Numerical Investigation of Abradable Coating Wear Through Plastic Constitutive Law: Application to Aircraft Engines

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 casings. Together with new technologies involving higher casing conicity for improved compression rates, direct contact is now considered as part of aircraft engines normal life. In order to avoid possibly catastrophic scenarios due to high contact efforts between the rotating and static components, implementation of abradable coatings has been widely recognized as a robust solution offering several advantages: reducing potential damage to the incurring blade as well as adjusting operating clearances, in-situ, to accept physical contact events. Nevertheless, the process of wear undergone by abradable coatings is not well understood and its consequences are still under investigation. In the present work, its macroscopic behavior is numerically approximated through a piecewise linear plastic constitutive law which allows for real time access to the current abradable layer profile. First results prove convergence in time and space of the proposed approach and show that the frequency content of the blade response is clearly affected by the presence of abradable coatings. It seems that opening the clearance between the blade tip and the casing during wear leads to large amplitudes of motion far from the usual linear conditions provided by the well-known Campbell diagrams.

Influence of Abradable Coating Wear Mechanical Properties on Rotor Stator Interaction

“…As described in [5], the proposed numerical tool embeds in an explicit time marching technique, a contact detection procedure together with the calculation of internal forces and plastic deformations arising in the abradable material, thus controlling the desired amount of wear. It allows for real time access to the current profile of the abradable, supposedly key feature for detecting such critical behaviors mentioned above.…”

“…Furthermore, the energy transferred from the blade to the casing during contact interaction is partially dissipated because of wear: this can be captured by a plastic constitutive law. Based on [5] 2 , the plastic constitutive law is enriched in order to allow for a more realistic description of contact forces on the blade tip.…”

Assessment of Two Harmonic Balance Method-Based Numerical Strategies for Blade-Tip/Casing Interactions: Application to NASA Rotor 67

“…The same harmonic decomposition is used to express the nonlinear forces f nl (x(t), ẋ(t), ω). Fourier coefficients are gathered in the so called multiharmonic vectors of dimension n(2N h + 1), as written in (5).…”

“…However, this design choice yields new challenges for designers particularly because phenomena that were once considered as purely accidental now occur within nominal operating conditions. Among these critical phenomena, blade-tip/casing structural contacts are of particular interest [1,2,3,4,5,6,7,8,9,10]. Since these situations are now expected in non-accidental configurations during the lifetime of engines, they must be accounted for in the design phase.…”

Phenomenological modeling of abradable wear in turbomachines

“…A Finite Element micro model of the bulk material without contact was proposed in [8]. Finally, two abradable coating models in the context of full three-dimensional simulations were suggested with a focus on the numerical efficiency rather than on the physical relevance of wear phenomena [12,29].…”