A numerical study on diffusion H2/air flames in Y-shaped mesoscale combustors

Abstract

Recently, we experimentally investigated the combustion characteristics of non-premixed H2 and air in Y-shaped mesoscale combustors. In the present study, we aim at numerically explaining some experimental phenomena and tendencies, and revealing more details of flame propagation which cannot be well captured in the experiments. The numerical results show that the flame propagates in premixed flame mode in the downstream and shifts to edge flame mode in the upstream, which is a result of the fuel/air mixing effectiveness associated with the longitudinal distance. The inclination direction of flame might change during the propagation process, depending on its original direction after ignition. Moreover, the flame propagates faster in edge flame mode than in premixed flame mode. In addition, the edge flame length increases with the increase of combustor width because a longer distance is needed for a well mixing in the wider channel. Furthermore, the edge flame in the combustor of L = 100 mm is evidently longer compared to that of L = 200 mm when the nominal equivalence ratio is below unity (e.g., ϕ = 0.7). This is because the heat loss ratio under L = 100 mm is less than that of L = 200 mm.