Effects of multiple early injection on the combustion and emission characterastics in a DI diesel engine

Diesel engine technologies have been improved owing to high pressure common rail injection system. Since emission regulation for diesel engine has been enhanced, researchers tried to find a way to decrease NOx and PM such as clean combustion and after treatment. Among these clean combustion, premixed charge compression ignition technology is spotlighted as one of candidates for reducing NOx and PM simultaneously. In order to establish the premixed charge compression ignition, fuel is injected during early compression stroke and it can make enough time for uniform air-fuel mixture formation. Therefore, it is necessary to inject the fuel early timing to make homogeneous mixture in a cylinder. In this paper, early injections were used to get better combustion stability and characteristics of combustion and emissions were investigated with early injection strategies such as various early injection numbers(?) and timings. As a result, smoke was increased a little but it was still low. In addition, THC and fuel consumption were also showed similar levels. However, NOx emission was reduced conspicuously with the use of early injection