Impingement-Film Heat Transfer Investigation
GENERAL ELECTRIC CO LYNN MA AIRCRAFT ENGINE BUSINESS GROUP
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This report covers the investigation of an impingement-film cooling system designed to cool the exhaust ducts of turboshaft engines thereby reducing infrared radiation levels. The program was initiated with a literature search which indicated the useful range of impingement hole size, spacing, and distance from impingement hole to cooled panel. It provided similar information for the cooling slot design. Test hardware incorporating these features was fabricated for testing. Seventeen configurations, four of which had no impingement film cooling only, were tested. The remaining 13 configurations were tested with different combinations of impingement hole size, spacing, and distance to cooled panel. Film cooling test results were in good agreement with the correlations and results quoted in the literature. The cooling effectiveness with impingement-film cooling was consistently superior to that with film cooling only. The highest effectiveness was achieved with the configuration having the largest impingement hole diameter, D 0.070 in. and spacing X sub nD 12. The optimum impingement distance Z sub n was in the neighborhood of 4 impingement hole diameters. While the largest hole spacing tested gave the highest cooling effectiveness it also required a relatively large pressure drop across the cooling system. Under the most difficult cooling conditions of hot gas Mach number equal to 0.4, the highest cooling effectiveness achieved within a specified impingement system pressure drop of 100 in. of water was 0.93.
- Infrared Detection and Detectors
- Jet and Gas Turbine Engines