Impact of Nozzle Guide Vane Trailing Edge Damage on High-Pressure Turbine Stage Performance

Abstract

Abstract. In this paper we consider the impact of nozzle guide vane trailing edge burn-back (damage) on cooled high-pressure turbine stage performance. We analyse four levels of simulated burn-back ranging from new parts to severely damaged. The burn-back geometries are based on a statistical analysis of real deterioration data from operating engines. We use unsteady stage simulations to predict the impact of burn-back on capacity, reaction, specific work, and efficiency, among other performance metrics. Experimental data from a full-annulus nozzle guide vane cascade test (operated at engine-matched conditions) was used to validate the computational fluid dynamics (CFD) predictions. We find that for fixed stage pressure ratio, increasing burn-back leads to: a significant decrease in vane efficiency due to the formation of a pair of counter-rotating vortices at the burn-back edges, an increase in rotor efficiency due to weakened secondary flow in the rotor passage, a marginal overall decrease in stage efficiency, a decrease in stage specific work despite an increase in mass-mean absolute turning angle due to a greater magnitude of contrary change in rotor inlet and outlet velocities, a significant increase in vane capacity due to an increase in the effective area of the controlling region, a milder decrease in vane capacity due to an increase in the intrastage static pressure, and a significant increase in stage reaction. Taken together with a related study on vane-only aerodynamic performance and flow capacity, these results improve understanding of the impact of burn-back on whole-life engine performance.