Research On Temperature Distribution Of Infrared Anti-radiation Cooling Surface In Space Cold-Shield System

As the hypersonic aircraft experiences complex space aerodynamic frictional heat transfer during operation,its surface temperature rises sharply,and the intensity of infrared radiation gradually increases.The infrared radiation characteristics of an aircraft are an important basis for space infrared detection and identification.Therefore,it is particularly important to reduce the intensity of infrared radiation on the surface of an aircraft.Liquid nitrogen cold-shield technology uses the principle of refrigerant phase change to absorb a large amount of heat to reduce the target's infrared radiation intensity.Its internal refrigeration involves two important processes: low-temperature liquid evaporation refrigeration and throttling refrigeration.At present,the basic theoretical support required for throttling refrigeration of a multi-target cold-shield system at near three-phase points in a space-complex environment is lacking.Therefore,research on the operation of a multi-target cold-shield system in the middle of space is of great significance.The operation of the multi-target aircraft in the middle of space is divided into two phases,that is,the mother cabin carries multiple sub-target vehicles to the maximum altitude and then releases the sub-target aircraft.After the sub-target aircraft leaves the mother cabin,it continues to follow the predetermined orbit.First,this article designs two different forms of multi-target cold-shield structure.One is a mother cabin carrying multiple sub-targets running in space,with a refrigerant outlet at the top;the other is a mother cabin carrying multiple sub-targets running in space,with a bottom.Refrigerant outlet for annular chassis.In order to reveal the changes in the physical parameters of the multi-target cold-shield system near the three-phase point during the mid-space operation,first,this paper aims at two models to change the refrigerant inlet flow rate,refrigerant inlet state,and refrigerant outlet The working conditions of the caliber are studied,and the distribution parameters of the system parameters of the two cold-shield structures under different working conditions are obtained.Secondly,the simulation results obtained by the two models are compared to obtain the optimal structural form.Finally,a subtarget aircraft was designed to run in the middle of space after leaving the mother cabin.The cold-shield system was filled with low-temperature liquid nitrogen.The RNGk-? turbulence model and evaporation-condensation model were used to simulate the changes in The influence of the inlet flow rate on the parameters of the cold-shield system,and the internal surface temperature distribution of the single target cold-shield system in the middle of the space is studied.The results show that: In the two multi-objective cold-shield systems,the saturated nitrogen gas shows similar rules after throttling.With the increase of the inlet flow rate,the temperature of the cold-shield surface gradually decreases,and the throttling effect is enhanced;Under the conditions of filling saturated nitrogen and superheated nitrogen,the cooling effect of the cold-shield when superheated nitrogen is added is better than when saturated nitrogen is added;When the cross-sectional area of the nitrogen outlet is reduced,the temperature and pressure of the two cold-shield systems gradually increase,and the cooling capacity decreases.By comparing the simulation results of the two multi-objective cold-shield systems,it is shown that the model with an outlet at the bottom has better cooling effect,but requires more materials.When filling low-temperature liquid nitrogen in a single-target cold-shield system,as the inlet flow rate of liquid nitrogen increases,the temperature of the cold-shield gradually decreases;By simulating the single-target cold-shield system under optimal conditions,the temperature distribution law during space operation in each time period is obtained.The results show that the cold-shield system can meet the expected goal of space cooling for 1200 s.The research content of this article provides a theoretical reference for the subsequent research of cold-shield system and its structural optimization design.