LES/CMC modelling of ignition and flame propagation in a non-premixed methane jet

Authors
Giusti, A 
Mastorakos, E 

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Article
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Abstract

The Large Eddy Simulation (LES) / Conditional Moment Closure (CMC) model with detailed chemistry is used for modelling spark ignition and flame propagation in a turbulent methane jet in ambient air. Two centerline and one off-axis ignition locations are simulated. We focus on predicting the flame kernel formation, flame edge propagation and stabilization. The current LES/CMC computations capture the three stages reasonably well compared to available experimental data. Regarding the formation of flame kernel, it is found that the convection dominates the propagation of its downstream edge. The simulated initial downstream and radial flame propagation compare well with OH-PLIF images from the experiment. Additionally, when the spark is deposited at off-centerline locations, the flame first propagates downstream and then back upstream from the other side of the stoichiometric iso-surface. At the leading edge location, the chemical source term is larger than others in magnitude, indicating its role in the flame propagation. The time evolution of flame edge position and the final lift-off height are compared with measurements and generally good agreement is observed. The conditional quantities at the stabilization point reflect a balance between chemistry and micro-mixing. This investigation, which focused on model validation for various stages of spark ignition of a turbulent lifted jet flame through comparison with measurements, demonstrates that turbulent edge flame propagation in non-premixed systems can be captured reasonably well with LES/CMC.

Publication Date
2019
Online Publication Date
2018-11-02
Acceptance Date
2018-09-18
Keywords
Flame kernel formation, Flame edge propagation, Flame stabilization, Large Eddy Simulation, Conditional Moment Closure
Journal Title
Proceedings of the Combustion Institute
Journal ISSN
1540-7489
1873-2704
Volume Title
37
Publisher
Elsevier BV
Sponsorship
Engineering and Physical Sciences Research Council (EP/K025791/1)