Combustion quality and regimes for standard and alternative fuels

Upcoming environmental constraints require the next generation internal combustion engine (ICE) to yield lower pollutant emissions and higher fuel efficiency. Various alternative fuels and combustion strategies and regimes have shown great potential in meeting these goals. The work done in this dissertation aims at exploring different alternative fuels and advanced combustion strategies through a combination of single-cylinder engine performance and emission tests, laser diagnostics in optical engines, and soot analysis using materials research techniques, in order to improve the combustion and emission performance of the modern ICE. Alcohols, especially n-butanol, have been studied as potential fuels and have shown to be a possible alternative to pure gasoline. In this work, the intermediate product in bio-butanol production through acetone-butanol-ethanol (ABE) fermentation, ABE, was studied for the first time as a potential alternative fuel in spark ignition (SI) engines. Various blends of ABE and gasoline, with different ratios of acetone, n-butanol, and ethanol were studied under various engine operating conditions. The results obtained affirm ABE’s potential as an alternative fuel and explain the effects of ABE components on the combustion process. This work also provides information regarding the optimum ABE ratio to be targeted in the ABE fermentation process. Finally, the datasets obtained are valuable for combustion mechanism and model validation. Another promising and attractive alternative fuel is natural gas. Dual-fuel Compressed Natural Gas (CNG)/diesel combustion in compression ignition (CI) engines has shown the ability to substantially reduce the NOx emission and at the same time produce very low particulate matter (PM) emissions. In this study, CNG/diesel dual-fuel combustion has been studied under various CNG substitution ratios and diesel injection strategies at a wide range of engine operating conditions. The results show how an effective pilot diesel injection strategy in dual-fuel combustion could match the efficiency of diesel combustion (CDC). Furthermore, CNG/diesel dual-fuel combustion was also studied in an optical engine in order to understand the mechanism of dual-fuel combustion. Very few studies have performed visualization of this phenomenon. Exhaust particulate matter from CNG/diesel dual-fuel combustion was also studied and characterized for the first time using materials research techniques such as Transmission electron microscopy (TEM), Thermogravimetric analysis (TGA), CHN elemental analysis, Raman spectroscopy, and Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy. The results would be invaluable for the design of exhaust after-treatment systems for vehicles using CNG/diesel combustion. Gasoline direct injection (GDI) engines have shown improved efficiency and reduced fuel consumption, however, GDI combustion faces the serious issue of PM emissions. This study investigated lean-burn GDI combustion of ethanol-gasoline blends in an optical engine and tested a novel injector and combustion chamber design, in order to obtain better atomization and hence better air/fuel mixing, as well as an overall lean air/fuel mixture that would prevent rich zones and hence the formation of soot. Through this work, a) ABE combustion was studied in gasoline engines for the first time and affirmed as an alternative fuel ; b) By developing improved pilot diesel injection strategies, CNG/diesel dual-fuel combustion was shown to obtain diesel-like efficiency; c) Exhaust particulate matter from CNG/diesel combustion was physically and chemically characterized for the first time using materials analysis techniques; d) CNG/diesel dual-fuel combustion was visualized using color high-speed imaging in an optical engine; e) Lean-burn combustion of ethanol-gasoline blends was investigated in an optical engine