液态锂铅合金鼓泡器的气泡行为数值模拟

 液态金属包层的氚燃料循环是实现聚变堆、聚变-裂变混合堆正常运行的核心技术之一。氚燃料循环系统由氚净化、氚提取、氚储存、氚测量、氦/水冷却、氚回收等子系统构成，而液态金属鼓泡器位于包层主回路与氚提取系统之间，具有氚在线监测与氚去除的重要功能，是不可缺少的关键部件。由于氢同位素在液态锂铅中的极低溶解度和液态合金的高温、活泼、物理等特性，鼓泡器的研制十分困难。为完成液态锂铅合金鼓泡器（LLLB）的设计与建造，采用流体力学方法建立了描述气泡直径与粒度分布、气含率特征等动力学行为的代数模型。数值模拟结果表明，床层气含率和稳定气泡粒度分布均不受喷嘴孔径的影响；低气速下气泡破碎远快于气泡的聚并，绝大部分初始气泡直径大于最大稳定直径，其破碎后的直径取决于最大稳定气泡直径的大小；气泡比表面积和传质表面积增大的主要因素是气泡直径分布的变化。

Numerical Simulation of Bubble Behavior in the Liquid Lithium Lead Bubbler

The tritium fuel cycle of the liquid metal blanket is a core technology for the normal operation of a fusion reactor or a fusion-fission hybrid reactor. The tritium fuel circulation system consists of the tritium purification, the tritium extraction, the tritium storage, the tritium measurement, the helium/water cooling and the tritium recovery subsystem. The liquid metal bubbler located between the blanket main circuit and the tritium extraction system is an indispensable key component for its important functions in tritium monitoring and removal. However, the development of a bubbler is difficult as the solubility of hydrogen isotopes in liquid lithium lead is very low and the liquid alloy has some unique characteristics in high temperature, with respect to an effective design and building of Liquid Lithium Lead Bubbler (LLLB) for the Tritium Breeding Module (TBM) of fusion reactor. An algebraic model to describe the gas holdup characterization, the bubbler diameter and the size distribution is developed under the assumptions that the gas phase is non-Newtonian and there is no frictional force between gas and liquid phases. Simulation results show that bubbles would break up much faster than while being coalesced under low gas velocity. In LLLB, the breakage is a dominant feature for bubbles after they leave the orifice. Initial bubbles formed over the orifice are mostly larger than the largest stable bubble. They would break up quickly and their sizes are reduced to below the maximum diameter ds of stable bubbles. Moreover, the gas-liquid surface area would be increased even though the gas holdup does not change significantly. A high mass transfer area could be obtained by injecting more small initial bubbles with diameters under ds.