CN104149967A - Low-Reynolds-number airfoil profile with cooperative fluidic control, and control method thereof - Google Patents

Abstract

The invention provides a low Reynolds number airfoil with coordinated jet control and a control method thereof. The low Reynolds number airfoil with coordinated jet control is as follows: an air jet (2) is arranged on the leading edge of the upper surface of the airfoil (1), An air suction port (3) is arranged on the rear edge of the upper surface of the airfoil (2); the air jet (2) and the air suction port (3) pass through the airflow duct (5) arranged inside the airfoil (1) ) is communicated; an air pump (4) for driving air suction and jetting simultaneously is installed in the air flow duct (5); and, the air injection port (2) and the air suction port (3) are connected The upper surface of the airfoil (1) is vertical. It achieves the purpose of greatly increasing the lift of the airfoil, and at the same time significantly reducing the drag and improving the stall characteristics of the airfoil, thereby achieving the purpose of efficiently improving the aerodynamic performance of the aircraft; in addition, it also has the advantage of low energy consumption.

Description

A low Reynolds number airfoil with cooperative jet control and its control method

technical field

The invention belongs to the technical field of fluid control, and in particular relates to a low Reynolds number airfoil with cooperative jet control and a control method thereof.

Background technique

The wing is the main part of the aircraft to generate lift, and its cross-sectional shape is the airfoil. The aerodynamic characteristics of the airfoil directly affect the lift and drag of the wing. At present, conventional design methods are difficult to greatly improve the aerodynamic characteristics of the airfoil, but the flow control method can break through the limitations of traditional design methods, achieve the effect of significantly improving the lift-drag characteristics of the airfoil, and thus significantly improve the performance of the aircraft.

At present, passive flow control methods have been widely used in engineering. Passive flow control refers to changing the flow environment through passive flow control devices, such as wing blades and vortex generators. Its disadvantage is that this kind of control is preset, and it cannot achieve the best control effect when it is not in the design state.

Active flow control is more flexible, and its advantage is that it can appear at the required time and place, and obtain local or global flow changes through local energy input, thereby significantly improving the flight performance of the aircraft. Compared with passive control methods, active flow control has higher efficiency and robustness, and has broad application prospects.

For low Reynolds number aircraft, such as high-altitude drones and stratospheric airships, the aerodynamic efficiency is not high due to the influence of their aerodynamic characteristics. At the same time, this type of aircraft is usually designed to stay in the air for a long time, and is limited by energy supply, so low aerodynamic efficiency is an urgent problem to be solved. However, the existing active flow control methods for improving the aerodynamic characteristics of the airfoil still have relatively large limitations, and it is difficult to significantly increase the lift force, greatly improve the stall characteristics, and then improve the performance of the aircraft.

Contents of the invention

Aiming at the defects existing in the prior art, the present invention provides a low Reynolds number airfoil with cooperative jet control and its control method, which is used to control the dynamic characteristics of the fluid near the airfoil to greatly increase the lift of the airfoil while significantly reducing the Small resistance, improved airfoil stall characteristics, so as to achieve the purpose of efficiently improving the aerodynamic performance of the aircraft; in addition, it also has the advantage of low energy consumption.

The technical scheme that the present invention adopts is as follows:

The invention provides a low Reynolds number airfoil with coordinated jet flow control, an air jet (2) is arranged on the leading edge of the upper surface of the airfoil (1), and an air suction port (3) is arranged on the trailing edge of the upper surface of the airfoil (2). ; The air injection port (2) and the air intake port (3) are communicated through the air flow duct (5) arranged inside the airfoil (1) to form a blowing and air suction circuit; in the air flow duct (5) An air pump (4) for simultaneously driving air suction and air injection is installed inside; and both the air injection port (2) and the air suction port (3) are perpendicular to the upper surface of the airfoil (1).

Preferably, the air jet (2) is set at 7.0% to 10% of the chord line, and the height of the air jet (2) is 0.8% to 1.5% of the chord length;

The air suction port (3) is arranged at the position of 80%-88% of the chord line, and the height of the air suction port (3) is 0.8%-1.5% of the chord length.

Preferably, the air flow duct (5) includes a front duct (51), a middle duct (52) and a rear duct (53); the middle duct (52) is a duct for arranging the air pump (4) , the front pipeline (51) is a pipeline positioned in front of the middle pipeline (52), and the rear pipeline (53) is a pipeline positioned behind the middle pipeline (52);

According to the direction from back to front, the section of the rear pipe (53) gradually expands; the section of the front pipe (51) gradually shrinks according to the direction from back to front.

Preferably, the airfoil is applied to fixed-wing aircraft, propellers or rotors.

The present invention also provides a cooperative jet control method for a low Reynolds number airfoil, comprising the following steps:

The air pump (4) simultaneously drives the air jet at the leading edge and the air suction at the trailing edge to actively control the airflow on the surface of the airfoil;

Among them, the process of jetting at the leading edge is: the jet port (2) ejects high-speed jets along the tangential direction of the upper surface of the airfoil (1), and the ejected high-speed jets inject energy into the fluid on the upper surface of the airfoil (1), and the main flow Accelerated by jet ejection, which in turn accelerates the flow of fluid on the upper surface and increases lift; in addition, the airflow generates suction on the surface of the leading edge of the airfoil (1), and the direction of the suction is perpendicular to the surface of the airfoil (1) and points to the external flow field. The component parallel to the flow direction is opposite to the flow direction and opposite to the resistance direction, thus reducing the resistance;

The trailing edge suction process is: the airflow is sucked into the rear pipe (53) tangentially along the upper surface at the suction port (3) of the trailing edge; the rear pipe (53) gradually expands along the flow direction, so that the airflow velocity gradually As the pressure increases, the airflow is sucked into the air pump, and then the airflow is boosted by the air pump and flows through the front pipe (51). As the front pipe (51) gradually shrinks, the flow rate increases and becomes the high-speed jet injected into the mainstream. middle.

In summary, the low Reynolds number airfoil with coordinated jet control and its control method provided by the present invention have the following advantages:

(1) Adopt the active flow control method of simultaneously injecting air at the leading edge and inhaling air at the trailing edge to achieve the purpose of increasing lift, reducing drag, and improving stall characteristics;

(2) Air injection and air suction do not require additional air sources, thus avoiding complicated ventilation pipeline design;

(3) The mechanism of airflow recycling can reduce energy consumption;

(4) No moving parts are needed, and it is easy to implement. It can be used for the wings of fixed-wing aircraft, and can also be used for rotating lift components such as propellers and rotors; it can be used for the take-off and landing stages of aircraft, and the sliding distance can be significantly reduced; It can also be used in the cruising phase to save fuel and reduce operating costs.

Description of drawings

Figure 1 is a cross-sectional view of a low Reynolds number airfoil with coordinated jet control of the present invention;

Figure 2 is a schematic diagram of the velocity distribution on the upper surface of the airfoil using cooperative jet control;

Fig. 3 is the schematic diagram of velocity distribution on the upper surface of the airfoil without control;

Fig. 4 is a schematic diagram of the flow field structure on the upper surface of the airfoil using cooperative jet flow control;

Fig. 5 is a schematic diagram of the structure of the flow field on the upper surface of the airfoil without control.

Detailed ways

The present invention is described in detail below in conjunction with accompanying drawing:

The present invention provides a low Reynolds number airfoil with coordinated jet flow control, as shown in Figure 1, which is a cross-sectional view of the airfoil, an air jet 2 is arranged on the leading edge of the upper surface of the airfoil 1, and an air suction port is arranged on the trailing edge of the upper surface of the airfoil 2. The gas port 3; the jet port 2 and the suction port 3 are connected through the air flow pipe 5 arranged inside the airfoil 1 to form a blowing and suction circuit; the air pump 4 for driving the air suction and the air injection simultaneously is installed in the air flow pipe 5; As a preferred method, the jet port 2 is set at 7.0% to 10% of the chord line, and the height of the jet port 2 is 0.8% to 1.5% of the chord length; the suction port 3 is set at 80% to 88% of the chord line , the height of the suction port 3 is 0.8% to 1.5% of the chord length. Among them, the chord line refers to the connection line from the most front end point to the last end point of the airfoil, and its length is the chord length. Moreover, both the air injection port 2 and the air intake port 3 are perpendicular to the upper surface of the airfoil 1, so as to ensure that the gas is ejected and inhaled tangentially along the upper surface.

In the present invention, the arrangement positions of the air jet port and the air suction port fully take into account the characteristics of flow around the airfoil. Since the airflow is accelerated at the leading edge of the airfoil, the area near the leading edge is the area with the highest air velocity in the entire flow field, that is, the area with the lowest pressure. Therefore, the arrangement of the air nozzle here is conducive to the ejection of gas; The airfoil flows through the upper surface of the airfoil, the speed gradually decreases, and the pressure rises near the trailing edge, which is conducive to the inhalation. It can be seen that the arrangement of the air injection port and the air suction port provided by the present invention can minimize the energy required for airflow circulation, reduce the power consumed by the air pump, reduce the burden on the air pump, and reduce energy consumption. Through the active flow control method provided by the present invention , can achieve obvious effect of increasing lift and reducing drag with lower power.

In addition, the air flow duct 5 involved in the present invention includes a front duct 51, a middle duct 52 and a rear duct 53; the middle duct 52 is a duct for placing the air pump 4, and the front duct 51 is a duct located in front of the middle duct 52. The rear duct 53 is the duct located behind the middle duct 52;

The rear duct 53 gradually expands its cross-section in the direction from back to front. After the airflow is sucked into the rear duct by the air inlet, as the duct cross-section gradually expands, the flow velocity of the airflow gradually decreases and the pressure increases. Under the action of pressure, it enters the air pump; the front pipe 51 gradually shrinks in cross-section according to the direction from back to front, and the air flow flows through the front pipe after being pressurized by the air pump, and gradually shrinks along with the cross-section of the pipe. The flow velocity increases and becomes a high-speed jet injected into the mainstream.

The present invention also provides a cooperative jet control method for a low Reynolds number airfoil, comprising the following steps:

The air pump 4 simultaneously drives the air jet at the leading edge and the air suction at the trailing edge to actively control the airflow on the surface of the airfoil;

Among them, the process of air injection at the leading edge is: the jet port 2 ejects a high-speed jet 8 along the tangential direction of the upper surface of the airfoil 1, the ejected high-speed jet injects energy into the fluid on the upper surface of the airfoil 1, and the main flow 9 is ejected by the jet Acceleration; the lift of the airfoil is proportional to the amount of circulation around the airfoil, that is, the lift of the airfoil depends on the speed difference between the upper and lower surfaces of the airfoil. Therefore, accelerating the flow on the upper surface can achieve the purpose of increasing lift. The conventional airfoil accelerates the airflow on the upper surface through the curvature change of the leading edge surface to generate lift. This acceleration effect is very limited. However, through the ejection acceleration of the high-speed jet, the airflow velocity on the upper surface can reach a high speed. The circulation value is beyond the reach of conventional airfoils. Therefore, the control method of the present invention can greatly increase the lift of the airfoil.

Another effect of the jet is reflected in the reduction of resistance. As before, the jet accelerates the velocity of the main flow in the upper surface region, including the flow near the leading edge. The high-velocity airflow produces a large suction force on the airfoil leading edge surface. The direction of the suction force is perpendicular to the surface and points to the external flow field. In addition, the force of jet ejection is favorable for reducing resistance. Through the effects of the above two aspects, the resistance is greatly reduced, and the control method of the present invention can even completely overcome the aerodynamic resistance and generate thrust.

The trailing edge suction process is as follows: the airflow is sucked into the rear pipe 53 tangentially along the upper surface at the suction port 3 of the trailing edge; the rear pipe 53 gradually expands along the flow direction, so that the flow velocity of the airflow gradually decreases and the pressure increases. The airflow is sucked into the air pump, and then the airflow is pressurized by the air pump and flows through the front pipe 51. As the front pipe 51 gradually shrinks, the flow velocity increases and becomes a high-speed jet injected into the mainstream. The effect of air suction can also accelerate the flow velocity at the trailing edge of the airfoil, so that the flow can maintain an attached state, suppress the generation of separation vortices, and improve the stall characteristics of the airfoil. The synergistic effect of jet and air intake can achieve the purpose of significantly increasing lift and reducing drag.

The cooperative jet control method provided by the present invention can change the characteristics of the local flow field. Referring to Figure 2, it is a schematic diagram of the velocity distribution on the upper surface of the airfoil using cooperative jet control, 10 is the velocity distribution near the downstream of the air jet, and 11 is near the upstream of the suction port. Velocity distribution, it can be seen that the velocity distribution on the upper surface becomes fuller due to the acceleration of the jet 8 and the suction effect, and the ability to inhibit separation is strengthened. Referring to Fig. 3, it is the velocity distribution diagram on the upper surface of the airfoil without control, 12 is the velocity distribution near the leading edge of the airfoil without control, and 13 is the velocity distribution near the trailing edge of the airfoil without control, due to the gas and airfoil surface Due to the viscous effect, the flow velocity decreases rapidly along the normal direction of the airfoil surface, and the ability of low-speed flowing gas to inhibit separation is weak. When the airfoil angle of attack is large, a large separation vortex is easily generated, that is, it enters a stall state, and the lift force decreases rapidly. The resistance increases dramatically. As shown in Figure 4, it is a schematic diagram of the flow field structure on the upper surface of the airfoil using cooperative jet control; as shown in Figure 5, it is a schematic diagram of the flow field structure on the upper surface of the airfoil without control. With the invented cooperative jet flow control method, the flow remains attached to the upper surface at high angles of attack, delaying the stall of the airfoil; however, stall occurs in the separation region 14 of the uncontrolled airfoil at high angles of attack.

It has been verified that by adopting the low Reynolds number airfoil with cooperative jet control and the control method provided by the present invention, the lift coefficient, maximum lift coefficient, and stall angle of attack of the airfoil are significantly improved. Among them, the lift coefficient at zero angle of attack can be increased to 70%, the maximum lift coefficient can be increased to about 150%, and the stall angle of attack can be increased by about 60%. At the same time, its zero-rise angle of attack and drag coefficient are significantly reduced, and it can even generate thrust in the range of small attack angles.

In summary, the low Reynolds number airfoil with coordinated jet control and its control method provided by the present invention have the following advantages:

(1) Adopt the active flow control method of simultaneously injecting air at the leading edge and inhaling air at the trailing edge to achieve the purpose of increasing lift, reducing drag, and improving stall characteristics;

(2) Air injection and air suction do not require additional air sources, thus avoiding complicated ventilation pipeline design;

(3) The mechanism of airflow recycling can reduce energy consumption;

(4) No moving parts are needed, and it is easy to implement. It can be used for the wings of fixed-wing aircraft, and can also be used for rotating lift components such as propellers and rotors; it can be used for the take-off and landing stages of aircraft, and the sliding distance can be significantly reduced; It can also be used in the cruising phase to save fuel and reduce operating costs.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (5)

1. a low Reynolds number airfoil with collaborative jet vectoring, is characterized in that, in aerofoil profile (1) upper surface leading edge, air nozzle (2) is set, and at aerofoil profile (2) upper surface trailing edge, air suctiton inlet (3) is set; Described air nozzle (2) and described air suctiton inlet (3) are communicated with by being arranged at the inner airflow line (5) of described aerofoil profile (1), form blowing suction loop; In described airflow line (5), be provided with for drive the air-breathing and jet air pump carrying out (4) simultaneously; And described air nozzle (2) is all vertical with the upper surface of described aerofoil profile (1) with described air suctiton inlet (3).

2. the low Reynolds number airfoil with collaborative jet vectoring according to claim 1, is characterized in that, described air nozzle (2) is arranged at the string of a musical instrument 7.0%～10% position, and described air nozzle (2) is highly 0.8%～1.5% of chord length;

Described air suctiton inlet (3) is arranged at the string of a musical instrument 80%～88% position, and described air suctiton inlet (3) is highly 0.8%～1.5% of chord length.

3. the low Reynolds number airfoil with collaborative jet vectoring according to claim 1, is characterized in that, described airflow line (5) comprises anterior pipeline (51), middle part pipeline (52) and rear portion pipeline (53); Described middle part pipeline (52) is for settling the pipeline of described air pump (4), described anterior pipeline (51) is for being positioned at described middle part pipeline (52) pipeline above, and described rear portion pipeline (53) is for being positioned at described middle part pipeline (52) pipeline below;

Described rear portion pipeline (53) is pressed direction from back to front, and its cross section is expanded gradually; Described anterior pipeline (51) is pressed direction from back to front, and shrink gradually in its cross section.

4. the low Reynolds number airfoil with collaborative jet vectoring according to claim 1, is characterized in that, described aerofoil profile is applied to fixed wing aircraft, screw propeller or rotor.

5. for a collaborative jet control method for low Reynolds number airfoil, it is characterized in that, comprise the following steps:

Air pump (4) drives leading edge jet air-breathing with trailing edge simultaneously, and airfoil surface air-flow is carried out to active Flow Control;

Wherein, the jet process of leading edge is: air nozzle (2) is along the tangential ejection high velocity jet of aerofoil profile (1) upper surface, the high velocity jet spraying is aerofoil profile (1) upper surface fluid Implantation Energy, main flow is accelerated by jet injection, and then accelerate flowing of upper surface fluid, increase lift; In addition, air-flow produces suction in aerofoil profile (1) leading edge surface, and the direction of suction is pointed to External airflow field perpendicular to aerofoil profile (1) surface, and the component that this suction is parallel to flow direction is contrary with flow direction, and contrary with drag direction, and then reduces resistance;

Trailing edge breathing process is: air-flow is tangentially inhaled into rear portion pipeline (53) at the air suctiton inlet (3) of trailing edge along upper surface; Rear portion pipeline (53) streamwise is expanded gradually, air current flow speed is reduced gradually, pressure raises, air-flow is inhaled into air pump, and then, air-flow is again by air pump acting supercharging, the anterior pipeline (51) of flowing through, along with anterior pipeline (51) shrinks gradually, flow velocity increases, and becomes high-speed jet and injects among main flow.