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

peer reviewe

A parametric study on the emissions from an HCCI alternative combustion engine resulting from the auto-ignition of primary reference fuels

The homogeneous charge compression ignition is an alternative combustion technology that can reduce automobile pollution, provided that the exhaust emission can be controlled. A parametric study can be useful in order to gain more understanding in the emission reduction possibilities via this new combustion technology. For this purpose, the inlet temperature, the equivalence ratio and the compression ratio are changed, respectively, from 30 to 70 degrees C, 0.28 to 0.41 and 6 to 14. Also the diluting, thermal and chemical effects of exhaust gas recirculation were studied. The emission of CO, CO2, O-2 and hydrocarbons has been measured using primary reference fuels. It appears that an increase in the inlet temperature, the EGR temperature, the equivalence ratio and the compression ratio results into a decrease of the emissions of CO and the hydrocarbons of up to 75%. The emission of CO2 increased, however, by 50%. The chemical parameters showed more complicated effects, resulting into a decrease or increase of the emissions, depending on whether the overall reactivity increased or not. If the reactivity increased, generally, the emissions of CO and hydrocarbons increased, while that of CO2 increased. The increase of CO2 emissions could be compensated by altering the compression ratio and the EGR parameters, making it possible to control the emission of the HCCI engine. (c) 2008 Elsevier Ltd. All rights reserved

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

Las organizaciones de la economía social en la reforma del estado en Venezuela: caso del estado Zulia 1989-2000

A finales de la década de los 70 empieza a manifestarse en Venezuela la crisis del modelo de desarrollo, consistente en una grave situación económica, un gran déficit fiscal, problemas de gobernabilidad, así como elementos de fragmentación social, agudizados en la década de los 90 por los programas de estabilización económica. Por ello, desde 1984 se inicia el proceso de reforma del Estado, cuyos factores predominantes han sido la modernización política, la descentralización, la disminución del Estado social y los requerimientos de una mayor participación de la sociedad civil. Dentro del proceso de descentralización, iniciado en 1989, las gobernaciones promueven políticas de apoyo a las organizaciones de la economía social. El presente trabajo pretende caracterizar la política de la gobernación del estado Zulia dirigida a ese sector durante el periodo 1989-2000, a partir del enfoque de las políticas públicas, con una perspectiva crítico-descriptiva del proceso, por tratarse de una primera aproximación al objeto de estudio. Se construye un enfoque operativo sobre la definición de la economía social, su papel y su significación en los procesos de formulación económica y redefinición del Estado. Se avanza en la caracterización de las organizaciones estudiadas (microempresas, cooperativas y organizaciones no gubernamentales (ONGs), para luego puntualizar las estrategias políticas de los gobiernos. Se concluye, de manera parcial, en la descripción del proceso de formulación de políticas, donde ha predominado la visión utilitaria del sector, sin trascender los procesos organizativos reales que impulsen de manera significativa a estas organizaciones, para que impacten en la economía regional y nacional

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

LAS ORGANIZACIONES DE LA ECONOMÍA SOCIAL EN LA REFORMA DEL ESTADO EN VENEZUELA: CASO DEL ESTADO ZULIA 1989-2000

A finales de la década de los 70 empieza a manifestarse en Venezuela la crisis del modelo de desarrollo, consistente en una grave situación económica, un gran déficit fiscal, problemas de gobernabilidad, así como elementos de fragmentación social, agudizados en la década de los 90 por los programas de estabilización económica. Por ello, desde 1984 se inicia el proceso de reforma del Estado, cuyos factores predominantes han sido la modernización política, la descentralización, la disminución del Estado social y los requerimientos de una mayor participación de la sociedad civil. Dentro del proceso de descentralización, iniciado en 1989, las gobernaciones promueven políticas de apoyo a las organizaciones de la economía social. El presente trabajo pretende caracterizar la política de la gobernación del estado Zulia dirigida a ese sector durante el periodo 1989-2000, a partir del enfoque de las políticas públicas, con una perspectiva crítico-descriptiva del proceso, por tratarse de una primera aproximación al objeto de estudio. Se construye un enfoque operativo sobre la definición de la economía social, su papel y su significación en los procesos de formulación económica y redefinición del Estado. Se avanza en la caracterización de las organizaciones estudiadas (microempresas, cooperativas y organizaciones no gubernamentales (ONGs), para luego puntualizar las estrategias políticas de los gobiernos. Se concluye, de manera parcial, en la descripción del proceso de formulación de políticas, donde ha predominado la visión utilitaria del sector, sin trascender los procesos organizativos reales que impulsen de manera significativa a estas organizaciones, para que impacten en la economía regional y nacional

Efficacy of nano-hydroxyapatite prepared by an aqueous solution combustion technique in healing bone defects of goat

The present study was undertaken to evaluate porous hydroxyapatite (HAp), the powder of which was prepared by a novel aqueous solution combustion technique, as a bone substitute in healing bone defects in vivo, as assessed by radiologic and histopathologic methods, oxytetracycline labeling, and angiogenic features in Bengal goat. Bone defects were created in the diaphysis of the radius and either not filled (group I) or filled with a HAp strut (group II). The radiologic study in group II showed the presence of unabsorbed implants which acted as a scaffold for new bone growth across the defect, and the quality of healing of the bone defect was almost indistinguishable from the control group, in which the defect was more or less similar, although the newly formed bony tissue was more organized when HAp was used. Histologic methods showed complete normal ossification with development of Haversian canals and well-defined osteoblasts at the periphery in group II, whereas the control group had moderate fibro-collagenization and an adequate amount of marrow material, fat cells, and blood vessels. An oxytetracycline labeling study showed moderate activity of new bone formation with crossing-over of new bone trabeculae along with the presence of resorption cavities in group II, whereas in the control group, the process of new bone formation was active from both ends and the defect site appeared as a homogenous non-fluoroscent area. Angiograms of the animals in the control group showed uniform angiogenesis in the defect site with establishment of trans-transplant angiogenesis, whereas in group II there was complete trans-transplant shunting of blood vessel communication. Porous HAp ceramic prepared by an aqueous combustion technique promoted bone formation over the defect, confirming their biologic osteoconductive property

CO2 reforming of methane: valorizing CO2 by means of Dielectric Barrier Discharge

peer reviewedThe impact of pollution on the environment is causing several problems that are to be reduced as much as possible. One important example is the production of CO2 that is emitted by many transport and industrial applications. An interesting solution is to view CO2 as a source instead of a product that can be stocked. The case considered in this work is the CO2 reformation of methane producing hydrogen and CO. It is an endothermic reaction, for which the activition barrier needs to be overcome. The method of Dielectric Barrier Discharge can do this efficiently. The process relies on the collision of electrons, which are accelerated under an electrical field that is created in the discharge area. This leads to the formation of reactive species, which facilitate the abovementioned reaction. The determination of the electron density is performed by PLASIMO. The study is subsequently continued using the Reaction Engineering module in COMSOL (with an incorporated kinetic mechanism) in order to model the discharge phase. Then COMSOL (continuity and Navier-Stokes equations) is used to model the flow in the post-discharge phase. The results showed that both a 2D and 3D model can be used to model the chemical-plasma process. These methods need strongly reduced kinetic mechanism, which in some cases can cause loss of precision. It is also observed that the present experimental set-up that is modeled needs to be improved. A suggestion is made

Influence of fuel type, dilution and equivalence ratio on the emission reduction from the auto-ignition in an Homogeneous Charge Compression Ignition engine

One technology that seems to be promising for automobile pollution reduction is the Homogeneous Charge Compression Ignition (HCCI). This technology still faces auto-ignition and emission-control problems. This paper focuses on the emission problem, since it is incumbent to realize engines that pollute less. For this purpose, this paper presents results concerning the measurement of the emissions of CO, NOx, CO2, O-2 and hydrocarbons. HCCI conditions are used, with equivalence ratios between 0.26 and 0.54, inlet temperatures of 70 degrees C and 120 degrees C and compression ratios of 10.2 and 13.5, with different fuel types: gasoline, gasoline surrogate, diesel, diesel surrogate and mixtures of n-heptane/toluene. The effect of dilution is considered for gasoline, while the effect of the equivalence ratio is considered for all the fuels. No significant amount of NOx has been measured. It appeared that the CO, O-2 and hydrocarbon emissions were reduced by decreasing the toluene content of the fuel and by decreasing the dilution. The opposite holds for CO2. The reduction of the hydrocarbon emission appears to compete with the reduction of the CO2 emission. Diesel seemed to produce less CO and hydrocarbons than gasoline when auto-ignited. An example of emission reduction control is presented in this paper. (C) 2010 Elsevier Ltd. All rights reserved