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This paper investigates the combined effect of EGR and emulsified fuels on engine performance. The influence of intake air temperature (25∼86°C) on engine performance was examined prior to uncooled EGR experiments. Compared with gas oil, emulsified fuel gave simultaneous improvements in NOx concentration, smoke density, and specific fuel consumption (BSFC) over the tested range. The effect of EGR on engine performance were investigated with various water to fuel ratios at two load conditions (BMEP=0.52MPa and 0.26MPa). It was confirmed that at 11% EGR with the emulsified fuel at the rated output resulted in a significant reduction in NOx concentration without worsening smoke density and BSFC.

This paper describes how cooling loss reductions influence engine performance with emulsified fuel operation. The cooling loss ϕw during combustion was determined from the gas pressure in the cylinder at various conditions and the cooling water loss ϕc through the whole of the engine cycle was measured by changing the cooling water temperature. It was found that the indicated thermal efficiency varies with the change in cooling loss ϕw and cooling water loss ϕc versus the change of cooling water temperature. As a feature of emulsified fuel combustion it was determined that the reduced cooling loss improves the indicated thermal efficiency.

This investigation reports diesel engine performance of water-in-gas oil emulsified fuel and gas oil at compression ratios of 13.6, 15.6, and 17.0. It was confirmed that without worsening the specific fuel consumption, low compression ratios with emulsified fuel operation result in significant reductions in NOx concentration, reduced maximum combustion pressure, and decreased smoke density when compared with the 17.0 compression ratio for gas oil operation.

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.

To improve engine performance parameters such as smoke, NOx, and BSFC in a DI diesel engine, water-in-gas oil emulsified fuel was used without high pressure or high injection rate. It was confirmed that when compared with high pressure and high injection rate operation with gas oil, emulsified fuel gives significant reductions in NOx concentration, improved fuel economy, and reduced smoke density at ordinary injection pressure and retarded timings.

With the aid of static mixer and non-ionic emulsifying agent, a comparatively stable water-fuel emulsion was obtained. Engine performance in a 4 cycle direct injection engine using these fuels were studied. A large reduction of NOx concentration was obtained over the wide range of engine operation, in spite of increased ignition lag and rapid combustion. Furthermore, improvements of economy and reduction of exhaust smoke were obtained. The reduction of NOx concentration, fuel consumption and smoke were even more remarkable when compared with operating same engine with water fumigation.