High-enthalpy plasma wind tunnel radiation heat flow measuring device

Abstract

The invention relates to the technical field of aircraft ground assessment tests, in particular to a high-enthalpy plasma wind tunnel radiation heat flux measuring device which comprises a shell, an inner sleeve and a thermocouple. A through hole is formed in the center of the shell along the axis, the lower end of the inner sleeve is inserted into the through hole, and the top and the inner wall of the shell are fixedly connected with the inner sleeve; a cooling water channel is arranged between the shell and the inner sleeve, the center of the inner sleeve is provided with a channel along the axis, the top of the channel is provided with an inner step, optical glass and a heat insulation sleeve are embedded in the channel from top to bottom, the top of the heat insulation sleeve is open, the bottom of the heat insulation sleeve is provided with a guide hole, and a probe core is embedded in the heat insulation sleeve; the thermocouple penetrates through the guide hole to be connected with the probe core and is used for measuring the temperature of the probe core. The device is easy to manufacture and convenient to install, the diameter and thickness of the probe core can be optimized according to the size of heat flow and the shape of a test model, and the device has high flexibility; and parts are convenient to replace, and repeated use is achieved.

Description

Technical Field

[0001] This invention relates to the field of aircraft ground testing technology, and in particular to a high-enthalpy plasma wind tunnel radiative heat flux measurement device. Background Technology

[0002] Hypersonic vehicles face aerodynamic heating during flight due to compression shock waves and gas friction. From the perspective of heat sources, this heating can be categorized into convective heating, chemical reaction heating, and radiative heating. The proportion and magnitude of each type of heat flux are related to flight conditions, vehicle shape, and material properties. For example, the thermal protection design of reentry vehicles for lunar exploration and interplanetary return must consider both convective and radiative heating.

[0003] High-enthalpy plasma wind tunnels, as core ground-based equipment for simulating such extreme thermal environments, can generate high-enthalpy, high-ionization plasma flow fields through methods such as arc discharge and induction heating. This accurately replicates the aerodynamic thermal environment during spacecraft reentry, making it a crucial platform for screening heat-resistant materials and verifying thermal protection schemes. Before ablation tests, the flow field needs to be calibrated, including airflow enthalpy, surface pressure, and cold-wall heat flux density. Currently, for cold-wall heat flux density, plug-type heat flux meters are mainly used to measure convective heat flux, neglecting the influence of radiative heat flux. However, to meet the needs of spacecraft development, the flow field calibration process requires accurate evaluation of the radiative heating heat flux of the arc flash and high-enthalpy flow field on the model to reasonably assess the thermal response of the test model.

[0004] In the flow field calibration process of a high-enthalpy plasma wind tunnel, it is usually necessary to first estimate the heater operating parameters based on the required test conditions, and then perform flow field calibration based on these parameters. During calibration, the heater is started, and after a certain period of time to establish a stable flow field, the calibration model equipped with heat flux or pressure sensors is sent into the flow field via a movable support. Once the support reaches the designated position and completes the parameter measurement within a short time, the heater stops operating. Then, based on the measurement results, the heater operating parameters are adjusted, and the above measurement process is repeated until all parameters meet the requirements. The entire measurement process, from the insertion of the support to the end of the measurement, takes approximately 2 seconds. During this process, the measuring device must possess characteristics such as high temperature resistance, moderate sensitivity, adjustable range, and reusability.

[0005] Therefore, a high-enthalpy plasma wind tunnel radiation heat flux measurement device is needed. Summary of the Invention

[0006] The purpose of this invention is to provide a high-enthalpy plasma wind tunnel radiation heat flux measurement device. This device can meet the requirements of the high-enthalpy plasma wind tunnel radiation heat flux measurement process and has the characteristics of moderate sensitivity, adjustable range, high temperature resistance, and reusability.

[0007] This invention provides a high-enthalpy plasma wind tunnel radiation heat flux measurement device, comprising a shell, an inner sleeve, and a thermocouple. The shell has a through hole along its central axis, and the lower end of the inner sleeve is inserted into the through hole. The top and inner wall of the shell are fixedly connected to the inner sleeve. A cooling water channel is provided between the shell and the inner sleeve. The inner sleeve has a channel along its central axis, and the top of the channel has an inner step. An optical glass and a heat insulation sleeve are embedded in the channel from top to bottom. The heat insulation sleeve has an open top and a guide hole at the bottom. A probe is embedded in the heat insulation sleeve. The lower part of the inner sleeve is threadedly connected to a fastening bolt, and the top of the fastening bolt abuts against the heat insulation sleeve. The thermocouple passes through the guide hole and is connected to the probe. The thermocouple is used to measure the temperature of the probe.

[0008] Preferably, the fastening bolt has a hollow structure inside, and the thermocouple passes through the hollow structure and the guide hole in sequence to connect to the probe core.

[0009] Preferably, the cooling water channel includes an inner ring and an outer ring, the tops of the inner ring and the outer ring are connected, the bottom of the outer ring is provided with a cooling water inlet, and the bottom of the inner ring is provided with a cooling water outlet. The preferred water cooling pressure is 1 MPa to 3 MPa.

[0010] Preferably, the top of the probe core is provided with a coating, which is a high-absorption ultra-black coating with a thickness of 0.1μm~1μm and a full-spectrum absorption rate of more than 95%.

[0011] Preferably, an air gap is provided between the coating and the optical glass.

[0012] Preferably, both the outer shell and the inner sleeve are made of a metal with high thermal conductivity, having a thermal conductivity greater than 250 W / (m•K).

[0013] Preferably, the optical glass has a melting point >1000℃ and a light transmission band within the range of 0.1μm to 14μm.

[0014] Preferably, the probe core is made of a material with high thermal conductivity, having a thermal conductivity greater than 250 W / (m•K).

[0015] Preferably, the heat insulation sleeve is made of heat insulation material with a thermal conductivity of less than 0.1 W / (m•K).

[0016] Preferably, the thermocouple is a nickel-chromium / nickel-silicon thermocouple. Preferably, its temperature measurement range is 1℃ to 1200℃, and its measurement accuracy is ≤0.4%.

[0017] Beneficial effects: The structure employed in this invention effectively isolates the convective heat flow of high-temperature gases. Through the nested structure of the outer shell and inner sleeve, a closed cooling water channel is formed between them. The circulating cooling water efficiently removes the heat generated during device operation, effectively preventing structural deformation or performance failure of the outer shell and inner sleeve due to the high temperature in the high-enthalpy plasma environment. Simultaneously, it provides a stable low-temperature operating environment for the core measuring components inside the inner sleeve, ensuring the continuity and reliability of the measurement process. The heat insulation sleeve further blocks the transfer of external high temperatures to the probe core, reducing the interference of ambient temperature on the probe core temperature measurement and ensuring that the probe core only receives heat from radiative heat flow, thus improving measurement accuracy. The water-cooled structure and the low thermal conductivity heat insulation sleeve reduce the heat conduction process between the calorimeter element and the outside, improving the accuracy of radiative heat flow measurement.

[0018] The present invention features a threaded connection between the lower part of the inner sleeve and the fastening bolt. By tightening the fastening bolt, the top of the bolt can be tightly pressed against the heat insulation sleeve, thereby axially fixing the optical glass, heat insulation sleeve, and probe core within the channel. This prevents displacement of the components under the impact of high enthalpy airflow and ensures the stability of the overall structure.

[0019] This invention is simple to manufacture and easy to install. Its probe diameter and thickness can be optimized according to the heat flow and the shape of the test model, which has great flexibility. Moreover, the parts are easy to replace, and it can be reused. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 for Figure 1 Enlarged schematic diagram of the structure at point A in the middle.

[0022] Explanation of reference numerals in the attached figures: 1-Outer shell, 2-Inner sleeve, 3-Fasting bolt, 4-Thermocouple, 5-Cooling water channel, 501-Cooling water inlet, 502-Cooling water outlet, 6-Optical glass, 7-Insulation sleeve, 8-Probe core, 9-Coating, 10-Guide hole. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] Example 1 like Figures 1-2 As shown, a high-enthalpy plasma wind tunnel radiation heat flux measurement device includes a shell 1, an inner sleeve 2, and a thermocouple 4. The shell 1 can fix and protect the internal components. The shell 1 has a through hole along the axis at its center. The top and inner wall of the shell 1 are fixedly connected to the T-shaped inner sleeve 2, which can be integrally formed by welding or 3D printing. The lower end of the inner sleeve 2 is inserted into the through hole. A cooling water channel 5 is provided between the shell 1 and the inner sleeve 2. The cooling water channel 5 includes an inner ring and an outer ring. The tops of the inner ring and the outer ring are connected. The bottom of the outer ring has a cooling water inlet 501, and the bottom of the inner ring has a cooling water outlet 502. The cooling water inlet 501 and the cooling water outlet 502 are arranged opposite to each other to ensure sufficient cooling water flow. The water cooling pressure is 1 MPa to 3 MPa.

[0027] The inner sleeve 2 has a channel along its central axis. The top of this channel has an inner step with a small circle diameter D1 at the top and a large circle diameter D2 at the bottom, satisfying D2 > D1 and D2 - D1 = 0.2mm~2mm. Optical glass 6 and a heat-insulating sleeve 7 are embedded inside the channel from top to bottom. The optical glass 6 has a melting point >1000℃, a light transmission range of 0.1μm~14μm, and a transmittance >0.95. Its material is preferably sapphire (Al2O3), magnesium fluoride (MgF2), or calcium fluoride (CaF2). The thickness of the optical glass 6 is 1mm~2mm. The optical glass 6 has good transmittance, allowing a large portion of the radiant heat generated by the gas to pass through it.

[0028] The optical glass 6 has a stepped shape and is embedded in the inner step of the inner sleeve 2. The upper small circle diameter D3 and the lower large circle diameter D4 of the step satisfy D3=D1 and D4≤D2, ensuring that there are no gaps between the optical glass 6 and the inner sleeve 2 after installation, preventing hot airflow from entering and ensuring its sealing effect; it also allows radiant heat to stably pass through the optical glass 6 and act on the probe core 8. The optical glass 6 and the inner sleeve 2 are installed and positioned by the inner step structure, ensuring that there are no protrusions on the end faces of either, so as not to interfere with supersonic flow, and at the same time ensuring that the optical glass 6 will not fall off under the action of airflow. At the same time, the cooling water channel 5 between the inner sleeve 2 and the outer shell 1 can cool the optical glass 6 and prevent it from failing due to high temperature.

[0029] The heat insulation sleeve 7 is embedded in the lower part of the inner step of the inner sleeve 2. The top of the heat insulation sleeve 7 is open, and the bottom has a guide hole 10. The thickness of each side wall is 0.5mm to 2mm. A probe core 8 is embedded inside the heat insulation sleeve 7. The probe core 8 is made of a high thermal conductivity material with a thermal conductivity greater than 250W / (m•K). The probe core 8 has a cylindrical structure, preferably with a diameter of 2mm to 7mm and a height-to-diameter ratio of 1 to 1.5. The top of the probe core 8 is covered with a coating 9, which is a high-absorption ultra-black coating with a thickness of 0.1μm to 1μm and a full-spectrum absorption rate greater than 95%. The ultra-black coating has a high absorption rate, and the radiant heat transmitted through the optical glass 6 can be almost completely absorbed. Due to the extremely thin thickness of the coating 9, the heat loss due to its own temperature rise can be ignored.

[0030] After installation, the top surface of the side wall of the heat insulation sleeve 7 is 0.1mm to 0.5mm higher than the top surface of the probe core 8, and it abuts against the bottom surface of the optical glass 6 to support the optical glass 6. An air gap is provided between the coating 9 and the optical glass 6 to block the heat conduction process between the optical glass 6 and the coating 9 and the probe core 8. The heat insulation sleeve 7 is made of heat insulation material with a thermal conductivity of less than 0.1W / (m•K) to prevent heat loss from the probe core 8 through heat conduction to the external environment.

[0031] The lower channel of the inner sleeve 2 is threadedly connected to the fastening bolt 3. The diameter of the lower channel of the inner sleeve 2 is larger than the diameter D2 of the lower large circle of the inner step of the inner sleeve 2. The top of the fastening bolt 3 abuts against the inner step and the bottom of the heat insulation sleeve 7, ensuring stable installation of the optical glass 6 and the heat insulation sleeve 7, while preventing excessive force from the fastening bolt 3 on the heat insulation sleeve 7. The fastening bolt 3 has a hollow structure inside to facilitate the passage of the thermocouple 4, preferably with a diameter of Φ2mm~Φ5mm. Thermocouple 4 passes through the hollow structure and the guide hole 10 in sequence to connect to the probe core 8. Thermocouple 4 is used to measure the temperature of the probe core 8 to calculate the magnitude of the radiative heat flux density. Thermocouple 4 is a nickel-chromium-nickel-silicon thermocouple with a temperature measurement range of 1℃~1200℃ and a measurement accuracy of ≤0.4%. Thermocouple 4 is connected to the bottom of the probe core 8 by welding or riveting to measure the temperature rise curve of the probe core 8. The magnitude of the radiative heat flux can be calculated by combining the solid thermal conductivity theory.

[0032] Both the outer shell 1 and the inner sleeve 2 are axisymmetric metal structures made of high thermal conductivity metal with a thermal conductivity greater than 250 W / (m•K).

[0033] After the above-mentioned parts are assembled using a nested structure, they are tightened and positioned by fastening bolts 3. The fastening screws are connected to the inner sleeve 2 by threads, avoiding the use of sealing rings, sealant, and other components or materials that are easily damaged at high temperatures. This facilitates parts replacement and allows for reusability. The fastening screws have a hollow structure, which allows the thermocouple 4 to pass through.

[0034] Work process: After the high-enthalpy plasma wind tunnel is started, the gas is heated to a very high temperature, and the gas flows through the Laval nozzle to form a supersonic high-enthalpy flow field. Once the flow field is fully established, the delivery mechanism carries the radiation heat flux measurement device of this invention into the flow field to measure the radiation heat flux generated by the high-enthalpy supersonic flow field.

[0035] The outer shell 1 and the inner sleeve 2 together form a deflector cooling water channel 5. During the measurement process, cooling water enters from the outer ring, deflects, and exits from the inner ring, thus cooling the main body of the device. Heat is conducted through the side wall of the outer shell 1 and then cooled by the cooling water, ensuring that the temperature of the measuring device body does not rise. At the same time, it cools the optical glass 6 to prevent it from failing due to high temperature.

[0036] The convective heat transfer of the high-temperature airflow is blocked by the optical glass 6, while the radiative heat passes through the optical glass 6 and can be almost completely absorbed by the coating 9. By setting an air gap between the optical glass 6 and the coating 9, the heat conduction process between the glass and the coating 9 is avoided.

[0037] The coating 9 heats up due to radiant heat flow, causing the core 8 to heat up as well. The core 8 is made of a highly thermally conductive material, and its temperature rise curve is obtained via thermocouple 4 at its bottom. By estimating the magnitude of the radiant heat flow, the diameter and height of the core 8 can be designed to improve testing accuracy. The insulation sleeve 7 isolates the heat transfer process between the core 8 and the inner sleeve 2.

[0038] The temperature rise curve of probe 8 is measured by thermocouple 4, and the magnitude of radiative heat flow can be calculated by combining the theory of solid thermal conductivity.

[0039] 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-enthalpy plasma wind tunnel radiative heat flux measurement device, characterized in that, The device includes an outer shell, an inner sleeve, and a thermocouple. The outer shell has a through hole along its center axis, and the lower end of the inner sleeve is inserted into the through hole. The top and inner wall of the outer shell are fixedly connected to the inner sleeve. A cooling water channel is provided between the outer shell and the inner sleeve. The inner sleeve has a channel along its center axis, and the top of the channel has an inner step. An optical glass and a heat insulation sleeve are embedded in the channel from top to bottom. The heat insulation sleeve has an open top and a guide hole at the bottom. A probe is embedded in the heat insulation sleeve. The lower part of the inner sleeve is threadedly connected to a fastening bolt, and the top of the fastening bolt abuts against the heat insulation sleeve. The thermocouple passes through the guide hole and is connected to the probe. The thermocouple is used to measure the temperature of the probe.

2. The high-enthalpy plasma wind tunnel radiative heat flux measuring device according to claim 1, characterized in that, The fastening bolt has a hollow structure inside, and the thermocouple passes through the hollow structure and the guide hole to connect to the probe core.

3. The high-enthalpy plasma wind tunnel radiative heat flux measuring device according to claim 1, characterized in that, The cooling water channel includes an inner ring and an outer ring, the tops of the inner ring and the outer ring are connected, the bottom of the outer ring is provided with a cooling water inlet, and the bottom of the inner ring is provided with a cooling water outlet.

4. The high-enthalpy plasma wind tunnel radiative heat flux measuring device according to claim 1, characterized in that, The probe core is coated with a high-absorption-rate ultra-black coating with a full-spectrum absorption rate of more than 95%.

5. The high-enthalpy plasma wind tunnel radiative heat flux measuring device according to claim 4, characterized in that, An air gap is provided between the coating and the optical glass.

6. The high-enthalpy plasma wind tunnel radiative heat flux measuring device according to claim 1, characterized in that, Both the outer shell and the inner sleeve are made of a metal with high thermal conductivity, with a thermal conductivity greater than 250 W / (m•K).

7. The high-enthalpy plasma wind tunnel radiative heat flux measuring device according to claim 1, characterized in that, The optical glass has a melting point >1000℃ and a light transmission band within the range of 0.1μm~14μm.

8. The high-enthalpy plasma wind tunnel radiative heat flux measuring device according to claim 1, characterized in that, The probe core is made of a high thermal conductivity material with a thermal conductivity greater than 250 W / (m•K).

9. The high-enthalpy plasma wind tunnel radiative heat flux measuring device according to claim 1, characterized in that, The heat insulation sleeve is made of heat insulation material with a thermal conductivity of less than 0.1 W / (m•K).

10. The high-enthalpy plasma wind tunnel radiative heat flux measuring device according to claim 1, characterized in that, The thermocouple is a nickel-chromium / nickel-silicon thermocouple.

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