Engine Evaluation of a Vibration Damping Treatment for Inlet Guide Vanes

Welded titanium inlet guide vanes in an Air Force turbojet engine, have been experiencing a high rate of vibration induced cracking after very short service The cause of this cracking has been identified as resonant vibration excited by pressure fluctuations occurring when the first-stage fan blades pass the inlet guide vanes A bonded vibration damping wrap has provided a cost effective fix which can be applied on a retrofit basis for major cost savings The damping wrap, which consists of multiple layers of energy dissipating adhesives separated by constraining layers of aluminum foil, is bonded to the vanes under high temperature and pressure in an autoclave. This paper describes the results of engine test-cell tests and the comparison of these results with actual service experience obtained under operational conditions Measured effects on engine performance, distortion tolerance, and anti-icing performance are presented along with measured stress reductions, as compared with increases in modal damping. Durability design considerations are discussed, along with the results of durability tests in an engine test stand and actual service experience.