Post-Doctorat et Contrat de recherche

Harsh CHALIYAWALA

Supervisors: Alessandro Faccinetto, Eric Therssen, Xavier Mercier

Duration and starting date: 18 months

Funding: ANR

L’objet du projet ANR INTERSTELLAR (StudyINg ThE photophysics of laRge aSTrophysical hydrocarbon molEcuLar systems using LAboRatory analogues) est d’explorer les similitudes entre les espèces formées dans les milieux interstellaires (ISM) et les flammes génératrices d’espèces carbonées comme les hydrocarbures aromatiques polycycliques (HAPs), les fullerènes et les nanoparticules carbonées, qui seraient susceptibles de jouer un rôle clé dans des phénomènes comme les bandes infrarouges aromatiques (AIBs) et d'autres signatures spectrales spécifiques de l'ISM.

Ce projet vise plus particulièrement à caractériser ces molécules de grande taille similaires à celles de l'ISM et leurs propriétés photophysiques, en utilisant des flammes de laboratoire originales comme sources d'analogues de ces grandes molécules interstellaires et de relier cela aux observations astrophysiques. Pour ce faire, il est prévu de combiner un ensemble de dispositifs expérimentaux de pointe reposant sur des diagnostics lasers in situ et des mesures en ligne dont les résultats seront exploités via des études théoriques.

Ces travaux seront menés en collaboration avec l’Institut des Sciences Moléculaires d'Orsay (ISMO) et le laboratoire Physique des Lasers, Atomes et Molécules (PhLAM) de l’Université de Lille dans un cadre scientifique clairement interdisciplinaire mettant en commun des compétences techniques et équipements de recherche de haut niveau issus des trois laboratoires impliqués dans ce projet, et reconnus internationalement chacun dans leur domaine d’expertise.

Il s’agira essentiellement de caractériser dans des flammes basses stabilisées à basse pression, des espèces potentiellement similaires à celles de l’ISM, au moyen de techniques laser de pointe telles que la fluorescence induite par laser (LIF) et l’incandescence induite par laser (LII) et de méthodes en ligne telles que la spectrométrie de masse (TOFSIMS) ou des dispositifs de type Scanning Mobilty Particle Sizer (SMPS). Des travaux théoriques menés en collaboration avec le laboratoire ISMO viendront compléter ce projet pour aider à l’interprétation des caractéristiques d'émission de la diversité des espèces formées.

Zainab SROUR

Supervisors: Florent LOUIS, Sonia TAAMALLI

Duration and starting date: 18 months

Funding: IRSN

During an accident in a nuclear facility involving a loss of containment, the radionuclides resulting from the fission of the fuel will be released into the environment in variable quantities depending on their volatility and the scenario. The development of tools for predicting the behavior of radionuclides once in the environment allows (i) to predict the environmental and health consequences and thus to be able to propose the implementation of countermeasures (evacuation, prophylaxis), (ii) to help implement interventions to manage the accident and post-accident situation, (iii) or even, according to Fukushima Daichi's experience feedback, to validate (by inverse method) the evaluations of reactor source terms when knowledge of the course of the accident situation is only fragmentary.

During the Fukushima Daichi accident, IRSN carried out release assessments and environmental dispersion simulations. _Comparisons between simulations of iodine deposition with the C3X platform (short-range pX module and large-scale ldX module) and in-situ measurements have highlighted significant differences for iodine, while conversely the predictions for cesium appeared to be satisfactory. The analyzes of these differences have led to the proposal of avenues for research and in particular the need to consider, in dispersion simulation tools, the physico-chemical reactivity of iodine in the atmosphere, a phenomenon which could partly explain these disagreements.

The modeling of the reactivity in the gaseous phase with the chemistry-transport code CTM (Chemistry Transport-Model) leads to the formation of organo-iodine compounds whose decomposition kinetics are not known. Part of Figueiredo's thesis at IRSN (2017-2021) consisted in studying this decomposition by theoretical chemistry, in particular that of four organo-iodine compounds from four distinct chemical families (c-C₃H₅IO, CH₂ICH₂OH, CH₂ICH(O) and CH₂ICOOH) by reaction with the HO radical. The first reaction paths of decomposition of these four compounds have been determined (thermodynamics, transition state and activation energy). Nevertheless, the kinetic constants of the decomposition reactions of these four organo-iodine compounds remain to be determined through this post-doctoral position in order to include them in the CTM code developed during two previous PhDs (Trincal, 2015 and Fortin, 2019). The second objective of this work is to develop a reaction mechanism to describe the chemical reactivity of the other halogens (Br and Cl) and the interactions between halogens that can influence the behavior of iodine. Bromine and chlorine belong as iodine to the family of halogens and thus are expected to have relatively similar properties. Their behavior in the atmosphere can therefore be quite similar and could influence or modify that of iodine. This influence could be significant for seaside sites due to the presence of chlorine and bromine in greater quantities than inland. After improving the reaction mechanism in the gaseous phase (by adding the decomposition kinetics of organo-iodine compounds and by integrating the so-called "box-model" to describe the chemical reactivity of halogens Br and Cl), a study will be conducted to assess the influence of these models on the speciation of iodine in the environment and thus update the knowledge developed during the theses of Trincal and Fortin.

References

[1].      PhD of Julien Trincal « Modélisation du comportement de l’iode dans l’atmosphère », 2015

[2].      PhD of Camille Fortin « Etudes par simulations numériques et moléculaires de la réactivité atmosphérique de l'iode », 2019

[3].      PhD of Alexandre Figueiredo « Etudes cinétiques de la photolyse hétérogène de l'iode moléculaire et modélisation de l'hydroxylation radicalaire en phase gazeuse d'iodures organiques oxygénés », 2021

[4].      PhD of Hanaa Houjeij « Etude expérimentale des réactions de capture/désorption des iodes gazeux (I₂, CH3I) sur des aérosols environnementaux », 2020

Keywords: halogens, atmospheric chemistry, molecular simulations, modelling

Perla TRAD

Supervisors: Guillaume VANHOVE, Laure PILLIER

Duration and starting date: 13 months

Funding: CPER ECRIN (https://ecrin.cper-hautsdefrance.fr/)

Combustion-driven processes are still responsible for a large proportion of energy production and conversion worldwide. Thus major reductions in pollutant emissions and improvements in fuel efficiency should be sought, and can be reached by means of fuel-lean mixtures of renewable fuels. Controlled initiation of the combustion is however a crucial step towards widespread application of such conditions, with wide ranges of application including piston engines, constant volume combustors, gas turbines and aeronautic engines. However, fuel ignition is highly dependent on the chemical kinetics associated with Low Temperature Combustion (LTC) [1].

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 a strong incentive towards the development of predictive models which must be validated with reliable data in this temperature regime and under rarely investigated fuel-lean conditions.

To this end, a burner dedicated to the study of stabilized cool flames has recently been designed and validated in PC2A [2-4]. The potential to perform detailed kinetic studies through a number of optical and analytical diagnostics, including Planar Laser Induced Fluorescence (PLIF), chemiluminescence, thermometry and gas chromatographic techniques, has been demonstrated. Moreover, the potential of Particle Imaging Velocimetry (PIV) techniques for the determination of cool flame propagation velocities has been established. This paves the way towards exciting upcoming experimental campaigns, which are planned in 2024 and to which the candidate will participate:

1- Among them, the panel of diagnostics associated to the burner will be extended to VUV photoionization mass spectrometry/PhotoElectron PhotoIonization Mass Spectrometry, in collaboration with the DESIRS beamline of Synchrotron SOLEIL, allowing the selective detection and quantification of elusive products, such as the hydroperoxides responsible for radical-chain branching.

2- Further development of the PIV technique towards determination of cool flame burning velocities for new fuels will be achieved in collaboration with CORIA and LMFL laboratories.

References

[1] S. S. Goldsborough, S. Hochgreb, G. Vanhove, M. S. Wooldridge, H. J. Curran, C. J. Sung, Advances in rapid compression machine studies of low- and intermediate-temperature autoignition phenomena. Prog. Energy Combust. Sci. 2017, 63, 1-78.

[2] T. Panaget, K. Potier, S. Batut, A. Lahccen, Y. Fenard, L. Pillier, G. Vanhove, How ozone affects the product distribution inside cool flames of diethyl ether, Proceedings of the Combustion Institute 39 (2023) 325-333.

[3] K. De Ras, T. Panaget, Y. Fenard, J. Aerssens, L. Pillier, J. W. Thybaut, G. Vanhove, K. M. Van Geem, An experimental and kinetic modelling study on the low-temperature oxidation of oxymethylene ether-2 (OME-2) by means of stabilized cool flames, Combustion and Flame 253 (2023) 112792.

[4] T. Panaget, N. Mokrani, S. Batut, A. Lahccen, Y. Fenard, L. Pillier and G. Vanhove, Insight into Ozone-Assisted Low-Temperature Combustion of Dimethyl Ether by Means of Stabilized Cool Flames, J. Phys. Chem. A 125 (2021) 9167−9179.

Keywords: Low Temperature Combustion, Kinetics, Pollutant reduction, bio- and e-fuels, optical and analytical diagnostics.

Academic Requirements: A PhD degree in the fields of Combustion Chemistry and/or Laser diagnostic techniques and a strong aspiration to perform experimental work are required.

Tirthankar MITRA

Supervisors: Pascale Desgroux, Nathalie Lamoureux,

Duration: 24 months, from March 2023

Funding: 100% PEPR MONTHY.

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In 2021, the French government launched a broad investment plan “France 2030”, in connection with the ecological transition. This plan aims to decarbonize French industry in order to reduce greenhouse gas emissions by 35% by 2030.  Hydrogen combustion is a promising energy source to reach the carbon neutrality in many applications, including transport, industrial processes and energy conversion. In particular, the French acceleration strategy on decarbonized hydrogen is supported by the Priority Research Program and Equipment (Programme et Equipements Prioritaires de Recherche) PEPR-H2 of the plan “France 2030”.

The MONTHY project is funded by PEPR-H2 for a period of 4 years. This project brings together three French laboratories internationally recognized for their research in combustion (CORIA, EM2C, PC2A) and allows the recruitment of several PhD and postdocs on fundamental research on H₂ combustion.

The objectives of MONTHY project are to understand through a joined experimental and numerical analysis the nitrogen oxides formation in an environment representative of future hydrogen-air industrial combustion chambers. Results will lead to the first understanding and modeling of the impacts of H₂ fuel dilution by H₂O on NOx production in a turbulent reactive flow.

PC2A laboratory is offering an 18-24 month postdoc position, mainly experimental, on topics related to NO formation in laminar premixed H₂/O₂/N₂ flames. Although the kinetic pathways responsible for the NO formation in hydrogen flames are known: thermal-NO at high temperature and NNH and N₂O pathways occurring at intermediate temperature, the latter two pathways are affected by large uncertainties while having  a large contribution in turbulent flames. Thus, there is a crucial need to validate a detailed kinetic model for NO formation in a wide range of hydrogen flames.

By implementing an original experimental strategy based on advanced laser diagnostics to quantitatively detect radicals and atoms in hydrogen flames and on an optimal selection of flames allowing to emphasize one NO pathway over the others, the objective of this postdoc position is to contribute to the elucidation of the NOx formation pathways in hydrogen flames. The experimental work will  consist in acquiring a unique experimental quantitative database of NO formation in laminar H2-air flames using in-situ advanced laser diagnostics (laser-induced fluorescence (LIF) and cavity ring-down spectroscopy (CRDS)) and probe sampling techniques (FTIR), detecting challenging trace species like NH and HNO to clarify the NNH-route of NO formation, and  finally assess the consistency of H₂O dilution as a primary NOx reduction strategy for H₂-air flames. LIF and CRDS techniques are already well mastered in the PC2A laboratory (https://pro.univ-lille.fr/nathalie-lamoureux/publications/#descr) but never applied in H₂/O₂/N₂ premixed flames. Depending on the candidate profile, he/she can be involved in the kinetic simulation work to identify the formation pathways of NOx and N₂O emissions.

Keywords: Combustion, Chemical kinetic, NOx emissions, Laser-based spectroscopic diagnostics

Academic requirements: PhD in the field of chemistry, chemistry-physics, and a strong aspiration to perform experimental work are required. Knowledge in the field of combustion chemistry and laser techniques are appreciated.

Laboratory: PC2A https://pc2a.univ-lille.fr/

Contact e-mail: pascale.desgroux[chez]univ-lille[point].fr,  nathalie.lamoureux[chez]univ-lille[point].fr,