Low-noise rotor wing for ducted vertical take-off and landing aircraft

Abstract

The invention relates to the field of propellers or rotors for airplanes, in particular to a low-noise rotor for a ducted vertical take-off and landing aircraft. The ducted low-noise rotor wing for the vertical take-off and landing aircraft comprises a ducted body (1), a support frame (21), a rotating shaft (22) and a rotor wing (3), and is characterized in that the rotor wing (3) is provided with a lower dihedral angle (31) and a sharp part (32), and the lower dihedral angle (31) is-5 degrees to-10 degrees; the sharpening ratio of the rotor wing (3) is 0.5-0.7; the diameter of the rotating surface of the rotor wing (3) is 2.1 R, the average chord length of the rotor wing (3) is 0.2 R, and the average thickness of the rear end of the rotor wing (3) is 0.04 R. Noise is effectively reduced, and lifting force is improved.

Description

Technical Field

[0001] The invention relates to the field of propellers or rotors for aircraft, in particular to a low-noise rotor for ducted vertical take-off and landing aircraft. Background Art

[0002] A ducted flying car is a flying car that wraps the propeller and power unit inside a ducted casing with a certain thickness and shape in cross section. Due to the ducted design, its rotor has a good noise suppression effect, but its ability to suppress low-frequency noise is relatively weak, and the increase in lift level requirements brought about by the addition of ducts still needs to be further resolved.

[0003] The main sources of noise when a ducted flying car is working are composed of three parts, namely the noise generated when the rotor rotates, the monopole and dipole sound sources formed when the blades rotate at high speed, and the jet noise generated by the impact and shear of the wake flow at the bottom of the duct on the surrounding static air. The existence of the duct has a certain blocking effect on the noise, so turbulent noise has become the main source of noise for the entire flying car. By optimizing and adjusting the structure of the shear layer, it can play a role in adjusting the generation and development of turbulence, thereby effectively controlling the turbulent characteristics of the velocity shear layer, thereby reducing the jet noise. At the same time, due to the introduction of the duct, the overall weight of the flying car increases, so the required lift is also increased. Without changing the structure of the ducted rotor, the working speed of the rotor will be increased, which will indirectly lead to the generation of noise. Therefore, it is also worth paying attention to the study of changing the structure of the ducted rotor to increase the lift level at the same speed.

[0004] The main means of rotor noise reduction include the modification of the rotor structure. Introducing designs such as bionic serrations on ducted rotors can effectively reduce noise levels and increase lift levels, but there is currently no noise reduction research and measures for bionic serrations or lower surface protrusion arrays used in ducted rotors. Existing research on rotor noise reduction mainly focuses on the serration of ordinary rotor blades. For example, Wang Bing used three biological characteristics of owls (trailing edge serration structure, leading edge protrusion structure, and wing lower surface texture structure) to improve the noise reduction of drone rotors, but the application of these three separately only has a certain effect on noise reduction or lift enhancement, and cannot take into account both noise reduction and lift improvement at the same time. Yang Chenghao et al. added trailing edge serration structures of different heights to the upstream and downstream static blades of the engine turbine blades, and verified them by numerical simulation. The trailing edge serrations will generate microjets at the tooth root to reduce the impact of the back jet and weaken the unsteady interference effect, reducing the noise by 8.7dB and 11.8dB at 1BPF and 2BPF respectively, thereby improving aerodynamic performance while reducing noise. However, the leading edge of the downstream blade will be affected by the dual influence of the adverse pressure gradient and the back jet, increasing the noise, resulting in a small improvement in the overall noise level. Summary of the invention

[0005] In order to overcome the defects of the prior art and provide an aircraft with reduced noise and improved lift, the present invention discloses a low-noise rotor for a ducted vertical take-off and landing aircraft.

[0006] The present invention achieves the purpose of the invention through the following technical solutions: A ducted low-noise rotor for a vertical take-off and landing aircraft comprises a duct body, a support frame, a rotating shaft and a rotor, wherein the duct body is an annular shell, the support frame is hollow, the support frame is fixed to the inner side surface of the duct body through the outer end, the rotating shaft is rotatably arranged at the center of the supporting frame through a bearing, the rotor is centrally symmetrical, the rotor is connected and fixed through the rotation center and the rotating shaft, the central axes of the duct body, the support frame, the rotating shaft and the rotor coincide with each other, and the invention is characterized in that: The angle of attack (2) of the rotor is not greater than 2°; The rotor is provided with an anhedral angle and a taper. If the distance from the outer end to the center of the rotor is R, then: The anhedral position is from 0.85R from the outer end of the rotor to the center of the rotor, and the anhedral angle is -5° to -10°; the taper position is from 0.7R from the outer end of the rotor to the center of the rotor, and the taper ratio of the rotor is 0.5 to 0.7; The diameter of the rotor rotating surface is 2.1R, the average chord length of the rotor is 0.2R, that is, the ratio of the rotor surface area to the rotor wingspan, and the average thickness of the rear end of the rotor is 0.04R.

[0007] The ducted low-noise rotor for a vertical take-off and landing aircraft is characterized by: Both the upper and lower surfaces of the rotor are provided with raised structures, which are arrays composed of raised units aligned vertically and horizontally or arranged in a criss-cross pattern, and the raised units are regular triangular pyramids whose bottom surfaces are regular triangles or regular triangular prisms whose cross sections are isosceles triangles; when the raised units are regular triangular pyramids, the raised units are fixed on the lower surface of the rotor with their bottom surfaces serving as fitting surfaces so that the apex of the raised units faces the outside of the rotor; when the raised units are regular triangular prisms, the raised units are fixed on the lower surface of the rotor with the side surfaces where the bottom edges of the top and bottom surfaces are located as fitting surfaces, with the side edges where the apex of the top and bottom surfaces of the raised units are located as top edges facing the outside of the rotor.

[0008] The ducted low-noise rotor for a vertical take-off and landing aircraft is characterized by: The raised structure starts from near the outer end of the rotor and ends near the center of the rotor. The chord length of the rotor at the starting end of the raised structure is 0.6R, and the chord length of the rotor at the end of the raised structure is 0.95R. The height of each protrusion unit is set in proportion to the distance between the protrusion unit and the outer end of the rotor, ranging from a minimum of 2.5 mm to a maximum of 19.3 mm.

[0009] The ducted low-noise rotor for a vertical take-off and landing aircraft is characterized by: When the raised unit is a regular triangular pyramid, the vertex angles θ of the three isosceles triangle sides at the vertex of the raised unit are all 12° to 16°, the distance between the vertices of two adjacent raised units is the center distance s, s is 10 mm, and the height of the regular triangle on the bottom of the raised unit is the thickness h, h is 0.83 mm; When the raised unit is a regular triangular prism, the angle θ formed by the two rectangular side surfaces at the top edge of the raised unit is 12° to 16°, the distance between the top edges of two adjacent raised units is the center distance s, s is 10 mm, and the height of the regular triangle on the bottom surface of the raised unit is the thickness h, h is 0.83 mm.

[0010] The ducted low-noise rotor for a vertical take-off and landing aircraft is characterized by: The duct body includes a front lip and a rear cone, the front lip is a rotating shell whose generatrix is ​​an arc, and the rear cone is a truncated cone shell, and the rear end face of the front lip and the large circular end face of the rear cone are smoothly connected; The support frame is star-shaped, and the connecting lines of the outer end points of the support frame form an inscribed regular polygon of the inner side wall of the duct body with the rotating shaft as the center.

[0011] The ducted low-noise rotor for a vertical take-off and landing aircraft is characterized by: Assume that the radius of the front lip generatrix is ​​r, the inner diameter d of the front end surface of the front lip is 9r~9.5r, the inner diameter D of the rear end surface of the front lip is 10r~11r, the thickness δ of the duct body does not exceed 0.2r, and the cone angle β of the rear cone is 5°~10°; The maximum thickness of the support frame is 12% to 20% of the side length of the square formed by connecting the four vertices of the support frame.

[0012] The ducted rotor for a vertical take-off and landing aircraft is characterized by: The support frame is cross-shaped, and the maximum thickness of the support frame is 18% of the side length of the square formed by the connecting lines of the four vertices of the support frame. The diameter of the rotor rotating surface is 2.05R.

[0013] The ducted rotor for vertical take-off and landing aircraft is characterized in that it also includes a top cover and a nut, the outer side surface of the rotating shaft is provided with an external thread that matches the internal thread of the nut, and the middle part of the top cover is provided with a through hole. After the top cover is inserted into the rotating shaft through the middle through hole, the nut is screwed into the rotating shaft to fix the top cover and the rotating shaft, thereby fastening the rotor to the rotating shaft; the design of the top cover can further maintain the rotor with better dynamic balancing performance, and is also convenient to use. The entire rotor can be pre-assembled or temporarily assembled.

[0014] Inspired by the feather structure of owl wings, the present invention designs and manufactures a raised structure 4 in the form of an array on the lower surface of the rotor 3 according to the actual requirements of the ducted rotor of a flying car, and debugs the parameter combination through experiments. The reason why the raised structure 4 can effectively improve the lift is mainly related to its influence on the airflow and the change in pressure distribution. In addition, the raised structure 4 on the lower surface can change the airflow flow characteristics of the lower surface of the rotor 3. When the airflow flows through the raised structure 4, first, the raised structure 4 will guide the airflow to the lower surface of the rotor 3, delay the detachment of the airflow on the lower surface, increase the surface vortex at the raised structure 4, and then increase the pressure on the lower surface of the rotor 3. Secondly, the raised structure 4 reduces the flow velocity of the airflow on the lower surface of the rotor 3 and increases the flow velocity on the upper surface of the rotor 3. This speed difference leads to a pressure difference between the upper and lower sides of the rotor 3, thereby generating lift. Experiments have shown that compared with ordinary ducted rotors, the rotor 3 of the present invention can effectively suppress the noise generated during takeoff and landing under the same flight conditions. In addition, when the present invention is in operation, the rotor (3) rotates under the drive of the rotating shaft (22), so that the airflow flows in from the front lip 11 of the duct body 1, and the airflow is accelerated under the drive of the rotor (3) and pushed to the tail of the duct body (1) through the rear cone 12 to flow out. In this process, the design of the protruding structure 4 on the lower surface of the rotor (3) improves the starting performance of the rotor 3, and under the condition of providing the same lift, the required rotation speed requirement is reduced, which also indirectly plays a role in reducing noise.

[0015] The ducted rotor of the present invention is also portable. In addition to being used in flying cars, it can also be used in other rotating machinery that requires noise reduction, such as fan blades, axial flow fans, etc., and can effectively reduce aerodynamic noise.

[0016] The present invention has the following beneficial effects: The present invention designs the airfoil thickness, airfoil angle of attack, airfoil taper and airfoil undercut; in the design of the lower surface of the airfoil, a protrusion structure array is designed, and the lower surface protrusion array effectively improves the pressure distribution at the trailing edge of the rotor and the adhesion state of the airflow at the lower surface of the rotor, which significantly improves the lift level. These measures have a significant suppressive effect on the noise of ducted flying cars, and also improve their lift level. It is used in flying cars to make the flight quieter and more suitable for flying in high-sound-sensitive areas such as cities, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention, Figure 2 is a front view of the duct body in the present invention, Figure 3 is an axonometric view of the duct body in the present invention, Figure 4 is a front view of the rotor in the present invention, Figure 5 is a top view of the rotor in the present invention, Figure 6 and Figure 7 These are partial enlarged views of the protruding structure on the lower surface of the rotor in the present invention. Figure 8 It is an axonometric view of the top cover in the present invention. DETAILED DESCRIPTION

[0018] The present invention is further described below by means of specific examples.

[0019] Example 1 A ducted low-noise rotor for a vertical take-off and landing aircraft comprises a ducted body 1, a support frame 21, a rotating shaft 22 and a rotor 3, as shown in FIG. Figures 1 to 8 As shown, the specific structure is: Duct body 1 Figures 1 to 3 As shown, the duct body 1 is an annular shell, the support frame 21 is hollow, the support frame 21 is fixed to the inner side of the duct body 1 through the outer end, the rotating shaft 22 is rotatably arranged at the center of the support frame 21 through a bearing, the rotor 3 is centrally symmetrical, the rotor 3 is connected and fixed to the rotating shaft 22 through the rotation center, and the central axes of the duct body 1, the support frame 21, the rotating shaft 22 and the rotor 3 coincide with each other; like Figure 4 and Figure 5 As shown, the angle of attack 2 of the rotor 3 is not greater than 2°; The rotor 3 is provided with an anhedral angle 31 and a taper 32. Assuming that the distance from the outer end to the center of the rotor 3 is R, and R=250mm, then: The position of the anhedral angle 31 is from 0.85R of the outer end of the rotor 3 to the center of the rotor 3, and the anhedral angle 31 is -10°; the position of the taper 32 is from 0.7R of the outer end of the rotor 3 to the center of the rotor 3, and the taper ratio of the rotor 3 is 0.7; The diameter of the rotating surface of the rotor 3 is 2.05R, the average chord length of the rotor 3 is 0.2R, that is, the ratio of the surface area of ​​the rotor 3 to the wingspan of the rotor 3, and the average thickness of the rear end of the rotor 3 is 0.04R.

[0020] In this embodiment: both the upper and lower surfaces of the rotor 3 are provided with a protrusion structure 4, which is an array composed of protrusion units 41 aligned vertically and horizontally or arranged in a crisscross pattern, and the protrusion unit 41 is a regular triangular pyramid with a regular triangle bottom surface or a regular triangular prism with an isosceles triangle cross section; when the protrusion unit 41 is a regular triangular pyramid, the protrusion unit 41 is fixed on the lower surface of the rotor 3 with its bottom surface as a fitting surface so that the vertex of the protrusion unit 41 faces the outside of the rotor 3; when the protrusion unit 41 is a regular triangular prism, the protrusion unit 41 is fixed on the lower surface of the rotor 3 with the side surfaces where the bottom edges of the top and bottom surfaces are located as fitting surfaces, with the side edges where the vertices of the top and bottom surfaces of the protrusion unit 41 are located as top edges facing the outside of the rotor 3.

[0021] In this embodiment: the protruding structure 4 starts from the outer end of the rotor 3 to the center of the rotor 3, the chord length of the rotor 3 at the starting end of the protruding structure 4 is 0.6R, and the chord length of the rotor 3 at the end of the protruding structure 4 is 0.95R; The height of each protrusion unit 41 is set in proportion to the distance between the protrusion unit 41 and the outer end of the rotor 3, ranging from a minimum of 2.5 mm to a maximum of 19.3 mm.

[0022] When the protruding unit 41 is a regular triangular pyramid, the vertex angles θ of the three isosceles triangle sides at the vertices of the protruding unit 41 are all 16°, the distance between the vertices of two adjacent protruding units 41 is the center distance s, s is 10 mm, and the height of the regular triangle at the bottom of the protruding unit 41 is the thickness h, h is 0.83 mm; When the protrusion unit 41 is a regular triangular prism, as Figure 6 As shown, the angle θ formed by the two rectangular sides at the top edge of the protruding unit 41 is 16°, and the distance between the top edges of two adjacent protruding units 41 is the center distance s, and s is 10 mm. Figure 7 As shown, the height of the equilateral triangle of the bottom surface of the protrusion unit 41 is taken as the thickness h, and h is 0.83 mm.

[0023] In this embodiment: Figure 2 As shown, the duct body 1 includes a front lip 11 and a rear cone 12, the front lip 11 is a rotating shell whose generatrix is ​​an arc, and the rear cone 12 is a truncated cone shell, and the rear end surface of the front lip 11 and the large circular end surface of the rear cone 12 are smoothly connected; The support frame 21 is in a cross shape, and the connecting line of each outer end point of the support frame 21 forms an inscribed square of the inner side wall of the duct body 1 with the rotating shaft 3 as the center.

[0024] In this embodiment: the radius of the generatrix of the front lip 11 is r, and r=60mm, the inner diameter d of the front end surface of the front lip 11 is 550mm, the inner diameter D of the rear end surface of the front lip 11 is 600mm, the thickness δ of the duct body 1 does not exceed 12mm, and the cone angle β of the rear cone 12 is 10°; The maximum thickness of the support frame 21 is 18% of the side length of the square formed by connecting the four vertices of the support frame 21 .

[0025] This embodiment also includes a top cover 5 and a nut. The outer surface of the rotating shaft 22 is provided with an external thread that matches the internal thread of the nut. A through hole is provided in the middle of the top cover 5. After the top cover 5 is inserted into the rotating shaft 22 through the middle through hole, the nut is screwed into the rotating shaft 22 to fix the top cover 5 and the rotating shaft 22, thereby fastening the rotor 3 to the rotating shaft 22. The thickness of the top cover 5 is 2 mm. The design of the top cover 5 can further maintain the rotor 3 with better dynamic balancing performance, and is also convenient to use. The entire rotor 3 can be pre-assembled or temporarily assembled.

[0026] In this embodiment, a protrusion structure 4 in the form of an array is provided on the lower surface of the rotor 3, and the parameter combination is debugged through experiments. The reason why the protrusion structure 4 can effectively improve the lift is mainly related to its influence on the airflow and the change of pressure distribution. In addition, the protrusion structure 4 on the lower surface can change the airflow flow characteristics of the lower surface of the rotor 3. When the airflow flows through the protrusion structure 4, firstly, the protrusion structure 4 will guide the airflow to the lower surface of the rotor 3, delay the detachment of the airflow on the lower surface, increase the surface vortex at the protrusion structure 4, and then increase the pressure on the lower surface of the rotor 3. Secondly, the protrusion structure 4 reduces the flow velocity of the airflow on the lower surface of the rotor 3 and increases the flow velocity on the upper surface of the rotor 3. This speed difference leads to a pressure difference between the upper and lower sides of the rotor 3, thereby generating lift. Experiments have shown that compared with ordinary ducted rotors, the rotor 3 using the present invention can effectively suppress the noise generated during takeoff and landing under the same flight conditions. In addition, when the present invention is in operation, the rotor 3 rotates driven by the rotating shaft 22, so that the airflow flows in from the front lip 11 of the duct body 1, and the airflow is accelerated by the drive of the rotor 3 and pushed to the tail of the duct body 1 through the rear cone 12 to flow out. In this process, the design of the raised structure 4 on the lower surface of the rotor 3 improves the starting performance of the rotor 3, and under the condition of providing the same lift, the required rotation speed requirement is reduced, which also indirectly plays a role in reducing noise.

Claims

1. A ducted low-noise rotor for a vertical take-off and landing aircraft, comprising a ducted body (1), a support frame (21), a rotating shaft (22) and a rotor (3), wherein the ducted body (1) is an annular shell, the support frame (21) is hollow, the support frame (21) is fixed to the inner side surface of the ducted body (1) through the outer end, the rotating shaft (22) is rotatably arranged at the center of the support frame (21), the rotor (3) is centrally symmetrical, the rotor (3) is connected and fixed to the rotating shaft (22) through the rotation center, and the central axes of the ducted body (1), the support frame (21), the rotating shaft (22) and the rotor (3) coincide with each other, and the invention is characterized in that: The angle of attack (2) of the rotor (3) is not greater than 2°; The rotor (3) is provided with an anhedral angle (31) and a taper (32). Assuming that the distance from the outer end to the center of the rotor (3) is R, then: The position of the anhedral angle (31) is from 0.85R of the outer end of the rotor (3) to the center of the rotor (3), and the anhedral angle (31) is -5° to -10°; the position of the taper (32) is from 0.7R of the outer end of the rotor (3) to the center of the rotor (3), and the taper ratio of the rotor (3) is 0.5 to 0.7; The diameter of the rotating surface of the rotor (3) is 2.1R, the average chord length of the rotor (3) is 0.2R, that is, the ratio of the surface area of ​​the rotor (3) to the wingspan of the rotor (3), and the average thickness of the rear end of the rotor (3) is 0.04R.

2. The ducted low-noise rotor for a vertical take-off and landing aircraft according to claim 1, characterized in that: The upper and lower surfaces of the rotor (3) are both provided with a protrusion structure (4), the protrusion structure (4) being an array composed of protrusion units (41) aligned vertically and horizontally or arranged in a crisscross pattern, the protrusion unit (41) being a regular triangular pyramid with a regular triangular bottom surface or a regular triangular prism with an isosceles triangle cross section; when the protrusion unit (41) is a regular triangular pyramid, the protrusion unit (41) is fixed on the lower surface of the rotor (3) with its bottom surface as a fitting surface so that the vertex of the protrusion unit (41) faces the outside of the rotor (3); when the protrusion unit (41) is a regular triangular prism, the protrusion unit (41) is fixed on the lower surface of the rotor (3) with the side surface where the bottom edge of the top surface and the bottom surface is located as a fitting surface, and the side edge where the vertex of the top surface and the bottom surface of the protrusion unit (41) is located as the top edge faces the outside of the rotor (3).

3. The ducted low-noise rotor for a vertical take-off and landing aircraft according to claim 2, characterized in that: The protruding structure (4) starts from a position close to the outer end of the rotor (3) and ends at a position close to the center of the rotor (3). The chord length of the rotor (3) at the starting end of the protruding structure (4) is 0.6R, and the chord length of the rotor (3) at the end end of the protruding structure (4) is 0.95R. The height of each protruding unit (41) is set in proportion to the distance between the protruding unit (41) and the outer end of the rotor (3), ranging from a minimum of 2.5 mm to a maximum of 19.3 mm.

4. The ducted low-noise rotor for a vertical take-off and landing aircraft as claimed in claim 3, characterized in that: When the protruding unit (41) is a regular triangular pyramid, the vertex angles θ of the three isosceles triangle sides at the apex of the protruding unit (41) are all 12° to 16°, the distance between the vertices of two adjacent protruding units (41) is the center distance s, s is 10 mm, and the height of the regular triangle at the bottom of the protruding unit (41) is the thickness h, h is 0.83 mm; When the protruding unit (41) is a regular triangular prism, the angle θ formed by the two rectangular side surfaces at the top edge of the protruding unit (41) is 12° to 16°, the distance between the top edges of two adjacent protruding units (41) is the center distance s, s is 10 mm, and the height of the regular triangle at the bottom of the protruding unit (41) is the thickness h, h is 0.83 mm.

5. The ducted low-noise rotor for a vertical take-off and landing aircraft according to any one of claims 1 to 4, characterized in that: The duct body (1) comprises a front lip (11) and a rear cone (12), wherein the front lip (11) is a rotating shell whose generatrix is ​​an arc, and the rear cone (12) is a truncated cone-shaped shell, and the rear end surface of the front lip (11) and the large circular end surface of the rear cone (12) are smoothly connected; The support frame (21) is star-shaped, and the connecting line of each outer end point of the support frame (21) forms an inscribed regular polygon of the inner side wall of the duct body (1) with the rotating shaft (3) as the center.

6. The ducted low-noise rotor for a vertical take-off and landing aircraft according to claim 5, characterized in that: Assuming that the radius of the generatrix of the front lip (11) is r, the inner diameter d of the front end surface of the front lip (11) is 9r to 9.5r, the inner diameter D of the rear end surface of the front lip (11) is 10r to 11r, the thickness δ of the duct body (1) does not exceed 0.2r, and the cone angle β of the rear cone (12) is 5° to 10°; The support frame (21) is in a cross shape, and the maximum thickness of the support frame (21) is 12% to 20% of the side length of a square formed by connecting lines of four vertices of the support frame (21).

7. The ducted rotor for a vertical take-off and landing aircraft according to claim 6, characterized in that: The maximum thickness of the support frame (21) is 18% of the side length of a square formed by connecting lines of four vertices of the support frame (21), and the diameter of the rotating surface of the rotor (3) is 2.05R.

8. The ducted rotor for a vertical take-off and landing aircraft according to claim 7, characterized in that: The invention also comprises a top cover (5) and a nut. The outer surface of the rotating shaft (22) is provided with an external thread matching the internal thread of the nut. A through hole is provided in the middle of the top cover (5). After the top cover (5) is inserted into the rotating shaft (22) through the middle through hole, the nut is screwed into the rotating shaft (22) to fix the top cover (5) and the rotating shaft (22), thereby fastening the rotor (3) to the rotating shaft (22).

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