A convective heat flux calibration device and calibration method

Abstract

The present invention discloses a convective heat flux calibration device and a calibration method. The device includes an air compressor air source, a regulating valve, an electric heater, a stabilization section, and a test section that are connected in sequence. The pure air flow generated by the air compressor air source is heated by the electric heater and then enters the stabilization section for rectification, and then enters the test section for acceleration. The test section includes a nozzle, a reference plate, a calibration plate, a shielding radiation source, and a thin-film thermocouple. The reference plate and the calibration plate have exactly the same external dimensions and are symmetrically located on both sides of the nozzle outlet. The shielding radiation source is located at the central position inside the nozzle, and the thin-film thermocouple is plated on the surface of the shielding radiation source. Two thin-film platinum resistors are symmetrically plated at the center of the reference plate as reference platinum resistors, and the heat flux meter to be calibrated is installed at the center of the calibration plate, and thin-film platinum resistors are plated around the heat flux meter to be calibrated. The present invention can provide a uniform and stable heat flux field that can be continuously adjusted within a certain working condition range, and can be used for the calibration or verification of convective heat flux meters.

Description

Technical Field

[0001] The present invention belongs to the technical field of air flow temperature measurement, and particularly relates to a convective heat flux calibration device and a calibration method. Background Art

[0002] During the high Mach number flight and reentry process of aerospace vehicles, accompanied by strong aerodynamic effects, a boundary layer with extremely high temperature is formed on the surface of the vehicle. The fluid in the boundary layer transfers high-temperature heat to the vehicle surface in the form of strong convective heat transfer, forming an extreme high-temperature thermal environment, which poses a severe test to the safety and reliability of the vehicle and increases the difficulty of realizing the design and development of the vehicle. Convective heat flux density (referred to as convective heat flux for short) is one of the most critical parameters in aerodynamic thermal parameters. When an aerospace plane reenters, the convective heat flux borne by its fuselage flaps, elevons, etc. can reach 30 W / cm2 or even higher. As an important technical basis for research such as aerodynamic heat theory research, thermal protection safety design, and engineering test verification, the convective heat flux density calibration technology is of great significance to the development of aerospace technology.

[0003] Currently, there is no research on convective heat flux calibration in China. There is no established convective heat flux measurement standard device, and there is also a lack of corresponding calibration methods. Only the measurement and calibration of radiant heat flux can be achieved for heat flux meters, and the calibration method of radiant heat flux is also used when calibrating heat flux meters, resulting in the calibration results being unable to truly reflect the measurement characteristics of heat flux meters. Therefore, it is urgent to establish a convective heat flux measurement standard device and study the convective heat flux calibration method. Summary of the Invention

[0004] The purpose of the present invention is to provide a convective heat flux calibration device and a calibration method, which can provide a uniform and stable heat flux field that can be continuously adjusted within a certain working condition range and can be used for the calibration or verification of convective heat flux meters.

[0005] To achieve the above purpose, one aspect of the present invention provides a convective heat flux calibration device, including an air compressor air source, a regulating valve, an electric heater, a stabilization section, and a test section connected in sequence. The pure air flow generated by the air compressor air source is heated by the electric heater and then enters the stabilization section for rectification, and then enters the test section for acceleration. The Mach number is adjusted through the regulating valve;

[0006] The test section includes a nozzle, a fast-response displacement mechanism, a reference plate, a calibration plate, a shielding radiation source, and a thin-film thermocouple. The reference plate and the calibration plate have exactly the same external dimensions, are installed on the fast-response displacement mechanism, are symmetrically located on both sides of the nozzle outlet, the center heights of the reference plate and the calibration plate are the same as the center height of the nozzle outlet, and the horizontal distance from the nozzle outlet is 1 - 2D, where D is the diameter of the calibration plate. The shielding radiation source is located at the center position inside the nozzle, and the thin-film thermocouple is plated on the surface of the shielding radiation source. The fast-response displacement mechanism is used to achieve the rapid position replacement of the reference plate and the calibration plate;

[0007] Two thin-film platinum resistors are symmetrically plated at the center of the reference plate as reference platinum resistors. The size of the sensing part of each reference platinum resistor is the same as that of the sensing part of the heat flux meter to be calibrated. The heat flux meter to be calibrated is installed at the center of the calibration plate, and thin-film platinum resistors are plated around the heat flux meter to be calibrated for calculating the surface temperature of the heat flux meter to be calibrated.

[0008] Preferably, the reference plate is made of the same material as the sensing part of the heat flux meter to be calibrated, and the calibration plate is made of a material with a low thermal conductivity and a large specific heat capacity.

[0009] Preferably, an insulating layer is first plated on the surface of the reference plate, then two thin-film platinum resistors are symmetrically plated at the center as reference platinum resistors, the distance between the two reference platinum resistors does not exceed 1 mm, and finally, a high-emissivity coating is applied to the surface of the reference plate to ensure that the surface emissivity is close to 1.

[0010] Preferably, an insulating layer and a thin-film thermocouple are successively plated on the surface of the shielding radiation source, and then a high-emissivity coating is applied to the surface to ensure that the surface emissivity is close to 1.

[0011] Preferably, the reference plate is made of constantan, and the calibration plate is made of aerogel ceramics.

[0012] Preferably, the single-action time of the fast-response displacement mechanism does not exceed 50 ms.

[0013] Preferably, the test section further includes a support rod, and the shielding radiation source is fixed at the center position inside the nozzle through the support rod.

[0014] Preferably, the test section further includes a mounting seat for the heat flux meter to be calibrated, and the heat flux meter to be calibrated is installed at the center of the calibration plate through the mounting seat for the heat flux meter to be calibrated.

[0015] Another aspect of the present invention provides a convective heat flux calibration method, which uses the above-mentioned convective heat flux calibration device for convective heat flux calibration, including:

[0016] The reference flat plate and the flat plate to be calibrated respectively receive the transient thermal shock of the air flow through a fast-response displacement mechanism. The total heat flux is calculated based on the temperature history of the reference platinum resistor on the reference flat plate. Heat is radiated to the reference flat plate by a shielded radiation source and the radiative heat flux is calculated. The convective heat flux of the reference flat plate is obtained by subtracting the radiative heat flux from the total heat flux. The convective heat transfer coefficient and the adiabatic wall temperature are calculated based on the values of the convective heat flux and the radiative heat flux of the reference flat plate at different times and are assigned to the calibration flat plate. Then, the convective heat flux is calculated based on the calculated convective heat transfer coefficient, the adiabatic wall temperature, and the measured surface temperature of the calibration flat plate, which is used as the standard value of the convective heat flux of the calibration flat plate.

[0017] Measure the surface temperatures of the shielded radiation source and the calibration flat plate, calculate the radiative heat flux of the calibration flat plate, subtract the ratio of the radiative heat flux of the calibration flat plate to the radiative heat flux sensitivity coefficient from the output voltage of the heat flux meter to be calibrated, obtain the voltage corresponding to the convective heat flux, and divide the standard value of the convective heat flux by this voltage to obtain the convective heat flux sensitivity coefficient.

[0018] According to the convective heat flux calibration device and calibration method of the above aspects of the present invention, a uniform and stable heat flux field that can be continuously adjusted within a certain operating condition range can be provided, and it can be used for the calibration or verification of convective heat flux meters. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts:

[0020] Figure 1 is a schematic diagram of the overall structure of a convective heat flux calibration device according to an embodiment of the present invention;

[0021] Figure 2 is a schematic diagram of the rear section structure of a test section according to an embodiment of the present invention;

[0022] Figure 3 is a schematic diagram of the front section structure of a test section according to an embodiment of the present invention;

[0023] Figure 4 is a flowchart of a convective heat flux calibration method according to an embodiment of the present invention.

[0024] Among them, 1 - air compressor air source, 2 - regulating valve, 3 - electric heater, 4 - stable section, 5 - test section, 6 - thin-film platinum resistor, 7 - calibration flat plate, 8 - mounting seat for heat flux meter to be calibrated, 9 - fast-response displacement mechanism, 10 - reference platinum resistor, 11 - reference flat plate, 12 - nozzle, 13 - shielded radiation source, 14 - thin-film thermocouple, 15 - support rod. DETAILED DESCRIPTION OF THE INVENTION

[0025] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0026] An embodiment of the present invention provides a convective heat flux calibration device, as Figure 1 shown. The convective heat flux calibration device according to the embodiment of the present invention includes an air compressor air source 1, a regulating valve 2, an electric heater 3, a stabilization section 4, and a test section 5, which are connected in sequence. The air compressor air source 1 generates pure air flow, which is heated by the electric heater 3 and then enters the stabilization section 4 for rectification, and then enters the nozzle section of the test section 5 for acceleration. The Mach number is adjusted through the regulating valve 2, and the high-temperature air flow blows the reference plate and the calibration plate at the test section 5 respectively to achieve convective heat flux calibration.

[0027] As Figure 2 and Figure 3 shown, the test section 5 includes a thin-film platinum resistance 6, a calibration plate 7, a heat flux meter mounting seat to be calibrated 8, a fast-response displacement mechanism 9, a reference platinum resistance 10, a reference plate 11, a nozzle 12, a shielding radiation source 13, a thin-film thermocouple 14, and a support rod 15.

[0028] The calibration plate 7 and the reference plate 11 have exactly the same external dimensions, for example, a diameter of 100 mm and a thickness of 10 mm. They are installed on the fast-response displacement mechanism 9 and symmetrically located on both sides of the nozzle outlet of the nozzle 12, with a center distance of, for example, 200 mm. The center height of the plate is the same as the center height of the nozzle outlet. The horizontal distance between the plate and the nozzle outlet is (1 - 2)D, where D is the diameter of the calibration plate 7. In one embodiment, the horizontal distance between the plate and the nozzle outlet is 100 mm. The shielding radiation source 13 is located at the central position inside the nozzle 12, and the thin-film thermocouple 14 is plated on the surface of the shielding radiation source 13. The fast-response displacement mechanism 9 is used to achieve rapid position replacement of the two plates, and the single-action time does not exceed 50 ms, for example, it is 50 ms.

[0029] The reference flat plate 11 is made of the same material as the sensing part of the heat flux meter to be calibrated. The calibration flat plate 7 is made of materials with low thermal conductivity and large specific heat capacity, including but not limited to aerogel ceramics, fused quartz, etc. In one embodiment, the reference flat plate 11 is made of constantan, and the calibration flat plate 7 is made of aerogel ceramics. First, an insulating layer is plated on the surface of the reference flat plate 11, and then two thin-film platinum resistors are symmetrically plated at the center as the reference platinum resistors 10. The size of the sensing part of each reference platinum resistor 10 is, for example, 3 mm, which is the same as that of the sensing part of the heat flux meter to be calibrated. The distance between the two reference platinum resistors 10 does not exceed 1 mm, for example, 1 mm. Finally, a coating with high emissivity is applied to the surface of the reference flat plate 11, such as the high-temperature black paint 1200 coating, to ensure that the surface emissivity is close to 1. The heat flux meter to be calibrated is installed at the center of the calibration flat plate 7 through the mounting seat 8 of the heat flux meter to be calibrated. Thin-film platinum resistors 6 are plated around the heat flux meter to be calibrated for calculating the surface temperature of the heat flux meter to be calibrated.

[0030] In one embodiment, the material of the shielding radiation source 13 is 310S stainless steel, with a diameter of 120 mm and a thickness of 4 mm. An insulating layer and a thin-film thermocouple 14 are successively plated on the surface of the shielding radiation source 13, and then a coating with high emissivity is applied to the surface to ensure that the surface emissivity is close to 1. The shielding radiation source 13 is fixed at the central position inside the nozzle 12 by a support rod 15, for example, 200 mm away from the nozzle outlet.

[0031] An embodiment of the present invention also provides a convective heat flux calibration method, which uses the convective heat flux calibration device of the embodiment of the present invention to perform convective heat flux calibration. The convective heat flux calibration method of the embodiment of the present invention adopts the double-flat-plate transient method for calibration, as Figure 4 shown, including:

[0032] The reference flat plate 11 and the calibration flat plate 7 are respectively subjected to transient thermal shocks of the air flow through the fast-response displacement mechanism 9. The total heat flux is calculated according to the temperature history of the reference platinum resistor 10 on the reference flat plate 11. The shielding radiation source 13 is used to radiate heat to the reference flat plate 11 and the radiation heat flux is calculated. The convective heat flux of the reference flat plate 11 is obtained by subtracting the radiation heat flux from the total heat flux. The convective heat transfer coefficient and the adiabatic wall temperature are calculated according to the numerical values of the convective heat flux and the radiation heat flux of the reference flat plate 11 at different times and are assigned to the calibration flat plate 7. Then, the convective heat flux is calculated according to the calculated convective heat transfer coefficient and adiabatic wall temperature and the measured surface temperature of the calibration flat plate 7, which is the standard value of the convective heat flux of the calibration flat plate 7. The surface temperatures of the shielding radiation source 13 and the calibration flat plate 7 are measured, and the radiation heat flux of the calibration flat plate 7 is calculated. The output voltage of the heat flux meter to be calibrated is subtracted by the ratio of the radiation heat flux of the calibration flat plate 7 to the radiation heat flux sensitivity coefficient (the voltage corresponding to the radiation heat flux) to obtain the voltage corresponding to the convective heat flux. The standard value of the convective heat flux is divided by this voltage to obtain the convective heat flux sensitivity coefficient.

[0033] The convective heat flux calibration device and calibration method according to the embodiments of the present invention have the following beneficial effects: It can provide a uniform and stable heat flux field that can be continuously adjusted within a certain working condition range, and can be used for the calibration or verification of convective heat flux meters, filling the gap in the convective heat flux parameter quantity transfer system in China, solving the problems that convective heat flux meters cannot be calibrated and data cannot be effectively traced in fields such as the development of aerospace vehicles, initially establishing a convective heat flux parameter quantity transfer system, and realizing the effective traceability of convective heat flux parameters.

[0034] Only some exemplary embodiments of the present invention have been described by way of illustration above. Without doubt, for those of ordinary skill in the art, the described embodiments can be modified in various different ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the protection scope of the claims of the present invention.

Claims

1. A convection heat flux calibration device, characterized in that: It includes an air compressor source, a regulating valve, an electric heater, a stable section, and a test section connected in sequence. The pure air flow generated by the air compressor source is heated by the electric heater and then enters the stable section for rectification, and then enters the test section for acceleration, and the Mach number is adjusted through the regulating valve. The test section includes a nozzle, a fast response displacement mechanism, a reference plate, a calibration plate, a shielded radiation source and a thin film thermocouple. The reference plate and the calibration plate have completely identical dimensions and are mounted on the fast response displacement mechanism and symmetrically located on both sides of the nozzle of the nozzle. The center heights of the reference plate and the calibration plate are consistent with the center height of the nozzle, and the horizontal distance from the nozzle is 1 to 2D, where D is the diameter of the calibration plate. The shielded radiation source is located at the center of the nozzle, and the thin film thermocouple is plated on the surface of the shielded radiation source. The fast response displacement mechanism is used to achieve rapid position replacement of the reference plate and the calibration plate. Two thin-film platinum resistors are symmetrically plated around the center of the reference plate as reference platinum resistors. The sensing part of each reference platinum resistor is the same size as the sensing part of the calibrated heat flux meter. The calibrated heat flux meter is installed in the center of the calibration plate. Thin-film platinum resistors are plated around the calibrated heat flux meter to calculate the surface temperature of the calibrated heat flux meter.

2. The convection heat flux calibration device according to claim 1, characterized in that: The reference plate is made of the same material as the sensing part of the calibrated heat flow meter, and the calibration plate is made of a material with low thermal conductivity and large specific heat capacity.

3. The convection heat flux calibration device according to claim 1 or 2, characterized in that: An insulating layer is first plated on the surface of the reference plate, and then two thin-film platinum resistors are plated symmetrically as reference platinum resistors. The distance between the two reference platinum resistors does not exceed 1 mm. Finally, a high-emissivity coating is coated on the surface of the reference plate to ensure that the surface emissivity is close to 1.

4. The convection heat flux calibration device according to claim 1 or 2, characterized in that: The surface of the shielded radiation source is plated with an insulating layer and a thin-film thermocouple in sequence, and then coated with a high-emissivity coating to ensure that the surface emissivity is close to 1.

5. The convection heat flux calibration device according to claim 1 or 2, characterized in that: The reference plate is made of constantan and the calibration plate is made of aerogel ceramic.

6. The convection heat flux calibration device according to claim 1 or 2, characterized in that: The single action time of the fast response displacement mechanism does not exceed 50ms.

7. The convection heat flux calibration device according to claim 1 or 2, characterized in that: The test section also includes a support rod, and the shielding radiation source is fixed at the inner center position of the nozzle through the support rod.

8. The convection heat flux calibration device according to claim 1 or 2, characterized in that: The test section also includes a calibrated heat flux meter mounting seat, through which the calibrated heat flux meter is mounted at the center of the calibration plate.

9. A convection heat flux calibration method, characterized in that: The convective heat flux calibration device according to any one of claims 1 to 8 is used to perform convective heat flux calibration, comprising: The reference plate and the plate to be calibrated are subjected to transient thermal shock of the airflow respectively through a fast response displacement mechanism, the total heat flux is calculated according to the temperature history of the reference platinum resistor on the reference plate, the shielded radiation source is used to radiate heat to the reference plate and the radiation heat flux is calculated, the convective heat flux of the reference plate is obtained by subtracting the radiation heat flux from the total heat flux, the convective heat transfer coefficient and the adiabatic wall temperature are calculated according to the values ​​of the convective heat flux and the radiation heat flux of the reference plate at different times, and the values ​​are assigned to the calibration plate, and the convective heat flux is calculated according to the calculated convective heat transfer coefficient and the adiabatic wall temperature and the measured surface temperature of the calibration plate as the standard value of the convective heat flux of the calibration plate; Measure the surface temperature of the shielded radiation source and the calibration plate, calculate the radiation heat flux of the calibration plate, subtract the ratio of the radiation heat flux of the calibration plate to the radiation heat flux sensitivity coefficient from the output voltage of the calibrated heat flux meter, and obtain the voltage corresponding to the convective heat flux. Divide the standard value of the convective heat flux by the voltage to obtain the convective heat flux sensitivity coefficient.

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