Abstract
A laser 2-focus velocimeter (L2F) has been applied for measurements of velocity and size of droplets in the core region of diesel spray. The L2F had a micro-scale probe which consisted of two foci. The focal diameter was about 3 μm, and the distance between two foci was 17 μm. The data sampling rate of the L2F system has been increased to 15 MHz. Investigated was the fuel spray injected intermittently into the atmosphere from an injector nozzle with the orifice diameter of 0.113 mm. The injection pressure was set at 40 MPa by using a common rail system. Measurement position was located at 15 mm from the nozzle. The number density of droplet was estimated with an interval of time between droplet appearances. It was confirmed that the velocity of droplet showed the highest at the spray center and decreased toward the off-axis direction. The spatial distributions of velocity and size of droplet were axisymmetric during injection. The mean number density in the spray core region was found to be about an order of 30,000 1/mm^3. It was understood that the mass flow rate was highest at the spray center and decreased towards the off-axis region.
