Time-Resolved Particle Image Velocimetry of dynamic interactions between hydrogen-enriched methane/air premixed flames and toroidal vortex structures

Time-Resolved Particle Image Velocimetry was used to study transient interactions between hydrogen-enriched methane/air premixed flames and toroidal vortex structures. Lean and stoichiometric mixtures with hydrogen mole fraction in the fuel (hydrogen plus   methane), xH2xH2, varying in the range of 0–0.5 were investigated.Results have shown that the hydrogen presence affects the flow field both quantitatively (increase of the velocity of the main toroidal vortex) and qualitatively (generation of different sub-vortices within the main vortex), enhancing the intensity of the interaction. Regardless of the mixture stoichiometry, the hydrogen substitution to methane leads to a transition from a regime in which the vortex only wrinkles the flame front (xH2<0.2xH2<0.2) to a more vigorous regime in which the interaction almost results in the separation of small flame pockets from the main front (xH2>0.2xH2>0.2). This transition was characterised in terms of time histories of flame surface area and burning rate.

► Interactions between H2-enriched CH4/air premixed flames and vortices were studied. ► H2-enrichement affects the flow field in both quantitative and qualitative terms. ► It causes a transition from wrinkled to breakthrough regime. ► This transition is accompanied by faster increase in flame surface area. ► The hydrogen presence also improves the burning quality.