Master thesis and internship[BR]- Master's thesis : Vibration under rotor-stator contact - Modelling and experiments correlation[BR]- Integration Internship

Abstract

In 2010, Safran developed a French turbofan called Silvercrest which would power super mid-size to large cabin business jets. During the engine tests, some unexpected vibrations occurred on the booster spool in 2014. These vibrations appeared only for some particular tests and their occurrences were not regular. As the source of this problem was unknown, several hypothesis were explored. The most probable cause was identified to be a contact instability due to the friction between the sealing element of the rotor and the abradable material of the stator. In 2015, partial tests on the booster spool were done to confirm the vibration root cause. In order to better understand this phenomenon, a numerical model was created in 2017 with the software Metafor to represent this instability induced by contact. Although, the vibrations could be observed in the numerical simulations, they couldn't be compared to experiments because no partial tests on booster spool were available at that time and because the contact conditions on engine tests are difficult to measure. The goal of this master thesis is to correlate the numerical results with the data from the recent experiments to determine if Metafor can reproduce the same phenomenon. To this aim, the experiments made by Safran Aero Booster are analysed and responses are observed every time a contact interaction appear between rotor and stator. Then, simulations are done with the Metafor model to represent the same phenomenon. The sensitivity of the numerical parameters identifies a strong influence of the damping ratio of the structure and the tangential force due to contact. Finally, these simulations are compared to the experiments and the influence of the rotation speed is highlighted. This work is carried out in collaboration with Safran Aero Booster and the University of Liège that previously developed the numerical model aiming to represent the phenomenon.