Simultaneous Laser-Induced Fluorescence and Mie Scattering for Droplet Cluster Measurements

Zimmer, Laurent; Domann, Roland; Hardalupas, Y.; Ikeda, Yuji

doi:10.2514/2.6835

Cited by 26 publications

(8 citation statements)

References 20 publications

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“…The interaction of a spray with the airflow field redistributes the droplets according to differences in droplet inertia, momentum and drag. Because of the different relaxation times of droplets of different sizes, interaction with various scales of eddies in a turbulent flow field can lead to cluster formation (Sanchez et al 2000;Zimmer et al 2003). "Centrifuging" of larger droplets out of eddies may lead to local droplet void regions resulting in large temporal and spatial variation of the distribution of droplets and possibly, also, local fuel vapour concentration.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous planar measurement of droplet velocity and size with gas phase velocities in a spray by combined ILIDS and PIV techniques

et al. 2010

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A new approach for simultaneous planar measurement of droplet velocity and size with gas phase velocities is reported, which combines the out-of-focus imaging technique 'Interferometric Laser Imaging Droplet Sizing' (ILIDS) for planar simultaneous droplet size and velocity measurements with the in-focus technique 'Particle Image Velocimetry' (PIV) for gas velocity measurements in the vicinity of individual droplets. Discrimination between the gas phase seeding and the droplets is achieved in the PIV images by removing the glare points of focused droplet images, using the droplet position obtained through ILIDS processing. Combination of the two optical arrangements can result in a discrepancy in the location of the centre of a droplet, when imaging through ILIDS and PIV techniques, of up to about 1 mm which may lead to erroneous identification of the glare points from droplets on the PIV images. The magnitude of the discrepancy is a function of position of the droplet's image on the CCD array and the degree of defocus, but almost independent of droplet size.Specifically, it varies approximately linearly across the image along the direction corresponding to the direction of propagation of the laser sheet for a given defocus setting in ILIDS. The experimental finding is supported by a theoretical analysis, which was based on geometrical optics for a simple optical configuration that replicates the essential features of the optical system. The discrepancy in the location was measured using a monodisperse droplet generator and this was subtracted from the droplet centres identified in the ILIDS images of a polydisperse spray without 'seeding' particles. This reduced the discrepancy between PIV and ILIDS droplet centres from about 1 mm to about 0.1 mm and hence increased the probability of finding the corresponding fringe patterns on the ILIDS image and glare points on the PIV image. In conclusion, it is shown that the proposed combined method can discriminate between droplets and 'seeding' particles and is capable of two-phase measurements in polydisperse sprays.

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Section: Introductionmentioning

confidence: 99%

Simultaneous planar measurement of droplet velocity and size with gas phase velocities in a spray by combined ILIDS and PIV techniques

et al. 2010

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“…The technique has been applied by a number of researchers to characterize sprays [25][26][27][28][29][30][31][32] even in regions when the droplet density makes the application of other laser diagnostic measurements difficult. However, not all researches agree on the correctness of the fundamental hypothesis of the LIF/Mie technique.…”

Section: Introductionmentioning

confidence: 99%

Numerical evaluation of droplet sizing based on the ratio of fluorescent and scattered light intensities (LIF/Mie technique)

Charalampous

Hardalupas

2011

Appl. Opt.

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“…planar droplet sizing technique (also know as optical patternator) has been proposed for the measurement of the Sauter Mean Diameter (SMD) of spray droplets, based on combined laser-induced fluorescence and scattered light (LIF/Mie) intensity imaging on a plane of a spray determined by a laser sheet [2][3][4][5][6][7][8][9][10]. The LIF/Mie technique has a significant advantage over other droplet sizing methods in that it is a planar technique that can size full planes of sprays, while the other methods are limited to "point" (Phase Doppler Velocimetry, PDV), line of sight (laser diffraction), or planes of small cross-sectional areas (Interferometric Laser Imaging Droplet Sizing, ILIDS) of sprays.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of a laser beam scanning method for correction of multiple scattering and attenuation effects in dense spray measurements

Charalampous

Hardalupas

2014

52nd Aerospace Sciences Meeting

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When applying laser imaging to dense sprays, the acquired measurements are hindered by optical noise due to multiple scattering, attenuation of the illuminating laser beam as it interacts with the spray and attenuation of the scattered light by droplets between the probed spray region and the detector. An investigation was performed to assess the possibility of addressing these issues by scanning a laser beam across a spray instead of illuminating with a laser sheet. A high precision opto-mechanical arrangement was assembled for measurements of scattered and fluorescent light intensity across a cross section of a flat spray. These measurements were used for applying a correction procedure, described by [1], to the attenuation of the incident and collected light intensity by a spray. Application of the correction methodology on the collected scattered light profiles across a plane of a spray provided quantitative measurements of the contributions of laser intensity attenuation along the beam path, attenuation of the scattered light intensity between the probed spray region and the imaging camera and the scattering cross section of the spray droplets. From the above, the full cross section of the spray was reconstructed in terms of the scattered light intensity profiles, which are representative of the droplet surface area and liquid volume densities. The reconstructed spray shape was elliptical and symmetric along the two normal axes, as expected for a flat spray, which demonstrates that the developed approach was appropriate. I. Introductionplanar droplet sizing technique (also know as optical patternator) has been proposed for the measurement of the Sauter Mean Diameter (SMD) of spray droplets, based on combined laser-induced fluorescence and scattered light (LIF/Mie) intensity imaging on a plane of a spray determined by a laser sheet [2-10]. The LIF/Mie technique has a significant advantage over other droplet sizing methods in that it is a planar technique that can size full planes of sprays, while the other methods are limited to "point" (Phase Doppler Velocimetry, PDV), line of sight (laser diffraction), or planes of small cross-sectional areas (Interferometric Laser Imaging Droplet Sizing, ILIDS) of sprays. In addition, this technique is applicable to dense spray regions, provided that appropriate compensation of multiple scattering effects and laser intensity attenuation along the sprays is included. The fundamental hypothesis of the LIF/Mie technique for droplet sizing [2, 3] is that when a spherical droplet doped with a fluorescing dye is illuminated with a laser, the intensity of the fluorescent light from a droplet is proportional to the volume of the illuminated droplet while the intensity of the scattered light is proportional to the surface area of the illuminated droplet. However, it has been shown that the above assumption is not always valid [6-9, 11, 12] and there is a need to develop appropriate processing for droplet sizing [6]. Recently, an extensive analysis of the operation of the LIF/Mie t...

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Simultaneous Laser-Induced Fluorescence and Mie Scattering for Droplet Cluster Measurements

Cited by 26 publications

References 20 publications

Simultaneous planar measurement of droplet velocity and size with gas phase velocities in a spray by combined ILIDS and PIV techniques

Simultaneous planar measurement of droplet velocity and size with gas phase velocities in a spray by combined ILIDS and PIV techniques

Numerical evaluation of droplet sizing based on the ratio of fluorescent and scattered light intensities (LIF/Mie technique)

Evaluation of a laser beam scanning method for correction of multiple scattering and attenuation effects in dense spray measurements

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