A fundamental investigation into brush seal fluid dynamics

刷式密封是燃气涡轮发动机中使用的一种轴封。它们保持一个压力降，这是由于一个静压环提供了高的流动阻力，这个静压环是由密集排列的细线刷毛（通常是金属的）组成的，它们与组件的旋转方向成一定的角度。非常低的泄漏是可能的，这种类型的密封使其成为燃气轮机设计师非常有吸引力的选择。虽然在燃气轮机中使用刷式密封的好处早已确立，但由于在役性能的迅速恶化，它们在航空航天应用中的应用尤其受到限制。已经确定了这种快速磨损的流体动力学机制，如鬃毛吹落和压力硬化。为了在整个燃气轮机中更容易地实施刷式密封，并允许利用潜在的好处，需要对这些影响有更深入的了解。刷式密封通常在理论上使用多孔介质方法进行建模，其中密封对流动的影响由一组阻力系数定义。这些系数必须使用实验数据进行校准，以便对发动机条件进行正确的外推。目前文献中明显缺乏已发表的实验值。本研究旨在通过大规模、简化的实验测量，提高对刷式密封的基本认识，并为多孔介质模型提供验证数据。该项目将与全球领先的燃气轮机刷式密封件供应商Cross Manufacturing Ltd.密切合作。获得的见解将提供一个数据库，该数据库将用于通知未来刷式密封配置的设计，不仅是Cross，而且是更广泛的燃气轮机行业。

Brush seals are one example of a type of shaft-seal used within gas turbine engines. They maintain a pressure drop by virtue of the high resistance to flow provided by a static ring of densely packed, fine wire bristles (usually metallic) that are angled in the direction of rotation of the component. Very low leakage is possible with this type of seal making it a highly attractive option for gas turbine designers.Although the benefits of using brush seals in gas turbines have long been established, their utilisation in aerospace applications especially has been limited due to the rapid deterioration of in-service performance. Fluid-dynamic mechanisms for this rapid wear have been identified such as bristle blow-down and pressure stiffening. For brush seals to be implemented more readily throughout gas turbines and to allow the potential benefits to be exploited, a greater understanding of these effects is required. Brush seals are typically modelled theoretically using a porous medium approach where the influence of the seal on the flow is defined by a set of resistance coefficients. These coefficients have to be calibrated using experimental data to enable correct extrapolation to engine conditions. There is currently a distinct lack of published experimental values available in the literature.This proposal aims to improve the fundamental understanding of brush seals and provide validation data for porous media models by making measurements in large-scale, simplified experiments. The programme will be conducted in close collaboration with Cross Manufacturing Ltd., a world-leading supplier of brush seals to the gas turbine industry. The insight obtained will provide a database which will be used to inform the design of future brush seal configurations, not only by Cross but also the wider gas turbine industry.