To clarify the detailed structure of high pressure fuel spray, 2-D sectional images of non-evaporating fuel sprays in a high pressure vessel were observed by using the laser light sheet of a copper vapor laser. By this system, many sectional and continuous photographs of the same spray were obtained, and were very effective for the detailed observation of the spray inner structure and its developing process. The spray inner structure was very complicated, and its fuel density distribution was very heterogeneous. And for its developing process, the spray advances straight immediately after injected, then meanders, and deforms into a branch-like structure. Advancing downstream, these branches distribute complicatedly and heterogeneously with low density droplets. The heterogeneity is owing to these branches. And, the developing process is divided into four regions.
Further, the effects of some parameters on this process were investigated. Selected parameters were injection pressure, ambient pressure and nozzle configurations. By changing parameters, the positions of each region and inner behavior scale were changed. And these changed the inner structure considerably. The effects of each parameter were as follows: By increasing injection pressure, the fuel density distribution became more homogeneous even though fine heterogeneity remained. And from the result of image analysis using cross-correlation coefficient of the photographic light intensity, the turbulence intensity in the spray became higher. By decreasing the hole length or diameter of the nozzle, the density distribution became more homogeneous.