| With the rapid development of China’s aerospace industry,optical measurement equipment has been widely used in the space industry.However,the aerospace environment is complex,and equipment used in this field needs to meet higher design requirements.Among them,the optical camera device used in the fuel storage tank of China’s new generation launch vehicle is facing an extreme low-temperature environment close to﹣183℃,which seriously limits the performance of the device.Studying and designing a thermal control system for the camera device used in extreme low-temperature environment,improving the environmental adaptability of the camera device,has great engineering value and significance.In order to enable the camera device to successfully complete imaging and monitoring tasks in extreme low-temperature environment,this thesis takes the optical camera device in the rocket’s liquid oxygen storage tank as the research object and conducts research on the design of its thermal control system.Firstly,the impact of extreme low-temperature environment on the camera device was analyzed.Based on the temperature response model,it was explained that extreme low-temperature can cause changes in the geometric parameters and refractive index of optical components,leading to a decrease in imaging quality.In addition,extreme lowtemperature can also cause the danger of low-temperature embrittlement of mechanical structures.This further indicates that thermal control design is necessary for camera devices operating in extreme low-temperature environments.Secondly,an analysis was conducted on the thermal environment where the camera device is located,and an overall thermal control plan combining active and passive measures was planned based on thermal control indicators.Phase-change material refers to a substance that changes its form with temperature and can provide latent heat.It has the advantages of high latent heat,high energy storage density,and long constant temperature time.Based on the heat transfer characteristics of phasechange materials,the thesis proposed a passive thermal control scheme for the design of phase change temperature controlled composite insulation layer structure.Thirdly,due to the use of phase-change temperature control technology in passive thermal control,based on the Solidification/Melting model of FLUENT software,the typical phase-change heat transfer characteristics of octadecane(phase-change temperature: 28 ℃)as a phase-change material in a two-dimensional rectangular space were analyzed,and the main factors affecting the numerical simulation of phase-change heat transfer were explored.The results indicate that phase-change temperature control technology based on phase-change materials has great thermal control application characteristics.In addition,natural convection,wall temperature,and phase-change layer thickness have different effects on the phase-change heat transfer process,which provides a basic basis and inspiration for phase-change temperature control design.The passive thermal control scheme adopts the structural design of a phase-change temperature control composite insulation layer,which is implemented based on numerical simulation technology.Eicosane(phase-change temperature: 36.7 ℃)is selected as the phase-change layer material,and polyurethane is used as the insulation layer material.By comparing and analyzing the combination schemes of phase-change layer and insulation layer thickness parameters,the requirement of meeting the normal operating temperature range(-40 ～ +60 ℃)of the camera device within 120 minutes is taken as the indicator,The final thickness of the phase-change layer was determined to be 15 mm and the insulation layer to be 9mm.Based on this,a systematic design and explanation of the thermal conductivity enhancement structure,packaging structure,and sealing structure of the phase-change temperature control were further carried out.Then,the active thermal control scheme is designed accordingly.Considering the structural characteristics of the optical camera device and specific thermal control requirements,the polyimide electric heating film is selected for active heating.The total heat consumption of the whole machine is calculated according to the natural convection and radiation heat transfer between the camera device and the external environment,so as to obtain the active heating power,Corresponding temperature control strategies were designed separately.Finally,a structural model of the entire camera device was established.In order to verify the effectiveness of the thermal control scheme design,the entire structure was simplified into a thermal simulation analysis model for non-steady state thermal simulation calculations.The corresponding simulations were conducted for insulation and heating conditions.The results showed that under-183℃ and power outage insulation conditions,the internal temperature decreased from 50℃ to-17℃ within120 minutes,meeting the insulation requirements of extreme low-temperature conditions(-40 ～ +60 ℃),The temperature curve is consistent with the typical heat transfer characteristics of phase-change temperature control,indicating that the structural design of the phase-change temperature controlled composite insulation layer has played a great insulation effect.In the temperature simulation of corresponding working conditions,it takes about 35 minutes to rise from-20℃ to 50℃;In addition,for normal working mode,the time for the temperature to decrease from 50℃ to 20℃is about 80 minutes.The temperature simulation results show that it takes about20 minutes for the temperature to rise from 20℃ to 50℃.By alternating dynamic active heating and passive insulation,the temperature inside the camera device can be maintained within the range of 20℃ to 50℃,achieving temperature control purposes. |
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