冷冻靶温度场瞬态响应特性及二级冷屏影响分析

Transient Temperature Characteristics of Cryogenic Target and Analysis on Influence of Fixed Thermal Shields

针对屏蔽结构开启过程中,外界大量辐射热的传入导致的冷冻靶燃料冰层均匀性恶化问题,建立了带低温屏蔽罩和二级冷屏结构的六端直柱腔冷冻靶三维模型,基于Boussinesq假设和离散坐标(DO)辐射模型,利用FLUENT软件进行数值模拟,探究了屏蔽结构开启过程靶丸表面温度场的瞬态响应规律,研究了二级冷屏结构及其位置对瞬态温度特性的影响。结果表明:低温屏蔽罩开启过程中,在外界辐射、黑腔内气体对流及充气管导热等因素的综合影响下,靶丸表面温度快速上升,靶丸表面最大温差则先迅速上升至峰值而后下降并趋于稳定;二级冷屏结构能有效阻挡外界高温辐射,使靶丸表面最高温度的温升降低了39.5%,靶丸表面温度均匀性改善了39%;缩小二级冷屏上下侧壁面的窗口或增大上下侧壁面与靶丸中心的距离,可以进一步降低靶丸表面温升、改善温度均匀性恶化程度;靶丸表面温度对二级冷屏前端上、下侧壁面位置变化的敏感程度远大于其他侧壁面。所得结果对屏蔽结构开启过程中靶丸表面温度场的控制具有指导意义。

When the cryogenic thermal shield is removed,the fuel ice uniformity of cryogenic target deteriorates significantly due to the introduction of a large amount of radiant heat from the ambient environment.For this problem,a threedimensional model was established for a sixentrance cylinderhohlraum cryogenic target with removable and fixed thermal shields based on the Boussinesq hypothesis and the discrete coordinate(DO)radiation model in the present study.The FLUENT software is used for numerical simulation to investigate transient temperature characteristics of the capsule surface during the thermal shield removal process,and analyze the influence of the structure and position of the fixed thermal shield on these transient temperature characteristics.The results show that during the removal of the cryogenic thermal shield,the temperature of the capsule surface increases rapidly under the combined effect of the external radiation,the convection in the hohlraum and the conduction through the fill tube,while the maximum temperature difference on the capsule surface first increases rapidly to the peak,then decreases,and finally tends to be stable.The fixed thermal shield structure can effectively prevent the external hightemperature radiation,reducing the temperature rise in the maximum temperature on the capsule surface by 39.5%and improving the uniformity of capsule surface temperature by 39%.Reducing the size of windows in the upper and lower side walls or increasing the distances from the walls to the capsule center can further reduce the temperature rise of the maximum temperature on the capsule surface and suppress the deterioration of temperature uniformity.The sensitivity of capsule surface temperature to the change in positions of the front upper and lower side walls of the fixed thermal shield is higher than that of other side walls.The results are instructive for the capsule surface temperature control during cryogenic thermal shield removal.