Hydrogen-air premixed laminar flames are likely to develop instabilities due to hydrodynamic effects (known as Darrieus-Landau instability) or thermodiffusive effects. The former is due to the change in fluid density through the flame while the latter is associated to the thermodiffusive properties of the species. The flame instability is recognized by the appearance of local combustion areas known as cells, characterized by their self-accelerating behavior.
The purpose of this Masters’ thesis was to study the influence of several parameters on the phenomenon of cellularity : the kinetic mechanism, the mixing law, the pressure and finally the initial condition of perturbation. In order to realize this study, a numerical model was set up : compressible, laminar and unsteady Navier-Stokes equations are solved on a 2D square computational domain having 160 000 cells using STAR-CCM+ and using a 2nd-order explicit spatiale discretization scheme and a 2nd-order temporal implicit discretization scheme.
Firstly, four kinetic mechanisms were tested. Although the global behaviour of the flame front of each kinetic mechanism was similar, there were still differences on the total number of cells but also on their sizes, probably due to the kinetic mechanims associated with each kinetic. The influence of the mixing law was also studied by using two different mixing laws : a mixing law based on mass fraction and the mixing law of Mathur-Saxena, based on molar fraction. It resulted in a substantial impact of this parameter on the cellularity because of the modification of the mixture thermal conductivity and so the modification of the Lewis number. The influence of pressure increasing resulted in more cells but also in a significant modification of the flame front as it became more chaotic and serrated. At last, the parameters of the initial perturbation were studied (amplitudes of perturbation and oscillation frequency) and the results indicated that it impacts both the flame front and the cells (size and number).
This study enabled to quantify the influence of several parameters on the cellularity phenomenon, by using a two-order simple model.
| Date | 11 Sept 2017 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Patrice Seers (Supervisor) |
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Le Corvec, L. (Author),
Seers (Supervisor),
11 Sept 2017Student thesis: Master's thesis › Master in Engineering: Engineering