Encapsulated Tuned Dampers for Jet Engine Component Vibration Control

Abstract

The papers in this section are from two sessions. The first session was chaired by Major Larry Gross, Ph.D., and Alien C. Royal. The second session was chaired Nomenclature = breadth of beam = Young's modulus = real part of complex Young's modulus of damping material = effective (complex/real) flexural rigidity of beam = Young's modulus of metal outer layer/viscoelastic core = resonant frequency in nth mode (Hz) = factor by which centrifugal loading exceeds unit gravity = thickness of wall = second moment of area of viscoelastic core/metal outer layer about neutral axis = length of beam = time dependent load per unit length = time = axial coordinate along beam, with root as origin = transverse displacement of point on beam = nondimensional parameter = loss factor of composite beam /damping material ** = first eigenvalue of cantilever beam ( ~ 12.36) = effective mass per unit length of composite beam = density of damping material/metal outer layers = resonant frequency at zero rotational speed = resonant frequency (rad/sec) Theme MANY jet engine components suffer from serious vibrational resonance problems induced by the engine environment. Examples are stator vanes, inlet guide vanes, combustor cans, hollow shafts and turbine 1 and compressor blades. This paper describes a preliminary investigation of a tuned damper, utilizing damping material encapsulation to withstand centrifugal load and erosion problems. The tests were conducted at room temperature for convenience, but the results are equally applicable to higher temperatures if the appropriate damper materials are used (high-temperature enamels and metals). Specific tests on control of one mode of a turbine blade show a great reduction in vibration levels resulting from proper tuning of the damper.