【作者】 刘晓瑜；

【导师】 郑洪涛；

【作者基本信息】 哈尔滨工程大学 ， 动力机械及工程， 2012， 硕士

【摘要】 Li/SF6液态金属燃料化学能源模式是一种拥有广阔应用前景的新型能源模式,因其能量密度高、反应物易存放、产物无排放可以构成闭式循环等优势在高温化学蓄热技术、水下推进技术等领域得到了广泛应用。表面喷射反应(熔池内Li/SF6缓慢燃烧)是一种新型反应形式,可以释放出大量能量,同时也容易对反应进行控制,对于这种反应形式进行深入研究具有现实意义,本文通过数值模拟方法对Li/SF6表面喷射闭式循环反应器内气液传质燃烧过程进行研究。本文对具体问题进行了合理简化,重点分析气液传质过程中气液两相化学反应的热量释放以及随温度升高过程出现的相变问题。基于经典的Whiteman膜理论的基本假设确立反应器内部气液传质模型,应用物料衡算法的基本思想求解气液传质系数,确定扩散控制的气液反应速率；建立反应器内传热、传质、相变过程数学模型,并且应用移动网格技术捕捉反应界面(液面)的变化过程；采用有限单元法进行离散求解,模拟得到了反应器内温度分布、速度分布、组分浓度分布、相变过程以及液面变化过程。通过数值模拟得到以下结论：首先,物料衡算法计算得到的气液传质系数与气体入口速度、喷嘴半径等参数有关；其次,气体由喷嘴进入反应器2s后与液体接触,开始发生化学反应,液面中心处的化学反应最剧烈,气体和液体消耗的最快,液面变化的位移最大；第三,反应释放热量使得反应器内温度升高,液面中心处温度值最高,随着反应不断进行高温区域向液面周围及反应器内其它位置扩展,反应进行20s后液面中心温度超过4000K,整个液面的温度都超过初始温度800K；第四,反应进行5s后液面中心温度达到锂的沸点,开始有锂蒸气形成,相变形成的锂蒸气通过分子扩散的形式传递到液面上方的气体区域,并且由于相变过程的发生,使得液体的温度与不考虑相变情况相比有所下降；最后,其它条件都相同时,六氟化硫气体的入口质量流量越大,化学反应发生的时间越短、反应器内温度越高；质量流量的变化还会对相变过程产生影响,质量流量增加会使相变过程发生的时间提前,并且随着质量流量的增大相变生成锂蒸气的浓度也增加。更多还原

【Abstract】 The Li/SF6metal fuel heat source system is an advanced system which takes molten lithium as fuel, and sulfur hexafluoride as oxider. As the characteristics such as high density of energy, can release a large quantity of energy in a short time, the production does not have to let out, etc, it has distinctive superiority when used as energy source not only in underwater power plants but also in energy storage technology. The surface injetion reaction(Li/SF6slow combustion in a molten pool reactor) is a new kind of reaction form which can be controlled easily, so researches on this type of reaction have practical significance. In this thesis, a numerical simulation was made to investigate the gas-liquid combustion progress in the Li/SF6surface injection closed cycle reactor.In the process of numerical simulation, it was paid more attention to the energy release of the gas-liquid reaction and the phase change problem accompanied by the high liquid temperature. The gas-liquid mass transfer model of the reactor was established based on the classical Whiteman film theory, a mass balance based approach was used for estimating the reaction rate of the diffusive-controlled gas-liquid reaction; equations that are globally suitable for the governing of momentum conservation, heat transfer and mass transfer of both liquid and gas in the computation region were established, and so did the phase change progress of liquid lithium. An ALE technology was employed to determine the position and morphology of the interface between gas and liquid. The FEM method was applied to discretize and resolve the governing equations, boundary conditions and initial conditions.On the basis of the mathematical model and the finite element method, with the help of COMSOL3.5a, the temperature field, velocity field, component concentration distributions, phase change and the position of the gas-liquid interface were numerical simulated and got converged results. The numerical simulation showed that, the gas-liquid mass transfer coefficient was related to the gas inflow velocity and nozzle diameter; combustion was first occurred on the gas-liquid interface, and energy was released in the middle of the interface firstly, so in this posotion the temperature was the most hightest, as time increased, reaction expanded to other positions of the interface. When the liquid temperature reached lithium’s boiling point, phase change occurred, it made the liquid temperature a little lower than the progress without phase change; The influence of the gas entrance mass flux was also considered, the reaction temperature increased as the entrance mass flux became larger, and the phase change of the liquid occurred earlier.更多还原