A composite cathode high-power plasma generator and arc striking method

Abstract

The present invention discloses a composite cathode high-power plasma generator and arc-starting method, including a composite cathode, an arc-starting electrode, an inter-electrode plug-in, and an anode. The composite cathode is composed of an end face cathode and a ring target cathode. The end face cathode is located at the top and is fixed by a cathode support cooling unit, and then the ring target cathode, the arc-starting electrode, a plurality of inter-electrode plug-ins and the anode are sequentially connected in sequence; the end face cathode, the cathode ring, the arc-starting electrode, the inter-electrode plug-in, and the outer ring of the anode are all fixed by independent insulating rings to form a modular structure, which are coaxially and tightly insulated by circumferentially distributed clamping rods, and an arc channel is formed in the middle of all electrodes. An air intake ring capable of generating vortex gas is provided between each ring; the cathode support cooling unit is provided with an independent cooling channel for cooling the end face cathode. The invention adopts a modular structural design, which is convenient and reliable to install, and the power can reach hundreds of millions to several megawatts. The composite cathode effectively reduces cathode ablation, has stable discharge, and has a long service life.

Description

Technical Field

[0001] The invention belongs to the technical field of plasma generation by direct current arc, and in particular relates to a composite cathode high-power plasma generator and an arc striking method. Background Art

[0002] High-temperature plasma generated by arc discharge is called arc plasma, which belongs to the category of thermal plasma. Thermal plasma has the characteristics of high temperature, high enthalpy, high energy density and controllable atmosphere, and can be widely used in mechanical processing, spraying, material preparation, waste treatment, energy and other fields. Large-scale application in industry requires plasma generators to have characteristics such as high stability, high power, high efficiency and long life.

[0003] The DC arc plasma generator has the advantages of simple structure, high stability, high power, and high electrothermal conversion efficiency, which is more in line with the needs of industrial applications. Most of the existing main forms of non-transferred arc plasma generators use high-frequency starting methods, introduce a trigger electrode, form a discharge at the cathode and the trigger electrode, and the discharge arc sprays to the anode to ignite the arc between the cathode and the cathode. The common point is that the distance between the cathode and the cathode is small, and it is impossible to obtain a large power through a simple two-electrode structure. Therefore, there are two ways to increase the power of these plasma generators. One is to increase the discharge current, and the other is to increase the discharge voltage. However, if the discharge current is too large, the thermal efficiency will decrease and the electrode life will be shortened. Therefore, increasing the discharge voltage, that is, increasing the arc length, is an effective way to increase the power. When the current remains unchanged, increasing the working gas flow rate can increase the arc length to increase the voltage, but the gas flow rate cannot be increased without limit. Excessive gas flow directly affects the plasma heating efficiency and discharge stability. When the gas flow rate reaches a certain value, the arc will be blown out. The power increase is restricted by many factors and generally does not exceed 300 kilowatts.

[0004] In order to improve the power of the plasma generator, the existing plasma generator is developing in the direction of having an inter-electrode insertion section. The plasma generator structure is composed of a cathode component, an anode component, an inter-electrode insertion section, and an inert gas and water-cooling component introduced between the electrodes. Since the inter-electrode insertion section has a complex structure and requires power, ventilation and water cooling, how to solve the above-mentioned manufacturing and installation difficulties is a problem that still exists in the prospects for industrialization and needs to be solved urgently.

[0005] Existing arc plasma generators generally use water-cooled solid cathodes, which have concentrated cathode arc spots, severe cathode ablation, and a short lifespan. Alternatively, tubular cathodes are used, which increase the ablation area but have poor stability during discharge. In addition, the anode and cathode water cooling systems are not separated, making disassembly and assembly, and leak detection difficult, and the water cooling effect is greatly reduced. When the power increases, these problems become more prominent, and the lifespan generally does not exceed 200 hours, which seriously restricts the industrial application of high-power plasma generators. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a composite cathode high-power plasma generator and an arc striking method, which have the characteristics of simple and reliable installation, stable discharge, high power and long service life.

[0007] In order to achieve the above-mentioned purpose, a composite cathode high-power plasma generator designed by the present invention comprises a composite cathode, an arc-starting electrode, an inter-electrode plug-in, and an anode;

[0008] The composite cathode is composed of an end face cathode and a ring target cathode. The ring target cathode is composed of a cathode ring and an internal target working fluid. The end face cathode is located at the uppermost end and is fixed by a cathode support cooling unit. The arc-starting electrode is connected to the cathode ring, and then a plurality of inter-electrode plug-ins are connected one by one in sequence downward, and finally the anode is connected. The end face cathode, cathode ring, arc-starting electrode, inter-electrode plug-in, and anode outer ring are all fixed by independent insulating rings to form a modular structure. They are coaxially and tightly insulated by circumferentially distributed clamping rods. An arc channel is formed in the middle of the cathode ring, arc-starting electrode, inter-electrode plug-in, and anode. An air intake ring capable of generating vortex gas is provided between each insulating ring.

[0009] The cathode support cooling unit is provided with an independent cooling channel for cooling the end face cathode, on which a cathode cooling water inlet and a cathode cooling water outlet are installed; the cathode ring, arc-starting electrode, inter-electrode plug-in, and anode outer wall are all water-cooled, cooled in series, and share a cooling water main channel, and the main water inlet and main water outlet are arranged on the anode.

[0010] Furthermore, the end face cathode is a flat cylindrical shape, the main body is copper or chromium-zirconium copper, the upper end face has a circle of water cooling grooves, and the lower end face is an inlaid flat conical tungsten rod or zirconium rod. The whole is fixed to the cathode support cooling unit by a cathode nut, and the end face cathode is replaceable.

[0011] Furthermore, the cathode ring is a cylindrical copper ring or a chromium-zirconium copper ring, the upper end of which is conductively contacted with the end surface cathode, and the lower end surface is a convex conical surface connected to the arc-starting electrode.

[0012] Furthermore, an air inlet is provided on the insulating ring of the outer ring of the cathode ring for providing discharge gas, and the target working medium inside the cathode ring is the discharge gas or plasma generated by discharge.

[0013] Furthermore, the discharge gas is one of N2, Ar, He, H2, CO, CO2, air, or a mixture of the above gases.

[0014] Furthermore, the arc-starting electrode is a cylindrical copper ring or a chromium-zirconium copper ring, the upper end surface of which is concave and the lower end surface is a convex conical surface, and a high-voltage terminal is installed on the insulating ring of the outer ring.

[0015] Furthermore, the high-voltage terminal passes through the insulating ring and is in conductive contact with the arc-starting electrode, so as to feed high voltage, form a discharge arc between the arc-starting electrode and the cathode ring, and then form a stable discharge arc in the entire arc channel between the end face electrode and the anode.

[0016] Furthermore, a plurality of inter-electrode plug-ins are sequentially connected after the arc-starting electrode. As the number of inter-electrode plug-ins increases, the power of the plasma generator is correspondingly improved. The inter-electrode plug-ins are cylindrical copper rings or chromium-zirconium copper rings.

[0017] Furthermore, the anode is a cylindrical copper ring or chromium-zirconium copper, located at the end of the arc channel and connected to the last inter-electrode plug-in, and the anode is replaceable.

[0018] Furthermore, the clamping rods are metal rods, 3 to 4 in number, evenly distributed circumferentially, and tightly connect all component modules.

[0019] Furthermore, the material of the insulating ring is a material with certain strength and good insulation, such as polytetrafluoroethylene, polyimide, high-strength ceramics, etc. The cross-section is arranged with a main water inlet hole, a main water outlet hole, an air path hole and a corresponding number of clamping rod holes, with a metal ring electrode in the middle. The insulating rings of each module are tightly connected to form a complete cooling water path and air supply path.

[0020] Furthermore, the connection between the cooling water channel and the air supply channel between the insulating rings is sealed with an O-ring.

[0021] Furthermore, the pressing rod is an insulating material rod with a certain strength.

[0022] The present invention also provides an arc striking method for a composite cathode high-power plasma generator, comprising the following steps:

[0023] 1) Open and adjust the cooling water valve and check the sealing of the cooling water circuit;

[0024] 2) Open and adjust the gas supply valve to ensure that there is no water at the outlet of the plasma generator arc channel;

[0025] 3) Turning on the power supply so that the end surface cathode (1) and the cathode ring (2) are in electrical contact;

[0026] 4) The arc starting cabinet applies a voltage of 0 to 2 μs with a maximum of 20 kV to the arc striking electrode (3) through the high-voltage terminal (31), thereby forming a gap discharge between the arc striking electrode (3) and the cathode ring (2);

[0027] 5) Simultaneously, a voltage of 1200V at maximum is applied between the end cathode (1) and the cathode ring (2) together or the end cathode (1) and the cathode ring (2) are disconnected from the anode (5) for 0.1 to 3 seconds, and an arc connection is completed between the end cathode (1) and the anode (5) through secondary arc initiation, and a stable discharge arc channel is formed under the action of airflow.

[0028] The advantages of the present invention compared with the prior art are:

[0029] 1) The present invention adopts a composite cathode structure, and through the transition of the ring target cathode, not only the arc starting is stable, but also the high-voltage impact of the end face cathode at the moment of arc starting can be effectively reduced, the ablation of the cathode is slowed down, and the service life of the cathode is extended, thereby improving the service life of the high-power plasma generator. The discharge stability is good during the working process, and it can be better applied in industry.

[0030] 2) When assembling the plasma generator of the present invention, the sealing of the water cooling circuit and the tight fit of the gas path contact surface must be ensured to avoid leakage of plasma discharge gas and cooling water. The present invention adopts a modular structure design, which is not only more convenient to install, but also can better ensure the sealing performance of each connection port during the installation of each module.

[0031] 3) The anode and end cathode of the present invention adopt independent water cooling circuits, which can achieve better cooling effect and better protection for the two key easily ablated components, and are more convenient to install, replace and detect leaks. Other components share a water cooling and air supply circuit with the anode, which can reduce external water and air circuit interfaces and greatly reduce external piping layout. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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 embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0033] Figure 1 This is a structural principle diagram of a composite cathode high-power plasma generator of the present invention;

[0034] Figure 2 This is a cross-sectional view of the middle component of a composite cathode high-power plasma generator of the present invention.

[0035] The meanings of the reference numerals in the figure are: 1. end face cathode; 2. cathode ring; 3. arc-striking electrode; 4. inter-electrode plug; 5. anode; 6. cathode support cooling unit; 7. air inlet; 8. clamping rod; 9. air inlet ring; 10. metal ring electrode; 11. insulating ring; 31. high-voltage terminal; 51. main water inlet; 52. main water outlet; 53. main water inlet hole; 54. main water outlet hole; 61. cathode nut; 62. cathode cooling water inlet; 63. cathode cooling water outlet; 71. air path hole; 81. clamping rod hole. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. It is obvious that the embodiments described below are only a part of the embodiments of the present invention, not all. Based on the embodiments recorded in the invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0037] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings:

[0038] like Figure 1 As shown, a composite cathode high-power plasma generator of the present invention comprises a composite cathode, an arc-starting electrode 3, an inter-electrode plug-in 4, and an anode 5. The composite cathode is composed of an end face cathode 1 and a ring target cathode. The ring target cathode is composed of a cathode ring 2 and an internal target working medium. The end face cathode 1 is located at the uppermost end and is fixed by a cathode support cooling unit 6. The arc-starting electrode 3 is connected to the cathode ring 2, and then a plurality of inter-electrode plug-ins 4 are connected one by one downward in sequence, and finally the anode 5 is connected. The end face cathode 1, cathode ring 2, arc-starting electrode 3, inter-electrode plug-in 4, and outer rings of the anode 5 are all fixed by independent insulating rings 11 to form a modular structure, which are coaxially and tightly insulated by circumferentially distributed clamping rods 8. An arc channel is formed in the middle of the cathode ring 2, arc-starting electrode 3, inter-electrode plug-in 4, and anode 5, and an intake ring 9 capable of generating vortex gas is arranged between each insulating ring 11.

[0039] The cathode support cooling unit 6 is provided with an independent cooling channel for cooling the end face cathode 1, on which a cathode cooling water inlet 62 and a cathode cooling water outlet 63 are installed; the cathode ring 2, arc-starting electrode 3, inter-electrode plug 4, and outer wall of the anode 5 are all water-cooled, cooled in series, and share a main cooling water channel, and the main water inlet 51 and the main water outlet 52 are arranged on the anode 5.

[0040] The end face cathode 1 is a flat cylindrical shape, the main body is copper or chromium-zirconium copper, the upper end face has a circle of water cooling grooves, and the lower end face is an inlaid flat conical tungsten rod or zirconium rod. The whole is fixed to the cathode support cooling unit 6 by a cathode nut 61. The end face cathode 1 is replaceable.

[0041] The cathode ring 2 is a cylindrical copper ring or a chromium-zirconium copper ring, the upper end of which is in conductive contact with the end surface cathode 1 , and the lower end surface is a convex conical surface connected to the arc-starting electrode 3 .

[0042] The outer insulating ring 11 of the cathode ring 2 is provided with an air inlet 7 for providing discharge gas. The target medium inside the cathode ring 2 is the discharge gas or the plasma generated by discharge. The ring target cathode is composed of a ring, a target and a gas.

[0043] The discharge gas is one of N2, Ar, He, H2, CO, CO2, air, or a mixture of the above discharge gases.

[0044] The arc-striking electrode 3 is a cylindrical copper ring or a chromium-zirconium copper ring, with a concave upper end surface and a convex conical lower end surface. A high-voltage terminal 31 is installed on the outer insulating ring for connecting to the arc-striking power supply cabinet to obtain instantaneous high voltage at arc-striking.

[0045] The high-voltage terminal 31 passes through the insulating ring 11 and is in conductive contact with the arc-starting electrode 3 for feeding high voltage to form a discharge arc between the arc-starting electrode 3 and the cathode ring 2 , and then forms a stable discharge arc in the entire channel between the end face electrode 1 and the anode 5 .

[0046] A plurality of inter-electrode plug-ins 4 are sequentially connected to the arc-starting electrode 3. As the number of inter-electrode plug-ins 4 increases, the power of the plasma generator also increases accordingly. The inter-electrode plug-ins 4 are cylindrical copper rings or chromium-zirconium copper rings.

[0047] The anode 5 is a cylindrical copper ring or chromium-zirconium copper, located at the end of the arc channel, connected to the last inter-electrode plug-in 4, and the anode 5 is replaceable.

[0048] The clamping rods 8 are metal rods or insulating material rods with a certain strength, preferably insulating material rods, and there are 3 to 4 of them, which are evenly distributed around the circumference to tightly connect all the component modules.

[0049] The insulating ring 11 is made of a material having a certain strength and good insulation, such as polytetrafluoroethylene, polyimide, high-strength ceramics, etc. Figure 2 As shown, its cross section is arranged with a main water inlet hole 53, a main water outlet hole 54, an air path hole 71 and a corresponding number of clamping rod holes 81, with a metal ring electrode 10 in the middle. The main water inlet hole 53 and the main water outlet hole 54 both establish channels with the metal ring electrode 10 so that cold water can pass through the outer wall of the metal ring electrode 10. After the insulating rings 11 are tightly connected, a complete cooling water path and air supply path are formed.

[0050] The water and gas connections between the insulating rings 11 are sealed with O-rings to ensure that water and gas do not leak.

[0051] The composite cathode high-power plasma generator of the present invention adopts a modular structure and a special cooling method, and overcomes the difficulties of manufacturing, installing and leak detection of a high-power plasma generator by inserting a section between electrodes; the cathode adopts a double composite method, one is that the end face cathode is composited with the ring target cathode, and the other is that the ring target cathode is composited by the ring, the target and the gas, so that stable arc starting and stable continuous discharge are achieved, the ablation of the cathode is slowed down, and the service life of the high-power is prolonged.

[0052] An embodiment of the present invention is:

[0053] The 500kW plasma generator designed and manufactured according to the present invention has the following main technical parameters: maximum power of 500kW, working voltage of 700-1200V, working current of 200-600A, working gas of nitrogen, outlet temperature of the plasma generator of 6000-8000K, thermal efficiency of about 80%, and life of about 1000 hours. The high-power plasma generator can be well used in the industrial field.

[0054] The present invention also provides an arc striking method for a 500kW composite cathode high-power plasma generator, comprising the following steps:

[0055] 1) Open and adjust the cooling water valve and check the sealing of the cooling water circuit;

[0056] 2) Open and adjust the gas supply valve to ensure that there is no water at the outlet of the plasma generator arc channel;

[0057] 3) Turning on the power supply so that the end surface cathode (1) and the cathode ring (2) are in electrical contact;

[0058] 4) The arc starting cabinet applies a voltage of 0 to 2 μs with a maximum of 20 kV to the arc striking electrode (3) through the high-voltage terminal (31), thereby forming a gap discharge between the arc striking electrode (3) and the cathode ring (2);

[0059] 5) Simultaneously, a voltage of 1200V at maximum is applied between the end cathode (1) and the cathode ring (2) together or the end cathode (1) and the cathode ring (2) are disconnected from the anode (5) for 0.1 to 3 seconds, and an arc connection is completed between the end cathode (1) and the anode (5) through secondary arc initiation, and a stable discharge arc channel is formed under the action of airflow.

[0060] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A composite cathode high-power plasma generator, comprising a composite cathode, an arc-starting electrode (3), an inter-electrode plug (4) and an anode (5), characterized in that: The composite cathode is composed of an end face cathode (1) and a ring target cathode, the ring target cathode being composed of a cathode ring (2) and an internal target working fluid, the end face cathode (1) being located at the uppermost end and being fixed by a cathode support cooling unit (6), the arc-starting electrode (3) being connected to the cathode ring (2), and then being connected one by one to a plurality of inter-electrode plug-ins (4) in sequence downward, and finally being connected to an anode (5); the outer rings of the end face cathode (1), cathode ring (2), arc-starting electrode (3), inter-electrode plug-in (4) and anode (5) are all fixed by independent insulating rings (11) to form a modular structure, and are coaxially and tightly insulatedly connected by circumferentially distributed clamping rods (8); an arc channel is formed between the cathode ring (2), arc-starting electrode (3), inter-electrode plug-in (4) and anode (5), and an air intake ring (9) capable of generating vortex gas is provided between each insulating ring (11); The cathode support cooling unit (6) is provided with an independent cooling channel for cooling the end face cathode (1), and is provided with a cathode cooling water inlet (62) and a cathode cooling water outlet (63); the cathode ring (2), arc-starting electrode (3), inter-electrode plug-in (4), and outer wall of the anode (5) are all water-cooled and cooled in series, and share a cooling water main channel, and the main water inlet (51) and the main water outlet (52) are provided on the anode (5).

2. A composite cathode high-power plasma generator according to claim 1, characterized in that: The end face cathode (1) is in the shape of a flat cylinder, the main body of which is red copper or chromium zirconium copper, the upper end face is provided with a circle of water cooling grooves, the lower end face is an inlaid flat conical tungsten rod or zirconium rod, and the whole is fixed to the cathode support cooling unit (6) via a cathode nut (61), and the end face cathode (1) is replaceable.

3. A composite cathode high-power plasma generator according to claim 1 or 2, characterized in that: The cathode ring (2) is a cylindrical copper ring or a chromium-zirconium copper ring, the upper end of which is in conductive contact with the end surface cathode (1), and the lower end surface is a convex conical surface connected to the arc-starting electrode (3).

4. A composite cathode high-power plasma generator according to claim 1, characterized in that: An inlet (7) is provided on the insulating ring (11) on the outer ring of the cathode ring (2) for providing discharge gas; the target working medium inside the cathode ring (2) is the discharge gas or plasma generated by discharge.

5. A composite cathode high-power plasma generator according to claim 4, characterized in that: The discharge gas is one of N2, Ar, He, H2, CO, CO2, air, or a mixture of the above discharge gases.

6. A composite cathode high-power plasma generator according to claim 1, characterized in that: The arc-starting electrode (3) is a cylindrical copper ring or a chromium-zirconium copper ring, the upper end surface of which is concave and the lower end surface of which is a convex conical surface. A high-voltage terminal (31) is mounted on the insulating ring (11) of the outer ring.

7. A composite cathode high-power plasma generator according to claim 6, characterized in that: The high-voltage terminal (31) passes through the insulating ring (11) and is in conductive contact with the arc-starting electrode (3) for feeding high voltage, forming a discharge arc between the arc-starting electrode (3) and the cathode ring (2), and then forming a stable discharge arc in the entire arc channel between the end electrode (1) and the anode (5).

8. The composite cathode high-power plasma generator according to claim 1, characterized in that: A plurality of inter-electrode plug-ins (4) are sequentially connected to the arc-starting electrode (3). As the number of inter-electrode plug-ins increases, the power of the plasma generator also increases accordingly. The inter-electrode plug-ins (4) are cylindrical copper rings or chromium-zirconium copper rings.

9. The composite cathode high-power plasma generator according to claim 1, characterized in that: The anode (5) is a cylindrical copper ring or chromium-zirconium copper, located at the end of the arc channel and connected to the last inter-electrode plug-in (4). The anode (5) is replaceable.

10. The composite cathode high-power plasma generator according to claim 1, characterized in that: The clamping rods (8) are metal rods, 3 to 4 in number, evenly distributed in the circumferential direction, and tightly connect all the component modules.

11. The composite cathode high-power plasma generator according to claim 1, characterized in that: The insulating ring (11) is made of polytetrafluoroethylene, polyimide or high-strength ceramics, and has a main water inlet hole (53), a main water outlet hole (54), an air path hole (71) and a corresponding number of clamping rod holes (81) arranged in a cross section, with a metal ring electrode (10) in the middle, and each insulating ring (11) is tightly connected to form a complete cooling water path and air supply path.

12. A composite cathode high-power plasma generator according to claim 1 or 11, characterized in that: The connection between the cooling water channel and the air supply channel between the insulating rings (11) is sealed by an O-ring.

13. The composite cathode high-power plasma generator according to claim 1, characterized in that: The pressing rod (8) is a rod made of insulating material with a certain strength.

14. An arc starting method for a composite cathode high-power plasma generator according to any one of claims 1 to 13, characterized in that: The following steps are involved: 1) Open and adjust the cooling water valve and check the sealing of the cooling water circuit; 2) Open and adjust the gas supply valve to ensure that there is no water at the outlet of the arc channel of the plasma generator; 3) Turning on the power supply so that the end surface cathode (1) and the cathode ring (2) are in electrical contact; 4) The arc starting cabinet applies a voltage of 0 to 2 μs and a maximum of 20 kV to the arc striking electrode (3) through the high-voltage terminal (31), thereby forming a gap discharge between the arc striking electrode (3) and the cathode ring (2); 5) Simultaneously, a voltage of 0.1 to 3 s and a maximum of 1200 V is applied between the end surface cathode (1) and the cathode ring (2) together or the end surface cathode (1) and the cathode ring (2) are disconnected from the circuit and the anode (5), and an arc connection is completed between the end surface cathode (1) and the anode (5) through secondary arc initiation, and a stable discharge arc channel is formed under the action of airflow.

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