Inlet Pressure and Cavitation Boundary Effects on the Orbit Jump Phenomenon in Squeeze Film Damper Operation

The theoretical analysis of squeeze film dampers requires a knowledge of the pressure distribution in the oil film, integrated to predict the fluid film forces. For film pressures below atmospheric, even though the more accurate 0-film model (wherein pressures below absolute zero are assumed to be at absolute zero) is utilized in preference to the more commonly used π-film model, the bi-stable or jump behaviour of circular orbit type dampers is incorrectly predicted. This investigation shows that the jump behaviour is not only dependent on the bearing parameter and unbalance but is also extremely sensitive to the inlet pressure to the damper and, indeed, to the exact determination of the cavitation boundary. Experimental results showed poor agreement with theoretical predictions, with jump obtained in theoretically jump-free regions. This discrepancy is probably due to uncertainties in the inlet pressure, the bearing parameter and particularly the precise location of the cavitation boundary. Qualitatively, however, it is confirmed experimentally that the higher the inlet pressure, the less likely that ‘jump’ will occur.