Ceramic matrix composites (CMCs) are quickly becoming more prevalent in the design of gas turbines due to their superior weight and thermal properties.  However, despite a great deal of research focused on the material properties of CMCs, little public work has been done to investigate the impact that CMCs have on the flow and heat transfer properties of turbine components. The surface profile of a CMC varies substantially from the smooth surface of a nickel superalloy given their weave patterns that contribute to relatively high roughness and anisotropic surface features. This considerable roughness substantially changes the boundary layer development and therefore the heat transfer coefficients when compared to a smooth surface.  The surface profiles of CMCs result in properties that are directionally dependent, which brings up the question as to how to orient CMCs in turbine components. In this study, a CMC weave pattern was scaled up and tested in a low speed wind tunnel to evaluate both heat transfer and flow field properties of a NASA geometry at two orientations. Using an IR camera, spatially-resolved heat transfer coefficients were measured for the different CMC orientations. In addition to the heat transfer measurements, boundary layer measurements are taken using a Laser Doppler Velocimeter across different surface features and Reynolds numbers. The CMC weave patterns result in augmented heat transfer and flow field properties that vary locally when compared to a smooth surface.     
 


Experimental Heat Transfer and Boundary Layer Measurements on a Ceramic Matrix Composite Surface

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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