Temperature and chemical composition of droplets by optical measurement techniques: a state-of-the-art review

Lemoine, Fabrice; Castanet, Guillaume

doi:10.1007/s00348-013-1572-9

Cited by 101 publications

(73 citation statements)

References 183 publications

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“…The decrease in this second peak with the temperature is less important than that in the main peak centered around 600 nm (Depré-durand et al 2008). According to Lemoine and Castanet (2013), the fluorescence intensity I f,i detected over a specific spectral band noted i can be expressed as:…”

Section: Droplet Temperature Measurementsmentioning

confidence: 99%

“…Different optical methods have been developed in the past to measure temperature. Without being exhaustive, one can mention Raman spectroscopy, morphology-dependent resonances (MDRs), rainbow refractometry and laser-induced fluorescence (LIF; Lemoine and Castanet 2013). Each method has its own advantages and limitations depending on its basic principles.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of the evaporation of interacting droplets using combined optical techniques

2015

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Section: Droplet Temperature Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characterization of the evaporation of interacting droplets using combined optical techniques

2015

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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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“…Examples of temperature measurements based on 2cLIF can be found in the literature. Application are related to single-phase liquid flows [8], monosized droplet streams [7] and sprays [5]. In most of these applications, a CW laser was used to induce fluorescence.…”

Section: Droplet Temperature Measurementsmentioning

confidence: 99%

“…The contributions of liquid evaporation and liquid heating to the overall heat exchange between the droplet and the wall are not obvious to evaluate if measurements are restricted to the wall heat flux. The droplet heating can be characterized using the two-color laser-induced fluorescence thermometry (2cLIF) which is one of the few proven techniques available to measure the temperature of droplets [5]. The liquid (in this case water) is seeded by a temperature-dependent fluorescent dye.…”

mentioning

confidence: 99%

Instantaneous heat transfers at the impact of a droplet onto a hot surface in the film boiling regime

Chaze¹,

Castanet²,

Caballina³

et al. 2017

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

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Heat and mass transfers at the impact of a droplet onto a hot solid surface are investigated experimentally. Millimetersized water droplets impinges onto a perfectly flat sapphire surface heated at 600°C. The temperature of the liquid inside the droplet is measured using the two-color laser-induced fluorescence (2cLIF) technique. Water is seeded with a temperature-sensitive fluorescent dye, while a nanosecond pulsed laser is used for the excitation of the fluorescence. The ratio of fluorescence signal detected in two appropriate spectral bands allows to determine the liquid temperature. One advantage of this non-intrusive optical technique is that it eliminates adverse effects associated with signal variations caused by droplet shape during its impact. In parallel, the temperature of the solid surface is characterized using infrared thermography. The latter measurements are made possible by the deposition of a nanosize coating of titanium aluminium nitride (TiAlN) on the upper surface of the sapphire window. Thanks to the high frame rate of the IR camera, the time evolution of the heat flux distribution at the solid surface can be reconstructed. A comparison of IR and 2cLIF techniques enable to correlate the heating of the liquid with the cooling of the wall. This reveals that most of the heat removed from the solid surface is devoted to the heating of the liquid, the energy used for liquid vaporization being significantly lower. IntroductionMany industrial applications require a rapid cooling of surfaces from high temperatures. Among the cooling technologies, spray cooling is certainly one of the most attractive for the thermal management of high heat flux systems. Compared to jet impingement, it has the capability of cooling a relatively wider surface area with a single nozzle. It also has an unrivalled cooling efficiency, meaning that significant quantities of coolant liquid can be saved to remove the same amount of heat. These features explain why it is widely employed in many industrial applications, especially in metal production and processing industry. However, while it is applied for decades, its integration remains a complex and cumbersome process because of still incomplete knowledge of the fluid flow and heat transfer characteristics. In particular, scientific investigations focused on individual droplets are still required to understand the underlying physics behind the interactions between droplets and a hot solid surface. When a drop impacts a hot wall, different behaviours are observed. The drop can spread over the solid surface and remain attached to it due to wettability forces. It can splash and creates several smaller secondary droplets or simply rebounds. Extensive experimental investigations were carried out in the past to characterize the parameters influencing the drop behavior at the impact. Among them, some can be related to the dynamic of the impacting droplets (velocity, diameter, etc.), the physical properties of the liquid (viscosity, surface tension, etc.), and the solid su...

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Temperature and chemical composition of droplets by optical measurement techniques: a state-of-the-art review

Cited by 101 publications

References 183 publications

Characterization of the evaporation of interacting droplets using combined optical techniques

Characterization of the evaporation of interacting droplets using combined optical techniques

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

Instantaneous heat transfers at the impact of a droplet onto a hot surface in the film boiling regime

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