This research uses computational modeling to explore methods to increase diesel engine power density while maintaining low pollutant emission levels. Previous experimental studies have shown that injection-rate profiles and injector configurations play important roles on the performance and emissions of particulate and NOx in DI diesel engines. However, there is a lack of systematic studies and fundamental understanding of the mechanisms of spray atomization, mixture formation and distribution, and subsequently, the combustion processes in spray/spray and spray/swirl interaction and flow configurations. In this study, the effects of split injections and multiple injector configurations on diesel engine emissions are investigated numerically using a multidimensional computer code. In order to be able to explore the effects of enhanced fuel-air mixing, the use of multiple injectors with different injector locations, spray orientations and impingement angles was studied. The interaction of the spray with the geometry of the combustion chamber was also systematically studied. The potential for the use of multiple injectors to increase engine power density and to significantly reduce particulate and NOx emissions in DI diesel engines is revealed. This work demonstrates that multidimensional modeling can now be used to gain insight into the combustion process and to provide direction for exploring new engine concepts.