A method, system, device and medium for measuring polarized spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled plume

Abstract

A method, system, device and medium for measuring the polarized spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled plume, the method comprising: establishing a multi-source vector spectral radiation transfer equation of gas-solid coupling, using the spherical harmonic discrete coordinate method, to establish a polarized spectral radiation model of the gas-solid coupled plume; the model considers the influence of the chemical fluorescence term, increases the coupling influence of the gas phase-solid phase extinction characteristics on the radiation transfer equation, and considers the influence of the heat source radiation term, the chemical fluorescence radiation term and the scattering term of the solid particles generated by the solid propellant combustion on the spectral radiation transfer equation; the system, device and medium are used to realize the method for measuring the polarized spectral radiation characteristics of the thermodynamic-chemical non-equilibrium gas-solid coupled plume; the application provides more dimensional polarization information, effectively improves the precision of the spectral radiation characteristic calculation for the gas-solid coupled plume, and improves the accuracy of the polarization detection of the gas-solid coupled plume in the non-equilibrium flow field of the hypersonic vehicle.

Description

Technical Field

[0001] This invention belongs to the field of computational technology related to exhaust flame spectral radiation, and particularly relates to a method, system, equipment and medium for measuring the polarization spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled exhaust flame. Background Technology

[0002] Currently, with the continuous development of the aerospace industry, the requirements for high-speed vehicle detection are constantly increasing. Improving the accuracy and effectiveness of hypersonic target detection is a key and challenging issue in target early warning, detection, and identification [J. Li, L. Bai, Z. Wu, et al. Ultraviolet scattering properties of alumina particle clusters at three phase states in aircraftplume[J]. Journal of Quantitative Spectroscopy and Radiative Transfer.2017,191, 40-45.]. The study of the spectral radiation characteristics of the gas-solid coupled exhaust plume of hypersonic vehicles is of great theoretical and practical strategic significance for effectively identifying the propellant type and combustion state of hypersonic vehicles, and for detecting their motion characteristics.

[0003] During the flight of hypersonic vehicles, their thrust mainly relies on engines with hypersonic propulsion capabilities, such as scramjet engines. The combustion of propellant within the engine generates enormous thrust, while simultaneously forming a tailpipe plume at the tail nozzle. Since the tailpipe plume carries a wealth of spectral information, research on early warning, detection, and feature recognition of tailpipe plumes based on spectral characteristics has significant theoretical research value and strategic importance [J. Li, L. Bai, Z. Wu, et al. Scattering properties of alumina particle clusters with different radius of monomers in aerocraft plume[J]. Journal of Quantitative Spectroscopy and Radiative Transfer.2017,202, 233-239.].

[0004] The characteristics of the exhaust plume vary greatly depending on the type of propellant. Liquid propellants produce exhaust plumes primarily characterized by a pure gaseous phase with multiple gaseous components, while solid propellants, such as those doped with aluminum powder as an oxidizer, exhibit exhaust plumes as a multiphase mixture of gas and solid phases. A key feature of the exhaust plume is the temperature rise of the gas or gas-solid two-phase flow. This temperature rise converts kinetic energy into thermal energy, resulting in a series of physical and chemical phenomena. These include complex physical-chemical-thermodynamic processes such as molecular rotation-vibration excitation, dissociation, various chemical reactions, molecular collisions-radiation, and molecular ionization into ions. Since the characteristic time required for the development and evolution of these physical and chemical phenomena is non-negligible, these processes related to collisions of elementary particles are thermodynamically and chemically non-equilibrium states.

[0005] Existing methods for modeling exhaust plumes primarily employ spectral radiative transfer equations for pure gaseous components. Commonly used methods for solving the radiative transfer equation (RTE) include the finite volume method, the Monte Carlo method (MCM), the spherical harmonics discrete ordinate method (SHDOM), and the line of sight (LOS) method [R. Pincus, KF Evans. Computational Cost and Accuracy in Calculating Three-Dimensional Radiative Transfer: Results for New Implementations of Monte Carlo and SHDOM[J]. Journal of the Atmospheric Sciences.2009, 66, 3131-3146.]. By solving the radiative transfer equation, the spectral radiation characteristics along the probe line of sight are obtained. Existing literature only considers the transmission and attenuation of spectral intensity information of pure gaseous particles, or approximates the aluminum oxide particles in the gas-solid coupled tail flame generated by the combustion of aluminum-containing solid propellants as spherical particles, and obtains the spectral radiation intensity of the gas-solid coupled tail flame by solving the spectral radiation transmission equation of the gas-solid coupling containing spherical particles.

[0006] Existing spectral radiation models for gas-solid coupled exhaust flames have the following drawbacks: 1) They only consider the spectral intensity term, neglecting the role of polarization in modeling the spectral radiation of gas-solid coupled exhaust flames; 2) They simplify the non-equilibrium process, ignoring the collision-radiation effects of molecules and atoms in the high-temperature gas effect. This approximation simplifies the calculation process but cannot truly describe the excited-state energy level layout of typical molecules in the dynamic non-equilibrium of a gas-solid coupled exhaust flame; 3) They neglect the mutual coupling between the gas phase and the solid particle phase.

[0007] In summary, existing gas-solid coupled exhaust flame spectral radiation models often lead to significant errors in the calculation results of spectral radiation characteristics due to technical simplifications and assumptions. The analysis of gas-solid coupled exhaust flame characteristics is relatively crude and cannot truly describe the microscopic dynamics of the spectral formation of gas-solid coupled exhaust flames and the non-equilibrium dynamic formation mechanism. Summary of the Invention

[0008] To overcome the shortcomings of the prior art, the present invention aims to propose a method, system, equipment, and medium for measuring the polarization spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled tail flame. Based on a typical flow field simulation of the gas-solid coupled tail flame, the temperature, pressure, and proportion of each component in the flame are obtained. The influence of non-equilibrium chemical reactions is considered, increasing the correlation of gas-solid coupling. By establishing a multi-source vector spectral radiative transfer equation for gas-solid coupling and utilizing the spherical harmonic discrete coordinate method, a polarization spectral radiation model of the gas-solid coupled tail flame is established. Through analysis of the influencing factors of this model, the accuracy of calculating the spectral radiation characteristics of the gas-solid coupled tail flame is improved, thereby significantly enhancing the accuracy of polarization detection of the gas-solid coupled tail flame in the non-equilibrium flow field of hypersonic vehicles.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for determining the polarization spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled exhaust flame, specifically including the following steps:

[0011] 1) The gas-solid coupled exhaust plume generated by the hypersonic vehicle is regarded as a cylindrical three-dimensional non-uniform medium with axisymmetric distribution along the central axis of the exhaust plume and along the radial direction perpendicular to the axis. The model is then modeled in three-dimensional space.

[0012] 2) Perform the parameter initialization process of the source functions, including: meshing the computational domain of the hypersonic vehicle's gas-solid coupled exhaust plume after modeling in step 1), assigning initial values ​​to the source functions of temperature, extinction coefficient, and chemical fluorescence radiation at each mesh node; Stokes vector initialization; obtaining the scattering phase matrix of aluminum oxide particles in the exhaust plume using the scattering transfer matrix method, and storing the above data sequentially for later use as the initial values ​​of the source functions in the gas-solid coupled exhaust plume vector spherical harmonic function method;

[0013] 3) Adaptive mesh generation: Define a complex generalized spherical harmonic function vector, and represent the spectral radiation source function vector of the gas-solid coupled tail flame at the mesh node obtained in step 2) using the coordinates of the defined complex generalized spherical harmonic function vector; transform the total source function vector of the i-th mesh node in the generalized spherical harmonic function vector coordinates to the discrete space coordinate representation;

[0014] 4) In discrete spatial coordinates, the Stokes vector at the (i+1)th grid node is obtained by integrating the source function vector of the i-th grid node along the discrete spatial coordinate direction;

[0015] 5) The Stokes vector at the (i+1)th grid point obtained in step 4) is transformed into the complex generalized spherical harmonic function representation in discrete coordinates. After obtaining the Stokes vector in the coordinate representation of the complex generalized spherical harmonic function vector, the source function vector of this grid node is solved.

[0016] 6) Determine whether the mesh nodes calculated in step 5) have reached the boundary of the calculation area of ​​the set exhaust flame model; if "no", start a new mesh calculation from step 3); if "yes", end the calculation and store the source function data on the boundary mesh point, and then calculate the Stokes vector value along the detection direction at the intersection of the detection direction and the boundary of the constructed exhaust flame model.

[0017] The specific method for step 2) is as follows:

[0018] 2.1) Based on the two-dimensional radial distribution data of the exhaust flow field, the temperature, extinction coefficient, and chemical emission coefficient distributions in the three-dimensional exhaust are obtained by linear interpolation. Then, the exhaust computational domain is meshed to obtain the physical properties of each mesh node in the three-dimensional non-uniform medium.

[0019] 2.2) Based on the simulation data of the gas-solid coupled exhaust flow field of each grid node, calculate the corresponding source function vector; consider the polarization radiation characteristics of the high-temperature gas-solid coupled exhaust of the hypersonic vehicle as the transmission result of the spectral radiation source in the high-temperature and high-pressure gas-solid coupled exhaust in a non-uniform three-dimensional medium; the specific expression of the vector source function of the gas-solid coupled exhaust is as follows:

[0020]

[0021] in, Indicated as in At the location, when propagating along the detection direction Ω, the total source function vector, , and These represent the thermal radiation term, the chemical fluorescence radiation vector term, and the intrinsic function vector term caused by the particle scattering effect within the tail flame during gas-solid coupling, respectively. The single-scattering albedo in the gas-solid coupled exhaust flame; For nonpolar heat source terms, The spectral distribution expression for absolute blackbody radiation is expressed as:

[0022]

[0023] Where, k B where λ is Boltzmann's constant, h is Planck's constant, and λ is the wavelength. Let be the absolute temperature of the particle, and c be the speed of light. This represents the emission coefficient of the chemiluminescence of CO in the gas-solid coupled exhaust plume of a hypersonic vehicle. Expressed as the extinction coefficient of the gas-solid coupled tail flame, The scattering phase matrix of Al2O3 particles in a gas-solid coupling hypersonic vehicle;

[0024] 2.3) The spherical harmonic discrete coordinate method (SHDOM) is introduced into the calculation of polarized ultraviolet spectral radiation of the gas-solid coupled exhaust plume of hypersonic vehicles. In the calculation of the chemical fluorescence radiation source, this radiation source is converted into a thermal radiation source, that is:

[0025]

[0026] In the above formula In the improved SHDOM algorithm's property file, the new temperature after chemiluminescence radiation is considered, and the effect of chemiluminescence radiation at each grid node is taken into account in subsequent calculations.

[0027] 2.4) Initialization of Stokes Vector: Before iteratively solving for any component value of the Stokes vector, solve the one-dimensional radiative transfer equation: first solve for the first component I value of the Stokes vector to initialize it, and set the other polarization components Q, U and V of the Stokes vector to zero.

[0028] The spectral radiation sources in the gas-solid coupled tail flame in step 2.2) include: thermal radiation terms of aluminum oxide particles generated by the combustion of aluminum-containing propellant at high temperature, chemical reaction terms of internal energy level excitation, ionization, dissociation and recombination that occur after collisions between multi-component gases in a thermochemical non-equilibrium state, spectral radiation terms generated by chemical fluorescence, and radiation terms in various detection directions caused by scattering terms of aluminum oxide particles in the gas-solid coupled tail flame.

[0029] The specific method for step 3) is as follows:

[0030] The vector representation of the complex generalized spherical harmonic function is defined as follows:

[0031]

[0032] This is the transformation matrix, which is a diagonal matrix, and is specifically calculated as follows: , It is a fourth-order identity matrix. , It is a real symmetric matrix containing the normalized Wigner-d function; where It is the direction of detection. That is, the orientation of a solid angle and its zenith angle in three-dimensional space, and the zenith angle and Relationship satisfaction ;

[0033] The spectral radiation source function vector of the gas-solid coupled tail flame at this grid point is represented by the defined complex generalized spherical harmonic function vector coordinates; the total source function vector of the i-th grid point in generalized spherical harmonic coordinates is transformed to discrete coordinate representation, i.e.:

[0034] .

[0035] The specific method for step 4) is as follows:

[0036] In discrete spatial coordinates, the Stokes vector is solved by integrating the source function vector along the discrete coordinate direction;

[0037]

[0038] in, This indicates the direction corresponding to discrete coordinates. The k-th component of the Stokes vector Ip, and S in the expression is obtained by multiplying the extinction coefficient and the source function vector, that is: Furthermore, in the integration of the iterative process, it is assumed that the extinction coefficient and the product of the extinction coefficient and the source function vector change linearly between each grid cell.

[0039] The specific method for step 5) is as follows:

[0040] The Stokes vector at the (i+1)th grid point is obtained by integrating the i-th grid point in step 4). The obtained Stokes vector is represented in discrete coordinates. The Stokes vector in discrete coordinates is then transformed into a complex generalized spherical harmonic function vector representation, specifically expressed as:

[0041]

[0042] Among them, Y H This represents the conjugate transpose of matrix Y. After obtaining the Stokes vector in the vector coordinate representation of the complex generalized spherical harmonic function, it is necessary to further solve for the source function vector at this grid point, which facilitates the integration solution for this grid point. The specific expression for solving the source function vector is as follows:

[0043]

[0044] matrix It is a block diagonal matrix:

[0045]

[0046] in, The matrix elements are related to the scattering phase matrix; the scattering phase matrix is ​​calculated based on Mie scattering theory as a six-element block diagonal matrix, i.e.:

[0047]

[0048] The meanings of the parameters in the scattering phase matrix are as follows: It is the scattering phase function of clustered particles, which describes the spatial distribution of the energy of the scattered light from the particles; It is the depolarization rate of linearly polarized light that is parallel and perpendicular to the scattering plane; , and Both describe the changes in incident light with different linear polarizations relative to the scattered light with the corresponding linear polarization; It describes the change in circularly polarized incident light corresponding to linearly polarized scattered light;

[0049] The matrix can be obtained by expanding each element of the scattering phase matrix using the Wigner-d function. ;T * It is the conjugate matrix of the transformation matrix.

[0050] A system for measuring the polarization spectral radiation characteristics of a gas-solid coupled exhaust flame under thermodynamic-chemical non-equilibrium conditions, based on the above-mentioned measurement method, includes:

[0051] The physical property parameter preprocessing module is used to assign initial values ​​to the initial parameters in the mesh partitioned within the computational domain of the gas-solid coupled exhaust flame.

[0052] The adaptive mesh generation module is used to perform adaptive mesh generation based on the radiation characteristics of the gas-solid coupled exhaust plume, and to represent the spectral radiation source function vector of the adaptive mesh generation point according to the defined complex generalized spherical harmonic function coordinates.

[0053] The polarization spectral radiation measurement module is used to measure the components of the Stokes vector along the detection direction.

[0054] The apparatus for measuring the polarization spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled exhaust flame based on the above measurement method includes:

[0055] Memory, used to store computer programs;

[0056] A processor is used to execute the computer program to implement the method for determining the polarization spectral radiation characteristics of the thermodynamic-chemical non-equilibrium gas-solid coupled tail flame described in steps 1) to 6).

[0057] A computer-readable storage medium storing a computer program that, when executed by a processor, enables the determination of the polarization spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled exhaust flame based on the measurement method.

[0058] The present invention has the following advantages:

[0059] 1. Based on the influence of the gas-solid coupling interaction in the gas-solid coupled tail flame of a hypersonic vehicle on the spectral radiation, this invention provides a specific formula and detailed procedure for measuring the spectral radiation of the gas-solid coupled tail flame under non-equilibrium conditions by establishing a spherical harmonic discrete coordinate method containing multi-source radiation terms.

[0060] 2. Based on the particle heat source radiation term, the chemical fluorescence radiation term of gas molecules, the scattering term of aluminum oxide particles generated by solid propellant combustion, and the extinction and absorption characteristic terms of gas and solid phase particles in the gas-solid coupled tail flame radiation, this invention establishes a multi-source gas-solid coupled tail flame spectral radiative transfer equation and gives the polarization solution of the equation.

[0061] 3. This invention correlates the linear polarization degree DLOP and the Stokes vector of the polarization degree DOP with the spectral radiative transfer equation of the gas-solid coupled tail flame, and provides a specific procedure for measuring the polarization spectrum of the gas-solid coupled tail flame under non-equilibrium conditions.

[0062] Compared with existing technologies, this invention provides a polarization spectral radiation calculation model for gas-solid coupled exhaust plumes. This model considers the influence of chemiluminescence terms, increases the coupling effect of gas-solid extinction characteristics on the radiative transfer equation, and considers the influence of heat source radiation terms, chemiluminescence radiation terms, and scattering terms of solid particles generated by solid propellant combustion on the spectral radiative transfer equation. Compared with ordinary models that only consider the spectral radiation intensity of exhaust plumes, this model provides more dimensions of polarization information, which can effectively improve the accuracy of feature recognition and provide a theoretical basis and technical support for research on early warning, detection, and identification of hypersonic targets. Attached Figure Description

[0063] Figure 1 This is a flowchart of the method of the present invention.

[0064] Figure 2 This is a schematic diagram of the simulation model of the technology of this invention.

[0065] Figure 3 The diagram shows the distribution of three-dimensional exhaust flame temperature (a), extinction coefficient (b), and emissivity (c).

[0066] Figure 4 To compare the Stokes results calculated in this invention with existing data, (a) is a comparison of I values, (b) is a comparison of Q values, and (c) is a comparison of U values.

[0067] Figure 5 The spectral radiance distribution of the aircraft exhaust plume (I, Q, U) was calculated for this invention. Detailed Implementation

[0068] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0069] See Figure 1 A method for determining the polarization spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled exhaust flame, specifically including the following steps:

[0070] 1) The gas-solid coupled exhaust plume generated by the hypersonic vehicle is considered as an axisymmetrically distributed cylindrical three-dimensional non-uniform medium along the central axis of the exhaust plume and along radial directions perpendicular to the axis. A three-dimensional spatial model is then created for this purpose. Figure 2 As shown;

[0071] 2) Perform the parameter initialization process of the source functions, including: meshing the computational domain of the hypersonic vehicle's gas-solid coupled exhaust plume after modeling in step 1), assigning initial values ​​to the source functions of temperature, extinction coefficient, and chemical fluorescence radiation at each mesh node; Stokes vector initialization; obtaining the scattering phase matrix of aluminum oxide particles in the exhaust plume using the scattering transfer matrix method, and storing the above data sequentially for later use as the initial values ​​of the source functions in the gas-solid coupled exhaust plume vector spherical harmonic function method;

[0072] 2.1) Based on the two-dimensional radial distribution data of the exhaust flow field, the temperature, extinction coefficient, and chemical emission coefficient distributions in the three-dimensional exhaust are obtained by linear interpolation. Then, the exhaust computational domain is meshed to obtain the physical properties of each mesh node in the three-dimensional non-uniform medium.

[0073] 2.2) Based on the simulation data of the gas-solid coupled exhaust flow field of each grid node, calculate the corresponding source function vector:

[0074] The polarization radiation characteristics of the high-temperature gas-solid coupled exhaust plume of a hypersonic vehicle are considered as the transmission result of a high-temperature and high-pressure radiation source in a non-uniform three-dimensional medium.

[0075] 2.2) Based on the simulation data of the gas-solid coupled tail flame flow field of each grid node, calculate the corresponding source function vector; consider the polarization radiation characteristics of the high-temperature gas-solid coupled tail flame of the hypersonic vehicle as the transmission result of the spectral radiation source in the high-temperature and high-pressure gas-solid coupled tail flame in a non-uniform three-dimensional medium; the spectral radiation source in the gas-solid coupled tail flame considered in this invention mainly includes: the thermal radiation term of aluminum oxide particles generated by the combustion of aluminum-containing propellant at high temperature, a series of chemical reaction terms such as internal energy level excitation, ionization, dissociation and recombination after collision between multiple components of gas in thermochemical non-equilibrium state, the spectral radiation term generated by chemical fluorescence, and the radiation terms in various detection directions caused by the scattering term of aluminum oxide particles in the gas-solid coupled tail flame, etc.

[0076] The specific expression for the vector source function of the gas-solid coupled exhaust flame is as follows:

[0077]

[0078] in, Indicated as in At the location, when propagating along the detection direction Ω, the total source function vector, , and These represent the thermal radiation term, the chemical fluorescence radiation vector term, and the intrinsic function vector term caused by the particle scattering effect within the tail flame during gas-solid coupling, respectively. The single-scattering albedo in the gas-solid coupled exhaust flame; For nonpolar heat source terms, The spectral distribution expression for absolute blackbody radiation is expressed as:

[0079]

[0080] Where, k B where λ is Boltzmann's constant, h is Planck's constant, and λ is the wavelength. Let be the absolute temperature of the particle, and c be the speed of light. This represents the emission coefficient of the chemiluminescence of CO in the gas-solid coupled exhaust plume of a hypersonic vehicle. Expressed as the extinction coefficient of the gas-solid coupled tail flame, The scattering phase matrix of Al2O3 particles in a gas-solid coupling hypersonic vehicle;

[0081] 2.3) The spherical harmonic discrete coordinate method (SHDOM) is introduced into the calculation of polarized ultraviolet spectral radiation of the gas-solid coupled exhaust plume of hypersonic vehicles. In the calculation of the chemical fluorescence radiation source, this radiation source is converted into a thermal radiation source, that is:

[0082]

[0083] In the above formula In the improved SHDOM algorithm's property file, the new temperature after chemiluminescence radiation is considered, and the effect of chemiluminescence radiation at each grid node is taken into account in subsequent calculations.

[0084] 2.4) Initialization of Stokes Vector: Before iteratively solving for any component value of the Stokes vector, solve the one-dimensional radiative transfer equation: first solve for the first component I value of the Stokes vector to initialize it, and set the other polarization components Q, U and V of the Stokes vector to zero.

[0085] 3) Adaptive mesh partitioning: The expression for the complex generalized spherical harmonic function vector is defined as follows:

[0086]

[0087] This is the transformation matrix, which is a diagonal matrix, and is specifically calculated as follows: , It is a fourth-order identity matrix. , It is a real symmetric matrix containing the normalized Wigner-d function; where It is the direction of detection. That is, the orientation of a solid angle and its zenith angle in three-dimensional space, and the zenith angle and Relationship satisfaction ;

[0088] The spectral radiation source function vector of the gas-solid coupled tail flame at the grid node obtained in step 2) is represented by the defined complex generalized spherical harmonic function vector coordinates; the total source function vector of the i-th grid point in generalized spherical harmonic coordinates is transformed to discrete coordinate representation, that is:

[0089]

[0090] 4) In discrete spatial coordinates, the Stokes vector at the (i+1)th grid node is obtained by integrating the source function vector of the i-th grid node along the discrete spatial coordinate direction;

[0091]

[0092] in, This indicates the direction corresponding to discrete coordinates. The k-th component of the Stokes vector Ip, and S in the expression is obtained by multiplying the extinction coefficient and the source function vector, i.e.: Furthermore, in the integration of the iterative process, it is assumed that the extinction coefficient and the product of the extinction coefficient and the source function vector change linearly between each grid cell.

[0093] 5) For the Stokes vector at the (i+1)th grid point obtained in step 4), transform the Stokes vector into a complex generalized spherical harmonic function vector representation in discrete coordinates. The specific expression is as follows:

[0094]

[0095] Among them, Y H This represents the conjugate transpose of matrix Y. After obtaining the Stokes vector in the vector coordinate representation of the complex generalized spherical harmonic function, it is necessary to further solve for the source function vector at this grid point, which facilitates the integration solution for this grid point. The specific expression for solving the source function vector is as follows:

[0096]

[0097] matrix It is a block diagonal matrix:

[0098]

[0099] in The matrix elements are related to the scattering phase matrix; the scattering phase matrix is ​​calculated based on Mie scattering theory as a six-element block diagonal matrix, i.e.:

[0100]

[0101] The meanings of the parameters in the scattering phase matrix are as follows: It is the scattering phase function of clustered particles, which describes the spatial distribution of the energy of the scattered light from the particles; It is the depolarization rate of linearly polarized light that is parallel and perpendicular to the scattering plane; , and Both describe the changes in incident light with different linear polarizations relative to the scattered light with the corresponding linear polarization; It describes the change in circularly polarized incident light corresponding to linearly polarized scattered light;

[0102] The matrix can be obtained by expanding each element of the scattering phase matrix using the Wigner-d function. ;T * It is the conjugate matrix of the transformation matrix.

[0103] 6) Determine whether the mesh nodes calculated in step 5) have reached the boundary of the computational region of the set exhaust plume model; if "no", start a new mesh calculation from step 3); if "yes", end the calculation and store the source function data on the boundary mesh points, and then calculate the point The Stokes vector value along the detection direction at that location. Figure 1 This is the overall flowchart.

[0104] The simulation is as follows:

[0105] Figure 4 The results show a comparison between the Stokes results calculated by this invention and existing data, where (a), (b), and (c) represent the values ​​of I, Q, and U, respectively. This invention can provide simulation data for the polarization detection results of aircraft exhaust plumes, and the simulation calculations also verify the correctness of the measurement method of this invention in atmospheric radiation.

[0106] Figure 5 The radiance distribution of the spectral polarization radiation of the non-equilibrium flow field of an aircraft exhaust plume, calculated using the process and method employed in this invention, is presented. From top to bottom, the spectral radiances of I, Q, and U represent the total radiance of the radiation spectrum. This invention addresses the problem in existing techniques that, when solving the spectral radiation model of gas-solid coupled exhaust plumes, only consider the spectral intensity term and neglect the role of polarization in the spectral radiation modeling of gas-solid coupled exhaust plumes.

[0107] from Figure 5 As can be seen, this invention provides more dimensions of polarization information; therefore, it can effectively improve the accuracy of feature recognition and provide a theoretical basis and technical support for research on early warning, detection and recognition of hypersonic targets.

[0108] This invention provides a polarization spectral radiation calculation model for gas-solid coupled exhaust plumes. This model considers the influence of chemiluminescence terms, increases the coupling effect of gas-solid extinction characteristics on the radiative transfer equation, and considers the influence of heat source radiation terms, chemiluminescence radiation terms, and scattering terms of solid particles generated by solid propellant combustion on solving the spectral radiative transfer equation. Compared with ordinary models that only consider the spectral radiation intensity of exhaust plumes, the description of the spectral radiation model of gas-solid coupled exhaust plumes provides more dimensions of polarization information, which can effectively improve the accuracy of feature recognition.

Claims

1. A method for determining the polarization spectral radiation characteristics of a gas-solid coupled exhaust flame in a thermodynamic-chemical non-equilibrium state, characterized in that, Specifically, the following steps are included: 1) The gas-solid coupled exhaust plume generated by the hypersonic vehicle is regarded as a cylindrical three-dimensional non-uniform medium with axisymmetric distribution along the central axis of the exhaust plume and along the radial direction perpendicular to the axis. The model is then modeled in three-dimensional space. 2) Perform the parameter initialization process of the source functions, including: meshing the computational domain of the hypersonic vehicle's gas-solid coupled exhaust plume after modeling in step 1), assigning initial values ​​to the source functions of temperature, extinction coefficient, and chemical fluorescence radiation at each mesh node; Stokes vector initialization; obtaining the scattering phase matrix of aluminum oxide particles in the exhaust plume using the scattering transfer matrix method, and storing the above data sequentially for later use as the initial values ​​of the source functions in the gas-solid coupled exhaust plume vector spherical harmonic function method; 3) Adaptive mesh generation: Define a complex generalized spherical harmonic function vector, and represent the spectral radiation source function vector of the gas-solid coupled tail flame at the mesh node obtained in step 2) using the coordinates of the defined complex generalized spherical harmonic function vector; transform the total source function vector of the i-th mesh node in the generalized spherical harmonic function vector coordinates to the discrete space coordinate representation; 4) In discrete spatial coordinates, the Stokes vector at the (i+1)th grid node is obtained by integrating the source function vector of the i-th grid node along the discrete spatial coordinate direction; 5) The Stokes vector at the (i+1)th grid point obtained in step 4) is transformed into the complex generalized spherical harmonic function representation in discrete coordinates. After obtaining the Stokes vector in the coordinate representation of the complex generalized spherical harmonic function vector, the source function vector of this grid node is solved. 6) Determine whether the mesh nodes calculated in step 5) have reached the boundary of the calculation area of ​​the set exhaust flame model; if "no", start a new mesh calculation from step 3); if "yes", end the calculation and store the source function data on the boundary mesh point, and then calculate the Stokes vector value along the detection direction at the intersection of the detection direction and the boundary of the constructed exhaust flame model.

2. The method for determining the polarization spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled tail flame according to claim 1, characterized in that, The specific method for step 2) is as follows: 2.1) Based on the two-dimensional radial distribution data of the exhaust flow field, the temperature, extinction coefficient, and chemical emission coefficient distributions in the three-dimensional exhaust are obtained by linear interpolation. Then, the exhaust computational domain is meshed to obtain the physical properties of each mesh node in the three-dimensional non-uniform medium. 2.2) Based on the simulation data of the gas-solid coupled exhaust flow field of each grid node, calculate the corresponding source function vector; consider the polarization radiation characteristics of the high-temperature gas-solid coupled exhaust of the hypersonic vehicle as the transmission result of the spectral radiation source in the high-temperature and high-pressure gas-solid coupled exhaust in a non-uniform three-dimensional medium; the specific expression of the vector source function of the gas-solid coupled exhaust is as follows: in, This is represented as the total source function vector at position s, propagating along the detection direction Ω. and denoted as the thermal radiation term, the chemical fluorescence radiation vector term, and the intrinsic function vector term caused by particle scattering effects in the exhaust flame during gas-solid coupling, respectively; ω0(s,λ) is the single-scattering albedo in the gas-solid coupling exhaust flame. For the nonpolar heat source term, B λ (T particles The expression for the spectral distribution of absolute blackbody radiation is: Where, k B Where is Boltzmann's constant, h is Planck's constant, λ is wavelength, and T particle Let be the absolute temperature of the particle, and c be the speed of light. denoted as the emission coefficient of the chemical fluorescence of CO in the gas-solid coupled tail flame of a hypersonic vehicle, σ(s,Ω) represents the extinction coefficient of the gas-solid coupled tail flame, and Z(s;λ;Ω′→Ω) is the scattering phase matrix of Al2O3 particles in the gas-solid coupled hypersonic vehicle. 2.3) The spherical harmonic discrete coordinate method (SHDOM) is introduced into the calculation of polarized ultraviolet spectral radiation of the gas-solid coupled exhaust plume of hypersonic vehicles. In the calculation of the chemical fluorescence radiation source, this radiation source is converted into a thermal radiation source, that is: In the above formula, T is the new temperature in the physical property file of the improved SHDOM algorithm after considering chemical fluorescence radiation. The effect of chemical fluorescence radiation at each grid node is considered in the subsequent calculations. 2.4) Initialization of Stokes Vector: Before iteratively solving for any component value of the Stokes vector, solve the one-dimensional radiative transfer equation: first solve for the first component I value of the Stokes vector to initialize it, and set the other polarization components Q, U and V of the Stokes vector to zero.

3. The method for determining the polarization spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled tail flame according to claim 2, characterized in that, The spectral radiation sources in the gas-solid coupled tail flame in step 2.2) include: thermal radiation terms of aluminum oxide particles generated by the combustion of aluminum-containing propellant at high temperature, chemical reaction terms of internal energy level excitation, ionization, dissociation and recombination that occur after collisions between multi-component gases in a thermochemical non-equilibrium state, spectral radiation terms generated by chemical fluorescence, and radiation terms in various detection directions caused by scattering terms of aluminum oxide particles in the gas-solid coupled tail flame.

4. The method for determining the polarization spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled tail flame according to claim 1, characterized in that, The specific method for step 3) is as follows: The vector representation of the complex generalized spherical harmonic function is defined as follows: T is the transformation matrix, which is a diagonal matrix, specifically calculated as follows: I4 is a fourth-order identity matrix, D = diag[1,1,-1,-1], P nm It is a real symmetric matrix containing the normalized Wigner-d function; where It is the direction of detection. That is, the orientation of the solid angle and the zenith angle in three-dimensional space, and the relationship between the zenith angle θ and μ satisfies μ=cosθ; The spectral radiation source function vector of the gas-solid coupled tail flame at this grid point is represented by the defined complex generalized spherical harmonic function vector coordinates; the total source function vector of the i-th grid point in generalized spherical harmonic coordinates is transformed to discrete coordinate representation, i.e.:

5. The method for determining the polarization spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled tail flame according to claim 1, characterized in that, The specific method for step 4) is as follows: In discrete spatial coordinates, the Stokes vector is solved by integrating the source function vector along the discrete coordinate direction; Among them, [I] kp This represents the direction corresponding to the discrete coordinates Ω. p The k-th component of the Stokes vector Ip is given, and S in the expression is obtained by multiplying the extinction coefficient and the source function vector, i.e.: S = σ ext J; Furthermore, in the integration of the iterative process, it is assumed that the extinction coefficient and the product of the extinction coefficient and the source function vector are linearly varied between each grid cell.

6. The method for determining the polarization spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled tail flame according to claim 1, characterized in that, The specific method for step 5) is as follows: The Stokes vector at the (i+1)th grid point is obtained by integrating the i-th grid point in step 4). The obtained Stokes vector is represented in discrete coordinates. The Stokes vector in discrete coordinates is then transformed into a complex generalized spherical harmonic function vector representation, specifically expressed as: Among them, Y H This represents the conjugate transpose of matrix Y. After obtaining the Stokes vector in the vector coordinate representation of the complex generalized spherical harmonic function, it is necessary to further solve for the source function vector at this grid point, which facilitates the integration solution for this grid point. The specific expression for solving the source function vector is as follows: Matrix G n It is a block diagonal matrix: Among them, G n The matrix elements are related to the scattering phase matrix; the scattering phase matrix is ​​calculated based on Mie scattering theory as a six-element block diagonal matrix, i.e.: The meanings of the parameters in the scattering phase matrix are as follows: F 11 (θ) is the scattering phase function of the cluster particles, which describes the spatial distribution of the scattered light energy; F 12 (θ) is the depolarization rate of linearly polarized light parallel and perpendicular to the scattering plane; F 22 (θ), F 33 (θ) and F 44 (θ) describes the variation of incident light with different linear polarizations relative to the scattered light with the corresponding linear polarization; F 34 (θ) describes the change in circularly polarized incident light corresponding to linearly polarized scattered light; By performing Wigner-d function expansion on each element of the scattering phase matrix, we can obtain matrix G. n ;T * It is the conjugate matrix of the transformation matrix.

7. A system for measuring the polarization spectral radiation characteristics of a gas-solid coupled tail flame in a thermodynamic-chemical non-equilibrium state based on the measurement method described in any one of claims 1 to 6, characterized in that, include: The physical property parameter preprocessing module is used to assign initial values ​​to the initial parameters in the mesh partitioned within the computational domain of the gas-solid coupled exhaust flame. The adaptive mesh generation module is used to perform adaptive mesh generation based on the radiation characteristics of the gas-solid coupled exhaust plume, and to represent the spectral radiation source function vector of the adaptive mesh generation point according to the defined complex generalized spherical harmonic function coordinates. The polarization spectral radiation measurement module is used to measure the components of the Stokes vector along the detection direction.

8. A device for measuring the polarization spectral radiation characteristics of a gas-solid coupled tail flame in a thermodynamic-chemical non-equilibrium state based on the measurement method described in any one of claims 1 to 6, characterized in that, include: Memory, used to store computer programs; A processor is used to execute the computer program to implement the method for determining the polarization spectral radiation characteristics of the thermodynamic-chemical non-equilibrium gas-solid coupled tail flame described in steps 1) to 6).

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, enables the determination of the polarization spectral radiation characteristics of a thermodynamic-chemical non-equilibrium gas-solid coupled tail flame based on the determination method described in claims 1 to 7.

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