Quantitative investigation of sooting dynamics in droplet combustion using an automated image analysis algorithm

Journal Article · 07 August 2023 · Fuel

DOI: https://doi.org/10.1016/j.fuel.2023.129313 · OSTI ID:1998035

Xu, Yuhao  ^[1]; Shen, Yiren  ^[2]; Avedisian, C. Thomas ^[2]; Hicks, Michael C. ^[3]; Choi, Mun Y. ^[4]

---

1. Prairie View A&M University, TX (United States); Clemson University, SC (United States); Fuel Journal
2. Cornell University, Ithaca, NY (United States)
3. NASA-Glenn Research Center, Cleveland, OH (United States)
4. University of Missouri, Columbia, MO (United States)

This paper reports an image analysis approach using a newly-developed open-source program to extract quantitative measurements of soot volume fraction (SVF) from digital video images of burning n-heptane droplets. The automated program developed in this work can analyze images of fixed and untethered droplets to quantify sooting dynamics. The images analyzed in the program were taken from experiments carried out in the Multi-user Droplet Combustion Apparatus (MDCA) onboard the International Space Station (ISS). In these experiments, video imaging of burning droplets was obtained using backlighting by a laser diode with a wavelength of 653 nm. Here, the light was collimated before it passed through the droplet and soot-containing region, after which the light was then attenuated and projected onto the camera’s sensors. This technique facilitates the measurements of SVF based on the principles of the full field light extinction method (FFLEM). The measurements provide quantitative data that reveal the sooting dynamics of liquid fuels during droplet combustion processes. The analyses of a soot-attenuating image (ISS n-heptane, untethered droplet) at an instant during the burning show that the SVF distribution has a peak at the soot shell location. It then decreases due to soot oxidation when the location is further away from the burning droplet. Regarding temporal effects on the maximum SVF (SVF_max), results show that SVF_max first increases after the burning is initiated until a peak value is reached, after which SVF_max decreases. The SVF_max values identified in this study for n-heptane are quantitatively consistent with previously reported values for fiber-supported droplets and are reached relatively early in the burning history. n-Heptane images are also analyzed to show the effects of initial droplet sizes on the maximum soot volume fraction. Results show that SVF_max decreases with increasing initial droplet size, which is consistent with visual observations of less soot formed and dimmer flame brightness as Do increases.

• Research Organization: Cornell University, Ithaca, NY (United States)
• Sponsoring Organization: National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Sustainable Transportation. Bioenergy Technologies Office (BETO)
• Grant/Contract Number: EE0007978
• OSTI ID: 1998035
• Journal Information: Fuel, Journal Name: Fuel Vol. 354; ISSN 0016-2361
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English