Response Analysis of a Linear Rotor-Bearing System Under Combined Non-stationary Seismic and Harmonic Excitations

摘要

An effective analysis method for response of a linear unbalance rotor-bearing system subjected to random seismic excitation was presented, which based on the pseudo excitation method and the Runge-Kutta numerical integration scheme. Under Kanai-Tajimi seismic model, displacement response and time-dependent variance of displacement response of an unbalance rotor system under the random seismic excitation or combined random seismic and harmonic excitations were analysed in a rotor-journal bearings system with four degrees of freedom. Influence of rotational speed on the time-dependent variance of displacement response and influence of sampling frequency on the time-dependent displacement response variance curve were discussed, respectively. The time-dependent variance of the displacement response is more than that of the angular displacement response. And the displacement response variance is larger in the direction where the rotor's stiffness is smaller. Rotor's imbalance has obvious influence on the time-dependent variance of the displacement response when the rotational speed is close to the critical rotational speed region of the rotor system. Therefore, the rotor imbalance cannot be disregarded in high speed rotating machines.