Amplitude and Wavelength Effects for Wavy Channels

Abstract

To improve the efficiency and durability of gas turbine components, advancements are needed in cooling technologies. To accomplish this task, some manufacturers are turning to additive manufacturing (AM), as it offers the ability to both rapidly iterate on component design as well as incorporate unique internal cooling structures directly into parts. As one example, wavy microchannels can be readily integrated into turbine components. This study investigates wavy channels of varying channel amplitude and wavelength through experimental measurements of heat transfer and pressure loss. In addition to experimental testing, computational fluid dynamics (CFD) predictions were made to identify internal flow features that impacted performance. Five channel geometries were integrated into test coupons that were additively manufactured out of Hastelloy-X using direct metal laser sintering. True coupon geometric characteristics and wall roughness values were captured non-destructively using computed tomography (CT) scans. Geometric analyses indicated that coupons were reproduced accurately with minimal deviation from design intent. Experimental results indicated that decreasing the channel wavelength and increasing the channel amplitude resulted in substantial increases in both bulk friction factor and Nusselt number with respect to the nominal case and were scaled using a relative waviness parameter. CFD simulations predicted significant mixing of flow in the cases with the smallest wavelength and greatest amplitude.