The development and introduction of new engine technologies are primarily motivated by the need to comply with increasingly stringent emissions legislation and to reduce fuel consumption. One of the most important of these new engine technologies is Gasoline Direct Injection (GDI), which is considered to be an important and cost-effective measure to meet both targets. Computational Fluid Dynamics (CFD) simulations and optical methods are important tools in the development of direct injection gasoline engines. The aim of this work was to develop models, methods, and a numerical platform for simulating the behavior of GDI engines using a variety of fuels, including gasoline-ethanol blends. One of the most important goals of this work was to devise improvements to OpenFOAM (a free, open source CFD package) that would increase its utility as a tool for studying GDI engines, as there is strong industrial demand for inexpensive software. This book addressed two important problems relevant to modelling combustion in a GDI engine, including combustion chemistry and spray modelling.