Multi-layered thruster working fluid and thruster

Abstract

The present invention relates to a thruster working fluid and a thruster with a multi-layer structure. The thruster working fluid comprises a heat absorbing layer, a heat conducting layer and an ablative layer which are stacked in sequence; the heat absorbing layer, the heat conducting layer and the ablative layer are coaxially arranged, and the heat conducting layer is located between the heat absorbing layer and the ablative layer; the heat conducting layer has a heat conducting skeleton, and the heat conducting skeleton is filled with an ablative propellant; the ablative layer is made of an ablative composite propellant material, which absorbs heat from the heat conducting layer, and ablates and ionizes to form a quasi-neutral plasma flow with an initial velocity. The thruster working fluid with a multi-layer structure provided by the present invention can reduce ineffective ablation in the thruster startup phase, improve the thruster specific impulse and propulsion efficiency, and has strong adaptability.

Description

Technical Field

[0001] The invention relates to the technical field of thrusters, and in particular to a thruster working medium and a thruster with a multi-layer structure. Background Art

[0002] As the core of the electric propulsion system, electric thrusters have been successfully developed after more than half a century of development, and more than a dozen types of electric thrusters have been successfully developed. In electric thrusters, the working fluid plays a material basis role, and its selection is crucial, especially for complex and diverse tasks such as space transportation. Screening and determining the optimal working fluid has become a key step.

[0003] Among the exploration of various types of working fluids, electric thrusters using solid as working fluid have shown many unique advantages. Since no additional gas storage device and pipeline transportation system are required, solid working fluid generally has the advantages of simple structure, light weight, low power consumption requirement, high robustness, no standby power consumption and thrust vector control.

[0004] However, there are many problems that need to be solved during the use of solid working fluids. First, there is the phenomenon of ineffective ablation during the thruster startup phase, which will cause a large amount of energy loss; second, the thruster specific impulse and propulsion efficiency are not significantly improved, which can easily affect the overall propulsion performance; third, the existing solid working fluids are not adaptable enough and are difficult to flexibly adjust according to different space transportation missions. Summary of the invention

[0005] Based on this, it is necessary to provide a thruster working fluid and thruster with a multi-layer structure that can solve the problem of ineffective ablation in the thruster startup phase, improve the thruster specific impulse and propulsion efficiency, and have strong adaptability in response to the above-mentioned technical problems.

[0006] A thruster working fluid with a multi-layer structure, the thruster working fluid comprising: a heat absorption layer, a heat conduction layer and an ablation layer stacked in sequence;

[0007] The heat absorption layer, the heat conduction layer and the ablation layer are coaxially arranged, and the heat conduction layer is located between the heat absorption layer and the ablation layer;

[0008] The heat-conducting layer has a heat-conducting skeleton, and the heat-conducting skeleton is filled with an ablative propellant;

[0009] The ablative layer is made of ablative composite propellant, which absorbs heat from the heat-conducting layer, and performs ablation and ionization to form a quasi-neutral plasma flow with an initial velocity.

[0010] In one of the embodiments, the heat absorption layer is made of a material with high heat absorption rate and high thermal conductivity.

[0011] In one embodiment, the heat absorption layer is black.

[0012] In one embodiment, the heat absorption layer is made of graphene or hexagonal boron nitride or aluminum nitride doped carbon material or carbon nanotube composite material.

[0013] In one embodiment, the heat-conducting skeleton has more than one layer; when it has more than two layers, each heat-conducting skeleton is tightly fitted.

[0014] In one of the embodiments, the heat conductive skeleton has a plurality of filling holes, wherein the filling holes are through holes extending through the thickness direction of the heat conductive skeleton, and ablative propellants are filled in the through holes.

[0015] In one of the embodiments, the heat conduction skeleton is made of a material with high heat absorption rate and high thermal conductivity.

[0016] In one of the embodiments, the heat conduction skeleton is made of aluminum or aluminum alloy or titanium and its alloy or magnesium and its alloy or zinc and its alloy.

[0017] In one embodiment, the ablative composite propellant includes a dopant and an ablative propellant; wherein the dopant is a metal or a metal oxide or a non-metal.

[0018] A thruster adopts the thruster working fluid with the multi-layer structure.

[0019] Compared with the prior art, the multi-layered thruster working fluid and thruster provided by the present invention have the following effects:

[0020] 1. The heat absorption layer can quickly absorb external heat, and then transfer it to the ablation layer through the heat conduction skeleton of the heat conductive layer. This clear and stable heat transfer path can avoid disordered diffusion of energy, ensure that heat is evenly transferred to the ablation layer, and make the ablation process more orderly on the entire ablation layer, reducing ineffective ablation.

[0021] 2. Fill the heat conductive skeleton with ablative propellant. The ablative propellant is preheated during the heat transfer process and its molecular activity is enhanced. When the ablative layer begins to ablate and ionize, the preheated ablative propellant can better participate in the reaction, making the ablation process more efficient and avoiding ineffective ablation caused by too low a temperature or insufficient activation of the ablative propellant.

[0022] 3. Through the multi-layer design of heat absorption layer, heat conduction layer and ablation layer, heat can be efficiently converted into kinetic energy of plasma flow. Under the same amount of ablative propellant, a greater impulse can be generated, thereby improving the specific impulse.

[0023] 4. The multi-layer working fluid structural design can be reasonably adjusted according to different working conditions, thereby maintaining a relatively stable working state and having strong adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0025] Figure 1 A schematic diagram of a multi-layer thruster working fluid structure provided in Example 1;

[0026] Figure 2 A schematic diagram of the heat-conducting layer structure provided in Example 1;

[0027] Figure 3 This is a schematic diagram of the working of the propeller provided in Example 2.

[0028] Description of reference numerals:

[0029] Heat absorption layer 1, heat conduction layer 2, heat conduction skeleton 21, ablation layer 3, discharge chamber 4, ceramic isolator 5, working medium 6, capacitor 7.

[0030] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0033] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0034] It can be understood that the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0035] The following will describe the implementation of the present invention in detail with reference to the accompanying drawings in the embodiment diagram of the present invention.

[0036] Example 1

[0037] The multi-layered thruster working fluid provided by the present invention is designed according to the physicochemical characteristics of the thruster at each stage of operation, so that the ablative propellant can have multiple characteristics, such as: moderate thermal conductivity, moderate laser absorption coefficient, low ionization energy and high heat release specific enthalpy, etc., thereby optimizing the ablation process, making it not only compatible with good ablation characteristics and electromagnetic characteristics, avoiding ineffective ablation in the thruster startup stage, but also matching the physical field characteristics in the thruster, improving the thruster specific impulse and propulsion efficiency, and having strong adaptability, which can significantly improve the performance of the thruster.

[0038] See also Figure 1 and Figure 2 The multi-layered thruster working fluid provided in this embodiment includes: a heat absorbing layer 1, a heat conducting layer 2 and an ablative layer 3 stacked in sequence; the heat absorbing layer 1, the heat conducting layer 2 and the ablative layer 3 are coaxially arranged and have the same cross-sectional shape. The cross-sectional shapes of the heat absorbing layer 1, the heat conducting layer 2 and the ablative layer 3 are adapted to the cross-sectional shape of the accommodation chamber in the thruster.

[0039] In this embodiment, Figure 1 In the structural direction shown, the heat absorption layer 1, the heat conduction layer 2 and the ablation layer 3 are arranged in sequence from left to right, and the walls between adjacent layers are tightly fitted. The cross-sections of the heat absorption layer 1, the heat conduction layer 2 and the ablation layer 3 are circular, and the heat conduction layer 2 is located between the heat absorption layer 1 and the ablation layer 3. The heat conduction layer 2 has a heat conduction skeleton 21, and the heat conduction skeleton 21 is filled with an ablative propellant; the ablation layer 3 is made of an ablative composite propellant, which absorbs heat from the heat conduction layer 2, and ablates and ionizes to form a quasi-neutral plasma flow with an initial velocity.

[0040] Specifically, the first layer of working fluid is a heat absorption layer 1, and the heat absorption layer 1 is made of a material with high heat absorption rate and high thermal conductivity, so that it can quickly absorb heat and reduce laser reflection, so as to reduce the energy loss in the initial stage of thruster operation and increase the heating temperature of the laser on the working fluid surface in the early stage of thruster operation. Furthermore, the heat absorption layer 1 is black, and the black color has better heat absorption effect characteristics, which can further improve the ignition success rate of the thruster. The heat absorption layer 1 can be made of graphene or hexagonal boron nitride (h-BN) or aluminum nitride (AlN) doped carbon material or carbon nanotube composite material, and can also be brushed on the heat conductive layer 2 in the form of a coating. Preferably, the heat absorption layer 1 adopts a graphene coating. Graphene is a hexagonal two-dimensional honeycomb carbon nanomaterial in which carbon atoms are connected by sp2 hybridization. Each carbon atom is connected to the other three carbon atoms by a strong covalent bond. These C-C bonds make the graphite sheet have excellent structural rigidity. The reason why graphene has high thermal conductivity is that the covalent bonds between its C-C bonds are strong and the mass of carbon atoms is small, and phonons have a high sound velocity, so it has excellent thermal conductivity (about 5000W / (m·K) at room temperature).

[0041] The heat-conducting layer 2 has a heat-conducting skeleton 21, and the heat-conducting skeleton 21 has more than one layer; when it has more than two layers, each heat-conducting skeleton 21 has the same structure, and the number and position of the filling holes opened thereon can be set according to the situation. When combined, each heat-conducting skeleton 21 fits tightly. Figure 2 It can be seen that the heat conduction skeleton 21 has a number of filling holes, which are through holes opened along the thickness direction of the heat conduction skeleton, and the ablative propellant is filled in the through holes. The filling holes can be arranged according to a certain rule or in an irregular manner. The shape of the filling holes can be set to a rhombus, square, polygon, etc. according to needs. In addition, the filling holes in the heat conduction skeleton 21 can be prepared by a punching process; or the material can be made into a wire and then formed by weaving. When assembling each heat conduction skeleton 21, the filling holes on each heat conduction skeleton 21 can be in a through state; or they can be in a staggered state. That is, in this embodiment, the number of layers, shape, filling hole size (punching density), thickness of the heat conduction skeleton, and porosity of the filling holes of the heat conduction skeleton can be reasonably adjusted according to different working conditions to maintain a relatively stable working state, which has strong adaptability.

[0042] In terms of material, the heat conducting skeleton 21 is made of materials with high heat absorption rate and high thermal conductivity, such as metal, alloy, etc. More specifically, it can be made of aluminum or aluminum alloy, titanium and its alloy, magnesium and its alloy, or zinc and its alloy.

[0043] In this embodiment, aluminum wire is used to make a three-layer heat-conducting skeleton 21, and the filling holes are regular hexagons, so that the entire heat-conducting skeleton 21 forms honeycomb-shaped filling holes. It can be understood that aluminum has good thermal conductivity. In this embodiment, aluminum wire is used to make a heat-conducting skeleton 21 with a certain frame structure, which can not only significantly enhance the heat transfer effect; compared with the traditional method of using aluminum powder or other metal / non-metal powder, it will not burn out particles, avoiding the particle exploitation effect.

[0044] The ablative propellant can be made of materials such as polytetrafluoroethylene, ammonium nitrate, carbon fiber resin, or polyvinyl chloride, and the ablative propellant is filled in the filling hole of the regular hexagon. When the heat is transferred to the heat conductive layer 2, the high electron number density product formed by the ablation of the heat conductive skeleton 21 induces the formation of a high temperature and high pressure plasma zone at the position of the aluminum wire mesh, resulting in the formation of a low speed area between the heat conductive skeleton 21 and the ablation surface. These two areas greatly slow down the decay rate of the ablation surface pressure after the laser ends, reduce the particle stripping effect, and improve the impulse characteristics comprehensively. In addition, the heat conductive skeleton 21 made of materials with high heat absorption rate and high thermal conductivity can increase the ablation of polytetrafluoroethylene and reduce the ionization energy with its excellent thermal conductivity. It can be understood that the ablation here refers to the formation of plasma by irradiating the aluminum with laser; the ablation surface refers to the area where the laser irradiates the working fluid and ablates it; the low speed area refers to the area where plasma is generated above the ablation surface, and aluminum is not easy to ablate.

[0045] The ablative layer 3 is mainly an ablative composite propellant. When the ablative composite propellant has a higher discharge success rate, its various performance parameters are better than those of the ablative propellant made of pure polytetrafluoroethylene (PTFE).

[0046] Specifically, the ablative composite propellant includes a dopant and an ablative propellant; wherein the dopant is a metal or a metal oxide or a non-metal, for example, the dopant may be an alloy dopant, an oxide dopant, a salt electrolyte dopant, a carbon dopant, etc.; the ablative propellant may be made of materials such as polytetrafluoroethylene, ammonium nitrate, carbon fiber resin, or polyvinyl chloride. Preferably, the ablative composite propellant in this embodiment uses polychlorotetrafluoroethylene doped with metal particles, such as polychlorotetrafluoroethylene doped with Al2O3 particles. For metal dopants, they have high laser absorption and thermal conductivity. When the ablative propellant doped with metal particles is irradiated by a laser, the temperature of the metal particles will rise rapidly, thereby forming a local hot zone, the temperature of which is much higher than the temperature of the polytetrafluoroethylene matrix around the metal particles. These dispersed multiple local hot zones transfer heat to the polytetrafluoroethylene matrix around them, promoting the decomposition, vaporization and ionization of the matrix. Therefore, using Al2O3 particles as a dopant for the working fluid can reduce the plume beam angle, increase the specific impulse, and improve the propulsion efficiency. Such a design is also in line with the working characteristics of the thruster during the stable working stage.

[0047] In addition, carbon dopants can enhance the laser energy absorption rate and improve the ionization degree of the ablation plume. Therefore, the element impulse, impulse coupling coefficient, specific impulse, propulsion efficiency and discharge success rate of carbon-doped ablative composite propellants are relatively high, and they are also preferred materials.

[0048] Example 2

[0049] See also Figure 3 , is a schematic diagram of the thruster operation provided in this embodiment, the working fluid 6 is located between the upper and lower ceramic isolators 5, and the working fluid 6 adopts the thruster working fluid of the multi-layer structure provided in Example 1. When installed, the heat absorption layer 1 in the working fluid 6 faces the side of the incident laser.

[0050] Before laser ignition, the capacitor 7 has been charged by direct current, providing an electromagnetic field inside the discharge chamber 4 composed of the cathode and the anode. When the laser irradiates the working medium 6, the heat absorption layer 1 absorbs heat and transfers the heat to the heat conducting layer 2. The heat conducting skeleton 21 in the heat conducting layer 2 preheats the ablative propellant and transfers the heat to the ablative layer 3. As the ablative propellant decomposes, the ablative propellant in the heat conducting layer 2 and the ablative composite propellant in the ablative layer 3 gradually retreat and cause ablation. The ablative propellant and the ablative composite propellant are ablated and ionized into a quasi-neutral plasma flow with an initial velocity. Subsequently, the plasma flow enters the discharge chamber 4 after a certain expansion and diffusion. The electromagnetic field in the discharge chamber 4 interacts with the plasma flow, and the plasma flow is accelerated and ejected to generate thrust.

[0051] It is worth noting that the thruster working schematic diagram provided in this embodiment is only for the purpose of providing a better understanding of the scheme and is not intended to limit the structure of the thruster. The multi-layer structure of the thruster working fluid in Embodiment 1 can also be used in other thrusters.

[0052] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0053] The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A multi-layered thruster working fluid, characterized in that: The thruster working medium comprises: a heat absorbing layer, a heat conducting layer and an ablative layer stacked in sequence; The heat absorption layer, the heat conduction layer and the ablation layer are coaxially arranged, and the heat conduction layer is located between the heat absorption layer and the ablation layer; The heat-conducting layer has a heat-conducting skeleton, and the heat-conducting skeleton is filled with an ablative propellant; The ablative layer is made of ablative composite propellant, which absorbs heat from the heat-conducting layer, and performs ablation and ionization to form a quasi-neutral plasma flow with an initial velocity.

2. The multi-layered thruster working fluid according to claim 1, characterized in that: The heat absorption layer is made of a material with high heat absorption rate and high thermal conductivity.

3. The multi-layered thruster working fluid according to claim 2, characterized in that: The heat absorbing layer is black.

4. The multi-layered thruster working fluid according to claim 3, characterized in that: The heat absorption layer is made of graphene or hexagonal boron nitride or aluminum nitride doped carbon material or carbon nanotube composite material.

5. The multi-layered thruster working fluid according to claim 1, characterized in that: The heat conduction skeleton has more than one layer; When there are two or more layers, each heat-conducting skeleton is tightly attached.

6. The multi-layered thruster working fluid according to claim 5, characterized in that: The heat-conducting skeleton has a plurality of filling holes, which are through holes extending through the thickness direction of the heat-conducting skeleton and are filled with ablative propellants.

7. The multi-layered thruster working fluid according to claim 6, characterized in that: The heat conduction skeleton is made of a material with high heat absorption rate and high thermal conductivity.

8. The multi-layered thruster working fluid according to claim 7, characterized in that: The heat conduction skeleton is made of aluminum or aluminum alloy or titanium and its alloy or magnesium and its alloy or zinc and its alloy.

9. The multi-layered thruster working fluid according to claim 1, characterized in that: The ablative composite propellant comprises a dopant and an ablative propellant; wherein the dopant is a metal or a metal oxide or a non-metal.

10. A thruster, characterized in that: The thruster adopts the thruster working fluid of the multi-layer structure as described in any one of claims 1 to 9.

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