Convective Heat Transfer and Cooling of Ceramic Matrix Composite Materials

Seminar Guest: Steve Lynch, Penn State University

Abstract: Ceramic matrix composites (CMCs) are being commercialized in gas turbine engines due to their low density and ability to tolerate even higher temperatures than superalloy materials. However, they can have irregular surface morphology that can impact the external flow, convective heat transfer, and use of film cooling over the part surface. Furthermore, manufacturing limitations can influence the possible internal cooling designs; it is imperative to make this cooling as efficient as possible to maintain the overall cycle benefit of incorporating CMCs. This presentation will describe two technical thrusts being pursued at Penn State: one to understand convective heat transfer and film cooling on the external surface of conventional woven-matrix-based CMCs; and a second to investigate the potential of polymer-derived ceramics to create additively manufactured (AM) CMCs with complex internal cooling features. For the first thrust, measurements of convective heat transfer and the local flowfield were taken on a scaled CMC surface in a large-scale wind tunnel at representative Reynolds numbers. The results indicate that the CMC weave pattern results in augmented heat transfer that significantly varies locally relative to a smooth surface, due to local separation/reattachment zones. Film cooling flow is similarly disturbed for low coolant flowrates but is resistant to blow-off at high flowrates due to the effect of the roughness in reattaching the separated coolant. In the second thrust, a 1X scale first stage turbine vane was additively manufactured in silicon oxycarbide (SiOC), with and without a complex internal cooling structure. The cooled vane was imaged with an infrared camera in a high speed linear cascade at matched Mach and Reynolds numbers and nearly 2X better cooling was observed for the vane with complex internal features enabled by AM.

Bio: Dr. Stephen Lynch is an associate professor of Mechanical Engineering at Penn State, and is the director of the Experimental and Computational Convection Laboratory (www.me.psu.edu/psuturbine), which investigates turbine cooling technologies and design and development of metal additive heat exchangers. He received his BSME from the University of Wyoming in 2003, and his MS and PhD from Virginia Tech in 2007 and 2011, respectively. He joined Penn State in 2013, after working as a senior research engineer for two years with United Technologies Research Center (now Raytheon Technologies Research Center).