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Lookup NU author(s): Freddie Young, Dr Umair AhmedORCiD, Professor Nilanjan ChakrabortyORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2024 The Authors. The influence of equivalence ratio on preferential diffusion effects and the resulting changes in the distributions of major species and their reaction rates have been analysed based on 2-D simulations of lean H2-air laminar premixed flames, at ϕ=0.4 and 0.7. The enhancements of burning rate, flame surface area, and stretch factor increase with decreasing equivalence ratio and the increase in stretch factor is particularly prominent when the burning rate and flame area are evaluated based on normalised mass fraction variation of H2. The preferential diffusion effects have been demonstrated to lead to significant deviations of mass fractions of major species and their reaction rates from the corresponding 1-D unstretched laminar premixed flame solution, and local variations of equivalence ratio. This tendency is particularly strong for H2 among all the major species. Moreover, mass fractions of O2 and H2O are found to assume super-adiabatic values at the super-adiabatic temperature zones and this trend is particularly strong for the ϕ=0.4 case. It has been demonstrated that the deviations of major species mass fractions and their reaction rates from their corresponding 1-D unstretched laminar premixed flame values arise principally due to preferential diffusion effects induced by relative focussing/defocussing of species and heat at the positively and negatively curved regions with the nature of the deviations being opposite to each other depending on the sign of the curvature. The variations of normalised species mass fractions of major species are found to be significantly affected by the local equivalence ratio within the 2-D laminar flame with ϕ=0.4 but these effects weaken with an increase in global equivalence ratio. It is also found that the reaction progress variable definition, relying on local mixture fraction, defined using H2 or O2 mass fractions remains bounded between 0.0 and 1.0 while showing monotonic variation with non-dimensional temperature.
Author(s): Young FW, Ahmed U, Chakraborty N
Publication type: Article
Publication status: Published
Journal: Fuel
Year: 2025
Volume: 381
Issue: Part B
Print publication date: 01/02/2025
Online publication date: 10/10/2024
Acceptance date: 02/10/2024
Date deposited: 03/10/2024
ISSN (print): 0016-2361
ISSN (electronic): 1873-7153
Publisher: Elsevier Ltd
URL: https://doi.org/10.1016/j.fuel.2024.133363
DOI: 10.1016/j.fuel.2024.133363
Data Access Statement: Data will be made available on request.
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