CN114646663A - High-efficiency measurement system and method for thermal radiation characteristics of materials with different thicknesses of high-temperature infrared hood - Google Patents
High-efficiency measurement system and method for thermal radiation characteristics of materials with different thicknesses of high-temperature infrared hood Download PDFInfo
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Abstract
A high-efficiency measurement system and method for thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared hood belong to the technical field of thermal radiation measurement. The method aims to solve the problem that reconstruction result precision is crossed due to the fact that the existing numerical simulation method is greatly influenced by the thickness of a material to be measured and measurement errors. According to the invention, an infrared hood test piece is equally divided along the radiation transfer direction, and the total radiation penetrating through the 1 st layer, the 1 st-2 nd layer, the … … and the 1-n th layer of the hood material is sequentially obtained according to the radiation transmission principle and the energy conservation relation; an algebraic relationship is then derived based on an energy method that is satisfied between the transmittance and self-irradiance of the infrared hood material having a thickness Δ and a temperature T and the transmittance and self-irradiance of the entire infrared detection hood. The transmittance of the infrared hood with the thickness x, the self-radiation characteristic and other heat radiation characteristics are measured through experiments, and the heat radiation characteristic data of the material with the unit thickness are calculated based on an algebraic relation. The infrared hood is mainly used for obtaining the heat radiation characteristic of the infrared hood.
Description
Technical Field
The invention belongs to the technical field of thermal radiation measurement, and particularly relates to a method for measuring thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared hood.
Background
When the aircraft flies in the atmosphere at ultrahigh speed, the high-temperature infrared hood quickly becomes a main factor of the aerodynamic heat radiation effect of the infrared detection system. The high temperature increases the self thermal radiation of the infrared hood, the radiation on the surface of the infrared hood is mainly concentrated on an infrared band, the high-temperature shock wave gas and the infrared hood generate strong pneumatic thermal radiation effect to form radiation interference on a detector and form interference on an infrared signal of a target, the background brightness of the detector is increased, the detection signal-to-noise ratio of the target is reduced, the detection and tracking capacity of the system on the target is reduced, even the infrared detector is saturated and cannot accurately distinguish the signal from the target, the target detection, tracking and identification capacity is weakened, and the imaging quality of the infrared detection system is reduced.
At present, measurement and research on infrared hood materials mostly focus on physical and chemical properties such as strength, hardness, melting point, refractive index, thermal conductivity and corrosion resistance, the research on thermal radiation transmission characteristics such as transmittance and attenuation coefficient is less, data in a high-temperature state is less, the development of the research on the aerodynamic thermal radiation effect of a high-temperature infrared optical window is influenced or even restricted, and the application of an infrared detection system in the field of hypersonic aircrafts is hindered.
The traditional method for testing the radiation characteristic of the infrared hood aims at the same material, one or even a plurality of repeated experiments are required to be carried out when the thickness of the material is changed, the environmental working conditions such as the temperature and the like of each experiment cannot be guaranteed to be completely consistent, the error between the radiation characteristic measured value and the true value of the infrared hood material is large, and extra experiment cost waste is caused. The traditional idea is to simulate the actual situation by adopting a numerical simulation method including a discrete coordinate method, a finite volume method and the like, and inversely reconstruct the radiation characteristic field in the medium, such as an absorption coefficient field, a refractive index field and the like, by combining the measurement results of the apparent radiation intensities at different angles. The reconstruction process is greatly affected by measurement errors and the like, and the reconstruction accuracy decreases as the thickness of the medium increases. Therefore, a method for realizing one-time measurement of thermal radiation characteristics of infrared hood materials with different thicknesses in a high-temperature state is urgently needed, and a high-temperature infrared hood transmission characteristic quantification model is established more efficiently.
Disclosure of Invention
The invention aims to solve the problem of cross-precision of the reconstruction result caused by the fact that the existing numerical simulation method is greatly influenced by the thickness of a material to be measured and measurement errors.
A high-efficiency measurement system for heat radiation characteristics of materials with different thicknesses of a high-temperature infrared hood comprises a Fourier transform infrared spectrometer, a heating furnace, a black body furnace, a temperature control patrol instrument and a data acquisition and processing system;
during measurement, the center of a detection lens of the Fourier infrared spectrometer, the center of the heating furnace and the center of the black body furnace cavity are arranged on the same horizontal line;
a blackbody furnace for emitting blackbody infrared radiation; in the measuring process, adjusting the blackbody furnace to change the temperature of the blackbody so as to emit infrared radiation at different blackbody temperatures;
the heating furnace is used for heating the infrared hood sample; in the measuring process, the temperature of the heating furnace is adjusted to provide different temperatures for the infrared hood sample material;
the temperature control polling instrument is used for detecting and controlling the temperature in the heating furnace;
the Fourier infrared spectrometer is used for acquiring black body infrared radiation penetrating through the infrared hood;
and the data acquisition and processing system is used for acquiring data of the Fourier infrared spectrometer and the temperature control patrol instrument, and calculating the normal phase spectrum apparent radiation intensity of the material at the temperature displayed by the temperature control patrol instrument by using the signals obtained by the Fourier infrared spectrometer.
A high-efficiency measurement method for the thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared hood comprises the following steps:
firstly, building a high-efficiency measuring system for the heat radiation characteristics of materials with different thicknesses of a high-temperature infrared hood according to claim 1;
step two, initial stage, without starting the heating furnace, the heating furnaceStarting the black body furnace without placing a sample therein, and setting the temperature of the black body furnace to be TbObtaining the infrared radiation L of the black body by using a Fourier infrared spectrometerobj；
Thirdly, placing the infrared hood sample in a high-temperature heating furnace for heating until the temperature of the infrared hood sample material reaches the specified temperature TwinAfter the infrared radiation L is uniformly distributed, the infrared radiation L penetrating through the infrared hood sample material is obtained by an infrared detectortot；
Step four, controlling the temperature of the sample material to keep the temperature of the sample material at TwinChanging the black body temperature T without changebIn the state, repeating the second step and the third step to obtain a plurality of groups of blackbody temperatures Tb,iInfrared radiation L in the stateobj,iAnd Ltot,i(ii) a Wherein the subscript i represents the ith measurement;
step five, when the temperature of the material is not changed, the radiation characteristic parameter is a fixed value, and through statistics of the test result, a least square method is utilized to fit a plurality of groups of blackbody temperatures Tb,iInfrared radiation L in the stateobj,iAnd Ltot,iAnd then the temperature T is obtainedwinTransmittance tau of uniformly distributed infrared hood sample materialT,winAnd self-radiation LT,win；
Step six, equally dividing the infrared hood sample into n layers along the thickness direction, and obtaining the apparent spectral transmittance of the infrared hood sample material with unit thickness delta according to the energy conservation relation
Self-radiation
And based on
Obtaining apparent normal spectral emissivity
Step seven, solving algorithm according to radiation transmission inverse problem, assuming infrared headThe refractive index of the mask sample material is
Absorption coefficient of
Calculating to obtain the apparent spectral radiation intensity of any angle on the emergent interface of the infrared hood sample material by solving a radiation transmission equation
Apparent normal spectral emissivity estimation
And an apparent spectral transmittance estimate
Step eight, the apparent normal spectral emissivity of the infrared hood sample material obtained in the step six
And apparent spectral transmittance
And seventhly, obtaining the estimated value of the apparent normal emissivity of the infrared hood sample material
And an apparent spectral transmittance estimate
Substituting the obtained target function value into the following target function calculation formula to obtain a target function value Fobj；
Step nine, judging the objective function value F in the step eightobjWhether or not it is smaller than a set threshold value xi,
if yes, the refractive index of the infrared hood sample material assumed in the step eight
Coefficient of absorption
The real refractive index and the absorption coefficient of the infrared hood sample material are obtained;
if not, returning to the seventh step, and updating the refractive index of the infrared hood sample material according to the inverse problem algorithm
Coefficient of absorption
Resetting the refractive index and absorption coefficient of the infrared hood sample material and recalculating until the objective function value F in the step eightobjIs less than a set threshold xi to obtain the real refractive index of the infrared hood sample material
Coefficient of absorption
In combination with step six, a temperature T is now obtainedwinSelf-irradiation of the sample material
Refractive index
Coefficient of absorption
Step ten, changing the temperature T of the sample materialwinRepeating the second step toStep nine, to obtain different temperatures Twin,jRefractive index of infrared hood sample Material
Coefficient of absorption
With self-radiation
Wherein the subscript j represents the jth set of measurements;
calculating to obtain self-radiation of infrared hood sample material with unit thickness delta in different directions
By different temperatures Twin,jRefractive index of sample material
Coefficient of absorption
And self-radiation
Establishing a radiation physical property database of infrared hood materials with different temperature unit thicknesses delta;
step eleven, uniformly dividing the infrared hood to be detected into m thin layers with the thickness of delta by using a physical dispersion idea; measuring by using a thermal infrared imager, and recording the temperature of each infrared hood thin layer as T under the working condition to be measuredwin,kWherein the subscript k ═ 1,2, …, m, denotes the kth thin layer; establishing a temperature field of the infrared hood according to the measurement result, and inquiring a radiation physical property database of the infrared hood materials with different temperature unit thicknesses delta established in the step ten to obtain the refractive index, the absorption coefficient, the self radiation distribution field and the radiation distribution fields in different directions of each infrared hood thin layer; thereby obtaining the refractive indexes of different positions in the infrared hoodAnd the absorption coefficient is obtained by superposing along the thickness direction, and the directional radiation intensity and the directional emissivity of the infrared hood to be detected are obtained.
Has the advantages that:
the traditional calculation method is used for dispersing the infrared optical window to be measured on a model level, but the traditional calculation method is influenced by the thickness of the material to be measured and measurement errors. Therefore, the invention develops a new method, the material is dispersed on the physical level, the material to be measured is divided into a plurality of thin layers with smaller thickness, the transmittance and the self radiation of the thin layers are measured, and a radiation transmission inverse problem calculation method is introduced to perform inversion reconstruction on the radiation characteristics of the material, such as the absorption coefficient and the refractive index. At the moment, the thickness of the model for inversion reconstruction is small, so that the reconstruction result can be ensured to have high precision.
Meanwhile, the invention also provides a method for measuring the transmittance and self-radiation and other thermal radiation characteristics of the infrared hood with different material thicknesses without repeated experiments according to a target characteristic transmission mechanism of the infrared hood, namely, when an infrared hood transmission characteristic quantification model is established in the previous period, the transmittance and self-radiation and other thermal radiation characteristics of the infrared hood with different material thicknesses can be obtained without repeated experiments after a radiometric property database of the infrared hood material with unit thickness is established on the basis of the refractive index, the absorption coefficient and the self-radiation of the sample material with different temperatures. Therefore, key data support is provided for evaluating the influence of the missile-borne condition on the infrared detection image and information processing, a more vivid infrared detection simulation image is formed, and the design and optimization of the hypersonic flight infrared detection system are promoted.
Drawings
FIG. 1 is a schematic view of a high-efficiency measurement system for thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared hood.
Detailed Description
The operation of the present invention will be described in further detail with reference to the accompanying drawings.
The first embodiment is as follows: the present embodiment is described in connection with figure 1,
the embodiment is a high-efficiency measurement system for the heat radiation characteristics of materials with different thicknesses of a high-temperature infrared hood, which comprises a Fourier transform infrared spectrometer 1, a heating furnace 2, a black body furnace 3, a temperature control patrol instrument 4 and a data acquisition and processing system 5;
when the device works, the center of a detection lens of the Fourier infrared spectrometer, the center of a heating furnace and the center of a black body furnace cavity are arranged on the same horizontal line;
a blackbody furnace for emitting blackbody infrared radiation; during the measurement work process, the blackbody furnace is adjusted to change the temperature of the blackbody so as to emit infrared radiation at different blackbody temperatures.
The heating furnace is used for heating the infrared hood sample; in the measuring process, the temperature of the heating furnace is adjusted to provide different temperatures for the infrared hood sample material;
the temperature control polling instrument is used for detecting and controlling the temperature in the heating furnace;
the Fourier infrared spectrometer is used for acquiring black body infrared radiation penetrating through the infrared hood;
and the data acquisition and processing system is used for acquiring data of the Fourier infrared spectrometer and the temperature control patrol instrument, and calculating the normal phase spectrum apparent radiation intensity of the material at the temperature displayed by the temperature control patrol instrument by using the signals obtained by the Fourier infrared spectrometer.
In the present embodiment, it is preferred that,
the Fourier transform infrared spectrometer is an FTIR-6100 Fourier transform infrared spectrometer, and the main indexes are as follows: (1) the highest spectral resolution is 0.022 nm; (2) the scanning spectrum range is 1.25-25; (3) the scanning frequency is 20 Hz; (4) the signal to noise ratio is 50000/1.
The heating furnace is an SGM.M6/14AE type heating furnace which is a double-door heating furnace, and the depth, width and height (mm) of a hearth are 230 multiplied by 180 multiplied by 150. Heating power: 4KW, the heating element is a silicon-molybdenum rod. Maximum temperature: 1700 ℃, the temperature stability is +/-1 ℃, the temperature uniformity is +/-6 ℃, and 45-50 minutes are required for heating from room temperature to 1400 ℃.
The black body furnace is an RT1500 type black body furnace, and the main index parameters are as follows: the maximum temperature is 1450 ℃, the effective emissivity is 0.99, the radiation aperture phi is 50, and the temperature range is as follows: the temperature is arbitrarily set within the range of 0-1450 ℃, the temperature control precision is +/-0.5 ℃, the stability is 1 ℃/3min, and the temperature rise time is as follows: room temperature to 1450 deg.c for not more than 1 hr.
The second embodiment is as follows:
the embodiment is a high-efficiency measuring method for the heat radiation characteristics of materials with different thicknesses of a high-temperature infrared hood, which comprises the following steps:
step one, building a high-efficiency measuring system for the heat radiation characteristics of materials with different thicknesses of the high-temperature infrared hood.
Step two, 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, and the temperature of the black body furnace is set to be TbObtaining the infrared radiation L of the black body by using a Fourier infrared spectrometerobj。
Thirdly, placing the infrared hood sample in a high-temperature heating furnace for heating until the temperature of the infrared hood sample material reaches the specified temperature TwinAfter the infrared radiation L is uniformly distributed, the infrared radiation L penetrating through the infrared hood sample material is obtained by an infrared detectortot；
Infrared hood materials, namely infrared optical window materials;
step four, controlling the temperature of the sample material to keep the temperature of the sample material at TwinChanging the black body temperature T without changebIn the state, repeating the second step and the third step to obtain a plurality of groups of blackbody temperatures Tb,iInfrared radiation L in stateobj,iAnd Ltot,i(ii) a Where the index i indicates the ith measurement.
Step five, when the temperature of the material is not changed, the radiation characteristic parameter is a fixed value, so that a plurality of groups of blackbody temperatures T can be fitted by utilizing a least square method through statistics of test resultsb,iInfrared radiation L in the stateobj,iAnd Ltot,iAnd then the temperature T is obtainedwinTransmittance tau of uniformly distributed infrared hood sample materialT,winAnd self-radiation LT,win。
Step six, equally dividing the infrared hood sample into n layers along the thickness direction, and obtaining the apparent spectral transmittance of the infrared hood sample material with unit thickness delta according to the energy conservation relation
Self-radiation
And based on
Obtaining apparent normal spectral emissivity
The apparent normal spectral emissivity can be calculated by the following formula
In the formula, LT,bIndicating that the temperature is the same as the temperature of the sample material per unit thickness, i.e. the temperature is TwinThe black body radiation intensity of (a).
Step seven, solving an algorithm according to the radiation transmission inverse problem, and assuming that the refractive index of the infrared hood sample material is
Absorption coefficient of
Calculating to obtain the apparent spectral radiation intensity of any angle on the emergent interface of the infrared hood sample material by solving a radiation transmission equation
Apparent normal spectral emissivity estimation
And an apparent spectral transmittance estimate
Step eight, red obtained in the step sixApparent normal spectral emissivity of outer hood sample material
And apparent spectral transmittance
And seventhly, obtaining the estimated value of the apparent normal emissivity of the infrared hood sample material
And an apparent spectral transmittance estimate
Substituting the obtained target function value into the following target function calculation formula to obtain a target function value Fobj；
Step nine, judging the objective function value F in the step eightobjWhether or not it is smaller than a set threshold value xi,
if yes, the refractive index of the infrared hood sample material assumed in the step eight
Coefficient of absorption
The real refractive index and the absorption coefficient of the infrared hood sample material are obtained;
if not, returning to the seventh step, and updating the refractive index of the infrared hood sample material according to the inverse problem algorithm
Coefficient of absorption
Resetting refractive index and absorption coefficient of infrared hood sample materialThe value is recalculated until the value of the objective function F in step eightobjIs less than a set threshold xi to obtain the real refractive index of the infrared hood sample material
Coefficient of absorption
In combination with step six, a temperature T is now obtainedwinSelf-irradiation of the sample material
Refractive index
Coefficient of absorption
Step ten, changing the temperature T of the sample materialwinRepeating the second to the ninth steps to obtain different temperatures Twin,jRefractive index of infrared hood sample Material
Coefficient of absorption
And self-radiation
Where the index j indicates the jth set of measurements.
The self-radiation of the infrared hood sample material with unit thickness delta in different directions can be obtained by calculation
(the intensities of radiation in different directions introduced here are calculated from the refractive index and absorption coefficient and are not measured). By different temperatures Twin,jFold of sample Material underRefractive index
Coefficient of absorption
And self-radiation
And establishing a radiation physical property database of infrared hood materials with different temperature unit thicknesses delta.
And step eleven, uniformly dividing the infrared hood to be measured into m thin layers with the thickness delta by using a physical discrete idea. Measuring by using a thermal infrared imager, and recording the temperature of each infrared hood thin layer as T under the working condition to be measuredwin,kWhere the subscript k ═ 1,2, …, m, denotes the kth layer. And (4) establishing a temperature field of the infrared hood according to the measurement result, and inquiring a radiation physical property database of the infrared hood materials with different temperature unit thicknesses delta established in the step ten to obtain the refractive index, the absorption coefficient, the self radiation distribution field and the radiation distribution fields in different directions of each infrared hood thin layer. And then can obtain the refractive index and the absorption coefficient of different positions department in the infrared hood, can acquire the direction radiation intensity and the direction emissivity of infrared hood that awaits measuring through stacking along thickness direction.
The third concrete implementation mode:
the embodiment is a high-efficiency measurement method for the thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared hood, and the apparent spectral transmittance of an infrared hood sample material with unit thickness delta is obtained in the sixth step
Self-radiation
Comprises the following steps:
infrared radiation L of infrared hood material measured by infrared detection system (system in Fourier transform infrared spectrometer)totIs the radiance L of the inner surface of the materialλ(s) fromTarget infrared radiation L reaching outer surface of infrared hood sampleobjAnd infrared head cover self-radiation LwinProduced by a combined action, i.e.
Ltot＝Lobjτwin+Lwin (3)
In the formula, τwinIs the transmittance of an infrared optical window.
Describing the transmission process of target radiation energy transmitting through an infrared hood test piece by using a radiation transmission equation, equally dividing an infrared hood material into n layers along the radiation transmission direction, and deducing a fixed algebraic relation between the transmittance and self-radiation of the infrared hood material with unit thickness and the transmittance and self-radiation of the whole infrared hood; according to the obtained algebraic relation, the heat radiation characteristic data such as transmittance, attenuation coefficient and the like of the infrared hood materials with different thicknesses under the working conditions such as the same temperature and the like can be directly calculated.
In order to realize the purpose, the invention adopts the technical scheme that: the infrared hood sample was equally divided into n layers in the thickness direction, assuming uniform temperature T distribution of the infrared optical window and apparent spectral transmittance of each layer
And self-radiation
Isotropy, the total radiation transmitted through the 1 st layer of the infrared hood material can be obtained according to the radiation transmission principle and the energy conservation relation
The infrared radiation transmitted through the 1 st to 2 nd layers is
Similarly, the total radiation transmitted through the 1 st to n th layers, i.e., the total radiation transmitted through the entire infrared hood, is
Furthermore, the apparent spectral transmittance of the infrared hood material having a thickness of Δ and a temperature of T can be estimated by the energy method
And self-radiation
Transmittance tau of whole infrared detection infrared hoodT,winAnd self-radiation LT,winAn algebraic relation satisfied between them is
By measuring the transmittance and the infrared radiation characteristic of the infrared hood with the thickness of x, the data of the apparent spectral transmittance, the self radiation and other thermal radiation characteristics of the infrared optical window material with the unit thickness delta are obtained.
Therefore, the thermal radiation characteristic data of the infrared optical window materials with different thicknesses under the same temperature and other environment working conditions can be directly calculated according to the obtained algebraic relation without repeated experiments for many times, and a transmission characteristic quantification model of the infrared hood is established.
The fourth concrete implementation mode:
the embodiment is a high-efficiency measurement method for the thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared hood, and in the seventh step, the apparent spectral radiation intensity of any angle on the emergent interface of the sample material of the infrared hood is calculated and obtained by solving a radiation transmission equation
Apparent normal spectral emissivity estimation
And an apparent spectral transmittance estimate
Comprises the following steps:
assuming an isotropic medium temperature of
Refractive index of
Absorption coefficient of
A reflectivity of
The thickness of the medium is delta; under one-dimensional conditions, when the medium is in steady state conditions and medium scattering is not considered, the radiation transfer equation can be reduced to:
solving the radiation transfer equation yields:
wherein,
which means the radiation in the forward direction,
representing backward radiation; theta is an included angle between the forward radiation and the normal line of the surface and an included angle between the backward radiation and the normal line of the surface;
at the inner boundary x-0, the intensity of the radiation propagating in the positive direction includes a portion that reflects the intensity of the radiation incident on the interface, and therefore:
similarly, at the inner boundary x ═ L, the intensity of the radiation propagating in the negative direction also includes the portion that reflects the intensity of the radiation incident on the interface, i.e.:
combining the radiation transfer equation in the medium along the positive direction and the negative direction, and two boundary conditions, the method can be simplified to obtain:
wherein,
and then the apparent spectral radiation intensity of any angle on the emergent interface is as follows:
the apparent normal spectral emissivity is:
in the formula, LT,bIs the black body radiation intensity corresponding to a temperature T and a wavelength λ;
apparent spectral transmittance
From bell's law:
due to the temperature of the isotropic medium
Refractive index
Coefficient of absorption
A reflectivity of
Is an assumed value and thus corresponds to the resulting apparent normal spectral emissivity
Apparent spectral transmittance
Namely the estimated value of the apparent spectral emissivity
Apparent spectral transmittance estimate
According to the infrared hood transmission quantitative model establishing method, the corresponding radiation characteristic of the infrared hood material with unit thickness is calculated by measuring the heat radiation transmission characteristic of the infrared hood material with one thickness, and then the heat radiation characteristic data such as the transmittance of the infrared hood material with different thicknesses under the same temperature working condition is calculated, so that the establishment of the infrared hood transmission quantitative model is realized.
The present invention is capable of other embodiments and its several details are capable of modifications in various obvious respects, all without departing from the spirit and scope of the present invention.
Claims (10)
1. A high-efficiency measurement system for heat radiation characteristics of materials with different thicknesses of a high-temperature infrared hood is characterized by comprising a Fourier transform infrared spectrometer, a heating furnace, a black body furnace, a temperature control polling instrument and a data acquisition and processing system;
during measurement, the center of a detection lens of the Fourier infrared spectrometer, the center of the heating furnace and the center of the black body furnace cavity are arranged on the same horizontal line;
a blackbody furnace for emitting blackbody infrared radiation; in the measuring process, adjusting the blackbody furnace to change the temperature of the blackbody so as to emit infrared radiation at different blackbody temperatures;
the heating furnace is used for heating the infrared hood sample; in the measuring process, the temperature of the heating furnace is adjusted to provide different temperatures for the infrared hood sample material;
the temperature control polling instrument is used for detecting and controlling the temperature in the heating furnace;
the Fourier infrared spectrometer is used for acquiring black body infrared radiation penetrating through the infrared hood;
and the data acquisition and processing system is used for acquiring data of the Fourier infrared spectrometer and the temperature control patrol instrument, and calculating the normal phase spectrum apparent radiation intensity of the material at the temperature displayed by the temperature control patrol instrument by using the signals obtained by the Fourier infrared spectrometer.
2. A high-efficiency measurement method for thermal radiation characteristics of materials with different thicknesses of a high-temperature infrared hood is characterized by comprising the following steps:
firstly, building a high-efficiency measuring system for the heat radiation characteristics of materials with different thicknesses of the high-temperature infrared hood according to claim 1;
step two, 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, and the temperature of the black body furnace is set to be TbObtaining the infrared radiation L of the black body by using a Fourier infrared spectrometerobj；
Thirdly, placing the infrared hood sample in a high-temperature heating furnace for heating until the temperature of the infrared hood sample material reaches the specified temperature TwinAfter the infrared radiation L is uniformly distributed, the infrared radiation L penetrating through the infrared hood sample material is obtained by an infrared detectortot；
Step four, controlling the temperature of the sample material to keep the temperature of the sample material at TwinChanging the black body temperature T without changebIn the state, repeating the second step and the third step to obtain a plurality of groups of blackbody temperatures Tb,iInfrared radiation L in the stateobj,iAnd Ltot,i(ii) a Wherein subscript i represents the ith measurement;
step five, when the temperature of the material is not changed, the radiation characteristic parameter is a fixed value, and through statistics of the test result, a least square method is utilized to fit a plurality of groups of blackbody temperatures Tb,iInfrared radiation L in the stateobj,iAnd Ltot,iAnd then the temperature T is obtainedwinTransmittance tau of uniformly distributed infrared hood sample materialT,winAnd self-radiation LT,win；
Step six, equally dividing the infrared hood sample into n layers along the thickness direction, and obtaining the apparent spectral transmittance of the infrared hood sample material with unit thickness delta according to the energy conservation relation
Self-radiation
And based on
Obtaining apparent normal spectral emissivity
Step seven, solving an algorithm according to the radiation transmission inverse problem, and assuming that the refractive index of the infrared hood sample material is
Absorption coefficient of
Calculating to obtain the apparent spectral radiation intensity of any angle on the emergent interface of the infrared hood sample material by solving a radiation transmission equation
Apparent normal spectral emissivity estimation
And an apparent spectral transmittance estimate
Step eight, obtaining the apparent normal spectral emissivity of the infrared hood sample material obtained in the step six
And apparent spectral transmittance
And seventhly, obtaining the estimated value of the apparent normal emissivity of the infrared hood sample material
And an apparent spectral transmittance estimate
Substituting into the following objective function calculation formula to obtain the objectiveValue of standard function Fobj；
Step nine, judging the objective function value F in the step eightobjWhether or not it is smaller than a set threshold value xi,
if yes, the refractive index of the infrared hood sample material assumed in the step eight
Coefficient of absorption
The real refractive index and the absorption coefficient of the infrared hood sample material are obtained;
if not, returning to the seventh step, and updating the refractive index of the infrared hood sample material according to the inverse problem algorithm
Coefficient of absorption
Resetting the refractive index and absorption coefficient of the infrared hood sample material and recalculating until the objective function value F in the step eightobjIs less than a set threshold xi to obtain the real refractive index of the infrared hood sample material
Coefficient of absorption
In combination with step six, a temperature T is now obtainedwinSelf-irradiation of sample material
Refractive index
Coefficient of absorption
Step ten, changing the temperature T of the sample materialwinRepeating the second to the ninth steps to obtain different temperatures Twin,jRefractive index of infrared hood sample Material
Coefficient of absorption
And self-radiation
Wherein the subscript j represents the jth set of measurements;
calculating to obtain self-radiation of infrared hood sample material with unit thickness delta in different directions
By different temperatures Twin,jRefractive index of sample material
Coefficient of absorption
And self-radiation
Establishing a radiation physical property database of infrared hood materials with different temperature unit thicknesses delta;
eleven, utilizing the idea of physical dispersion to shield the infrared head to be detectedUniformly dividing the mixture into m thin layers with the thickness delta; measuring by using a thermal infrared imager, and recording the temperature of each infrared hood thin layer as T under the working condition to be measuredwin,kWherein the subscript k ═ 1,2, …, m, denotes the kth thin layer; establishing a temperature field of the infrared hood according to the measurement result, and inquiring a radiation physical property database of the infrared hood materials with different temperature unit thicknesses delta established in the step ten to obtain the refractive index, the absorption coefficient, the self radiation distribution field and the radiation distribution fields in different directions of each infrared hood thin layer; and further obtaining the refractive index and the absorption coefficient of different positions in the infrared hood, and obtaining the directional radiation intensity and the directional emissivity of the infrared hood to be detected through superposition along the thickness direction.
3. The method of claim 2, wherein six steps are used to obtain the apparent spectral transmittance of the sample material of infrared hood at unit thickness Δ
Self-radiation
Comprises the following steps:
describing the transmission process of target radiation energy through an infrared hood test piece by using a radiation transmission equation, equally dividing an infrared hood material into n layers along the energy conservation in the radiation transmission direction, and assuming that the temperature T of an infrared optical window is uniformly distributed and the apparent spectral transmittance of each layer is uniform
And self-radiation
Isotropy, the total radiation transmitted through the 1 st layer of the infrared hood material is obtained according to the radiation transmission principle and the energy conservation relation
The infrared radiation transmitted through the 1 st to 2 nd layers is
Similarly, the total radiation transmitted through the 1 st to n th layers, i.e., the total radiation transmitted through the entire infrared hood, is
Further, the apparent spectral transmittance of the infrared hood material having a thickness of Δ and a temperature of T was estimated by the energy method
Transmittance tau of infrared detection infrared hoodT,winAlgebraic relationship of (c), and apparent spectral transmittance
Transmittance tau of infrared detection infrared hoodT,winAlgebraic relations with self radiation;
measuring the transmittance and the infrared radiation characteristic of an infrared hood with the thickness of x to further obtain the apparent spectral transmittance and the self-radiation thermal radiation characteristic data of the infrared optical window material with the unit thickness delta; infrared optical window material is infrared hood material.
4. The method of claim 3, wherein the apparent spectral transmittance of said material of said infrared hood is measured by measuring the thermal radiation characteristics of said material of different thickness
Infrared hood for infrared detectionTransmittance of (d) isT,winHas an algebraic relationship of
5. The method of claim 4, wherein the apparent spectral transmittance is measured by measuring the thermal radiation characteristic of a material of different thickness in a high temperature infrared hood
Transmittance tau of infrared detection infrared hoodT,winThe algebraic relation between the radiation and the self-radiation is
6. A method for efficiently measuring the thermal radiation characteristics of materials with different thicknesses for high temperature infrared hoods according to claim 3, 4 or 5, characterized in that the apparent normal spectral emissivity obtained in step six
The following were used:
in the formula, LT,bMeans that the temperature is the same as the temperature of the sample material per unit thickness, i.e. the temperature is TwinThe black body radiation intensity of (a).
7. The method for efficiently measuring the thermal radiation characteristics of materials with different thicknesses for a high-temperature infrared hood as claimed in claim 6, wherein the apparent spectral radiation intensity of any angle on the exit interface of the sample material of the infrared hood is calculated by solving the radiation transfer equation in step seven
Apparent normal spectral emissivity estimation
Comprises the following steps:
assuming an isotropic medium temperature of
Refractive index of
Absorption coefficient of
A reflectivity of
The thickness of the medium is delta; under one-dimensional conditions, when the medium is in steady state conditions and medium scattering is not considered, the radiation transfer equation reduces to:
solving the simplified radiation transfer equation to obtain the forward radiation
And backward radiation
Theta is an included angle between the forward radiation and the surface normal line and between the backward radiation and the surface normal line;
at the inner boundary x-0, the intensity of the radiation propagating in the positive direction includes a portion that reflects the intensity of the radiation incident on the interface, and therefore:
similarly, at the inner boundary x ═ L, the intensity of the radiation propagating in the negative direction also includes the portion that reflects the intensity of the radiation incident on the interface, i.e.:
combining the radiation transfer equation along the positive direction and the negative direction in the medium and two boundary conditions, and simplifying to obtain:
wherein,
and then the apparent spectral radiation intensity of any angle on the emergent interface is as follows:
the apparent normal spectral emissivity is:
in the formula, LT,bIs the black body radiation intensity corresponding to a temperature T and a wavelength λ;
due to the temperature of the isotropic medium
Refractive index
Coefficient of absorption
A reflectivity of
Is an assumed value and thus corresponds to the resulting apparent normal spectral emissivity
Namely the estimated value of the apparent spectral emissivity
8. The method of claim 7, wherein the forward radiation obtained by solving the simplified radiation transfer equation is used as a measure of the thermal radiation characteristics of materials of different thicknesses in high temperature infrared hoods
And backward radiation
The following:
9. the method of claim 7, wherein the apparent spectral transmittance estimate of step seven is used to determine the thermal radiation characteristics of materials of different thickness for high temperature infrared hoods
Calculated by bell's law.
10. The method of claim 9, wherein the estimate of apparent spectral transmittance obtained in step seven is used to determine the thermal radiation characteristics of materials of different thickness for high temperature infrared hoods
The specific process comprises the following steps:
apparent spectral transmittance
From bell's law:
due to the temperature of the isotropic medium
Refractive index
Coefficient of absorption
A reflectivity of
Is assumed to be a value, thereby obtaining an apparent spectral transmittance
Namely the estimated value of apparent spectral transmittance
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| CN115825145B (en) * | 2022-11-18 | 2023-07-11 | 哈尔滨工业大学 | High-temperature liquid molten salt heat radiation and heat conduction parameter combined measurement device and inversion method |
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