Stratospheric airship three-dimensional transient thermodynamics analysis method and system

Abstract

The invention discloses a stratospheric airship three-dimensional transient thermodynamics analysis method and system, and the method comprises the steps: obtaining an analysis result through the analysis of a stratospheric airship air-staying thermal environment; based on an analysis result, constructing an airship three-dimensional transient thermodynamic internal and external coupling heat transfer model; and completing thermal analysis of the airship by using the airship three-dimensional transient thermodynamic internal and external coupling heat transfer model. The three-dimensional transient thermodynamics internal and external coupling heat transfer model of the airship is established, the model couples internal gas flow, skin surface heat exchange and external gas flow of the airship, and the day and night change characteristics of the temperature of the airship can be analyzed. And meanwhile, the problems that local flow heat exchange characteristics are ignored and influence factors are not comprehensively considered due to the fact that an empirical formula is used in the aspect of treating internal and external convective heat exchange of the skin by an airship thermodynamic model at present are solved. In addition, UDF is used for supplementing and realizing an infrared long-wave radiation part, and the simulation calculation of a solar radiation model is corrected, so that the simulation calculation is more consistent with the actual situation.

Description

Technical Field

[0001] The present application relates to the technical field of flow and heat transfer analysis, and in particular to an analysis method and system for three-dimensional transient thermodynamics of a stratospheric airship. Background Art

[0002] The stratosphere generally refers to the atmospheric space from the top of the troposphere to about 50 km above the ground. At the bottom of the stratosphere, the atmospheric temperature basically does not change with altitude, and the temperature difference between day and night is very small; while in the stratosphere above 20 km from the ground, the atmospheric temperature rises with increasing altitude. The meteorological conditions in the stratosphere are relatively stable, and the atmospheric convection is mainly horizontal flow, which is suitable for long-term fixed-point flight of aircraft. With the development of space technology, the unique space resources of the stratosphere have received more and more attention from various countries and have broad application prospects.

[0003] Due to the thin air in the stratosphere, the size of airships is generally very large. During the flight of airships, their thermal characteristics are greatly affected by the external environmental heat source and heat exchange mode, and show obvious day and night changes. Therefore, stratospheric airships are also called thermal aircraft. Thermodynamic modeling of stratospheric airships plays a vital role in the safety and stability of their operation. At present, different thermodynamic models of stratospheric airships have been established. According to the degree of simplification of the model, it can be divided into two categories: node model and dimensional model. The node model regards different parts of the airship as different heat exchange nodes and considers the heat transfer between nodes. Specifically, it includes single-node model, two-node model and multi-node model. The zero-node model simplifies the airship into an overall single node, the two-node model divides the airship skin into upper and lower parts, and the multi-node model divides the airship into more typical parts, such as treating the solar cell on the skin as a node and considering its heat dissipation. Compared with the node model, the dimensional model abandons the node heat transfer and considers the heat transfer of the actual airship. Specifically, the one-dimensional model describes the radial steady-state unidirectional heat transfer of the airship; the two-dimensional model regards the airship as a two-dimensional infinitely long cylinder, while taking into account the influence of the external flow wind speed; and the three-dimensional model fully considers the three-dimensional heat exchange between the airship skin and the surrounding environment.

[0004] However, the current thermodynamic modeling technology and analysis methods for stratospheric airships have the following deficiencies: (1) The node model simplifies the airship into multiple nodes and only considers the heat transfer at the nodes, without paying attention to the influence of the internal and external gas flow on the heat transfer of the airship; (2) The dimensional model considers the convective heat transfer inside and outside the airship on the basis of the node model, but the convective heat transfer characteristics of the skin wall are calculated by empirical formulas, without considering the actual flow heat transfer characteristics inside and outside, especially the local temperature characteristics of the internal floating gas; (3) The study of the transient thermal characteristics of the airship requires the investigation of the day and night changes of the airship skin temperature and the internal floating gas temperature over time. At present, the analysis of the three-dimensional temperature field of some airship skins is a steady-state model, which does not consider its transient characteristics over time. Summary of the invention

[0005] In order to solve the technical problems in the above background, this application analyzes the thermal environment of stratospheric airships in the air and clarifies the internal and external coupled heat transfer mechanism of airships. On this basis, a three-dimensional transient thermodynamic internal and external coupled heat transfer model of airships is established. The model couples the internal gas flow, skin surface heat transfer and external gas flow of the airship, overcoming the problem that the current thermodynamic model of airships uses empirical formulas to deal with the convective heat transfer inside and outside the skin, resulting in the neglect of local flow heat transfer characteristics and incomplete consideration of the influencing factors in the simulation.

[0006] To achieve the above objectives, the present application provides a method for analyzing the three-dimensional transient thermodynamics of a stratospheric airship, the steps comprising:

[0007] The analysis results are obtained by analyzing the thermal environment of the stratospheric airship in the air;

[0008] Based on the analysis results, a three-dimensional transient thermodynamic internal and external coupled heat transfer model of the airship is constructed;

[0009] The thermal analysis of the airship is completed by using the three-dimensional transient thermodynamics internal and external coupled heat transfer model of the airship.

[0010] Preferably, the analysis results include: external radiation, skin radiation and convective heat transfer; wherein, the external radiation includes: direct solar radiation, diffuse solar radiation, reflected solar radiation and infrared long-wave radiation; skin radiation includes: radiative heat transfer between the outer surface of the skin and the external atmosphere, radiative heat transfer between different positions of the outer surface of the skin, radiative heat transfer between different positions of the inner surface of the skin, and radiative heat transfer between the inner surface of the skin and the internal filling gas; convective heat transfer includes: mixed convective heat transfer between the outer surface of the skin and the external atmosphere and natural convective heat transfer between the inner surface of the skin and the internal filling gas.

[0011] Preferably, the three-dimensional transient thermodynamic internal and external coupled heat transfer model of the airship is a combined model, including: an external radiation heat source model, a skin surface radiation model and an internal and external convection model of the aerostat.

[0012] Preferably, the external radiation heat source model includes: a solar radiation heat load model and a long-wave radiation heat load model; the solar radiation heat load model is used to calculate the loads of the direct solar radiation, the diffuse solar radiation and the reflected solar radiation; the long-wave radiation heat load model is used to calculate the load of the infrared long-wave radiation.

[0013] Preferably, UDF is used to simulate and calculate the infrared long-wave radiation and the reflected solar radiation. The specific steps include: calculating the heat loads of the reflected solar radiation and the infrared long-wave radiation, and adding them to the skin of the airship model in the form of a body heat source to participate in the coupling calculation.

[0014] Preferably, the skin surface radiation model specifically adopts a discrete coordinate radiation model to solve the radiation transfer equation for a finite number of discrete solid angles, and converts the radiation transfer equation into a transport equation for radiation intensity under spatial coordinates; then, the radiation transfer equation in the vector direction is regarded as a field equation for solution.

[0015] Preferably, the internal and external convection model of the aerostat is based on a flow control equation that takes into account the viscosity effect near the wall, and uses the Reynolds average method to solve and obtain the dynamic characteristics and convection heat transfer characteristics of the flow.

[0016] Preferably, when calculating the internal and external convection heat transfer of the airship, the skin is treated as the interface between the internal gas and the external gas, and targeted processing is performed; the specific steps include: when calculating the internal and external convection of the airship, the skin is treated as a fixed no-slip wall; when calculating the heat transfer of the airship, the skin is used as the heat transfer boundary of the internal and external gases, and the wall heat flux of the inner and outer surfaces is calculated respectively.

[0017] The present application also provides a system for analyzing three-dimensional transient thermodynamics of stratospheric airships, the system being used to implement the above method, comprising: an analysis module, a construction module, and a result generation module;

[0018] The analysis module is used to obtain analysis results by analyzing the thermal environment of the stratospheric airship in the air;

[0019] The construction module is used to construct a three-dimensional transient thermodynamic internal and external coupled heat transfer model of the airship based on the analysis results;

[0020] The result generation module is used to complete the thermal analysis of the airship by using the three-dimensional transient thermodynamics internal and external coupled heat transfer model of the airship.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. A three-dimensional transient thermodynamic internal-external coupled heat transfer model of the airship was established. The model couples the internal gas flow, skin surface heat transfer and external gas flow of the airship, and can analyze the day and night variation characteristics of the airship temperature.

[0023] 2. It overcomes the problem that the current airship thermodynamic model uses empirical formulas to deal with convective heat transfer inside and outside the skin, which leads to the neglect of local flow heat transfer characteristics and incomplete consideration of influencing factors.

[0024] 3. UDF is used to supplement the simulation calculation of infrared long-wave radiation, making the solar radiation model more consistent with the actual situation.

[0025] 4. UDF was used to correct the ground and cloud reflected radiation in the solar radiation model, comprehensively considering the impact of different terrains and different weather on the thermal characteristics of the airship, and expanding the scope of application of the airship thermodynamic model. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solution of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0027] Figure 1 A schematic diagram of a method flow of an embodiment of the present application;

[0028] Figure 2 A schematic diagram of a three-dimensional transient thermodynamic internal and external coupled heat transfer model of an airship according to an embodiment of the present application;

[0029] Figure 3 This is a flow chart of data processing using UDF in an embodiment of the present application;

[0030] Figure 4 This is a schematic diagram of the change of the average temperature of the filling gas inside the airship of the embodiment of the present application within 24 hours; wherein, Figure 4 a is under different terrain conditions; Figure 4 b is under different weather conditions;

[0031] Figure 5 The three views of the airship skin temperature distribution under the condition of sunny day on the grass terrain in the embodiment of the present application for 12 hours;

[0032] Figure 6 Schematic diagram of the system structure of an embodiment of the present application. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0034] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0035] Embodiment 1

[0036] like Figure 1As shown, it is a schematic diagram of the method flow of an embodiment of the present application, and the steps include:

[0037] S1. The analysis results are obtained by analyzing the thermal environment of the stratospheric airship.

[0038] In this embodiment, the analysis results are mainly the main heat sources and heat transfer that affect the thermodynamic characteristics of the airship's outer surface skin and internal filling gas, which are finely divided into three categories, including: external radiation, skin radiation, and convection heat transfer. Among them, external radiation consists of four parts: direct solar radiation, diffuse solar radiation, reflected solar radiation (ground and cloud reflected radiation), and infrared long-wave radiation (ground and atmospheric long-wave radiation); skin radiation can be divided into four parts: radiation heat transfer between the outer surface of the skin and the external atmosphere, radiation heat transfer between different positions on the outer surface of the skin, radiation heat transfer between different positions on the inner surface of the skin, and radiation heat transfer between the inner surface of the skin and the internal filling gas; convection heat transfer consists of two parts: mixed convection heat transfer between the outer surface of the skin and the external atmosphere and natural convection heat transfer between the inner surface of the skin and the internal filling gas.

[0039] S2. Based on the analysis results, a three-dimensional transient thermodynamic internal and external coupled heat transfer model of the airship is constructed.

[0040] After clarifying the internal and external coupling heat transfer mechanism of the airship through the above analysis results, it can be seen that the external thermal environment factors of the airship and the internal heat exchange factors are coupled through the skin. Then, according to the heat transfer mechanism of the airship, a three-dimensional transient thermodynamic model of the airship is established, which is an internal and external coupling heat transfer model considering convective heat transfer.

[0041] like Figure 2 As shown in the figure, the three-dimensional transient thermodynamic internal and external coupled heat transfer model of the airship is a combined model, which is composed of an external radiation heat source model, a skin surface radiation model and an internal and external convection model of the aerostat, which correspond to the three major types of parameters in the above analysis results.

[0042] The external radiation heat source model includes: solar radiation heat load model and long-wave radiation heat load model; the solar radiation heat load model is used to calculate the heat load of solar radiation; the long-wave radiation heat load model is used to calculate the load of infrared long-wave radiation.

[0043] Solar radiation specifically includes: direct solar radiation, diffuse solar radiation and reflected solar radiation (radiation reflected from the ground and clouds). Since solar radiation varies with different locations, times and dates on the earth, in order to calculate solar radiation, it is necessary to determine the spatial position of the sun and the relative position of the sun and the surface of the irradiated object. The solar altitude α is the angle between the line connecting the sun and the earth and the horizon, and the solar azimuth Φ is the angle between the projection of the line connecting the sun and the earth on the horizon and the local meridian (due south). It can be calculated by the following formula:

[0044] sinαsinLsin0(1)

[0045]

[0046] Where L is the local latitude, H is the solar hour angle, and δ is the declination angle.

[0047] There are three control angles for the incident solar radiation and the surface it illuminates. The surface solar azimuth γ is the angle between the projection of the sun-earth line on the ground plane and the projection of the surface normal on the ground plane. The angle of incidence θ is the angle between the sun-earth line and the surface normal. The tilt angle of surface from horizontal Σ is the angle between the object surface and the ground plane. There is also a conversion relationship between the three:

[0048] cosθ=cosαcosγsin+·sinαcos∑ (3)

[0049] For the horizontal plane, cosθ H = sinα; for the vertical plane, cosθ V =cosαcosγ.

[0050] After the sun's spatial position and the orientation of the irradiated surface are determined, the direct solar radiation heat flux (irradiance) is calculated first. Referring to the ASHRAE manual, the direct solar radiation under the clear weather condition method is:

[0051]

[0052] Where EDN is the direct radiation heat flux, A is the apparent solar irradiance when the atmospheric mass is zero, and B is the atmospheric extinction coefficient.

[0053] The calculation of diffuse radiation heat flux in the solar model is divided into the diffuse radiation of vertical surfaces and the diffuse radiation of other surfaces. The diffuse heat flux of the sun on the vertical surface is:

[0054] E d =CYE DN (5)

[0055] Where C is a constant and Y is the ratio of the diffuse radiation from the vertical surface to the diffuse radiation from the horizontal surface, as a function of the angle of incidence, as follows:

[0056]

[0057] The diffuse solar radiation from other surfaces is:

[0058]

[0059] The reflected solar radiation is:

[0060]

[0061] In the formula, ρ g is the reflectivity of the ground clouds. The total diffuse radiation on a given surface is the sum of Ed and Er.

[0062] For a given surface, the total solar radiation is calculated as follows:

[0063] E t =E DN cosθ+E d +E r (9)

[0064] In addition to the above solar radiation (short-wave radiation), for a flying aerostat, the external thermal environment also includes long-wave radiation from the earth's surface and the surrounding atmosphere. For ground long-wave radiation, the earth can generally be regarded as a gray body, and its radiation intensity mainly depends on the gray body temperature and gray body emissivity. The calculation formula for ground long-wave radiation intensity can be written as:

[0065]

[0066] Among them, ε Earth is the ground emissivity, and σ is the Stefan-Boltzmann constant, which is 5.67×10 -8 W / (m 2 ·K 4 ), T E rath is the surface temperature, τ a is the longwave radiation transmittance of the Earth’s surface and is calculated as follows:

[0067]

[0068] Among them, p a is the atmospheric pressure around the aerostat, and p0 is the atmospheric pressure on the ground.

[0069]

[0070] Among them, T a is the ambient temperature of the aerostat, ε sky is the sky equivalent emissivity, which can be calculated by the following formula:

[0071]

[0072] Among them, p w is the partial pressure of water vapor in the atmosphere, in kPa, calculated as follows:

[0073]

[0074] Rh is the relative humidity, which can be calculated by the following formula:

[0075]

[0076] Calculate the ground long-wave radiation intensity I Earth and the atmospheric longwave radiation intensity I sky After that, the amount of long-wave radiation absorbed by the skin unit i of the aerostat surface per unit time can be calculated by the following formula:

[0077]

[0078]

[0079] Among them, ε skin，i is the infrared emissivity of the skin outer surface unit i, A skin，i is the area of ​​unit i on the aerostat surface.

[0080] Fluent's built-in solar radiation model does not take into account the ground and atmospheric long-wave radiation. Moreover, although it calculates the ground and cloud reflected radiation, it cannot be directly reflected in the calculation results (that is, the reflected radiation on the surface of the object irradiated by the sun is zero). Therefore, a user-defined function UDF is used to correct the ground and cloud reflected radiation and supplement the ground and atmospheric long-wave radiation. The specific operation idea is to calculate the ground and cloud reflected radiation and the ground and atmospheric long-wave radiation respectively through the formulas introduced above, and add them to the skin of the airship model in the form of body heat source to participate in the coupling calculation. The data processing flow is as follows: Figure 3 shown.

[0081] The skin surface radiation model is used to calculate the radiation heat transfer between the outer surface of the skin and the external atmosphere, the radiation heat transfer between different positions on the outer surface of the skin, the radiation heat transfer between different positions on the inner surface of the skin, and the radiation heat transfer between the inner surface of the skin and the internal filling gas.

[0082] The skin surface radiation model specifically uses the discrete coordinate (DO) radiation model to solve the radiation transfer equation (RTE) for a finite number of discrete solid angles, each of which is related to the vector direction s in the global Cartesian coordinate system (x, y, z). The DO radiation model converts the RTE into a transport equation for the radiation intensity under the spatial coordinates (x, y, z). The DO radiation model treats the RTE in the direction s as a field equation for solution.

[0083] When computing gray body radiation, opaque walls are treated as gray bodies. Radiative energy incident on an opaque wall can be reflected back into the surrounding medium and absorbed by the wall. The reflected radiation can be diffuse or specular, depending on the diffuse fraction f. d . Let q in is the radiation energy incident on the opaque wall, then the general physical quantity for calculating the opaque wall is:

[0084] Wall surface radiation

[0085] Diffuse reflection energy——f d (1-ε w )q in

[0086] Specular reflection energy——(1-f d )(1-ε w )q in

[0087] Radiation absorbed by the wall——ω w q in

[0088] Where n is the refractive index of the adjacent medium, ε w is the wall emissivity, σ is the Stefan-Boltzmann constant, T w is the wall temperature. The absorption of the wall assumes that the absorptivity is equal to the emissivity. For a purely diffuse wall, f d is equal to 1, and there is no specular reflection energy. Similarly, for a purely specular wall, f d When the reflectance is between 0 and 1, there is both some diffuse reflection energy and some specular reflection energy.

[0089] During the operation of the airship, there is forced convection heat transfer between the outer surface of the skin and the surrounding atmosphere, and natural convection heat transfer between the inner surface of the skin and the gas filled inside the capsule. Convection heat transfer is related to gas flow, and it is necessary to solve the conservation equation of gas flow and heat transfer (that is, the constructed internal and external convection model of the aerostat) to obtain the heat transfer and other thermodynamic characteristics.

[0090] The convection model inside and outside the aerostat is based on the flow control equation (Navier-Stokes equation) considering the viscosity effect near the wall. The Reynolds average (RANS) method is used to solve the dynamic characteristics of the flow (pressure, shear force, etc.) and the convection heat transfer characteristics (temperature, heat flow, etc.). The RANS method specifically uses the RNG k-ε turbulence model.

[0091] For natural convection in a gas-filled airship, the Boussinesq model is used to simplify the fluid density in the flow control equations. This converges faster than solving the fluid density as a function of temperature. Except for the buoyancy term in the momentum equation, this model treats the density as a constant in the remaining equations. Specifically, the gravity term in the momentum equation is simplified by the Boussinesq approximation of the gas model, i.e., ρ=ρ0(1-βΔT). Processing:

[0092] (ρ-ρ0)g≈-ρ0β(T-T0)g (18)

[0093] Where ρ is the fluid density, T is the flow temperature, ρ0 is the reference density of the fluid, T0 is the ambient temperature, and is the thermal expansion coefficient (β = 1 / T m , T m is the qualitative temperature), g is the gravitational acceleration. When the actual density change is small (ie, β(T-T0)<<1), the approximate processing accuracy is higher.

[0094] When calculating the internal and external convection heat transfer of the airship, the skin, as the interface between the internal gas and the external gas, needs to be treated specifically. For internal and external convection, the skin can be treated as a fixed no-slip wall. As for heat transfer, the skin is the heat exchange boundary of the internal and external gases, and its inner and outer surfaces need to consider the wall heat flux respectively. At the same time, there is also a solid film heat conduction process inside the skin. Specifically, there is the following heat transfer process: external gas-skin outer surface-skin inside-skin inner surface-internal gas. In order to deal with the thermal boundary conditions of the skin, the skin is used as the interface between the internal and external flow fields, and the coupled heat transfer method is used to solve the heat exchange between the skin and the internal and external gases.

[0095] When using coupled heat transfer boundaries, the skin wall needs to be pre-processed as a double-sided wall, that is, there is a fluid domain on each side of the wall. When solving the energy equation, the heat exchange between the flow and the wall will be calculated directly based on the solution in the adjacent fluid grids on both sides of the wall. In addition, for the heat conduction process inside the skin, the skin is regarded as a thin wall and the thin wall heat conduction is solved. The wall surface adjacent to the internal and external flow field grids is regarded as the wall surface. When solving the heat conduction inside the skin, the thermal resistance of the wall is calculated by the one-dimensional steady-state heat conduction equation. By setting the thermal conductivity and thickness of the wall, the thermal resistance of the wall can be obtained as Δx / k, where k is the thermal conductivity and Δx is the skin thickness.

[0096] S3. Use the airship's three-dimensional transient thermodynamics internal and external coupled heat transfer model to complete the airship's thermal analysis.

[0097] Finally, the three-dimensional transient thermodynamics model of the airship constructed in the above steps is used to complete the analysis of the three-dimensional transient thermodynamics of the stratospheric airship.

[0098] Embodiment 2

[0099] In this example, a typical aerostat shape is selected as an example to evaluate the day and night characteristics of the aerostat and explore the influence of different terrain and weather conditions on the thermodynamic characteristics of the aerostat. The selected aerostat shape is a typical axisymmetric rotating body, with a length of 250m and a width of 75m. The specific geometric parameters are shown in Table 1.

[0100] Table 1

[0101]

[0102] The time is June 21st, and the specific calculation status parameter table is planned, as shown in Table 2. The reflectivity and ground emissivity in the table comprehensively consider the influence of terrain and weather.

[0103] Table 2

[0104]

[0105]

[0106] Figure 4 (a) Comparison of the changes in the average temperature of the filling gas inside the airship within 24 hours under different terrain conditions, i.e., the four conditions of Experiment No. 1 to 4 in Table 3 above. Figure 4 (b) Comparison of the changes in the average temperature of the airship filling gas within 24 hours under different weather conditions, namely, the three conditions of Experiment No. 3, 5, and 6 in Table 3 above. Taking Experiment No. 4 in Table 3 above (i.e., sunny grass conditions) as an example, the three-view diagram of the airship skin temperature distribution at a certain moment predicted by the model is shown as follows Figure 5 shown.

[0107] Embodiment 3

[0108] like Figure 6 As shown, it is a schematic diagram of the system structure of this embodiment, including: an analysis module, a construction module and a result generation module; the analysis module is used to obtain analysis results by analyzing the thermal environment of the stratospheric airship in the air; the construction module is used to construct a three-dimensional transient thermodynamic internal and external coupling heat transfer model of the airship based on the analysis results; the result generation module is used to use the three-dimensional transient thermodynamic internal and external coupling heat transfer model of the airship to complete the thermal analysis of the airship.

[0109] The analysis results include: external radiation, skin radiation and convective heat transfer; among them, external radiation includes: direct solar radiation, diffuse solar radiation, reflected solar radiation and infrared long-wave radiation; skin radiation includes: radiation heat transfer between the outer surface of the skin and the external atmosphere, radiation heat transfer between different positions on the outer surface of the skin, radiation heat transfer between different positions on the inner surface of the skin, and radiation heat transfer between the inner surface of the skin and the internal filling gas; convective heat transfer includes: mixed convective heat transfer between the outer surface of the skin and the external atmosphere and natural convective heat transfer between the inner surface of the skin and the internal filling gas.

[0110] The embodiments described above are only descriptions of the preferred methods of the present application, and are not intended to limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements made to the technical solutions of the present application by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present application.

Claims

1. A method for analyzing the three-dimensional transient thermodynamics of a stratospheric airship, characterized in that the steps include: The analysis results are obtained by analyzing the thermal environment of the stratospheric airship in the air; Based on the analysis results, a three-dimensional transient thermodynamic internal and external coupled heat transfer model of the airship is constructed; The thermal analysis of the airship is completed by using the three-dimensional transient thermodynamics internal and external coupled heat transfer model of the airship.

2. The method for analyzing three-dimensional transient thermodynamics of stratospheric airship according to claim 1, characterized in that: The analysis results include: external radiation, skin radiation and convective heat transfer; wherein, the external radiation includes: direct solar radiation, diffuse solar radiation, reflected solar radiation and infrared long-wave radiation; the skin radiation includes: radiative heat transfer between the outer surface of the skin and the external atmosphere, radiative heat transfer between different positions of the outer surface of the skin, radiative heat transfer between different positions of the inner surface of the skin, and radiative heat transfer between the inner surface of the skin and the internal filling gas; convective heat transfer includes: mixed convective heat transfer between the outer surface of the skin and the external atmosphere and natural convective heat transfer between the inner surface of the skin and the internal filling gas.

3. The method for analyzing three-dimensional transient thermodynamics of stratospheric airship according to claim 2, characterized in that: The three-dimensional transient thermodynamic internal and external coupled heat transfer model of the airship is a combined model, including: an external radiation heat source model, a skin surface radiation model and an internal and external convection model of the aerostat.

4. The method for analyzing three-dimensional transient thermodynamics of stratospheric airship according to claim 3, characterized in that: The external radiation heat source model includes: a solar radiation heat load model and a long-wave radiation heat load model; the solar radiation heat load model is used to calculate the loads of the direct solar radiation, the diffuse solar radiation and the reflected solar radiation; the long-wave radiation heat load model is used to calculate the load of the infrared long-wave radiation.

5. The method for analyzing three-dimensional transient thermodynamics of stratospheric airship according to claim 3, characterized in that: The infrared long-wave radiation and the reflected solar radiation are simulated and calculated using UDF; the specific steps include: calculating the heat loads of the reflected solar radiation and the infrared long-wave radiation, and adding them to the skin of the airship model in the form of body heat sources to participate in coupling calculations.

6. The method for analyzing three-dimensional transient thermodynamics of stratospheric airship according to claim 3, characterized in that: The skin surface radiation model specifically adopts a discrete coordinate radiation model to solve the radiation transfer equation of a finite number of discrete solid angles, and converts the radiation transfer equation into a transport equation of radiation intensity under spatial coordinates; then, the radiation transfer equation in the vector direction is regarded as a field equation for solution.

7. The method for analyzing three-dimensional transient thermodynamics of stratospheric airship according to claim 3, characterized in that: The internal and external convection model of the aerostat is based on the flow control equation considering the viscosity effect near the wall, and adopts the Reynolds average method to solve the dynamic characteristics and convection heat transfer characteristics of the flow.

8. The method for analyzing three-dimensional transient thermodynamics of stratospheric airship according to claim 7, characterized in that: When calculating the internal and external convection heat transfer of the airship, the skin is treated as the interface between the internal gas and the external gas, and targeted treatment is performed; the specific steps include: when calculating the internal and external convection of the airship, the skin is treated as a fixed no-slip wall; when calculating the heat transfer of the airship, the skin is treated as the heat exchange boundary of the internal and external gases, and the wall heat flux of its inner and outer surfaces is calculated respectively.

9. A system for analyzing three-dimensional transient thermodynamics of stratospheric airships, the system being used to implement the method according to any one of claims 1 to 8, characterized in that: include: Analysis module, construction module and result generation module; The analysis module is used to obtain analysis results by analyzing the thermal environment of the stratospheric airship in the air; The construction module is used to construct a three-dimensional transient thermodynamic internal and external coupled heat transfer model of the airship based on the analysis results; The result generation module is used to complete the thermal analysis of the airship by using the three-dimensional transient thermodynamics internal and external coupled heat transfer model of the airship.

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