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.