Ballistic Imaging and Scattering Measurements for Diesel Spray Combustion: Optical Development and Phenomenological Studies

Ballistic imaging using a 15 picosecond pulse laser in high-injection-pressure diesel sprays is reported. An optical Kerr effect shutter, constructed from a CS2 liquid cell and activated by a 15 picosecond pulse at 1064 nm, produces effective 532 nm imaging pulses between 7and 15 picoseconds. The performance of the imaging system is characterized using an Air Force target positioned before an optical cell filled with polystyrene spheres in a water suspension. The impact of spatial filtering, temporal filtering, and scattering path length on image resolution are reported. The technique is demonstrated by imaging the near-orifice region of methyl oleate and methyl butyrate sprays injected using a high-pressure single-hole fuel injector with direct comparison against simultaneous orthogonal shadowgraphy.