Han Wu1, Cong Liu1, Chunze Cen2, Chien-Er Huang3, Sheng-Lun Lin  This email address is being protected from spambots. You need JavaScript enabled to view it.1

1 School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China
2 Department of Mechanical, Aerospace and Civil Engineering, University of Manchester, Oxford RD, M13 9PL, UK
3 Center for Environmental Toxin and Emerging-contaminant Research, Cheng Shiu University, Kaohsiung 83347, Taiwan


Received: October 26, 2022
Revised: December 30, 2022
Accepted: January 3, 2023

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.


Download Citation: ||https://doi.org/10.4209/aaqr.220366  

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Cite this article:

Wu, H., Liu, C., Cen, C., Huang, C.E., Lin, S.L. (2023). Study on Dynamic Characteristics of Single Droplet Impingement on Heated Liquid Film. Aerosol Air Qual. Res. 23, 220366. https://doi.org/10.4209/aaqr.220366


HIGHLIGHTS

  • The impact interaction between single droplet and heated liquid film was explored.
  • With the change of We and film temperature, six typical phenomena were found.
  • The crown diameter, height, and existence time increase with We and temperature.
  • At high We, the proportion of large diameter sputtering droplets decreases.
  • The ratio of small-diameter sputtering droplets increases with the temperature.
 

ABSTRACT


The wall combustion is one of the soot and unburned hydrocarbon formation sources in the engine cylinders, which is affected by both spray and wall parameters. The impingement dynamics of the droplets on liquid films have been widely studied. However, there is less focus on the droplet impingements on hot liquid film, which is more representative as a pre-wall combustion condition. This work investigates the impingement dynamics of ethanol on heated glycerol liquid film. The Weber number (10 ≤ We ≤ 275) and liquid film temperature (70°C ≤ T ≤ 175°C) are two main parameters that lead to a comprehensive understanding of impinging phenomena. In the experiment, a high-speed camera was used to visualize the droplets impingement behaviors, which could be classified to six categories: deposition-spreading, rebounding-sputtering, rebounding-floating, stable crown-spreading, stable crown-sputtering, and splash crown-sputtering. The critical temperature for sputtering is about 125°C, independent of the We. The dynamic phenomena were quantified by the diameter and height of the crown, sputtering time and droplet size distribution. The dimensionless diameter, dimensionless height, and maintenance time of the crown all increase with the increasing We or temperature. When the We is greater than 172, the dimensionless diameter increases less. The relationship between the maximum dimensionless height of the crown and the We is H*max = 0.0026 We. The change of the crown diameter with time is independent from the temperature. Additionally, the sputtering time decreases with the increasing We and temperature. For the diameter distribution of sputtering droplets, the fractions of the larger sputtering droplets increased at low We, while the smaller droplets increased their contributions at high We. With the increase of temperature, the proportion of small diameter sputtering droplets increases.


Keywords: Droplet impingement, Liquid film, Weber number, Temperature, Sputtering




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