An experimental study on the droplet-air flow characteristics in an intermittent multi-hole diesel spray

摘要

This study is to investigate the droplet-air flow characteristics of a multi-hole diesel spray. A multi-hole nozzle has a 2-spring nozzle holder, and its hole number is 5(d{sub}n=0.32mm). The droplet diameter and velocity of a spray injected intermittently into still ambient air were simultaneously measured by using a 2-D PDPA (phase Doppler particle analyzer), The intermittent characteristics of fuel droplets(10＜D≤500 μm) and the air flow were examined, but the behavior of small droplets(D≤10μm) was regarded as a air flow. In normalized axial and radial droplet-air relative-velocity, comparatively high axial and radial relative-velocity is observed near the half width of the spray and in the leading edge of the spray. The mean axial and radial relative-velocity normalized by centerline velocity shows higher near the nozzle tip, and it continuously decreases with increasing axial distance until axial distance of 50mm. Overall mean axial and radial droplet-air relative-velocity is evaluated as 0.13 and 0.023 respectively.