A thin-wall narrow-edge duct fan capable of reducing side wind interference

Abstract

This invention discloses a thin-walled, narrow-edge ducted fan that reduces crosswind interference. The fan comprises a duct shell, a multi-faceted frame, a trailing edge fairing, and a leading edge fairing. A drive motor is housed within the trailing edge fairing, and the bottom of the fairing is connected to the drive motor's base via screws. A motor rod extends from the drive motor, passing through the multi-faceted frame. The duct shell and leading edge fairing are fixedly connected by screws, and the motor rod is rotatably connected to the hub frame of the multi-faceted frame via bearings. The duct shell features a thin-walled, narrow-edge design, with the ratio of the duct shell's side length L to its inner diameter d being L / d ≤ 1 / 6. The interior of the duct shell is filled with foam, and the maximum wall thickness h of the outer wall satisfies either h = 1.5 mm, L ≤ 20 mm or 1.5 mm ≤ h ≤ 0.075L, L ≥ 20 mm. This design significantly reduces the weight of the shell compared to ordinary ducted fans, and when mounted on drones, it can reduce drag during high-speed level flight and mitigate crosswind effects during hovering and vertical takeoff and landing.

Description

Technical Field

[0001] This invention relates to the field of ducted fan technology, and more particularly to a thin-walled, narrow-sided ducted fan that can reduce crosswind interference. Background Technology

[0002] Ducted fans, with their annular duct structure actively constraining the blade flow field, significantly improve aerodynamic efficiency and safety (such as preventing blade impacts with foreign objects and suppressing tip vortex diffusion), and have become an important propulsion solution for low-altitude aircraft. In terms of application scenarios, ducted fan UAVs, due to their low noise characteristics and compact layout, are particularly suitable for the quiet takeoff and landing requirements and covert operation needs of urban air traffic (UAM), as well as the precise control requirements for stable near-wall flight in industrial facility inspections. However, traditional ducted fans, in order to maintain structural rigidity and aerodynamic containment, often employ a large diameter-to-depth ratio duct design, resulting in a significant increase in parasitic mass. When applied to UAVs, this structure leads to a dual aerodynamic disadvantage: under high-speed level flight conditions, the high wetting area generated by the duct outer wall induces frictional drag, causing a surge in the overall drag coefficient, limiting cruise efficiency and flight time; in vertical takeoff and landing / hovering states, the wider duct annular wall increases the lateral windward area, leading to greater crosswind interference and affecting hovering stability. How to reduce the system weight and lateral windwardness of ducted fans is a crucial issue for the widespread application of electric ducted fans.

[0003] Several design methods for ducted fan propellers have been published. Chinese invention patent application CN201611108844.3 proposes a high-efficiency aerodynamic duct body. By slotting the inner wall of the duct, the weight of the duct system is reduced, and the radius of the fan inside the duct is increased, thereby increasing the lift generated by the fan, effectively suppressing the flow environment around the propeller tip, reducing tip loss, and improving fan efficiency. Invention patent application CN202211558786.X proposes a design method for a high thrust-to-weight ratio ducted fan structure. Its blade assembly can withstand higher tensile forces, has high performance, is easy to maintain, and is suitable for various application scenarios. Chinese invention patent application CN202310769643.1 proposes an electric ducted fan device and aircraft. Its ducted fan device uses an elliptical lip design, and the ratio of the duct length to the axial length of the fan blade does not exceed 2, which is shorter than traditional ducts and effectively reduces system weight. The invention patent application CN202111273147.4 proposes a ducted fan inlet structure suitable for level flight and hovering. The duct inlet features intersecting static air ducts along the circumference and at the duct lip, reducing structural weight. This design also eliminates airflow separation inside the duct during hovering, resulting in low total pressure loss at the inlet and ensuring the ducted fan generates significant thrust. The duct length design of the ducted fan described in the above patent prioritizes aerodynamic performance and flight requirements; however, the relatively long duct makes it more susceptible to crosswinds when applied to UAVs. The utility model patent application CN202221695788.9 discloses a ducted fan structure consisting of a ring-shaped first duct and one or more second ducts extending outward from and communicating with the first duct. This structure is smaller and lighter, improving propulsion efficiency when mounted on a UAV, offering a compact structure and improved speed regulation characteristics. However, this structure requires the duct to bear load, placing high demands on the duct materials. The currently published patents related to ducted fans mainly use thicker and wider duct shells, which can cause significant crosswind interference when integrated into drones.

[0004] This invention addresses the needs of ducted fan structures to reduce weight, aerodynamic drag, and crosswind impact by proposing a novel thin-walled narrow-side ducted fan. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problems existing in the prior art and to provide a thin-walled narrow-side ducted fan that can reduce crosswind interference.

[0006] To achieve the above objectives, the technical solution provided by this invention is: a thin-walled, narrow-edge ducted fan that can reduce crosswind interference, comprising a duct shell, a multi-faceted frame, a trailing edge fairing, and a leading edge fairing. The duct shell adopts a thin-walled, narrow-edge design, with the ratio of the side length L of the duct shell to its inner diameter d being L / d≤1 / 6. The interior of the duct shell is filled with foam, and the maximum wall thickness h of the outer wall of the duct shell satisfies: h=1.5mm, L≤20mm or 1.5mm≤h≤0.075L, L≥20mm. The inner diameter of the duct shell is the minimum value of the inner wall diameter. An annular groove is reserved at the rear of the duct shell. The multi-faceted frame includes a head annular frame and a rear hub frame. The head annular frame mates with the reserved annular groove, and the head annular frame and the rear hub frame are fixedly connected by prisms. The head of the trailing edge fairing is fixedly connected to the rear of the hub frame.

[0007] A drive motor is installed inside the trailing edge fairing. The bottom of the trailing edge fairing is connected to the base of the drive motor by screws. The drive motor is located on the central axis of the duct housing. A motor rod extends out of the drive motor. The motor rod passes through the polygonal frame, the duct housing and the leading edge fairing and is fixedly connected by screws. The motor rod is rotatably connected to the hub frame of the polygonal frame through bearings.

[0008] The duct housing contains a blade assembly, which includes a blade hub that is fixedly connected to the motor rod, and a propeller is fixedly connected to the blade hub.

[0009] Preferably, the ratio of the maximum outer diameter D to the inner diameter d of the duct housing lip satisfies: 1.05≤D / d≤1.25.

[0010] Preferably, the outer contour expansion angle θ of the duct shell satisfies: θ≤8°.

[0011] Preferably, the minimum clearance δ between the propeller tip and the inner wall of the duct shell (1) satisfies: δ=1.2mm, D≤120mm or 0.01D≤δ≤0.02D, D≥120mm.

[0012] Preferably, both the duct shell and the polygonal frame are made of composite carbon fiber composite material, and the duct shell and the polygonal frame are designed as an integrated carbon fiber composite material structure. The inner wall of the duct shell is coated with a thermoplastic PEEK-based self-healing coating.

[0013] Beneficial effects of this invention:

[0014] This invention adopts a thin-walled, narrow-sided duct design. The side length of the duct shell does not exceed 1 / 6 of the inner diameter of the duct shell. The interior of the duct shell adopts a foam-filled structure, which greatly reduces the weight of the shell. The weight is significantly reduced compared to ordinary ducted fans. When mounted on a drone, it can reduce drag during high-speed level flight and reduce the crosswind impact during hovering and vertical take-off and landing. Attached Figure Description

[0015] The accompanying drawings, which are provided to further illustrate the invention and constitute a part of this invention, are illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0016] Figure 1 This is a cross-sectional outline of the ducted fan of the present invention;

[0017] Figure 2 These are three views of the ducted fan of the present invention;

[0018] Figure 3 This is a schematic diagram of the connection between the multi-faceted frame and the drive motor of the present invention;

[0019] Figure 4 This is a schematic diagram of the connection between the multi-faceted frame and the duct of the present invention;

[0020] Figure 5 This is a partially enlarged cross-sectional view of the duct housing of the present invention.

[0021] Attached image captions:

[0022] 1-Duct housing, 2-Multi-faceted frame, 3-Drive motor, 4-Trail edge fairing, 5-Propeller assembly, 6-Trail edge fairing. Detailed Implementation

[0023] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0024] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0025] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0026] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0027] Reference Figures 1-5 In a preferred embodiment of the present invention, the ducted housing 1, the polygonal frame 2, the trailing edge fairing 4, and the leading edge fairing 6 are included. The ducted housing 1 adopts a thin-walled, narrow-sided design. The ratio of the side length L of the ducted housing 1 to its inner diameter d is L / d ≤ 1 / 6. Specifically, increasing the length of the ducted housing 1 results in a slow increase in the propeller thrust coefficient, but instead increases the system weight. A shorter side length of the ducted housing 1 can also effectively reduce the crosswind impact on the ducted fan when applied to a UAV. The interior of the ducted housing 1 is filled with foam. The maximum wall thickness h of the outer wall of the ducted housing 1 satisfies: h = 1.5 mm, L ≤ 20 mm or 1.5 mm ≤ h ≤ 0.075L. L≥20mm; the inner diameter of the duct housing 1 is the minimum inner wall diameter of the duct housing 1; the rear of the duct housing 1 has a pre-reserved annular slot; the multi-faceted frame 2 includes a head annular frame and a rear hub frame; the head annular frame fits into the pre-reserved annular slot; the head annular frame and the rear hub frame are fixedly connected by prisms; the head of the trailing edge fairing 4 is fixedly connected to the rear of the hub frame; preferably, the trailing edge fairing 4 is connected to the hub frame by screws.

[0028] A drive motor 3 is installed inside the trailing edge fairing 4. The bottom of the trailing edge fairing is connected to the base of the drive motor by screws. The drive motor 3 is located on the central axis of the duct housing 1. The drive motor 3 is fixedly connected to the hub frame (both the drive motor 3 and the hub frame have threaded holes) by screws. A motor rod extends out of the drive motor 3. The motor rod passes through the polygonal frame 2, the duct housing 1 and is fixedly connected to the leading edge fairing 6 by screws. The motor rod is rotatably connected to the hub frame of the polygonal frame 2 by bearings.

[0029] The duct housing 1 is provided with a blade assembly 5. The blade assembly 5 includes a blade hub that is fixedly connected to a motor rod. A propeller is fixedly connected to the blade hub. The motor rod connects to the blade hub to drive the propeller in the blade assembly 5 to rotate.

[0030] Furthermore, the ratio of the maximum outer diameter D to the inner diameter d of the duct shell 1 lip satisfies: 1.05≤D / d≤1.25, which takes into account the characteristics of reducing aerodynamic drag during level flight and increasing air intake during hovering after the duct fan is integrated into the UAV.

[0031] Furthermore, the outer contour expansion angle θ of the duct shell 1 satisfies: θ≤8°, which can have better propeller efficiency compared to the straight inner contour, and avoid excessive expansion of high-pressure airflow leading to energy dissipation.

[0032] Furthermore, the minimum clearance δ between the propeller tip and the inner wall of the duct housing 1 satisfies: δ=1.2mm, D≤120mm or 0.01D≤δ≤0.02D, D≥120mm; this improves the aerodynamic performance of the ducted fan and the ease of processing and assembly of the propeller and duct housing 1.

[0033] Both the duct shell 1 and the polygonal frame 2 are manufactured using composite carbon fiber composite materials, which ensures a smooth inner surface, reduces airflow friction, and reduces weight while meeting the structural strength requirements of the shell. Furthermore, the duct shell 1 and the polygonal frame 2 are designed as a single unit. Figure 4 As shown, the duct shell 1 and the polygonal frame 2 are made into an integrated carbon fiber composite material structure, which facilitates ensuring the accuracy of the propeller tip clearance and the reliability of the connection between the duct shell 1 and the polygonal frame 2.

[0034] Furthermore, the inner wall of the duct housing 1 is coated with a thermoplastic PEEK-based self-healing coating, which can automatically fill micro-cracks at high operating temperatures, avoiding the problem of the duct housing 1 vibrating and causing the propeller tip to scrape against the inner wall of the duct housing 1 when there is a small gap between the propeller tip and the propeller tip.

[0035] It should be further explained that the ducted fan structure in this invention adopts a modular installation method, with the duct shell 1 and the polygonal frame 2 being integrated into one unit; the polygonal frame 2, the drive motor 3, and the rear edge rectifier 4 are all connected with anti-loosening screws, which facilitates disassembly.

[0036] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.

[0037] The above description is only a preferred embodiment of the present invention. Any technical solution that achieves the purpose of the present invention by essentially the same means is within the protection scope of the present invention.

Claims

1. A thin-wall narrow-edge ducted fan capable of reducing side-wind interference, characterized in that: The duct shell (1), the polygonal frame (2), the trailing edge fairing (4) and the leading edge fairing (6) are as follows: The duct shell (1) adopts a thin-walled and narrow-edge design. The ratio of the side length L of the duct shell (1) to the inner diameter d of the duct shell (1) is: L / d≤1 / 6. The interior of the duct shell (1) adopts a foam-filled structure. The maximum wall thickness h of the outer wall of the duct shell (1) satisfies: h=1.5mm, L≤20mm or 1.5mm≤h≤0.075L, L≥20mm. The inner diameter of the duct shell (1) is the minimum value of the inner wall diameter of the duct shell (1). The rear of the duct shell (1) is reserved with an annular slot. The polygonal frame (2) includes a head annular frame and a rear hub frame. The head annular frame is matched with the reserved annular slot. The head annular frame and the rear hub frame are fixedly connected by prisms. The head of the trailing edge fairing (4) is fixedly connected to the rear of the hub frame. A drive motor (3) is installed inside the trailing edge fairing (4). The bottom of the trailing edge fairing is connected to the base of the drive motor by screws. The drive motor (3) is located on the central axis of the duct housing (1). A motor rod extends out of the drive motor (3). The motor rod passes through the polygonal frame (2), the duct housing (1), and is fixedly connected to the leading edge fairing (6) by screws. The motor rod is rotatably connected to the hub frame of the polygonal frame (2) by bearings. The duct housing (1) is provided with a blade assembly (5), which includes a blade hub that is fixedly connected to the motor rod, and a propeller is fixedly connected to the blade hub.

2. The thin-wall narrow-edge ducted fan capable of reducing side-wind interference according to claim 1, characterized in that: The ratio of the maximum outer diameter D to the inner diameter d of the duct shell (1) satisfies: 1.05≤D / d≤1.

25.

3. The thin-wall narrow-span ducted fan with reduced side-of-fan interference according to claim 1, characterized in that: The outer contour expansion angle θ of the duct shell (1) satisfies: θ≤8°.

4. The thin-wall narrow-span ducted fan with reduced side-of-fan interference according to claim 1, characterized in that: The minimum clearance δ between the propeller tip and the inner wall of the duct shell (1) satisfies: δ=1.2mm, D≤120mm; 0.01D≤δ≤0.02D, D≥120mm.

5. The thin-wall narrow-span ducted fan with reduced side-of-fan interference according to claim 1, characterized in that: Both the duct shell (1) and the polygonal frame (2) are made of composite carbon fiber composite material. The duct shell (1) and the polygonal frame (2) are designed as an integrated unit, and the duct shell (1) and the polygonal frame (2) are made into an integrated carbon fiber composite material structure. The inner wall of the duct shell (1) is coated with a thermoplastic PEEK-based self-healing coating.

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