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The paper deals with the modelling of turbine rotors, including a foundation and stator parts, and with their dynamic analysis. The dynamics of turbines can be strongly influenced by the effects of a rotor foundation, and therefore suitable modelling approaches should be developed to obtain proper analysis tools. The standard methods for the modelling of rotating shafts are summarized in the paper, and two approaches to including foundation effects into dynamic models are introduced. The approach based on the dynamic compliance of the foundation with respect to the rotor angular velocity is compared with the approach based on the modal synthesis of rotor and foundation models. The calculation of modal properties is then demonstrated, and the characteristics of both presented methods are discussed. A comparison of the steady-state dynamic response calculated using both methods is shown. It can be concluded that both approaches can be advantageously used for several analyses, and our final recommendations are given in the conclusions.

Friction forces can be advantageously used as a source of passive damping in various mechanical systems. This paper deals with an experimental modelling and numerical simulation of blades interaction by means of a friction element placed in the shroud between the blade heads. The radial force, which represents the centrifugal force acting on the friction element, determines the values of contact forces between the element and blades. The experimental set-up for a couple of non-rotating blades is described in the paper, and the measured dynamic response of two blades is documented. The same situation is modelled by means of a basic and a more complex dynamical model of two blades with a friction element. The effect of friction is studied for the case of harmonic excitation by suitable frequency and subsequent free vibration attenuation. Both mathematical models are based on the finite element method combined with lumped rigid bodies. The interaction of the friction element and blades is described by normal contact and tangential friction forces derived for particular geometrical parameters of the studied mechanical system. The performed comparison of experimental and numerical results shows the satisfactory agreement and the modelling methodology could be used for possible parameter optimization.