Influence of the Injector Geometry at 250 MPa Injection in a Light-Duty Diesel Engine 2017-01-0693

This paper investigated the influence of the injector nozzle geometry on fuel consumption and exhaust emission characteristics of a light-duty diesel engine with 250 MPa injection. The engine used for the experiment was the 0.4L single-cylinder compression ignition engine. The diesel fuel injection equipment was operated under 250MPa injection pressure. Three injectors with nozzle hole number of 8 to 10 were compared. As the nozzle number of the injector increased, the orifice diameter decreased 105 μm to 95 μm. The ignition delay was shorter with larger nozzle number and smaller orifice diameter. Without EGR, the particulate matter(PM) emission was lower with larger nozzle hole number. This result shows that the atomization of the fuel was improved with the smaller orifice diameter and the fuel spray area was kept same with larger nozzle number. However, the NOx-PM trade-offs of three injectors were similar at higher EGR rate and higher injection pressure. The effect of high injection pressure was dominant for reducing PM emissions, and the effect of nozzle geometry on the PM emissions wasn’t distinguishable at these conditions. The deeper penetration from larger nozzle orifice diameter was also beneficial to reduce the PM emissions under this condition. The indicated specific fuel consumptions of three injectors were on the same level because of their identical fuel volumetric flow rates and similar in-cylinder pressure traces. Also, the effect of nozzle hole number with the same orifice diameter (95 μm) was identified with 8- and 10-hole injectors. The higher fuel injection rate and increased nozzle and spray number from 8 to 10 resulted in the lower fuel consumption and PM emission. This research provides a standard on the optimal design of hole number and diameter in automotive engine injector nozzles.