Design Tools to the Best Coupling of Dry-Friction Solid Underplatform Dampers to Turbine Blades

Abstract

Abstract This work completes the recent authors efforts in the frame of solid dampers optimization, whose goal are to develop systematic design tools to identify the best choice of an underplatform damper (shape, size) matching with a blade (size, modal features) in a turbomachine. Step 1 was to filter out all those geometries that would lead to undesirable kinematics and contact forces. Step 2 was to identify those ranges of parameters that are better in terms of added stiffness and damping. The purpose of this third and final step is to complete the picture by exploring how the basic geometrical design parameters of blades interact with the damper parameters and where (i.e., for which parameters combination) a designer may find the best match in view of the vibratory response under resonant excitation. The main focus is on the blades HCF safety. While steps 1 and 2 are based on simple geometrical considerations, this step 3 requires a non-linear coupled dynamic analysis of the system. It is demonstrated how the variation of crucial parameters (e.g. neck thickness, damper geometry, centrifugal force) affects the performance of a real damper coupled to a realistic blade. The method, based on reasonable simplifications, is illustrated and proposed as a tool to make the analysis attractive to designers in the early design stage by guiding their initial choice of an optimal dry friction damper.