Heat Transfer Measurements in a Turbine Center Frame at Realistic Mach Number—Part I: Baseline Study

Abstract

Abstract. This paper investigates heat transfer in a turbine center frame (TCF), a transition duct that guides the flow from the high-pressure to the low-pressure turbine. Experimental results were acquired in a high-speed wind tunnel facility at the Institute of Thermal Turbomachinery and Machine Dynamics, Graz University of Technology. The setup was operated at a realistic Mach number and featured a 90-deg 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 represents a novel addition to the institute's heat transfer studies and 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 center frame—Part II.