Droplet thermometry based on an optimized two dye two-color laser-induced fluorescence concept

Ulrich, Hannah; Sigl, Sophie; Möhnle, Michael; Berrocal, Edouard; Zigan, Lars

doi:10.3389/fphy.2023.1235847

Cited by 7 publications

(1 citation statement)

References 41 publications

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“…Among these, optical measurement methods are preferred due to their high accuracy, non-destructiveness, and ability to provide in situ and on-line measurements. Noteworthy optical methods employed for droplet measurements encompass direct imaging [1,2], shadowgraphy [3], laser interferometric particle imaging [4][5][6], phase doppler technique [7,8], laser induced fluorescence [9][10][11][12], digital holography [13][14][15][16], Raman spectroscopy [17], and other light scattering techniques [18,19]. Rainbow refractometry, a form of backscattered light interferometry, emerges as a pivotal optical technique.…”

Section: Introductionmentioning

confidence: 99%

Right partial rainbow refractometry for measuring droplet refractive index and size

Li,

Peng,

et al. 2023

Front. Phys.

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Rainbow refractometry can be employed for measuring the parameters of droplets or sprays. Considering the diversity of different measurement environments and droplet components, there are instances in experiments where optics fail to record the complete rainbow signal. To enhance the experimental data utilization, this paper investigates rainbow refractometry using the incomplete rainbow signal on the right side, focusing on its feasibility and accuracy. The concept that defines the incompleteness of the right-sided rainbow signal is termed as the dimensionless right signal partial ratio (RSPR). The study conducts a comprehensive analysis of refractive index, droplet diameter, and size distributions retrieved from the partial rainbow signals simulated by the Lorenz-Mie theory with varying RSPR values. For both partial standard and global rainbows, the critical value of the retrieval error is found to be whether the primary peak of the rainbow is preserved or not, i.e., RSPR = 1. Laboratory experiments verify the feasibility and effectiveness of employing rainbow refractometry with right partial rainbow signals. The study addresses the challenge of incomplete recording of rainbow signals in experiments, and is expected to improve experimental efficiency and data utilization.

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Section: Introductionmentioning

confidence: 99%

Right partial rainbow refractometry for measuring droplet refractive index and size

Li,

Peng,

et al. 2023

Front. Phys.

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Simultaneous film temperature and film thickness measurements for jet impingement applications using two-color laser-induced fluorescence

Koegl,

Mil‘to,

Zigan

2024

Exp Fluids

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The study investigates a jet impingement cooling process of a cylindrical geometry relevant for electric and electronic applications. The applied two-color detection technique enables a simultaneous determination of film temperature and film thickness. For this purpose, the heat transfer oil Marlotherm LH was doped with the temperature-sensitive fluorescence tracer nile red. The temperature determination was realized by suitable band pass filters. Preliminary spectral investigations were carried out in terms of varying dye concentration, temperature and film thickness. At high dye concentrations (up to 37.5 mg/L), reabsorption effects lead to a spectral shift toward higher wavelengths with increasing film thickness. Low dye concentrations (0.29 mg/L, 0.59 mg/L) show no film thickness dependent spectral shift. A film temperature investigation at low dye concentration showed no bias of the intensity ratio due to film thickness, i.e., no additional spectral shift toward lower wavelengths was observed. The investigations on the jet impingement setup revealed an increasing film temperature and decreasing film thickness with increasing solid temperature. The average film temperature increases with increasing solid temperature from 298 (solid temperature 298 K) to 308 K (solid temperature 398 K). At higher solid temperatures, the film temperature increases with distance to the stagnation zone. The average film thickness decreases with increasing solid temperature from 0.24 to 0.17 mm. At high solid temperatures, the film temperature increased with radial distance to the stagnation zone. This behavior is caused by the increasing temperature gradient with increasing solid temperature and decreasing viscosity with increasing film temperature.

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Two-dye two-color laser-induced fluorescence spectroscopy on droplets of green solvent water/ethanol mixtures for thermometry and mixture composition

Ulrich,

Weiß,

Zigan

2024

Exp Fluids

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This work shows new insights on the application of two-color laser-induced-fluorescence (2c-LIF) thermometry in a droplet chain. A two-dye mixture is used in ethanol, water and ethanol/water mixtures in order to reach a high-temperature sensitivity and avoid the detection of lasing effects in the droplets. Various droplet sizes are recorded in regard to the limitation of the detection system for very small micrometric droplets. The breakup of a droplet chain is measured to assess the spectral detection system in applications with liquid structures of different sizes. Additionally, a proposal to expand the 2c-LIF application for studying ethanol/water droplets regarding mixture composition with a third color channel is presented. Forming two intensity ratios, the spectra can be used to obtain information on the mixture composition of the solvent. Measurements in different ethanol/water mixtures containing 0–100 vol% water are evaluated to show this possibility.

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Droplet thermometry based on an optimized two dye two-color laser-induced fluorescence concept

Cited by 7 publications

References 41 publications

Right partial rainbow refractometry for measuring droplet refractive index and size

Right partial rainbow refractometry for measuring droplet refractive index and size

Simultaneous film temperature and film thickness measurements for jet impingement applications using two-color laser-induced fluorescence

Two-dye two-color laser-induced fluorescence spectroscopy on droplets of green solvent water/ethanol mixtures for thermometry and mixture composition

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