Experimental Study of a Squeeze Film Damper With Eccentric Circular Orbits

An experiment was carried out to investigate the distribution of oil pressure within a squeeze film damper. The damper was made so that its operation turned out to be as simple as possible, in order to highlight the main causes of practical deviation from theoretical prediction, with particular reference to cavitating mechanisms and regardless of inertia effects. The journal of the damper was given an eccentric orbital precession, with adoption of two distinct values of the offset. A groove placed laterally to the film secured the oil feeding. An outlet plenum at the opposite side of the film was operated with two different levels of exposure to the ambient air. Observation of the oil pressure was restricted to the film section midway between the inlet and outlet border, by means of three piezoelectric transducers plus a strain gage sensor. Theoretical prediction with a simple isoviscous short bearing uncavitated model was shown to be a significant reference for the experimental data. Analysis of the pressure levels and shape of the pressure waves made it possible to recognize operating conditions with the presence of tensile stresses and rupture of the film. The latter conditions were chiefly due to vapour cavitation. Spikes with tensile strength preceded in many circumstances the ruptured region. Air entrainment and its effects proved to be restricted at high frequency regimes with very low supply pressures and coexisted with vapour cavitation. The influence of moderate orbital distortion on pressure signals was highlighted. Significant differences in the pressure behaviour from one sensor location to the other, for the same operating conditions, were frequently observed.