Measurement of flame front structure and burning velocity of premixed turbulent flames of CH₄/air and C₃H₈/air

Measurement of the instantaneous flame front structure of premixed turbulent flames of CH₄/air and C₃H₈/air mixtures was conducted using OH-PLIF technique. A variety of stable turbulence intensity was generated by perforated plates and laminar flame parameters were calculated. The effects of turbulence intensity and flame characteristics on turbulent flame structure and turbulent burning velocity were analyzed.Results showed that with the increase of turbulence intensity, the wrinkled intensity of flame front structure increased.For the same turbulence intensity, CH₄/air mixtures have more wrinkled flame front than C₃H₈/air mixtures.The flame front structure was obtained from the OH-PLIF images and the turbulent burning velocity was calculated by angle method and area method.The correlation was proposed to fit the turbulent burning velocity and turbulence intensity under weak turbulence. Meanwhile, at the same density ratio, i.e., with the same hydrodynamic instability, CH₄/air with greater thermo-diffusive instability shows higher turbulent burning velocity than C₃H₈/air. Moreover, with similar Lewis number and less significant role of thermo-diffusive instability, CH₄/air with larger density ratio has greater hydrodynamic instability, which has a significant influence on turbulent burning velocity.