High power arc heater with porous inner wall and method of processing and testing thereof

Abstract

The application belongs to the technical field of hypersonic vehicle aerodynamic heat protection ground test equipment, and discloses a high-power arc heater with a porous inner wall and a processing and test method thereof. The high-power arc heater with the porous inner wall comprises a cathode section, a porous inner wall section, an anode section and a nozzle section connected in sequence from front to back. The cathode section, the anode section and the nozzle section are all provided with cooling structures, and the cooling structures are connected with a cooling water source. The front-to-back through center cavities of the cathode section, the porous inner wall section and the anode section are arc chambers of the arc heater. The porous inner wall section is a specially-made porous inner wall. The tube wall of the porous inner wall is distributed with a plurality of radial slender holes which grow along the radial direction and pass through the tube wall of the porous inner wall from inside to outside. The high-power arc heater with the porous inner wall and the processing and test method thereof can improve the thermal efficiency of the high-power arc heater, improve the gas flow temperature at the outlet of the nozzle of the high-power arc heater, and provide support for the heat protection research of the hypersonic vehicle.

Description

Technical Field

[0001] This invention belongs to the technical field of aerodynamic heat-resistant ground test equipment for hypersonic aircraft, specifically relating to a high-power electric arc heater with a porous inner wall and its processing and testing methods. Background Technology

[0002] High-power arc heaters can realistically simulate the thermal environment of hypersonic vehicles on the ground for extended periods, making them a core component in hypersonic vehicle thermal protection research. The high-power arc heater creates an electric arc between two electrodes to heat the air. The heated, high-temperature air is then ejected from the nozzle, forming high-temperature, high-speed air that creates the thermal environment of the hypersonic vehicle.

[0003] As the flight speed of hypersonic vehicles increases, the friction between the hypersonic vehicle and the air increases, and the temperature of the incoming thermal environment of the hypersonic vehicle becomes higher and higher. High-power arc heaters are needed to provide airflow at higher temperatures to simulate the thermal environment of hypersonic vehicles.

[0004] Existing high-power arc heaters are divided into tubular arc heaters and plate arc heaters. Both types are long-axis shaped, with the arc located at the central axis. As the length of the central axis increases, the arc becomes longer, and the power of the arc heater increases. However, with the increase in the length of the central axis, the cooling area of ​​the arc heater also increases, making it difficult to raise the air temperature. It is also possible to increase the power of the arc heater and thus increase the outlet airflow temperature of the arc heater nozzle by increasing the current without increasing the cooling area; however, as the arc heater current increases, electrode erosion also increases rapidly. Existing high-power arc heaters already operate at currents of 3000A to 6000A. If the current is further increased, the electrodes of high-power arc heaters will rapidly erode and fail, failing to meet the requirements for ground testing of hypersonic vehicles.

[0005] Therefore, how to increase the nozzle exit temperature of a high-power electric arc heater to meet the thermal environment requirements of hypersonic vehicles is a current technical challenge. Currently, there is an urgent need to develop a high-power electric arc heater with a porous inner wall and its fabrication and testing methods. Summary of the Invention

[0006] The first technical problem to be solved by the present invention is to provide a high-power arc heater with a porous inner wall. The second technical problem to be solved by the present invention is to provide a test method for a high-power arc heater with a porous inner wall. The third technical problem to be solved by the present invention is to provide a porous inner wall for a high-power arc heater. The fourth technical problem to be solved by the present invention is to provide a porous inner wall processing apparatus for a high-power arc heater. The fifth technical problem to be solved by the present invention is to provide a porous inner wall processing method for a high-power arc heater.

[0007] The present invention relates to a high-power arc heater with a porous inner wall, characterized in that the high-power arc heater is a tubular structure with a closed front end and an open rear end, comprising a cathode section, a porous inner wall section, an anode section, and a nozzle section connected sequentially from front to back; the cathode section and the porous inner wall section, the porous inner wall section and the anode section are insulated and sealed together, and the anode section and the nozzle section are sealed together; the cathode section, the anode section, and the nozzle section are all provided with cooling structures, and the cooling structures are connected to an external cooling water source; the central cavity through which the cathode section, the porous inner wall section, and the anode section pass is the arc chamber of the arc heater; The front end of the cathode section is sealed with a cap; the inner wall of the cathode section is provided with an annular cathode, the outer wall of the cathode section is fitted with an annular magnetic field coil, and the outer wall of the cathode section is also provided with a cathode end head connected to the cathode. The porous inner wall section is provided with a porous inner wall, and a cold air inlet connected to an external cold air source is opened on the porous inner wall section. The inner wall of the anode section is provided with an annular anode, the outer wall of the anode section is fitted with an annular magnetic field coil, and the outer wall of the anode section is also provided with an anode end connected to the anode. The nozzle section is equipped with nozzles.

[0008] Furthermore, the magnetic field coil is coaxial with the cathode and anode; The magnetic field coil of the cathode section is connected in series between the cathode end and the cathode, and the magnetic field coil of the anode section is connected in series between the anode end and the anode; or the magnetic field coil is powered separately. The magnetic field coil generates magnetic induction intensity, causing the electric arc to rotate at high speed on the inner walls of the cathode and anode. The magnetic force exerted on the electric arc by the magnetic field is equal to the resistance of the airflow in the arc chamber of the electric arc heater.

[0009] The test method for a high-power electric arc heater with a porous inner wall according to the present invention is characterized by comprising the following steps: S10. Deionized cooling water is introduced into the cooling structures of the cathode section, anode section and nozzle section; S11. Cold air flow is introduced into the cold air inlet of the porous inner wall section; S12. An electric arc is established between the cathode and the anode by means of contact arc ignition or high-frequency arc ignition; S13. The cold air flow velocity is controlled between 1m / s and 30m / s. The electric arc heats the cold air flow that flows into the porous inner wall to obtain hot air flow. The hot air flow is ejected from the nozzle and exits as nozzle outlet airflow. The nozzle outlet airflow simulates the thermal environment of a hypersonic vehicle.

[0010] The porous inner wall of the present invention for a high-power electric arc heater is characterized in that the porous inner wall is a circular tube, and the tube wall of the porous inner wall has a plurality of radially growing, reflective elongated holes that penetrate the tube wall from the inside to the outside. The angle between the axis of the elongated holes of the porous inner wall and the cross-section of the porous inner wall at the outlet is in the range of 80°~90°. The diameter of the elongated pores in the porous inner wall 0.05-0.5mm, porosity The length of the elongated pores in the porous inner wall is 5%-30%. Based on the nozzle exit gas temperature Confirmed, nozzle exit gas temperature The higher the diameter, the longer the length of the slender hole. The longer it is, the more it satisfies the following formula: ; in, The radiation coefficient of the porous inner wall is given. The Stephen-Polhertz constant is 5.67 × 10⁻⁶. -8 W / (m 2 K 4 ), The heat exchange coefficient between the cold airflow and the porous inner wall. This represents the temperature difference between the cold air entering from the outer wall of the porous inner wall and the air exiting from the inner wall of the porous inner wall; the heat flux density of the porous inner wall surface is in the range of 2 MW / m². 2 ~20MW / m 2 ; The porous inner wall is made of high thermal conductivity materials, including copper and silver.

[0011] The present invention relates to a porous inner wall processing device for a high-power electric arc heater, characterized in that the porous inner wall processing device includes a crucible with a closed bottom surface and an insulation layer wrapped around the outer wall of the crucible; below the crucible, from top to bottom, are a temperature control layer and a tray, and a cooling water channel is provided in the tray, which is connected to a cooling water source; molten metal for making a porous inner wall is injected into the annular cavity inside the crucible. The crucible in question is a graphite crucible.

[0012] The method for processing the porous inner wall of a high-power electric arc heater according to the present invention is characterized by comprising the following steps: S21. High thermal conductivity material is heated and melted into molten metal in high-pressure gas; S22. Pour the molten metal into the crucible; S23. Controlling the radial growth rate of slender pores during the cooling of molten metal into a porous inner wall through an insulation layer; S24. By controlling the flow rate and temperature of cooling water in the temperature control layer and cooling water channel, the axial growth rate of the slender holes is controlled during the process of the molten metal cooling into a porous inner wall. S25. After the molten metal is cooled, a porous inner wall blank is obtained; S26. Machining the porous inner wall blank to obtain the desired porous inner wall; S27. Install the porous inner wall into the high-power electric arc heater and perform assembly and adjustment until the installation requirements are met. The porous inner wall processing is now complete.

[0013] Furthermore, the high-pressure gas has high solubility in liquid metal but low solubility in solid metal; the high-pressure gas is selected according to the porous inner wall material, and the high-pressure gas is one of high-pressure argon, high-pressure nitrogen or high-pressure hydrogen; the pressure range of the high-pressure gas is 2MPa~50MPa.

[0014] The high-power arc heater with a porous inner wall and its processing and testing method of the present invention replace the traditional copper inner wall with a porous inner wall. With a traditional copper inner wall, the high-power arc heater loses approximately 50% of its energy due to convective heat transfer, resulting in a thermal efficiency of about 50% and a low nozzle outlet gas temperature. However, with a porous inner wall, an air film forms, blocking convective heat transfer and increasing the thermal efficiency of the high-power arc heater to over 95%, thereby increasing the nozzle outlet gas temperature.

[0015] The present invention relates to a high-power arc heater with a porous inner wall and its processing and testing methods, specifically the porous inner wall processing apparatus and method. Through controlled solidification, a porous inner wall that cannot be machined by mechanical means is obtained. The elongated pores of the porous inner wall are smooth, have low flow resistance, and are uniformly distributed along a specific direction, which is beneficial for controlling the flow rate and pressure of the injected cold air. Even a small amount of cold air injected from the outside at a low pressure can form a cold air flow in a certain direction on the porous inner wall surface. Furthermore, the porous inner wall is made of a high thermal conductivity metal, which can timely and uniformly distribute heat across the entire porous inner wall. Due to the very small diameter of the elongated pores, the heat exchange area between the cold air flow and the porous inner wall is greatly increased, ensuring that the cold air flow can carry away the heat from the porous inner wall. Moreover, by controlling the length of the elongated pores, a balance between the cooling heat of the cold air flow and the heat radiation can be achieved, ensuring the long-term safe and stable operation of the porous inner wall. The high thermal conductivity metal used to create the porous inner wall dissolves into a liquid metal under high pressure. The selection principle for the high-pressure gas is: high solubility in liquid metals and low solubility in solid metals, such as argon, nitrogen, and hydrogen. The porous inner wall can withstand 2MW / m 2 ~20MW / m 2 The wall heat flux density plays a crucial role in increasing the outlet gas temperature of the nozzle of the high-power electric arc heater.

[0016] In summary, the high-power arc heater with porous inner wall and its processing and testing methods of the present invention can improve the thermal efficiency of high-power arc heaters and increase the outlet gas temperature of high-power arc heater nozzles, which has engineering practicality and provides equipment support for the development of hypersonic aircraft. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the high-power electric arc heater with a porous inner wall according to the present invention; Figure 1 In the middle section, 1. Cathode end; 2. Cathode; 3. Porous inner wall; 4. Cold air inlet; 5. Magnetic field coil; 6. Anode end; 7. Anode; 8. Nozzle; 9. Nozzle outlet airflow; 10. Arc heater arc chamber; 11. Arc; 12. End cap; Figure 2 This is a schematic diagram of the porous inner wall processing device for a high-power electric arc heater according to the present invention; Figure 2 In the middle, 31. Insulation layer; 32. Crucible; 33. Molten metal; 34. Temperature control layer; 35. Cooling water channel; 36. Tray; Figure 3 This is a microscope image of the porous inner wall of the high-power arc heater of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] Example 1: like Figure 1 As shown, the high-power electric arc heater with a porous inner wall of the present invention is a tubular structure with a closed front end and an open rear end, including a cathode section, a porous inner wall section, an anode section and a nozzle section connected sequentially from front to back; the cathode section and the porous inner wall section, the porous inner wall section and the anode section are insulated and sealed, and the anode section and the nozzle section are sealed; the cathode section, the anode section and the nozzle section are all provided with cooling structures, and the cooling structures are connected to an external cooling water source; the central cavity through the cathode section, the porous inner wall section and the anode section is the arc chamber 10 of the electric arc heater; The front end cap 12 of the cathode section is closed; the inner wall of the cathode section is provided with an annular cathode 2, the outer wall of the cathode section is fitted with an annular magnetic field coil 5, and the outer wall of the cathode section is also provided with a cathode end head 1 connected to the cathode 2. The porous inner wall section is provided with a porous inner wall 3, and a cold air inlet 4 is opened on the porous inner wall section to connect with an external cold air source; The inner wall of the anode section is provided with an annular anode 7, the outer wall of the anode section is fitted with an annular magnetic field coil 5, and the outer wall of the anode section is also provided with an anode end 6 connected to the anode 7. The nozzle section is equipped with nozzle 8.

[0020] Furthermore, the magnetic field coil 5 is coaxial with the cathode 2 and the anode 7; The magnetic field coil 5 of the cathode section is connected in series between the cathode end 1 and the cathode 2, and the magnetic field coil 5 of the anode section is connected in series between the anode end 6 and the anode 7; or the magnetic field coil 5 is powered separately. The magnetic field coil 5 generates magnetic induction intensity, causing the electric arc 11 to rotate at high speed on the inner walls of the cathode 2 and anode 7. The magnetic force on the electric arc 11 is equal to the resistance of the airflow in the arc chamber of the electric arc heater.

[0021] The test method for a high-power electric arc heater with a porous inner wall according to the present invention includes the following steps: S10. Deionized cooling water is introduced into the cooling structures of the cathode section, anode section and nozzle section; S11. Cold air flow is introduced into the cold air inlet 4 of the porous inner wall section; S12. An electric arc 11 is established between the cathode 2 and the anode 7 by means of contact arc ignition or high-frequency arc ignition; S13. The cold air flow velocity is controlled between 1m / s and 30m / s. The electric arc 11 heats the cold air flow that flows in from the porous inner wall 3 to obtain hot air flow. The hot air flow is ejected from the nozzle 8 and exits as nozzle outlet airflow 9. Nozzle outlet airflow 9 simulates the thermal environment of a hypersonic vehicle.

[0022] The porous inner wall of the present invention for a high-power electric arc heater is characterized in that the porous inner wall 3 is a circular tube, and the tube wall of the porous inner wall 3 is distributed with a number of radially growing, reflective slender holes that penetrate the tube wall of the porous inner wall 3 from the inside to the outside. The angle between the axis of the slender holes of the porous inner wall 3 and the cross-section of the porous inner wall 3 at the outlet is in the range of 80°~90°. The diameter of the elongated holes in the porous inner wall 3 0.05-0.5mm, porosity The length of the elongated pores in the porous inner wall 3 is 5%-30%. Based on the nozzle exit gas temperature Confirmed, nozzle exit gas temperature The higher the diameter, the longer the length of the slender hole. The longer it is, the more it satisfies the following formula: ; in, The radiation coefficient of the porous inner wall 3 is given. The Stephen-Polhertz constant is 5.67 × 10⁻⁶. -8 W / (m 2 K 4 ), The heat exchange coefficient between the cold airflow and the porous inner wall 3 is given. The temperature difference is the temperature difference between the cold air entering from the outer wall of the porous inner wall 3 and the cold air exiting from the inner wall of the porous inner wall 3; the heat flux density of the wall surface of the porous inner wall 3 ranges from 2MW / m³. 2 ~20MW / m 2 ; The porous inner wall 3 is made of high thermal conductivity materials, including copper and silver.

[0023] like Figure 2 As shown, the porous inner wall processing device for a high-power electric arc heater of the present invention includes a crucible 32 with a closed bottom surface, and an insulation layer 31 covering the outer wall of the crucible 32; below the crucible 32, from top to bottom, are a temperature control layer 34 and a tray 36, and a cooling water channel 35 is provided in the tray 36, which is connected to a cooling water source; molten metal 33 for making the porous inner wall 3 is injected into the annular cavity inside the crucible 32. The crucible 32 is a graphite crucible.

[0024] The present invention provides a method for processing the porous inner wall of a high-power arc heater, comprising the following steps: S21. The high thermal conductivity material is heated and melted into a liquid metal in a high-pressure gas 33; S22. Pour the molten metal 33 into the crucible 32; S23. The radial growth rate of the elongated pores is controlled by the insulation layer 31 during the cooling of the molten metal 33 into a porous inner wall 3. S24. By controlling the flow rate and temperature of the cooling water in the temperature control layer 34 and the cooling water channel 35, the axial growth rate of the slender holes is controlled during the process of the molten metal 33 being cooled into the porous inner wall 3. S25. After the molten metal 33 is cooled, a porous inner wall blank is obtained; S26. Machining the porous inner wall blank to obtain the following: Figure 3 The required porous inner wall 3 is shown; S27. Install the porous inner wall 3 into the high-power electric arc heater and perform assembly and adjustment until the installation requirements are met. The porous inner wall 3 is now complete.

[0025] Furthermore, the high-pressure gas has high solubility in the liquid metal 33, but low solubility in the solid metal; the high-pressure gas is selected according to the material of the porous inner wall 3, and the high-pressure gas is one of high-pressure argon, high-pressure nitrogen or high-pressure hydrogen; the pressure range of the high-pressure gas is 2MPa~50MPa.

[0026] In this embodiment, the high-pressure gas is high-pressure hydrogen, with a pressure range of 2MPa to 8MPa, and the high thermal conductivity material is pure copper.

[0027] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-power electric arc heater with a porous inner wall, characterized in that, The high-power electric arc heater is a tubular structure with a closed front end and an open rear end, including a cathode section, a porous inner wall section, an anode section, and a nozzle section connected sequentially from front to back; the cathode section and the porous inner wall section, the porous inner wall section and the anode section are insulated and sealed, and the anode section and the nozzle section are sealed; the cathode section, the anode section and the nozzle section are all equipped with cooling structures, and the cooling structures are connected to an external cooling water source; the central cavity through the cathode section, the porous inner wall section and the anode section is the arc chamber (10) of the electric arc heater. The front end cap (12) of the cathode section is closed; the inner wall of the cathode section is provided with an annular cathode (2), the outer wall of the cathode section is fitted with an annular magnetic field coil (5), and the outer wall of the cathode section is also provided with a cathode end head (1) connected to the cathode (2). The porous inner wall section is provided with a porous inner wall (3), and a cold air inlet (4) is opened on the porous inner wall section to connect with an external cold air source. The porous inner wall (3) is a round tube. The tube wall of the porous inner wall (3) has several radially growing, reflective slender holes that penetrate the tube wall of the porous inner wall (3) from the inside to the outside. The angle between the axis of the slender holes of the porous inner wall (3) and the cross-section of the porous inner wall (3) at the outlet is 80°~90°. The pore diameter of the elongated pores in the porous inner wall (3) 0.05-0.5mm, porosity The length of the slender holes in the porous inner wall (3) is 5%-30%. Based on the nozzle exit gas temperature Confirmed, nozzle exit gas temperature The higher the diameter, the longer the length of the slender hole. The longer it is, the more it satisfies the following formula: ； in, The radiation coefficient of the porous inner wall (3) is given. The Stephen-Polhertz constant is 5.67 × 10⁻⁶. -8 W / (m 2 K 4 ), The heat exchange coefficient between the cold airflow and the porous inner wall (3) is the coefficient of heat exchange. The temperature difference between the cold air entering from the outer wall of the porous inner wall (3) and exiting from the inner wall of the porous inner wall (3); the heat flux density of the wall surface of the porous inner wall (3) is in the range of 2MW / m. 2 ~20MW / m 2 ; The porous inner wall (3) is made of a high thermal conductivity material, including copper and silver. The inner wall of the anode section is provided with an annular anode (7), the outer wall of the anode section is fitted with an annular magnetic field coil (5), and the outer wall of the anode section is also provided with an anode end (6) connected to the anode (7). The nozzle section is equipped with a nozzle (8).

2. The high-power arc heater with a porous inner wall according to claim 1, characterized in that, The magnetic field coil (5) is coaxial with the cathode (2) and the anode (7); The magnetic field coil (5) of the cathode section is connected in series between the cathode end (1) and the cathode (2), and the magnetic field coil (5) of the anode section is connected in series between the anode end (6) and the anode (7); or the magnetic field coil (5) is powered separately. The magnetic field coil (5) generates magnetic induction intensity, causing the electric arc (11) to rotate at high speed on the inner walls of the cathode (2) and anode (7). The magnetic force of the electric arc (11) is equal to the resistance of the airflow in the arc chamber of the electric arc heater.

3. A test method for a high-power arc heater with a porous inner wall, used for the high-power arc heater with a porous inner wall as described in claim 1 or 2, characterized in that, Includes the following steps: S10. Deionized cooling water is introduced into the cooling structures of the cathode section, anode section and nozzle section; S11. Cold air flow is introduced into the cold air inlet (4) of the porous inner wall section; S12. An electric arc (11) is established between the cathode (2) and the anode (7) by means of contact arc ignition or high-frequency arc ignition. S13. The cold air flow velocity is controlled at 1m / s~30m / s. The electric arc (11) heats the cold air flow that flows in from the porous inner wall (3) to obtain hot air flow. The hot air flow is ejected from the nozzle (8) and the nozzle outlet air flow (9) simulates the thermal environment of the hypersonic vehicle.

4. A porous inner wall processing apparatus for processing the porous inner wall of a high-power electric arc heater as described in claim 1 or 2, characterized in that, The porous inner wall processing device includes a crucible (32) with a closed bottom surface, and an insulation layer (31) covering the outer wall of the crucible (32); below the crucible (32) from top to bottom are a temperature control layer (34) and a tray (36), and a cooling water channel (35) is provided in the tray (36), and the cooling water channel (35) is connected to a cooling water source; molten metal (33) for making porous inner wall (3) is injected into the annular cavity inside the crucible (32); The crucible (32) is a graphite crucible.

5. A method for processing the porous inner wall of a high-power electric arc heater, wherein the method is used to process the porous inner wall of a high-power electric arc heater as described in claim 1 or 2, characterized in that, The porous inner wall processing method includes the following steps: S21. The high thermal conductivity material is heated and melted into a liquid metal in a high-pressure gas (33). S22. Pour the molten metal (33) into the crucible (32); S23. Controlling the radial growth rate of the elongated pores during the process of cooling the molten metal (33) into a porous inner wall (3) through the insulation layer (31); S24. By controlling the flow rate and temperature of cooling water in the temperature control layer (34) and cooling water channel (35), the axial growth rate of the slender holes is controlled during the process of cooling the molten metal (33) into a porous inner wall (3). S25. After the molten metal (33) is cooled, a porous inner wall blank is obtained; S26. Machining the porous inner wall blank to obtain the required porous inner wall (3); S27. Install the porous inner wall (3) into the high-power electric arc heater and perform assembly and adjustment until the installation requirements are met. The porous inner wall (3) is then processed.

6. The method for processing the porous inner wall of a high-power arc heater according to claim 5, characterized in that, The high-pressure gas has high solubility in liquid metal (33) but low solubility in solid metal; the high-pressure gas is selected according to the material of the porous inner wall (3), and the high-pressure gas is one of high-pressure argon, high-pressure nitrogen or high-pressure hydrogen; the pressure range of the high-pressure gas is 2MPa~50MPa.

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