Large Area Spray Phase Transformation Cooling And Cryogenic Control Study Of Thin Shell Structure

When the aircraft is cruising at high speed at high altitude,the aerodynamic heat generated on the outer surface of the aircraft skin is large.With the improvement of infrared detection technology and the improvement of infrared signal resolution,the detection distance,recognition distance and identification distance have made great progress.In order to achieve infrared stealth,it is still difficult to escape the monitoring of infrared detection equipment by reducing the emissivity of skin.Therefore,people consider reducing the skin temperature to the same state as the ambient temperature to achieve background fusion.According to the cooling demand of large area,fast response and long time in the above background,combined with spray cooling mechanism and two-phase flow mechanism,heating mechanism and measuring system principle,a large area spray cooling experimental platform with thin shell structure was designed and built.The temperature response measurement and analysis experiments of the heating surface of large-area shell structure under the boundary conditions of different heat flux and different temperature zone are carried out.The main work of this paper is as follows:Firstly,the atomization process of spray cooling and the interaction mechanism between droplet and liquid film and wall are analyzed.The flow and heat transfer mechanism of two-phase flow liquid in the experimental section are expounded.This paper analyzes the shortcomings of traditional heating methods in providing heat flow boundary for rapid response experiments,and then expounds the non-contact heating of quartz lamp and the contact heating principle of small heat capacity of electric heating plate.The factors of measuring errors caused by thermocouples in the process of radiation heating and the temperature measurement mechanism of infrared thermal imager are explained and the whole control principle of the experimental system is analyzed.These provide the design basis and theoretical basis for the construction of large area spray cooling experimental platform with thin shell structure.Secondly,according to the design principle,the components of the experimental system are selected and verified,including the liquid supply system,heating system and measuring system in the experimental section.The selection of experimental components such as nozzles,coolants,liquid storage tanks,solenoid valves and piping,spray chamber design and insulation are introduced.The heating system introduces the selection of quartz lamp heating,electric heating plate and voltage regulator.The measurement system includes the selection and installation of thermocouples,data acquisition instrument,infrared thermal imager and heat flow meter parameters,as well as the setting of controller parameters of cooling and heating control components.Finally,aiming at the low heat flux,high heat flux and different temperature regions,combined with the test requirements of infrared radiation characteristics of thin shell structure,the principle of large area spray cooling experiments is carried out.The uniformity of heating and heating of quartz heating lamps is analyzed.The temperature response curve of the outer surface temperature of the shell structure from the initial temperature to the set temperature is obtained under different heat flux density and different temperature zone.