Summary
Chaotic dynamics occur in rotating shafts mounted on sliding bearings under specific design and operating conditions. Despite the fact that chaos does not definitely prevent the operation of rotating machines, it may result to higher frictional power loss and temperature rise in bearings, compared to the case when periodic or quasi-periodic motions evolve in the operation; it is also likely to compromise the integrity of the system when whirling orbits evolve in a large extent. A rotor-bearing system consisting of a rigid rotor mounted on two journal bearings is used in this work to produce chaotic dynamics. The chaotic operation regimes of the system are first detected estimating Lyapunov exponents, 0-1 test for chaos, and Poincare maps. Sliding bearings of active geometry are included in the physical model to enable the Ott-Grebogi-Yorke (OGY) control method as a reference solution to convert chaotic oscillations to periodic. The benefits from controlling chaos in the rotating system are investigated for a set of designs, considering frictional power loss, together with further aspects of integrity and operability of the system. It is found that the OGY method is able to control the chaotic response to periodic with low control effort, and creates potential for smooth periodic motions in high-speed systems like automotive turbochargers and turbopumps.
