基于格子Boltzmann方法的两相液滴绕流的数值模拟

发布时间：2019-03-01 19:17

【摘要】：泡沫金属生物柴油反应器是一种具有高产能的生物柴油制备装置,为对反应器进行优化,对泡沫金属内两相液滴运动此类具有复杂界面变化的两相流问题进行研究,本文采用格子Boltzmann方法(LBM)对以下内容进行研究,并获得结论如下：(1)采用LBGK模型模拟典型单相流动：Poiseuille流和单相圆柱绕流问题,验证了LBM的可行性；通过两相方形液滴演化、Lapalce定律和接触角问题的模拟验证伪势模型程序的正确性。(2)利用伪势模型模拟两相液滴的单柱绕流运动,考察液滴绕柱时的运动状态。研究发现,液滴的柱体绕流状态受到柱体形状及柱体偏置率等因素的影响。破裂形成液滴的聚合距离Lr与柱体形状和大小、雷诺数Re等因素有关。聚合距离与雷诺数基本成对数关系,柱体尺寸和形状对聚合距离的影响均与雷诺数相关,存在临界数值。(3)利用伪势模型模拟液滴的两并列柱体的绕流运动。研究发现液滴恰好穿过两并列柱体间隙的临界间距hr基本随速度的增加而增大,且大尺寸液滴或小尺寸柱体均产生较大的临界间距；此外,研究发现柱体形状对临界间距的影响不明显。(4)利用伪势模型模拟泡沫金属内的两相液滴运动。相对柱体障碍而言,泡沫金属更有利于液滴的破裂。此外,具有较大PPI值的泡沫金属能产生更小的破裂液滴,但所需压降更大,因此PPI值并非越大越好,需合理选取。
[Abstract]:The foam metal bio-diesel reactor is a kind of biodiesel preparation device with high productivity. In order to optimize the reactor, the two-phase flow with complex interface changes such as the movement of two-phase droplets in the foam metal is studied. In this paper, the lattice Boltzmann method (LBM) is used to study the following contents, and the conclusions are as follows: (1) the LBGK model is used to simulate the typical single-phase flow: Poiseuille flow and single-phase cylindrical flow, and the feasibility of LBM is verified; The correctness of the pseudo-potential model is verified by the evolution of two-phase square droplets, Lapalce's law and contact angle problem. (2) the pseudo-potential model is used to simulate the flow around a single column of two-phase droplets, and the motion state of the droplets around a column is investigated. It is found that the flow state of the droplet around the cylinder is affected by the shape of the cylinder and the deviation rate of the cylinder. The polymerization distance (Lr) of the fractured droplets is related to the shape and size of the cylinder and the Reynolds number (Re). The polymerization distance has a logarithmic relation with Reynolds number, and the influence of cylinder size and shape on the polymerization distance is related to Reynolds number. (3) the pseudo-potential model is used to simulate the flow around two parallel cylinders of liquid droplets. It is found that the critical distance between the droplets passing through the gap between the two parallel cylinders increases with the increase of the velocity, and the critical spacing of the liquid droplets with large or small sizes is larger than that between the two parallel cylinders. The critical spacing of the hr increases with the increase of the velocity. In addition, it is found that the shape of the cylinder has little effect on the critical spacing. (4) the pseudo-potential model is used to simulate the two-phase droplet motion in the foam metal. Foam metal is more conducive to the rupture of droplets than columnar barriers. In addition, the foam metal with higher PPI value can produce smaller ruptured droplets, but the required pressure drop is greater, so the higher the PPI value is, the better it needs to be selected.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE667

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