A New Combustion Chamber Concept for Low Emissions in Small DI Diesel Engines 2001-01-3263
This study proposes a new combustion chamber concept for small DI diesel engines. Reduction of fuel adhering to the cavity wall, improvements in mixture formation, and an optimum distribution of mixture inside and outside the cavity are the main characteristics of the combustion chamber.
The spray formation and it's distribution inside and outside the combustion chamber was investigated photographically in a small DI diesel engine with transparent cylinder and piston. Optimization of the fuel spray distribution inside and outside the cavity was attempted by changing the shape of the cavity entrance and the location where spray impinges on the lip. In addition improvements in the mixture formation of the impinging spray and reductions in the fuel adhering to the cavity wall were attempted by introducing a small step on the cavity side wall.
The results were confirmed by analyzing the combustion and emission in an actual DI diesel engine. Especially the effects of the entrance and side wall shapes were evaluated by measuring the HC, NOx, and smoke emissions. It was concluded that a round lip and spray impingement just on the lip can reduce HC and smoke emissions by 30% compared with a conventional cylindrical cavity. Moreover a 40% improvement in the HC and smoke emission is achieved with a slight penalty in NOx emissions if a small step is placed at the cavity side wall.