This paper addresses the impact of H2 addition on lean blowout in premixed swirling flames. Previous work shows that the manner in which the flame blows off varies with percentage of H2 [1,2]. The objective of this paper is to follow up on these observations and systematically characterize the blowoff phenomenology as a function of the H2 levels in the fuel. This is accomplished through high speed visualizations of the flame emission and velocity field measurements. Near blowoff, a variety of highly dynamic flow features are observed, which vary substantially with the H2 levels in the fuel. These features involve complex interactions between the vortex breakdown bubble, outer recirculation zone of the rapid expansion, and flame extinction/reignition phenomenon. Key questions for future studies are the relative roles of fluid mechanics and chemical kinetics in causing the phenomenological variations in near blowoff dynamics, and which features are geometry specific and which are generic to near blowoff flame dynamics.

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