Measurement of turbulent burning velocity of CH₄/H₂/air mixtures using OH-PLIF

Instantaneous flame front structure and turbulent burning velocities of CH₄/H₂/air mixtures were measured using OH-PLIF technique. Various turbulence intensities were generated by perforated plates with different hole diameter and opening ratio. Stabilized turbulent premixed flames were obtained at the outlet of the Bunsen burner for long-duration OH-PLIF measurement. 500 single shot images were averaged to obtain turbulent burning velocity by conventional angel method. The effects of hydrogen addition and turbulence intensity on turbulent burning velocity were analyzed and a power law correlation of turbulent burning velocity was obtained. Results show that turbulent burning velocity increases with the increase of turbulence intensity due to the increase of flame front area. Hydrogen addition increases the flame intrinsic instability and leads to the active response of laminar flame to turbulence, resulting in the much wrinkle flame front structure, larger flame front area and subsequently the increased turbulent burning velocity. A correlation between turbulent burning velocity and turbulence intensity was derived in the form of S_T/S_L∝a(u'/S_L)ⁿ, and n remained a constant value of 0.35.