Effects of hydrogen enrichment ratio and turbulence on the structures of methane/hydrogen/air turbulent swirling premixed flames in a cuboid combustor

Direct numerical simulations of stoichiometric CH₄/H₂/air turbulent swirling flames in a cuboid combustor have been conducted to clarify the effects of hydrogen enrichment ratio and turbulence on the flame structures. The dimension of combustor, L_x x L_y x L_z is 15 mm x 10 mm x 10 mm and swirl number S is 1.2. The fuel mixture and wall temperature is 700 K and pressure is 0.1 MPa. In this study two cases of fuel composition, of which volumetric ratio of CH₄:H₂ equals 1:1 (M05H05) and 4:1 (M08H02) are simulated by using a reduced chemical mechanism consists of 25 species and 111 reactions. For M08H02, the concentrations of hydrogen molecules remain high and production reaction prevails in the boundary of shear layers. Quantitative evaluation in phase space suggests that the hydrogen mass fraction profile is almost flat for M08H02, whereas decreases similarly to unstrained laminar flame for M05H05. The rates of elementary reactions related to the hydrogen are suppressed compared to the laminar flames. Finally, the effects of turbulence on the reactions and heat release rates will be discussed.