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

超声波空化处理为传统和先进金属材料的熔融处理提供了可持续、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，这项先进而有希望的技术向工业转移的障碍是，在处理连铸等工艺所需的大量液态金属方面遇到了困难。现在是解决这个问题的时候了，因为该行业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。选择这个主题是恰当的，也是雄心勃勃的。目前的知识无法回答一个看似简单的问题：在最小的能量输入、成本和复杂性下，用超声源处理一定体积的液体需要多长时间？这项研究旨在回答这个问题，为超声波熔体处理的广泛工业应用铺平道路，同时改善轻质结构合金的性能，同时减少对脱气和细化晶粒添加剂的需求-污染(Cl，F)和昂贵的(Zr，T，B，Ar)-并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，对潜在现象、原因和影响的科学理解是必不可少的。该项目旨在通过以下方式应对有效处理大体积液体的挑战：(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间歇处理转变为连续液流处理。该方法的创新之处在于对(I)一次空化区和扩展空化区、(Ii)声学和二次流、(Iii)通过空化区边界的传质和(Iv)移动体积(流)中的过程进行了全三维、量化的实验表征和数值描述。本研究的结果为用较少的超声源、在较短的时间内处理大量熔体开辟了道路。为实现这些目标，将结合先进的建模技术，进行专门的、具有三维特征的可量化实验，并使用反应灵敏的处理效率指标；桥接和耦合不同长度和时间的尺度和物理现象，从单个空化气泡的振动生长和崩溃，到气泡团在主体流体中的传输和在强声区可能的再夹带，以及整个处理体积的传质。气泡破裂对流动动量、能量和湍流的影响将包含在一个完全耦合的系统中。实验结果将被用作输入，并在整个模型开发过程中用于验证。

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.