Reduction of soot emissions in diesel engines due to increased air utilization by new spray hole configurations

Abstract

With conventional combustion processes there remain unused regions with air between the injection jets. To use these, a 14-hole-nozzle and a nozzle with six smaller and six larger spray hole diameters were developed. Both nozzles show strongly increased soot emissions. The optical analysis shows that the combustion zones of the 14-hole-nozzle overlap and create very rich local combustion zones. Furthermore, the small spray hole diameters reduce the spray momentum and a backflow from the piston bowl which would lead to improved air utilization cannot be created. The small spray holes of the 6+6-nozzle create a spray momentum that is too large to only use the air in the middle of the combustion chamber. At the same time the injection jets restrain the backflow generated by the larger spray holes.