CHARACTERISTICS OF SPRAYS THROUGH A WALL IMPINGEMENT INJECTOR

The behavior of a liquid film generated by the impingement of a liquid jet onto a solid wall was investigated for the purpose of its application to the design of an injector equipped with a direct-injection spark-ignition (DISI) engine. The liquid nozzle newly developed by the authors generates little turbulence in a liquid flow. The characteristics of a liquid film issuing from the edge of a solid wall (such as film spread angle and spray tip penetration) were measured by varying the injection conditions. The fuel injector was developed based on these basic experiments. The size of spray droplets injected through this injector was measured using a phase Doppler particle analyzer (PDPA), and the results were compared with those from the conventional slit-type injector. At the center of the spray, the droplet size distribution peaks at the small droplet diameter. At the periphery, this distribution peaks at a larger droplet diameter than at the center, but the distribution becomes narrower. The mean droplet size decreases gradually toward the periphery and then increases in size. The Sauter mean diameter of the spray injected through the newly developed injector ranges from 17 to 27 μm. The wall impingement-type injector has the potential to control the spray configuration by the impingement conditions and the shape of the wall surface.