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Tuesday, July 9 • 12:10 - 12:30
EFFECT OF VARIATION IN CONTACT FRICTION ON THE PERFORMANCE OF THE UNDER-PLATFORM DAMPERS.

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Under platform-dampers (UPDs) are commonly used devices in turbomachinery to mitigate the turbine blade vibrations caused by periodically fluctuating stresses. These dampers are placed in the underside of two adjacent blades and vibration energy is partly dissipated by friction at the blade/damper interfaces. As a result, the vibration amplitude is reduced with beneficial effects on the blade fatigue life. At LAQ AERMEC a novel test rig has been developed to accurately measure the response of a single turbine blade and the kinematics/dynamics of two adjacent UPDs. In this newly developed test rig, each damper is in contact with the under-platform of the blade on one side and with ground/fixed platform on its other side. The dampers are pressed against the blade platform by static forces applied by dead weights. A static force is also radially applied to root of the blade to clamp it to the rig, simulating the effect of the actual centrifugal force in operating conditions. Finally, a transverse periodic excitation is applied in order to excite the blade's first resonances. In this paper, performance of different UPDs in terms of reduction of the blade vibration amplitude and shift in resonance frequency is studied at two different contact friction conditions (normal and low friction). Low friction conditions are obtained by introducing a thin layer of oil between the damper-blade contact interfaces. Experiments are performed on a real turbine blade to investigate a set of dampers characterized by different masses and geometries. Moreover, the effect of low friction coefficient on the nonlinear contact forces has also been investigated. This profound study of UPDs provides a strong basis to understand the effect of different dampers and their contact conditions, to limit the blade vibration for a given set of conditions.

Moderators
EP

Elsa Piollet

Dr, Polytechnique Montréal
avatar for Mohammad Rafiee

Mohammad Rafiee

Postdoctoral Fellow, Polytechnique Montréal
Mohammad Rafiee received his Ph.D. degree in Mechanical Engineering from the University of Ottawa in 2018. Currently, he is a Postdoctoral Fellow at Polytechnique Montreal in Canada. His research interests are primarily focused on the development of advanced composite materials, smart... Read More →
AR

Annie Ross

Professor, Polytechnique Montreal

Authors

Tuesday July 9, 2019 12:10 - 12:30 EDT
St-Laurent 8
  T07 Struct. dyn. & nonlin. vib., RS02 Vibr & cntrl of nonlin mech syst