Eddy Current Damping: A Concept Study for Steam Turbine Blading

Abstract

In gas and steam turbine applications a common approach to prevent the blades from high cycle fatigue failures due to high vibration amplitudes is the usage of friction damping elements. Besides the intended amplitude reduction this procedure also features some possibly unwanted side effects like a shift in resonance frequencies due to stiffening effects caused by the contact. Thus, as an alternative an eddy current based non-contacting damping concept for the application in turbo machinery is investigated. In this paper two different types of eddy current dampers are considered. Theoretical models for both are established by applying electromagnetic-mechanical theory. The theoretical models are compared to forced response measurements that are performed at a stationary test rig.

Vibration Prediction of Bladed Disks Coupled by Friction Joints

“…Also, the application of active or semi-active vibration control strategies is hampered by the requirement of fail-safe operation. Noteworthy alternatives to friction damping include piezoelectric shunt damping [58,178], eddy current damping [88,87], viscoelastic material damping of coatings [177,60], and impact or particle damping. Friction damping takes place in mechanical joints that are either inherent to bladed disks, such as the ones between blades and roots, or can be introduced additionally, e. g. in the form of underplatform dampers.…”

Vibration Reduction of Mistuned Bladed Disks Via Piezoelectric-Based Resonance Frequency Detuning

“…Sodano and Bae provide a more comprehensive review on the concept of eddy-current damping and their role in damping structural vibrations. [34] Laborenz et al investigated two eddy-current damping concepts to damp blade vibrations by using the relative motion between neighboring blade tips [35]. The first concept utilized a copper plate located on one blade tip situated across from a permanent magnet on the neighboring blade tip, and the second concept utilized a permanent magnet fixed behind a copper plate on one blade tip with a mirrored version of the same assembly on the neighboring blade tip.…”

Dynamic Vibration Absorber with Negative Stiffness for Rotor System

“…The negative stiffness can be calculated by (8), and the stiffness of different ℎ is shown in Figure 3. It can be seen from Figure 3 that the nonlinearity is weak when ℎ is large, and the nonlinearity increases with the decrease of ℎ and becomes suddenly evident when ℎ is 2.5 mm.…”

“…The second kind of method is by adjusting parameters of the rotor system such as stiffness, damping, and eccentricity, which can be carried out by using shape memory alloy metals [5], discontinuous springs [6], and so forth. In all these methods, the damping adjusting methods are more popular and many approaches are used, such as squeeze film dampers [7], eddy current damping [8,9], piezoceramic induced damping [10], magnetorheological elastomer damping [11][12][13], and friction controlled damping [14]. Eccentricity adjusting is another kind of popular method and is mainly realized by using an automatic ball balancer [15,16], which can be very efficient when the rotating speed is above the critical speed.…”