Evaporation of closely-spaced interacting droplets arranged in a single row

Castanet, Guillaume; Perrin, Lionel; Caballina, Ophélie; Lemoine, Fabrice

doi:10.1016/j.ijheatmasstransfer.2015.09.064

Cited by 74 publications

(50 citation statements)

References 24 publications

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“…This demonstrates the radial transport of acetone vapor in the laminar channel flow. A similar growth of vapor column width for increasing distance from the injector has also been observed in a recent numerical simulation of a monodisperse droplet chain [16]. From the corresponding shadowgraphy images, the droplet size is estimated as ≈125 µm for both positions, i.e.…”

Section: Results For Non-reacting Conditionsupporting

confidence: 80%

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: Results For Non-reacting Conditionsupporting

confidence: 80%

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 fluorescence spectrum of sulforhodamine B is broadband and presents a temperature-dependent shape. Thus, the fluorescence intensity Ifi collected on a spectral band i can be expressed by [21]:…”

Section: Principles Of the Three-color Lif Thermometrymentioning

confidence: 99%

“…A calibration, conducted in a similar process as described in Depredurant et al, [27], leads to a temperature sensitivity of about 0.9%/K. In the work of Labergue et al, [21], a residual effect of the droplet diameter on the fluorescence ratio, not included in eqn (2), was highlighted. For instance, Figure 4, extracted from [21], depicts the evolutions of the normalized fluorescence ratio as function of the droplet diameter D in the particular case of single calibrated water droplets seeded with sulforhodamine B.…”

Section: Principles Of the Three-color Lif Thermometrymentioning

confidence: 99%

“…In the work of Labergue et al, [21], a residual effect of the droplet diameter on the fluorescence ratio, not included in eqn (2), was highlighted. For instance, Figure 4, extracted from [21], depicts the evolutions of the normalized fluorescence ratio as function of the droplet diameter D in the particular case of single calibrated water droplets seeded with sulforhodamine B. Although these experiments were conducted under isothermal conditions, a significant increase of the fluorescence ratio is observed when decreasing the droplet diameter; otherwise the normalized fluorescence ratio tends to 1 for the largest droplet diameters.…”

Section: Principles Of the Three-color Lif Thermometrymentioning

confidence: 99%

“…To account for the effect of the droplet size on the fluorescence ratio, an empirical function g12(D) was added in eqn. (2) [21]:…”

Section: Principles Of the Three-color Lif Thermometrymentioning

confidence: 99%

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Combined three-color LIF-PDA measurements and infrared thermography applied to the study of the spray impingement on a heated surface above the Leidenfrost regime

Labergue

Pena-Carillo

Gradeck

et al. 2017

International Journal of Heat and Mass Transfer

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This experimental study deals with the impingement of sprays on a heated wall in close to semiindustrial conditions. Therefore, an experimental setup was specifically designed: high liquid mass flux (up to 8 kg/m²/s), large droplets (up to 300 µm) and high surface temperature widely above the Leidenfrost point (up to 800°C). The surface to be cooled is a 175 mm diameter nickel disk with 5 mm thickness heated by electromagnetic induction. The spraying devices consist in full cone sprays. Several studies, performed under these particular conditions, has allowed characterizing the heat flux removed by the spray by using techniques based on thermocouples or infrared thermography (IRT). However, to investigate more finely the heat transfer mechanism, it is necessary to measure the droplet temperature but, to date, no measurement for sprays are available in the literature. Therefore, the objective of the present work is to demonstrate the ability of the three-color Laser Induced Fluorescence (3cLIF) to meet this challenge. The combination of the 3cLIF with a Phase Doppler system allows also determining the droplet temperature per size class before and after impact. By adding the IRT measurements combined to an inverse heat conduction model, an energy balance is done in order to estimate the evaporated liquid mass. The influence of the normal Weber number on the liquid vaporization is investigated by using three sprays (Normal Weber numbers up to about 1500). Thereby, main results show that the droplets temperature after impact increases with the incident Weber number before to reach a plateau, attributed to the apparition of the splashing regime. The analysis of the energy balance shows that the mass of evaporated liquid decreases with the incident Weber number and the droplet heating. These first results are in well agreement with previous works conducted with single calibrated droplets, validating as the same time the use of combined 3cLIF-PDA measurements in the case of sprays.

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Heating and Evaporation of Mono-component Droplets

Sazhin

2022

Droplets and Sprays: Simple Models of Complex Processes

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Evaporation of closely-spaced interacting droplets arranged in a single row

Cited by 74 publications

References 24 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

Combined three-color LIF-PDA measurements and infrared thermography applied to the study of the spray impingement on a heated surface above the Leidenfrost regime

Heating and Evaporation of Mono-component Droplets

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