An arc heater based on spontaneous cathode arc and a test method thereof

Abstract

The application belongs to the technical field of hypersonic vehicle aerodynamic heat protection ground test equipment, and discloses an arc heater based on cathode spontaneous arc separation and a test method thereof. The arc heater comprises a cylindrical cathode, the inner wall of the cathode is made of a low work function element phase material, the outer wall of the cathode is wrapped with a magnetic field coil, and a power supply line is arranged on the magnetic field coil; an anode is arranged on the central axis of the cathode, and the rear end of the cathode is connected with a nozzle. The test method is that a plasma power supply is connected to the arc heater to supply electricity, a plasma is established between the cathode and the anode through contact arc ignition or high-frequency arc ignition, and a test gas flow is supplied to the arc heater, the test gas flow is heated by the arc heater and then sprayed from the nozzle, and a high-enthalpy and high-pressure thermal environment of a hypersonic vehicle is simulated. The test method of the arc heater based on cathode spontaneous arc separation can meet the demand of high-enthalpy and high-pressure thermal environment simulation of a hypersonic vehicle.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hypersonic vehicle aerodynamic heat protection ground test equipment, and particularly relates to an electric arc heater based on cathode self-arc and a test method thereof. BACKGROUND

[0002] A high-power electric arc heater is currently the only device that can simulate a high-temperature environment of a hypersonic vehicle on the ground for a long time, and is a core device for heat protection research of the hypersonic vehicle. The high-power electric arc heater forms an electric arc between two electrodes to heat air, and high-temperature air after heating is ejected from a nozzle to form high-temperature and high-speed air, which forms the high-temperature environment of the hypersonic vehicle.

[0003] With the increasing of the flight Mach number and the flight space of the hypersonic vehicle, a high-enthalpy and high-pressure thermal environment of the hypersonic vehicle needs to be simulated, and the electrodes of the high-power electric arc heater are required to discharge at a larger current (3000-6000A) and a higher pressure (15MPa-20MPa) to heat air to simulate a higher temperature and a higher pressure thermal environment, which puts forward higher requirements for the ablation resistance of the electrodes (especially the cathode). The current oxygen-free copper electrode cannot meet such ablation resistance requirements, and electrode ablation has become a bottleneck problem restricting the heat protection research of the hypersonic vehicle.

[0004] In order to reduce electrode ablation, various arc control technologies have been researched and developed at present, including magnetic field rotating arc root technology, multi-electrode technology, multi-heater technology, etc., forming two existing and relatively mature types of electric arc heaters: a tubular electric arc heater and a sheet electric arc heater. Although the tubular electric arc heater and the sheet electric arc heater can reduce electrode ablation to a certain extent, they still have respective limitations.

[0005] The electric arc length of the tubular electric arc heater is dominated by the strength of the air flow, and the tubular electric arc heater is characterized by large air flow and short electric arc length, so the tubular electric arc heater can only simulate a low-enthalpy and high-pressure thermal environment of the hypersonic vehicle.

[0006] Plate-type arc heaters have a fixed arc length, allowing for longer arc lengths under low airflow conditions to simulate the high-enthalpy thermal environment of hypersonic vehicles. However, because plate-type arc heaters are composed of hundreds of stacked plates, they have numerous sealing surfaces, making thermal protection difficult. Furthermore, the multi-electrode technology used in plate-type arc heaters increases the operating current. When operating at high pressure, seal failure can occur, and the increased pressure leads to a greater difference in arc resistance between the electrodes. This can cause interference between the arcs, resulting in uneven current distribution, sometimes arc separation, and sometimes arc merging into multi-arc loops, leading to decreased stability of the plate-type arc heater. Therefore, plate-type arc heating can only simulate the high-enthalpy, low-pressure thermal environment of hypersonic vehicles.

[0007] In short, as hypersonic vehicles develop towards higher Mach numbers and wider airspace, arc heaters are needed to simulate the high enthalpy and high-pressure thermal environment of hypersonic vehicles, requiring electrodes to operate under higher currents and pressures. However, electrode ablation is extremely severe under high current and high pressure. Limited by the ablation characteristics of existing oxygen-free copper electrodes, current high-power arc heaters are insufficient to meet the simulation requirements of the high enthalpy and high-pressure thermal environment of hypersonic vehicles. Solving the electrode ablation problem and developing a high-power arc heater capable of operating under high current and high pressure is the core work of hypersonic vehicle thermal protection research.

[0008] Currently, there is an urgent need to develop an arc heater based on spontaneous arc splitting of the cathode and its testing method that can simulate the high enthalpy and high pressure thermal environment of hypersonic vehicles. Summary of the Invention

[0009] One technical problem to be solved by the present invention is to provide an arc heater based on spontaneous arc splitting of the cathode. Another technical problem to be solved by the present invention is to provide a test method for an arc heater based on spontaneous arc splitting of the cathode.

[0010] The present invention relates to an arc heater based on spontaneous arc splitting of a cathode, characterized in that the arc heater includes a cylindrical cathode, the inner wall of which is made of a material containing a low work function element, and a magnetic field coil wrapped around the outer wall of the cathode, with power supply lines arranged on the magnetic field coil; the cathode includes several parallel annular cathode rings, which are sealed together by insulating rings; the magnetic field coil includes several annular magnetic field coils that correspond one-to-one with the annular cathode rings.

[0011] The front end of the cathode is insulated and sealed to the flange; the front end face of the flange is provided with a cathode end and a anode end, both of which are insulated from the flange; the flange is also provided with an air inlet, a cooling water inlet and a cooling water outlet; the rear end of the cathode is connected to the spray pipe.

[0012] The anode is arranged on the central axis of the cathode, and the front end of the anode is in insulating and sealing connection with the flange plate; the anode is divided into an inner pipe body and an outer pipe body, the inner pipe body is an anode water outlet pipe, the front end of the anode water outlet pipe is connected with a cooling water outlet, and the rear end of the anode water outlet pipe is open; the front end of the outer pipe body is connected with the rear end surface of the flange plate, and the rear end of the outer pipe body is closed; an annular cavity between the anode water outlet pipe and the outer pipe body is connected with a cooling water inlet; cooling water enters the anode from the cooling water inlet, flows along the annular cavity to the rear end of the outer pipe body, and then converges to flow out from the central cavity of the anode water outlet pipe through the cooling water outlet; test gas flows into the annular cavity between the cathode and the anode from the gas inlet channel and flows out from the nozzle.

[0013] The cathode, the anode and the nozzle are further provided with a cooling water structure.

[0014] The front end of the cathode is electrically connected with a power supply line, the power supply line is electrically connected with a magnetic field coil, and the magnetic field coil is electrically connected with the cathode; the front end of the anode is electrically connected with the anode.

[0015] Further, the material of the cathode is a high-thermal-conductivity base material including copper and silver.

[0016] Further, the inner diameter D of the cathode and the outer diameter d of the anode satisfy the formula: (D-d) / 2>kI c +h, I c I is an arc current, k is a coefficient, the value range of k is 0.03-0.06, h is a constant, and the value range of h is 0.1-3. , I is a total current of the arc heater, I is a current of a single cathode, The value range of I is 3000A-9000A.

[0017] Further, the low work function phase material contains a low work function phase, the low work function phase includes a eutectic phase, a peritectic phase or a high-temperature second phase of a low work function element; the atomic percentage of the low work function element in the cathode metal matrix ranges from 0.1% to 3%; the low work function element is added to the cathode metal matrix by alloy smelting to form an integral alloy cathode, or is formed into a coating type alloy cathode on the inner wall of the cathode by laser cladding, spraying or other forms, and the thickness of the coating ranges from 0.5mm to 3mm.

[0018] Further, the low work function phase is one or two or more of CaB6, SrO, CaO, SrB6, ThO2, BaB6, HfO2, LaB6, Cr2Nb, Y2O3, BaO or La2O3.

[0019] Further, the low work function element containing phase material is subjected to electron emission performance improvement treatment before being added to the cathode metal matrix, so as to obtain the electron emission capacity different from the cathode matrix, and the treatment method comprises: alloy element and cathode substrate electron transport matching treatment, alloy element activation treatment, alloy element aging treatment, and alloy element and cathode substrate atomic electron cloud overlap forming potential well adjustment treatment.

[0020] Further, the test gas flow at the inlet of the gas inlet channel has an included angle of 5°-30° with the arc root movement direction of the cathode. ,

[0021] Further, the difference between the inner diameter of the outer layer of the anode pipe body and the outer diameter of the anode water outlet pipe is 3mm-10mm.

[0022] Further, the magnetic induction intensity of the magnetic field coil satisfies the following formula:

[0023] ,

[0024] In the formula, is the rotation speed of the arc root in the inner wall of the cathode, is the gas density inside the electric arc heater.

[0025] The test method of the electric arc heater based on the self-arc of the cathode comprises the following steps:

[0026] S10. Cooling water is introduced into the cooling water structure of the cathode, the anode and the nozzle, and the cooling water is deionized cooling water;

[0027] S20. 10g / s-100g / s of test gas flow is introduced into the gas inlet channel;

[0028] S30. The cathode end and the anode end are powered through an external plasma power supply, and the plasma is established between the cathode and the anode through contact arc ignition or high-frequency arc ignition, and the output current of the plasma power supply is 1000A-3000A;

[0029] S40. The output current of the plasma power supply is gradually increased first, and then the test gas flow pressure and flow of the gas inlet channel are increased, and the time of increasing the gas inlet pressure and flow lags behind the time of increasing the current by 1s-3s, and after the set values are reached, the electric arc heater enters stable operation; the test gas flow is heated by the electric arc heater and then sprayed from the nozzle, so as to simulate the high-enthalpy and high-pressure thermal environment of the hypersonic vehicle.

[0030] ​The inner wall of the cathode of the cathode self-spontaneous arc based electric arc heater of the application adopts a low work function element phase material.The selection principle of the low work function element is as follows:a. the alloy element has a high solid solubility in the cathode matrix at high temperature and a low solid solubility in the cathode matrix at room temperature;b. the alloy element mainly exists in the form of precipitates in the cathode matrix, and the precipitates have high temperature stability;c. the alloy element has little influence on the thermal conductivity of the cathode alloy, and the addition amount of the alloy element is controlled to maintain a high thermal conductivity of the electrode matrix.The low work function element phase material improves the electron emission performance of the cathode matrix and obtains a difference in electron emission capacity from the cathode matrix; after the low work function element phase material is added to the cathode matrix, a uniformly dispersed low work function phase is formed, and the low work function phase has a stronger electron emission capacity, and the arc preferentially emits electrons at these low work function phases.

[0031] The arc current in the cathode self-spontaneous arc based electric arc heater of the application includes electron current, anion current and cation current, and the cation current heats the cathode and is the main heat input causing electrode ablation.The low work function element phase material has excellent electron emission performance, greatly increases the electron current in the arc current, greatly reduces the anion current and the cation current, reduces the heating effect of the cation current on the cathode, and at the same time, the large amount of electron current emitted by the low work function element phase material has a Nothernham cooling effect, and a large amount of heat is taken away from the cathode, greatly reducing the electrode ablation.

[0032] The cathode arc spot position is the electron lowest energy barrier emission area, and the arc spot is concentrated and has a large heat flux density.The cathode self-spontaneous arc based electric arc heater of the application not only can distribute the current to multiple cathodes, but also can spontaneously decompose the cathode arc spot from a single arc spot into multiple spot-shaped arc spots on a single cathode, and a single arc spot has a kiloampere-level current, and the current of the multiple spot-shaped arc spots is reduced by 1-2 orders of magnitude compared with the kiloampere-level current.Due to the dispersion of the arc spot, the low current of the spot-shaped arc spot and the reduced heat input of the electrode, the cathode ablation rate is reduced by 2-3 orders of magnitude, and accordingly, the anode as the electron receiving end also has a reduced ablation rate due to the dispersion of the arc spot.

[0033] The cathode self-spontaneous arc based electric arc heater of the application adopts multiple cathodes connected in parallel, and with the increase of the total current, arcs are formed on multiple cathodes, and spot-shaped arc spots can be spontaneously formed on a single cathode, and the single cathode current can be controlled at 3000A-9000A; therefore, the cathode self-spontaneous arc based electric arc heater of the application can work at a current of 1kA-1000kA, and the number of cathodes increases correspondingly with the increase of the total current.

[0034] Compared to the hundreds of sealing surfaces of a plate-type arc heater, the arc heater based on spontaneous arc splitting of the cathode of the present invention has a significantly reduced number of sealing surfaces and a simple structure, and can operate under high pressure.

[0035] The cathode-spontaneous arc heater of this invention features multiple arcs over a short distance, operates at low voltage, and has low design difficulty in withstand voltage of each component. Furthermore, the concentrated short arcs result in a small overall size, a small cooling area, and significantly improved thermal efficiency. It can operate under high current and high pressure with a low electrode ablation rate. The experimental method for the cathode-spontaneous arc heater of this invention can meet the requirements for simulating the high enthalpy and high pressure thermal environment of hypersonic vehicles. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the arc heater based on cathode spontaneous arc splitting according to the present invention;

[0037] Figure 1 In the middle, 1. Cathode end; 2. Flange; 3. Power supply line; 4. Magnetic field coil; 5. Cathode; 6. Insulating ring; 7. Nozzle; 8. Anode; 9. Anode outlet pipe; 10. Air inlet channel; 11. Anode end; 12. Test airflow; 13. Cooling water.

[0038] Figure 2 The image shows a spot-like arc pattern of a spontaneously dispersed cathode arc obtained in Example 1. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0040] like Figure 1 As shown, the arc heater based on spontaneous arc splitting of the cathode of the present invention includes a cylindrical cathode 5, the inner wall of the cathode 5 is made of a phase material containing low work function elements, the outer wall of the cathode 5 is wrapped with a magnetic field coil 4, and power supply lines 3 are arranged on the magnetic field coil 4; the cathode 5 includes a plurality of parallel annular cathode rings, and each cathode ring is sealed and connected by an insulating ring 6; the magnetic field coil 4 includes a plurality of annular magnetic field coils 4 corresponding one-to-one with the annular cathode rings.

[0041] The front end of the cathode 5 is connected to the flange 2 in an insulating and sealed manner; the front end surface of the flange 2 is provided with a cathode end 1 and an anode end 11, and the cathode end 1 and the anode end 11 are both connected to the flange 2 in an insulating manner; the flange 2 is also provided with an air inlet channel 10, a cooling water inlet and a cooling water outlet; the rear end of the cathode 5 is connected to the nozzle 7;

[0042] The center axis of the cathode 5 is provided with an anode 8, and the front end of the anode 8 is connected to the rear end surface of the flange 2 in an insulating and sealed manner; the anode 8 is divided into an inner layer pipe body and an outer layer pipe body, the inner layer pipe body is an anode water outlet pipe 9, the front end of the anode water outlet pipe 9 is connected to the cooling water outlet, and the rear end of the anode water outlet pipe 9 is open; the front end of the outer layer pipe body is connected to the rear end surface of the flange 2, and the rear end of the outer layer pipe body is closed; the annular cavity between the anode water outlet pipe 9 and the outer layer pipe body is connected to the cooling water inlet; the cooling water 13 enters the anode from the cooling water inlet, flows along the annular cavity to the rear end of the outer layer pipe body, and then converges, flows out from the cooling water outlet through the central cavity of the anode water outlet pipe 9; the test gas flow 12 enters the annular cavity between the cathode 5 and the anode 8 from the air inlet channel 10 and flows out from the nozzle 7;

[0043] The cathode 5, the anode 8 and the nozzle 7 are also provided with a cooling water structure;

[0044] The cathode end 1 is electrically connected to the power supply line 3, the power supply line 3 is electrically connected to the magnetic field coil 4, and the magnetic field coil 4 is electrically connected to the cathode 5; the anode end 11 is electrically connected to the anode 8.

[0045] Further, the material of the cathode 5 is a high-thermal-conductivity base material including copper and silver.

[0046] Further, the inner diameter D of the cathode 5 and the outer diameter d of the anode 8 satisfy the formula: D-d / 2>kI c +h, I c is the arc current, k is a coefficient, the value range of k is 0.03-0.06, h is a constant, and the value range of h is 0.1-3; the number of the cathodes 5 , is the total current of the arc heater, is the current of a single cathode, and the value range of I is 3000A-9000A.

[0047] Further, the low work function element phase material contains a low work function phase, and the low work function phase includes a eutectic phase, a peritectic phase or a high-temperature second phase of a low work function element; the atomic percentage of the low work function element in the metal matrix of the cathode 5 ranges from 0.1% to 3%; the low work function element is added to the metal matrix of the cathode 5 by alloy smelting to form an integral alloy cathode, or is added to the inner wall of the cathode 5 by laser cladding, spraying or other forms to form a coated alloy cathode, and the thickness of the coating ranges from 0.5mm to 3mm.

[0048] Further, the low work function phase is one or more of CaB6, SrO, CaO, SrB6, ThO2, BaB6, HfO2, LaB6, Cr2Nb, Y2O3, BaO or La2O3.

[0049] Further, the low work function phase material is subjected to an electron emission performance improvement treatment before being added to the cathode metal matrix, so as to obtain a difference in electron emission capacity from the cathode matrix, and the treatment method comprises: alloy element and cathode 5 base electron transport matching treatment, alloy element activation treatment, alloy element aging treatment, alloy element and cathode 5 base atomic electron cloud overlap formation potential well adjustment treatment.

[0050] Further, the test gas flow 12 at the inlet of the gas inlet channel 10 is at an angle of 5°~30° with the arc root movement direction of the cathode 5. ,

[0051] Further, the difference between the inner diameter of the outer layer pipe body of the anode 8 and the outer diameter of the anode water outlet pipe 9 is 3mm~10mm.

[0052] Further, the magnetic induction intensity of the magnetic field coil 4 satisfies the following formula:

[0053] ,

[0054] In the formula, is the rotation speed of the arc root in the cathode inner wall, is the gas density inside the arc heater.

[0055] The test method of the cathode self-arc-based arc heater of the application comprises the following steps:

[0056] S10. Cooling water 13 is introduced into the cooling water structure of the cathode 5, the anode 8 and the nozzle 7, and the cooling water 13 is deionized cooling water;

[0057] S20. The test gas flow 12 of 10g / s~100g / s is introduced into the gas inlet channel 10;

[0058] S30. The cathode tip 1 and the anode tip 11 are powered by an external plasma power supply, and the plasma is established between the cathode 5 and the anode 8 by means of contact arc or high-frequency arc, and the output current of the plasma power supply is 1000A~3000A;

[0059] ​S40. First gradually increase the output current of the plasma power supply, then increase the test gas flow 12 pressure and flow rate of the gas inlet channel 10, the time of increasing the gas inlet pressure and flow rate lags behind the time of increasing the current by 1s~3s, after reaching the set values, the arc heater enters stable operation; the test gas flow 12 is heated by the arc heater and then sprayed out from the nozzle 7 as a gas flow, simulating the high-enthalpy, high-pressure thermal environment of a hypersonic vehicle.

[0060] Embodiment 1:

[0061] The cathode 5 of this embodiment uses copper base material, uses low work function element La, La exists in the form of LaB6, and the LaB6 is treated to improve electron emission capability; the treated LaB6 is added to the copper base to prepare the cathode 5; the anode 8 uses oxygen-free copper. Discharge test is performed, and the spot-like arc spots of the cathode spontaneous dispersion arc are obtained by online observation through online test technology as shown in Figure 2 It can be seen from Figure 2 that the single arc spot is converted into multiple spot-like arc spots.

[0062] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An arc heater based on spontaneous cathode arc, characterized in that, The arc heater comprises a cylindrical cathode (5), the inner wall of the cathode (5) is made of a low work function element phase material, the outer wall of the cathode (5) is wrapped with a magnetic field coil (4), the magnetic field coil (4) is arranged with a power supply line (3); the cathode (5) comprises a plurality of annular cathode rings connected in parallel, and the cathode rings are connected by an insulating ring (6); the magnetic field coil (4) comprises a plurality of annular magnetic field coils (4) corresponding to the annular cathode rings. The front end of the cathode (5) is connected with the flange (2) in an insulating and sealing manner; the front end surface of the flange (2) is provided with a cathode end (1) and an anode end (11), and the cathode end (1) and the anode end (11) are connected with the flange (2) in an insulating manner; the flange (2) is further provided with an air inlet channel (10), a cooling water inlet and a cooling water outlet; the rear end of the cathode (5) is connected with a nozzle (7). An anode (8) is arranged on the central axis of the cathode (5), and the front end of the anode (8) is connected with the flange (2) in an insulating and sealing manner; the anode (8) comprises an inner layer pipe body and an outer layer pipe body, the inner layer pipe body is an anode water outlet pipe (9), the front end of the anode water outlet pipe (9) is connected with the cooling water outlet, and the rear end of the anode water outlet pipe (9) is open; the front end of the outer layer pipe body is connected with the rear end surface of the flange (2), and the rear end of the outer layer pipe body is closed; the annular cavity between the anode water outlet pipe (9) and the outer layer pipe body is connected with the cooling water inlet; cooling water (13) enters the anode from the cooling water inlet, flows along the annular cavity to the rear end of the outer layer pipe body, converges, flows out from the cooling water outlet through the central cavity of the anode water outlet pipe (9); test gas flow (12) enters the annular cavity between the cathode (5) and the anode (8) from the air inlet channel (10) and flows out from the nozzle (7). The cathode (5), the anode (8) and the nozzle (7) are further provided with a cooling water structure. The cathode end (1) is electrically connected with the power supply line (3), the power supply line (3) is electrically connected with the magnetic field coil (4), and the magnetic field coil (4) is electrically connected with the cathode (5); the anode end (11) is electrically connected with the anode (8).

2. The cathode-spontaneous-arc-based electric-arc heater according to claim 1, characterized in that, The material of the cathode (5) is a high thermal conductivity base material including copper and silver.

3. The cathode-spontaneous-arc-based electric-arc heater according to claim 1, characterized in that, The inner diameter D of the cathode (5) and the outer diameter d of the anode (8) satisfy the formula: (D-d) / 2>kI c +h, I c I is the arc current, k is a coefficient, the value range of k is 0.03-0.06, h is a constant, the value range of h is 0.1-3; the number of the cathode (5) , I is the total current of the arc heater, I is the current of a single cathode, The value range of k is 3000A-9000A.

4. The cathode-spontaneous-arc-based electric-arc heater according to claim 1, characterized in that, The low work function element phase material contains a low work function phase, and the low work function phase includes a eutectic phase, a peritectic phase or a high-temperature second phase of a low work function element; the atomic percentage of the low work function element in the metal matrix of the cathode (5) ranges from 0.1% to 3%; the low work function element is added to the metal matrix of the cathode (5) by alloy smelting to form an integral alloy cathode, or is added to the inner wall of the cathode (5) by laser cladding, spraying or other forms to form a coated alloy cathode, and the thickness of the coating ranges from 0.5mm to 3mm.

5. The cathode-spontaneous-arc-based electric-arc heater according to claim 4, characterized in that, The low work function phase is one or more than two of CaB6, SrO, CaO, SrB6, ThO2, BaB6, HfO2, LaB6, Cr2Nb, Y2O3, BaO or La2O3.

6. The cathode self-sparking arc-based electric arc heater of claim 4, wherein, The low work function element containing phase material is subjected to electron emission performance improvement treatment before being added to the cathode metal matrix, so as to obtain the electron emission capacity different from the cathode matrix, and the treatment method comprises the following steps: alloy element and cathode (5) base electron transport matching treatment, alloy element activation treatment, alloy element aging treatment, and alloy element and cathode (5) base atomic electron cloud overlapping to form potential well adjustment treatment.

7. The cathode-spontaneous-arc-based arc heater of claim 1, wherein, The test gas flow (12) is at an angle of 5°~30° with the arc root movement direction of the cathode (5) at the inlet of the gas inlet channel (10).

8. The cathode-spontaneous-arc-based electric-arc heater according to claim 1, characterized in that, The difference between the inner diameter of the outer layer pipe body of the anode (8) and the outer diameter of the anode water outlet pipe (9) is 3mm~10mm.

9. The cathode-spontaneous-arc-based electric-arc heater according to claim 1, characterized in that, The magnetic induction intensity of the magnetic field coil (4) satisfies the following formula: ， wherein is the arc root rotation speed on the cathode inner wall, is the arc heater internal gas density.

10. A test method of an arc heater based on cathode spontaneous arc discharge, for the arc heater based on cathode spontaneous arc discharge according to any one of claims 1 to 9, characterized by, The method comprises the following steps: S10. Cooling water (13) is introduced into the cooling water structure of the cathode (5), the anode (8) and the nozzle (7), and the cooling water (13) is deionized cooling water; S20. 10g / s~100g / s of test gas flow (12) is introduced into the gas inlet channel (10); S30. The cathode end (1) and the anode end (11) are powered through the external plasma power supply, the plasma is established between the cathode (5) and the anode (8) through the contact arc ignition or high frequency arc ignition mode, and the output current of the plasma power supply is 1000A~3000A; S40. The output current of the plasma power supply is gradually increased first, and then the pressure and flow of the test gas flow (12) of the gas inlet channel (10) are increased, the time of increasing the inlet pressure and flow lags behind the time of increasing the current, the lag time is 1s~3s, and after the set values are reached, the arc heater enters the stable operation; the test gas flow (12) is sprayed from the nozzle (7) after being heated by the arc heater, so as to simulate the high enthalpy and high pressure thermal environment of the hypersonic vehicle.

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