Flame multi-parameter field detection method based on hyperspectral camera and double optical comb technology

Abstract

The invention belongs to the technical field of high-temperature flame combustion diagnosis, and discloses a flame multi-parameter field detection method based on a hyperspectral camera and a double-optical-comb technology, which comprises the following steps of: acquiring a laser absorption spectrum and an optical field signal of flame by using the hyperspectral camera and the double-optical-comb technology, calculating spectral radiation physical property parameters, and calculating a spectral radiation parameter; and further solving flame emergent radiation intensity and blackbody spectrum radiation intensity, and obtaining a flame temperature field by combining the Planck law. And substituting a preset flame concentration field, a pressure field and a temperature field into the radiation transfer equation for solving to obtain a laser detection radiation intensity estimation value. Constructing an objective function equation of the concentration field and the pressure field, solving and judging whether an objective function value is smaller than a preset threshold value, and if not, resetting and iterating; and if yes, determining that the set field is real flame distribution, and completing flame multi-parameter field detection. According to the technical scheme, online real-time cooperative detection of multiple parameters such as the temperature, the concentration and the pressure of the high-temperature flame can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature flame combustion diagnosis, and particularly relates to a method for detecting multi-parameter fields of flames based on hyperspectral cameras and dual-comb technology. Background Art

[0002] High-temperature combustion phenomena widely exist in fields such as aerospace, energy and power, iron and steel metallurgy, and chemical engineering. It is crucial to detect the flame state in combustion phenomena. By measuring, internal parameters of the flame can be obtained, such as temperature and component concentration distributions, concentrations of gas products such as CO 2 、H 2 O, CO, etc., concentrations of soot particulate matter, and spectral radiation characteristic fields. Understanding these parameters is of great significance for evaluating combustion performance, monitoring safety conditions, and optimizing the design of combustion systems. Traditional measurement methods often have problems such as invasiveness, slow response speed, and low resolution, while the development of modern non-contact measurement technologies provides solutions to these problems.

[0003] As an advanced imaging technology, a hyperspectral camera can provide detailed information in the spatial and spectral dimensions of a flame. It captures hyperspectral images of the flame, revealing the inherent characteristics of the object being photographed and ambient light. The application of this technology in the field of combustion can help measure the combustion state of the flame, judge reaction products, and reconstruct temperature and concentration fields. Compared with traditional color cameras, a hyperspectral imaging system can obtain projection data in the spatial and spectral dimensions of the flame and reconstruct a model using the method of inverse ray tracing. As an emerging non-contact measurement method, dual-comb spectroscopy technology has shown broad application prospects in fields such as environmental monitoring and medical detection with its ultra-high resolution and real-time performance. This technology uses two optical frequency combs with slightly different repetition frequencies as interference light sources, replacing the mechanical moving arm in traditional Fourier spectrometers, greatly improving the stability of the measurement system, increasing the spectral resolution to the kHz level, and shortening the sampling time to the microsecond level, equivalent to real-time sampling.

[0004] However, the detection by a single surface-scanning hyperspectral camera has problems such as being able to collect multi-parameter field information only for steady-state flames, slow collection speed, and inability to simultaneously reconstruct information such as temperature and concentration of fast turbulent flames. The application of dual-comb spectroscopy technology in the field of combustion diagnosis is still limited to the extraction of the average value of gas parameters on a single laser path and has not been widely applied to the reconstruction of three-dimensional distributions of parameters such as temperature and gas concentration in a certain area. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for detecting multi-parameter fields of flames based on hyperspectral cameras and dual-comb technology to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides a method for detecting a multi-parameter field of a flame based on a hyperspectral camera and a dual-comb technology, including:

[0007] Step 1: Obtain the laser absorption spectrum information and the optical field measurement signal of the flame based on the hyperspectral camera and the dual-comb technology;

[0008] Step 2: Calculate the spectral radiation physical property parameters of the flame under the laser detection spectrum according to the laser absorption spectrum information;

[0009] Step 3: Solve the outgoing radiation intensity of the flame based on the spectral radiation physical property parameters, and determine the blackbody spectral radiation intensity of the flame;

[0010] Step 4: Calculate the internal temperature of the flame based on the blackbody spectral radiation intensity in combination with Planck's law to obtain the flame temperature field;

[0011] Step 5: Substitute the set flame concentration field, flame pressure field and the flame temperature field into the radiation transfer equation for solution to obtain an estimated value of the laser detection radiation intensity;

[0012] Step 6: Construct an objective function equation for the concentration field and the pressure field based on the estimated value of the laser detection radiation intensity, solve the objective function value. When the objective function value is greater than a preset threshold, return to Step 5 to reset the flame concentration field and the flame pressure field; when the objective function value is less than the preset threshold, it is determined that the flame concentration field and the flame pressure field set in Step 5 are the true distributions of the flame, and the detection of the multi-parameter field of the flame is completed.

[0013] Optionally, the process of obtaining the laser absorption spectrum information specifically includes:

[0014] Generate two optical frequency comb signals with a specific frequency interval by using a dual-comb system, merge each optical frequency comb signal using a grating coupler, evenly divide the merged optical signal into several light beams based on an optical fiber splitter, and arrange each light beam as a measurement beam at equal intervals on one side of the flame;

[0015] Use a detector array to receive the measurement beam passing through the flame, and transmit it to a photodetector to calculate the laser absorption spectrum information and calculate the multi-parameter field distribution of the flame.

[0016] Optionally, the process of obtaining the optical field measurement signal specifically includes:

[0017] Collect two-dimensional optical field images of the flame using several groups of visible hyperspectral cameras and near-infrared hyperspectral cameras, and combine the two-dimensional optical field images collected by each group of cameras to obtain the optical field measurement signal.

[0018] Optionally, the spectral radiation physical property parameters of the flame under the laser detection spectrum are calculated based on the laser absorption spectrum information, and the specific calculation formula is:

[0019]

[0020] In the formula, I t represents the laser radiation intensity passing through the flame, that is, the multi-angle and multi-spectral laser tomography transmission signal received by the photodetector. The laser measurement signal I l is the vector form of this transmission signal; l represents the position; I 0 represents the incident laser radiation intensity; k a represents the absorption coefficient of the medium; v represents the central wave number of the incident laser spectrum; exp represents the natural exponential function; represents the absorption coefficient distribution obtained by the nth iteration; μ (n) represents the convergence factor at the nth iteration; I represents the projection coefficient matrix until the value of the absorption coefficient makes ‖I l -k a I‖ obtain the minimum value. At this time, the absorption coefficient k a is the spectral radiation physical property parameter distribution k.

[0021] Optionally, the specific steps of step three include:

[0022] Convert the underdetermined ill-posed inverse problem into an overdetermined inverse problem based on the spectral radiation physical property parameters and the light field measurement signal, and solve the overdetermined inverse problem to obtain the outgoing radiation intensity of the flame;

[0023] Solve the blackbody spectral radiation intensity of the flame based on the outgoing radiation intensity combined with the Landeweber algorithm.

[0024] Optionally, the specific calculation process of solving the blackbody spectral radiation intensity of the flame based on the outgoing radiation intensity combined with the Landeweber algorithm is as follows:

[0025] Determine the projection coefficient matrix A λ based on the reverse tracking of the sensor pixels, and determine the linear equation system I bλ with the blackbody spectral radiation intensity I n of the flame as the variable:

[0026] I n = A λ I bλ

[0027] Solve the blackbody spectral radiation intensity I bλ of the flame based on the Landeweber algorithm:

[0028]

[0029] where \(p\geq2\) is a given positive integer, \(S\) n is the transition matrix at the \(n\)-th step in the calculation process, \(S\) 0 is the initial value of the transition matrix; \(E\) is the identity matrix; \(\alpha\) is the relaxation factor; \(A\) T is the transpose matrix of \(A\), and \(A\) is equal to the projection coefficient matrix \(A\) λ ; \(A\) n represents the coefficient matrix updated at the \(n\)-th iteration; \(X\) represents the unknown quantity to be solved;

[0030] After \(M\) iterations, when the maximum number of iterations is reached or the minimum convergence accuracy is reached, we get:

[0031]

[0032] where \(X\) M is the blackbody spectral radiation intensity \(I\) of the flame itself bλ , and \(M = 0,1,\cdots,j\).

[0033] Optionally, calculating the internal temperature of the flame based on the blackbody spectral radiation intensity in combination with Planck's law, the specific calculation formula is:

[0034]

[0035] where \(T\) h is the internal temperature of the flame, \(c\) 1 is the first radiation constant of Planck's law, \(c\) 2 is the second radiation constant, \(\lambda\) is the radiation wavelength, \(I\) bλ is the blackbody spectral radiation intensity.

[0036] Optionally, the objective function equation is specifically:

[0037]

[0038] where \(F\) obj represents the objective function of the flame pressure component concentration field, \(I\) l is the measurement signal, \(P\) is the pressure, \(C\) is the component concentration, is an equation about variables \(P\) and \(C\), \(P\) l and \(C\) l represent the pressure and component concentration at position \(l\), \(l\) represents the position, \(I\) 0 represents the incident laser radiation intensity, \(v\) represents the central wave number of the incident laser spectrum, \(S\) v (·) represents the line strength function, represents the line shape function, \(I'\) l (v) represents the estimated value of the laser detection radiation intensity, \(T\) l is the temperature field.

[0039] The technical effects of the present invention are as follows:

[0040] The present invention is equipped with two types of visible hyperspectral cameras and infrared hyperspectral cameras. Through synchronous photographing and acquisition by these hyperspectral cameras, the three-dimensional temperature distribution and the three-dimensional concentration information of water can be retrieved, and the limitation of the traditional hyperspectral camera in the acquisition speed can be overcome, and it is no longer limited to sampling steady-state flames; the present invention utilizes the wide spectral characteristics of the dual-comb spectroscopy technology, allowing simultaneous measurement of multiple absorption spectral lines, providing a high-speed and high-precision method for detecting flame temperature and concentration. The present invention projects dual-comb lasers into the flame region through wavelength-division multiplexing technology, and at the same time uses a detector to receive the intensity of the outgoing spectral radiation after passing through the flame, combines the absorption spectral theory with the inverse problem method to solve for the infrared spectral radiation characteristics of the flame, and reconstructs the three-dimensional temperature field of the flame according to the flame image collected by the hyperspectral camera. Further, combining the known temperature field and the intensity of the outgoing spectral radiation, the three-dimensional distribution of the component concentration and pressure of the flame is calculated by using the inverse problem method of collaborative reconstruction. Through the simulation technology of the present invention, the collaborative detection of multiple parameters such as temperature, concentration, and pressure of high-temperature flames can be realized, which has the advantages of a short processing process and the ability to realize online real-time monitoring of the flame, providing a theoretical basis for the extended research of online diagnosis of high-temperature flames. Description of the Drawings

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0042] The drawings constituting a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation of this application. In the drawings:

[0043] Figure 1 It is a schematic diagram of a three-dimensional temperature and concentration detection device for flame combustion based on a hyperspectral camera and dual-comb technology in an embodiment of the present invention;

[0044] Figure 2 It is a flowchart of a method for detecting three-dimensional temperature and concentration of flame combustion based on a hyperspectral camera and dual-comb technology in an embodiment of the present invention.

[0045] Reference numerals: 1. Dual-comb system; 2. Grating coupler; 3. Fiber optic splitter; 4. Photoelectric detector; 5. Hyperspectral camera group; 6. Data processing system. Detailed Embodiments

[0046] A detailed description of various exemplary embodiments of the present invention will now be given. This detailed description should not be considered as a limitation on the present invention, but rather as a more detailed description of certain aspects, features, and implementation schemes of the present invention.

[0047] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0048] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention's specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of this application are merely exemplary.

[0049] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0050] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will refer to the accompanying drawings and combine with embodiments to detail this application.

[0051] As Figure 1 - Figure 2 shown, in this embodiment, a method for detecting a multi-parameter field of a flame based on a hyperspectral camera and dual-comb technology is provided, including: obtaining laser absorption spectral information and light field measurement signals of the flame based on the hyperspectral camera and dual-comb technology; calculating spectral radiation physical property parameters of the flame under the laser detection spectrum according to the laser absorption spectral information; solving the outgoing radiation intensity of the flame based on the spectral radiation physical property parameters and determining the blackbody spectral radiation intensity of the flame; calculating the internal temperature of the flame based on the blackbody spectral radiation intensity in combination with Planck's law to obtain the flame temperature field; substituting the set flame concentration field, flame pressure field, and the flame temperature field into the radiation transfer equation for solution to obtain an estimated value of the laser detection radiation intensity.

[0052] A device for detecting a multi-parameter field of a flame based on a hyperspectral camera and dual-comb technology described in this embodiment includes: a dual-comb system 1, a grating coupler 2, an optical fiber splitter 3, a photodetector 4, a hyperspectral camera group 5, and a data processing system 6;

[0053] The dual optical frequency comb system 1 is used to generate optical frequency comb signals, and the optical frequency comb signals are incident on the grating coupler 2; the grating coupler 2 is used to couple two optical frequency comb signals into one beam and transmit it to the fiber optic splitter 3 through an optical fiber; the fiber optic splitter 3 is used to divide the optical frequency comb signal into n beams of light with the same intensity, and these n beams of light are arranged at equal intervals on one side of the soot flame as measurement beams and incident on the soot flame. After passing through the soot flame, they are received by the detector array and transmitted to the photodetector 4 through an optical fiber; the photodetector 4 is used to convert the received optical signal into an electrical signal and transmit the electrical signal to the data processing system 6; the hyperspectral camera group 5 is used to photograph the soot flame, obtain the color light field image of the soot flame, and transmit the color light field image to the data processing system 6; the data processing system 6 is used to obtain the light field measurement signal according to the color light field image of the soot flame, and use the measurement signal and the light field measurement electrical signal, combined with the inverse problem algorithm, to obtain the temperature field T of the soot flame, and then use the temperature field T, combined with the radiation transfer equation in the spectral theory, to calculate and obtain the component concentration field C and pressure field P of the flame. Further, when the hyperspectral camera group 5 photographs the soot flame, the dual optical frequency comb system 1 is turned off.

[0054] The specific implementation process of this embodiment includes:

[0055] Step 1: Generate two optical frequency comb signals through the dual optical frequency comb system. First, use the grating coupler to combine the two optical frequency comb signals into one beam, and then use the fiber optic splitter to equally divide this beam of optical signal into n beams. These n beams of light are arranged at equal intervals on one side of the soot flame as measurement beams to form a laser array. At the same time, the detector array is placed opposite the laser array with the flame as the center. When these measurement beams pass through the soot flame, they are received by the detector array and transmitted to the photodetector through an optical fiber. The multi-angle and multi-spectral laser tomography transmission signals obtained by the photodetector are transmitted to the data processing system, thereby obtaining the laser absorption spectrum information I of the combustion flame l ; In this embodiment, the flame is a high-temperature flame, and its temperature range is in the interval of 1000K - 3000K.

[0056] Among them, the optical frequency comb signal is:

[0057]

[0058] f a = af rl + f ceo1

[0059] f b = bf r2 + f ceo2

[0060] Among them, a and b are respectively the longitudinal mode orders of two optical frequency combs, f ceo1, f ceo2 are respectively the carrier offset frequencies of two optical frequency combs, and respectively represent the initial phases of the ath and bth longitudinal modes in two optical frequency combs, f a and f b respectively represent the frequencies of the ath and bth longitudinal modes in two optical frequency combs, A and B are respectively the sets of longitudinal mode ordinals a and b that satisfy the passband range of the filter, E a and E b are respectively the electric field strengths of the ath and bth longitudinal modes in two optical frequency combs, and t is time.

[0061] The part of the interference signal of the optical frequency comb after passing through the gas that contains the information of the absorption spectrum (measurement signal I l ) can be expressed as:

[0062]

[0063] The reference signal is:

[0064]

[0065] where, α(f a ) and α(f b ) are the absorption rates of gas molecules at optical frequencies f a and f b ; f r1 is the frequency of the first frequency comb in the dual optical frequency comb system, f r2 is the frequency of the second frequency comb in the dual optical frequency comb system, and f r1 < f r2 .

[0066] Step 2: While turning on the dual optical frequency comb system, synchronously turn on three groups of visible hyperspectral cameras and near-infrared hyperspectral cameras. The central wavelength of the visible hyperspectral camera is selected as 700 nm, and the central wavelength of the near-infrared hyperspectral camera is selected as 950 nm. Collect the two-dimensional light field image of the combustion flame, and combine the three groups of collected light field images to obtain the light field measurement signal I lf , and transmit this signal to the data processing system; selecting the central wavelength of the visible hyperspectral camera as 700 nm and the central wavelength of the near-infrared hyperspectral camera as 950 nm can reconstruct the temperature and gas concentration of the combustion flame; selecting the central wavelength of the visible hyperspectral camera as 700 nm and the central wavelength of the near-infrared hyperspectral camera as 900 nm can reconstruct the temperature and particle concentration of the combustion flame.

[0067] Step 3: According to the absorption spectrum theory, use the measurement signal I l in Step 1 to calculate the distribution k of the spectral radiation physical property parameters of the flame under the laser detection spectrum;

[0068] Absorption spectrum theory, i.e., Beer-Lambert law:

[0069]

[0070] Among them, I t represents the intensity of laser radiation passing through the flame, that is, the multi-angle and multi-spectral laser tomography transmission signal received by the photodetector. The laser measurement signal I l is the vector form of this transmission signal; l represents the position; I 0 represents the intensity of the incident laser radiation; k a represents the absorption coefficient of the medium; v represents the central wavenumber of the incident laser spectrum, and exp represents the natural exponential function.

[0071] An iterative algorithm-based method is used to solve the distribution of spectral radiation physical property parameter k:

[0072]

[0073] Among them, represents the absorption coefficient distribution obtained in the nth iteration; μ (n) represents the convergence factor in the nth iteration; I represents the projection coefficient matrix. For k a , first assume an initial k a , and solve it through the above algorithm by cyclic iteration until the value of k a makes ||I l -k a I|| obtain the minimum value. At this time, take this k a as the physical property parameter of the flame to be solved, that is, the distribution of spectral radiation physical property parameter k.

[0074] Step 4: Combine the spectral radiation physical property parameter k calculated in Step 3 with the optical field measurement signal I lf measured in Step 2, transform the underdetermined ill-posed inverse problem into an overdetermined inverse problem that is easier to solve, and obtain the outgoing radiation intensity I n of the flame by solving this overdetermined inverse problem.

[0075] Among them, I lf and I n correspond to each other. The optical field signal I lf measured in Step 2, that is, the gray-scale image distribution of the flame, can obtain the radiation intensity distribution I n of the flame after being calibrated by the data processing system.

[0076] Step 5: According to the spectral radiation physical property parameter k calculated in Step 3 and the outgoing radiation intensity I nand combined with the inverse problem algorithm, after the structural parameters and positional relationships of the hyperspectral camera are determined, the projection coefficient matrix A is determined by backtracking the sensor pixels λ and solved by the linear inverse problem method to further determine the blackbody spectral radiation intensity distribution I of the flame itself bλ ;

[0077] Considering that the scattering effect of particles inside the flame is much smaller than its absorption effect, the influence of scattering on radiation transmission is ignored, and only the absorption and emission effects of the flame on radiation are considered. The flame is regarded as a pure absorption medium, and the radiation transmission equation in any one direction is as follows:

[0078]

[0079] where s represents the position, s represents the direction (vector), I λ represents the spectral radiation intensity at wavelength λ, and I bλ represents the blackbody radiation intensity at wavelength λ.

[0080] Integrating the radiation transmission equation in any one of the directions along one of the detection directions, the radiation intensity I received by a single pixel of the camera is obtained n Integrating along nine different detection directions, the outgoing spectral radiation intensity distribution I detected by the hyperspectral camera is obtained n .

[0081] Therefore, in step five, after discretizing the radiation transmission equation in differential form of the pure absorption flame and integrating along different detection line directions, a linear equation system with the blackbody spectral radiation intensity I bλ of the flame as the variable can be obtained:

[0082] I n = A λ I bλ

[0083] where A λ represents the projection coefficient matrix obtained by backtracking the detector pixels; the linear inverse problem algorithm Landeweber is used to solve the blackbody spectral radiation intensity I bλ of the flame:

[0084]

[0085] In the formula, p ≥ 2 is a given positive integer, S n is the transition matrix at the nth step in the calculation process, and S 0 is the initial value of the transition matrix; E is the identity matrix; α is the relaxation factor; A T is the transpose matrix of A, and A is equal to the projection coefficient matrix A λ ; A nIt represents the coefficient matrix updated at the n-th iteration step; X represents the unknown quantity to be solved;

[0086] After M iterations, when the maximum number of iterations is reached or the minimum convergence accuracy is achieved, we have:

[0087]

[0088] In the formula, X M is the blackbody spectral radiation intensity I of the flame itself bλ , where M = 0, 1... j.

[0089] Step Seven: Based on the flame temperature field T calculated in Step Six, assuming the flame component concentration field is C and the pressure field is P, substitute the temperature field T, concentration field C, and pressure field P into the radiation transfer equation in the absorption spectroscopy theory, and solve it in combination with the inverse problem algorithm to obtain the estimated value I' of the laser detection radiation intensity l .

[0090] The radiation transfer equation is as follows:

[0091]

[0092] Among them, P l and C l represent the pressure and component concentration at position l, l represents the position, I 0 represents the incident laser radiation intensity, v represents the central wave number of the incident laser spectrum, S v (·) represents the line strength function, represents the line shape function, I' l (v) represents the estimated value of the laser detection radiation intensity. Since the wavelength is a fixed value, therefore, is an equation about variables P and C.

[0093] Step Eight: Based on the laser absorption spectrum information I l measured in Step One and the estimated value I' of the laser detection radiation intensity calculated in Step Seven l , construct the objective function equation for the flame concentration field and pressure field, solve this equation to obtain the objective function values corresponding to the concentration field and pressure field in the objective function equation. Compare the given objective function threshold with the solved objective function value. If the objective function value is less than the given objective function threshold, then the assumed flame component concentration field C and pressure field P in Step Seven are the true distributions of the flame. Thus, the three-dimensional spatial distribution reconstruction of the multi-parameter fields of the flame temperature, concentration, and pressure is completed. If the objective function value is greater than the given objective function threshold, then return to Step Seven to reset the concentration field C and pressure field P.

[0094] The objective function equation for the flame concentration field and pressure field is:

[0095]

[0096] Among them, F obj represents the objective function of the flame pressure component concentration field.

[0097] In this embodiment, two optical frequency combs are projected onto the flame region through wavelength division multiplexing technology. At the same time, a detector is used to receive the intensity of the outgoing spectral radiation after passing through the flame. The absorption spectrum theory and the inverse problem method are combined to solve for the infrared spectral radiation characteristics of the flame, and the three-dimensional temperature field of the flame is reconstructed based on the flame image collected by the hyperspectral camera. Further, combining the known temperature field and the intensity of the outgoing spectral radiation, the three-dimensional distributions of the component concentration and pressure of the flame are calculated using the inverse problem method of collaborative reconstruction. In this embodiment, two types of visible hyperspectral cameras and infrared hyperspectral cameras are equipped. Through synchronous photographing and collection by these hyperspectral cameras, the three-dimensional temperature distribution and the three-dimensional concentration information of water can be retrieved, and the limitation of the traditional hyperspectral camera in the acquisition speed can be overcome, and it is no longer limited to sampling steady-state flames; the coherent light source is two optical frequency combs with slightly different repetition frequencies, rather than the traditional Fourier transform spectrometer or dispersive spectrometer, avoiding the limitation of the measurement accuracy and speed by the spectral splitting element or the scanning speed and effective distance of the robotic arm, and enabling near-real-time spectral detection; the light source of the optical frequency comb is a nonlinear polarization rotation mode-locked pulsed fiber laser, which has the advantages of adjustable pulse repetition frequency, high flexibility, and stable structure; the working wavelengths of the two optical frequency combs cover the ultraviolet, visible, near-infrared to mid-infrared ranges, with the ability to expand the wavelength, and strong practicability; the dual-comb spectroscopy technology can detect the gas absorption spectrum, and the temperature and concentration information of the flame can be analyzed by comparing with the molecular fingerprint spectrum; the wide spectral characteristics of the dual-comb spectroscopy technology allow simultaneous measurement of multiple absorption lines, providing a high-speed and high-precision method for detecting the temperature and concentration of the flame. Through the simulation technology of this embodiment, the collaborative detection of multiple parameters such as the temperature, concentration, and pressure of the high-temperature flame can be realized, which has the advantages of short processing process and the ability to monitor the flame online in real time, providing a theoretical basis for the extended research of online diagnosis of high-temperature flames.

[0098] As described above, the above are only the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A flame multi-parameter field detection method based on a hyperspectral camera and dual optical comb technology, characterized in that: include: Step 1: Obtain the laser absorption spectrum information and light field measurement signal of the flame based on the hyperspectral camera and dual optical comb technology; Step 2: Calculate the spectral radiation physical property parameters of the flame under the laser detection spectrum according to the laser absorption spectrum information; Step 3: Solve the outgoing radiation intensity of the flame based on the spectral radiation physical property parameters, and determine the blackbody spectral radiation intensity of the flame; Step 4: Calculate the internal temperature of the flame based on the blackbody spectral radiation intensity combined with Planck's law to obtain the flame temperature field; Step 5: Substitute the set flame concentration field, flame pressure field and the flame temperature field into the radiation transfer equation for solution to obtain an estimated value of the laser detection radiation intensity; Step 6: Construct the objective function equation of the concentration field and pressure field based on the estimated value of the laser detection radiation intensity, and solve the objective function value. When the objective function value is greater than the preset threshold, return to step 5 to reset the flame concentration field and flame pressure field; when the objective function value is less than the preset threshold, the flame concentration field and flame pressure field set in step 5 are deemed to be the true distribution of the flame, and the flame multi-parameter field detection is completed.

2. The flame multi-parameter field detection method based on a hyperspectral camera and dual optical comb technology according to claim 1 is characterized in that: The process of acquiring the laser absorption spectrum information specifically includes: A dual optical comb system is used to generate two optical frequency comb signals with specific frequency intervals. The optical frequency comb signals are combined using a grating coupler. The combined optical signal is evenly divided into several beams based on an optical fiber beam splitter. Each beam is used as a measurement beam and is arranged at an equal interval on one side of the flame. The detector array is used to receive the measurement light beam after passing through the flame and transmit it to the photoelectric detector to calculate the laser absorption spectrum information and the multi-parameter field distribution of the flame.

3. The flame multi-parameter field detection method based on a hyperspectral camera and dual optical comb technology according to claim 1 is characterized in that: The process of acquiring the light field measurement signal specifically includes: Several groups of visible hyperspectral cameras and near-infrared hyperspectral cameras are used to collect two-dimensional light field images of the flame. The two-dimensional light field images collected by each group of cameras are combined to obtain light field measurement signals.

4. The flame multi-parameter field detection method based on a hyperspectral camera and dual optical comb technology according to claim 1 is characterized in that: The specific calculation formula for calculating the spectral radiation physical property parameters of the flame under the laser detection spectrum according to the laser absorption spectrum information is: In the formula, I t It represents the intensity of laser radiation passing through the flame, that is, the multi-angle multi-spectral laser tomography transmission signal received by the photoelectric detector, and the laser measurement signal I l is the vector form of the transmission signal; l represents the position; I0 represents the incident laser radiation intensity; k a represents the absorption coefficient of the medium; v represents the central wave number of the incident laser spectrum; exp represents the natural exponential function; represents the absorption coefficient distribution obtained at the nth iteration; μ (n) represents the convergence factor at the nth iteration; I represents the projection coefficient matrix until the value of the absorption coefficient makes ||I l -k a I|| reaches the minimum value, at which point the absorption coefficient k a That is the spectral radiation property parameter distribution k.

5. The flame multi-parameter field detection method based on a hyperspectral camera and dual optical comb technology according to claim 1 is characterized in that: The step three specifically includes: Based on the spectral radiation physical property parameters and the light field measurement signal, the underdetermined ill-conditioned inverse problem is converted into an overdetermined inverse problem, and the overdetermined inverse problem is solved to obtain the outgoing radiation intensity of the flame; The blackbody spectral radiation intensity of the flame is solved based on the emergent radiation intensity combined with the Landeweber algorithm.

6. The flame multi-parameter field detection method based on a hyperspectral camera and dual optical comb technology according to claim 5 is characterized in that: The blackbody spectrum radiation intensity of the flame is solved based on the outgoing radiation intensity combined with the Landeweber algorithm. The specific calculation process is: Determine the projection coefficient matrix A based on the backtracking of sensor pixels λ Based on the projection coefficient matrix, the flame blackbody spectral radiation intensity I is determined bλ The linear equation system I with variables n : I n =A λ I bλ The flame blackbody spectral radiation intensity I based on Landeweber algorithm bλ To solve: In the formula, p≥2 is a given positive integer, S n is the transition matrix of the nth step in the calculation process, S0 is the initial value of the transition matrix; E is the unit matrix; α is the relaxation factor; A T is the transposed matrix of A, which is equal to the projection coefficient matrix A λ ; A n represents the coefficient matrix updated in the nth iteration; X represents the unknown quantity to be solved; After iterating M steps, when the maximum number of iterations or the minimum convergence accuracy is reached, we get: Where, X M That is the black body spectral radiation intensity I of the flame itself bλ , M=0,1...j.

7. The flame multi-parameter field detection method based on a hyperspectral camera and dual optical comb technology according to claim 1 is characterized in that: The flame internal temperature is calculated based on the black body spectral radiation intensity combined with Planck's law, and the specific calculation formula is: Where, T h is the internal temperature of the flame, c1 is the first radiation constant of Planck's law, c2 is the second radiation constant, λ is the radiation wavelength, I bλ is the blackbody spectral radiation intensity.

8. The flame multi-parameter field detection method based on a hyperspectral camera and dual optical comb technology according to claim 1 is characterized in that: The objective function equation is specifically: In the formula, F obj represents the objective function of the flame pressure component concentration field, I l is the measurement signal, P is the pressure, C is the component concentration, is an equation about variables P and C, P l and C l represents the pressure and component concentration at l, l represents the position, I0 represents the incident laser radiation intensity, v represents the central wave number of the incident laser spectrum, S v (·) represents the line intensity function, Represents a linear function, I' l (v) represents the estimated value of the laser detection radiation intensity, T l is the temperature field.

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