CN103291498B - Laser propulsion device and method based on principle of laser-induced water drop breakdown - Google Patents

Abstract

The invention discloses a laser propulsion device based on the principle of laser-induced water droplet breakdown, including a laser, a water droplet injection device, a laser propeller and a pulse signal generator; the laser generates and emits laser light to the laser propeller; The laser thruster is arranged coaxially with the laser; the water drop injection device is arranged at the head of the laser thruster and provides water droplets to the laser thruster; the pulse signal generator includes a A first pulse signal generator and a second pulse signal generator for controlling the water drop ejection device. The water droplet breakdown is more thorough than the water droplet vaporization, and the utilization rate of the working medium is higher, which can effectively avoid the waste of the working medium, and further improve the comprehensive propulsion performance, and obtain greater specific impulse, impulse coupling coefficient and energy conversion efficiency.

Description

A laser propulsion device and method based on the principle of laser-induced water droplet breakdown

technical field

The invention relates to the field of laser propulsion, in particular to a laser propulsion device and method based on the principle of laser-induced water droplet breakdown.

Background technique

Laser propulsion is a new type of propulsion technology, which uses the interaction between high-energy laser and working medium to generate thrust to push the lightship forward. Compared with traditional chemical propulsion, laser propulsion has the advantages of large specific impulse, low cost, safety and environmental protection. It has broad development prospects in the fields of micro-satellite launch, satellite attitude and orbit control, and space junk cleaning.

Scholars at home and abroad have conducted detailed research on the propulsion mechanism and performance of gas working fluid, solid working fluid and liquid working fluid. After the gas working medium is broken down, it forms a plasma and a laser-supported detonation wave, which propels the lightship forward through the recoil effect of the plasma and laser-supported detonation wave. The gas working medium has a large breakdown threshold, and the requirements for the laser are very high. ; The specific impulse of laser propulsion by gas working medium is large, but the impulse coupling coefficient is small. The solid working medium undergoes ablation reaction under the action of laser irradiation, forming steam or plasma on the ablation surface, and the steam or plasma leaves the ablation surface to generate reverse thrust. When the incident laser power density is high, the plasma further evolves into laser Detonation waves are supported, and detonation waves have a strong recoil effect; solid working medium laser propulsion has a large specific impulse, and the impulse coupling coefficient is small, which is in the same order of magnitude as the gas working medium impulse coupling coefficient. The liquid working medium is violently vaporized under the irradiation of low-power-density laser to produce explosive steam, and the steam is ejected backward to generate reverse thrust. Under the irradiation of high-power-density laser, a breakdown effect occurs, forming plasma and laser-supported detonation The plasma and laser support the recoil generated by the expansion of the detonation wave to push the lightship forward; the laser propulsion impulse coupling coefficient of the liquid working medium is large, but the specific impulse and energy conversion efficiency are very small, and serious damage will occur when explosive vaporization occurs. Waste of working fluid.

For example, the Chinese patent with the publication number CN101737201A discloses a laser propulsion device, which includes a laser, a propellant supply device, a laser focusing device, and a combustion chamber; wherein the laser is used to generate laser light; the laser focusing device is used to focus the The laser is applied to the propellant; the propellant supply device is used to supply the propellant, and the propellant in the laser irradiation area is basically converted into plasma; the combustion chamber is used to convert the propellant The energy of the plasma is transmitted to the lightship. The propellant used in the laser propulsion device is thin-film propellant or lightweight foam propellant, which can avoid the heat conduction and propellant loss caused by material sputtering when laser ablation fixed propellant to a certain extent, but the laser The comprehensive performance of propulsion is not high.

In order to reduce the breakdown threshold of the working medium and improve the comprehensive performance of laser propulsion, a new idea is to use water droplets instead of large-volume liquid working medium for laser propulsion. At present, only Li Xiuqian and others from the Institute of Equipment Command Technology have proposed The propulsion performance was carried out related experimental research. In his experimental research, the relevant experimental device was designed according to the thrust test method. The laser is focused through the lens, and the water droplets are injected from the top of the thruster (laser thruster) through the working fluid injection system, and are heated by the laser in the thruster to produce explosive vaporization. Phenomenon, the steam is coupled with the thruster to form reverse thrust. The experimental results show that the impulse coupling coefficient is 5.2×10 ^-4 N/W, the specific impulse is about 100s, the energy conversion efficiency reaches 26%, and the comprehensive propulsion performance has been greatly improved.

However, in their experimental research, the power density of the incident laser is less than the breakdown threshold of water droplets, and the breakdown effect of water droplets does not occur and further form plasma and laser-supported detonation waves. Only the propulsion performance of water droplets under vaporization is studied. There is still room for further improvement; there is still room for further optimization of the laser focusing method and the injection method of water droplets; there is still room for further innovation in the laser propulsion method.

Contents of the invention

The invention provides a laser propulsion device and method based on the principle of laser-induced water droplet breakdown, which achieves the effects of reducing the breakdown threshold of working fluid and improving the comprehensive performance of laser propulsion.

A laser propulsion device based on the principle of laser-induced water droplet breakdown, including a laser, a water droplet injection device, a laser thruster and a pulse signal generator;

the laser to generate and emit laser light to the laser thruster;

The laser thruster is arranged coaxially with the laser;

The water drop injection device is arranged at the head of the laser thruster and provides water drop working fluid to the laser thruster;

The pulse signal generator includes a first pulse signal generator for controlling the laser and a second pulse signal generator for controlling the water droplet injection device.

The water drop injection device includes a storage tank, a pipeline and a nozzle, the storage tank is connected to the nozzle through the pipeline, and the nozzle is close to the head of the laser thruster and injects water droplets to the laser thruster.

The water drop injection device and the laser thruster are integrated into one body. The integrated arrangement of the water drop injection device and the laser thruster enables the nozzle in the water drop injection device to be placed on the head of the laser thruster, and the two are firmly connected.

The laser thruster is in the shape of a parabola, and the parallel laser light emitted by the laser is focused at the focal point of the parabola after being reflected by the inner wall of the laser thruster. The head of the laser thruster is the top of the parabolic laser thruster.

The Sauter average diameter of the water droplets produced by the nozzle is on the order of 10 μm.

The laser is a CO ₂ laser, and the laser generated and emitted by the CO ₂ laser is a high-energy pulsed laser. The wavelength of the generated and emitted laser light is 10.6 μm, and the power density is on the order of 10 ⁹ W/cm ² . The direction of incidence is parallel, and the cross-sectional area of the laser beam is equivalent to the cross-sectional area of the laser thruster. The wavelength of the laser emitted by the CO ₂ laser is similar to the Sauter mean diameter of the water droplet, which can obtain good propulsion performance.

The water drop injection device injects water droplets into the laser thruster through the nozzle; the injection direction of the nozzle points to the focus of the parabolic laser thruster; the projected area of the nozzle along the axial direction of the laser thruster is as small as possible to reduce the internal Influenced by the reflected laser on the wall, the projection point of the nozzle position in the axial direction of the thruster is located between the apex and the focal point of the parabolic laser thruster; there are at least 3 nozzles, which are evenly and symmetrically distributed around the axis of the laser thruster, and the number of nozzles is too large. It is easy to weaken the reflective effect of the inner wall facing the laser; the spray angle of the nozzle should be as large as possible on the basis of ensuring that the sprayed water droplets will not spray on the inner wall of the laser thruster, and the spray angle should be smaller than the focal point of the nozzle and the parabolic laser thruster. The angle formed by the connection line of the nozzle and the tangent of the nozzle on the parabolic laser thruster is the most suitable.

The operating frequencies of the first pulse signal generator and the second pulse signal generator are consistent. The first pulse signal generator triggers the laser to emit laser light through the control signal, the second pulse signal generator opens the nozzle to spray water droplets through the control signal, and sets the operating frequency of the first pulse signal generator and the second pulse signal generator to be consistent, so The injection frequency of the nozzle is consistent with the emission frequency of the laser, so that the moment when the water droplet is injected is just broken down by the incident laser, ensuring that the water droplet injection process is synchronized with the laser incident and breakdown process.

A laser propulsion method based on the principle of laser-induced water droplet breakdown, comprising the following steps:

(1) The first pulse signal generator generates a control signal to trigger the laser to emit laser light to the laser thruster;

(2) After a preset delay time, the second pulse signal generator generates another control signal, and opens the nozzle to inject water droplets into the laser thruster;

(3) The laser is focused in the laser thruster, which breaks down the water droplets to form high-temperature and high-pressure plasma, and the plasma further forms the laser to support the detonation wave. The plasma and laser support the rapid development of the detonation wave. When the plasma and laser After the inner wall of the thruster is in contact, the laser supports the detonation wave to continue to expand to form a pulse thrust, which pushes the lightship connected to the laser propulsion device forward.

By repeating steps (1)-(3) at a certain frequency, a continuous pulse laser propulsion process can be realized to provide continuous thrust for the lightship. The frequency of the repeated steps must be less than 100 Hz, so that the two reactions before and after do not affect each other.

In step (2), the delay time depends on the specific time difference between the transmission of the laser light to the laser propeller and the movement of the water droplet to the focus area.

The power density of the laser light emitted by the laser is greater than the breakdown threshold of water droplets and smaller than the breakdown threshold of air.

The breakdown effect of the laser breakdown water droplet working medium first occurs at the focal point of the parabolic laser thruster; the plasma rapidly forms and expands to the surroundings, and further forms the laser supporting detonation wave; the plasma and the inner wall of the laser thruster are coupled , to produce the anti-thrust for the lightship to advance; the laser supports the detonation wave to propagate outward at supersonic speed, and is further accelerated in the parabolic laser thruster to generate pulse thrust.

The duration of the breakdown reaction between the laser and the water droplet is on the order of 1ms, which is less than the time between laser pulses, and each repeated reaction does not affect each other.

Compared with the prior art, the beneficial effects of the present invention are as follows:

(1) The breakdown threshold of the water droplet working medium is smaller than that of the gas working medium, and the breakdown phenomenon is easy to occur, which is easy to realize in engineering practice.

(2) The water droplet breakdown is more thorough than the water droplet vaporization reaction, and the utilization rate of the working medium is higher, which can effectively avoid the waste of the working medium, and further improve the comprehensive propulsion performance, and obtain greater specific impulse, impulse coupling coefficient and energy Conversion efficiency.

Description of drawings

1 is a schematic diagram of a laser propulsion device based on the principle of laser-induced water droplet breakdown in the present invention;

Fig. 2 is the schematic diagram of the embodiment of a laser propulsion device adopting the thrust test method of the present invention;

Fig. 3 is A-A sectional schematic diagram among Fig. 2;

FIG. 4 is a schematic diagram of the configuration of the parabolic laser thruster in FIG. 2 .

In the figure: 101 is a _CO2 laser, 102 is a first pulse signal generator, 103 is a laser support detonation wave, 104 is a plasma, 105 is a laser focusing area, 106 is a laser thruster, 107 is a nozzle, 108 is a tube 109 is the second pulse signal generator, 110 is the storage tank, 111 is the bareboat, S11 and S12 are the control signals generated by the pulse signal generator; 201 is the _CO2 laser, 202 is the laser supporting detonation wave, and 203 is Plasma, 204 is the laser focusing area, 205 is the laser thruster, 206 is the nozzle, 207 is the oscilloscope, 208 is the pulse signal generator, 209 is the storage tank, 210 is the piezoelectric sensor, 211 is the pipeline, 212 is the metal needle , S21 and S22 are the control signals generated by the pulse signal generator, and S23 is the thrust test signal induced by the piezoelectric sensor.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following is merely illustrative and does not limit the scope of the present invention.

Example 1

As shown in Figure 1, a laser propulsion device based on the principle of laser-induced water droplet breakdown includes a _CO2 laser 101, a water droplet injection device, a laser propulsion device 106 and a pulse signal generator. _CO2Laser 101 generates and emits laser light to laser propeller 106; the water droplet injection device and laser propeller 106 are integrated and coaxially arranged with _CO2 laser device 101, and the water droplet injection device is located at the head of laser propeller 106, The water drop injection device is used to provide the water drop working medium to the laser propeller 106; the water drop injection device includes a storage tank 110, a pipeline 108 and a nozzle 107, the storage tank 110 is connected with the nozzle 107 through the pipeline 108, and the nozzle 107 is close to the laser The head of the thruster 106 injects water drop working medium to the laser thruster 106 . The shape of the laser thruster 106 is parabolic. The pulse signal generator includes a first pulse signal generator 102 for controlling the CO ₂ laser 101 and a second pulse signal generator 109 for controlling the water droplet injection device.

The first pulse signal generator 102 generates a control signal S11 to start the _CO2 laser 101 to emit high-energy pulsed laser light, which is incident on the laser thruster 106 in parallel and focuses at the laser focus region 105 of the parabola, while the second pulse signal generator 109 generates The control signal S12 starts the nozzle 107, the hydraulic medium in the storage tank 110 enters the nozzle 107 through the pipeline 108 to be sprayed, injects the water drop working medium into the laser propeller 106, the laser focuses and breaks down the water drop working medium to form a plasma 104, The plasma 104 further forms a laser-supported detonation wave 103, the rapid expansion of the plasma 104 is coupled with the laser thruster 106, and the laser-supported detonation wave 103 is accelerated in the parabolic laser thruster 106, generating a recoil force to push the bareboat 111 forward .

Example 2

As shown in Figure 2, Figure 2 is a schematic diagram of an embodiment of a laser propulsion device using a thrust test method in the present invention, including a _CO2 laser 201, a water droplet injection device, a laser thruster 205, a pulse signal generator and a test unit. The _CO2 laser 201 generates and emits laser light to the laser thruster 205; the water droplet injection device and the laser thruster 205 are integrated and coaxially arranged with the _CO2 laser 201, and the water droplet injection device is arranged at the head of the laser thruster 205, The water drop injection device is used to provide the water drop working fluid to the laser propeller 205; the water drop injection device includes a storage tank 209, a pipeline 211 and a nozzle 206, the storage tank 209 is connected with the nozzle 206 through the pipeline 211, and the nozzle 206 is close to the laser The head of the thruster 205 injects water drop working medium to the laser thruster 205 . The shape of the laser thruster 205 is parabolic. Owing to be to operate in the laboratory, can use a pulse signal generator 208 to control _CO2laser 201 and nozzle 206 simultaneously; Draw a metal needle 212 along the axial direction at the head of parabolic laser thruster 205 simultaneously, guarantee Breakdown can also occur at lower power densities; the piezoelectric sensor 210 is closely attached to the head of the laser thruster 205 , and the thrust test signal S23 induced by the piezoelectric sensor is sent to the oscilloscope 207 in real time.

In the specific implementation project, the axis direction of the laser thruster 205 is taken as the x-axis, the longitudinal direction as the y-axis, and the origin is located at the apex of the inner wall.

^y2 = 2px,

Among them, p is taken as 20mm, the diameter of the end face of the laser thruster 205 is 100mm, the height is 62.5mm, the focal point is 10mm from the head of the laser thruster 205, and the length of the metal needle 212 is 20mm; the smoothness of the inner wall is 0.32, and the wall thickness is 1mm , the material is 2A12 aluminum alloy.

The hydraulic medium in the storage tank 210 enters the nozzle 206 through the pipeline 211 for spraying, and injects water droplets into the laser thruster 205. The position of the nozzle 206 has the following requirements: (1) The spraying direction of the nozzle 206 points to the focus of the parabola; ( 2) The projected area of the nozzle 206 along the x-axis direction is as small as possible to reduce the influence of the inner wall on the laser emission; (3) The injection angle of the nozzle 206 is smaller than the angle formed by the line connecting the point and the focal point and the tangent direction of the point, Avoid spraying water droplets on the inner wall surface, which will affect the reflection effect of the inner wall facing the laser; (4) The number of nozzles 206 should not be too many, and the number of nozzles 206 should be evenly and symmetrically distributed around the x-axis. Combining the above requirements, four nozzles were used in this experiment. As shown in Figure 3, four nozzles 206 are arranged on the back of the laser thruster 205, which are evenly and symmetrically distributed; the spray angle of the nozzle 206 is 90°, and the nozzle 206 is located at the vertical angle direction, and point to the focus of the parabola, as shown in Figure 2.

In the experiment, the pulse signal generator 208 was used to control the CO ₂ laser 201 and the nozzle 206 respectively, and the time interval between every two laser pulses was set to 10ms.

The implementation steps are as follows: the control signal S21 generated by the pulse signal generator 208 starts the CO2 laser 201 to emit high-energy pulsed laser light, which is parallel incident to the laser thruster 205 and focuses at the focal point 204, and the control signal S22 generated by the pulse signal generator 208 starts the nozzle 206, the hydraulic medium in the storage tank 209 enters the nozzle 206 through the pipeline 211 for injection, injects the water droplet working medium into the laser propeller 205, and the focused laser breaks down the water droplet working medium on the surface of the metal needle 212 to form a plasma 203, and the plasma 203 further forms the laser-supported detonation wave 202, the rapid expansion of the plasma 203 is coupled with the thruster 205, the laser-supported detonation wave 202 is accelerated in the parabolic laser thruster 205, and the reverse thrust generated by the coupling will simultaneously trigger the piezoelectric The sensor 210 generates a thrust test signal S23 induced by the piezoelectric sensor 210 , and the thrust test signal S23 is displayed on the oscilloscope 207 in real time. The magnitude of the impulse can be obtained by integrating the thrust curve with time on the oscilloscope 207 , and then the value of the impulse coupling coefficient can be obtained. It is known that the weight of water droplets injected by the water droplet injection device is a fixed value, and then the specific impulse can be obtained. The research results show that the theoretical maximum value of specific impulse is about 700s, and the propulsion performance has been greatly improved.

Claims (6)

1. A laser propulsion device based on the principle of laser-induced water droplet breakdown, comprising a laser, a water droplet injection device, a laser thruster and a pulse signal generator; the laser to generate and emit laser light to the laser thruster; The laser thruster is arranged coaxially with the laser; The water drop injection device is arranged at the head of the laser thruster and provides water droplet working medium to the laser thruster; The water drop injection device includes a storage tank, a pipeline and a nozzle, the storage tank is connected to the nozzle through the pipeline, the nozzle is close to the head of the laser thruster and injects water droplets to the laser thruster; The laser thruster is parabolic, and the parallel laser emitted by the laser is focused at the focal point of the parabola after being reflected by the inner wall of the laser thruster; The injection direction of the nozzle points to the focus of the parabola; there are at least three nozzles, which are evenly and symmetrically distributed around the axis of the laser propeller; The pulse signal generator includes a first pulse signal generator for controlling the laser and a second pulse signal generator for controlling the water droplet injection device. 2. The laser propulsion device based on the principle of laser-induced water droplet breakdown according to claim 1, wherein the Sauter mean diameter of the water droplets generated by the nozzle is on the order of 10 μm. 3. The laser propulsion device based on the principle of laser-induced water droplet breakdown according to claim 1, wherein the laser is a CO ₂ laser, the wavelength of the generated and emitted laser light is 10.6 μm, and the power density is 10 ⁹ W /cm ² level, the cross-sectional area of the laser beam is equivalent to the cross-sectional area of the laser thruster. 4 . The laser propulsion device based on the principle of laser-induced water droplet breakdown according to claim 1 , wherein the operating frequencies of the first pulse signal generator and the second pulse signal generator are the same. 5 . The laser propulsion device based on the principle of laser-induced water droplet breakdown according to claim 1 , wherein the power density of the laser emitted by the laser is greater than the breakdown threshold of water droplets and smaller than the breakdown threshold of air. 6. A laser propulsion method based on the principle of laser-induced water droplet breakdown, comprising the following steps: (1) The first pulse signal generator generates a control signal to trigger the laser to emit laser light to the laser thruster; (2) After a preset delay time, the second pulse signal generator generates another control signal, and opens the nozzle to inject water droplets into the laser thruster; (3) The laser is focused in the laser thruster, which breaks down the working medium of water droplets to form high-temperature and high-pressure plasma, and the plasma further forms the laser-supported detonation wave, and the plasma and laser support the rapid development of the detonation wave. When the plasma and laser After the inner wall of the thruster is in contact, the laser supports the detonation wave to continue to expand to form a pulse thrust, which pushes the lightship connected to the laser propulsion device forward.