Abstract
In order to estimate the spray characteristics using a swirl-type injector, the spatial distribution of droplet size is one of the most important factors. In this study, two-dimensional measurements of spray droplet size distribution caused by a swirl-type injector are performed using an improved ILIDS (Interferometric Laser Imaging Droplet Sizing) method, which was developed by the authors. Also, measurements of the velocity of droplets using a PIV (Particle Image Velocimetry) method are carried out. The defect of the ILIDS method is the difficulty to distinguish overlapped interference images by droplets. In order to overcome this issue, lenses compressing images are set between a collecting lens and an image plane (CCD sensor). And the circular images are concentrated together with fringes retaining the information for circle diameter and involved fringe number. The experimental setup is illustrated schematically in Fig. 1. The fuel injection system consists of a pressure pump, a feeding tank, a swirl-type injector and a driver. As a light source, a double-pulse YAG laser is employed. A laser sheet with a thickness of 0.5mm is formed at measuring field by transmitting lenses. The scattered lights are collected by collecting lenses. The instantaneous images are captured by a mega-pixel CCD camera synchronizing the light source emissions. As a result, the spatial distributions of droplet-diameter were widely measured at several regions on a vertical cross section including the center-axis. By increasing the injection pressure, the mode diameter shifted to a small value. The distribution was curve-fitted to the Nukiyama-Tanasawa's distribution function and Rosin-Rammler's distribution function by changing the parameters. Estimation of the parameters was experimentally performed.
