Investigation of cooling performance degradation of impingement/effusion structure on pressure side of nozzle guide vane

The cooling performance of the impingent/effusion structure on the pressure side of nozzle guide vanes tested in an engine operating for the various duration of 100 h, 300 h, and 500 h was evaluated in this study via infrared thermal imaging. The original vane was also examined as a comparison. The examined impingement/effusion structure consisted of 4 rows of impinging hole and 5 rows of film hole. The tested coolant-to-mainstream mass flow ratios was 0.0392–0.0784. Reynolds number was 624000 based on the vane chord and cascade inlet velocity. Cooling performance degradation in the impingent/effusion structure was investigated as it relates to oxidation and dust deposition after various durations of engine operation. The two-dimensional temperature distributions in the vane wall became nonuniform over time. The cooling performance quickly degraded after the vane was tested for 100 h in the engine; this degradation grew less intense as operation duration continually increased. The surface-averaged values of the overall cooling effectiveness of the impingent/effusion structure decreased by 9%–11% dependent on the mass flow ratio after the vane was tested for 500 h of engine operation. The coolant flow resistance increased with engine operation time as well.