A vertical take-off and landing fixed wing aircraft based on thrust vectoring nozzles

Abstract

The application discloses a vertical take-off and landing fixed-wing aircraft based on thrust vector nozzles, which comprises four engines, four thrust vector nozzles, a wing, a fuselage, a T-shaped tail wing and a support; four sets of power devices adopt a four-point isosceles trapezoidal symmetrical layout, and front and rear power devices are symmetrically arranged about the gravity center of the whole machine. The transverse spacing of the front power device is 2.5-3 times that of the rear power device, the spanwise projection is located at 40%-60% of the wing span length, and the height is matched with the wing leading edge to realize jet flow lift increase; the height and horizontal position of the rear power device are optimized to ensure stable air intake. The thrust vector nozzle takes the horizontal axis of the fuselage as the 0° reference, the vector angle adjustment range is not less than -95°-+15°, and the hovering, mode transition and steady switching of the flat flight are realized through differential adjustment. The application cancels the tilting mechanism, reduces the structural dead weight, reduces the aerodynamic interference, and improves the cruising speed and flight safety.

Description

Technical Field

[0001] This invention relates to an aircraft structure, specifically to a vertical takeoff and landing fixed-wing aircraft. Background Technology

[0002] With the development of science and technology and the increasingly urgent practical application needs in the low-altitude economy, vertical take-off and landing fixed-wing aircraft have become an important development direction in the field of aviation equipment.

[0003] To achieve compatible operation of vertical takeoff and landing (VTOL) and fixed-wing level flight, the power system of this type of aircraft must simultaneously possess the dual functions of directly providing lift and providing thrust for level flight. It must meet the operational requirements of VTOL and hovering in helicopter mode while also adapting to the high-speed level flight needs of fixed-wing mode. Due to the significant differences in aerodynamic principles and flight control methods between helicopters and conventional fixed-wing aircraft, achieving stable and reliable switching between the two flight modes has become the core challenge in the design of VTOL fixed-wing aircraft.

[0004] Meanwhile, due to the significant differences in the power operation modes and aerodynamic layouts of helicopters and fixed-wing aircraft, reducing the mutual interference between the two flight modes and improving overall flight efficiency and safety are also pressing technical problems that need to be solved in this field. The typical workflow of a vertical takeoff and landing (VTOL) fixed-wing aircraft is as follows: vertical takeoff in helicopter mode, mode switching in mid-air to fixed-wing level flight mode, flight to the target area along the mission route, mode switching again, and vertical landing in helicopter mode. In the entire workflow, the stable mode switching during the in-flight transition phase is the most challenging, placing stringent requirements on the aircraft's aerodynamic layout, power system, and control logic.

[0005] Currently, most mainstream vertical takeoff and landing fixed-wing aircraft in this field adopt tiltrotor technology, which adjusts the thrust direction by changing the direction of the rotor's rotation axis, thereby achieving vertical takeoff and landing and mode switching. However, this approach has significant drawbacks: the tilt drive mechanism has a complex structure, significantly increasing the overall structural weight of the aircraft in fixed-wing flight; complex aerodynamic interference exists between the rotor, wing, and fuselage, reducing flight stability and flight quality; the overall operating noise is high, and it is difficult to achieve higher-speed cruise flight.

[0006] Therefore, developing a vertical takeoff and landing fixed-wing aircraft that can effectively improve hovering efficiency and flight quality during the mode transition phase, reduce aerodynamic interference between the power system and the wings and fuselage, and increase cruise speed is of great practical significance and engineering application value for promoting the development of low-altitude economy and general aviation equipment. Summary of the Invention

[0007] Purpose of the invention: In view of the above-mentioned prior art, a vertical take-off and landing fixed-wing aircraft based on a thrust vectoring nozzle is proposed. The aircraft completes the flight mode conversion through the thrust vectoring nozzle, and uses an optimized overall aerodynamic layout of the aircraft to complete the flight mode conversion through the thrust vectoring nozzle. Combined with the optimized aerodynamic layout and four-point symmetrical power arrangement, the structural dead weight is reduced, aerodynamic interference is reduced, and flight efficiency and control safety are improved.

[0008] Technical Solution: A vertical takeoff and landing fixed-wing aircraft based on thrust vectoring nozzles, comprising four engines, four thrust vectoring nozzles, wings, fuselage, and a T-tail; the engines and thrust vectoring nozzles form the power plant, with a total of four power plants arranged in a four-point isosceles trapezoidal symmetrical layout, two sets symmetrically arranged at the front of the fuselage and two sets symmetrically arranged at the rear of the fuselage, and the front and rear power plants are symmetrically arranged about the center of gravity of the entire aircraft; the lateral spacing between the two front power plants is 2.5 to 3 times the lateral spacing between the two rear power plants; the geometric centerline of the front power plant is vertically projected onto the spanwise reference plane of the wing, and the spanwise distance from this projection position to the midpoint of the wing root chord is 40% to 60% of the total wing span. The vertical height of the forward power unit's centerline is higher than the wing's leading edge height reference line, and the lowest point of the thrust vectoring nozzle's outer wall is not higher than this height reference line, with the vertical height difference between the two not exceeding 200% of the nozzle's exit radius; the lowest point of the rear power unit's air intake's outer wall is not lower than the apex of the wing's maximum thickness; the lowest point of the rear power unit's air intake's outer wall is not higher than the highest point of the fuselage, and the vertical height difference between the centerlines of the rear and forward power units is 1 to 1.5 times the radius of the power unit's air intake; the horizontal distance between the rear power unit's centerline and the outermost edge of the fuselage is not less than the diameter of the power unit's air intake; the thrust vectoring nozzle's thrust vector angle can be continuously adjusted within a range of not less than -95° to +15°.

[0009] Furthermore, the cross-sectional area of ​​the single forward power unit perpendicular to the wing span is 95% to 100% of the maximum cross-sectional area of ​​the fuselage at the same wing span position.

[0010] Furthermore, the wing has a sweep angle ≤15° and an aspect ratio ≥6.

[0011] Furthermore, the horizontal tail fin of the T-tail fin is a swept trapezoidal fin.

[0012] Furthermore, the frontal area of ​​the bracket connecting the power unit and the fuselage is no more than 20% of the maximum cross-sectional area of ​​the engine.

[0013] Furthermore, during the vertical takeoff and landing phase, the exhaust direction of the front thrust vector nozzle is outward V-shaped, and the angle between the thrust line and the vertical direction is no greater than 15°.

[0014] Furthermore, during the transition from hovering to level flight, the thrust vector angle adjustment angular velocity of the front power unit is 10% to 15% slower than that of the rear power unit, and the aircraft's angle of attack is no greater than 10°.

[0015] Furthermore, in level flight mode, the thrust vector angle of the rear power unit is maintained within ±10°.

[0016] Furthermore, the engine is an electric ducted engine or a turbojet engine; the thrust vectoring nozzle is a mechanical-hydraulic or fluid-type thrust vectoring nozzle.

[0017] Furthermore, in hovering mode, the total thrust of the front power unit is greater than that of the rear power unit. Attitude control is achieved by changing the thrust line direction of the front thrust vectoring nozzle and cooperating with the control surfaces of the T-tail.

[0018] Beneficial effects: 1. Eliminating the tilt rotor mechanism and using a thrust vectoring nozzle to achieve mode conversion significantly reduces structural dead weight.

[0019] 2. The thrust vector angle is continuously adjustable, and the front power unit is independently controlled, making mode switching and attitude control more flexible and precise.

[0020] 3. The four-point symmetrical power layout and its structural optimization significantly reduce the aerodynamic interference between the power unit and the fuselage and wings, thereby improving flight stability.

[0021] 4. Employing jet propulsion, it effectively improves cruising speed and flight efficiency compared to existing vertical takeoff and landing fixed-wing aircraft.

[0022] 5. The outward-pointing nozzle layout reduces the risk of attitude instability caused by the difference in thrust during takeoff and landing. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of a vertical takeoff and landing fixed-wing aircraft based on a thrust vectoring nozzle.

[0024] Figure 2 This is a front view schematic diagram of a vertical takeoff and landing fixed-wing aircraft based on a thrust vectoring nozzle;

[0025] Figure 3 This is a schematic diagram of the left-side structure of a vertical takeoff and landing fixed-wing aircraft based on a thrust vectoring nozzle;

[0026] Figure 4 This is a top-view structural diagram of a vertical takeoff and landing fixed-wing aircraft based on a thrust vectoring nozzle;

[0027] Figure 5 This is a schematic diagram of the thrust line direction of a hovering mode engine for a vertical takeoff and landing fixed-wing aircraft based on a thrust vectoring nozzle.

[0028] Reference numerals: 1-engine, 2-thrust vectoring nozzle, 3-wing, 4-fuselage, 5-T-tail, 6-support. Detailed Implementation

[0029] The invention will now be further explained with reference to the accompanying drawings.

[0030] A vertical takeoff and landing fixed-wing aircraft based on a thrust vectoring nozzle consists of an engine 1, a thrust vectoring nozzle 2, a T-tail fin 5, a wing 3, a fuselage 4, and a support 6. The engine 1 and the thrust vectoring nozzle 2 are combined to form a power unit, and the entire aircraft is equipped with four power units.

[0031] 1. Overall layout:

[0032] The entire aircraft uses a carbon fiber composite fuselage, and wing 3 is a straight wing. The four power plants are arranged in a four-point isosceles trapezoidal symmetrical layout: two are symmetrically arranged at the front of fuselage 4, and two are symmetrically arranged at the rear of fuselage 4. The front and rear power plants are longitudinally symmetrical about the center of gravity of the aircraft, which is used to balance the pitch moment of the fuselage and reduce torque interference.

[0033] The thrust vector nozzle 2 adopts the existing mechanical hydraulic thrust vector nozzle or fluid thrust vector nozzle. The thrust vector angle can be continuously adjusted within a range of not less than -95° to +15°, with the fuselage axis of the level aircraft as the 0° reference, downward is negative and upward is positive.

[0034] Engine 1 uses mature power forms such as electric ducted engines and turbojet engines. The cross-sectional area of ​​the single power plant at the front (engine and thrust vectoring nozzle assembly) perpendicular to the wing span is 95% to 100% of the maximum cross-sectional area of ​​the fuselage at the same wing span position.

[0035] Wing 3 is the main part that provides lift. Different types can be selected according to different mission requirements. If used in urban operation scenarios, the sweep angle of wing 3 should be ≤15° and the aspect ratio should be ≥6 to ensure a high lift-to-drag ratio and balance speed and range.

[0036] The bracket 6 is used to connect the power unit and the fuselage 4. The frontal area of ​​the bracket 6 is no more than 20% of the maximum cross-sectional area of ​​the engine 1 in order to reduce pressure resistance. Specifically, existing mature mounting bracket designs can be used.

[0037] The T-tail configuration 5 places the horizontal tail at the top of the vertical tail, which reduces the impact of the downwash and maintains maneuverability during stall, thus enhancing aircraft safety. The horizontal tail of the T-tail 5 uses a swept trapezoidal wing to improve aerodynamic efficiency during high-speed cruise, reduce wave drag, and increase the lift-to-drag ratio.

[0038] 2. Front power unit constraints:

[0039] The lateral spacing between the two front power units is 2.5 to 3 times that of the lateral spacing between the two rear power units.

[0040] The geometric centerline of the forward power unit is vertically projected onto the spanwise reference plane of the wing. The spanwise distance from this projection position to the midpoint of the wing root chord is 40% to 60% of the total wing span, which is used to achieve the optimal lift enhancement effect.

[0041] The geometric centerline of the forward power unit is higher than the height reference line of the leading edge of the wing in the vertical height direction, and the lowest point of the outer wall of the thrust vector nozzle is not higher than the height reference line of the leading edge of the wing in the vertical height direction. The height difference between the two does not exceed 200% of the nozzle exit radius, so that the jet of the thrust vector nozzle 2 flows along the upper surface of the wing to achieve aerodynamic lift.

[0042] 3. Rear power unit constraints:

[0043] The vertical height of the lowest point of the outer wall of the rear power unit air intake is not lower than the vertical height of the top vertex of the maximum thickness of the wing, in order to reduce the influence of the airflow passing through the wing 3 and optimize the air intake conditions of the rear power unit.

[0044] The vertical height of the lowest point of the outer wall of the rear power unit is not higher than the vertical height of the highest point of the fuselage, and the vertical height difference between the central axis of the rear power unit and the geometric central axis of the front power unit is 1 to 1.5 times the radius of the power unit's air intake, in order to ensure the longitudinal stability of the aircraft.

[0045] The horizontal distance between the centerline of the rear power unit and the outermost point of the fuselage is not less than the diameter of the power unit's air intake, so as to reduce the influence of airflow near the fuselage surface.

[0046] The flight mode control of the vertical takeoff and landing fixed-wing aircraft with the above structure is as follows:

[0047] Vertical Takeoff and Landing Phase / Hovering Mode: The thrust line of the front thrust vectoring nozzle forms an angle α with the vertical direction, α≤15°, and the nozzle exhaust is outward-pointing to improve the lateral stability of the aircraft and reduce the aircraft attitude instability caused by possible thrust difference between the power plants during takeoff and landing; the total thrust of the front power plant is greater than that of the rear power plant to achieve thrust balance between the front and rear of the aircraft in the vertical direction. Preferably, the ratio of total front thrust to total rear thrust is 1.5~1.6:1; by changing the thrust line direction of the front thrust vectoring nozzle, and coordinating with the yaw and pitch rudders of the T-tail, hovering attitude rotation control is achieved.

[0048] Hovering to level flight transition mode: During mode switching, the thrust vector angle adjustment angular velocity of the forward power unit is 10%~15% slower than that of the aft power unit to maintain a slight pitch-up attitude (aircraft angle of attack ≤10°), utilizing aerodynamic angle of attack to increase lift and achieve smooth mode switching. Preferably, the angular velocity of the aft power unit is used as a reference, with a reference velocity of 10° / s~15° / s.

[0049] Level flight mode: The thrust vector angle of the rear power plant is kept within ±10°, so that the thrust of the rear power plant is in a horizontal state; the two front power plants are independently controlled. By adjusting the thrust vector angle of the two power plants respectively, combined with the deflection of the ailerons and T-tail control surfaces, pitch, roll and yaw full attitude control can be achieved.

[0050] In this embodiment, the wings 3, fuselage 4, and T-tail 5 are all made of carbon fiber and composite materials, and the overall structure is lightweight while meeting the strength requirements for flight. The overall length of the aircraft is 990mm, the wingspan of wing 3 is 1190mm, the chord sweep angle of wing 3 is 12.5°, the aspect ratio is 6, and the horizontal tail section of the T-tail 5 has a span of 370mm; the effective area of ​​the wing control surfaces is 10% of the overall effective aerodynamic area of ​​wing 3; the maximum deflection angle of the wing control surfaces is ±20°; the maximum cross-sectional diameter of the engine is 70mm, and the total length of a single power plant is 300mm; the full-load power of engine 1 is approximately 1640W, and the maximum thrust is 22.5N; the takeoff weight is 6kg; the center of gravity of the aircraft is located in the area between the leading edge of wing 3 and 1 / 3 of the chord length of wing 3; the lateral spacing between the forward power plants is 2.8 times that of the aft power plants; the spanwise projection of the forward power plants is 50% of the wing root; the height difference between the centerlines of the forward and aft power plants is 1.2 times the air intake radius; the horizontal distance between the centerline of the aft power plant and the outermost part of the fuselage is 1.2 times the air intake diameter.

[0051] To verify the improvements in structural dead weight, control accuracy, and flight stability of the vertical takeoff and landing fixed-wing aircraft in this embodiment, a conventional tiltrotor fixed-wing aircraft of the same class was selected as a comparison object for comparative analysis and simulation verification under unified design specifications and mission profiles. Compared with the typical layout of "multi-rotor tiltrotor vertical takeoff and landing," this embodiment does not require an additional tilt mechanism under both vertical takeoff and landing and level flight conditions, meaning there is virtually no structural dead weight, thus avoiding the problem of the power system becoming a redundant load in the traditional configuration.

[0052] Regarding control accuracy, the airflow deflection angular velocity of the power unit and the time required to reach the final deflection angle under the same allowable error conditions under a specified initial deflection angle were used as indicators. The results showed that the airflow deflection angular velocity of the comparative configuration was 500° / s, and the time required to reach the specified angle was 0.8s. In this embodiment, the airflow deflection angular velocity was 750° / s, an improvement of about 50%, and the time required to reach the specified angle was less than 0.3s, an improvement of about 62.5%. This improvement significantly enhanced the control accuracy and flexibility of the aircraft.

[0053] Regarding flight stability, simulation calculations of the directional static stability derivative show that the directional static stability derivative of the comparative configuration is 0.069, while that of this embodiment is improved to 0.092, an improvement of approximately 33.4%. This improvement is mainly due to the more rational layout of the power plant with the fuselage and wings, reducing the interference of the airflow generated by the power plant on the airflow flowing through the wings. At the same time, the symmetrical layout of the entire aircraft and the more rational center of gravity constraint improve lateral aerodynamic center stability. In addition, the T-tail configuration is less affected by the airflow flowing through the fuselage and wings, which also improves pitch stability during flight.

[0054] In summary, under the same conditions, this embodiment has virtually no structural dead weight, improves control accuracy by more than 56%, and improves flight stability by more than 30%, significantly enhancing the overall performance and practicality of the aircraft.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A vertical takeoff and landing fixed-wing aircraft based on a thrust vectoring nozzle, characterized in that, It includes four engines (1), four thrust vectoring nozzles (2), wings (3), fuselage (4), and T-tail (5); The engine (1) and the thrust vector nozzle (2) form a power unit. A total of four power units adopt a four-point isosceles trapezoidal symmetrical layout. Two sets are symmetrically arranged at the front of the fuselage and two sets are symmetrically arranged at the rear of the fuselage. The front and rear power units are symmetrically arranged about the center of gravity of the whole machine. The lateral spacing between the two front power units is 2.5 to 3 times the lateral spacing between the two rear power units; The geometric centerline of the forward power unit is vertically projected onto the spanwise reference plane of the wing. The spanwise distance from the projection position to the midpoint of the root chord of the wing is 40% to 60% of the total wing span. The centerline of the forward power unit is higher than the leading edge height baseline of the wing in the vertical height direction, and the lowest point of the outer wall of the thrust vectoring nozzle is not higher than this height baseline. The difference in vertical height between the two does not exceed 200% of the nozzle exit radius. The lowest point of the outer wall of the rear power unit air intake shall not be lower than the top vertex of the maximum thickness of the wing; The lowest point of the outer wall of the rear power unit's air intake is not higher than the highest point of the fuselage, and the vertical height difference between the central axis of the rear and front power units is 1 to 1.5 times the radius of the power unit's air intake. The horizontal distance between the central axis of the rear power unit and the outermost outermost part of the fuselage shall not be less than the diameter of the power unit's air inlet. The thrust vector angle of the thrust vector nozzle can be continuously adjusted within a range of not less than -95° to +15°.

2. The vertical takeoff and landing fixed-wing aircraft according to claim 1, characterized in that, The cross-sectional area of ​​the single forward power unit perpendicular to the wing span is 95% to 100% of the maximum cross-sectional area of ​​the fuselage at the same wing span position.

3. The vertical takeoff and landing fixed-wing aircraft according to claim 1, characterized in that, The sweep angle of the wing (3) is ≤15° and the aspect ratio is ≥6.

4. The vertical takeoff and landing fixed-wing aircraft according to claim 1, characterized in that, The horizontal tail of the T-tail (5) is a swept trapezoidal wing.

5. The vertical takeoff and landing fixed-wing aircraft according to claim 1, characterized in that, The frontal area of ​​the bracket connecting the power unit and the fuselage shall not exceed 20% of the maximum cross-sectional area of ​​the engine.

6. The vertical takeoff and landing fixed-wing aircraft according to claim 1, characterized in that, During vertical takeoff and landing, the exhaust direction of the front thrust vector nozzle is outward V-shaped, and the angle between the thrust line and the vertical direction is no more than 15°.

7. The vertical takeoff and landing fixed-wing aircraft according to claim 1, characterized in that, During the transition from hovering to level flight, the thrust vector angle adjustment angular velocity of the front power unit is 10% to 15% slower than that of the rear power unit, and the aircraft's angle of attack is no greater than 10°.

8. The vertical takeoff and landing fixed-wing aircraft according to claim 1, characterized in that, In level flight mode, the thrust vector angle of the rear power unit is maintained within ±10°.

9. The vertical takeoff and landing fixed-wing aircraft according to claim 1, characterized in that, The engine is an electric ducted engine or a turbojet engine; the thrust vectoring nozzle is a mechanical-hydraulic or fluid thrust vectoring nozzle.

10. The vertical takeoff and landing fixed-wing aircraft according to claim 6, characterized in that, In hovering mode, the total thrust of the front power unit is greater than that of the rear power unit. Attitude control is achieved by changing the thrust line direction of the front thrust vector nozzle and cooperating with the control surfaces of the T-tail (5).

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