EFFECTS OF CROSS-FLOW ON FUEL SPRAY INJECTED BY HOLE-TYPE INJECTOR FOR DIRECT-INJECTION GASOLINE ENGINE. SECOND REPORT: SPRAY PATTERN, DROPLET SIZE, AND VORTEX STRUCTURE

摘要

To further investigate the effect of cross-flow on the fuel spray, the characteristics of the spray were analyzed under a uniform cross-flow field by visualizing various sections. The fuel was injected into a chamber under room pressure and temperature using a valve covered orifice (VCO) nozzle. Tomographic images of the spray in a vertical and several horizontal planes were taken using a high-speed video camera. The size of the spray droplets was measured along the spray direction, as well as along the cross-flow direction. Tiny droplets, which were distributed in wavy structures, were observed in the streamwise direction in the vertical plane by the observation of successive images. In addition, under the cross-flow condition, the expansion on both sides of the spray in the vertical sections increased compared with that under the no-cross-flow condition. This expansion was quantified by measuring the projected spray angles, which were based on the spray images in the horizontal planes in the crossflow. The projected spray angles were extremely enlarged compared with that under the no-cross-flow condition. In addition, large droplets were distributed in the upstream edge of the spray according to measurements acquired using a laser diffraction size analyzer. The droplet size decreased gradually along the streamwise direction. The vortex phenomenon was observed in the upper leeward part of the spray. Moreover, the spray structure and frequency of the vortices were examined based on the tomography images in various vertical positions. This indicated that the vortices were caused by the interactions of the upper spray beam and the cross-flow.