Rotor–Stator Contact in a Hydropower Machine with Squeeze-Film Damper

Rotating machines may encounter rubbing due to contact between stationary and rotating structures, leading to large mechanical vibrations that can cause catastrophic failure. In hydropower machines, rubbing contact could occur for many reasons, such as mass imbalance or mechanical/electrical misalignments. This paper investigates whether squeeze film dampers can improve the contact dynamics of a 45 MW hydropower unit. The squeeze film dampers were installed in series with the upper and lower generator guide bearings, and the reaction forces were predicted based on short bearing approximation. A finite element model was established, and the equation of motion of the rotor–stator system was solved numerically using a MATLAB inbuilt function (ode23tb), taking the rotor speed, the retainer spring stiffness, and damper clearance as control parameters. The simulation results are presented using a bifurcation diagram, Poincaré map, orbit, frequency spectrum and maximum contact force. The results indicated that squeeze film dampers improved the damping characteristics of the hydropower machine and reduced the vibration amplitudes. Consequently, it curtailed the risk of rubbing contact at a critical speed for larger range of load cases, ensuring safe operations. Besides, retainer spring stiffness and damper clearance play an important role in the contact dynamics of the hydropower machine with squeeze film damper.