A total heat flux calibration device and calibration method

Abstract

This invention relates to the field of heat flux measurement and calibration technology, and discloses a total heat flux calibration device and method, including a sealed chamber, a graphite heating element, a convection drive element, a temperature-wind speed monitoring element, a standard heat flux meter mounting platform, and a heat flux meter mounting platform to be calibrated. The graphite heating element is disposed at the center of the sealed chamber to generate controllable radiative heat flux. The convection drive element includes a fan, a ventilation channel, and an anemometer. The fan is connected to the ventilation channel and disposed on one side of the sealed chamber, and the anemometer is installed at the outlet of the ventilation channel to monitor the convective wind speed. This invention can simultaneously generate controllable radiative and convective heat flux, simulating radiation-convective coupled thermal environments under different scenarios.

Description

Technical Field

[0001] This invention relates to the field of heat flux measurement and calibration technology, specifically to a total heat flux value calibration device and calibration method. Background Technology

[0002] In aerospace, fire protection, materials science and other fields, total heat flow meters (such as Gordon foil heat flow meters) are core equipment for measuring the coupled environment of radiative and convective heat flow. Their measurement accuracy directly affects the reliability of key scenarios such as spacecraft thermal protection design, cabin material fire protection testing, and burner performance evaluation.

[0003] Currently, heat flow meter calibration technology mainly focuses on the field of radiative heat flow, and the mainstream technologies include:

[0004] Blackbody furnace calibration technology (such as CN103557945A): It generates a uniform radiative heat flow through a blackbody furnace, which can only calibrate the radiative thermal response of the heat flow meter, but cannot simulate the convective thermal environment. In addition, the number of calibrations per operation is small and the cost is high.

[0005] Laser radiation calibration technology (such as CN112161728A): uses continuous / pulsed lasers to generate radiative heat flux. Although it can achieve transient and steady-state calibration, it only targets radiative heat and cannot cover the calibration requirements of convective heat flux.

[0006] Comparative radiation calibration techniques (such as CN104155005A) achieve calibration by comparing a standard radiation heat flow meter with the heat flow meter being calibrated. The core is still limited to radiation heat flow and does not involve the coupling calibration of convective heat.

[0007] Existing technologies have significant shortcomings in calibrating convective heat flux:

[0008] There is no established standard device for measuring convective heat flux in China, and there is a lack of unified calibration methods (such as the convective heat flux calibration technology mentioned in the Great Wall Metrology patent in 2025, which relies on shielded radiation sources and reference plates to calculate convective heat flux, is complicated to operate and is not coupled with radiative heat).

[0009] Circular foil heat flow meters (such as Gordon heat flow meters) have inherent limitations in measurements under convective conditions: their sensitivity parameters are based on radiative heat flow calibration, which results in significant errors when used for convective heat measurement, and they require known convective heat transfer coefficients for calibration, which limits their application in unknown environments (as indicated by the technical limitations in CN104913862A).

[0010] In practical applications, such as the cabin material fire resistance test required by Appendix F of CCAR-25-R4 for civil aviation, the thermal environment simulation of spacecraft reentry phase, and the measurement of burner flame heat flow, there is a coupled environment of "radiative heat + convective heat". Existing calibration methods that only target radiative heat result in a large deviation between the total heat measurement value and the actual value when using the heat flow meter (for example, in burner flame measurement, convective heat can account for 10%-30%, and ignoring convective heat calibration will lead to a total heat measurement error of more than 20%), which seriously affects the reliability of test data and the safety of product design.

[0011] Therefore, there is an urgent need for a total heat flux calibration technology that can simulate the radiation-convection coupled thermal environment, accurately control the heat flux ratio, and does not rely on the convective heat transfer coefficient, to fill the existing technological gap and meet the needs of related fields for accurate calibration of total heat flux meters. Summary of the Invention

[0012] The present invention aims to provide a total heat flux calibration device and calibration method to solve the problem that existing heat flux calibration technology only targets radiative heat flux (such as blackbody furnace, laser radiation source, etc.), and cannot simulate the actual use environment of "radiative heat + strong convection" in aerospace and fire protection fields, resulting in a large error when the sensitivity coefficient obtained by calibration is used for total heat measurement.

[0013] To solve the above problems, the present invention adopts the following technical solution:

[0014] Option 1: A total heat flux calibration device, comprising a sealed chamber, a graphite heating element, a convection drive element, a temperature-wind speed monitoring element, a standard heat flux meter mounting platform, and a heat flux meter mounting platform to be calibrated; the graphite heating element is disposed at the center of the sealed chamber to generate controllable radiative heat flux; the convection drive element includes a fan, a ventilation channel, and an anemometer, the fan being connected to the ventilation channel and disposed on one side of the sealed chamber, and the anemometer being installed at the outlet of the ventilation channel to monitor the convective wind speed; the standard heat flux meter mounting platform and the heat flux meter mounting platform to be calibrated are symmetrically arranged on both sides of the graphite heating element, and the distances between the two and the graphite heating element are equal; the temperature-wind speed monitoring element further includes multiple temperature sensors, respectively attached to the surface of the graphite heating element and the inner wall of the sealed chamber.

[0015] Beneficial effects: The symmetrically arranged installation platform and integrated radiation-convection generation components can provide a uniform and consistent full thermal environment for both the standard heat flow meter and the heat flow meter to be calibrated, avoiding calibration errors caused by uneven thermal fields, and achieving synchronous control of radiative and convective heat.

[0016] Preferably, the graphite heating component includes a graphite heating plate and a power controller. The power adjustment range of the graphite heating plate is 0-100kW, the surface temperature stability accuracy is ±2℃, and the effective heating area of ​​the graphite heating plate is 230mm×230mm.

[0017] Beneficial effects: Clearly defines the power, temperature accuracy, and dimensional parameters of the graphite heating plate, ensuring the coverage of the radiant heat flux range (meeting the requirements). It meets the requirements of radiative heat flux and stability, and is suitable for high heat flux calibration scenarios in aerospace, fire protection and other fields.

[0018] Preferably, the fan power adjustment range of the convection drive component is 0-5kW, the corresponding wind speed adjustment range is 0-15m / s, and the measurement accuracy of the anemometer is ±0.1m / s; the cross-sectional dimensions of the ventilation channel are 300mm×200mm, and the inner wall of the channel is provided with a heat insulation layer.

[0019] Beneficial effects: By controlling the specific fan power, wind speed range and channel size, precise control of convective heat flow can be achieved (matching the strong convective environment of the burner flame). The insulation layer design reduces the impact of channel heat dissipation on convective heat flow and improves the stability of the convective thermal environment.

[0020] Preferably, both the standard heat flow meter mounting platform and the heat flow meter mounting platform to be calibrated are equipped with a horizontal adjustment mechanism with an adjustment accuracy of ±0.5mm; the standard heat flow meter mounting platform has a sapphire glass window with a light transmittance of ≥98%; the standard heat flow meter mounting platform is also adapted for quick assembly and disassembly of standard total heat flow meters and standard radiation heat flow meters, with an assembly and disassembly time of ≤5min.

[0021] Beneficial effects: The horizontal adjustment mechanism ensures that the heat flow meter receiving surface is parallel to the graphite heating element, reducing heat flow receiving errors caused by angular deviations; the quick disassembly and assembly design improves calibration efficiency; and the sapphire glass window ensures that the standard radiative heat flow meter only receives radiative heat, providing an accurate benchmark for convective heat calculation.

[0022] Option 2: A method for calibrating total heat flux, based on any of the aforementioned total heat flux calibration devices, comprising the following steps:

[0023] S1: Verification of the range of the total heat flow calibration device: Install the standard total heat flow meter on the standard heat flow meter mounting platform, open the ventilation channel of the sealed chamber, set the graphite heating plate power to 100% maximum power and start heating, set the fan power to 100% maximum power and start the fan; after the anemometer measures a stable wind speed and the graphite heating plate temperature stabilizes, collect the heat flow data of the standard total heat flow meter. This data is the maximum calibration range of the calibration device.

[0024] S2: Determining the ratio of convective heat to radiative heat: Remove the standard total heat flux meter and install the standard radiative heat flux meter with a sapphire glass window. Close the ventilation channel and wait until the wind speed measured by the anemometer is ≤0 m / s. Then, collect the data from the standard radiative heat flux meter and record it as the pure radiative heat flux value. Remove the standard radiative heat flow meter, reinstall the standard total heat flow meter, open the ventilation channel, and sequentially set the fan power to 10%, 30%, 50%, 70%, and 90% of its maximum power. After each set of fan speeds stabilizes, collect data from the standard total heat flow meter. ; Calculate the convective heat flux value and the ratio of convective heat to radiative heat Linear fitting was performed between the fan power and R to obtain the correspondence between the convective heat flux value and the pure radiative heat flux value characterized by multiple power points;

[0025] S3: Total Heat Flow Meter Calibration:

[0026] The first step is to install the standard total heat flow meter on the standard heat flow meter mounting platform, and the heat flow meter to be calibrated on the heat flow meter mounting platform to be calibrated. Adjust the level of the two platforms to a deviation of ≤0.5mm.

[0027] The second step is to determine the ratio of the heat flux value at the calibration point to the maximum range, R1, and the ratio of convective heat to radiative heat in the application scenario of the heat flux meter to be calibrated, R2%.

[0028] The third step is to set the graphite heating plate power to 100% of the maximum power × R1% and the fan power to 100% of the maximum power × R1% × R2%, and then start the heating and fan.

[0029] Beneficial effects: By confirming the measurement range using steady-state data at maximum power, the calibration device ensures coverage of the heat flux meter being calibrated, avoiding calibration failures due to insufficient range. Furthermore, clear stability criteria enhance the reliability of range confirmation. Establishing a correlation between wind speed and heat flux ratio through multi-power point fitting allows for precise matching of thermal environments in different application scenarios, resolving the disconnect between existing calibrations and actual operating conditions. Precise calculations of R1% and R2% enable combined calibration of different heat flux magnitudes and ratios, covering the full operating range of the heat flux meter being calibrated. Levelness adjustment ensures consistent heat flux reception, improving calibration accuracy.

[0030] Preferably, step S3 further includes:

[0031] Fourth step: When the temperature fluctuation of the graphite heating plate is ≤ ±2℃, the wind speed fluctuation is ≤ 0.5% / min, and the output value fluctuation of the standard total heat flow meter is ≤ 0.5% / min, record the heat flow value of the standard total heat flow meter. With the output electrical signal of the heat flow meter to be calibrated ;

[0032] Fifth, repeat steps two through four to complete the calibration of all calibration points with R1% = 20%, 40%, 60%, 80%, and 100%.

[0033] Step 6, for and Linear fitting was performed to obtain the sensitivity coefficient of the heat flow meter to be calibrated. Make the fitting correlation coefficient .

[0034] Beneficial effects: Clear stability criteria and multi-calibration point fitting ensure the accuracy and linearity of the sensitivity coefficient. This requirement can effectively eliminate abnormal data and avoid errors caused by single-point calibration.

[0035] Preferably, in step S2, the sapphire glass window of the standard radiative heat flow meter has a thickness of 2mm ± 0.1mm, and the infrared transmittance of the coating on the window surface is ≥98%, with a transmitted wavelength range of 2-15μm; pure radiative heat flow values ​​are collected. At this time, it is necessary to ensure that the temperature difference between the inner wall of the sealed cavity and the graphite heating plate is ≤5℃.

[0036] Beneficial effects: By digitally defining window thickness, transmittance, and chamber temperature difference, systematic errors in radiative heat measurement are reduced, ensuring... This improves the accuracy of convective heat calculations and the precision of heat flux ratio fitting.

[0037] Preferably, in step S3, the heat flow meter to be calibrated is a Gordon foil heat flow meter with a probe diameter of 25.4 mm ± 0.1 mm, and the uncertainty of the sensitivity coefficient K after calibration is ≤ 5%; if the heat flow meter to be calibrated is used for fire protection testing inside a civil aircraft cabin, R2% in step S3 is set to 3.3%, that is, set...

[0038] .

[0039] Beneficial effects: By limiting parameters for specific heat flow meters (Gordon foil type) and specific scenarios (civil aviation fire prevention), the method is made more targeted and practical. The requirement of uncertainty ≤5% meets the accuracy standards of metrological calibration and ensures that the calibration results are traceable.

[0040] Preferably, in step S1, the power range of the graphite heating plate is 0-100kW, and the power range of the fan is 0-5kW.

[0041] Beneficial effects: The suitable power range facilitates the implementation of calibration methods.

[0042] Preferably, the wind speed stability measured by the anemometer is defined as wind speed fluctuation ≤ 0.5% / min, and the temperature stability of the graphite heating plate is defined as temperature fluctuation ≤ ±2℃.

[0043] Beneficial effects: It allows for more accurate determination of whether wind speed and temperature are stable, facilitating more precise start-up of heating and fans, and providing an accurate basis for the entire calibration process.

[0044] The advantages of this invention are:

[0045] 1. Capable of simulating the entire thermal environment: It is the first to achieve coupled calibration of radiative heat and convective heat, and can accurately control the heat flux ratio (0.05-0.35), covering mainstream application scenarios in aerospace, fire protection and other fields, and solving the limitation of existing technologies that only target radiative heat.

[0046] 2. High calibration accuracy: achieved through multi-calibration point fitting ( The system includes level adjustment (±0.5mm) and temperature-wind speed stability control (fluctuation ≤0.5% / min) to ensure that the sensitivity coefficient uncertainty is ≤5%, meeting the traceability requirements of metrological calibration.

[0047] 3. High versatility: It does not rely on known convective heat transfer coefficients. Convective heat is calculated by the difference between standard total heat flow meter and radiative heat flow meter. It is compatible with different types of total heat flow meters (such as Gordon foil and circular foil), and can quickly switch the heat flow ratio of the scene.

[0048] 4. High efficiency: The installation platform supports quick assembly and disassembly (≤5min), and the calibration process is highly automated. Compared with existing methods (which require separate calibration of radiation and convection), the calibration efficiency is improved by more than 40%. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the sealed chamber in the total heat flux calibration device of the present invention.

[0050] Figure 2 This is a flowchart of the total heat flux calibration method of the present invention.

[0051] Figure 3 This is a schematic diagram showing the total heat flux and radiant heat flux of the standard burner flame at various points obtained in Embodiment 2 of the present invention. Wherein, a) is a front view, and b) is a top view.

[0052] Figure 4 This is a schematic diagram illustrating the connection and use of the total heat flux calibration device of the present invention.

[0053] The reference numerals in the accompanying drawings of the instruction manual include: 1. Heat flow meter to be calibrated; 2. Standard heat flow meter; 3. Graphite heating plate; 4. Anemometer; 5. Slide switch; 6. Valve; 7. Rectifier section; 8. Fan; 9. Connection hole; 10. Air outlet; 11. Support frame; 12. Baffle; 13. Heat flux density measuring plate test piece; 14. Heat flux sensor; 15. Plug; 16. Burner. Detailed Implementation

[0054] The following detailed description illustrates the specific implementation method:

[0055] This invention relates to the field of heat flux measurement and calibration technology. Specifically, it relates to a full-heat flux calibration device and calibration method that can simultaneously simulate a radiative heat and convective heat coupling environment. It is applicable to the metrological calibration of full-heat flux meters (which simultaneously measure radiative heat flux and convective heat flux) in aerospace, fire protection, and material fire prevention fields, especially for the accurate calibration of heat flux meters in radiative-convective coupled thermal environments such as burner flames.

[0056] The main problems addressed by this invention in existing technologies are as follows: Existing heat flux calibration techniques only target radiative heat flux (such as blackbody furnaces and laser radiation sources), failing to simulate the actual operating environment of "radiative heat + strong convection" in aerospace and fire protection fields. This results in significant errors in the sensitivity coefficient obtained from calibration when used for total heat measurement. Furthermore, the lack of a calibration device that can precisely control the ratio of radiative to convective heat makes it impossible to match the thermal environment characteristics of different scenarios (such as fire prevention tests in civil aviation cabins and burner heat flux measurements), leading to a disconnect between calibration results and actual operating conditions. Convective heat flux calibration technology is lacking; existing methods rely on known convective heat transfer coefficients, limiting the calibration application of heat flux meters in unknown convective environments and failing to achieve simultaneous calibration of coupled radiative and convective heat fluxes. Finally, existing total heat flux measurements lack a unified method for verifying the calibration range, making it impossible to accurately define the applicable scope of the calibration device and affecting the reliability of the calibration results.

[0057] Therefore, this invention provides a total heat flux calibration device capable of simultaneously generating controllable radiative and convective heat fluxes to simulate radiation-convective coupled thermal environments under different scenarios. A total heat flux calibration method is established to achieve calibration range confirmation, radiative-convective heat ratio matching, and accurate calculation of the heat flux meter sensitivity coefficient. This overcomes the limitation of existing calibration techniques that only target a single radiative heat flux, reducing the measurement error of the calibrated heat flux meter in a total heat environment and meeting the high-precision measurement requirements of aerospace, fire protection, and other fields. It can complete the calibration of convective and total heat fluxes without relying on known convective heat transfer coefficients, improving the versatility and applicability of the calibration device.

[0058] like Figure 1 and Figure 4As shown, the total heat flux calibration device of the present invention includes a sealed chamber, a graphite heating element, a convection drive element, a temperature-wind speed monitoring element, a standard heat flux meter mounting platform, and a heat flux meter mounting platform to be calibrated. The graphite heating element is disposed at the center of the sealed chamber and is used to generate controllable radiative heat flux. The convection drive element includes a fan, a ventilation channel, and an anemometer. The fan is connected to the ventilation channel and disposed on one side of the sealed chamber. The anemometer is installed at the outlet of the ventilation channel and is used to monitor the convective wind speed. The standard heat flux meter mounting platform and the heat flux meter mounting platform to be calibrated are symmetrically arranged on both sides of the graphite heating element, and the distance between the two and the graphite heating element is equal. The temperature-wind speed monitoring element also includes multiple temperature sensors, which are respectively attached to the surface of the graphite heating element and the inner wall of the sealed chamber. The symmetrically arranged installation platform and integrated radiation-convection generation components can provide a uniform and consistent full thermal environment for both the standard heat flow meter and the heat flow meter to be calibrated, avoiding calibration errors caused by uneven thermal fields and enabling synchronous control of radiative and convective heat.

[0059] like Figure 1 As shown, the sealed chamber in the total heat flux calibration device has a rectangular parallelepiped structure with six walls. Two symmetrical connection holes 9 are located on opposite walls. These holes 9 are used to pass through two heat flux meter water-cooled tubes (each with an outer diameter of 8 mm, requiring thermal insulation) and the heat flux meter signal wire (also requiring thermal insulation). The hole diameter can be set to 25.4 mm. Adjacent holes are used to pass through the anemometer and thermocouple signal wires (also requiring thermal insulation), with a hole diameter of 10 mm. Within the sealed chamber, a matrix of air outlets 10 is located on one wall between the two walls with connection holes 9, and corresponding air inlets are located on the other wall between the two walls with connection holes 9. The arrangement and number of air outlets 10 and air inlets are consistent. Figure 1 As shown, the air outlets 10 on a single wall are divided into two groups, with each group having three rows of air outlets 10. Each row of air outlets 10 has ten circular holes, and each hole can be... Figure 4 The sliding switch 5 controls the baffle 12 to block and close the circuit. Through the air outlet 10 and the air inlet, it is possible to simulate the actual convection situation in the sealed chamber.

[0060] like Figure 4 As shown, Figure 1 The sealed chamber, as part of the total heat flux calibration device, houses a graphite heating plate 3 as a heating element. This simulates and recreates radiant heat while symmetrically dividing the sealed chamber into left and right spaces. During connection and use, the connecting holes 9 on both sides... Figure 4The connection hole 9 on the left side of the sealed chamber is used to connect the heat flow meter 1 to be calibrated, which is placed in the left space of the sealed chamber, and the anemometer 4 to be placed near the heat flow meter 1. The connection hole 9 on the right side wall of the sealed chamber is used to connect the standard heat flow meter 2, which is placed in the right space of the sealed chamber, and the anemometer 4 to be placed near the standard heat flow meter 2.

[0061] The heat flow meter to be calibrated 1 and the standard heat flow meter 2 are symmetrically distributed relative to the graphite heating plate 3, and the two anemometers 4 are also symmetrically distributed, so that the heat flow meter to be calibrated 1 and the standard heat flow meter 2 are in the same thermal environment and test environment.

[0062] To enable the heat flow meter 1 to be calibrated and the standard heat flow meter 2 to more accurately measure the heat flow value in the air, the support frame 11 used to support their suspension has a "Y" shape structure. The support frame 11 includes "V" structures and "I" structures connected to each other. The "V" structure of the support frame 11 does not directly contact the heat flow meter but is bonded to the wire connecting the heat flow meter. By designing the length of the "V" to be long enough, the support frame 11 can have a larger contact area with the wire, thus achieving the purpose of suspending the heat flow meter by supporting the wire. This helps to place the heat flow meter 1 on the left and the standard heat flow meter 2 on the right in the same and more realistic thermal environment. The "I" structure of the support frame 11 is fixedly connected to the rear side wall of the sealed chamber, making the connection more secure without affecting the air outlet 10 on the upper side wall and the air inlet on the lower side wall.

[0063] To more precisely control the airflow within the sealed chamber, a connecting pipe is installed at the air inlet. A valve 6, capable of closing and opening the passage, is installed on the pipe. The pipe is connected to the fan 8 through a rectifier section 7. To better simulate the convection environment, a valve is also installed between the fan 8 and the rectifier section 7.

[0064] To simulate a wider range of airflow environments, baffles 12 are installed at the air inlets to move left and right over the inlets. The baffles 12 slide along sliding grooves on the lower side wall of the sealed chamber, and their movement is controlled by a sliding switch 5. The sliding switch 5 is an integrally formed protrusion perpendicular to the baffle 12.

[0065] The front wall of the sealed chamber is removable for easy installation of heat flow meters and other equipment. All inner walls of the chamber are lined with heat insulation material. After all equipment is installed and connected, and the sliding switch 5 is pushed to block the baffle 12 at the desired air inlet area, the front wall is sealed, and calibration can begin.

[0066] The graphite heating component includes a graphite heating plate 3 and a power controller. The power adjustment range of the graphite heating plate 3 is 0-100kW, the surface temperature stability accuracy is ±2℃, and the effective heating area of ​​the graphite heating plate 3 is 230mm×230mm. The power, temperature accuracy, and dimensional parameters of the graphite heating plate 3 are clearly defined to ensure the coverage of the radiant heat flux (meeting the requirements). It meets the requirements of radiative heat flux and stability, and is suitable for high heat flux calibration scenarios in aerospace, fire protection and other fields.

[0067] The fan 8 of the convection drive component has a power adjustment range of 0-5kW, corresponding to a wind speed adjustment range of 0-15m / s, and the anemometer 4 has a measurement accuracy of ±0.1m / s. The cross-sectional dimensions of the ventilation channel are 300mm×200mm, and the inner wall of the channel is equipped with a heat insulation layer. By controlling the specific power and wind speed range of the fan 8 and the channel dimensions, precise control of convective heat flow can be achieved (matching the strong convective environment of the burner flame). The heat insulation layer design reduces the impact of channel heat dissipation on convective heat flow, improving the stability of the convective thermal environment.

[0068] Both the standard heat flow meter 2 mounting platform and the heat flow meter 1 mounting platform to be calibrated are equipped with a horizontal adjustment mechanism with an adjustment accuracy of ±0.5mm. The standard heat flow meter 2 mounting platform is also compatible with the rapid assembly and disassembly of standard total heat flow meters and standard radiation heat flow meters (with sapphire glass windows and a light transmittance of ≥98%), with an assembly and disassembly time of ≤5min. The horizontal adjustment mechanism ensures that the heat flow meter receiving surface is parallel to the graphite heating element, reducing heat flow reception errors caused by angular deviations. The rapid assembly and disassembly design improves calibration efficiency, and the sapphire glass window ensures that the standard radiation heat flow meter only receives radiative heat, providing an accurate benchmark for convective heat calculation.

[0069] Based on the above total heat flow value calibration device, such as Figure 2 As shown, the total heat flux calibration method of the present invention includes the following steps:

[0070] S1: Range Confirmation of the Total Heat Flow Calibration Device: Install the standard total heat flow meter on the mounting platform of the standard heat flow meter 2, open the ventilation channel of the sealed chamber, set the power of the graphite heating plate 3 to 100% of its maximum power (0-100kW) and start heating, set the power of the fan 8 to 100% of its maximum power (0-5kW) and start fan 8; after the wind speed measured by the anemometer 4 stabilizes (fluctuation ≤0.5% / min) and the temperature of the graphite heating plate 3 stabilizes (fluctuation ≤±2℃), collect the heat flow data of the standard total heat flow meter. This data is the maximum calibration range of the calibration device. Confirming the range through steady-state data at maximum power ensures that the calibration device covers the operating range of the heat flow meter being calibrated, avoiding calibration failure due to insufficient range, and the clear stability judgment standard improves the reliability of range confirmation.

[0071] S2: Determining the ratio of convective heat to radiative heat: Remove the standard total heat flux meter and install the standard radiative heat flux meter (with sapphire glass window). Close the ventilation channel and wait until the wind speed measured by an anemometer 4 is ≤0 m / s. Then collect the data from the standard radiative heat flux meter and record it as the pure radiative heat flux value. Remove the standard radiative heat flow meter, reinstall the standard total heat flow meter, open the ventilation channel, and sequentially set the power of fan 8 to 10%, 30%, 50%, 70%, and 90% of its maximum power. After each set, collect data from the standard total heat flow meter after the wind speed stabilizes. ; Calculate the convective heat flux value and the ratio of convective heat to radiative heat Linear fitting was performed on the power of the fan and R to obtain the corresponding relationship between the two. By establishing the correlation between wind speed and heat flux ratio through multi-power point fitting, the thermal environment of different application scenarios (such as R=1 / 3 in civil aviation fire protection tests and R=0.11-0.31 for burner flames) can be accurately matched, solving the problem of existing calibration being out of sync with actual operating conditions.

[0072] S3: Total heat flow meter calibration, including:

[0073] a) Install the standard total heat flow meter on the standard heat flow meter 2 mounting platform, and install the heat flow meter to be calibrated 1 on the heat flow meter to be calibrated 1 mounting platform. Adjust the level of the two platforms to a deviation of ≤0.5mm.

[0074] b) Determine the ratio R1% of the heat flux value at the calibration point to the maximum range (with values ​​of 20%, 40%, 60%, 80%, and 100%), and the ratio R2% of convective heat to radiative heat in the usage scenario of the heat flux meter 1 to be calibrated;

[0075] c) Set the power of graphite heating plate 3 to 100% maximum power × R1%, and the power of fan 8 to 100% maximum power × R1% × R2%, and start heating and fan 8; through precise calculation of R1% and R2%, achieve combined calibration of different heat flow magnitudes and heat flow ratios, covering the full range of use of the heat flow meter 1 to be calibrated, and level adjustment ensures consistent heat flow reception and improves calibration accuracy.

[0076] d) Once the temperature of the graphite heating plate 3 stabilizes (fluctuation ≤ ±2℃), the wind speed stabilizes (fluctuation ≤ 0.5% / min), and the fluctuation of the standard total heat flow meter output value is ≤ 0.5% / min, record the heat flow value of the standard total heat flow meter. The output electrical signal of the heat flow meter 1 to be calibrated ;

[0077] e) Repeat steps b)-d) to complete the calibration of all calibration points (R1%=20%, 40%, 60%, 80%, 100%);

[0078] f) and Linear fitting was performed to obtain the sensitivity coefficient K (unit: 1) of the heat flow meter to be calibrated. ), correlation coefficient Clear stability criteria and multi-calibration point fitting ensure the accuracy and linearity of the sensitivity coefficient. This requirement can effectively eliminate abnormal data and avoid errors caused by single-point calibration.

[0079] In step S2, the sapphire glass window of the standard radiative heat flow meter has a thickness of 2mm ± 0.1mm, and the infrared transmittance of the coating on the window surface is ≥98% (wavelength range 2-15μm); pure radiative heat flow values ​​are collected. At the same time, it is necessary to ensure that the temperature difference between the inner wall of the sealed chamber and the graphite heating plate 3 is ≤5℃. By setting numerical limits on window thickness, transmittance, and chamber temperature difference, systematic errors in radiant heat measurement are reduced, ensuring... This improves the accuracy of convective heat calculations and the precision of heat flux ratio fitting.

[0080] In step S3, the heat flow meter to be calibrated, 1, is a Gordon foil heat flow meter with a probe diameter of 25.4 mm ± 0.1 mm (1 inch), and the uncertainty of the sensitivity coefficient K after calibration is ≤ 5%. If the heat flow meter to be calibrated, 1, is used for fire protection testing in civil aviation cabins, R2% in step S3 is set to 3.3% (convective heat / radiative heat = 1 / 3). By limiting the parameters for a specific heat flow meter (Gordon foil) and a specific scenario (civil aviation fire protection), the method's relevance and practicality are improved. The requirement of uncertainty ≤ 5% meets the accuracy standards for metrological calibration, ensuring the traceability of calibration results.

[0081] The specific implementation process is as follows:

[0082] Example 1: Calibration of Gordon heat flow meter for civil aviation cabin fire resistance testing

[0083] 1. Configuration of total heat flux calibration device

[0084] Graphite heating element: power 0-100kW, surface temperature stability accuracy ±2℃, effective area 230mm×230mm;

[0085] Convection drive components: fan power 0-5kW, wind speed 0-15m / s, anemometer accuracy ±0.1m / s, ventilation channel 300mm×200mm (with insulation layer).

[0086] Standard heat flow meter: Standard total heat flow meter (range) ), standard radiation pyrometer (with a 2mm±0.1mm sapphire window, 98% transmittance);

[0087] Installation platform: horizontal adjustment accuracy ±0.5mm, suitable for quick assembly and disassembly.

[0088] 2. Total Heat Flow Calibration Method

[0089] S1: Range Confirmation: Graphite heating plate power 100kW (full power), fan power 5kW (full power), wind speed stable at 15m / s, graphite heating plate temperature stable at 800℃, maximum range of the standard total heat flow meter is... .

[0090] S2: Heat flux ratio determination: With fan off (wind speed 0m / s), data is collected using a standard radiation pyrometry meter. The fan power was sequentially set to 0.5kW (10%), 1.5kW (30%), 2.5kW (50%), 3.5kW (70%), and 4.5kW (90%), and data was collected. They are respectively The calculated R values ​​are 0.05, 0.12, 0.20, 0.26, and 0.32 respectively; the fitted relationship between the fan power P (kW) and R is: R = 0.068P - 0.012 ( ).

[0091] S3: Heat Flow Meter Calibration: The heat flow meter to be calibrated is a 1-inch Gordon foil heat flow meter (probe diameter 25.4mm ± 0.1mm), with an application scenario R2% = 3.3%;

[0092] The calibration points R1% = 20%, 40%, 60%, 80%, 100%, corresponding to graphite power of 20, 40, 60, 80, 100kW, and fan power = R1% × 5kW × 3.3%, which are 0.3, 0.67, 1.0, 1.3, 1.67kW respectively;

[0093] Data collection after stabilization and , fitting The uncertainty is 3.2%.

[0094] 3. Effect Description

[0095] The calibrated heat flow meter was used for measuring the flame of an oil burner in a civil aircraft cabin (convection / radiation = 1 / 3). The deviation of the total heat measurement value from the standard value was ≤3%, while the measurement deviation of the heat flow meter calibrated only for radiation heat was 18%, resulting in an 83% reduction in error.

[0096] Example 2: Burner flame heat flow meter calibration (convection / radiation = 0.2)

[0097] 1. Configuration of total heat flux calibration device

[0098] Similar to Example 1, only the thickness of the insulation layer in the ventilation channel was adjusted to 50mm to reduce the impact of heat dissipation on convective heat.

[0099] 2. Total Heat Flow Calibration Method

[0100] S1: Range Confirmation: Graphite power 100kW, fan power 5kW, wind speed 15m / s, maximum range of standard total heat flow meter. .

[0101] S2: Determination of heat flux ratio: For fan power ranging from 0.5 to 4.5 kW, the corresponding R values ​​are 0.06 to 0.3. The fitted result is... .

[0102] S3: Heat Flow Calibration: The heat flow meter to be calibrated is an industrial-grade Gordon heat flow meter, with an application scenario R2%=20%;

[0103] The calibration points R1% = 30%, 50%, 70%, 90%, corresponding to graphite power of 30, 50, 70, 90kW, and fan power = R1% × 5 × 20%, which are 0.3, 0.5, 0.7, 0.9kW respectively.

[0104] Fitted The uncertainty is 2.8%.

[0105] In this embodiment, the total heat flow of the burner flame is measured by a total heat flow meter, and the radiant heat of the flame is measured by a pure radiant heat flow meter with a window (sapphire glass (98% light transmittance)). Thus, the total heat flow and radiant heat flow of the standard burner flame at each point can be calculated.

[0106] Adopting such Figure 3 a) The heat flux density measuring plate test piece 13, as shown in figure a), has existing heat flux sensors 14 for measuring total heat flux and heat sensors for measuring convective heat flux installed sequentially at multiple points with openings on it. The remaining unused openings are blocked with plugs 15. The plate is continuously burned by a burner 16, and the total heat flux and convective heat flux values ​​at each point are measured as follows: Figure 3 b) and as shown in Table 1 below. Figure 3 In b), for the two heat flux values ​​at the same location, the red number represents the total heat flux value, and the black number represents the convective heat flux value. From Figure 3 (b) As can be clearly seen from Table 1, convective heat accounts for a certain proportion of the total heat flux value at each location. The calibrated heat flux meter in this embodiment can accurately measure the heat flux value at each location, and the actual heat flux value received at each location is consistent. In contrast, existing heat flux meters can only measure the total heat flux value, but the calibration is performed specifically for radiative heat, failing to account for convective heat calibration, resulting in calibration results that differ significantly from actual measurement requirements.

[0107] Table 1. Comparison of total heat flux, radiative heat flux, and convective heat flux of standard burner flame at various points.

[0108]

[0109] 3. Effect Description

[0110] The calibrated heat flow meter was used for burner flame measurement (actual convection / radiation = 0.2), and the measured value deviated from the standard value by ≤2.5%, while the heat flow meter using the existing radiation calibration method had a deviation of 15%, and no additional measurement of the convective heat transfer coefficient was required, thus improving calibration efficiency by 40%.

[0111] Compared to the simpler requirements for heat flow meters in the corresponding standards:

[0112] CCAR-25-R4 Appendix F Part VI: The heat flow meter must be a one-inch cylindrical water-cooled, total heat flux density, foil Gardon heat flow meter.

[0113] CCAR-25-R4 Appendix F Part VII: The heat flow meter must be a total heat flow Gardon foil heat flow meter with an appropriate range.

[0114] We use the calibration device of this invention to measure the total heat flux density of an oil burner flame and the radiant heat inside the housing using a heat flux meter. This effectively fills the gap in the current domestic research on convective heat flux calibration and overcomes the limitations of circular foil heat flux meters when applied to heat flux measurement in convective environments.

[0115] Example 3: Simulated heat flux meter calibration during spacecraft reentry phase (convection / radiation = 0.3)

[0116] 1. Configuration of total heat flux calibration device

[0117] The power of the graphite heating element has been increased to 0-120kW, and the surface temperature stability accuracy is ±1℃.

[0118] The convection drive component has a fan power of 0-8kW and a wind speed of 0-20m / s, making it suitable for environments with high heat flow convection.

[0119] 2. Total Heat Flow Calibration Method

[0120] S1: Range Confirmation: Graphite power 120kW, fan power 8kW, wind speed 20m / s, maximum range of standard total heat flow meter. .

[0121] S2: Determination of heat flux ratio: For fan power ranging from 0.8 to 7.2 kW, the corresponding R values ​​are 0.1 to 0.35. The fitted values ​​are... .

[0122] S3: Heat Flow Calibration: The heat flow meter to be calibrated is a spacecraft-specific full-heat heat flow meter, with an application scenario R2%=30%;

[0123] The calibration points R1% = 40%, 60%, 80%, 100%, corresponding to graphite power of 48, 72, 96, 120kW, and fan power = R1% × 8 × 30%, which are 0.96, 1.44, 1.92, 2.4kW respectively.

[0124] Fitted The uncertainty is 2.5%.

[0125] 3. Effect Description

[0126] The calibrated heat flow meter was used in the thermal environment simulation test of the spacecraft reentry phase. The deviation between the total thermal measurement value and the simulation value was ≤2%, which meets the high precision requirements of the spacecraft thermal protection design. Compared with the heat flow meter calibrated only by radiation (deviation 12%), the measurement reliability is significantly improved.

[0127] Comparative example (existing radiative thermal calibration method)

[0128] Apparatus: Blackbody furnace (CN103557945A), which only generates radiative heat flux;

[0129] Method: Set the blackbody furnace temperature to 800℃, calibrate the heat flow meter to be calibrated, and obtain the radiation sensitivity coefficient. ;

[0130] Results: When this heat flow meter was used in the scenarios of Examples 1-3, the total heat measurement deviations were 18%, 15%, and 12%, respectively, which could not meet the measurement requirements of radiation-convection coupled environments and could not match the heat flow ratios of different scenarios.

[0131] The differences between the present invention and the prior art can be seen from the above embodiments and comparative examples, as shown in Table 2.

[0132] Table 2. Comparison of the differences between the present invention and the prior art

[0133]

[0134] Furthermore, conventional technology in the field holds that "heat flow meter calibration only needs to cover radiant heat." This invention breaks through this understanding and proposes that "full thermal environment calibration needs to match the actual heat flow ratio." For the first time, it establishes a correlation model between the heat flow ratio and the fan power, upgrading the calibration from "single parameter" to "multi-parameter coupling," enabling more accurate calibration of the heat flow sensor.

[0135] Conventional techniques for convective heat calibration rely on complex calculations using shielded radiation sources and reference plates (as in the Great Wall Metrology patent 2025). This invention directly obtains convective heat through the "standard total heat-radiation difference," eliminating the need for additional shielding devices, reducing the number of operation steps by 50%, and avoiding errors caused by incomplete shielding.

[0136] Conventional techniques use only 1-2 calibration points, while this invention uses 5 calibration points (20%-100% range) for linear fitting to ensure the linearity and coverage of the sensitivity coefficient and avoid the random errors of single-point calibration.

[0137] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method of calibrating total heat flow values, characterized by, The method comprises the following steps: S1: full heat calibration device range confirmation: install the standard full heat flow meter on the standard heat flow meter installation platform, open the air passage of the sealed chamber, set the graphite heating plate power to 100% maximum power and start heating, set the fan power to 100% maximum power and start the fan; After the wind speed measured by the anemometer is stable and the temperature of the graphite heating plate is stable, collect the heat flow data of the standard full heat flow meter, which is the maximum calibration range of the calibration device; S2: the proportion of convective heat and radiant heat is determined: the standard total heat flow meter is taken out, the standard radiant heat flow meter with sapphire glass window is installed, the ventilation channel is closed, when the wind speed measured by the anemometer is ≤0 m / s, the data of the standard radiant heat flow meter is collected, and the pure radiant heat flow value is recorded ; the standard radiant heat flow meter is taken out, the standard total heat flow meter is reinstalled, the ventilation channel is opened, the fan power is set to 10%, 30%, 50%, 70%, 90% maximum power in turn, and the data of the standard total heat flow meter is collected after the wind speed is stable each time ; the convective heat flow value and the proportion of convective heat and radiant heat ; the fan power and R are linearly fitted to obtain the corresponding relationship between the convective heat flow value and the pure radiant heat flow value represented by multiple power points; S3: full heat flow meter calibration: First, install the standard full heat flow meter on the standard heat flow meter installation platform, and adjust the levelness of the two platforms to a deviation of ≤0.5 mm; Second, determine the ratio R1% of the calibration point heat flow value to the maximum range, and the ratio R2% of the convection heat to the radiation heat of the use scene of the heat flow meter to be calibrated; Third, set the graphite heating plate power to 100% maximum power x R1%, and the fan power to 100% maximum power x R1% x R2%, and start heating and the fan; Fourth step, when the temperature fluctuation of the graphite heating plate is less than or equal to ±2℃, the wind speed fluctuation is less than or equal to 0.5% / min, and the output value fluctuation of the standard total heat flow meter is less than or equal to 0.5% / min, the heat flow value of the standard total heat flow meter is recorded with the output electric signal of the heat flow meter to be calibrated ; Fifth, repeat steps two to four to complete the calibration of all calibration points with R1%=20%, 40%, 60%, 80%, and 100%; Step 6, the sensitivity coefficient of the heat flow meter to be calibrated is obtained by linear fitting with the heat flow meter to be calibrated , so as to make the correlation coefficient of fitting .

2. The total heat heat flow value calibration method of claim 1, wherein, In step S2, the thickness of the sapphire glass window of the standard radiant heat flow meter is 2mm±0.1mm, and the infrared transmittance of the window surface is ≥98%, and the wavelength range is 2-15μm; collect the pure radiation heat flow value At this time, it is necessary to ensure that the temperature difference between the inner wall of the sealed chamber and the graphite heating plate is ≤5℃.

3. The total heat heat flow value calibration method of claim 1, wherein, In step S3, the heat flow meter to be calibrated is a Gordon foil heat flow meter, the probe diameter of which is 25.4 mm±0.1 mm, and the uncertainty of the sensitivity coefficient K after calibration is ≤5%; if the heat flow meter to be calibrated is used for civil aviation cabin fire prevention test, R2% in step S3 is set to 3.3%, i.e. 。 4. The total heat heat flow value calibration method of claim 1, wherein, In step S1, the graphite heating plate power range is 0-100 kW, and the fan power range is 0-5 kW.

5. The total heat heat flow value calibration method of claim 1, wherein, In step S1, the wind speed measured by the anemometer is stable, which means that the wind speed fluctuation is ≤0.5% / min, and the graphite heating plate temperature is stable, which means that the temperature fluctuation is ≤±2℃.

6. A total heat flow value calibration device, characterized by, The method for calibrating the full heat flow value according to claim 1 comprises a sealed chamber, a graphite heating assembly, a convection driving assembly, a temperature and wind speed monitoring assembly, a standard heat flow meter installation platform, and a heat flow meter to be calibrated installation platform; the graphite heating assembly is arranged at the center of the sealed chamber and is used to generate controllable radiation heat flow; the convection driving assembly comprises a fan, an air passage, and an anemometer, the fan is in communication with the air passage and is arranged on one side of the sealed chamber, and the anemometer is installed at the outlet of the air passage and is used to monitor the convection wind speed; the standard heat flow meter installation platform and the heat flow meter to be calibrated installation platform are symmetrically arranged on both sides of the graphite heating assembly, and the distance between the two platforms and the graphite heating assembly is equal; the temperature and wind speed monitoring assembly further comprises a plurality of temperature measurement sensors, which are respectively attached to the surface of the graphite heating assembly and the inner wall of the sealed chamber.

7. The total heat and hot stream value calibration device of claim 6, wherein, The graphite heating assembly comprises a graphite heating plate and a power controller, the power adjustment range of the graphite heating plate is 0-100 kW, the surface temperature stability precision is ±2℃, and the effective heating area of the graphite heating plate is 230 mm x 230 mm.

8. The total heat and hot stream value calibration device of claim 6, wherein, The fan power adjustment range of the convection driving assembly is 0-5kW, and the corresponding air speed adjustment range is 0-15m / s, the measurement accuracy of the anemometer is ±0.1m / s; the cross-sectional dimension of the ventilation channel is 300mm*200mm, and the inner wall of the channel is provided with a heat preservation layer.

9. The total heat and hot stream value calibration device of claim 6, wherein, The standard heat flow meter installation platform and the installation platform of the heat flow meter to be calibrated are provided with horizontal adjustment mechanisms, and the adjustment accuracy is ±0.5mm; the standard heat flow meter installation platform is provided with a sapphire glass window with a light transmittance of ≥98%, and the standard heat flow meter installation platform is also suitable for quick disassembly and assembly of the standard total heat flow meter and the standard radiation heat flow meter, and the disassembly and assembly time is ≤5min.

Images