Interaction of Squeeze Film Dampers and Hole Feed Systems and Its Influence on the Dynamics of a Jeffcott Rotor

Abstract

The oil feeding of a squeeze film damper through holes can be an interesting solution to improve the damper's energy dissipation capability since it increases the journal's effective squeezing surface. While groove feeding has been extensively studied, only a few works have addressed the problem of hole fed dampers. The squeeze film damper model may be able to estimate the pressure at the feed holes as well as the flow into the film. A fundamental issue in the modeling of the hole feed system is the choice of the adequate boundary conditions. Existing published models consider the supply pressure to be constant at a specific section of the hydraulic system. The pressures at the oil injection holes are then obtained via local flow balances taking into account a linear flow resistance across the feed conduits. The model developed in the present work is based on the application of the simplified form of the energy equation commonly used in hydraulics, with approximate pressure drop coefficients. As a boundary condition we impose the power supplied to the pump. The nonlinear hydraulics problem is coupled with the squeeze flow and the Newton-Raphson method is employed to solve the set of nonlinear equations. The influence of the hole feed system on the unbalance response and stability of a Jeffcott rotor is analyzed in regards to the number of feed holes and the power supplied to the pump. The feed system behavior is also studied. A significant number of theoretical and experimental works have been published since the 1960s as the interest in the application of this kind of damper grew strong. As far as the oil film pressure distribution is concerned, the majority of the studies have focused on cavitation modeling, fluid inertia effects, non-Newtonian fluid behavior, and operation with bubbly oil. Despite the consensus about the importance of the damper's boundary conditions, namely the feed system and the leakage conditions, a relatively limited number of works addressed these issues. Regarding the feed system, circumferential groove-fed dampers have already been extensively examined by San Andres (1992) and Arauz and San Andres (1994), who evidenced the influence of the interaction between land and groove flows on the SFD performance. However, for hole fed dampers, a configuration which can turn out to be an interesting way to improve damping capability (Wang and Hahn, 1995), only a few models have been proposed.The hole feed system affects the damper performance in a direct way, in view of the pressure build up resulting from the interaction between the film land flow and the injection holes. An indirect influence can also show up whenever the feeding capability is not high enough to prevent air entrainment into the film, which leads to operation with a bubbly oil (Diaz and San Andres, 2001). Hence, the hole feed system model must be able to provide good estimates of the pressure at the oil injection holes as well as of the flow into the film. Marmol and Vance (1978) proposed a finite difference discretization of ...

Stability Analysis of a Flexible Bladed-Rotor

“…Hence it is desirable to reduce the clearance by as much as possible. It cannot be reduced below a certain minimum level due to uncertainties in the dynamics, fluid dynamics [3,4], thermal loads [5], the machining tolerances and material properties [6,7]. The more accurately these parameters are known, the smaller the clearance that can be made.…”