Numerical Research On The Thermal-deformation Behavior Of Stratospheric Aerostat During Ascent

In the process of launching,the stratospheric aerostat will experience complex atmospheric environment,which will cause the temperature,pressure,density and other parameters of the gas in the airship to fluctuate violently,resulting in dramatic thermal characteristics and structural changes of the airship.Therefore,the study of stratospheric airship in the rising stage is of great significance.In view of the above problems,this paper analyzes the thermal kinematic characteristics and the deformation of the membrane structure during the ascent of the stratospheric aerostatFirstly,The atmospheric environment of stratospheric aerostat is introduced.Various environment factors affecting the thermal characteristics of the stratospheric aerostat are analyzed,such as wind speed,solar radiation,infrared radiation,convection,and heat transfer between helium and airship envelope.Based on the above mathematical model of thermal environment factors and the force analysis of airship,the thermal motion model of stratospheric aerostat during lift off is established.And the model is solved and verified.Secondly,using the established thermal motion model of stratospheric aerostat,the MATLAB numerical simulation program is compiled,and the model is used to simulate the shape keeping and ascending process of the twin balloon stratospheric airship.The results show that the phenomenon of "super cooling" of the inner gas is obvious in the process of shape maintaining and rising of the stratospheric aerostat.Especially in the early stage of the rising process,due to the large volume of the air bag,the "super cooling" phenomenon is more obvious due to the effect of expansion and exhaust,and the air temperature is 50 K lower than the maximum temperature of the outside air.In the initial stage of the airship rise,the temperature of the air bag is too low and the density is relatively high,which leads to the decrease of the net buoyancy and the rise speed of the airship,and even result in the phenomenon of the airship slowly rising with fluctuation in a certain height.At the same time,the effects of solar radiation absorptivity and long wave radiation absorptivity on thermal characteristics are analyzed.The simulation results can be used to guide the design and control of stratospheric airship.At last,the variation laws of geometry(shape,height,volume)and mechanical parameters(strain and stress distribution)are analyzed when the stratospheric aerostat is inflated.In this paper,the mathematical model of partial inflation of stratospheric balloon is studied,and the matlab program is compiled to find out the relationship between the maximum radius,height of partial inflation balloon and the pressure difference at the bottom of the balloon;the theoretical solution method of stratospheric airship with elliptic bus under certain inflation pressure is given.Using ANSYS finite element analysis software,the stress and strain distribution of airship under certain inflation pressure are simulated.According to the calculation results,it is concluded that the stress in the middle of stratospheric airship is the largest,and the stress distribution of airship skin is related to the curvature of airship bus.Finally,the conclusion is used to improve the design of airship.