2D effects in laminar premixed flames stabilized on a flat flame burner

In the present work non-idealities of flat burner-stabilized flames at atmospheric and low pressures are examined using PIV measurements, which are supported by and analyzed with the help of CFD modeling. Radial and axial velocity profiles measured in the cold flow and in the flames at atmospheric and at lower pressures are presented. Two possible reasons for the drop in the apparent laminar burning velocity at low pressures (below 20 kPa) were considered: the non-uniformity of the velocity profile issuing from the burner mouth and diffusion of the gas mixture from the original gas flow. At very low pressures an outward velocity at the edge of the burner plate is detected. A part of the fuel–air mixture therefore seems to escape the flow at the edge of the burner. Further experiments, however, revealed that diffusion of the fuel from the fresh mixture and of the ambient atmosphere into the flame is less important as compared to the diffusive loss of H atoms from the flame at low pressures. This was substantiated by the numerical analysis and assessment of the earlier observations from the literature. A critical relation between the size of the burner and the lowest pressure for ensuring the stabilization of a flat flame is demonstrated.

► 2D velocity profiles in the cold flow and in the flames at atmospheric and at lower pressures using PIV.
► These measurements are supported by and analyzed with the help of CFD modeling.
► Critical phenomenon is radial diffusion of radicals and atoms from the flame.
► It affects flame burning velocity and causes flow non-uniformity.
► Relation between the size of the burner and lowest pressure to obtain a flat flame is demonstrated.