Experimental Study of Impact of In-Service Deterioration on Thermal Performance of High-Pressure Nozzle Guide Vanes

Abstract

In this paper, we analyze the impact of in-service deterioration on the overall thermal performance (metal effectiveness) of heavily cooled high-pressure nozzle guide vanes of a design typical of large civil jet engines. We study 15 deteriorated parts (increased surface roughness, thermal barrier coating spallation and sintering, damaged film cooling holes, and trailing edge burn-back) from operational engines and compare their thermal performance to that of equivalent new parts. A companion paper focuses on the aerodynamic impact of in-service deterioration. Overall cooling effectiveness measurements were performed in the Engine Component AeroThermal (ECAT) Facility at the University of Oxford, at engine-representative conditions of Mach number, Reynolds number, coolant-to-mainstream pressure ratio, and turbulence intensity. We characterize the degradation of overall cooling effectiveness with service time. This is an important result for whole-life modeling. Changes in overall cooling effectiveness were greatest on the pressure surface and early suction surface of the parts. Area-averaged differences in overall cooling effectiveness of −1.83% and −10.41% were measured on the pressure surfaces of mid-life and end-of-life vanes, respectively. In the analysis, we attempt to decouple the contributions from independent deterioration effects and compare the philosophy of this top-down approach to the bottom-up approach in which effects are studied in isolation and then superposed in modeling.