Flame stabilization mechanisms and shape transitions in a 3D printed, hydrogen enriched, methane/air low-swirl burner

Flame shapes and their transitions of premixed hydrogen enriched methane flames in a 3D-printed low-swirl burner are studied using simultaneous OHxCH(2)O planar laser induced fluorescence and stereoscopic particle image velocimetry. Three different flame shapes are observed, namely bowl-shape, W-shape, and crown-shape. The bowl-shaped flame has its base stabilized through flame-flow velocity balance and its sides stabilized in the inner shear layer. While the bulges of the W-shaped flame rely on a similar stabilization mechanism in the central flow, its outer edges are stabilized by large-scale eddies in the outer shear layer. The crown-shaped flame is also aerodynamically stabilized in the center, but its outer edges are anchored to the burner hardware. At a fixed equivalence ratio, the statistical transitions between flame shapes across test conditions are jointly dominated by hydrogen fraction and bulk velocity. Dynamically, W-to-crown transition is attributed to the upstream propagation and attachment of the flame outer edges. Crown Copyright (C) 2021 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. All rights reserved.