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

Abstract

In this paper we experimentally evaluate the impact of in-service deterioration on the aerodynamic performance of heavily film-cooled high-pressure nozzle guide vanes from large civil jet engines. We study 15 mid-life to end-of-life parts removed from operational engines, and compare their performance to those of new parts. Deterioration features included: increased surface roughness; thermal barrier coating spallation; damaged film cooling holes; and trailing edge burn-back. We characterize and present statistics for the surface roughness. Aerodynamic measurements were performed in the high technology readiness level Engine Component AeroThermal (ECAT) facility at the University of Oxford, at engine-representative conditions of exit Mach number, exit Reynolds number, coolant-to-mainstream pressure ratio, and turbulence intensity. We present detailed experimental measurements of the coolant capacity characteristics, downstream loss, and downstream flow structures. The results show that service time has the following effects on high-pressure nozzle guide vanes: increased equivalent sandgrain roughness of (up by 1056% change); reduced coolant flow capacity (maximum change of −6.27% for film cooling holes and −24.7% for the trailing edge slot); increased overall mixed-out kinetic energy loss coefficient by (up to 33% change); leads to greater downstream flow angle variation (change of −6 deg). This is one of the first significant studies of its type in the open literature, and is an important step towards whole-life engine performance assessment.