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The enhancement of vortex development, fuel-air mixing and heat release in diesel spray flame by inversed-delta injection rate shaping, having been predicted via LES simulation with detailed chemical kinetics, is experimentally confirmed for the first time. Newly developed 3-injector TAIZAC (TAndem Injector Zapping ACtivation) injector realizing aggressive inversed-delta injection rate shaping was used for single-shot combustion experiments in a constant volume combustion vessel. Simultaneous high-speed (120,000fps) and high-resolution (1,280 x 704 pixels) laser schlieren and UV OH* chemiluminescence imaging combined with subsequent Flame Imaging Velocimetry (FIV) analysis was employed to elucidate the correlation between vortex development and enhanced heat release.

For better understanding, model development and its validation of in-cylinder soot formation processes of Gasoline Direct Injection (GDI) engines, visualization of piston surface fuel wetting, vaporization and soot formation processes of in-cylinder pool fire via high-speed UV (266nm) and visible (445nm) laser shadowgraphy was attempted in an optically accessible Rapid Compression and Expansion Machine (RCEM). A direct-injection, spark-ignition and single-shot combustion event was achieved in the RCEM under engine-equivalent, simplified and well-defined conditions operated with engine speed 600 rpm, compression ratio 9.0, equivalence ratio 0.9 and natural aspiration. The tested fuel was composed of 70% iso-octane and 30% toluene by volume and the UV absorption by toluene enabled visualization of the in-cylinder fuel distribution.

As a new method to examine the extremely unsteady and spatially varying wall heat transfer phenomena on diesel engine combustion chamber wall, high-speed imaging of infrared thermal radiation from the chromium coated window surface impinged by a diesel spray flame has been conducted in a constant volume combustion chamber. The infrared radiation from a back surface of the chromium layer was successfully visualized at 10kHz frame rate and 128 × 128 pixel resolution through the window. The distributions of infrared radiation, temperature and heat flux exhibited coherent and streaky structure with radial stripes extending and waving from a stagnation point likely reflecting the near-wall turbulent structure in a wall impinging diesel flame. The experiments were conducted with various parameters such as fuel injection pressure, ambient gas oxygen concentration, wall impinging distance, wall surface roughness and wall materials.