Dynamic analysis of rotors under interference rubs

Theories and applications are developed for complex multi-level flexible rotor/bearing systems based on the finite element method. The complex system of equations is simplified by the static condensation method to reduce the number of degrees-of-freedom without losing much of the accuracy. An efficient subspace iteration technique for damped eigenvalue problem is applied to the damped natural frequency analysis of rotor systems. The method has been modified and extended to take advantage of the nature of the sparse matrix in a typical problem so that both the computer memory requirement and computation times can be reduced.
Interference rub phenomenon between rotor and stator are studied using both linear and non-linear models. In a steady state linear model, the rub force is decomposed into harmonies using Fourier transformation. The overall response of the rotor is the summation of the individual rotor response at each of the harmonies. Non-linear models are also developed and the equations of motion are solved in the time domain to assess the overall response and stability of the system. Two example cases are presented to demonstrate the applications of the analysis. A computer program is developed based on the non-linear models presented.