In this project, the effects of fuel injection parameters, equivalence ratios, EGR, intake charge temperature and alcohol-gasoline blends on HCCI combustion, performance and emissions were investigated. In this project, a direct injection diesel engine was converted to an electronically controlled DI-HCCI engine. The engine tests were conducted under the same energy input and constant speed conditions. At the end of the experimental study, it was seen that the second fuel injection timings are higher effective on HCCI combustion than the first fuel injection timings. This case showed that the second fuel injection timing is an important parameter for directly control of combustion phase on the HCCI combustion. When alcohol-gasoline blends was used, knock tendency increased at the earlier first injection timing for high equivalence ratio. With this project, the operating range of HCCI combustion can be extended by optimum usage of second fuel injection timing, injection ratio and EGR for alcohol-gasoline fuel blends. Maximum effective efficiency was obtained when methanolgasoline fuel blends was used. It was obtained that the effective efficiencies of alcoholgasoline fuel blends values were higher than those of pure gasoline when using optimal second fuel injection timing and intake charge temperature. When the emission values was analyzed, it was seen that unburned HC and CO emissions were less affected by the second fuel injection timing compared with NOx emissions. Within the Project, in terms of solution methods two different simulation software were used for engine analysis study. One of these software is SRM Suit that solves the zero dimensional mathematical equations for stochastically distributed particles inside the dimensionally predefined combustion chamber. Combustion in HCCI engine was analyzed with SRM Suit software in same conditions defined at experimental study with using proper chemical mechanism for pure gasoline, ethanol-gasoline and methanol-gasoline blends. Three Dimensional (3-D) analyses performed with using a Computational Fluid Dynamics (CFD) code known as Ansys-Fluent. Due to the limitation on number of species using at the chemical mechanism (maximum 50 species) at the Ansys-Fluent software, 3-D analyses performed only for gasoline fuel. Results from both two simulation technique showed good agreement with the experimental study