Better Bubblers: Jet Impingement Within a Dead-End Channel

在高压铝压铸(HPADC)和注塑(IM)行业中，一种独特的流场被用来冷却细长的模具突起：限制在死端通道内的射流冲击，在工业上被称为“鼓泡器”。这些设备被广泛使用，但它们在模具中的实施受到2D加工的限制；添加剂制造(AM)的最新进展现在为改进它们的设计提供了及时和新颖的机会。我们面临的挑战是，与鼓泡器相关的热和流动状态在文献中得到的关注有限，因此需要更好地了解这些设备的AM可以实现的最佳冷却性能。因此，该项目的目标是建立与鼓泡器相关的热和流动现象，并开发新的方法，使其设计能够针对AM进行优化，通过以下目标实现：1)开发高分辨率计算流体动力学(CFD)数据集，详细揭示鼓泡器的热和流动结构。将对基本共环流场进行等温和共轭换热(CHT)壁面分辨大涡模拟(LES)，并与实验数据进行验证。2)通过收集和分析实验结果来阐明流动物理。粒子图像测速(PIV)数据将利用一种新型冷流光学实验台获得，并用于基本流场的参数化和等温模拟的验证。将使用考文垂现有的铝铸件实验获得热传递数据，以验证CHT模拟。3)为HPADC刀片开发新的形状优化方法。伴随方法找到了控制Navier-Stokes方程的梯度，使得能够在追求特定目标函数的过程中实现量身定制的形状变形，该目标函数将需要被开发以使得能够最大化散热和整个突起的热流均匀。优化后的几何形状将由我们在CastAlum有限公司的合作伙伴进行激光烧结，以在工业环境中进行实验测试和演示。这将导致：-通过应用LES和PIV，彻底描述环形受限射流冲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，并将新的重点放在通过撞击表面和环形隔离壁的传热上，导致；-显著改进的鼓泡器操作参数，提供有效的热清除率，以及它们对一整套结构的预测的关联式；-HPADC的优化策略，最大限度地提高散热和热流均匀度，这将加速在行业内采用AM方法。同时，该项目将推进建模技术，并在射流撞击的数值模拟方面设定新的基准，其用途将远远超出名义上的应用。这项工作将直接惠及英国HPADC和IM行业，奠定严格的理论基础，再加上AM提供的设计灵活性，将更好地控制模具最有问题的区域的散热，从而缩短周期时间，从而增加产品体积，延长昂贵工具的使用寿命，并在更长的(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。鼓泡器的流场出现在其他工程系统中，从高压喷射切割到电子冷却，甚至到人工肺通风。

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.