The formation and breakup of molten oxide jets under periodic excitation

The experiments on the capillary breakup of slag jets at high temperatures are presented in this article. The impact of external excitations on the disintegration process was investigated in a furnace with optical access filmed at frame rates up to 10,000 fps. A synthetic calcia‐alumina slag was used to form jets at different temperatures (1570–1660°C) and jet velocities (0.6–1.4 ms^?1). The impact of external vibration on the breakup was evident: for low jet velocities, the jet length decreased, the droplet size increased, satellite droplet formation was hindered, and a distinct “pumping mechanism” was observed. For jets with higher velocity, the jet length decreased by 30%, the droplet generation frequency increased from 20 to 250 droplets per second, the drop sizes were uniform, and satellite formation was also suppressed. In this case, the ideal case in which the volume of one wave instability forms one droplet was achieved. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3350–3361, 2014     

Computational modeling of microbubble coalescence and breakup using large eddy simulation and Lagrangian tracking

The flow of dispersed microbubbles was studied with an Eulerian–Lagrangian technique using large eddy simulation to predict the continuous liquid flow and Lagrangian tracking to compute bubble trajectories. The model fully accounts for bubble coalescence and breakup and was applied to horizontal and vertical channel flows. With low levels of turbulence, gravity in horizontal, and lift in vertical, channel flows govern the bubble spatial and collision distribution. When turbulence is sufficiently high to, at least partially, oppose bubble preferential concentration, more uniform collision and coalescence distributions are found, although these remain peaked near the wall in both configurations. Almost 100% coalescence efficiency was always found, due to bubbles colliding along similar trajectories, with breakup only recorded in a flow of low surface tension refrigerant R134a. Models like this can provide the required quantitative understanding of the microbubbles complex behavior, as well as supporting the development of more macroscopic modeling closures.     

用背角准弹散射研究近库仑势垒能区重离子核反应

利用背角准弹散射的方法开展了近库仑势垒（近垒）能区重离子核反应机制的研究。高精度测量了深垒下能区16O+152,154Sm、184W、¹⁹⁶Pt和²⁰⁸Pb等体系的背角准弹散射激发函数,用耦合道计算抽取了核势的表面弥散参数,结果表明考虑耦合道效应得到的表面弥散参数值正常。基于背角准弹散射势垒分布对核结构的敏感性,尝试用深垒下能区16O+152Sm、170Er和174Yb等体系的背角准弹散射来抽取形变靶核的十六极形变参数,所抽取值与已有结果趋势一致,说明了该方法的可行性。此外,研究了弱束缚核体系的破裂效应,其表现为背角准弹势垒分布较全熔合势垒分布向低能移动,所得结果进一步说明势垒分布同时含有核结构和核反应机制的信息。     

Drop Deformation and Breakup Mechanisms in Viscoelastic Model Fluid Systems and Polymer Blends

This paper reviews the dispersion mechanisms in viscoelastic systems under relatively high shear rate conditions. In particular, two non‐Newtonian deformation and breakup mechanisms were revealed by flow visualization in a transparent Couette shearing setup. The first one is the dispersed droplet elongation perpendicular to the flow direction. This was observed only for viscoelastic drops and had been associated to normal force buildup in the droplet. The second deformation/breakup mechanism was observed in very high viscosity ratio polymer systems. It consists in erosion at the drop surface. Clouds of very small ribbons and sheets were developed around the drop then stretched and finally broken into very small droplets, rapidly distributed in the matrix.     

A unified theoretical model for breakup of bubbles and droplets in turbulent flows

Pressure has a significant effect on bubble breakup, and bubbles and droplets have very different breakup behaviors. This work aimed to propose a unified breakup model for both bubbles and droplets including the effect of pressure. A mechanism analysis was made on the internal flow through the bubble/droplet neck in the breakup process, and a mathematical model was obtained based on the Young–Laplace and Bernoulli equations. The internal flow behavior strongly depended on the pressure or gas density, and based on this mechanism, a unified breakup model was proposed for both bubbles and droplets. For the first time, this unified breakup model gave good predictions of both the effect of pressure or gas density on the bubble breakup rate and the different daughter size distributions of bubbles and droplets. The effect of the mother bubble/droplet diameter, turbulent energy dissipation rate and surface tension on the breakup rate, and daughter bubble/droplet size distribution was discussed. This bubble breakup model can be further used in a population balance model (PBM) to study the effect of pressure on the bubble size distribution and in a computational fluid dynamics‐population balance model (CFD‐PBM) coupled model to study the hydrodynamic behaviors of a bubble column at elevated pressures. © 2014 American Institute of Chemical Engineers AIChE J, 61: 1391–1403, 2015     

Three‐dimensional numerical simulation of coalescence and interactions of multiple horizontal bubbles rising in shear‐thinning fluids

The dynamics of multiple horizontal bubbles rising from different orifice arrangements in shear‐thinning fluids was simulated numerically by three‐dimensional Volume of Fluid method. The effects of bubble size, rheological properties of shear‐thinning fluids, and orifice structure arrangements on multiple bubbles interaction and coalescence were analyzed, and the mechanisms of bubble coalescence and breakup were fully discussed and elucidated. The variation of bubble rising velocity during coalescence process and freely rising processes for different orifice arrangements was also deeply investigated. The critical initial horizontal intervals for coalescence of multiple horizontal bubbles with various orifice arrangements were attained by simulation, which could serve as the critical criterion of bubble coalescence or noncoalescence. Furthermore, the critical bubble interval was predicted based on the film drainage model, the prediction accords well with the simulation result and is quite conducive for the design and optimization of perforated gas–liquid contact equipment. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3528–3546, 2015     

针形喷嘴射流特性的实验研究

本文针对针形喷嘴的主要结构参数,对射流破碎长度和破碎液滴的尺寸进行了一系列的实验研究,得出了针形喷嘴的主要几何参数与射流破碎长度之间的关系,以及射流破碎后的液滴情况,为针形喷嘴的设计提供了依据。     

液液静电雾化特性

对水静电雾化弥散于玉米油的液-液雾化过程进行了实验研究。通过拍照对雾滴形态进行了观察。观察表明,不同电压下液-液雾化会呈现出滴状和云状雾化两种较为典型的雾化形态,在两种形态下液滴具有不同的形貌和运动特点,本文给出了两种雾化形态的出现条件及特征描述。通过Winner99颗粒图像分析仪及雾滴尺寸的分布理论,对不同静电电压下雾滴直径的分布规律进行了定量分析。研究结果表明,液-液静电雾化中雾滴的直径分布服从Rosin-Rammler分布规律。随着电压的升高,雾滴直径分布趋向均匀,雾化细度得到改善。与在空气中雾化有所不同,液-液雾化中雾滴分布的概率密度曲线峰值两边呈现出显著的不对称性,小液滴数尺寸分布较窄而大雾滴数的尺寸分布较宽。随着电压的升高,大雾滴尺寸分布有所变窄,概率密度曲线趋近对称。     

Influence of atomizer exit area ratio on the breakup morphology of coaxial air and round water jets

The goal of this article is to study the effect of atomizer exit area ratio on atomizer performance. The experiments are performed on the round liquid jet breakup of seven coaxial air‐blast atomizers with water–air systems. The breakup morphology of liquid jet is observed first. The membrane‐type breakup can be divided into two subregimes called bag‐type breakup and membrane‐fiber breakup, and a correlation of characteristic length on bag‐type breakup regime is obtained. Then, we analyze the influence of atomizer exit area ratio on the breakup morphology of water‐air jets. To obtain reasonable atomization morphology criterions, the atomizer exit area ratio is used to modify the Weber number and momentum flux ratio per unit volume. This method is found to be able to explain different experimental results in the literature, which is also close to the results of round liquid jet in cross air flow and secondary atomization. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2335–2345, 2014