Fundamental Study of Cavitation Melt Processing: Opening the Way to Treating Large Volumes (UltraMelt)

超声空化处理为传统和先进金属材料的熔融加工提供了可持续、经济和无污染的解决方案，从而显著提高了质量和性能。然而，这种先进的和有前途的技术转移到工业中，由于在处理如连续铸造等工艺所需的大量液态金属方面的困难而受到阻碍。现在是解决这个问题的时候了，因为工业界正在寻找新的先进技术来实现可持续制造，而我们的经济竞争对手，如美国和中国，正在这一领域进行广泛的科学研究。选择这一专题既恰当又雄心勃勃。目前的知识无法回答一个看似简单的问题：用超声波源处理一定体积的液体需要多长时间才能实现最小的能量输入、成本和复杂性？这项研究旨在回答这个问题铺平了道路，以广泛的工业应用的超声波熔融加工的好处，提高轻质结构合金的性能，同时减少需要脱气和晶粒细化添加剂-污染（Cl，F）和昂贵的（Zr，T，B，Ar）-和消除复杂的加工步骤，如助熔剂和旋转脱气。在取得技术进步之前，必须从科学上了解潜在的现象、原因和影响。该项目旨在通过以下方式应对有效处理大量液体的挑战：（1）开发一个综合的数值模型，该模型耦合了空化区域内外发生的各种多尺度和多物理现象，以及（2）将重点从传统的静态批量处理转变为连续液体流中的处理。所提出的方法的新奇在于一个完全三维的，量化的实验表征和数值描述（i）的主要和扩展的空化区域，（ii）声学和二次流，（iii）通过边界的空化区域的质量传递，和（iv）在一个移动的体积（流）的处理。该研究结果为用较少的超声波源和较短的时间处理大体积熔体开辟了道路。为了实现这些目标，将把专门的、可量化的三维表征实验以及使用治疗效率的响应指标与先进的建模相结合;桥接和耦合不同的长度和时间尺度和物理现象，从单个空化气泡的振动增长和崩溃，气泡簇在主体流体中的传输和在强声学区中可能的再夹带，以及在整个处理体积中的质量传递。溃灭气泡对流动动量、能量和湍流的影响将包括在一个完全耦合的系统中。实验结果将被用作输入和验证模型在其整个发展。

Ultrasonic cavitation treatment offers sustainable, economical and pollution-free solutions to melt processing of conventional and advanced metallic materials with resulting significant improvement of quality and properties. However, the transfer of this advanced and promising technology to industry has been hindered by difficulties in treating large volumes of liquid metal as required by processes such as continuous casting. The time is right to tackle the problem as the industry is looking for new advanced technologies for sustainable manufacturing and our economic competitors, e.g. USA and China, are performing extensive scientific research in this area. The selection of this topic is both appropriate and ambitious. Current knowledge cannot answer a seemingly simple question: how long does it take to treat a certain volume of liquid with an ultrasonic source for minimum energy input, cost and complexity? This research aims to answer this question paving the way to extensive industrial use of ultrasonic melt processing with the benefit of improving the properties of lightweight structural alloys, simultaneously reducing the need for degassing and grain refinement additives - polluting (Cl, F) and expensive (Zr, T, B, Ar) - and eliminating complicated processing steps such as fluxing and rotary degassing. Before technological advances can be made, scientific understanding of the underlying phenomena, causes and effects, is essential. This project aims to respond to the challenge of efficiently treating large liquid volumes by: (1) developing a comprehensive numerical model that couples various multi-scale and multiphysics phenomena occurring inside and outside the cavitation region and by (2) changing emphasis from conventional static batch treatment to processing in continuous liquid flow. The novelty of the suggested approach lies in a fully three-dimensional, quantified experimental characterization and numerical description of (i) the primary and extended cavitation region, (ii) acoustic and secondary flows, (iii) mass-transfer through the boundary of the cavitation region, and (iv) processing in a moving volume (flow). The results of this research open the way to treating large volumes of melt with fewer ultrasonic sources and in a shorter time. To achieve the aims, dedicated, quantifiable experiments with three-dimensional characterization plus the use of responsive indicators of treatment efficiency will be combined with advanced modelling; bridging and coupling different length and time-scales and physical phenomena, ranging from the vibrational growth and collapse of individual cavitation bubbles, to the transport of bubble clusters in the bulk fluid and possible re-entrainment in the intense acoustic zone, and to the mass transfer throughout the treated volume. The influence of collapsing bubbles on flow momentum, energy and turbulence will be included in a fully coupled system. The experimental results will be used both as input and for validation of the model throughout its development.