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Abstract
It has been shown that the squeeze-film damper can be a very effective means of reducing the effects of vibration in rotor system, particularly lightly damped system such as the aero gas turbine. However, since the response of the squeeze-film damper is found to be very nonlinear, considerable interest is currently being shown in the development of computational schemes for the prediction of the response of system which can include a number of squeeze-film dampers. Such computational schemes require adequate modelling of the squeeze-film damper in order that an accurate evaluation of the fluid-film forces acting within the device, and, hence, a correct prediction of the rotor amplitudes, can be made.
In the paper, three possible fluid-film models are considered, and the rotor amplitudes predicted with the aid of each of these models compared with measured values. The rotor system employed for the experimental work, and mathematically modelled for the theoretical studies, is a simple flexible shaft supported between two squeeze-film dampered rolling-element bearings with a single disk positioned midway between the bearings.
It was found that the popular Π-film (half-film) model led to predicted amplitudes which were qualitatively correct in terms of orbit shape and position of the resonance peak. However, the use of this simple, and computationally efficient, model in the theoretical analysis produced amplitudes which were always smaller than the measured values.
A film model which was considered capable of supporting sub-atmospheric pressures, and which was assumed to consist of a linear combination of the film forces produced in the full-film (2Π) and half-film (Π) models, was found to give results which were nearest to those obtained experimentally. However, there is obviously need for more work in this area in order to establish an improved model which will give closer agreement with the experimental results.