Ballistic imaging of diesel sprays using a picosecond laser: characterization and demonstration

Ballistic imaging using a 15 ps pulse laser in high-injection-pressure diesel sprays is reported. An optical Kerr effect shutter, constructed from a CS sub(2) liquid cell and activated by a 15 ps pulse at 1064 nm, produces effective 532 nm imaging pulses between 7 and 15 ps. 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.