2D Axisymmetric Coupled Computational Fluid Dynamics–Kinetics Modeling of a Nonthermal Arc Plasma Torch for Diesel Fuel Reforming

International audienceThe present study is dedicated to the 2D axisymmetric coupled computational fluid dynamics–kinetics modeling of a plasma-assisted diesel fuel reformer developed for two different applications: (i) onboard H2 production for fuel-cell feeding and (ii) NOx trap regeneration. These cases correspond to very different reaction conditions. In the first case, diesel fuel reacts with air, while in the second case, it reacts with diesel engine exhaust gas. The plasma is modeled with a simple power source domain. n-Heptane has been chosen as a surrogate molecule for diesel fuel. A reduced kinetic mechanism is used for the study. Both cases have been studied under adiabatic and nonadiabatic postreactor conditions. We can distinguish four zones in the torch: a reactant heating zone, a plasma zone, a mixing zone, and a postdischarge zone. The main precursors of the reforming reactions are H, O, and OH radicals. The oxygen rate is a key point of the application. The thermal losses make the reforming reaction difficult to ignite and beget a lower syngas production and a lower postdischarge temperature. For the nonadiabatic reactor, the results have been compared to experimental data. The model predicts relevant gas fractions

3D MHD modelling of low current-high voltage dc plasma torch under restrike mode

International audienceWe present in this paper a magnetohydrodynamic (MHD) modelling of the gliding arc behaviour of a dc plasma torch operating with air under low current and high voltage conditions. The low current leads to instabilities and difficulties with simulating the process because the magnetic field is not sufficient to constrict the arc. The model is 3D, time dependent and the MHD equations are solved using CFD software Code_Saturne®. Although the arc is definitively non-local thermodynamic equilibrium (LTE), the LTE assumption is considered as a first approach. The injection of air is tangential. A hot gas channel reattachment model has been used to simulate the restriking process of the arc root. After the description of the model, the most appropriate electrical voltage breakdown parameter has been selected in comparing with experimental results. A typical operating point is then studied in detail and shows the helical shape of the arc discharge in the nozzle. Finally, the mass flow rate and the current have been varied in the range 0.16-0.5 g s−1 and 100-300 mA, respectively, corresponding to typical glidarc operating points of our experimental plasma torch. The model shows good consistency with experimental data in terms of global behaviour, arc length, mean voltage and glidarc frequency

Theoretical study of Diesel fuel reforming by a non-thermal arc discharge

International audienceNitrogen oxides are in the center of future EURO VI norm, the European anti-pollution norm namely for Diesel powered vehicles. NOx (NO, NO2,...) are very irritant pollutants for people and are considered as tropospherical ozone precursors. Their effect is observed when ozone peak pollution is noticed during rush hours. A promising post-treatment technology is to add a NOx trap in exhaust line to store NOx under nitrate form. An alternative to fuel-air ratio increase and catalytic tech-nologies purge is the use of non-thermal plasma. Plasma reforming of diesel fuel and exhaust gas mix-ture creates reducing chemical species like hydrogen and carbon monoxide, which are able to purge the NOx trap

Experimental and theoretical study of exhaust gas fuel reforming of Diesel fuel by a non-thermal arc discharge for syngas production

Available on: http://ispc20.plasmainstitute.org/my_ispc/papers/105.pdfInternational audienceAn experimental set-up has been developed to study two typical operating points of Diesel powered vehicle, corresponding to high load and low load points. A sensibility study over O/C ratio, injected electric current and mass flow rate have been carried out. The plasma reformer performances have been evaluated in terms of energy efficiency and conversion rate. At low engine load, an energy efficiency of 40% and a conversion rate of 95% have been reached which correspond to a syngas dry molar fraction of 25%. For the most favorable case, only 12 s are needed to regenerate the NOx trap catalyst. The 1D multistage kinetic model developed has shown good trend correlation with experimental results. It has been demonstrated that the oxygen from CO2 and H2O almost does not intervene in the exhaust gas Diesel fuel reforming. At the contrary, CO2 and H2O decrease temperatures, the kinetic reaction speed and the energy efficiency compared to POx reaction. To higher the temperature, more oxygen is needed but local combustion can happen and promote H2O and CO2 production

Exhaust gas fuel reforming of Diesel fuel by non-thermal arc discharge for NOx trap regeneration application

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Energy and Fuels copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/ef101674rInternational audienceThe present study is dedicated to the reforming of diesel fuel with diesel engine exhaust gas (i.e., air, CO2, and H2O mixture) using a nonthermal plasma torch for a NOx trap regeneration application. The plasma technology developed is based on a high voltage/low current nonthermal plasma torch. In the first part of the paper, experimental results on synthesis gas production from exhaust gas fuel reforming of diesel fuel are reported. In the second part of the paper, these experimental results are compared with a 1D multistage model using n-heptane as a surrogate molecule for diesel fuel. Two compositions of synthetic diesel engine exhaust gas, corresponding to high and low engine loads, have been studied. It has been demonstrated that the oxygen from CO2 and H2O hardly ever intervenes in the reforming reactions. In the most favorable condition corresponding to a higher O2 rate, a production of 7 × 10−3 mol*s−1 of syngas has been reached, corresponding to an energy efficiency and a conversion rate of 40% and 95%, respectively. The 1D multistage model shows fair trends with experimental results despite an important shift mainly due to thermal losses, which are not taken into account in the 1D model. From these results and considering a real NOx trap regeneration onboard application, it can be estimated for the most favorable case that, during the regeneration phase (approximately 12 s every 11 km), the power needed to run the plasma will be around 2.2% of the engine power

3D MHD unsteady state modeling of a high voltage - low current plasma torch operating with air

Available on: http://ispc20.plasmainstitute.org/my_ispc/papers/170.pdfInternational audienceA non-transferred high voltage - low current DC plasma torch operating with air has been simulated using Code_Saturne CFD software for current lower than 1 A. The 3D MHD model considers two injection configurations: axial and vortex. The current and the air flow rate have been tuned in the range 0.3 to 0.6 A and 0.16 to 0.5 g/s, respectively. The influence of these parameters on the arc behavior and the arc characteristics has been studied in terms of temperature, velocity, electrical potential and Joule heating

Optimisation de la géométrie d'une torche plasma pour le réformage de l'essence

International audienceL'hydrogène est potentiellement considéré comme un vecteur énergétique du futur, se substituant aux hydrocarbures liquides actuels. La production d'hydrogène embarquée par exemple pour l'alimentation d'une pile à combustible reste néanmoins un enjeu technologique de taille

Post-synaptic Release of the Neuronal Tissue-Type Plasminogen Activator (tPA)

The neuronal serine protease tissue-type Plasminogen Activator (tPA) is an important player of the neuronal survival and of the synaptic plasticity. Thus, a better understanding the mechanisms regulating the neuronal trafficking of tPA is required to further understand how tPA can influence brain functions. Using confocal imaging including living cells and high-resolution cell imaging combined with an innovating labeling of tPA, we demonstrate that the neuronal tPA is contained in endosomal vesicles positives for Rabs and in exosomal vesicles positives for synaptobrevin-2 (VAMP2) in dendrites and axons. tPA-containing vesicles differ in their dynamics with the dendritic tPA containing-vesicles less mobile than the axonal tPA-containing vesicles, these laters displaying mainly a retrograde trafficking. Interestingly spontaneous exocytosis of tPA containing-vesicles occurs largely in dendrites

Antiplasmodial Activities of Homogentisic Acid Derivative Protein Kinase Inhibitors Isolated from a Vanuatu Marine Sponge Pseudoceratina sp.

As part of our search for new antimalarial drugs in South Pacific marine sponges, we have looked for inhibitors of Pfnek-1, a specific protein kinase of Plasmodium falciparum. On the basis of promising activity in a preliminary screening, the ethanolic crude extract of a new species of Pseudoceratina collected in Vanuatu was selected for further investigation. A bioassay-guided fractionation led to the isolation of a derivative of homogentisic acid [methyl (2,4-dibromo-3,6-dihydroxyphenyl)acetate, 4a] which inhibited Pfnek-1 with an IC50 around 1.8 μM. This product was moderately active in vitro against a FcB1 P. falciparum strain (IC50 = 12 μM). From the same sponge, we isolated three known compounds [11,19-dideoxyfistularin-3 (1), 11-deoxyfistularin-3 (2) and dibromo-verongiaquinol (3)] which were inactive against Pfnek-1. Synthesis and biological evaluation of some derivatives of 4a are reported

Kinase Inhibitors from Marine Sponges

Protein kinases play a critical role in cell regulation and their deregulation is a contributing factor in an increasing list of diseases including cancer. Marine sponges have yielded over 70 novel compounds to date that exhibit significant inhibitory activity towards a range of protein kinases. These compounds, which belong to diverse structural classes, are reviewed herein, and ordered based upon the kinase that they inhibit. Relevant synthetic studies on the marine natural product kinase inhibitors have also been included