Application of Flame-Sprayed Coatings as Heating Elements for Polymer-Based Composite Structures
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Adria´n Lopera-Valle and Andre´ McDonald (Submitted March 27, 2015; in revised form July 27, 2015) Flame-sprayed nickel-chromium-aluminum-yttrium (NiCrAlY) and nickel-chromium (NiCr) coatings were deposited on fiber-reinforced polymer composites for use as heating elements of structures that were exposed to cold environments. Electrical current was applied to the coatings to increase the surface temperature by way of Joule heating. The surface temperature profiles of the coatings were measured under free and forced convection conditions at different ambient temperatures, ranging from 225 to 23 °C. It was found that at ambient air temperatures below 0 °C, the surface temperature of the coating remained above 0 °C for both the forced and free convection conditions, and there was a nearly homogeneous temperature distribution over the coating surface. This suggests that flame-sprayed coatings could be used as heating elements to mitigate ice accretion on structures, without the presence of areas of localized high temperature.
Keywords
fiber-reinforced composite, flame spray process, heating element, icing, Joule heating
1. Introduction Icing is a common problem in structures that are exposed to cold weather environments (Ref 1-9). Particularly, ice growth affects the airfoils of airplanes (the wings) and wind turbines (the blades) by decreasing their performance, safety, and durability. In planes, icing during flight produces a significant threat to safety, representing around 9% of large-scale safety accidents of aircraft during flights (Ref 10, 11). In wind turbines, ice accretion, which is the formation of ice at nucleation sites on the blade surface, has been found to produce mechanical and electrical failures, errors in the measurement of temperature, humidity and wind velocity, overproduction, and power losses up to 50% (Ref 4, 5, 7, 9). These problems may occur for over as much as 6 months of a year (Ref 6). Therefore, finding methods to avoid and mitigate the effect of ice accretion is necessary for the aerospace and
This article is an invited paper selected from presentations at the 2015 International Thermal Spray Conference, held May 11-14, 2015, in Long Beach, California, USA, and has been expanded from the original presentation. Adria´n Lopera-Valle and Andre´ McDonald, Department of Mechanical Engineering, University of Alberta, 10-230 DICE, 9211 - 116 Street NW, Edmonton, AB T6G 1H9, Canada. Contact e-mail: [email protected].
Journal of Thermal Spray Technology
energy industries since it would increase the safety and performance of equipment. In low-temperature climates, wind turbines will have increased power output due to the cold dense air, since power output is proportional to air density (Ref 5, 8). However, icing issues such as accretion on the wind turbine blades will be detrimental to the overall turbine performance, longevity, and safety during operation. Ice accretion on wind turbine blades has caused full shutdown of turbine operation, overloading that adversely affects the genera
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