Alcohols with carbon numbers ranging from C1 to C5 were individually blended with unleaded test gasoline. All the alcohol-gasoline blends had the same oxygen mass content. The performance characteristics of the blends were quantified using a single-cylinder spark ignition engine. The knock-limiting spark timing was determined by analysis of the third derivative of the measured in-cylinder gas pressure versus crank angle. The engine operating conditions were optimized for each (C1-C5) blend with two different values of matched oxygen mass content (2.5 and 5.0 per cent). Emission mass rates of carbon monoxide (CO), nitric oxides (NOx), total unburned hydrocarbons (THCs), alcohols and aldehydes were quantified. The brake power specific rate emissions were compared with that of neat gasoline. Adding lower alcohols (C1, C2 and C3) to gasoline improved the knock resistance. Further improvement was achieved by increasing the oxygen content of the fuel blend. Blends with higher alcohols (C4 and C5) showed degraded knock resistance when compared with neat gasoline. Generally, all alcohol-gasoline blends showed reduction in CO emissions. Higher alcohol-gasoline blends with an oxygen mass content of 5.0 per cent showed a pronounced increase in NOx emission rates when operating at high compression ratios and 5° before top dead centre timing. This is attributed to their lower enthalpy of vaporization and higher flame temperature. All blends tested at optimized operating conditions showed reduction in THC emission rates. Unburned alcohol emission rates were higher for blends with higher content of alcohol, and aldehyde emissions were higher for all blends with formaldehyde as the main constituent.
The use of alternative fuels is considered to be an effective measure to meet strict emissions regulations of particulate matter (PM) and oxides of nitrogen (NO x ). In response to these requirements, emissions data from inuse alternative fuel and diesel-powered heavy-duty vehicles have been measured and collected from 32 transit agencies in 17 states using the two West Virginia University (WVU) transportable heavy-duty vehicle emissions testing laboratories (THDVETLs). More than 600 tests have been performed on over 300 buses and heavy trucks operating on alternative fuels such as natural gas, methanol, and ethanol and also operating on conventional fuel diesel. Regulated emissions of PM, NO x , carbon monoxide (CO), and total hydrocarbon (HC) have been measured and analyzed. In this study, emissions data from alternative fuel buses and diesel control buses are carefully compared. The results show that natural gas, methanol, and ethanol have a strong potential to reduce PM and NO x emissions levels.
Emissions levels for CO, NOx, and unburned fuel (UBF) from a stationary four-cylinder Chrysler engine were measured under a variety of operating conditions for gasoline and three different 20 vol percent alcohol-gasoline blends. In tests of separate isobutanol, ethanol, and methanol blends, lower CO and NOx emissions were observed for the alcohol blends relative to gasoline, particularly for fuel-rich operation. Generally, on a volume (mole) basis unburned fuel emissions were highest for methanol blends and lowest for gasoline, but on a mass or OMHCE basis only small differences were noted. For a given fuel, the separate effects of engine speed, load, and equivalence ratio were examined.
Since air pollution by automotive exhaust gases is of increasing concern around the world, an examination of the work that has been done with regard to evaluating and reducing it can help focus future efforts in dealing with it. Alcohol-containing fuels not only have been shown to have the potential to produce less of many of the polluting gases, but they also constitute a viable alternative to gasoline from the standpoint of efficiency and reducing dependence on the rapidly dwindling supply of petroleum fuel. This report provides a survey of the literature concerning research reported since 1975 on emissions from IC engines operating on alcohol-gasoline fuel blends. The effects of alcohol on the exhaust emissions (carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and the aldehydes (CHO)) are reviewed. A comparison is made of the emissions benefits achieved when methanol or ethanol is used either in neat form or as the blending agent with gasoline. The primary dependent variable considered is emission level (reported on various bases) with the main independent variables being fuel composition, equivalence ratio, and ignition timing. Brief mention is also made of the potential emissions reduction that may be achieved by using dissociated methanol.
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