Eulerian-Eulerian Computational Fluid Dynamics (CFD) techniques continue to show promise for characterizing the internal flow and near-field spray for various fuel injection systems. These regions are difficult to observe experimentally, and simulations of such regions are limited by computational expense or reliance on empiricism using other methods. The physics governing spray atomization are first introduced. Impinging jet sprays and Gasoline Direct Injection (GDI) are selected as applications, and modern computational/experimental approaches to their study are reviewed. Two in-house CFD solvers are described and subsequently applied in several case studies. Accurate prediction of the liquid distribution in a like-doublet impinging jet spray is demonstrated via validation against X-Ray data. Turbulence modeling approaches are compared for GDI simulations with dynamic mesh motion, with results validated against previously available experimental data. A new model for turbulent mixing is discussed. Code performance is thoroughly tested, with new mesh motion techniques suggested to improve scaling. Finally, a new workflow is developed for incorporating X-Ray scanned geometries into moving-needle GDI simulations, with full-duration injection events successfully simulated for both sub-cooled and flash-boiling conditions.