Multistage cusped field thruster of focusing plume

Abstract

The invention discloses a multistage cusped field thruster for focusing plume. The multistage cusped field thruster is characterized in that the outer wall of a main discharge structure is sleeved with a plurality of sections of permanent magnets; the tail end face of the anode structure is perpendicular to the axis of the main discharge structure, the axis of the anode structure and the axis of the discharge structure are coaxial, and the center point of the tail end face of the anode structure coincides with the highest point of the magnetic field intensity of a cusped magnetic field corresponding to the first-stage permanent magnet at the axis. Wherein the permanent magnet closest to the inlet end of the main discharge structure serves as a first-stage permanent magnet; the multiple wedge-shaped ring structures are fixedly installed in the main discharging structure in the axial direction. The wedge-shaped ring structure is preferably arranged from the permanent magnet at the tail (i.e., downstream) of the main discharge structure. According to the channel configuration, the defects of an existing thruster plume optimization technology can be overcome, the engineering technical problem of hollow plume of the thruster is fundamentally solved (the plume divergence efficiency can be improved by about 30%), and cusped magnetic field thrusters of different power levels can be universally applied.

Description

Technical Field

[0001] The invention relates to a multi-stage cusp field thruster with a focused plume, belonging to the technical field of electric propulsion. Background Art

[0002] The multistage cusped magnetic field thruster is a new type of plasma electric propulsion device. The thruster can greatly reduce the ion erosion of the wall by using the cusped magnetic field to confine the plasma, making it show a significant long-life performance advantage. Looking at the multistage cusped magnetic field thrusters of various structures in various research units at home and abroad, from Thales' HEMP-T (High Efficient Multistage Plasma thruster), to MIT's DCFT (Diverging Cusped Field Thruster), to Stanford University's CCFT (Cylindrical Cusped Field Thruster). Under different discharge conditions, there is a serious hollow phenomenon. The emitted high-energy ion beam is mainly distributed in the large-angle area, and the ion flux near the thruster axis is extremely low. This hollow plume will reduce the divergence efficiency of the thruster plume. The high-energy ion beam will not only cause serious corrosion to the thruster cathode, greatly shortening the service life of the thruster, but also cause serious corrosion and damage to the surrounding parts of the thruster. Therefore, optimizing the thruster plume is an important issue that needs to be solved in the engineering application of multi-stage cusped-field thrusters.

[0003] Dr. Taylor of the Massachusetts Institute of Technology optimized the thruster plume structure by adding a magnetic shielding structure and adding additional coils. According to the experimental results of his doctoral thesis "An Exploration of Prominent Cusped-Field Thruster Phenomena: The Hollow Conical Plume and Anode Current Bifurcation", magnetic shielding will aggravate the divergence of the plume, and the additional coil can only move the density peak of the ion current near 35° toward a smaller angle, while the ion current density at other angles remains basically unchanged, so the divergent hollow plume structure always exists. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the existing thruster plume optimization technology, and to propose a multi-stage cusped field thruster with a focused plume. The channel configuration has a simple structure, can fundamentally solve the engineering and technical problems of the thruster hollow plume, and can be generally used for cusped magnetic field thrusters of different power levels.

[0005] The technical solution of the present invention is:

[0006] A multi-stage cusped field thruster with a focused plume, comprising: a main discharge structure, a wedge ring structure, a permanent magnet, an anode structure and a shell;

[0007] The permanent magnet and the main discharge structure are fixedly mounted on the shell respectively;

[0008] A plurality of permanent magnets are mounted on the outer wall of the main discharge structure, and the axes of the permanent magnets and the main discharge structure are coaxial;

[0009] The multiple segments of permanent magnets do not contact each other, and the inner wall of the permanent magnets and the main discharge structure do not contact each other;

[0010] The main discharge structure is a cylindrical structure, and the outlet end of the main discharge structure is processed with a conical expansion section;

[0011] An anode structure is fixedly installed inside the inlet end of the main discharge structure; a central through hole is processed on the head end face of the anode structure as an inlet through hole, and a plurality of circumferentially evenly distributed through holes are processed on the tail end face of the anode structure as outlet through holes;

[0012] A gas buffer cavity is machined inside the anode structure to connect the inlet through hole and the outlet through hole;

[0013] The tail end face of the anode structure is perpendicular to the axis of the main discharge structure, the axis of the anode structure is coaxial with the axis of the discharge structure, and the center point of the tail end face of the anode structure coincides with the point at the axis where the magnetic field intensity of the corresponding cusp magnetic field of the first-stage permanent magnet is the highest; wherein the permanent magnet closest to the entrance end of the main discharge structure is used as the first-stage permanent magnet;

[0014] A plurality of wedge-shaped ring structures are fixedly installed in the main discharge structure along the axial direction; a tapered hole section and a through hole section are processed in the center of the wedge-shaped ring structure, the tapered hole section is located at the front end of the through hole section, and the tapered hole section of the wedge-shaped ring structure opens toward the anode structure;

[0015] The total number of wedge ring structures is less than the total number of permanent magnets; the wedge ring structures are preferentially arranged starting from the permanent magnets located at the tail (ie downstream) of the main discharge structure, and at most one wedge ring structure is arranged within the axial length range of each permanent magnet.

[0016] Preferably, the axial gap between two adjacent permanent magnets is in the range of 2-3 mm.

[0017] Preferably, the single-side gap between the inner wall of the permanent magnet and the outer wall of the main discharge structure is in the range of 1 to 2.5 mm.

[0018] Preferably, the axial length of the tapered expansion section is in the range of 6-8 mm.

[0019] Preferably, the diameter of the outlet through hole at the tail end face of the anode structure ranges from 0.5 to 1 mm.

[0020] Preferably, the diameter of the circle where the multiple circumferentially evenly distributed outlet through holes are located is larger than the inner diameter of the wedge-shaped ring structure.

[0021] Preferably, the anode structure is made of metal material; and the wedge ring structure and the main discharge structure are made of boron nitride material.

[0022] Preferably, the radial thickness H of the wedge-shaped ring structure is i (i.e. wall thickness) and taper wedge angle α i The calculation formula is as follows:

[0023] From the inlet end to the outlet end of the main discharge structure, the wedge-shaped ring structure is graded in sequence;

[0024] When i=1, the radial thickness H of the first-stage wedge ring structure is i =2R a -R; wedge angle of the cone hole section of the first-stage wedge ring structure

[0025] Among them, R a is the radius of the circle where multiple circumferentially distributed through holes are located on the tail end face of the anode structure, R is the inner diameter of the main discharge structure, and L is i is the axial length of the permanent magnet corresponding to the i-th wedge ring structure, k is the ratio of the axial distance between the front end face of the wedge ring structure and the front end face of the corresponding permanent magnet, and the value range is 1 / 3 to 1 / 2;

[0026] When i=2, 3, 4..., M, the wall thickness H of the remaining wedge ring structures except the first wedge ring structure is i =2H i-1 -R; for the wedge angle of the tapered hole section of the remaining wedge ring structures except the first wedge ring structure

[0027]

[0028] Preferably, the axial length Z of the through hole section of the wedge-shaped ring structure is 内i The calculation formula is as follows:

[0029] Z 内i =Z 外i -H i tanα i

[0030] Where i = 1, 2, 3, 4, ..., M, Z 外i is the axial length of the outer wall of the wedge ring structure.

[0031] Preferably, the axial length Z of the outer wall of the wedge-shaped ring structure is 外i The value range is 5 to 8 mm.

[0032] The beneficial effects of the present invention compared with the prior art are:

[0033] 1) The main discharge structure of the thruster of the present invention is provided with a variable cross-section structure at the outlet magnetic tip, which can reduce the degree of interaction between the plasma and the wall surface, thereby reducing the channel corrosion rate and increasing the service life of the thruster.

[0034] 2) The wedge-shaped ring structure is arranged at the final magnetic tip in the main discharge structure of the thruster of the present invention, which can reduce the leakage probability of the working fluid atoms near the wall of the main discharge structure and focus the atoms to the main ionization zone of the channel axis, thereby effectively improving the ionization efficiency of the thruster.

[0035] 3) Multiple wedge-shaped ring structures are arranged in the main discharge structure of the thruster of the present invention, which can reduce the plasma density in the ionization zone of the thruster outlet plume, thereby suppressing the thruster plume divergence and achieving plume focusing.

[0036] 4) The present invention can gradually adjust the radial dimensions of multiple ionization zones in the thruster by changing the number and wedge angle of the wedge ring structure, thereby reducing the wall loss of the plasma, thereby increasing the output flux of ions at the thruster outlet and improving the overall efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a structural diagram of the focusing plume channel of the present invention;

[0038] Figure 2(a) is a schematic diagram of a multi-stage cusped field thruster with a focused plume;

[0039] Figure 2(b) is a schematic diagram of the focused plume distribution;

[0040] Figure 3 It is the position and structure diagram of the thruster wedge ring;

[0041] Figure 4 This is a plume distribution diagram of the focused multi-stage cusp field thruster of the present invention under different working conditions. DETAILED DESCRIPTION

[0042] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] The present invention provides a multi-stage cusp field thruster with a focused plume, such as Figure 1 As shown, it includes: a main discharge structure 1, a wedge ring structure 2, a permanent magnet 3, an anode structure 4 and a shell. The permanent magnet 3 and the main discharge structure 1 are fixedly mounted on the shell respectively; multiple sections of permanent magnets 3 are mounted on the outer wall of the main discharge structure 1, and the axes of the permanent magnets 3 and the main discharge structure 1 are coaxial; the multiple sections of permanent magnets 3 do not contact each other, and the inner wall of the permanent magnet 3 does not contact the main discharge structure 1; the main discharge structure 1 is a cylindrical structure, and a conical expansion section is processed at the outlet end of the main discharge structure 1 to avoid high-energy ion beams.

[0044] The anode structure 4 is fixedly installed inside the inlet end of the main discharge structure 1; the head end face of the anode structure 4 is processed with a central through hole as the inlet through hole, and the tail end face of the anode structure 4 is processed with multiple circumferentially evenly distributed through holes as outlet through holes. A gas buffer cavity is processed inside the anode structure 4 to connect the inlet through hole and the outlet through hole; the working gas enters the gas buffer cavity from the inlet through hole on the head end face of the anode structure 4, and after being homogenized in the gas buffer cavity, the working gas enters the main discharge structure 1 through the circumferentially evenly distributed outlet through holes on the tail end face.

[0045] The tail end face of the anode structure 4 serves as the discharge end face, the tail end face of the anode structure 4 is perpendicular to the axis of the main discharge structure 1, the axis of the anode structure 4 is coaxial with the axis of the discharge structure 1, and the center point of the tail end face of the anode structure 4 coincides with the point at the axis where the magnetic field intensity of the corresponding tangent magnetic field of the first-stage permanent magnet 3 is the highest; wherein the permanent magnet 3 closest to the entrance end of the main discharge structure 1 serves as the first-stage permanent magnet 3;

[0046] A plurality of wedge-shaped ring structures 2 are fixedly installed in the main discharge structure 1 along the axial direction; a tapered hole section and a through hole section are processed in the center of the wedge-shaped ring structure 2, the tapered hole section is located at the front end of the through hole section, and the tapered hole section of the wedge-shaped ring structure 2 opens toward the anode structure 4;

[0047] The total number of wedge-shaped ring structures 2 is less than the total number of permanent magnets 3 ; the wedge-shaped ring structures 2 are preferentially arranged starting from the permanent magnets 3 located at the tail (ie, downstream) of the main discharge structure 1 , and at most one wedge-shaped ring structure 2 is arranged within the axial length range of each permanent magnet 3 .

[0048] The axial gap between two adjacent permanent magnets 3 is in the range of 2-3 mm. The single-side gap between the inner wall of the permanent magnet 3 and the outer wall of the main discharge structure 1 is in the range of 1-2.5 mm. The axial length of the conical expansion section is in the range of 6-8 mm. The diameter of the outlet through hole at the tail end face of the anode structure 4 is in the range of 0.5-1 mm.

[0049] The diameter of the circle where the multiple circumferentially evenly distributed outlet through holes are located is greater than the inner diameter of the wedge-shaped ring structure 2 .

[0050] The anode structure 4 is made of metal material; the wedge ring structure 2 and the main discharge structure 1 are made of boron nitride material.

[0051] M wedge-shaped ring structures 2 are fixedly installed inside the main discharge structure 1. N segments of permanent magnets 3 are coaxially mounted on the outer wall of the main discharge structure 1. The magnetic lines of force generated form N magnetic tips. The mathematical relationship between M and N is as follows:

[0052] 1≤M≤N-1

[0053] M wedge-shaped ring structures 2 are arranged in the main discharge structure 1, so that the working fluid atoms near the wall of the main discharge structure 1 are directed toward the zero magnetic point P of the axis. iFocusing, which corresponds to the radial thickness H of the wedge ring structure 2 i (i.e. wall thickness) and taper wedge angle α i The calculation formula is as follows:

[0054] From the inlet end to the outlet end of the main discharge structure 1, the wedge-shaped ring structure 2 is graded in sequence;

[0055] When i=1, the radial thickness H of the first-stage wedge ring structure 2 is i =2R a -R; wedge angle of the cone hole section of the first wedge ring structure 2

[0056] Among them, R a is the radius of the circle where the multiple circumferentially distributed through holes are located on the tail end surface of the anode structure 4, R is the inner diameter of the main discharge structure 1, and L i is the axial length of the permanent magnet 3 corresponding to the i-th wedge-shaped ring structure 2, k is the ratio of the axial distance between the front end face of the wedge-shaped ring structure 2 and the front end face of the corresponding permanent magnet 3, and the value range is 1 / 3 to 1 / 2;

[0057] When i=2, 3, 4..., M, that is, the wall thickness H of the remaining wedge ring structures 2 except the first wedge ring structure 2 is i =2H i-1 -R; for the wedge angle of the tapered hole section of the remaining wedge ring structures 2 except the first wedge ring structure 2

[0058] The axial length Z of the through hole section of the wedge ring structure 2 内i The calculation formula is as follows:

[0059] Z 内i =Z 外i -H i tanα i

[0060] Where i = 1, 2, 3, 4, ..., M, Z 外i is the axial length of the outer wall of the wedge-shaped ring structure 2.

[0061] The axial length Z of the outer wall of the wedge ring structure 2 外i The value range is 5 to 8 mm.

[0062] Example

[0063] In the embodiment of the present invention, the upstream port of the main discharge structure 1 is a semi-closed structure, the middle part is a cylindrical structure, and the downstream end is a variable cross-section opening structure. M wedge-shaped ring structures 2 are coaxially arranged downstream of the annular magnetic tip of the thruster. Taking the three-level magnetic field (M=1, N=3) shown in Figure 2 (a) (b) as an example, the length of the main discharge structure 1 is consistent with the axial length of the thruster, and the wall thickness is 3-4 mm. The semi-closed structure upstream is coaxially installed with the anode of the thruster, and the variable cross-section opening structure downstream is coaxially installed with the outer magnetic level of the thruster. The gap between the variable cross-section opening structure and the outer magnetic level of the thruster is controlled within the range of 0.5-1.0 mm, and the angle between the surface of the variable cross-section opening structure and the axis of the thruster is 30°-60°, and the opening of the cone angle is downstream. The radial height of the wedge-shaped ring structure 2 is controlled within the range of 3-5 mm, and the angle between the wedge surface and the axis is 45°-60°. The wedge-shaped ring structure 2 is coaxially installed into the discharge channel from the variable-section opening side of the main discharge structure 1, with its annular conical surface located on the upstream side of the main discharge structure 1, and its annular plane located on the downstream side of the main discharge structure 1. The wedge-shaped ring structure 2 is placed downstream of the annular magnetic tip of the thruster, and in the embodiment of the present invention, the distance between its position and the annular magnetic tip at the upstream end face of the corresponding permanent magnet 3 is controlled within a range of 5 to 10 mm.

[0064] Under this channel configuration, the ionization of the thruster fluid and the acceleration process of the ions will change significantly. These changes are the key to the thruster producing a focused plume:

[0065] First, the wedge-shaped ring structure 2 can reduce the leakage probability of the working fluid atoms near the wall surface. After the working fluid atoms collide with the cone surface of the wedge-shaped ring, they are reflected to the main ionization zone near the axis, which is beneficial to improve the ionization efficiency of the main ionization zone in the channel. Figure 3 As shown; at the same time, the enhanced ionization in the ionization zone can reduce the density of working fluid atoms in the plume region, thereby suppressing the ionization process in the divergent magnetic field of the plume ionization region.

[0066] Second, the wedge-shaped ring structure 2 limits the radial expansion range of the ionization zone, and the axial distribution of the ionization zone is expanded, forming a high-density ion jet with ion aggregation at the axis, forming a focused plume distribution, such as Figure 4 shown.

[0067] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the spirit and scope of the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall belong to the protection scope of the technical solution of the present invention. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other.

[0068] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A multi-stage cusp field thruster with a focused plume, characterized in that: include: A main discharge structure (1), a wedge ring structure (2), a permanent magnet (3), an anode structure (4) and a shell; The permanent magnet (3) and the main discharge structure (1) are respectively fixedly mounted on the housing; A plurality of permanent magnets (3) are mounted on the outer wall of the main discharge structure (1), and the axes of the permanent magnets (3) and the main discharge structure (1) are coaxial; The multiple segments of permanent magnets (3) do not contact each other, and the inner wall of the permanent magnet (3) and the main discharge structure (1) do not contact each other; The main discharge structure (1) is a cylindrical structure, and the outlet end of the main discharge structure (1) is processed with a conical expansion section; An anode structure (4) is fixedly installed inside the inlet end of the main discharge structure (1); a central through hole is processed on the head end surface of the anode structure (4) as an inlet through hole, and a plurality of circumferentially evenly distributed through holes are processed on the tail end surface of the anode structure (4) as outlet through holes; A gas buffer cavity is processed inside the anode structure (4) to connect the inlet through hole and the outlet through hole; The tail end surface of the anode structure (4) is perpendicular to the axis of the main discharge structure (1), the axis of the anode structure (4) is coaxial with the axis of the discharge structure (1), and the center point of the tail end surface of the anode structure (4) coincides with the highest point of the tangent magnetic field intensity of the first-stage permanent magnet (3); wherein the permanent magnet (3) closest to the entrance end of the main discharge structure (1) serves as the first-stage permanent magnet (3); A plurality of wedge-shaped ring structures (2) are fixedly installed in the axial direction inside the main discharge structure (1); a tapered hole section and a through hole section are processed at the center of the wedge-shaped ring structure (2), the tapered hole section is located at the front end of the through hole section, and the tapered hole section of the wedge-shaped ring structure (2) opens toward the anode structure (4); The total number of wedge-shaped ring structures (2) is less than the total number of permanent magnets (3); the wedge-shaped ring structures (2) are preferentially arranged starting from the permanent magnets (3) located at the tail of the main discharge structure (1), and at most one wedge-shaped ring structure (2) is arranged within the axial length range of each section of the permanent magnet (3).

2. A multi-stage cusped field thruster with a focused plume according to claim 1, characterized in that: The axial gap between two adjacent permanent magnets (3) has a value ranging from 2 to 3 mm.

3. A multi-stage cusp field thruster with a focused plume according to claim 2, characterized in that: The single-side gap between the inner wall of the permanent magnet (3) and the outer wall of the main discharge structure (1) has a value ranging from 1 to 2.5 mm.

4. A multi-stage cusped field thruster with a focused plume according to claim 1, characterized in that: The axial length of the tapered expansion section ranges from 6 to 8 mm.

5. A multi-stage cusped field thruster with a focused plume according to claim 1, characterized in that: The diameter of the outlet through hole on the tail end face of the anode structure (4) ranges from 0.5 to 1 mm.

6. A multi-stage cusped field thruster with a focused plume according to claim 5, characterized in that: The diameter of the circle where the multiple outlet through holes evenly distributed in the circumferential direction are located is greater than the inner diameter of the wedge-shaped ring structure (2).

7. A multi-stage cusped field thruster with a focused plume according to any one of claims 1 to 6, characterized in that: The anode structure (4) is made of metal material; the wedge ring structure (2) and the main discharge structure (1) are made of boron nitride material.

8. A multi-stage cusped field thruster with a focused plume according to claim 7, characterized in that: The radial thickness H of the wedge ring structure (2) i and the wedge angle α of the tapered hole i The calculation formula is as follows: The wedge-shaped ring structure (2) is graded sequentially from the inlet end to the outlet end of the main discharge structure (1); When i=1, the radial thickness H of the first-stage wedge ring structure (2) is i =2R a -R, wedge angle of the cone hole section of the first wedge ring structure (2) Among them, R a is the radius of the circle where the multiple circumferentially distributed through holes are located on the tail end surface of the anode structure (4), R is the inner diameter of the main discharge structure (1), and L i is the axial length of the permanent magnet (3) corresponding to the i-th level wedge-shaped ring structure (2), k is the ratio of the axial distance between the front end face of the wedge-shaped ring structure (2) and the front end face of the corresponding permanent magnet (3), and the value range is 1 / 3 to 1 / 2; When i=2, 3, 4, ..., M, the wall thickness H of the remaining wedge ring structures (2) except the first wedge ring structure (2) is i =2H i-1 -R, for the wedge angle of the tapered hole section of the remaining wedge ring structures (2) except the first wedge ring structure (2) 9. A multi-stage cusped field thruster with a focused plume according to claim 8, characterized in that: Axial length Z of the through hole section of the wedge ring structure (2) 内i The calculation formula is as follows: Z 内i =Z 外i -H i tanα i Where i = 1, 2, 3, 4, ..., M, Z 外i is the axial length of the outer wall of the wedge-shaped ring structure (2).

10. A multi-stage cusped field thruster with a focused plume according to claim 9, characterized in that: The axial length Z of the outer wall of the wedge ring structure (2) 外i The value range is 5 to 8 mm.

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