Combustion in a propane/air burner is analyzed by means of imaging molecular constituents present in the plane of a laser light sheet and by recording the local refractive index distribution with a shearing interlerometer. The pulsed illumination with a UV light sheet yields an instantaneous image of the distribution of propane by elastic scattering, and of OH and CH radicals by laser-induced fluorescence. Spectral separation allows simultaneous and separate imaging of elastic and inelastic scattering, thus providing a means to analyze the spatial inter-relation of propane, CH, and OH. In a fuel-rich flame, laser-induced incandescence of soot particles is observed. Calibration of propane concentration levels is achieved by the refractive index measurements, which also help to estimate flame temperatures.
"Flame diagnostics by light sheet imaging and by shearing interferometry," Optical Engineering 32(5), (1 May 1993). https://doi.org/10.1117/12.133341