【作者】 李嘉；

【导师】 黄素逸；

【作者基本信息】 华中科技大学 ， 工程热物理， 2007， 博士

【摘要】 高品质的蒸汽是保证核动力装置安全和经济运行的重要条件。波形板汽水分离器由于其分离效率较高,广泛应用于核动力装置中,并且作为汽水分离系统最后一级分离器,在核电站中占有重要的地位。同时鉴于气液分离过程是两相流中的一个普遍现象,所涉及的液膜破裂和液滴碰壁飞溅等也是工程热物理领域中一个常见的问题,因此对波形板汽水分离器的分离过程进行深入的理论和实验研究有利于设计和改造分离装置使之高效化、紧凑化,对于核潜艇一体化蒸汽发生器的设计也有现实的军事意义。波形板汽水分离器的流道内是极其复杂的两相流流动,其形成的流场为两相三流场,这给分离器的数值模拟和实验测量带来了一定的困难。针对分离器内部的这种复杂气-液两相湍流运动,本文通过开展冷态和热态不同工况条件下的分离器工作机理研究,分析二次液滴产生的原因,建立描述分离器流动过程的数学模型,采用流体计算软件实现了对流场、液滴运动轨迹、二次携带现象等的数值模拟,同时,采用自主设计的冷态试验台架和外协单位的热态试验台架进行了实验研究,对模型及计算结果进行验证。论文的研究结果有助于了解气液分离装置特别是波形板精细分离器性能和提高其分离效率,同时也为寻求高效波形板结构的奠定了基础。本论文主要完成了以下几个方面的工作:完成了国内外波形板汽水分离器研究资料的收集,对汽水分离装置的分离原理进行了介绍;分析了蒸汽发生器中液滴产生的过程,得到了不同机制下形成的液滴直径的计算公式,并研究了冷态和热态工况下二次液滴产生的原因;通过借鉴环状流的经验关系式,建立了波形板汽水分离器的两相三流场数学模型,为了使方程封闭,补充了界面处的摩擦力方程以及液滴密度数方程;利用FLUENT软件,针对冷态和热态工况,完成了波形板汽水分离器中汽相流场的数值模拟,得到了各种板型的汽流场特征;对波形板流道内的液滴行为进行了模拟计算,分析了湍流效应对液滴行为的影响,指出大液滴的分离机理主要是依靠惯性力,而细小液滴的分离机理主要是依靠湍流效应;对各种板型的分离效率进行了计算对比,指出2h板型在热态工况下要优于1h型波形板;采用壁面液膜模型来模拟二次携带现象,分析了它对分离效率的影响,指出1h型板型更容易发生二次携带,在入口流速较高时,分离效率很快下降;对波形板汽水分离器进行了冷态和热态实验研究,主要针对压降和分离效率这两个主要指标参数与数值模拟结果进行了对比,验证了数值模拟方法的可靠性;论文最后还为波形板汽水分离器的进一步深入研究提出了建议。本文的研究成果,无论是理论上还是实践上,都对波形板汽水分离器的推广应用、优化设计具有积极的指导意义。本文研究的课题受到了国防预研基金的资助。更多还原

【Abstract】 The high quality steam is important to the safety and economical work of nuclear-powered equipments. Due to the high separating efficiency, steam-water separator with corrugated plates is used to nuclear-powered equipments widely as the last stage of the steam separation system. At the same time, the steam-water separating process relating to breake of film and splash of droplets is a universal phenomenon in the two-phase flow, and the field of Engineering Thermophysics. So an improved understanding of the behavior of steam-water separation could benefit the design and optimization of steam separation system and is significant in the incorporated design of steam generator in nuclear submarine.The complicatedl turbulent two-phase flow in corrugated plates which comes into being the two–phase and three-flow-field caused major difficulties in modeling and experimentally simulating their internal flows. In this thesis, the separating mechanism of steam-water separator with corrugated plates is researched under the different work status including cold state and actual state. The mathematic equations describing the flow process are founded and the flow field and disperse are numerically simulated by FLUENT software. Then, the test-beds of cold and actual state are manufactured by indoor and 105 graduate school respectively. The tests are complished and the results are compared with the numerical value of the simulation. The research benefits to the understanding of the mechanism of separating process and increasing greatly the system efficiency, which is the base to optimize the structure.The main characteristics of the research in the thesis are as follows: A wide range of documentations about the steam-water separator with corrugated plates are reviewed worldwidely and the separating mechanism is introduced. The formation process of injected droplet is analysed and the diameter distribution resulted from different mechanisms are obtained. The mechanism of second droplets generation is analyzied; The two–phase and three-flow-field mathmatics model of separation process in corrugated plates considering about secondary droplets is built up by using the experiential correlations attained in annular two phase flow experiment; The separation process in the condition of cold and actual operation state of steam-water separator with corrugated plates is simulatd by the FLUENT computation code, the turbulent effect on the droplet trajectories is discussed expecailly due to its importance to separated the fine droplets. The pressure drop and separation efficiency, which varies with the geometric parameters and flow parameters in theseparator, are discussed. It could be concluded that the 2h type corrugated plate outperform the 1h type in the actual operation condition. The experiments under the cold and actual operation state of steam-water separator with corrugated plates are performed, and the experiment results agreed well with the numerical results.The bringouts in this thesis are very helpful to spreading and optimizing the application of steam-water separator with corrugated plates.更多还原