微腔内气体抽离的多尺度模拟与分析

Multi-scale simulation and analysis of gas evacuation processes in a microcavity

基于适用于整个克努森数范围的流动理论,建立了去除惯性约束聚变实验中靶丸内空气的理论模型,并设计实验验证了此模型的可靠性。物理实验要求靶丸内空气浓度低于10×10^(−6),数值模拟了去除靶丸内空气的过程,重点分析了靶丸内空气浓度、压力与除气时间的关系。计算并比较了单管路一次抽气法、单管路循环抽气法与双管路流洗法三种去除靶丸内空气方法的时间成本。数值计算结果表明:单管路一次抽气法中,靶丸上的微通道的存在对去除靶丸内空气所需时间的影响不可忽略,在考虑靶丸上微通道与充气管的情况下,需要1961.77 h才能使靶丸内的空气浓度达到标准。单管路循环抽气法中,抽气次数与单次抽气程度会影响去除靶丸内空气所需总时间,在单次抽气程度值取最优的情况下,采用充三次,抽四次的方案可使达标总时间减少至1 h左右,此方案下单次充气和抽气时间分别为6 min和10 min。而采用双管路流洗法则仅需11 min便可使靶丸内空气浓度达标。

Based on the flow theory applicable to the whole Knudsen number range,a theoretical model for removing air from the target shot in inertial confinement fusion was established,and the reliability of the model was verified by designed experiments.The physical experiment requires the air concentration in the target capsule to be lower than 10×10^(−6),the process of removing air in the capsule was simulated numerically,and the relationship between the air concentration in the capsule,the pressure in the capsule and time was emphatically analyzed.The time consumed by three methods for removing the air in the capsule,namely the single-pipe one-time gas evacuation method,the single-pipe circulation gas evacuation method and the double-pipe flow washing method,was calculated and compared.Numerical calculation results show that:in the single-pipe one-time gas evacuation method,the existence of the micro-channel on the capsule has a non-negligible effect on the time required to remove the air in the capsule,and it takes 1961.77 h for the air concentration in the target shot to reach the standard when the micro-channel on the capsule and the gas-filling pipe is considered.In the single-pipe cycle gas evacuation method,the number of evacuation times and the degree of single gas evacuation will affect the total time required to remove the air in the capsule.When the single gas evacuation degree is at the optimal value,the scheme that filling three times and evacuating four times can reduce the total time to reach the standard to about 1 h,while the single gas filling time and gas evacuation time are 6 min and 10 min,respectively.However,it takes only 11 minutes for the air concentration in the capsule to reach the standard by using the double-pipe flow washing method.