Study on imaging method for measuring droplet size in large sprays--颗粒学报PARTICUOLOGY

Zhou, W., Hu, J., Feng, M., Yang, B., & Cai, X. (2015). Study on imaging method for measuring droplet size in large sprays. Particuology, 22, 100-106. https://doi.org/10.1016/j.partic.2014.12.003

Study on imaging method for measuring droplet size in large sprays

Wu Zhou, Jiarui Hu, Mingliang Feng, Bin Yang ^*, Xiaoshu Cai

School of Energy and Power Engineering, University of Shanghai for Science and Technology, 516 Jungong Road, Shanghai 200093, China

10.1016/j.partic.2014.12.003

Volume 22, October 2015, Pages 100-106

Received 18 September 2014, Revised 13 November 2014, Accepted 4 December 2014, Available online 11 March 2015, Version of Record 4 August 2015.

E-mail: usst_yangbin@163.com

Highlights

• A backward illumination imaging system was established to characterize large sprays.

• Wide size distribution, large and non-spherical droplets could be measured by this method.

• Image capturing system and processing algorithm were developed.

• Spray experiments were carried out for different operation conditions.

Abstract

Information of droplet size and size distribution lays the basis for investigations of atomization mechanisms and performance optimization. However, the laser diffraction and phase Doppler particle analyzers have difficulty in accurately characterizing sprays with a wide range of droplet sizes and very large droplets, especially if a large number of droplets are aspherical. A method to measure size in such large-droplet sprays based on digital imaging with backward illumination was developed, including an image acquisition system and image process programs. Calibration of the measurement system was performed using a dot calibration target with different dot sizes. An experimental setup was designed and established to characterize spray nozzles under different operation loads, as well as different nozzle arrangements. Results show that the droplet size of sprays ranges from dozens of microns to several millimeters. The superiority of wide load range for such nozzles was indicated by the size-measurement results under half-load to full-load operations. The present study revealed that the image processing technique can be effectively implemented for in-line size measurements of sprays with a wide distribution of droplet size and aspherical droplets, which would be difficult to characterize by other methods.

Graphical abstract

Keywords

Digital image; Spray size; Wide size distribution; Large droplets

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