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Alain Batailly – 1st expert on this subject based on the ideXlab platform
Sensitivity Analysis of Rotor/Stator Interactions Accounting for Wear and Thermal Effects within Low- and High-Pressure Compressor StagesTHE Coatings, 2020Co-Authors: Florence Nyssen, Alain BataillyAbstract:
In the current design of turbomachines, engine performance is improved by reducing the clearances between the rotating components and the stator, which allows for loss decrease. Due to these clearance reductions, contact events may occur between the rotor and the stator. An Abradable Coating is deposited along the stator circumference as a sacrificial material to lower the contact severity. However, experiments highlighted the occurrence of rotor/stator interactions with high wear depth on the Abradable Coating as well as high temperature increases within the Abradable Coating following contacts. This work focuses on the sensitivity analysis of rotor/stator interactions with respect to the rotor angular speed and the initial clearances between the rotor and the stator, taking into account thermal effects within the Abradable Coating. Convergence analyses are first conducted to validate the numerical model. Then, after a calibration of the thermal model of the Abradable Coating based on two experimental test cases, the numerical model is used to investigate the cross effects of the angular speed and the initial clearances on the obtained rotor/stator interactions.
Multi-physics numerical simulation of an experimentally predicted rubbing event in aircraft enginesJournal of Sound and Vibration, 2019Co-Authors: Quentin Agrapart, Florence Nyssen, Déborah Lavazec, Philippe Dufrenoy, Alain BataillyAbstract:
Abstract This paper provides new insight on the simulation of blade-tip/casing rubbing events within aircraft engines accounting for thermomechanical effects within the casing. A multi-physics numerical strategy is presented in order to simulate an interaction experimentally witnessed on a full-scale low-pressure compressor. Experimental data are used for an accurate representation of the blade’s incursion depth within the Abradable Coating. This numerical strategy combines Safran’s in-house tool for rotor/stator interaction simulations with a finite element based thermomechanical analysis carried out with Ansys. This work underlines the distinct contributions of both dynamical and thermomechanical phenomena in the simulated interaction. Competition between wear and thermal expansions is investigated as well as their consequences on blade dynamics. The proposed numerical strategy yields an accurate description of the interaction phenomenon as wear patterns, critical speed, amplitude growth rate of the blade vibration and temperature levels may be predicted.
Strongly Coupled Thermo-Mechanical Casing/Abradable Model for Rotor/Stator InteractionsVolume 7B: Structures and Dynamics, 2019Co-Authors: Florence Nyssen, Thibaut Vadcard, Elsa Piollet, Alain BataillyAbstract:
Modern turbomachine designs feature reduced nominal clearances between rotating bladed-disks and their surrounding casings in order to improve the engine efficiency. Unavoidably, clearance reduction increases the risk of contacts between static and rotating components which may yield hazardous interaction phenomena. In this context, the deposition of an Abradable Coating along the casing inner surface is a common way to enhance operational safety while mitigating interaction phenomena thus allowing for tighter clearances. Nonetheless, interactions leading to unexpected wear removal phenomena between a bladed-disk and a casing with Abradable Coating have been observed experimentally. Beside of blade damages such as cracks resulting from high amplitudes of vibration, experimental observations included very significant temperatures increase, particularly within the Abradable Coating, to a point that thermo-mechanical effects may not be neglected anymore. The aim of this work is to investigate the numerical modeling of thermal effects in the Abradable Coating and the casing due to contact interactions. In particular, the proposed model provides insight on the sensitivity of engines to contact events when the plane had reduced tarmac times between two consecutive flights.
A strongly coupled thermo-mechanical model of the casing and its Abradable Coating is first described. A 3D cylindrical mesh is employed, it may be decomposed in two parts: (1) along the casing contact surface, a cylindrical thermal mesh is constructed to compute the temperature elevation and heat diffusion in the three directions of space within the Abradable Coating, and (2) the casing itself is represented by a simplified cylindrical thermo-mechanical mesh to compute both temperature elevation and the induced deformations following temperature changes. This 3D hybrid mesh is combined with a mechanical mesh of the Abradable layer, dedicated to wear modeling and the computation of normal and tangential contact forces following blade/Abradable Coating impacts. The heat flux resulting from contact events is related to the friction forces and only heat transfer by conduction is considered in this work. In order to reduce computational times, the time integration procedure is twofold: the explicit time integration scheme featuring reduced time steps required for contact treatment is combined with a larger time step time integration scheme used for the casing thermo-mechanical model. An extensive validation procedure is carried out from a numerical standpoint, it underlines the convergence of the model with respect to time and space parameters.
Mathias Legrand – 2nd expert on this subject based on the ideXlab platform
Phenomenological modeling of Abradable wear in turbomachinesMechanical Systems and Signal Processing, 2018Co-Authors: Bérenger Berthoul, Mathias Legrand, Alain Batailly, Laurent Stainier, Patrice CartraudAbstract:
Abradable materials are widely used as Coatings within compressor and turbine stages of modern aircraft engines in order to reduce operating blade-tip/casing clearances and thus maximize energy efficiency. However, rubbing occurrences between blade tips and Coating liners may lead to high blade vibratory levels and endanger their structural integrity through fatigue mechanisms. Accordingly, there is a need for a better comprehension of the physical phenomena at play and for an accurate modeling of the interaction, in order to predict potentially unsafe events. To this end, this work introduces a phenomenological model of the Abradable Coating removal based on phenomena reported in the literature and accounting for key frictional and wear mechanisms including plasticity at junctions, ploughing, micro-rupture and machining. It is implemented within an in-house software solution dedicated to the prediction of full three-dimensional blade/Abradable Coating interactions within an aircraft engine low pressure compressor. Two case studies are considered. The first one compares the results of an experimental Abradable test rig and its simulation. The second one deals with the simulation of interactions in a complete low-pressure compressor. The consistency of the model with experimental observations is underlined, and the impact of material parameter variations on the interaction and wear behavior of the blade is discussed. It is found that even though wear patterns are remarkably robust, results are significantly influenced by Abradable Coating material properties.
Full Three-Dimensional Rotor/Stator Interaction Simulations in Aircraft Engines With Time-Dependent Angular SpeedJournal of Engineering for Gas Turbines and Power-transactions of The Asme, 2016Co-Authors: Alain Batailly, Mathias Legrand, Christophe PierreAbstract:
Modern aircraft engine designs feature reduced clearances that may initiate structural contacts between rotating and static components. A numerical strategy dedicated to the simulation of such interactions is here enriched in order to account for time-dependent angular speeds. This contribution first details the evolution of the numerical strategy before validating the developments by comparing numerical results with experimental observations made on an industrial test bench. Further numerical investigations allow to assess the sensitivity of numerical results to acceleration and deceleration rates. Results, obtained with and without Abradable Coating, underline the fundamental nonlinear nature of the analyzed system. It is found that lower acceleration rates favour the arisal of interaction phenomena and that amplitudes of vibration at a given angular speed are generally lower when the blade decelerates.
Full 3D Rotor/Stator Interaction Simulations in Aircraft Engines With Time-Dependent Angular SpeedVolume 7A: Structures and Dynamics, 2016Co-Authors: Alain Batailly, Mathias Legrand, Christophe PierreAbstract:
Modern aircraft engine designs feature reduced clearances that may initiate structural contacts between rotating and static components. A numerical strategy dedicated to the simulation of such interactions is here enriched in order to account for time-dependent angular speeds. This contribution first details the evolution of the numerical strategy before validating the developments by comparing numerical results with experimental observations made on an industrial test bench. Further numerical investigations allow to assess the sensitivity of numerical results to acceleration and deceleration rates. Results, obtained with and without Abradable Coating, underline the fundamental nonlinear nature of the analysed system. It is found that lower acceleration rates favour the arisal of interaction phenomena and that amplitudes of vibration at a given angular speed are generally lower when the blade decelerates.
Corentin Delebarre – 3rd expert on this subject based on the ideXlab platform
High speed interaction between an Abradable Coating and a labyrinth seal in turbo-engine application, 2020Co-Authors: Corentin Delebarre, Vincent Wagner, Jean-yves Paris, Gilles Dessein, Jean Denape, Julien Gurt-santanachAbstract:
The design of gas turbine aims to enhance the engine efficiency by developing new materials able to work at higher temperatures, or to promote new technologies, fuel management and airflow direction. One solution is the reduction of clearance between rotary parts in turbomachinery air systems. This clearance reduction causes direct interactions in the secondary air system of a turbo-engine when a rotary seal, called labyrinth seal, rubs on the turbo-engine as a result of successive starts and stops, thermal expansions and vibrations. The purpose of the present paper is to study interaction phenomena between an Abradable material (Al-Si 6%) and a nickel alloy (718 alloy) during high speed contacts. A high speed test rig has been designed to simulate interactions between labyrinth seals and Abradable Coatings in similar operating conditions of turbo-engine in terms of geometries, rotational and linear velocities. A series of experiments has been carried out in order to get a first assessment under different turbo-engine operating conditions. Experimental results are presented using visual observations of test samples, quantitative approaches of interacting forces and micrographic observations. This work provides new basic data for a preliminary study of the interaction between a labyrinth seal teeth tips and its casing for turbo-engine applications.
an experimental study of the high speed interaction between a labyrinth seal and an Abradable Coating in a turbo engine applicationWear, 2014Co-Authors: Corentin Delebarre, Vincent Wagner, Jean-yves Paris, Gilles Dessein, Jean Denape, Julien GurtsantanachAbstract:
A new high-speed test rig was designed to simulate the interactions between labyrinth seals and Abradable Coatings in similar turbo-engine operating conditions. To determine a solution for turbo-engine efficiency enhancement, we investigated the clearance reduction between the rotary parts in air systems, the successive starts and stops, the thermal expansion and the vibrations that might cause direct rub interactions between a rotary seal, known as a labyrinth seal, and a turbo-engine housing coated with a sacrificial Abradable material. High interaction speeds from 0 to 130 m s−1 were obtained using a 5-axis milling machine fitted with a unique magnetic bearings spindle developed specifically for the study. The purpose of this paper is to study the interaction phenomena between an Abradable material (Al–Si 6%) and a nickel alloy (Alloy 718) to obtain a first contact assessment under different turbo-engine operating conditions. The experimental results are first presented by visual observations of the posttest samples, as specified by accurate profile measurements. A quantitative approach to the interaction forces recorded during the tests and micrographic observations complete the preliminary study. This work provides new basic data for a preliminary study of the interaction between labyrinth seal teeth tips and Abradable Coatings in turbo-engine applications.