Effect of nozzle orifice size on soot particle size in a di diesel engine

The effect of nozzle orifice size on smoke emission was examined experimentally in a turbochar-ged DI diesel engine. The nozzle orifice size was varied from 0.26 to 0.18 mm under various engine operation condition. The rates of NO-formation, soot-formation and soot-oxidation were analyzed by using the two-zone model based on the measured combustion pressure time history. The changes due to orifice size in the excess air ratio of the burned zone, the soot particle size and the number of soot particles were estimated. It is shown that the soot size is primarily dependent on the orifice size and secondarily but more markedly on the spray penetration for the ignition delay period, and the number of soot particles is primarily dependent on the amount of fuel injected and secondarily on the excess air ratio of the burned zone.