Experimental study on the explosion flame propagation behavior of premixed CH4/H2/air mixtures with inert gas injection

The active injection system was designed to study the explosion flame propagation behavior of premixed CH4/H-2/air mixtures in the closed tube with inert gas injection. The injection of inert gases (N-2, CO2, and air) was controlled by the injection time, t(inject), which is set from 0 ms to 210 ms. The effects of injection disturbance and inert gas dilution on flame morphology, flame tip dynamics, and overpressure build-up have been investigated. Results show that the injection of inert gas into premixed CH4/H-2/air flame wrinkles the early laminar flame, changing the flame structure. The increase in t(inject) shortens the flame propagation time and increases the maximum explosion pressure, but the maximum value is attained at t(inject) = 120 ms. The linear relationship between maximum explosion pressure and maximum flame tip velocity is presented. The addition of inert gas dilutes the fuel-air mixture, but the inert gas shows some inhibition effect on the turbulent explosion flame propagation at t(inject) > 120 ms. The injection disturbance plays a dominant role in the flame propagation process compared to inert gas dilutions. Finally, the effect of Darrieus-Landau and Rayleigh-Taylor instabilities on explosion flame propagation behavior has been examined. The injection of inert gas into premixed CH4/H-2/air flames creates local turbulence, enhances flame instabilities, and provides positive feedback on the flame's acceleration and oscillation.