Electromagnetic regulation system for propulsion performance and discharge oscillation of flat plate hall thruster

Abstract

The application provides an electromagnetic regulation and control system for propulsion performance and discharge oscillation of a flat plate type Hall thruster, and is characterized in that the system is composed of a thruster base, an excitation coil, a heat conduction channel, a hollow cathode, an outer ring permanent magnet, an inner ring permanent magnet, a ceramic outer wall and an anode gas distributor; the connection relationship between the components is that the anode gas distributor is nested in a groove in the center of the ceramic outer wall, the outer ring permanent magnet and the inner ring permanent magnet are pressed in the heat conduction channel through bolts, the excitation coil is tightly and orderly coiled in the groove of the heat conduction channel, finally, the ceramic outer wall is fixed on the heat conduction channel through bolt cooperation, and the heat conduction channel is fixed on the thruster base through bolt cooperation. The application can realize the post-design regulation and control of the magnetic field of the flat plate type Hall thruster, realize the optimal regulation and control of the propulsion performance and discharge oscillation of the flat plate type Hall thruster, and prolong the working time and on-orbit working life of the flat plate type Hall thruster under optimal or better working conditions.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of flat plate type Hall thruster of electric propulsion technology, and particularly relates to an electromagnetic regulation and control system for propelling performance and discharge oscillation of a flat plate type Hall thruster. BACKGROUND

[0002] Compared with chemical propulsion, electric propulsion has the advantages of high specific impulse, long service life, and accurate thrust adjustment, and has developed rapidly in the past century and has been widely applied in satellite position maintenance, orbit transfer, deep space exploration and the like. The Hall thruster has become one of the electric thrusters most applied in orbit at present due to simple structure, high thrust-to-power ratio and large thrust.

[0003] The biggest problem of the traditional Hall thruster is that the face capacity ratio increases and the discharge loss of the thruster increases under small power working condition, which seriously reduces the efficiency of the thruster. Therefore, researchers have proposed various ways to solve this problem, and the flat plate type Hall thruster is one of the effective methods. By moving the anode of the traditional Hall thruster to the outlet plane of the thruster, the ceramic channel structure in the Hall thruster is removed, the erosion of the plasma to the ceramic channel is reduced, and the on-orbit working life of the Hall thruster is prolonged. However, due to the lack of channel constraints, the beam divergence angle is large when the thruster works, especially after a long time of work, since the demagnetization degrees of the inner and outer permanent magnets are inconsistent, the magnetic field deviates from the optimized design state, which will be more serious; on the other hand, the discharge oscillation phenomenon in the flat plate type Hall thruster is also very severe in the experiment, which will also affect the working state of the thruster and the satellite.

[0004] The common flat plate type Hall thruster at present adopts a permanent magnet as an excitation component, moves a metal anode to the channel outlet plane, so that the discharge plasma is completely located outside the thruster, and the ceramic channel of the thruster is removed, as shown in Figure 6a , Figure 6b .

[0005] Adding a biased discrete electrode to the flat plate type Hall thruster, such as the discrete anode added outside the main anode as shown in Figure 7 , can reduce the beam divergence angle of the flat plate type Hall thruster and improve the performance of the thruster. However, the effects of the discrete electrode at different positions of the thruster are different, and the mechanism is unknown.

[0006] Literatures about the flat plate type Hall thruster:

[0007] [1] Mazouffre S, Tsikata S, Vaudolon J. Development and characterization of a wall-less Hall thruster [C] / / 50th AIAA / ASME / SAE / ASEE Joint Propulsion Conference, 2014: 3513.

[0008] [2] Ren L, Wang Y, Jin L, et al. Effect of magnetic field strength on the performance characterization of a low-power wall-less Hall thruster [J]. Vacuum, 2024, 220: 112820.

[0009] Literature on the use of segmented electrodes for controlling the divergence angle of a planar Hall thruster:

[0010] [3] Simmonds J, Raitses Y. Mitigation of breathing oscillations and focusing of the plume in a segmented electrode wall-less Hall thruster [J]. Applied Physics Letters, 2021, 119(21).

[0011] [4] Simmonds J, Raitses Y. Alteration of Ion Plume by Central Segmented Electrode in a Wall-less Hall Thruster [C] / / 37th International Electric Propulsion Conference, 2022: IEPC-2022-395.

[0012] For planar Hall thrusters, the existing design shortcomings and problems are as follows:

[0013] The existing design is difficult to guarantee the magnetic field as the optimal magnetic field of the flat Hall thruster under the design, and the magnetic field compensation effect is not considered after long time work. For the flat Hall thruster, there is no recognized and effective method for the design of the magnetic field, and it is difficult to directly design the optimal magnetic field for the propulsion performance and discharge oscillation characteristics. Even if a suitable magnetic field is designed, the permanent magnet will demagnetize after the flat Hall thruster works for a long time, which cannot guarantee that the flat Hall thruster can maintain the excellent propulsion performance and discharge oscillation characteristics for a long time. In addition, the use of discrete electrodes with bias cannot always improve the propulsion performance of the flat Hall thruster, and the effect of this process cannot be determined in advance. SUMMARY

[0014] The present application provides an electromagnetic regulation system for the propulsion performance and discharge oscillation of a flat Hall thruster, which realizes the regulation of the magnetic field of the flat Hall thruster after the design, realizes the optimization of the propulsion performance and discharge oscillation of the flat Hall thruster, and prolongs the working time and on-orbit working life of the flat Hall thruster under the optimal or better working condition.

[0015] In order to achieve the goal of regulating the propulsion performance and discharge oscillation characteristics of the flat Hall thruster, the present application designs an electromagnetic regulation system for the propulsion performance and discharge oscillation of a flat Hall thruster. This scheme improves the ability of the magnetic field regulation of the flat Hall thruster, optimizes the magnetic field design of the flat Hall thruster, and enhances the optimal performance maintenance ability of the flat Hall thruster under the condition of permanent magnet demagnetization on orbit for a long time.

[0016] The overall structure of the present application is shown in the exploded view as Figure 2 The main structure is composed of a thruster base 1, an excitation coil 2, a heat conduction channel 3, a hollow cathode 4, an outer ring permanent magnet 5, an inner ring permanent magnet 6, a ceramic outer wall 7, and an anode gas distributor 8. The connection relationship between the components is that the anode gas distributor 8 is nested in the groove in the center of the ceramic outer wall 7, the outer ring permanent magnet 5 and the inner ring permanent magnet 6 are tightly pressed in the heat conduction channel 3 through bolts, the excitation coil 2 is tightly and orderly coiled in the groove of the heat conduction channel 3, finally the ceramic outer wall 7 is fixed on the heat conduction channel 3 through bolt cooperation, and the heat conduction channel 3 is fixed on the thruster base 1 through bolt cooperation.

[0017] The thruster base 1 is the base of the thruster, made of stainless steel, aluminum alloy or other metals, used for flat Hall thruster ground test and assembly on spacecraft, plays the role of structure and heat conduction, and has a hollow frame structure and a convex plate for mounting the hollow cathode 4.

[0018] The excitation coil 2 is a component for generating a magnetic field, which is coiled by a high-temperature-resistant wire and has a cylindrical spiral shape, and the number of turns is between 100 and 300 turns and the resistance is between 3 and 10 ohms according to the specific magnetic field adjustment requirement, and the coil is coiled on the heat-conducting channel 3 during assembly of the thruster, and coil joints are left in front and back for connection with external circuits.

[0019] The heat-conducting channel 3 is one of the important parts of the thruster, which conducts heat between the downstream anode gas distributor 8, plasma, excitation coil 2 and the upstream thruster base 1 of the thruster, and is crucial for the normal operation of the thruster in the appropriate temperature range, so generally high-thermal-conductivity materials such as brass and red copper are selected, and the whole is in a cylindrical shape, with flange protrusions on both sides and a rounded groove for fixing the excitation coil 2 joint.

[0020] The hollow cathode 4 is the cathode of the thruster for generating electrons, which is generally lanthanum hexaboride or barium tungsten emitter, and the whole is in a cylindrical shape with a round hole at the front end to lead out electrons.

[0021] The outer ring permanent magnet 5 and the inner ring permanent magnet 6 are used to generate the reference magnetic field of the thruster, and since the working temperature in the thruster is relatively high, the material is selected as samarium-cobalt permanent magnet, and the two are in a circular ring structure, and the magnetic fields of the two are relative during installation.

[0022] The ceramic outer wall 7 mainly plays a structural support role, on the one hand it contains the anode gas distributor 8, and on the other hand it is fixed outside the outer ring permanent magnet 5 and the inner ring permanent magnet 6, protecting the permanent magnets from being eroded by the plasma, and the whole is in a top hat structure with a flange plane protruding from the center.

[0023] The anode gas distributor 8 plays the role of gas guiding, electricity guiding and supporting, and as the anode of the flat plate type Hall thruster, the ceramic outer wall 7 and the outer side of the anode gas distributor 8 are located in the same plane after assembly, and the anode gas distributor 8 has a circular ring structure with two symmetrically welded pins at the rear end for connecting the anode wire and the gas circuit.

[0024] The research on the flat plate type Hall thruster is currently in the initial development stage, and researchers are still exploring the working characteristics of this type of thruster, and the optimization of the thruster itself is still limited to the optimization of the fixed magnetic field, and it is difficult to directly think of combining the permanent magnet and the excitation coil to regulate the propulsion performance and discharge oscillation characteristics of the flat plate type Hall thruster, and if only the excitation coil is used, it will result in insufficient magnetic field strength to constrain the electrons in the flat plate type Hall thruster to maintain stable and efficient discharge. The present application considers combining the permanent magnet and the excitation coil, so that the magnetic field can be maintained in an optimal state during the operation of the flat plate type Hall thruster.

[0025] It is common to use excitation coil for traditional Hall thruster of medium and high power, and then for plate type Hall thruster, which mainly works in the state of small power below 200W, the small structure at this time causes that if excitation coil is used, the heat will be very serious. The application reasonably conducts heat of plasma and coil to outside of the thruster through reasonable heat conduction path, and maintains the whole thruster in reasonable temperature range.

[0026] Compared with the prior art, the application has the beneficial effects:

[0027] 1. The plate type Hall thruster propulsion performance and discharge oscillation electromagnetic regulation system designed by the application considers the magnetic field optimization of the plate type Hall thruster, can adjust the plate type Hall thruster propulsion performance and discharge oscillation characteristics, can reduce the divergence angle of the thruster, and effectively improves the thrust and efficiency.

[0028] 2. The plate type Hall thruster propulsion performance and discharge oscillation electromagnetic regulation system designed by the application can adjust the magnetic field of the plate type Hall thruster by changing the excitation coil current size and direction in the ground test, without repeatedly opening and closing the vacuum chamber and repeatedly pumping, and improves the test efficiency.

[0029] 3. The plate type Hall thruster propulsion performance and discharge oscillation electromagnetic regulation system designed by the application can make the plate type Hall thruster maintain the magnetic field of the plate type Hall thruster in the state of optimal propulsion performance of the thruster through the way of adjusting the excitation coil current size in the case of long time work and demagnetization of the permanent magnet due to heat, and prolongs the optimal work time of the plate type Hall thruster performance. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is the overall structure diagram of the application.

[0031] Figure 2 It is the overall structure explosion diagram of the application.

[0032] Figure 3a , Figure 3b It is the different working mode diagram of the application.

[0033] Figure 4 It is the beam current change effect diagram after using the application.

[0034] Figure 5a , Figure 5b , Figure 5c It is the discharge oscillation change effect diagram after using the application.

[0035] Figure 6a , Figure 6b It is the literature of Mazouffre, a typical plate type Hall thruster.

[0036] Figure 7 For Simmonds' literature, with additional electrodes, flat Hall thruster.

[0037] The figure label is explained as follows:

[0038] Thruster base 1 Excitation coil 2 Heat conduction path 3 Hollow cathode 4

[0039] Outer ring permanent magnet 5 Inner ring permanent magnet 6 Ceramic outer wall 7 Anode gas distributor 8 DETAILED DESCRIPTION

[0040] In the present invention, a flat Hall thruster propulsion performance and discharge oscillation electromagnetic control system is designed and implemented. The alternatives that can be carried out are as follows:

[0041] 1. The excitation mode of the thruster can be changed. As shown in Figure 3a 、 Figure 3b , the thruster can work in two different modes of additional excitation mode and self-excitation mode, which will improve the beam convergence degree and efficiency of the flat Hall thruster under suitable working parameters (anode voltage 100-500V, anode flow 6-10 SCCM, cathode flow 1-2 SCCM), and regulate the discharge oscillation.

[0042] 2. The structure of the thruster excitation coil 2 can be changed. The purpose of the excitation coil 2 is to regulate the magnetic field of the flat Hall thruster, change the shape of its magnetic interface, and thus affect the propulsion performance and discharge oscillation characteristics of the thruster. Therefore, adjusting the position of the excitation coil 2, or increasing the number of excitation coils 2, does not change the essence of this design.

[0043] The present invention is suitable for electromagnetic regulation of the propulsion performance and discharge oscillation characteristics of the flat Hall thruster. In order to prevent the thruster from being damaged due to overheating, the high-temperature resistant wire diameter of the excitation coil 2 is 0.5-1.5mm, the thickness of the heat conduction path 3 is 2-5mm, and the coil current is between-6A and +6A.

[0044] The working process of the system is as follows:

[0045] The specific implementation of the present invention for electromagnetic regulation of the propulsion performance and discharge oscillation of a flat Hall thruster is as follows:

[0046] The thruster base 1 is made of aluminum alloy 3D printing, which reduces the cost and the structure weight, and is used for the installation of the ground test bench. The excitation coil 2 uses high-temperature-resistant wire, and the outer layer is woven with glass fiber. The wire diameter is about 0.8 mm, which can withstand high temperature above 600 DEG C. The wire is coiled on the heat conduction channel 3, and the coiling diameter is about 10 cm. The number of turns is 250 turns, and the coil resistance is about 8 ohms. The heat conduction channel 3 selects high-heat-conductivity brass and is completed by subtractive manufacturing. The outer diameter is about 15 cm, and the thickness is 3 mm. The hollow cathode 4 selects barium tungsten emitter, and the front end has a circular hole to lead out electrons. The rated holding current is 2 A, and the flow is 1.5 SCCM. The outer ring permanent magnet 5 and the inner ring permanent magnet 6 select high-temperature-resistant samarium-cobalt permanent magnets, and the two are in a circular ring structure. When installed, the magnetic fields of the two are relative to the installation. After installation, the radial magnetic field size of the anode surface is about 900 Gs. The ceramic outer wall 7 selects boron nitride ceramic. The anode gas distributor 8 is made of stainless steel by subtractive manufacturing, and the diameter is about 30 mm. The connection relationship between the components is that the anode gas distributor 8 is nested in the groove in the center of the ceramic outer wall 7, the outer ring permanent magnet 5 and the inner ring permanent magnet 6 are tightly pressed in the heat conduction channel 3 through bolts, the excitation coil 2 is tightly and orderly coiled in the groove of the heat conduction channel 3, and finally the ceramic outer wall 7 is fixed on the heat conduction channel 3 through bolt cooperation, and the heat conduction channel 3 is fixed on the thruster base 1 through bolt cooperation.

[0047] In the actual experiment, when the working mode of the flat plate type Hall thruster is selected as the additional excitation mode, as shown in Figure 3a When the excitation coil 2 of the flat plate type Hall thruster applies a current of 0 A, the current density distribution of the thruster beam is a relatively standard single peak, and the curve slope from the edge to the peak is relatively uniform, as shown in Figure 4 However, when the excitation coil 2 of the flat plate type Hall thruster applies a current of +3 A (the "+" sign represents that the magnetic field direction of the coil is the same as the original axial magnetic field direction of the anode surface), it can be seen that the beam current of the thruster obviously converges, the divergence angle decreases, the thrust increases by about 9% (from 6.2 mN to 6.8 mN) under the same working condition, the efficiency increases by more than 2% (from 21% to 23%), and the amplitude of discharge oscillation changes significantly, as shown in Figure 5a , Figure 5b , Figure 5c

[0048] When the working mode of the flat plate type Hall thruster is selected as the self-excitation mode, as shown in Figure 3b ​At this time, the flat Hall thruster is in normal working condition before ignition, and there is no current in the excitation coil 2, so ignition is normal. Once the thruster plasma discharge is established, a current appears in the excitation coil 2. Since the circuit is connected in a self-excitation mode, the current in the excitation coil 2 is equal to the current in the anode gas distributor 8, and the typical value is 0.5 A. At this time, even if the power loss of the excitation coil 2 is considered, the efficiency of the flat Hall thruster will be improved by about 1%.

[0049] In summary, the flat Hall thruster can be more stable and long-lasting in excellent propulsion state under normal working condition and long-time working permanent magnet demagnetization.

Claims

1. An electromagnetic system for regulating the discharge oscillation and propulsion performance of a flat-plate Hall thruster, characterized in that: The system is composed of a thruster base, an excitation coil, a heat conduction path, a hollow cathode, an outer ring permanent magnet, an inner ring permanent magnet, a ceramic outer wall, and an anode gas distributor; the connection relationship between the components is as follows: the anode gas distributor is nested in the groove in the center of the ceramic outer wall, the outer ring permanent magnet and the inner ring permanent magnet are pressed in the heat conduction path through bolts, the excitation coil is tightly and orderly coiled in the groove of the heat conduction path, finally the ceramic outer wall is fixed on the heat conduction path through bolt cooperation, and the heat conduction path is fixed on the thruster base through bolt cooperation; the working mode of the flat plate type Hall thruster includes two different modes of extra excitation mode and self excitation mode.

2. The electromagnetic control system of propulsion performance and discharge oscillation of a flat-plate Hall thruster according to claim 1, characterized in that: The thruster base is the base of the thruster as a whole, made of stainless steel or aluminum alloy, used for flat plate type Hall thruster ground test and assembly on the spacecraft, and has a hollow frame structure, and is connected with a convex plate for mounting the hollow cathode.

3. The electromagnetic control system of propulsion performance and discharge oscillation of a flat-plate Hall thruster according to claim 1, characterized in that: The excitation coil is a component for generating a magnetic field, coiled by high-temperature-resistant wire, in a cylindrical spiral shape, with 100-300 turns and a resistance of 3-10 ohms, coiled on the heat conduction path during thruster assembly, with coil joints in front and back for connection with external circuit.

4. The electromagnetic control system of propulsion performance and discharge oscillation of a flat-plate Hall thruster according to claim 1, characterized in that: The heat conduction path conducts heat between the anode gas distributor, the plasma, the excitation coil downstream of the thruster and the thruster base upstream of the thruster; high-thermal-conductivity brass and red copper materials are selected, the whole is in a cylindrical shape, with flange protrusions on both sides, and a rounded groove for fixing the excitation coil joint is opened.

5. The electromagnetic control system of the propulsion performance and discharge oscillation of a flat-plate Hall thruster according to claim 1, characterized in that: The hollow cathode is the cathode of the thruster for generating electrons, which is a lanthanum hexaboride or barium tungsten emitter, and is in a cylindrical shape with a round hole at the front end to lead out electrons.

6. The electromagnetic control system of propulsion performance and discharge oscillation of a flat-plate Hall thruster according to claim 1, characterized in that: The outer ring permanent magnet and the inner ring permanent magnet are used to generate the reference magnetic field of the thruster, and high-temperature-resistant samarium-cobalt permanent magnets are selected, which are in a circular ring structure.

7. The electromagnetic control system of the propulsion performance and discharge oscillation of a flat-plate Hall thruster according to claim 1, characterized in that: The ceramic outer wall contains the anode gas distributor and is fixed outside the outer ring permanent magnet and the inner ring permanent magnet to protect the permanent magnets from plasma erosion, and is in a top hat structure with a flange plane protruding from the center.

8. The electromagnetic control system of the propulsion performance and discharge oscillation of a flat-plate Hall thruster according to claim 1, characterized in that: The anode gas distributor plays the role of gas guiding, electricity guiding and supporting, and maintains the plasma as the anode of the flat plate type Hall thruster; after assembly, the ceramic outer wall and the outside of the anode gas distributor are located in the same plane, the anode gas distributor is in a circular ring structure, and the rear end has two symmetrically welded pins connected to the anode wire and the gas circuit respectively.

Images