SPATIAL DYNAMICS OF TUNED AND MISTUNED BLADED DISKS WITH CYLINDRICAL AND WEDGE SHAPED FRICTION DAMPERS

摘要

One of the main tasks in the design of turbomachines like turbines, compressors and fans is to increase the reliability and efficiency of the arrangement. Failures due to blade cracks are still a problem and have to be minimized with respect to costs and safety aspects. To reduce the maximum stresses, the blades can be coupled via friction damping devices such as underplatform dampers that are pressed onto the blade platforms by centrifugal forces. In this work, a method will be presented to optimize two different types of underplatform dampers in bladed disk applications with respect to a maximum damping effect. In practice, underplatform dampers with different geometric properties like a cylindrical and a wedge shaped damper are commonly used - leading to different contact conditions. A discretization of the contact areas between the blade platforms and the dampers is applied to be able to investigate nearly arbitrary contact geometries and spatial blade vibrations. The functionality of the two mentioned damper types will be studied in detail under different working conditions of the assembly. The advantages and disadvantages of both damper types will be pointed out and strategies will be presented to improve the damper design. In this context the influence of mistuning effects will be discussed Different types of underplatform dampers have been investigated concerning a statistical mistuning of the blades' natural frequencies due to manufacturing tolerances as well as a systematical mistuning due to a deliberate slight variation of the blade masses or geometries.