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The use of gasoline fuels in compression ignition engines, with or without diesel pilots, has shown encouraging progress in engine efficiency and emissions. The dual fuel combustion of gasoline-diesel offers the flexibility of modulating the cylinder charge reactivity, but an accurate and reliable control over the ignition in the dual fuel applications is more challenging than in classical engines. In this work, the gasoline-diesel dual fuel operation is investigated on a single cylinder research engine. The effects of the intake boost, exhaust gas recirculation (EGR) rates, diesel/gasoline ratio, and diesel injection timing are studied in regard to the ignition control. The results indicate that at low load, a diesel pilot can improve the cylinder charge reactivity and reduce emissions of incomplete combustion products.

Micro-explosions and vaporizing behaviors of droplets of various emulsified fuels were investigated to determine the influence of emulsified fuel properties such as water content, water particle size, and viscosity of base fuel on combustion in a diesel engine. The investigation used gas oil, A heavy oil, and B heavy oil mixed with water and evaporated on a hot surface under atmospheric pressure. The influence on the engine performance was also investigated. It was confirmed that the viscosity of the base fuel, the water content, and the water particle size influenced the droplet evaporation on the hot surface and the occurrence and intensity of micro-explosions. There were remarkable differences in the BSFC for emulsified fuels in or outside the range where micro-explosions occurred on the hot surface.

Compression ignition internal combustion engines provide unmatched power density levels, making them suitable for numerous applications including heavy-duty freight trucks, marine shipping, and off-road construction vehicles. Fossil-derived diesel fuel has dominated the energy source for CI engines over the last century. To mitigate the dependency on fossil fuels and lessen anthropogenic carbon released into the atmosphere within the transportation sector, it is critical to establish a fuel source which is produced from renewable energy sources, all the while matching the high-power density demands of various applications. Dimethyl ether (DME) has been used in non-combustion applications for several decades and is an attractive fuel for CI engines because of its high reactivity, superior volatility to diesel, and low soot tendency. A range of feedstock sources can produce DME via the catalysis of syngas.

Exhaust particulate in diesel engines is affected by fuel properties, but the reason for this is not clear. Interest in using low-grade fuels in diesel engines has made it necessary to understand the particulate formation mechanism and factors to decrease it. Particulate formation has been reported to start with thermal cracking of the fuel to lower boiling point hydrocarbons followed by condensation polymerization and production of benzene ring compounds; the formation of particulate takes place via polycyclic aromatic hydrocarbons. This report investigates the amount and configuration of particulate with a fluid reaction tube and in a nitrogen atmosphere, and analyzes polycyclic aromatic hydrocarbons (PAH) of fuels with different molecular structure and carbon number.

To clarify the microcrystal structure of soot particulate in the combustion chamber, we examined sampling methods which freeze the reaction of sample specimens from the combustion chamber and collected the soot particulates on microgrids. We investigated the microcrystal structure with a high resolution transmission electron microscope. The results were: the particle size distribution and the microcrystal structure of the soot particulates is little different for the cooled freezing method and room temperature sampling. The typical layer plane structure which characterizes graphite carbon is not observed in the exhaust of diesel engines, but some particulates display a somewhat similar layer plane structure. The structure of soot particulate is a turbostratic structure as the electron diffraction patterns show polycrystals. The soot particulates in the combustion chamber is similar to exhaust soot particulates.