Calculation method for ultraviolet spectral radiation of nitric oxide in high-temperature non-equilibrium flow

Abstract

The invention relates to a method for calculating ultraviolet spectral radiation of nitric oxide in high-temperature non-equilibrium flow, and relates to the technical field of related calculation of molecular spectral radiation. Comprising the steps that flow field parameters of the hypersonic aircraft are obtained in a certain determined sight line direction, and the flow field parameters comprise temperature, pressure intensity and component mole fraction data; layering the obtained flow field parameters to obtain flow field parameters of each layer; constructing an extended collision-radiation model, and deriving a matrix form of the extended collision-radiation model; and calculating the NO energy level density in the sight line direction based on the flow field parameters of each layer and the matrix form of the expanded collision-radiation model, and calculating the NO spectral radiance along the determined sight line in the flow field through an apparent ray method based on the NO energy level density. The method solves the problems that a traditional method cannot calculate the high-order excited state energy series density under the high temperature and non-equilibrium state, and the ground state and low-order excited state energy series density and spectrum calculation are not accurate enough.

Description

Technical Field

[0001] The present invention relates to the field of relevant calculation technology of molecular spectral radiation, and in particular to a calculation method of ultraviolet spectral radiation of nitric oxide (NO) in high-temperature non-equilibrium flow. Background Art

[0002] With the continuous development of aerospace, the limitations of hypersonic aircraft in terms of flight speed and altitude have been gradually broken, and people's requirements for accurate and rapid detection and identification of high-speed aircraft are also constantly increasing. It is extremely important to study the spectral radiation characteristics of hypersonic aircraft. During the high-speed flight of an aircraft, due to the strong disturbance and friction between the aircraft and the atmospheric airflow, the temperature and pressure of the air around the high-speed aircraft will increase, and a bow-shaped shock wave layer will be formed around the aircraft.

[0003] Depending on the flight speed and altitude of the aircraft, the types of atoms and molecules produced in the shock layer, the composition of the components, the types and processes of the chemical reactions involved, and the states and processes of molecular vibration and rotation are significantly different.

[0004] As a typical gas component in the shock layer, NO exhibits obvious radiation characteristics in the ultraviolet band due to the structural characteristics of the internal energy levels of its molecules. In particular, the radiation corresponding to the transition of NO from the first electronic excited state to the ground state of NO(γ) is one of the main radiation characteristic bands in the ultraviolet band. The study of the radiation characteristics of NO in the ultraviolet band can provide important references and bases for the analysis of the motion state of high-speed aircraft, the microscopic reaction process of the shock layer and other related studies.

[0005] Therefore, it is necessary to establish a more accurate model for solving the NO excited state energy level density for the high-temperature shock layer around hypersonic vehicles.

[0006] At present, the classical collision-radiation (CR) model is mainly used to solve the energy level layout of the NO electronic excited state. This model only considers the first electronic excited state of NO (NO(A)) and the first electronic excited state of N2 (N2(A)). Under the assumption of quasi-steady state, the classical CR model can be expressed in matrix form. Combined with the temperature, pressure and mole fraction of each component in the flow field, the number density of the first electronic excited state energy level of NO is obtained by solving the chemical reaction rate, molecular number density and other parameters in the matrix.

[0007] The existing models for solving the non-equilibrium NO energy level density have the following disadvantages: 1) The influence of high electronic energy levels on NO radiation is not considered. Although the coupling mechanism between NO and N2 is included in the classical CR model, only the first electronic excited state of NO (NO(A)) and the first electronic excited state of N2 (N2(A)) are considered, and any higher electronic energy levels of NO and N2 are not included. The influence of the energy level layout of high excited states of NO and N2 on the particle number density of NO(A) state in the collision and radiation mechanism is ignored. This simplified analysis problem is relatively rough and cannot accurately describe the layout of the molecular excited state energy level; 2) The particle number density of high energy level excited states of NO cannot be calculated. The classical CR model can only solve the particle number density of the first electronic excited state of NO and N2. However, the particle number density of high energy level excited states such as the second, third, and fourth levels of NO cannot be calculated. The particle number density of excited states will directly affect the calculation results of the shock layer spectral radiation. Therefore, the existing CR model is relatively simple in analyzing the problem of excited state particle number density, and cannot accurately describe the excited state energy level layout of NO molecules. Summary of the invention

[0008] The technical problems to be solved by the present invention are:

[0009] In order to solve the problem that traditional methods cannot calculate the number density of high-order excited state energy levels in high-temperature, non-equilibrium states, and the number density of ground state and low-order excited state energy levels and spectrum calculation are not accurate enough, the present invention provides a method for calculating the ultraviolet spectral radiation of nitric oxide in high-temperature non-equilibrium flow, which provides a solution for the refined detection of targets in the high-speed, non-equilibrium shock layer of hypersonic aircraft.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0011] A method for calculating ultraviolet spectral radiation of nitric oxide in a high-temperature non-equilibrium flow, characterized by comprising:

[0012] Acquiring flow field parameters of a hypersonic vehicle in a certain line of sight direction, wherein the flow field parameters include temperature, pressure and component mole fraction data;

[0013] The acquired flow field parameters are layered to obtain the flow field parameters of each layer;

[0014] Add excited states B, C, D based on NO and excited states B and C based on N2 to the collision-radiation model, construct an extended collision-radiation model, and derive the matrix form of the extended collision-radiation model;

[0015] Based on the flow field parameters of each layer and the matrix form of the extended collision-radiation model, the NO energy level number density NO(i) in the nth layer in the line of sight direction is calculated, where i represents the NO ground state X, excited states A, B, C, and D, respectively;

[0016] Based on the NO energy level number density NO(i), the NO spectral radiance along a certain line of sight in the flow field is calculated by the apparent ray method.

[0017] A further technical solution of the present invention is to use Fluent simulation to obtain the flow field parameters of the hypersonic aircraft.

[0018] A further technical solution of the present invention is as follows: the matrix form of the extended collision-radiation model is specifically:

[0019]

[0020]

[0021]

[0022] Wherein, NO(X), NO(A), NO(B), NO(C), and NO(D) are the number densities of the ground state and excited state A, B, C, and D energy levels of NO, respectively; N2(X), N2(A), N2(B), and N2(C) are the number densities of the ground state and excited state A, B, C, and energy levels of N2, respectively; [N2] represents the number density of nitrogen molecules, [N] represents the number density of nitrogen atoms, [O] represents the number density of oxygen atoms, and [M] represents the number density of heavy particles (N, O, N2, O2, NO); represents the reaction rate of NO transition from energy level j to i induced by heavy particle collision, represents the reaction rate of N2 transition from energy level j to i induced by heavy particle collision, Respectively The reaction rate of the reverse reaction process; and They represent the recombination reaction rates of NO(i) and N2(i) under the induction of heavy particles, and represent the dissociation reaction rates of NO(i) and N2(i) induced by heavy particles, and Respectively represent the compound reaction rates of NO(i) and N2(i), and represents the dissociation reaction rate of NO(i) and N2(i), and They represent the spontaneous radiation rates of NO and N2 transitioning from energy level j to i, respectively. represents the coupled forward reaction rate, Represents the coupled forward reaction The reverse reaction rate; the b and a elements not given in the matrices B and A are all 0.

[0023] A further technical solution of the present invention is to calculate the NO spectral radiance along a certain line of sight in the flow field by the apparent ray method based on the NO energy level number density NO(i), including:

[0024] Calculate the line strength at different temperatures based on the line-by-line method and the HITRAN high temperature molecular database:

[0025]

[0026] Where Q(T) represents the partition function at temperature T, E″ represents the transition lower state energy, ν represents the wave number, c2 represents the second radiation constant, and T0 represents the reference temperature 296K;

[0027] The absorption coefficient of each layer is calculated based on the line intensity and the number density of NO levels NO(i), where Φ is a linear function and N is the number density of NO levels NO(i);

[0028] Calculate the absorption rate of each layer based on the absorption coefficient 1-e -α·l , l represents the thickness of a single layer; transmittance e -α·l ;

[0029] Blackbody radiation is selected as the initial radiance I0 of the target, based on the apparent integration method Calculate the spectral radiance after the entire path, where the optical thickness τ λ =κ sλ l,I bλ represents the blackbody radiation function; when calculating the radiance of the nth layer, it will be affected by the attenuation of the previous n-1 layers, that is, the discrete form of the equation is The subscript λ denotes a physical quantity related to wavelength.

[0030] A computer system, characterized in that it comprises: one or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned method.

[0031] A computer-readable storage medium, characterized in that it stores computer-executable instructions, which are used to implement the above method when executed.

[0032] A computer program product, characterized by comprising computer executable instructions, wherein the instructions are used to implement the above method when executed.

[0033] The beneficial effects of the present invention are:

[0034] The present invention provides a method for calculating the ultraviolet spectral radiation of nitric oxide in a high-temperature non-equilibrium flow. The method is based on a traditional collision-radiation (CR) model, takes into account the thermochemical reaction equations and reaction types under a high-temperature non-equilibrium state, expands the matrix elements in the collision-radiation main equation, and proposes an extended collision-radiation model. The excited state particle number density calculated by the model is combined with an apparent light method to solve the radiation transfer equation of the high-temperature non-equilibrium flow, and the ultraviolet spectral radiation characteristics of NO are obtained.

[0035] The extended collision-radiation model proposed in the present invention takes into account the influence of highly excited states of NO and N2 on the ultraviolet emission spectrum in the NO collision-radiation model, adds the B, C, D states of NO and the B, C states of N2, and can cover a wide range of collision frequencies. By calculating each element in the matrix, the number density of the NO ground state, the first, second, third, and fourth excited state energy levels and the number density of the N2 ground state, the first, second, and third excited state energy levels can be obtained, and the description of the NO collision-radiation model is more comprehensive and accurate. The present invention proposes a more accurate model for calculating the number density of excited state particles of NO in the ultraviolet band. The proposal of this model is of great significance for accurately calculating the ultraviolet radiation spectrum of NO, and is also of great significance for related research such as early warning, detection and identification of high-speed aircraft. Compared with the prior art, it has the following advantages:

[0036] (1) Compared with the traditional collision-radiation model, the influence of high energy states is taken into account, making the method of the present invention more suitable for research fields in higher temperature ranges and non-equilibrium states.

[0037] (2) The traditional collision-radiation model can only calculate the energy level number density of the first excited state. The extended collision-radiation model proposed in the present invention can calculate the particle number density of higher energy level excited states.

[0038] (3) The excited state energy level density results calculated by the extended collision-radiation model proposed in the present invention are combined with the apparent light method to solve the radiation transfer characteristics. The spectral radiation results of the shock layer are significantly better than those obtained by using the traditional collision-radiation model. The spectral radiation characteristics in the ultraviolet band are more consistent with the NO experimental data obtained in the literature. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0040] Figure 1 Flow chart of the method of the present invention.

[0041] Figure 2 Simulated flow field data of bow shock wave at a flight altitude of 38 km: (a) geometric dimensions of the blunt body calculation model; (b) translational-rotational temperature; (c) vibrational-electronic temperature; (d) pressure; (e) NO mole fraction.

[0042] Figure 3 Schematic diagram of the collision-radiation model: (a) Schematic diagram of the classic collision-radiation model; (b) Schematic diagram of the extended collision-radiation model of the present invention.

[0043] Figure 4 The number density of the first electronic excited state energy levels of NO and N2 along the stagnation line.

[0044] Figure 5 Comparison of the calculated results of the spectral radiance of NO as a function of wavelength with the experimental results in the literature.

[0045] Figure 6 Electron energy level number density diagram: (a) Extended CR model along the stagnation line NO excited state electron energy level number density diagram; (b) Extended CR model along the stagnation line N2 excited state electron energy level number density diagram. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] The present invention provides a method for calculating the ultraviolet spectral radiation of nitric oxide in a high-temperature non-equilibrium flow. Combined with the temperature, pressure, mole fraction of each component and the like of the shock layer flow field, based on the classical collision-radiation model, the influence of highly excited NO and N2 on the ultraviolet emission spectrum is considered, the B, C, D states of NO and the B, C states of N2 are added, and each element of the matrix in the CR model is re-derived, combined with the chemical reaction equation and chemical reaction type of the high-temperature non-equilibrium state, an extended collision-radiation model is established. The particle number density of the NO ground state, the first, second, third, and fourth electron excited states and the N2 ground state, the first, second, and third electron excited states obtained by solving the model is compared with the literature data by combining the solution of the apparent light method of the radiation transmission equation, and it is verified that the extended collision-radiation model proposed by the present invention is better consistent with the experimental data in the literature. By improving the CR model and expanding the elements of the matrix, the calculation accuracy of the NO(A) energy level density is improved, so that the NO ultraviolet spectral radiation characteristics of hypersonic vehicles under non-equilibrium conditions can be calculated more accurately.

[0048] like Figure 1 As shown, the specific steps include:

[0049] Step 1: Extract the temperature, pressure and component mole fraction data in the hypersonic vehicle flow field in a certain line of sight direction.

[0050] Figure 2 The simulation data of the bow shock wave flow field are given. Taking a typical blunt body as the calculation model, Figure 2 (a) is the geometrical dimensions of the blunt body model. The bottom radius R n =0.1016m, half cone angle α=7.5°, the height of the blunt body is L=0.25m. The origin of the horizontal x-axis coordinate is taken at the vertex of the blunt body. Since the aircraft is a cycloid symmetric body, only the structural schematic diagram of half of the rotational symmetry is given in the schematic diagram. The flight state of the aircraft includes: flight altitude of 38km, speed of 3500m / s, Mach number of 11Ma, pressure of 377.1pa, and temperature of 244.82K. Figure 2 (b)(c)(d)(e) respectively give the translational-vibrational temperature, vibrational-electronic temperature, pressure and NO mole fraction of the flow field obtained by Fluent simulation;

[0051] Step 2: Layer the line of sight data in step 1, using an appropriate number of layers while ensuring computational efficiency and accuracy. Obtain data such as temperature, pressure, and component mole fraction for each layer;

[0052] Step 3: Derive the matrix form of the master equation for adding NO and N2 electronic excited states under the quasi-steady state assumption;

[0053] Step 3a: According to the flow field distribution, in the CR model of NO, the influence of high electronic excited states, i.e., the first four electronic excited states of NO and the first three electronic excited states of N2, are considered. There are several types of chemical reactions:

[0054] Heavy particle induced annihilation of excitations: M represents heavy particles (N, O, N2, O2, NO);

[0055] Heavy particle collision-induced dissociation recombination: M represents heavy particles (N, O, N2, O2, NO);

[0056] Dissociation complex reaction: Spontaneous emission: NO and N2 coupling reaction: The above reaction rates can be found in existing public literature.

[0057] Step 3b: Give the matrix form corresponding to the main equation of the CR model of NO.

[0058]

[0059] Under the assumption of quasi-steady state, the left side of the equation is always equal to zero, where N is the number density of electronic state layout. The matrix form corresponding to the classical CR model is:

[0060]

[0061] Then the quasi-steady-state number density of NO(A) and N2(A) is solved by the following equation:

[0062]

[0063] The matrix form corresponding to the extended collision-radiation model (Extended CR) proposed in the present invention is:

[0064]

[0065] Among them, NO(X), NO(A), NO(B), NO(C), and NO(D) are the number densities of the ground state and excited state A, B, C, and D energy levels of NO, respectively; N2(X), N2(A), N2(B), and N2(C) are the number densities of the ground state and excited state A, B, C, and energy levels of N2, respectively;

[0066] Step 3c: Under the quasi-steady-state assumption, derive the calculation expressions for each element in the expanded matrix B and the matrix A:

[0067]

[0068]

[0069] in, represents the reaction rate of NO transition from energy level j to i induced by heavy particle collision, represents the reaction rate of N2 transition from energy level j to i induced by heavy particle collision, Respectively The reaction rate of the reverse reaction process; and They represent the recombination reaction rates of NO(i) and N2(i) under the induction of heavy particles, and represent the dissociation reaction rates of NO(i) and N2(i) induced by heavy particles, and Respectively represent the compound reaction rates of NO(i) and N2(i), and represents the dissociation reaction rate of NO(i) and N2(i), and They represent the spontaneous radiation rates of NO and N2 transitioning from energy level j to i, respectively. represents the coupled forward reaction rate, Represents the coupled forward reaction The reverse reaction rate, the b and a elements not given in the matrices B and A are all 0. [N2] represents the number density of nitrogen molecules, [N] represents the number density of nitrogen atoms, [O] represents the number density of oxygen atoms, and [M] represents the number density of heavy particles (N, O, N2, O2, NO). Since the molecular atoms extracted by the flow field are mole fractions x, for the convenience of calculation, according to the ideal equation of state, the mole fraction x is converted into the number density N. Where P is pressure, T is temperature, and k is the Boltzmann constant.

[0070] Step 4: Substitute the flow field parameters in step 2 into the CR model of NO in step 3, and write a program to calculate the number density NO(i) of the NO energy level and the number density N2(i) of the N2 energy level in the nth layer in the line of sight direction.

[0071] like Figure 3 As shown in the figure, the main differences between the present invention and the classical collision-radiation model in the calculation process are given in terms of the excited states, matrix dimensions, chemical reaction types, and the excited state number density that can be obtained. The red part indicates the main difference between the two. Figure 2 The extracted simulation flow field data are used to calculate the particle number density of NO(A) and N2(A) along the stagnation line with the distance from the blunt body wall using the classical collision-radiation model and the extended collision-radiation model. Figure 4 The results of calculating the number density of the first electronic excited state energy levels of NO and N2 using two collision-radiation models are compared. The black solid line and the black dashed line are the number density results of NO(A) calculated by the extended collision-radiation model and the classical collision-radiation model, respectively, and the red solid line and the red dashed line are the number density results of N2(A) calculated by the extended collision-radiation model and the classical collision-radiation model, respectively.

[0072] Step 5: According to the apparent ray method, calculate the NO spectral radiance along the determined line of sight in the flow field.

[0073] Step 5a: Calculate the line intensities at different temperatures based on the line-by-line method and the HITRAN high temperature molecular database

[0074] Where Q(T) represents the partition function at temperature T, E″ represents the transition lower state energy, ν represents the wave number, c2 represents the second radiation constant, and T0 represents the reference temperature 296K. The energy level number density NO(i) obtained in step (4) can be used to calculate the absorption coefficient of the single layer α=S·N·Φ, where Φ is a linear function, and the Voigt linear function can obtain a more accurate absorption coefficient;

[0075] Step 5b: Calculate the absorbance 1-e of each layer -α·l , l represents the thickness of a single layer; transmittance e -α·l ;

[0076] Step 5c: Select blackbody radiation as the initial radiance I0 of the target, based on the apparent integration method Calculate the spectral radiance after the entire path, where the optical thickness τ λ =κ sλ l,I bλ It is important to note that when calculating the radiance of the nth layer, it will be affected by the attenuation of the previous n-1 layers, that is, the discrete form of the equation is

[0077] Figure 5 The variation of NO spectral radiance with wavelength is given. The black curve represents the experimental data in the reference, and the blue and red curves represent the spectral radiance of NO (γ) band calculated by the classical CR model and the extended CR model adopted by the present invention, respectively.

[0078] Figure 6 The variation of the number density of highly excited electron energy levels of NO and N2 along the stagnation line with the distance from the wall is given by using the extended CR model of the present invention, where the calculation parameters are selected as follows: Figure 2 Flow field data.

[0079] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A method for calculating the ultraviolet spectral radiation of nitric oxide in a high-temperature non-equilibrium flow, characterized in that: include: Acquiring flow field parameters of a hypersonic vehicle in a certain line of sight direction, wherein the flow field parameters include temperature, pressure and component mole fraction data; The acquired flow field parameters are layered to obtain the flow field parameters of each layer; Add excited states B, C, D based on NO and excited states B and C based on N2 to the collision-radiation model, construct an extended collision-radiation model, and derive the matrix form of the extended collision-radiation model; Based on the flow field parameters of each layer and the matrix form of the extended collision-radiation model, the NO energy level number density NO(i) in the nth layer in the line of sight direction is calculated, where i represents the NO ground state X, excited states A, B, C, and D, respectively; Based on the NO energy level number density NO(i), the NO spectral radiance along a certain line of sight in the flow field is calculated by the apparent ray method.

2. The method for calculating the ultraviolet spectral radiation of nitric oxide in a high-temperature non-equilibrium flow according to claim 1, characterized in that: Fluent simulation is used to obtain the flow field parameters of hypersonic aircraft.

3. The method for calculating the ultraviolet spectrum radiation of nitric oxide in a high-temperature non-equilibrium flow according to claim 1, characterized in that: The matrix form of the extended collision-radiation model is specifically: Wherein, NO(X), NO(A), NO(B), NO(C), and NO(D) are the number densities of the ground state and excited state A, B, C, and D energy levels of NO, respectively; N2(X), N2(A), N2(B), and N2(C) are the number densities of the ground state and excited state A, B, C, and energy levels of N2, respectively; [N2] represents the number density of nitrogen molecules, [N] represents the number density of nitrogen atoms, [O] represents the number density of oxygen atoms, and [M] represents the number density of heavy particles (N, O, N2, O2, NO); represents the reaction rate of NO transition from energy level j to i induced by heavy particle collision, represents the reaction rate of N2 transition from energy level j to i induced by heavy particle collision, Respectively The reaction rate of the reverse reaction process; and They represent the recombination reaction rates of NO(i) and N2(i) under the induction of heavy particles, and represent the dissociation reaction rates of NO(i) and N2(i) induced by heavy particles, and Respectively represent the compound reaction rates of NO(i) and N2(i), and represents the dissociation reaction rate of NO(i) and N2(i), and They represent the spontaneous radiation rates of NO and N2 transitioning from energy level j to i, respectively. represents the coupled forward reaction rate, Represents the coupled forward reaction The reverse reaction rate; the b and a elements not given in the matrices B and A are all 0.

4. The method for calculating the ultraviolet spectrum radiation of nitric oxide in a high-temperature non-equilibrium flow according to claim 1, characterized in that: Based on the NO energy level number density NO(i), the NO spectral radiance along a certain line of sight in the flow field is calculated by the apparent ray method, including: Calculate the line strength at different temperatures based on the line-by-line method and the HITRAN high temperature molecular database: Where Q(T) represents the partition function at temperature T, E″ represents the transition lower state energy, ν represents the wave number, c2 represents the second radiation constant, and T0 represents the reference temperature 296K; The absorption coefficient of each layer is calculated based on the line intensity and the number density of NO levels NO(i), where Φ is a linear function and N is the number density of NO levels NO(i); Calculate the absorption rate of each layer based on the absorption coefficient 1-e -α·l , l represents the thickness of a single layer; transmittance e -α·l ; Blackbody radiation is selected as the initial radiance I0 of the target, based on the apparent integration method Calculate the spectral radiance after the entire path, where the optical thickness τ λ =κ sλ l,I bλ represents the blackbody radiation function; when calculating the radiance of the nth layer, it will be affected by the attenuation of the previous n-1 layers, that is, the discrete form of the equation is The subscript λ indicates a physical quantity related to wavelength.

5. A computer system, characterized in that include: One or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors are enabled to implement the method of claim 1.

6. A computer-readable storage medium, characterized in that Computer executable instructions are stored, and when the instructions are executed, they are used to implement the method of claim 1.

7. A computer program product, characterized in that The invention comprises computer executable instructions, which are used to implement the method of claim 1 when being executed.

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