Accession Number : ADA305380

Title :   Friction Damping of Hollow Airfoils: Part 2 - Experimental Verification,

Corporate Author : NAVAL AIR WARFARE CENTER AIRCRAFT DIV PATUXENT RIVER MD

Personal Author(s) : El-Aini, Yehia M. ; Benedict, Barry K. ; Wu, Wen-Te ; McAdams, Stoney

PDF Url : ADA305380

Report Date : DEC 1995

Pagination or Media Count : 7

Abstract : The use of hollow airfoils in turbomachinery applications, in particular fans and turbines, is an essential element in reducing the overall engine weight. However, state-of-the-art airfoil geometries are of low aspect ratio and exhibit unique characteristics associated with plate-like modes. These modes are characterized by a chordwise form of bending and high modal density within the engine operating speed range. These features combined with the mistuning effects resulting from manufacturing tolerances make accurate frequency and forced response predictions difficult and increase the potential for High Cycle Fatigue (HCF) durability problems. The present paper summarizes the results of an experimental test program on internal damping of hollow blade-like specimens. Friction damping is provided via sheet metal devices configured to fit within a hollow cavity with various levels of preload. The results of the investigation indicate that such devices can provide significant levels of damping provided the damper location and preload is optimized for the modes of concern. The transition of this concept to actual engine hardware would require further optimization with regard to wear effects and loss of preload particularly in applications where the preload is independent of rotational speed. Excellent agreement was achieved between the experimental results and the analytical predictions using a micro-slip friction damping model.

Descriptors :   *DAMPING, *ROTOR BLADES(TURBOMACHINERY), TEST AND EVALUATION, VELOCITY, FREQUENCY, POSITION(LOCATION), OPTIMIZATION, MANUFACTURING, PREDICTIONS, ENGINE COMPONENTS, STATE OF THE ART, EXPERIMENTAL DESIGN, ACCURACY, CAVITIES, AIRFOILS, CYCLES, MATHEMATICAL PREDICTION, PLATES, RESPONSE, INTERNAL, WEIGHT, HIGH DENSITY, LOW LEVEL, FATIGUE(MECHANICS), TURBINES, RANGE(EXTREMES), TOLERANCES(MECHANICS), ROTATION, FRICTION, ASPECT RATIO, TURBOMACHINERY, LIQUID OXYGEN, SHEET METAL.

Subject Categories : Aircraft
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE