Characterization of the evaporation of interacting droplets using combined optical techniques

Perrin, Lionel; Castanet, Guillaume; Lemoine, Fabrice

doi:10.1007/s00348-015-1900-3

Cited by 50 publications

(41 citation statements)

References 11 publications

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“…A classical canonical configuration for the investigation of droplet evaporation and combustion is the linear monodisperse droplet chain. Several quantities have been characterized experimentally for this configuration, such as, e.g., gas phase temperature using coherent anti-stokes Raman spectroscopy (CARS) [1][2][3], droplet temperature using laser-induced fluorescence (LIF) [4][5] and rainbow thermometry (RT) [6][7][8], vapor concentration using planar LIF (PLIF) [9,10], and droplet size using RT, interferometric laser imaging for droplet sizing (ILIDS) [10,11] and droplet imaging [12,13] (mentioning only a part of the numerous works). The dynamics of the liquid-vapor mass transfer, however, is governed by strong gradients of concentration and temperature in the close vicinity of the gas-liquid interface.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of liquid-vapor mass transfer in non-reacting and reacting droplet chains

Stöhr¹,

Werner²,

Meier³

2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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The dynamics of liquid-vapor mass transfer largely determines the performance of internal and gas turbine spray combustors. The key mechanisms however typically take place on small spatial scales of less than 100 μm which have been difficult to measure. The present work thus aims at the development and application of an experimental technique for the characterization of droplet evaporation with high spatial resolution. Single chains of monodisperse acetone droplets with diameters of 125 and 225 μm are injected into a channel with a cross-section of 60x60 mm² and quartz glass side walls for optical access. The droplet chains are surrounded by a laminar air flow with velocity and temperature of about 0.1 m/s and 300 K, respectively. The distribution of acetone vapor around the droplets is measured using planar laser-induced fluorescence (PLIF) excited by the 4th harmonic of a Nd:YAG laser at 266 nm. The measurements are performed in thin transversal sections between the droplets in order to avoid signal corruption by halation effects that occur when the laser directly hits the droplets as reported in previous studies. In addition, the spatial resolution of the PLIF setup was enhanced by using proper sheetforming and imaging optics. The resulting in-plane resolution and out-plane-resolution (i.e. thickness of the laser sheet) are both determined to about 20 μm, which thus allows an accurate characterization of the small-scale vapor distribution near the droplets. Using a separate calibration measurement, quantitative acetone concentrations are obtained for non-reacting conditions. As a complementary technique, the droplet evaporation is measured using shadowgraphy droplet sizing. Both non-reacting and reacting droplet chains are studied. The results for the non-reacting cases show that the droplet chains are surrounded by a column of nearly-saturated acetone vapor with a concentration maximum at the centerline. For increasing radial distances, the vapor concentration decays quickly with a half width of 0.5 mm and reaches almost zero for r>1 mm. It is further seen that the width of the vapor column increases with streamwise distance. For the experiment with a reacting droplet chain, which is continuously ignited by a heating wire at the channel inlet, a cylindrical reaction zone around the chain with a radius of about 1.5 mm is observed. The shadowgraphy measurements show that the rate of droplet evaporation is significantly enhanced for the reacting conditions. This is attributed to the high rate of heat transfer from the flame to the droplets and the resulting enhanced acetone mass transfer to the sink at the reaction zone. KeywordsDroplet evaporation, Laser-induced fluorescence, Monodisperse droplet chain, Liquid-vapor mass transfer Introduction Several important energy conversion devices such as internal combustion engines and gas turbines are driven by the combustion of liquid fuels. The liquid fuels are typically first atomized into a spray of small droplets, which are then dispersed in a turbulent flo...

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Section: Introductionmentioning

confidence: 99%

Experimental study of liquid-vapor mass transfer in non-reacting and reacting droplet chains

Stöhr¹,

Werner²,

Meier³

2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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“…Earlier work also outlines how WGM analysis can be used in this field [17]. WGM enabled lasing is not always desirable however, and in [183] the dyes used are changed to prevent lasing as this can obscure fluorescence measurements designed to measure droplet temperature.…”

Section: Applications and Outlookmentioning

confidence: 99%

Droplet lasers: a review of current progress

McGloin

2017

Rep. Prog. Phys.

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Abstract. It is perhaps surprising that something as fragile as a microscopic droplet could possibly form a laser. In this article we will review some of the underpinning physics as to how this might be possible, and then examine the state of the art in the field. The technology to create and manipulate droplets will be examined, as will the different classes of droplet lasers. We discuss the rapidly developing fields of droplet biolasers, liquid crystal laser droplets and explore how droplet lasers could give rise to new bio and chemical sensing and analysis. The challenges that droplet lasers face in becoming robust devices, either as sensors or as photonic components in lab on a chip devices is assessed.

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“…Division of two "noisy" intensity values results in a ratio of in average one. According to the temperature calibration, a ratio value of one corresponds to a fluid temperature of about 350 K and thus a valid temperature 13 . Therefore, regions of multiply scattered light cannot be clearly distinguished from the actual spray.…”

Section: Development Steps Of Pulsed 2d-2clif With Mdr-enhanced Energmentioning

confidence: 99%

“…MDR-lasing makes 2cLIF thermometry unfeasible, especially for planar detection, where bright intensity peaks limit the usability of intensified CCDs. In order to clear the emission spectrum of pyrromethene 597-8C9 (PM597) from MDR-lasing, Perrin et al suggest using an additional dye called Oil Blue N (OBN) [13]. The two-dye combination allows MDR-enhanced energy transfer (EET) from one dye to another.…”

Section: Introductionmentioning

confidence: 99%

“…MDRs occur regardless of the presence of any fluorescent dye. If a fluorescent dye is present, its emission spectrum is changed by the MDRs and reliable 2cLIF thermometry is prevented [2,12,13]. The term MDR describes light being trapped inside a droplet due to almost total internal reflection at the droplet's inner surface and going into resonances.…”

Section: Introductionmentioning

confidence: 99%

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Development steps of 2-color laser-induced fluorescence with MDR-enhanced energy transfer for instantaneous planar temperature measurement of micro-droplets and sprays

Palmer

Reddemann

Kirsch

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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A new method for instantaneous measurement of temperature, size and velocity of micro-droplets has been developed. The method is based on the well-known 2-color laser-induced fluorescence (2cLIF) technique, but uses a pulsed laser for 2-dimensional imaging without motion blur and an adjusted dye mixture for suppression of LIFMDRs by utilizing the MDR-enhanced energy transfer effect. This work presents the development steps that are necessary to verify feasibility of pulsed 2D-2cLIF-EET for micro droplet and hollow-cone spray applications.

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Characterization of the evaporation of interacting droplets using combined optical techniques

Cited by 50 publications

References 11 publications

Experimental study of liquid-vapor mass transfer in non-reacting and reacting droplet chains

Experimental study of liquid-vapor mass transfer in non-reacting and reacting droplet chains

Droplet lasers: a review of current progress

Development steps of 2-color laser-induced fluorescence with MDR-enhanced energy transfer for instantaneous planar temperature measurement of micro-droplets and sprays

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