Novel aerodynamic layout of vertical take-off and landing fixed-wing unmanned aerial vehicle

Abstract

The invention discloses a novel aerodynamic layout of a vertical take-off and landing fixed-wing unmanned aerial vehicle, belongs to the technical field of aerodynamic layout and propulsion integrated design of aircrafts, and provides a step-streamline composite contour airframe which comprises an airframe head, an airframe body, an airframe tail and wings. The center body is sequentially provided with an air inlet channel, a ducted fan cabin and an exhaust channel from front to back. The wings comprise main wings and empennages; an air inlet device is installed on the upper half portion in the center body, an exhaust device is installed on the lower half portion in the center body, and a ducted fan is installed between the air inlet device and the exhaust device. The invention provides a novel vertical take-off and landing fixed-wing unmanned aerial vehicle aerodynamic layout which aims at solving the contradiction that in a traditional layout, space needs to be provided for a large-volume propelling system in a fuselage and pursuing of low-resistance cruising efficiency from the outside is difficult to consider, and the problems that the structure is heavy and the efficiency is low due to switching of multiple sets of power systems are avoided through integrated design.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aircraft aerodynamic layout and propulsion integrated design, in particular to a new vertical take-off and landing fixed-wing unmanned aerial vehicle aerodynamic layout. BACKGROUND

[0002] The aircraft with vertical or short take-off and landing capability is gradually becoming the focus of research and innovation in the field of aerospace due to its flexibility in take-off and landing. The biggest advantage of this new type of aircraft is that it can operate in a limited space, which greatly reduces the dependence of traditional aircraft flight on airport runways.

[0003] In the prior art, in order to meet the vertical take-off and landing requirement, the following aerodynamic layout schemes are usually adopted: Multi-rotor + fixed-wing composite, tilting rotor / fan, wing internal / wingtip duct fan and fuselage internal duct fan. However, these schemes all have inherent technical bottlenecks: on the one hand, in order to meet the required thrust for vertical take-off and landing, some schemes often use complex tilting mechanisms or multiple sets of power systems, which not only brings the problems of complex structure and high maintenance cost, but also due to the low aerodynamic efficiency of the rotor / fan in the vertical mode, the endurance capability is severely limited. On the other hand, in order to accommodate large-sized duct fans, the fuselage design usually needs to be partially thickened, which will significantly increase the aerodynamic resistance at high speed, sacrificing the cruising efficiency and range. Most importantly, the scheme using two independent power systems to cover different flight modes, the non-working state of the power device will become "dead weight" that cannot be unloaded in another mode, which seriously occupies the effective payload and mission radius. Therefore, the core contradiction faced by the prior art is the conflict between the large internal space required by the power system and the pursuit of low resistance external aerodynamic shape. The industry urgently needs a new aerodynamic layout that can break this contradiction, that is, an innovative design that can efficiently arrange large-sized power channels, maintain low resistance shape, and realize mode seamless switching by using vector exhaust.

[0004] In view of the dual requirements of vertical take-off and landing and high-speed flight, the air-driven duct fan is used as the aircraft power system device. In order to accommodate the large volume of duct fans, air inlet and outlet devices, etc., the conventional vertical take-off and landing design inevitably causes the problem of non-streamlined shape. The non-streamlined shape will greatly increase the overall resistance of the aircraft during high-speed flight, affecting the aerodynamic performance of the aircraft, resulting in high energy consumption during take-off and landing, and failing to meet the requirements of efficient vertical take-off and landing and high-speed flight of the vertical take-off and landing aircraft. In summary, the vertical take-off and landing aircraft with a duct fan needs a low-resistance external flow shape and can contain a large volume of power devices. SUMMARY

[0005] The application aims to provide a novel VTOL fixed-wing UAV aerodynamic layout, which realizes the high integration of low-resistance body shape and controllable vector thrust through innovative aerodynamic layout design, so as to improve the VTOL efficiency, safety of flight mode transition and cruising performance of the aircraft under the premise of ensuring that the ducted fan and its inlet / outlet passages have sufficient and efficient flow cross section and length.

[0006] To achieve the above-mentioned purpose, the application provides a novel VTOL fixed-wing UAV aerodynamic layout, which comprises a nose, a fuselage, a tail and a wing, the fuselage comprises a front section, a middle section and a rear section, the front section is an upper and lower symmetrical spindle body, and the length / diameter ratio is slightly larger than that of the rear section, the middle section is internally provided with a central body, the central body is sequentially provided with an inlet passage, a ducted fan cabin and an outlet passage from front to back; the wing comprises a main wing and a tail wing. The upper half of the central body is internally provided with an inlet device, and the lower half is internally provided with an outlet device, and the inlet device and the outlet device are internally provided with a ducted fan. The lip of the inlet device and the outer surface of the middle section of the fuselage are smoothly connected to form an integrated outer surface, and the inlet device and the outlet device are connected to the inlet surface of the ducted fan through a variable cross-section passage; the entire aircraft presents a streamlined body.

[0007] The outlet device is provided with a variable vector guide vane, which can be deflected in the range of -25° to 90° to change the direction of the outlet, so as to switch and control the thrust vector of the aircraft between the vertical take-off and landing mode and the flat flight mode.

[0008] Preferably, the passage between the inlet device, the ducted fan and the outlet device is continuous and smooth in area ratio, curvature and torsion angle, which is used to reduce total pressure loss and improve the inlet distortion degree of the ducted fan; the smoothness of the interface between the central body and the middle section of the fuselage is constrained.

[0009] Preferably, the outer side of the central body and the middle section of the fuselage jointly form a ladder-streamline composite profile, the upper part is integrated with the inlet device to ensure that the airflow can enter the inlet passage efficiently and with low resistance, and the lower part converges to form a rear lower outlet surface, so as to reduce the shape resistance of the fuselage while ensuring the passage volume.

[0010] Preferably, the ducted fan is driven by two sets of power devices, and the two sets of power devices are arranged in series along the longitudinal direction of the body and are arranged in staggered layers in the height direction.

[0011] Preferably, the ducted fan is arranged in the central body at an installation inclination angle of 10° to 35° (preferably about 25°) relative to the body reference plane, and in the running process, the ducted fan compresses and accelerates the air introduced from the inlet passage, so that the gas enters the outlet device at a specific speed.

[0012] Preferably, the exhaust device includes an exhaust inlet, a transition section disposed on one side of the exhaust inlet, an exhaust outlet disposed on the side of the exhaust inlet away from the transition section, and a vector guide vane disposed at the exhaust outlet. The inclination angle of the exhaust inlet is consistent with the installation angle of the ducted fan, and the interface is connected in a transitional manner, so that the airflow flows out from the outlet surface of the ducted fan and transitions to the transition section.

[0013] Preferably, the exhaust device's end channel fits tightly against the lower rear section of the fuselage, and the exhaust device and transition section form a smooth Y-shaped cross-section connection to prevent internal gas leakage and ensure an integrated lower rear exhaust design. The vector guide vanes are configured as rectangular plate-like structures to change the exhaust angle, with the angle variation range of the vector guide vanes being [missing information]. By changing the direction of the vector guide vanes, the vector thrust can be used to switch between vertical takeoff and landing and high-speed level flight modes.

[0014] Preferably, the wing adopts a supercritical airfoil and is located in a position close to the center of gravity, with an installation angle of -4° to 0° and no dihedral or a small dihedral (≤2°).

[0015] Preferably, a tail section is provided on the rear section of the fuselage away from the midsection; the tail section includes a horizontal tail and a vertical tail with symmetrical airfoil, wherein the vertical tail is located above the rear section of the fuselage to provide yaw stability, and the horizontal tail is symmetrically arranged on both sides of the rear section of the fuselage to provide pitch stability.

[0016] Therefore, the present invention adopts the above-mentioned novel aerodynamic layout of a vertical take-off and landing fixed-wing UAV, which has the following beneficial effects: (1) Taking into account both the "internal large volume requirement" and the "external low drag shape", the layout method of longitudinally arranging the power unit at the front and rear makes full use of the internal space of the fuselage and is more suitable for the principle of streamlined fuselage model. While achieving efficient vertical take-off and landing and hovering capabilities, it also takes into account the key performance indicators such as high lift-to-drag ratio and high speed of fixed-wing aircraft in high-speed cruise state. (2) The inlet section of the air intake device is at a certain angle to the horizontal plane, which ensures that sufficient and uniform incoming flow can be captured in multiple modes of flight. The appropriate lip guides the external airflow to enter the air intake smoothly, reducing airflow separation and vortices, providing more uniform airflow for the ducted fan below, and ensuring its stability and performance. (3) The exhaust system adopts an adjustable vector guide vane design, which can actively adjust the exhaust direction and achieve precise control of the thrust vector. This key design enables the aircraft to efficiently complete the seamless switching from vertical lift to horizontal thrust through a single power system, completely eliminating the structural complexity, weight increase and "waste weight" problems brought about by the traditional dual-power scheme, simplifying the system and increasing the effective payload. (4) Due to the aerodynamic layout where the power units are all integrated into the fuselage, the noise of the power system can be effectively shielded by the fuselage, greatly reducing the acoustic characteristics to the outside world and improving stealth. Secondly, the integrated design of the high-temperature exhaust channel with the fuselage structure effectively manages the heat signal and reduces the risk of infrared detection. These characteristics provide the aircraft with stronger environmental adaptability and survivability in missions requiring high stealth, such as reconnaissance and surveillance, and provide more possibilities for its multi-functional operations.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the UAV of the present invention; Figure 2 This is a front view schematic diagram of the UAV of the present invention; Figure 3 This is a side view of the UAV of the present invention; Figure 4 This is a bottom-view schematic diagram of the UAV of the present invention; Figure 5 This is a schematic diagram showing the integrated transition between the air intake device and the fuselage of the UAV of the present invention; Figure 6 This is a schematic diagram of the structure of the unmanned aerial vehicle exhaust device of the present invention when the vector guide vane angle is 0°; Figure 7 This is a schematic diagram of the structure of the unmanned aerial vehicle (UAV) exhaust device of the present invention when the vector guide vane angle is 45°. Figure 8 This is a schematic diagram of the structure of the unmanned aerial vehicle (UAV) exhaust device of the present invention when the vector guide vane angle is 90°. Figure 9 This is a schematic diagram of the aerodynamic streamlines of the UAV during high-speed level flight according to the present invention; Figure 10 This is a schematic diagram of the aerodynamic streamlines of the UAV for vertical takeoff and landing of the present invention; Figure Labels 1. Forward section of fuselage; 2. Air intake; 3. Center body; 4. Ducted fan; 5. Exhaust system; 5-1. Exhaust inlet; 5-2. Transition section; 5-3. Exhaust outlet; 5-4. Vectoring guide vane; 6. Rear section of fuselage; 7. Wing; 8. Vertical tail; 9. Horizontal tail. Detailed Implementation

[0019] The following detailed description of embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0020] Example 1 (Basic Layout) Please see Figures 1-4 A novel aerodynamic layout for a vertical takeoff and landing fixed-wing unmanned aerial vehicle (UAV) is described. The fuselage includes a forward section 1, a mid-section, and a rear section 6. A central body 3 is located within the mid-section, and from front to rear, the central body 3 contains an air intake channel, a ducted fan nacelle, and an exhaust channel. To accommodate the large power unit while ensuring efficient air intake by the air intake device 2 and vector exhaust by the exhaust device 5, the mid-section and central body 3 form a stepped-streamlined composite profile: the upper part bulges to create an integrated transition with the air intake device 2, while the lower part converges to form the rear-lower exhaust shape.

[0021] like Figure 1 , 3 As shown, the forward section 1 of the fuselage is a symmetrical spindle shape with a continuously varying cross-sectional area along its longitudinal axis. The cross-sectional area transitions smoothly from the smallest section at the nose to the rear, and its length-to-diameter ratio is slightly larger than that of the rear section 6 to reduce drag and provide an induced airflow profile. The mid-section of the fuselage tapers towards the forward section 1 to allow sufficient space for airflow into the intake device 2, while maintaining a constant cross-section. The lip of the intake device 2 smoothly connects to the upper surface of the mid-section, and its interior is a gradually expanding and gently curving variable cross-section channel, connecting at its end to the circular inlet of the ducted fan 4. The channel expansion ratio and curvature continuously change to avoid boundary layer separation and reduce inlet distortion. The ducted fan 4 is installed at an angle of approximately 25° to accommodate both vertical and level-flight thrust components. The exhaust system 5 is located at the lower rear of the fuselage. Its exhaust inlet 5-1 and the outlet surface of the ducted fan 4 smoothly transition at an angle of about 25°, and after passing through the transition section 5-2, it reaches the exhaust outlet 5-3. A variable vector guide vane 5-4 is installed at the outlet. The vector guide vane 5-4 can deflect from -25° to 90° to adjust the thrust direction between vertical / transition / level flight modes. It can provide lift for vertical take-off and landing as well as thrust for level flight. This design covers multiple flight modes through a single power system, fundamentally avoiding the structural redundancy and ineffective load problems caused by using multiple independent power plants, and achieving a high degree of integration and lightweight of the power system.

[0022] The design and installation position of wing 7 take into account the weight distribution and aerodynamic requirements of the aircraft. It is positioned close to the center of gravity to ensure optimal lift distribution and flight stability. The installation angle is -2.2° (which can be optimized within the range of -4° to 0°), with no dihedral or a small dihedral. The design of wing 7 is based on aerodynamic principles and uses an optimized supercritical airfoil (NASA SC(2)-0714). The leading edge radius of the airfoil is slightly reduced, the curvature of the upper surface is reduced, and the thickness remains basically unchanged. The rear section 6 of the fuselage, far from the mid-section of the fuselage, is equipped with a tail, including a horizontal tail 9 and a vertical tail 8. Both tails use symmetrical airfoils. The vertical tail 8 is installed above the rear section 6 of the fuselage to provide yaw stability, and the horizontal tail 9 is symmetrically arranged on both sides of the rear section 6 of the fuselage to provide pitch stability. The aerodynamic area of ​​the vertical tail 8 is 0.895m². 2 The horizontal tail fin has an aerodynamic area of ​​1.227m². 2 .

[0023] Example 2 (Power unit and guide vane drive) like Figure 1 , 3 As shown, the UAV is driven by two ducted fan 4 power units. The two power units are arranged in series along the longitudinal direction of the fuselage and staggered in the height direction to reduce the thickness of the fuselage and the drag of the shape. The two units are connected to the ducted fan 4 channel through a merging / diverting section to ensure flow rate and pressure matching.

[0024] like Figure 5 As shown, in the integrated design of the air intake 2 and the fuselage, the fuselage on the side of the air intake has a continuously smooth stepped-streamline composite profile in terms of area ratio, curvature, and twist angle. Specifically, in order to accommodate the difference between the smaller diameter of the air intake and the larger diameter of the ducted fan 4, the side of the upper half of the fuselage adopts a smooth transition profile that increases in stages from top to bottom and gradually increases from front to back. This design reduces the frontal area during flight.

[0025] like Figures 6-8As shown, the exhaust device 5 includes an exhaust inlet 5-1, a transition section 5-2 located on one side of the exhaust inlet 5-1, an exhaust outlet 5-3 located on the side of the exhaust inlet 5-1 away from the transition section 5-2, and a vector guide vane 5-4 located at the exhaust outlet 5-3. The exhaust device 5 is located in the lower rear section of the fuselage. The tilt angle of the exhaust inlet 5-1 is consistent with the installation angle of the ducted fan 4 and is connected to its circular outlet surface. The figure (from top to bottom) shows three states of the vector guide vane 5-4 of the exhaust device 5 from vertical takeoff and landing to transition mode to high-speed level flight mode. The deflection angles are 0°, 45°, and 90°, respectively. The transition mode only captures the deflection angle of the vector guide vane 5-4 at a certain moment. The vector guide vane 5-4 deflects to achieve vector thrust to meet the mission requirements of the aircraft. The vector guide vane 5-4 is a rectangular plate. The vector guide vane 5-4 uses a plate-shaped blade and a central rotating shaft. It is driven by a servo-reducer-linkage mechanism. An angle sensor provides position feedback. The controller realizes closed-loop angle control and locking according to the operating condition command.

[0026] The exhaust outlet 5-3 fits snugly against the lower rear section of the fuselage midsection. The exhaust system and the fuselage transition section 5-2 form a smooth Y-shaped connection to prevent internal gas leakage and ensure the integrated design of the lower rear exhaust. The vector guide vane 5-4 is a rectangular plate structure used to change the exhaust angle. The airflow transitions from the circular outlet of the ducted fan 4 to the transition section 5-2 of the exhaust system 5, and finally flows through the variable vector guide vane 5-4 for discharge. The angle of the vector guide vane 5-4 varies from -25° to 90°. By changing the direction of the vector guide vane 5-4, the vector thrust can be used to switch between vertical takeoff and landing and high-speed level flight modes.

[0027] Example 3 (Thermal Sealing and Structure) A sealing and heat insulation layer is used between the exhaust channel and the lower rear of the fuselage to prevent high-temperature gas leakage and reduce heat load; the periphery of the exhaust port and the fuselage structure are made of heat-resistant materials or thermal barrier coatings. The central body is connected to the fuselage frame / bulge to form a load-bearing channel, ensuring the continuity of the thrust and external load transmission path of the ducted fan 4.

[0028] Operating conditions and mode switching: like Figure 9 , 10As shown, in vertical takeoff and landing (VTOL) mode, the vector guide vane 5-4 deflects to nearly 90°, drawing air through the intake device 2 and expelling it vertically downwards. At this time, the thrust is downwards. The near-constant cross-section design of the central body 3 reduces downward drag during VTOL. In transition mode, the angle of the vector guide vane 5-4 is continuously adjusted according to the flight control law, balancing lift and acceleration. During level flight cruise, the angle of the vector guide vane 5-4 approaches 0°, drawing air through the intake device 2 and expelling it horizontally backwards. The transition between the lower rear section of the fuselage and the converging exhaust device 5 reduces rearward drag during level flight and even suppresses flow separation at that point. At this time, the thrust is directed backwards. The effective area of ​​the intake channel and the lip angle ensure sufficient intake margin under all the above operating conditions.

[0029] Therefore, the present invention adopts the above-mentioned novel aerodynamic layout of a vertical take-off and landing fixed-wing UAV, which addresses the contradiction between the large volume required for the fuselage and the pursuit of low-drag outflow performance, taking into account the performance requirements of vertical take-off and landing aircraft and the size limitations of the internal power unit.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A novel aerodynamic layout for a vertical takeoff and landing fixed-wing unmanned aerial vehicle (UAV), characterized in that: It includes the nose, fuselage, tail and wings. The fuselage includes the forward section, the middle section and the rear section. The middle section contains a central body, and the central body has an air intake, a ducted fan nacelle and an exhaust channel arranged from front to back. The wings include the main wing and the tail. The upper part of the center is equipped with an air intake device, the lower part with an exhaust device, and a ducted fan is installed between the air intake device and the exhaust device. The lip of the air intake device smoothly transitions to the outer surface of the middle section of the fuselage to form an integrated outer surface, and is smoothly connected to the inlet surface of the ducted fan through a variable cross-section channel; The exhaust system is equipped with variable vector guide vanes, which deflect within the range of -25° to 90° to change the exhaust direction.

2. The aerodynamic layout of a novel vertical takeoff and landing fixed-wing UAV according to claim 1, characterized in that: The passage between the intake device, ducted fan, and exhaust device is continuously smooth in terms of area ratio, curvature, and torsion angle to reduce total pressure loss and improve the inlet distortion of the ducted fan; the smoothness of the interface between the center body and the fuselage midsection is constrained.

3. The aerodynamic layout of a novel vertical takeoff and landing fixed-wing UAV according to claim 2, characterized in that: The outer side of the central body and the middle section of the fuselage together form a stepped-streamline composite profile. The upper part is raised and integrated with the air intake device, while the lower part converges to form the rear lower exhaust outer surface.

4. The aerodynamic layout of a novel vertical takeoff and landing fixed-wing UAV according to claim 3, characterized in that: The ducted fan is driven by two power units, which are arranged in series along the longitudinal direction of the machine body and staggered in the height direction.

5. The aerodynamic layout of a novel vertical takeoff and landing fixed-wing UAV according to claim 4, characterized in that: The ducted fan is installed in the center body at an installation angle of 10° to 35° relative to the reference plane of the machine body.

6. The aerodynamic layout of a novel vertical takeoff and landing fixed-wing unmanned aerial vehicle according to claim 5, characterized in that: The exhaust device includes an exhaust inlet, a transition section located on one side of the exhaust inlet, an exhaust outlet located on the side of the exhaust inlet away from the transition section, and a vector guide vane located at the exhaust outlet. The inclination angle of the exhaust inlet is consistent with the installation angle of the ducted fan, and the interface is connected by a transition. The airflow flows out from the outlet surface of the ducted fan and transitions to the transition section.

7. The aerodynamic layout of a novel vertical takeoff and landing fixed-wing unmanned aerial vehicle according to claim 1, characterized in that: The exhaust device's end channel fits tightly against the lower rear section of the fuselage, and the exhaust device and transition section form a smooth Y-shaped cross-section connection to prevent internal gas from flowing out. The vector guide vanes are designed as rectangular plate structures to change the exhaust angle, with the angle variation range of the vector guide vanes being -25° to 90°.

8. The aerodynamic layout of a novel vertical takeoff and landing fixed-wing unmanned aerial vehicle according to claim 1, characterized in that: The wing adopts a supercritical airfoil and is located close to the center of gravity. The wing installation angle is -4° to 0°, with no dihedral or a small dihedral.

9. The aerodynamic layout of a novel vertical takeoff and landing fixed-wing unmanned aerial vehicle according to claim 5, characterized in that: The rear section of the fuselage, away from the midsection, is equipped with a tail fin; the tail fin includes a symmetrical airfoil horizontal tail and a vertical tail, wherein the vertical tail is located above the rear section of the fuselage to provide yaw stability, and the horizontal tail is symmetrically arranged on both sides of the rear section of the fuselage to provide pitch stability.

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