INVESTIGATION ON THE DYNAMIC RESPONSE OF BLADES WITH ASYMMETRIC UNDER PLATFORM DAMPERS

The paper presents the experimental activity about the dynamic response of the blades of a gas turbine for power generation carrying underplatform dampers. The final aim of the activity is to provide an experimental data base to validate the results of a numerical tool which calculates the response of the blades with underplatform dampers. The blades have fir tree attachments and an asymmetric damper is fitted between the blade platforms. The dynamic behavior of the blades is detected by an experimental campaign on two blades mounted in a test rig. Stepped sine measurements are performed with a closed-loop control system on the excitation amplitude. Different levels of excitation amplitude and centrifugal force on the damper are tested. The test campaign pointed out the presence of damping due both to the underplatform damper and to the blade attachment. The contribution of the different damping sources are discussed and analyzed. A method is suggested to identify the root damping which is not constant but proved to depend on the excitation force on the blades.