This thesis presents a systematic investigation of advanced dual-fuel low temperature combustion (LTC) strategy, reactivity-controlled compression ignition (RCCI), on a modified diesel engine to obtain high thermal efficiency and low engine-out emissions using hydrous ethanol as the primary fuel. Direct use of hydrous ethanol in internal combustion engines has been shown to provide significant energy savings in the bio-ethanol production process, substantially improving life-cycle energy use and economics compared to commercially available anhydrous ethanol. While many studies have reported high thermal efficiency and extremely low soot and NOX emissions without exhaust aftertreatment systems in RCCI engines fueled with petroleum-based fuels, limited work has been done regarding the characteristics of performance and emissions of RCCI operation using hydrous ethanol. In this work, a systematic experimental investigation has been conducted to explore the operability region, characterize the performance and emissions, and optimize the key operating parameters of RCCI operation using hydrous ethanol as the primary fuel. It has been shown that hydrous ethanol with water content of up to 25% by volume can be effectively used in RCCI operation with ethanol energy fraction up to 75% over a wide engine load range. However, intake charge heating is needed at low loads and exhaust gas recirculation (EGR) is required under high load conditions. Response surface methodology (RSM) has been shown to be an efficient approach of identifying and optimizing the key engine operating parameters of RCCI operation with reduced experimentation. The performance and emissions characteristics of RCCI combustion have been shown to be different and subject to the influence of different engine operating parameters under different engine operating conditions. NOX and soot emissions have been considerably reduced with the optimal settings of operating parameters generated from the RSM models. The fumigated low reactivity fuel has been shown to primarily contribute to the relatively high hydrocarbon emissions from the RCCI combustion. The particulate matter (PM) emissions from RCCI combustion have been shown to be primarily composed of semi-volatile organic compounds and a smaller fraction of solid carbonaceous particles. The characteristics of RCCI PM emissions vary when using different low reactivity fuels and they are highly sensitive to dilution conditions such as dilution ratio and sampling system temperature.
University of Minnesota Ph.D. dissertation. 2016. Major: Mechanical Engineering. Advisors: David Kittelson, William Northrop. 1 computer file (PDF); 148 pages.
An Experimental Investigation Of Reactivity-Controlled Compression Ignition Combustion In Diesel Engines Using Hydrous Ethanol.
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