To investigate local flame structures of turbulent swirling premixed flame, direct numerical simulation (DNS) of hydrogen-air swirling premixed flame with swirl numbers of S = 0.6 and 1.2 in a cuboid combustor is conducted by considering a detailed kinetic mechanism. Heat release rate of turbulent swirling premixed flame is lower than that of laminar flame in the same inflow condition. For S = 0.6, the heat release rate distribution conditioned by reaction progress variable, which is defined by temperature in this study, has a peak at the reaction progress variable where laminar flame with same premixed gas takes the maximum heat release rate. However, for S = 1.2, the conditioned heat release rate distribution is much lower than the laminar condition in the region of low reaction progress variable, and that takes the maximum in high reaction progress variable region. Analysis on contribution of elementary reactions on heat release rate reveals that elementary reactions which contribute to heat release rate in low temperature region are disturbed because of low mass fraction of H for the case of S = 1.2. Furthermore, relations between tangential strain rate at flame front and heat release rate are investigated to understand local flame structures in detail.
