Degradation of the cooling performance of the double wall nozzle guide vane in an engine

The overall cooling effectiveness of the original nozzle guide vanes and the vanes tested in engine operating for about one hundred hours was measured using infrared thermal imaging at a fan-shaped cascade pressure ratio of 2.378 and coolant-to-mainstream mass flow ratios of 0.0294-0.0784. Carbon dioxide was used as the coolant to provide density ratios of 3.2-4.2 and a dynamic viscous ratio of 0.8. The velocity magnitude of 57 m/s in the cascade inlet led to a Reynolds number of 624,000 based on the chord of the vane. About 5% turbulence intensity was recorded at the same location. The objective of the study was to determine the degradation of the cooling performance on the leading edge and trailing edge of the vane in an engine test. The results showed that the arc-averaged overall cooling effectiveness decreased by 0.03-0.17 depending on the various spanwise positions. The surface-averaged overall cooling effectiveness decreased by 0.08-0.13, 0.04-0.07 and 0.03-0.08 on the leading edge, impingement region and cut-back film cooling region of the trailing edge respectively. The values of the additional thermal resistance of the vane tested in the engine were determined by conducting a one-dimensional heat transfer model analysis based on the obtained experimental data of the overall cooling effectiveness.