EXPERIMENTAL INVESTIGATION OF NEAR NOZZLE SPRAY STRUCTURE AND VELOCITY FOR A GDI HOLLOW CONE SPRAY

摘要

Previous experiments and numerical investigations of engine sprays show string-like structures at the exit of outwardly opening nozzles applied in gasoline direct injection (GDI) engines. These structures were further analyzed using visualization techniques and laser correlation velocimetry (LCV). Ambient conditions of 0.1 MPa and 300 K were chosen for all experiments, while injection pressure and injector energizing time were varied to resolve the influence of injection parameters on structure and velocity. Through application of a visualization measurement technique with a far-field microscope the string-like structures and their evolution during the injection period have been identified. In addition the influence of the injection parameters on the shape and location of the strings has been analyzed. After resolving the differences in string structure, the influence of the string structure on the velocity distribution at the nozzle exit was investigated for obtaining a correlation between string structure and spray velocity. Finally, the dependency of spray exit velocity on injection pressure and injection duration was determined. The information about string structure and nozzle exit velocity can be used to deduce different influences on the primary breakup of a hollow cone spray generated by an outwardly opening nozzle.