References of "Léonard, Olivier"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailAnalysis versus synthesis for trending of gas-path measurement time series
Borguet, Sébastien ULg; Léonard, Olivier ULg; Dewallef, Pierre ULg

in Proceedings of ASME Turbo Expo 2014 (2014, June)

Gas-path measurements used to assess the health condition of an engine are corrupted by noise. Generally, a data cleaning step occurs before proceeding with fault detection and isolation. Classical linear ... [more ▼]

Gas-path measurements used to assess the health condition of an engine are corrupted by noise. Generally, a data cleaning step occurs before proceeding with fault detection and isolation. Classical linear filters such as the exponentially weighted moving average filter are traditionally used for noise removal. Unfortunately, these low-pass filters distort trend shifts indicative of faults, which increases the detection delay. The present paper investigates two new approaches to non-linear filtering of time series. On one hand, the synthesis approach reconstructs the signal as a combination of elementary signals chosen from a pre-defined library. On the other hand, the analysis approach imposes a constraint on the shape of the signal (e.g., piecewise constant). Both approaches incorporate prior information about the signal in a different way, but they lead to trend filters that are very capable at noise removal while preserving at the same time sharp edges in the signal. This is highlighted through the comparison with a classical linear filter on a batch of synthetic data representative of typical engine fault profiles. [less ▲]

Detailed reference viewed: 10 (3 ULg)
Full Text
Peer Reviewed
See detailAircraft Engine Gas Path Diagnostic Methods: Public Benchmarking Results
Simon, Donald; Borguet, Sébastien ULg; Léonard, Olivier ULg et al

in Journal of Engineering for Gas Turbines & Power (2014), 136(4), 041201

Recent technology reviews have identified the need for objective assessments of aircraft engine health management (EHM) technologies. To help address this issue, a gas path diagnostic benchmark problem ... [more ▼]

Recent technology reviews have identified the need for objective assessments of aircraft engine health management (EHM) technologies. To help address this issue, a gas path diagnostic benchmark problem has been created and made publicly available. This software tool, referred to as the Propulsion Diagnostic Method Evaluation Strategy (Pro- DiMES), has been constructed based on feedback provided by the aircraft EHM community. It provides a standard benchmark problem enabling users to develop, evaluate, and compare diagnostic methods. This paper will present an overview of ProDiMES along with a description of four gas path diagnostic methods developed and applied to the problem. These methods, which include analytical and empirical diagnostic techniques, will be described and associated blind-test-case metric results will be presented and compared. Lessons learned along with recommendations for improving the public benchmarking processes will also be presented and discussed. [less ▲]

Detailed reference viewed: 9 (2 ULg)
Full Text
Peer Reviewed
See detailAircraft engine gas path diagnostic methods: public benchmarking results
Simon, Donald; Borguet, Sébastien ULg; Léonard, Olivier ULg et al

in Proceedings of ASME Turbo Expo 2013 (2013, June)

Recent technology reviews have identified the need for objective assessments of aircraft engine health management (EHM) technologies. To help address this issue, a publicly available gas path diagnostic ... [more ▼]

Recent technology reviews have identified the need for objective assessments of aircraft engine health management (EHM) technologies. To help address this issue, a publicly available gas path diagnostic benchmarking problem has been created and made publicly available. This software tool, referred to as the Propulsion Diagnostic Method Evaluation Strategy (ProDiMES), has been constructed based on feedback provided by individuals within the aircraft EHM community. It provides a standard benchmarking problem enabling users to develop, evaluate and compare diagnostic methods. This paper will present an overview of ProDiMES along with a description of four gas path diagnostic methods developed and applied to the problem. These methods, which include analytical and empirical diagnostic techniques, will be described and associated blind test case metric results will be presented and compared. Lessons learned along with recommendations for improving the public benchmarking processes will also be presented and discussed. [less ▲]

Detailed reference viewed: 41 (13 ULg)
Full Text
Peer Reviewed
See detailToward a High Order Throughflow - Investigation of the Nonlinear Harmonic Method Coupled With an Immersed Boundary Method for the Modeling of the Circumferential Stresses
Thomas, Jean-Philippe ULg; Léonard, Olivier ULg

in Journal of Turbomachinery (2012), 134(1),

Capturing a level of modeling of the flow inside a multi-stage turbomachine, such as unsteadiness for example, can be done at different degrees of details, either by capturing all deterministic features ... [more ▼]

Capturing a level of modeling of the flow inside a multi-stage turbomachine, such as unsteadiness for example, can be done at different degrees of details, either by capturing all deterministic features of the flow with a pure unsteady method or by settling for an approximated solution at a lower computational cost. The harmonic methods stand in this second category. Amongst them the "Nonlinear Harmonic Method'' from He revealed the most efficient. This method consists of solving the fully nonlinear 3D steady problem and a linearized perturbation system in the frequency domain. As it has been shown by the authors that the circumferential variations exhibit a harmonic behavior, it is proposed here to adapt this method to the throughflow model, where the main nonlinear system would be the common throughflow equations and the auxiliary system would give access to the circumferential stresses. As the numerical local explicit impermeability conditions are unsupported by Fourier series, the adaptation of this technique to the throughflow model passes through a reformulation of the blade effect by a smooth force field as in the "Immersed Boundary Method'' from Peskin. A simple example of an inviscid flow around a cylinder will illustrate the preceding developments, bringing back the mean effect of the circumferential non uniformities into the meridional flow. [less ▲]

Detailed reference viewed: 67 (8 ULg)
Full Text
Peer Reviewed
See detailConstrained sparse estimation for improved fault isolation
Borguet, Sébastien ULg; Léonard, Olivier ULg

in Journal of Engineering for Gas Turbines & Power (2011), 133(12), 121602

Detailed reference viewed: 23 (2 ULg)
Full Text
Peer Reviewed
See detailA study on engine health monitoring in the frequency domain
Borguet, Sébastien ULg; Henriksson, Mattias; McKelvey, Tomas et al

in Journal of Engineering for Gas Turbines & Power (2011), 133(08), 081604-1--081604-8

Most of the techniques developed to date for module performance analysis rely on steady-state measurements from a single operating point to evaluate the level of deterioration of an engine. One of the ... [more ▼]

Most of the techniques developed to date for module performance analysis rely on steady-state measurements from a single operating point to evaluate the level of deterioration of an engine. One of the major difficulties associated with this estimation problem comes from its underdetermined nature. It results from the fact that the number of health parameters exceeds the number of available sensors. Among the panel of remedies to this issue, a few authors have investigated the potential of using data collected during a transient operation of the engine. A major outcome of these studies is an improvement in the assessed health condition. The present study proposes a framework that formalizes this observation for a given class of input signals. The analysis is performed in the frequency domain, following the lines of system identification theory. More specifically, the mean-squared estimation error is shown to drastically decrease when using transient input signals. This study is conducted with an engine model representative of a commercial turbofan. [less ▲]

Detailed reference viewed: 31 (4 ULg)
Full Text
Peer Reviewed
See detailConstrained sparse estimation for improved fault isolation
Borguet, Sébastien ULg; Léonard, Olivier ULg

in Proceedings of ASME Turbo Expo 2011 (2011)

Least-squares-based methods are very popular in the jet engine community for health monitoring purpose. Their isolation capability can be improved by using a prior knowledge on the health parameters that ... [more ▼]

Least-squares-based methods are very popular in the jet engine community for health monitoring purpose. Their isolation capability can be improved by using a prior knowledge on the health parameters that better matches the expected pattern of the solution i.e., a sparse one as accidental faults impact at most one or two component(s) simultaneously. On the other hand, complimentary information about the feasible values of the health parameters can be derived in the form of constraints. The present contribution investigates the effect of the addition of such constraints on the performance of the sparse estimation tool. Due to its quadratic programming formulation, the constraints are integrated in a straightforward manner. Results obtained on a variety of fault conditions simulated with a commercial turbofan model show that the inclusion of constraints further enhance the isolation capability of the sparse estimator. In particular, the constraints help resolve a confusion issue between high pressure compressor and variable stator vanes faults. [less ▲]

Detailed reference viewed: 29 (3 ULg)
Full Text
Peer Reviewed
See detailAssessment of an anomaly detector for jet engine health monitoring
Borguet, Sébastien ULg; Léonard, Olivier ULg

in International Journal of Rotating Machinery (2011), 2011

The goal of module performance analysis is to reliably assess the health of the main components of an aircraft engine. A predictive maintenance strategy can leverage this information to increase ... [more ▼]

The goal of module performance analysis is to reliably assess the health of the main components of an aircraft engine. A predictive maintenance strategy can leverage this information to increase operability and safety as well as to reduce costs. Degradation undergone by an engine can be divided into gradual deterioration and accidental events. Kalman filters have proven very efficient at tracking progressive deterioration but are poor performers in the face of abrupt events. Adaptive estimation is considered as an appropriate solution to this deficiency. This paper reports the evaluation of the detection capability of an adaptive diagnosis tool on the basis of simulated scenarios that may be encountered during the operation of a commercial turbofan engine. The diagnosis tool combines a Kalman filter and a secondary system that monitors the residuals. This auxiliary component implements a generalised likelihood ratio test in order to detect abrupt events. [less ▲]

Detailed reference viewed: 17 (2 ULg)
Full Text
Peer Reviewed
See detailTowards a High Order Throughflow. Part I : Investigating the Effectiveness of a Harmonic Reconstruction for 3D Flows
Thomas, Jean-Philippe ULg; Léonard, Olivier ULg

in Proceedings of the ASME Turbo Expo 2010 (2010, July)

The computation time and the extraction of useful information remain severe drawbacks to systematic use of modern three-dimensional Navier-Stokes codes in a design procedure of multistage turbomachines ... [more ▼]

The computation time and the extraction of useful information remain severe drawbacks to systematic use of modern three-dimensional Navier-Stokes codes in a design procedure of multistage turbomachines. That explains why throughflow simulation is still widely used at industrial scale. The main limitation of throughflow is however the need for empirical models to reproduce blade-flow interactions and major 3D flow features. The purpose of this work is to investigate the degree to which empiricism could be reduced by using the averaged-passage equations of Adamczyk, combined with a harmonic closure strategy. To that aim, results of a computation performed with a steady three-dimensional Navier-Stokes code are used to calculate some of the additional terms of the circumferentially-averaged equations, the so-called circumferential stresses. The importance of the latter to bring back the mean effect of circumferential non-uniformities, linked to 3D phenomena, is illustrated by injecting them into a throughfow simulation. Then the ability of truncated Fourier series to reproduce the level of non-uniformity in the core flow and near the walls is detailed. It is finally shown that the harmonic approximated stresses can lead to a good reproduction of local 3D flow features in throughflow simulation and to a better accuracy. [less ▲]

Detailed reference viewed: 33 (14 ULg)
Full Text
Peer Reviewed
See detailTowards a High Order Throughflow. Part II : Investigation of the Nonlinear Harmonic Method Coupled With an Immersed Boundary Method for the Modeling of the Circumferential Stresses
Thomas, Jean-Philippe ULg; Léonard, Olivier ULg

in Proceedings of the ASME Turbo Expo 2010 (2010, July)

Capturing a level of modeling of the flow inside a multi-stage turbomachine, such as unsteadiness for example, can be done at different degrees of details, either by capturing all deterministic features ... [more ▼]

Capturing a level of modeling of the flow inside a multi-stage turbomachine, such as unsteadiness for example, can be done at different degrees of details, either by capturing all deterministic features of the flow with a pure unsteady method or by settling for an approximated solution at a lower computational cost. The harmonic methods stand in this second category. Amongst them the "Nonlinear Harmonic Method'' from He revealed the most efficient. This method consists of solving the fully nonlinear 3D steady problem and a linearized perturbation system in the frequency domain. As it has been shown by the authors that the circumferential variations exhibit a harmonic behavior, it is proposed here to adapt this method to the throughflow model, where the main nonlinear system would be the common throughflow equations and the auxiliary system would give access to the circumferential stresses. As the numerical local explicit impermeability conditions are unsupported by Fourier series, the adaptation of this technique to the throughflow model passes through a reformulation of the blade effect by a smooth force field as in the "Immersed Boundary Method'' from Peskin. A simple example of an inviscid flow around a cylinder will illustrate the preceding developments, bringing back the mean effect of the circumferential non uniformities into the meridional flow. [less ▲]

Detailed reference viewed: 52 (19 ULg)
Full Text
Peer Reviewed
See detailA study on engine health monitoring in the frequency domain
Borguet, Sébastien ULg; Henriksson, Mattias; Mc Kelvey, Tomas et al

in Proceedings of the ASME Turbo Expo 2010 (2010, June)

Most of the techniques developed to date for module performance analysis rely on steady-state measurements from a single operating point to evaluate the level of deterioration of an engine. One of the ... [more ▼]

Most of the techniques developed to date for module performance analysis rely on steady-state measurements from a single operating point to evaluate the level of deterioration of an engine. One of the major difficulties associated with this estimation problem comes from its underdetermined nature. It results from the fact that the number of health parameters exceeds the number of available sensors. Among the panel of remedies to this issue, a few authors have investigated the potential of using data collected during a transient operation of the engine. A major outcome of these studies is an Improvement in the assessed health condition. The present contribution proposes a framework that formalises this observation for a given class of input signals. The analysis is performed in the frequency domain, following the lines of system identification theory. More specifically, the meansquared estimation error is shown to drastically decrease when using transient input signals. The study is conducted with an engine model representative of a commercial turbofan. [less ▲]

Detailed reference viewed: 62 (10 ULg)
Full Text
Peer Reviewed
See detailA Sparse Estimation Approach to Fault Isolation
Borguet, Sébastien ULg; Léonard, Olivier ULg

in Journal of Engineering for Gas Turbines & Power (2010), 132(2), 021601-1021601-7

Least-squares-based methods are very popular in the jet engine community for health monitoring purposes. In most practical situations, the number of health parameters exceeds the number of measurements ... [more ▼]

Least-squares-based methods are very popular in the jet engine community for health monitoring purposes. In most practical situations, the number of health parameters exceeds the number of measurements, making the estimation problem underdetermined. To address this issue, regularization adds a penalty term on the deviations of the health parameters. Generally, this term imposes a quadratic penalization on these deviations. A side effect of this technique is a relatively poor isolation capability. The latter feature can be improved by recognizing that abrupt faults impact at most one or two component(s) simultaneously. This translates mathematically into the search for a sparse solution. The present contribution reports the development of a fault isolation tool favoring sparse solutions. It is very efficiently implemented in the form of a quadratic program. As a validation procedure, the resulting algorithm is applied to a variety of fault conditions simulated with a generic commercial turbofan model. [less ▲]

Detailed reference viewed: 42 (7 ULg)
Full Text
Peer Reviewed
See detailComparison of adaptive filters for gas turbine performance monitoring
Borguet, Sébastien ULg; Léonard, Olivier ULg

in Journal of Computational & Applied Mathematics (2010), 234(7), 2202-2212

Kalman filters are widely used in the turbine engine community for health monitoring purpose. This algorithm has proven its capability to track gradual deterioration with a good accuracy. On the other ... [more ▼]

Kalman filters are widely used in the turbine engine community for health monitoring purpose. This algorithm has proven its capability to track gradual deterioration with a good accuracy. On the other hand, its response to rapid deterioration is either a long delay in recognizing the fault, and/or a spread of the estimated fault on several components. The main reason of this deficiency lies in the transition model of the parameters that assumes a smooth evolution of the engine condition. The aim of this contribution is to compare two adaptive diagnosis tools that combine a Kalman filter and a secondary system that monitors the residuals. This auxiliary component implements on one hand a covariance matching scheme and on the other hand a generalised likelihood ratio test to improve the behaviour of the diagnosis tool with respect to abrupt faults. [less ▲]

Detailed reference viewed: 74 (9 ULg)
Full Text
See detailFrom Manual to Model-Based Control of a Small Jet Engine
Léonard, Olivier ULg; Denis, François; Thomas, Jean-Philippe ULg et al

in Proceedings of the 19th ISABE Conference (2009, September)

Detailed reference viewed: 77 (16 ULg)
Full Text
See detailDetection of abrupt events within a jet engine health monitoring procedure
Borguet, Sébastien ULg; Léonard, Olivier ULg

in Proceedings of the 19th ISABE Conference (2009, September)

Detailed reference viewed: 30 (3 ULg)
Full Text
Peer Reviewed
See detailA Sparse Estimation Approach to Fault Isolation
Borguet, Sébastien ULg; Léonard, Olivier ULg

in Proceedings of the ASME Turbo Expo 2009 (2009, June)

Least-squares-based methods are very popular in the jet engine community for health monitoring purpose. In most practical situations, the number of health parameters exceeds the number of measurements ... [more ▼]

Least-squares-based methods are very popular in the jet engine community for health monitoring purpose. In most practical situations, the number of health parameters exceeds the number of measurements, making the estimation problem underdetermined. To address this issue, regularisation adds a penalty term on the deviations of the health parameters. Generally, this term imposes a quadratic penalisation on these deviations. A side-effect of this technique is a relatively poor isolation capability. The latter feature can be improved by recognizing that abrupt faults impact at most one or two component(s) simultaneously. This translates mathematically into the search for a sparse solution. The present contribution reports the development of a fault isolation tool favouring sparse solutions. It is very efficiently implemented in the form of a quadratic program. As a validation procedure, the resulting algorithm is applied to a variety of fault conditions simulated with a generic commercial turbofan model. [less ▲]

Detailed reference viewed: 41 (6 ULg)
Peer Reviewed
See detailOn the Role of the Deterministic and Circumferential Stresses in Throughflow Calculations
Simon, Jean-Francois; Thomas, Jean-Philippe ULg; Léonard, Olivier ULg

in Journal of Turbomachinery (2009), 131(3),

This paper presents a throughflow analysis tool developed in the context of the average-passage flow model elaborated by Adamczyk. The Adamczyk's flow model describes the 3D time-averaged flow field ... [more ▼]

This paper presents a throughflow analysis tool developed in the context of the average-passage flow model elaborated by Adamczyk. The Adamczyk's flow model describes the 3D time-averaged flow field within a blade row passage. The set of equations that governs this flow field is obtained by performing a Reynolds averaging, a time averaging, and a passage-to-passage averaging on the Navier–Stokes equations. The throughflow level of approximation is obtained by performing an additional circumferential averaging on the 3D average-passage flow. The resulting set of equations is similar to the 2D axisymmetric Navier–Stokes equations, but additional terms resulting from the averages show up: blade forces, blade blockage factor, Reynolds stresses, deterministic stresses, passage-to-passage stresses, and circumferential stresses. This set of equations represents the ultimate throughflow model provided that all stresses and blade forces can be modeled. The relative importance of these additional terms is studied in the present contribution. The stresses and the blade forces are determined from 3D steady and unsteady databases (a low-speed compressor stage and a transonic turbine stage) and incorporated in a throughflow model based on the axisymmetric Navier–Stokes equations. A good agreement between the throughflow solution and the averaged 3D results is obtained. These results are also compared to those obtained with a more “classical” throughflow approach based on a Navier–Stokes formulation for the endwall losses, correlations for profile losses, and a simple radial mixing model assuming turbulent diffusion. [less ▲]

Detailed reference viewed: 81 (28 ULg)
Full Text
Peer Reviewed
See detailCoupling principal component analysis and Kalman filtering algorithms for on-line aircraft engine diagnostics
Borguet, Sébastien ULg; Léonard, Olivier ULg

in Control Engineering Practice (2009), 17(4), 494-502

Engine health monitoring has been an area of intensive research for more than three decades. Numerous methods have been developed with the goal of performing an accurate assessment of the engine condition ... [more ▼]

Engine health monitoring has been an area of intensive research for more than three decades. Numerous methods have been developed with the goal of performing an accurate assessment of the engine condition. It is generally accepted that a practical implementation of a monitoring tool will rely on a combination of several techniques. In this framework, the present contribution proposes an original approach for coupling two diagnostic tools in order to enhance the capability of an engine health monitoring system. One tool is based on a principal component analysis scheme and the other is based on a Kalman filter technique. The three methodologies are compared and the benefit of the combined tool is demonstrated on simulated fault cases which can be expected in a commercial turbofan layout. (C) 2008 Elsevier Ltd. All rights reserved. [less ▲]

Detailed reference viewed: 47 (7 ULg)
Full Text
Peer Reviewed
See detailA Generalized Likelihood Ratio Test for Adaptive Gas Turbine Performance Monitoring
Borguet, Sébastien ULg; Léonard, Olivier ULg

in Journal of Engineering for Gas Turbines & Power (2009), 131(1),

Kalman filters are widely used in the turbine engine community for health monitoring purposes. This algorithm has proven its capability to track gradual deterioration with good accuracy. On the other hand ... [more ▼]

Kalman filters are widely used in the turbine engine community for health monitoring purposes. This algorithm has proven its capability to track gradual deterioration with good accuracy. On the other hand, its response to rapid deterioration is a long delay in recognizing the fault and/or a spread of the estimated fault on several components. The main reason for this deficiency lies in the transition model of the parameters that is blended in the Kalman filter and assumes a smooth evolution of the engine condition. This contribution reports the development of an adaptive diagnosis tool that combines a Kalman filter and a secondary system that monitors the residuals. This auxiliary component implements a generalized likelihood ratio test in order to detect and estimate all abrupt fault. The enhancement in terms of accuracy and reactivity brought by this adaptive Kalman filter is highlighted for a variety of simulated fault cases that may be encountered on a commercial aircraft engine. [DOI: 10.1115/1.2967493] [less ▲]

Detailed reference viewed: 92 (12 ULg)
Full Text
Peer Reviewed
See detailTen Years of Experience With a Small Jet Engine as a Support for Education
Léonard, Olivier ULg; Borguet, Sébastien ULg; Thomas, Jean-Philippe ULg

in Journal of Engineering for Gas Turbines & Power (2009), 131(1),

In 1997 the Turbomachinery Group of the University of Liege decided to acquire a small jet engine to illustrate the courses in propulsion and to provide the students with the opportunity to get some ... [more ▼]

In 1997 the Turbomachinery Group of the University of Liege decided to acquire a small jet engine to illustrate the courses in propulsion and to provide the students with the opportunity to get some experience on data measurement, acquisition, and interpretation. Among others, the SR-30 engine from Turbine Technology Ltd. Chetek, WI was chosen. It consists of a single spool, single flow engine with a centrifugal compressor, a reversed combustion chamber an axial turbine, and a fixed convergent nozzle. This engine was installed on a test bench allowing for manual control and providing fuel and oil to the engine. The original setup included measurements of intercomponent pressure and temperatures, exhaust gas temperature, and rotational speed. Since then both the engine and the test bench have been deeply modified These modifications were led by a triple objective: the improvement and the enrichment of the measurement chain, the widening of the engine operational domain, and, last but not the least, the wish to offer appealing hands-on projects to the students. All these modifications were performed at the University of Liege and were conducted by the students as part of their Master theses. Several performance models of the engine were developed to support data validation and engine condition diagnostic. This paper summarizes the developments conducted with and by the students, and presents the experience that was gained by using this engine as a support for education. [less ▲]

Detailed reference viewed: 149 (19 ULg)