DYNAMIC ANALYSIS OF SQUEEZE FILM DAMPER SUPPORTED ROTORS USING EQUIVALENT LINEARIZATION

The technique of equivalent linearization is presented in this paper a s a powerful technique to perform nonlinear dynamic analysis of squeez e film damper (SFD) supported rotors using linear rotor-dynamic method s. Historically, it is customary to design SFDs for rotor-dynamic anal ysis by assuming circular-centered orbits, which is convenient in maki ng the nonlinear damper coefficients time independent and thus can be used in an iterative approach to determine the rotor-dynamic character istics. However, the general synchronous orbit is elliptic in nature d ue to possible asymmetry in the rotor support. This renders the nonlin ear damper coefficients time dependent, which would require extensive numerical computation using numerical integration to determine the rot or dynamic characteristics. Alternatively, it is shown that the equiva lent linearization, which is based on a least-squares approach, can be used to obtain time-independent damper coefficients for SFDs executin g eccentric elliptic orbits, which are nonlinear in the orbit paramete rs. The resulting equivalent linear forces are then used in an iterati ve procedure to obtain the unbalance response of a rigid rotor-SFD sys tem. Huge savings over numerical integration are reported for this sim ple rotor. The technique can be extended to be used in conjunction wit h currently available linear rotor-dynamic programs to determine the r otor-dynamic characteristics through iteration. It is expected that fo r multirotor multibearing systems this technique will result in even m ore economical computation.