The effect of EGR on HCCI combustion – impact of diluting, thermal and chemical aspects: experimental and numerical approaches

peer reviewe

DBD PLASMA CATALYSIS PROCESS FOR CARBON RECOVERY

Since many years carbon dioxide reduction by hydrogen through catalyst processes is a usual way from the Paul Sabatier reaction to produce CH4. this process is able to be done from thermal process by using an heterogeneous catalyst such as zirconia cerium support with nickel sites for the hydrogen reduction of CO2 .However this reaction is well working ( 85%-90%) at 350?c and its selectivity depends of the secondary reactions such us carbon monoxide or carbon deposit which appears above 350?C.199-19

Mise en place de l'extraction liquide-liquide en microsystèmes établir des écoulements segmentés à façon pour optimiser le transfert de masse

National audienceLiquid-liquid extraction is commonly used for radiochemical analysis. When miniaturized, it can benefitfrom the advantages of microfluidic tools i.e. possible coupling, precise control of the interfacial areabetween the aqueous and organic phases, and contact time. A first study, dedicated to liquid-liquidextraction with parallel flows of europium diluted in nitric acid by the N,N′-dimethyl-N,N′-dibutyltetradecylmalonic diamide [1, 2], allowed us to highlight the limitations of parallel flows for aslow chemical system. One way to optimize yields of extraction of the kinetically slow systems is toincrease the specific interfacial area. For this reason, segmented flows formation and characteristicswere investigated, as a function of the physicochemical properties of a biphasic system, flow rates andthe dimensions of a focalized flux junction. In the following, two multiphase models of the droplets sizecorresponding to the transition and dripping regimes were validated and will be used for theoptimization of the specific interfacial area.L’extraction liquide-liquide est couramment utilisée pour les analyses radiochimiques. Miniaturisée,elle peut bénéficier des avantages des outils microfluidiques qui sont la possibilité de réaliser descouplages, le contrôle précis de l’aire interfaciale entre les phases aqueuse et organique en présence,et des temps de contact. Une première étude, dédiée à l’extraction liquide-liquide en flux parallèlesd’europium en milieu nitrique par le N,N’-dimethyl N,N’-dibutyl tetradecylmalonamide [1, 2], a permisde mettre en évidence les limitations des flux parallèles pour un système chimique lent. Une façond’optimiser les rendements d’extraction des systèmes cinétiquement lents est de mettre en œuvre desécoulements permettant d’augmenter l’aire interfaciale spécifique. C’est pourquoi nous étudions laformation d’écoulements segmentés à façon en fonction des propriétés physico-chimiques d’un systèmechimique biphasique, des débits et des dimensions d’une jonction en flux focalisé. L’utilisation de deuxmodèles de calcul des tailles de gouttes en régimes d’écoulements transitoire

on the Minimax Theorem and the Solution of Finite Games.

The purpose of this thesis is to present three proofs of the minimax theorem and some theorems on the solution of finite games. The treatment is more detailed than in the original references. The necessary theory of convex sets and the basic concepts of the theory of games are introduced in the first two chapters of the thesis

HCCI engine modeling and experimental investigations - Part 1: The reduction, composition and validation of a n-heptane/iso-octane mechanism

A certain possible approach for the control of HCCI chemistry is to use kinetic chemistry mechanisms. This opens a field of interest that lead to the composition of a validated reduced PRF chemistry mechanism. For this purpose a skeletal chemical reaction mechanism for n-heptane and for iso-octane are constructed from a detailed n-heptane and iso-octane mechanism of the Chalmers University of Technology. Subsequently these two mechanisms are forged into one reduced chemical reaction mechanism for mixtures of n-heptane and isooctane (39 species and 47 reactions). This mechanism is numerically validated against the Chalmers mechanisms, respecting the HCCI application range. The reduced mechanism is also successfully numerically validated against another more detailed mechanism provided by LLNL. Engine experiments are performed validating this mixture mechanism with respect to the fuel composition containing n-heptane and iso-octane. The influence of the compression ratio and the equivalence ratio is also studied and used to validate the reduced PRF mechanism

DBD PLASMA CATALYSIS PROCESS FOR CARBON RECOVERY

199-199Since many years carbon dioxide reduction by hydrogen through catalyst processes is a usual way from the Paul Sabatier reaction to produce CH4. this process is able to be done from thermal process by using an heterogeneous catalyst such as zirconia cerium support with nickel sites for the hydrogen reduction of CO2 .However this reaction is well working ( 85%-90%) at 350?c and its selectivity depends of the secondary reactions such us carbon monoxide or carbon deposit which appears above 350?C

Reduced chemical reaction mechanisms: experimental and HCCI modelling investigations of autoignition processes of iso-octane in internal combustion engines

A semi-reduced (70 species, 210 reactions) and a skeletal (27 species, 29 reactions) chemical reaction mechanism for iso-octane are constructed from a semi-detailed iso-octane mechanism (84 species, 412 reactions) of the Chalmers University of Technology in Sweden. The construction of the reduced mechanisms is performed by using reduction methods such as the quasi-steady-state assumption and the partial equilibrium assumption. The obtained reduced iso-octane mechanisms show, at the mentioned conditions, a perfect coherence with another more detailed iso-octane mechanism of ENSIC-CNRS (2411 reactions and 473 species) and the semi-detailed iso-octane mechanism of Chalmers. The validity of this mechanism with regard to the ignition delay is determined for several engine parameters adhering to HCCI conditions: inlet temperature (303-363 K), equivalence ratio (0.2-0.7) and compression ratio (10-16). The ignition delay is found to be decreased by an increase in the inlet temperature, a decrease in the equivalence ratio and an increase in the compression ratio. In order to validate the effects of the inlet temperature, compression ratio on the auto-ignition delay, experiments are performed on a CFR engine. A good agreement is obtained between experimental results and calculations. (c) 2005 Elsevier Ltd. All rights reserved