阅读说明：本技术 一种用于高超声速飞行器减阻的狭缝平行吹气方法 (Slit parallel blowing method for drag reduction of hypersonic aircraft ) 是由 高振勋 莫凡 韩冰 蒋崇文 李椿萱 于 2021-01-27 设计创作，主要内容包括：本发明属于飞行器设计领域,特别涉及一种可用于高超声速飞行器减阻的狭缝平行吹气方法,包括在所述飞行器的迎风面上设置狭缝,然后通过所述狭缝向壁面边界层内平行吹气。本发明针对高超声速飞行器提出了新的狭缝平行吹气减阻技术的应用方案,不仅实现了利用狭缝吹气技术降低高超声速飞行器表面摩擦阻力,同时又不改变高超声速飞行器的力矩特性。不同于逆向喷流和安装激波杆等针对激波阻力的减阻方式,本发明的主要实现途径是采用狭缝平行吹气的方式降低高超声速飞行器表面的摩擦阻力,从而达到降低飞行器总阻力的目的。(The invention belongs to the field of aircraft design, and particularly relates to a slit parallel blowing method for drag reduction of a hypersonic aircraft. The invention provides a new application scheme of a slit parallel air blowing resistance reduction technology for the hypersonic aerocraft, which not only realizes the reduction of the surface friction resistance of the hypersonic aerocraft by using the slit air blowing technology, but also does not change the moment characteristic of the hypersonic aerocraft. Different from resistance reduction modes aiming at shock resistance, such as reverse jet flow, shock rod installation and the like, the invention mainly realizes the way of reducing the frictional resistance on the surface of the hypersonic aircraft by adopting a slit parallel air blowing mode, thereby achieving the purpose of reducing the total resistance of the aircraft.)

1. A slit parallel air blowing method for drag reduction of a hypersonic aircraft is characterized by comprising the steps of arranging a slit on the windward side of the hypersonic aircraft and then blowing air into a wall boundary layer in parallel through the slit.

2. The method of claim 1, wherein the slit is spaced from the windward front end by 40% of the windward flow direction length.

3. The method of claim 1, wherein the depth of the slit is 0.005 times the aircraft flow direction length.

4. The method according to claim 1, wherein the blowing mach number is 1 to 3, and the blowing pressure is 3 times of the incoming flow pressure.

5. Method according to one of claims 1 to 4, characterized in that the slit is symmetrical with respect to the plane of symmetry of the aircraft and is 70 to 90 ° to the plane of symmetry of the aircraft.

6. Method according to one of claims 1 to 4, characterized in that the source of gas used for blowing is air or nitrogen.

Technical Field

The invention belongs to the field of aircraft design, and particularly relates to a slit parallel blowing method for drag reduction of a hypersonic aircraft.

Background

When the hypersonic aircraft flies at high altitude with high Mach number, the total resistance mainly comprises shock wave resistance and frictional resistance, and the existing hypersonic aircraft resistance reduction technology is mainly aimed at the shock wave resistance, such as common stagnation point reverse jet flow resistance reduction and shock rod resistance reduction technology. As shown in FIG. 1 (see "Chang Chaulyan. Effect of reciprocal flow jet on a super sonic recording capsule. AIAA 2006-) 4776, 2006" and "Gauer M, Paul A.numerical information of a specific non-sonic resin at super sonic speeds. journal of space and rocks, 2008 (3)"), the reverse jet of the return deck head (FIG. (a) shows a reverse jet flow field) increases the dislocation distance of the strong bow shock, so that the pressure of the return deck head wall is reduced, and thus the effect of reducing the shock resistance can be achieved. The shock wave rod is arranged at the head of the bluff body (figure (b) shows that the bluff body is provided with a shock wave rod flow field), so that the shock wave separation distance is increased, the strong bow-shaped shock wave is changed into an oblique shock wave, and the wave-rear pressure is obviously reduced. This demonstrates that both techniques reduce the shock resistance of the aircraft.

However, for a hypersonic aircraft which is designed based on a waverider profile and has a high flying height, on one hand, the proportion of shock resistance in total resistance is reduced, the proportion of friction resistance is increased, and the effect of reducing the total resistance is poor due to common stagnation point reverse jet flow, shock rods and the like; on the other hand, the existing scheme of stagnation point reverse jet flow resistance reduction and shock rod resistance reduction can obviously influence the moment characteristic of the aircraft and can bring about the problems of vibration and instability of a flow field. Therefore, there is a need for a drag reduction technique that can effectively reduce the frictional resistance of hypersonic aircraft without changing the moment characteristics of the aircraft.

The slit parallel blowing technique has attracted attention in recent decades, and domestic and foreign scholars have conducted a series of experiments and numerical simulation researches on the technique, but mainly conducted experimental researches by arranging slits in a flat plate. Chinese patent CN1089913 discloses an air-blowing type wing front airflow inducing device for a subsonic passenger plane, which introduces the airflow of the lower wing surface of the wing into the upper wing surface through the device to improve the wing lift force of the subsonic passenger plane. But the device can not effectively reduce the frictional resistance of the hypersonic flight vehicle.

Disclosure of Invention

Aiming at the problems, the invention provides a slit parallel blowing technical scheme for drag reduction of a hypersonic aircraft from the perspective of reducing the frictional resistance of the hypersonic aircraft. The slit parallel blowing means that gas is blown into the boundary layer through the slit, and the effect of reducing the wall surface speed and the temperature gradient is achieved by increasing the thickness of the boundary layer, so that the frictional resistance and the heat flow density of the surface of the aircraft are reduced. The invention provides a new application scheme of a slit parallel air blowing resistance reduction technology for the hypersonic aerocraft, which not only realizes the reduction of the surface friction resistance of the hypersonic aerocraft by using the slit air blowing technology, but also does not change the moment characteristic of the hypersonic aerocraft. Different from resistance reduction modes aiming at shock resistance, such as reverse jet flow, shock rod installation and the like, the method mainly realizes the way of reducing the frictional resistance on the surface of the hypersonic aircraft by adopting a slit parallel blowing mode on the windward side of the aircraft, thereby achieving the purpose of reducing the total resistance of the aircraft.

In order to achieve the aim, the invention provides a slit parallel air blowing method for drag reduction of a hypersonic aircraft, which comprises the steps of arranging a slit on the windward side of the aircraft and then blowing air to a wall boundary layer in parallel through the slit.

Preferably, the distance between the slit and the front end of the windward side is about 40% of the length of the windward side in the flow direction.

Preferably, the depth of the slit is about 0.005 times the length of the aircraft flow direction.

Preferably, the blowing Mach number is 1-3 Mach, and the blowing pressure is 3 times of the incoming flow pressure.

Preferably, the slits are symmetrical about the plane of symmetry of the aircraft and are 70-90 ° to the plane of symmetry of the aircraft.

Preferably, the source of gas used for blowing is air or nitrogen.

The invention has the beneficial effects that:

1) the invention can effectively reduce the surface friction resistance of the aircraft, and further can effectively reduce the total resistance of the hypersonic aircraft which is designed based on the waverider profile and has higher flying height;

2) the invention can directly reduce the frictional resistance of the surface of the aircraft by utilizing the slit parallel air blowing technology on the windward side of the aircraft, and simultaneously can play an equivalent anti-drag effect through the additional thrust generated by air blowing, thereby having higher anti-drag efficiency;

3) compared with the reverse jet flow resistance reduction and shock rod resistance reduction technologies, the invention uses the parallel blowing of the slit to have little influence on the flow field, and hardly changes the longitudinal force characteristic of the aircraft;

4) the slit parallel blowing is used on the windward side of the aircraft, so that the effect of reducing the resistance of the hypersonic aircraft can be achieved, and the wall surface heat flux density in the blowing action area can be reduced to a certain degree;

5) the invention uses air as the air source for slit parallel blowing, and the mass flow of the slit blowing at the high altitude of 60km is about 10^-2The magnitude of kg/s, so the invention has the characteristics of convenient material acquisition, low cost, light carrying weight and good economical efficiency.

Drawings

FIG. 1 is a schematic diagram of a prior art reverse jet drag reduction and shock rod drag reduction scheme;

FIG. 2 is a simplified model diagram of an exemplary hypersonic aircraft having a waverider profile in accordance with an embodiment of the present invention;

FIG. 3 is a side view of an embodiment of the invention with the slits in a windward arrangement;

FIG. 4 is a bottom view of a slot of an embodiment of the present invention in a windward arrangement;

FIG. 5 is an enlarged view of a slit according to an embodiment of the present invention;

FIG. 6 is a graph showing the comparison of the friction coefficient of a wall surface under no-blowing and slit-blowing according to the embodiment of the present invention, wherein (a) is a cloud of the friction coefficient of no-blowing and (b) is a cloud of the friction coefficient of blowing at 3 times the pressure of incoming flow;

FIG. 7 is a graph showing a comparison of the heat flux density of a wall under no-blow and slit-blow in accordance with an embodiment of the present invention, wherein (a) is a heat flux cloud of the no-blow wall and (b) is a heat flux cloud of the blow wall at 3 times the incoming flow pressure.

Detailed Description

The invention is further described below with reference to the accompanying drawings and examples, it being understood that the examples described below are intended to facilitate the understanding of the invention, and are not intended to limit it in any way.

The slit blowing method for drag reduction of the hypersonic aircraft comprises the following steps:

step 1: and selecting proper slit depth, slit blowing parameters and the like.

The typical hypersonic aircraft with the shape of a wave multiplier is selected in the embodiment, the head of the hypersonic aircraft is pointed, the hypersonic aircraft has the characteristics of small shock resistance and large friction resistance when flying at high altitude with high Mach number, and the slit parallel blowing device is suitable for the hypersonic aircraft. Considering that some structures on the appearance of the aircraft have small influence on the wall surface friction and the heat flow of the aircraft, the aircraft is simplified to a certain extent, only a fuselage is considered in the numerical simulation process, a tail wing and a flap are removed, the final flow direction length is 5m, the width is 2m, and the appearance of the aircraft is shown in figure 2. For this simplified model, the incoming flow condition of the present embodiment takes mach number Ma as 20, altitude H as 60km, and angle of attack as 5 degrees. The layout scheme of the slits is shown in figures 3-5, the slits are arranged on the windward side of the aircraft, the depth of the slits is 20mm, the blowing Mach number Ma is 2, the blowing pressure is 3 times of the incoming flow pressure, and the blowing component is air.

Step 2: the slits are arranged at suitable positions on the windward side of the hypersonic aerocraft, and the positions of the slits are related to the shape of the hypersonic aerocraft. Considering that when the hypersonic aircraft flies at an angle of attack, a region with large friction resistance is concentrated near a front body of a windward side, blowing cannot reduce the friction resistance of the high friction resistance region when a slit is too far back, and a blowing action region becomes small due to the limitation of the appearance of the aircraft when the slit is too far front, so that the final slit position needs to be optimally determined according to the shape of the aircraft. The present embodiment preferably has the slit position near the first 40% of the windward side. As shown in fig. 4, the slit position of the present embodiment is located at a flow direction x of 2.25 m.

And step 3: the slit is opened to blow air in parallel in a high-altitude high-Mach-number flight state, and air storage devices carried on aircrafts can be used for blowing air in parallel in the wall boundary layer through the slit. The wall friction in the blowing action area can be obviously reduced, and the large-area heat flow can be reduced to a certain extent. Meanwhile, the additional thrust generated by the parallel air blowing of the slits plays a role in reducing the resistance to a certain degree. The resistance-reducing and heat-reducing effects of slit parallel blowing of the aircraft of the embodiment under different heights and different Mach numbers are shown in Table 1. From the results, it was found that the friction reduction rate was 22.3% and the total resistance reduction rate reached 12.7% at Ma 15 and H50 km, on the one hand. Meanwhile, with the increase of the Mach number and the increase of the flight altitude, the total resistance reduction rate is maintained at 12-15%. On the other hand, the wall heat flux density is reduced to a certain extent in the range of action of the slit parallel blowing, for example, the average value of the wall heat flux density in the range of action of the slit blowing is 1.47 × 10 under the conditions that Ma is 20 and H is 50km⁵W/m²Reduced to 3.1 × 10⁴W/m²The reduction rate was about 78.9%.

Table 1 drag reduction and heat reduction effects of the present embodiment of the air vehicle in parallel blowing through the slits at different altitudes and different mach numbers

In addition, comparing the slit parallel air blowing scheme of the present invention with the un-blown air, as shown in fig. 6 and 7, the large area friction coefficient and the heat flux density of the wall surface under the slit blown air are both significantly reduced compared with the un-blown air. In conclusion, the slit parallel blowing technical scheme for reducing drag and heat of the hypersonic aircraft is feasible.

It will be apparent to those skilled in the art that various modifications and improvements can be made to the embodiments of the present invention without departing from the inventive concept thereof, and these modifications and improvements are intended to be within the scope of the invention.