液氢是一种常用的沸点低、易蒸发的空间低温推进剂，基于其密度小，热值高，无毒无污染的优势，在未来航天探测任务中有着广阔的应用背景。但是做为一种理想的“未来能源”，氢能源在实现长期存储方面依然存在很大的挑战。当液氢做为空间推进剂存储在储罐中执行空间任务时处于微重力环境，在微重力环境中，一些在地面上的次级作用力如表面张力等会成为主要作用力，而由重力引起的作用力的影响会减小变为次级作用力，因此微重力环境中的储罐内部浮力对流被极大减弱甚至完全抑制，在这种情形下，当储罐壁面存在漏热现象时，储罐内部气液两相流体系会出现环绕漏热源的温度分层现象，引起流体局部过热沸腾，导致储罐内部压力急剧增大，危害系统结构安全，因此非常有必要采取措施抑制储罐内部的温度分层现象，进而实现压强控制。

尽管随着科学技术的进步，科研工作者研发了多种绝热材料避免储罐壁面发生漏热现象，但是目前还是无法做到完全绝热，而且采用绝热材料对于执行长期太空探索任务的航天器会带来负重增加等多方面的不利影响，多年来科研工作者都在尝试探索其他高效的方法避免储罐局部高温区的形成，利用低温射流抑制温度分层现象是一种有效手段。低温流体通过设置在储罐内部的射流喷嘴进入储罐内部并与内部原有的流体混合，促进储罐内部流体流动进而消减储罐内部的局部高温，实现温度的均匀化。本文首先采用全充满的二维缩比储罐模型，对微重力条件下液氢储罐内局部漏热引起的温度分层现象进行了数值模拟，分析了射流喷嘴形状，射流喷嘴在储罐内部位置，入射体积流量等不同低温射流条件对于消除微重力条件下液氢储罐内部温度分层效果的影响。研究得到的主要结论如下：对于同一种形状的射流喷嘴，当入射体积流量相同时，射流喷嘴距离出口位置更近，罐内形成的最终流场整体性更好，低温流体能影响到的区域也更广，因此温度分层消除效果更好；在同等低温射流置换率情况下，改变低温射流速度对温度分层消除效果有影响，但是并不明显。另一方面，当射流喷嘴位于储罐内部同一相对位置且入射流量相同时，圆形低温射流喷嘴低温射流出流方向更集中，罐内流场演变更快，因此消除效果比半球形射流喷嘴更好。文章还对大尺寸储罐对于采用低温射流方法抑制温度分层的模拟结果进行了模拟研究，结果发现对于大尺寸储罐，当采用圆形射流喷嘴时，射流喷嘴的位置对罐体内部温度分层消除效果的影响不是很明显，在本文的大尺寸储罐入射条件下，当低温射流置换率达到2%，即低温射流时间持续700s时，罐体内部温度分层的消除效果最显著；同时，当射流喷嘴位于储罐内部同一相对位置且入射流量相同时，圆形射流喷嘴因出流方向更集中，罐内流场演变更快，温度分层消除效果比半球形射流喷嘴更好，这一点与小尺寸储罐得到的结论是一致的。

为了进一步符合工程实际问题，我们研究了低温射流对大尺寸储罐内部气液两相体系温度分层现象的抑制,主要研究了入射质量流量、储罐填充率等因素对消除温度分层现象的影响。得到的结论如下：当填充比一定时，较高的入射质量流量破坏储罐温度分层，促进罐内流体流动的作用更明显，而且填充率越高，贯穿气相区所需的质量流量越大；当入射质量流量一定时，填充率越低，储罐内部平均温度和平均压强上升速度越快，要抑制其上升速度，需要的入射质量流量越大；在较高入射质量流量下，填充率越小，平均速度曲线越容易变平缓，且平缓后速度值越大；填充率越小，由蒸发引起的质量转移越高。

Liquid hydrogen is a commonly used space cryogenic propellant with low boiling point and easy evaporation. Based on its advantages of abundant reserves, high calorific value and no pollution from combustion products, it has a broad application background in future space exploration missions. But as an ideal "energy of the future", hydrogen still faces big challenges in achieving long-term storage. As we all know, in the microgravity environment, some secondary force on the ground such as surface tension becomes the main force, and reduce the influence caused by the gravitational force a secondary reaction. When liquid hydrogen is stored as a space propellant in a storage tank to perform space missions, the tank internal buoyancy convection in the low gravity environment is greatly reduced or even completely suppressed, when there is local heat leakage on the wall of the propellant tank, temperature stratification will happen around the heat leakage source, causing local overheating.This affects the interfacial heat and mass transfer, causing the tank pressure to rise , and jeopardize the structural safety of the system. Therefore, it is very necessary to take measures to restrain the temperature stratification in the tank, so as to achieve pressure control.

Although with the advancement of science and technology, researchers have developed a variety of thermal insulation materials to avoid heat leakage on the tank wall, but it is still impossible to achieve complete thermal insulation, moreover, the use of thermal insulation materials will bring about a variety of adverse effects, such as increased load on spacecraft on long-term space exploration missions. For many years, researchers have been trying to explore other efficient methods to avoid the formation of local high temperature zones in the storage tank. The use of cryogenic jets to suppress temperature stratification is an effective method. The cryogenic fluid enters the interior of the storage tank through a jet nozzle and mixes with the original internal fluid to promote the fluid flow in the storage tank and thereby reduce the local high temperature in the storage tank. This paper firstly uses a full-filled two-dimensional scaled storage tank model to numerically simulate the temperature stratification caused by local heat leakage in a liquid hydrogen storage tank under microgravity conditions. The effects of jet nozzle shape, jet nozzle position in tank, incident volume flow rate and other conditions on the effect of temperature stratification are analyzed. The main conclusions of the study are as follows: for the same shape of the jet nozzle, when the incident volume flow is the same, the jet nozzle is closer to the outlet, the final flow field formed in the tank is more integrated, and the area affected by the cryogenic fluid is also wider, so the temperature stratification elimination effect is better; At the same crypgenic jet replacement rate, changing the cryogenic jet velocity has an effect on the temperature stratification elimination effect, but it is not obvious. On the other hand, when the jet nozzles are located at the same relative position inside the storage tank and the incident flow rate is the same, the circular cryogenic jet nozzles have a more concentrated flow direction, and the flow field in the tank evolves faster, so the elimination effect is more than that of a hemispherical jet nozzle. The article also simulates large-scale storage tanks. The results show that for large-scale storage tanks, when a circular jet nozzle is used, the e effect of position of the jet nozzle is not very obvious. Under the conditions of the large-scale storage tank in this article, when thecryogenic jet replacement rate reaches 2%, that is, the cryogenic jet time lasts 700s, the elimination effect of the temperature stratification inside the tank is the most significant; When the jet nozzles are located at the same relative position inside the storage tank and the incident flow is the same, the circular jet nozzle is more concentrated due to the outflow direction, the flow field in the tank evolves faster, and the temperature stratification elimination effect is better than the hemispherical jet nozzle. That is consistent with the conclusions obtained from the small size tank.

In order to further solve the actual engineering problems, we have studied the suppression of temperature stratification of gas-liquid two phase system in large-scale storage tanks by cryogenic jet. The conclusions reached are as follows: when the filling ratio is constant, the higher incident mass flow rate is , the more obvious the temperature stratification of the tank is destroyed; when the incident mass flow rate is constant, the lower the filling rate is, the faster the average temperature and average pressure will rise.Under the condition of high incident mass flow rate, the smaller the filling rate is, the easier the average velocity curve is to flatten, and the larger the velocity value is after flatten.The smaller the filling rate, the higher the mass transfer caused by evaporation.