Browse Publications Technical Papers 2000-01-0254
2000-03-06

Exhaust Emissions from a Direct-Injection Spark-Ignition (DISI) Engine Equipped with an Air-Forced Fuel Injector 2000-01-0254

The effects of fuel injection and spark timing on engine-out, regulated (total HC, NOx, and CO) and speciated HC emissions have been investigated for a 0.31L, single-cylinder, direct-injection, spark-ignition (DISI) engine equipped with an air-forced fuel injector. When the timing of the start of the air injection (SOA) is varied during high stratification operation, the mole fractions of all regulated emissions vary sharply over relatively small (20-30 crank angle degrees) changes in SOA. In addition, the distribution of exhaust hydrocarbon species changes significantly. As stratification increases, the contribution of unburned paraffinic fuel components to the HC emissions decreases by a factor of two while the olefinic partial oxidation products increase. When the spark timing is varied during high stratification operation, the HC emissions increase sharply as the spark timing is retarded relative to MBT. This is opposite to the trend observed in homogeneous charge PFI engines and in this engine when it is operated in PFI mode. The trends with changes in both fuel injection timing and spark timing at high stratification are similar to those obtained previously from a multi-cylinder DISI engine with a totally different geometry and fuel injection system. These results show that the details of the fuel cloud evaporation, mixing, and location relative to the spark plug strongly influence the emissions from DISI engines.

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