Analysis of multiphase flows for functional coatings

这项关于多相流的研究计划主要是由于对应用新兴的悬浮热喷涂工艺来生产所谓的“功能性”涂层的大量和日益增长的兴趣。传统的热喷涂工艺，如等离子体和高速氧燃料（HVOF），已经广泛应用于航空航天、汽车和发电行业，用于发动机、起落架和涡轮部件的保护涂层，这些部件暴露在高温、腐蚀、侵蚀和磨损中。他们将直径几十微米的颗粒送入喷枪，加热并加速到高速。最近，大量的研究工作已经应用于新兴的悬浮热喷涂（STS）系统，该系统可以沉积更小的纳米颗粒，并产生性能优越的涂层。在STS中，将分散的纳米颗粒液体悬浮液注入热喷雾火焰中，使悬浮液滴雾化。然后液滴蒸发，使得液滴中的纳米颗粒加速并熔化，就像传统的热喷涂过程一样。这项技术显示出巨大的希望，可以创造出适合许多工业应用的进料速率涂料。例如，通过悬浮喷涂技术沉积的纳米结构涂层具有显著的耐磨性、增强的催化性能和优异的隔热性能。

This proposed research program on multiphase flows has been motivated primarily by the substantial and growing interest in applying the emerging suspension thermal spray process to produce so-called “functional” coatings. Conventional thermal spray processes such as plasma and high velocity oxygen fuel (HVOF) are already used extensively in the aerospace, automotive, and power generation industries to apply protective coatings on engine, landing gear, and turbine components that are exposed to heat, corrosion, erosion, and wear. They use particle diameters of tens of microns that are fed into the spray gun and heated and accelerated to high velocities. Recently, substantial research efforts have been applied to emerging suspension thermal spray (STS) systems that deposit much smaller nanoparticles and create coatings with superior performance. In STS, a liquid suspension of dispersed nanoparticles is injected into thermal spray flames, which atomize the suspension droplets. The liquid droplets then evaporate allowing the nanoparticles contained in the droplets to accelerate and melt as in a conventional thermal spray process. This technology shows significant promise to create coatings with feed rates suitable for many industrial applications. For example, the nano-structured coatings deposited by the suspension spraying technique demonstrate remarkable wear resistance, enhanced catalytic behaviour and superior thermal insulation. In STS, coating quality and functionality depend primarily on the suspension penetration into the jet, the primary and secondary atomization of the suspension, and the slurry droplet evaporation. Characterizing the multiphase flow and heat transfer associated with the suspension atomization in an all speed (subsonic to supersonic) flow is a challenging research topic requiring numerical and experimental studies. The proposed research program addresses both these aspects by studying multiscale multiphase spray process flows and the resultant functional coatings. We will explore the development of environmentally friendly durable omniphobic coatings, specifically, superhydrophobic, icephobic, and slippery liquid-infused porous surfaces. The computer codes that we generate to simulate the atomization process in industrial sprays also have broad applications in the design of nozzles for metal powder manufacturing, engine fuel systems, agricultural sprayers, dryers, and inhaled drug delivery systems. We anticipate that the results of this study will facilitate the manufacture 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.