Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Optimization of Band Gap Formation in Periodic Rotors
Submission Author:
Rodrigo Nicoletti , SP , Brazil
Co-Authors:
Patrick Bueno Lamas, Rodrigo Nicoletti
Presenter: Patrick Bueno Lamas
doi://10.26678/ABCM.COBEM2021.COB2021-0069
Abstract
Rotating machines with components periodically mounted along the shaft present band gaps in their frequency spectrum. That means, the natural frequencies of the rotor tend to group together, leaving some modal spacing in regions of the frequency spectrum. Such modal spacing is characterized by a large bandwidth where the structure presents no natural frequencies and a low frequency response. The bandwidth and the region where these band gaps appear depend on the geometry and on the inertia distribution of the periodic rotor. In the present work, we show that it is possible to shift the band gap towards higher or lower frequency regions of the spectrum of a given periodic rotor by optimizing the position of the rotor elements. The rotor is modeled by finite elements and the position of the impellers on the rotor is optimized by a hybrid procedure: genetic algorithm + direct search (Sequential Quadratic Program - SQP). The genetic algorithm is used to reduce the solution domain, whereas the SQP is used to find the optimum solution within this reduced domain. The results show that it is possible to move the band gap without significantly affecting its bandwidth. In addition, it is easier to move the band gap towards higher frequencies (up to 20% above the original central frequency of the band gap) than towards lower frequencies (down to 7% below the original central frequency of the band gap). The optimization of the band gap region represents an interesting tool in the design of rotating machines.
Keywords
Rotordynamics, metamaterial, mechanical vibrations, natural frequency, Finite Element Method
