Quantitative local equivalence ratio determination in laminar premixed methane–air flames by laser induced breakdown spectroscopy (LIBS)

Laser induced breakdown spectroscopy has been used in order to obtain quantitative local equivalence ratio measurements in laminar premixed methane–air Bunsen flames. The total emission intensities of the 656.3 nm Hα and the 777 nm O(I) atomic spectral lines were simultaneously measured and a linear relation of the H/O intensity ratio with the flame equivalence ratio ϕ was established. Axial and radial profiles of local equivalence ratio were thus obtained for both lean and rich flames and were used to provide information regarding flame structure and dynamics.