Abstract
In a small direct injection diesel engine, the distance between the injection nozzle and the combustion chamber wall is short owing to the small cavity diameter. As the result, much fuel spray impinges on the chamber wall and the hydrocarbon (HC) and soluble organic fraction (SOF) increase at light loading conditions. In this paper the changes of the emission characteristics with increasing temperature or pressure at the compression end by using the combustion chamber materials with low thermal conductivity and the higher compression ratio were investigated. It is clear that these factors are effective in reducing the unburnt emissions at light load, however, the smoke density deteriorates at heavy load by the change of combustion pattern. In this study, the chemical analysis of unburnt HC and SOF components were done with the gas chromatograph. It was found that the correlation between HC and SOF is strong at light load but week at heavy load due to the difference of the boiling range of these unburnt components at each load.
