and a plenum having at least one other opening that can be fully opened and closed, communicating with a set of vanes that can be fully opened and closed, and which can be fully opened and closed to send the fan-discharged air from the fan to a secondary thrust enhancement system.

[0047] A secondary thrust augmentation system is a system that generates an augmentation of 1.25 to 3.

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

[0049] A system that allows for the opening and closing of additional ports.

[0050] A secondary thrust system that can rotate from a completely vertical position to a completely horizontal position, and can also be stored or embedded in the fuselage in a simplified manner.

[0051] A system having a movable vane system that can rotate, accelerate air to forward cruising speed, or completely close to supply air to an augmentation system.

[0052] An aircraft that uses a system in which a gas turbine can be used as the mechanical input for the fan.

[0053] An aircraft that uses a system that allows electric motors to be used as the drive mechanism for the fan.

[0054] An aircraft that uses a system that can employ a hybrid system as the drive mechanism for its fans.

[0055] An aircraft employing multiple systems where, while the fan's airflow is directed entirely through a single propulsion nozzle, a secondary thrust system rotates to minimize drag and become inactive.

[0028]

[0056] While the preceding text provides a detailed description of numerous different embodiments, it should be understood that the scope of protection is defined by the following claims. The detailed description should be interpreted as illustrative only and does not describe all possible embodiments, as it would be impractical, if not impossible, to describe all possible embodiments. Numerous alternative embodiments may be implemented using either the current art or art developed after the filing date of this patent, and these remain within the scope of the claims.

[0029]

[0057] Accordingly, many modifications and alterations can be made to the techniques and structures described and illustrated herein without departing from the spirit and scope of the claims. Therefore, it should be understood that the methods and apparatus described herein are illustrative only and do not limit the scope of the claims.

Claims

1. A propulsion system for aircraft, 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 fluidly coupled to the plenum via one or more valves, and is configured to compress ambient air entering the intake port. A nozzle is located within the output port, wherein the nozzle comprises a set of vanes. Equipped with, The system operates in a first configuration in which the nozzle vanes are closed and the compressed ambient air exits the plenum to the one or more ejectors through only the one or more valves. The system operates in a second configuration in which 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 claim 1, wherein the ejector is rotatable at an angle of at least 90 degrees relative to the plenum.

3. The one or more ejectors mentioned above are: Convex surface and, A diffusion structure bonded to the convex surface, At least one conduit coupled to the convex surface and configured to introduce a primary fluid generated 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 diffusion structure, wherein the diffusion structure comprises a terminal portion configured to provide an outlet from the system for the introduced primary and secondary fluids. The system according to claim 1, including the following:

Images