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The objective of this investigation is to characterize the influence of injection parameters and spray-wall interaction on atomization and gas entrainment processes of high-pressure non-evaporative sprays injected into a high-pressure vessel using several imaging techniques. The effects of injection pressure on the droplet distribution, size and velocity were quantified using single and double nano second exposure photography techniques. A laser-sheet imaging method was employed to measure the two-dimensional gas velocity around the spray and to clarify the effects of the above parameters on the gas entrainment into the impinging sprays. It was found that increasing the injection pressure causes an increase in droplet number in both free and wall-jet regions of the sprays. Spray-wall impingement creates a large-scale gas vortex around the spray, which promotes the gas entrainment into sprays typically at the impinging zone, and it also affects the spatial distribution of droplets.

In this study it is tried to reduce NOx and particulate emissions simultaneously in a direct injection diesel engine based on the concept of two-stage combustion. At initial combustion stage, NOx emission is reduced with fuel rich combustion. At diffusion combustion stage, particulate emission is reduced with high turbulence combustion. The high squish combustion chamber with reduced throat diameter is used to realize two-stage combustion. This combustion chamber is designed to produce strong squish that causes high turbulence. When throat diameter of the high squish combustion chamber is reduced to some extent, simultaneous reduction of NOx and particulate emissions is achieved with less deterioration of fuel consumption at retarded injection timing. Further reduction of NOx emission is realized by reducing the cavity volume of the high squish combustion chamber. Analysis by endoscopic high speed photography and CFD calculation describes the experimental results.