Simultaneous measurements of PIV, anisole-PLIF and OH-PLIF for investigating back-supported stratified flame propagation in lean and nonflammable mixtures

International audienceIn an effort to reduce pollutant emissions and increase energy efficiency, partially premixed combustion has been integrated into many new combustion technologies. The present study investigated lean back-supported flames in a stratified combustion regime. This strategy leads to hybrid combustion regimes, ranging between fully premixed and fully non-premixed reactants, with a large panel of flame structures and properties requiring to be characterized. Outwardly propagating flames were observed following ignition under laminar stratification conditions generated in a constant volume vessel. The quantitative analysis of the flame properties relied on simultaneous PIV measurements to obtain local flame burning velocities and stretch rates and used anisole-PLIF measurements to calculate the equivalence ratio. Simultaneous OH-PLIF measurements were used to differentiate between the burned gas boundaries and the active flame front. This differentiation was necessary to investigate the nonflammable mixture. The OH-gradient measurement proved to be suitable for distinguishing burned gas interfaces from active flame fronts. Simultaneous OH-and anisole-PLIF measurements were used to estimate the thermal flame thickness. Two flame families were investigated: in family A the flame was ignited in a lean mixture (φ=0.6) with a rich stratification; in family B the mixture in the chamber was nonflammable. In rich mixtures ignition compensated for the non-equidiffusive effects of the lean propane flame and reinforced the flame's stretch resistance. Both a flammable and a nonflammable mixture were investigated to determine the time scales of the back-supported propagation for the given stratification. The enhanced combustion regime allowed the flame to propagate with an active flame front, even in the nonflammable mixture. Combustion continued for a few milliseconds before the flame extinguished. The richer the stratification, the longer the combustion lasted in the nonflammable mixture

Bioavailable Trace Metals in Neurological Diseases

Medical treatment in Wilson’s disease includes chelators (d-penicillamine and trientine) or zinc salts that have to be maintain all the lifelong. This pharmacological treatment is categorised into two phases; the first being a de-coppering phase and the second a maintenance one. The best therapeutic approach remains controversial, as only a few non-controlled trials have compared these treatments. During the initial phase, progressive increase of chelators’ doses adjusted to exchangeable copper and urinary copper might help to avoid neurological deterioration. Liver transplantation is indicated in acute fulminant liver failure and decompensated cirrhosis; in cases of neurologic deterioration, it must be individually discussed. During the maintenance phase, the most important challenge is to obtain a good adherence to lifelong medical therapy. Neurodegenerative diseases that lead to a mislocalisation of iron can be caused by a culmination of localised overload (pro-oxidant siderosis) and localised deficiency (metabolic distress). A new therapeutic concept with conservative iron chelation rescues iron-overloaded neurons by scavenging labile iron and, by delivering this chelated metal to endogenous apo-transferrin, allows iron redistribution to avoid systemic loss of iron

Simultaneous measurements of PIV, anisole-PLIF and OH-PLIF for investigating back-supported stratified flame propagation in lean and nonflammable mixtures

International audienceIn an effort to reduce pollutant emissions and increase energy efficiency, partially premixed combustion has been integrated into many new combustion technologies. The present study investigated lean back-supported flames in a stratified combustion regime. This strategy leads to hybrid combustion regimes, ranging between fully premixed and fully non-premixed reactants, with a large panel of flame structures and properties requiring to be characterized. Outwardly propagating flames were observed following ignition under laminar stratification conditions generated in a constant volume vessel. The quantitative analysis of the flame properties relied on simultaneous PIV measurements to obtain local flame burning velocities and stretch rates and used anisole-PLIF measurements to calculate the equivalence ratio. Simultaneous OH-PLIF measurements were used to differentiate between the burned gas boundaries and the active flame front. This differentiation was necessary to investigate the nonflammable mixture. The OH-gradient measurement proved to be suitable for distinguishing burned gas interfaces from active flame fronts. Simultaneous OH-and anisole-PLIF measurements were used to estimate the thermal flame thickness. Two flame families were investigated: in family A the flame was ignited in a lean mixture (φ=0.6) with a rich stratification; in family B the mixture in the chamber was nonflammable. In rich mixtures ignition compensated for the non-equidiffusive effects of the lean propane flame and reinforced the flame's stretch resistance. Both a flammable and a nonflammable mixture were investigated to determine the time scales of the back-supported propagation for the given stratification. The enhanced combustion regime allowed the flame to propagate with an active flame front, even in the nonflammable mixture. Combustion continued for a few milliseconds before the flame extinguished. The richer the stratification, the longer the combustion lasted in the nonflammable mixture

Fourty years of weather data to understand recent climate Change in the Artic (Svalbard, 79°N)

International audienc

Impact of climate conditions on the hydrological response of a polar glacier system - Austrelovénbreen - Svalbard

International audienc

Area, volume and freshwater flux inferred from the change in geometry of a high Arctic glacier since the 1960s (Austre Lovénbreen, Svalbard)

International audienc

Thermo-Mechanical Modeling of a Glacier-Permafrost System in Spitsbergen, Implications for Subglacial Hydrology

International audienceWithin the framework of climate change, a small polar glacierized watershed was monitored. Field surveys show winter discharges causing large icings. A 2D modeling approach along the main axis of the system is developed to study the evolution of the glacier-bed system. Two codes are chained (one for the glacier and one for the porous media). Results confirm that the glacier is polythermal with a cold based terminus. Its rapid retreat (20 m.a -1 ) should lead to a cold glacier within decades to a century. Simulations show that permafrost development precedes glacier retreat (thin glacier tongue with -5°C mean annual air temperatures measured at Ny Alesund) while in the mountainous part with a somewhat stable glacier position, permafrost could develop over longer times and extend deep. The unfrozen porous medium extension below the glacier will progressively reduce resulting in the disappearance of winter discharges most probably within this century