Local Flame Structure of Turbulent Premixed Flames-DNS and CH /

In this study, three-dimensional direct numerical simulation (DNS) of H2-air premixed flames has been performed to clarify local flame structure in turbulent premixed flames. The heat release rate tends to increase at the flame convex toward burned side regardless of turbulent characteristics. Threedimensional handgrip structure generated by fine scale eddy leads to increase heat release rate compared with that of laminar flame. Two-dimensional DNS of CH4-air turbulent premixed flames are also conducted to investigate the local flame structure as well as the relation between heat release rate and species mole fraction. A pocket is observed in both unburned and burned side, which is consistent with the result of three-dimensional DNS. The distribution of heat release rate agrees with that of CH mole fraction even in high intensity turbulent premixed flames. Finally, the local flame structure and pressure fluctuations in the oscillating turbulent premixed flame are investigated by CH/OH PLIF and pressure measurement. The degree of wrinkling changed in terms of Reynolds number and equivalence ratio, and the local flame structure became more complicated with increasing Reynolds number. The observed scale of weak wrinkled flame front and flame cusps corresponds to integral length scale and Taylor micro scale of unburned mixture, respectively. The local flame structure is influenced by pressure fluctuations in the oscillation turbulent flames, and a relation between local flame structure and long period of pressure fluctuation is observed.