C / C composite material thermochemical response and pore scale structure evolution prediction method

Abstract

The invention belongs to the technical field of computer aided design, and provides a C / C composite material thermochemical response and pore scale structure evolution prediction method, which comprises the following steps: constructing a geometric model of the pore scale of a rocket engine jet pipe; establishing a fluid flow model in a D2Q9 form; establishing a multi-component mass transport model in a D2Q5 form; establishing a heat transfer model in a D2Q5 form; establishing a heterogeneous chemical reaction model of the fluid-solid boundary; establishing an updating model of the composite material based on a volume pixel method; and based on a geometric model, a fluid flow model, a multi-component mass transport model, a heat transfer model, a heterogeneous chemical reaction model and an update model, predicting the thermochemical response and pore scale structure evolution of the C / C composite material in the rocket engine nozzle. The method is provided for studying the ablation process of the C / C composite material, and theoretical basis and guidance direction are provided for thermal performance study and fine design of the spray pipe.

Description

Technical Field

[0001] The present invention relates to the technical field of computer-aided design, and in particular to a method for predicting the thermochemical response and pore-scale structural evolution of a C / C composite material. Background Art

[0002] During rocket engine operation, key propulsion system components, such as the combustion chamber, nozzle, and throat, must withstand the impact of high-temperature combustion gases. Within the engine combustion chamber, temperatures in most combustion zones can exceed 2000°C. This, coupled with the high-velocity gases containing oxidants such as water and residual oxygen after combustion, accelerates the oxidation and thermal erosion of thermal structural materials. Furthermore, the increased gas velocity within the combustion chamber introduces severe aerodynamic heating. Carbon fiber-reinforced carbon-based (C / C) composites offer advantages such as low weight, low thermal expansion coefficient, high specific strength and modulus, and high strength retention at high temperatures. They are considered ideal high-temperature structural materials for inert environments. Based on the requirements for lightweight aircraft, in-depth research on the ablation mechanisms experienced by porous C / C composites at high temperatures can help provide a theoretical basis and technical guidance for nozzle design.

[0003] Thermochemical ablation of C / C composites involves the coupled effects of flow, heat transfer, chemical reactions, and structural evolution, making its ablation mechanism highly complex and a key challenge in rocket engine research. Existing research methods can be broadly categorized into two types: experimental and numerical simulation. Experimental methods typically involve ground-based tests in wind tunnels and arc jets, obtaining experimental data under specific conditions. However, due to the highly variable airflow conditions in actual rocket nozzle operation, these ground-based tests do not provide sufficient information, providing limited insight into the ablation mechanism. Furthermore, these tests present numerous challenges, such as expensive equipment, complex implementation, and significant material loss. Existing numerical simulations are primarily categorized into macroscale and molecular-scale simulations. Macroscale simulations are primarily performed using commercial software developed using the finite element method or the finite volume method. These simulations fail to couple chemical reactions with flow and heat transfer processes and lack insight into microscopic mechanisms. Molecular-scale simulations are primarily based on reaction molecular dynamics, studying the formation and dissociation of covalent bonds. This results in lengthy computational times and neglects the coupling between surface reactions and the external flow environment, significantly deviating from actual conditions. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention proposes a method for predicting the thermochemical response and pore-scale structural evolution of C / C composites. This prediction method, based on the lattice Boltzmann method, models the pore scale to investigate the microscopic mechanisms of the ablation process. A coupled model is established through self-programming using the lattice Boltzmann method and the volume pixel method, accounting for the coupling of flow, heat transfer, chemical reaction, and ablation recession during the ablation process. Furthermore, the implementation of boundary conditions accounts for the complexities of the fluid-solid interface. This method addresses the existing inability to accurately analyze the microscopic morphological evolution of C / C composites during ablation, the failure to account for the coupling of flow, heat transfer, chemical reaction, and ablation recession, and the neglect of the fluid-solid interface in molecular-scale simulations.

[0005] The technical solutions of the present invention are as follows: A method for predicting the thermochemical response and pore-scale structural evolution of a C / C composite material comprises the following steps: Step S1: constructing a pore-scale geometric model of the rocket engine nozzle; Step S2: establishing a fluid flow model in the form of D2Q9; Step S3: establishing a multi-component mass transport model in the form of D2Q5; Step S4: establishing a heat transfer model in the form of D2Q5; Step S5: establishing a heterogeneous chemical reaction model at the fluid-solid boundary; Step S6: establishing an updated model of the composite material based on the volume pixel method; Step S7: Based on the geometric model, fluid flow model, multi-component mass transport model, heat transfer model, heterogeneous chemical reaction model and update model, the thermochemical response and pore-scale structural evolution of the C / C composite material in the rocket engine nozzle are predicted.

[0006] Preferably, the step S1 specifically includes: Step S1-1: Construct a rectangular geometric model with multiple circles evenly arranged inside the rectangle to represent carbon fibers, and perform mesh division; Step S1-2: Determine the boundary conditions of the geometric model; Step S1-3: Initialize the velocity, concentration and temperature of the fluid in the geometric model; set the velocity, concentration and temperature of the water vapor at the inlet; the velocity field, concentration field and temperature field of the fluid at the outlet adopt zero gradient; at the top and bottom walls, the flow of the fluid, the temperature of the fluid and the transport of the fluid adopt no-slip boundary, adiabatic boundary and zero flux boundary respectively; at the fluid-solid interface, the fluid flow adopts no-slip boundary conditions.

[0007] Preferably, the step S2 specifically includes: Step S2-1: Obtain the discrete velocity of fluid particles in the velocity field :

[0008] in, represents the discrete directions of fluid particles, , represents the velocity of the mesh in the geometric model, , represents the time step, Indicates the grid spacing; Step S2-2: Obtaining the macroscopic density of the fluid and momentum :

[0009] in, In discrete directions i The density distribution function of the fluid, Indicates time, represents the spatial position vector, Indicates the velocity of the fluid; Step S2-3: Establish the flow in discrete directions i The equilibrium density distribution function :

[0010] in, Represents discrete directions The weight coefficient of represents the velocity of the fluid, represents the speed of sound on the mesh in the geometry model, ; Step S2-4: Obtain the dynamic viscosity coefficient of the fluid :

[0011] in, is the flow field relaxation time of the fluid; Step S2-5: Establish a fluid flow model in the form of D2Q9: .

[0012] Preferably, the step S3 specifically includes: Step S3-1: Obtain the discrete velocity of fluid particles in the concentration field :

[0013] in, represents the discrete directions of fluid particles, ; Step S3-2: Obtain the diffusivity and component concentration of the fluid:

[0014]

[0015] in, Indicates the fluid The concentration of each component, Indicates the fluid The diffusion rate of each component, The first components in discrete directions j The concentration distribution function of Indicates the fluid Concentration field relaxation time of each component; Step S3-3: Construct the components in discrete directions j The equilibrium concentration distribution function :

[0016] in, Discrete direction The weight coefficient of Step S3-4: Establish a multi-component mass transport model in the form of D2Q5: .

[0017] Preferably, the step S4 specifically includes: Step S4-1: Obtaining the thermal diffusivity of the fluid and macroscopic temperature :

[0018]

[0019] in, represents the relaxation time of the concentration field, is a discrete direction j Temperature distribution function of Step S4-2: Establish the equilibrium temperature distribution function of the geometric model Expressed as: ; Step S4-3: Obtaining the source term of heat absorbed by the oxidation reaction of carbon fiber :

[0020] in, represents the oxidation reaction rate, represents the concentration of the fluid that reacts with the carbon fiber, represents the enthalpy of the oxidation reaction, represents the specific heat capacity of the fluid at constant pressure, Indicates the velocity of water vapor at the inlet; Step S4-4: Construct a heat transfer model in the form of D2Q5: .

[0021] Preferably, the step S5 specifically includes: Step S5-1: The heterogeneous reaction occurring on the carbon fiber surface is set as follows: ; Step S5-2: Mesh nodes at the fluid-solid interface R At , we get the control equation:

[0022] in, Represents a grid node The first The concentration of each component, Represents a grid node The first The concentration of each component, grid node F is the grid node adjacent to the grid node R in the fluid region, y represents the direction perpendicular to the fluid-solid interface y axis; Step S5-3: Determine the first Concentration distribution function of each component in 5 discrete directions , : ; Step S5-4: Setting boundary conditions:

[0023]

[0024]

[0025] in, represents the normal direction of the fluid-solid interface, represents the concentration of the component H2O, represents the diffusion rate of the component H2O, represents the concentration of component CO, represents the diffusion rate of component CO, represents the concentration of component H2, represents the diffusion rate of component H2, represents the gradient operator.

[0026] Preferably, the step S6 specifically includes: Using volume pixels, the geometric model is divided into multiple pixels, each pixel has a control volume, and at each time step , the updated volume of carbon fiber is: ; in, Indicates time t The dimensionless volume of carbon fiber, is the oxidation reaction area, is the molar volume; When the dimensionless volume of the carbon fiber drops to zero, indicating that the carbon fiber is completely consumed, the carbon fiber node is converted to a fluid node, and the density, concentration, density distribution function, and concentration distribution function at the fluid node are initialized.

[0027] Compared with the prior art, the present invention has the following advantages: The present invention provides a method for predicting the thermochemical response and pore-scale structural evolution of C / C composite materials. The volume pixel method is used to characterize the movement of the fluid-solid interface during the ablation process. By identifying and reconstructing the microscopic ablation morphology of the carbon fiber composite surface, the coupling mechanism among the diffusion of products at the ablation wall of the carbon fiber composite, thermochemical reaction, interface movement, temperature, and velocity is considered, and a pore-scale ablation model of the porous carbon fiber composite material is established. This provides a method for studying the ablation process of C / C composite materials and offers a theoretical basis and guiding direction for the thermal performance research and refined design of nozzles. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. By referring to the drawings, the features and advantages of the present invention can be more clearly understood. The drawings are schematic and should not be understood as limiting the present invention in any way. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0029] Figure 1 It is a flow chart of the method for predicting the thermochemical response and pore-scale structural evolution of C / C composite materials of the present invention.

[0030] Figure 2 Schematic diagram of the fluid-solid interface in Example 1.

[0031] Figure 3 It is the pore-scale geometric model of the rocket engine nozzle in Example 1.

[0032] Figure 4 This is the morphological evolution of carbon fiber at different times in Example 1.

[0033] Figure 5 is the distribution of temperature at the midline at different times in Example 1.

[0034] Figure 6 1 is the distribution of (a) H2O, (b) H2, (c) CO, and (d) Damkohler number at the center line in Example 1. DETAILED DESCRIPTION

[0035] 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 the embodiments of the present invention and the features therein can be combined with each other without conflict.

[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0037] The present invention proposes a method for predicting the thermochemical response and pore-scale structural evolution of C / C composite materials, such as Figure 1 As shown, the main steps include: constructing a pore-scale geometric model of the rocket engine nozzle; establishing a fluid flow model in the form of D2Q9; establishing a multi-component mass transport model in the form of D2Q5; establishing a heat transfer model in the form of D2Q5; establishing a heterogeneous chemical reaction model at the fluid-solid boundary; establishing an update model of the composite material based on the volume pixel method; based on the geometric model, fluid flow model, multi-component mass transport model, heat transfer model, heterogeneous chemical reaction model and update model, predicting the thermochemical response and pore-scale structural evolution of the C / C composite material in the rocket engine nozzle.

[0038] In order to verify the effectiveness of the numerical simulation method proposed in the present invention, the thermochemical ablation behavior of porous carbon fibers is taken as an example to further illustrate in detail.

[0039] Example 1 Step 1: Construct a pore-scale geometric model of the rocket engine nozzle.

[0040] Based on the rocket engine nozzle, a rectangular geometric model is constructed, such as Figure 2-3As shown, the circular area within the rectangular area represents the carbon fiber solid, and the fluid within the rectangular area is composed of carbon monoxide, water vapor, and hydrogen. A 300*200 grid is divided within this rectangular area, and the top, bottom, left, and right of the rectangular area are the calculation boundaries. Initialize the velocity and concentration of the fluid within the rectangular area to zero, and the temperature of the fluid to 2000K. Set the water vapor concentration at the entrance of the rectangular area to 0.1mol / m 3 , the velocity of water vapor is 0.0006m / s, and the temperature of water vapor is 3000K. At the outlet of the rectangular area, the velocity field of the fluid, the temperature field of the fluid, and the concentration field of water vapor all adopt zero gradient. At the top and bottom walls of the rectangular area, the flow of fluid, the temperature of fluid, and the transport of fluid adopt no-slip boundary, adiabatic boundary, and zero flux boundary, respectively. At the fluid-solid interface, the fluid flow adopts no-slip boundary conditions. The chemical reaction occurring at the fluid-solid interface is The chemical reaction rate is , A represents the pre-exponential factor, E represents the activation energy, R represents the molar gas constant, T s represents the reaction surface temperature, b In this embodiment, , as the input of the geometric model.

[0041] Step 2: Establish a fluid flow model in the form of D2Q9.

[0042] Set the discrete velocity of fluid particles in the velocity field of the geometric model for:

[0043] in, represents the discrete directions of fluid particles, , represents the velocity of the mesh in the geometric model, , represents the time step, Indicates the grid spacing; Get the macroscopic density of the fluid and momentum :

[0044] in, In discrete directions i The density distribution function of the fluid, Indicates time, represents the spatial position vector, Indicates the velocity of the fluid; Establishing flow in discrete directions i The equilibrium density distribution function :

[0045] in, Represents discrete directions The weight coefficient of represents the velocity of the fluid, represents the sound velocity of the grid in the geometric model. In this embodiment, the D2Q9 grid model is used. w 0 = 4 / 9, w 1 = w 2 = w 3 = w 4 = 1 / 9, w 5 = w 6 = w 7 = w 8 = 1 / 36. .

[0046] Get the dynamic viscosity coefficient of the fluid :

[0047] in, is the flow field relaxation time of the fluid; Establish a fluid flow model in the form of D2Q9: .

[0048] Step 3: Establish a multi-component mass transport model in the form of D2Q5.

[0049] Obtaining the discrete velocity of fluid particles in the concentration field :

[0050] in, represents the discrete directions of fluid particles, .

[0051] Obtain the diffusivity and species concentrations of the fluid:

[0052]

[0053] in, Indicates the fluid The concentration of each component, Indicates the fluid The diffusion rate of each component, The first components in discrete directions j The concentration distribution function of Indicates the fluid Concentration field relaxation time of each component; Build the components in discrete directions j The equilibrium concentration distribution function :

[0054] in, Discrete direction In this embodiment, the D2Q5 grid model is adopted. = 1 / 3， = = = = 1 / 6.

[0055] Establish a multi-component mass transport model in the form of D2Q5: .

[0056] Step 4: Establish a D2Q5 heat transfer model.

[0057] Get the thermal diffusivity of the fluid and macroscopic temperature :

[0058]

[0059] in, represents the relaxation time of the concentration field, is a discrete direction j Temperature distribution function of Establishing the equilibrium temperature distribution function of the geometric model Expressed as: ; Obtain the source of heat absorbed by the oxidation reaction of carbon fiber :

[0060] in, represents the oxidation reaction rate, represents the concentration of the fluid that reacts with the carbon fiber, represents the enthalpy of the oxidation reaction, represents the specific heat capacity of the fluid at constant pressure, Indicates the velocity of water vapor at the inlet; Construct a heat transfer model in the form of D2Q5: .

[0061] Step 5: Establish a heterogeneous chemical reaction model at the fluid-solid boundary.

[0062] In this embodiment, the heterogeneous reaction occurring on the carbon fiber surface is as follows:

[0063] Set the boundary conditions for each component in the reaction:

[0064]

[0065]

[0066] in, represents the normal direction of the fluid-solid interface, represents the concentration of the component H2O, represents the diffusion rate of the component H2O, represents the concentration of component CO, represents the diffusion rate of component CO, represents the concentration of component H2, Represents the diffusion rate of component H2.

[0067] The lattice Boltzmann method is the evolution of the particle distribution function, so at each time step the Concentration distribution function of each component in 5 discrete directions , :

[0068] Figure 2 Shown is a schematic diagram of the fluid-solid interface. and Corresponding to the x-axis parallel to the fluid-solid interface, and Corresponding to the x-axis perpendicular to the fluid-solid interface, after each migration, is a known quantity, is an unknown quantity; because it is perpendicular to the normal direction, and There is no effect on the flow field, and the reaction wall is static. R At , we can get the control equation:

[0069] in, Represents a grid node The first The concentration of each component, Represents a grid node The first The concentration of each component, grid node F is the grid node adjacent to the grid node R in the fluid region, y represents the direction perpendicular to the fluid-solid interface y axis.

[0070] Taking the concentration of H2O as an example, combined with the boundary conditions:

[0071] in, Represents a grid node The concentration of water vapor in the fluid, Represents a grid node The concentration of water vapor in the fluid.

[0072] Calculated After that, the unknown quantity can be further calculated This method can be used to obtain the concentration boundaries in four directions.

[0073] Step 6: Establish an updated model of the composite material based on the volume pixel method.

[0074] During the reaction, the carbon fibers are consumed by oxidation and the matrix is ​​consumed by pyrolysis, so their volume decreases. In this embodiment, volume pixels are used to update the volume of the carbon fibers in real time.

[0075] In this embodiment, the entire geometric model is divided into multiple pixels. Each pixel has a control volume. For 2D simulation, the control volume in the lattice unit V The initial volume of 0 is 1×1 in grid units.

[0076] At each time step , the updated volume of carbon fiber is: ; in, Indicates time t The dimensionless volume of carbon fiber, is the oxidation reaction area, is the molar volume; When the dimensionless volume of the carbon fiber drops to zero, indicating that the carbon fiber is completely consumed, the carbon fiber node is converted to a fluid node, and the density, concentration, density distribution function, and concentration distribution function at the fluid node are initialized.

[0077] Step 7: Based on the geometric model, fluid flow model, multi-component mass transport model, heat transfer model, heterogeneous chemical reaction model and update model, boundary conditions and calculation time are set to predict the thermochemical response and pore-scale structural evolution of C / C composite materials in rocket engine nozzles.

[0078] After the prediction is completed, the morphology evolution of the carbon fibers obtained at different times in this embodiment is as follows Figure 4 As shown in the figure, it can be seen that the consumption of carbon fiber is basically parallel. Due to the slight asymmetry between the upper and lower boundaries, the fluid velocity at the bottom is faster, and the carbon fiber is consumed faster. The temperature distribution at the midline at different times is shown in the figure. Figure 5 As shown in Figure 2, it is clear that the temperature distribution does not decrease linearly before the reaction front. This is because there are no carbon fibers to affect heat transfer through chemical reactions or in the form of solid phase. The heat absorbed by the carbon after ablation affects the temperature field through convection. The closer the fluid is to the remaining carbon fibers, the faster the temperature drops. After the reaction front, t = 0.25 s is significantly different from the others. t = 0.25 s, the remaining carbon fibers still occupy most of the space in the entire domain, which will increase the flow resistance. Therefore, the heat transfer in this area is mainly conducted rather than convective, making t = 0.25 s, the temperature distribution is linear. As the carbon fiber is gradually consumed, the resistance decreases and the heat convection becomes stronger. t = 0.50 s and t = 0.75 s, a nonlinear distribution is observed. Note that the minimum temperature is approximately 2500 K, 2000 K higher than the initial temperature, indicating that heat conduction and convection from the inlet high-temperature flow are much stronger than heat absorption from the reaction. However, the temperature drop around the reaction front due to heat absorption can be clearly seen in the enlarged image in the lower right corner. Figure 6 The concentration distribution of each component at the highest point in the region is given, where the zero point and other discontinuities are the carbon fibers and the fluid-solid interface. The concentration of H2O gradually decreases in the reaction zone and reaches zero in the unreacted zone, while the concentrations of CO and H2 gradually increase and then remain unchanged. The maximum concentrations of H2 and CO remain basically unchanged at different ablation stages, indicating that the reaction rate is fast enough. In order to gain a deeper understanding of the reaction mechanism, the Damkohler number (dimensionless number) is used. , ) represents the relative strength of reaction to diffusion, where H Indicates the height of the calculation area. Figure 6(d) shows the distribution of Damkohler numbers at different time domains, where the vertical short dashed line indicates the position of the reaction front. Since the reaction rate varies with temperature, the Damkohler number varies greatly in the entire rectangular calculation domain. It can be seen that the distribution of Damkohler numbers is similar to the temperature distribution. This is because the chemical reaction rate is positively correlated with temperature, and H and is constant. At the front end of the reaction, at different times, the Damkohler numbers of the reaction of H2O and C are all much greater than 1 (all greater than 100); that is, the reaction rate of H2O and C is fast enough, and the H2O diffused to the carbon surface is quickly consumed. The chemical reaction of this embodiment is mainly controlled by the diffusion rate of the substance, which is called diffusion control. In summary, the present invention can conduct an in-depth exploration of the ablation mechanism of porous carbon fibers at the pore scale, and can predict the changes in the micromorphology of carbon fibers through transient simulation, providing data support and scientific basis for the design and optimization of new materials for rocket engine nozzles.

[0079] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for predicting the thermochemical response and pore-scale structural evolution of C / C composite materials, characterized in that: The following steps are involved: Step S1: constructing a pore-scale geometric model of the rocket engine nozzle; Step S2: establishing a fluid flow model in the form of D2Q9; Step S3: establishing a multi-component mass transport model in the form of D2Q5; Step S4: establishing a heat transfer model in the form of D2Q5; Step S5: establishing a heterogeneous chemical reaction model at the fluid-solid boundary; Step S6: establishing an updated model of the composite material based on the volume pixel method; Step S7: Based on the geometric model, fluid flow model, multi-component mass transport model, heat transfer model, heterogeneous chemical reaction model and update model, the thermochemical response and pore-scale structural evolution of the C / C composite material in the rocket engine nozzle are predicted.

2. The method for predicting the thermochemical response and pore-scale structural evolution of C / C composite materials according to claim 1, characterized in that: Step S1-1: Construct a rectangular geometric model with multiple circles evenly arranged inside the rectangle to represent carbon fibers, and perform mesh division; Step S1-2: Determine the boundary conditions of the geometric model; Step S1-3: Initialize the velocity, concentration and temperature of the fluid in the geometric model; set the velocity, concentration and temperature of the water vapor at the inlet; the velocity field, concentration field and temperature field of the fluid at the outlet adopt zero gradient; at the top and bottom walls, the fluid flow, fluid temperature and fluid transport adopt no-slip boundary, adiabatic boundary and zero flux boundary respectively; at the fluid-solid interface, the fluid flow adopts no-slip boundary conditions.

3. The method for predicting the thermochemical response and pore-scale structural evolution of C / C composite materials according to claim 2, characterized in that: The step S2 specifically includes: Step S2-1: Obtain the discrete velocity of fluid particles in the velocity field : in, represents the discrete directions of fluid particles, , represents the velocity of the mesh in the geometric model, , represents the time step, Indicates the grid spacing; Step S2-2: Obtaining the macroscopic density of the fluid and momentum : in, In discrete directions i The density distribution function of the fluid, Indicates time, represents the spatial position vector, Indicates the velocity of the fluid; Step S2-3: Establish the flow in discrete directions i The equilibrium density distribution function : in, Represents discrete directions The weight coefficient of represents the velocity of the fluid, represents the speed of sound on the mesh in the geometry model, ; Step S2-4: Obtain the dynamic viscosity coefficient of the fluid : in, is the flow field relaxation time of the fluid; Step S2-5: Establish a fluid flow model in the form of D2Q9: 。 4. The method for predicting the thermochemical response and pore-scale structural evolution of C / C composite materials according to claim 3, characterized in that: The step S3 specifically includes: Step S3-1: Obtain the discrete velocity of fluid particles in the concentration field : in, represents the discrete directions of fluid particles, ; Step S3-2: Obtain the diffusivity and component concentration of the fluid: in, Indicates the fluid The concentration of each component, Indicates the fluid The diffusion rate of each component, The first components in discrete directions j The concentration distribution function of Indicates the fluid Concentration field relaxation time of each component; Step S3-3: Construct the components in discrete directions j The equilibrium concentration distribution function : in, Discrete direction The weight coefficient of Step S3-4: Establish a multi-component mass transport model in the form of D2Q5: 。 5. The method for predicting the thermochemical response and pore-scale structural evolution of C / C composite materials according to claim 4, characterized in that: The step S4 specifically includes: Step S4-1: Obtaining the thermal diffusivity of the fluid and macroscopic temperature : in, represents the relaxation time of the concentration field, is a discrete direction j Temperature distribution function of Step S4-2: Establish the equilibrium temperature distribution function of the geometric model Expressed as: ； Step S4-3: Obtaining the source term of heat absorbed by the oxidation reaction of carbon fiber : in, represents the oxidation reaction rate, represents the concentration of the fluid that reacts with the carbon fiber, represents the enthalpy of the oxidation reaction, represents the specific heat capacity of the fluid at constant pressure, Indicates the velocity of water vapor at the inlet; Step S4-4: Construct a heat transfer model in the form of D2Q5: 。 6. The method for predicting the thermochemical response and pore-scale structural evolution of C / C composite materials according to claim 5, characterized in that: The step S5 specifically includes: Step S5-1: The heterogeneous reaction occurring on the carbon fiber surface is set as follows: ； Step S5-2: Mesh nodes at the fluid-solid interface R At , we get the control equation: in, Represents a grid node The first The concentration of each component, Represents a grid node The first The concentration of each component, grid node F is the grid node adjacent to the grid node R in the fluid region, y represents the direction perpendicular to the fluid-solid interface y axis; Step S5-3: Determine the first Concentration distribution function of each component in 5 discrete directions , : ； Step S5-4: Setting boundary conditions: in, represents the normal direction of the fluid-solid interface, represents the concentration of the component H2O, represents the diffusion rate of the component H2O, represents the concentration of component CO, represents the diffusion rate of component CO, represents the concentration of component H2, represents the diffusion rate of component H2, represents the gradient operator.

7. The method for predicting the thermochemical response and pore-scale structural evolution of C / C composite materials according to claim 6, characterized in that: The step S6 specifically includes: Using volume pixels, the geometric model is divided into multiple pixels, each pixel has a control volume, and at each time step , the updated volume of carbon fiber is: ； in, Indicates time t The dimensionless volume of carbon fiber, is the oxidation reaction area, is the molar volume; When the dimensionless volume of the carbon fiber drops to zero, indicating that the carbon fiber is completely consumed, the carbon fiber node is converted to a fluid node, and the density, concentration, density distribution function, and concentration distribution function at the fluid node are initialized.

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