Whole Engine Interaction in a Bladed Rotor-to-Stator Contact

Abstract

Reducing the clearances between rotating and fixed parts is an important factor in increasing the performances of turbomachines. The physical counterpart however is an evolution in possible rotor-stator contacts capable of causing unstable dynamic behavior. A proper prediction of the rotor-stator contact occurrences and associated induced phenomena, has therefore become of a great interest for aero-engine mechanical engineers. Most numerical simulations involving rotor-stator contact can be divided into two types of physical behavior. The first focuses on contact induced blade/casing interactions, in only taking into account the blades and casing flexibility. The second type of behavior takes into account the shaft dynamic while neglecting blade flexibility. Future designs of aircraft engines will however raise the need to combine these two types of models. Since, the structural components are more flexible, the dynamic coupling between engine modules is increased. This paper proposes a study based on a structure representative of the whole aircraft engine, including the contacts that may arise between the fan-blade tips and fan casing. We have introduced a fully-coupled phenomenological model with flexible blades, shaft and casing. Furthermore, this model includes an elastic link between shaft and casing to simulate the fan frame behavior. We begin by explaining the linear results, which highlight the dynamic couplings between these various model components. During a second step, this paper presents the nonlinear results obtained by introducing a contact law. These results demonstrate the influence of the whole engine dynamic on contact-related behavior with special focus on the system dynamic stability.