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In this study, the main properties of two types of gas-to-liquid (GTL) fuels were investigated. Then, performance and emission characteristics of a compression ignition engine fueled with GTLs were investigated by comparison with diesel fuel. GTL1 was composed of 100% paraffin by volume, and GTL2 was composed of 99.8% paraffin and 0.2% aromatics by volume. Most GTL fuel properties were comparable to those of diesel fuel, while both fuels have a higher cetane number and lower sulphur. A diesel engine could be operated with GTL fueling without any special engine modifications. Our tests showed that with the high cetane number of GTLs, the ignition delay was shorter, and combustion started earlier than with diesel fuel. With GTL1 operation, THC and soot emissions were lower than with diesel fuel operation, and even lower with GTL2 fueling.

A feasibility study of an LPG DI diesel engine has been carried out to study the effectiveness of two selected cetane enhancing additives: Di-tertiary-butyl peroxide (DTBP) and 2-Ethylhexyl nitrate (EHN). When more than either 5 wt% DTBP or 3.5 wt% 2EHN was added to the base fuel (100 % butane), stable engine operation over a wide range of engine loads was possible (BMEPs of 0.03 to 0.60 MPa). The thermal efficiency of LPG fueled operation was found to be comparable to diesel fuel operation at DTBP levels over 5 wt%. Exhaust emissions measurements showed that NOx and smoke levels can be significantly reduced using the LPG+DTBP fuel blend compared to a light diesel fuel at the same experimental conditions. Correlations were derived for the measured ignition delay, BMEP, and either DTBP concentration or cetane number. When propane was added to a butane base fuel, the ignition delay became longer.