Effect of jet-jet interactions on soot formation in a small-bore diesel engine

This study presents planar laser-induced fluorescence of fuel and hydroxyl (fuel- and OH-PLIF) and incandescence of soot (soot-PLII) together with morphology and nanostructure information of soot particles sampled via thermophoresis to clarify the in-cylinder soot processes under the influence of jet to jet interactions. The experiments were carried out in a single-cylinder, small-bore optical diesel engine fuelled by a low-sooting methyl decanoate fuel for diagnostic purposes. Two different nozzle configurations of one hole and two holes were used to simulate isolated single-jet and double-jet conditions, respectively. Results show that fuel-rich mixture formed in the jet-jet interaction region causes the faster initial growth of soot that persists for a longer period of time, compared to the soot formed in the wall-impingement region of the single jet. These soot particles impacted by the jet-jet interaction have larger aggregates composed of larger primaries, and the nanoscale internal structures show higher carbon fringe-to-fringe separations, both of which indicate higher particle reactivity and the formation stage of soot.