scholarly journals Abradable Coating Removal in Turbomachines: A Macroscopic Approach Accounting for Several Wear Mechanisms

2015 ◽  
Author(s):  
Bérenger Berthoul ◽  
Alain Batailly ◽  
Mathias Legrand ◽  
Laurent Stainier ◽  
Patrice Cartraud
Keyword(s):  
Wear Mechanisms ◽  
Structural Integrity ◽  
Aircraft Engine ◽  
Contact Forces ◽  
Macroscopic Model ◽  
3D Interaction ◽  
Abradable Coating ◽  
Blade Tip ◽  
Coating Removal ◽  
Physical Phenomena

Abradable materials are widely used as a coating within compressor and turbine stages of modern aircraft engines in order to reduce operating blade-tip/casing clearances and thus maximize the engine energy efficiency. However, recent investigations revealed that the interaction between a blade and these materials may threaten blades structural integrity. Consequently, there is a need for a better understanding of the physical phenomena at play and for an accurate modelling of the interaction in order to predict hazardous events. The cornerstone of related numerical investigations lies in the modelling of the abradable coating removal due to the blade/abradable coating interaction and the associated contact forces along the contact interface. In this context, this article presents a macroscopic model for abradable coating removal accounting for key wear mechanisms including adhesive wear, abrasive wear, micro-rupture wear and machining wear. It is coupled with an in-house numerical strategy for the modelling of full 3D blade/abradable coating interactions within turbomachines and applied to an aircraft engine. Numerical results are compared with respect to existing models and available experimental data. The applicability of the proposed model for 3D interaction simulations is underlined as well as the consistency of the obtained results with experimental observations.

scholarly journals Two-Dimensional Modeling of Shaft Precessional Motions Induced by Blade/Casing Unilateral Contact in Aircraft Engines

2014 ◽  
Author(s):  
Nicolas Salvat ◽  
Alain Batailly ◽  
Mathias Legrand
Keyword(s):  
Structural Integrity ◽  
Rotational Velocity ◽  
Equations Of Motion ◽  
Aircraft Engine ◽  
Operating Conditions ◽  
Contact Forces ◽  
Curved Beams ◽  
Bladed Disk ◽  
Blade Tip ◽  
Time Marching

In the present work, the focus is made on the occurrence of precessional motions of the shaft — whirling motions — in bladed-disk assemblies, initiated by direct blade/casing contacts in one stage of an aircraft engine. These contact events are favored by increasingly reduced blade-tip clearances and are expected to occur during standard operating conditions. However, it has been shown that potentially harmful interactions may arise and threaten the engine structural integrity. A 2D in-plane model of an aircraft engine fan stage is built with a set of curved beams for the casing and an assembly straight beams for the bladed-disk. The flexibility of the shaft is reflected by two linear springs attached to the center node of the disk. Contact is initiated through a prescribed casing distortion and the two structures are then left free to interact. Equations of motion are solved via explicit time-marching and contact forces are computed with Lagrange multipliers method allowing to fully satisfy non-penetration conditions. Friction is accounted for through a Coulomb law and permanent sliding is assumed. Three types of regimes are identified, namely: (1) damped, (2) sustained, (3) divergent, and both forward and backward shaft precessional motions are witnessed. It is shown that the vibratory response of the bladed-disk mainly lies on the first nodal diameter of the first family of modes regardless of the rotational velocity or the type of regime detected. The risk of failure arising from these contact events is highlighted, in particular in the presence of forward whirl, and the need for accurate predictive tools in early design phases of the engine is emphasized.

scholarly journals Snecma’s Viewpoint on the Numerical and Experimental Simulation of Blade-Tip/Casing Unilateral Contacts

2015 ◽  
Author(s):  
Antoine Millecamps ◽  
Alain Batailly ◽  
Mathias Legrand ◽  
François Garcin
Keyword(s):  
Material Removal ◽  
Aircraft Engine ◽  
3D Models ◽  
Operating Conditions ◽  
Experimental Simulation ◽  
Critical Parameters ◽  
Design Stage ◽  
Experimental Investigations ◽  
Abradable Coating ◽  
Blade Tip

Aircraft engine manufacturers are developping a new generation of turbojet engines featuring a lower impact on the environment, increased performances as well as reduced gas consumption. The efficiency of an engine is mostly driven by the operating clearance between the rotating parts and the stator. Accordingly, modern designs focus on the minimization of these clearances. In this context, unavoidable rotor imbalances or mistuning stemming from manufacturing processes as well as distortions resulting from thermal expansion or assembly conditions may generate blade-tip/casing contacts that are now considered as non-accidental operating conditions. In order to minimize the consequences of such events, an abradable coating is sprayed along the inner surface of the casing and acts as a fuse when the blade and the casing are in contact. However, even when an abradable coating is used, significant structural damages and wear as well as blade failures have been witnessed experimentally. The understanding of the physical phenomena at play called, on one hand, for throrough experimental investigations of rotor/stator contacts on full-scale stages of compressors and underlined that blade failure is mainly due to vibratory fatigue although the abradable coating is worn. On the other hand, numerical simulations have been performed to better understand the blade dynamics: over the last decade Snecma and its academic partners jointly developed a code for the simulation of contacts between rotor and stator: COROS. This code allows for the simulation of contacts — with a Lagrange multiplier contact treatment procedure — between full 3D models of engine components and accounts for abradable coating material removal. In particular, the simulation of experimental set-ups with COROS highlighted the correlation between the blade vibratory response and the abradable material removal. Yet still an experimental code, this paper addresses the integration of COROS within the design process of aircraft engine blades at Snecma. The paper focuses on on-going research for the identification of critical parameters in the arising of interactions as early as the design stage of components. A particular attention is paid to the mechanical properties of the abradable coating for which both experimental and numerical investigations are detailed.

Implementation of a Rig Test for Rotor/Stator Interaction of Low-Pressure Compressor Blades and Comparison of Experimental Results With Numerical Model

2020 ◽  
Author(s):  
Laura Pacyna ◽  
Alexandre Bertret ◽  
Alain Derclaye ◽  
Luc Papeleux ◽  
Jean-Philippe Ponthot
Keyword(s):  
Low Cost ◽  
Low Pressure ◽  
Angular Speed ◽  
Compressor Blades ◽  
Abradable Coating ◽  
Rotor Stator Interaction ◽  
Blade Tip ◽  
Numerical Tool ◽  
Short Time ◽  
Pressure Compressor

Abstract To investigate the contact phenomenon between the blade tip and the abradable coated casing, a rig test was designed and built. This rig test fills the following constraints: simplification of the low-pressure compressor environment but realistic mechanical conditions, ability to test several designs in short time, at low cost and repeatability. The rig test gives the opportunity to investigate the behavior of different blade designs regarding the sought phenomenon, to refine and mature the phenomenon comprehension and to get data for the numerical tool validation. The numerical tool considers a 3D finite elements model of low-pressure compressor blades with a surrounding rigid casing combined with a specialized model to take into account the effects of the wear of the abradable coating on the blade dynamics. Numerical results are in good agreement with tests in terms of: critical angular speed, blade dynamics and wear pattern on the abradable coated casing.

scholarly journals Conjectural Bifurcation Analysis of an Aircraft Engine Blade Undergoing 3D Unilateral Contact Constraints

2014 ◽  
Author(s):  
Alain Batailly ◽  
Mathias Legrand
Keyword(s):  
Spline Interpolation ◽  
Sudden Change ◽  
Aircraft Engine ◽  
Rotational Frequency ◽  
Compressor Blade ◽  
Structural Behaviour ◽  
Mode Decomposition ◽  
Abradable Coating ◽  
Set Up ◽  
Pressure Compressor

Prediction of rotor/stator interaction phenomena between a blade-tip and the surrounding abradable coating deposited on the casing has seen recent promising numerical developments that revealed consistency with several experimental set-up. In particular, the location of critical rotational frequencies, damaged blade areas as well as the wear pattern along the casing circumference were accurately predicted for an interaction scenario involving a low-pressure compressor blade and the surrounding abradable coating deposited on a perfectly rigid casing. The structural behaviour of the blade in the vicinity of a critical rotational frequency however remains unclear as brutal amplitude variations observed experimentally could not be numerically captured without assuming contact loss or an improbable drastic and sudden change of the abradable coating mechanical properties during the interaction. In this paper, attention is paid to the structural behaviour of a high-pressure compressor blade at the neighbourhood of a critical rotational frequency. The interaction scenarios for two close rotational frequencies: Ωc and Ωc* are analyzed using empirical mode decomposition based on an adjusted B-spline interpolation of the time responses. The obtained results are compared to the interaction scenario dictated by the abradable coating removal history and the location of contact areas. The unstable nature of the blade vibratory response when the rotational frequency exceeds a critical rotational frequency is underlined and a plausible scenario arises for explaining a sudden and significant decrease of the blade amplitude of vibration without contact separation.

scholarly journals Computational analysis of micro wind turbine with bamboo blades for domestic applications

2021 ◽  
Vol 70 (9&10) ◽  
pp. 150
Author(s):  
J. Suraj Sayed ◽  
P. V. Sreeram ◽  
R. Ramesh Kumar
Keyword(s):  
Wind Turbine ◽  
Pressure Distribution ◽  
Wind Velocity ◽  
Structural Integrity ◽  
Average Value ◽  
Average Wind ◽  
Blade System ◽  
Blade Tip ◽  
Average Wind Velocity ◽  
Domestic Purpose

A domestic purpose micro wind turbine realised using bamboo blade is tested for the power generation at an interval of two years and compared the performance. A CFD analysis of turbine with five blade system is carried out for an average wind velocity of 2.5m/s and structural integrity of the bamboo blade unit based on the pressure distribution is assessed. For the input wind velocity, a stream lined out flow of 5.9 m/s is found when wind turbine rotates at 300 rpm and corresponding pressure distribution is found to be maximum at the expected location of blade tip as129 Pa. The static analysis shows a good margin. For 2.5 m/s, a wind turbine generates an average value of 3.8V with 0.25A (based on 15 <span>Ω</span>/10W load). The wind turbine has produced nearly the same power even after a period of two years.

Investigation of Fan Blades Vibration due to Blade/Casing Rubbing Interactions Using In-Plane Two-Dimensional Model

2018 ◽  
Author(s):  
Jiaguangyi Xiao ◽  
Yong Chen ◽  
Hua Ouyang ◽  
Anjenq Wang
Keyword(s):  
Travelling Waves ◽  
Golden Section ◽  
Contact Forces ◽  
Two Dimensional ◽  
Rotating Speed ◽  
Bladed Disk ◽  
Speed Range ◽  
Blade Vibrations ◽  
Blade Tip ◽  
External Forces

Interactions between casings and bladed-disks of modern turbofan engines may occur through various mechanisms: casing distortions, rotor vibrations and casing vibrations to name a few. These interactions might lead to nonlinear blade vibrations, which could then induce severe damages to both structures. The impacts of casing vibrations on the vibration behaviors of engine blades are studied in this paper. A two-dimensional in-plane model is established in this paper. Fan blade, disk and casing are modeled using beam element. Craig-Bampton model reduction is applied to simplify the model. Penalty method mixed with golden section method is created and used for contact treatments. The interaction is initiated by the external forces acting on the casing. The casing is excited to two-, three- and four-nodal diameter vibration patterns, respectively. In order to capture the core of the problem, contact forces applied to the casing, and casing damping are neglected. Steady casing vibrations could thus be generated. Blade vibrations are calculated in a wide rotating speed range, maximum amplitudes are recorded and studied. The results show that the bladed-disk will have several vibration peaks in the calculated rotating speed range. To figure out the physical mechanisms of these peaks, Fourier spectrums as well as different bladed-disk materials are introduced. Almost all vibration peaks can be explained by three kinds of mechanisms found and summarized in this paper. Two of them are related to travelling waves and the third is related to harmonics. Speed and frequency margins that are related to blade-tip-rub induced vibrations are defined and analyzed. The findings and ideas shown in this paper can be used as a reference in engine preliminary structural design to avoid potential blade tip-rub induced damages.

Dynamic characteristics analysis of blade-casing rubbing faults with abradable coatings

2020 ◽  
pp. 095440622094155
Author(s):  
Junhong Zhang ◽  
Xin Lu ◽  
Jiewei Lin ◽  
Liang Ma ◽  
Huwei Dai
Keyword(s):  
Rotor System ◽  
Rotating Speed ◽  
Fundamental Frequencies ◽  
Abradable Coating ◽  
Characteristics Analysis ◽  
Blade Tip ◽  
System Vibration ◽  
Initial Clearance ◽  
Abradable Coatings ◽  
Dynamic Characteristics Analysis

In this paper, a dynamic model of a “0-2-1” rotor system with rubbing fault between blade and abradable coated casings is developed. The sub-model of rubbing force considers scraping work energy of coating, casing stiffness, and initial clearance between blade tip and casing. A rotor rig is established and samples of abradable coatings are introduced into the rubbing experiment. Vibration characteristics of the rotor system under blade-casing rubbing fault are analyzed. Effects of rotating speed and initial clearance on the rub force and the system vibration are studied. Results show that the vibration of rotor focuses on the fundamental and multiple fundamental frequencies due to the blade-casing rubbing with the abradable coating. The multiple fundamental frequencies, the 2 × and 3 × in particular, are greatly affected by the rotating speed. The fractional harmonic frequencies are strongly influenced by the initial clearance between the blade tip and casing. Besides, the rotating speed and the initial clearance between the blade tip and abradable coating on the casing also affect the amplitude and distribution of the rub force.

Experimental Analysis of Blade-Casing Contacts in a Centrifugal Compressor: Vibration and Thermal Aspects

2021 ◽  
Author(s):  
Nicolas Guerin ◽  
Claude Gibert ◽  
Fabrice Thouverez ◽  
Patricio Almeida
Keyword(s):  
High Temperatures ◽  
Experimental Tests ◽  
Material Transfer ◽  
Full Spectrum ◽  
Abradable Coating ◽  
Engine Compressor ◽  
Coating Removal ◽  
Temperature Levels ◽  
Post Trial ◽  
Thermal Phenomena

Abstract Due to an increasing need for efficiency of turboengines, rotor--stator clearances are being lowered. Therefore, new designs show higher probability for contacts between rotors and casings. When contacts occur, high dynamic excitation levels as well as high temperatures due to dissipative mechanical phenomena may be expected. While numerical investigations have been proposed in the past, experiments are of high interest to fully understand the underlying phenomena behind rotor-stator contact interactions. In order to assess this situation, and based on former work performed by part of the authors, a rotor--stator contact rig has been used to investigate the mechanical and thermal behavior of a centrifugal low-pressure helicopter engine compressor. This rig operates under vacuum conditions to significantly reduce influence of the air surrounding the studied components. During the tests, multiple contact phases have been identified through increased vibration and temperature levels, as well as torque and rotational speed variations. A comprehensive analysis of the dynamic and thermal phenomena occurring during these experimental tests is proposed in this paper. Dynamic measurements are analyzed in the time and frequency domains, and nodal diameter contents are evaluated as well through full spectrum analyses. As a result, major influences from synchronous excitations in the frequency range of interest but also of higher modal families are highlighted. Post-trial observations indicate severe contact conditions leading to very high temperatures, abradable coating removal and material transfer between blade and casing.

scholarly journals High-Pressure Compressor Blade Dynamics Under Aerodynamic and Blade-Tip Unilateral Contact Forcings

2014 ◽  
Author(s):  
Alain Batailly ◽  
Mathias Legrand ◽  
Antoine Millecamps ◽  
François Garcin
Keyword(s):  
High Pressure ◽  
Aircraft Engine ◽  
Aerodynamic Pressure ◽  
High Pressure Compressor ◽  
Frequency Domains ◽  
Unilateral Contacts ◽  
Blade Tip ◽  
Structural Instabilities ◽  
Pressure Compressor ◽  
Numerical Strategy

Recent studies focused on the numerical prediction of structural instabilities that may arise in rotating components of an aircraft engine. These instabilities are commonly classified into two categories: those induced by aerodynamic phenomena (such as the pressure applied on the blade by the incoming air flow) and those related to structural phenomena (such as potential blade/casing contacts). Based on an existing numerical strategy for the analysis of rotor/stator interactions induced by unilateral contacts between rotating and static components, this paper aims at combining both types of instabilities and provides a qualitative analysis of structural interactions that may arise within the high-pressure compressor of an aircraft engine. The aerodynamic pressure on the blade is simplified as a sinusoidal external load whose frequency depends on the number of upstream guide vanes. Results are presented both in time and frequency domains. Detailed bifurcation diagrams and Poincaré maps underline the fundamental differences in the nature of the witnessed interactions with and without aerodynamic loading on the blade.

scholarly journals Chemtrails are Not Contrails: Radiometric Evidence

2020 ◽  
pp. 22-29
Author(s):  
J. Marvin Herndon ◽  
Raymond D. Hoisington ◽  
Mark Whiteside
Keyword(s):  
Coal Fly Ash ◽  
Aircraft Engine ◽  
Ice Crystal ◽  
Engine Exhaust ◽  
The Public ◽  
Radiometric Measurements ◽  
Tropospheric Aerosol ◽  
Typical Instance ◽  
Life On Earth ◽  
Physical Phenomena

Aims: Concerted efforts are made to deceive the public into falsely believing the jet-emplaced tropospheric aerosol trails, called chemtrails by some, are harmless ice-crystal contrails from aircraft engine exhaust-moisture. Our objective is to use radiometric measurements in the range 250-300 nm to show that a typical chemtrail is not a contrail, and to generalize that finding with additional data.  Methods: We utilized International Light Technologies ILT950UV Spectral Radiometer mounted on a Meade LXD55 auto guider telescope tripod and mount assembly. Results: Radiometric solar irradiance spectra data that included the transit of a typical tropospheric aerosol trail between radiometer-sensor and the solar disc showed significant absorption during    the transit period. The during-transit absorption is wholly inconsistent with the almost negligible adsorption by ice, but is wholly consistent with absorption by aerosolize particulates, including coal fly ash. This result is consistent with other aerosol-trail physical phenomena observations. Conclusions: The public and the scientific community have been systematically deceived into falsely believing that the pervasive, jet-sprayed ‘chemtrails’ are harmless ice-crystal contrails. We have presented radiometric measurements which unambiguously prove the falsity of that characterization for one specific, but typical instance. We show in a more general framework that the physical manifestations of the aerial trails are inconsistent with ice-crystal contrails, but entirely consistent with aerosol particulate trails. We describe potential reasons for the deception, and cite the extremely adverse consequences of the aerial particulate spraying on human and environmental health. For the sake of life on Earth, the modification of the natural environment by aerial particulate spraying and other methodologies must immediately and permanently end.

Sign in / Sign up

Export Citation Format

Share Document