CN114646663A - High-efficiency measurement system and method for thermal radiation characteristics of materials with different thicknesses of high-temperature infrared hood - Google Patents

Abstract

The invention discloses a high-efficiency measuring system and method for thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared hood, belonging to the technical field of thermal radiation measurement. In order to solve the problem that the existing numerical simulation method is greatly influenced by the thickness of the material to be measured and the measurement error, the accuracy of the reconstruction results is crossed. The invention divides the infrared head cover test piece into equal parts along the radiation transmission direction, and sequentially obtains the total radiation passing through the first layer, the first to the second layer, ..., the 1 to n layers of the head cover material according to the radiation transmission principle and the energy conservation relationship; Then based on the energy method, the algebraic relationship satisfied between the transmittance and self-radiation of the infrared head cover material with a thickness of Δ and a temperature of T and the transmittance and self-radiation of the entire infrared detection head cover was deduced. The thermal radiation characteristics such as the transmittance and self-radiation of the infrared head cover of thickness x are measured experimentally, and the thermal radiation characteristics data of the material per unit thickness are calculated based on the algebraic relationship. It is mainly used to obtain the thermal radiation characteristics of the infrared hood.

Description

High-efficiency measurement system and method for thermal radiation characteristics of high-temperature infrared hood materials with different thicknesses

technical field

The invention belongs to the technical field of thermal radiation measurement, in particular to a method for measuring thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared head cover.

Background technique

When the aircraft is flying at hypersonic speed in the atmosphere, the high temperature infrared hood quickly becomes the main factor of the aerodynamic thermal radiation effect of the infrared detection system. The high temperature increases the thermal radiation of the infrared hood itself, and the radiation on the surface of the infrared hood is mainly concentrated in the infrared band. Form interference, increase the background brightness of the detector, reduce the detection signal-to-noise ratio of the target, reduce the detection and tracking ability of the system to the target, and even cause the infrared detector to be saturated and unable to accurately distinguish the signal from the target, causing target detection, tracking and The weakening of the recognition ability reduces the imaging quality of the infrared detection system.

At present, the measurement research on infrared head cover materials mostly focuses on the physical and chemical properties such as strength, hardness, melting point, refractive index, thermal conductivity and corrosion resistance, while the research on thermal radiation transmission characteristics such as transmittance and attenuation coefficient is less. The data of the state is less, which affects or even restricts the development of the research on the aerothermal radiation effect of the high-temperature infrared optical window, and hinders the application of the infrared detection system in the field of hypersonic vehicles.

The traditional infrared hood radiation characteristic test method is aimed at the same material, and it is necessary to carry out one or even multiple repeated experiments when the material thickness changes. The environmental conditions such as temperature of each experiment cannot be guaranteed to be completely consistent. The measured value of the infrared hood material radiation characteristics The error with the real value is large and the extra experiment cost is wasted. The traditional idea is to use numerical simulation methods including discrete coordinate method, finite volume method, etc. to simulate the actual situation, and combine the apparent radiation intensity measurement results from different angles to invert and reconstruct the radiation characteristic field inside the medium, such as the absorption coefficient field, Refractive index field, etc. The reconstruction process is greatly affected by measurement errors, and the reconstruction accuracy decreases with the increase of the thickness of the medium. Therefore, there is an urgent need for a method to measure the thermal radiation characteristics of infrared head cover materials with different thicknesses at one time under high temperature conditions, and to establish a more efficient quantitative model of the transmission characteristics of high temperature infrared head cover materials.

SUMMARY OF THE INVENTION

The present invention solves the problem that the accuracy of the reconstruction result is crossed due to the large influence of the thickness of the material to be measured and the measurement error in the existing numerical simulation method.

An efficient measurement system for thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared hood, comprising a Fourier transform infrared spectrometer, a heating furnace, a blackbody furnace, a temperature control inspection instrument, and a data acquisition and processing system;

During measurement, the center of the detection lens of the Fourier transform infrared spectrometer, the center of the heating furnace and the center of the blackbody furnace cavity are set on the same horizontal line;

The black body furnace is used to emit black body infrared radiation; during the measurement process, the black body furnace is adjusted to change the black body temperature to emit infrared radiation at different black body temperatures;

Heating furnace, used for infrared hood sample heating; during the measurement process, adjust the temperature of the heating furnace to provide different temperatures for the infrared hood sample material;

Temperature control inspection instrument, used to detect and control the temperature in the heating furnace;

Fourier infrared spectrometer, used to obtain black body infrared radiation through the infrared hood;

The data acquisition and processing system is used to collect the data of the Fourier transform infrared spectrometer and the temperature control inspection instrument, and use the signal obtained by the Fourier infrared spectrometer to calculate the normal phase spectrum of the material at the temperature displayed by the temperature control inspection instrument. apparent radiation intensity.

An efficient method for measuring thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared hood, comprising the following steps:

Step 1, building the high-temperature infrared head cover material thermal radiation characteristic high-efficiency measurement system with different thicknesses according to claim 1;

Step 2. In the initial stage, the heating furnace is not started, the sample is not placed in the heating furnace, the black body furnace is started, the temperature of the black body furnace is set as T _b , and the infrared radiation L _obj of the black body is obtained with a Fourier transform infrared spectrometer;

Step 3: Place the infrared hood sample in a high-temperature heating furnace for heating. After the temperature of the infrared hood sample material reaches the specified temperature T _win and is uniformly distributed, use an infrared detector to obtain the infrared radiation L _{tot passing} through the infrared hood sample material. ;

Step 4: Control the temperature of the sample material to keep the temperature T _win unchanged, and repeat steps 2 and 3 under the state of changing the black body temperature T _b to obtain multiple sets of infrared radiation L _obj,i under the state of the black body temperature T _b, i and L _tot,i ; where subscript i denotes the ith measurement;

Step 5. When the temperature of the material remains unchanged, its radiation characteristic parameter is a fixed value. Through the statistics of the test results, the least squares method is used to fit the infrared radiation L _{obj,i and} L _tot,i , and then the transmittance τ _T,win and self-radiation L _T,win of the infrared hood sample material with uniform distribution of temperature T _win are obtained;

自身辐射

并基于

获得表观法向光谱发射率

Step 6: Divide the infrared head cover sample into n layers equally along the thickness direction, and obtain the apparent spectral transmittance of the infrared head cover sample material with unit thickness Δ according to the energy conservation relationship

self-radiation

and based on

Obtain the apparent normal spectral emissivity

吸收系数为

通过求解辐射传输方程计算得到该红外头罩样品材料的出射界面上任意角度的表观光谱辐射强度

表观法向光谱发射率估计值

以及表观光谱透过率估计值

Step 7. According to the algorithm for solving the inverse problem of radiation transmission, it is assumed that the refractive index of the sample material of the infrared head cover is

The absorption coefficient is

The apparent spectral radiation intensity at any angle on the exit interface of the infrared mask sample material is calculated by solving the radiation transfer equation

Apparent Normal Spectral Emissivity Estimates

and an estimate of apparent spectral transmittance

与表观光谱透过率

和步骤七得到的红外头罩样品材料的表观法向发射率估计值

与表观光谱透过率估计值

代入如下目标函数计算公式，计算得到目标函数值F_obj；Step 8. Calculate the apparent normal spectral emissivity of the infrared hood sample material obtained in Step 6

and apparent spectral transmittance

and the estimated apparent normal emissivity of the infrared hood sample material obtained in step 7

and apparent spectral transmittance estimates

Substitute the following objective function calculation formula, and calculate the objective function value F _obj ;

Step 9: Determine whether the objective function value F _obj in step 8 is less than the set threshold ξ,

吸收系数

即为该的红外头罩样品材料的真实折射率、吸收系数；If yes, then the refractive index of the infrared mask sample material assumed in step 8

absorption coefficient

That is, the real refractive index and absorption coefficient of the infrared head cover sample material;

吸收系数

重新设定红外头罩样品材料的折射率和吸收系数重新计算，直至步骤八中的目标函数值F_obj小于设定阈值ξ，得到该的红外头罩样品材料的真实折射率

吸收系数

If not, go back to step 7 and update the refractive index of the infrared hood sample material according to the inverse problem algorithm

absorption coefficient

Re-set the refractive index and absorption coefficient of the infrared mask sample material and recalculate until the objective function value F _obj in step 8 is less than the set threshold ξ, and obtain the real refractive index of the infrared mask sample material

absorption coefficient

折射率

吸收系数

Combined with step 6, the self-radiation of the sample material with temperature T _win is now obtained

refractive index

absorption coefficient

吸收系数

与自身辐射

其中下标j表示第j组测量；Step 10. Change the temperature T _win of the sample material, and repeat steps 2 to 9 to obtain the refractive index of the sample material of the infrared mask per unit thickness Δ under different temperatures T _win,j

absorption coefficient

with self-radiation

where the subscript j represents the jth group of measurements;

The self-radiation in different directions of the sample material of the infrared head cover per unit thickness Δ is obtained by calculation

吸收系数

与自身辐射

建立不同温度单位厚度Δ红外头罩材料的辐射物性数据库；By the refractive index of the sample material at different temperatures T _win,j

absorption coefficient

with self-radiation

Establish a database of radiation properties of infrared head cover materials with different temperature unit thickness Δ;

Step 11. Using the idea of physical dispersion, divide the infrared head cover to be measured into m layers with a thickness of Δ evenly; use an infrared thermal imager to measure the temperature of each infrared head cover thin layer under the working condition to be measured, record is T _win,k , where the subscript k=1,2,...,m represents the kth thin layer; according to the measurement results, the temperature field of the infrared head cover is established, and the infrared head with different temperature unit thickness Δ established in step 10 is queried. The radiation physical property database of the cover material is used to obtain the refractive index, absorption coefficient, self-radiation distribution field and radiation distribution field in different directions of each infrared head cover thin layer; and then the refractive index and absorption coefficient at different positions in the infrared head cover are obtained. The thickness direction superposition obtains the directional radiation intensity and directional emissivity of the infrared head cover to be tested.

Beneficial effects:

The traditional calculation method discretizes the infrared optical window to be measured at the model level, but the traditional calculation method is affected by the thickness of the material to be measured and the measurement error. Therefore, the present invention takes a different approach, using discrete materials at the physical level, dividing the material to be measured into several thin layers with smaller thickness, measuring the transmittance and self-radiation of the thin layers, and introducing a calculation method for the inverse problem of radiation transmission, Inversion reconstruction of the material's radiative properties, such as absorption coefficient and refractive index. At this time, since the thickness of the model reconstructed by inversion is small, the reconstruction result can be guaranteed to have high accuracy.

At the same time, the present invention also provides a method for measuring the thermal radiation characteristics such as transmittance and self-radiation of the infrared head cover with different material thicknesses without repeated experiments, according to the transmission mechanism of the target characteristics of the infrared head cover. In the quantitative model of the transmission characteristics of the head cover, as long as the radiation physical database of the infrared head cover material per unit thickness is established based on the refractive index, absorption coefficient and self-radiation of the sample material at different temperatures, the infrared head can be obtained for different material thicknesses without repeating the experiment. The transmittance of the cover and the thermal radiation characteristics such as self-radiation. Therefore, it provides key data support for evaluating the impact of missile loading conditions on infrared detection images and information processing, forms more realistic infrared detection simulation images, and promotes the design and optimization of hypersonic flight infrared detection systems.

Description of drawings

Figure 1 is a schematic diagram of a high-efficiency measurement system for thermal radiation characteristics of materials with different thicknesses of high-temperature infrared hoods.

Detailed ways

The working principle of the present invention will be further described in detail below with reference to the accompanying drawings.

Embodiment 1: This embodiment is described with reference to FIG. 1 ,

This embodiment is an efficient measurement system for thermal radiation characteristics of materials with different thicknesses of high-temperature infrared hoods, including a Fourier transform infrared spectrometer 1, a heating furnace 2, a black body furnace 3, a temperature control inspection instrument 4, and a data acquisition and processing system 5 ;

When working, the center of the detection lens, the center of the heating furnace and the center of the blackbody furnace cavity of the Fourier transform infrared spectrometer are set on the same horizontal line;

The black body furnace is used to emit black body infrared radiation; during the measurement process, the black body furnace is adjusted to change the black body temperature to emit infrared radiation at different black body temperatures.

Heating furnace, used for infrared hood sample heating; during the measurement process, adjust the temperature of the heating furnace to provide different temperatures for the infrared hood sample material;

Temperature control inspection instrument, used to detect and control the temperature in the heating furnace;

Fourier infrared spectrometer, used to obtain black body infrared radiation through the infrared hood;

The data acquisition and processing system is used to collect the data of the Fourier transform infrared spectrometer and the temperature control inspection instrument, and use the signal obtained by the Fourier infrared spectrometer to calculate the normal phase spectrum of the material at the temperature displayed by the temperature control inspection instrument. apparent radiation intensity.

In this embodiment,

The Fourier transform infrared spectrometer is FTIR-6100 Fourier transform infrared spectrometer. The main indicators are: (1) the highest spectral resolution is 0.022nm; (2) the scanning spectral range is 1.25-25; (3) the scanning frequency is 20Hz; (4) The signal-to-noise ratio is 50000/1.

The heating furnace is a SGM.M6/14AE heating furnace, which is a double-door heating furnace, and the depth, width and height (mm) of the furnace chamber are 230×180×150. Heating power: 4KW, the heating element is silicon molybdenum rod. Maximum temperature: 1700°C, temperature stability is ±1°C, temperature uniformity is ±6°C, and it takes 45-50 minutes to rise from room temperature to 1400°C.

The black body furnace is RT1500 type black body furnace. The main index parameters are: maximum temperature 1450℃, effective emissivity 0.99, radiation aperture φ50, temperature range: arbitrarily set within the range of 0-1450℃, temperature control accuracy ±0.5℃, stability 1 ℃/3min, heating time: room temperature to 1450 ℃ not more than 1 hour.

Specific implementation two:

The present embodiment is an efficient method for measuring the thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared head cover, including the following steps:

Step 1: Build an efficient measurement system for thermal radiation characteristics of materials with different thicknesses of high-temperature infrared hoods.

Step 2. In the initial stage, the heating furnace is not started, the sample is not placed in the heating furnace, the black body furnace is started, the temperature of the black body furnace is set as T _b , and the infrared radiation L _obj of the black body is obtained with a Fourier infrared spectrometer.

Step 3: Place the infrared hood sample in a high-temperature heating furnace for heating. After the temperature of the infrared hood sample material reaches the specified temperature T _win and is uniformly distributed, use an infrared detector to obtain the infrared radiation L _{tot passing} through the infrared hood sample material. ;

Infrared head cover material is infrared optical window material;

Step 4: Control the temperature of the sample material to keep the temperature T _win unchanged, and repeat steps 2 and 3 under the state of changing the black body temperature T _b to obtain multiple sets of infrared radiation L _obj,i under the state of the black body temperature T _b, i and L _tot,i ; where subscript i denotes the ith measurement.

Step 5. When the temperature of the material is constant, its radiation characteristic parameter is a fixed value. Therefore, through the statistics of the test results, the least squares method can be used to fit the infrared radiation L _obj under the state of multiple groups of black body temperatures T _{b, i} , _i and L _tot,i , and then obtain the transmittance τ _T,win and self-radiation L _T,win of the infrared hood sample material with uniform temperature T _win distribution.

自身辐射

并基于

获得表观法向光谱发射率

Step 6: Divide the infrared head cover sample into n layers equally along the thickness direction, and obtain the apparent spectral transmittance of the infrared head cover sample material with unit thickness Δ according to the energy conservation relationship

self-radiation

and based on

Obtain the apparent normal spectral emissivity

The apparent normal spectral emissivity can be calculated by

In the formula, L _T,b indicates that the temperature is the same as the temperature of the sample material per unit thickness, that is, the black body radiation intensity with temperature T _win .

吸收系数为

通过求解辐射传输方程计算得到该红外头罩样品材料的出射界面上任意角度的表观光谱辐射强度

表观法向光谱发射率估计值

以及表观光谱透过率估计值

Step 7. According to the algorithm for solving the inverse problem of radiation transmission, it is assumed that the refractive index of the sample material of the infrared head cover is

The absorption coefficient is

The apparent spectral radiation intensity at any angle on the exit interface of the infrared mask sample material is calculated by solving the radiation transfer equation

Apparent Normal Spectral Emissivity Estimates

and an estimate of apparent spectral transmittance

与表观光谱透过率

和步骤七得到的红外头罩样品材料的表观法向发射率估计值

与表观光谱透过率估计值

代入如下目标函数计算公式，计算得到目标函数值F_obj；Step 8. Calculate the apparent normal spectral emissivity of the infrared hood sample material obtained in Step 6

and apparent spectral transmittance

and the estimated apparent normal emissivity of the infrared hood sample material obtained in step 7

and apparent spectral transmittance estimates

Substitute the following objective function calculation formula, and calculate the objective function value F _obj ;

Step 9: Determine whether the objective function value F _obj in step 8 is less than the set threshold ξ,

吸收系数

即为该的红外头罩样品材料的真实折射率、吸收系数；If yes, then the refractive index of the infrared mask sample material assumed in step 8

absorption coefficient

That is, the real refractive index and absorption coefficient of the infrared head cover sample material;

吸收系数

重新设定红外头罩样品材料的折射率和吸收系数值重新计算，直至步骤八中的目标函数值F_obj小于设定阈值ξ，得到该的红外头罩样品材料的真实折射率

吸收系数

结合步骤六，目前获得了温度为T_win的样品材料的自身辐射

折射率

吸收系数

If not, go back to step 7 and update the refractive index of the infrared hood sample material according to the inverse problem algorithm

absorption coefficient

Re-set the refractive index and absorption coefficient values of the infrared hood sample material and recalculate until the objective function value F _obj in step 8 is less than the set threshold ξ, and obtain the true refractive index of the infrared hood sample material

absorption coefficient

Combined with step 6, the self-radiation of the sample material with temperature T _win is now obtained

refractive index

absorption coefficient

吸收系数

与自身辐射

其中下标j表示第j组测量。Step 10. Change the temperature T _win of the sample material, and repeat steps 2 to 9 to obtain the refractive index of the sample material of the infrared mask per unit thickness Δ under different temperatures T _win,j

absorption coefficient

with self-radiation

where the subscript j denotes the jth group of measurements.

(这里引入的不同方向的辐射强度是通过折射率和吸收系数计算得到的，不是测量得到的)。通过不同温度T_win,j下的样品材料的折射率

吸收系数

与自身辐射

建立不同温度单位厚度Δ红外头罩材料的辐射物性数据库。The self-radiation in different directions of the sample material of the infrared hood per unit thickness Δ can be obtained by calculation

(The radiation intensity in different directions introduced here is calculated from the refractive index and absorption coefficient, not measured). By the refractive index of the sample material at different temperatures T _win,j

absorption coefficient

with self-radiation

A database of radiation properties of infrared head cover materials with different temperature and unit thickness Δ is established.

Step 11: Using the idea of physical dispersion, divide the infrared head cover to be measured into m layers with a thickness of Δ. Using an infrared thermal imager to measure, under the working conditions to be measured, the temperature of each infrared hood thin layer is denoted as T _win,k , where the subscript k=1,2,...,m represents the kth thin layer. According to the measurement results, the temperature field of the infrared head cover is established, and the radiation properties database of the infrared head cover material with different temperature unit thickness Δ established in step 10 is inquired, and the refractive index, absorption coefficient, and self-radiation distribution field of each infrared head cover thin layer can be obtained. And the radiation distribution field in different directions. Then, the refractive index and absorption coefficient at different positions in the infrared head cover can be obtained, and the directional radiation intensity and directional emissivity of the infrared head cover to be measured can be obtained by superimposing along the thickness direction.

Specific implementation three:

自身辐射

的过程包括以下步骤：This embodiment is an efficient method for measuring the thermal radiation characteristics of materials with different thicknesses of high-temperature infrared hoods. Step 6 obtains the apparent spectral transmittance of the infrared hood sample material with unit thickness Δ

self-radiation

The process includes the following steps:

The infrared radiation L _tot of the infrared head cover material measured by the infrared detection system (the system in the Fourier transform infrared spectrometer) is the radiance L _λ (s) of the inner surface of the material, which is determined by the target reaching the outer surface of the infrared head cover sample. The combined action of the infrared radiation L _obj and the radiation L _win of the infrared hood itself, namely

L _tot =L _obj τ _win +L _win (3)

where τ _win is the transmittance of the infrared optical window.

The radiation transfer equation is used to describe the transfer process of the target radiant energy through the infrared hood specimen. The energy is conserved along the radiation transmission direction. The infrared hood material is divided into n equal layers, and the transmittance and the unit thickness of the infrared hood material are deduced. There is a fixed algebraic relationship between self-radiation and the transmittance of the entire infrared head cover and self-radiation; according to the obtained algebraic relationship, the transmittance, Thermal radiation characteristic data such as attenuation coefficient.

和自身辐射

各向同性，根据辐射传输原理和能量守恒关系可以得到透过红外头罩材料第1层的总辐射为In order to achieve this purpose, the technical solution adopted in the present invention is: divide the infrared head cover sample into n layers equally along the thickness direction, assuming that the temperature T distribution of the infrared optical window is uniform, and the apparent spectral transmittance of each layer is

and self-radiation

Isotropic, according to the principle of radiation transfer and the relationship of energy conservation, the total radiation passing through the first layer of the infrared head cover material can be obtained as

The infrared radiation transmitted through the 1st to 2nd layers is

In the same way, the total radiation passing through the first to n layers, that is, the total radiation passing through the entire infrared head cover is:

和自身辐射

与整个红外探测红外头罩的透过率τ_T,win和自身辐射L_T,win之间所满足的代数关系式为Furthermore, the apparent spectral transmittance of the infrared head cover material with a thickness of Δ and a temperature of T can be deduced by the energy method.

and self-radiation

The algebraic relationship satisfied between the transmittance τ _T,win of the entire infrared detection infrared hood and the self-radiation L _T,win is:

By measuring the transmittance and infrared radiation characteristics of the infrared head cover with a thickness of x, the apparent spectral transmittance and self-radiation characteristics of the infrared optical window material with a unit thickness Δ are obtained.

Therefore, without repeating the experiment many times, the thermal radiation characteristic data of other infrared optical window materials with different thicknesses under the same temperature and other environmental conditions can be directly calculated according to the obtained algebraic relationship, and the quantitative model of the transmission characteristics of the infrared head cover is established.

Specific implementation four:

表观法向光谱发射率估计值

以及表观光谱透过率估计值

的过程包括以下步骤：This embodiment is an efficient method for measuring the thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared head cover. In step 7, the apparent spectral radiation intensity at any angle on the exit interface of the infrared head cover sample material is calculated by solving the radiation transfer equation.

Apparent Normal Spectral Emissivity Estimates

and an estimate of apparent spectral transmittance

The process includes the following steps:

折射率为

吸收系数为

反射率为

介质厚度为Δ；在一维条件下，当介质处于稳态条件下且不考虑介质散射时，辐射传递方程可化简为：Assuming that the temperature of the isotropic medium is

The refractive index is

The absorption coefficient is

reflectivity

The thickness of the medium is Δ; under one-dimensional conditions, when the medium is in a steady state and the scattering of the medium is not considered, the radiative transfer equation can be simplified to:

Solving the radiation transfer equation yields:

表示前向辐射，

表示后向辐射；θ为前向辐射、后向辐射分别与面法线的夹角；in,

represents forward radiation,

Represents the backward radiation; θ is the angle between the forward radiation and the backward radiation respectively and the surface normal;

At the inner boundary x=0, the radiation intensity propagating in the positive direction includes the part that reflects the radiation intensity incident on the interface, thus:

Similarly, at the inner boundary x=L, the radiation intensity propagating in the negative direction also includes the part that reflects the radiation intensity incident on the interface, namely:

Combining the radiation transfer equations along the positive and negative directions in the medium and the two boundary conditions, it can be simplified to get:

in,

Then the apparent spectral radiation intensity at any angle on the exit interface is:

The apparent normal spectral emissivity is:

where L _T,b is the black body radiation intensity corresponding to temperature T and wavelength λ;

由贝尔定律可以得到：Apparent spectral transmittance

From Bell's law we can get:

折射率

吸收系数

反射率为

为假设值，因此对应得到的表观法向光谱发射率

表观光谱透过率

即为表观光谱发射率估计值

表观光谱透过率估计值

Due to isotropic medium temperature

refractive index

absorption coefficient

reflectivity

is an assumed value and therefore corresponds to the apparent normal spectral emissivity obtained

Apparent spectral transmittance

is the apparent spectral emissivity estimate

Apparent spectral transmittance estimate

In the present invention, by measuring the thermal radiation transmission characteristics of an infrared head cover material of one thickness, the corresponding radiation characteristics of the infrared head cover material per unit thickness are calculated, and then the transmission characteristics of other infrared head cover materials with different thicknesses under the same temperature condition are calculated. The thermal radiation characteristic data such as over-rate has realized the establishment of the quantitative model of infrared head cover transmission.

The present invention can also have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations are all It should belong to the protection scope of the appended claims of the present invention.

Claims (10)

1. a high-temperature infrared hood material thermal radiation characteristic high-efficiency measurement system with different thicknesses, is characterized in that, comprises Fourier transform infrared spectrometer, heating furnace, black body furnace, temperature control inspection instrument and data acquisition and processing system; During measurement, the center of the detection lens of the Fourier transform infrared spectrometer, the center of the heating furnace and the center of the blackbody furnace cavity are set on the same horizontal line; The black body furnace is used to emit black body infrared radiation; during the measurement process, the black body furnace is adjusted to change the black body temperature to emit infrared radiation at different black body temperatures; Heating furnace, used for infrared hood sample heating; during the measurement process, adjust the temperature of the heating furnace to provide different temperatures for the infrared hood sample material; Temperature control inspection instrument, used to detect and control the temperature in the heating furnace; Fourier infrared spectrometer, used to obtain black body infrared radiation through the infrared hood; The data acquisition and processing system is used to collect the data of the Fourier transform infrared spectrometer and the temperature control inspection instrument, and use the signal obtained by the Fourier infrared spectrometer to calculate the normal phase spectrum of the material at the temperature displayed by the temperature control inspection instrument. apparent radiation intensity. 2. a high-temperature infrared hood high-efficiency measuring method for thermal radiation characteristics of different thickness materials, is characterized in that, comprises the following steps: Step 1, building the high-temperature infrared head cover material thermal radiation characteristic high-efficiency measurement system with different thicknesses according to claim 1; Step 2. In the initial stage, the heating furnace is not started, the sample is not placed in the heating furnace, the black body furnace is started, the temperature of the black body furnace is set as T _b , and the infrared radiation L _obj of the black body is obtained with a Fourier transform infrared spectrometer; Step 3: Place the infrared hood sample in a high-temperature heating furnace for heating. After the temperature of the infrared hood sample material reaches the specified temperature T _win and is uniformly distributed, use an infrared detector to obtain the infrared radiation L _{tot passing} through the infrared hood sample material. ; Step 4: Control the temperature of the sample material to keep the temperature T _win unchanged, and repeat steps 2 and 3 under the state of changing the black body temperature T _b to obtain multiple sets of infrared radiation L _obj,i under the state of the black body temperature T _b, i and L _tot,i ; where subscript i denotes the ith measurement; Step 5. When the temperature of the material remains unchanged, its radiation characteristic parameter is a fixed value. Through the statistics of the test results, the least squares method is used to fit the infrared radiation L _{obj,i and} L _tot,i , and then the transmittance τ _T,win and self-radiation L _T,win of the infrared hood sample material with uniform distribution of temperature T _win are obtained; Step 6: Divide the infrared head cover sample into n layers equally along the thickness direction, and obtain the apparent spectral transmittance of the infrared head cover sample material with unit thickness Δ according to the energy conservation relationship

self-radiation

and based on

Obtain the apparent normal spectral emissivity

Step 7. According to the algorithm for solving the inverse problem of radiation transmission, it is assumed that the refractive index of the sample material of the infrared head cover is

The absorption coefficient is

The apparent spectral radiation intensity at any angle on the exit interface of the infrared mask sample material is calculated by solving the radiation transfer equation

Apparent Normal Spectral Emissivity Estimates

and an estimate of apparent spectral transmittance

Step 8. Calculate the apparent normal spectral emissivity of the infrared hood sample material obtained in Step 6

and apparent spectral transmittance

and the estimated apparent normal emissivity of the infrared hood sample material obtained in step 7

and apparent spectral transmittance estimates

Substitute the following objective function calculation formula, and calculate the objective function value F _obj ;

Step 9: Determine whether the objective function value F _obj in step 8 is less than the set threshold ξ, If yes, then the refractive index of the infrared mask sample material assumed in step 8

absorption coefficient

That is, the real refractive index and absorption coefficient of the infrared head cover sample material; If not, go back to step 7 and update the refractive index of the infrared hood sample material according to the inverse problem algorithm

absorption coefficient

Re-set the refractive index and absorption coefficient of the infrared mask sample material and recalculate until the objective function value F _obj in step 8 is less than the set threshold ξ, and obtain the real refractive index of the infrared mask sample material

absorption coefficient

Combined with step 6, the self-radiation of the sample material with temperature T _win is now obtained

refractive index

absorption coefficient

Step 10. Change the temperature T _win of the sample material, and repeat steps 2 to 9 to obtain the refractive index of the sample material of the infrared mask per unit thickness Δ under different temperatures T _win,j

absorption coefficient

with self-radiation

where the subscript j represents the jth group of measurements; The self-radiation in different directions of the sample material of the infrared head cover per unit thickness Δ is obtained by calculation

By the refractive index of the sample material at different temperatures T _win,j

absorption coefficient

with self-radiation

Establish a database of radiation properties of infrared head cover materials with different temperature unit thickness Δ; Step 11. Using the idea of physical dispersion, divide the infrared head cover to be measured into m layers with a thickness of Δ evenly; use an infrared thermal imager to measure the temperature of each infrared head cover thin layer under the working condition to be measured, record is T _win,k , where the subscript k=1,2,...,m represents the kth thin layer; according to the measurement results, the temperature field of the infrared head cover is established, and the infrared head with different temperature unit thickness Δ established in step 10 is queried. The radiation physical property database of the cover material is used to obtain the refractive index, absorption coefficient, self-radiation distribution field and radiation distribution field in different directions of each infrared head cover thin layer; and then the refractive index and absorption coefficient at different positions in the infrared head cover are obtained. The thickness direction superposition obtains the directional radiation intensity and directional emissivity of the infrared head cover to be tested. 3. a kind of high-temperature infrared head cover material heat radiation characteristic high-efficiency measurement method with different thicknesses according to claim 2, is characterized in that, described step 6 obtains the apparent spectral transmittance of the infrared head cover sample material of unit thickness Δ

self-radiation

The process includes the following steps: The radiation transfer equation is used to describe the transfer process of the target radiant energy through the infrared head cover specimen. The energy is conserved along the radiation transmission direction, and the infrared head cover material is divided into n layers. It is assumed that the temperature T distribution of the infrared optical window is uniform, and each Apparent spectral transmittance of the layer

and self-radiation

Isotropic, according to the principle of radiation transfer and the relationship of energy conservation, the total radiation passing through the first layer of the infrared head cover material is obtained as

The infrared radiation transmitted through the 1st to 2nd layers is

In the same way, the total radiation passing through the first to n layers, that is, the total radiation passing through the entire infrared head cover is:

Then, the apparent spectral transmittance of the infrared head cover material with thickness Δ and temperature T is deduced by the energy method

Algebraic relationship with the transmittance τ _T,win of the infrared detection infrared hood, and the apparent spectral transmittance

The algebraic relationship between the transmittance τ _T,win of the infrared detection infrared hood and its own radiation; By measuring the transmittance and infrared radiation characteristics of the infrared head cover with a thickness of x, the apparent spectral transmittance and self-radiation thermal radiation characteristics data of the infrared optical window material with a unit thickness Δ are obtained; the infrared optical window material is the infrared head cover material. 4. a kind of high temperature infrared head cover material heat radiation characteristic efficient measurement method of different thickness according to claim 3, is characterized in that, the apparent spectral transmittance of described infrared head cover material

The algebraic relationship with the transmittance τ _T,win of the infrared detection infrared hood is:

5. The method for efficiently measuring the thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared head cover according to claim 4, wherein the apparent spectral transmittance is

The algebraic relationship between the transmittance τ _T,win of the infrared detection infrared hood and its own radiation is:

6. The method for efficiently measuring the thermal radiation characteristics of a high temperature infrared head cover material with different thicknesses according to claim 3, 4 or 5, wherein the apparent normal spectral emissivity obtained in step 6

as follows:

In the formula, L _T,b indicates that the temperature is the same as the temperature of the sample material per unit thickness, that is, the black body radiation intensity with temperature T _win . 7. The method for efficiently measuring the thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared hood according to claim 6, characterized in that, in step 7, the radiation transfer equation is calculated to obtain on the exit interface of the sample material of the IR hood Apparent spectral radiant intensity at any angle

Apparent Normal Spectral Emissivity Estimates

The process includes the following steps: Assuming that the temperature of the isotropic medium is

The refractive index is

The absorption coefficient is

reflectivity

The thickness of the medium is Δ; under one-dimensional conditions, when the medium is in a steady state and the scattering of the medium is not considered, the radiation transfer equation simplifies to:

The forward radiation is obtained by solving the simplified radiation transfer equation

and backward radiation

θ is the angle between the forward radiation and the backward radiation respectively and the surface normal; At the inner boundary x=0, the radiation intensity propagating in the positive direction includes the part that reflects the radiation intensity incident on the interface, thus:

Similarly, at the inner boundary x=L, the radiation intensity propagating in the negative direction also includes the part that reflects the radiation intensity incident on the interface, namely:

Combining the radiative transfer equations along the positive and negative directions in the medium and the two boundary conditions, we can get:

in,

Then the apparent spectral radiation intensity at any angle on the exit interface is:

The apparent normal spectral emissivity is:

where L _T,b is the black body radiation intensity corresponding to temperature T and wavelength λ; Due to isotropic medium temperature

refractive index

absorption coefficient

reflectivity

is a hypothetical value and therefore corresponds to the obtained apparent normal spectral emissivity

is the apparent spectral emissivity estimate

8 . The method for efficiently measuring the thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared head cover according to claim 7 , wherein the forward radiation obtained by solving the simplified radiation transfer equation is obtained. 9 .

and backward radiation

as follows:

9 . The method for efficiently measuring the thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared head cover according to claim 7 , wherein the estimated value of apparent spectral transmittance in step 7 is

Calculated by Bell's Law. 10. The method for efficiently measuring the thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared head cover according to claim 9, wherein the estimated value of apparent spectral transmittance is obtained in step 7

The specific process includes the following steps: Apparent spectral transmittance

From Bell's law we can get:

Due to isotropic medium temperature

refractive index

absorption coefficient

reflectivity

is a hypothetical value, so the corresponding apparent spectral transmittance is obtained

is the estimated value of apparent spectral transmittance

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