阅读说明：本技术 一种基于激光等离子体的高超声速飞行器减阻方法 (Hypersonic aircraft drag reduction method based on laser plasma ) 是由 尤延铖 黄笠舟 陈荣钱 于 2020-04-22 设计创作，主要内容包括：一种基于激光等离子体的高超声速飞行器减阻方法,首先通过CFD数值模拟计算得到高超声速飞行器在不同超音速飞行状态下弓形激波产生的位置,将这些位置信息提前输入机载计算机；随后在飞行器上布置飞秒激光发生器,飞行过程中机载计算机通过将当前飞行状态与数值计算结果进行对比,获得飞行器前方弓形激波的大致位置,控制飞秒激光发生器调整发射方向和焦距,使得发射的激光聚焦在弓形激波产生的区域。飞秒激光发生器能够使激光击穿空气产生高温高压的等离子体,当冲击波传播到钝体头部时,会使头部压力稍有增加,进而阻力稍有增加,随后等离子体冲击波与钝体头部的弓形激波相互作用,使其变为较弱的斜激波,此时飞行器的气动阻力迅速减小。(A hypersonic aircraft drag reduction method based on laser plasma, firstly, the positions of the hypersonic aircraft generated by bow shock waves in different supersonic flight states are obtained through CFD numerical simulation calculation, and the position information is input into an onboard computer in advance; and then arranging a femtosecond laser generator on the aircraft, comparing the current flight state with the numerical calculation result by an onboard computer in the flight process to obtain the approximate position of the bow shock wave in front of the aircraft, and controlling the femtosecond laser generator to adjust the emission direction and the focal length so that the emitted laser is focused in the area where the bow shock wave is generated. The femtosecond laser generator can make laser breakdown air generate high-temperature and high-pressure plasma, when shock waves are transmitted to the blunt body head, the pressure of the head can be slightly increased, and then the resistance is slightly increased, then the plasma shock waves interact with the bow shock waves of the blunt body head to change the plasma shock waves into weaker oblique shock waves, and the aerodynamic resistance of the aircraft is rapidly reduced at the moment.)

1. A hypersonic aircraft drag reduction method based on laser plasma is characterized by comprising the following steps:

1) firstly, the positions of the hypersonic aircraft generated by bow shock waves in different supersonic flight states are obtained through CFD numerical simulation calculation, and the position information is input into an onboard computer in advance;

2) arranging a femtosecond laser generator on the aircraft, comparing the current flight state with the numerical calculation result by an onboard computer in the flight process to obtain the approximate position of the bow shock wave in front of the aircraft, and controlling the femtosecond laser generator to adjust the emission direction and the focal length so that the emitted laser is focused in the area where the bow shock wave is generated.

2. The method for drag reduction of a hypersonic aerocraft based on laser plasma as claimed in claim 1, wherein: according to the shock wave intensity distribution of the front part of the aircraft, the power of the femtosecond laser generators installed at different positions of the aircraft is different, wherein the power of the femtosecond laser generator close to the aircraft nose is higher, and the power of the femtosecond laser generator close to the wing tip is lower.

3. The method for drag reduction of a hypersonic aerocraft based on laser plasma as claimed in claim 1, wherein: in the step 2), when the femtosecond laser generator is installed, an aircraft wing plane is selected as an installation plane, the femtosecond laser generators which are axisymmetric with an aircraft central axis are sequentially designed from the head position to the tail direction, and a laser point source is required to be kept above the aircraft wing plane as much as possible during working so as to improve the lift force of the aircraft.

4. The method for drag reduction of a hypersonic aerocraft based on laser plasma as claimed in claim 3, wherein: eight femtosecond laser generators are arranged from the wing tip of the left side wing of the aircraft to the right side wing, wherein two groups of femtosecond laser generators are symmetrically arranged at the head part, and one group of femtosecond laser generators are symmetrically arranged at the corner of the wing and the position of the wing tip.

5. The method for drag reduction of a hypersonic aerocraft based on laser plasma as claimed in claim 4, wherein: due to the differences of the configuration and the size of the hypersonic flight vehicle and the Mach number of different flights, the standard value of the emission power of the femtosecond laser generator is set as follows:

wherein k is an aircraft configuration coefficient, 0.8 is taken when the aircraft is in a waverider configuration, 1.2 is taken when the aircraft is in the waverider configuration, M is the instantaneous flight Mach number of the aircraft, L is the fuselage length of the aircraft, and C is the wingspan length of the aircraft;

eight femtosecond laser generators arranged from the wing tip of the left side wing of the set aircraft to the right side wing are numbered 1-8 in sequence, the power of the femtosecond laser generators 1 and 8 is 0.6P, the power of the femtosecond laser generators 2 and 7 is 0.8P, the power of the femtosecond laser generators 3 and 6 is 1.2P, and the power of the femtosecond laser generators 4 and 5 is 1.4P.

6. The method for drag reduction of a hypersonic aerocraft based on laser plasma as claimed in claim 5, wherein: no. 4 and No. 5 femtosecond laser generators respectively generate three parallel laser point sources, the other femtosecond laser generators respectively generate one laser point source, and the airborne computer gives the spatial position of the laser point source according to the corresponding flight state to form twelve laser point source distributions in total.

7. The method for drag reduction of a hypersonic aerocraft based on laser plasma as claimed in claim 1, wherein: and when the aircraft is in a subsonic flight state, the femtosecond laser generator is turned off.

8. The method for drag reduction of a hypersonic aerocraft based on laser plasma as claimed in claim 1, wherein: the fixed base of the femtosecond laser generator adopts a three-axis stabilizing pan-tilt, and the bottom of the three-axis stabilizing pan-tilt is fixedly connected with an aircraft fuselage structure.

9. The method for drag reduction of a hypersonic aerocraft based on laser plasma as claimed in claim 1, wherein: when the aircraft performs large-attack-angle maneuvering flight, the direction of the light path is adjusted through the adjustable reflector, so that the laser beam passes through the transparent window through the adjustable reflector.

Technical Field

The invention relates to the field of hypersonic aircrafts, in particular to a hypersonic aircraft drag reduction method based on laser plasma.

Background

The hypersonic aircraft has the advantages of high remote combat efficiency, rapid target hitting, rapid and violent target hitting, and the like, and becomes the weapon development direction concerned by military and strong countries in the world. The excellent lift-increasing and drag-reducing performance is always the target pursued by the hypersonic aircraft, so that the research on the drag-reducing method of the hypersonic aircraft has important application value and economic benefit.

The head of the aircraft can generate strong detached shock waves during hypersonic flight, and the head of the general hypersonic aircraft can be made into a blunt body from the perspective of structural performance and thermal protection, so that high-strength normal shock waves are generated during hypersonic flight, air is highly compressed under the normal shock waves, the air pressure and density after shock waves are increased very high, the intensity of the shock waves is very high, when hypersonic airflow passes, air micelles are blocked most strongly, the speed is greatly reduced, the kinetic energy consumption is very high, and huge wave resistance can be generated. During hypersonic flight, shock waves and wave resistance are generated, and the influence on the flight performance of the aircraft is great. The occurrence of a strong bow shock is a major factor leading to increased drag. The large drag not only means that the aircraft is carrying more fuel to overcome the drag effect, but also results in a reduction in its payload. Shock resistance is one of the biggest obstacles affecting hypersonic flight, so reducing wave resistance is one of the most important considerations in hypersonic aircraft research. To effectively realize the design research of hypersonic flight and hypersonic aircrafts, the problem of how to reduce the shock resistance must be considered.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides a resistance reducing method for a hypersonic aircraft based on laser plasma.

In order to achieve the purpose, the invention adopts the following technical scheme:

a hypersonic aircraft drag reduction method based on laser plasma comprises the following steps:

1) firstly, the positions of the hypersonic aircraft generated by bow shock waves in different supersonic flight states are obtained through CFD numerical simulation calculation, and the position information is input into an onboard computer in advance;

2) arranging a femtosecond laser generator on the aircraft, comparing the current flight state with the numerical calculation result by an onboard computer in the flight process to obtain the approximate position of the bow shock wave in front of the aircraft, and controlling the femtosecond laser generator to adjust the emission direction and the focal length so that the emitted laser is focused in the area where the bow shock wave is generated.

According to the invention, according to the shock wave intensity distribution at the front part of the aircraft, the power of the femtosecond laser generators arranged at different positions of the aircraft is different, wherein the power of the femtosecond laser generator close to the aircraft nose is higher, and the power of the femtosecond laser generator close to the wing tip is lower.

In the step 2), when the femtosecond laser generator is installed, an aircraft wing plane is selected as an installation plane, the femtosecond laser generators which are axisymmetric with an aircraft central axis are sequentially designed from the head position to the tail direction, and a laser point source is required to be kept above the aircraft wing plane as much as possible during working so as to improve the lift force of the aircraft.

Eight femtosecond laser generators are arranged from the wing tip of the left side wing to the right side wing of the aircraft, wherein two groups of femtosecond laser generators are symmetrically arranged at the head part, and one group of femtosecond laser generators are symmetrically arranged at the corner of the wing and the position of the wing tip.

Due to the differences of the configuration and the size of the hypersonic flight vehicle and the Mach number of different flights, the standard value of the emission power of the femtosecond laser generator is set as follows:

wherein k is an aircraft configuration coefficient, 0.8 is taken when the aircraft is in a waverider configuration, 1.2 is taken when the aircraft is in the waverider configuration, M is the instantaneous flight Mach number of the aircraft, L is the fuselage length of the aircraft, and C is the wingspan length of the aircraft;

eight femtosecond laser generators arranged from the wing tip of the left side wing of the set aircraft to the right side wing are numbered 1-8 in sequence, the power of the femtosecond laser generators 1 and 8 is 0.6P, the power of the femtosecond laser generators 2 and 7 is 0.8P, the power of the femtosecond laser generators 3 and 6 is 1.2P, and the power of the femtosecond laser generators 4 and 5 is 1.4P.

The number 4 and the number 5 femtosecond laser generators respectively generate three parallel laser point sources, the other femtosecond laser generators respectively generate one laser point source, and the airborne computer gives the spatial position of the laser point source according to the corresponding flight state to form twelve laser point source distributions in total.

And when the aircraft is in a subsonic flight state, the femtosecond laser generator is turned off.

The fixed base of the femtosecond laser generator adopts a three-axis stabilizing pan-tilt, and the bottom of the three-axis stabilizing pan-tilt is fixedly connected with an aircraft fuselage structure.

When the aircraft performs large-attack-angle maneuvering flight, the direction of the light path is adjusted through the adjustable reflector, so that the laser beam passes through the transparent window through the adjustable reflector.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

1. the femtosecond laser generator can make laser breakdown air generate high-temperature and high-pressure plasma, when shock waves are transmitted to the blunt body head, the pressure of the head can be slightly increased, and then the resistance is slightly increased, then the plasma shock waves interact with the bow shock waves of the blunt body head to change the plasma shock waves into weaker oblique shock waves, the pneumatic resistance of the aircraft is rapidly reduced at the moment, and the resistance reduction effect is completed by adopting a femtosecond laser point source deposition mode.

2. The drag reduction ratio can be controlled by adjusting the power of the femtosecond laser generator: the method for installing 8 femtosecond laser generators near the head of the aircraft can reduce the resistance of the fuselage part of the aircraft and simultaneously reduce the interference of the detached shock waves generated in the hypersonic flight process of the aircraft on the air inlet channel.

3. Reducing the thermal effect: the front edge of the head of the hypersonic speed aircraft is one of the most serious places of aerodynamic heat, and the application of the laser plasma drag reduction technology in the hypersonic speed aircraft can effectively reduce the thermal stress of the front edge of the head, reduce the thermal protection requirement of the aircraft and increase the effective load.

4. Reducing sonic boom: the difference of the phases of the generated shock waves is utilized to induce the shock waves to mutually cancel each other, so that the strength of the N-shaped waves transmitted to the ground is reduced, and the influence of sonic boom is reduced.

5. Generating a lift force: when the laser ignition position is positioned above the symmetry axis, the pressure of the upper surface is reduced, and the corresponding pressure is not balanced with the lower surface, so that the aircraft can obtain a strong shock wave lift force, and meanwhile, the resistance is reduced, so that the lift-drag ratio of the hypersonic aircraft is greatly improved, the fuel consumption is reduced, and the economic benefit of the aircraft is improved.

Drawings

FIG. 1 is a schematic diagram of the installation position of a femtosecond laser generator and the arrangement position of a laser point source at the front end of an aircraft;

FIG. 2 is a schematic plan view of an installation of the femtosecond laser generator;

FIG. 3 is a schematic diagram of an arrangement of laser point sources in a shock cone section;

FIG. 4 is a diagram showing a rated power distribution of a number 1-8 femtosecond laser generator;

FIG. 5 is a schematic view of an installation structure of a femtosecond laser generator and a three-axis stabilization holder;

FIG. 6 is a schematic diagram of the adjustment of the reflective laser beam path.

Reference numerals: the cloud platform is fixedly connected with a stud 1, a horizontal rotating mechanism 2, a pitching rotating mechanism 3, a femtosecond laser generator 4, a femtosecond laser generator body 5, a transparent window 6 and an adjustable reflector 7.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

A hypersonic aircraft drag reduction method based on laser plasma comprises the following steps:

1) firstly, the positions of the hypersonic aircraft generated by bow shock waves in different supersonic flight states are obtained through CFD numerical simulation calculation, and the position information is input into an onboard computer in advance;

2) arranging a femtosecond laser generator on the aircraft, comparing the current flight state with the numerical calculation result by an onboard computer in the flight process to obtain the approximate position of the bow shock wave in front of the aircraft, and controlling the femtosecond laser generator to adjust the emission direction and the focal length so that the emitted laser is focused in the area where the bow shock wave is generated.

As shown in fig. 1-2, when the femtosecond laser generator is installed, an aircraft wing plane is selected as an installation plane, the femtosecond laser generators which are axisymmetric with respect to a central axis of the aircraft are sequentially designed from a head position to a tail direction, and a laser point source is required to be kept above the aircraft wing plane as much as possible during working, so as to improve the lift force of the aircraft;

specifically, eight femtosecond laser generators are arranged from the wing tip of the left side wing to the right side wing of the aircraft, wherein two groups of femtosecond laser generators are symmetrically arranged at the head part, and one group of femtosecond laser generators are symmetrically arranged at the corner of the wing and the wing tip; eight femtosecond laser generators arranged from the wing tip of the left side wing of the set aircraft to the wing of the right side wing are sequentially numbered as No. 1-8.

And when the aircraft is in a subsonic flight state, the femtosecond laser generator is turned off. After the aircraft enters a supersonic flight state, due to the differences of the configuration, the size and different flight Mach numbers of the hypersonic aircraft, the emission power of the laser generator at different positions is conveniently set, and the standard value (unit: kilowatt) of the emission power of the femtosecond laser generator is set as follows:

wherein k is an aircraft configuration coefficient, 0.8 is taken when the aircraft is in a waverider configuration, 1.2 is taken when the aircraft is in the configuration, M is the instantaneous flight Mach number of the aircraft, L (unit: M) is the fuselage length of the aircraft, and C (unit: M) is the wingspan length of the aircraft;

in order to improve the economic effect and reduce unnecessary energy waste, the femtosecond laser generators installed at different positions of the aircraft have different powers according to the intensity distribution of the shock waves at the front part of the aircraft, wherein the femtosecond laser generator close to the aircraft nose has higher power to weaken the bow shock waves with higher intensity at the front end of the aircraft nose, and the femtosecond laser generator close to the wing tip has lower power to save energy; specifically, as shown in fig. 4, the power of the No. 1 and No. 8 femtosecond laser generators is 0.6P, the power of the No. 2 and No. 7 femtosecond laser generators is 0.8P, the power of the No. 3 and No. 6 femtosecond laser generators is 1.2P, and the power of the No. 4 and No. 5 femtosecond laser generators is 1.4P.

The principle of the invention is as follows:

femtosecond laser refers to laser with a temporal pulse width on the order of femtoseconds (femtoseconds). The femtosecond laser is not monochromatic light, but is a combination of light with continuously changed wavelength around the central wavelength, and the spatial coherence of the continuous wavelength light in the range is utilized to obtain the time great compression, thereby realizing the femtosecond-level pulse output. Because the peak power of the femtosecond laser is very high, the light intensity can reach kilowatt/square centimeter magnitude after focusing. The strength of the plasma is far higher than the coulomb field of the interaction in the atom, so that the femtosecond laser pulse can easily remove the electrons from the constraint of the atom to form plasma. After the plasma absorbs the laser energy, the internal temperature and the pressure are increased rapidly, and the laser energy is absorbed continuously, so that the plasma rapidly expands outwards from a focus area to push the surrounding air to generate shock waves. The shock wave interacts with the normal shock wave of the blunt body aircraft head to change the shock wave into an oblique shock wave, and the wave is still supersonic airflow, so that the resistance of the aircraft in the supersonic flying process can be reduced.

Specific examples are given below: