A flow control device and method for improving the efficiency of a ducted fan propulsion

Abstract

The application provides a flow control device and method for improving the efficiency of a ducted fan propulsion, comprising a duct and a ducted propeller device; an annular duct is arranged on the outer periphery of the ducted propeller device; the duct comprises a blowing flow channel, a blowing port, a suction port, a suction flow channel and a gas source device; the blowing port is arranged on the inner surface of the duct, that is, the upper surface of the duct airfoil, and is close to the leading edge of the duct airfoil; the suction port is arranged on the upper surface of the duct airfoil and is away from the leading edge of the duct airfoil; the application introduces a cooperative jet active flow control on the ducted fan, greatly improves the overall propulsion efficiency of the ducted fan, improves the wind resistance of the ducted fan, and enhances the controllability of the ducted fan.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of active flow control, and particularly relates to a flow control device and method for improving the propulsive efficiency of a ducted fan. BACKGROUND

[0002] As a high-efficiency propulsion device, a ducted fan is widely used in tail rotor of a helicopter, airship, vertical take-off and landing aircraft, hovercraft and other carriers. Compared with a traditional propeller, the ducted fan has the advantages of high propulsive efficiency, good safety and small size. With the gradual deepening of the research on the design method of the ducted fan, how to more effectively improve the aerodynamic propulsive efficiency of the ducted fan is the focus and difficulty of the current research. SUMMARY

[0003] In view of the defects in the prior art, the application provides a flow control device and method for improving the propulsive efficiency of a ducted fan, which can effectively solve the above problems.

[0004] The technical scheme adopted by the application is as follows:

[0005] The application provides a flow control device for improving the propulsive efficiency of a ducted fan, which comprises a duct (100) and a ducted propeller device (200).

[0006] The outer periphery of the ducted propeller device (200) is provided with an annular duct (100). The duct (100) comprises a blowing flow channel (101), a blowing port (102), a suction port (103), a suction flow channel (104) and a gas source device (105). The blowing port (102) is arranged on the inner surface of the duct (100), that is, the upper surface of the duct airfoil, and close to the leading edge of the duct airfoil. The suction port (103) is arranged on the upper surface of the duct airfoil of the duct (100) and away from the leading edge of the duct airfoil. The blowing flow channel (101) in communication with the blowing port (102), the suction flow channel (104) in communication with the suction port (103) and the gas source device (105) located between the blowing flow channel (101) and the suction flow channel (104) are arranged in the duct (100). Under the driving of the gas source device (105), the air sucked from the suction port (103) flows through the suction flow channel (104) and the blowing flow channel (101) and is blown out from the blowing port (102), thereby forming air flow circulation.

[0007] Preferably, the blowing flow rate of the blowing port (102) is equal to the suction flow rate of the suction port (103), so as to realize zero mass jet and actively control the external flow field.

[0008] Preferably, the blowing port (102) is arranged at a position 0.05c-0.08c from the leading edge of the ducted airfoil on the upper surface of the ducted airfoil, the blowing port (102) has a width of 0.003c-0.008c, and the center line of the blowing port (102), i.e. the jet direction, forms an angle of 30°-40° with the chord line of the ducted airfoil.

[0009] The suction port (103) is arranged at a position 0.7c-0.9c from the leading edge of the ducted airfoil on the upper surface of the ducted airfoil, the suction port (103) has a width of 0.008c-0.012c, and the center line of the suction port (103), i.e. the inlet direction, forms an angle of 15°-30° with the chord line of the ducted airfoil; wherein c is the chord line of the ducted airfoil.

[0010] Preferably, the blowing port (102) is arranged continuously or discretely on the inner surface of the duct (100), and correspondingly, the suction port (103) is arranged continuously or discretely on the inner surface of the duct (100).

[0011] Wherein: continuous arrangement refers to that the inner surface of the duct (100) is continuously opened with the blowing port (102) and the suction port (103) in a 360° ring shape;

[0012] Discrete arrangement refers to that the inner surface of the duct (100) is provided with a plurality of blowing ports (102) and a plurality of suction ports (103) at intervals along the ring shape; at the same time, when the blowing port (102) and the suction port (103) are discretely arranged, each blowing port (102) forms a blowing and suction unit with a corresponding suction port (103) through an independent airflow flow channel and an independent air source device (105); by independently controlling the blowing and suction amounts of each group of blowing and suction units, asymmetric thrust is generated, and then pitch moment and yaw moment are generated, so as to vector control the ducted fan.

[0013] Preferably, the ducted propeller device (200) comprises a ducted fan engine nacelle (201) and a ducted fan blade (202).

[0014] The outer periphery of the ducted fan engine nacelle (201) is provided with a plurality of ducted fan blades (202) in a ring shape, and the ducted fan engine nacelle (201) drives each ducted fan blade (202) to rotate; and the outer periphery of each ducted fan blade (202) is provided with a ring-shaped duct (100).

[0015] The application also provides an active flow control method of the flow control device for improving the propulsive efficiency of the ducted fan, comprising the following steps:

[0016] Simultaneously start the air supply device (105) of the duct (100) and the ducted fan engine nacelle (201) of the ducted propeller device (200);

[0017] For the ducted propeller unit (200), its ducted fan engine nacelle (201) drives the ducted fan blades (202) to rotate, generating aerodynamic thrust;

[0018] For the duct (100), the airflow is ejected from the air outlet (102), flows over the upper surface of the duct airfoil, and is drawn in from the air inlet (103). Under the action of the air source device (105), the airflow is ejected again from the air outlet (102), thereby forming a CFJ jet cycle. The airflow rate of the air outlet (102) and the airflow rate of the air inlet (103) are equal.

[0019] During the CFJ jet circulation process, since the blowing port (102) is located at the lip position of the leading edge of the ducted airfoil, the lip position becomes an airflow acceleration region due to the suction effect; since the intake port (103) is located on the rear side of the ducted fan blade (202), under the work action of the ducted fan blade (202), the intake port (103) is also located in the airflow acceleration region.

[0020] Therefore, both the air inlet (102) and the air inlet (103) are arranged in the high kinetic energy region of the airflow to drive the CFJ jet to circulate efficiently and work in conjunction with the ducted propeller device (200) to improve the overall propulsion efficiency of the ducted fan.

[0021] The flow control device and method for improving the propulsion efficiency of ducted fans provided by this invention have the following advantages:

[0022] This invention significantly improves the overall propulsion efficiency of ducted fans by introducing cooperative jet active flow control, while also enhancing the wind resistance and maneuverability of ducted fans. Attached Figure Description

[0023] Figure 1 A cross-sectional view of the flow control device for improving the propulsion efficiency of a ducted fan provided by the present invention;

[0024] Figure 2 This is a partially enlarged schematic diagram of the air inlet provided by the present invention;

[0025] Figure 3 This is a partially enlarged schematic diagram of the air intake provided by the present invention;

[0026] Figure 4 Numerical simulation results of a ducted fan equipped with a CFJ provided for this invention;

[0027] Figure 5This is a schematic diagram illustrating vector control of a ducted fan using discrete CFJ, as provided by the present invention.

[0028] Figure 6 A perspective view of a specific structure of the flow control device for improving the propulsion efficiency of a ducted fan provided by the present invention;

[0029] Figure 7 An internal diagram of a specific structure of the flow control device for improving the propulsion efficiency of a ducted fan provided by the present invention;

[0030] Figure 8 A cross-sectional view of a specific structure of the flow control device for improving the propulsion efficiency of a ducted fan provided by the present invention;

[0031] Figure 9 A perspective view of a specific structure of the flow control device for improving the propulsion efficiency of a ducted fan provided by the present invention, with the duct shell concealed.

[0032] Figure 10 A partial view of a specific structure of the flow control device for improving the propulsion efficiency of a ducted fan provided by the present invention;

[0033] Figure 11 A cross-sectional view of the I-beam ring-rib in a specific structure of the flow control device for improving the propulsion efficiency of a ducted fan provided by the present invention;

[0034] Figure 12 A cross-sectional view of an I-beam ring-micro fan in a specific structure of the flow control device for improving the propulsion efficiency of a ducted fan provided by the present invention;

[0035] in:

[0036] 100 - duct; 200 - ducted propeller assembly; 300 - ducted support base;

[0037] 101-Airflow duct; 102-Air inlet; 103-Air intake; 104-Air intake duct; 105-Air source device; 106-Duct outer shell; 107-Duct inner shell; 108-I-beam ring; 109-Front rib; 110-Rear rib; 111-Miniature fan; 112-Rib fixing screw; 113-Duct outer shell fixing countersunk screw; 114-Duct inner shell fixing countersunk screw; 201-Duct fan engine nacelle; 202-Duct fan blade;

[0038] 1061 - Front section of duct shell; 1062 - Rear section of duct shell; 1081 - Web of I-beam; 1082 - Outer ring of I-beam; 1083 - Inner ring of I-beam; 1111 - Fan wiring hole; 1112 - Fan mounting hole. Detailed Implementation

[0039] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.

[0040] To further improve the overall propulsion efficiency of ducted fans, this invention introduces cooperative jet active flow control into ducted fans, which significantly improves the overall propulsion efficiency of ducted fans, while also enhancing the wind resistance and maneuverability of ducted fans.

[0041] Specifically, this invention controls the flow on the upper surface of the airfoil by blowing air near the low-pressure area at the leading edge and drawing air near the high-pressure area at the trailing edge, i.e., Co-flow Jet (CFJ). Furthermore, the mass flow rates of the blowing and drawing air are equal, exhibiting low energy consumption and zero-mass jet characteristics, with total energy consumption far lower than other active flow control methods.

[0042] See Figures 1-12 The present invention provides a flow control device for improving the propulsion efficiency of a ducted fan, which is an efficiency enhancement method for applying active flow control technology to a ducted fan, including a duct 100 and a ducted propeller device 200.

[0043] A ring-shaped duct 100 is provided around the outer periphery of the ducted propeller device 200. The duct 100 includes an air blowing channel 101, an air blowing port 102, an air intake port 103, an air intake channel 104, and an air source device 105. The air blowing port 102 is arranged on the inner surface of the duct 100, which is the upper surface of the duct airfoil, and near the leading edge of the duct airfoil. The air intake port 103 is arranged on the upper surface of the duct airfoil of the duct 100 and away from the leading edge of the duct airfoil. Inside the duct 100, the air blowing channel 101, which communicates with the air blowing port 102, the air intake channel 104, which communicates with the air intake port 103, and the air source device 105 located between the air blowing channel 101 and the air intake channel 104 are arranged. Driven by the air source device 105, the air drawn in from the air intake port 103 flows through the air intake channel 104 and the air blowing channel 101, and is blown out from the air blowing port 102, forming an airflow circulation.

[0044] In this invention, when the ducted fan with integrated CFJ is in operation, the air source device 105 is activated based on the rotation of the blades of the ducted propeller device 200. The air source device 105 consumes energy to drive the air in the internal flow channel to flow forward. The air flows out from the air outlet 102 and flows in from the air inlet 103, forming a cycle. The airflow blown out has a control effect on the external flow.

[0045] As a specific embodiment, the blowing flow rate of the blowing port 102 is equal to the suction flow rate of the suction port 103, thereby achieving a zero-mass jet and actively controlling the flow of the external flow field.

[0046] As a specific example, such as Figure 2 As shown, the air inlet 102 is arranged on the upper surface of the duct airfoil at a position 0.05c to 0.08c away from the leading edge of the duct airfoil. The width of the air inlet 102 is 0.003c to 0.008c, and the angle between the centerline of the air inlet 102, i.e. the jet direction, and the duct airfoil chord is 30° to 40°.

[0047] like Figure 3 As shown, the air intake 103 is located on the upper surface of the ducted airfoil at a distance of 0.7c to 0.9c from the leading edge of the ducted airfoil. The width of the air intake 103 is 0.008c to 0.012c, and the angle between the centerline of the air intake 103 (i.e., the air intake direction) and the ducted airfoil chord line is 15° to 30°; where c is the ducted airfoil chord line. Figure 2 and Figure 3 In the middle, the airflow direction is from left to right, with the left side being the leading edge of the ducted airfoil and the right side being the trailing edge of the ducted airfoil.

[0048] In this invention, an air source device 105 arranged within the duct 100 consumes energy to drive the airflow forward. The air source device 105 can be a miniature fan, air pump, etc. The area within the blowing port 102 and the suction port 103 is connected by a blowing air channel 101 and a suction air channel 104 embedded within the duct 100. The flow channel shapes of the blowing air channel 101 and the suction air channel 104 are mainly determined by the external shape and internal structure of the duct, ensuring smooth airflow.

[0049] In this invention, the air inlets 102 are arranged continuously or discretely on the inner surface of the duct 100, and correspondingly, the air inlets 103 are arranged continuously or discretely on the inner surface of the duct 100.

[0050] Among them, "continuous arrangement" means that the inner surface of the duct 100 is continuously circumferentially opened with an air inlet 102 and an air intake 103 in a 360° circle.

[0051] Discrete arrangement refers to the following: multiple air inlets 102 and multiple air inlets 103 are spaced apart along the inner surface of the duct 100. When the air inlets 102 and air inlets 103 are discretely arranged, each air inlet 102 forms a set of air blowing and air intake units with a corresponding air intake unit 103 through an independent airflow channel and an independent air source device 105. By independently controlling the air blowing and air intake volume of each set of air blowing and air intake units, asymmetric thrust is generated, which in turn generates pitching moment and yaw moment, thereby vectoring the ducted fan.

[0052] As a specific structure, the bottom of the duct 100 is supported by the duct support base 300.

[0053] As a specific structure, the ducted propeller assembly 200 includes a ducted fan engine nacelle 201 and ducted fan blades 202;

[0054] Multiple ducted fan blades 202 are arranged in a ring-shaped pattern around the outer periphery of the ducted fan engine nacelle 201, and the ducted fan engine nacelle 201 drives each ducted fan blade 202 to rotate; a ring-shaped duct 100 is arranged around the outer periphery of each ducted fan blade 202.

[0055] This invention provides a flow control device for improving the propulsion efficiency of ducted fans, which has the following features and advantages:

[0056] 1. The thrust of the duct is effectively increased:

[0057] Numerical simulations were performed on a ducted fan equipped with the CFJ of this invention. The numerical simulation results are as follows: Figure 4 As shown. In Figure 4 In the diagram: S1 represents the pressure cloud diagram of the ducted fan with CFJ installed; S2 represents the pressure cloud diagram of the ducted fan without CFJ installed; S3 represents the pressure distribution curve of the duct airfoil profile of the ducted fan with the CFJ of this invention installed; S4 represents the pressure distribution curve of the duct airfoil profile of the ducted fan without CFJ installed; S5 represents the negative pressure increment on the inner surface of the duct after installing the CFJ of this invention, which is the source of the duct thrust increment; wherein, when plotting the pressure distribution curve, the negative Y-axis direction is upward.

[0058] from Figure 4 As can be seen, after the addition of CFJ, the CFJ jet significantly increases the negative pressure peak at the leading edge lip of the duct airfoil and increases the area of ​​the negative pressure region, thereby increasing the duct thrust. At the same time, the CFJ jet itself generates considerable thrust. Compared with the original duct fan, the overall propulsion efficiency of the CFJ duct fan of the present invention can be increased by about 15%. If the jet intensity is increased, the overall propulsion efficiency of the duct fan can be further improved.

[0059] 2. Low energy consumption:

[0060] Because the air inlet of this invention is located at the leading edge lip of the ducted airfoil, where the airflow acceleration region is due to the suction effect, and the air inlet is located behind the blades, where the blades' work also contributes to airflow acceleration, both the air inlet and air inlet are positioned in high-energy airflow regions. This results in lower energy consumption required to drive the CFJ airflow circulation. According to CFD numerical simulation results, with a 15% increase in the overall propulsion efficiency of the CFJ ducted fan, the total energy consumption of the blades and air source device only increases by 5%.

[0061] 3. Ducted fan's resistance to crosswinds:

[0062] The CFJ jet of this invention can effectively suppress the leading edge separation of the ducted airfoil, improve the crosswind resistance of the ducted fan, and broaden the operating range of the ducted fan.

[0063] 4. Enables vector control of ducted fans:

[0064] In this invention, the air inlets / outlets can be arranged in a continuous 360° annular pattern or in a discrete pattern. When several air inlets / outlets are discretely arranged, each equipped with an independent flow channel and air source device, asymmetric air blowing and suction can be achieved by controlling the air source device through a switching mechanism. This generates asymmetric force, thereby enabling vector control of the ducted fan and giving the CFJ ducted fan the potential for vector control. Figure 7 The figure shows a schematic diagram of vector control of a ducted fan using discrete CFJ, where F represents the pitching and yaw moments generated by non-uniform thrust.

[0065] The present invention also provides an active flow control method for a flow control device to improve the propulsion efficiency of a ducted fan, comprising the following steps:

[0066] Simultaneously start the air supply device 105 of the duct 100 and the ducted fan engine nacelle 201 of the ducted propeller device 200.

[0067] For the ducted propeller device 200, its ducted fan engine nacelle 201 drives the ducted fan blades 202 to rotate, generating aerodynamic thrust.

[0068] For the duct 100, the airflow is ejected from the air outlet 102, flows over the upper surface of the duct airfoil, and is drawn in through the air inlet 103. Under the action of the air source device 105, the airflow is ejected again from the air outlet 102, thereby forming a CFJ jet cycle. The airflow rate of the air outlet 102 and the airflow rate of the air inlet 103 are equal.

[0069] During the CFJ jet circulation process, since the blowing port 102 is located at the lip position of the leading edge of the ducted airfoil, the lip position becomes an airflow acceleration region due to the suction effect; since the intake port 103 is located behind the ducted fan blade 202, under the work of the ducted fan blade 202, the intake port 103 is also located in the airflow acceleration region.

[0070] Therefore, both the air inlet 102 and the air inlet 103 are arranged in the high-energy region of the airflow to drive the CFJ jet to circulate efficiently. They work in conjunction with the ducted propeller device 200 to improve the overall propulsion efficiency of the ducted fan.

[0071] Combination Figures 6-12 The following is a specific embodiment:

[0072] like Figures 6-12The diagram shows a specific flow control device for improving the propulsion efficiency of a ducted fan, as provided by the present invention.

[0073] In this embodiment, the bottom of the duct 100 is supported by a duct support base 300. A ducted propeller assembly 200 is coaxially mounted inside the duct 100; wherein, the ducted propeller assembly 200 includes a ducted fan engine nacelle 201 and ducted fan blades 202.

[0074] The duct 100 includes a duct outer shell 106, a duct inner shell 107, an I-beam ring 108, a front rib 109, a rear rib 110, and a miniature fan 111;

[0075] The I-beam ring 108 includes an I-beam web 1081, an I-beam outer ring 1082, and an I-beam inner ring 1083; wherein, the I-beam web 1081 is vertically arranged, and the outer ring 1082 and the inner ring 1083 are fixedly arranged at the outer end and the inner end of the I-beam web 1081, respectively;

[0076] On the web 1081 of the I-beam, multiple ribs are installed at intervals along the circumference; each rib includes a pair of front ribs 109 and rear ribs 110; the front ribs 109 and rear ribs 110 are arranged in a straight line on the front and rear sides of the web 1081 of the I-beam, and are assembled and fixed to the web 1081 of the I-beam by rib fixing screws 112; specifically, the rib fixing screws 112 can pass through the lugs on both sides of the web 1081 of the I-beam, so as to realize the connection and fixation of the front ribs 109, rear ribs 110 and web 1081 of the I-beam.

[0077] In the section of the web 1081 of the I-beam between every two ribs, multiple fan mounting holes 1112 and fan wiring holes 1111 are provided; each fan mounting hole 1112 is used to assemble and install a miniature fan 111; the fan wiring hole 1111 is used for the cable passage of the miniature fan 111; when the fan mounting holes 1112 and the fan wiring holes 1111 are not in use, they are sealed with foam blocks.

[0078] On the outer surface of the outer ring 1082 of the I-beam, the duct housing 106 is assembled and installed by countersunk screws 113 for fixing the duct housing; and the duct housing 106 is divided into two sections, namely the front section 1061 and the rear section 1062 of the duct housing located on both sides of the web 1081 of the I-beam.

[0079] On the lower surface of the inner ring 1083 of the I-beam, the inner shell 107 of the duct is assembled and installed by countersunk screws 114 for fixing the inner shell of the duct.

[0080] Using the structure of the above culvert 100, the main load-bearing structure of the model consists of I-beam ring 108, front rib 109, rear rib 110, and culvert support base 300. I-beam ring 108, front rib 109, and rear rib 110 are all made of aluminum alloy and CNC machined; culvert support base 300 is made of 45# steel and welded.

[0081] The duct outer shell 106 and duct inner shell 107 are 3D printed. The duct outer shell 106 and duct inner shell 107 combine to form an airfoil, with the internal cavity serving as a CFJ internal flow channel. The front section 1061 of the duct outer shell and the duct inner shell 107 combine to form an air inlet 102, and the rear section 1062 of the duct outer shell and the duct inner shell 107 combine to form an air intake 103. The duct outer shell 106 and duct inner shell 107 are connected and fixed to the I-beam ring 108 by countersunk screws. The ribs contact the duct outer shell 106 and duct inner shell 107 to provide support.

[0082] When used as a ducted fan wind tunnel test model, the duct 100 is connected to the external test bench via the duct support base 300.

[0083] In this embodiment, a miniature fan 111 is used as the air source device 105. The miniature fan 111 has a diameter of 50mm and a rated power of 0.66kW. The web plate 1081 of the I-beam has 24 fan mounting holes 1112 and 24 fan wiring holes 1111. The miniature fan 111 passes through the fan mounting holes 1112 for fixation. In actual testing, only a portion of the miniature fans 111 can be installed for testing; for example, 12 miniature fans 111 can be installed for testing. This device can accommodate up to 24 miniature fans 111. Unused fan mounting holes 1112 and fan wiring holes 1111 are sealed with foam board. The speed control of the miniature fan 111 is achieved through open-loop PWM signal control, and the control system is implemented via computer input.

[0084] The ducted fan blade 202 is made of aluminum alloy and is CNC machined into one piece. It can achieve variable pitch operation when used with the blade hub. The rotation of the ducted fan blade 202 is driven by another motor with a maximum power of 100kW.

[0085] The structure of the above-mentioned duct 100 has the following advantages:

[0086] The I-beam ring 108 facilitates the installation of multiple miniature fans 111, as well as the installation of the duct outer shell 106 and the duct inner shell 107, offering the advantage of easy assembly. The ribs spaced along the circumference enhance the support for the duct outer shell 106 and the duct inner shell 107, ensuring the structural strength of the entire duct 100.

[0087] The I-beam ring 108 and the ribs are load-bearing structures. The miniature fan 111 is installed on the web plate 1081 of the I-beam ring 108 of the culvert. The installation is convenient and can ensure the structural strength.

[0088] A single-chip microcomputer can simultaneously control several micro fans 111, enabling computer command input and real-time control of the behavior of all micro fans 111.

[0089] The duct 100 involved in this invention can be a duct model used for wind tunnel testing, or a duct device installed on an actual aircraft. This invention is not limited in this respect.

[0090] This invention significantly improves the overall propulsion efficiency of ducted fans by introducing cooperative jet active flow control, while also enhancing the wind resistance and maneuverability of ducted fans.

[0091] 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 flow control device for improving the propulsive efficiency of a ducted fan, characterised in that, The duct (100) and the duct propeller device (200) are included. The outer periphery of the duct propeller device (200) is provided with an annular duct (100); the duct (100) includes a blowing flow channel (101), a blowing port (102), a suction port (103), a suction flow channel (104) and a gas source device (105); the blowing port (102) is arranged on the inner surface of the duct (100), that is, the upper surface of the duct airfoil, and close to the position of the leading edge of the duct airfoil; the suction port (103) is arranged on the upper surface of the duct airfoil of the duct (100) and away from the leading edge of the duct airfoil; the blowing flow channel (101) communicated with the blowing port (102), the suction flow channel (104) communicated with the suction port (103) and the gas source device (105) located between the blowing flow channel (101) and the suction flow channel (104) are arranged in the duct (100); under the driving of the gas source device (105), the air sucked from the suction port (103) flows through the suction flow channel (104) and the blowing flow channel (101) and is blown out from the blowing port (102), forming air flow circulation; The blowing port (102) is arranged at a position of 0.05c-0.08c away from the leading edge of the duct airfoil on the upper surface of the duct airfoil, the width of the blowing port (102) is 0.003c-0.008c, and the center line of the blowing port (102), that is, the jet direction, forms an angle of 30°-40° with the chord line of the duct airfoil; The suction port (103) is arranged at a position of 0.7c-0.9c away from the leading edge of the duct airfoil on the upper surface of the duct airfoil, the width of the suction port (103) is 0.008c-0.012c, and the center line of the suction port (103), that is, the air inlet direction, forms an angle of 15°-30° with the chord line of the duct airfoil; wherein c is the chord line of the duct airfoil; A specific flow control device for improving the efficiency of duct fan propulsion is: The bottom of the duct (100) is supported by a duct support base (300); the inside of the duct (100) is coaxially installed with a duct propeller device (200); wherein the duct propeller device (200) includes a duct fan engine nacelle (201) and a duct fan blade (202); The duct (100) includes a duct outer shell (106), a duct inner shell (107), an I-beam circular ring (108), a front rib (109), a rear rib (110) and a micro fan (111); The I-beam circular ring (108) includes an I-beam web (1081), an I-beam outer circular ring (1082) and an I-beam inner circular ring (1083); wherein the I-beam web (1081) is vertically arranged, and the outer end and the inner end of the I-beam web (1081) are each fixedly provided with the I-beam outer circular ring (1082) and the I-beam inner circular ring (1083); A plurality of ribs are installed on the I-beam web (1081) at intervals along the circumference; each rib includes a pair of front ribs (109) and rear ribs (110); the front ribs (109) and the rear ribs (110) are arranged in a straight line on the front and rear sides of the I-beam web (1081) and are assembled and fixed with the I-beam web (1081) by rib fixing screws (112); specifically, the rib fixing screws (112) pass through the ears on both sides of the I-beam web (1081) to realize the connection and fixation of the front ribs (109), the rear ribs (110) and the I-beam web (1081); A plurality of fan mounting holes (1112) and fan wiring holes (1111) are arranged on the section of the I-beam web (1081) between every two ribs; each fan mounting hole (1112) is assembled and installed with a micro fan (111); the fan wiring hole (1111) is used for the cable of the micro fan (111); the fan mounting hole (1112) and the fan wiring hole (1111) are plugged with foam blocks when not in use; On the outer surface of the I-beam outer ring (1082), the culvert outer shell (106) is assembled and installed by fixing the countersunk screws (113) on the culvert outer shell body; and the culvert outer shell (106) is divided into two sections, namely the culvert outer shell front section (1061) and the culvert outer shell rear section (1062) located on both sides of the I-beam web (1081); On the lower surface of the I-beam inner ring (1083), the culvert inner shell (107) is assembled and installed by fixing the countersunk screws (114) on the culvert inner shell body; With the above structure of the culvert (100), the main load-bearing structure of the model is the I-beam ring (108), the front rib (109), the rear rib (110) and the culvert support base (300); the I-beam ring (108), the front rib (109) and the rear rib (110) are all made of aluminum alloy and are CNC processed; the culvert support base (300) is made of 45# steel and is welded; The culvert outer shell (106) and the culvert inner shell (107) are 3D printed; the combination of the culvert outer shell (106) and the culvert inner shell (107) forms an airfoil shape, and the internal cavity is a CFJ internal flow passage; the combination of the culvert outer shell front section (1061) and the culvert inner shell (107) forms a blowing port (102), and the combination of the culvert outer shell rear section (1062) and the culvert inner shell (107) forms a suction port (103); the culvert outer shell (106) and the culvert inner shell (107) are connected and fixed with the I-beam ring (108) by countersunk screws, and the ribs contact the culvert outer shell (106) and the culvert inner shell (107) to provide support; When used as a culvert fan wind tunnel test model, the culvert (100) is connected with the external rack through the culvert support base (300). The micro fan (111) is used as the air source device (105), the diameter of the micro fan (111) is 50 mm, the rated power is 0.66 kW, 24 fan mounting holes (1112) and 24 fan wiring holes (1111) are formed on the web (1081) of the I-beam, and the micro fan (111) is fixed by penetrating through the fan mounting hole (1112); in actual test, the micro fan (111) is installed for test, the idle fan mounting hole (1112) and the fan wiring hole (1111) are blocked by a foam board; the rotation speed of the micro fan (111) is controlled by open loop control through a PWM signal, and the control system is realized by computer input; The ducted fan blade (202) is made of aluminum alloy and is integrally processed by CNC, and can realize variable pitch operation in cooperation with the hub. The rotation of the ducted fan blade (202) is driven by another motor, and the maximum power is 100 kW. The structure of the above duct (100) has the following advantages: Through the I-beam ring (108), it is convenient to install multiple micro fans (111), convenient to install the duct shell (106) and the duct inner shell (107), and has the advantages of convenient assembly; by arranging ribs along the circumference, the support effect on the duct shell (106) and the duct inner shell (107) is enhanced, and the structural strength of the entire duct (100) is guaranteed. The I-beam ring (108) and the rib are force-bearing structures, the micro fan (111) is installed on the web (1081) of the I-beam ring (108) of the duct, which is convenient to install and can guarantee the structural strength. A single-chip microcomputer can control several micro fans (111) at the same time, realize computer instruction input, and control the behavior of all micro fans (111) in real time.

2. A flow control device for improving the efficiency of a ducted fan propulsion system according to claim 1, wherein, The blowing flow of the blowing port (102) is equal to the suction flow of the suction port (103), realizing zero mass jet flow and actively controlling the external flow field.

3. The flow control device of claim 1, wherein, The blowing port (102) is continuously arranged or discretely arranged on the inner surface of the duct (100), and correspondingly, the suction port (103) is continuously arranged or discretely arranged on the inner surface of the duct (100). Wherein: continuous arrangement refers to that the blowing port (102) and the suction port (103) are continuously arranged in a 360° annular manner on the inner surface of the duct (100); Discrete arrangement refers to that a plurality of blowing ports (102) and a plurality of suction ports (103) are arranged at intervals along the circumference of the annular inner surface of the duct (100); at the same time, when the blowing port (102) and the suction port (103) are discretely arranged, each blowing port (102) forms a blowing and suction unit with a corresponding suction port (103) through an independent air flow channel and an independent air source device (105); by independently controlling the blowing and suction amount of each group of blowing and suction units, an asymmetric thrust is generated, and then a pitch moment and a yaw moment are generated, so as to vector control the ducted fan.

4. The flow control device of claim 1, wherein, The ducted propeller device (200) comprises a ducted fan engine nacelle (201) and a ducted fan blade (202). The outer periphery of the turbofan engine nacelle (201) is annularly provided with a plurality of turbofan blades (202), and the turbofan engine nacelle (201) drives each turbofan blade (202) to rotate; the outer periphery of each turbofan blade (202) is provided with an annular duct (100).

5. An active flow control method of a flow control device for improving the propulsive efficiency of a ducted fan according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: Simultaneously start the air source device (105) of the duct (100) and the turbofan engine nacelle (201) of the duct propeller device (200); For the duct propeller device (200), the turbofan engine nacelle (201) drives the turbofan blade (202) to rotate, thereby generating aerodynamic thrust; For the duct (100), the air flow is jetted out from the air outlet (102), flows through the upper surface of the duct airfoil, is then sucked in from the air inlet (103), and is jetted out from the air outlet (102) again under the action of the air source device (105), thereby forming a CFJ jet cycle, and the air outlet flow of the air outlet (102) is equal to the air inlet flow of the air inlet (103); During the CFJ jet cycle, the air outlet (102) is arranged at the lip position of the leading edge of the duct airfoil, so that the lip position is an air flow acceleration area due to the suction effect; the air inlet (103) is arranged at the back side of the turbofan blade (202), and is also located in the air flow acceleration area under the working action of the turbofan blade (202); Therefore, the air outlet (102) and the air inlet (103) are arranged in the high kinetic energy area of the air flow, drive the CFJ jet to circulate efficiently, and work together with the duct propeller device (200) to improve the overall propulsion efficiency of the turbofan.

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