A laser 2-focus velocimeter (L2F) was used for the measurements of the velocity and size of droplets in the dense region of diesel spray which was intermittently injected into the atmosphere. The diameter of the nozzle orifice was 0.113 mm. The injection pressure was set at 40 MPa by using a common rail system. The L2F had a micro-scale measuring volume which consisted of two foci. The distance between two foci was 17 p.m, and the focal diameter was about 3|am. The maximum data sampling rate of the L2F system wajs markedly high as 15 MHz. Measurements were conducted at 15mm and 20mm downstream from the nozzle. The number density was calculated at several specified times from the measured velocity, size and arrival time of droplets. The sizes of droplets were larger at the spray center and the spray periphery than at the spray off-center. The result shows a strong inverse correlation between the droplet size and droplet number density.
