Blanc SIMI 9 - Blanc - SIMI 9 - Sciences de l'ingéniérie, matériaux, procédés, énergie

Effets cinétiques et hydrodynamiques dans les interactions plasma-flamme – PLASMAFLAME


Effets cinétiques et hydrodynamiques dans les interactions plasma - flamme

Enjeux et objectif

The vision behind this project is to provide a novel method to control combustion in internal combustion engines, especially finding new ways to control ignition delays, speed of flame propagation, combustion efficiency, and to reduce pollutant production. Over the past decade, many experiments have demonstrated that plasma discharges can significantly enhance combustion processes, and it is important to note that these effects can be obtained with plasma powers that are much lower than the power released by the flame, thus making the process of plasma-assisted combustion a highly realistic candidate for improving combustion strategies. However, two questions must still be considered. First, what is the effect of the active species (radicals, electronically excited species, …) created by the plasma on the flame kinetics. Indeed, most combustion mechanisms have not been validated for the high levels of radicals, mainly O atoms, produced by the discharge. Furthermore the effect of these active species might be especially important in the low and intermediate temperature regimes that precede autognition, and in where kinetic mechanisms of combustion are very complex. Second, what is the effect of hydrodynamic interactions between the active species created inside the discharge and the overall fuel/air flowfield.<br />Therefore, the overall scientific objective of the project is to provide a clear understanding of these two main modes of interaction of the plasma discharge with the flame, namely via kinetic mechanisms and hydrodynamic transport of active species.

The Project PLASMAFLAME focuses on a comprehensive fundamental experimental and numerical study of the influence of low temperature nonequilibrium plasma on combustion process. Ignition and combustion, which are sustained by nonequilibrium plasma, are caused by the interaction of a number of physical and chemical phenomena. To give an adequate physical description of plasma-assisted ignition/combustion it is necessary to combine detailed fundamental knowledge in gas discharge physics, hydrodynamics, and chemical kinetics. Targeted experiments to obtain quantitative data on active species produced by a discharge, on ignition delay times and to gain a profound understanding of the role of hydrodynamics in plasma-flame interaction combined with detailed numerical modeling are proposed. Experiments will be carried out at relatively low initial temperatures (about 1000 K) and high pressures (5-40 bars) combining pulsed nanosecond plasma reactors with rapid compression machines. The discharge impact and combustion process will be subdivided in time, the total duration of the discharge will be a few orders of magnitude less than the typical ignition delay time; in situ measurements in nanosecond and millisecond time scales will be conducted with high spatial and temporal resolution. Chemical kinetics of discharge and combustion initiated/sustained by plasma will be analyzed in detail. The numerical codes to describe plasma assisted ignition and plasma-flame hydrodynamics interaction under low temperatures and high pressures will be developed. Finally, the results obtained will culminate in practical testing in a real automotive engine facility to assess the impact of the advances obtained in the project.

- LPP: System of high-voltage electrodes for rapid compression machine has been developed and successfully tested; ANDOR spectrometer available in the laboratory has been repaired and used for the experiments to measure the electric field in a surface nanosecond dielectric barrier discharge (SDBD) in non-combustible gases;
- EM2C: System of high-voltage electrodes for application of NRP discharges is being setup in a fixed volume combustion chamber. The Schlieren system has been developed and implemented. Spectroscopic equipment and laser imaging are also in place.
- PC2A: First tests on the rapid compression machine with combustible mixtures (CH4 and C4H10 as combustible components) with oxygen or air diluted with nitrogen or argon has been performed. The RCM has been prepared for the experiments on plasma-assisted ignition. The preliminary experiments to verify the regimes available both for autoignition and for plasma assisted ignition have been carried out;
- PPRIME: a first meeting between EM2C and PPRIME has been organized on the 20th of April 2012 in Poitiers. The characteristics of the experimental setup that will be used in PPRIME to study plasma in non-reactive conditions have been defined.
- IFPEN: Experiments will be performed in the 4th year of the project on a single cylinder internal combustion engine with optical access. Various laser diagnostic techniques will be employed in order to evaluate the influence of the NRP device on engine combustion characteristics. A dedicated project team (project leader, engineer and technician) will be assigned to this experimental study.

The improved understanding of the principles of ignition and combustion control by nonequilibrium plasma will help develop high pressure plasma research in France, potentially enabling a wide variety of applications such as ignition and flame stabilization in fast flow reactors, flame control under conditions of lean combustible mixtures, initiation of ignition in the operating conditions of homogeneous charge compression ignition engines and so on. By maintaining regular participant meetings, by students, researchers and PIs participation in French and international scientific conferences, and by publishing the results in well-recognized scientific journals, the obtained results will be rapidly disseminated to the scientific community on a world-wide scale.

Kick-off meeting for the Project PLASMAFLAME has been organized in Palaiseau, Ecole Polytechnique, by Laboratory for Plasma Physics (LPP), on 14 of March 2012.
PhD student (Mohamed Amine BOUMEDHI), starts from September 2012. He has been already participated in his first training on Rapid Compression Machine (RCM) and high-voltage nanosecond surface dielectric barrier discharge (SDBD) and has been taken part in the first series of experiments in combined RCM-SDBD reactor in PC2A in Lille in July 2012.
- EM2C: Schlieren experiments have started in quiescent air mixtures, showing the gas heating zone and associated shock waves, under the influence of a Nanosecond Repetitively Pulsed (NRP) discharge. The simulations tools are also being developed for the simulations of plasma/flow interactions.
- PPRIME: A grant for a Ph D student has been obtained. The selected Ph D student (Allassane SEYDOU MOUMOUNI) will start his research work in October 2012.

La compréhension des processus d’inflammation de combustibles demeure une question fondamentale et pratique de la recherche en combustion. Bien que le principe de l’allumage par étincelle ou de l’autoallumage soit couramment utilisé dans l’industrie automobile, l’utilisation de décharges par plasma peut être très bénéfique, notamment dans le cas de mélanges pauvres ou dilués, ou encore d’écoulements à grande vitesse de mélanges combustible/air basse pression (par ex. écoulements supersoniques).

Le projet PLASMAFLAME est dédié à l’étude fondamentale, expérimentale et numérique, de l’effet d’un plasma hors-équilibre basse-température sur les processus de combustion. L’incidence d’un plasma hors-équilibre sur l’inflammation et la propagation de flamme est due à l’interaction de phénomènes physico-chimiques complexes. La description détaillée des processus de combustion assistée par plasma nécessite des connaissances approfondies en physique des décharges plasma, hydrodynamique et cinétique chimique. Le projet s’appuie sur la mise en place d’expériences dédiées à l’obtention de données quantitatives sur les concentrations espèces actives produites par la décharge et sur les délais d’inflammation et à la compréhension de l’impact de l’hydrodynamique sur l’interaction flamme/plasma, en s’appuyant notamment sur des simulations numériques détaillées. Les expériences seront réalisées dans des réacteurs de décharge plasma nanoseconde et des machines à compression rapide permettant de couvrir un domaine de « basse » température (max de l’ordre de 1000K) et de haute pression (5-40 bars). L’analyse de la décharge et de la combustion sera résolue en temps ; la durée totale de la décharge est de plusieurs ordres de grandeur plus courte que le délai d’inflammation. Les mesures seront réalisées in situ avec une haute résolution spatiale et temporelle (échelle de temps de la ns à la ms). La cinétique chimique de la décharge et de l’inflammation assistée par plasma sera analysée en détail. Des codes numériques décrivant l’inflammation assistée par décharge et l’interaction hydrodynamique plasma/flamme dans un domaine basse température/haute pression seront développés. Enfin, l’ultime finalité du projet concernera la mise en place du processus de décharge-plasma dans un moteur réel, en vue de l’étude de son impact sur la combustion.

En plus de son ambition scientifique fondamentale, l’impact du projet proposé devrait être important dans d’autres domaines. En particulier, la meilleure connaissance des principes de l’inflammation et de la combustion assistée par plasma seront bénéfiques pour promouvoir la recherche sur les plasmas haute pression en France, ouvrant ainsi un large éventail d’applications comme l’inflammation et la stabilisation de flamme dans des réacteurs à écoulement, le contrôle de la combustion en régime pauvre, l’autoinflammation dans les moteurs HCCI (Homogeneous Charge Compression Ignition) etc. La dissémination des résultats à l’échelle internationale sera garantie par une participation active des partenaires du projet (chercheurs, doctorants etc) à des congrès nationaux et internationaux.

Coordinateur du projet


L'auteur de ce résumé est le coordinateur du projet, qui est responsable du contenu de ce résumé. L'ANR décline par conséquent toute responsabilité quant à son contenu.



Aide de l'ANR 749 999 euros
Début et durée du projet scientifique : novembre 2012 - 48 Mois

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