Research On Surface Temperature Distribution Of Multi-Target Space Cold-Shield System

The space cold-shield system is one of the most important structural parts of a multi-target space hypersonic vehicle.Its special conical shape structure is not only conducive to the flight process of the space vehicle,but also a powerful backing to protect the safety of its internal sub-targets when the space vehicle implements strike missions.The radiation characteristic of the space cold-shield system surface is the most critical indicator for the hypersonic vehicle defense system to perform infrared detection.Therefore,to ensure that the multi-target space hypersonic vehicle completes the attack task,the infrared radiation intensity of the multi-target space cold-shield system surface must be less than 0.5W/m~2 in the flight time of 1800s,and its surface temperature is less than 100K.The most effective way to achieve this goal is based on the distribution law of the surface temperature of the multi-target space cold-shield system.Refrigeration of the cold-shield system reduces its surface temperature and weakens its surface infrared radiation characteristics.Realize the infrared stealth purpose of multi-target space hypersonic vehicle.The complete flight process of the multi-target space hypersonic vehicle generally includes the first stage of propulsion,the second stage of propulsion,the middle flight stage,and the reentry stage.During the entire flight process,the space environment and its own structure are constantly changing.Therefore,the comprehensive research work on the surface temperature distribution of the multi-target space cold-shield system needs to be based on factors such as the space environment during different flight phases and the operating state of the aircraft.The numerical simulation part of this paper is based on the DF-41 entity size according to the ratio of 1:1.Solidworks is used to establish the physical model of the multi-target space cold-shield system when the multi-target space hypersonic vehicle is placed in the wind tunnel in the primary propulsion stage and the secondary flight stage and the multi-target space cold-shield system is not placed in the wind tunnel during the middle flight stage,and then the grid is divided and the grid independence verification and the simulation conditions are set,And then with the help of Fluent numerical simulation software,the distribution cloud diagram of the surface parameters of the cold-shield system at different flight speeds of the multi-target space hypersonic vehicle during the first stage and the second stage of the propulsion stage and the parameter streamline diagram that directly displays the flow field of the cold screen system And the two cold screen models based on the design during the flight.The parameter distribution cloud diagram and parameter streamline diagram of the cold screen surface obtained by changing the nitrogen inlet flow rate and nitrogen state.Finally,a summary analysis of the post-processing work of the simulation results reveals the distribution law of the surface temperature of the multi-target space cold-shield system during the entire flight of the aircraft.The results show that the temperature,pressure,and fluid density distribution on the surface of the multi-target space cold-shield system during the first and second propulsion stages are relatively uniform and distributed symmetrically along the central axis of the aircraft,gradually from the bottom to the top of the cold-shield system.Increase and present a cascade distribution;the velocity distribution on the surface of the cooling screen is relatively uniform,and gradually decreasing from the bottom to the top of the cooling screen and showing a cascade distribution.Through the comparative analysis of numerical simulation results,it is finally determined that the multi-target space hypersonic vehicle is in The total pressure value of the cold-shield system surface at different flight speeds(3Ma,5Ma,7Ma,9Ma)in the first stage of propulsion is 10~5～10~7Pa;the dynamic pressure value is 10~5～10~6Pa;the temperature value is 478.7～2618.2K;the speed value is 655.9～2804.7m/s;fluid density value is 0.31～1.3kg/m~3;the total pressure value of the cold-shield system surface of the spacecraft at different flight speeds(10Ma,12Ma,14Ma,16Ma)in the second stage of propulsion is 10~6～10~8Pa;dynamic pressure The value is 10~5～10~7Pa;the temperature value is between 2111.3～10753.1K;the speed value is between 1797.1～5093.3m/s;the fluid density value is between 0.23～1.33kg/m~3,In the mid-flight,by comparing the two cold-screen models designed,the"bottom-in and bottom-out"model can control the pressure of the cold-screen system around 13100Pa and the temperature to below 66.36K.The“bottom-in and top-out”model can control the pressure of the cold screen system at the triple point pressure of the nitrogen working fluid at 12520Pa and reduce the temperature to below 70.82K;both models can control the pressure of the cold screen system and reduce the surface temperature.Surface parameters are required,but the"bottom-in and bottom-out"model is more prominent in maintaining the pressure and temperature stability of the cold screen system.At the same time,for the two models,the nitrogen inlet flow rate is increased,and the nitrogen with a certain degree of superheat is added for throttling.During cooling,the surface temperature of the cold-shield system can be controlled to be lower.Therefore,the design of a cold screen model with a“bottom-in and bottom-out”structure,an increase in the nitrogen inlet flow rate,and a certain superheated nitrogen refrigerant can reduce the surface of the cold screen system.The infrared radiation intensity is better,and the effect of achieving the infrared stealth purpose of the multi-target space hypersonic vehicle is better.The research content and results of this paper can provide a certain degree of theoretical reference for the relevant personnel who are committed to the internal low-temperature refrigeration of the multi-target space cold-shield system,the overall structure design,the in-depth study of surface parameters,and the practical engineering application of infrared stealth technology.