Better Bubblers: Jet Impingement Within a Dead-End Channel

在高压铝压铸（HPADC）和注塑（IM）行业中，一种独特的流场用于冷却细长的模具突出物：一种在死角通道内的射流撞击，在工业中称为“起泡器”。这些设备被普遍使用，但是它们在模具内的实现受到2D加工的限制；增材制造（AM）的最新进展现在为改进其设计提供了及时和新颖的机会。我们面临的挑战是，与起泡器相关的热量和流动状况在文献中受到的关注有限，因此需要更好的理解，以获得这些设备的AM可以实现的最佳冷却性能。因此，该项目的目标是建立与起泡器相关的热流现象，并开发新的方法，使其设计能够针对AM进行优化，通过以下目标来实现：1)开发高分辨率的计算流体动力学（CFD）数据集，详细揭示起泡器的热流配置。将对基本共环流场进行等温和共轭传热（CHT）壁面分辨大涡模拟（LES），并对实验数据集进行验证。2)通过对实验结果的收集和分析，阐明流动物理。粒子图像测速（PIV）数据将使用一种新型的冷流光学实验装置获得，并用于参数化基本流场和验证等温模拟。传热数据将使用考文垂现有的铝铸造实验获得，以验证CHT模拟。3)开发新型HPADC刀片形状优化方法。伴随方法找到控制Navier-Stokes方程的梯度，实现特定目标函数的定制形状变形，这将需要开发以实现最大的热量去除和热通量均匀性。然后，我们在CastAlum有限公司的合作伙伴将对优化的几何形状进行激光烧结，进行实验测试并在工业环境中进行演示。这将导致：-通过应用LES和PIV，对环形受限射流撞击中固有的和诱导的边界和自由剪切层湍流引起的流体动力学和传热行为的耦合进行全面描述，并将新的重点放在通过撞击表面和环形受限壁的传热上，从而导致；显着改善起泡器操作参数，提供高效的排热率，以及预测全套配置的相关性；- HPADC的优化策略，最大限度地减少热量和热通量均匀性，这将加速AM方法在行业内的采用。与此同时，该项目将推进建模技术，并在射流撞击的数值模拟中设定新的基准，这将远远超出名义应用范围。这项工作将直接有利于英国HPADC和IM行业，奠定严格的理论基础，与AM提供的设计灵活性相结合，将更好地控制模具最成问题区域的热量排出，从而减少周期时间，从而增加产品体积，延长昂贵工具的使用寿命，并在延长（150k+）周期内保持产品质量。因此，它将为工业提供明显的商业优势，并降低整个生产工厂的生命周期成本。起泡器的流场出现在其他工程系统中，从高压射流切割，到电子冷却，甚至到人工肺通气。

In the high pressure aluminium die casting (HPADC) and injection moulding (IM) industries, a unique flow field is used to cool slender mould protrusions: a jet impingement confined within a dead-end channel, known in industry as a 'bubbler'. These devices are used ubiquitously, however their implementation within a mould has been constrained by the limitations of 2D machining; recent advances in Additive Manufacturing (AM) now offer timely and novel opportunities to improve their design. Our challenge is that the heat- and flow-regime associated with a bubbler has received limited attention in the literature, so an improved understanding is required to access the optimum cooling performance that the AM of these devices can enable. The goal of this project is therefore to establish the heat and flow phenomenology associated with bubblers, and to develop novel methods that will enable their design to be optimised for AM, to be achieved though the following objectives:1) Development of a highly-resolved computational fluid dynamics (CFD) dataset that reveals the bubbler heat- and flow-configuration in detail. Isothermal and conjugate heat transfer (CHT) wall-resolved large eddy simulations (LES) of the basic co-annular flow-field will be performed, and validated against the experimental dataset.2) Elucidation of the flow physics via the collection and analysis of experimental results. Particle image velocimetry (PIV) data will be obtained using a novel cold-flow optical experimental rig, and used to parameterise the basic flow-field and to validate the isothermal simulations. Heat transfer data will be obtained using Coventry's existing aluminium casting experiment, for validation of the CHT simulations.3) Development of novel shape optimisation methods for HPADC inserts. The adjoint method finds the gradient of the governing Navier-Stokes equations, enabling tailored shape deformation in pursuit of a particular objective function, which will need to be developed to enable the maximisation of heat removal and heat-flux uniformity across the protrusion. An optimised geometry will then be laser sintered by our partners at CastAlum Ltd., to be tested experimentally and demonstrated in an industrial setting.This will lead to:- A thorough description of the coupling of fluid dynamics and heat-transfer behaviour arising from inherent and induced boundary and free shear-layer turbulence in annularly confined jet-impingement, achieved through the application of LES and PIV, with a novel focus upon heat transfer through both the impingement surface and the annular confining wall, leading to;- Significantly improved bubbler operating parameters providing efficient heat removal rates, and correlations for their prediction for a full suite of configurations;- An optimisation strategy for HPADC that maximises heat removal and heat flux uniformity, that will accelerate the adoption of AM methods within the industry.In parallel, the project will advance modelling techniques, and set new benchmarks in the numerical simulation of jet-impingement that will have use far-beyond the nominal application. The work will be of direct benefit to UK HPADC and IM industries, laying rigorous theoretical foundations that, allied with the flexibility in design provided by AM, will better control the heat removal from the most problematic areas of their moulds, resulting in reduced cycle times thereby increasing product volume, extending the life of the expensive tools, and maintaining product quality over extended (150k+) cycles. It will therefore provide industry with a pronounced commercial advantage and reduction in the overall production plant life cycle costs. A bubbler's flow field arises in other engineered systems, from high pressure jet cutting, to electronics cooling, and even to artificial lung ventilation.