Effect of Disc Offset Distance on Transverse and Torsional Vibration of Rotor Shaft

Vibrations play a very important role in rotor systems. In the manufacturing of the rotor system, the imbalance caused by the offset impeller and eccentricity produces unwanted vibrations. Various studies were carried out on unbalanced factors of rotor systems like eccentricity, crack, etc. But the effect of impeller offset due to manufacturing fault is not given much attention. In this study, the change in natural frequencies with respect to disc offset distance was calculated using numerical analysis and experimental analysis for the steel Jeffcott rotor system. Finite element analysis of the offset rotor shaft is carried out in the ANSYS workbench. Experimental modal analysis is carried out using the DAQ system. The accuracy of the model and the solution technique has been observed by comparing experimental results with the numerical simulation results from ANSYS. It is observed that when the disc is shifted from the center, it has a significant effect on transverse and torsional vibrational frequencies. As the disc is shifted towards bearing supports, the stiffness of the system increases, which leads to an increase in vibration frequency.

Keywords: Effect of disc offset, Experimental modal analysis, Jeffcott rotor system.