Insert Damping of Hollow Airfoils

Abstract

This paper describes a new mechanical damping device for hollow airfoils. The concept combines cooling and damping systems in one single element. Damping is achieved by frictional contact between an insert and specially selected contact locations on internal airfoil surfaces. The mechanical damping system is optimized for the first torsion mode of a shroud-less turbine blade and leads to very high damping effectiveness. In parallel an acceptable damping of the first flap mode was observed. In addition studies indicating the role of main parameters such as friction coefficient, excitation amplitude, geometry and location of damper elements are presented.