Rocket diversion trench ablation process simulation method

Abstract

The invention provides a rocket diversion trench ablation process simulation method which comprises the following steps: fitting ablation test data of a refractory material for a diversion trench to obtain a linear ablation rate formula; establishing a target model of the diversion trench; according to preset thermal environment parameters and the linear ablation rate formula, ablation profiles corresponding to multiple target moments are drawn on the target model; according to the physical property parameters of the refractory material for the diversion trench, the preset thermal environment parameters and the target model drawn with the ablation molded surface corresponding to each target moment, the ablation retreating process of the diversion trench is simulated in finite element analysis software; and simulation analysis results of the temperature field and the thermal stress field which change along with time and correspond to the ablation retreating process of the refractory material are obtained.

Description

Technical Field

[0001] The invention relates to the field of aerospace technology, and in particular to a method for simulating a rocket guide groove ablation process. Background Art

[0002] After the spacecraft is ignited, the gas flow ejected from the engine has a strong impact and corrosiveness. As a key basic facility of the rocket launch platform, the guide trough must not only withstand the erosion of the high-temperature, high-pressure, and high-speed gas flow generated during the launch, but also divert the high-temperature toxic gas and quickly guide it to a space away from the launch tower, providing safety for the buildings, facilities, engines, and related equipment around the spacecraft. In order to improve the high-temperature resistance of the guide trough, special refractory concrete is usually poured on the surface of the guide trough to ensure the safety of the test launch. However, with the rapid development of aerospace technology, new and higher requirements have been put forward for the carrying capacity of spacecraft. The ablation problem of the guide trough is becoming more and more serious. New technologies and methods are urgently needed to study and predict its ablation behavior, and provide technical support for the construction of the spacecraft launch platform.

[0003] At present, the ablation performance of the refractory concrete of the guide groove is generally predicted by the test piece test. This method can only verify whether the material meets the national military standard, but cannot determine the ablation of the guide groove during the actual launch and test. Moreover, the test requires the use of a kerosene engine with the nozzle outlet gas temperature, speed, and pressure that meet the requirements, and multiple cubic specimens must be prepared in advance, which is costly and time-consuming. Summary of the invention

[0004] In view of this, the purpose of an embodiment of the present invention is to provide a method for simulating the ablation process of a rocket guide groove, so as to solve the technical problem that the ablation performance of the guide groove refractory concrete is predicted through specimen-level tests in the prior art, but the ablation condition of the guide groove during the actual launch and test run cannot be obtained.

[0005] To achieve the above-mentioned purpose, an embodiment of the present invention provides a method for simulating the ablation process of a rocket guide groove, comprising:

[0006] The ablation test data of the refractory material used in the diversion channel was fitted to obtain the linear ablation rate formula;

[0007] Establish the target model of diversion channel;

[0008] According to the preset thermal environment parameters and the linear ablation rate formula, ablation profiles corresponding to multiple target moments are drawn on the target model; wherein the ablation profiles corresponding to different target moments are located at different positions;

[0009] According to the physical parameters of the refractory materials for the guide trough, the preset thermal environment parameters and the target model with the ablation profile corresponding to each target moment, the ablation retreat process of the guide trough is simulated in the finite element analysis software, and the simulation analysis results of the temperature field and thermal stress field that change with time corresponding to the ablation retreat process of the refractory materials for the guide trough on the target model are obtained.

[0010] The beneficial technical effect of the above technical scheme is that: the linear ablation rate formula of the guide trough refractory concrete under high-temperature and high-speed gas flow conditions is obtained through a fitting algorithm, and on this basis, the ablation morphology of the guide trough model is simulated based on the finite element method analysis software, and the simulation analysis results of the temperature field and thermal stress field corresponding to the ablation retreat process of the refractory material for the guide trough on the guide trough model that change with time are obtained, so that the simulation analysis results can be visualized, which can provide ablation prediction means for the engineering design of the guide trough and launch tower of future high-thrust carrier rockets, and provide technical support for the smooth implementation of spacecraft launch missions. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0012] Figure 1 This is a flow chart of a simulation of a rocket guide groove ablation process according to one embodiment of the present invention;

[0013] Figure 2 This is a material layer diagram formed during high-temperature ablation of a refractory concrete according to one embodiment of the present invention;

[0014] Figure 3 This is an energy balance relationship diagram of a refractory concrete surface during a high temperature ablation process according to one embodiment of the present invention;

[0015] Figure 4 is a schematic diagram of an ablation profile when the target model is a cross-sectional two-dimensional model according to one embodiment of the present invention;

[0016] Figure 5 This is a cloud diagram of the ablation retreat amount and the temperature field when the target time is 6 seconds in one embodiment of the present invention;

[0017] Figure 6 This is a cloud diagram of the ablation retreat amount and the temperature field when the target time is 7 seconds in one embodiment of the present invention;

[0018] Figure 7is a cloud diagram of the ablation retreat amount and the thermal stress field when the target time is 6 seconds in one embodiment of the present invention;

[0019] Figure 8 This is a cloud diagram of the ablation retreat amount and the thermal stress field when the target time is 7 seconds according to one embodiment of the present invention. DETAILED DESCRIPTION

[0020] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In the detailed description below, many specific details are proposed in order to provide a comprehensive understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by illustrating examples of the present invention. In the drawings and the following description, at least part of the known structures and technologies are not shown in order to avoid unnecessary ambiguity of the present invention; and, for clarity, the size of some structures may be exaggerated. In addition, the features, structures or characteristics described below may be combined in one or more embodiments in any suitable manner.

[0021] like Figure 1 As shown, an embodiment of the present invention provides a method for simulating a rocket guide groove ablation process, comprising:

[0022] Step S11, fitting the ablation test data of the refractory material for the guide groove to obtain a linear ablation rate formula;

[0023] Step S12, establishing a target model of the diversion trough;

[0024] Step S13, drawing a plurality of ablation profiles corresponding to target moments on the target model according to the preset thermal environment parameters and the linear ablation rate formula; wherein the ablation profiles corresponding to different target moments are located at different positions;

[0025] Step S14, based on the physical parameters of the refractory material for the guide trough, the preset thermal environment parameters and the target model with the ablation profile corresponding to each target moment, the ablation retreat process of the guide trough is simulated in the finite element analysis software, and the simulation analysis results of the temperature field and thermal stress field corresponding to the ablation retreat process of the refractory material for the guide trough on the target model that change with time are obtained.

[0026] The embodiment of the present invention has the following technical effects: a linear ablation rate formula of the refractory concrete of the guide groove under the condition of high-temperature and high-speed gas flow is obtained through a fitting algorithm, and on this basis, the ablation morphology of the actual guide groove model is simulated based on the finite element method analysis software, and the simulation analysis results of the temperature field and thermal stress field corresponding to the ablation retreat process of the refractory material for the guide groove on the guide groove model that change with time are obtained, which is closer to the actual ablation process of the guide groove in the rocket launch, and solves the technical problem that the ablation performance of the refractory concrete of the guide groove cannot be predicted by the test piece level test in the prior art, and the ablation condition of the guide groove in the actual launch and test run process cannot be obtained. It can provide ablation prediction means for the engineering design of the guide groove and the launch tower of the future large-thrust carrier rocket, and provide technical support for the smooth implementation of the spacecraft launch mission.

[0027] In some embodiments, the ablation test data can be obtained by pre-testing the test piece made of the refractory material for the guide groove under the preset heat flow ablation by performing a test piece-level ablation test. The test piece-level ablation test can be performed on the test piece under different thermal environment parameters; the structure and material of the test piece are the same as the structure and material of the refractory material of the guide groove. The ablation test data obtained by the test piece-level ablation test is used as the external input data of the embodiment of the present invention. The mathematical model based on which the ablation test data is fitted includes but is not limited to a multi-parameter exponential mathematical model. The structural parameters of the guide groove are known, and the target model of the guide groove can be established according to the structural parameters of the guide groove. The target model can be established as a three-dimensional model or a two-dimensional model according to the specific needs of subsequent analysis. The three-dimensional model can be created according to the three-dimensional structure of the entire guide groove. The two-dimensional model can only create a cross-sectional model of the guide groove, and the hierarchical structure and ablation retreat of the refractory material of the guide groove can also be reflected in the cross-sectional model. The position with the worst working condition of the heat flow ablation can be selected to construct the corresponding cross-sectional model, so that the ablation condition of the guide groove under the worst working condition can be determined by processing less simulation data. The thermal environment parameters are obtained by simulating the flow field of the process of rocket spraying the guide groove according to the actual launch conditions in advance. For the embodiment of the present invention, it is known data input externally. Those skilled in the art know how to obtain or construct the thermal environment parameters. Preferably, the thermal environment parameters include heat flux, enthalpy value, and surface pressure; the preset thermal environment parameters are input into the linear ablation rate formula to obtain the linear ablation rate, and then the relationship between the rate and time can be used to draw the ablation profiles corresponding to multiple target moments on the target model. At different target moments, the degree of ablation of the ablation surface is different, so the position of the ablation profile corresponding to different target moments is different. Through finite element software including but not limited to Abaqus (Abaqus) finite element analysis software, the guide groove is simulated in the ablation retreat process according to the physical properties of the refractory material, the preset thermal environment parameters and the ablation profiles at different target moments on the target model, and the simulation output obtains the calculation results of the ablation retreat amount, temperature field and thermal stress field corresponding to the ablation retreat process that changes with time, and the calculation results can be visualized in the form of cloud maps, which is convenient for technicians to observe and analyze intuitively. For example, based on the calculation results of the temperature field and thermal stress field that change with time, the cloud map of the temperature field and the cloud map of the thermal stress field are output. The time granularity corresponding to the cloud map will be significantly finer than the time granularity of the target moment. The finite element software simulation can simulate the change of the temperature field and thermal stress field with time between the initial moment to the first target moment and between adjacent target moments, so as to obtain the change of the temperature field and thermal stress field with finer time granularity with time.The cloud map of the ablation retreat and temperature field that changes with time, and the cloud map of the ablation retreat and thermal stress field are composed of multiple cloud maps, which can show the continuous changes of the temperature field and thermal stress field in the ablation process in a visual way according to time changes. Since the change of the temperature field will cause the change of the thermal stress of the refractory material, the cloud map can reflect the coupling of the temperature field and the thermal stress field at each time point. In this way, the ablation process is simulated close to the actual situation, and the dynamic process of ablation is visualized, so that technicians can observe the ablation process more intuitively and improve the efficiency and accuracy of the guide groove design.

[0028] The embodiment of the present invention has the following technical effects: a linear ablation rate formula of the refractory concrete of the guide groove under the condition of high-temperature and high-speed gas flow is obtained through a fitting algorithm, and on this basis, the ablation morphology of the actual guide groove model is simulated based on the finite element method analysis software, and the simulation analysis results of the temperature field and thermal stress field corresponding to the ablation retreat process of the refractory material for the guide groove on the guide groove model that change with time are obtained, which is closer to the actual ablation process of the guide groove in the rocket launch, and solves the technical problem that the ablation performance of the refractory concrete of the guide groove cannot be predicted by the test piece level test in the prior art, and the ablation condition of the guide groove in the actual launch and test run process cannot be obtained. It can provide ablation prediction means for the engineering design of the guide groove and the launch tower of the future large-thrust carrier rocket, and provide technical support for the smooth implementation of the spacecraft launch mission. Preferably, the simulation analysis results can also be visualized based on the simulation analysis results, by drawing cloud maps to visualize the cloud maps of the ablation setback and temperature field that change with time, as well as the cloud maps of the ablation setback and thermal stress field, reflecting the process of synchronous changes of the ablation setback, temperature field, and thermal stress field with time during the ablation process, and visualizing the ablation process of the guide groove in the actual rocket launch. The embodiment of the present invention can also be used for the simulation analysis of other ablative heat-resistant composite materials used on rockets or other aircraft, especially for the simulation analysis of large heat flux ablative heat-resistant composite materials.

[0029] Furthermore, according to the preset thermal environment parameters and the linear ablation rate formula, ablation profiles corresponding to multiple target moments are drawn on the target model, including:

[0030] Selecting a plurality of ablation feature regions on the ablation surface of the target model;

[0031] For each of the multiple target moments, the ablation retreat amount at multiple ablation feature areas on the target model corresponding to the target moment is determined according to the preset thermal environment parameters and the linear ablation rate formula; the multiple target moments are multiple time points selected sequentially within the entire time range of the ablation of the guide groove;

[0032] According to the ablation retreat amounts at the multiple ablation feature regions on the target model corresponding to each target moment, the ablation profile corresponding to the target moment is drawn on the target model.

[0033] In some embodiments, the ablation characteristic area includes but is not limited to a point, a line or a set small surface; the thermal environment parameter can be related to the ablation time and the ablation characteristic area at the same time. The thermal environment parameters at different times in the ablation process vary, and the thermal environment parameters at different ablation characteristic areas also vary. The parameters corresponding to different ablation characteristic areas and different target moments can be obtained from the thermal environment parameters as the input required for the line ablation rate formula. In other embodiments, the thermal environment parameter can only be related to the ablation characteristic area, and the thermal environment parameters corresponding to different ablation characteristic areas can be obtained from the thermal environment parameters as the input required for the line ablation rate formula; according to the input obtained from the thermal environment parameters and the line ablation rate formula, the ablation retreat at different target moments and different ablation characteristic areas is determined. Multiple target moments are multiple time points selected sequentially within the entire time range of the ablation of the guide groove. The target moment can be defined as a time point with relatively coarse granularity, for example, a target moment is defined every 1 second. The selection of the ablation characteristic area should be based on the principle of drawing the ablation profile as accurately as possible, and the selected ablation characteristic area should include the position with the maximum ablation rate. At the same target moment, according to the ablation retreat amount corresponding to each ablation feature area relative to the surface of the guide groove (or target model), the corresponding ablation profile at that moment can be drawn on the target model. On the target model, the ablation profile may be represented by a curved surface (corresponding to a three-dimensional target model) or a curve (corresponding to a two-dimensional target model). The part retreated after ablation corresponds to the part of the guide groove surface that is ablated, thereby forming a new guide groove (target model) surface (ablation profile).

[0034] Furthermore, the ablation test data include: mass ablation rate, enthalpy, heat flow and surface pressure obtained from the specimen-level ablation test; the linear ablation rate formula, specifically:

[0035]

[0036]

[0037] Among them, a, b, c, and d are fitting coefficients related to thermal protection materials. is the mass ablation rate, in kg / (m 2 ·s)(kg / (m2·s)), H s is the enthalpy value, unit is kJ / kg (kilojoule / kilogram), Q is the heat flow, unit is W / m 2 (Watts / square meter), p is the surface pressure, unit is Pa (Pascal), ρ is the material density, unit is kg / m3 (kg / m3), is the linear ablation rate, in m / s (meters per second).

[0038] In some embodiments, during the ablation test, the thermal environment parameters of the thermal environment formed by the ejected flame on the surface of the guide groove were measured in the experiment. Multiple groups of tests were conducted, and each group of tests tested parameters such as heat flux, enthalpy value, and surface pressure during the test. The experimental research results show that the mass ablation rate A multi-parameter exponential mathematical model associated with the three parameters of enthalpy (Hs), heat flow (Q), and surface pressure (p) can be established, for example, it can be expressed by formula (1).

[0039] Taking the logarithm of both sides of formula (1), we get formula (3):

[0040]

[0041] Among them, a, b, c, and d are fitting coefficients related to thermal protection materials, which will vary depending on the thermal protection materials. The specific values ​​of these coefficients can be determined by fitting the ablation test data. The total ablation mass can be obtained by integrating the mass ablation rate over time t. Mass ablation rate and line ablation rate The relationship between is shown in formula (2). Line ablation rate By integrating over time t, the ablation retreat amount δ can be obtained.

[0042] To determine the coefficients in formula (1), we only need to use the multiple linear regression method to solve formula (3). The mathematical model of multiple linear regression analysis is formula (4):

[0043]

[0044] There are m+1 coefficients to be calculated in formula (4), while the number of equations is n. For precision measurement, the number of measurements is generally required to be n>m+1. Formula (4) constitutes a contradictory set of equations that cannot be solved. In order to solve this problem, the least squares principle is used and expressed as: (y-Xb) T (y-Xb)=min(5) Using MATLAB software for regression calculation, we can get the values ​​of coefficients a, b, c, and d of formula (3);

[0045] Substituting the coefficients in formula (3) back into formula (1), we can obtain the formula for mass ablation rate.

[0046] Further, establishing a target model of the guide groove includes: taking a cross-sectional two-dimensional model formed by a cross-sectional surface perpendicular to the guide groove as the target model;

[0047] Selecting a plurality of ablation feature regions on the ablation surface of the target model includes: uniformly selecting a plurality of ablation feature regions on the target model along a direction parallel to the ablation surface;

[0048] In some embodiments, a two-dimensional cross-sectional model of the guide groove is used as the target model, and when selecting the cross-sectional position, a two-dimensional cross-sectional model corresponding to the direction of the worst working condition in the preset thermal environment parameters of the guide groove is used as the target model, so that less data can be used to simulate the worst working condition. As long as the guide groove is safe and available under the worst working condition, the entire guide groove can be ensured to be safe and available. This can improve data processing efficiency, reduce the demand for computing device resources during the simulation process, and reduce simulation processing time. Figure 4 As shown, the target model is a cross-sectional two-dimensional model, which is a plane corresponding to the cross-section of the guide groove. Multiple ablation feature areas are equidistantly specified in the horizontal direction of the plane. The more ablation feature areas there are, the more accurate the simulation is, and it can be defined as needed. Figure 4 The number 40 in the figure represents the cross section of the guide groove, the number 41 represents the position of the ablation surface of the guide groove before ablation, the dotted line corresponding to the number 42 and the intersection of multiple dotted lines parallel to it and the ablation surface of the backflow groove represent multiple ablation feature areas, each dotted line corresponds to an ablation feature area, and the multiple curves corresponding to the number 43 represent the ablation profiles corresponding to different target moments. Since the target model is a cross-sectional two-dimensional model, the ablation profile seen is a curve, and the arrow pointed to by the number 44 represents the direction of the rocket jet heat flow.

[0049] Further, for each of the multiple target moments, according to the preset thermal environment parameters and the linear ablation rate formula, the ablation retreat amount at the multiple ablation feature areas on the target model corresponding to the target moment is determined, specifically including:

[0050] For each target moment, according to the thermal environment parameters at each ablation feature area and the linear ablation rate formula, the linear ablation rate corresponding to the ablation feature area is determined;

[0051] For each ablation characteristic area at each target moment, the linear ablation rate corresponding to the ablation characteristic area is integrated over time from the initial moment to the target moment to obtain the ablation retreat amount corresponding to each ablation characteristic area at the target moment; the initial moment is the rocket ignition moment, or the starting moment of starting to ablate the guide groove.

[0052] In some embodiments, the preset thermal environment parameters can be simulated and constructed in advance, and the preset thermal environment parameters are used as external input quantities of this embodiment. The preset thermal environment parameters include the input quantities required for the linear ablation rate formula, and these input quantities can be the same or different constants corresponding to different ablation feature regions, or they can be variables related to time (target moment) and ablation feature regions, so that the linear ablation rate can be a quantitative value corresponding to the ablation feature region, or it can be an expression related to the ablation feature region and time (target moment). The thermal environment parameters at each ablation feature region can be obtained from the preset thermal environment parameters. For each different ablation feature region, the linear ablation rate is integrated with respect to time from the initial moment to each target moment, and the ablation retreat amount corresponding to the position at each target moment can be obtained.

[0053] Further, according to the ablation retreat amounts at the multiple ablation feature areas on the target model corresponding to each target moment, the ablation profile corresponding to the target moment is drawn on the target model, specifically including:

[0054] For each target moment, the ablation retreat amounts at multiple ablation feature areas on the target model corresponding to the target moment are taken as the distance of surface downward movement due to ablation at the ablation feature area of ​​the target model at the target moment, thereby determining the new surface position of the target model at the ablation feature area, and connecting the new surface positions at all the ablation feature areas to obtain the ablation profile corresponding to the target moment.

[0055] In some embodiments, the ablation setback represents the portion of the refractory material that has been ablated relative to the initial surface of the guide groove (or target model) at the corresponding ablation feature area at the corresponding target moment due to the scouring and ablation of the rocket tail flame; after the refractory material on the surface of the guide groove (or target model) is ablated, a new surface, namely, an ablation profile, will be formed; during simulation, multiple target moments of interest will be pre-selected, such as the 1st, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th, 9th, and 10th seconds from the initial moment, to determine the ablation setback of each ablation feature area corresponding to the multiple target moments, so that the ablation profile corresponding to the target moment can be determined based on the ablation setback of each ablation feature area at each target moment. Figure 4 The cross-sectional two-dimensional model shown is used as the target model. Four concave curves are drawn on the upper half of the target model. Each curve corresponds to an ablation profile. Each curve is low in the middle and high on both sides. This corresponds to the fact that the heat flow ejected by the rocket is directly facing the low part in the middle. Therefore, the low part in the middle is severely ablated, and the ablation degree on both sides is relatively light. Each curve on the cross-sectional two-dimensional model corresponds to a target moment, and a curve represents a corresponding ablation profile. If the target model is a three-dimensional model, then the ablation profile is a curved surface.

[0056] Furthermore, according to the physical parameters of the refractory material for the guide groove, the preset thermal environment parameters and the target model with the ablation profile corresponding to each target moment, the ablation retreat process of the guide groove is simulated in the finite element analysis software, and the simulation analysis results of the temperature field and thermal stress field corresponding to the ablation retreat process of the refractory material for the guide groove on the target model that change with time are obtained, including:

[0057] In the finite element analysis software, input boundary conditions and physical parameters of the refractory material for the guide channel; the boundary conditions include: preset thermal environment parameters; the physical parameters of the refractory material for the guide channel include: density, thermal conductivity, specific heat capacity, thermal expansion coefficient;

[0058] In the finite element analysis software, import the target model, define the thermodynamic analysis step corresponding to the ablation surface at each target moment, and configure each thermodynamic analysis step to enable the birth-death unit method and set the simulation type to thermal stress field and temperature field coupling analysis;

[0059] On the target model, divide the finite element analysis mesh for simulation analysis;

[0060] Finite element simulation analysis was performed to obtain simulation analysis results of the temperature field and thermal stress field that change with time corresponding to the ablation and retreat process of the refractory material used in the guide groove on the target model.

[0061] In some embodiments, the boundary conditions also include: initial temperature, and / or environmental conditions; the initial temperature is the temperature of the guide trough structure before the rocket launch or before the test, usually room temperature; environmental conditions include ambient temperature, and / or ambient airflow, etc.; environmental conditions are the conditions of the external environment where the guide trough is located. Each thermodynamic analysis step also defines the step size, calculation time (total calculation time and calculation time for each ablation profile), initial iteration step size, and convergence criteria, etc. In this implementation, there is no order requirement between the various configuration steps of the finite element software before performing finite element simulation analysis. Input the input data required for the simulation to the finite element analysis software: In the finite element analysis software, input the boundary conditions and the physical properties of the refractory material for the guide trough; the physical properties of the refractory material for the guide trough are measured in advance for the refractory material for the guide trough, and the physical properties of the refractory material for the guide trough include: density, thermal conductivity, specific heat capacity, and thermal expansion coefficient. In the finite element analysis software, the target model is imported, the thermodynamic analysis step corresponding to the ablation profile at each target moment is defined, and the birth-and-death unit method and the simulation type are configured to be the coupled analysis of thermal stress field and temperature field in each thermodynamic analysis step; on the target model, the finite element analysis grid for simulation analysis is divided; and the finite element simulation analysis is performed. During the simulation analysis process, the thermodynamic analysis step corresponding to the top ablation profile is simulated from the initial moment to the target moment corresponding to the top ablation profile by the configured birth-and-death unit method and the coupled analysis of thermal stress field and temperature field, and the data of the ablation retreat amount, temperature field, and thermal stress field varying with time at a finer time granularity (e.g., 1, 5, 10 milliseconds or continuous time) from the initial moment to the target moment are obtained. The other thermodynamic analysis steps obtain the data of the ablation retreat amount, temperature field, and thermal stress field varying with time at a finer time granularity between adjacent target moments, thereby simulating the entire time range from the initial moment to the last target moment, and obtaining the data of the ablation retreat amount, temperature field, and thermal stress field varying with time. The finite element analysis software will automatically calculate the ablation setback of each finite element analysis grid at the current time point. Through the birth and death unit method, the finite element grid corresponding to the finite element analysis grid whose ablation setback is lower than the position of the finite element analysis grid is released, thereby simulating the situation of refractory material being ablated. At the same time, the changes in temperature field and thermal stress field are simulated, and finally the cloud map of ablation setback and temperature field that change with time corresponding to the ablation process, as well as the cloud map of ablation setback and thermal stress field are obtained. Select the Model change function in the finite element analysis software, that is, the birth and death unit method. The more ablation profiles there are, the more corresponding thermodynamic analysis steps there are, and the more accurate the simulation results are. The number of ablation profiles can be determined according to specific needs. Figure 5 This is the cloud diagram of the ablation retreat and temperature field at the target time of 6 seconds. Figure 6 This is the cloud diagram of the ablation retreat and thermal stress field at the target time of 6 seconds. Figure 7This is the cloud diagram of the ablation retreat and temperature field at the target time of 7 seconds. Figure 8 This is the cloud diagram of the ablation retreat and thermal stress field at the target time of the 7th second. Figures 5 to 8 It can be seen from the comparison that at the 6th second, the guide groove has been ablated, and the ablated surface of the target model at the 7th second has further ablated back on the basis of the 6th second. Since ablation takes away heat, the maximum surface temperature is basically maintained at around 1800°C (the starting temperature of refractory concrete). As time goes on, the internal temperature shows a trend of continuous increase. The change of thermal stress is closely related to the temperature gradient. The more drastic the temperature change, the greater the thermal stress. The position with the largest thermal stress in the figure is mainly concentrated on the ablation surface, and the thermal stress inside the model decreases successively. Through the cloud map of the ablation retreat and temperature field at multiple sequential time points and the cloud map of the ablation retreat and thermal stress field at the corresponding time points, the dynamic change process of the ablation retreat, temperature field, and thermal stress field during the ablation process can be observed.

[0062] Furthermore, a two-dimensional cross-sectional model formed by a cross-section perpendicular to the ablated surface of the guide groove is used as the target model, specifically including: selecting a cross-sectional two-dimensional model corresponding to the worst direction of ablation conditions under preset thermal environment parameters as the target model.

[0063] Furthermore, a target model of the diversion trough is established, including:

[0064] According to the structural parameters of the diversion trough, a three-dimensional model of the diversion trough is established as a target model;

[0065] Select multiple ablation feature areas on the ablation surface of the target model, including:

[0066] The ablation surface on the three-dimensional model is evenly divided into multiple grid areas, and the vertices of the grid areas are used as ablation feature areas.

[0067] In some embodiments, according to the structural parameters of the guide groove, a three-dimensional model of the guide groove is established as a target model; the top surface of the three-dimensional model is evenly divided into a plurality of small cells by a grid on the top surface of the three-dimensional model, and all cells (grid areas) have the same size and are aligned in rows and columns, with the vertices of the cells as the ablation feature areas. At this time, a more comprehensive simulation can be performed on the entire guide groove, and based on the more comprehensive simulation data obtained, the entire ablation surface of the guide groove can be comprehensively simulated based on the three-dimensional model, so that the data of each part of the ablation surface can be obtained, so that each part of the refractory material on the ablation surface of the guide groove can be optimized in a targeted manner. The more small cells are divided, the higher the simulation accuracy is, and the number of small cells can be set as needed.

[0068] The above technical solution of the embodiment of the present invention is described in detail below in conjunction with specific application examples. For technical details not introduced during the implementation process, please refer to the relevant description in the previous text.

[0069] When refractory concrete is subjected to high-temperature airflow ablation, the hydrated compounds in the concrete first decompose to produce a dehydration reaction; as the temperature further increases, a series of chemical reactions occur between the dehydrated products and between the products and the aggregate, resulting in transformation and sintering to form a sintered layer; then part of the products reach the melting point and become liquid, forming a liquid layer attached to the surface of the material. The material layers in the high-temperature ablation process of refractory concrete are as follows: Figure 2 As shown, A represents the liquid layer, B represents the sintered layer, C represents the decomposed layer, D represents the original material layer, and E represents the direction of surface ablation retreat. Figure 3 is the energy balance relationship diagram of the ablation surface, and the energy balance equation of the ablation surface is established as follows:

[0070] q conv -q rout +q rin +q cond -(ρv)H w -q py +q reac =0 (8)

[0071] In the formula, q conv is the convection heating term; q rout and q rin are the heat radiated outward and the external radiation heating respectively; q cond is the heat transferred to the interior of the material; (ρv)H w is the convective heat dissipation term, which represents the heat removed from the ablation surface by the gases produced by the dehydration reaction and chemical reaction; q py The heat removed by the dehydration process; q reac Heat generated by chemical reactions.

[0072] A method for simulating the ablation process of rocket guide troughs, a method for simulating the ablation process of rocket guide troughs based on the life and death unit method, and a method for determining the ablation amount of refractory concrete for rocket guide troughs based on the life and death unit method. The specific steps are as follows: the ablation test data of refractory concrete specimens are tested on a high-temperature jet test platform, and the calculation formula of the out-line ablation rate and the ablation retreat amount is fitted; when conducting the ablation test, multiple groups of tests are carried out, and each group of tests tests the heat flux, enthalpy value, surface pressure and other parameters during the test. The experimental research results show that the mass ablation rate A multi-parameter exponential mathematical model can be established that is associated with the three parameters of enthalpy (Hs), heat flow (Q), and surface pressure (p), which can be expressed, for example, by formula (1). The total ablation mass can be obtained by integrating the mass ablation rate represented by formula (1) over time t. The relationship between is as follows: Line ablation rate By integrating over time t, the ablation retreat amount δ can be obtained.

[0073] The ablation retreat amount at different positions at different times is calculated by the ablation retreat amount calculation formula, and the guide groove model (target model) is created in the CAD software and the ablation profile at different ablation times is drawn;

[0074] The guide groove model (target model) with the ablation profile at different times drawn is imported into the finite element calculation program (finite element analysis software). In order to reduce the amount of calculation and improve the speed of numerical simulation, the segmented simulation method is used to simulate the change of the shape during the ablation process. The corresponding thermodynamic analysis steps are set for the ablation profile corresponding to different times, and the simulation is performed in segments at different times to reduce the amount of calculation;

[0075] Based on the birth-death element method, the ablation process of refractory concrete when it is flushed by high-temperature gas is simulated, and the temperature field and stress distribution at different times during the ablation process are solved, as follows:

[0076] According to the actual ablation process (ablation profiles at different times on the guide groove model and preset thermal environment parameters), a finite element analysis model is established;

[0077] Set physical property parameters (including but not limited to material density, thermal conductivity, and specific heat capacity of refractory materials) and divide the grid;

[0078] Using the birth and death unit technology, according to the actual ablation process of the diversion trough refractory concrete, the units in the model that have reached the ablation condition (according to the ablation retreat amount at the current moment, the corresponding unit or grid has been ablated) are released layer by layer;

[0079] The finite element analysis software automatically calculates the temperature field / stress coupling calculation results at each moment during the material ablation and stripping process based on boundary conditions such as heat flow.

[0080] 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 can be rearranged without departing from the scope of protection of the present disclosure. The attached method claims present the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy described.

[0081] In the above detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than those set forth in each claim. On the contrary, as reflected in the appended claims, the invention is in a state of having less than all the features of the disclosed individual embodiments. Therefore, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0082] The disclosed embodiments are described above to enable any person skilled in the art to implement or use the present invention. Various modifications of these embodiments are obvious to those skilled in the art, and the general principles defined herein may also be applied to other embodiments without departing from the spirit and scope of the present disclosure. Therefore, the present 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.

[0083] The above description includes examples of one or more embodiments. Of course, it is impossible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it should be recognized by those skilled in the art that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the word is covered in a manner similar to the term "including". In addition, any term "or" used in the specification of the claims is intended to mean "non-exclusive or".

[0084] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.

Claims

1. A method for simulating the ablation process of a rocket guide groove, characterized in that: The method comprises: The ablation test data of the refractory material used in the diversion channel was fitted to obtain the linear ablation rate formula; Establish the target model of diversion channel; According to the preset thermal environment parameters and the linear ablation rate formula, ablation profiles corresponding to a plurality of target moments are drawn on the target model; wherein the ablation profiles corresponding to different target moments are located at different positions; According to the physical parameters of the refractory material for the guide trough, the preset thermal environment parameters and the target model with the ablation profile corresponding to each target moment, the ablation retreat process of the guide trough is simulated in the finite element analysis software, and the simulation analysis results of the temperature field and thermal stress field corresponding to the ablation retreat process of the refractory material for the guide trough on the target model that change with time are obtained.

2. The rocket guide groove ablation process simulation method according to claim 1, characterized in that: Drawing a plurality of ablation profiles corresponding to target moments on the target model according to the preset thermal environment parameters and the linear ablation rate formula includes: Selecting a plurality of ablation feature regions on the ablation surface of the target model; For each of the multiple target moments, the ablation retreat amount at the multiple ablation feature areas on the target model corresponding to the target moment is determined according to the preset thermal environment parameters and the linear ablation rate formula; the multiple target moments are multiple time points selected sequentially within the entire time range of the ablation of the guide groove; According to the ablation retreat amounts at the multiple ablation feature regions on the target model corresponding to each target moment, the ablation profile corresponding to the target moment is drawn on the target model.

3. The rocket guide groove ablation process simulation method according to claim 1, characterized in that: The ablation test data include: mass ablation rate, enthalpy value, heat flow and surface pressure obtained from the specimen-level ablation test; the linear ablation rate formula is specifically: Among them, a, b, c, and d are fitting coefficients related to thermal protection materials. is the mass ablation rate, in kg / (m 2 ·s), H s is the enthalpy value in kJ / kg, Q is the heat flow in W / m 2 , p is the surface pressure, unit is Pa, ρ is the material density, unit is kg / m 3 , is the linear ablation rate in m / s.

4. The rocket guide groove ablation process simulation method as claimed in claim 2, characterized in that: Establishing a target model of the guide groove includes: taking a cross-sectional two-dimensional model formed by a cross-sectional surface perpendicular to the guide groove as the target model; Selecting a plurality of ablation feature regions on the ablation surface of the target model includes: uniformly selecting a plurality of ablation feature regions on the target model along a direction parallel to the ablation surface.

5. The rocket guide groove ablation process simulation method as claimed in claim 2, characterized in that: The step of determining, for each target moment among the multiple target moments, the ablation retreat amounts at the multiple ablation feature regions on the target model corresponding to the target moment according to the preset thermal environment parameters and the linear ablation rate formula specifically includes: For each target moment, according to the thermal environment parameters at each ablation feature area and the linear ablation rate formula, determine the linear ablation rate corresponding to the ablation feature area; For each ablation characteristic area at each target moment, the linear ablation rate corresponding to the ablation characteristic area is integrated over time from the initial moment to the target moment to obtain the ablation retreat amount corresponding to each ablation characteristic area at the target moment; the initial moment is the rocket ignition moment.

6. The rocket guide groove ablation process simulation method as claimed in claim 2, characterized in that: Drawing the ablation profile corresponding to the target moment on the target model according to the ablation retreat amounts at the multiple ablation feature regions on the target model corresponding to each target moment specifically includes: For each target moment, the ablation retreat amount at multiple ablation feature areas on the target model corresponding to the target moment is used as the distance of surface downward movement due to ablation at the ablation feature area of ​​the target model at the target moment, thereby determining the new surface position of the target model at the ablation feature area, and connecting the new surface positions at all the ablation feature areas to obtain the ablation profile corresponding to the target moment.

7. The rocket guide groove ablation process simulation method according to claim 1, characterized in that: According to the physical parameters of the refractory material for the guide groove, the preset thermal environment parameters and the target model with the ablation profile corresponding to each target moment, the ablation retreat process of the guide groove is simulated in the finite element analysis software, and the simulation analysis results of the temperature field and thermal stress field corresponding to the ablation retreat process of the refractory material for the guide groove on the target model that change with time are obtained, including: In the finite element analysis software, input boundary conditions and physical parameters of the refractory material for the guide channel; the boundary conditions include: preset thermal environment parameters; the physical parameters of the refractory material for the guide channel include: density, thermal conductivity, specific heat capacity, thermal expansion coefficient; In the finite element analysis software, the target model is imported, the thermodynamic analysis step corresponding to the ablation profile at each target moment is defined, and in each thermodynamic analysis step, the birth-death unit method is enabled and the simulation type is configured as the coupled analysis of thermal stress field and temperature field; On the target model, dividing a finite element analysis grid for simulation analysis; Finite element simulation analysis is performed to obtain simulation analysis results of the temperature field and thermal stress field that change with time corresponding to the ablation and retreat process of the refractory material used for the guide groove on the target model.

8. The rocket guide groove ablation process simulation method according to claim 1, characterized in that: The thermal environment parameters are obtained by performing flow field simulation on the process of rocket jetting guide grooves in advance according to actual launch conditions.

9. The rocket guide groove ablation process simulation method according to claim 4, characterized in that: The target model is formed by a two-dimensional cross-sectional model formed by a cross-sectional view perpendicular to the ablated surface of the guide groove, which specifically includes: selecting a cross-sectional view corresponding to the worst direction of ablation conditions under preset thermal environment parameters, and forming a two-dimensional cross-sectional model as the target model.

10. The rocket guide groove ablation process simulation method according to claim 2, characterized in that: Establishing a target model of the guide trough includes: establishing a three-dimensional model of the guide trough as the target model according to the structural parameters of the guide trough.

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