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An experimental study aiming to investigate the effects of combustion chamber geometry on combustion process has been carried out in an optically accessible DI diesel engine. The combustion processes of three different chamber geometries, included the production type, were revealed and the flame movement behaviors such as the distribution of flame velocity vectors and the averaged flame velocity inside and outside the combustion chamber were measured by means of a cross-correlation method. Meanwhile, an endoscope system was used to acquire information about the distribution of flames inside and outside the chamber. BY comparing the flame movement and distribution between different chambers and nozzle protrusions, the results showed that; The chamber geometry has significant effect on the flame velocity, the flame velocities of the reentrant chamber were larger than that of the dish chamber during expansion period.

Tier 2 Emission standards enacted by the U.S. Environmental Protection Agency (EPA) require substantial emission reductions for new vehicles, including those with diesel engines. The standards are fuel neutral, and all light duty vehicles must eventually meet a fleet averaged emission level of Bin 5. To improve the emission capability for diesel engines, several advanced technologies have been investigated. These technologies include: common rail FIE with multi-injection capability, enhanced cooled EGR system with increased flow capability, variable geometry turbo charger, and a lower compression ratio piston. A new combustion approach using premixed diesel combustion was applied in the low load area for improving NOx and soot emissions significantly in the FTP-75 test cycle. Applying these technologies, engine out NOx was substantially reduced while maintaining similar soot levels.