The current energy crisis highlights the need for the design of more powerful, fuel-efficient, and environmentally friendly combustion systems. With the development of increasingly affordable and powerful computers, advanced computer simulation modelling, using Computational Fluid Dynamics (CFD), has become a valuable tool that can be used to improve efficiency of combustion systems and to reduce high cost and time-consuming experimental investigations in modern engineering development processes. The understanding of the complex nature of the multiphase flows, combustion processes and pollutants formation in experimental investigations is limited and this understanding can be significantly improved by numerical modelling and simulations. In this overview, one can find a current modelling work performed by CFD combustion modelling group, which is a part of Power engineering and energy management chair at the Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb. The CFD group activities are focused on the research and development of numerical models and simulation tool FIRE™, which can provide detailed insight into the complex interacting physical and chemical processes required for design and optimization of the various combustion systems.