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

Research output: Contribution to journalArticle

Abstract

Planar droplet sizing (PDS) is a technique relying on the assumption that laser-induced 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.

Details

Authors
  • Matthias Koegl
  • Bernhard Hofbeck
  • Kevin Baderschneider
  • Yogeshwar Nath Mishra
  • Franz J.T. Huber
  • Edouard Berrocal
  • Stefan Will
  • Lars Zigan
Organisations
External organisations
  • Friedrich-Alexander University Erlangen-Nürnberg
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Atom and Molecular Physics and Optics
Original languageEnglish
Pages (from-to)31750-31766
Number of pages17
JournalOptics Express
Volume26
Issue number24
Publication statusPublished - 2018
Publication categoryResearch
Peer-reviewedYes