TRANSIENT RESPONSE OF ROTOR SYSTEM UNDER DIFFERENT STARTUP SPEED PROFILES

During startup process of rotating machinery and due to the rotor’s inherent unbalance, transient vibration is introduced as the machinery passes through critical speeds. In the present paper, time domain simulation is performed using ANSYS software to investigate the transient unbalance response of rotor – bearing system. The transient vibration response of the rotor system passing through the critical speeds is analysed under different startup speed profiles. Startup speed profile is represented by exponential formula with single parameter (δ) that indicates whether the startup speed is rapid or slow. The results show that for slow machine startup; the system will remain at the critical speeds for a long period allowing the vibration response to be increased. On the other hand, rapid machine startup passing through the critical speeds will reduce the vibration response. In addition, the numerical simulation results show that applying initial slow startup speed profile followed by instantaneous switch to rapid startup speed profile can reduce the vibration response significantly and more than for applying only rapid startup speed profile.