The initiation outwardly propagating spherical flames has been studied experimentally and numerically using n-Decane/air mixtures at atmospheric pressure. The flame trajectories, laminar flame speeds, and the critical radius have been measured and simulated at various equivalence ratios. A kinetic model has been used to study the flame structure of transient flame initiation to propagation phenomena. Both experiments and computations show that the Lewis number (preferential diffusion of heat and mass affects) both spherical flame initiation and flame kernel evolution after ignition. It is found that the generation of the radical pool plays important role in initiation of the flame kernel and sequential transition from ignition, unstable branch, and to the normal stable flame regimes. Paticualarly, the critical radius for the successful flame irritation is investigated and the results indicate that the outwardly propagating spherical flames in a stable branch can be achieved by overcoming the critical stretch rates at the critical radius.
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