Modélisation et techniques d'inversion avancées appliquées à l'imagerie hyperspectrale de flammes turbulentes

Offre de thèse

Date limite de candidature

15-06-2025

Date de début de contrat

01-10-2025

Directeur de thèse

PARENT Gilles

Encadrement

Directeur de thèse : Gilles PARENT - Professeur au LEMTA, Université de Lorraine Co-directeur de thèse : Frédéric ANDRÉ - Directeur de recherche au LOA, Université de Lille. Un suivi régulier, hebdomadaire au minimum, sera assuré en présentiel avec M. Gilles Parent. Ce suivi sera complété par un point mensuel organisé mensuellement avec les deux directeurs de thèse, en visioconférence. Une réunion d'avancement annuelle en présentiel sera organisée. Une formation initiale sur les modèles de spectroscopie des gaz sera assurée en présentiel par M. Frédéric André. **************************************************************************************************** The thesis will be supervised by Gilles PARENT, Professor at LEMTA, University of Lorraine, and Frédéric André, Director of Research at LOA, University of Lille. Regular monitoring, at least once a week, will be carried out in person with Mr. Gilles Parent. This monitoring will be supplemented by a monthly review organized with both thesis supervisors via videoconference. An annual progress meeting will be organized in person. Initial training on gas spectroscopy models will be provided in person by Mr. Frédéric ANDRÉ.

Type de contrat

ANR Financement d'Agences de financement de la recherche

Candidater à cette offre

école doctorale

SIMPPÉ - SCIENCES ET INGENIERIES DES MOLECULES, DES PRODUITS, DES PROCEDES ET DE L'ÉNERGIE

équipe

Groupe Energie et Transferts

contexte

Des mesures fiables, résolues dans l'espace et dans le temps, de la température et des concentrations d'espèces sont essentielles pour le développement des futures générations de systèmes de combustion propres et efficaces. Les informations sur ces profils scalaires sont nécessaires : 1/ pour comprendre les structures complexes des flammes dues aux interactions entre l'écoulement des fluides, la chimie, le transfert radiatif, la production de suie et la turbulence, et 2/ pour améliorer/évaluer les modèles physiques utilisés dans les simulations numériques, y compris la cinétique chimique. Les techniques de spectroscopie d'émission, y compris les mesures spatialement résolues (hyperspectrales), sont particulièrement intéressantes. Les dispositifs d'imagerie hyperspectrale enregistrent un spectre d'émission de flamme pour chaque pixel d'un capteur bidimensionnel, produisant une image spectrale appelée hypercube. Leur application dans le domaine de la combustion a bénéficié du développement de bases de données spectroscopiques précises à haute résolution et haute température pour interpréter les données. En pratique, les spectres d'émission de flamme dans la ligne de visée sont enregistrés. Des profils scalaires (température et concentration en espèces/suie) peuvent ensuite être déduits de ces spectres par application de techniques d'inversion combinées à des modèles directs précis. L'application de cette méthode à chaque pixel de la caméra hyperspectrale permet, en principe, de reconstruire l'ensemble du champ de combustion. Les dispositifs hyperspectraux sont de plus en plus utilisés comme diagnostics optiques pour étudier les flammes laminaires. Il a été démontré qu'ils peuvent également être utilisés pour les flammes turbulentes. Cependant, les interactions entre turbulence et rayonnement compliquent considérablement le processus d'inversion et le nombre d'articles scientifiques consacrés à l'application de l'imagerie hyperspectrale aux champs turbulents reste marginal à l'heure actuelle. De plus, les chambres de combustion industrielles présentent des configurations et des géométries complexes qui s'écartent généralement de manière significative d'une flamme axisymétrique simple. Ce travail de doctorat s'inscrit dans le cadre du projet « Radiative Analysis of Glass furnaces: Novel AppROaches for Computational Hyperspectral imaging » (Ragnaroch) financé par l'Agence nationale de la recherche (ANR) https://anr.fr/Projet-ANR-24-CE51-2798. *********************************************************************************************************** Reliable space- and time-resolved measurements of temperature and species concentrations are essential in the development of future generations of clean and efficient combustion systems. Information about these scalar profiles is required: 1/ to understand the complex flame structures due to fluid flow / chemistry / radiative transfer / soot production / turbulence interactions, and, 2/ to improve / assess the physical models involved in numerical simulations, including chemical kinetics. Emission spectroscopy techniques, including non-imaging and imaging (hyperspectral) measurements, are particularly attractive. Hyperspectral imaging devices record one flame emission spectrum for each pixel of a two-dimensional sensor producing a spectral image called hypercube. Their application in the field of combustion has benefited from the development of accurate high-resolution high-temperature spectroscopic databases to interpret the data. In practice, line-of-sight flame emission spectra are recorded. Scalar (temperature and species / soot concentration) profiles can then be inferred from these spectra by application of inversion techniques combined with accurate forward models. Application of the method to each pixel of the hyperspectral camera allows, in principle, reconstructing the entire combustion field. Hyperspectral devices have been increasingly used as optical diagnostics to probe laminar flames. It was shown that they can be used for turbulent flames too. However, turbulence / radiation interactions complicate significantly the inversion process. Gore and co-workers have shown that the first- and second-statistical moments of temperature, species mole fractions and soot volume fraction fluctuations can be estimated by combining hyperspectral measurements and tomography techniques in statistically-steady axi-symmetric turbulent flames. Nevertheless, the amount of scientific papers dedicated to the application of hyperspectral imaging to turbulent fields remains marginal at the present time. Moreover, industrial combustion chambers show complex configurations and geometries that usually depart significantly from the idealized axi-symmetric flame. This PhD work is part of the project “Radiative Analysis of Glass furnaces: Novel AppROaches for Computational Hyperspectral imaging” (Ragnaroch) funded by the French National Research Agency (ANR) https://anr.fr/Projet-ANR-24-CE51-2798.

spécialité

Énergie et Mécanique

laboratoire

LEMTA – Laboratoire Energies & Mécanique Théorique et Appliquée

Mots clés

Imagerie hyperspectrale, Inversion, Transfert radiatif, Spectroscopie des gaz, Combustion

Détail de l'offre

Cette thèse s'inscrit dans le cadre du projet ANR « Radiative Analysis of Glass furnaces: Novel AppROaches for Computational Hyperspectral imaging » (Ragnaroch) et vise à développer des outils théoriques et numériques pour exploiter l'imagerie hyperspectrale dans l'analyse de flammes à haute température, y compris dans des configurations industrielles complexes. L'objectif est de permettre l'estimation non-intrusive de champs scalaires (température, concentrations de particules chimiques et suie) à partir de mesures spectrales. Contrairement aux diagnostics laser classiques souvent limités aux laboratoires, l'imagerie hyperspectrale offre une solution prometteuse, mais son application à des flammes turbulentes industrielles reste encore très peu explorée.

Le travail consistera à adapter des techniques issues de la télédétection atmosphérique (PCA, réseaux de neurones, ALD) aux besoins spécifiques de la combustion, en validant ces méthodes sur des flammes numériques simulées avec le logiciel de CFD ProLB, avant de les appliquer à des mesures expérimentales. Le doctorant participera également à des campagnes expérimentales et au développement d'algorithmes d'inversion pour reconstruire les champs de température et de composition à partir des données hyperspectrales.

************************************************************************************************************

This PhD is part of the ANR-funded “Radiative Analysis of Glass furnaces: Novel AppROaches for Computational Hyperspectral imaging” (Ragnaroch) project and aims to develop theoretical and numerical tools to enable the use of hyperspectral imaging for analyzing high-temperature flames, including in complex industrial environments. The goal is to retrieve non-intrusive, space- and time-resolved measurements of scalar fields (temperature, species concentrations, and soot) from spectral data. While traditional laser diagnostics are common in labs, their application in industrial settings is limited. Hyperspectral imaging offers a promising alternative, though its use in turbulent industrial flames remains underexplored.

The research will involve adapting methods from atmospheric sensing (e.g., Principal Component Analysis, Neural Networks, Augmented l-distribution) to combustion applications. These techniques will be validated on numerically simulated flames (using ProLB) before being applied to real experimental data. The PhD candidate will also take part in experimental campaigns (lab- and industry-scale) and contribute to the development of inversion algorithms to extract scalar field information from hyperspectral measurements using previously built forward radiation models.

Keywords

Hyperspectral imagery, Inversion, Radiative transfer, Gas spectroscopy, Combustion

Subject details

Reliable space- and time-resolved measurements of temperature and species concentrations are essential in the development of future generations of clean and efficient combustion systems. Information about these scalar profiles is required: 1/ to understand the complex flame structures due to fluid flow / chemistry / radiative transfer / soot production / turbulence interactions, and, 2/ to improve / assess the physical models involved in numerical simulations, including chemical kinetics. Emission spectroscopy techniques, including non-imaging and imaging (hyperspectral) measurements, are particularly attractive. Hyperspectral imaging devices record one flame emission spectrum for each pixel of a two-dimensional sensor producing a spectral image called hypercube. Their application in the field of combustion has benefited from the development of accurate high-resolution high-temperature spectroscopic databases to interpret the data. In practice, line-of-sight flame emission spectra are recorded. Scalar (temperature and species / soot concentration) profiles can then be inferred from these spectra by application of inversion techniques combined with accurate forward models. Application of the method to each pixel of the hyperspectral camera allows, in principle, reconstructing the entire combustion field. Hyperspectral devices have been increasingly used as optical diagnostics to probe laminar flames. It was shown that they can be used for turbulent flames too. However, turbulence / radiation interactions complicate significantly the inversion process. Gore and co-workers have shown that the first- and second-statistical moments of temperature, species mole fractions and soot volume fraction fluctuations can be estimated by combining hyperspectral measurements and tomography techniques in statistically-steady axi-symmetric turbulent flames. Nevertheless, the amount of scientific papers dedicated to the application of hyperspectral imaging to turbulent fields remains marginal at the present time. Moreover, industrial combustion chambers show complex configurations and geometries that usually depart significantly from the idealized axi-symmetric flame. This PhD work is part of the project “Radiative Analysis of Glass furnaces: Novel AppROaches for Computational Hyperspectral imaging” (Ragnaroch) funded by the French National Research Agency (ANR) https://anr.fr/Projet-ANR-24-CE51-2798. The aim of the PhD work is to contribute to the field of radiative analysis in high temperature configurations. Its objective is to develop and fully validate theoretical and numerical tools to allow the use of hyperspectral imaging in real flame scenarios, including actual industrial configurations. For this purpose, the PhD work will first consist of adapting theoretical and numerical tools used in atmospheric sensing studies (Principal Component Analysis (PCA), Neural Networks, Augmented l-distribution (ALD)) to combustion applications. This will require understanding the methods before to suggest the modifications needed to apply the techniques to flame configurations. Model parameters will be constructed and fully validated on numerical flames calculated using ProLB as part of the project, before to be applied in real applications. The PhD candidate will then participate to the experiments on real flames (laboratory scale and industrial configuration) and also to the development of inversion methods to retrieve scalar fields in flames (temperature, species concentrations) from experimental radiative images. The inversion process will use the previously developed forward models of flame radiation.

Profil du candidat

Ecole d'ingénieur ou master de physique. De solides compétences en méthodes numériques, de sérieuses connaissances en mathématiques et en statistiques et/ou une expérience préliminaire significative en transfert radiatif dans les gaz à haute température seront appréciées.

Pour toute thèse proposée au sein de l'Ecole Doctorale, le futur doctorant devra bien être titulaire d'un master (diplôme de master/d'ingénieur français ou étranger, …) justifiant d'un parcours remarquable.
Dans tous les cas (diplôme de master ou d'ingénieur français ou étranger, …) le dossier doit comporter :
• le CV du candidat et lettre de motivation
• les notes obtenues au diplôme conférant le grade de master, mention 'Assez Bien' requise au minimum et copie du diplôme s'il est disponible
• des lettres de recommandations émanant du Responsable de la filière de formation et du tuteur de stage de fin d'études
• des éléments tangibles sur l'initiation à la recherche (mémoire de recherche, publication, ...).
Le dossier complet de candidature doit être envoyé à la direction de thèse par les adresses messageries des directeurs de thèses :
Mr Parent : gilles.parent@univ-lorraine.fr
Mr André : frederic.andre@univ-lille.fr

Candidate profile

Engineering school or equivalent. Solid skills in numerical methods, serious background in mathematics and statistics and/or a significant preliminary experience in radiative transfer in high temperature gases will be appreciated

All applicants to the Doctoral School SIMPPÉ must have successfully completed a Master degree or its equivalent with a grade comparable to or better than the French grade AB (corresponding roughly to the upper half of a graduating class). In all cases (French or foreign Master degree, engineering degree, etc.) the counsel of the doctoral school will examine the candidate's dossier, which must include:
• CV and letter of motivation
• the grades obtained for the Master (or equivalent) degree and a copy of the diploma if it is available
• 2 letters of recommendation, preferably from the director of the Master program and the supervisor of the candidate's research project
• written material (publications, Master thesis or report, etc.) related to the candidate's research project.
The complete application file must be sent to the thesis supervisors by email :
Mr Parent : gilles.parent@univ-lorraine.fr
Mr André : frederic.andre@univ-lille.fr

Référence biblio

[1] M. Aldén, “Spatially and temporally resolved laser/optical diagnostics of combustion processes: From fundamentals to practical applications”, Proc. Combustion 2 Inst. 39 (2023) 1185–1228.
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[3] Y. Zheng, J.P. Gore, “Measurements and inverse calculations of spectral radiation intensities of a turbulent ethylene/air jet flame”, Proc. Combustion Inst. 30 (2005) 727–734.
[4] B.A. Rankin, G. Magnotti, R.S. Barlow, J. P. Gore, “Radiation intensity imaging measurements of methane and dimethyl ether turbulent nonpremixed and partially premixed jet flames”, Combust. Flame 161 (2014) 2849–2859.
[5] M.R. Rhoby, D. Blunck, K.C. Gross, “Mid-IR hyperspectral imaging of laminar flames for 2-d scalar values”, Opt. Express 22 (2014) 21600–17.
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[9] G. Parent, F. André, M. Kühni, Z. Acem, M. Norman, E. Bodin, C. Galizzi, “Medium resolution (0.25 cm-1) spectrum of a hydrogen flame using imaging Fourier transform spectroscopy (IFTS) and its inversion using the l-distribution approach”, in: Proceedings of the 10th International Symposium on Radiative Transfer, RAD-23 (2023).
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[15] J.L. Consalvi, F. Nmira, F. André, V. P. Solovjov, B. W. Webb, “Large eddy simulation of fire-induced flows using Lattice-Boltzmann methods”, in revision, J. Quant. Spectrosc. Rad. Transf. (2024)
[16] F. Nmira, J.L. Consalvi, “Local contributions of resolved and subgrid turbulence-radiation interaction in LES/presumed FDF modelling of large-scale methanol pool fires”, Int. J. Heat Mass Transfer 190 (2022) 122746. [17] S. Souai, S. S. Baakeem, S. Trabelsi, E. Sediki, A. Mohamad, “Numerical study of thermal radiation heat transfer using lattice Boltzmann method”, Numer. Heat Transf., Part B: Fundamentals, 82 (2022) 164-184.
[18] J.L. Consalvi, F. Nmira, “A detailed of analysis of joint soot volume fraction/temperature statistics in non-premixed jet flame: Implication for soot emission turbulence/radiation interaction”, J. Quant. Spectrosc. Rad. Transf 314 (2024), pp. 108845.
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