Comportement dynamique non linéaire d'un arbre vertical de turbopompe monté dans des paliers lubrifiés à l'eau

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The dynamic behavior prediction of vertical canned motor pump shaft is very important for industrial applications. The performances and reliability of these components depend on a large part of the dynamic behavior. The present study characterizes the behavior of a vertical shaft mounted on two water lubricated journal bearings under radial magnetic and impeller load. Trajectories in the bearings are very unstable and the modelisation is presented and the obtained results on a vertical shaft are commented. The rotor calculation is a step by step non linear computation with at each step the resolution of the pressure field in journal bearings. These pressure fields are obtained by resolution (finite differences) of the differential Reynolds Equation. The shaft is taken rigid with 4 degrees of freedom. This study confirms the high level of unstability of a vertical shaft mounted in journal bearings. The main reason of that unstability is the pressure feed (0.45 MPa and 0.8 MPa), in association with magnetic attraction and with a low radial load.