Chemical kinetics measurement method for air dissociation process

Abstract

The invention provides a chemical kinetics measurement method for an air dissociation process, which comprises the following steps: synchronously detecting an air dissociation area by using a multi-channel spectrograph and a wide-spectrum radiometer to respectively obtain a multi-band spectral signal and a wide-spectrum thermal radiation energy spectrum signal; on the basis of the multiband spectral signal, identifying characteristic spectral lines of the target component and the free electron, and determining radiation intensity corresponding to each dissociation product; according to the radiation intensity corresponding to each dissociation product, combining with a local thermodynamic equilibrium or non-equilibrium radiation transfer model to invert instantaneous concentration distribution of each dissociation product; analyzing the dynamic thermal relaxation characteristic of the wide-spectrum thermal radiation energy spectrum signal to obtain the real-time temperature field and electron density data of the reaction area; and taking the instantaneous concentration distribution, the electron density and the temperature field data of each dissociation product as boundary conditions, substituting the boundary conditions into a rate equation set containing a non-equilibrium chemical-ionization reaction path, and determining a rate constant and a dominant path of a target reaction.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature flow field diagnostic technology, and specifically relates to a chemical kinetic measurement method and system for air dissociation processes. Background Technology

[0002] With the development of high-speed aircraft and advanced propulsion systems, the chemical kinetics of ultra-high temperature air dissociation processes has become a core challenge in the field of gas dynamics for extreme environments. Within the temperature range of 2000K to 20000K, air components (N2, O2, etc.) undergo complex dissociation, ionization, and excited-state reactions, forming non-equilibrium multi-component mixed systems. Accurate measurement of the chemical kinetic parameters of such transient processes (such as reaction rate constants, component concentration gradients, and vibrational / electron temperature distributions) is of great significance for verifying high-temperature air chemical models and optimizing the design of thermal protection systems.

[0003] Traditional diagnostic methods have significant limitations. Mass spectrometry is constrained by equipment response time, unable to capture microsecond-level non-equilibrium transient processes, and sampling probes are susceptible to ablation interference in high-temperature environments. Single-spectral techniques face challenges in ultra-high-temperature environments, such as spectral line broadening and overlap, strong thermal radiation background noise, and difficulty in separating the coupling effects of vibrational-translational-electronic states. Traditional optical diagnostic systems rely on complex laser configurations, making it difficult to achieve simultaneous multi-component measurements in extreme transient environments such as shock tunnels. Existing spectroscopic techniques rely on single measurements for inversion, but thermal deformation of optical components in ultra-high-temperature environments causes optical path drift, resulting in cross-interference between temperature and concentration measurements, especially in non-equilibrium regions where vibrational and translational temperatures differ significantly. These shortcomings make it difficult for existing experimental data to meet the validation requirements of high-temperature aerodynamic models. For example, NASA's Gupta model and Park model differ by as much as 2 times in predicting NO formation rates, primarily due to the lack of high-confidence ultra-high-temperature non-equilibrium experimental benchmarks. Furthermore, in the design of thermal protection materials for reentry vehicles, traditional methods cannot accurately quantify the O / N atomic concentration gradient in the boundary layer, leading to significant errors in heat flux prediction.

[0004] This invention proposes a chemical kinetic measurement method for air dissociation processes, which is capable of adapting to multi-physics field collaborative measurement technology in ultra-high temperature and transient non-equilibrium environments. It breaks through the limitations of traditional methods in terms of time resolution, multi-parameter decoupling and anti-interference ability, and provides a reliable in-situ diagnostic means for high-temperature gas dynamics research. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the inventors have conducted intensive research and provided a chemical kinetic measurement method for the air dissociation process, aiming to solve the problem of chemical kinetic measurement of the air dissociation process and provide technical means for the diagnosis of ultra-high temperature non-equilibrium flow fields.

[0006] The technical solution provided by this invention is as follows: Firstly, a chemical kinetic measurement method for an air dissociation process includes: Acquiring multi-band spectral signals and broadband thermal radiation energy spectrum signals includes: using a multi-channel spectrometer and a broadband radiometer to simultaneously detect the air dissociation region and acquire multi-band spectral signals and broadband thermal radiation energy spectrum signals respectively; Based on multi-band spectral signals, the target components O2, N2, N, O, and N2 are identified. + O2 + NO, N + O + NO + The characteristic spectral lines of free electrons e in electronic excited state, vibrational state and rotational state were determined, and the radiation intensity corresponding to each dissociation product was determined; Based on the radiation intensity corresponding to each dissociation product, and combined with the local thermodynamic equilibrium or non-equilibrium radiation transfer model, the instantaneous concentration distribution of each dissociation product is inverted. The dynamic thermal relaxation characteristics of the broadband thermal radiation energy spectrum signal were analyzed to obtain real-time temperature field and electron density data of the reaction region. By using the instantaneous concentration distribution, electron density, and temperature field data of each dissociation product as boundary conditions, and substituting them into a set of rate equations containing non-equilibrium chemical-ionization reaction pathways, the rate constant and dominant pathway of the target reaction can be determined.

[0007] Secondly, a chemical kinetics measuring device for an air dissociation process includes: One or more processors; Storage device for storing one or more programs. When the one or more programs are executed by the one or more processors, the one or more processors implement the chemical kinetic measurement method for the air dissociation process described in the first aspect.

[0008] Thirdly, a readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the chemical kinetic measurement method for the air dissociation process described in the first aspect.

[0009] Fourthly, a computer program product comprising: a computer program (also referred to as code or instructions) that, when run, executes the chemical kinetic measurement method for the air dissociation process described in the first aspect.

[0010] The chemical kinetic measurement method for air dissociation process provided by the present invention has the following beneficial effects: This invention provides a chemical kinetics measurement method for air dissociation processes. By integrating multi-band spectral detection and a high-temperature radiometer array, it achieves simultaneous monitoring of chemical kinetic parameters across the entire spectrum under extreme conditions. Based on multi-band spectral signals, it identifies the characteristic spectral lines of target components and free electrons, and determines the radiation intensity corresponding to each dissociation product. According to the radiation intensity corresponding to each dissociation product, combined with a local thermodynamic equilibrium or non-equilibrium radiative transfer model, it inverts the instantaneous concentration distribution of each dissociation product. It analyzes the dynamic thermal relaxation characteristics of the broadband thermal radiation energy spectrum signal to obtain real-time temperature field and electron density data of the reaction region. Using the instantaneous concentration distribution, electron density, and temperature field data of each dissociation product as boundary conditions, it substitutes them into a set of rate equations containing non-equilibrium chemical-ionization reaction paths to determine the rate constant and dominant path of the target reaction. The above method solves the problem of chemical kinetics measurement of air dissociation processes and provides a technical means for the diagnosis of ultra-high temperature non-equilibrium flow fields. Attached Figure Description

[0011] Figure 1 This is a flowchart of the chemical kinetic measurement method for the air dissociation process of the present invention. Detailed Implementation

[0012] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0013] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0014] This invention provides a chemical kinetic measurement method for air dissociation processes, such as... Figure 1 As shown, it includes the following steps: Step 1: Using a multi-channel spectrometer and a broadband radiometer, the air dissociation region is simultaneously detected under high temperature or plasma excitation to acquire multi-band spectral signals and broadband thermal radiation energy spectrum signals, respectively.

[0015] In this step, the multichannel spectrometer covers the 100 nm to 14000 nm wavelength band and is configured with dedicated detection channels for the following components: (1) 100–200 nm: used for detecting N2 + First negative zone (B²Σ) u + → X²Σg + (391.4 nm harmonics), O atom Lyman-α (121.6 nm) and O2 + Schumann-Runge continuous absorption; (2) 200–800 nm: used to monitor NI (746.8 nm), OI (777.4 nm), NO γ band (200–240 nm), and N2 second positive band (300–400 nm). (3) 800–14000 nm: used to identify the infrared triplet of O atoms (1128.7 nm), the vibrational-rotation band of NO (5–6 μm) and the continuous spectrum of free electron bremsstrahlung.

[0016] In this step, the synchronous detection time resolution reaches 0.1 μs, which is sufficient to distinguish N2. + The kinetic timing differences between generation (<1 μs) and NO synthesis (1–10 μs).

[0017] Step 2: Identify the target components O2, N2, N, O, and N2 based on multi-band spectral signals. + O2 + NO, N + O + NO + The characteristic spectral lines of free electrons e in electronically excited states, vibrational states, and rotational states were determined, and the radiation intensities corresponding to each dissociation product were identified.

[0018] In this step, the radiation intensity satisfy:

[0019] in, N i The energy level particle number density of the target component; h Let be Planck's constant. c At the speed of light, A iq The spontaneous emission coefficient, g i For statistical weighting, E i For excited state energy, k B Boltzmann's constant, T exc To generate temperature, φ ( λ ) represents the instrument response function. For wavelength, q It represents an energy level.

[0020] Step 3: Based on the radiation intensity corresponding to each dissociation product, and combined with the local thermodynamic equilibrium or non-equilibrium radiation transfer model, invert the instantaneous concentration distribution of each dissociation product.

[0021] In this step, the radiative transfer model is as follows:

[0022] in, The radiation intensity corresponding to the dissociation products. Background radiation intensity, s The length of the radiation propagation path. The element that differentiates the path length. and These are the emission coefficient and absorption coefficient, respectively, which depend on the local component temperature. T With component concentration [ X [Applicable to non-equilibrium environments from 2000 K to 20000 K. Instantaneous concentrations include: [N], [O], [N2], [O2], [NO], [N2], [O2], [NO], [N2], [O2], [NO], [NO2 ... + ], [O + ], [NO + ], [N2 + ], [O2 + ].

[0023] Step 4: Analyze the dynamic thermal relaxation characteristics of the broadband thermal radiation energy spectrum signal to obtain real-time temperature field and electron density data of the reaction region.

[0024] Temperature field T ( t The electron density [e] was obtained by fitting a modified Planck-bremsstrahlung model to the broadband radiation signal.

[0025] In the formula, The first term represents the theoretical total radiation intensity, and the second term represents the contribution of free electron bremsstrahlung. C br This is the Gaunt factor correction coefficient. Wherein, the material emissivity... (λ) is dynamically calibrated in the range of 2000 K–20000 K, with background term. B bg ( λ The noise is suppressed by wavelet threshold denoising preprocessing.

[0026] Using the temperature field data obtained in this step, the detector response drift of the multichannel spectrometer at high temperatures (>2000 K) is compensated in real time, and the system stability after compensation is better than ±0.2% FS.

[0027] Step 5: Using the instantaneous concentration distribution, electron density, and temperature field data of each dissociation product as boundary conditions, substitute them into the rate equation set containing non-equilibrium chemical-ionization reaction pathways to determine the rate constant and dominant pathway of the target reaction.

[0028] In this step, the rate equations are:

[0029] Among them, the forward reaction rate constant Inversion is performed in the range of 2000K to 20000K with a relative deviation of less than ±2% and a time resolution of less than 0.5μs. The stoichiometric coefficients for the forward reaction are... The stoichiometric coefficients for the reverse reaction. is the rate constant for the reverse reaction. , reactant concentration, For product concentration, This represents the concentration of the product of the reverse reaction.

[0030] The above method is applicable to the following scenarios: (a) Region following the bow shock of a hypersonic reentry vehicle (T ≈ 2000~20,000 K, [e]>10 15 cm -3 ); (b) Nanosecond pulsed plasma torch (dominant component: N2) + (、O、e); (c) Laser-induced air breakdown (early stage: O) + N + ; Later stage: NO, N).

[0031] The above scheme is implemented using a chemical kinetics measurement system, including: (a) Full-band spectral acquisition module (100~14,000 nm), integrating: Vacuum ultraviolet channel (100~200 nm): MgF2 window + Cs-Te photomultiplier tube, used for N2 detection. + First negative zone (B²Σ) u + → X²Σg + (391.4 nm harmonics), O atom Lyman-α (121.6 nm) and O2 + Schumann-Runge continuous absorption; UV-VIS channel (200~800 nm): Back-illuminated sCMOS + tunable filter, used to monitor NI (746.8 nm), OI (777.4 nm), NO γ band (200–240 nm), and N2 second positive band (300–400 nm). IR channel (1~14μm): Liquid nitrogen-cooled InSb detector, used to identify the O atom infrared triplet (1128.7 nm), NO vibrational-rotation band (5–6 μm) and free electron bremsstrahlung continuum; (b) Broadband radiometer array: containing a GaN-based ultraviolet radiometer (anti-plasma interference) and a miniature thermopile to support temperature field T Joint inversion with electron density [e]; (c) Adaptive timing control unit: FPGA + femtosecond laser trigger, synchronization accuracy ±20 ps; (d) Chemical kinetics analysis module: It has built-in energy level database, Einstein coefficient table and Zeldovich-Park reaction mechanism library for the above 11 components, and outputs the concentration-time curves and Arrhenius parameters of each component. (e) Anti-interference shielding structure: adopts double-layer magnetic shielding + fast air curtain protection for optical window, suitable for [e]>10 16 cm -3 Strongly ionized environment.

[0032] The present invention also provides a chemical kinetic measurement device for the air dissociation process, comprising: One or more processors; Storage device for storing one or more programs. When the one or more programs are executed by the one or more processors, the one or more processors implement the chemical kinetic measurement method for the air dissociation process described in the first aspect.

[0033] The present invention also provides a readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the chemical kinetic measurement method for the air dissociation process described in the first aspect.

[0034] The readable storage media include, but are not limited to, USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, optical disks, and other media capable of storing program code.

[0035] The present invention also provides a computer program product comprising: a computer program (also referred to as code or instructions) that, when the computer program is run, executes the chemical kinetic measurement method for the air dissociation process described in the first aspect.

[0036] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, microwave, etc.) means.

[0037] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0038] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0039] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A chemical kinetic measurement method for an air dissociation process, characterized in that, include: Acquiring multi-band spectral signals and broadband thermal radiation energy spectrum signals includes: using a multi-channel spectrometer and a broadband radiometer to simultaneously detect the air dissociation region and acquire multi-band spectral signals and broadband thermal radiation energy spectrum signals respectively; Based on multi-band spectral signals, the target components O2, N2, N, O, and N2 are identified. + O2 + NO, N + O + NO + The characteristic spectral lines of free electrons e in electronic excited state, vibrational state and rotational state were determined, and the radiation intensity corresponding to each dissociation product was determined; Based on the radiation intensity corresponding to each dissociation product, and combined with the local thermodynamic equilibrium or non-equilibrium radiation transfer model, the instantaneous concentration distribution of each dissociation product is inverted. The dynamic thermal relaxation characteristics of the broadband thermal radiation energy spectrum signal were analyzed to obtain real-time temperature field and electron density data of the reaction region. By using the instantaneous concentration distribution, electron density, and temperature field data of each dissociation product as boundary conditions, and substituting them into a set of rate equations containing non-equilibrium chemical-ionization reaction pathways, the rate constant and dominant pathway of the target reaction can be determined.

2. The chemical kinetic measurement method for the air dissociation process according to claim 1, characterized in that, The multichannel spectrometer covers the 100 nm to 14000 nm wavelength range and is configured with the following detection channels: 100–200 nm detection channel: used for detecting N2 + First negative band, O atom Lyman-α and O2 + Schumann-Runge continuous absorption; 200–800 nm probe channel: used to monitor the γ bands of NI, OI, NO, and the second positive band of N2; 800–14000 nm detection channel: used to identify the infrared triplet of O atoms, the vibrational-rotation band of NO, and the continuous spectrum of free electron bremsstrahlung.

3. The chemical kinetic measurement method for the air dissociation process according to claim 1, characterized in that, The radiation intensity corresponding to each dissociation product is determined by the following formula: in, N i The energy level particle number density of the target component; h Let be Planck's constant. c At the speed of light, A iq The spontaneous emission coefficient, g i For statistical weighting, E i For excited state energy, k B Boltzmann's constant, T exc To generate temperature, φ ( λ ) represents the instrument response function. For wavelength, q It represents an energy level.

4. The chemical kinetic measurement method for the air dissociation process according to claim 3, characterized in that, The instantaneous concentration distribution of each dissociation product is inverted using the following radiative transfer model: in, The radiation intensity corresponding to the dissociation products. Background radiation intensity, s The length of the radiation propagation path. The element that differentiates the path length. and These are the emission coefficient and absorption coefficient, respectively, which depend on the local component temperature. T With component concentration [ X ].

5. The chemical kinetic measurement method for the air dissociation process according to claim 4, characterized in that, The real-time temperature field and electron density data of the reaction region are determined by the following formula: in, This represents the theoretical total radiation intensity. C br This is the Gaunt factor correction coefficient. (λ) represents the material emissivity. B bg ( λ ) is the background item, [ e [ ] represents electron density.

6. The chemical kinetic measurement method for the air dissociation process according to claim 5, characterized in that, The method further includes, after analyzing the dynamic thermal relaxation characteristics of the broadband thermal radiation energy spectrum signal and obtaining real-time temperature field and electron density data of the reaction region, using the temperature field data to perform real-time compensation for the detector response drift of the multi-channel spectrometer at >2000 K.

7. The chemical kinetic measurement method for the air dissociation process according to claim 1, characterized in that, The rate constant and dominant pathway of the target reaction were determined using the following set of rate equations: in, Forward reaction rate constant, The stoichiometric coefficients for the forward reaction are... The stoichiometric coefficients for the reverse reaction. The rate constant for the reverse reaction is... , reactant concentration, For product concentration, This represents the concentration of the product of the reverse reaction.

8. A chemical kinetic measuring device for an air dissociation process, characterized in that, include: One or more processors; Storage device for storing one or more programs. When the one or more programs are executed by the one or more processors, the one or more processors implement the chemical kinetic measurement method for the air dissociation process as described in any one of claims 1 to 7.

9. A readable storage medium, characterized in that, It contains a computer program that, when executed by a processor, implements the chemical kinetic measurement method for the air dissociation process as described in any one of claims 1 to 7.

10. A computer program product, characterized in that, The computer program product includes: a computer program that, when run, performs the chemical kinetic measurement method for the air dissociation process as described in any one of claims 1 to 7.

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