Viscosity effects on liquid-liquid dispersion in laminar flows

Efficiency of liquid/liquid dispersion is an important stake in numerous sectors, such as the chemical, food, cosmetic and environmental industries. In the present study, dispersion is achieved in an open-loop reactor consisting of simple curved pipes, either helically coiled or chaotically twisted. In both configurations, we investigate the drop breakup process of two immiscible fluids (W/O) and especially the effect of the continuous phase viscosity, which is varied by addition of different fractions of butanol in the native sunflower oil. The global Reynolds numbers vary between 40 and 240, so that the flow remains laminar while the Dean roll-cells in the bends develop significantly. Different fractions of butanol are added to the oil in each case to examine the influence of the continuous phase viscosity on the drop size distribution of the dispersed phase (water). When the butanol fraction is decreased, the dispersion process is intensified and smaller drops are created. The Sauter mean diameters obtained in the chaotic twisted pipe are compared with those in a helically coiled pipe flow. The results show that chaotic advection intensifies the droplet breakup till 20% in droplet size reduction, and also reduces polydispersity

Construction and characterization of two BAC libraries representing a deep-coverage of the genome of chicory (Cichorium intybus L., Asteraceae)

<p>Abstract</p> <p>Background</p> <p>The Asteraceae represents an important plant family with respect to the numbers of species present in the wild and used by man. Nonetheless, genomic resources for Asteraceae species are relatively underdeveloped, hampering within species genetic studies as well as comparative genomics studies at the family level. So far, six BAC libraries have been described for the main crops of the family, <it>i.e</it>. lettuce and sunflower. Here we present the characterization of BAC libraries of chicory (<it>Cichorium intybus </it>L.) constructed from two genotypes differing in traits related to sexual and vegetative reproduction. Resolving the molecular mechanisms underlying traits controlling the reproductive system of chicory is a key determinant for hybrid development, and more generally will provide new insights into these traits, which are poorly investigated so far at the molecular level in Asteraceae.</p> <p>Findings</p> <p>Two bacterial artificial chromosome (BAC) libraries, CinS2S2 and CinS1S4, were constructed from <it>Hin</it>dIII-digested high molecular weight DNA of the contrasting genotypes C15 and C30.01, respectively. C15 was hermaphrodite, non-embryogenic, and <it>S</it>₂<it>S</it>₂for the <it>S</it>-locus implicated in self-incompatibility, whereas C30.01 was male sterile, embryogenic, and <it>S</it>₁<it>S</it>₄. The CinS2S2 and CinS1S4 libraries contain 89,088 and 81,408 clones. Mean insert sizes of the CinS2S2 and CinS1S4 clones are 90 and 120 kb, respectively, and provide together a coverage of 12.3 haploid genome equivalents. Contamination with mitochondrial and chloroplast DNA sequences was evaluated with four mitochondrial and four chloroplast specific probes, and was estimated to be 0.024% and 1.00% for the CinS2S2 library, and 0.028% and 2.35% for the CinS1S4 library. Using two single copy genes putatively implicated in somatic embryogenesis, screening of both libraries resulted in detection of 12 and 13 positive clones for each gene, in accordance with expected numbers.</p> <p>Conclusions</p> <p>This indicated that both BAC libraries are valuable tools for molecular studies in chicory, one goal being the positional cloning of the <it>S</it>-locus in this Asteraceae species.</p

Biofuel emulsifier using high velocity impinging flows and singularities in micro-channels

ASME 2016 Internal Combustion Engine Division Fall Technical ConferenceGreenville, South Carolina, USA, October 9–12, 2016Conference Sponsors: Internal Combustion Engine DivisionISBN: 978-0-7918-5050-3International audienceThe objective of this work is to design an original microfluidic mixer for continuous emulsification of small fractions of water in a lipid phase. This system is aimed to be integrated on-line in the process so as to avoid the use of a surfactant. The targeted application is a better combustion of alternative biofuels in boilers, turbines or internal combustion engines in general. The developed micro-system which includes impinging flows and elbows, is performed on the basis of a specific design of micro-channels, adapted to the respective flow rates and the characteristics of the fluids to be emulsified (viscosity, surface tension). The variation of different parameters is tested in this study such as the nature of the lipid phase (viscosity, density, surface tension and components), the length of micro-channels in the elbow and the flow rate of the dispersed phase. The dispersion of water is much more efficient with this microsystem using gasoil rather than vegetable oil as the continuous phase

Comparison between numerical and experimental water-in-oil dispersion in a microchannel

International audienceThe dispersion of water inside a flow of oil is investigated in a microfluidic device, producing a water-in-oilemulsion. The liquid–liquid flow mainly differs from those presented in existing literature through its high capillarynumber (between 3 and 14), and in the head-on collision between water and oil streams. By comparing withexperimental data, numerical simulations can provide more information about the topology of the flow. A coupledVolume of Fluid and Level Set method (CLSVOF) is used to treat the interface between both phases andincompressible Navier-Stokes equations are solved. Three set of parameters, close to those in the experimentalsetup, are investigated to compare experimental and numerical results. The comparison between experimentsand simulation provides a precise knowledge of the liquid-liquid dispersion process and the overall flow patternwithin the microfluidic device

Study of the micro-explosion temperature of water in oil emulsion droplets during the Leidenfrost effect

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Recyclage d’un composite à base d’une résine thermodurcissable par de l’eau en condition subcritique

Nous présentons dans cet article certains résultats de recyclage thermochimique d’un composite utilisé dans le domaine de l’aéronautique, fabriqué à partir d’une résine époxyde (Hexply914®) et des fibres de carbone, en utilisant un processus de dégradation dans l’eau en condition subcritique. Le but des expériences est de définir les valeurs optimales des principaux paramètres contrôlant le procédé : la température, le temps, la pression et la quantité de composite. Des fibres de carbone propres, le polymère fractionné en petites molécules de faible poids moléculaires, et d’autres produits ont été récupérés. Les différents produits issus du processus ont été analysés par microscopie électronique à balayage (MEB), analyse thermogravimétrique (ATG), chromatographie en phase gazeuse (GC) et chromatographie couplée spectrométrie de masse (GC-MS). L’effet de la quantité de composite par rapport à la quantité de solvant a été étudié, il s’avère qu’à partir d’un ratio de 17 %, l’eau atteint sa limite de solubilisation, ce qui mène à la formation d’une quantité très élevée de goudrons. La chaleur de dégradation a été étudiée et montre que la réaction globale est athermique

Distribution of thermal energy of child-droplets issued from an optimal micro-explosion

The micro-explosion phenomenon is involved in emulsified fuel droplets placed in a hot atmosphere, such as spray combustion. Droplets of water-in-sunflower oil emulsion are used, since they are representative of a class of emulsions used in practical applications of biofuels. Once the micro-explosion is triggered after a short delay, the rapid (<= 1 ms) vaporization of the inside water droplets and the subsequent disintegration of the emulsion droplet blow the fragmented droplets away. These fragmented droplets are called "child-droplets", and they are too small and fast for an on-the-fly infra-red imaging thermal characterization. The present study focuses on the thermal reaction of a thin plate when impacted by them. Thorough and detailed tests are carried out, to make sure that the plate and the acquisition system are collecting a data that is actually representative of the child-droplets thermal energy. A quantitative post-processing is applied to the transient temperature field on the plate. It leads to the thermal energy of the whole plate, and of representative samples of individual child-droplets. The results show that their thermal energy is governed by a log-normal distribution

Distribution of thermal energy of child-droplets issued from an optimal micro-explosion

The micro-explosion phenomenon is involved in emulsified fuel droplets placed in a hot atmosphere, such as spray combustion. Droplets of water-in-sunflower oil emulsion are used, since they are representative of a class of emulsions used in practical applications of biofuels. Once the micro-explosion is triggered after a short delay, the rapid (&lt;= 1 ms) vaporization of the inside water droplets and the subsequent disintegration of the emulsion droplet blow the fragmented droplets away. These fragmented droplets are called "child-droplets", and they are too small and fast for an on-the-fly infra-red imaging thermal characterization. The present study focuses on the thermal reaction of a thin plate when impacted by them. Thorough and detailed tests are carried out, to make sure that the plate and the acquisition system are collecting a data that is actually representative of the child-droplets thermal energy. A quantitative post-processing is applied to the transient temperature field on the plate. It leads to the thermal energy of the whole plate, and of representative samples of individual child-droplets. The results show that their thermal energy is governed by a log-normal distribution

Performance and emissions of a CI optical engine fuelled with water in diesel emulsion through microchannels emulsification

International audienc