Experimental Study on the Influence of Nozzle Orifice Number on Comustion and Emissions Formation of a Heavy Duty DI Diesel Engine

Paper in proceeding, 2003

This paper presents an investigation of flame development and soot distribution in the flame at four operating points of a heavy duty D.I. diesel engine for two different nozzle configurations (one with six and one with nine orifices). To facilitate the comparison the orifice size was adjusted in order to ensure that the injection pressure and duration were the same in both cases. For this reason, however, the jet penetration differed between the two configurations. The measurement techniques used in the study included both “conventional” measuring methods and two-colour pyrometry. For the latter, the cylinder head was modified to allow an endoscope and light unit to be mounted at three different positions. Test results showed that use of the nine-orifice nozzle at high load leads to higher soot emissions, apparently because air utilisation is less efficient under such conditions, except with late injection. For late injection, reductions in both NOx and soot were observed as a result of increases in the ignition delay period, which countered the disadvantageous effects of the weaker jet penetration associated with the smaller orifices of the nine-orifice nozzle. For low loads, the nine-orifice nozzle gave better fuel distribution, thus improving the NOx/soot trade-off curves and providing more intensive soot oxidation.