An Experimental Study of Whirling Characteristics of Gear-Pinion Rotor System

Geared rotor system analysis is a very challenging problem because of the complicated dynamic behaviour of composite rotors. For example, the whirling motion and critical speed of the system has to be found by considering all the rotors in the system as well as interactions between them, which makes the solution process as well as proper interpretation of the solution extremely complicated. Complex variable approach, which is proposed for the analysis of a single rotor system, is very powerful for this purpose. The approach is expanded to the analysis of combined rotor system to apply it to the gear system dynamics. A finite-element model of a geared rotor system on flexible shaft bearings has been developed. The model includes the bearing stiffness and shaft flexibility taken in two mutually perpendicular directions and the stiffness of the gear mesh. It is shown that the lateral vibrations have considerable effect when the natural frequencies of the lateral vibration and torsional vibration are close to each other. The whirling response of the system is studied for strong lateral-torsional coupling, thereby; the nature of the coupling effect is discussed.