ABSTRACT Laser-induced incandescence (LII) measurements using fiber-delivered laser pulses were made in an ethylene flame and compared under similar conditions to conventional open-optics measurements. For the same laser fluence, the signal magnitudes from the fiber delivered laser pulses were up to four times more intense and decayed faster than those from the open optics. However, when normalized with the intensity at maximum fluence, the fiber-delivered excitation LII (FDE-LII) signal showed similar relative laser fluence dependence with the conventional LII. The normalized signals from both methods also show very similar relative intensity variation profiles across the flame radius. These results indicate that the peak intensities of FDE-LII could be used in a very similar manner as conventional OO-LII to determine soot concentration; however additional analysis or development is required to infer the soot size characteristics from the signal decay rate.
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