Heat Transfer Measurements in a Turbine Centre Frame at Realistic Mach Number - Part 1: Baseline Study

Abstract This paper investigates heat transfer in a turbine centre frame (TCF), a transition duct that guides the flow from the highto the low-pressure turbine. Experimental results were acquired in a high-speed wind tunnel facility at Graz University of Technology. The setup was operated at a realistic Mach number and featured a 90° sector cascade of an engine-representative TCF geometry equipped with a flow conditioning grid. Heat transfer coefficient (HTC) measurements were conducted using an advanced infrared thermography technique developed at the institute, covering the hub and struts, as well as the challenging shroud surface. This ensures complete surface coverage of a TCF passage for the first time. The HTC distribution on the hub and struts is consistent with the previous findings from similar studies, whereas the newly investigated shroud exhibits a significant increase in heat transfer around the pronounced convex bend. Heat transfer correlations, both common and adapted, are included in the discussion for additional analytical insight and interpretation. Furthermore, the results are compared with a test campaign that included a high-pressure turbine (HPT) upstream of the TCF. Finally, an attempt was made to estimate the total pressure loss of the TCF from the full surface coverage heat transfer measurements. The work presented here contributes to a deeper understanding of thermal management in TCFs and establishes a baseline for the following study that investigates the effects of combustor hot streaks on heat transfer in the turbine centre frame - Part 2.