Application of femtosecond lasers to the polarization ratio technique for droplet sizing

Bareiss, Stefan; Bork, B.; Bakić, Saša; Tropea, Cameron; Irsig, Robert; Tiggesbäumker, J.; Dreizler, Andreas

doi:10.1088/0957-0233/24/2/025203

Cited by 15 publications

(11 citation statements)

References 29 publications

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“…Similar conclusions are also reported by Charalampous et al [12]. Another experimental technique to reduce intensity oscillations within the Mie-scattering is the usage of femtosecond lasers as reported in [47] which also relies on the above mentioned effects.…”

Section: Discussiosupporting

confidence: 86%

Analysis of LIF and Mie signals from single micrometric droplets for instantaneous droplet sizing in sprays

et al. 2018

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Planar droplet sizing (PDS) is a technique relying on the assumption that laserinduced fluorescence (LIF) and Mie scattering optical signals from spherical droplets depend on their volume and surface area, respectively. In this article, we verify the validity of this assumption by experimentally analyzing the light intensity of the LIF and Mie optical signals from micrometric droplets as a function of their diameter. The size of the droplets is controlled using a new flow-focusing monodisperse droplet generator capable of producing droplets of the desired size in the range of 21 µm to 60 µm. Ethanol droplets doped with eosin dye and excited at 532 nm are considered in this study, and the individual droplets were imaged simultaneously at microscopic and macroscopic scale. The effects of laser power, dye concentration, and temperature variation are systematically studied as a function of LIF/Mie ratio in the whole range of droplet sizes. Finally, a calibration curve at tracer concentration of 0.5 vol% is deduced and used to extract the droplet Sauter mean diameter (SMD) from instantaneous images of a transient ethanol spray. This droplet size mapping is done using structured laser illumination planar imaging (SLIPI), in order to suppress the artifacts induced by multiple light scattering.

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Section: Discussiosupporting

confidence: 86%

Analysis of LIF and Mie signals from single micrometric droplets for instantaneous droplet sizing in sprays

et al. 2018

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“…In addition, a collection of PDA derived SMD allows only to acquire temporally averaged data, and no information on the cyclic variation of single injections is delivered. Because of their optical sectioning capabilities, intensity ratio-based laser sheet imaging approaches such as LIF/Mie ratio [7], Exciplex-LIF/Mie ratio [8], Raman/Mie ratio [9], and Polarization ratio [10] have been used as various attempts for obtaining 2D maps of droplet size. By now combining those laser sheet imaging approaches with a scanning procedure (e.g.…”

Section: Introductionmentioning

confidence: 99%

3D mapping of droplet Sauter mean diameter in sprays

et al. 2019

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In this study, we report on the 3D (three-dimensional) characterization of a spray in terms of its droplet SMD (Sauter Mean Diameter) using the LIF (Laser-Induced Fluorescence)/Mie ratio technique. The spray structure is analyzed for a multi-hole DISI (Direct-Injection Spark Ignition) injector. A calibration curve to convert LIF/Mie ratio to droplet diameter is deduced using LIF/Mie imaging and analysis of single droplets generated by a droplet generator. The DISI spray investigated here is optically sectioned by means of two-phase SLIPI (Structured Laser Illumination Planar Imaging) to suppress the intensity of multiple light scattering from LIF and Mie images prior to their ratio. A series of calibrated LIF/Mie ratio images of spray is then recorded at several depths along the Z-direction following the light sheet scanning of the spray. The droplet SMD is ranging from less than 5 µm up to a maximum of 50 µm in single-shot images. The averaged SMD results (1-30 µm) obtained by using the calibration curve from the droplet generator are compared with measurement results from Phase-Doppler Anemometry (PDA). Finally, a 3D map is reconstructed from the successive 2D layers generated from spray scanning. The resulting 3D representation of the droplet SMD shows a non-symmetric spray structure produced by the studied multi-hole injector, which cannot be resolved by analyzing only one central plane.

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“…The measurement of atomized droplet particle size is an important support link for the study of nozzle atomization characteristics. At present, there are many methods for measuring atomized droplet particle size, which can be roughly classi ed as phase Doppler anemometry (PDA) [21,22], the polarization ratio technique [23,24], digital holography technique [25,26], Laser Induced Fluorescence/Mie scattering drop sizing (LIF/Mie) [27,28], and the laser interference particle measurement technology (IPI) [29][30][31], etc. Among them, IPI technology has the advantages of simple system structure, easy construction, and large measurement range.…”

Section: Measurement Methods Of Atomization Characteristicsmentioning

confidence: 99%

Influence of Collision Angle Micro-deviation of Symmetric Nozzles on Collision Atomization Characteristics

Cui

Tan

2022

Preprint

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The large-scale high-precision machining of the nozzles in the collision atomizer is quite difficult. The slight deviation of the nozzle inclination causes the collision angle to change doubly, which affects the collision position and the spatial distribution of the atomized droplets and reduces the combustion efficiency of the combustion chamber. In order to improve the atomization performance of the dual jet collision atomizer, this study firstly investigates the influence of the collision angle micro-deviation on the atomization characteristics based on the laser interference particle measurement technology (IPI). To jointly study the real-time characteristics of the internal flow and atomization field, a collision atomizer with transparent nozzles is independently designed, and the collision angle is controlled by a high-precision rotary stage. The cavitation phenomenon in the internal flow field is analyzed by simulation and experiment. The hydraulic parameters and atomization performance of the collision atomization field are measured and analyzed. The experimental results show that under the same injection pressure, the increase of the collision angle leads to the decrease of the Sauter Mean Diameter (SMD) and the increase of the atomization cone angle. Taking 60° as the benchmark, within the variation range of ± 5°, the collision angle deviation has little effect on the spatial distribution of atomized droplets.

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Application of femtosecond lasers to the polarization ratio technique for droplet sizing

Cited by 15 publications

References 29 publications

Analysis of LIF and Mie signals from single micrometric droplets for instantaneous droplet sizing in sprays

Analysis of LIF and Mie signals from single micrometric droplets for instantaneous droplet sizing in sprays

3D mapping of droplet Sauter mean diameter in sprays

Influence of Collision Angle Micro-deviation of Symmetric Nozzles on Collision Atomization Characteristics

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