Technical Paper
OH Radical Imaging in a DI Diesel Engine and the Structure of the Early Diffusion Flame
1996-02-01
960831
Laser-sheet imaging studies have considerably advanced our understanding of diesel combustion; however, the location on and nature of the flame zones within the combusting fuel jet have been largely unstudied. To address this issue, planar laser-induced fluorescence (PLIF) imaging of the OH radical has been applied to the reacting fuel jet of a direct-injection diesel engine of the “heavy-duty” size class, modified for optical access. An Nd:YAG-based laser system was used to pump the overlapping Q19 and Q28 lines of the (1,0) band of the A→X transition at 284.01 nm, while the fluorescent emission from both the (0,0) and (1,1) bands (308 to 320 nm) was imaged with an intensified video camera. This scheme allowed rejection of elastically scattered laser light, PAH fluorescence, and laser-induced incandescence. OH PLIF is shown to be an excellent diagnostic for diesel diffusion flames.