Towards a simplified three-dimensional model for the prediction of plain bearings wear in the Variable Stator Vane system
Creators: name:  M. HARNAFI 
name:   C. PALECZNY 
name:   P. GUIDAULT 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: STRUCTURES
MATERIALS
MODELLING
TESTING
VALIDATION

description: The wear prediction of the aircraft engine parts is fundamental in the purpose of its service life extension. This work addresses in particular the Variable Stator Vanes system plain bearings which ensure the rotational guiding of the vanes axes. These simple mechanical components are integrated in a complex system and are exposed to high thermomechanical stresses. Their excessive damage can lead to several technical incidents from a decrease of the aircraft engine compressor performance to the compressor surge due to an alteration of the stator vane adjustment in extreme cases [1]. Their replacement requires a disassembly of the high-pressure engine compressor which generates high maintenance costs. Thus, it is necessary to predict precisely the Variable Stator Vanes plain bearings wear with computational models. Several computational approaches were previously developed: simplified two-dimensional [2] and three dimensionnal [3] analytical models for contact pressure and wear estimation applied to conformal contact as well as two-dimensional [4] and three-dimensional [5] finite element models which compute the contact pressure and wear depth. The former class of models gives good results in a fairly efficient way regarding the wear prediction compared with experimental results. However, it still requires a systematic recalibration to predict the wear in an engine-like environment. The latter, although more accurate, does not allow the simulation of thousands of cycles at the VSV system scale [6] due to its high computational cost. The aim of this work is to develop a reliable and effective computational model that predicts the wear seen by the Variable Stator Vanes system plain bearings in an engine-like environment. The proposed model considers rigid non-deformable solids with an elastic behavior in the contact zones that leads to the resolution of a highly non-linear kinematic problem applied to a multi-body system under variable and combined loads. This problem is addressed in three dimensions for one bearing. A global-local formulation of the problem is presented and solved by a classical Newton-Raphson algorithm. As the convergence of the algorithm is strongly influenced by the initial configuration of the system, the analytical expression of the initial configuration as a function of the clearance and the components relative positions have been established. The problem takes into account a large number of parameters in which it depends as the temperature, the clearances, the axial and radial loads, the internal pressure as well as the precise geometries. Finally, the validation is carried out by confronting the proposed model with a dimensioning tool developed by Safran Aircraft Engines. This software is based on a two-dimensional analytical formulation of the problem. An extension of the model for multiple bearings will then be proposed. The longer-term objective is to identify test cases over complete flight cycles in order to be able to carry out a full wear calculation to estimate the service life of the Variable Stator Vanes system plain bearings. References [1] ATSB. Powerplant/propulsion event Launceston aerodrome 20 August 2009. Transport Safety Report, Australian Transport Safety Bureau, Australia, 2010. [2] Aibin Zhu, Shengli He, Jianwei Zhao, and Wencheng Luo. A nonlinear contact pressure distribution model for wear calculation of planar revolute joint with clearance. Nonlinear Dynamics, 88(1):315328, April 2017. [3] Shuai Cheng, Xianghui Meng, Rui Li, Ruichao Liu, and Rui Zhang. A rough surface damping contact model and its application in spatial variable stator vane mechanism with dry friction joint. preprint, In Review, March 2021. [4] Saad Mukras, Nam H. Kim, Nathan A. Mauntler, Tony Schmitz, and W. Gregory Sawyer. Comparison Between Elastic Foundation and Contact Force Models in Wear Analysis of Planar Multibody System. Journal of Tribology, 132(3):031604, July 2010. [5] Adrian A. Schmidt, Timo Schmidt, Oliver Grabherr, and Dirk Bartel. Transient wear simulation based on three-dimensional finite element analysis for a dry running tilted shaft-bushing bearing. Wear, 408-409:171179, August 2018. [6] Christian Paleczny, Anna Selvi, and Eros Gabellini. 3D Kinematics Study with SAMCEF MECANO Motion on a nozzle of a turbojet engine - Pre and post- processing in SAMCEF Field. page 9, France, 2003.