Genie G.M. Stoffels

Methods to correct planar laser-induced fluorescence distributions for local nonuniform laser attenuation

Planar laser-induced fluorescence is often used to obtain two-dimensional density distributions of specific molecules in reactive or nonreactive flows. In opaque environments, such as sooty flames or dusty air flows, the laser intensity decrease over the field of view must be taken into account. We describe two methods to determine the local extinction factor, and, from that, the local laser intensity. Both methods are based on elastic light scattering, one of which employs two elastic light scattering images, recorded simultaneously from the same probe volume, but illuminated from opposite directions. Although exact in principle, this method requires considerable experimental expenditure, and for this reason a more approximate method by use of only a single elastic scattering image is described as well. The results of both methods, applied to combustion diagnostics in an optically accessible Diesel engine, are compared.