A ducted fan

Abstract

The application relates to the technical field of fans and discloses a ducted fan, which comprises a duct body, a fan blade assembly arranged on the air inlet side of the duct body and a power unit for driving the rotation of the fan blade assembly, the air inlet side of the duct body is curled outward along the periphery to form an air inlet lip, the air outlet side of the duct body is arranged with an air outlet inner cone which is inwardly contracted along the periphery, the power unit is located on one side of the connecting section of the duct body and the air outlet inner cone and extends into the air outlet inner cone, a nonlinear flow guide channel is formed between the outer shell of the power unit and the inner wall of the air outlet inner cone, a plurality of groups of rectifying cutting blades are annularly and uniformly distributed along the inner side wall of the duct body, the air inlet side of the rectifying cutting blade is arranged as a flat section, and the air outlet side of the rectifying cutting blade is inclined and curved towards the outer shell of the power unit. Compared with the previous aerodynamic design, the overall aerodynamic efficiency of the ducted fan can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fan, in particular to a ducted fan. BACKGROUND

[0002] With the rapid development of general aviation manufacturing industry and the rise of low-altitude economy, the performance requirements of unmanned aerial vehicles, light aircraft and other equipment for aviation power systems are becoming more and more demanding. The traditional open rotor has three major problems: first, the aerodynamic efficiency is low, the airflow is easy to diffuse, resulting in serious thrust loss; second, the structure is heavy, the metal material accounts for a high proportion, which is difficult to adapt to the demand of lightweight; third, the running noise is high, the vortex noise and mechanical noise generated by the high-speed rotation of the rotor pollute significantly.

[0003] Although the existing ducted fan technology improves the efficiency by constraining airflow through the duct structure, the air inlet lip of the existing ducted fan technology is mostly circular arc structure, which is easy to cause airflow separation, and the vortex at the tail of the fan blade is not effectively suppressed, resulting in that the overall efficiency is only maintained at 65%-70%, and the aerodynamic efficiency is still poor. At the same time, the heat dissipation system is disconnected with the airflow channel, so that the heat generated by the power unit cannot be quickly discharged, and long-time operation is easy to cause performance attenuation.

[0004] Therefore, there is an urgent need for a ducted fan that integrates high-efficiency aerodynamic design, strengthens heat dissipation, is low-noise and lightweight. SUMMARY

[0005] In view of this, the purpose of the present application is to provide a ducted fan to solve the technical problems mentioned in the prior art.

[0006] A ducted fan, comprising a duct body, a fan blade assembly arranged on the air inlet side of the duct body, and a power unit for driving the rotation of the fan blade assembly, wherein the power unit is mounted on the duct body through a support, the air inlet side of the duct body is curled outward along the periphery to form an air inlet lip, the air outlet side of the duct body is provided with an exhaust inner cone which is arranged inward along the periphery, the power unit is located on one side of the connecting section between the duct body and the exhaust inner cone and extends into the exhaust inner cone, and a nonlinear flow guide channel is formed between the outer shell of the power unit and the inner wall of the exhaust inner cone.

[0007] A wind direction control structure is arranged on the inner side wall of the duct body on the air outlet side of the fan blade assembly, and the wind direction control structure comprises a plurality of groups of rectifier cutting blades which are uniformly distributed along the inner side wall of the duct body.

[0008] One end of the rectifier cutting blade is mounted on the duct body, and the other end of the rectifier cutting blade extends to or is connected with the outer shell of the power unit.

[0009] The air inlet side of the rectification cutting blade is provided as a flat section, and the air outlet side of the rectification cutting blade is inclined and curved towards the outer shell of the power unit.

[0010] Optionally, the duct body is made of an inner layer and an outer layer in composite;

[0011] The outer layer is provided as a carbon fiber composite material, and the impact load of the outer layer is greater than 200kN;

[0012] The inner layer is provided as a ceramic-based coating, and the high-temperature resistance of the inner layer is greater than 600℃.

[0013] Optionally, the fan blade assembly comprises:

[0014] A blade disc is mounted at the output end of the power unit;

[0015] And a plurality of wide-chord composite blades are mounted radially uniformly along the blade disc, and the outer profile of the wide-chord composite blades is made of a curved sweep twist coupling; wherein the low-speed area of the wide-chord composite blades is provided as a large chord length, the high-speed area of the wide-chord composite blades is provided as a small chord length, and the chord length size ratio of the large chord length to the small chord length is provided as 2.5-2.7:1;

[0016] The low-speed area and the high-speed area of the wide-chord composite blades are linearly and smoothly connected, and the chord length size of the intermediate transition area is provided as the intermediate value of the large chord length and the small chord length.

[0017] Optionally, the wide-chord composite blades comprise:

[0018] A substrate layer is provided as a honeycomb sandwich structure made of carbon fiber;

[0019] A protective layer at least wraps the air inlet side of the substrate layer.

[0020] Optionally, the protective layer is provided as:

[0021] A titanium alloy layer with a thickness of 1-2mm.

[0022] Optionally, the distance between the blade tip of the wide-chord composite blade and the inner side wall of the duct body is ≤0.5mm.

[0023] Optionally, the cross section of the air inlet lip is provided as an elliptical curve, and the ratio of the major axis to the minor axis of the elliptical curve is provided as 2-3:1.

[0024] Optionally, the inner side of the air inlet lip is circumferentially and uniformly provided with a plurality of groups of boundary layer suction holes, the boundary layer suction holes penetrate the inner side wall of the duct body, and the hole diameter of the boundary layer suction holes is provided as Φ1-3mm;

[0025] The interval between two adjacent suction holes of the boundary layer is 5-10 mm.

[0026] Optionally, the power unit is a brushless motor, and the tail of the outer shell of the brushless motor is stepped and sequentially shrunk along the airflow direction.

[0027] The air inlet side of the exhaust cone is provided with a stepped hole matched with the tail of the outer shell of the brushless motor.

[0028] Optionally, the cross-sectional area of the flow passage of the rectification cutting blade gradually increases along the axial direction of the duct body, and the ratio of the cross-sectional areas at both ends is 1.1-1.2:1.

[0029] The beneficial effects that can be produced by the present application include:

[0030] 1. The duct fan provided by the present application effectively reduces the airflow separation by designing the air inlet side of the duct body as an elliptical curve air inlet lip (long axis: short axis = 3:1) compared with the traditional circular arc lip. At the same time, the wind direction control structure and the nonlinear guide channel are sequentially arranged along the air inlet direction, which can cut the spiral airflow sucked by the fan blade assembly through the wind direction control structure, and convert the flow direction to linear flow, thereby realizing the rectification effect, suppressing the vortex at the tail of the fan blade assembly, reducing the vibration noise caused by airflow disturbance, and reducing the impact of the vortex on the inner wall of the duct body. The air outlet side of the rectification cutting blade is inclined and curved towards the outer shell of the power unit, so as to gather the airflow after the first rectification towards one side of the nonlinear guide channel, realize the secondary rectification effect, and improve the heat exchange efficiency between the external air and the power unit. Moreover, the nonlinear guide channel can change the exhaust direction and air pressure, thereby increasing the additional thrust, improving the overall aerodynamic efficiency, prolonging the heat dissipation time of the power unit, and improving the heat dissipation effect. Compared with the previous aerodynamic design, the overall aerodynamic efficiency of the duct fan can be improved to 82%-85%.

[0031] 2. In the present application, the cross-sectional area of the flow passage of the rectification cutting blade increases along the axial direction, which can reduce the airflow velocity; and the cooperation of the air inlet lip and the boundary layer suction hole can reduce airflow separation and turbulence. Thus, the airflow turbulence noise is reduced by reducing the airflow velocity, and the aerodynamic noise is further reduced by suppressing the airflow separation, thereby improving the running quietness.

[0032] 3. The wide-chord composite blade of this invention adopts a "swept torsional coupling" shape (i.e., a large chord length in the low-speed range and a small chord length in the high-speed range, with a smooth linear transition), and the distance between the blade tip and the inner wall of the duct is ≤0.5mm, which can effectively reduce tip shock wave loss (to adapt to the airflow characteristics in different speed ranges) and suppress tip vortices, thereby reducing airflow leakage loss. Simultaneously, the wide-chord composite blade adopts a "carbon fiber honeycomb sandwich substrate + titanium alloy protective layer" structure, wherein the honeycomb sandwich structure reduces weight and increases structural strength, and the titanium alloy protective layer enhances the impact resistance and wear resistance of the inlet side. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of a ducted fan according to the present invention;

[0034] Figure 2 In this invention Figure 1 Sectional view along axis AA;

[0035] Figure 3 In this invention Figure 1 The schematic diagram of the intake lip design of the duct body; where a is the major axis of the ellipse and b is the minor axis of the ellipse;

[0036] Figure 4 In this invention Figure 1 A schematic diagram of the exhaust inner cone structure; where direction c is the intake direction of the nonlinear guide channel;

[0037] Figure 5 In this invention Figure 1 A schematic diagram of the cross-section of a wide-chord composite blade;

[0038] Figure 6 In this invention Figure 1 A schematic diagram of the cross-section of the duct body;

[0039] In the diagram: 1. Duct body, 101. Inner layer, 102. Outer layer, 11. Inlet lip, 12. Boundary layer suction hole, 2. Exhaust inner cone, 3. Nonlinear guide channel, 4. Wind direction control structure, 41. Rectifying and cutting blade, 42. Support ring, 5. Fan blade assembly, 51. Blade disk, 52. Wide chord composite blade, 521. Substrate layer, 522. Protective layer, 6. Power unit, 61. Motor shaft, 62. Rotor, 63. Bearing assembly, 64. Stator, 65. Housing, 7. Bracket, 8. Mounting base. Detailed Implementation

[0040] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0041] As shown in FIG. 1, Figure 1 As shown in FIG. 1, the present application provides a ducted fan, which comprises a duct body 1, a fan blade assembly 5 arranged at the air inlet side of the duct body 1, and a power unit 6 for driving the rotation of the fan blade assembly 5. The power unit 6 is mounted on the duct body 1 through a support 7. The air inlet side of the duct body 1 is curled outward along the periphery to form an air inlet lip 11, thereby reducing the aerodynamic loss. The air outlet side of the duct body 1 is arranged with an exhaust inner cone 2 which is inwardly retracted along the periphery. The power unit 6 is located at the connecting section between the duct body 1 and the exhaust inner cone 2 and extends into the exhaust inner cone 2. A nonlinear flow guide channel 3 is formed between the outer shell of the power unit 6 and the inner wall of the exhaust inner cone 2, thereby increasing the additional thrust, improving the overall aerodynamic efficiency, prolonging the heat dissipation time of the power unit 6, and improving the heat dissipation effect. The inner side wall of the duct body 1 is arranged with a wind direction control structure 4 at the air outlet side of the fan blade assembly 5. The wind direction control structure 4 comprises a plurality of groups of rectifying cutting blades 41 which are uniformly distributed along the inner side wall of the duct body 1. One end of the rectifying cutting blade 41 is mounted on the duct body 1, and the other end of the rectifying cutting blade 41 extends to the outer shell of the power unit 6 or is connected with the outer shell of the power unit 6. The air inlet side of the rectifying cutting blade 41 is arranged as a flat section for cutting the spiral airflow drawn in by the fan blade assembly 5 and converting the flow direction of the airflow to linear flow, thereby achieving the rectifying effect, suppressing the vortex at the tail of the fan blade assembly 5, reducing the vibration noise and the impact on the duct body 1. The air outlet side of the rectifying cutting blade 41 is inclined and curved towards the outer shell of the power unit 6, so as to gather the airflow after the first rectification towards one side of the nonlinear flow guide channel 3, thereby achieving the second rectification effect and improving the heat exchange efficiency between the external air and the power unit 6. Compared with the previous aerodynamic design, the overall aerodynamic efficiency of the ducted fan can be effectively improved.

[0042] Further, as shown in FIG. 2, Figure 6 The duct body 1 is made of an inner layer 101 and an outer layer 102. The outer layer 102 is made of carbon fiber composite material (T300 carbon fiber can be selected). The impact load of the outer layer 102 is greater than 200 kN. The inner layer 101 is made of ceramic-based coating. The high temperature resistance of the inner layer 101 is greater than 600℃. The continuous and stable operation of the power unit 6 can be ensured, the operation time of the power unit 6 can be greatly prolonged, the performance degradation can be avoided, and the lightweight, impact resistance and high temperature resistance of the power system can be met.

[0043] Further, as shown in FIG. 2,Figure 1 As shown, the fan assembly 5 comprises a blade disc 51 and a plurality of wide-chord composite blades 52 mounted radially uniformly along the blade disc 51, the wide-chord composite blades 52 can be fixedly installed on the blade disc 51 by means of tenon and slot type tenon heads, and the blade disc 51 is fixedly installed on the output end of the power unit 6 through a shaft coupling; the outer profile contour of the wide-chord composite blades 52 is made by means of a cambered sweep twist coupling; wherein the low speed region of the wide-chord composite blades 52 is set to have a large chord length, the high speed region of the wide-chord composite blades 52 is set to have a small chord length, the chord length size ratio of the large chord length to the small chord length is set to be 2.5-2.7:1, and the low speed region and the high speed region of the wide-chord composite blades 52 are linearly and smoothly connected. It should be noted that the chord length refers to the maximum projection length of the blade along the airflow direction, the chord length size of the intermediate transition region is set to be the intermediate value of the large chord length and the small chord length, so as to realize linear and smooth connection, prevent airflow sudden change disturbance, ensure that the airflow can stably pass through in different speed regions, reduce airflow separation, effectively reduce the tip shock loss of the wide-chord composite blades 52. In the above embodiment, as shown in Figure 5 As shown, in order to optimize the aerodynamic load distribution, the wide-chord composite blades 52 comprise a substrate layer 521 and a protective layer 522, the substrate layer 521 is set to be a honeycomb sandwich structure made of carbon fiber; the protective layer 522 at least wraps the air inlet side of the substrate layer 521. Wherein, the protective layer 522 is set to be a titanium alloy layer with a thickness of 1-2 cm. And the distance between the tip of the wide-chord composite blades 52 and the inner side wall of the duct body 1 is set to be ≤0.5 mm, which can effectively suppress the tip vortex.

[0044] In some embodiments, in order to optimize the aerodynamic load distribution and suppress the formation of airflow vortex inside the duct body 1, the wide-chord composite blades 52 are prepared by adopting an arc-shaped bending design method along the radial direction outward (forming a twist angle) and a sweep design method along the airflow direction (forming a sweep angle). Wherein, the arc-shaped bending design method is that the blade is bent outward in an arc shape along the radial direction (from the blade root to the blade tip), the bending radius is 3-4 times the total radial length of the blade, the radial offset amount of the blade tip relative to the blade root is 8-10 mm, and the offset direction is consistent with the rotation direction of the fan, so as to reduce the airflow resistance during rotation. The sweep design method is that the blade is in a sweep shape along the airflow direction, the sweep angle is the included angle between the chord line of the blade and the radial direction of the duct body 1, the sweep angle of the blade root section is set to be 5°-7°, the sweep angle of the blade tip section is set to be 12°-14°, and the sweep angle linearly increases along the radial direction. In this embodiment, the angle ratio of the sweep angle to the twist angle is set to be 1.1-1.3:1, and is preferably set to be 1.2:1, so as to ensure the synergistic optimization of aerodynamic parameters and further reduce airflow sudden change disturbance.

[0045] Further, as shown in Figure 3As shown, the cross section of the air inlet lip 11 is set as an elliptical curve, and the ratio of the major axis to the minor axis is set as 2-3:1 (preferably 3:1), which can effectively reduce the separation of the inlet airflow compared with the traditional circular arc lip. At the same time, a plurality of boundary layer suction holes 12 are uniformly arranged on the inner side of the air inlet lip 11, the boundary layer suction holes 12 penetrate the inner side wall of the duct body 1, the diameter of the boundary layer suction hole 12 is set as Φ1-3mm, preferably Φ2mm; the spacing between adjacent two boundary layer suction holes 12 is set as 5-10mm (preferably 10mm), which can reduce the airflow loss. At the same time, in order to facilitate the installation and use of the duct body, two mounting bases 8 are symmetrically arranged along the outer circumferential side, as shown in Figure 1 and Figure 2 As shown, mounting holes are arranged on the mounting base 8, so that it can be detachably mounted with other components, which is convenient for maintenance.

[0046] Further, the power unit 6 is set as a brushless motor, as shown in Figure 1 The tail part of the outer shell of the brushless motor is stepped and shrinks in sequence along the airflow direction. As shown in Figure 4 The air inlet side of the exhaust inner cone 2 is provided with a stepped hole matched with the tail part of the outer shell of the brushless motor, which can generate vector thrust by guiding and deflecting the airflow, which helps to improve the overall aerodynamic efficiency and improve the heat dissipation efficiency of the power unit 6.

[0047] Further, as shown in Figure 2 The flow passage cross-sectional area of the rectification cutting blade 41 gradually increases along the axial direction of the duct body 1, and the ratio of the flow passage cross-sectional area at both ends is set as 1.1-1.2:1, preferably 1.2:1, which can reduce the flow area by gradually increasing the blade thickness, thereby reducing the airflow velocity and reducing the airflow turbulent noise.

Claims

1. A ducted fan comprising a duct body (1), a fan blade assembly (5) arranged at the air inlet side of the duct body (1), and a power unit (6) for driving the rotation of the fan blade assembly (5), the power unit (6) being mounted on the duct body (1) by a support (7), characterized in that, The air inlet side of the duct body (1) is curled outward along the periphery to form an air inlet lip (11), the air outlet side of the duct body (1) is provided with an exhaust inner cone (2) which is inwardly contracted along the periphery, the power unit (6) is located on the side of the connecting section of the duct body (1) and the exhaust inner cone (2) and extends into the exhaust inner cone (2), and a nonlinear flow guide channel (3) is formed between the outer shell of the power unit (6) and the inner wall of the exhaust inner cone (2); The air direction control structure (4) is arranged on the inner side wall of the duct body (1) on the air outlet side of the fan blade assembly (5), the air direction control structure (4) comprises a plurality of groups of rectifying cutting blades (41) which are uniformly distributed in a ring shape along the inner side wall of the duct body (1), wherein: One end of the rectifying cutting blade (41) is mounted on the duct body (1), and the other end of the rectifying cutting blade (41) extends to the outer shell of the power unit (6) or is connected with the outer shell of the power unit (6); The air inlet side of the rectifying cutting blade (41) is provided as a flat section, and the air outlet side of the rectifying cutting blade (41) is inclined and curved towards the outer shell of the power unit (6); The fan blade assembly (5) comprises: A blade disc (51) mounted on the output end of the power unit (6); And a plurality of wide-chord composite blades (52) which are uniformly mounted in a radial direction along the blade disc (51), the outer shape contour of the wide-chord composite blade (52) is made of a sweep-twist coupling, wherein the low-speed region of the wide-chord composite blade (52) is provided as a large chord length, the high-speed region of the wide-chord composite blade (52) is provided as a small chord length, and the chord length size ratio of the large chord length to the small chord length is 2.5-2.7:1; The low-speed region and the high-speed region of the wide-chord composite blade (52) are linearly and smoothly connected, and the chord length size of the intermediate transition region is set as the intermediate value of the large chord length and the small chord length; The cross section of the air inlet lip (11) is provided as an elliptical curve, and the ratio of the major axis to the minor axis of the elliptical curve is set as 2-3:

1.

2. A ducted fan according to claim 1, wherein, The duct body (1) is made of an inner layer (101) and an outer layer (102); The outer layer (102) is provided as a carbon fiber composite material, and the impact load of the outer layer (102) is greater than 200kN; The inner layer (101) is provided as a ceramic-based coating, and the high-temperature resistance of the inner layer (101) is greater than 600℃.

3. The ducted fan of claim 1, wherein, The wide-chord composite blade (52) comprises: A substrate layer (521) provided as a honeycomb sandwich structure made of carbon fiber; A protective layer (522) which at least wraps the air inlet side of the substrate layer (521).

4. A ducted fan according to claim 3, wherein, The protective layer (522) is provided as: A titanium alloy layer with a thickness of 1-2mm.

5. The ducted fan of claim 1, wherein, The distance between the blade tip of the wide-chord composite blade (52) and the inner side wall of the duct body (1) is ≤0.5mm.

6. The ducted fan of claim 1, wherein, The inner side of the air inlet lip (11) is circumferentially and uniformly provided with a plurality of groups of boundary layer suction holes (12), the boundary layer suction holes (12) penetrate the inner side wall of the duct body (1), and the hole diameter of the boundary layer suction holes (12) is set as Φ1-3mm; The interval between two adjacent boundary layer suction holes (12) is 5-10 mm.

7. The ducted fan of claim 1 wherein, The power unit (6) is a brushless motor, and the tail of the outer shell of the brushless motor is stepped and sequentially shrunk along the airflow direction. The air inlet side of the exhaust inner cone (2) is provided with a stepped hole matched with the tail of the outer shell of the brushless motor.

8. The ducted fan of claim 1, wherein, The flow passage cross-sectional area of the rectification cutting blade (41) gradually increases along the axial direction of the duct body (1), and the cross-sectional area ratio at both ends is 1.1-1.2:1.

Images