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The effect of temporally-splitting high pressure injection on Diesel spray combustion and soot formation processes was studied by using the high-speed video camera. The spray was injected by the single-hole nozzle with a hole diameter of 0.11mm into the high-pressure and high-temperature constant volume vessel. The free spray and the spray impingement on the two dimensional (2D) piston cavity wall were examined. Injection pressures of 100 and 160 MPa for the single injection and 160 MPa for the split injection were selected. The flame structure and soot formation process were examined by using the two-color pyrometry. The soot generated in the flame under the split injection under 160 MPa becomes higher than that of the single injection under 160 MPa.

The effect of spray/wall interaction on diesel spray flame characteristics was investigated by applying LAS (Laser Absorption-Scattering) technique, OH* chemiluminescence and two color pyrometry in a constant volume vessel. To insure the precision of this investigation, following necessary verification experiments were carried out: (1) OH* chemiluminescence and two color pyrometry were synchronously employed to analyze the influence of soot incandescence on OH* chemiluminescence signal intensity; and (2) frontal view and side view OH* images of a linearly arranged three holes injector were concentrated on to investigate the effect of soot on optical intensity attenuation under line-of-sight image recording condition. And then the effect of impinging distance (30,40,50,60 mm and free) on diesel spray and combustion behaviors were studied. The results reveal that the impinging distance plays a significant role in mixture formation.

The effects of spray/wall interaction on diesel combustion and soot formation in a two-dimensional piston cavity were studied with a high speed color video camera in a constant volume combustion vessel. The two-dimensional piston cavity was applied to generate the impinging spray flame. In the cavity, the flat surface which plays a role as the cylinder head has a 13.5 degree angle with the injector axis and the impinging point was located 30 mm away from the nozzle tip. Three injection pressures of 100, 150, and 200 MPa and a single hole diesel injector (hole diameter: 0.133mm) were selected. The flame structure and combustion process were examined by using the color luminosity images. Two-color pyrometry was used to measure the line-of sight soot temperature and concentration by using the R and B channels of the color images. The soot mass generated by impinging spray flame is higher than that of the free spray flame.

Spray characteristics are of great importance to achieve fuel economy and low emissions for a D.I. gasoline engine. In this study, the characteristics of the fuel spray as well as its interaction with a cross-flow were investigated. The fuel was injected by a VCO injector into an optically accessible rectangular wind tunnel under the normal temperature and pressure, in which the direction of the injection was perpendicular to the direction of the cross-flow. The velocity of the cross-flow varied from 0 to 10 m/s while the injection pressure was 5 and 10 MPa. With using the high speed video camera and the PIV system, the spray profile, velocity distribution and the penetration distance were measured. The lower penetration distance can be obtained with the lower injection pressure and the increased velocity of the cross-flow, however the injected fuel expands along the direction of the cross-flow, which indicates that spray atomization and mixing of fuel and air are enhanced.