A tubular arc plasma heating test device with jetting at both ends

Abstract

The present invention discloses a tubular arc plasma heating test device with jetting at both ends, which includes a rear nozzle, a rear gas mixing chamber, a rear magnetic field coil, a rear electrode, a rear electrode insulating sheet, an air inlet chamber, a front electrode insulating sheet, a front electrode, a front magnetic field coil, a front gas mixing chamber and a front nozzle. The front and rear electrode insulating sheets, the front and rear electrodes, the front and rear gas mixing chambers and the front and rear nozzles are symmetrically arranged on both sides in sequence with the air inlet chamber as the center. After the gas entering from the air inlet chamber is heated by the arc inside, it is mixed with the entering gas in the gas mixing chamber and is symmetrically ejected through the rear nozzle and the front nozzle respectively to form a rear high-temperature jet and a front high-temperature jet. The present invention improves the service life of the rear electrode and the long-time test ability of the entire tubular arc plasma heating test device. By using the high-temperature jets with completely consistent parameters such as total pressure and total enthalpy symmetrically ejected from both ends, the assessment of two identical heat protection materials or the screening of two different heat protection materials can be completed through a single test, doubling the test efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of low-temperature thermal plasma, and particularly relates to a tubular arc plasma heating test device with air jets at both ends. Background Art

[0002] Arc plasma has physical and chemical characteristics of high temperature, high enthalpy, and high chemical activity. Since the 1920s, it has been continuously applied to research on overcoming the "thermal barrier" encountered by aerospace vehicles when re-entering the atmosphere and solving the "blackout" problem caused by plasma near high-speed aircraft. In the late 1950s, with the emergence of hypersonic missiles, space entry vehicles, and re-entry vehicles, arc plasma heating technology was first used in aerodynamic heating tests. Since the 1970s, great progress has also been made in the application of arc plasma technology in industrial fields such as machining, metallurgy, and electric power. Currently, the arc plasma heating test device is the only test tool that can continuously generate near the true flight airflow temperature and pressure of the aircraft on the ground. Therefore, arc plasma technology is still an irreplaceable technology for conducting high-temperature gas dynamics experiments, burning tests of aircraft thermal protection materials, and assessment tests of thermal protection structures.

[0003] The tubular arc plasma heating test device is one of the most widely used types in the aerospace field at present. It mainly consists of a rear electrode, a front electrode, an air inlet chamber, a nozzle, etc. It can be seen that it has the advantages of fewer components, simple structure, convenient operation and maintenance. At the same time, the heater has good insulation and sealing performance, and can reach a relatively high arc chamber pressure. It is mainly used for the thermal protection research of aerospace vehicle thermal protection materials and scramjet engine tests. However, in actual applications, the tubular arc heater has problems such as a high specific ablation rate of the rear electrode and a short service life. The service life of the rear electrode is only one-tenth to several tenths of the service life of the front electrode, which severely limits the long-term test ability and stable operation of the entire arc plasma heating device, and increases the maintenance cost. The difference in the service life of the front and rear electrodes is largely related to the structure of the electrodes and the aerodynamic characteristics inside the electrodes. Usually, the rear electrode is a deep cup-shaped structure (tail blind end) with or without air intake at the bottom, and the airflow forms 1-2 axial circulation zones and a zero-velocity zone inside the rear electrode. The arc root inside the rear electrode will be linearly ablated in the zero-velocity zone under the action of aerodynamic force, resulting in severe local heating of the inner wall of the electrode and a high ablation rate. The front electrode is an output electrode, usually designed as a thin-walled circular tubular structure. The airflow rotates unidirectionally inside the front electrode. Coupled with the bypass breakdown effect, the arc root ablates on the inner wall of the front electrode within a certain range, greatly improving the heating condition of the arc landing area on the inner wall of the front electrode and reducing the specific ablation rate of the electrode, so the working life of the electrode is long. Summary of the Invention

[0004] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, providing a tubular arc plasma heating test device with jetting at both ends, enabling the front and rear electrodes of the arc heater to have the same long service life, and at the same time improving the test efficiency of the test device.

[0005] The technical solution of the present invention is: a tubular arc plasma heating test device with jetting at both ends, including a rear nozzle, a rear gas mixing chamber, a rear magnetic field coil, a rear electrode, a rear electrode insulating sheet, an air inlet chamber, a front electrode insulating sheet, a front electrode, a front magnetic field coil, a front gas mixing chamber and a front nozzle. The air inlet chamber is designed with tangential air inlet holes, and the air inlet holes are evenly distributed in n1 planes axially and evenly distributed circumferentially with n2 air inlet holes in each plane. The working gas with a mass flow rate of m1 enters the interior tangentially through the n1×n2 air inlet holes on the air inlet chamber. The rear electrode insulating sheet and the front electrode insulating sheet are annular sheet structures made of insulating materials, with the same size and symmetrically arranged on both sides of the air inlet chamber. The interiors of the rear electrode and the front electrode are circular tubular structures with equal diameters, and the exteriors are water jacket structures. The inner diameters of the rear electrode and the front electrode are both d1, and the lengths are both L1. The direction close to the air inlet chamber is defined as the upstream, and the direction away from the air inlet chamber is defined as the downstream. The upstream end of the rear electrode is tightly connected to the rear electrode insulating sheet, and the upstream end of the front electrode is hermetically and firmly connected to the front electrode insulating sheet. The rear excitation coil and the front excitation coil are uniformly and closely wound spiral copper coil structures. The rear excitation coil is coaxially sleeved outside the downstream of the rear electrode, and the current direction in the rear excitation coil is the same as the rotation direction of the rotating air flow inside the rear electrode. The front excitation coil is coaxially sleeved outside the downstream of the front electrode, and the current direction in the front excitation coil is opposite to the rotation direction of the rotating air flow inside the front electrode. The rear gas mixing chamber and the front gas mixing chamber have the same structure and size, and the interior is a tapered expansion - straight section - tapered contraction structure, and the exterior is a water jacket structure. The inner tapered expansion and tapered contraction angles are α, the diameter of the straight section is d2, and n3 radial air inlet holes are evenly arranged circumferentially on the cross-section at a distance of L2 from the upper edge of the straight section. The gas with a mass flow rate of m2 enters the interior evenly through the n3 small holes. A radial small hole with a diameter of d3 is arranged on the cross-section at a distance of L3 from the lower edge of the straight section for measuring the total pressure in the gas mixing chamber. The upstream end of the rear gas mixing chamber is hermetically and firmly connected to the downstream end of the rear electrode, and the upstream end of the front gas mixing chamber is hermetically and firmly connected to the downstream end of the front electrode. The rear nozzle and the front nozzle have the same structure and size, and the interior is a contraction - expansion structure, and the exterior is a water jacket structure. The upstream end of the rear nozzle is hermetically and firmly connected to the downstream end of the rear gas mixing chamber, and the upstream end of the front nozzle is hermetically and firmly connected to the downstream end of the front gas mixing chamber. An arc is generated by gas breakdown between the rear electrode and the front electrode. The gas entering from the air inlet chamber flows symmetrically to both sides and is heated by the arc. The gas flowing towards the rear electrode is mixed with the entering gas in the rear gas mixing chamber and then ejected through the rear nozzle to form a rear high-temperature jet. The gas flowing towards the front electrode is mixed with the entering gas in the front gas mixing chamber and then ejected through the front nozzle to form a front high-temperature jet.

[0006] The number n1 of planes with equally spaced intake holes in the intake chamber is 1 - 4, and the number n2 of intake holes on each plane is 3 - 6.

[0007] The materials of the rear electrode insulating sheet and the front electrode insulating sheet are high-temperature resistant (long-term service temperature ≥ 200 °C), wear-resistant plastics such as polyimide and polyether ether ketone, or insulating ceramic materials such as alumina, zirconia, and silicon nitride.

[0008] The ratio of the length L1 to the inner diameter d1 of the rear electrode and the front electrode is: 4 ≤ L1 / d1 ≤ 8.

[0009] The direction of the current in the rear excitation coil is the same as the rotation direction of the rotating air flow inside the rear electrode, and the direction of the current in the front excitation coil is opposite to the rotation direction of the rotating air flow inside the front electrode.

[0010] The internal conical expansion and conical contraction angles α of the rear mixing chamber and the front mixing chamber are: 30° ≤ α ≤ 60°, and the internal straight section diameter d2 is: 2.5d1 ≤ d2 ≤ 4d1.

[0011] The number n3 of intake holes in the mixing chamber and the front mixing chamber is 2 - 6, and the distance L2 from the plane where the intake holes are located to the upper edge of the straight section is ≤ 10 mm.

[0012] The diameter d3 of the pressure measuring holes in the mixing chamber and the front mixing chamber is 1 - 2 mm, and the distance L3 from the section where the pressure measuring holes are located to the lower edge of the straight section is ≤ 5 mm.

[0013] The relationship between the gas mass flow rate m1 passing through the intake chamber and the gas mass flow rate m2 passing through the mixing chamber is: h t ×m1 + 600×m2 / (m1 + 2×m2) = h0, where h t is an empirical value of the tubular arc heating device, which is taken within the range of 5000 - 6000 kJ / kg, and h0 is a test design value determined by the heating test requirements.

[0014] The applicable power of the tubular arc heating test device with jetting at both ends is 1 - 100 MW.

[0015] The advantages of the present invention compared with the prior art are as follows:

[0016] (1) The rear electrode of the present invention is a circular tubular structure with openings at both ends and has the same structural dimensions as the front electrode, enabling the working gas entering from the intake chamber between the electrodes to flow symmetrically to both sides completely. The same flow characteristics and bypass breakdown effect are formed inside the rear electrode as inside the front electrode. The arc landing area on the inner wall of the rear electrode changes from linear ablation to surface ablation within the range of plane F1 to F2 consistent with the front electrode, greatly reducing the specific ablation rate of the rear electrode and improving the service life of the electrode.

[0017] (2) Since the high-temperature gas generated in the arc heating device of the present invention is ejected symmetrically from both ends, the stability of thermal parameters is improved.

[0018] (3) For the tubular arc plasma heating test device with gas ejection at both ends of the present invention, parameters such as the total pressure and total enthalpy of the high-temperature jets ejected symmetrically from both ends are exactly the same. Test models can be installed at both ends respectively, and the assessment of two identical heat protection materials or the screening of two different heat protection materials can be completed through a single test, improving the test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of the present invention.

[0020] 1 - Rear high-temperature jet; 2 - Rear nozzle; 3 - Rear mixing chamber; 4 - Rear magnetic field coil; 5 - Rear electrode; 6 - Rear electrode insulating sheet; 7 - Intake chamber; 8 - Front electrode insulating sheet; 9 - Front electrode; 10 - Arc; 11 - Front magnetic field coil; 12 - Front mixing chamber; 13 - Front nozzle; 14 - Front high-temperature jet. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be further described in detail below with reference to the accompanying drawings.

[0022] As Figure 1As shown in the figure, a tubular arc plasma heating test device with jetting at both ends includes a rear nozzle 2, a rear gas mixing chamber 3, a rear magnetic field coil 4, a rear electrode 5, a rear electrode insulating sheet 6, an air inlet chamber 7, a front electrode insulating sheet 8, a front electrode 9, a front magnetic field coil 11, a front gas mixing chamber 12, and a front nozzle 13. The air inlet chamber 7 is designed with tangential air inlet holes, and the air inlet holes are evenly distributed axially in n1 planes, and n2 air inlet holes are evenly distributed circumferentially in each plane. The working gas with a mass flow rate of m1 enters the interior tangentially through the n1×n2 air inlet holes on the air inlet chamber. The rear electrode insulating sheet 6 and the front electrode insulating sheet 8 are annular sheet structures made of insulating materials, with the same size and symmetrically arranged on both sides of the air inlet chamber 7. The interiors of the rear electrode 5 and the front electrode 8 are circular tube structures with equal diameters, and the exteriors are water jacket structures. The inner diameters of the rear electrode 5 and the front electrode 8 are both d1, and the lengths are both L1. The direction close to the air inlet chamber 7 is defined as the upstream, and the direction away from the air inlet chamber 7 is defined as the downstream. The upstream end of the rear electrode 5 is tightly connected to the rear electrode insulating sheet 6, and the upstream end of the front electrode 9 is hermetically and tightly connected to the front electrode insulating sheet 8. The rear excitation coil 4 and the front excitation coil 11 are uniformly and closely wound spiral copper coil structures. The rear excitation coil 4 is coaxially sleeved outside the downstream of the rear electrode 5, and the current direction in the rear excitation coil 4 is the same as the rotation direction of the rotating air flow inside the rear electrode 5. The front excitation coil 11 is coaxially sleeved outside the downstream of the front electrode 9, and the current direction in the front excitation coil 11 is opposite to the rotation direction of the rotating air flow inside the front electrode 9. The rear gas mixing chamber 3 and the front gas mixing chamber 12 have the same structure and size. The interior is a tapered expansion - straight section - tapered contraction structure, and the exterior is a water jacket structure. The inner tapered expansion and tapered contraction angles are α, the diameter of the straight section is d2, and n3 radial air inlet holes are evenly arranged circumferentially on the cross - section at a distance of L2 from the upper edge of the straight section. The gas with a mass flow rate of m2 enters the interior evenly through the n3 small holes. A radial small hole with a diameter of d3 is arranged on the cross - section at a distance of L3 from the lower edge of the straight section for measuring the total pressure inside the gas mixing chamber. The upstream end of the rear gas mixing chamber 3 is hermetically and tightly connected to the downstream end of the rear electrode 5, and the upstream end of the front gas mixing chamber 12 is hermetically and tightly connected to the downstream end of the front electrode 9. The rear nozzle 2 and the front nozzle 13 have the same structure and size. The interior is a contraction - expansion structure, and the exterior is a water jacket structure. The upstream end of the rear nozzle 2 is hermetically and tightly connected to the downstream end of the rear gas mixing chamber 3, and the upstream end of the front nozzle 13 is hermetically and tightly connected to the downstream end of the front gas mixing chamber 12.

[0023] The number of planes n1 in which the air inlet holes of the air inlet chamber 7 are evenly distributed is 1 - 4, and the number of air inlet holes n2 on each plane is 3 - 6.

[0024] The materials of the rear electrode insulating sheet 6 and the front electrode insulating sheet 8 are high - temperature - resistant plastics such as polyimide and polyether ether ketone with a long - term service temperature ≥200°C, wear - resistant plastics, or insulating ceramic materials such as alumina, zirconia, and silicon nitride.

[0025] The ratio of the length L1 to the inner diameter d1 of the rear electrode 5 and the front electrode 9 is: 4 ≤ L1 / d1 ≤ 8.

[0026] The internal conical expansion and conical contraction angles α of the rear mixing chamber 3 and the front mixing chamber 12 are: 30° ≤ α ≤ 60°, and the diameter d2 of the internal straight section is: 2.5d1 ≤ d2 ≤ 4d1.

[0027] The number n3 of the air inlet holes of the mixing chamber 3 and the front mixing chamber 12 is 2 - 6, and the distance L2 from the plane where the air inlet holes are located to the upper edge of the straight section is L2 ≤ 10 mm.

[0028] The diameter d3 of the pressure measuring holes of the mixing chamber 3 and the front mixing chamber 12 is 1 - 2 mm, and the distance L3 from the section where the pressure measuring holes are located to the lower edge of the straight section is L3 ≤ 5 mm.

[0029] The relationship between the gas mass flow rate m1 passing through the air inlet chamber 7 and the gas mass flow rate m2 passing through the mixing chamber is: h t ×m1 + 600×m2 / (m1 + 2×m2) = h0, where h t is an empirical value of the tubular arc heating device, which is taken in the range of 5000 - 6000 kJ / kg, and h0 is the test design value, which is determined by the heating test requirements.

[0030] The applicable power of the tubular arc heating test device with jetting at both ends is 1 - 100 MW.

[0031] The working principle of the present invention is as follows: The rear electrode 5 serves as the anode, and the front electrode 9 serves as the cathode. After applying direct current by the upstream power supply device, the gas between the rear electrode 5 and the front electrode 9 is broken down to generate an arc 10. The gas entering from the intake chamber 7 flows symmetrically to both sides. The gas interacts with the arc 10, and the gas blows the arc root of the arc 10 downstream. The arc 10 heats the flowing gas under the action of Joule heat. A rear excitation coil 4 is arranged outside the downstream of the rear electrode 5, and a front excitation coil 11 is arranged outside the downstream of the front electrode 9. By applying an excitation current in the designed direction to the coil, the coil acts as a magnetic lens to restrict the axial position of the arc root of the arc 10, preventing the gas flow from blowing off the arc or blowing the arc root to the downstream mixing chamber 3 or the front mixing chamber 12 to cause damage to the mixing chamber. The gas heated by the arc 10 in the rear electrode 5 flows into the rear mixing chamber 3, mixes with the entering gas, and is ejected through the rear nozzle 2 to form a rear high-temperature jet 1. The gas heated by the arc 10 in the front electrode 9 flows into the front mixing chamber 12, mixes with the entering gas, and is ejected through the front nozzle 13 to form a front high-temperature jet 14. Since the rear electrode 5 and the front electrode 9 are designed as the same circular tubular structure with open ends at both ends, the same flow characteristics and bypass breakdown effects are generated inside the rear electrode 5 as inside the front electrode 9. The arc landing area on the inner wall of the rear electrode 5 changes from line ablation to surface ablation within the range of the plane F1 to F2, which is consistent with that of the front electrode 9, greatly reducing the specific ablation rate of the rear electrode 9 and improving the service life of the electrode and the long-term test ability of the entire tubular arc plasma heating test device. At the same time, the gas in the device is ejected symmetrically from both ends to form high-temperature jets with completely consistent parameters such as total pressure and total enthalpy, enabling test models to be installed at both ends respectively, completing the assessment of two identical heat-resistant materials or the screening of two different heat-resistant materials through a single test, doubling the test efficiency.

[0032] The content not described in detail in the specification of the present invention belongs to the well-known technology in the art.

Claims

1. A tubular arc plasma heating test device with jetting at both ends, characterized in that, It includes a rear nozzle (2), a rear mixing chamber (3), a rear magnetic field coil (4), a rear electrode (5), a rear electrode insulating sheet (6), an intake chamber (7), a front electrode insulating sheet (8), a front electrode (9), a front magnetic field coil (11), a front mixing chamber (12) and a front nozzle (13); A number of tangential intake holes are distributed on the intake chamber (7); the rear electrode insulating sheet (6) and the front electrode insulating sheet (8) are symmetrically arranged on both sides of the intake chamber (7); the inner parts of the rear electrode (5) and the front electrode (9) are circular tube structures with equal diameters, and the outer parts are water jacket structures. The direction close to the intake chamber (7) is defined as the upstream, and the direction away from the intake chamber (7) is defined as the downstream. The upstream end of the rear electrode (5) is connected to the rear electrode insulating sheet (6), and the upstream end of the front electrode (9) is hermetically connected to the front electrode insulating sheet (8); the rear magnetic field coil (4) is coaxially sleeved outside the downstream of the rear electrode (5), and the front magnetic field coil (11) is coaxially sleeved outside the downstream of the front electrode (9); the inner parts of the rear mixing chamber (3) and the front mixing chamber (12) include a conical expansion section, a straight section and a conical contraction section, and the outer parts are water jacket structures. A number of radial intake holes are evenly arranged along the circumferential direction on the straight section, and radial holes for measuring the total pressure in the mixing chamber are arranged on the straight section. The upstream end of the rear mixing chamber (3) is hermetically connected to the downstream end of the rear electrode (5), and the upstream end of the front mixing chamber (12) is hermetically connected to the downstream end of the front electrode (9); the inner parts of the rear nozzle (2) and the front nozzle (13) include a contraction section and an expansion section, and the outer parts are water jacket structures. The upstream end of the rear nozzle (2) is hermetically connected to the downstream end of the rear mixing chamber (3), and the upstream end of the front nozzle (13) is hermetically connected to the downstream end of the front mixing chamber (12).

2. The tubular arc plasma heating test device with jetting at both ends according to claim 1, wherein, An arc (10) is generated by gas breakdown between the rear electrode (5) and the front electrode (9). The gas entering from the intake chamber (7) flows symmetrically to both sides and is heated by the arc (10). The gas flowing towards the rear electrode (5) is mixed with the entering gas in the rear mixing chamber (3) and then ejected through the rear nozzle (2) to form a rear high-temperature jet (1). The gas flowing towards the front electrode (9) is mixed with the entering gas in the front mixing chamber (12) and then ejected through the front nozzle (13) to form a front high-temperature jet (14).

3. A tubular arc plasma heating test device with jetting at both ends according to claim 1, characterized in that, The intake holes on the intake chamber (7) are evenly distributed axially in n1 planes, and n2 intake holes are evenly distributed along the circumferential direction in each plane. The working gas with a mass flow rate of m1 enters the interior tangentially through the n1×n2 intake holes on the intake chamber (7). Both n1 and n2 are positive integers.

4. A tubular arc plasma heating test device with jetting at both ends according to claim 3, characterized in that, The value range of n1 is 1 to 4, and the value range of n2 is 3 - 6.

5. A tubular arc plasma heating test device with jetting at both ends according to claim 1, characterized in that, The rear electrode insulating sheet (6) and the front electrode insulating sheet (8) are annular sheet structures with the same size, and the material is plastic or insulating ceramic material.

6. A tubular arc plasma heating test device with jetting at both ends according to claim 3, characterized in that, The inner diameters of the rear electrode (5) and the front electrode (9) are both d1, and the lengths are both L1. The ratio of the length L1 to the inner diameter d1 is: 4 ≤ L1 / d1 ≤ 8.

7. A tubular arc plasma heating test device with jetting at both ends according to claim 1, characterized in that, The rear magnetic field coil (4) and the front magnetic field coil (11) are helical copper coil structures wound uniformly. The current direction in the rear magnetic field coil (4) is the same as the rotation direction of the rotating air flow inside the rear electrode (5), and the current direction in the front magnetic field coil (11) is opposite to the rotation direction of the rotating air flow inside the front electrode (9).

8. A tubular arc plasma heating test device with jetting at both ends according to claim 6, characterized in that, The rear mixing chamber (3) and the front mixing chamber (12) have the same structure and size. The cone angles of the internal conical expansion section and the conical contraction section are α, the diameter of the straight section is d2, and n3 radial air inlet holes are arranged circumferentially uniformly in the cross-section at a distance L2 from the upstream end edge of the straight section. Gas with a mass flow rate of m2 enters uniformly through the n3 air inlet holes. A radial hole with a diameter of d3 for measuring the total pressure in the mixing chamber is arranged in the cross-section at a distance L3 from the downstream end edge of the straight section. n3 is a positive integer; The cone angle α and the diameter d2 satisfy: 30° ≤ α ≤ 60°, 2.5d1 ≤ d2 ≤ 4d1; the value range of n3 is 2 to 6, L2 ≤ 10 mm; the value range of the diameter d3 is 1 to 2 mm, L3 ≤ 5 mm.

9. A tubular arc plasma heating test device with jetting at both ends according to claim 8, characterized in that, The relationship between the gas mass flow rate m1 through the intake chamber (7) and the gas mass flow rate m2 through the mixing chamber is: h t ×m1 + 600×m2 / (m1 + 2×m2) = h0, Among them, h t is the empirical value of the tubular arc heating device, which is taken in the range of 5000 - 6000 kJ / kg, and h0 is the test design value, which is determined by the requirements of the heating test.

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