A study on the emissions of butanol using a spark ignition engine and their reduction using electrostatically assisted injection

摘要

Butanol is a potential alternative to ethanol and offers many benefits including a much higher heating value and lower latent heat of vaporization. It also has a higher cetane number than ethanol and improved miscibility in diesel fuel. Additionally, butanol is less corrosive and less prone to water absorption than ethanol, which allows it to be transported using the existing fuel supply pipelines. However, while some previous research on the emissions of butanol-gasoline blends is available, little research exists on the emissions of neat butanol. This thesis focuses on two areas of study. The first area relates to on the comparison of UHC, NOx, and CO emissions of several butanol-gasoline and ethanol-gasoline blended fuels during combustion in an SI engine. The objective was to compare the emissions of butanol combustion to the ones of ethanol and gasoline. The second part of the study relates to the use of electrostatically assisted injection as a means of reducing the UHC emissions of butanol by decreasing the fuel droplet size using a charge electrode and extraction ring designed for a port fuel injector. Emissions measurements taken with and without a charge applied to the injector were used to determine the effect of applying a voltage to the fuel spray on engine emissions.It was established that the UHC emissions of neat butanol were approximately double the UHC emissions of gasoline and were appreciably higher than ethanol. CO emissions decreased and NOx emissions increased as the amount of butanol in gasoline was increased. Additionally, the CO emissions of butanol were lower than ethanol while it was not clear whether butanol had increased or decreased NOx emissions. It was also established that addition of 25% ethanol to butanol resulted in UHC emissions that were approximately 33% higher than those of neat butanol despite ethanol producing approximately 33% less UHC emissions than butanol. The results of the electrostatically assisted injection tests showed that, at certain engine operating conditions, application of 2000 V to the fuel spray resulted in a 10% increase in peak cylinder pressure, 4% reduction in UHC emissions, a 13.5% increase in NOx emissions, and a 13.5% reduction in CO emissions, which is consistent with the hypothesis that the voltage increased fuel atomization. However, tests at lower engine loads showed results contradictory to those at the higher engine load which suggested that the fuel droplet size may vary depending on engine operating conditions.