Condition monitoring of a rotor bearing system.

Abstract

The key objective for this research was to construct an experimental test rig along with a finite element model. Both had to accommodate a certain extent of misalignment and unbalance to provide induced vibrations in the system. Misalignment and unbalance was then varied in magnitude to identify the effect it has on the system. The next variable was the rotor speed and its effects. Finally the experimental and theoretical results were compared and the slight differences have been outlined and described. A rotor supported by two bearings with a disk attached to the middle and a three jaw coupling at the one end was considered for this research. The three jaw coupling consists out of two hub elements with concave jaws and a rubber element that fits in-between the jaws. The rotor-bearing system was subjected to unbalance at the disk and both angular and parallel misalignment at the coupling. Misalignment was achieved by offsetting the centre of rotation of the rotor and the motor shaft. Finite element analysis, along with Lagrange method, was used to model the behaviour of the system. A mathematical model for the three jaw coupling was derived to simulate its behaviour. The second order Lagrange model was reduced to a first order and solved using the Runge-Kutta method. Experimental results were obtained from a test rig and used to validate the theoretical results. Time domain and frequency spectrum were used to display the results.