The chemical and physical limits of cycle-to-cycle combustion variability and engine out emissions of a gasoline port fuelled spark ignition engine have been investigated. The experimental investigations were carried out on a V8 engine with port fuel injection and variable intake valve timing. The chemical limits of stable combustion have been shown to be a function of burned gas, fuel and air mixture. The widest limit, gas fuel ratio of <24, burned gas fraction <0.27 and AFR >9 was found at maximum brake torque spark timing. Retarding the spark timing by 10oCA caused a small reduction in the stable area, 20oCA retard reduced the stable combustion area significantly, whereby stable combustion occurred within an area of gas fuel ratio of <19, burned gas fraction <0.2 and AFR >10. Burn rate analysis indicated increased variability in both the flame development and rapid burn period. The increase in variability in the rapid burn period is greater than that associated with the flame development. The variability is magnified from flame development through the rapid burn phase. This finding was consistent for unstable combustion caused by exceeding chemical and physical limits. Engine out emissions were investigated and characterised using engine global state parameters, for example AFR, burned gas fraction, for both stable and unstable combustion conditions. Carbon monoxide and oxides of nitrogen emissions correlations were unaffected by the presence of unstable combustion events whereas hydrocarbon emissions showed a significant increase. The incorporation of these findings were implemented into an engine simulation (Nu-SIM V8) investigating the impact for the New European Drive Cycle condition.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:514811 |
| Date | January 2009 |
| Creators | Brown, Nicholas M. |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://eprints.nottingham.ac.uk/10821/ |
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