Numerical Investigation of Abradable Coating Removal in Aircraft Engines Through Plastic Constitutive Law

Abstract

In the field of turbomachines, better engine performances are achieved by reducing possible parasitic leakage flows through the closure of the clearance distance between blade tips and surrounding stationary casings and direct structural contact is now considered as part of the normal life of aircraft engines. In order to avoid catastrophic scenarios due to direct tip incursions into a bare metal housing, implementation of abradable coatings has been widely recognized as a robust solution offering several advantages: reducing potential nonrepairable damage to the incurring blade as well as adjusting operating clearances, in situ, to accept physical contact events. Nevertheless, the knowledge on the process of material removal affecting abradable coatings is very limited and it seems urgent to develop dedicated predicting numerical tools. The present work introduces a macroscopic model of the material removal through a piecewise linear plastic constitutive law which allows for real time access to the current abradable liner profile within a time-stepping approach of the explicit family. In order to reduce computational loads, the original finite element formulation of the blade of interest is projected onto a reduced-order basis embedding centrifugal stiffening. First results prove convergence in time and space and show that the frequency content of the blade response is clearly sensitive to the presence of abradable material. The continuous opening of the clearance between the blade tip and the casing due to the material removal yields larger amplitudes of motion and new scenarios of structural divergence far from the usual linear conditions provided by the well-known Campbell diagrams.

Numerical Study of a Rotor/Stator Interaction Case Experimentally Simulated With an Industrial Compressor

“…It was shown that a bilinear plastic law could accurately represent the mechanical behavior of abradable material. Consistently, recent numerical developments focused on the modeling of abradable coating through mono-dimensional plastic elements [10] in the context of full 3D blade-tip/abradable coating simulation. Recent applications of this strategy [11] proved promising results in good agreement with the experimental data.…”

“…Most of those developments are only briefly recalled and more information may be found in [10] regarding abradable coating modeling, reduced order model taking into account centrifugal effects as well as the contact algorithm.…”

“…The numerical strategy proposed in [10] is summarized and the comparison with the existing analysis is presented. Finally, sensitivity of the interaction phenomenon and possible related divergence to new blade designs is explored.…”

Towards Full 3D Numerical Simulation of Whirl Motions Stemming From Unilateral Contact Constraints in Aircraft Engines

“…These interaction phenomena are intrisically non-linear and indeed require dedicated computational tools to overcome the current limitations of commercial softwares such as: (1) the absence of efficient strategies for the modeling of abradable coating removal [2] or, (2) the impossibility to build physically relevant reduced-order models (ROM) of rotating structures subjected to contacts [3]. The physical relevance of rotor reduced-order models is intimately related to the modeling of both centrifugal and gyroscopic effects.…”

Rotor-Stator Interaction Scenarios for the Centrifugal Compressor of a Helicopter Engine

“…It is thus of great interest to assess the severity of this phenomenon for other types of compressor such as centrifugal compressors, also named impellers. Several references, both dealing with numerical simulations [3,4,2] and experimental set-ups [5,6,7], may be found on interaction phenomena or rubbing and abradable sealing properties in fan or axial compressors. However, the exploration of interaction phenomena for centrifugal compressors is not yet documented.…”