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.

Experimental and numerical simulation of a rotor/stator interaction event localized on a single blade within an industrial high-pressure compressor

“…As a counterpart, structural contacts between these components may occur more frequently and must now be accounted for as part of nor-mal engine running conditions in non-accidental configurations. Subsequent vibratory phenomena may involve a single blade-it is then usually referred to as rubbing [1][2][3]-a full bladed disk and the surrounding casing-with possible modal coincidence yielding very high amplitudes of vibration [4,5]or precessional shaft motions such as backward or forward whirl motions [6][7][8][9]. A usual strategy employed by engine manufacturers in order to mitigate such vibratory phenomena involves the deposition of an abradable coating along the casing contact surface [10,11].…”

Blade/casing rubbing interactions in aircraft engines: Numerical benchmark and design guidelines based on NASA rotor 37

“…However, reduced tip clearances lead to increased risks of contact between the blades and the casing. Contact events can lead to potentially destructive interactions [3]: single blade vibration (rubbing) [4,5,6], full bladed disk and casing vibration with modal interaction [7,8] or whole engine interactions featuring shaft orbital motion [9,10,11,12].…”

“…As contact interactions are multi-physical, multi-scale and nonlinear, involving vibrations, wear, and thermal effects among others [16], commercial software packages are generally not applicable: as a consequence, ad hoc numerical strategies are developed by most of the engine manufacturers in house or in partnership with academic research laboratories (e.g. Rolls Royce [17,18,19], GE Aviation [5,10,14] and Safran [12,20]).…”

Continuation techniques for analysis of whole aeroengine dynamics with imperfect bifurcations and isolated solutions

“…His approach was also used by Lesaffre [5] and extended to a dual shaft by Gruin [6]. Parent [7] used the same model to analyse the divergence and flutter of a whole engine model with interaction in a bladed rotor-tostator contact. Choy and Padovan [8,9] studied the transient response of the bladed rotor interaction with a flexible casing.…”