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Lookup NU author(s): Professor Nilanjan ChakrabortyORCiD
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).
The effects of droplet diameter, overall equivalence ratio (0.8–1.5), and primary evaporation zone length (2–10 mm) on the burning velocity and thermal flame thickness in laminar n-heptane monodisperse spray flames under varying pressures (1.0–2.0 bar) have been analysed using 1D numerical simulations. It is observed that for gaseous premixed flames, both flame speed and thickness decrease with increasing pressure. However, in spray flames, flame thickness increases while burning velocity decreases as pressure rises, primarily due to reduced evaporation rates that limit fuel vapor availability. Larger droplet sizes further diminish evaporation rates, which lowers burning velocity and increases flame thickness, regardless of pressure. The finite evaporation rate also results in local equivalence ratios that are lower than the overall equivalence ratio in the heat release zone within the flame, especially at high pressures and with large droplets. In overall fuel-rich mixtures (e.g., for an overall equivalence ratio of 1.5), this can lead to more reactive gaseous mixtures and higher burning velocities than corresponding gaseous premixed flames, particularly for small droplets. Notably, the burning velocity in some spray flames can exceed the burning velocity of the corresponding premixed flames at the same gaseous-phase equivalence ratio at the heat release rate location. Enhanced burning velocity is also attributed to the generation of reactive species (e.g., H₂, C₂H₂, C₂H₄) from droplet evaporation and pyrolysis behind the flame front, which diffuse back into the reaction zone and accelerate the combustion process. However, the formation of these species diminishes at higher pressures, reducing this enhancement effect.
Author(s): Ozel-Erol G, Kucuk M, Chakraborty N
Publication type: Article
Publication status: Published
Journal: Applications of Energy and Combust. Science
Year: 2025
Volume: 23
Print publication date: 01/09/2025
Online publication date: 09/08/2025
Acceptance date: 08/08/2025
Date deposited: 01/09/2025
ISSN (electronic): 2666-352X
Publisher: Elsevier
URL: https://doi.org/10.1016/j.jaecs.2025.100366
DOI: 10.1016/j.jaecs.2025.100366
Data Access Statement: Data will be made available on request.
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