Effect of a Preprocessing Method on the Inversion of OH * Chemiluminescence Images Acquired for Visualizing SNG Swirl-stabilized Flame Structure

ABSTRACTFlame structure, which contains a useful information for studying combustion instability of the flame, is often quantitatively visualized with PLIF (planar laser-induced fluorescence) and/or chemiluminescence images. The latter, a line-integral of a flame property, needs to be preprocessed before being inverted, mainly due to its inherent noise and the axisymmetry assumption of the inversion. A preprocessing scheme utilizing multi- division of ROI (region of interest) of the chemiluminescence image is proposed. Its feasibility has been tested with OH PLIF and OH* chemiluminescence images of SNG (synthetic natural gas) swirl-stabilized flames taken from a model gas turbine combustor. It turns out that the multi-division technique outperforms two conventional ones: those are, one without preprocessing and the other with uni-division preprocessing, re-constructing the SNG flame structure much better than its two counterparts, when compared with the corres-ponding OH PLIF images. It is also found that the Canny edge detection algorithm used for detecting edges in the multi-division method works better than the Sobel algorithm does.