レーザドップラー法によるディーゼル機関用傘状噴霧流の特性解析 : 第1報,位相ドップラー法による粒径分布の解析

抄録

To study the characteristics of flow and particle diameters in large-angle conical spray proposed for Diesel engines of premixed combustion, unsteady conical spray in the air has been analyzed using a phase Doppler anemometer (PDA). In experiments, the frequency of injction is 20.8 Hz and the amount of injection fuel is 10.3 mg in each cycle. Axial and radial distributions of bulk velocity and mean diameter of particles are obtained. As a result, it is found that the profile of mean velocity distribution is close to the Goertler distribution, and the Sauter mean diameter of droplets in the conical spray is as small as 30μm. Correlation between particle diameter and velocity in the entire spray is negative and unusual, but is found to be normal if the spray is divided into parts and studied. We also find that particles with small diameter (20μm) which are emitted at high speed (60m/s) at the earliest stage lose velocity rapidly, merge into bigger particles, and are overtaken by bigger but slower particles which are emitted at the later stage. Particles with large diameter (50μm) gather at the tip of the spray as they travel farther from the nozzle exit.