抄録
To study the flow characteristics and particle diameters in a wide-angle conical spray proposed for premixed combustion diesel engines, an unsteady conical spray in air has been analyzed using a phase Doppler anemometer (PDA). In these experiments, the injection frequency is 20.8 Hz and the fuel injection quanTITY is 10.3 mg per cycle. Axial and radial bulk particle velocities and mean particle diameter distributions are obtained. As a result, it is found that the mean velocity distribution profile resembles the Goertler distribution, and the Sauter mean droplet diameter in the conical spray is as small as 30 μm. The relationship between particle diameter and velocity over the entire spray is negative and unusual compared with steady pressure spray flows, but is found to be normal if the spray is divided into several parts. We also find that small-diameter particles (20 μm) which are injected at a high speed (60 m/s) in the earliest stage lose velocity rapidly, merge into bigger particles, and are overtaken by bigger but slower particles which are emitted during a later stage. Large-diameter (50 μm) particles gather at the tip of the spray since they travel further from the nozzle exit.
