Analysis of Two-phase flows for Spraying Processes

热喷涂广泛用于航空航天、汽车、发电和生物医学行业，为暴露在热、腐蚀和磨损中的起落架、发动机、涡轮机和植入部件提供保护涂层。在传统的热喷涂系统中，如等离子、高速氧气燃料(HVOF)或冷喷涂，尺寸为数十微米的涂层颗粒被送入喷嘴，在那里它们被加热并加速到高速。因此，热喷涂涂层是通过熔融或半熔融的粒子流在表面上撞击和固化而形成的。我们设计和制造了护罩附件，大大扩展了HVOF工艺在沉积效率和灵活性方面的能力，允许使用陶瓷粉末涂层(美国专利号6,845,929)。 在拟议的研究中，我们希望通过使用悬浮原料促进纳米和亚微米尺寸涂层颗粒的喷射和沉积，进一步扩大热喷涂工艺的能力。为此，我们需要对所有速度的气体流动状态下的雾化和液体破碎有一个透彻的了解。拟议的工作将通过计算和实验相结合的研究来解决这一需求。将对悬浮注射进行建模和表征，以满足工业对以适中成本喷洒纳米粉末的需求。我们预计，这项研究的结果将促进关键航空航天部件的制造，并对魁北克航空航天产业产生巨大影响。这项技术还将在汽车、发电和生物医药行业找到许多应用，所有这些行业对加拿大经济都很重要。 此外，可以模拟工业喷雾中的雾化过程的计算机代码在发动机、燃烧器和锅炉中输送燃料的喷嘴的设计以及农业喷雾器、干燥器、吸入性药物输送系统等方面具有广泛的应用。

Thermal sprays are extensively used in the aerospace, automotive, power generation, and biomedical industries to provide protective coatings on landing gear, engine, turbine, and implant components that are exposed to heat, corrosion, and wear. In a conventional thermal spray system such as plasma, high velocity oxygen fuel (HVOF), or cold spray, coating particles with a size of tens of microns are fed into the spray nozzle where they are heated and accelerated to high velocities. Consequently, thermally sprayed coatings are formed by the impact and solidification of a stream of molten or semi-molten particles on a surface. We have designed and built a shroud attachment which considerably expands the capabilities of the HVOF process in the areas of deposition efficiency and flexibility to allow coating with ceramic powders (U.S. Patent No. 6,845,929). In the proposed study, we would like to further expand the capabilities of thermal spray processes by facilitating the injection and deposition of nano and submicron sized coating particles using a suspension feedstock. For this purpose, we need to have a thorough understanding of the atomization and liquid fragmentation in all speed gas flow regimes. The proposed work will address this need through a combined computational and experimental study. Suspension injection will be modelled and characterized to address the need of industries for spraying nanopowders at moderate cost. We expect that the results of this study will facilitate manufacturing of key aerospace components, and have a great impact on the Quebec aerospace industry. The technology will also find many applications in the automotive, power generation, and biomedical industries, all of which are important to the Canadian economy. Furthermore, a computer code which can simulate the process of atomization in industrial sprays has broad applications in the design of nozzles for delivering fuel in engines, burners, and boilers, as well as for agricultural sprays, dryers, inhaled drug delivery systems, etc.