Abstract
This paper presents the experimental-numerical comparison of a bladed system with flexible strip dampers. The experimental results constitute, to the authors’ knowledge, the first published experimental evidence on strip dampers. They explore the in-phase and out-of-phase mode of vibration of two blades coupled by a strip damper. The great influence the mode of vibration has on the strip behaviour and consequent effect on the blades’ response is highlighted, analyzed and successfully simulated numerically. Experiments are made possible by a purposely developed loading system based on compressed air. This non-contact system enables the experimenter to apply a realistic value of contact pressure on the strip without adding spurious stiffness to the system or modifying the contact conditions. The availability of experimental data obtained by imposing realistic contact conditions constitutes a true added value. It is here shown how the full stick linear FRFs (Frequency Response Functions), typically used to predict the response in case of limited excitation on blades coupled by rigid dampers, do not offer significant results in the case of flexible strip dampers.
Highlights
One of the key points in the structural design of a turbine bladed disk is to avoid that the excitation frequencies of the aerodynamic forces are in the same range of the natural frequencies of the bladed disk
This paper presents the experimental-numerical comparison of a bladed system with flexible strip dampers
The availability of experimental data obtained by imposing realistic contact conditions constitutes a true added value. It is here shown how the full stick linear frequency response functions (FRFs) (Frequency Response Functions), typically used to predict the response in case of limited excitation on blades coupled by rigid dampers, do not offer significant results in the case of flexible strip dampers
Summary
One of the key points in the structural design of a turbine bladed disk is to avoid that the excitation frequencies of the aerodynamic forces are in the same range of the natural frequencies of the bladed disk. The UPDs are metal masses inserted between the blades, pushed against the blade platforms by the centrifugal force They are extensively used in turbine designs, especially as “solid dampers” in several shapes, cylindrical, curved flat, wedge damper, etc. Sci. 2018, 8, 2174 seal and blade platforms, the friction forces dissipate vibrational energy and the dynamic response of the system is damped. For all these reasons, a sound and robust turbine dynamic design should consider the seal influence on the response in terms of its frequency shift and damping contribution. The numerical results’ sensitivity to changes in the contact parameters used to simulate the friction interfaces are discussed in detail
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