A calculation method for carbon / carbon nozzle throat liner ablation based on parameter identification
The method enhances ablation calculation accuracy in carbon/carbon nozzle throat liners by integrating structured grids, fluid-solid coupling, and machine learning to identify optimal chemical reaction parameters, achieving precise ablation rate prediction.
Patent Information
- Application Number
- CN202411522604.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-29
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2044-10-29
AI Technical Summary
Traditional ablation calculation methods for carbon/carbon nozzle throat liners in solid rocket engines are inaccurate due to ignoring the real physical process, leading to engine performance loss from thermochemical ablation.
A method involving structured grid construction, fluid-solid coupling calculation, Latin hypercube sampling, and extreme learning machine to identify optimal pre-exponential factors and activation energies for chemical reactions, coupled with dynamic grid movement and post-processing to calculate accurate ablation rates.
Accurately simulates the thermochemical ablation process, improving precision and reducing calculation complexity while maintaining low costs, enabling precise ablation rate prediction.
Smart Images
Figure CN119026528B_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of spacecraft thermal protection design, and in particular to a method for calculating carbon / carbon nozzle throat liner ablation based on parameter identification. Background Art
[0002] During the operation of a solid rocket engine, high-temperature gas flows over the nozzle wall, forming a turbulent boundary layer, transferring heat to the nozzle wall, causing the wall temperature to rise. After reaching a certain temperature, the oxidizing components in the gas react with the carbon / carbon material in a heterogeneous chemical reaction, resulting in thermochemical ablation, which causes the nozzle wall to decay. Especially for nozzles that run for a long time, thermochemical ablation will cause the nozzle throat area to increase, resulting in engine performance loss. Therefore, it is of great practical significance to study the thermochemical ablation of carbon / carbon composite nozzles. It is urgent to establish an ablation model that reflects the real physical process and accurately predict the nozzle ablation rate.
[0003] Traditional ablation calculation is a theoretical calculation, which calculates the vertical surface ablation rate of thermal protection materials based on parameters such as temperature, pressure, and gas flow. However, this method can no longer meet current design requirements, so it is urgent to develop a more accurate ablation calculation method. Summary of the invention
[0004] Based on this, it is necessary to provide a carbon / carbon nozzle throat liner ablation calculation method based on parameter identification to solve the calculation error problem caused by ignoring the real physical process in the ablation rate calculation of the existing technology and improve the accuracy of carbon / carbon nozzle throat liner ablation calculation.
[0005] A method for calculating ablation of a carbon / carbon nozzle throat liner based on parameter identification, the method comprising:
[0006] Construct structured grids for the fluid domain and throat liner solid domain of the internal flow field of the carbon / carbon nozzle;
[0007] Without considering ablation, the fluid-solid coupling calculation is performed according to the bidirectional fluid-solid coupling effect between the fluid domain and the solid domain, and the initial values of the ablation calculation parameters of the fluid domain and the solid domain are obtained.
[0008] Based on the initial values of the ablation calculation parameters, Latin hypercube sampling and extreme learning machine are combined to perform parameter identification and solve the pre-exponential factors and activation energies of two types of chemical reactions occurring on the fluid-solid boundary, and the optimal pre-exponential factors and optimal activation energies of the two types of chemical reactions are obtained.
[0009] Based on the optimal pre-exponential factors and optimal activation energies of the two types of chemical reactions, the UDF file is compiled for ablation calculation. The grid coordinates of the fluid-solid boundary are controlled to move according to the set calculation time step according to the calculated ablation rate, and the ablation calculation parameters of the fluid domain and the solid domain are updated according to the moved fluid-solid boundary grid coordinates.
[0010] According to the updated ablation calculation parameters, parameter identification and solution, ablation calculation and fluid-solid boundary grid coordinate movement are continued until all calculation time steps are completed. After the calculation is completed, post-processing is performed to obtain the average ablation rate of carbon / carbon nozzle throat liner ablation.
[0011] In one embodiment, constructing a structured grid of a fluid domain and a throat liner solid domain in a carbon / carbon nozzle internal flow field includes:
[0012] By considering the axisymmetric characteristics of the carbon / carbon nozzle structure, the ICEMCFD software is used to construct the structured grids of the fluid domain and the throat liner solid domain of the internal flow field of the carbon / carbon nozzle.
[0013] In one embodiment, without considering ablation, a fluid-solid coupling calculation is performed according to the bidirectional fluid-solid coupling effect generated by the fluid domain and the solid domain to obtain the initial values of the ablation calculation parameters of the fluid domain and the solid domain, including:
[0014] Without considering ablation, according to the bidirectional fluid-solid coupling effect between the fluid domain and the solid domain, the flow field control equation, turbulence model and the instantaneous thermal conductivity equation of the solid phase material are constructed to perform fluid-solid coupling calculation, and the initial values of the ablation calculation parameters of the fluid domain and the solid domain are obtained; among them, the flow field control equation adopts the two-dimensional compressible Reynolds average Equation solving; turbulence model uses two equations Turbulence model; the instantaneous thermal conductivity equation of the solid material is expressed as
[0015] ;
[0016] in, is the density of the solid phase material; is the specific heat of the solid material; is the temperature of the solid phase material; is the thermal conductivity of the solid phase material; is the radial coordinate; For time; is the axial coordinate.
[0017] In one embodiment, the fluid-structure coupling calculation uses Fluent software to perform steady-state calculation.
[0018] In one embodiment, Latin hypercube sampling and extreme learning machine are combined to perform parameter identification and solution on the pre-exponential factors and activation energies of two types of chemical reactions occurring on the fluid-solid boundary, and the optimal pre-exponential factors and optimal activation energies of the two types of chemical reactions are obtained, including:
[0019] The Latin hypercube sampling algorithm is used to divide and obtain the range of the initial guess of the pre-exponential factor and activation energy of two types of chemical reactions occurring on the fluid-solid boundary; the two types of chemical reactions include the chemical reaction between carbon and water and the chemical reaction between carbon and carbon dioxide;
[0020] Within the range of values, the initial guess values of the pre-exponential factors and activation energies of the two types of chemical reactions are sampled to obtain multiple groups of samples; wherein each group of samples includes the initial guess values of the pre-exponential factors corresponding to the two types of chemical reactions and the initial guess values of the activation energies corresponding to the two types of chemical reactions;
[0021] Each group of samples is input into the extreme learning machine. The mathematical model constructed by the extreme learning machine and the numerical value of the carbon / carbon nozzle throat lining ablation rate measured in advance is used to identify and solve the optimal parameters of the pre-exponential factors and activation energies of the two types of chemical reactions. By traversing multiple groups of samples, the optimal pre-exponential factors and optimal activation energies of the two types of chemical reactions are obtained.
[0022] In one embodiment, the mathematical model is expressed as
[0023] ;
[0024] in, Indicates The input vector of group samples, and is the number of sample groups; express The elements; represents the input weight and Each component in represents the difference between each element in the input vector and the The connection weights between hidden layer nodes, for The Quantity, superscript represents transpose; the total number of hidden layer nodes is represented by ; represents the output weight and Each component in represents the The connection weights between hidden layer nodes and each output vector; Indicates The bias vector of hidden layer nodes, is the activation function, It is The output vector corresponding to the group sample;
[0025] Among them, The input vector of the group sample includes the initial guess values of the pre-exponential factors corresponding to the two types of chemical reactions and the initial guess values of the activation energies corresponding to the two types of chemical reactions; the output vector is the carbon / carbon nozzle throat liner ablation rate value measured in advance.
[0026] In one embodiment, based on the optimal pre-exponential factors and optimal activation energies of two types of chemical reactions, a UDF file is compiled to perform ablation calculations, including:
[0027] Based on the optimal pre-exponential factors and optimal activation energies of the two types of chemical reactions obtained by parameter identification, the UDF file is compiled for ablation calculation to obtain the ablation rate; the compilation formula of the UDF file is expressed as
[0028] ;
[0029] ;
[0030] ;
[0031] in, For the The rate of a chemical reaction is governed by the Arrhenius equation; Indicates Optimal pre-exponential factor of a chemical reaction; is the inner wall temperature of the carbon / carbon nozzle, is the temperature index; Indicates The optimal activation energy of a chemical reaction; is the universal gas constant; and In the chemical reaction process The mass fraction and partial pressure of the components; and denote the molecular weight of the mixed gas and the pressure at the fluid-solid boundary, respectively. Indicates The molecular weight of the components, is the ablation rate.
[0032] In one embodiment, controlling the grid coordinates of the fluid-solid boundary to move according to a set calculation time step according to the calculated ablation rate includes:
[0033] The formula for the mesh coordinate movement of the fluid-solid boundary is expressed as
[0034] ;
[0035] ;
[0036] in, is the vertical coordinate of the grid point on the fluid-solid boundary, is the computation time step.
[0037] In one embodiment, after the calculation is completed, post-processing is performed to obtain an average ablation rate of carbon / carbon nozzle throat liner ablation, including:
[0038] After the calculation is completed, the EnSight software is used to export the longitudinal coordinates of the grid points on the fluid-solid boundary before and after the ablation of the carbon / carbon nozzle throat liner. The longitudinal coordinates are subtracted to obtain the total ablation retreat distance of the carbon / carbon nozzle throat liner. The average ablation rate of the carbon / carbon nozzle throat liner ablation is obtained by dividing the total ablation retreat distance by the total retreat time.
[0039] The above-mentioned carbon / carbon nozzle throat lining ablation calculation method based on parameter identification realizes accurate simulation analysis of the physical process of carbon / carbon nozzle throat lining ablation by coupling carbon / carbon nozzle structured grid division, fluid-solid coupling calculation, chemical reaction parameter identification and solution, and dynamic grid technology, and has the advantages of low cost and high precision in solving the problem of carbon / carbon nozzle throat lining ablation. In addition, by combining Latin hypercube sampling and extreme learning machine to perform parameter identification and solution for the pre-exponential factor and activation energy of two types of chemical reactions occurring on the fluid-solid boundary, while reducing the calculation complexity, the calculation accuracy of the ablation chemical reaction parameters is improved, and the fluid-solid bidirectional precise coupling between the flow field in the nozzle and the carbon / carbon throat lining is realized, which can more accurately simulate the thermochemical ablation process and realize more accurate ablation rate prediction calculation. It has good universality and can be widely used in the calculation needs of various ablation scenarios. BRIEF DESCRIPTION OF THE DRAWINGS
[0040] Figure 1 A schematic flow chart of a method for calculating ablation of a carbon / carbon nozzle throat liner based on parameter identification in one embodiment;
[0041] Figure 2 A schematic diagram of a structured grid in one embodiment;
[0042] Figure 3 Schematic diagram of regression results of parameter identification in one embodiment; wherein, Figure 3 (a) is the training error; Figure 3 (b) is the verification error; Figure 3 (c) is the test error; Figure 3 (d) is the total error;
[0043] Figure 4 A schematic diagram showing the comparison of a carbon / carbon nozzle throat liner before and after ablation in one embodiment;
[0044] Figure 5A schematic diagram of the average ablation rate of carbon / carbon nozzle throat liner ablation in one embodiment; DETAILED DESCRIPTION
[0045] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.
[0046] In one embodiment, Figure 1 As shown, a method for calculating the ablation of a carbon / carbon nozzle throat liner based on parameter identification is provided, comprising the following steps:
[0047] Step S1, constructing structured grids of the fluid domain and throat liner solid domain of the internal flow field of the carbon / carbon nozzle.
[0048] Among them, in step S1, if Figure 2 As shown, by considering the axisymmetric characteristics of the carbon / carbon nozzle structure, the ICEMCFD software is used to construct the structured grids of the fluid domain and the throat liner solid domain of the internal flow field of the carbon / carbon nozzle.
[0049] Step S2, without considering ablation, performing fluid-solid coupling calculation according to the bidirectional fluid-solid coupling effect generated by the fluid domain and the solid domain, and obtaining initial values of ablation calculation parameters of the fluid domain and the solid domain.
[0050] In step S2, without considering ablation, according to the bidirectional fluid-solid coupling effect between the fluid domain and the solid domain, the flow field control equation, the turbulence model and the instantaneous thermal conductivity equation of the solid phase material are constructed to perform fluid-solid coupling calculation to obtain the initial values of the ablation calculation parameters of the fluid domain and the solid domain; the flow field control equation adopts a two-dimensional compressible Reynolds average (Navier-Stokes) equations are solved; the turbulence model uses two equations (shear stress transport) turbulence model; the instantaneous thermal conductivity equation of the solid phase material is expressed as
[0051] ;
[0052] in, is the density of the solid phase material; is the specific heat of the solid material; is the temperature of the solid phase material; is the thermal conductivity of the solid phase material; is the radial coordinate; For time; Specifically, the fluid-solid coupling calculation uses Fluent (fluid simulation) software for steady-state calculation.
[0053] Step S3, based on the initial values of the ablation calculation parameters, Latin hypercube sampling and extreme learning machine are combined to perform parameter identification and solution on the pre-exponential factors and activation energies of the two types of chemical reactions occurring on the fluid-solid boundary, and obtain the optimal pre-exponential factors and optimal activation energies of the two types of chemical reactions.
[0054] Among them, in step S3, the specific process of parameter identification and solution includes:
[0055] Firstly, the Latin hypercube sampling algorithm is used to divide the range of initial guess values of the pre-exponential factor and activation energy of two types of chemical reactions occurring on the fluid-solid boundary; the two types of chemical reactions include the chemical reaction between carbon (C) and water (H2O) and the chemical reaction between carbon (C) and carbon dioxide (CO2).
[0056] Specifically, the ranges of the initial guess values of the pre-exponential factors and activation energies of the two types of chemical reactions are shown in Table 1.
[0057] Table 1 Preliminary guess ranges of pre-exponential factors and activation energies for two types of chemical reactions
[0058]
[0059] Then, within the range of values shown in Table 1, the initial guess values of the pre-exponential factors and activation energies of the two types of chemical reactions are sampled to obtain multiple groups of samples; wherein each group of samples includes the initial guess values of the pre-exponential factors corresponding to the two types of chemical reactions and the initial guess values of the activation energies corresponding to the two types of chemical reactions.
[0060] It can be understood that the Latin hypercube sampling algorithm is a method of approximate random sampling from a multivariate parameter distribution. It belongs to the stratified sampling technique. It divides the value range of each component into the same interval and performs uniform sampling in each interval to reduce the correlation between input variables. It can obtain higher sampling accuracy at a smaller sampling scale, thereby achieving similar or better accuracy levels at a lower computational cost.
[0061] Specifically, the five groups of samples extracted based on the Latin hypercube sampling algorithm are shown in Table 2.
[0062] Table 2 Five groups of samples extracted
[0063]
[0064] Finally, each group of samples is input into the extreme learning machine, and the mathematical model constructed by the extreme learning machine and the numerical value of the carbon / carbon nozzle throat lining ablation rate measured in advance is used to identify and solve the optimal parameters of the pre-exponential factors and activation energies of the two types of chemical reactions. By traversing multiple groups of samples, the optimal pre-exponential factors and optimal activation energies of the two types of chemical reactions are obtained.
[0065] The mathematical model is expressed as
[0066] ;
[0067] in, Indicates The input vector of group samples, and is the number of sample groups; express The elements; represents the input weight and Each component in represents the difference between each element in the input vector and the The connection weights between hidden layer nodes, for The Quantity, superscript represents transpose; the total number of hidden layer nodes is represented by ; represents the output weight and Each component in represents the The connection weights between hidden layer nodes and each output vector; Indicates The bias vector of hidden layer nodes, is the activation function, It is Output vector corresponding to the group samples.
[0068] Among them, The input vectors of the sample group include the initial guess values of the pre-exponential factors corresponding to the two types of chemical reactions and the initial guess values of the activation energies corresponding to the two types of chemical reactions; the output vector is the numerical value of the carbon / carbon nozzle throat lining ablation rate measured in the previous experiment. The mathematical model is mainly used to establish the mapping relationship between the four input vectors (pre-exponential factor (C+H2O), activation energy (C+H2O), pre-exponential factor (C+CO2), activation energy (C+CO2)) in the sample and an output vector (the numerical value of the carbon / carbon nozzle throat lining ablation rate measured in the previous experiment).
[0069] Specifically, the carbon / carbon nozzle throat liner ablation rate value measured in the previous experiment is 0.3531 mm / s. By traversing multiple groups of samples, the optimal pre-exponential factor and optimal activation energy of the two types of chemical reactions are obtained as follows: optimal pre-exponential factor (C+H2O) = 1458.2534 kg / (m 2 ·s), optimal activation energy (C+H2O) = 287651.3096 J / mol, optimal pre-exponential factor (C+CO2) = 28.5101 kg / (m 2·s), optimal activation energy (C+CO2) = 284962.5734 J / mol.
[0070] The regression results of parameter identification in this application are as follows Figure 3 As shown, Figure 3 (a) is the training error; Figure 3 (b) is the verification error; Figure 3 (c) is the test error; Figure 3 (d) is the total error. Figure 3 Y=T in the equation means predicted value = actual value.
[0071] Step S4, based on the optimal pre-exponential factors and optimal activation energies of the two types of chemical reactions, compile the UDF (user defined function) file to perform ablation calculations, control the mesh coordinates of the fluid-solid boundary to move according to the set calculation time step according to the calculated ablation rate, and update the ablation calculation parameters of the fluid domain and the solid domain according to the moved fluid-solid boundary mesh coordinates.
[0072] In step S4, based on the optimal pre-exponential factors and optimal activation energies of the two types of chemical reactions obtained by parameter identification, the UDF file is compiled to perform ablation calculation to obtain the ablation rate; wherein the compilation formula of the UDF file is expressed as:
[0073] ;
[0074] ;
[0075] ;
[0076] in, For the The rate of a chemical reaction is governed by the Arrhenius equation; Indicates Optimal pre-exponential factor of a chemical reaction; is the inner wall temperature of the carbon / carbon nozzle, is the temperature index; Indicates i The optimal activation energy of a chemical reaction; is the universal gas constant; and In the chemical reaction process i The mass fraction and partial pressure of the components; and denote the molecular weight of the mixed gas and the pressure at the fluid-solid boundary, respectively. Indicates The molecular weight of the components, is the ablation rate.
[0077] Specifically, the chemical reaction parameters used in this compilation calculation are shown in Table 3.
[0078] Table 3 Chemical reaction parameters
[0079]
[0080] Wherein, parameter b represents the temperature index of the chemical reaction.
[0081] In step S4, the formula for moving the grid coordinates of the fluid-solid boundary is expressed as:
[0082] ;
[0083] ;
[0084] in, is the vertical coordinate of the grid point on the fluid-solid boundary, is the calculation time step. By using a loop statement for the movement formula, the loop is iterated repeatedly until the calculation is completed.
[0085] Step S5, continue to perform parameter identification and solution, ablation calculation and fluid-solid boundary grid coordinate movement according to the updated ablation calculation parameters until all calculation time steps are completed, and perform post-processing after the calculation is completed to obtain the average ablation rate of carbon / carbon nozzle throat liner ablation.
[0086] Among them, in step S5, after the calculation is completed, the EnSight software is used to derive the vertical coordinates of the grid points on the fluid-solid boundary before and after the ablation of the carbon / carbon nozzle throat liner. The comparison diagram of the carbon / carbon nozzle throat liner before and after ablation is shown in FIG. Figure 4 As shown, the vertical coordinate is subtracted to obtain the total ablation retreat distance of the carbon / carbon nozzle throat liner. According to the total ablation retreat distance divided by the total retreat time, the average ablation rate of the carbon / carbon nozzle throat liner ablation is obtained, as shown in Figure 5 shown.
[0087] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequentially, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.
[0088] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0089] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.
Claims
1. A method for calculating the ablation of a carbon / carbon nozzle throat liner based on parameter identification, characterized in that: The method comprises: Construct structured grids for the fluid domain and throat liner solid domain of the internal flow field of the carbon / carbon nozzle; Without considering ablation, the fluid-solid coupling calculation is performed according to the bidirectional fluid-solid coupling effect between the fluid domain and the solid domain, and the initial values of the ablation calculation parameters of the fluid domain and the solid domain are obtained. Based on the initial values of the ablation calculation parameters, Latin hypercube sampling and extreme learning machine are combined to perform parameter identification and solution on the pre-exponential factors and activation energies of two types of chemical reactions occurring on the fluid-solid boundary, and the optimal pre-exponential factors and optimal activation energies of the two types of chemical reactions are obtained; Based on the optimal pre-exponential factors and optimal activation energies of the two types of chemical reactions, the UDF file is compiled to perform ablation calculations, and the grid coordinates of the fluid-solid boundary are controlled to move according to the set calculation time step according to the calculated ablation rate, and the ablation calculation parameters of the fluid domain and the solid domain are updated according to the moved fluid-solid boundary grid coordinates; According to the updated ablation calculation parameters, parameter identification and solution, ablation calculation and fluid-solid boundary grid coordinate movement are continued until all calculation time steps are completed. After the calculation is completed, post-processing is performed to obtain the average ablation rate of carbon / carbon nozzle throat liner ablation.
2. The method according to claim 1, characterized in that Construct structured grids for the fluid domain and throat liner solid domain of the internal flow field of the carbon / carbon nozzle, including: By considering the axisymmetric characteristics of the carbon / carbon nozzle structure, the ICEMCFD software is used to construct the structured grids of the fluid domain and the throat liner solid domain of the internal flow field of the carbon / carbon nozzle.
3. The method according to claim 1, characterized in that Without considering ablation, the fluid-solid coupling calculation is performed according to the bidirectional fluid-solid coupling effect between the fluid domain and the solid domain, and the initial values of the ablation calculation parameters of the fluid domain and the solid domain are obtained, including: Without considering ablation, according to the bidirectional fluid-solid coupling effect between the fluid domain and the solid domain, the flow field control equation, turbulence model and the instantaneous thermal conductivity equation of the solid phase material are constructed to perform fluid-solid coupling calculation, and the initial values of the ablation calculation parameters of the fluid domain and the solid domain are obtained; wherein, the flow field control equation adopts a two-dimensional compressible Reynolds average Equation solution; the turbulence model uses two equations Turbulence model; the instantaneous thermal conductivity equation of the solid phase material is expressed as ； in, is the density of the solid phase material; is the specific heat of the solid material; is the temperature of the solid phase material; is the thermal conductivity of the solid phase material; is the radial coordinate; For time; is the axial coordinate.
4. The method according to claim 3, characterized in that The fluid-solid coupling calculation adopts Fluent software to perform steady-state calculation.
5. The method according to claim 1, characterized in that Combining Latin hypercube sampling with extreme learning machine, we can identify and solve the pre-exponential factors and activation energies of two types of chemical reactions occurring on the fluid-solid boundary, and obtain the optimal pre-exponential factors and activation energies of the two types of chemical reactions, including: The Latin hypercube sampling algorithm is used to divide and obtain the range of the initial guess of the pre-exponential factor and activation energy of two types of chemical reactions occurring on the fluid-solid boundary; the two types of chemical reactions include the chemical reaction between carbon and water and the chemical reaction between carbon and carbon dioxide; Within the range of values, the initial guess values of the pre-exponential factors and activation energies of the two types of chemical reactions are sampled to obtain multiple groups of samples; wherein each group of samples includes the initial guess values of the pre-exponential factors corresponding to the two types of chemical reactions and the initial guess values of the activation energies corresponding to the two types of chemical reactions; Each group of samples is input into the extreme learning machine. The mathematical model constructed by the extreme learning machine and the numerical value of the carbon / carbon nozzle throat lining ablation rate measured in advance is used to identify and solve the optimal parameters of the pre-exponential factors and activation energies of the two types of chemical reactions. By traversing multiple groups of samples, the optimal pre-exponential factors and optimal activation energies of the two types of chemical reactions are obtained.
6. The method according to claim 5, characterized in that The mathematical model is expressed as ； in, Indicates The input vector of group samples, and is the number of sample groups; express The elements; represents the input weight and Each component in represents the difference between each element in the input vector and the The connection weights between hidden layer nodes, for The Quantity, superscript represents transpose; the total number of hidden layer nodes is represented by ; represents the output weight and Each component in represents the The connection weights between hidden layer nodes and each output vector; Indicates The bias vector of hidden layer nodes, is the activation function, It is The output vector corresponding to the group sample; Among them, The input vector of the group sample includes the initial guess values of the pre-exponential factors corresponding to the two types of chemical reactions and the initial guess values of the activation energies corresponding to the two types of chemical reactions; the output vector is the carbon / carbon nozzle throat liner ablation rate value measured in advance.
7. The method according to claim 5, characterized in that Based on the optimal pre-exponential factors and optimal activation energies of two types of chemical reactions, UDF files are compiled for ablation calculations, including: Based on the optimal pre-exponential factors and optimal activation energies of the two types of chemical reactions obtained by parameter identification, the UDF file is compiled for ablation calculation to obtain the ablation rate; wherein the compilation formula of the UDF file is expressed as: ； ； ； in, For the The rate of a chemical reaction is governed by the Arrhenius equation; Indicates Optimal pre-exponential factor of a chemical reaction; is the inner wall temperature of the carbon / carbon nozzle, is the temperature index; Indicates The optimal activation energy of a chemical reaction; is the universal gas constant; and In the chemical reaction process i The mass fraction and partial pressure of the components; and denote the molecular weight of the mixed gas and the pressure at the fluid-solid boundary, respectively. Indicates The molecular weight of the components, is the ablation rate.
8. The method according to claim 7, characterized in that According to the calculated ablation rate, the grid coordinates of the fluid-solid boundary are controlled to move according to the set calculation time step, including: The formula for the grid coordinate movement of the fluid-solid boundary is expressed as ； ； in, is the vertical coordinate of the grid point on the fluid-solid boundary, is the computation time step.
9. The method according to claim 1, characterized in that: After the calculation is completed, post-processing is performed to obtain the average ablation rate of carbon / carbon nozzle throat liner ablation, including: After the calculation is completed, the EnSight software is used to export the longitudinal coordinates of the grid points on the fluid-solid boundary before and after the ablation of the carbon / carbon nozzle throat liner. The longitudinal coordinates are subtracted to obtain the total ablation retreat distance of the carbon / carbon nozzle throat liner. The average ablation rate of the carbon / carbon nozzle throat liner ablation is obtained by dividing the total ablation retreat distance by the total retreat time.