Method for rapidly analyzing performance of thermal protection phase change cooling structure

Abstract

The invention provides a rapid performance analysis method for a thermal protection phase change cooling structure. The rapid performance analysis method comprises the following steps: carrying out geometric simplification and grid division on a phase change cooling system; setting related material physical property parameters and interaction boundary conditions; performing theoretical analysis on a main heat source of the phase change cooling system, and selecting a thermal boundary condition method; the comprehensive density, the cooling liquid heat specific volume and the cooling liquid heat conductivity after the cooling liquid and the liquid storage medium are combined are calculated, and the gas production starting time and the vaporization amount are obtained through simulation; performing risk assessment on the phase change cooling structure, and assessing the risk generated when the produced gas enters the corresponding thermal environment; and repeating the steps to obtain a design scheme of the phase change cooling system in the high-heat area of the aircraft with a certain engineering margin. By applying the technical scheme, the technical problems that in the prior art, a test method is long in preparation period and high in cost, the use environment of the phase change cooling system is difficult to completely recover, and effective guidance is difficult to provide at the initial stage of design are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of aircraft structure thermal control, and particularly to a method for rapidly analyzing the performance of a thermal protection phase change cooling structure. Background Art

[0002] With the increase of flight speed, the aerodynamic heating amount continuously increases. The heat flux distribution on different regions of the aircraft surface is different, and some high-heat regions will be generated. It is an effective method to use phase change cooling to cool the high-heat regions to take away or block heat. By analyzing the cooling performance and related designs, the corresponding thermal environment temperature can be controlled not to exceed the allowable value.

[0003] Currently, the evaluation of the effectiveness of the phase change cooling system is mainly carried out based on the CFD method and the experimental method.

[0004] The CFD method can capture specific information such as the flow of the coolant, heat transfer characteristics, and phase change interface. However, for the phase change cooling system in high-heat regions, its flow and heat transfer processes are related to the form of coolant storage and the specific implementation structure of phase change cooling. It is difficult for the traditional CFD method to couple and consider the heat transfer influence of the above structures for the performance analysis and design of the phase change thermal control structure. The experimental method has a long preparation period, high cost, and it is difficult to fully restore the usage environment of the phase change cooling system, and it is difficult to provide effective guidance in the initial stage of design. Summary of the Invention

[0005] The present invention provides a method for rapidly analyzing the performance of a thermal protection phase change thermal control structure for an aircraft, which can solve the technical problems in the prior art that the experimental method has a long preparation period, high cost, and it is difficult to fully restore the usage environment of the phase change cooling system, and it is difficult to provide effective guidance in the initial stage of design.

[0006] The present invention provides a method for rapidly analyzing the performance of a phase change thermal control structure for aircraft thermal protection. The method for rapidly analyzing the performance of a phase change thermal control structure for aircraft thermal protection includes: Step 1, geometric simplification and mesh generation of the entire phase change cooling system including relevant injection heat sources; Step 2, setting the physical property parameters of relevant materials other than the coolant, the contact modes between various structures, and the interaction boundary conditions of heat conduction, convection, and radiation between each structure and the outside; Step 3, theoretically analyzing the main heat sources of the phase change cooling system and selecting a heat boundary condition method that combines accuracy and calculation speed; Step 4, applying the heat source using the heat boundary condition method selected in Step 3, setting the physical property parameters of the coolant using a theoretical simplification method, calculating and obtaining the combined density of the coolant and the liquid storage medium, the specific heat capacity of the coolant, and the thermal conductivity of the coolant, and obtaining the starting time of gas generation and the gasification amount through simulation; Step 5, based on the combined density of the coolant and the liquid storage medium, the specific heat capacity of the coolant, the thermal conductivity of the coolant, the starting time of gas generation, and the gasification amount obtained in Step 4, conducting a risk assessment of the phase change cooling structure and assessing the risks generated by the gas entering the corresponding thermal environment; Step 6, if the risk assessment result in Step 5 is that there is a risk, then at least one of the coolant form, the coolant injection amount, and the coolant storage form is changed, and then Steps 1 to 5 are repeated until the risk assessment result is risk-free; if the risk assessment result is risk-free, then it is possible to choose to iterate or not iterate the above steps.

[0007] Further, in Step 1, in the case of no internal heat source, the phase change cooling system consists of a heat insulation layer, a phase change coolant, a coolant storage structure, and other media; in the case of an internal heat source, the phase change cooling system consists of a heat insulation layer, a phase change coolant, a coolant storage structure, other media, and an internal heat source. Geometric simplification of the phase change cooling system is carried out, and then mesh generation is performed, and the quality of the meshes after division is checked.

[0008] Further, in Step 2, the physical property parameters of the aerodynamic heating surface heat insulation material, the coolant encapsulation material, and the internal heat source heat insulation material all include the density, thermal conductivity, and specific heat capacity at different temperatures, and the physical property parameters of the air when the gas enters the corresponding thermal environment are taken as the physical property parameters of the air at the average temperature.

[0009] Further, in Step 3, the pneumatic heating heat source can be loaded in three ways. The first way is as follows: At the initial stage of engineering design, several sets of characteristic region points of the cold-wall heat flux and the recovery enthalpy on the pneumatic surface are extracted. When the heat flux actually injected into the structure is 0, the heat transfer on the structure surface reaches equilibrium. The radiation equilibrium temperature of each point is calculated and averaged according to the heat flux calculation formulas for the hot wall and the cold wall and the heat flux formula for the actually injected structure, and the average value is taken as the temperature boundary condition for loading. The second way is as follows: The gas surface is divided into several sets of regions, and for each region, several points are selected to calculate the radiation equilibrium temperature using the cold-wall heat flux and the gas enthalpy value at the recovery temperature in the heat flux calculation formulas for the hot wall and the cold wall, and the average value is used as the temperature boundary condition for each region for loading. The third way is as follows: The pneumatic heat data is three-dimensionally interpolated using the hot surface calculation grid to obtain the pneumatic heat data of each point on the pneumatic surface, and the heat flux of each point is loaded using the heat flux calculation formulas for the hot wall and the cold wall and the heat flux formula for the actually injected structure to obtain the real-time heat flux.

[0010] Further, the heat flux calculation formulas for the hot wall and the cold wall are The heat flux formula for the actually injected structure is where q 冷 is the cold-wall heat flux, α 冷 is the convective heat transfer coefficient in the case of the cold wall, h 恢复 is the gas enthalpy value at the recovery temperature, h 冷 is the gas enthalpy value at the cold-wall temperature, q 热 is the hot-wall heat flux, α 热 is the convective heat transfer coefficient in the case of the hot wall, h 热 is the gas enthalpy value at the hot-wall temperature, q 注入 is the heat flux of the actually injected structure, q 辐射 is the radiative heat flux between the external environment and the structure.

[0011] Further, in Step 3, the internal heat source heating can be loaded using the real-time heating temperature or the real-time heating heat flux, and it can be selected to directly load at the boundary of the internal heat source entity or on the outer surface of the corresponding heat insulation layer of the internal heat source entity.

[0012] Further, in Step 4, the combined density of the coolant and the liquid storage medium is obtained according to ρ cooling = φρ l for calculation, the specific heat capacity of the coolant is obtained according to for calculation, and the thermal conductivity of the coolant is obtained according to T 1 <T<T 2 for calculation, where ρ cooling is the combined density of the coolant and the liquid storage medium, φ is the conversion coefficient, ρ l is the density of the coolant, cp is the actual specific heat capacity of the coolant at the current temperature, T is the current actual temperature of the coolant, T 1 is the temperature at the start of the coolant phase change, T 2 is the temperature at the end of the coolant phase change. It should be noted that this is an engineering means for rapid calculation convergence and obtaining the coolant consumption, not exactly representing the start and end temperatures of the actual physical process phase change, T 2 -T 1 The temperature range of is generally taken as 10°C - 50°C, r is the latent heat of vaporization of the coolant, c p,raw is the specific heat capacity of the coolant in the liquid state, k l is the thermal conductivity of the coolant, c p,vapor is the specific heat capacity of the coolant after boiling and converting to the gas state, k con is the overall thermal conductivity of the composite of the coolant and the storage medium, k ske is the thermal conductivity of the storage structure framework.

[0013] Further, in step four, when the coolant temperature is greater than T 1 , obtain the starting time point T 1 of gas production; when the coolant temperature is greater than T 1 , set the thermal conductivity to 5000 W·m -1 ·K -1 -20000 W·m -1 ·K -1 , and statistically calculate the overall average temperature T ave of the entire coolant layer, the gas production volume m gas and the average gas production rate are: Wherein, t total is the total heating duration, m l is the mass of the coolant, m l = ρ l ·V l , V l is the volume of the coolant.

[0014] Further, in step five, evaluating the risks generated by the gas production entering the corresponding thermal environment specifically includes: According to , estimate the temperature T emission of the gas discharged into the corresponding thermal environment. According to 1) the corresponding relationship between the temperature T emission of the gas discharged into the corresponding thermal environment and the saturation temperature corresponding to the pressure of the corresponding thermal environment, judge whether condensation occurs after the gas is injected. 2) According to whether the low-temperature region cools the discharged steam below the saturation steam temperature corresponding to the pressure of the corresponding thermal environment at this time, judge whether there is a risk of local condensation. Among them, h coolingis the enthalpy value of the gas that has undergone a phase change in the coolant storage device, p cooling is the pressure maintained in the coolant storage device, h emission , T emission , p emission are respectively the enthalpy value, temperature and known ambient pressure of the discharged gas, T 1 is the temperature at the start of the coolant phase change, T 2 is the temperature at the end of the coolant phase change.

[0015] Furthermore, in step six, if the risk assessment result is risk-free, then it is possible to choose whether to iterate the above steps or not. Specifically, if the risk assessment result is risk-free and the engineering design margin is greater than the safety margin, then choose not to iterate; if the risk assessment result is risk-free and the engineering design margin is less than or equal to the safety margin, then choose to repeat steps one to five for iteration.

[0016] Applying the technical solution of the present invention provides a method for quickly analyzing the performance of a phase change thermal control structure for aircraft thermal protection. This method uses existing general engineering software combined with theoretical analysis methods to conduct a coupled analysis and evaluation of the working efficiency of the phase change evaporation cooling system, and comprehensively considers the comprehensive influence of liquid-gas conversion and discharge into the corresponding thermal environment. According to this method, the performance and risk of the aircraft phase change cooling thermal protection system can be quickly evaluated. Compared with the prior art, the method for quickly analyzing the performance of the phase change thermal control structure for aircraft thermal protection provided by the present invention has the following advantages: (1) The present invention provides a method for analyzing the performance of a thermal control structure using coolant phase change cooling. Compared with the CFD method and the experimental method, it is easy to implement quickly and conveniently in engineering and can be effectively evaluated in the aircraft thermal control scheme design stage. (2) The present invention provides a method for analyzing the performance of a thermal control structure using coolant phase change cooling, including three hot surface condition loading methods, which can be selected according to engineering requirements. All three loading methods use cold wall heat flux and recovery enthalpy as input conditions and are easy to implement. (3) The present invention provides a method for setting the physical properties of the liquid storage material / coolant material and a simulation method, which can consider the performance of the thermal control structure during the entire heating process of the coolant, comprehensively consider the influence of two physical processes, namely the heat conduction stage and the exhaust stage, is easy to implement, and can directly obtain the true temperature distribution, gas production volume, and average gas production rate of the coolant. (4) The present invention considers the influence and risk assessment of coolant exhaust into the corresponding thermal environment and has high engineering application value. (5) The present invention can provide a reliable design reference for the phase change cooling method through multiple iterations of the entire cycle process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings included are used to provide a further understanding of the embodiments of the present invention, which form a part of the specification, illustrate the embodiments of the present invention, and together with the written description explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0018] Figure 1 The structural schematic diagram of a phase change cooling system provided according to a specific embodiment of the present invention is shown. Detailed implementation manners

[0019] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments may be combined with each other. The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present invention and its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of the present invention.

[0020] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and values set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn according to the actual proportional relationship. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and devices should be regarded as part of the authorized specification. In all the examples shown and discussed herein, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0022] As Figure 1As shown in the figure, a method for quickly analyzing the performance of a phase change thermal control structure for aircraft thermal protection is provided according to a specific embodiment of the present invention. The method for quickly analyzing the performance of a phase change thermal control structure for aircraft thermal protection includes: Step 1, geometric simplification and mesh generation of the entire phase change cooling system including relevant injection heat sources; Step 2, setting the physical property parameters of relevant materials except the coolant, the contact mode between each structure, and the interaction boundary conditions of heat conduction, convection, and radiation between each structure and the outside; Step 3, theoretically analyzing the main heat sources of the phase change cooling system and selecting a heat boundary condition method with both accuracy and calculation speed; Step 4, applying the heat source using the heat boundary condition method selected in Step 3, setting the physical property parameters of the coolant using the theoretical simplification method, calculating and obtaining the combined density of the coolant and the storage medium, the specific heat capacity of the coolant, and the thermal conductivity of the coolant, and obtaining the starting time of gas generation and the vaporization amount through simulation; Step 5, based on the combined density of the coolant and the storage medium, the specific heat capacity of the coolant, the thermal conductivity of the coolant, the starting time of gas generation, and the vaporization amount obtained in Step 4, conducting a risk assessment of the phase change cooling structure and evaluating the risk generated by the gas entering the corresponding thermal environment; Step 6, if the risk assessment result in Step 5 is that there is a risk, then make at least one change in the form of the coolant, the injection amount of the coolant, and the storage form of the coolant, and then repeat Steps 1 to 5 until the risk assessment result is risk-free; if the risk assessment result is risk-free, then it is possible to choose to iterate or not iterate the above steps.

[0023] Applying this configuration method, a method for quickly analyzing the performance of a phase change thermal control structure for aircraft thermal protection is provided. This method uses existing general engineering software combined with theoretical analysis methods to conduct a coupled analysis and evaluation of the working efficiency of the phase change evaporation cooling system, and comprehensively considers the comprehensive influence of liquid-gas conversion and discharge into the corresponding thermal environment. According to this method, the performance and risk assessment of the aircraft phase change cooling thermal protection system can be quickly carried out. Compared with the prior art, the method for quickly analyzing the performance of a phase change thermal control structure for aircraft thermal protection provided by the present invention has the following advantages:

[0024] (1) The present invention provides a method for analyzing the performance of a thermal control structure using the phase change cooling of a coolant. Compared with the CFD method and the experimental method, it is easy to implement quickly and conveniently in engineering and can be effectively evaluated in the aircraft thermal control scheme design stage.

[0025] (2) The present invention provides a method for analyzing the performance of a thermal control structure using the phase change cooling of a coolant, including three ways of loading the hot surface conditions, which can be selected according to engineering requirements. All three loading methods use the cold wall heat flux and the recovery enthalpy as input conditions and are easy to implement.

[0026] (3) The present invention provides a method for setting physical properties of a liquid storage material / coolant material and a simulation method, which can consider the thermal control structure performance during the entire heating process of the coolant, comprehensively consider the effects of two physical processes, namely the heat conduction stage and the exhaust stage, is easy to implement, and can directly obtain the coolant temperature distribution.

[0027] (4) The present invention considers the influence and risk assessment of the coolant exhaust entering the corresponding thermal environment, and has high engineering application value.

[0028] (5) The present invention can provide a reliable design reference for the phase change cooling method through multiple iterations of the entire circulation process.

[0029] Specifically, the present invention provides a method for quickly analyzing the thermal protection phase change cooling structure performance. Its advantage is that on the premise of ensuring reliable calculation, an engineering software is combined with a theoretical analysis method to quickly evaluate the thermal control effect of the phase change cooling system and the influence of the phase change gas discharged into the corresponding thermal environment. The specific steps mainly include S1 to S6.

[0030] S1: Geometric simplification and mesh generation are performed on the entire phase change cooling system including relevant injection heat sources. In step one, in the case of no internal heat source, the phase change cooling system consists of a heat insulation layer, a phase change coolant, a coolant storage structure, and other media; in the case of an internal heat source, the internal heat source needs to be considered. Common internal heat sources such as engine heat generation, etc. The phase change cooling system consists of a heat insulation layer, a phase change coolant, a coolant storage structure, other media, and an internal heat source. Geometric simplification of the phase change cooling system is carried out, and then mesh generation is performed, and the quality of the meshes after division is checked.

[0031] S2: Set the physical property parameters of relevant materials, the contact modes between structures, and the interaction boundary conditions of heat conduction, convection, and radiation between each structure and the external environment (except for the coolant). In step two, for the purpose of quickly evaluating requirements, all components included in the present invention are treated as solid materials: the physical property parameters of the aerodynamic heating surface heat insulation material, the coolant encapsulation material, and the internal heat source heat insulation material, including density, thermal conductivity, and specific heat capacity at different temperatures; the physical property parameters of the air discharged into the corresponding thermal environment are estimated and selected according to the average temperature of the current thermal environment.

[0032] S3: Conduct a theoretical analysis on the main heat sources affecting the entire phase change cooling system, and select a thermal boundary condition method with both accuracy and calculation speed.

[0033] Generally speaking, it includes two heat source forms, namely the aerodynamic heating heat source (external heat source) and the internal heat source. The aerodynamic heating heat source can be loaded in three ways. The first way is: in the initial stage of engineering design, extract the cold wall heat flux and recovery enthalpy of several set characteristic region points on the aerodynamic surface. When the actual injected heat flux q in formula (2) 注入When it is 0, the heat exchange on the surface of the structure reaches equilibrium. At this time, the existing engineering method formula hot wall and cold wall heat flow calculation formula (1) and the actual injection structure heat flow formula (2) can be combined to calculate the radiation equilibrium temperature of each point and average it, and take the average value as the temperature boundary condition for loading; the second method is: divide the gas surface into several set areas, take several points in each area and use the hot wall and cold wall heat flow calculation formula (1) and the actual injection structure heat flow formula (2) to calculate the radiation equilibrium temperature, and use the average value as the temperature boundary condition for loading; the third method is: use the thermal surface calculation grid to perform three-dimensional interpolation on the aerodynamic thermal data to obtain the aerodynamic thermal data of each point on the aerodynamic surface, and apply the hot wall and cold wall heat flow calculation formula (1) and the actual injection structure heat flow formula (2) to load the heat flow at each point to obtain the real-time heat flow. Loading method 1) and loading method 2) ignore the inward heat transfer of the surface insulation material, but the temperature loading method is convenient and fast; loading method 3) uses the cold wall heat flow-recovery enthalpy method to give the outer surface of the insulation material real-time three-dimensional heating heat flow boundary conditions.

[0034] In the case of cold wall and hot wall:

[0035]

[0036] Among them, q 冷 is the cold wall heat flux, α 冷 is the convective heat transfer coefficient under cold wall conditions, h 恢复 is the gas enthalpy at the recovery temperature, h 冷 is the gas enthalpy at the cold wall temperature, q 热 is the wall heat flux, α 热 is the convective heat transfer coefficient under hot wall conditions. 热 is the gas enthalpy at the hot wall temperature and T 热 (radiation equilibrium temperature), the engineering calculation formula is h 热 =B 0 +B 1 T 热 +B 2 T 热 2 +B 3 T 热 3 +B 4 T 热 4 +B 5 T 热 5 , where B 0 -B 5 All are specific constants.

[0037] Adopting a separated solution method, it can be considered that the convective heat transfer coefficient of the boundary layer is the same in the case of a cold wall and a hot wall, which is α 冷 = α 热 , and at this time, it can be deduced that:

[0038]

[0039] Among them, q 注入 is the heat flux of the actual injection structure; q 辐射 is related to the radiative heat flux between the external environment and the structure and T 热 (radiation equilibrium temperature), and the specific relationship is q 辐射 = σεT 4 , where σ is the Stefan-Boltzmann constant; ε is the spectral average emissivity of the wall surface, which is determined according to the inherent properties of the structure surface.

[0040] For the internal heat source heating, real-time heating temperature or real-time heating heat flux can be used for loading, and it can be selected to be directly loaded at the engine boundary or on the corresponding heat insulation layer of the engine.

[0041] S4: Apply the heat source using the thermal boundary condition method selected in step S3. Then, set the physical properties of the coolant using the theoretical simplification method provided by the present invention. Using this simplification method, the starting time of gas production and the gasification amount can be obtained through simulation, and these two parameters, together with density, specific heat capacity, and thermal conductivity, are involved in the subsequent risk assessment of the phase change cooling structure.

[0042] Specifically, set the physical properties of the phase change coolant, and obtain the starting time of gas production and the gasification amount through simulation. In the actual application process, in order to meet the actual flight requirements, the coolant is often combined with liquid storage materials such as liquid storage media in the form of molecular bonds. At this time, the physical process before phase change is equivalent to a pure heat conduction process until the gas is produced and discharged at the saturation temperature corresponding to the pressure of the storage device. The density of the coolant can be reduced according to the usage rate of the coolant.

[0043] ρ cooling = φρ l (3)

[0044] Among them, ρ cooling is the combined density of the coolant and the liquid storage medium, φ is the reduction coefficient, and ρ l is the density of the coolant.

[0045] During the whole simulation process, in order to better make the calculation converge, taking the saturation temperature corresponding to the pressure of the storage device as a reference, it can be set that T1 - T2 is the interval where phase change occurs, and the specific heat capacity is loaded in a triangular manner. At this time, the mass conservation principle is used to calculate ρ cooling = φρ l .

[0046] The specific heat capacity of the coolant is determined as follows:

[0047]

[0048] where \(c_p\) is the actual specific heat capacity of the coolant at the current temperature, \(T\) is the current actual temperature of the coolant, \(T_1\) is the temperature at the start of the phase change of the coolant, \(T_2\) is the temperature at the end of the phase change of the coolant, \(r\) is the latent heat of vaporization of the coolant, \(c\) p,raw is the specific heat capacity of the coolant in the liquid state, \(c\) p,vapor is the specific heat capacity of the coolant after boiling and converted into the gas state.

[0049] The coolant is often combined with liquid storage materials such as liquid storage media in the form of molecular bonds. Before the phase change, it is equivalent to a pure heat conduction process, and gas is generated and discharged at the saturation temperature corresponding to the pressure of the storage device. To obtain the true temperature distribution of the coolant and judge the risk of the device, the thermal conductivity of the coolant can be set in the following manner.

[0050]

[0051] where \(k\) con is the overall thermal conductivity after the coolant is combined with the storage medium, \(k\) ske is the thermal conductivity of the storage structure framework. When the coolant temperature is greater than \(T_1\), the above method can obtain the starting time point \(t_1\) of gas production. To obtain the gas production volume during the entire cooling process, the thermal conductivity can be set to \(5000\ W\cdot m\) -1 \(\cdot K\) -1 \(^{-20000}\ W\cdot m\) -1 \(\cdot K\) -1 when the coolant temperature is greater than \(T_1\), and the overall average temperature \(T_{ave}\) of the entire coolant layer, the gas production volume \(m\) gas and the average gas production rate are:

[0052]

[0053] where \(t\) total is the total heating duration, \(m\) l is the mass of the coolant, \(m\) l \(=\rho\) l \(\cdot V\) l where \(V\) l is the volume of the coolant.

[0054] S5. Conduct a risk assessment of the phase change cooling structure and evaluate the impact of the generated gas entering the corresponding thermal environment.

[0055] Conduct a risk assessment of the phase change cooling structure, and use the methods described in formulas (3) - (6) to conduct a risk assessment of the phase change cooling structure. If an area with insufficient liquid storage of the coolant is found, improve the storage method to increase the liquid storage volume;

[0056] Further, in step five, the assessment of the risks generated by the generated gas entering the corresponding thermal environment specifically includes: according to the temperature T of the gas discharged into the corresponding thermal environment is estimated. According to 1), the temperature T of the gas discharged into the corresponding thermal environment emission and the corresponding relationship between the saturation temperature corresponding to the pressure of the corresponding thermal environment are used to judge whether condensation occurs after the gas is injected. 2), according to whether the low-temperature region at this time cools the discharged steam below the saturation steam temperature corresponding to the pressure of the corresponding thermal environment gas to judge whether there is a risk of local condensation. Among them, h emission is the enthalpy value of the gas that has undergone a phase change in the coolant storage device, p cooling is the pressure maintained in the coolant storage device, h cooling is, T emission , T emission , p emission are the enthalpy value, temperature and known discharge gas ambient pressure of the discharged gas respectively. T 1 and T 2 have the same meaning as the previous step.

[0057] Specifically, if the temperature T of the gas discharged from the coolant storage structure emission is less than the saturation temperature corresponding to the gas discharge environment, condensation will occur. If the temperature T of the gas discharged from the coolant storage structure emission is greater than the saturation temperature corresponding to the gas discharge environment, condensation will not occur. For a specific area, it is also necessary to consider whether there is a local cold area that cools the discharged gas below the saturation temperature corresponding to the discharge environment and causes condensation.

[0058] S6. Repeat steps S1 to S5. Iterate the coolant form, coolant injection volume, and coolant storage form multiple times to obtain a design scheme for the phase change cooling system in the high-temperature area of the aircraft with a certain engineering margin.

[0059] Specifically, in step six, if the risk assessment result is risk-free, the selection of whether to perform the above step iteration or not specifically includes: if the risk assessment result is risk-free and the engineering design margin is greater than the safety margin, then choose not to iterate; if the risk assessment result is risk-free and the engineering design margin is less than or equal to the safety margin, then choose to repeat steps one to five for iteration.

[0060] The innovative points to be protected by the present invention

[0061] (a) A method for analyzing the performance of a phase change thermal control structure. For the phase change thermal control form of storing liquid in a liquid storage medium, an engineering simulation calculation method and a thermal control performance analysis method are proposed. The analysis objects include the insulation layer material, the storage structure, the phase change liquid layer, the corresponding thermal environment, and the internal heat source;

[0062] (b) A method for analyzing the performance of a phase change thermal control structure adopts an engineering-friendly and applicable pneumatic hot surface boundary loading method as follows: 1) Extract the cold wall heat flux and recovery enthalpy of several characteristic region points on the pneumatic surface, calculate the radiation equilibrium temperature of each point and take the average value, and use the average value as the temperature boundary condition for loading; 2) Divide the pneumatic surface into several regions, take several points in each region to calculate the radiation equilibrium temperature using the cold wall heat flux and recovery enthalpy, and use the average value as the temperature boundary condition for each region for loading; 3) Use the hot surface calculation grid to perform three-dimensional interpolation on the pneumatic heat data to obtain the pneumatic heat data of each point on the pneumatic surface, and perform loading to obtain the real-time heat flux;

[0063] (c) A method for analyzing the performance of a phase change thermal control structure adopts an engineering-friendly and applicable cooling liquid phase change treatment method as follows: The thermal conductivity is expressed by a piecewise function to characterize the heat transfer situation of the coolant from the heat conduction-dominated stage to the exhaust stage, and the latent heat of vaporization is incorporated into the specific heat capacity in a certain temperature range.

[0064] (d) A method for analyzing the performance of a phase change thermal control structure provides a set of theoretical simplification methods for setting the physical property parameters of the coolant. Using this simplification method, the starting time of gas production and the vaporization amount can be obtained through simulation.

[0065] (e) The method provided by a method for analyzing the performance of a phase change thermal control structure can predict the risk of local overheating in phase change cooling.

[0066] (f) A method for analyzing the performance of a phase change thermal control structure provides a method for evaluating the thermal environment impact and risk of exhaust entering the corresponding thermal environment, which can predict the gas temperature discharged into the corresponding thermal environment and predict the risks brought by condensation and thermal environment disturbance.

[0067] The present invention has the following beneficial effects:

[0068] (1) Compared with the traditional CFD simulation method, the consumption of computing resources is greatly reduced and the computing time is shortened.

[0069] (2) Compared with the experimental method, the analysis method can evaluate the corresponding risks of the phase change cooling scheme through calculation, greatly shortening the evaluation cycle and reducing the evaluation cost;

[0070] (3) Using this method, the impacts of various engineering design parameters can be obtained to serve engineering design, such as the form of the coolant, the liquid injection amount, etc.;

[0071] (4) Through multiple rounds of iteration based on this method, a design scheme for the phase change cooling system in the high-temperature area of the aircraft with a certain engineering margin can be obtained;

[0072] The present invention will be described in detail below with reference to embodiments. In the following description, specific details are set forth for the purpose of explanation and not limitation, so as to help fully understand the present invention. However, it will be apparent to those skilled in the art that the present invention may also be practiced in other embodiments without these specific details.

[0073] It should be noted here that in order to avoid obscuring the present invention with unnecessary details, only the processing steps closely related to the present invention are shown, while other details less related to the present invention are omitted. S1: Geometric simplification and mesh generation are performed on the entire phase change cooling system including the relevant injection heat source.

[0074] In this embodiment, the UG modeling software is used to establish a parametric geometric model and export the x_t format file of the parametric geometric model. The parametric geometric components include: insulation layer material, titanium metal coolant storage structure, coolant, air in the corresponding thermal environment, and engine insulation layer. The x_t format file of the parametric geometric model is imported into the hyperworks software, and hypermesh in the hyperworks software is used for mesh generation. The mesh quality inspection tool meshcheck in the hyperworks software is used to inspect the quality of the mesh model, and the mesh file is output and imported into the Abaqus software for calculation.

[0075] In this example, a total of 560,816 meshes are output, including 387,852 tetrahedral meshes and 172,964 hexahedral meshes.

[0076] S2. Set the relevant material property parameters and interaction boundary conditions (except for the coolant).

[0077] The thermal insulation material uses the material property parameters obtained through experiments that change with temperature. The titanium alloy coolant storage structure is set with material property parameters according to the material manual. The air is set by conversion using the ideal gas state equation based on the estimated average temperature of 150°C.

[0078] The heat transfer between the thermal insulation material and the coolant and the coolant storage structure can be regarded as interface heat transfer by conduction, with continuous temperature and continuous heat flow. In this example, the sub-region mesh generation method is adopted to establish the contact pair ContactPairs of the corresponding surface. When the contact distance is less than a fixed value, the thermal conductivity is set to 10,000. The heat transfer between the coolant storage structure, the air in the corresponding thermal environment, and the engine insulation layer includes heat conduction, convection, and radiation. The air convection can be ignored due to the small spacing in the corresponding thermal environment. The radiation is calculated using the Abaqus cavity radiation module, and the emissivity of the outer surfaces of the coolant storage metal box and the engine insulation layer is set to 0.3.

[0079] S3. Analyze the main heat sources of the phase change cooling system and select a thermal boundary condition method that combines accuracy and calculation speed.

[0080] Establish the heating boundary conditions for the two heat sources. In this example, the engine is an internal heat source, and a varying temperature heating boundary condition is adopted with an insulation layer. The aerodynamic heat is an external heat source, and the third three-dimensional non-uniform recovery enthalpy and cold wall heat flux method is used to obtain the three-dimensional distributed real-time heat flux for aerodynamic heat heating.

[0081] S4. Set the physical property parameters of the phase change coolant and obtain the starting time of gas production and the vaporization amount through simulation.

[0082] Set the phase change interval T of the coolant 1 -T 2 , and use the methods described in formulas (3) to (5) to obtain the true temperature distribution of the phase change cooling structure; use the method described in formula (6) to obtain the coolant utilization rate and gas production rate. In this example, the calculated coolant utilization rate is approximately 32%, and the average gas production rate is 1.2 g / s.

[0083] S5. Conduct a risk assessment of the phase change cooling structure and evaluate the impact of the gas production entering the corresponding thermal environment on its internal thermal environment.

[0084] In this example, there is a surplus of coolant in the global phase change cooling structure, and there is no obvious risk in the phase change cooling structure. After calculation, the discharged gas exceeds the corresponding saturation temperature, and there is no local cold source to cool it below the saturation temperature, so there is no condensation risk.

[0085] S6. Iterate the coolant form, coolant injection amount, and coolant storage form multiple times to obtain a design scheme for the phase change cooling system in the high-temperature area of the aircraft with a certain engineering margin.

[0086] There is still an engineering margin in this round of iteration, and the design can be further carried out based on the current design parameters.

[0087] For the sake of convenience in description, spatial relative terms such as "above...", "over...", "on the upper surface of...", "upper" etc. can be used here to describe the spatial position relationship between a device or feature shown in the figure and other devices or features. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation described in the figure for the device. For example, if the device in the figure is inverted, the device described as "above other devices or structures" or "over other devices or structures" will be positioned as "below other devices or structures" or "under other devices or structures" afterwards. Thus, the exemplary term "above..." can include both the orientations of "above..." and "below...". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the corresponding explanations for the spatial relative descriptions used here will be made.

[0088] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Without additional declaration, the above terms have no special meaning, so it should not be construed as a limitation on the protection scope of the present invention.

[0089] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for rapid analysis of the performance of a phase-change thermal control structure for aircraft thermal protection, characterized in that: The method for rapid analysis of the performance of a phase-change thermal control structure for thermal protection of an aircraft comprises: Step 1: geometrically simplify and mesh the entire phase change cooling system including the relevant injected heat source; Step 2: Set the physical properties of related materials except the coolant, the contact mode between the structures, and the boundary conditions of the interaction between the structures and the external heat conduction, convection, and radiation; Step 3: Conduct theoretical analysis on the main heat sources of the phase change cooling system and select a thermal boundary condition method that has both accuracy and calculation speed. Step 4: Apply the heat source using the thermal boundary condition method selected in step 3, set the physical property parameters of the coolant using a theoretical simplification method, calculate and obtain the comprehensive density of the coolant combined with the liquid storage medium, the coolant thermal specific volume and the coolant thermal conductivity, and obtain the gas production start time and vaporization amount through simulation; Step 5, based on the comprehensive density of the coolant and the liquid storage medium obtained in step 4, the coolant thermal specific volume, the coolant thermal conductivity, the gas production start time and the vaporization amount, the phase change cooling structure risk assessment is performed, and the risk of the gas production entering the corresponding thermal environment is assessed; Step six, if the risk assessment result in step five is that there is a risk, change at least one of the coolant form, coolant injection amount and coolant storage form, and then repeat steps one to five until the risk assessment result is no risk; if the risk assessment result is no risk, you can choose to iterate the above steps or not.

2. The method for rapid performance analysis of a phase-change thermal control structure for aircraft thermal protection according to claim 1, characterized in that: In the step one, in the absence of an internal heat source, the phase change cooling system consists of an insulation layer, a phase change coolant, a coolant storage structure and other media; in the presence of an internal heat source, the phase change cooling system consists of an insulation layer, a phase change coolant, a coolant storage structure, other media and an internal heat source, the geometry of the phase change cooling system is simplified, and then meshing is performed, and the quality of the mesh after division is checked.

3. The method for rapid performance analysis of aircraft thermal protection phase change thermal control structure according to claim 1, characterized in that: In step 2, the physical properties of the pneumatic heating surface insulation material, the coolant packaging material, and the internal heat source insulation material include density, thermal conductivity, and specific heat capacity at different temperatures, and the physical properties of the air that produces gas and enters the corresponding thermal environment are the physical properties of the air at the average temperature.

4. The method for rapid performance analysis of a phase-change thermal control structure for aircraft thermal protection according to claim 3 is characterized in that: In the step three, the aerodynamic heating heat source can be loaded in three ways. The first way is: in the early stage of engineering design, the cold wall heat flux and recovery enthalpy of several set characteristic area points of the aerodynamic surface are extracted. When the heat flux actually injected into the structure is 0, the heat exchange on the surface of the structure reaches equilibrium. The radiation equilibrium temperature of each point is calculated and averaged according to the hot wall and cold wall heat flux calculation formula and the heat flux formula of the actual injection structure, and the average value is used as the temperature boundary condition for loading; the second way is: the gas surface is divided into several set areas, and several points in each area are taken to calculate the radiation equilibrium temperature using the cold wall heat flux and the gas enthalpy at the recovery temperature in the hot wall and cold wall heat flux calculation formula, and the average value is used as the temperature boundary condition for loading; the third way is: the aerodynamic thermal data is interpolated in three dimensions using the thermal surface calculation grid to obtain the aerodynamic thermal data of each point on the aerodynamic surface, and the heat flux calculation formula of the hot wall and cold wall and the heat flux formula of the actual injection structure are used for heat flux loading to obtain real-time heat flux.

5. The method for rapid performance analysis of aircraft thermal protection phase change thermal control structure according to claim 4 is characterized in that: The calculation formula for the hot wall and cold wall heat flux is: The heat flow formula of the actual injection structure is: Among them, q 冷 is the cold wall heat flux, α 冷 is the convective heat transfer coefficient under cold wall conditions, h 恢复 is the gas enthalpy at the recovery temperature, h 冷 is the gas enthalpy at the cold wall temperature, q 热 is the wall heat flux, α 热 is the convective heat transfer coefficient under hot wall conditions, h 热 is the gas enthalpy at the hot wall temperature, q 注入 is the heat flux actually injected into the structure, q 辐射 The radiation heat flow between the external environment and the structure.

6. The method for rapid performance analysis of aircraft thermal protection phase change thermal control structure according to claim 3, characterized in that: In step three, the internal heat source heating can be loaded using real-time heating temperature or real-time heating heat flow, and can be loaded directly at the boundary of the internal heat source entity or on the outer surface of the insulation layer corresponding to the internal heat source entity.

7. The method for rapid performance analysis of aircraft thermal protection phase change thermal control structure according to claim 3, characterized in that: In step 4, the combined density of the coolant and the storage medium is calculated according to ρ cooling =φρ l Calculated and obtained, the coolant thermal capacity is based on Calculated and obtained, the thermal conductivity of the coolant is based on Calculate and obtain, where ρ cooling The combined density of the coolant and the storage medium, φ is the conversion coefficient, ρ l is the coolant density, c p is the actual specific heat capacity of the coolant at the current temperature, T is the current actual temperature of the coolant, T1 is the temperature at the beginning of the phase change of the coolant, T2 is the temperature at the end of the phase change of the coolant, r is the latent heat of vaporization of the coolant, c p,raw is the specific heat capacity of the coolant in liquid state, k l is the thermal conductivity of the coolant, c p,vapor is the specific heat capacity of the coolant after boiling and converting into gas state, k con is the overall thermal conductivity of the coolant and storage medium after compounding, k ske is the thermal conductivity of the storage structure skeleton.

8. The method for rapid performance analysis of aircraft thermal protection phase change thermal control structure according to claim 7, characterized in that: In step 4, when the coolant temperature is greater than T1, the start time point t1 of gas production is obtained; when the coolant temperature is greater than T1, the thermal conductivity is set to 5000 W·m -1 ·K -1 -20000W·m -1 ·K -1 , calculate the overall average temperature T of the overall cooling liquid layer ave , gas production m gas , average gas production rate for: Among them, t total is the total heating time, m l is the mass of coolant, m l =ρ l ·V l , V l is the coolant volume.

9. The method for rapid performance analysis of a phase-change thermal control structure for thermal protection of an aircraft according to any one of claims 1 to 8, characterized in that: In step 5, the risk of the produced gas entering the corresponding thermal environment is evaluated by: The temperature of the gas discharged into the corresponding hot environment is T emission Estimation, based on 1) the temperature of the gas discharged into the corresponding hot environment T emission 1) Determine whether condensation occurs after gas injection based on the corresponding relationship between the saturation temperature and the corresponding thermal environment pressure. 2) Determine whether there is a risk of local condensation based on whether the low-temperature area cools the discharged steam to below the saturated steam temperature corresponding to the corresponding thermal environment gas pressure. cooling is the enthalpy of the gas that has undergone phase change in the coolant storage device, p cooling is the pressure maintained in the coolant storage device, h emission , T emission , p emission are the exhaust gas enthalpy, temperature and known exhaust gas ambient pressure respectively, T1 is the temperature at the beginning of the coolant phase change, and T2 is the temperature at the end of the coolant phase change.

10. The method for rapid performance analysis of a phase-change thermal control structure for thermal protection of an aircraft according to any one of claims 1 to 8, characterized in that: In step six, if the risk assessment result is no risk, you can choose to iterate the above steps or not, specifically including: if the risk assessment result is no risk and the engineering design margin is greater than the safety margin, choose not to iterate; if the risk assessment result is no risk and the engineering design margin is less than or equal to the safety margin, choose to repeat steps one to five for iteration.

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