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New empirical equations to represent the Sauter mean diameter of a spray injected by a diesel nozzle are presented in this paper. In order to determine the new equations, drop sizes of a diesel spray were analyzed by a laser diffraction technique. Liquids with different viscosities and different surface tensions were tested to obtain the generalized empirical equations. The maximum injection and maximum ambient pressures were 90 MPa and 3.0 MPa respectively. Both the minimum value of the injection pressure to produce a fine spray and the Sauter mean diameter increase the greater the viscosity and the surface tension of the liquid. At a high injection velocity, the Sauter mean diameter increases with an increase in ambient pressure, but it decreases when ambient pressure is increased at a low injection velocity.

The behavior of diesel spray impinging on an inclined wall was experimentally investigated in a pressurized vessel. To clarify the wall effect on a diesel spray, a relative angle of the inclined wall to a spray axis was varied. Spray penetration along the wall was observed optically and it was compared with that of a free spray. To evaluate various spray motion quantitatively, a spray path penetration which described a development of a spray tip along the wall was newly introduced. To observe an internal structure of the spray, it was visualized by a YAG laser sheet light and its tomographic image was captured on a film. The photo-image on a film was taken into an image analyzing computer using a high resolved image scanner. A high density zone in the tomographic image was extracted to clarify the internal structure of an impinging spray. The main parameter of the relative position of the wall was its inclined angle which was defined as the angle between the spray axis and wall.

In this study, formation behaviors of soot in laminar diffusion flames of diesel fuel with fatty acid or fatty acid methyl ester (FAME) were investigated. Oleic acid and oleic acid methyl ester were selected as fatty acid and fatty acid methyl ester. Combustion gas emitted from the laminar diffusion flame was sampled, and PM composition in the gas was analyzed. Laser induced incandescence (LII) and laser induced fluorescence (LIF) techniques were applied to measure soot and polycyclic aromatic hydrocarbon (PAH) distributions in the laminar diffusion flames. As the results, soot emission and soot incandescence distributions were decreased by the addition of fatty acid or fatty acid methyl ester. Moreover, PAH concentration in the closed flame became high by addition of fatty acid or fatty acid methyl ester.