Proposition de stages, thèses et post-docs

Laboratoire de Physicochimie des Processus de Combustion et de l'Atmosphère
PC2A - UMR 8522 CNRS/Lille1
Université Lille 1 Sciences et Technologies
Cité scientifique, Bâtiment C11/C5
59655 Villeneuve d'Ascq Cedex, France

Le Laboratoire de Physicochimie des Processus de Combustion et de l'Atmosphère de l'Université Lille1 Sciences et Technologies cherche des physico-chimistes, chimistes ou physiciens de formation, pour préparer un stage de recherche Master (Année universitaire 2018-2019), une thèse de doctorat (à partir d'Octobre 2019), ou un Post-Doc dans le domaine de l'énergétique et de l'environnement.

Les sujets de recherche proposés concernent les domaines de la combustion, de la sûreté nucléaire et de l'environnement. Ils s'inscrivent dans des axes de recherche soutenus par le Ministère de l'Enseignement Supérieur et de la Recherche, le CNRS-INSIS, l'Institut de Radioprotection et de Sûreté Nucléaire (IRSN) et le Contrat de Projet Etat-Région Hauts de France.

Les candidatures, comportant un CV et une lettre de motivation, doivent être soumises auprès des chercheurs responsables des sujets proposés.

Master 2

Measurement of carbonaceous particles in the exhaust line of a combustion system using scanning mobility particle sizing and laser induced incandescence

This subject concerns the control of soot particles emission at the exhausts of gasoline engines. Today, emission standards are limited to particles greater than 23 nm. The next emission standards will be more restrictive in number of particles and will be extended to smaller particles down to 10 nm. The measurement of such small particles can be performed in principle using commercial scanning mobility particle sizers (SMPS) or using laser diagnostic such as laser induced incandescence (LII). However, measuring such small particle size remains a challenging task.

The objective of the internship is to perform a comparative study of the above mentioned techniques for different experimental conditions. SMPS requires that particles are sampled from the exhausts, while LII can be applied in-situ. The sensitivity and accuracy of the techniques will be evaluated for different size classes of the particles which will be generated either by a carbon nanoparticle generator or by a sooting flame. Then, the penetration function of the particles in the exhaust line will be analyzed to assess the effect of thermophoresis and sedimentation, possibly by class of the primary particle and aggregate size, and compared to theoretical models.

 

The master student will be in charge to install and to operate the overall setup under appropriate support from his/her supervisors.

 

This internship takes part of the European contract PEMS4nano. http://www.pems4nano.eu/

Keywords: soot, SMPS, laser diagnostics, environmental regulation

Linked to the workpackage of the Labex CaPPA : WP 5

Supervisor(s): Pascale DESGROUX and Alessandro FACCINETTO

Study of the reactivity of radical species in atmospheric chemistry

In the atmosphere, organic pollutants such as Volatile Organic Compounds (VOCs) from biogenic and anthropogenic sources are photochemically oxidized to form peroxy radicals such as hydroperoxy HO2 and alkylperoxy RO2 radicals, which play a major role in tropospheric chemistry. The reactivity of these radicals controls the oxidative capacity of the atmosphere and the formation of tropospheric ozone and secondary pollutants. However, the reactivity of HOx (OH and HO2) and RO2 radicals is still poorly understood and controversial in the literature, particularly in “clean” environments containing low NOx concentrations (remote regions: marine boundary layer or tropical forest).

 

The objective of this project is the study of the reactions between RO2 and HOx radicals for a better understanding of atmospheric chemistry. For that, a new and unique experimental set-up has been developed at the PC2A, it consists of a fast flow reactor coupled to three complementary techniques:

-Laser Induced Fluorescence (LIF) for in-situ OH radicals measurements

-continuous wave Cavity Ring-Down Spectroscopy (cw-CRDS) for HO2 radicals measurements

-Mass Spectrometry with Molecular Beam sampling (MB/MS) for the measurement of stable reaction products and radical species.

Rate constants and branching ratios measurements of the reactions RO2 + HOx will be performed.

 

This project is addressed to candidates interested in the experimental aspects of research and having knowledge in atmospheric chemistry.

Keywords: atmospheric chemistry, radicals reactivity, laser techniques, mass spectrometry

Linked to the workpackage of the Labex CaPPA : WP 1

Supervisors: Laure Pillier

Kinetic study of reactions with interest to atmospheric and combustion chemistry by simultaneous detection of OH and RO2 radicals coupled to laser photolysis

OH radicals as well as peroxy radicals (HO2 and RO2) are key species not only in the atmospheric chemistry reaction mechanism, but also in combustion processes, two research domains that are developed in the laboratory PC2A. In this frame, we have set-up an experimental technique able to determine the concentrations of these radicals in a time resolved manner with the goal of studying kinetics of elementary reactions involving these radicals. The set-up is composed of a photolysis laser, initiating the reaction by a pulsed photolysis of an appropriate precursor in the reaction (i.e. H2O2 for generating OH radicals), coupled to two detection techniques:

- OH radicals by Laser Induced Fluorescence (LIF) at high repetition rate (10 kHz)

- Peroxy radicals by continuous wave Cavity Ring Down Spectroscopy (cw-CRDS) in the near IR

In the frame of the proposed PhD work, this experimental set-up will be used to study different reaction systems of atmospheric or combustion interest, for example:

- the degradation of isoprene, a biogenic volatile organic compound (VOC)emitted in large quantities by vegetation

- the cross reactions between HO2 and other RO2 radicals, a very important class of reaction in remote environment, only poorly understood. The simultaneous measurement of OH and HO2 / RO2 radicals will allow determining the branching ratios of such reactions.

Keywords: Peroxy radicals, OH radicals, laser photolysis, laser spectroscopy

Linked to the workpackage of the Labex CaPPA : WP 1

Supervisors: Christa Fittschen / Coralie Schoemaecker

 

Optical properties of aerosols measured in the IR and UV range

 

Because of their ability to absorb and to scatter radiations, airborne particles play an important role in the energy budget of the earth-atmosphere system. It is assumed that aerosols are one of the atmospheric constituents participating to the cooling effect, but estimates are highly uncertain owing to the large spatial and temporal variability of aerosol concentration and physical properties.

The measurements from space-borne instruments are the only means for observing aerosol distributions from local to global scale. However, to fully exploit the instruments capabilities it is essential to have reference optical properties of various particles and mainly their complex refractive indices.

The aim of this work is to measure transmittance spectra of model airborne particles in the infrared and the UV-vis spectral region using a dedicated experimental setup developed in PC2A. The extinction spectra of the aerosol are measured by Fourier Transform InfraRed (FTIR) spectrometer and UV-vis spectrometer and the corresponding size distributions are recorded using optical counters. The whole methodology has been validated using model silica particles and volcanic ashes. The team wants to extend this methodology to other particles of atmospheric interest, e.g., pure water droplets, water droplets containing bioaerosols or silica particles with water adsorbed on their surface. Thus the objective of the internship is to transform the set-up in order to generate such particles and to measure their optical properties in parallel with chemical composition and some physical properties such as the size and the concentration of the particles. The experimental data are then processed in order to retrieve the complex refractive indexes of these aerosols (collaboration with LOA).

                 

This project is addressed to physicist or chemist candidates, interested in the experimental aspects of the research and motivated by the atmospheric impact of aerosols.

                 

Keywords: atmospheric particles, metrology of the aerosol, FTIR and UV-vis spectroscopy

Workpackage of the Labex CaPPA: WP2

Supervisors: Denis Petitprez (PC2A) - Hervé Herbin (LOA) - Olivier Pujol (LOA)

Modelling iodine interactions with atmospheric aerosols

 

Following a severe nuclear power reactor accident, radionuclides like caesium and iodine are released into the atmosphere. Models could predict health impact and organize population evacuation if the need arises. The computer codes used by the IRSN in case of accidental release of radioactive products do not consider the dispersion and drawdown effects; the source term is chemically inert. However, the reactivity of iodine in the atmosphere is well known, and this hypothesis has to be reassessed.

During the Fukushima accident, the simulations have defined quantities of caesium relatively close to those measured in the field, this is not the case for iodine. This discrepancy could be explained by the chemical reactivity of iodine in the atmosphere, which is not implemented in the codes. Indeed, parameters like deposition velocity or the dose-effect factor depends on Iodine chemical speciation and physical form (gas, particle, liquid, solid). Therefore, heterogeneous reactions are important to evaluate the radiologic impact.

The purpose of this internship is to make a critical review of the literature to complete the iodine chemical mechanism with the heterogeneous reactions. 0D modelling studies will be conducted to evaluate the iodine species speciation under various atmospheric conditions (temperature, photolysis, gas and aerosols concentration, ...). The iodine reactivity will be added in heterogeneous phase to the chemical transport models (Chimere and Polair3D in our case) to have a better understanding of the Fukushima accident.

This project will be performed in the framework of the Laboratoire de Recherche Commun C3R (Cinétique Chimique, Combustion, Réactivité) IRSN/CNRS/Lille1 and the Labex CaPPA – WP6 (Chemical and Physical Properties of the Atmosphere).

 

Keywords:  Iodine, Chemistry-transport, Heterogeneous Reactivity, Fukushima

Linked to the workpackage of the Labex CaPPA : WP6

Supervisors: Valérie FEVRE-NOLLET / Patrick LEBEGUE

Biomarkers of Air Pollution on Pollen

Pollen grain has a brief atmospheric airborne life ranging from hours to days during pollination period. Pollen grain is modified by gaseous and particulate pollution during its transport in the atmosphere.

     The modifications of pollen grains by atmospheric pollution induce an inhibition of the germinative capability of the pollen, an increase of its allergenic potential and facilitate the dispersion of allergens in the fine fraction of atmospheric aerosols (1).

     Pollen lipidic fraction can be modified in laboratory conditions by air pollutants, particularly by ozone (2). With this internship, pollen will be exposed to oudoor atmospheric pollution in situ. The candidate will have to design suitable exposure conditions of pollen to outdoor pollution. The lipidic fraction of pollen will be used as a marker of pollution. Lidids will be extracted and analyzed by chromatographic techniques (GC-MS, GC-FID and HPLC).

     Rupture of pollen will also be studied by measuring size distributions with an Aerodynamic Particle Spectrometer (APS).

(1) Sénéchal, H. et al. A Review of the Effects of Major Atmospheric Pollutants on Pollen Grains, Pollen Content and Allergenicity. The Scientific World Journal 2015, ID 940243 (2015).

(2) Naas, O. et al. Chemical modification of coating of Pinus halepensis pollen by ozone exposure. Environmental Pollution 214, 816–821 (2016).

 

Keywords: Heterogeneous Chemistry, Analytical Chemistry, Allergy

Linked to the workpackage of the Labex CaPPA: WP 2

Supervisor: Nicolas Visez

Gas phase reactivity of iodine-containing species of atmospheric interest

The goal of this internship is to improve the understanding of the homogeneous reactivity of iodine-containing species with major photo-oxidants, to better address the lack of data in the field of atmospheric chemistry and nuclear safety, and to provide a set of reliable kinetic and mechanistic data on gas-phase iodine reactivity. These data will improve the relevance and accuracy of iodine dispersion models.

 

Quantum chemistry is more and more used to determine rate constants for gas-phase elementary reactions because the power of the current generation of computers allows to obtain reliable kinetic parameters. It permits to understand the mechanism of global and elementary reactions. It allows to calculate the molecular properties (geometrical data, molecular mass, vibrational frequencies, inertia moments) of reactants, products, transition states, and molecular complexes for an elementary reaction. Then, the macroscopic quantities such as the thermodynamical functions (internal energy, enthalpy, and Gibbs free energy) are calculated from molecular properties using statistical thermodynamics. Finally, temperature and pressure dependencies of rate constants are determined using kinetic theories from thermodynamical functions.

 

This project will be performed in the framework of the Laboratoire de Recherche Commun C3R (Cinétique Chimique, Combustion, Réactivité) IRSN/CNRS/Lille1 and the Labex CaPPA – WP6 (Chemical and Physical Properties of the Atmosphere). The subject of this research project can be pursued through a Ph-D.

 

Keywords: Iodine, theoretical chemistry, reactivity, kinetics, atmospheric chemistry, nuclear safety

Linked to the workpackage of the Labex CaPPA : WP6

Supervisor(s): Florent LOUIS / Marc RIBAUCOUR

Soil spreading of organic waste products: source of secondary organic aerosols?

Agricultural lands occupy about 40-50% of the Earth’s land surface. In order to assess the potential of agricultural ecosystems to act as a source or sink for ozone and volatile organic compounds (VOC), it is necessary to determine the emissions and deposition within the interface soil-atmosphere.

The valorisation of different types of organic waste products (OWP) from farms (cattle, pigs...), urban origin (sewage sludge, green waste) or industrial (sweets, etc.) is currently promoted as a substitute for mineral fertilizers. OWPs have a wide variety of characteristics due to their origin and the treatments that they may undergo before spreading and this diversity of characteristics could have a significant impact on gaseous emissions following soil application.

The agricultural soils emit volatile organic compound (VOC) that contribute to the formation of secondary pollutants such as ozone but also to the formation of secondary organic aerosols (SOA), both pollutants being under regulation.

The present project is focused in the study of SOA formation and ozone deposition and reactivity at the soil-atmosphere interface. Laboratory based measurements will investigate the related emissions of VOC from OWPs and their subsequent reaction with ozone to form aerosols. The experiments will be performed in an aerosol flow tube where the VOC will react with the ozone. An high panel of scientific equipment will be deployed and allow the physical and chemical characterisation of the VOCs and freshly formed aerosols (proton transfer mass spectrometer, scanning mobility particle sizer,…). Filter measurements of aerosols will allow their chemical and molecular characterisation by off-line analysis (gas chromatography, time of flight secondary ions mass spectrometry).The interested candidate will participate at the development of the experimental set-up and will perform experiments.

    

 This project is addressed to agronomist, physicist or chemist candidates interested in the experimental aspects of the research and motivated by the atmospheric impact of aerosols.

 

Labs: PC2A and INRA

Period: from February 1st 2017 to June 30 2017

Gratification: €554.40 per month

Keywords: volatile organic compounds, organic waste products, aerosols, mass spectrometry

Supervisors: RalucaCiuraru (INRA) and Denis Petitprez (PC2A)

 

 

 

Thèses

Développement d'une procédure de mesure par absorption pour contrôler les émissions particulaires provenant des moteurs à combustion internes.

Les particules présentes dans l’atmosphère sont responsables de la dégradation de la qualité de l’air. Elles entraînent un niveau élevé de maladies respiratoires et cardiovasculaires, voire de mortalité. Une partie importante de ces particules est émise par les processus de combustion, notamment les moteurs. Pour limiter ces émissions, il est nécessaire de disposer d’outils permettant de qualifier ces particules. Dans ce cadre, IFPEN a développé un système de mesure optique basé sur les phénomènes d'absorption. La réponse de ce système de mesure en présence de certaines particules est à approfondir dans le cadre d’une thèse.

La première phase de la thèse doit permettre au doctorant (e) d’acquérir une connaissance solide sur les particules carbonées ainsi qu’une vision claire et exhaustive des différentes méthodes de mesure et de caractérisation de ces particules, qu’elles soient présentes dans l’atmosphère ou à l’émission des moteurs. Une attention particulière sera portée sur les méthodes de caractérisation des particules par absorption dans l’UV. L’objectif ici sera d’appréhender la physique de l’interaction lumière matière d’intérêt pour notre étude

La seconde phase de la thèse portera sur la réalisation d’expériences dans un réacteur de laboratoire, représentatif d’une ligne d’échappement de moteur, et permettant d’acquérir une base de données nécessaire à la compréhension des phénomènes physiques en jeu. Les particules présentes dans l’échantillon étudié seront caractérisées en taille et en nombre par des appareils de référence (SMPS, DMS…). Les caractéristiques physiques (forme, structure) et chimiques des particules (composition) seront obtenues en s’appuyant sur les outils analytiques dont disposent IFPEN et le laboratoire de Lille. Cette phase est le cœur de la thèse car elle permettra de relier le signal d’absorption observé aux caractéristiques des particules ainsi que de définir le domaine de validité de notre approche.

Localisation du doctorant : IFP Energies nouvelles, Rueil-Malmaison, France

Programmes de recherche en lien avec le sujet :  CLIMIBIO – Labex CaPPA

Mots clés :         Absorption, particules, diagnostic optique

Pour en savoir plus (français, english)

Responsables et coordonnées :

PC2A :                   Pascale Desgroux              pascale.desgroux@univ-lille.fr         Tel : 0320434930

                              Alessandro Faccinetto       alessandro.faccinetto@univ-lille.fr   Tel :0320434485

IFPEN :                  Matthieu Lecompte         matthieu.lecompte@ifpen.fr        Tel : 0437702168

Financement  : 100 % IFPEN

 

Mise en évidence et caractérisation des espèces chimiques à l'origine de la nucléation des particules de suies dans les flammes

 

La formation des particules de suies dans les processus de combustion est une problématique de recherche majeure du fait de l’impact négatif de ces composés sur notre santé et notre environnement. Le lien entre l’ingestion de ces particules et certaines pathologies touchant principalement les voies respiratoires est en effet bien établi et il est également avéré que ces particules participent notablement au réchauffement climatique. C’est pourquoi leur taux d’émission au sortir de dispositifs mettant en jeu des processus de combustion (réacteurs d’avions, moteurs thermiques ou hybrides des véhicules terrestres ou maritimes, chaudières à bois…) est de plus en plus règlementé. Ainsi, pour développer des technologies moins polluantes et limiter ces émissions, il apparait donc indispensable de connaître les processus chimiques responsables de la formation de ces particules.

Or, l’état de l’art concernant ces mécanismes chimiques fait apparaître de nombreuses carences notamment dans la nature des espèces chimiques impliqués et des voies réactionnels mises en jeu. Plus particulièrement, l’étape de nucléation, qui est l’étape cruciale de ces mécanismes puisqu’elle correspond à la transformation des précurseurs gazeux en particules de suies solides, soulèvent de nombreuses questions et interrogations. Actuellement, plusieurs hypothèses sont envisagées dans la littérature mettant notamment en jeu la formation d’hydrocarbures aromatiques polycycliques (HAPs) et potentiellement celle de dimères de HAPs, mais sans aucune réelle certitude.

Pour tenter d’apporter des réponses à ces questions, nous proposons au cours de cette thèse de mettre en œuvre un certain nombre de dispositifs expérimentaux innovants et complémentaires afin d’obtenir un panel de données suffisamment conséquent pour permettre la caractérisation des principales espèces moléculaires et voies réactionnelles impliquées spécifiquement dans le processus de nucléation. Il est notamment envisagé d’associer des techniques laser de hautes sensibilités pour la mesure des HAPs et dimères de HAPs (fluorescence induite par laser (LIF) / fluorescence induite par laser en jet froid (JCLIF)/ absorption IR après photodissociation) associées à des techniques de spectrométrie de masse de pointe (TOF-SIMS). Ces mesures seront principalement réalisées dans la zone de nucléation de flammes de diffusion. Parallèlement à ces mesures, un travail de caractérisation inédit de la spectroscopie des dimères de HAPs, générés par collisions au sein d’un jet supersonique, sera également engagé. L’obtention de cette base de données permettra ainsi l’analyse très fine des spectres de fluorescence obtenus en condition de flamme. Des analyses supplémentaires sont également envisagées dans le cadre de cette thèse au synchrotron SOLEIL (Gif-sur-Yvette). Les processus de formation des suies reposent sur des mécanismes physico-chimique d’une grande complexité. Cette complexité implique la mise en œuvre de dispositifs expérimentaux variés et complémentaires pour aboutir à une caractérisation précise de ces phénomènes, comme nous le proposons à travers ce sujet de thèse.

Ce projet s'adresse donc spécifiquement à des candidats chimistes ou physiciens à vocation clairement expérimentale et souhaitant acquérir des compétences dans les domaines des diagnostics lasers et de la chimie analytique.

 

Programmes de recherche en lien avec le sujet : CPER Climibio / Labex CAPPA

Mots clés :   Suies, HAPs, nucléation, combustion, diagnostics laser

Responsables et coordonnées :

Xavier Mercier                       xavier.mercier@univ-lille.fr                Tel: 03 20 43 48 04

Alessandro Faccinetto          alessandro.faccinetto@univ-lille.fr  Tel: 03 20 43 49 85

Financement envisagé :  Région / Labex CaPPA

 

Etude de la réactivité d'espèces radicalaires de type peroxyles d'intérêt atmosphérique

Dans l’atmosphère, les polluants organiques, tels que les Composés Organiques Volatils (COV) issus de sources biogéniques et anthropogéniques, sont oxydés par photochimie pour former les radicaux peroxyles HO2 et RO2, qui jouent un rôle prépondérant dans la chimie troposphérique. La réactivité de ces radicaux contrôle la capacité oxydante de l’atmosphère et la formation d’ozone troposphérique et de polluants secondaires. Cependant la réactivité des radicaux RO2 et HOx (OH et HO2) est encore mal comprise et controversée dans la littérature, particulièrement en atmosphère propre contenant des concentrations faibles en oxydes d’azote NOx (forêts tropicales, couche limite marine). Les incertitudes ou le manque de données sur les constantes de vitesse et les rapports de branchement des réactions entre les radicaux RO2, OH et HO2 peuvent conduire à d’importantes erreurs sur la modélisation des concentrations en ozone et en radicaux dans l’atmosphère.

Ainsi, de nouvelles mesures expérimentales, avec une caractérisation plus détaillée à la fois des radicaux et des produits de réaction sont indispensables pour une meilleure compréhension des mécanismes chimiques de l’atmosphère.

L’objectif de ce projet est l’étude des réactions RO2+HOx dans un dispositif expérimental récemment développé et validé au PC2A, il comprend un réacteur à écoulement rapide couplé à trois techniques expérimentales complémentaires : la cw-CRDS (continuous-wave Cavity Ring Down Spectroscopy) pour la mesure du radical HO2, la Fluorescence Induite par Laser (FIL) pour la mesure du radical OH et la Spectrométrie de Masse avec prélèvement par Faisceau Moléculaire (FM/SM) pour la mesure des espèces stables et réactives.

L’étude des réactions RO2+HOx débutera par les radicaux RO2 les plus simples (R= CH3, C2H5, C3H7, etc) pour comparaison avec les résultats de la littérature puis nous poursuivrons avec des systèmes plus complexes, notamment les radicaux peroxyles issus de l’isoprène, COV biogénique le plus émis dans l’atmosphère.

 

Programmes de recherche en lien avec le sujet :  CPER Climibio / Labex CaPPA

Mots clés : Chimie atmosphérique, réactivité, radicaux peroxyles, techniques laser, spectrométrie de masse          

Responsables et coordonnées :

Laure PILLIER                     laure.pillier@univ-lille.fr                     Tel 0320336466

Christa FITTSCHEN             christa.fittschen@univ-lille.fr            Tel 0320337266

Financement envisagé : Région / ULille

 

Experimental kinetic studies of assisted low-temperature combustion in stabilized cool flames

The future of combustion engines is dependent on significant reduction in pollutant emissions, as well as improvement in fuel efficiency and substantial reduction in fuel consumption. Controlled initiation of the combustion is a crucial step towards these goals, with wide ranges of application including piston engines, constant volume combustors, gas turbines and aeronautic engines. In all these cases, reproducible initiation of the combustion phase is sought, multipoint or volumetric ignition being preferred. However, fuel ignition is highly dependent on the chemical kinetics associated with Low Temperature Combustion (LTC).

The chemical mechanisms relevant to LTC include the formation of unstable peroxides, the structure of which reflects the initial fuel. The reactivity of a fuel in this temperature regime is therefore highly constrained by its structure. This is also true for next generation biofuels, whose oxidation pathways can be strongly different from “traditional” fossil fuels.

To ensure volumetric ignition, recent work has shown that nanosecond discharges can induce multipoint ignition in high pressure environments through the formation of excited species and radicals that accelerate both the high temperature and low temperature combustion kinetics. In some conditions, it has recently been shown that nanosecond barrier discharges can initiate cool flames by stimulating the LTC chemistry. There is therefore a need for further clarification of the interaction of plasma and LTC kinetics.

A burner operating between atmospheric and higher pressures, equipped with a high voltage electrode to produce nanosecond plasma discharges or seeded with ozone, will be built and characterized. Detailed structures will be obtained for stabilized cool flames, using the following spectroscopic and chemical methods: Planar Laser Induced Fluorescence (PLIF) of formaldehyde will be used to measure the relative concentration profile of this species, which is directly associated to LTC chemistry. For modeling purposes it is crucial to determine the temperature profile in between the burners, so NO LIF thermometry will be used. To gain insight on the stable species formed in the cool flame, samples will be extracted from the flame front using a quartz sampling microprobe, and analyzed by means of gas chromatography, yielding qualitative and quantitative information on the LTC chemistry intermediates. These preliminary data will be used to validate a kinetic model of the LTC chemistry of DME in these conditions.

 

Programmes de recherche en lien avec le sujet : ANR SPARC / CPER Climibio

Mots clés : Low Temperature Combustion, Cool flames, Laser diagnostics, Chemical kinetics

Responsables et coordonnées :

Guillaume Vanhove           guillaume.vanhove@univ-lille.fr     Tel : 03 20 43 44 85

Financement envisagé : ANR ou ULille

 

Développement des techniques optiques pour la caractérisation in-situ de la suie dans des foyers de combustion haute pression

The predicted significant growth in air traffic urges for new research in combustion, particularly in two directions: 1) to improve fuel efficiency which copes with diminishing fossil resources and 2) to curb down combustion emissions with respect to environmental and climate issues. The solution to the first issue seems to lie in combustion at higher temperatures and pressures but this can have a negative impact on the second issue particularly concerning soot emissions. ONERA can play a key role in this research as it has a long experience in combustion studies carried in its large panel of facilities and with the help of non-intrusive optical diagnostics tools. The objective of the thesis work is to extend and/or develop the techniques, which can characterize soot formation and emissions at high temperature and pressure conditions. Laser Induced Incandescence (LII), sensitive to soot particles, is the key technique on which efforts will be concentrated. However, the coupling of LII to other techniques can be quite helpful to complete our understanding on soot kinetics. These complementary tools are Laser Induced Fluorescence (LIF), a technique used to detect soot precursors and other combustion parameters like OH, Laser Extinction (LE) which can help distinguish different soot types using different excitation/emission wavelengths and quantify the LII signal and Soot Spectral Emissions (SSE) that is used for soot temperature estimations. The experimental work will start by studying the coupling of these techniques in well-known atmospheric pressure conditions (McKenna and/or classical burners). Then, gradually, their response will be studied at higher pressures on a monodisperse burner implemented on a 20 bar high-pressure chamber and further on a newly research test rig (MICADO). In order to extend the feasibility of the techniques they will be implemented on other available test rigs at ONERA, which are working at pressures as high as 60 bars.

 

Programmes de recherche en lien avec le sujet : CPER Climibio / Labex CAPPA

Mots clés :   Suies, HAPs, nucléation, combustion, diagnostics laser

Responsables et coordonnées :

PC2A : Xavier Mercier                       xavier.mercier@univ-lille.fr                Tel: 03 20 43 48 04

ONERA : Cornelia Irimiea                 cornelia.irimiea@onera.fr                                 Tel: 01 80 38 60 19

Financement envisagé :  ONERA / CNES

 

Etude de l’impact des alcools sur l’oxydation des essences dans les conditions de flammes produisant des suies

De nombreuses projections montrent que la part des véhicules électriques va poursuivre sa croissance dans les prochaines années. Néanmoins, le moteur à allumage commandé représentera encore au moins 50 % des véhicules légers, tandis que la part de moteur Diesel va diminuer, surtout en raison des émissions de suies. Le moteur à allumage commandé à injection directe (ID), caractérisé par une économie substantielle du carburant, va devenir le moteur piston le plus utilisé, avec l’augmentation de l’hybridation. Cependant, ces moteurs souffrent, comme le moteur Diesel mais à un degré moindre, de la problématique de formation des particules de suies. L’une des solutions envisagée est l’enrichissement significatif des essences en composés oxygénés en particulier l’éthanol. La substitution de la composante aromatique des essences par ces molécules oxygénées devrait en effet réduire considérablement la teneur des HAPs formés, responsables directs, de la formation des suies. Cette substitution peut, en revanche, activer d’autres émissions nocives notamment certains aldéhydes qui feront l’objet d’une réglementation dans la future norme Euro 7.

L’objet de ce projet est l’étude de la structure chimique des flammes des essences en présence d’un alcool. Des dispositifs analytiques et optiques, performants et hautement sensibles, seront mis en œuvre pour mettre en évidence l’impact de la structure de l’alcool et sa proportion dans le mélange réactif. Pour ce faire, une substitution de la composante aromatique sera réalisée à différentes proportions d’éthanol ou du butanol dans un surrogate de référence. Celui-ci comprendra un alcane supérieur linéaire (et éventuellement un second ramifié) et un composé aromatique mono-alkyl.

L’analyse de la phase gazeuse consistera à générer des données quantitatives sur des espèces clés en particulier les espèces aliphatiques et aromatiques considérées comme des précurseurs des particules de suies. L’analyse de la phase particulaire permettra de dresser les profils de fraction volumique des suies et la distribution en taille. L’ensemble de ces données expérimentales sera complété par l’analyse des aldéhydes dont la formation constitue une problématique majeure dans le cas de l’oxydation d’un fuel oxygéné.

Un travail de modélisation conséquent sera également réalisé à l’aide des Packages Chemkin et Cantera. L’objectif étant de s’appuyer sur les données précédentes afin d’étendre la validité de nos mécanismes cinétiques antérieurs dédiés à la description de l’oxydation d’hydrocarbures dans les conditions de flamme produisant des suies. Ce travail nécessitera notamment l’évaluation des données thermocinétiques pour des espèces pertinentes, en particulier les hydrocarbures aromatiques polycycliques.

 

Programmes de recherche en lien avec le sujet : CPER Climibio / Labex CAPPA

Mots clés :   HAPs, Suies, Essences oxygénées, techniques laser, Chromatographie, Flammes

Responsables et coordonnées :

Abderrahman El Bakali        abderrahman.el-bakali@univ-lille.fr               Tel: 03 20 43 48 04

Luc-Sy TRAN                      Luc-Sy.Tran@univ-lille.fr                             Tel 03 20 43 49 78

Financement envisagé :  ANR ou ULille

 

Theoretical study of the atmospheric reactivity of iodinated compounds

Chemical reactions associated with atmospheric iodine have attracted increasing attention of experimentalists and theoreticians in recent years. The role of iodine in tropospheric chemistry has been documented in a number of papers over the last four decades, showing that both inorganic and organic species are emitted from the Marine Boundary Layer (MBL). While inorganic emissions of HOI and I2 account for the main source of iodine in the MBL, organic compounds include methyl, ethyl, and propyl iodide (CH3I, C2H5I, C3H7I) together with diiodomethane (CH2I2). Among them, CH3I is viewed as the dominant species with the highest mixing ratio and longest atmospheric lifetime. Rate coefficient data for reaction of OH with iodoalkanes have been experimentally determined for a series of alkyl iodides (CH3I, C2H5I, 1-C3H7I, and 2-C3H7I) as well as for CH2I2. Following their emission in the atmosphere, inorganic and organic iodine will be subject to photolysis under UV−visible light and quickly release I atoms, which play an active role in ozone destruction.

Gas-phase chemistry of iodine containing species is complex and studying its reactivity is challenging. The goal of this thesis is to improve the understanding of the homogeneous reactivity of iodine-containing species with major atmospheric photo-oxidants using theoretical approaches. This work is associated with the activities, which are already supported by the PIA Labex CaPPA (Chemical and Physical Properties of the Atmosphere, ANR-11-LABX-0005-01) in the work package 6 entitled "Hazard: dispersion, reactivity, deposition of radionuclides".

Theoretical chemistry is increasingly used to determine rate constants for elementary reactions in the gas phase. In fact, the power of the actual computers allows now to obtain quantitative kinetic parameters within chemical accuracy (± 4.18 kJ mol-1). Quantum chemistry permits to understand the mechanism of the global reaction and of the different elementary pathways. It also allows to compute the molecular properties (molecular mass, vibrational frequencies, inertia moments) for the reactants, products, transition states, and molecular complexes in the ground and excited states. Then, the macroscopic properties such as the thermodynamical functions (internal energy, enthalpy, entropy, and Gibbs free energy) are computed from molecular properties using statistical thermodynamics. Finally, temperature and pressure (fall-off behaviour and high-pressure limit) dependencies of rate constants are estimated with kinetic theories (such as the Transition State Theory (TST) or Rice-Ramsperger-Kassel-Marcus (RRKM) theory) using with the previously determined thermodynamical functions. This computational procedure has been already used at the PC2A laboratory for reactions involving iodinated compounds

 

Programmes de recherche en lien avec le sujet : Labex CAPPA

Mots clés :   Iodine, atmosphere, molecular simulations

Responsables et coordonnées :

Florent Louis                       florent.louis@univ-lille.fr                    Tel : 03 20 33 63 32

Financement envisagé :  Bourse Conacyt (Mexique)

 

Unravelling the atmospheric iodine chemistry using molecular simulations in case of nuclear accident of a nuclear facility

The goal is to improve the understanding of the heterogeneous reactivity between gaseous iodinated species and aerosols present in the troposphere. To date, these heterogeneous interactions have not been considered in the atmospheric iodine dispersion models in case of a severe nuclear power plant accident. This is worrisome since such heterogeneous reactivity may play a major role in the iodine transport far from their emission sources. The importance of iodine in atmospheric chemistry has been highlighted by recent reviews. However, the atmospheric iodine heterogeneous reactivity studies have focused almost exclusively on determining the uptake coefficient of inorganic iodinated compounds (for example, I2, HI, and HOI) by water or ice. Those conditions are not fully relevant for our applications and have to be extended. Furthermore, photo-oxidation of gaseous CH3I and I2 in presence of O3 is known to produce IxOy aerosols, which are measured in the field campaigns. To the best of our knowledge, the influence of aerosols on the iodine photolysis processes in gas phase is not documented. Finally, the field measurements in Arctic and Antarctica pointed out the role of the low temperature in iodine chemistry in gas phase and in the formation of iodine-rich aerosols.

As a result, this thesis will provide a set of reliable kinetic and mechanistic data on iodine (photo)reactivity with atmospheric aerosols in order to improve the relevance and accuracy of iodine chemistry in dispersion models. The work will be based on molecular simulations; systems associating both the main iodinated gaseous species and representative atmospheric aerosols will be carefully selected.

Both molecular iodine (I2) and iodomethane (CH3I) are key iodine compounds of marine and biogenic origin that appears to be of central importance in understanding iodine chemistry in the troposphere. Further, in addition to their atmospheric interest, the reactivity of those compounds has gained much interest in the field of nuclear safety as they are the most probable gaseous iodine species to be released to the troposphere during a severe nuclear power plant accident of the type in Fukushima, Japan. As a result, this work will start on gaseous molecular iodine and iodomethane surface reactivity as a function of key inorganic and organic aerosols classes from the nanometric up to micrometric size. Model primary and secondary aerosols from marine origin will be considered, such as sodium chloride, sulphate, nitrate, and low to high oxidized organic aerosols.

 

Programmes de recherche en lien avec le sujet : Labex CAPPA

Mots clés :   Iodine, aerosols, atmosphere, nuclear power plant, molecular simulations

Responsables et coordonnées :

PC2A :                   Florent Louis                       florent.louis@univ-lille.fr                    Tel : 03 20 33 63 32

PhLAM                 Céline Toubin                      celine.toubin@univ-lille.fr                  Tel : 03 20 43 43 80

Financement envisagé :  AAP I-SITE Sustain 2018 / Labex CaPPA (IRSN + PC2A + PhLAM)

 

 

 

Post-docs

Optimization of multi-line laser induced fluorescence (LIF) thermometry technique for application in different flames

Context

Laser induced fluorescence (LIF) is a laser diagnostic allowing in situ measurements of flame temperature. The technique relies on the excitation of several rovibronic transitions of a fluorescent molecule using a tunable laser source and to the subsequent collection of the fluorescence signal. Among the species used for thermometry, NO is a good candidate because this molecule can be seeded as a tracer in the reactive mixture, allowing the measurement of the complete temperature profile from the burner surface to the burnt gases. NO LIF thermometry was shown to be well suited for stationary flames from low pressure to high pressure and from non sooting to sooting flames.

Several procedures were proposed in the literature aiming to improve the accuracy of multi-line LIF thermometry while reducing the duration of the spectral scan. However we observed* in different investigations that we performed at PC2A that this accuracy is very dependent on the selected spectral range and that this spectral range needs to be adjusted according to the kind of flames.

* Lamoureux et al. Combust. Flame 157(2010)1929 ; Bejaoui et al. Appl. Phys. B118 (2015)449; El Bakali et al. Fuel 211 (2018)548

 

Objectives

The objective of the postdoctoral position is to perform a thorough investigation of the performances of the NO LIF thermometry in order to tend towards a universal procedure that could be applied in a large range of combustion conditions. The postdoctoral researcher will have an already complete operating LIF thermometry set-up composed by a frequency-doubled Nd:YAG-seeded laser pumping a dye laser, an imaging spectrometer, a camera ICCD, a fast oscilloscope and a PMT. The experiment and data acquisition is driven through Labview program. Several burners and flame conditions will be available. Signal post-treatment and spectral simulation tools will be applied. The optimization of the experimental procedure will rely partly on the achievement of the best fit between the experimental excitation LIF spectrum and a library of simulated spectra calculated on a large range of temperatures.

The postdoctoral researcher will be supported by the laser diagnostics team. However he/she will take part in the combustion team, involved in various chemical flame structure studies. The temperature profiles being crucial data for flame modelling, the postdoctoral researcher will be associated in several projects in parallel.

 

Essential Education and Research Skills

Following is a list of skills being desired. 

  • Ph.D. degree in Chemical or Mechanical Engineering.
  • Experience in tunable laser metrology is required
  • Basic knowledge of LIF, laser absorption, spectral simulation
  • Working experience with photomultiplier tube, image intensifier ICCD camera, spectrometers
  • Data post processing techniques will be considered an asset.
  • Fluent english is required

 

Position details: This work is supported by CPER CLIMIBIO (http://climibio.univ-lille.fr/). Month salary depends on candidate experience. Duration: 12 months. Possibility of extension. Starting from March 2019.

 

Contact Person

Please send your application to Pascale Desgroux (pascale.desgroux@univ-lille.fr) and Nathalie Lamoureux (nathalie.lamoureux@univ-lille.fr) including a cover letter, CV, two references and publication list.

 

Metrology and kinetic studies of HOx radicals for atmospheric applications

 

Context:

This post-doctoral position is proposed in the frame of the CPER CLIMIBIO project and will focus on the understanding of the gas phase chemical oxidation processes taking place in the atmosphere through a twofold approach: experiments in laboratory to study kinetics of reactions involving the radicals OH, HO2 and RO2 and field deployment to quantify these radicals as well as the OH reactivity in the atmosphere. The experiments will be carried out with a FAGE instrument developed in our laboratory and under improvement to be able to measure simultaneously all these parameters.

Post-doc tasks:

For the kinetic studies, the recruited post-doc will have to carry out measurements on reactions of interest with the FAGE instrument in the reactivity mode, under controlled and variable conditions to study the influence of parameters such as the humidity and pressure on rate constants.

For the quantification studies, the recruited post-doc will have in charge to optimize the conditions of use of the instrument for field deployment and in particular for RO2 quantification. A participation to a field campaign in July 2019 is probable.

Profile:

The applicant should hold a PhD in the field of atmospheric chemistry and experimental development. Knowledge in optical spectroscopy (in particular Laser Induced Fluorescence), with experimental skills in the kinetic studies will be appreciated. The research involves improving and using a FAGE instrument set-up as well as data collection and analysis. Skills in data analysis and computer programming (LabView or equivalent) will be also appreciated.

 

Funding: This post-doctoral position is proposed in the frame of a regional project (CPER CLIMIBIO) involving 16 laboratories on the understanding of the climate change and its impact. Month salary depends on candidate experience.

Duration: 12 months.

Starting date: February 2019

Working place: University of Lille- Sciences and Technologies

PC2A laboratory- UMR CNRS 8522

To apply: send by e-mail to the contacts a detailed CV, including the list of publications, a covering letter detailing your motivation for the position and your expertise in regard of the profile, 2 reference letters and a list of people to contact for complementary references

Contacts:

Coralie Schoemaecker: coralie.schoemaecker@univ-lille.fr

Christa Fittschen: christa.fittschen@univ-lille.fr

PC2A laboratory- PhysicoChimie des Processus de Combustion et de l'Atmosphère