To study characteristics of the flow and particle diameters in a large angle conical spray proposed for Diesel engines with premixed combustion, an unsteady conical spray in air has been analyzed using laser Doppler anemometer (LDA) and phase Doppler anemometer (PDA).
In experiments, the frequency of injection was 20.8Hz and the amount of injection fuel was 10.3mg each cycle. Axial and radial distributions of bulk velocity and intensity of turbulence are obtained. As a result, it is found that the profile of mean velocity distribution is close to the normal distribution and the relative intensity of fluctuation is about 20%, Sauter mean diameter of droplets in the conical spray is as small as 30 μm. Correlation between particle diameter and velocity in the whole spray is negative and unusual but this is explained if the spray is divided into parts and studied. Particles of small diameter (20 μm) which come out at high speed (60m/s) in the earliest stage, lose velocity rapidly and are overtaken by bigger but slower particles which come out at the later time of injection. Particles of large diameter (50 μm) then gather at the tip of spray as they move away from the nozzle exit.