Investigations regarding the measurement of relevant flow conditions for droplet deformation and disruption in high pressure homogenization with orifices and scalability of mechanisms

高压均质化是生产含有亚微米范围内液滴的乳液的成熟工业方法。这项技术已经应用了几十年。然而，导致液滴破碎的机制仍然没有完全理解。因此，过程和中断单元的优化仍然是在试错的基础上实现的。其原因是由于高的速度梯度和波动以及多相的存在而导致的破碎单元内部的复杂流场。此外，获得小的几何形状受到诸如高压的工艺条件的限制。这些情况对在线测量技术提出了很高的要求。该研究项目的目的是在实际条件下，在高压均质过程中表征流动条件和液滴破碎的物理机制。应用光学测量技术µPIV可以高精度地实现这一目标。最初，拟议的项目将只集中在单相，牛顿，非空化流体。在流动表征之后，将使用没有表面活性添加剂的单液滴（分散相分数<<1%）来研究液滴破碎。然而，空间和时间分辨率限制了在现实的微观尺度上的完整过程的表征。因此，在按比例放大的器械（M = 5和50）中研究了具体问题。该程序允许验证液滴破碎的可扩展性。在真实的微尺度（M = 1，孔径d = 0.2mm）上进行了实验研究。以及M = 5（d = 1 mm）的按比例放大系统将由卡尔斯鲁厄的KIT进行。多年的乳化技术经验将用于系统地研究流动条件和液滴破碎。将改变的参数是雷诺数、孔口的几何形状、尺寸和液滴的起始位置。材料参数，如各相的粘度和表面张力也会发生同样的变化。慕尼黑的UniBw将利用他们在流量测量技术方面的专业知识，重点研究大型系统（M = 50，孔直径d = 10 mm）中的选定方面。在这里，主要的重点在于在选定的参数，以及描述液滴的形状和动力学的液滴破碎机制的详细采集。该研究项目将为从材料、工艺和几何参数等边界条件预测所得液滴尺寸分布奠定基础。因此，将开发描述液滴破裂的函数。从长远来看，这将有助于以有针对性的方式改善高压均质工艺，包括选择性、产品收率以及能量输入。

High pressure homogenization is a well established industrial process for the production of emulsions containing droplets within a submicron range. This technology has been applied for many decades. However, mechanisms leading to droplet breakup are still not completely understood. As a consequence, the optimization of process and disruption units is still realized on a trial and error basis. Reasons for this are the complex flow field inside a disruption unit due to high velocity gradients and fluctuations as well as the presence of multiple phases. Additionally, access to small geometries is limited by process conditions such as high pressures. These cirsumstances set high demands on inline measurement techniques. The aim of this research project is to characterize flow conditions and physical mechanisms of droplet breakup during high pressure homogenization under realistic conditions. Applying the optical measurement technique µPIV allows the realization of this objective with high pre-cision. Initially, the proposed project will focus only on single-phase, Newtonian, non-cavitating fluids. After flow characterization, droplet breakup will be investigated using single droplets (dispersed phase fraction << 1 %) without surface-active additives. However, spatial and temporal resolution limit the characterization of the complete process on a realistic microscale. Therefore, specific questions are investigated in scaled up devices (M = 5 und 50). This procedure allows verifying the scalability of droplet breakup. The investigations on a realistic microscale (M = 1, orifice diameter d = 0.2 mm, resp.) as well as a scaled up system of M = 5 (d = 1 mm) will be conducted by the KIT in Karlsruhe. Years of experience in emulsification technology will be used to systematically study flow conditions and droplet breakup. Parameters that will be varied are the Reynolds number, geometry of the orifice, size, and starting position of the droplets. Material parameters such as viscosity of each phase and surface tension will be changed likewise. By utilizing their knowhow in flow measurement techniques, the UniBw in Munich will focus on investigating selected aspects within a large scale system (M = 50, orifice diameter d = 10 mm, resp.). Here, the main emphasis lies on a detailed acquisition of droplet disruption mechanisms at selected parameters as well as describing the droplets' shape and dynamics. This research project will build the foundation to predict resulting droplet size distributions from boundary conditions like material, process and geometrical parameters. Therefore, a function describing the disruption of droplets will be developed. In the long term, this will help to improve high pressure homogenization processes in a targeted way regarding selectivity, product yield as well as energy input.