A heat protection structure simulation method and system

Abstract

The embodiment of the present application provides a kind of heat protection structure simulation method and system, the method comprises: based on the structure size and material physical property parameters of the heat protection structure obtained, the initial geometric model and initial finite element model of heat protection structure are constructed;In each current time step, boundary condition is applied to current finite element model to carry out force-thermal coupling simulation, and the coupling simulation result of current time step is obtained;Update current geometric model to obtain updated geometric model, and carry out mesh division to obtain updated finite element model;Next time step is updated to current time step, and step 2 and step 3 are sequentially executed, in step 2, the coupling simulation result of current time step is applied to updated finite element model as boundary condition, until simulation is completed for all time steps. By force-thermal coupling simulation, the real use environment of heat protection structure can be more close, and the accuracy of heat protection structure simulation can be improved.

Description

Technical Field

[0001] This invention relates to the field of thermal protection technology, specifically to a method and system for simulating thermal protection structures. Background Technology

[0002] The bottom of the first-stage tail section of a large liquid-fueled launch vehicle is heated by the engine exhaust during flight. To protect against heat and engine oscillation, a flexible, airtight heat shield structure is typically used. Due to the pressure difference between the inside and outside of the capsule, the flexible heat shield structure is not only affected by the heat from the exhaust but also withstands certain pressure conditions.

[0003] In the process of developing this invention, the applicant discovered at least the following problems in the prior art:

[0004] Existing simulation technologies typically decouple the mechanical and heat transfer simulations of flexible thermal protection structures. In thermal protection design, only the temperature field of the material is considered, while in structural design, only the stress state of the material under engine oscillation or pressure conditions is considered. In reality, the working process of a flexible thermal protection structure is a multi-physics field coupling state of heat and force, meaning that force and heat simultaneously affect the performance of the flexible thermal protection structure. However, if the simulation only focuses on the stress state of the material under engine oscillation or pressure conditions, it cannot reflect the real usage environment of the flexible thermal protection structure, resulting in poor simulation accuracy. Summary of the Invention

[0005] This invention provides a method and system for simulating heat-resistant structures, which can solve the technical problems in the prior art.

[0006] To achieve the above objectives, in a first aspect, embodiments of the present invention provide a method for simulating a heat-resistant structure, comprising:

[0007] Step 1: Based on the obtained structural dimensions and material properties of the heat-resistant structure, construct the initial geometric model of the heat-resistant structure, and mesh the initial geometric model to obtain the initial finite element model;

[0008] Step 2: At each current time step, apply boundary conditions to the current finite element model and perform a force-thermal coupling simulation on the current finite element model to obtain the coupling simulation results for the current time step. Wherein, when the first time step is the current time step, the current finite element model refers to the initial finite element model; from the second time step onwards, at each current time step, the current finite element model refers to the updated finite element model obtained at the end of the force-thermal coupling simulation of the previous time step.

[0009] Step 3: Based on the coupling simulation results of the current time step, update the current geometric model to obtain the updated geometric model. Mesh the updated geometric model to obtain the updated finite element model. Wherein, when the first time step is the current time step, the current geometric model refers to the initial geometric model. From the second time step onwards, the current geometric model refers to the updated geometric model obtained at the end of the force-thermal coupling simulation of the previous time step.

[0010] Update the next time step to the current time step, and execute steps 2 and 3 in sequence. In step 2, apply the coupled simulation results of the current time step as boundary conditions to the updated finite element model until the simulation is completed for all time steps.

[0011] Secondly, embodiments of the present invention provide a thermal protection structure simulation system, comprising:

[0012] The model building unit is used to construct the initial geometric model of the heat-resistant structure based on the obtained structural dimensions and material property parameters of the heat-resistant structure, and to mesh the initial geometric model to obtain the initial finite element model.

[0013] The coupled simulation unit is used to apply boundary conditions to the current finite element model at each current time step, perform mechanical and thermal coupled simulation on the current finite element model, and obtain the coupled simulation result of the current time step; wherein, when the first time step is the current time step, the current finite element model refers to the initial finite element model; and in each current time step from the second time step onwards, the current finite element model refers to the updated finite element model obtained at the end of the mechanical and thermal coupled simulation of the previous time step.

[0014] The model update unit is used to update the current geometric model based on the coupled simulation results of the current time step to obtain an updated geometric model, and to mesh the updated geometric model to obtain an updated finite element model. In the first time step, the current geometric model refers to the initial geometric model. In each current time step from the second time step onwards, the current geometric model refers to the updated geometric model obtained at the end of the force-thermal coupled simulation of the previous time step.

[0015] The next time step is updated to the current time step, and the coupled simulation unit and the model update unit are executed sequentially. In the coupled simulation unit, the coupled simulation result of the current time step is applied as a boundary condition to the updated finite element model until the simulation is completed for all time steps.

[0016] The above technical solution has the following beneficial effects:

[0017] By simulating the temperature field of the heat-resistant structure through thermal simulation, the force simulation can take into account the thermal strain caused by temperature. By simulating the stress and strain of the heat-resistant structure through steady-state structural simulation, the next thermal simulation can take into account the stress and strain of the heat-resistant structure. This achieves force-thermal coupling simulation, which can more closely approximate the real use environment of the heat-resistant structure. Therefore, it can improve the accuracy of the heat-resistant structure simulation and facilitate the selection of a more scientific and reasonable design scheme for the heat-resistant structure. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of a heat-resistant structure simulation method according to an embodiment of the present invention;

[0020] Figure 2 This is a structural diagram of a heat-resistant structure simulation system according to an embodiment of the present invention;

[0021] Figure 3 This is a simplified flowchart of the thermal protection structure simulation method according to an embodiment of the present invention.

[0022] Figure 4 This is a flowchart of a force-thermal coupling simulation using the first force-thermal coupling simulation method according to an embodiment of the present invention;

[0023] Figure 5 This is a schematic diagram of the geometric and temperature field update of the heat-resistant structure in the ablation process according to an embodiment of the present invention;

[0024] Figure 6 This is a schematic diagram of the boundary condition settings for steady-state structure simulation according to an embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] like Figure 1 As shown, in conjunction with embodiments of the present invention, a method for simulating a heat-resistant structure is provided, comprising:

[0027] Step 1: Based on the obtained structural dimensions and material properties of the heat-resistant structure, construct the initial geometric model of the heat-resistant structure, and mesh the initial geometric model to obtain the initial finite element model. The initial geometric model represents the physical shape and size model of the heat-resistant structure. The mesh is the discretization of the continuous initial geometric model into multiple small, simple and discontinuous elements.

[0028] Step 2: At each current time step, apply boundary conditions to the current finite element model and perform a force-thermal coupling simulation on the current finite element model to obtain the coupling simulation results for the current time step. In the first time step, the current finite element model refers to the initial finite element model. From the second time step onwards, the current finite element model refers to the updated finite element model obtained at the end of the force-thermal coupling simulation of the previous time step.

[0029] Step 3: Based on the coupling simulation results of the current time step, update the current geometric model to obtain the updated geometric model. Mesh the updated geometric model to obtain the updated finite element model. In the first time step, the current geometric model refers to the initial geometric model. From the second time step onwards, the current geometric model refers to the updated geometric model obtained at the end of the force-thermal coupling simulation of the previous time step.

[0030] Update the next time step to the current time step, and execute steps 2 and 3 in sequence. In step 2, apply the coupled simulation results of the current time step as boundary conditions to the updated finite element model until the simulation is completed for all time steps.

[0031] The force-thermal coupling simulation includes transient thermal simulation and steady-state structural simulation. Transient thermal simulation simulates the temperature field of the heat-resistant structure, allowing the steady-state structural simulation to account for thermal strain caused by temperature. Steady-state structural simulation simulates the stress and strain of the heat-resistant structure, ensuring that the next transient thermal simulation will also consider these stresses and strains. This achieves force-thermal coupling simulation, which more closely approximates the actual operating environment of the heat-resistant structure, thus improving the accuracy of the simulation and facilitating the selection of a more scientifically sound and reasonable design scheme. Preferably, the heat-resistant structure is a flexible heat-resistant structure.

[0032] Preferably, step 2 involves performing a force-thermal coupling simulation on the current finite element model at each current time step to obtain the coupling simulation results for the current time step, including:

[0033] Step 21: At each current time step, perform force-thermal coupling simulation using the first force-thermal coupling simulation method; wherein, step 21 includes:

[0034] Step 21-1: In each current time step, within the time period corresponding to the current time step, since the heat shield structure is located below the tail of the rocket engine, the heat flow conditions of the rocket engine exhaust flame, the heat radiation inside and outside the tail section where the rocket engine is located, and the convective heat are applied as boundary conditions to the current finite element model to perform transient temperature simulation and obtain the temperature field of the heat shield structure changing with time in the current time step; where, in the first time step, the heat flow condition refers to the launch environment temperature of the rocket engine tail, and in each current time step from the second time step onwards, the heat flow condition refers to the temperature field changing with time obtained from the force-thermal coupling simulation of the previous time step;

[0035] Step 21-2: Update the current geometric model to obtain an intermediate geometric model, then mesh the intermediate geometric model to obtain an intermediate finite element model; for example... Figure 5 As shown, (a) represents the current geometric model before the nth transient thermal simulation, the black area in (b) represents the part of the heat protection structure that was burned off at the end of the nth transient thermal simulation, and (c) represents the intermediate geometric model obtained by updating the current geometric model, that is, after removing the burned area on the heat protection structure (i.e., the black area in (b)).

[0036] Step 21-3: At the end of the current time step, construct boundary conditions based on the pressure of the tail section where the rocket engine is located, the rocket engine sway angle, the fixed boundary, and the temperature field of the heat shield structure during the current time step. Apply these boundary conditions to the intermediate finite element model to perform steady-state structural simulation and obtain the stress and strain distribution of the heat shield structure at the end of the current time step. Use the stress and strain distribution of the heat shield structure at the end of the current time step as the coupled simulation result of the current time step.

[0037] At each time step, the temperature field of the heat-resistant structure is first simulated through transient thermal simulation, so that the steady-state structural simulation can take into account the thermal strain caused by temperature. The stress and strain of the heat-resistant structure are then simulated through steady-state structural simulation, so that the transient thermal simulation of the next time step can take into account the stress and strain of the heat-resistant structure. Through the temperature field transfer and geometric model update between transient thermal simulation and steady-state structural simulation, the simulation boundary conditions are made closer to the actual working state of the heat-resistant skirt.

[0038] Preferably, step 21 further includes:

[0039] Step 21-4: After step 21-1, based on the change of the temperature field of the heat-resistant structure with time in the current time step, determine whether the temperature of the heat-resistant structure exceeds the ignition point of the material of the heat-resistant structure; the ignition point of the material is the critical temperature at which the material undergoes ablation.

[0040] Step 21-5: If the temperature of the heat-resistant structure exceeds the ignition point of the heat-resistant structure material, calculate the ablation retreat in the thickness direction of the heat-resistant structure according to the local temperature change and ablation rate of the heat-resistant structure, and calculate the scorched area corresponding to the ablation retreat.

[0041] Step 21-6: If the ablation retreat is greater than the ablation thickness threshold and the proportion of the burned area is greater than the burned area proportion threshold, it is determined that the heat protection structure has been burned through, and the force-thermal coupling simulation is stopped. After stopping the force-thermal coupling simulation, the designer should evaluate the ablation situation. If the material is burned through and cannot be used, subsequent simulations are unnecessary. It is recommended to modify the heat protection structure, such as increasing the thickness, and start a new round of simulation. Otherwise, proceed with steps 21-2 and 21-7.

[0042] Step 21-2 includes: after removing the scorched area on the heat-resistant structure from the current geometric model, updating the current geometric model to obtain an intermediate geometric model;

[0043] Steps 21-4, 21-5, 21-6, and 21-2 can yield a heat-resistant structure that is closer to reality.

[0044] Step 22 also includes:

[0045] Step 21-7: Set the edge temperature of the ablation area to the ignition point temperature to update the temperature field obtained in Step 21-1 over time. From the physical process of ablation, ablation occurs once the temperature of the heat-resistant structure exceeds the ignition point. Energy is continuously consumed during ablation, and the ablated surface remains at the ignition point temperature. Therefore, it is necessary to update the temperature field obtained from the transient thermal simulation by setting the ablation edge to the ignition point temperature, which will more closely approximate the real temperature field. Figure 5 In (c), the temperature at the thick black line is updated to the temperature of the ignition point.

[0046] Preferably, in steps 21-3, the pressure in the tail section where the rocket engine is located is obtained based on the pressure difference environment within the tail section where the rocket engine is located at the end of the current time step; the connection between the outer edge of the heat-resistant structure at the fixed support boundary and the tail section support of the rocket engine; and the rocket engine swing angle are used to apply forced displacement conditions to the connection between the heat-resistant structure and the rocket engine. Figure 6 The diagram shows the boundary condition settings for steady-state structural simulation. The ring represents the heat shield structure, and the top of it is the tail section where the engine is located. In the steady-state structural simulation calculation of step n, the boundary conditions include: (1) tail section pressure conditions, such as Figure 6The middle arrow indicates the pressure in the tail section where the rocket engine is located, which is used to apply pressure load to the heat protection structure; (2) the engine swing condition, which is used to apply forced displacement to the connection between the heat protection structure and the engine based on the rocket engine swing angle at the end of the current time step. Figure 6 The dashed line in the inner ring of the circle (when the arrow engine swing angle is α, in) Figure 6 In the middle, the solid line corresponding to α is the axis of the rocket engine when it is not swinging, and the dashed line is the axis of the rocket engine after it swings. If the distance between the mounting surface of the heat protection structure and the origin of the swing is L, then the calculation method of the forced displacement dx is: dx = Lsinα); (3) The temperature field of the heat protection structure, the change of the temperature field obtained by the transient temperature simulation with time is used as the boundary condition of the steady-state structure simulation; that is, the temperature field is used as the input to calculate the thermal strain. Taking the one-dimensional form as an example, the thermal strain The calculation formula is ,in is the linear expansion coefficient of the material, with the unit being [1 / K]. From this, we can intuitively understand the influence of the structural temperature field on the stress and strain of the structure; (4) Fixed boundary conditions, the outer edge of the heat-resistant structure is fixed to the tail cabin support by bolts and pressure plates, such as Figure 6 The solid line of the outer ring in the middle, therefore the connection between the heat protection structure and the tail section support is set as a fixed support boundary condition.

[0047] Preferably, step 21 further includes:

[0048] Step 21-8: After step 21-3, based on the stress distribution and strain distribution of the heat-resistant structure at the end of the current time step, determine whether the heat-resistant structure has failed.

[0049] Steps 21-9: If the stress in the heat-resistant structure exceeds the preset area ratio (e.g., 10%), it is determined that the heat-resistant structure has torn and failed, and the force-thermal coupling simulation is stopped; otherwise, proceed to step 3. When proceeding to step 3, if the position of the connection with the flange is displaced due to the engine swing angle, or if the heat-resistant structure expands when the pressure inside the tail compartment is higher than the external environmental pressure, the current geometric model needs to be updated, and the updated geometric model needs to be meshed to obtain the updated finite element model.

[0050] Preferably, step 2 involves performing a force-thermal coupling simulation on the current finite element model at each current time step to obtain the coupling simulation results for the current time step, including:

[0051] Step 22: At each current time step, perform force-thermal coupling simulation using the second force-thermal coupling simulation method; wherein, step 22 includes:

[0052] Step 22-1: At the beginning of each current time step, construct boundary conditions based on the pressure of the tail section where the rocket engine is located, the rocket engine sway angle, the fixed support boundary, and the temperature field of the heat protection structure within the current time step. Apply these conditions to the current finite element model to perform steady-state structural simulation and obtain the stress and strain distribution of the heat protection structure at the beginning of the current time step.

[0053] Step 22-2: Update the current geometric model to obtain an intermediate geometric model, then mesh the intermediate geometric model to obtain an intermediate finite element model; for example... Figure 5 As shown, (a) represents the current geometric model before the nth transient thermal simulation, the black area in (b) represents the part of the heat protection structure that was burned off at the end of the nth transient thermal simulation, and (c) represents the intermediate geometric model obtained by updating the current geometric model, that is, after removing the burned area on the heat protection structure (i.e., the black area in (b)).

[0054] Step 22-3: In the time period corresponding to the current time step, apply the heat flow conditions of the rocket engine exhaust flame, the heat radiation inside and outside the tail section where the rocket engine is located, and the convective heat as boundary conditions to the intermediate finite element model to perform transient temperature simulation and obtain the temperature field of the heat shield structure changing with time in the current time step; take the temperature field of the heat shield structure changing with time in the current time step as the coupled simulation result of the current time step; where, in the first time step, the heat flow condition refers to the launch environment temperature of the rocket engine tail, and in each current time step from the second time step onwards, the heat flow condition refers to the temperature field changing with time obtained from the mechanical-thermal coupled simulation of the previous time step.

[0055] At each time step, the stress and strain of the heat-resistant structure are first simulated through steady-state structural simulation, so that the transient thermal simulation can take into account the stress and strain of the heat-resistant structure. Then, the temperature field of the heat-resistant structure is simulated through transient thermal simulation, so that the steady-state structural simulation at the next time step can take into account the thermal strain caused by temperature. Through the transfer of temperature field and updating of geometric model between transient thermal simulation and steady-state structural simulation, the simulation boundary conditions are made closer to the actual working state of the heat-resistant skirt.

[0056] Preferably, in step 22-1, the pressure in the tail section where the rocket engine is located is obtained based on the pressure difference environment within the tail section where the rocket engine is located at the end of the current time step; the connection between the outer edge of the heat-resistant structure at the fixed support boundary and the tail section support of the rocket engine; and the rocket engine swing angle are used to apply forced displacement conditions to the connection between the heat-resistant structure and the rocket engine. Figure 6The diagram shows the boundary condition settings for steady-state structural simulation. The ring represents the heat shield structure, and the top of it is the tail section where the engine is located. In the steady-state structural simulation calculation of step n, the boundary conditions include: (1) tail section pressure conditions, such as Figure 6 The middle arrow indicates the pressure in the tail section where the rocket engine is located, which is used to apply pressure load to the heat protection structure; (2) the engine swing condition, which is used to apply forced displacement to the connection between the heat protection structure and the engine based on the rocket engine swing angle at the end of the current time step. Figure 6 The dashed line in the inner ring of the circle (when the arrow engine swing angle is α, in) Figure 6 In the middle, the solid line corresponding to α is the axis of the rocket engine when it is not swinging, and the dashed line is the axis of the rocket engine after it swings. If the distance between the mounting surface of the heat protection structure and the origin of the swing is L, then the calculation method of the forced displacement dx is: dx = Lsinα); (3) The temperature field of the heat protection structure, the change of the temperature field obtained by the transient temperature simulation with time is used as the boundary condition of the steady-state structure simulation; that is, the temperature field is used as the input to calculate the thermal strain. Taking the one-dimensional form as an example, the thermal strain The calculation formula is ,in is the linear expansion coefficient of the material, with the unit being [1 / K]. From this, we can intuitively understand the influence of the structural temperature field on the stress and strain of the structure; (4) Fixed boundary conditions, the outer edge of the heat-resistant structure is fixed to the tail cabin support by bolts and pressure plates, such as Figure 6 The solid line of the outer ring in the middle, therefore the connection between the heat protection structure and the tail section support is set as a fixed support boundary condition.

[0057] Preferably, step 22 further includes:

[0058] Step 22-4: After step 22-1, based on the stress distribution and strain distribution of the heat-resistant structure at the beginning of the current time step, determine whether the heat-resistant structure has failed.

[0059] Step 22-5: If the stress in the heat-resistant structure that exceeds the preset area ratio is greater than the tensile limit strength, it is determined that the heat-resistant structure has torn and failed, and the force-thermal coupling simulation is stopped; otherwise, proceed to step 22-2. When proceeding to step 22-2, for example, if the position of the connection with the flange is displaced due to the engine swing angle, or if the heat-resistant structure expands when the pressure inside the tail compartment is higher than the pressure outside the compartment, the current geometric model needs to be updated to obtain an intermediate geometric model, and the intermediate geometric model is meshed to obtain an intermediate finite element model.

[0060] Preferably, step 22 further includes:

[0061] Step 22-6: After step 22-3, based on the change of the temperature field of the heat-resistant structure over time in the current time step, determine whether the temperature of the heat-resistant structure exceeds the ignition point of the material of the heat-resistant structure;

[0062] Step 22-7: If the temperature of the heat-resistant structure exceeds the ignition point of the heat-resistant structure material, calculate the ablation retreat in the thickness direction of the heat-resistant structure according to the local temperature change and ablation rate of the heat-resistant structure, and calculate the scorched area corresponding to the ablation retreat.

[0063] Step 22-8: If the ablation retreat is greater than the ablation thickness threshold and the proportion of the burned area is greater than the burning area proportion threshold, it is determined that the heat protection structure has been burned through, and the mechanical-thermal coupling simulation is stopped; otherwise, proceed to step 3.

[0064] Step 3 includes: after removing the scorched area on the heat-resistant structure from the current geometric model, updating the intermediate geometric model to obtain the updated geometric model;

[0065] Step 22 also includes:

[0066] Step 22-9: Set the edge temperature of the ablation area to the temperature of the ignition point to update the temperature field obtained in step 22-3 over time.

[0067] Steps 22-6, 22-7, 22-8, and 22-9 can yield a more realistic heat-resistant structure.

[0068] like Figure 2 As shown, in conjunction with an embodiment of the present invention, a thermal protection structure simulation system is provided, comprising:

[0069] Model building unit 101 is used to build an initial geometric model of the heat-resistant structure based on the obtained structural dimensions and material properties of the heat-resistant structure, and to mesh the initial geometric model to obtain an initial finite element model.

[0070] The coupled simulation unit 102 is used to apply boundary conditions to the current finite element model at each current time step, perform force-thermal coupled simulation on the current finite element model, and obtain the coupled simulation result of the current time step; wherein, when the first time step is the current time step, the current finite element model refers to the initial finite element model; and in each current time step from the second time step onwards, the current finite element model refers to the updated finite element model obtained at the end of the force-thermal coupled simulation of the previous time step.

[0071] The model update unit 103 is used to update the current geometric model based on the coupling simulation results of the current time step to obtain an updated geometric model, and to mesh the updated geometric model to obtain an updated finite element model. In the first time step, the current geometric model refers to the initial geometric model. From the second time step onwards, the current geometric model refers to the updated geometric model obtained at the end of the force-thermal coupling simulation of the previous time step.

[0072] The next time step is updated to the current time step, and the coupled simulation unit 102 and the model update unit 103 are executed sequentially. In the coupled simulation unit 102, the coupled simulation result of the current time step is applied as a boundary condition to the updated finite element model until the simulation is completed for all time steps.

[0073] Among them, the force-thermal coupling simulation includes transient thermal simulation and steady-state structural simulation. By performing thermal simulation, i.e., transient thermal simulation, the temperature field of the heat-resistant structure is simulated, so that the force simulation, i.e. steady-state structural simulation, can take into account the thermal strain caused by heat. By simulating the stress and strain of the heat-resistant structure through steady-state structural simulation, the stress and strain of the heat-resistant structure can be taken into account in the next transient thermal simulation. This achieves force-thermal coupling simulation. Through force-thermal coupling simulation, the actual use environment of the heat-resistant structure can be more closely approximated, thus improving the accuracy of the heat-resistant structure simulation and facilitating the selection of a more scientific and reasonable design scheme for the heat-resistant structure.

[0074] Preferably, the coupled simulation unit 102 includes:

[0075] The first force-thermal coupling simulation subunit is used to perform force-thermal coupling simulation using the first force-thermal coupling simulation method at each current time step.

[0076] The first force-thermal coupling simulation subunit is specifically used for:

[0077] The first transient temperature simulation module is used to apply the heat flow conditions of the rocket engine exhaust flame, the heat radiation inside and outside the tail section where the rocket engine is located, and the convective heat as boundary conditions to the current finite element model at each current time step and within the time period corresponding to the current time step, to perform transient temperature simulation and obtain the temperature field of the heat shield structure changing with time in the current time step; where, when the first time step is the current time step, the heat flow condition refers to the launch environment temperature of the rocket engine tail section, and in each current time step from the second time step onwards, the heat flow condition refers to the temperature field change with time obtained from the force-thermal coupling simulation of the previous time step;

[0078] The first model update module is used to update the current geometric model to obtain an intermediate geometric model, and then mesh the intermediate geometric model to obtain an intermediate finite element model; for example... Figure 5As shown, (a) represents the current geometric model before the nth transient thermal simulation, the black area in (b) represents the part of the heat protection structure that was burned off at the end of the nth transient thermal simulation, and (c) represents the intermediate geometric model obtained by updating the current geometric model, that is, after removing the burned area on the heat protection structure (i.e., the black area in (b)).

[0079] The first steady-state structure simulation module is used to construct boundary conditions at the end of the current time step based on the pressure of the tail section where the rocket engine is located, the rocket engine sway angle, the fixed boundary, and the temperature field of the heat shield structure changing with time within the current time step. These boundary conditions are then applied to the intermediate finite element model to perform steady-state structure simulation, obtaining the stress and strain distribution of the heat shield structure at the end of the current time step. The stress and strain distribution of the heat shield structure at the end of the current time step are used as the coupled simulation results for the current time step.

[0080] At each time step, the temperature field of the heat-resistant structure is first simulated through transient thermal simulation, so that the steady-state structural simulation can take into account the thermal strain caused by temperature. The stress and strain of the heat-resistant structure are then simulated through steady-state structural simulation, so that the transient thermal simulation of the next time step can take into account the stress and strain of the heat-resistant structure. Through the temperature field transfer and geometric model update between transient thermal simulation and steady-state structural simulation, the simulation boundary conditions are made closer to the actual working state of the heat-resistant skirt.

[0081] Preferably, the first force-thermal coupling simulation subunit further includes:

[0082] The first temperature judgment module is used to determine whether the temperature of the heat protection structure exceeds the ignition point of the heat protection structure material based on the change of the temperature field of the heat protection structure over time in the current time step.

[0083] The first ablation retreat calculation module is used to calculate the ablation retreat in the thickness direction of the heat-resistant structure if the temperature of the heat-resistant structure exceeds the ignition point of the material. It also calculates the scorched area corresponding to the ablation retreat. Typically, the ablation temperature Ta [K] and the linear ablation rate k [mm / s] are used to evaluate the ablation retreat. For example, if the temperature at a certain point on the heat-resistant structure reaches the ablation temperature Ta during the time period t1~t2, the calculated ablation retreat Δs is: .

[0084] The first burn-out judgment module is used to determine that the heat protection structure has been burned through and cannot continue to be used if the ablation retreat is greater than the ablation thickness threshold and the proportion of the burned area is greater than the burned area proportion threshold (e.g., 20%). In this case, the force-thermal coupling simulation is stopped. After the force-thermal coupling simulation is stopped, the designer shall evaluate the ablation situation. If the material is burned through and cannot continue to be used, no further simulation is required. It is recommended to modify the heat protection structure, such as increasing the thickness, and to carry out a new round of simulation. Otherwise, the relevant operations are performed through the first model update module and the first temperature update module.

[0085] The first model update module is specifically used to update the current geometric model after removing the scorched area on the heat-resistant structure, so as to obtain an intermediate geometric model.

[0086] By performing the above-mentioned module operations, a heat protection structure that is closer to reality can be obtained.

[0087] The first force-thermal coupling simulation subunit also includes:

[0088] The first temperature update module sets the edge temperature of the ablation area to the ignition point temperature to update the temperature field obtained from the first transient temperature simulation module over time. From the physical process of ablation, ablation occurs once the temperature of the heat-resistant structure exceeds the ignition point. Energy is continuously consumed during ablation, and the ablated surface remains at the ignition point temperature. Therefore, updating the temperature field obtained from the transient thermal simulation by setting the ablation edge to the ignition point temperature more closely approximates the real temperature field. Figure 5 In (c), the temperature at the thick black line is updated to the temperature of the ignition point.

[0089] Preferably, in the first steady-state structure simulation module, the pressure of the tail section where the rocket engine is located is obtained based on the pressure difference environment of the tail section where the rocket engine is located at the end of the current time step; the connection between the outer edge of the heat-resistant structure and the tail section support of the rocket engine is set at the fixed support boundary; the rocket engine swing angle is used to apply forced displacement conditions to the connection between the heat-resistant structure and the rocket engine. Figure 6 The diagram shows the boundary condition settings for steady-state structural simulation. The ring represents the heat shield structure, and the top of it is the tail section where the engine is located. In the steady-state structural simulation calculation of step n, the boundary conditions include: (1) tail section pressure conditions, such as Figure 6 The middle arrow indicates the pressure in the tail section where the rocket engine is located, which is used to apply pressure load to the heat protection structure; (2) the engine swing condition, which is used to apply forced displacement to the connection between the heat protection structure and the engine based on the rocket engine swing angle at the end of the current time step. Figure 6 The dashed line in the inner ring of the circle (when the arrow engine swing angle is α, in) Figure 6In the middle, the solid line corresponding to α is the axis of the rocket engine when it is not swinging, and the dashed line is the axis of the rocket engine after it swings. If the distance between the mounting surface of the heat protection structure and the origin of the swing is L, then the calculation method of the forced displacement dx is: dx = Lsinα); (3) The temperature field of the heat protection structure, the change of the temperature field obtained by the transient temperature simulation with time is used as the boundary condition of the steady-state structure simulation; that is, the temperature field is used as the input to calculate the thermal strain. Taking the one-dimensional form as an example, the thermal strain The calculation formula is ,in is the linear expansion coefficient of the material, with the unit being [1 / K]. From this, we can intuitively understand the influence of the structural temperature field on the stress and strain of the structure; (4) Fixed boundary conditions, the outer edge of the heat-resistant structure is fixed to the tail cabin support by bolts and pressure plates, such as Figure 6 The solid line of the outer ring in the middle, therefore the connection between the heat protection structure and the tail section support is set as a fixed support boundary condition.

[0090] Preferably, the first force-thermal coupling simulation subunit further includes:

[0091] The first failure judgment module is used to determine whether the heat protection structure has failed based on the stress and strain distribution of the heat protection structure at the end of the current time step. If the stress of the heat protection structure exceeds the tensile limit strength in more than a preset area percentage (e.g., 10%), it is determined that the heat protection structure has failed due to tearing, and the force-thermal coupling simulation is stopped. Otherwise, the model update unit 103 is used to perform related operations, such as displacement of the connection position with the flange due to the engine swing angle, or expansion of the heat protection structure when the pressure inside the tail compartment is higher than the external environmental pressure. In all these cases, the current geometric model needs to be updated, and the updated geometric model is meshed to obtain the updated finite element model.

[0092] The coupled simulation unit 102 also includes:

[0093] The second force-thermal coupling simulation subunit is used to perform force-thermal coupling simulation using a second force-thermal coupling simulation method at each current time step; wherein, the second force-thermal coupling simulation subunit includes:

[0094] The second steady-state structure simulation module is used to construct boundary conditions at the beginning of each current time step based on the pressure of the tail section where the rocket engine is located, the rocket engine sway angle, the fixed support boundary, and the temperature field of the heat protection structure within the current time step. These boundary conditions are then applied to the current finite element model to perform steady-state structure simulation, thereby obtaining the stress and strain distribution of the heat protection structure at the beginning of the current time step.

[0095] The second model update module is used to update the current geometric model to obtain an intermediate geometric model, and then mesh the intermediate geometric model to obtain an intermediate finite element model; for example... Figure 5 As shown, (a) represents the current geometric model before the nth transient thermal simulation, and the black area in (b) represents the part of the heat protection structure that was burned off at the end of the nth transient thermal simulation. (c) represents the intermediate geometric model obtained by updating the current geometric model, that is, after removing the burned area on the heat protection structure (i.e., the black area in (b)).

[0096] The second transient temperature simulation module is used to apply the heat flow conditions of the rocket engine exhaust flame, the thermal radiation inside and outside the tail section where the rocket engine is located, and the convective heat as boundary conditions to the intermediate finite element model during the time period corresponding to the current time step, and to perform transient temperature simulation to obtain the temperature field of the heat shield structure changing with time in the current time step. The change of the temperature field of the heat shield structure with time in the current time step is used as the coupled simulation result of the current time step. Among them, when the first time step is the current time step, the heat flow condition refers to the launch environment temperature of the rocket engine tail. From the second time step onwards, the heat flow condition refers to the change of the temperature field obtained from the mechanical-thermal coupled simulation of the previous time step with time.

[0097] At each time step, the stress and strain of the heat-resistant structure are first simulated through steady-state structural simulation, so that the transient thermal simulation can take into account the stress and strain of the heat-resistant structure. Then, the temperature field of the heat-resistant structure is simulated through transient thermal simulation, so that the steady-state structural simulation at the next time step can take into account the thermal strain caused by temperature. Through the transfer of temperature field and updating of geometric model between transient thermal simulation and steady-state structural simulation, the simulation boundary conditions are made closer to the actual working state of the heat-resistant skirt.

[0098] Preferably, in the second steady-state structure simulation module, the pressure of the tail section where the rocket engine is located is obtained based on the pressure difference environment of the tail section where the rocket engine is located at the end of the current time step; the connection between the outer edge of the heat-resistant structure and the tail section support of the rocket engine is set at the fixed support boundary; the rocket engine swing angle is used to apply forced displacement conditions to the connection between the heat-resistant structure and the rocket engine. Figure 6 The diagram shows the boundary condition settings for steady-state structural simulation. The ring represents the heat shield structure, and the top of it is the tail section where the engine is located. In the steady-state structural simulation calculation of step n, the boundary conditions include: (1) tail section pressure conditions, such as Figure 6 The middle arrow indicates the pressure in the tail section where the rocket engine is located, which is used to apply pressure load to the heat protection structure; (2) the engine swing condition, which is used to apply forced displacement to the connection between the heat protection structure and the engine based on the rocket engine swing angle at the end of the current time step. Figure 6The dashed line in the inner ring of the circle (when the arrow engine swing angle is α, in) Figure 6 In the middle, the solid line corresponding to α is the axis of the rocket engine when it is not swinging, and the dashed line is the axis of the rocket engine after it swings. If the distance between the mounting surface of the heat protection structure and the origin of the swing is L, then the calculation method of the forced displacement dx is: dx = Lsinα); (3) The temperature field of the heat protection structure, the change of the temperature field obtained by the transient temperature simulation with time is used as the boundary condition of the steady-state structure simulation; that is, the temperature field is used as the input to calculate the thermal strain. Taking the one-dimensional form as an example, the thermal strain The calculation formula is ,in is the linear expansion coefficient of the material, with the unit being [1 / K]. From this, we can intuitively understand the influence of the structural temperature field on the stress and strain of the structure; (4) Fixed boundary conditions, the outer edge of the heat-resistant structure is fixed to the tail cabin support by bolts and pressure plates, such as Figure 6 The solid line of the outer ring in the middle, therefore the connection between the heat protection structure and the tail section support is set as a fixed support boundary condition.

[0099] Preferably, the second force-thermal coupling simulation subunit further includes:

[0100] The second failure judgment module is used to determine whether the heat protection structure has failed based on the stress and strain distribution of the heat protection structure at the start of the current time step. If the stress of the heat protection structure exceeding the preset area ratio is greater than the tensile limit strength, it is determined that the heat protection structure has failed due to tearing, and the force-thermal coupling simulation is stopped. Otherwise, the second model update module is used to perform relevant operations, such as displacement of the connection position with the flange due to the engine swing angle, or expansion of the heat protection structure when the pressure inside the tail compartment is higher than the external environmental pressure. In these cases, the current geometric model needs to be updated to obtain an intermediate geometric model, and the intermediate geometric model is meshed to obtain an intermediate finite element model.

[0101] Preferably, the second force-thermal coupling simulation subunit further includes:

[0102] The second temperature judgment module is used to determine whether the temperature of the heat-resistant structure exceeds the ignition point of the heat-resistant structure material based on the change of the temperature field of the heat-resistant structure over time in the current time step.

[0103] The second ablation retreat calculation module is used to calculate the ablation retreat in the thickness direction of the heat protection structure according to the local temperature change and ablation rate of the heat protection structure if the temperature of the heat protection structure exceeds the ignition point of the material of the heat protection structure, and to calculate the scorched area corresponding to the ablation retreat.

[0104] The second burn-out judgment module is used to determine that the heat protection structure has been burned through if the ablation retreat amount is greater than the ablation thickness threshold and the proportion of the burned area is greater than the burned area proportion threshold, and to stop the force-thermal coupling simulation; otherwise, the model update unit 103 is used to perform related operations.

[0105] The model update unit 103 is specifically used to update the intermediate geometric model after removing the scorched area on the heat-resistant structure from the current geometric model, so as to obtain the updated geometric model.

[0106] The second force-thermal coupling simulation subunit also includes:

[0107] The second temperature update module is used to set the edge temperature of the ablation area to the temperature of the ignition point in order to update the temperature field obtained in the second transient temperature simulation module over time.

[0108] The above modules enable the creation of a more realistic heat-resistant structure.

[0109] Figure 3 This is a simplified flowchart for the first type of force-thermal coupling simulation. Boundary conditions are applied. In each time step of the thermal coupling simulation, transient thermal simulation is performed first, followed by steady-state structural simulation. Then, it is determined whether the thermal protection structure has failed. If it has failed, the simulation ends; if it has not failed, it is determined whether the total duration requirement is met. If yes, the simulation ends; otherwise, the force-thermal coupling simulation proceeds to the next time step.

[0110] Figure 4 The flowchart for force-thermal coupling simulation using the first force-thermal coupling simulation method is as follows:

[0111] First, construct the initial geometric model.

[0112] Based on the structural dimensions and material properties of the heat shield structure located outside the rocket engine's tail section, an initial geometric model of the heat shield structure is constructed. The material properties include at least one of the following: material density or equivalent density, thermal conductivity, specific heat capacity, Poisson's ratio, and elastic modulus. Simultaneously, the operating environment of the heat shield structure during flight is determined, including the heat flux caused by the engine exhaust, the pressure in the tail section, and the engine oscillation angle; all of these conditions change over time.

[0113] Second, construct the initial finite element model.

[0114] The initial geometric model is meshed to obtain the initial finite element model.

[0115] Third, apply boundary conditions, and perform transient thermal simulation in step n.

[0116] Set the total simulation duration T. 仿真(Time), in seconds (s), represents the total time required for simulation analysis. It is given according to the actual flight process and can be the time length of the entire first-level flight segment or the time length of the flight time interval of focus.

[0117] Set the time step Δt, in seconds (s). Δt is the time interval between one force-thermal coupling simulation and one "transient thermal simulation - steady-state structural simulation." It can be set according to actual needs; it can be a constant value, meaning one coupling simulation is performed at equal intervals of Δt, or it can be a time-dependent variable, i.e., Δt = f(t), where t is the moment corresponding to the flight process. Δt and T 仿真 The relationship is: .

[0118] Transient temperature simulation is performed first, followed by steady-state structural simulation. For example, if the total duration of the first-stage flight segment is 100 seconds, 10 simulations are performed at equal intervals, with a data transfer interval of 10 seconds.

[0119] The time step for the first transient thermal simulation is 0~10s, the time step for the second transient thermal simulation is 10~20s, and so on.

[0120] After the first step of transient thermal simulation is completed, the temperature change within the time interval 0 to Δt is obtained. After the nth step of transient thermal simulation is completed after the first step, the temperature field within the time interval (n-1)Δt to nΔts is obtained.

[0121] Fourth, determine whether ablation has occurred. If not, proceed directly to step n, steady-state structural simulation. If yes, determine whether the heat-resistant material has ablated (i.e., whether the material has ablated). If yes, the simulation ends.

[0122] Fifth, if not, determine whether the material has burned. If yes, the simulation ends; if no, calculate the ablation retreat Δs, update the current geometric model and temperature field, and update the finite element model.

[0123] Sixth, step n: steady-state structural simulation

[0124] The pressure in the tail section where the rocket engine is located, the rocket engine's sway angle, the fixed boundary, and the temperature field changes over time in the nth step transient thermal simulation are used to construct boundary conditions. These boundary conditions are applied to the intermediate finite element model, and the nth step steady-state structural simulation is performed to obtain the simulation results at time nΔt, which is the stress and strain distribution of the thermal protection structure at the end of the current time step.

[0125] Seventh, determine whether the heat protection structure has failed (i.e., whether the structure has completely failed). If so, the simulation ends.

[0126] Eighth, if not, calculate whether the total duration meets the requirements; if yes, the simulation ends.

[0127] Ninth, if not, update the current geometric model and the current finite element model, update step n to step n+1: n=n+1, and continue to execute the transient thermal simulation of step n to perform the next round of force-thermal coupling simulation.

[0128] The beneficial technical effects achieved by the embodiments of the present invention are as follows:

[0129] In existing technologies, the mechanical and thermal protection properties of heat-resistant structures are usually simulated using a decoupled method. That is, mechanical simulation does not consider thermal stress or ablation effects, while thermal protection simulation only considers thermal insulation performance and ablation retreat. This method differs significantly from the actual usage environment, and therefore the simulation results may not accurately assess the actual effectiveness of the heat-resistant structure.

[0130] In this embodiment of the invention, the temperature field of the heat-resistant structure is simulated through transient thermal simulation, enabling the steady-state structure simulation to account for the thermal strain caused by temperature. The stress and strain of the heat-resistant structure are simulated through steady-state structure simulation, allowing the next transient thermal simulation to take into account the stress and strain of the heat-resistant structure. Through temperature transfer and geometric model updates between transient thermal simulation and steady-state structure simulation, force-thermal coupling simulation is achieved. This force-thermal coupling simulation can more closely approximate the actual usage environment of the heat-resistant structure, thus improving the accuracy of the heat-resistant structure simulation and facilitating the selection of a more scientific and reasonable design scheme for the heat-resistant structure.

[0131] The simulation method of this invention can more accurately assess the margin of the heat protection structure, facilitate the rational selection of the thickness and material of the heat protection structure, realize the fine design of the heat protection structure, and help reduce the weight of the structure.

[0132] The method described in this invention has been applied to the verification of the thermal protection structure of our company's launch vehicles, enabling the assessment of the safety margin in the design of the thermal protection structure and the determination of the location of potential damage points. The simulation results are consistent with the trends of our company's experimental conclusions, and the assessment of risk locations is close to the experimental results. Using the method described in this invention for verification in subsequent thermal protection structure designs can save on experimental costs.

[0133] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0134] In the above detailed description, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features of the single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, wherein each claim stands alone as a preferred embodiment of the invention.

[0135] The disclosed embodiments have been described above to enable any person skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit and scope of this disclosure. Therefore, this disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0136] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as interpreted when used as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

[0137] Those skilled in the art will also understand that the various illustrative logical blocks, units, and steps listed in the embodiments of the present invention can be implemented by electronic hardware, computer software, or a combination of both. To clearly demonstrate the interchangeability of hardware and software, the functions of the various illustrative components, units, and steps described above have been generally described. Whether such functionality is implemented through hardware or software depends on the specific application and the overall system design requirements. Those skilled in the art can implement the described functions using various methods for each specific application, but such implementation should not be construed as exceeding the scope of protection of the embodiments of the present invention.

[0138] The various illustrative logic blocks or units described in the embodiments of this invention can be implemented or operate the described functions using a general-purpose processor, digital signal processor, application-specific integrated circuit (ASIC), field-programmable gate array or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof. The general-purpose processor can be a microprocessor; alternatively, it can be any conventional processor, controller, microcontroller, or state machine. The processor can also be implemented using a combination of computing devices, such as a digital signal processor and a microprocessor, multiple microprocessors, one or more microprocessors combined with a digital signal processor core, or any other similar configuration.

[0139] The steps of the methods or algorithms described in the embodiments of this invention can be directly embedded in hardware, a software module executed by a processor, or a combination of both. The software module can be stored in RAM, flash memory, ROM, EPROM, EEPROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium in the art. Exemplarily, the storage medium can be connected to the processor so that the processor can read information from and write information to the storage medium. Optionally, the storage medium can also be integrated into the processor. The processor and storage medium can be housed in an ASIC, which can be housed in a user terminal. Optionally, the processor and storage medium can also be housed in different components of the user terminal.

[0140] In one or more exemplary designs, the functions described in the embodiments of the present invention can be implemented in hardware, software, firmware, or any combination of these three. If implemented in software, these functions can be stored on a computer-readable medium or transmitted on a computer-readable medium in the form of one or more instructions or code. Computer-readable media include computer storage media and communication media that facilitate the transfer of computer programs from one place to another. Storage media can be any available media that can be accessed by a general-purpose or special-purpose computer. For example, such computer-readable media can include, but is not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store program code in the form of instructions or data structures and other forms that can be read by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Furthermore, any connection can be suitably defined as a computer-readable medium, for example, if the software is transmitted from a website, server, or other remote resource via a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wirelessly, such as infrared, wireless, and microwave, it is also included in the defined computer-readable medium. The disks and discs mentioned include compressed disks, laser discs, optical discs, DVDs, floppy disks, and Blu-ray discs. Disks typically copy data magnetically, while discs typically copy data optically using lasers. Combinations of the above can also be contained in computer-readable media.

[0141] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for simulating a heat-resistant structure, characterized in that, include: Step 1: Based on the obtained structural dimensions and material properties of the heat-resistant structure, construct the initial geometric model of the heat-resistant structure, and mesh the initial geometric model to obtain the initial finite element model; Step 2: At each current time step, apply boundary conditions to the current finite element model and perform a force-thermal coupling simulation on the current finite element model to obtain the coupling simulation results for the current time step. Wherein, when the first time step is the current time step, the current finite element model refers to the initial finite element model; from the second time step onwards, at each current time step, the current finite element model refers to the updated finite element model obtained at the end of the force-thermal coupling simulation of the previous time step. Step 3: Based on the coupling simulation results of the current time step, update the current geometric model to obtain an updated geometric model, and mesh the updated geometric model to obtain an updated finite element model; wherein, when the first time step is the current time step, the current geometric model refers to the initial geometric model, and in each current time step from the second time step onwards, the current geometric model refers to the updated geometric model obtained at the end of the force-thermal coupling simulation of the previous time step. Update the next time step to the current time step, and execute steps 2 and 3 in sequence. In step 2, the coupled simulation result of the current time step is applied to the updated finite element model as the boundary condition until the simulation is completed for all time steps. Step 2: At each current time step, apply boundary conditions to the current finite element model and perform a force-thermal coupling simulation on the current finite element model to obtain the coupling simulation results for the current time step, including: Step 21: At each current time step, perform force-thermal coupling simulation using the first force-thermal coupling simulation method; wherein, step 21 includes: Step 21-1: At each current time step, within the time period corresponding to the current time step, the heat flow conditions of the rocket engine exhaust flame, the heat radiation inside and outside the tail section where the rocket engine is located, and the convective heat are applied as boundary conditions to the current finite element model to perform transient temperature simulation and obtain the temperature field of the heat protection structure changing with time in the current time step; wherein, when the first time step is the current time step, the heat flow condition refers to the launch environment temperature of the rocket engine tail section, and at each current time step from the second time step onwards, the heat flow condition refers to the temperature field changing with time obtained from the mechanical-thermal coupling simulation of the previous time step; Step 21-2: Update the current geometric model to obtain an intermediate geometric model, and mesh the intermediate geometric model to obtain an intermediate finite element model; Step 21-3: At the end of the current time step, construct boundary conditions based on the pressure of the tail section where the rocket engine is located, the rocket engine sway angle, the fixed boundary, and the temperature field of the heat shield structure during the current time step. Apply these boundary conditions to the intermediate finite element model to perform steady-state structural simulation and obtain the stress and strain distribution of the heat shield structure at the end of the current time step. Use the stress and strain distribution of the heat shield structure at the end of the current time step as the coupled simulation result of the current time step.

2. The thermal protection structure simulation method according to claim 1, characterized in that, Step 21 also includes: Step 21-4: After step 21-1, based on the change of the temperature field of the heat-resistant structure over time in the current time step, determine whether the temperature of the heat-resistant structure exceeds the ignition point of the material of the heat-resistant structure; Step 21-5: If the temperature of the heat-resistant structure exceeds the ignition point of the material of the heat-resistant structure, calculate the ablation retreat in the thickness direction of the heat-resistant structure according to the local temperature change and ablation rate of the heat-resistant structure, and calculate the scorched area corresponding to the ablation retreat. Step 21-6: If the ablation retreat is greater than the ablation thickness threshold and the proportion of the burned area is greater than the burned area proportion threshold, it is determined that the heat protection structure has been burned through, and the mechanical-thermal coupling simulation is stopped; otherwise, steps 21-2 and 21-7 are executed. Step 21-2 further includes: after removing the scorched area on the heat-resistant structure from the current geometric model, updating the current geometric model to obtain an intermediate geometric model; Step 21 further includes: Step 21-7: Set the edge temperature of the ablation area to the temperature of the ignition point to update the temperature field obtained in step 21-1 over time.

3. The thermal protection structure simulation method according to claim 1, characterized in that, In steps 21-3, the pressure in the tail section where the rocket engine is located is obtained based on the pressure difference environment of the tail section where the rocket engine is located at the end of the current time step; the fixed support boundary is the connection between the outer edge of the heat protection structure and the tail section support of the rocket engine; the rocket engine swing angle is used to apply forced displacement conditions to the connection between the heat protection structure and the rocket engine.

4. The thermal protection structure simulation method according to claim 1, characterized in that, Step 21 also includes: Step 21-8: After step 21-3, based on the stress distribution and strain distribution of the heat protection structure at the end of the current time step, determine whether the heat protection structure has failed. Steps 21-9: If the stress in the heat-resistant structure that exceeds the preset area ratio is greater than the tensile limit strength, then it is determined that the heat-resistant structure has torn and failed, and the force-thermal coupling simulation is stopped; otherwise, proceed to step 3.

5. The thermal protection structure simulation method according to claim 1, characterized in that, Step 2: At each current time step, apply boundary conditions to the current finite element model and perform a force-thermal coupling simulation on the current finite element model to obtain the coupling simulation results for the current time step, including: Step 22: At each current time step, perform force-thermal coupling simulation using the second force-thermal coupling simulation method; wherein, step 22 includes: Step 22-1: At the beginning of each current time step, construct boundary conditions based on the pressure of the tail section where the rocket engine is located, the rocket engine sway angle, the fixed support boundary, and the temperature field of the heat protection structure within the current time step. Apply these conditions to the current finite element model to perform steady-state structural simulation and obtain the stress distribution and strain distribution of the heat protection structure at the beginning of the current time step. Step 22-2: Update the current geometric model to obtain an intermediate geometric model, and mesh the intermediate geometric model to obtain an intermediate finite element model; Step 22-3: In the time period corresponding to the current time step, the heat flow conditions of the rocket engine exhaust flame, the heat radiation inside and outside the tail section where the rocket engine is located, and the convective heat are applied as boundary conditions to the intermediate finite element model to perform transient temperature simulation, and obtain the temperature field of the heat protection structure changing with time in the current time step; the temperature field of the heat protection structure changing with time in the current time step is taken as the coupled simulation result of the current time step; wherein, when the first time step is the current time step, the heat flow condition refers to the launch environment temperature of the rocket engine tail, and in each current time step from the second time step onwards, the heat flow condition refers to the temperature field changing with time obtained from the mechanical-thermal coupled simulation of the previous time step.

6. The thermal protection structure simulation method according to claim 5, characterized in that, In step 22-1, the pressure in the tail section where the rocket engine is located is obtained based on the pressure difference environment of the tail section where the rocket engine is located at the end of the current time step; the fixed support boundary is the connection between the outer edge of the heat protection structure and the tail section support of the rocket engine; the rocket engine swing angle is used to apply forced displacement conditions to the connection between the heat protection structure and the rocket engine.

7. The thermal protection structure simulation method according to claim 5, characterized in that, Step 22 also includes: Step 22-4: After step 22-1, based on the stress distribution and strain distribution of the heat protection structure at the beginning of the current time step, determine whether the heat protection structure has failed. Step 22-5: If the stress in the heat-resistant structure that exceeds the preset area ratio is greater than the tensile limit strength, it is determined that the heat-resistant structure has torn and failed, and the force-thermal coupling simulation is stopped; otherwise, proceed to step 22-2.

8. The thermal protection structure simulation method according to claim 6, characterized in that, Step 22 also includes: Step 22-6: After step 22-3, based on the change of the temperature field of the heat-resistant structure over time in the current time step, determine whether the temperature of the heat-resistant structure exceeds the ignition point of the material of the heat-resistant structure; Step 22-7: If the temperature of the heat-resistant structure exceeds the ignition point of the material of the heat-resistant structure, calculate the ablation retreat in the thickness direction of the heat-resistant structure according to the local temperature change and ablation rate of the heat-resistant structure, and calculate the scorched area corresponding to the ablation retreat. Steps 22-8: If the ablation retreat is greater than the ablation thickness threshold and the proportion of the burned area is greater than the burned area proportion threshold, it is determined that the heat protection structure has been burned through, and the mechanical-thermal coupling simulation is stopped; otherwise, proceed to step 3. Step 3 includes: after removing the scorched area on the heat-resistant structure from the current geometric model, updating the intermediate geometric model to obtain an updated geometric model; Step 22 also includes: Step 22-9: Set the edge temperature of the ablation area to the temperature of the ignition point to update the temperature field obtained in step 22-3 over time.

9. A thermal protection structure simulation system, used to implement the thermal protection structure simulation method according to any one of claims 1-8, characterized in that, include: The model building unit is used to construct the initial geometric model of the heat shield structure based on the structural dimensions and material properties of the heat shield structure located outside the tail of the rocket engine, and to mesh the initial geometric model to obtain the initial finite element model. The coupled simulation unit is used to apply boundary conditions to the current finite element model at each current time step, perform mechanical and thermal coupled simulation on the current finite element model, and obtain the coupled simulation result of the current time step; wherein, when the first time step is the current time step, the current finite element model refers to the initial finite element model; and in each current time step from the second time step onwards, the current finite element model refers to the updated finite element model obtained at the end of the mechanical and thermal coupled simulation of the previous time step. The model update unit is used to update the current geometric model based on the coupled simulation results of the current time step to obtain an updated geometric model, and to mesh the updated geometric model to obtain an updated finite element model. In the first time step, the current geometric model refers to the initial geometric model. In each current time step from the second time step onwards, the current geometric model refers to the updated geometric model obtained at the end of the force-thermal coupled simulation of the previous time step. The next time step is updated to the current time step, and the coupled simulation unit and the model update unit are executed sequentially. In the coupled simulation unit, the coupled simulation result of the current time step is applied as a boundary condition to the updated finite element model until the simulation is completed for all time steps.

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