| The liquid fuel film breakup phenomenon that occurs in an intake port of a coldstart port-fuel-injected engine is of great importance in regard to engine emissions. To enhance the understanding of this phenomenon, the fundamental nature of a shear-driven liquid film flow around a sharp corner was investigated in this dissertation.; A numerical model was developed to simulate the film behavior both before and after the sharp corner. Two computational units, predicting the turbulent gas field and the liquid wall film propagation, were coupled to take into account their interactions. An analytical separation criterion was proposed to determine whether the liquid film separates from the corner or continues to stay attached to the surface. Upon film separation at the corner, a breakup submodel was employed to describe the droplet field.; As an initial step in validating the models, a simple 2D test section was built, which serves as a rough representation of the sharp valve edge. The liquid film behavior around the comer was studied both qualitatively and quantitatively. The various submodels were validated by experimental data from this study and others. It was found that the film separation point and the resulting droplet field depended mainly on the film characteristics before the corner, as well as the gas phase conditions. The thicker the film is, and the faster the film-flows, the easier it gets separated. With the parametric variations, it was also shown that the liquid surface tension and the gas flow velocity played important roles in determining the liquid film separation point and the final droplet sizes, while the effects of the liquid flow rate was diminishing under high gas velocities. |
