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6577 |
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Wednesday, June 10, 2020, Hall D 4:10 PM Session Young Professionals |
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Thermally sprayed coating-based heating elements for boundary layer transition detection - An experimental approach |
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Manuel Machulla* / Fraunhofer Institute for Material and Beam Technology, Germany Shahed Taghian Dehaghani / University of Alberta / Department for Mechanical Engineering, Canada Stefan Scheitz/ Fraunhofer Institute for Material and Beam Technology (Fh-IWS), Germany Christoph Leyens/ Technische Universität Dresden / Institute of Materials Science, Germany André McDonald/ University of Alberta / Department for Mechanical Engineering, Canada |
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Boundary layers on surfaces will transition from laminar to turbulent after a critical length. Due to the different heat transfer coefficients of laminar and turbulent flow, the point of transition can be detected by heating the surface and measuring the surface temperature by thermographic imaging. Locating the transition point is crucial for many industries such as aerospace. In this study, fiber reinforced polymer composites (FRPCs) were chosen as the substrates for the experiments. Nickel-chromium-aluminum-yttrium (NiCrAlY) coatings were deposited by flame spraying directly onto the FRPC surface. Multilayered coatings consisting of an aluminum bond coat, a layer of alumina as electrical insulation, and a heating layer of titania were fabricated by using atmospheric plasma spray. Wind tunnel experiments were conducted on flat plates in order to test the ability of thermally sprayed coating heating elements to detect the location of transition of the flow regime. The results showed that these heating elements can be employed to heat a surface uniformly, with sufficient surface radiation losses for thermographic imaging. It was observed that a sudden decrease in surface temperature occurs at the transition point. The results suggested that thermography of thermally sprayed coating heating layers on complex geometries such as winglets may be implemented to examine their aerodynamic properties during free flight conditions. |