Diesel fuel spray droplet sizes and volume fractions from the region 25 mm below the orifice

Droplet diameter and volume fraction measurements are reported for three different fuels (diesel fuel, dodecane, and metlyl oleate) as a function of radial position within a pressure-atomized spray typical of diesel systems. Injection system parameters were peak pressures of 62 MPa and a single-orifice injector with a 0.31-mm orifice diameter and an L/D ratio of approximately 2. Results are for individual injection events into atmospberic-pressure and ambient-temperature air at an axial distance of 25 mm from the nozzle. Measurements relied on infrared scattering, which was specifically chosen due to the high droplet number densities of these sprays . Details of the measurement technique are presented along with results. Results indicate droplet diameters are the smallest at the spray center line (2-3.25 mum), and grow with radial distance from the center line(6-mum at the spray periphery). Volume fractions greater than 1% are seen at the spray centerline, and, once the spray has developed, the majority of the mass is contained in the central 0.75-mm -radial region. Spray details presented include the deftnition of transient time periods for the spray, the spray width as a function of time, the coupling between injection pressure and observed diameters (SMD) and volume fractions, and the differences in the spray properties as a function of fuel type.