SiC-based heat-proof material gas-solid interface unbalanced reaction analysis method under high enthalpy

Abstract

The invention provides a SiC-based heat-proof material gas-solid interface unbalanced reaction analysis method under high enthalpy, which mainly comprises the following steps: (1) on the basis of a SiC-based composite ceramic material, constructing a multi-physical field coupling thermal environment by utilizing a high-enthalpy plasma wind tunnel and regulating and controlling flow field parameters, structures and material surface reaction conditions; and (2) then, cooperatively applying four spectroscopy diagnostic technologies of radiation spectrum, narrow-band imaging spectrum, laser absorption spectrum and infrared radiation, and synchronously measuring multiple physical quantities of spatial and temporal distribution of a near-wall flow field of the SiC-based composite ceramic material to extract associated characteristics of the surface macroscopic thermal response and near-wall flow of the SiC-based composite ceramic material. And furthermore, the catalysis-oxidation-nitridation competitive coupling rule in the gas-solid interface unbalanced reaction of the SiC-based material under the long-time high enthalpy is systematically disclosed. According to the invention, multi-dimensional analysis can be provided for gas-solid interface non-equilibrium reaction mechanism research, and fine simulation and quantitative characterization of multi-field coupling phenomena such as passive oxidation, active oxidation, passive / active oxidation transition and the like can be realized.

Description

Technical Field

[0001] This invention relates to the field of aerodynamic thermal protection research technology for hypersonic vehicles, specifically to a method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based thermal protection materials under high enthalpy. Background Technology

[0002] SiC-based ceramic composites, such as C f / SiC、SiC f SiC, ZrB2-SiC, and other materials, with their high hardness, high specific strength, high melting point, and high wear resistance, are among the main material systems used in current high-speed aircraft. The "anti-ablation / non-ablation" properties of SiC-based materials originate from the dense condensed phase protective layer of SiO2 and B2O3 formed by surface oxidation, effectively slowing down the diffusion rate of oxygen / nitrogen atoms and inhibiting deep oxidation of the material. With the development of various new types of aerospace vehicles, the new layout features and service environments determine increasingly complex aerodynamic and thermal environments. However, there is currently a severe lack of characterization technologies and corresponding testing systems for the key parameters of the thermal protection performance of SiC-based materials under high enthalpy, long-term environments.

[0003] When aerospace vehicles re-enter the atmosphere, the coupled competition between the high-enthalpy incoming flow and the non-equilibrium reactions (catalytic recombination, oxidation, and nitridation) of the heat-resistant materials at the gas-solid interface is a crucial factor influencing the aerodynamic thermal environment. Taking catalysis as an example, it describes the process by which the heat-resistant materials excite high-enthalpy dissociated oxygen and nitrogen atoms to participate in surface catalytic recombination reactions. This not only exacerbates the thermal load through chemical exothermia but also affects the oxidation rate of the material. Simultaneously, the oxidation reaction on the material surface may not only form new solid phase components, altering its surface properties (such as structure, composition, and roughness) and thus changing its catalytic characteristics, but also create new gaseous particles that enter the flow field, altering fluid characteristics. Furthermore, existing research has demonstrated that the role of nitrogen atoms in high-enthalpy, nitrogen-rich environments cannot be ignored. They participate in gas-solid interface chemical reactions through nitridation or catalytic recombination, leading to increased boundary layer temperature and exacerbating surface thermal load. Therefore, a correct understanding of the non-equilibrium reaction patterns at the gas-solid interface is of great significance for predicting the changes in thermal load on spacecraft and for the development of thermal protection technologies.

[0004] In experimental research, high-enthalpy wind tunnels, which effectively simulate extreme aerodynamic thermal environments, serve as the primary testing platform. Measuring surface heat flux density, monitoring surface temperature changes during ablation, and analyzing the microstructure and composition of the material before and after ablation are the main techniques employed in this field, with significant technological advancements both domestically and internationally. Taking the study of catalytic properties as an example, the principle involves referencing known catalytic properties of materials, analyzing the net heat flux of the test material, and calculating the catalytic composite coefficient by leveraging the correlation between the release of dissociation energy at the surface in the boundary layer and the surface catalytic properties. It is particularly important to note that, given the extreme sensitivity of catalytic effects to flow field composition, high-frequency plasma wind tunnel testing systems with electrode-free ablation contamination are widely used internationally.

[0005] Objectively speaking, high-frequency plasma wind tunnels can effectively simulate the thermal environment of reentry vehicles, and their material ablation data strongly support the development of high-enthalpy reentry technology in my country. However, due to the lack of key process parameters in the multi-field coupling process—especially the component density and vibrational temperature within the boundary layer—the understanding of core scientific issues such as the competitive coupling mechanism of non-equilibrium reactions at the gas-solid interface lags behind engineering practice, resulting in a typical contradiction between the feasibility of engineering applications and insufficient understanding of mechanisms in this field in my country. In particular, both domestic and international studies have observed a sudden surface temperature jump in SiC-based materials under high-enthalpy plasma wind tunnel inflow conditions (without changing inflow parameters, the surface temperature of the material suddenly jumps by about 400-500K, which means a sudden increase in heat load and may directly cause the failure of the vehicle's thermal protection system). Limited macroscopic thermal response data such as surface temperature and heat flow cannot quantify and analyze the coupling relationship and influence of changes in surface catalytic properties, passive / active oxidation conversion, nitriding, and nitrogen atom catalytic recombination caused by changes in Si-containing compounds (such as SiC and SiO2). Summary of the Invention

[0006] To address the technical problems mentioned above, this invention proposes a method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy. This method overcomes the limitations of existing methods in single-scale / parameter characterization and can provide multi-dimensional analysis for the study of non-equilibrium reaction mechanisms at the gas-solid interface. It can achieve precise simulation and quantitative characterization of multi-field coupling phenomena such as passive oxidation, active oxidation, and passive / active oxidation transition, thereby more effectively sorting out and revealing the competitive coupling laws of non-equilibrium reaction processes such as catalysis and oxidation at the gas-solid interface.

[0007] To address the aforementioned technical problems, this invention provides a method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy, which mainly includes the following steps:

[0008] (1) Based on SiC-based composite ceramic materials, a multi-physics field coupled thermal environment is constructed by using a high-enthalpy plasma wind tunnel and adjusting the flow field parameters, structure and material surface reaction conditions of the plasma wind tunnel.

[0009] (2) Then, by synergistically applying four spectroscopic diagnostic techniques, namely radiation spectroscopy, narrowband imaging spectroscopy, laser absorption spectroscopy, and infrared radiation, and by simultaneously measuring multiple physical quantities of the spatiotemporal distribution of the near-wall flow field of SiC-based composite ceramic materials, the correlation characteristics between the macroscopic thermal response of the SiC-based composite ceramic material surface and the near-wall flow are extracted, thereby systematically revealing the competitive coupling law of catalysis-oxidation-nitridation in the non-equilibrium reaction of the gas-solid interface of SiC-based materials under long-term high enthalpy.

[0010] As a preferred embodiment of the present invention, step (1) is to construct a multi-physics field coupled thermal environment with typical boundary layer structure, different oxidation characteristics and high-temperature aerodynamic heating environment as basic elements using a high-enthalpy plasma wind tunnel. Specifically, the incoming enthalpy, pressure and composition of the plasma wind tunnel flow field are adjusted to form a high-temperature reactive airflow. The nozzle structure used to adjust the beam size, flow rate or energy distribution of the plasma jet and the installation state of the thermal protection material sample under test are adjusted to construct a typical boundary layer flow structure. Different oxidation reaction characteristics are induced by controlling the surface temperature of the thermal protection material sample under test and the ambient atmosphere.

[0011] As a preferred embodiment of the present invention, the high enthalpy plasma wind tunnel is an electric arc wind tunnel, or a radio frequency or high frequency plasma wind tunnel, with a simulated enthalpy value of 10 MJ / kg or higher.

[0012] As a preferred embodiment of the present invention: the typical boundary layer structure is mainly divided into two types: stagnation point compression flow and deformation structure shear flow; the different oxidation characteristics are passive oxidation, active oxidation, and passive-active oxidation transition state.

[0013] As a preferred embodiment of the present invention: the construction of the different oxidation characteristics is based on a comprehensive consideration of the surface and back surface temperatures during the ablation process, the microstructure and composition of the surface or cross-section after ablation, and the near-wall ablation products Si, SiO, CN, or N2. + The dynamic variation characteristics of the radiation spectrum, represented by multi-parameter data, were determined.

[0014] As a preferred embodiment of the present invention, the radiation spectroscopy technique in step (2) is used to determine the composition of the ablation products by measuring the radiation spectrum in the ultraviolet-visible-near-infrared band. Its main applications are threefold:

[0015] ① Obtain non-equilibrium temperature parameters, including at least vibrational and rotational temperatures, by analyzing spectral information;

[0016] ② The presence of active oxidation and nitriding reactions is determined by the spectral composition characteristics of the ablation products, and the radiation intensity of the corresponding ablation products is used as a characterization of the degree of reaction. The strength of the reaction is determined by analyzing the changes in the radiation intensity.

[0017] ③ Guide the selection of appropriate filters for narrowband spectral imaging.

[0018] As a preferred embodiment of the present invention: the narrowband imaging spectroscopy technology in step (2) mainly consists of a narrowband filter for ablation radiation characteristics and a high-speed camera. The center wavelength and bandwidth of the narrowband filter are determined according to the radiation spectrum. Based on the narrowband imaging spectroscopy image of the model flow, the gas-solid interface reaction zone is visualized on the one hand, and the optical path design of radiation spectroscopy and absorption spectroscopy is guided on the other hand.

[0019] As a preferred embodiment of the present invention: the laser absorption spectroscopy technology in step (2) can realize the translational temperature and component density measurement of atoms or generated molecules participating in the gas-solid interface reaction at different axial positions on the material surface, which is used to quantitatively analyze the consumption characteristics of reactive components and the ablation behavior of materials during the non-equilibrium reaction competition process; the measurement position of the laser absorption spectrum is determined according to the narrowband imaging spectroscopy results, ensuring at least two simultaneous measurements, one passing through the area that can intuitively reflect the intensity of the gas-solid interface reaction for non-equilibrium reaction analysis, and the other being the edge of the reaction zone for monitoring the incoming flow.

[0020] As a preferred embodiment of the present invention: the macroscopic thermal response of the SiC-based composite ceramic material surface includes the surface temperature and back surface temperature during the ablation test, as well as the microstructure and elemental composition of the surface or cross-section after ablation.

[0021] As a preferred embodiment of the present invention, the method for extracting the correlation features between the macroscopic thermal response of the material surface and the near-wall flow is as follows: taking the surface and back temperature change curves as reference objects, the method performs time-synchronous comparative analysis on the change patterns of near-wall flow and reaction characterization parameters such as radiation characteristics, translational temperature, and component density, so as to extract the correlation features between the macroscopic thermal response of the material and the near-wall flow state.

[0022] By adopting the above technical solution, the present invention has the following beneficial effects:

[0023] This invention presents a method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy. It overcomes the limitations of existing methods that rely on single-scale / parameter characterization. By synergistically applying spectroscopic diagnostic techniques such as absorption, radiation, and imaging, it constructs a multi-source data fusion framework centered on the mapping relationship between near-wall flow parameters (O / N number density, non-equilibrium temperature, ablation products CN / Si, etc.) with spatiotemporal resolution (time resolution ≤ 0.5 ms, spatial resolution ≤ 0.5 mm) and the macroscopic thermal response of the material (surface temperature / back temperature, etc.). This provides a multi-dimensional analytical method for studying the non-equilibrium reaction mechanism at the gas-solid interface.

[0024] This invention provides a method for constructing a multi-physics coupled thermal environment at a gas-solid interface with typical boundary layer characteristics. It is based on a long-term high-enthalpy flow environment constructed using a high-frequency plasma wind tunnel. This method integrates the surface and back surface temperatures of SiC-based materials possessing typical boundary layer configurations (stagnation point compressive flow, deformable structure shear flow), the microstructure and composition of the ablation-induced surface or cross-section, and especially the near-wall ablation products such as Si, SiO, CN, or N2. +Multi-parameter data, such as radiation spectra, represented by [data type name], enabled controllable simulation of complex coupled scenarios such as passive oxidation, active oxidation, passive / active oxidation transition, and oxidation-nitrification competition, laying an experimental foundation for the study of non-equilibrium reaction mechanisms and laws at the gas-solid interface.

[0025] This invention is based on the construction of a controllable simulated multi-field coupled thermal environment and the simultaneous analysis of physical quantities of multiple processes. By extracting the correlation characteristics between the macroscopic thermal response of SiC-based material surface and near-wall flow under high enthalpy conditions, it can systematically reveal the competitive coupling law of catalysis-oxidation-nitridation in the non-equilibrium reaction of high enthalpy gas-solid interface of SiC-based materials, and provide a theoretical basis for predicting the thermal load variation law of SiC-based heat protection materials and the development of thermal protection technology.

[0026] The advantages of this invention compared to the prior art are as follows:

[0027] (1) Breaking through the limitations of existing single-scale / parameter characterization, by simultaneously measuring multiple process physical quantities, especially spatiotemporally resolved near-wall flow parameters, and then constructing a multi-source data fusion framework with the correspondence between the physical quantities and the macroscopic thermal response of the material (surface temperature / back temperature, etc.), a multi-dimensional analysis method can be provided for the study of non-equilibrium reaction mechanism of gas-solid interface.

[0028] Currently, there is no real-time measurement of multiple physical quantities proposed and practically implemented in this invention.

[0029] (2) In addition to the surface and back surface temperatures during the ablation process and the microstructure composition of the surface or cross section after ablation, near-wall ablation products such as Si, SiO, CN or N2 are introduced. + Dynamic information from radiation spectra, represented by [examples of such information], enables precise simulation and quantitative characterization of multi-field coupling phenomena such as passive oxidation, active oxidation, and passive / active oxidation transition. This, in turn, allows for a more effective understanding and revelation of the competitive coupling laws in non-equilibrium reaction processes such as gas-solid interface catalysis and oxidation.

[0030] Currently, there is no precise simulation of the gas-solid interface multiphysics coupled thermal environment proposed and practically implemented in this invention. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 This is a flowchart of the method for analyzing the non-equilibrium reaction at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy conditions, as described in this invention.

[0033] Figure 2 Typical surface temperatures and microstructures of SiC-based materials include: a) the surface temperature jump phenomenon of C / SiC composite materials observed by the Von Kármán Institute of Fluid Dynamics; b) the surface temperature jump and ablation morphology analysis of a SiC ceramic in a high-frequency plasma wind tunnel test at the China Aerodynamics Research and Development Center.

[0034] Figure 3 The shape of the SiC sample: a) Design drawing; b) Sample photograph (left) and assembly drawing with cooling water fixing device (right);

[0035] Figure 4 This is a schematic diagram showing the time-varying curves of the ICP heater pressure, front surface temperature, and rear surface temperature under two different conditions.

[0036] Figure 5 SEM and EDS images of SiC samples: a) before testing, b) after experiment in state 1, c) after experiment in state 2;

[0037] Figure 6 The ultraviolet (378–392 nm) emission spectra (in arbitrary units) of state 1 and state 2 at three time points;

[0038] Figure 7 A specific implementation plan for the spatiotemporally resolved synchronous measurement of multiple physical quantities in the material boundary layer;

[0039] Figure 8 This is a comparison between the original video image and the filtered image in state 2.

[0040] Figure 9 For SiC surface a) translational temperature (T) in state 2 tr a) and b) Oxygen and nitrogen atomic number density (n O With n N The spatiotemporal distribution results of ). Detailed Implementation

[0041] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The present invention will be further explained below with reference to specific embodiments.

[0043] like Figure 1 As shown in this embodiment, a method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy is mainly divided into the construction of a multi-field coupled thermal environment and the analysis of multiple process physical quantities:

[0044] (1) Based on SiC-based composite ceramic materials, a multi-physics field coupled thermal environment is constructed by using a high-enthalpy plasma wind tunnel and adjusting the flow field parameters, structure and material surface reaction conditions of the plasma wind tunnel.

[0045] The above step (1) is to construct a multi-physics field coupled thermal environment with typical boundary layer structure, different oxidation characteristics and high-temperature aerodynamic heating environment as basic elements by using a high-enthalpy plasma wind tunnel; specifically, by adjusting the incoming enthalpy, pressure and composition to form a high-temperature reactive gas flow, adjusting the nozzle structure and sample (the nozzle structure includes replaceable or adjustable nozzle components to adjust the beam size, flow rate or energy distribution of the plasma jet; the sample is the thermal protection material sample to be tested) installation state to construct a typical boundary layer flow structure, and by controlling the surface temperature of the thermal protection material sample to be tested and the ambient atmosphere to induce different oxidation reaction characteristics.

[0046] The high-enthalpy plasma wind tunnel mentioned above is an electric arc wind tunnel, but it can also be a radio frequency or high-frequency plasma wind tunnel, with a simulated enthalpy value of 10 MJ / kg or higher.

[0047] The typical boundary layer structures mentioned above are mainly divided into two types: stagnation point compression flow and deformable structure shear flow.

[0048] For SiC-based materials with typical boundary layer configurations, the construction of different oxidation characteristics is based on a comprehensive consideration of the surface and back surface temperatures during the ablation process, the microstructure and composition of the surface or cross-section after ablation, and the elemental composition, especially the near-wall ablation products such as Si, SiO, CN, or N2. + The determination of multi-parameter data representing the dynamic changes in radiation spectra, such as passive oxidation, active oxidation, and passive-active oxidation transitions, enables clear differentiation and reliable simulation of multi-field coupling phenomena (see typical examples). Figure 2 Specifically, when SiC-based materials are tested under different high-enthalpy wind tunnel inflow conditions, if the surface temperature is consistently below 1400℃ and a dense SiO2 oxide layer is observed on the surface after ablation as determined by SEM and EDS, it can be preliminarily determined that the surface oxidation characteristics are mainly passive oxidation. Simultaneously, by measuring the presence of Si or SiO radiation spectra during the ablation process, it can be determined whether active oxidation occurred even when passive oxidation was dominant, and the strength of active oxidation can be determined by the Si radiation intensity. Furthermore, by measuring the presence of CN radiation spectra during the ablation process, it can be determined whether a nitriding reaction occurred, and the strength of the nitriding reaction can be determined by the CN radiation intensity.

[0049] (2) By synergistically applying four spectroscopic diagnostic techniques, namely radiation spectroscopy, narrowband imaging spectroscopy, laser absorption spectroscopy, and infrared radiation, and by simultaneously measuring multiple physical quantities of the spatiotemporal distribution of the near-wall flow field of SiC-based composite ceramic materials, and comprehensively considering the microscopic morphology and elemental composition of the surface and cross-section of the material before and after the test, the correlation characteristics between the macroscopic thermal response of the surface of the SiC-based composite ceramic material and the near-wall flow in the ablation test are extracted. In this way, the competitive coupling law of catalysis-oxidation-nitridation in the non-equilibrium reaction of the gas-solid interface of SiC-based materials under long-term high enthalpy is systematically revealed.

[0050] The method for extracting the correlation features between the macroscopic thermal response of the material surface and the near-wall flow in step (2) above is as follows: taking the surface and back temperature change curves as reference objects, the time-synchronous comparison analysis is performed on the change law of near-wall flow and reaction characterization parameters such as radiation characteristics, translational temperature, and component density, so as to extract the correlation features between the macroscopic thermal response of the material and the near-wall flow state.

[0051] The infrared radiation technology in step (2) above uses an infrared pyrometer or thermal imager to measure the dynamic changes in the surface temperature of the model. Taking the stationary model as an example, the radiation spectroscopy technology measures the radiation spectra of atoms, molecules, and free radicals in the boundary layer, which can analyze ablation products, reaction paths, and resolve vibration and rotation temperatures, etc.

[0052] The radiation spectroscopy technique in step (2) above determines the composition of ablation products by measuring radiation spectra in the ultraviolet-visible-near-infrared bands. Its main applications are threefold:

[0053] ① Obtain non-equilibrium temperature parameters, including at least vibrational and rotational temperatures, by analyzing spectral information;

[0054] ② The presence of active oxidation and nitriding reactions is determined by the spectral composition characteristics of the ablation products, and the radiation intensity of the corresponding ablation products is used as a characterization of the degree of reaction. The strength of the reaction is determined by analyzing the changes in the radiation intensity.

[0055] ③ Guide the selection of appropriate filters for narrowband spectral imaging.

[0056] The narrowband imaging spectroscopy technique in step (2) above mainly consists of a narrowband filter targeting ablation radiation characteristics and a high-speed camera. The center wavelength and bandwidth of the narrowband filter are determined according to the radiation spectrum.

[0057] The narrowband imaging spectroscopy technique in step (2) above selects narrowband filters (such as CN-389nm for ablation products, O-777.2nm for plasma inflow, etc.) based on the radiation spectroscopy results to obtain the structure of the plasma flow radiation field. On the one hand, it can be used to characterize the non-equilibrium reaction process of the gas-solid interface, and on the other hand, it can guide the design of the optical path for radiation spectroscopy and absorption spectroscopy measurement through the visualization of the reaction zone.

[0058] The aforementioned laser absorption spectroscopy technique can measure the translational temperature and component density of atoms or generated molecules such as oxygen, nitrogen, silicon, CN, CO, and NO participating in gas-solid interface reactions at different axial positions on the material surface. This can be used to quantitatively analyze the consumption characteristics of reactive components and the ablation behavior of materials (e.g., O → oxidation / surface composite catalysis; N → oxidation) in gas-solid interface catalytic reactions, oxidation reactions, and nitriding reactions. (Non-equilibrium reaction competition processes are a general description of the interaction between high-enthalpy non-equilibrium flow fields and heat-resistant materials; specifically, they are cross-scale physicochemical processes in which high-enthalpy fluids and heat-resistant materials interact through fluid-solid coupling interfaces. Their complexity is not only reflected in the distinct characteristics of high-temperature non-equilibrium and unsteady flow, but also encompasses the coupling and competition of multiple physicochemical reactions such as material-dependent catalysis, oxidation, nitriding, and pyrolysis.) → Nitriding / composite catalysis; Si → source of ablation / volatilization / oxidation products; CN → source of ablation / oxynitridation products); The measurement position of the laser absorption spectrum is determined based on the narrowband imaging spectrum results, ensuring at least two simultaneous measurements. One path passes through the region that can intuitively reflect the intensity of the gas-solid interface reaction for non-equilibrium reaction analysis, and the other path is at the edge of the reaction zone for monitoring the incoming flow.

[0059] In addition to the four spectroscopic diagnostic techniques mentioned above, contact thermocouples are also used to monitor temperature changes on the back of the material.

[0060] The present invention will be further described below with reference to specific embodiments:

[0061] First, a multi-field coupled thermal environment capable of reflecting different oxidation states was constructed. The experiment was conducted in a 1MW inductively coupled plasma (ICP) wind tunnel. This wind tunnel utilizes the principle of electrodeless radio frequency induction heating to generate a chemically pure and long-term stable high-enthalpy dissociation air plasma jet. This pure environment is crucial for eliminating external contamination and accurately studying the intrinsic gas-solid interface chemical reactions of the material. The plasma generated in the wind tunnel, after being accelerated by a supersonic nozzle, forms a flow environment with significant thermochemical non-equilibrium characteristics within the low-pressure test chamber, providing ideal experimental conditions for simulating hypersonic flight. The SiC sample, in a sheet configuration, was embedded in a specially designed water-cooled support during testing to ensure that its front surface interacted with the high-temperature plasma. (See...) Figure 3 .

[0062] The definition and distinction of oxidation states are based on three real-time or near-real-time physicochemical criteria. These criteria include the sample stagnation point surface temperature monitored in real time by a non-contact infrared pyrometer, used to determine whether it has crossed the SiC oxidation reaction temperature threshold of approximately 1400℃. Figure 4 ); By characterizing the microstructure of the sample surface using scanning electron microscopy (SEM) after the experiment, a qualitative analysis of the degree of oxidation can be achieved. Figure 5 Near-wall flow field radiation characteristics captured in real time by emission spectroscopy (OES), where the characteristic radiation of Si atoms at 390.55 nm is considered a clear indicator of active oxidation. Figure 6 Based on this, the experimental states constructed by the two experiments exemplified in this embodiment are respectively determined to be a passive oxidation state (state 1) and a passive-active oxidation transition state (state 2).

[0063] Secondly, multi-process physical quantity analysis was performed, employing four spectroscopic diagnostic techniques in synergy: radiation spectroscopy, narrowband imaging spectroscopy, laser absorption spectroscopy, and infrared radiation. The model's back temperature was monitored using thermocouples. A schematic diagram of the measurement system is shown below. Figure 7 .

[0064] To simplify the description, taking the experimental situation of stagnation model state 2 as an example, this invention uses four spectroscopic diagnostic techniques in combination: radiation spectroscopy, narrowband imaging spectroscopy, laser absorption spectroscopy, and infrared radiation to measure the flow parameters of the material surface and near the wall. The results of the radiation spectroscopy measurement have been mentioned earlier.

[0065] The narrowband imaging spectral results for state 2 are shown in Figure 8 A narrowband filter with a center wavelength of 387 nm and a bandwidth of 3 nm was used to obtain the plasma flow radiation field structure of CN radicals. The figure shows the video recording of state 2 SiC and the narrowband spectral radiation imaging results with a center wavelength of 387 nm. Time t1-t4 correspond to 10, 40, 70, and 100 seconds after the model was input, respectively. For each time, 25 images before and after the input were selected, and the gray values ​​of the corresponding pixels were averaged and then processed into pseudo-color to present the final results. There is a luminescent region on the material surface with an average thickness of about 2.0 mm. Therefore, the measurement position 1 of the absorption spectrum was set with the center of the laser beam close to the model wall, and position 2 was located at the edge of the luminescent region, with the center of the laser beam 2 mm away from the model surface.

[0066] The spatiotemporally resolved absorption spectra in state 2 are shown in Figure 9 The translational temperature showed a continuous decreasing trend throughout the heating process. This is mainly due to active oxidation. Evaporation and decomposition products (i.e., pyrolysis gases) are injected in large quantities into the boundary layer. These cooler gases mix with the hot incoming flow, acting as a "cooling" agent, thus leading to a continuous decrease in the translational temperature within the boundary layer. Atom number density exhibits complex dynamic competition. Over time, the O atom number density (n...) O After reaching a steady state, the atomic number density (n) remains essentially unchanged, while the atomic number density (n) of N remains essentially unchanged. N The oxidation state (N atoms) exhibits a slow upward trend throughout the heating process. This differentiated behavior profoundly reveals the competition between catalysis and oxidation: for N atoms, the SiC surface forms [a specific oxidation state] at high temperatures. After the layer, the catalytic recombination efficiency of nitrogen atoms decreases (i.e., the surface becomes more "inert"), leading to a reduction in the consumption of N atoms near the wall, thus lowering its number density (n). N The efficiency gradually increases; for O atoms, although the surface catalytic efficiency also decreases (which should have led to n...). O The surface oxidation reaction continuously consumes O atoms, and these two effects compete with each other, ultimately leading to a decrease in the O atom number density (n). O On a macroscopic level, it exhibits dynamic stability.

[0067] This invention is based on the construction of a controllable simulated multi-field coupled thermal environment and the simultaneous analysis of physical quantities of multiple processes. By extracting the correlation characteristics between the macroscopic thermal response of SiC-based material surface and near-wall flow under high enthalpy conditions, it can systematically reveal the competitive coupling law of catalysis-oxidation-nitridation in the non-equilibrium reaction of high enthalpy gas-solid interface of SiC-based materials, and provide a theoretical basis for predicting the thermal load variation law of SiC-based heat protection materials and the development of thermal protection technology.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy, characterized in that... The main steps include: (1) Based on SiC-based composite ceramic materials, a multi-physics field coupled thermal environment is constructed by using a high-enthalpy plasma wind tunnel and adjusting the flow field parameters, structure and material surface reaction conditions of the plasma wind tunnel. (2) Then, by synergistically applying four spectroscopic diagnostic techniques, namely radiation spectroscopy, narrowband imaging spectroscopy, laser absorption spectroscopy, and infrared radiation, and by simultaneously measuring multiple physical quantities of the spatiotemporal distribution of the near-wall flow field of SiC-based composite ceramic materials, the correlation characteristics between the macroscopic thermal response of the SiC-based composite ceramic material surface and the near-wall flow are extracted, thereby systematically revealing the competitive coupling law of catalysis-oxidation-nitridation in the non-equilibrium reaction of the gas-solid interface of SiC-based materials under long-term high enthalpy.

2. The method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy as described in claim 1, characterized in that... Step (1) involves using a high-enthalpy plasma wind tunnel to construct a multi-physics coupled thermal environment with typical boundary layer structures, different oxidation characteristics, and a high-temperature aerodynamic heating environment as basic elements. Specifically, this involves: adjusting the incoming enthalpy, pressure, and composition of the plasma wind tunnel flow field to form a high-temperature reactive airflow; adjusting the nozzle structure used to adjust the beam size, flow rate, or energy distribution of the plasma jet and the installation state of the thermal protection material sample to be tested to construct a typical boundary layer flow structure; and controlling the surface temperature of the thermal protection material sample and the ambient atmosphere to induce different oxidation reaction characteristics.

3. The method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy as described in claim 2, characterized in that: The high-enthalpy plasma wind tunnel is an electric arc wind tunnel, but it can also be a radio frequency or high-frequency plasma wind tunnel, with a simulated enthalpy value of 10 MJ / kg or higher.

4. The method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy as described in claim 2, characterized in that: The typical boundary layer structures are mainly divided into two types: stagnation point compression flow and deformable structure shear flow. The different oxidation characteristics are passive oxidation, active oxidation, and a passive-active oxidation transition state.

5. The method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy as described in claim 2, characterized in that: The different oxidation characteristics are constructed by comprehensively considering the surface and back temperatures during the ablation process, the microstructure and composition of the surface or cross-section after ablation, and the near-wall ablation products Si, SiO, CN, or N2. + The dynamic variation characteristics of the radiation spectrum, represented by multi-parameter data, were determined.

6. The method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy as described in claim 1, characterized in that... The radiation spectroscopy technique in step (2) is used to determine the composition of ablation products by measuring the radiation spectrum in the ultraviolet-visible-near-infrared band. Its main applications are threefold: ① Obtain non-equilibrium temperature parameters, including at least vibrational and rotational temperatures, by analyzing spectral information; ② The presence of active oxidation and nitriding reactions is determined by the spectral composition characteristics of the ablation products, and the radiation intensity of the corresponding ablation products is used as a characterization of the degree of reaction. The strength of the reaction is determined by analyzing the changes in the radiation intensity. ③ Guide the selection of appropriate filters for narrowband spectral imaging.

7. The method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy as described in claim 1, characterized in that: The narrowband imaging spectroscopy technique in step (2) mainly consists of a narrowband filter for ablation radiation characteristics and a high-speed camera. The center wavelength and bandwidth of the narrowband filter are determined according to the radiation spectrum. Based on the narrowband imaging spectroscopy image of the model flow, the gas-solid interface reaction zone is visualized on the one hand, and the optical path design of radiation spectroscopy and absorption spectroscopy is guided on the other hand.

8. The method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy as described in claim 1, characterized in that: The laser absorption spectroscopy technique in step (2) can measure the translational temperature and component density of atoms or generated molecules participating in the gas-solid interface reaction at different axial positions on the material surface. This is used to quantitatively analyze the consumption characteristics of reactive components and the ablation behavior of materials during the non-equilibrium reaction competition process. The measurement position of the laser absorption spectrum is determined based on the narrowband imaging spectroscopy results. At least two simultaneous measurements are required. One measurement passes through the region that can intuitively reflect the intensity of the gas-solid interface reaction and is used for non-equilibrium reaction analysis. The other measurement is at the edge of the reaction zone and is used to monitor the incoming flow.

9. The method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy as described in claim 1, characterized in that: The macroscopic thermal response of the SiC-based composite ceramic material surface includes the surface temperature and back surface temperature during the ablation test, as well as the microstructure and elemental composition of the surface or cross-section after ablation.

10. The method for analyzing non-equilibrium reactions at the gas-solid interface of SiC-based heat-resistant materials under high enthalpy as described in claim 1, characterized in that... The method for extracting the correlation features between the macroscopic thermal response of the material surface and the near-wall flow is as follows: taking the surface and back temperature change curves as reference objects, the method performs time-synchronous comparative analysis on the change patterns of near-wall flow and reaction characterization parameters such as radiation characteristics, translational temperature, and component density, in order to extract the correlation features between the macroscopic thermal response of the material and the near-wall flow state.

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