Influence of Abradable Coating Wear Mechanical Properties on Rotor Stator Interaction

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. Accordingly, direct contact is now commonly accepted as part of aircraft engines everyday life. In order to avoid possibly catastrophic scenarii due to high contact forces 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. In the present work, macroscopic behavior of the abradable coating is numerically approximated through a piecewise linear plastic constitutive law which allows for real time access to the current abradable layer profile. Contact simulations are carried out considering a three-dimensional industrial finite element model of a blade from a compressor stage and its surrounding casing, assumed perfectly rigid. Due to the large number of degrees of freedom, component mode synthesis methods are used. Simulations are repetitively carried-out over a wide rotational velocity range, and a large number of distinct values for two mechanical parameters of the abradable material are considered. Results show that the amplitude of vibration is highly sensitive to the Young modulus and the plastic modulus of the abradable and that a local maximum is detected. Also, a more realistic description of the contact forces allowing for a contribution in the tangential direction is suggested.