A laser extinction based sensor for simultaneous droplet size and vapor measurement--颗粒学报PARTICUOLOGY

Sun, X., Ewing, D. J., & Ma, L. (2012). A laser extinction based sensor for simultaneous droplet size and vapor measurement. Particuology, 10(1), 9–16. https://doi.org/10.1016/j.partic.2011.09.004

A laser extinction based sensor for simultaneous droplet size and vapor measurement

Xueqiang Sun ^a, David J. Ewing ^b, Lin Ma ^b *

a College of Automatic Control and Mechanical Engineering, Kunming University, Kunming 650214, China
b Department of Aerospace and Ocean Engineering, Virginia Tech, Blacksburg, VA 24063, USA

10.1016/j.partic.2011.09.004

Volume 10, Issue 1, February 2012, Pages 9-16

Received 13 July 2011, Revised 18 September 2011, Accepted 23 September 2011, Available online 4 January 2012.

E-mail: LinMa@vt.edu

Highlights

► Introduced a WMLE (wavelength-multiplexed laser extinction) technique.

► Systematically examined WMLE's application to two-phase flows.

► Evaluated applicable range of WMLE for simultaneous vapor and droplet measurements.

Abstract

Multiphase flows involving liquid droplets in association with gas flow occur in many industrial and scientific applications. Recent work has demonstrated the feasibility of using optical techniques based on laser extinction to simultaneously measure vapor concentration and temperature and droplet size and loading. This work introduces the theoretical background for the optimal design of such laser extinction techniques, termed WMLE (wavelength-multiplexed laser extinction). This paper focuses on the development of WMLE and presents a systematic methodology to guide the selection of suitable wavelengths and optimize the performance of WMLE for specific applications. WMLE utilizing wavelengths from 0.5 to 10 μm is illustrated for droplet size and vapor concentration measurements in an example of water spray, and is found to enable unique and sensitive Sauter mean diameter measurement in the range of ∼1–15 μm along with accurate vapor detection. A vapor detection strategy based on differential absorption is developed to extend accurate measurement to a significantly wider range of droplet loading and vapor concentration as compared to strategies based on direct fixed-wavelength absorption. Expected performance of the sensor is modeled for an evaporating spray. This work is expected to lay the groundwork for implementing optical sensors based on WMLE in a variety of research and industrial applications involving multi-phase flows.

Graphical abstract

Keywords

Wavelength-multiplexed laser extinction; Droplet; Measurement; Laser; Extinction; Absorption; Spectroscopy

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