Transient Thermal Model And Thermal Characteristics Analysis Of Stratospheric Airships

Stratospheric airships have a great range of attractive advantages,such as long durations,low cost and wide application prospects.As the atmosphere of the stratosphere is very thing,the airships are generally very large and thus very sensitive to the external thermal environment.The strong solar radiation and poor convective heat transfer in the stratosphere greatly affect the internal temperature field of the airship.The large temperature difference between day and night will cause the volume change of the airbag inside the airship,affecting the buoyancy of the airship,and thus changing its balance height and flight path.The study of the thermal balance between the airship skin and the internal filling gas can promote the development of the design and control of the stratospheric airships,ensuring its stability and controllability.Therefore,it is of great research significance and application value to establish a complete and accurate thermal model for the stratospheric airship and carry out the analysis of its thermal characteristics.In this paper,a series of researches have been carried out around the thermal model and thermodynamic properties of the stratospheric airships during vacancy.The main work and achievements of the paper are as follows:(1)The complete thermal model of the stratospheric airship is established by the finite split method,and the thermodynamic equations of the skin and the internal filling gas were established.The atmospheric environment,heat source and heat transfer mode of the stratospheric airship are analyzed,and the atmospheric environment model,the solar short-wave radiation model,the long-wave radiation model and the convective heat transfer model are established,and the thermodynamic calculation methods for both opaque skin material airships and translucent skin material airships are given respectively.In order to make the established thermal model applicable to different types of airships,the surface of the airship skin is discretized,the thermodynamic equation of the airship skin is established by the distributed parameter method,and the thermodynamic equation of the internal filling gas is established by the lumped parameter method,(2)The reliability of the established model and its solution method is verified.Firstly,the implementation method of the research is summarized,and the flow chart of the thermal analysis of the vacant state of the airship is drawn.The initial parameters of the numeral calculations are designed,and in order to improve the computational efficiency under the premise of ensuring the accuracy of the results,the influence of time step and grid numbers on the calculation results is studied.Finally,the reliability and validity of the established model and its solving method are verified through the comparative analysis with the experimental data of related research.(3)The distribution of the relevant parameters of the airships at typical times is analyzed,and a simplified thermal model of the stratosphere airship is established.Firstly,the distribution and trend of various heat sources and related parameters on the surface of the airships were analyzed at 12 o'clock and 24 o'clock.Then,the contribution of different heat sources to the thermal characteristics of the airships is compared,and the heat sources with little influence on the thermal characteristics of the airships are analyzed.Finally,a simplified calculation model for the thermal characteristics of the airship is established,and the reliability of the simplified model is verified by comparison with the complete model.(4)The thermal sensitivity factors of the stratospheric airships were analyzed.Firstly,the factors that may affect the thermal characteristics of the airship are theoretically analyzed.Then,the influence of nine influence factors,including the altitude,the season,the longitude and the latitude of the airship,cloud cover rate,airspeed,internal filling gas,size of the airship and surface skin thickness,on the temperature of the skin and internal filling gas of airships are analyzed.The main sensitive factors affecting the thermal characteristics of the airships and its influence law are obtained,which provides an effective reference value for the future research of the thermal characteristics of the stratosphere airships...