Review to Determine the Benefits of Increasing Octane Number on Gasoline Engine Efficiency

摘要

The stated objective of the project is to conduct a broad and comprehensive literature review to determine the effects of gasoline octane number on light-duty spark ignition engine efficiency. The literature review is to be used to create a comprehensive database on the relationship between fuel properties and engine efficiency using the collected information. Comprehensive data on the relationship between fuel octane/composition and efficiency exist for naturally aspirated PFI engines at near full load. Data at light-load conditions and vehicle data on the FTP are more limited. However, many different output metrics are provided and an analytical framework to present the results of different papers on a comparable basis is required. This issue of different output metrics is true for all engine technologies examined in this study. Data for turbocharged PFI engines are more limited than for naturally-aspirated engines. Data on turbocharged engines have the additional complication that many factors such as boost availability (at low RPM), enrichment, waste-gate control, and turbine inlet temperature limitations affect the findings and are sometimes undocumented. Data on the octane effects for DI engines are also limited and many papers on DI engines have focused on the benefits of ethanol. However, there is enough data to develop at least a preliminary estimate of octane effects and fuel composition effects. The data set on turbo-charged DI engines has drawbacks similar to those for the turbocharged PFI engine data set. Data on stratified charge lean burn engines are very limited but interesting in that some of the available data suggests that increasing octane number reduces engine efficiency, which is not noted for any other technology reviewed in this study. Vehicle data are poorly supported with documentation of engine specifications, and the results from different vehicle studies appear somewhat contradictory, at least in this initial review.