Autoignition-induced flashback in hydrogen-enriched laminar premixed burners

This paper investigates the possibility of autoignition as a flashback initiation mechanism in laminar premixed burners powered by an increasing content hydrogen fuel blend. A specific experimental setup provides optical access inside generic burner reproducing main features domestic boilers. window is used to gather high-speed intensified images during transition flashback. Zooms into location provide clear evidence for existence two distinct regimes. In first one, initiated flame stabilized above that able propagate upstream through one holes. second regime, fresh gases burner, they flow along hot metallic internal wall. These observations are corroborated over large range equivalence ratio and content. They demonstrate dependence regime on wall temperature highlight role crossover hydrogen-enriched mixtures triggering autoignition. An Damkohler number Dai compares residence time delay defined. The found be more than order magnitude higher autoignition-induced cases compared propagating upstream, further supporting mechanisms leading results carry substantial implications design process H2-enriched burners.