CN113295629B - Spectral absorptivity distribution acquisition method and system - Google Patents
Spectral absorptivity distribution acquisition method and system Download PDFInfo
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Abstract
The invention belongs to the technical field of laser absorption spectrum, and discloses a spectral absorptivity distribution acquisition method and a system, wherein the spectral absorptivity distribution acquisition method comprises the following steps: acquiring real transmission tracks of multi-path lasers in a strong deflection field and deflection characteristic parameters including deflection paths and deflection angles by using a light ray tracing optimization algorithm based on self-adaptive step length; rearranging and correcting the spectral absorption rate projection matrix and the path matrix based on the deflection characteristic parameters so as to establish a spectral absorption rate distribution reconstruction equation set under a deflection path; and performing stable optimization solution on the reconstruction equation set by using an improved synchronous iterative reconstruction algorithm, and finally realizing high-precision acquisition of spectral absorption rate distribution in the strong deflection combustion field. The method can reduce the calculation complexity while ensuring the solving precision, realizes the high-precision acquisition of the spectral absorption rate distribution in the strong deflection combustion field, and has good application potential in the fine diagnosis of the strong deflection combustion field.
Description
Technical Field
The invention belongs to the technical field of laser absorption spectroscopy, and particularly relates to a spectral absorption rate distribution acquisition method and system.
Background
At present, the engine has an important strategic position in the field of energy power in China, and the development level of the engine directly reflects the national defense strength and comprehensive national strength of China. The engine combustion chamber is subject to a series of difficulties in the development process, wherein the problem of oscillatory combustion caused by thermoacoustic coupling is a key problem to be solved. The diagnosis of the key parameters in the oscillatory combustion in the aspects of refinement and low cost is helpful for deeply exploring the oscillatory combustion mechanism, so as to effectively control the problem of the oscillatory combustion, reduce the development cost of the engine and improve the safety and reliability of the engine. The laser absorption spectrum technology is one of the main means for measuring the parameters of the combustion process, and has the advantages of no need of pretreatment, high measurement response speed, simultaneous detection of multiple parameters, no influence of tiny particles, strong environmental adaptability, simple system, low cost and the like, so the laser absorption spectrum technology is widely applied to combustion diagnosis. The distribution reconstruction of parameters such as temperature, component concentration and the like in the detected region can be realized by combining the laser absorption spectrum technology with the tomography technology. Therefore, the laser absorption spectrum tomography technology has good development potential in the refined diagnosis of the oscillation combustion field.
In the laser absorption spectrum tomography technology, the reconstruction of the distribution of the spectral absorptivity is a necessary prerequisite for the subsequent inversion of the flow field parameter distribution. Therefore, how to realize high-precision reconstruction of spectral absorption rate distribution in a flow field based on multi-angle and multi-light path projection data is a key problem in the technical research. In the existing research of absorption spectrum tomography technology, the mainly adopted image reconstruction algorithm comprises an analytic reconstruction algorithm based on Randon transformation and an iterative reconstruction algorithm based on solution equations. In the above reconstruction algorithm, the assumption that light rays go straight is used in both the derivation of the analytic reconstruction algorithm and the transformation of the projection information in the iterative reconstruction algorithm, that is, the integral path of the projection is a straight line. However, during turbulent combustion, changes in gas expansion ratio and turbulence density gradients cause dramatic changes in the refractive index profile gradient in the combustion field. In a gradient index medium, the laser beam will no longer travel along a straight line, but will be randomly deflected and travel along a curved path. In most turbulent combustion environments, the light deflection effect is relatively small, and the assumption of straight-going light paths is reasonable, i.e. linear integration can be used instead of curved path integration in the reconstruction process. Many of the previous studies have also fully demonstrated that tomographic reconstruction performed under this assumption can meet the accuracy requirements for combustion field diagnostics. However, compared with the conventional steady-state combustion state in the engine, the oscillatory combustion process is accompanied by large-amplitude pressure and heat oscillation and extremely high combustion and heat transfer rates, the flame structure of the oscillatory combustion process is changed remarkably, and the flow and coupling mechanisms are more complicated. Therefore, the random turbulence intensity in the oscillatory combustion state is larger, the non-uniformity is stronger, and a complex wave propagation process also exists. This causes a more pronounced gradient in the refractive index profile in the oscillating combustion field, which ultimately leads to a randomly strong deflection effect. Under the strong deflection effect, the mathematical premise of the straight advance of the optical path is destroyed by the physical strong deflection effect, and the approximation of the straight advance of the optical path is continuously adopted in the reconstruction process, so that obvious reconstruction errors are brought.
At present, the research on the light ray deflection effect in the laser absorption spectrum technology mainly focuses on adopting corresponding measures at a laser receiving end to eliminate light intensity distortion caused by deflection, but cannot inhibit the influence of the light ray deflection transmission process on tomography. Few researches on laser interference tomography and light deflection tomography technologies relate to the problem of tomography correction in a strong deflection environment, and can provide reference ideas for the researches of the project, but due to the difference of measurement principles, particularly during laser absorption spectrum tomography reconstruction, a plurality of key technical problems exist. In order to realize reliable monitoring of parameters of the oscillatory combustion process, it is necessary to develop a high-precision spectral absorption rate distribution reconstruction method in a strong-deflection combustion field, so as to overcome reconstruction errors in the conventional reconstruction method in which the optical path is directly advanced and assumed in the strong-deflection combustion field, and provide technical support for fine diagnosis of the oscillatory combustion.
Through the above analysis, the problems and defects of the prior art are as follows:
(1) in the turbulent combustion process, the change of the gas expansion ratio and the turbulent density gradient can cause the drastic change of the refractive index distribution gradient in the combustion field; in a gradient index medium, the laser beam will no longer travel along a straight line, but will randomly deflect and travel along a curved path.
(2) Compared with the conventional steady-state combustion state in an engine, the oscillatory combustion process is accompanied by large-amplitude pressure and heat oscillation and extremely high combustion and heat transfer rates, the flame structure of the oscillatory combustion process is obviously changed, and the flow and coupling mechanisms are more complicated.
(3) Under the strong deflection effect, the mathematical premise of the straight advance of the optical path is destroyed by the physical strong deflection effect, and the approximation of the straight advance of the optical path is continuously adopted in the reconstruction process, so that obvious reconstruction errors are brought.
(4) At present, the research on the light ray deflection effect in the laser absorption spectrum technology mainly focuses on adopting corresponding measures at a laser receiving end to eliminate light intensity distortion caused by deflection, but cannot inhibit the influence of the light ray deflection transmission process on tomography.
The difficulty in solving the above problems and defects is: under the light deflection effect, laser does not propagate along a straight line any more but along a curve, and the analytic imaging reconstruction problem under the curve path is a complex nonlinear inversion problem and is difficult to solve.
The significance of solving the problems and the defects is as follows: the invention provides a spectral absorption rate distribution method based on a deflection path, which is characterized in that a discrete deflection path is used for approaching a curve path in practice, a nonlinear inversion problem is converted into a linear inversion problem, the high-precision acquisition of the spectral absorption rate in a strong deflection environment is finally realized, and a technical support is provided for the fine diagnosis of a complex flow field.
Disclosure of Invention
The invention provides a spectral absorption rate distribution acquisition method and system aiming at the problem of tomographic reconstruction of laser absorption spectra in a strong deflection field, and particularly relates to a high-precision spectral absorption rate distribution acquisition method and system based on deflection path inversion.
The present invention is achieved as described above, and a spectral absorptance distribution acquisition method includes:
acquiring real transmission tracks of multi-path laser in a strong deflection field and deflection characteristic parameters including deflection paths and deflection angles by using a light ray tracing optimization algorithm based on self-adaptive step length; (active effect: obtaining discrete deflection path and providing basic data for subsequent tomography)
Rearranging and correcting the spectral absorption rate projection matrix and the path matrix based on the deflection characteristic parameters, thereby establishing a spectral absorption rate distribution reconstruction equation set under a deflection path; (active effect: fusion of specific problems under the deflected path, realization of inversion of distribution under the deflected path)
And thirdly, performing stable optimization solution on the reconstruction equation set by using an improved synchronous iterative reconstruction algorithm, and finally realizing high-precision acquisition of the spectral absorption rate distribution in the strong deflection combustion field. (active effect: overcoming the problem of solving the sick equation set and obtaining high-precision spectral absorption rate)
Further, the spectral absorptance distribution acquisition method further includes:
under the single-angle fan-shaped beam optical path layout, when a beam frequency is v cm-1]The fan-shaped laser beam passes through the interested area NXN and is received by a detector with the distance d, and M projection values can be obtainedI.e. the absorption area A of the M integral ratesv. Projection value A obtained by ith laser beamv,iI.e. the integrated absorption rate can be expressed as:
where i and j denote the laser beam and the grid number, respectively. a isv,jRepresents A within the jth meshvDensity of (D), LijIndicating the path length of the ith laser beam in the jth grid.
At this time, the reconstruction equation set can be expressed as:
Lav＝Av；
where, the mxn path matrix L is:
column vector av＝{av,1,av,2,…,av,N,}T，Av＝{Av,1,Av,2,…,Av,M,}T. When the geometric position of the laser beam is determined, L can be determined, and the spectral absorption rate distribution a can be calculated by a 'hard field' reconstruction algorithmv。
Further, in the first step, according to the refractive index distribution gradient in each reconstruction grid, iterative tracking is carried out on the ray path in each reconstruction grid by using a self-adaptive step length ray tracking method, a discretization deflection path of the light beam in each reconstruction grid is obtained, and the discretization deflection path is used for approaching the light beam integral path in actual transmission.
Further, in the second step, based on the discretized deflection path of the light beam obtained in the first step, a reconstruction grid sequence through which each light ray actually passes is determined, and a projection matrix A of the spectral absorptivity is obtainedvAnd rearranging and correcting the path matrix L so as to establish a spectral absorption rate distribution reconstruction equation set under the deflection path and obtain a coefficient matrix L' and a projection matrix A under the deflection pathv' further, a reconstruction equation set under the deflection path is constructed:
L′aν＝Av′。
furthermore, in the third step, because the measurement angle and the projection data are limited, the number of projection values is often smaller than the number of equations to be solved, and the reconstruction equation set under the deflection path has strong ill-conditioned performance. Solving the reconstruction equation set by adopting an improved synchronous iterative reconstruction algorithm, determining a relaxation factor by utilizing a 'line search' method, and obtaining the spectral absorption rate a through repeated iterative optimizationvAnd (4) reconstructing the result.
Using SNRPIndexes evaluate reconstruction errors:
where K is the dimension of the matrix, R (x, y) and O (x, y) are the reconstructed and original values, respectively, at (x, y) locations within the location area, R is the value of the matrixmaxIs the maximum value of R, SNR of the reconstruction resultPIs 40.6 dB. The value of the quantization error depends on the temperature and spectral absorption range in the circular area and the quantization division, and distortion occurs in a discrete process.
Another object of the present invention is to provide a spectral absorptance distribution acquisition system to which the spectral absorptance distribution acquisition method is applied, the spectral absorptance distribution acquisition system including:
the deflection characteristic parameter acquisition module is used for acquiring the deflection characteristic parameters including the real transmission track, the deflection path and the deflection angle of the multi-path laser in a strong deflection field by using a light ray tracing optimization algorithm based on self-adaptive step length;
the rearrangement and correction module is used for rearranging and correcting the spectral absorption rate projection matrix and the path matrix based on the deflection characteristic parameters;
the system comprises a reconstruction equation set establishing module, a spectrum absorption rate distribution reconstruction equation set and a spectrum absorption rate distribution reconstruction equation set, wherein the reconstruction equation set establishing module is used for establishing the spectrum absorption rate distribution reconstruction equation set under a deflection path;
a stable optimization solving module for performing stable optimization solving on the reconstruction equation set by using an improved synchronous iterative reconstruction algorithm,
and the spectral absorption rate distribution acquisition module is used for realizing high-precision acquisition of spectral absorption rate distribution in the strong deflection combustion field.
It is a further object of the invention to provide a computer device comprising a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to perform the steps of:
aiming at the non-uniform refractive index distribution characteristic of a strong deflection combustion field, acquiring real transmission tracks, deflection paths, deflection angles and other deflection characteristic parameters of laser in the strong deflection field by using a light ray tracing optimization method based on local refractive index gradient and self-adaptive step length;
approximating a curve integral path in actual transmission by using a discretized deflection integral path, and rearranging and correcting a spectral absorption rate projection matrix and a path matrix based on deflection characteristic parameters so as to establish a spectral absorption rate distribution reconstruction equation set under the deflection path;
and performing stable optimization solution on the reconstruction equation set by using an improved synchronous iterative reconstruction algorithm, and finally realizing high-precision acquisition of spectral absorption rate distribution in the strong deflection combustion field.
It is another object of the present invention to provide a computer-readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the steps of:
aiming at the non-uniform refractive index distribution characteristic of a strong deflection combustion field, acquiring real transmission tracks, deflection paths, deflection angles and other deflection characteristic parameters of laser in the strong deflection field by using a light ray tracing optimization method based on local refractive index gradient and self-adaptive step length;
approximating a curve integral path in actual transmission by using a discretized deflection integral path, and rearranging and correcting a spectral absorption rate projection matrix and a path matrix based on deflection characteristic parameters so as to establish a spectral absorption rate distribution reconstruction equation set under the deflection path;
and performing stable optimization solution on the reconstruction equation set by using an improved synchronous iterative reconstruction algorithm, and finally realizing high-precision acquisition of spectral absorption rate distribution in the strong deflection combustion field.
Another object of the present invention is to provide an information data processing terminal for implementing the spectral absorbance distribution acquisition system.
By combining all the technical schemes, the invention has the advantages and positive effects that: the method for acquiring the spectral absorptivity distribution provided by the invention utilizes a light ray tracing optimization algorithm based on self-adaptive step length to acquire deflection characteristic parameters such as a real transmission track, a deflection path, a deflection angle and the like of multi-path laser in a strong deflection field; rearranging and correcting the spectral absorption rate projection matrix and the path matrix based on the deflection characteristic parameters so as to establish a spectral absorption rate distribution reconstruction equation set under a deflection path; the reconstruction equation set is stably and optimally solved by using an improved synchronous iterative reconstruction algorithm, the calculation complexity is reduced while the solving precision is ensured, the high-precision acquisition of the spectral absorption rate distribution in the strong deflection combustion field is finally realized, and the method has good application potential in the refined diagnosis of the strong deflection combustion field.
The invention provides a spectral absorption rate distribution acquisition method based on non-linear path (deflection path) inversion aiming at the non-uniform refractive index distribution characteristic of a strong deflection combustion field, and a discretized deflection integral path is used for approaching a curve integral path in actual transmission, so that the high-precision reconstruction of the spectral absorption rate distribution is realized. Compared with the conventional laser absorption spectrum tomography reconstruction method based on the straight path, the method overcomes the reconstruction error caused by the straight-forward approximation of the optical path, improves the reconstruction accuracy of the spectral absorption rate, and provides technical support for the refined diagnosis of the strong deflection combustion field.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a flowchart of a method for acquiring a spectral absorption rate distribution according to an embodiment of the present invention.
FIG. 2 is a block diagram of a spectral absorbance distribution acquisition system according to an embodiment of the present invention;
in the figure: 1. a deflection characteristic parameter acquisition module; 2. a rearrangement and correction module; 3. a reconstruction equation set establishing module; 4. a stability optimization solving module; 5. a spectral absorbance distribution acquisition module.
Fig. 3 is a schematic diagram of an inverse projection model of spectral absorbance distribution according to an embodiment of the present invention.
Fig. 4 is a schematic diagram of a process for reconstructing a spectral absorptance distribution under a deflected path according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of a deflected path obtaining process according to an embodiment of the present invention.
Fig. 6(a) -6 (b) are schematic diagrams comparing the original distribution of the spectral absorptance and the reconstructed result provided by the embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
In view of the problems in the prior art, the present invention provides a method and a system for acquiring spectral absorption rate distribution, which are described in detail below with reference to the accompanying drawings.
As shown in fig. 1, the method for acquiring spectral absorption rate distribution according to the embodiment of the present invention includes the following steps:
s101, acquiring real transmission tracks, deflection paths and deflection characteristic parameters including deflection angles of multi-path laser in a strong deflection field by using a light ray tracing optimization algorithm based on self-adaptive step length;
s102, rearranging and correcting the spectral absorption rate projection matrix and the path matrix based on the deflection characteristic parameters, so as to establish a spectral absorption rate distribution reconstruction equation set under a deflection path;
s103, carrying out stable optimization solution on the reconstruction equation set by using an improved synchronous iterative reconstruction algorithm, and finally realizing high-precision acquisition of spectral absorption rate distribution in the strong deflection combustion field.
As shown in fig. 2, a spectral absorption rate distribution acquisition system according to an embodiment of the present invention includes:
the deflection characteristic parameter acquisition module 1 is used for acquiring a real transmission track, a deflection path and a deflection angle of the multi-path laser in a strong deflection field by using a light ray tracing optimization algorithm based on self-adaptive step length;
the rearrangement and correction module 2 is used for rearranging and correcting the spectral absorption rate projection matrix and the path matrix based on the deflection characteristic parameters;
the reconstruction equation set establishing module 3 is used for establishing a spectral absorption rate distribution reconstruction equation set under the deflection path;
a stable optimization solving module 4 for performing stable optimization solving on the reconstruction equation set by using an improved synchronous iterative reconstruction algorithm,
and the spectral absorption rate distribution acquisition module 5 is used for realizing high-precision acquisition of spectral absorption rate distribution in the strong deflection combustion field.
The technical solution of the present invention will be further described with reference to the following examples.
The invention provides a high-precision spectral absorptivity distribution acquisition method based on deflection path inversion, aiming at the problem of tomographic reconstruction of laser absorption spectrum in a strong deflection field. The method has the basic idea that the real deflection transmission path of the laser in the strong deflection combustion field is obtained, and the distribution inversion of the spectral absorption rate distribution is realized based on the deflection path. Firstly, aiming at the non-uniform refractive index distribution characteristic of a strong deflection combustion field, acquiring the real transmission track, deflection path, deflection angle and other deflection characteristic parameters of laser in the strong deflection field by using a light ray tracing optimization method based on local refractive index gradient and self-adaptive step length; secondly, approximating a curve integral path in actual transmission by using a discretized deflection integral path, and rearranging and correcting the spectral absorption rate projection matrix and the path matrix based on the deflection characteristic parameters so as to establish a spectral absorption rate distribution reconstruction equation set under the deflection path; and finally, performing stable optimization solution on the reconstruction equation set by using an improved synchronous iterative reconstruction algorithm, reducing the computational complexity while ensuring the solution precision, and finally realizing high-precision acquisition of the spectral absorption rate distribution in the strong deflection combustion field. The method overcomes reconstruction errors caused by the straight-ahead approximation of the optical path, improves the spectral absorption rate reconstruction accuracy, and provides technical support for the refined diagnosis of the strong deflection combustion field.
In this embodiment, a circular spectral absorption rate distribution area with an obvious refractive index distribution characteristic is constructed by referring to the flow field characteristic of the strongly deflected combustion field, and the original distribution rule of the spectral absorption rate in the circular spectral absorption rate distribution area is given for verifying the reconstruction algorithm provided by the present invention. The following describes the implementation of the method in detail by taking the reconstruction of the spectral absorptance under the single-angle fan beam optical path layout as an example.
Under the single-angle fan-beam optical path layout, as shown in FIG. 3, when a beam has a frequency of v cm-1]Passes through the region of interest (N × N) and is received by a detector with a distance d, and M projection values, i.e. M absorption areas a of the integration rate, are obtainedv. Projection value A obtained by ith laser beamv,i(integrated absorbance) can be expressed as:
where i and j denote the laser beam and the grid number, respectively. a isv,jRepresents A within the jth meshvDensity of (D), LijIndicating the path length of the ith laser beam in the jth grid.
At this time, the reconstruction equation set may be expressed as:
Lav＝Av (2)
wherein, the path matrix L of mxn is:
column vector av＝{av,1,av,2,…,av,N,}T，Av＝{Av,1,Av,2,…,Av,M,}T. When the geometric position of the laser beam is determined, L can be determined, and the spectral absorption rate distribution a can be calculated by a 'hard field' reconstruction algorithmv。
However, when the light is deflected, the sequence and path length of the reconstruction grid passing through are changed, and the projection matrix AvAnd the path length matrix L also change accordingly, it is necessary to correct the above reconstruction process in combination with the deflected path of the light beam, which is the object of the present invention, and fig. 4 is a schematic diagram of the reconstruction process of the spectral absorption rate distribution under the deflected path.
The implementation steps of the present invention are further described below with reference to the above reconstruction principles and the accompanying drawings:
step one, a circular region of interest is divided into 15 × 15 grids, and in each grid, the temperature and the component concentration are considered to be constant values, but the refractive index distribution is not uniform. And according to the refractive index distribution gradient in each grid, carrying out iterative tracking on the ray path in each reconstruction grid by using a self-adaptive step length ray tracking method to obtain the beam deflection path in each reconstruction grid, and further obtain the real transmission track and the deflection path of the beam passing through the whole circular region of interest. FIG. 5 is a schematic diagram of a process for obtaining a deflected path in a reconstruction grid, where n isiThe index of refraction for the ith trace step.
Step two, based on the beam deflection path obtained in the step one, determining a reconstruction grid sequence through which each light ray actually passes, and projecting a matrix A to the spectral absorptivityvRearranging and correcting the path matrix L so as to establish a spectral absorption rate distribution reconstruction equation set under the deflection path; obtaining a coefficient matrix L' and a projection matrix A under the deflection pathv' further, a reconstruction equation set under the deflection path is constructed:
L′aν＝Av′ (4)
and step three, because the measurement angle and the projection data are limited, the number of the projection values is often smaller than that of the equations to be solved, and the reconstruction equation set under the deflection path has strong ill-conditioned property. Solving a reconstruction equation set (4) by adopting an improved synchronous iterative reconstruction algorithm, determining a relaxation factor by utilizing a 'line search' method, and obtaining the spectral absorption rate a through repeated iterative optimizationvAnd (4) reconstructing the result. Fig. 6 is a comparison of the original distribution of spectral absorptance with the reconstructed results.
Using SNRPIndexes evaluate reconstruction errors:
where K is the dimension of the matrix, R (x, y) and O (x, y) are the reconstructed and original values, respectively, at (x, y) locations within the location area, R is the value of the matrixmaxIs the maximum value of R, SNR of the reconstruction resultPIs 40.6 dB. The value of the quantization error depends on the temperature and spectral absorption range in the circular area and the quantization division, and distortion occurs in a discrete process. In summary, the spectral absorption rate reconstruction method based on the deflection path can ensure the distribution reconstruction quality in the strong deflection field.
The simulation results are provided in fig. 6.
In the above embodiments, all or part of the implementation may be realized by software, hardware, firmware, or any combination thereof. When used in whole or in part, can be implemented in a computer program product that includes one or more computer instructions. When loaded or executed on a computer, cause the flow or functions according to embodiments of the invention to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, the computer instructions may be transmitted from one website site, computer, server, or data center to another website site, computer, server, or data center via wire (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL), or wireless (e.g., infrared, wireless, microwave, etc.)). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server, a data center, etc., that includes one or more of the available media. The usable medium may be a magnetic medium (e.g., floppy Disk, hard Disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., Solid State Disk (SSD)), among others.
The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.
Claims (8)
1. A spectral absorptance distribution acquisition method, characterized by comprising:
firstly, aiming at the non-uniform refractive index distribution characteristic of a strong deflection combustion field, acquiring the real transmission track, the deflection path and the deflection angle deflection characteristic parameters of laser in the strong deflection field by using a light ray tracing optimization method based on local refractive index gradient and self-adaptive step length;
secondly, approximating a curve integral path in actual transmission by using a discretized deflection integral path, and rearranging and correcting the spectral absorption rate projection matrix and the path matrix based on the deflection characteristic parameters so as to establish a spectral absorption rate distribution reconstruction equation set under the deflection path; based on the obtained discretized deflection path of the light beam, determining a reconstruction grid sequence which each light ray actually passes through, and projecting a matrix A to a spectral absorptivityvAnd rearranging and correcting the path matrix L so as to establish a spectral absorption rate distribution reconstruction equation set under the deflection path and obtain a coefficient matrix under the deflection pathL' and projection matrix Av', spectral absorptance av(ii) a And further constructing a reconstruction equation set under the deflection path:
L′aν＝A′v；
and finally, carrying out stable optimization solution on the reconstruction equation set by using an improved synchronous iterative reconstruction algorithm, and finally realizing high-precision acquisition of spectral absorption rate distribution in the strong deflection combustion field.
2. The method for acquiring spectral absorption rate distribution according to claim 1, wherein the light ray path in each reconstruction grid is iteratively tracked by using an adaptive step-size light ray tracing method according to the refractive index distribution gradient in each reconstruction grid to obtain a discretized deflection path of the light beam in each reconstruction grid, and the discretized deflection path is used to approximate the light beam integral path in actual transmission.
3. The method for obtaining spectral absorbance distribution according to claim 1, wherein the system of reconstruction equations is solved using an improved simultaneous iterative reconstruction algorithm, the relaxation factor is determined using a "line search" method, and the spectral absorbance a is obtained by multiple iterative optimizationvThe result of the distribution reconstruction;
using SNRPIndexes evaluate reconstruction errors:
where K is the dimension of the matrix, R (x, y) and O (x, y) are the reconstructed and original values, respectively, at (x, y) locations within the location area, R is the value of the matrixmaxIs the maximum value of R, SNR of the reconstruction resultP40.6 dB; the value of the quantization error depends on the temperature and spectral absorption range in the circular area and the quantization division, and the distortion occurs in a discrete process.
4. A spectral absorptance distribution acquisition system for implementing the spectral absorptance distribution acquisition method according to any one of claims 1 to 3, the spectral absorptance distribution acquisition system comprising:
the deflection characteristic parameter acquisition module is used for acquiring the deflection characteristic parameters including the real transmission track, the deflection path and the deflection angle of the multi-path laser in a strong deflection field by using a light ray tracing optimization algorithm based on self-adaptive step length;
the rearrangement and correction module is used for rearranging and correcting the spectral absorption rate projection matrix and the path matrix based on the deflection characteristic parameters;
the system comprises a reconstruction equation set establishing module, a spectrum absorption rate distribution reconstruction equation set and a spectrum absorption rate distribution reconstruction equation set, wherein the reconstruction equation set establishing module is used for establishing a spectrum absorption rate distribution reconstruction equation set under a deflection path;
a stable optimization solving module for performing stable optimization solving on the reconstruction equation set by using an improved synchronous iterative reconstruction algorithm,
and the spectral absorption rate distribution acquisition module is used for realizing high-precision acquisition of spectral absorption rate distribution in the strong deflection combustion field.
5. A computer device, characterized in that the computer device comprises a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to carry out the steps of:
aiming at the non-uniform refractive index distribution characteristic of a strong deflection combustion field, acquiring the real transmission track, the deflection path and the deflection angle deflection characteristic parameters of laser in the strong deflection field by using a light ray tracing optimization method based on local refractive index gradient and self-adaptive step length;
approximating a curve integral path in actual transmission by using a discretized deflection integral path, and rearranging and correcting a spectral absorption rate projection matrix and a path matrix based on deflection characteristic parameters so as to establish a spectral absorption rate distribution reconstruction equation set under the deflection path; based on the obtained discretized deflection path of the light beam, determining a reconstruction grid sequence which each light ray actually passes through, and projecting a matrix A to a spectral absorptivityvAnd rearranging and correcting the path matrix L to establish the spectral absorption rate distribution under the deflection pathReconstructing an equation set to obtain a coefficient matrix L' and a projection matrix A under the deflection pathv', spectral absorptance av(ii) a And further constructing a reconstruction equation set under the deflection path:
L′aν＝A′v；
and performing stable optimization solution on the reconstruction equation set by using an improved synchronous iterative reconstruction algorithm, and finally realizing high-precision acquisition of spectral absorption rate distribution in the strong deflection combustion field.
6. A computer-readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the steps of:
aiming at the non-uniform refractive index distribution characteristic of a strong deflection combustion field, acquiring the real transmission track, the deflection path and the deflection angle deflection characteristic parameters of laser in the strong deflection field by using a light ray tracing optimization method based on local refractive index gradient and self-adaptive step length;
approximating a curve integral path in actual transmission by using a discretized deflection integral path, and rearranging and correcting a spectral absorption rate projection matrix and a path matrix based on deflection characteristic parameters so as to establish a spectral absorption rate distribution reconstruction equation set under the deflection path; based on the obtained discretized deflection path of the light beam, determining a reconstruction grid sequence which each light ray actually passes through, and projecting a matrix A to a spectral absorptivityvAnd rearranging and correcting the path matrix L so as to establish a spectral absorption rate distribution reconstruction equation set under the deflection path and obtain a coefficient matrix L' and a projection matrix A under the deflection pathv', spectral absorptance av(ii) a And further constructing a reconstruction equation set under the deflection path:
L′aν＝A′v；
and performing stable optimization solution on the reconstruction equation set by using an improved synchronous iterative reconstruction algorithm, and finally realizing high-precision acquisition of spectral absorption rate distribution in the strong deflection combustion field.
7. An information data processing terminal, characterized in that the information data processing terminal is equipped with the spectral absorptance distribution acquisition system according to claim 4.
8. A laser absorption spectrum tomography method, characterized in that the laser absorption spectrum tomography method adopts the spectral absorption rate distribution acquisition method of any one of claims 1 to 3.
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