Droplet collisions and interaction with turbulent flows for powder manufacturing

粉末制造中的液滴碰撞和与湍流的相互作用

• 批准号: EP/K019732/1
• 负责人: Yannis Hardalupas
• 金额: $ 48.3万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FK019732%2F1
• 关键词: Droplet; collisions; interaction; turbulent; flows

The following may be a key to the faster growth of powders in spray dryers: - control of droplet and particle collisions and appropriate outcomes {e.g. droplet coalescence as opposed to separation or bounce-off}, - generation of appropriate droplet or particle concentration 'patterns' - increased 'clustering' in space and time - to increase probability of collisions, - maintaining these qualities over a wider range of operating conditions. Although spray drying is an old technology - 'drying' including the process of collision and agglomeration of droplets, semidried and dried particles amongst each other - remarkably little fundamental knowledge exists which would reliably answer the simple question: given this geometry of spray drying tower, what kind of spray(s) and air flow(s) should I produce in order to manufacture powder of the following quality (e.g. humidity, mean size, size distribution, morphology)? The answer must include an explanation of how and why small modifications to the location of atomisers and flow conditions radically changes powder quality. To formulate the answer, we need better and more extensive measurements of the 'fundamental' processes than hitherto: and we must generate new understanding and ideas that will advance our ability to calculate the location, number and outcome (bouncing, coalescence/agglomeration, sticking) of collisions in turbulent flows for realistic liquids (initially feedstock frequently has the consistency of toothpaste on a cold day) and geometries - and check the advance against fundamental, simple yet representative flow geometries.The overall aim of the proposal is to innovate powder manufacturing in spray dryers by improving the understanding of the probability of droplet or particle collisions in turbulent flows and of the outcome of droplet-droplet, particle-particle or droplet-particle collisions with emphasis on liquid properties and geometries used in powder production through spray drying or other similar processes. The research hypothesis is that the growth of powders in spray drying processes can occur much faster than currently believed through simultaneous multiple droplet collisions, initiated by binary droplet collisions. This is because collisions have a relatively long duration and result in deformed transient shapes (ligaments, discs, etc.) with relatively large 'target' surface area. The ligaments formed during droplet pair collisions can interact with the flow turbulence during a collision event and break up, instead of coalescing into larger droplets. Both these events are not currently taken into account in the design of industrial spray dryers nor in computational models of droplet collisions used for predictions. Our approach will be to make novel time- and spatially- resolved measurements of the liquid, spray and gas motions using optical instrumentation in flow configurations that allow the study of the microscale physics of droplet collisions and in model spray dryers that allow the study of macroscale processes. We will use these results to establish new 'collision kernels' and unique semi-empirical correlations of droplet collision outcomes in turbulent flows and breakup of non-spherical ligaments and propose novel methods for control of powder manufacturing in, and new computational models for predictions of, spray dryers.

以下可能是粉末在喷雾干燥器中更快生长的关键：- 控制液滴和颗粒碰撞和适当的结果（例如，与分离或反弹相反的液滴聚结），-产生适当的液滴或颗粒浓度“模式”-在空间和时间上增加“聚集”-以增加碰撞的概率，- 在更宽的操作条件范围内保持这些品质。虽然喷雾干燥是一种古老的技术-“干燥”包括液滴、半干燥和干燥颗粒相互碰撞和团聚的过程-但存在的基本知识非常少，可以可靠地回答这个简单的问题：考虑到喷雾干燥塔的几何形状，我应该产生什么样的喷雾和气流，以生产以下质量的粉末（例如湿度、平均尺寸、尺寸分布、形态）？答案必须包括一个解释，如何和为什么小的修改的位置雾化器和流动条件从根本上改变粉末质量。为了给出答案，我们需要对“基本”过程进行比迄今为止更好、更广泛的测量：我们必须产生新的理解和想法，以提高我们计算地点、数量和结果的能力，（弹跳、聚结/附聚，粘滞）的碰撞在湍流的现实液体（最初原料通常具有寒冷天气牙膏的稠度）和几何形状-并对照基本面检查进展，该提案的总体目标是通过提高对湍流中液滴或颗粒碰撞概率的理解，通过喷雾干燥或其他类似工艺生产粉末时所使用的液体性质和几何形状，了解液滴-液滴、颗粒-颗粒或液滴-颗粒碰撞的结果。研究假设是，喷雾干燥过程中粉末的生长速度比目前认为的要快得多，这是通过二元液滴碰撞引发的同时多液滴碰撞实现的。这是因为碰撞具有相对较长的持续时间并且导致变形的瞬时形状（韧带、盘等）。具有相对大的“目标”表面积。在液滴对碰撞期间形成的韧带可以在碰撞事件期间与流动湍流相互作用并破裂，而不是聚结成更大的液滴。这两个事件目前都没有考虑到在工业喷雾干燥器的设计，也没有在用于预测的液滴碰撞的计算模型。我们的方法将是使新的时间和空间分辨测量的液体，喷雾和气体运动，使用光学仪器在流动配置，允许研究微尺度物理的液滴碰撞和模型喷雾干燥器，允许研究宏观过程。我们将使用这些结果来建立新的“碰撞内核”和独特的半经验的相关性液滴碰撞结果在湍流和破碎的非球形韧带，并提出新的方法来控制粉末制造，和新的计算模型的预测，喷雾干燥器。

项目成果

Influence of droplet clustering in sprays on liquid deposition rate on spherical targets

喷雾中液滴聚集对球形目标液体沉积速率的影响

• DOI: 10.4995/ilass2017.2017.4673
• 发表时间: 2017
• 作者: Andrade P

Impingement and splashing of droplets on spherical targets

• DOI: 10.2514/6.2016-1448
• 发表时间: 2016-01
• 作者: George Charalampous;Y. Hardalupas

Spray Impingement on Spherical Targets in Homogeneous, Isotropic Turbulence

均匀各向同性湍流中球形目标的喷雾撞击

• 发表时间: 2016
• 作者: Andrade P.

Breakup of non-spherical droplets

非球形液滴的破碎

• 发表时间: 2016
• 作者: Bergeles K.

Application of Proper Orthogonal Decomposition to the morphological analysis of confined co-axial jets of immiscible liquids with comparable densities

• DOI: 10.1063/1.4900944
• 发表时间: 2014-11
• 期刊: Physics of Fluids
• 影响因子: 4.6
• 作者: G. Charalampous;Y. Hardalupas