A temperature field testing method based on colorimetric temperature measurement combined with multispectral imaging

Abstract

The present invention relates to the field of optical elements, systems or instrument technology, specifically to a temperature field testing method based on colorimetric temperature measurement combined with multispectral imaging, which solves the technical problems of low temperature field temperature measurement reconstruction accuracy and low temporal and spatial resolution in existing temperature measurement methods, and includes constructing a temperature field measurement system for a solid engine combustion chamber, using LIBS technology to determine the spectral range and temperature measurement range of the temperature field of the solid engine combustion chamber, coupling and packaging a multispectral filter with a CMOS sensor, calibrating the multispectral camera using the blackbody furnace, obtaining a spectral image of the temperature field using the multispectral camera, obtaining a two-dimensional temperature field of the solid engine combustion chamber using a colorimetric temperature measurement method, and performing a comprehensive evaluation. The present invention can obtain multispectral information of a flame in a solid propellant combustion chamber, and realize high temporal and spatial resolution detection of a two-dimensional temperature field in a solid engine combustion chamber.

Description

Technical Field

[0001] The present invention relates to the field of optical elements, systems or instrument technology, and in particular to multispectral imaging and colorimetric temperature measurement technology, and specifically to a temperature field testing method based on colorimetric temperature measurement combined with multispectral imaging. Background Art

[0002] The combustion temperature is an important factor affecting the energy of the solid propellant in the combustion chamber of the solid engine. Studying the temperature, combustion state and law in the combustion chamber of the solid engine is an important basis for avoiding combustion instability and improving engine performance. It can support the optimization of engine structure and the improvement of propellant formula, and lay a technical foundation for improving the safety and operating efficiency of solid engines. Therefore, it is of great significance to improve the temperature field test system in the complex environment of aerospace.

[0003] The high temperature environment of 2000℃~4000℃ generated by the combustion temperature of the propellant puts forward more stringent requirements on the throat lining structure and materials, insulation layer materials, nozzle structure and materials of the engine combustion chamber, and the hot end components will be in an unstable high temperature environment for a long time, which will lead to reduced strength, creep and even fracture, which will have serious consequences, thus restricting the performance improvement of my country's solid engine. Although there are many temperature sensors suitable for different temperature ranges, the temperature sensing parts of the temperature sensor have low temperature measurement accuracy in complex environments, and most of the existing non-contact temperature measurement optical equipment cannot take into account spectral information and high spatiotemporal resolution at the same time, resulting in the existing temperature measurement methods. Problems such as low temperature field temperature measurement reconstruction accuracy and low spatiotemporal resolution. Summary of the invention

[0004] In order to overcome the technical defects of low temperature field measurement reconstruction accuracy and low spatiotemporal resolution in existing temperature measurement methods, the present invention provides a temperature field testing method based on colorimetric temperature measurement combined with multispectral imaging.

[0005] The present invention provides a temperature field testing method based on colorimetric temperature measurement combined with multispectral imaging, comprising the following steps:

[0006] S1. Construct a temperature field measurement system for a solid engine combustion chamber, wherein the temperature field measurement system comprises a solid engine combustion chamber, a multispectral camera, a black body furnace and a host computer, wherein the solid engine combustion chamber is a temperature field to be detected; and the host computer is used to obtain a spectral image collected by the multispectral camera;

[0007] S2. Determine the spectral range and temperature measurement range of the temperature field of the solid motor combustion chamber by using LIBS technology;

[0008] S3. According to the spectral range of the temperature field determined in step S2, a multispectral filter is manufactured by using a mosaic pixel coating technology, and the multispectral filter is coupled and packaged with a CMOS sensor, wherein the size of the multispectral filter is equal to the size of the CMOS sensor, so as to ensure that each pixel can receive radiation information of a specific wavelength, and the multispectral camera is obtained after coupling and packaging;

[0009] S4, using the blackbody furnace to calibrate the multispectral camera, and establish a functional relationship between the image grayscale value and the radiation intensity of the multispectral camera;

[0010] S5, using the multispectral camera to obtain a spectral image of the temperature field of the solid motor combustion chamber;

[0011] S6, the host computer obtains the spectral image of the temperature field of the solid engine combustion chamber obtained in S5, and obtains the two-dimensional temperature field of the solid engine combustion chamber by using the colorimetric temperature measurement method;

[0012] The principle of colorimetric temperature measurement is Planck's radiation law, in which the relationship between the intensity of spectral monochromatic radiation emitted by an object and the wavelength and temperature is as follows: :

[0013] ,

[0014] formula middle, is a given wavelength, T is a given temperature, is the monochromatic emissivity at a given wavelength, is the first radiation constant, , is the second radiation constant, ,in is Planck's constant, is the Boltzmann constant, is the speed of light;

[0015] when When Planck's law is replaced by Wien's law, then:

[0016] ,

[0017] ,

[0018] formula and formula middle, is the intensity of monochromatic blackbody radiation;

[0019] The wavelength is given as The monochromatic radiation intensity of the spectral line is , given the wavelength The monochromatic radiation intensity of the spectral line is , then the colorimetric ratio equation is:

[0020] I ( l 1 , T ) I ( l 2 , T ) = k l 1 S ( l 1 , T ) k l 2 S ( l 2 , T ) = ( e l 1 e l 2 ) l 2 5 l 1 5 × exp [ - C 2 T ( 1 l 1 − 1 l 2 ) ] ,

[0021] formula middle, and is the measured radiation intensity, the calibration factor and It is related to the characteristics of the temperature field measurement system and is obtained by calibration of the black body furnace; the emissivity is selected and The ratio of the two spectral lines is approximately 1, then according to the given wavelength The spectral lines and given wavelengths are The temperature of the measured object is obtained by the spectrum line:

[0022] ,

[0023] S6. Comprehensive assessment.

[0024] Preferably, in step S5, the emissivity is selected and The method to make the ratio of two spectral lines close to 1 is:

[0025] Use the emissivity calculation model to calculate the emissivity values ​​corresponding to different temperatures and wavelengths :

[0026] ,

[0027] The given wavelength is The spectral lines and given wavelengths are The emissivity approximate function Q of the spectral line is defined as:

[0028] ,

[0029] If the emissivity approximation function Q is closest to 1 at any two wavelengths, the flame emissivity at these two wavelengths is considered to be approximately equal.

[0030] Preferably, in step S4, at a given temperature T, the energy radiated by the blackbody furnace enters and is imaged on the CMOS sensor, establishing the monochromatic blackbody radiation intensity at different wavelengths. Gray value The functional relationship between them is:

[0031] ,

[0032] formula In the equation, A and B are constants and can be obtained by calibration tests.

[0033] Preferably, in step S6, according to the Class A assessment of the standard uncertainty of temperature, it can be known that the estimated input quantity assuming n independent repeated observations is The average value of n independent repeated experiments is , so the Bessel calculation formula for type A uncertainty is:

[0034] ,

[0035] Type B uncertainty is expressed as:

[0036] ,

[0037] formula middle, is the estimated value of the limit error of the temperature field measurement system, taking the confidence level of twice the standard deviation of the normal distribution law, that is, , that is, the confidence factor ,Right now:

[0038] ,

[0039] So the combined standard uncertainty and expanded uncertainty As the formula and formula As shown, :

[0040] ,

[0041] ,

[0042] Using expanded uncertainty The uncertainty of the temperature measured in step S5 can be evaluated.

[0043] Compared with the prior art, the technical solution provided by the present invention has the following technical effects: the temperature field testing method described in the present invention utilizes an emissivity approximate mathematical model to solve the technical problem that emissivity is difficult to measure in traditional non-contact temperature field testing, and uses an optimal dual-line colorimetric temperature measurement method to improve the temperature measurement accuracy of a solid engine combustion chamber; the present invention proposes a snapshot multispectral imaging temperature measurement system based on a multispectral camera that has both high spatial resolution and a multispectral filter array, which can obtain multispectral information of a solid propellant combustion chamber flame and realize high temporal and spatial resolution detection of a two-dimensional temperature field in a solid engine combustion chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0046] Figure 1 It is a structural schematic diagram of a temperature field measurement system for a solid engine combustion chamber according to a certain embodiment of the present invention;

[0047] Figure 2 The figure is a flow chart of a temperature field testing method based on colorimetric temperature measurement combined with multispectral imaging described in an embodiment of the present invention.

[0048] In the figure: 1. Solid rocket combustion chamber; 2. Multispectral camera; 3. Blackbody furnace; 4. Host computer; 5. Multispectral filter; 6. CMOS sensor. DETAILED DESCRIPTION

[0049] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0050] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0051] The following is combined with Figure 1 and Figure 2 The specific embodiments of the present invention are described in detail.

[0052] In one embodiment, Figure 1 As shown, a temperature field testing method based on colorimetric temperature measurement combined with multispectral imaging is disclosed, comprising the following steps:

[0053] S1. Construct a temperature field measurement system for a solid engine combustion chamber, wherein the temperature field measurement system comprises a solid engine combustion chamber 1, a multispectral camera 2, a black body furnace 3 and a host computer 4, wherein the solid engine combustion chamber 1 is a temperature field to be detected; and the host computer 4 is used to obtain a spectral image collected by the multispectral camera 2;

[0054] S2. Determine the spectral range and temperature measurement range of the temperature field of the solid engine combustion chamber 1 by using LIBS technology;

[0055] S3, according to the spectral range of the temperature field determined in step S2, a multispectral filter 5 is manufactured by using a mosaic pixel coating technology, and the multispectral filter 5 is coupled and packaged with a CMOS sensor 6, wherein the size of the multispectral filter 5 is equal to the size of the CMOS sensor 6, so as to ensure that each pixel can receive radiation information of a specific wavelength, and after coupling and packaging, the multispectral camera 2 having both high spatial resolution and a multispectral filter array is obtained;

[0056] S4, using the black body furnace 3 to calibrate the multi-spectral camera 2, and establish a functional relationship between the image gray value and the radiation intensity of the multi-spectral camera 2;

[0057] S5, using the multispectral camera 2 to obtain a spectral image of the temperature field of the solid engine combustion chamber 1;

[0058] S6, the host computer 4 obtains the spectral image of the temperature field of the solid engine combustion chamber 1 obtained in S5, and obtains the two-dimensional temperature field of the solid engine combustion chamber by using the colorimetric temperature measurement method;

[0059] The principle of colorimetric temperature measurement is Planck's radiation law, in which the relationship between the intensity of spectral monochromatic radiation emitted by an object and the wavelength and temperature is as follows: :

[0060] ,

[0061] formula middle, is a given wavelength, T is a given temperature, is the monochromatic emissivity at a given wavelength, is the first radiation constant, , is the second radiation constant, ,in is Planck's constant, is the Boltzmann constant, is the speed of light;

[0062] when When Planck's law is replaced by Wien's law, then:

[0063] ,

[0064] ,

[0065] formula and formula middle, is the intensity of monochromatic blackbody radiation;

[0066] The wavelength is given as The monochromatic radiation intensity of the spectral line is , given the wavelength The monochromatic radiation intensity of the spectral line is , then the colorimetric ratio equation is:

[0067] I ( l 1 , T ) I ( l 2 , T ) = k l 1 S ( l 1 , T ) k l 2 S ( l 2 , T ) = ( e l 1 e l 2 ) l 2 5 l 1 5 × exp [ - C 2 T ( 1 l 1 − 1 l 2 ) ] ,

[0068] formula middle, and is the measured radiation intensity, the calibration factor and It is related to the characteristics of the temperature field measurement system, which is obtained by calibration of the black body furnace 3; the emissivity is selected and The ratio of the two spectral lines is approximately 1, then according to the given wavelength The spectral lines and given wavelengths are The temperature of the measured object is obtained by the spectrum line:

[0069] ,

[0070] S6. Comprehensive assessment.

[0071] When detecting the temperature inside the high-temperature combustion chamber, due to the high temperature and high pressure environment of the solid engine combustion chamber, the solid propellant combustion flame is thermally excited to radiate continuous spectral information outward. By detecting the rich radiation spectral information of the combustion flame, an emissivity calculation model is established, and the optimal dual spectrum line is selected. The colorimetric temperature measurement technology based on Planck's radiation law is used to achieve non-contact, rapid and high-precision detection of the solid rocket combustion chamber temperature.

[0072] After the solid propellant burns, the flame radiates a large amount of spectral information. The spectral information of the composite solid propellant with an aluminum mass fraction of 12% after combustion was studied using LIBS technology. It was found that the spectrum has the characteristics of solid radiation continuous spectrum and metal atomic characteristic spectrum dispersion. In addition, the composite propellant contains metal elements such as aluminum and sodium. These elements form gaseous free atoms and ions through thermal ionization. These free atoms and ions emit strong atomic characteristic lines. These discrete atomic characteristic spectral lines are superimposed on the solid continuous radiation spectrum to form the flame radiation spectrum of the solid propellant. The solid propellant combustion flame spectral information is mainly concentrated in the 560-900nm band.

[0073] Since the radiation of solid propellant flames is mainly solid radiation, it can be known from the basic theory of radiation heat transfer that the emissivity of solid propellant flames in the visible band will not vary greatly with wavelength. The wavelength range used to calculate the temperature is selected based on the following principles; first, spectral lines with a large range of spectral intensity changes in the flame must be avoided, and secondly, a high signal-to-noise ratio of the spectral measurement data should be ensured to avoid selecting the beginning and end of the measurement spectral range. The colorimetric method is usually based on the assumption that the emissivity of the two wavelengths is the same. If this assumption is not true in practice, it will affect the accuracy of the results. If the spectral emissivity varies with wavelength and the relationship between them is unknown, the colorimetric method is not suitable for temperature measurement. Therefore, when using the colorimetric temperature measurement method, it is necessary to ensure that the flame meets the gray body characteristics in the selected spectral line range, that is, the emissivity is approximately equal.

[0074] The spectral emissivity of solid propellant combustion flame is an important factor affecting the accuracy of colorimetric temperature measurement. Therefore, it is necessary to establish a calculation model for the radiation spectrum of solid propellant combustion flame and select paired wavelengths with small emissivity differences as the working bands of colorimetric temperature measurement to achieve high-precision temperature measurement.

[0075] For the design of the multispectral filter 5 in the multispectral imaging model, it is necessary to consider the number and type of bandpass filters. Generally speaking, the number of filters must be a square number, and in order to facilitate the subsequent spectral information recovery, different filters with close center wavelengths should be in adjacent positions. Based on the above embodiment, in a preferred embodiment, in step S5, the emissivity is selected. and The method to make the ratio of two spectral lines close to 1 is:

[0076] Use the emissivity calculation model to calculate the emissivity values ​​corresponding to different temperatures and wavelengths :

[0077] ,

[0078] The given wavelength is The spectral lines and given wavelengths are The emissivity approximate function Q of the spectral line is defined as:

[0079] ,

[0080] If the emissivity approximation function Q at any two wavelengths is closest to 1, the flame emissivity at these two wavelengths is considered to be approximately equal. Therefore, it can be considered that the flame emissivity at these two wavelengths is approximately equal, and these two optimal wavelengths can use the colorimetric method to obtain high-precision temperature information of the solid propellant flame.

[0081] On the basis of the above embodiments, in a preferred embodiment, the image output by the multi-spectral camera 2 is a digital quantity, and it is necessary to establish the relationship between the image grayscale value and the radiation intensity at different temperatures, adjust the distance between the multi-spectral camera 2 and the blackbody furnace 3, the camera exposure time, and the temperature of the blackbody furnace 3 to obtain the spectral image of the blackbody furnace 3 at different temperatures; in step S4, at a given temperature T, the energy radiated by the blackbody furnace 3 enters and is imaged on the CMOS sensor 6, and the monochromatic blackbody radiation intensity at different wavelengths is established. Gray value The functional relationship between them is:

[0082] ,

[0083] formula In the equation, A and B are constants and can be obtained by calibration tests.

[0084] Based on the above embodiment, in a preferred embodiment, in step S6, according to the Class A assessment of the standard uncertainty of temperature, it can be known that the estimated input quantity assuming n independent repeated observations is The average value of n independent repeated experiments is , so the Bessel calculation formula for type A uncertainty is:

[0085] ,

[0086] Type B uncertainty is expressed as:

[0087] ,

[0088] formula middle, is the estimated value of the limit error of the temperature field measurement system, taking the confidence level of twice the standard deviation of the normal distribution law, that is, , that is, the confidence factor ,Right now:

[0089] ,

[0090] So the combined standard uncertainty and expanded uncertainty As the formula and formula As shown, :

[0091] ,

[0092] ,

[0093] Using expanded uncertainty The uncertainty of the temperature measured in step S5 can be evaluated.

[0094] The present invention uses LIBS technology to detect the radiation spectrum of the solid engine combustion chamber, realizes the spectral information detection of the temperature distribution in the combustion chamber according to the spectral information, establishes an emissivity approximation function, selects the optimal dual spectrum line, and realizes high-precision acquisition of temperature information in combination with the colorimetric temperature measurement mechanism. According to the radiation spectrum characteristics of the engine combustion chamber, the spectral filter array is coupled to the CMOS sensor 6 to construct a multi-spectral imaging sensitive structure, realizes high-temporal and spatial resolution spectral imaging of the engine combustion chamber, and performs sensitivity calibration on the snapshot spectral imaging colorimetric temperature measurement system.

[0095] The above is only a specific implementation of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions are given with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A temperature field testing method based on colorimetric temperature measurement combined with multispectral imaging, characterized in that: The following steps are involved: S1. Constructing a temperature field measurement system for a solid engine combustion chamber, the temperature field measurement system comprising a solid engine combustion chamber (1), a multispectral camera (2), a black body furnace (3) and a host computer (4), wherein the solid engine combustion chamber (1) is a temperature field to be detected; and the host computer (4) is used to obtain a spectral image collected by the multispectral camera (2); S2. Determine the spectral range and temperature measurement range of the temperature field of the solid engine combustion chamber (1) by using LIBS technology; S3, according to the spectral range of the temperature field determined in step S2, a multispectral filter (5) is manufactured by using a mosaic pixel coating technology, and the multispectral filter (5) is coupled and packaged with a CMOS sensor (6), wherein the size of the multispectral filter (5) is equal to the size of the CMOS sensor (6), so as to ensure that each pixel can receive radiation information of a specific wavelength, and the multispectral camera (2) is obtained after coupling and packaging; S4, using the black body furnace (3) to calibrate the multi-spectral camera (2), and establish a functional relationship between the image gray value and the radiation intensity of the multi-spectral camera (2); S5, using the multispectral camera (2) to obtain a spectral image of the temperature field of the solid engine combustion chamber (1); S6, the host computer (4) obtains the spectral image of the temperature field of the solid engine combustion chamber (1) obtained in S5, and obtains the two-dimensional temperature field of the solid engine combustion chamber by using a colorimetric temperature measurement method; The principle of colorimetric temperature measurement is Planck's radiation law, in which the relationship between the intensity of spectral monochromatic radiation emitted by an object and the wavelength and temperature is as follows: : ， formula middle, is a given wavelength, T is a given temperature, is the monochromatic emissivity at a given wavelength, is the first radiation constant, , is the second radiation constant, ,in is Planck's constant, is the Boltzmann constant, is the speed of light; when When Planck's law is replaced by Wien's law, then: ， ， formula and formula middle, is the intensity of monochromatic blackbody radiation; The wavelength is given as The monochromatic radiation intensity of the spectral line is , given the wavelength The monochromatic radiation intensity of the spectral line is , then the colorimetric ratio equation is: ， formula middle, and is the measured radiation intensity, the calibration factor and It is related to the characteristics of the temperature field measurement system and is obtained by calibration of the black body furnace (3); the emissivity is selected and The ratio of the two spectral lines is approximately 1, then according to the given wavelength The spectral lines and given wavelengths are The temperature of the measured object is obtained by the spectrum line: ， S6. Comprehensive assessment.

2. The temperature field testing method based on colorimetric temperature measurement combined with multispectral imaging according to claim 1 is characterized in that: In step S5, select the emissivity and The method to make the ratio of two spectral lines close to 1 is: Use the emissivity calculation model to calculate the emissivity values ​​corresponding to different temperatures and wavelengths : ， The given wavelength is The spectral lines and given wavelengths are The emissivity approximate function Q of the spectral line is defined as: ， If the emissivity approximation function Q is closest to 1 at any two wavelengths, the flame emissivity at these two wavelengths is considered to be approximately equal.

3. The temperature field testing method based on colorimetric temperature measurement combined with multispectral imaging according to claim 1 is characterized in that: In step S4, at a given temperature T, the energy radiated by the blackbody furnace (3) enters and is imaged on the CMOS sensor (6), establishing the monochromatic blackbody radiation intensity at different wavelengths. Gray value The functional relationship between them is: ， formula In the equation, A and B are constants and can be obtained by calibration tests.

4. A temperature field testing method based on colorimetric temperature measurement combined with multispectral imaging according to any one of claims 1 to 3, characterized in that: In step S6, according to the Class A assessment of the standard uncertainty of temperature, it can be known that the estimated input quantity assuming n independent repeated observations is The average value of n independent repeated experiments is , so the Bessel calculation formula for type A uncertainty is: ， Type B uncertainty is expressed as: ， formula middle, is the estimated value of the limit error of the temperature field measurement system, taking the confidence level of twice the standard deviation of the normal distribution law, that is, , which is the confidence factor ,Right now: ， So the combined standard uncertainty and expanded uncertainty As the formula and formula As shown, : ， ， Using expanded uncertainty The uncertainty of the temperature measured in step S5 can be evaluated.

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