【作者】 田涛；

【导师】 刘海笑； 刘振纹；

【作者基本信息】 天津大学 ， 水利工程， 2019， 硕士

【摘要】 泡状流拥有较好的传热和传质能力,被广泛地应用于工业领域。在泡状流管道中,气相以气泡的形式存在于液相之中。通过对气泡的受力和运动分析可以得到泡状流流场的气液两相结构形式和结构特点。在泡状流中,气泡最显著的行为就是气泡的碰撞和破碎,这两个行为不断地发生在泡状流的运动过程中。气泡碰撞通常是由拖曳力、浮力、壁面作用力和湍流耗散力引起的。气泡合并是气泡碰撞行为的一个结果,通过分析气泡的有效碰撞可以对气泡合并进行描述。本文根据对湍流漩涡的概率场分析,建立了新的气泡破碎理论。通过计算单个气泡的碰撞和破碎概率来获得大规模不同尺寸气泡的生成和消亡速率。结合对单个气泡和整个气泡组随机运动规律的研究,在充分发展的泡状流中以概率分析为基础,首次建立了一个可以预测气泡尺寸分布和不同尺寸气泡空隙率的理论模型。概率模型对气泡尺寸分布和不同尺寸气泡空隙率的预测结果与实验数据基本一致,从而验证了理论模型的适用性,证明了概率模型是可以用来预测泡状流中气泡空隙率的分布。最后,通过设计多组工况,进一步考察了不同影响因素对气泡空隙率的影响、以及各个影响因素之间的耦合作用。更多还原

【Abstract】 Bubble flow has good characteristics of mass and heat transfer,and is widely used in industrial practice.In bubble flow,the gas phase is mixed with the liquid phase in the form of bubbles.The gas-liquid two-phase structure of bubble flow is investigated by analyzing the motion and force states of bubbles.The most crucial bubble behaviors include the bubble collision and breakup,which continuously occur in the movement process of bubble flow.The bubble collision is usually brought by the drag force,buoyancy force,wall force and turbulence dispersion force.The coalescence efficiency of bubble collisions is analyzed to describe the bubble coalescence behavior.A novelty theory of bubble breakup is established according to the probability field analyses of the turbulent eddy.Then,the generation and elimination rates of an entire bubble group can be obtained by calculating the collision and breakup probabilities of a single bubble.Combing with the investigations on the random motion rules of a single bubble and an entire bubble group,a theoretical model is firstly established to predict the overall bubble size distribution based on the probability analyses of fully developed bubble flow.The predictions from the probability model agree well with the experimental data in terms of the bubble size distribution,and this demonstrates the availability of the theoretical model.Finally,the influences of different factors on the void fraction of bubbles and the coupling effects of various factors are investigated by calculating numerous designed conditions.更多还原