Multi-scale prediction method for oxidative ablation behavior of carbon / carbon porous heat-proof material

Abstract

The invention relates to a multi-scale prediction method for the oxidative ablation behavior of a carbon / carbon porous heat-proof material, and belongs to the technical field of aerospace science, in particular to a multi-scale prediction model for the oxidative ablation behavior of the carbon / carbon porous heat-proof material. A chemical reaction standard enthalpy value and reaction activation energy are analyzed based on a gas-solid interface micro-model of a carbon / carbon porous heat-proof material, and then pore scale fluid mechanics calculation is performed in combination with a porous medium model; explaining an evolution mechanism between gas-solid interfaces by using a micro-scale and pore-scale simulation method, and predicting an ablation process surface evolution process; according to the invention, fluid flow, thermal reaction and heterogeneous chemical reaction in the porous medium in the ablation process can be coupled and simulated at the same time; according to the method, the action mechanism of the heterogeneous chemical reaction at the gas-solid interface in the oxidation ablation process of the carbon / carbon porous heat-proof material can be disclosed, and the distance change after ablation and the ablation surface roughness in the ablation process can be predicted more accurately.

Description

Technical Field

[0001] The present invention relates to the field of aerospace science and technology, and in particular to a multi-scale prediction method for oxidation and ablation behavior of a carbon / carbon porous thermal protection material. Background Art

[0002] Ablative materials offer advantages such as high thermal protection efficiency, reliable operation, and strong adaptability to flow field variations. They are widely used in aviation, aerospace, missiles, the nuclear industry, furnace manufacturing, and other industries with demanding operating conditions. For example, see Chinese patent applications with publication numbers CN119666638A and CN119290728A, and Chinese patent publication number CN110308178B. During hypersonic flight, intense shock wave compression and viscous frictional drag significantly convert kinetic energy into internal energy, raising the vehicle's surface temperature to thousands of degrees Celsius. The combined effects of high temperature, high pressure, and high-velocity gas or flame erosion during operation make hot-end components highly susceptible to structural deformation, performance degradation, and severe aging due to ablation. Consequently, stringent requirements are placed on advanced thermal protection systems.

[0003] Carbon / carbon ablative materials are widely used due to their low density, low thermal expansion coefficient, high strength, and excellent chemical stability at high temperatures. Due to the highly porous structure of carbon / carbon ablative materials during use, in high-enthalpy airflow environments, dissociated atomic oxygen (O) enters the pores and contacts the carbon material, causing an oxidative ablation reaction. This reaction, coupled with multiple parameters such as porosity, incoming flow velocity, incoming flow concentration, and temperature within the porous medium, triggers a dynamic evolution of the ablative material's surface morphology, exhibiting a significant ablation regression phenomenon, ultimately affecting thermal protection performance.

[0004] The multi-scale prediction method for the oxidation and ablation behavior of pore-scale carbon / carbon ablative materials under high enthalpy flow can be well applied.

[0005] The interface oxidation mechanism and ablation process of carbon / carbon porous thermal protection materials under the flow-solid-heat-chemical coupling at the pore scale are predicted, which helps to refine and integrate the thermal protection system from a cross-scale perspective and provide the necessary scientific theoretical support for the development and research of hypersonic aircraft in high enthalpy environments.

[0006] At present, for pore-scale research under high-enthalpy flow, high-temperature ablation experimental research can only simply characterize the ablated surface morphology and overall ablation resistance of the material, which is not enough to clarify the chemical reaction mechanism of the oxidation ablation process and the microscopic influence of different flow conditions on the ablation evolution process.

[0007] Numerical simulation methods can effectively compensate for the shortcomings of experiments. Currently, in the field of ablative thermal protection systems at the pore scale in high-enthalpy flows, there is no complete multi-scale coupled numerical simulation method that can not only explain the heterogeneous reaction mechanism at the gas-solid interface but also provide high-precision thermal predictions for thermal protection systems at the mesoscopic scale. Summary of the Invention

[0008] In view of the above problems, the present invention provides a multi-scale prediction method for the oxidation and ablation behavior of carbon / carbon porous thermal protection materials. The present invention establishes a multi-scale prediction model for the ablation behavior of carbon / carbon ablation materials. Based on the gas-solid interface micromodel analysis of the carbon / carbon ablation material, the standard enthalpy of the chemical reaction and the reaction activation energy are obtained, and then the porous medium model is combined to perform pore-scale fluid mechanics calculations. The microscale and pore-scale simulation methods are used to explain the evolution mechanism between the gas-solid interface and predict the surface evolution process of the ablation process.

[0009] The present invention provides a multi-scale prediction method for the oxidation and ablation behavior of carbon / carbon porous thermal protection materials, comprising:

[0010] Step S1, establishing a gas-solid interface microscopic model and a porous medium model of a carbon / carbon porous heat-resistant material;

[0011] Step S2: inputting multiple reaction temperatures into the gas-solid interface micromodel to perform a chemical reaction to produce small molecule gas products corresponding to each reaction temperature;

[0012] Step S3, simulating and analyzing the chemical reaction process of the gas-solid interface micromodel at various reaction temperatures to obtain the chemical reaction path and the amount of small molecule gas products produced at various reaction temperatures;

[0013] Step S4: determining the standard enthalpy of the chemical reaction based on the chemical reaction path;

[0014] The reaction activation energy is obtained by the amount of small molecule gas products produced at each reaction temperature;

[0015] Step S5, let t = 0, when t = 0, it represents the initial reaction time;

[0016] Step S6: inputting the chemical reaction standard enthalpy ΔH and the reaction activation energy Ea into the improved ablation prediction dbsFoam solver, performing ablation simulation, and obtaining the flow state at the reaction time t;

[0017] Based on the flow state at reaction time t, the ablation retreat distance at reaction time t and the transient change results of the ablation surface morphology at reaction time t are obtained, recorded, and used as the initial flow state at reaction time t+Δt;

[0018] The initial flow state at reaction time t+Δt is simulated to obtain the flow state at reaction time t+Δt;

[0019] Step S7, determine whether t is greater than or equal to T', where T' represents the total reaction time. If so, obtain the transient change result of the oxidation ablation reaction. If not, set t = t + Δt, where Δt represents the transient time step, and return to step S6.

[0020] Optionally, the gas-solid interface microscopic model of the carbon / carbon porous heat-resistant material includes a gaseous atomic oxygen phase and a solid graphene carbon layer.

[0021] Optionally, the specific steps of establishing the porous medium model include: performing pore-scale modeling on the carbon / carbon porous thermal protection material to obtain the porous medium model.

[0022] Optionally, the specific steps of obtaining the chemical reaction path and the amount of small molecule gas products generated at each reaction temperature in step S3 include:

[0023] Simulate the chemical reaction process of the gas-solid interface micromodel at various reaction temperatures to obtain the atomic motion trajectory at various reaction temperatures;

[0024] The chemical reaction mechanism is analyzed based on the atomic motion trajectory to obtain the chemical reaction path and the amount of small molecule gas products produced at each reaction temperature.

[0025] Optionally, the specific steps of obtaining the reaction activation energy in step S4 include:

[0026] The carbon conversion degree was obtained by normalizing the amount of small molecule gas products produced at each reaction temperature;

[0027] Substituting the carbon conversion degree into the gas-solid reaction mechanism function, the reaction activation energy is obtained.

[0028] Optionally, the expression for the reaction activation energy is:

[0029] Ea=R g T(lnA-ln(k F(c) ))

[0030] Among them, Ea is the activation energy of the reaction, A is the pre-factor, R g is the gas constant, T is the temperature, k F(.) is the slope of the gas-solid reaction mechanism function value changing with time, F(.) is the gas-solid reaction mechanism function value, and c represents the carbon conversion degree.

[0031] Optionally, the transient change results of the oxidation ablation reaction are multi-scale transient change results in the porous medium, including the velocity in the porous medium at each reaction moment, the temperature distribution in the porous medium at each reaction moment, the concentration distribution in the porous medium at each reaction moment, the ablation retreat distance at each reaction moment, and the ablation surface roughness at each reaction moment.

[0032] Optionally, the expression of the ablation surface roughness is:

[0033]

[0034] Where Ra represents the roughness of the ablation surface, l represents the width of the calculation domain, and x′(y′) represents the distance from the y′th point on the ablation surface to the inlet.

[0035] Optionally, the improved ablation prediction dbsFoam solver includes a velocity equation, a mass equation, a temperature equation and a concentration equation.

[0036] Optionally, the temperature equation of the improved ablation prediction dbsFoam solver is expressed as:

[0037]

[0038] Where ρ is the density of the incoming flow, C p is the specific heat of solid at constant pressure, T is the temperature, t is the reaction time, C pf is the specific heat of the fluid at constant pressure, is the velocity, λ is the thermal conductivity, S T is the chemical reaction source term of the temperature equation.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects:

[0040] (1) The present invention can realize the coupled simulation of fluid flow, thermal reaction and heterogeneous chemical reaction in porous media during the ablation process of carbon / carbon porous thermal protection materials;

[0041] (2) The present invention can reveal the mechanism of heterogeneous chemical reaction at the gas-solid interface during the ablation of carbon / carbon porous heat-resistant materials and the main path of chemical reaction at the interface, and make more accurate predictions of the material ablation retreat distance and the ablation surface roughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings are only for purposes of illustrating particular embodiments and are not to be considered limiting of the invention.

[0043] Figure 1 A schematic diagram of a flow chart for multi-scale prediction of oxidation and ablation behavior of carbon / carbon porous thermal protection materials in an embodiment of the present invention;

[0044] Figure 2 Schematic diagram of a graphene carbon layer in an embodiment of the present invention;

[0045] Figure 3 Schematic diagram of a gas-solid interface microscopic model of a carbon / carbon ablation material in an embodiment of the present invention;

[0046] Figure 4 Schematic diagram of the change of gaseous small molecule products over time in an embodiment of the present invention;

[0047] Figure 5 Schematic diagram of the linear fitting of the slope of the gas-solid reaction mechanism function value changing with time and the inverse of temperature in an embodiment of the present invention;

[0048] Figure 6 Schematic diagram of the porous medium calculation domain in an embodiment of the present invention;

[0049] Figure 7 Schematic diagram of the dynamic ablation evolution process in an embodiment of the present invention;

[0050] Figure 8 Schematic diagram of the change of ablation retreat distance over time in an embodiment of the present invention;

[0051] Figure 9 Schematic diagram of the change of ablation surface roughness over time in an embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. In addition, the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0053] A specific embodiment of the present invention, as Figure 1-9 , discloses a multi-scale prediction method for the oxidation and ablation behavior of carbon / carbon porous thermal protection materials. The specific implementation steps are as follows:

[0054] Step S1, establishing a gas-solid interface microscopic model and a porous medium model of a carbon / carbon porous heat-resistant material;

[0055] Optionally, the gas-solid interface microscopic model of the carbon / carbon porous heat-resistant material includes a gaseous atomic oxygen phase and a solid graphene carbon layer;

[0056] Optionally, pore-scale modeling is performed on the carbon / carbon porous thermal protection material to obtain a porous medium model;

[0057] Step S2, determining multiple reaction temperatures;

[0058] Multiple reaction temperatures are input into the gas-solid interface microscopic model. At these reaction temperatures, the gaseous atomic oxygen phase and the solid graphene carbon layer undergo a chemical reaction to produce small molecule gas products corresponding to each reaction temperature.

[0059] Optionally, the reaction temperature includes 2250K, 2500K, 2750K, 3000K, 3250K and / or 3500K;

[0060] The small molecule gas products include O2, CO and / or CO2;

[0061] Optionally, the specific steps of establishing the gas-solid interface micromodel include:

[0062] Identify carbon / carbon porous thermal protection materials as solid carbon layers;

[0063] A blank area above the surface of the solid carbon is preset as a gas environment to obtain a simulation box;

[0064] A gaseous atomic oxygen phase was set in the blank area of ​​each simulation box to obtain a microscopic model of the gas-solid interface.

[0065] Setting periodic boundary conditions, and extending multiple simulation boxes infinitely in the x and y directions according to the periodic boundary conditions to obtain a surface model of the solid graphene carbon layer;

[0066] Optionally, the carbon / carbon porous heat-protective material is a graphene carbon layer;

[0067] The graphene carbon layer is an atomic-level graphite material, consisting of a layer-by-layer graphene structure.

[0068] It will be appreciated that the gaseous atomic oxygen phase comprises oxygen atoms;

[0069] Oxygen atoms are randomly placed above the graphene layer. During the reaction, the oxygen atoms undergo oxidation reaction and catalytic reaction with the graphene layer. The oxidation reaction produces CO and CO2, and the catalytic reaction produces O2.

[0070] For example, the solid carbon layer includes 403 carbon atoms, the solid phase plane is located on the x and y direction plane, and the size is Effectively improve computing efficiency;

[0071] The present invention selects 403 carbon atoms as the graphene layer, saving resources and time.

[0072] Optionally, the boundary conditions include x and y directions of each simulation box being parallel to the graphene plane, and a reflective boundary condition being set in the z direction;

[0073] For example, the size of the simulation box in the z direction is

[0074] Optionally, the atoms at the four corners of the solid carbon are fixed to ensure that the center of mass of the solid carbon in the z direction remains stable, thereby preventing the solid carbon from moving downward under the continuous collision of high-temperature gas components, thereby maintaining the overall position of the graphene layer stable without affecting its local deformation and reaction.

[0075] For example, Materials Studio is used to perform microscopic modeling of the gas-solid interface of carbon-based ablative materials;

[0076] Optionally, the gaseous atomic oxygen phase comprises 200 randomly distributed oxygen atoms.

[0077] The reaction temperature in the present invention is the high-enthalpy interface temperature. The high-enthalpy interface is the contact surface between substances under extremely high temperature conditions. In the aerospace field, when an aircraft enters the atmosphere at hypersonic speed, the extremely high temperature generated by air friction causes a series of complex phenomena on the surface of the material, namely the high-enthalpy interface.

[0078] Step S3, using LAMMPS, an open-source numerical simulation software for molecular dynamics, to simulate the chemical reaction process of the gas-solid interface micromodel at various reaction temperatures. After the chemical reaction stabilizes, the atomic motion trajectories at various reaction temperatures are obtained.

[0079] Analyze chemical reaction mechanisms based on atomic motion trajectories to obtain chemical reaction paths and the amount of small molecule gas products produced at various reaction temperatures;

[0080] Alternatively, the open source numerical simulation software LAMMPS for molecular dynamics has a calculation time of 500 ps at each reaction temperature;

[0081] Optionally, the chemical reaction pathway is expressed as:

[0082] C (s) +O (g) →CO (g) ;

[0083] Among them, C (s) is a solid-phase graphene carbon layer, O (g) For gaseous atomic oxygen, CO (g) It is carbon monoxide gas.

[0084] Optionally, the atomic motion trajectory includes the coordinates and velocity of the atom at each time point;

[0085] Optionally, the molecular dynamics results visualization and analysis software OVITO is used to observe the atomic motion trajectories.

[0086] Optionally, the specific steps for determining the amount of small molecule gas products produced at various reaction temperatures include:

[0087] Determining a tracking element; the tracking element includes carbon element C and oxygen element O;

[0088] Observe the reaction process at various reaction temperatures and track the small molecules composed of elements, including carbon monoxide CO, carbon dioxide CO2 and oxygen O2.

[0089] Obtain the amount of small molecule gas products produced at each reaction temperature;

[0090] Optionally, write the molecular species file species.out of the number of gaseous small molecule products through the matrix laboratory MATLAB;

[0091] For example, the tracking element is simulated using the ReaxFF command to obtain the small molecules generated by the tracking element during the reaction process at various reaction temperatures, and output them in the molecular species file species.out;

[0092] The number of small molecule gas products produced at each reaction temperature was obtained based on MATLAB statistics in the matrix laboratory;

[0093] Step S4: determining the standard enthalpy value ΔH of the chemical reaction based on the chemical reaction path;

[0094] By normalizing the amount of small molecule gas products produced at each reaction temperature, the carbon conversion degree c is obtained, which is expressed as:

[0095]

[0096] Among them, m i is the mass of the solid graphene layer before the reaction occurs; m t is the mass of the solid phase graphene layer during the reaction; m f is the mass of the solid graphene layer after the reaction is completed.

[0097] Substituting the carbon conversion degree into a gas-solid reaction mechanism function to obtain a gas-solid reaction mechanism function value;

[0098] Optionally, the chemical reaction standard enthalpy value ΔH=-358.046 kJ / mol;

[0099] Optionally, the gas-solid reaction mechanism function expression is:

[0100]

[0101] Where, F(.) is the value of the gas-solid reaction mechanism function; ln is the natural logarithm, and c is the carbon conversion degree;

[0102] Get the slope k of the gas-solid reaction mechanism function value changing with time F(c) , the expression is;

[0103]

[0104] Based on the slope of the gas-solid reaction mechanism function value changing with time, the reaction activation energy Ea is obtained, and the expression is:

[0105] Ea=R g T(ln A-ln(k F(c) ))

[0106] Among them, A is the pre-factor, R g is the gas constant, R g =8.314 J / mol·K, T is temperature.

[0107] The present invention obtains the standard enthalpy values ​​of the main chemical reaction paths and the reaction activation energy through the study of the action mechanism of heterogeneous chemical reactions.

[0108] Step S5, let t = 0, when t = 0, it represents the initial reaction time;

[0109] Step S6: inputting the chemical reaction standard enthalpy ΔH and the reaction activation energy Ea into the improved ablation prediction dbsFoam solver, performing ablation simulation, and obtaining the flow state at the reaction time t;

[0110] Based on the flow state at reaction time t, the ablation retreat distance at reaction time t and the transient change results of the ablation surface morphology at reaction time t are obtained, recorded, and used as the initial flow state at reaction time t+Δt;

[0111] The initial flow state at reaction time t+Δt is simulated to obtain the flow state at reaction time t+Δt;

[0112] Step S7: Determine whether t is greater than or equal to T′, where T′ represents the total reaction time. If so, obtain the ablation retreat distance at reaction time t and the transient change result of the ablation surface morphology at reaction time t for each reaction time as the transient change result of the oxidation ablation reaction. If not, set t = t + Δt, where Δt represents the transient time step, and return to step S6.

[0113] It can be understood that the improved ablation prediction dbsFoam solver is used to perform pore-scale fluid dynamics CFD calculations on porous media models based on flow rules;

[0114] Optionally, the transient change results of the oxidation ablation reaction are multi-scale transient change results in the porous medium, including the velocity in the porous medium at each reaction moment, the temperature distribution in the porous medium at each reaction moment, the concentration distribution in the porous medium at each reaction moment, the ablation retreat distance at each reaction moment, and the ablation surface roughness at each reaction moment.

[0115] Optionally, the expression of the ablation surface roughness is:

[0116]

[0117] Where Ra represents the roughness of the ablation surface, l represents the width of the calculation domain, and x′(y′) represents the distance from the y′th point on the ablation surface to the inlet.

[0118] Optionally, the specific steps of obtaining the ablation retreat distance at the reaction time t include:

[0119] Meshing the porous medium model to obtain a meshed porous medium model, performing ablation simulation on the meshed porous medium model to obtain an ablated porous medium model, and performing porosity analysis on each mesh of the ablated porous medium model at reaction time t to obtain a porosity analysis result of each mesh of the porous medium model at reaction time t;

[0120] Based on the porosity analysis results of each grid of the porous medium model at the reaction time t, the maximum and minimum distances between the ablation surface and the inlet at the reaction time t are obtained;

[0121] The ablation retreat distance at reaction time t is obtained based on the maximum distance and the minimum distance between the ablation surface and the entrance at reaction time t.

[0122] Optionally, the ablation retreat distance x abl The expression is:

[0123]

[0124] Among them, x abl is the ablation retreat distance, x max is the maximum distance between the ablation surface and the inlet, x min is the minimum distance between the ablation surface and the inlet.

[0125] Optionally, the improved ablation prediction dbsFoam solver includes a velocity equation, a mass equation, a temperature equation, and a concentration equation;

[0126] Optionally, the temperature equation is expressed as:

[0127]

[0128] Where ρ is the density of the incoming flow, C p is the specific heat of solid at constant pressure, T is the temperature, t is the reaction time, C pf is the specific heat of the fluid at constant pressure, is the velocity, λ is the thermal conductivity, S T is the chemical reaction source term of the temperature equation, ΔH is the reaction heat, ρ s is the solid phase density, k is the gas-solid heterogeneous reaction chemical reaction rate, ε s is the solid ratio in the grid, is the dimensionless value of concentration, Ea is the activation energy of reaction, A is the pre-factor, R g is the gas constant.

[0129] The present invention adds a chemical reaction source term to the temperature equation, taking into account the influence of the temperature increase in the porous medium caused by the exothermic reaction between the solid carbon layer and the gas oxygen atoms on the ablation process.

[0130] Optionally, the porous medium model includes carbon fiber filaments;

[0131] The initial porosity of the porous medium model is 0-1;

[0132] Exemplarily, the diameter of each carbon fiber filament is 8-16 μm;

[0133] The size of the porous medium is 750×250 μm.

[0134] Optionally, setting simulation conditions for the porous media model and chemical reaction, including: initial conditions and boundary conditions;

[0135] Furthermore, the initial conditions include an initial state and a flow state: the initial state includes an initial fluid velocity of 0 m / s inside the porous medium model and the surrounding environment; the incoming flow is a fluid containing atomic oxygen, and the initial oxygen atomic concentration is 0; the initial temperature T=2500K;

[0136] The flow state includes the fluid flow property of incompressible fluid with a density of 0.00536 kg / m 3 , the viscosity is 5.2059×10 -4 m 2 / s, and the diffusion coefficient is 2.5×10 -5 m 2 / s;

[0137] The boundary conditions include: the incoming flow velocity is 1m / s, the inlet temperature is 2500K, the oxygen atomic concentration in the incoming flow is 10mol / m 3 ; Zero gradient conditions are imposed on the velocity, temperature and concentration fields at the outlet;

[0138] The velocity at the upper and lower walls inside the porous media model is a no-slip boundary, the temperature is an adiabatic boundary, and all species are zero flux.

[0139] The parameters of the porous medium model include porosity and permeability.

[0140] Optionally, the total mesh size of the porous medium model is 2.646 million to 3.65 million;

[0141] Optionally, the transient time step Δt is 0.001s, the total ablation time is 5s, and the physical time for each calculation example is about 6 hours.

[0142] The improved dbsFoam solver designed in the present invention can be used for two-dimensional plane, three-dimensional flow analysis and unsteady flow analysis, and can realize the coupled simulation of flow, thermal reaction and heterogeneous chemical reaction in porous media.

[0143] The improved dbsFoam solver designed in this invention supports multi-core parallel computing and has good pre-processing and post-processing interfaces. The pre-processing interface supports meshing software such as ICEMCFD, and the post-processing interface supports post-processing software such as Tecplot and Paraview to output a variety of cloud maps.

[0144] The bond-level chemical reaction force field used in this paper is the ReaxFF (Reactive Force Field) reaction force field, which is used to simulate chemical reactions that may occur in atomic and molecular systems. It can simulate possible chemical reaction processes without pre-defined reaction paths, thereby significantly improving the rationality and accuracy of molecular simulations. The ReaxFF reaction force field has a wide range of applications and is particularly suitable for simulating heterogeneous chemical reactions occurring at gas-solid interfaces.

[0145] The present invention provides an explanation for the evolution mechanism of the gas-solid interface of the carbon / carbon porous heat-proof material and improves the prediction accuracy of the ablation surface morphology evolution of the carbon / carbon porous heat-proof material.

[0146] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A multi-scale prediction method for oxidation and ablation behavior of carbon / carbon porous thermal protection materials, characterized in that: include: Step S1, establishing a gas-solid interface microscopic model and a porous medium model of a carbon / carbon porous heat-resistant material; Step S2: inputting multiple reaction temperatures into the gas-solid interface micromodel to perform a chemical reaction to produce small molecule gas products corresponding to each reaction temperature; Step S3, simulating and analyzing the chemical reaction process of the gas-solid interface micromodel at various reaction temperatures to obtain the chemical reaction path and the amount of small molecule gas products produced at various reaction temperatures; Step S4: determining the standard enthalpy of the chemical reaction based on the chemical reaction path; The reaction activation energy is obtained by the amount of small molecule gas products produced at each reaction temperature; Step S5, let t = 0, when t = 0, it represents the initial reaction time; Step S6: inputting the chemical reaction standard enthalpy ΔH and the reaction activation energy Ea into the improved ablation prediction dbsFoam solver, performing ablation simulation, and obtaining the flow state at the reaction time t; Based on the flow state at reaction time t, the ablation retreat distance at reaction time t and the transient change results of the ablation surface morphology at reaction time t are obtained, recorded, and used as the initial flow state at reaction time t+Δt; The initial flow state at reaction time t+Δt is simulated to obtain the flow state at reaction time t+Δt; Step S7, determine whether t is greater than or equal to T', where T' represents the total reaction time. If so, obtain the transient change result of the oxidation ablation reaction. If not, set t = t + Δt, where Δt represents the transient time step, and return to step S6.

2. The multi-scale prediction method for oxidation and ablation behavior of carbon / carbon porous thermal protection materials according to claim 1, characterized in that: The gas-solid interface microscopic model of the carbon / carbon porous heat-proof material includes a gaseous atomic oxygen phase and a solid-phase graphene carbon layer.

3. The multi-scale prediction method for oxidation and ablation behavior of carbon / carbon porous thermal protection materials according to claim 1, characterized in that: The specific steps of establishing the porous medium model include: performing pore-scale modeling on the carbon / carbon porous thermal protection material to obtain the porous medium model.

4. The multi-scale prediction method for oxidation and ablation behavior of carbon / carbon porous thermal protection materials according to claim 1, characterized in that: The specific steps of step S3 for obtaining the chemical reaction path and the amount of small molecule gas products generated at each reaction temperature include: Simulate the chemical reaction process of the gas-solid interface micromodel at various reaction temperatures to obtain the atomic motion trajectory at various reaction temperatures; The chemical reaction mechanism is analyzed based on the atomic motion trajectory to obtain the chemical reaction path and the amount of small molecule gas products produced at each reaction temperature.

5. The multi-scale prediction method for oxidation and ablation behavior of carbon / carbon porous thermal protection materials according to claim 1, characterized in that: The specific steps of obtaining the reaction activation energy in step S4 include: The carbon conversion degree was obtained by normalizing the amount of small molecule gas products produced at each reaction temperature; Substituting the carbon conversion degree into the gas-solid reaction mechanism function, the reaction activation energy is obtained.

6. The multi-scale prediction method for oxidation and ablation behavior of carbon / carbon porous heat-resistant materials according to claim 5, characterized in that: The expression of the reaction activation energy is: Ea=R g T(ln A-ln(k F(c) )) Among them, Ea is the activation energy of the reaction, A is the pre-factor, R g is the gas constant, T is the temperature, k F(c) is the slope of the gas-solid reaction mechanism function value changing with time, F(.) is the gas-solid reaction mechanism function value, and c represents the carbon conversion degree.

7. The multi-scale prediction method for oxidation and ablation behavior of carbon / carbon porous thermal protection materials according to claim 1, characterized in that: The transient change results of the oxidation ablation reaction are multi-scale transient change results in the porous medium, including: the velocity in the porous medium at each reaction moment, the temperature distribution in the porous medium at each reaction moment, the concentration distribution in the porous medium at each reaction moment, the ablation retreat distance at each reaction moment, and the ablation surface roughness at each reaction moment.

8. The multi-scale prediction method for oxidation and ablation behavior of carbon / carbon porous heat-resistant materials according to claim 7, characterized in that: The expression of the ablation surface roughness is: Where Ra represents the roughness of the ablation surface, l represents the width of the calculation domain, and x′(y′) represents the distance from the y′th point on the ablation surface to the inlet.

9. The multi-scale prediction method for oxidation and ablation behavior of carbon / carbon porous thermal protection materials according to claim 1, characterized in that: The improved ablation prediction dbsFoam solver includes a velocity equation, a mass equation, a temperature equation and a concentration equation.

10. The multi-scale prediction method for oxidation and ablation behavior of carbon / carbon porous heat-resistant materials according to claim 9, characterized in that: The temperature equation of the improved ablation prediction dbsFoam solver is expressed as: Where ρ is the density of the incoming flow, C p is the specific heat of solid at constant pressure, T is the temperature, t is the reaction time, C pf is the specific heat of the fluid at constant pressure, is the velocity, λ is the thermal conductivity, S T is the chemical reaction source term of the temperature equation.

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