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Some papers on the combustion in a diesel engine have been already presented to discuss the effect of the additive called ADOIL TAC. A bottom view DI diesel engine driven at 980rpm with no load was used in the experiment presented here, in order to make clear this effect. JIS second class light diesel fuel oil was injected through a hole nozzle at the normal test run. The additive was intermixed 0.01 vol. % in this fuel oil, in the experiments to compare with the normal combustion. The flame was taken by direct high-speed photography. Profiles of flame temperature and KL were detected on the film by image processing, applying the two-color method. Soot was visualized by high-speed laser shadowgraphy, and the heat release rate was calculated using the cylinder pressure diagram. Discussion on the effect of the additive on the combustion phenomena was made by using all the data.

Ignition, combustion and emissions characteristics of dual-component fuel spray were examined for ranges of injection timing and intake-air oxygen concentration. Fuels used were binary mixtures of gasoline-like component i-octane (cetane number 12, boiling point 372 K) and diesel fuel-like component n-tridecane (cetane number 88, boiling point 510 K). Mass fraction of i-octane was also changed as the experimental variable. The experimental study was carried out in a single cylinder compression ignition engine equipped with a common-rail injection system and an exhaust gas recirculation system. The results demonstrated that the increase of the i-octane mass fraction with optimizations of injection timing and intake oxygen concentration reduced pressure rise rate and soot and NOx emissions without deterioration of indicated thermal efficiency.

This paper confirms a structure for the soot formation process inside a burning diesel jet plume of oxygenated fuels. An explanation of how the soot formation process changes by the use of oxygenated fuel in comparison with that for using a conventional diesel fuel, and why oxygenated fuel drastically suppresses the soot formation has been derived from the chemical kinetic analysis. A detailed chemical kinetic mechanism, which is combined with various proposed chemical kinetic models including normal paraffinic hydrocarbon oxidation, oxygenated hydrocarbon oxidation, and poly-aromatic hydrocarbon (PAH) formation, was developed in present study. The calculated results are presented to elucidate the influence of fuel mixture composition and fuel structure, especially relating to oxygenated fuels, on PAH formation. The analysis also provides a new insight into the initial soot formation process in terms of the temperature range of PAH formation.

This paper provides new insights on the mechanism of the smokeless diesel combustion with oxygenated fuels, based on a combination of soot kinetic modeling and optical diagnostics. The chemical effects of fuel compositions, including aromatics - paraffins blend, neat oxygenated fuels and oxygenate additives, on sooting equivalence ratio ‘ϕ’ - temperature ‘T’ dependence were numerically examined using a detailed soot kinetic model. To better understand the physical factors affecting soot formation in oxygenated fuel sprays, the effects of injection pressure and ambient gas temperature on the flame lift-off length and relative soot concentration in oxygenated fuel jets were experimentally investigated. The computational results show that the leaner mixture side of soot formation peninsula on the ϕ - T map, rather than the lower temperature one, should be utilized to suppress the formation of PAHs and ultra-fine particles together with the large reduction in particulate mass.

The spray structure under the pressurized atmosphere at a room temperature was examined by the various photographic methods. The fuel flow inside the nozzle was investigated by the transparent model nozzles. The experimental analysis of sprays yielded the spray dispersing angle, the distribution of fuel droplets inside the spray and the jet intact core length. The obtained results of those spray characteristics showed that the spray structure is divided into two spatial regimes due to their formation mechanisms. Within 10 mm from the nozzle, the spray dispersion is dominated by the turbulent states of fuel which are initiated inside the nozzle. At distance from the nozzle z > 20 - 40 mm, the spray consists of an induced gas vortex street whose length is about half of the spray width. It is proposed that the kinematic viscosity of ambient gas is a important factor which rules the process of momentum exchange form the fuel jet to the ambient gas.

In this paper, spray characteristics were examined to deduce the effect of ambient gas properties. Considered ambient properties were the viscosity μa and density ρa, and thus the kinematic viscosity νa. The objective of this paper is to reveal the effect of compressibility of the ambient gas to spray formation. In the experiments, the changed ranges were And a standard-sac volume nozzle of hole diameter dn =0.25 mm (ln/dn=3.0) was used at constant injection pressure difference (Δp=16.2 MPa). Also the injection pressure was varied in the range of 55 to 120 MPa with a mini-sac volume nozzle of hole diameter dn =0.20 mm (ln/dn =5.5). Several different gases were used to change the ambient viscosity at a room temperature. From the experiments, it is obtained that larger the viscosity, the more the spray spreads in the radial direction, thus the spray angle gets larger and the tip penetration became shorter.

We propose a new concept on simultaneous reduction of NO and soot emissions in Diesel engine exhaust by the diesel fuel oil (n-Tridecane) with liquefied CO2 dissolved. The CO2 dissolved fuel is expected to undergo flash boiling or gas separation when being injected into the combustion chamber and improve spray atomization and mixing process both of which are primary factors to govern soot formation. Also the internal EGR effect caused by CO2 injected with the fuel is expected to NO formation. In order to assess this concept, combustion experiments were carried out using a rapid compression and expansion machine. Thus, flame characteristics and heat release rate were analyzed for the combustion process of diesel fuel and CO2 mixed fuel. And, it is revealed that the diesel fuel-liquefied CO2 mixed fuel can successfully reduce NO emission in a diesel combustion system.

The purposes of this study are to clarify the atomization mechanism, the change over time in droplet size distribution, and the change in spray characteristics dependent on back pressure on diesel fuel spray. Diesel spray injected into a quiescent gaseous environment under high pressure is observed by taking direct microscopic photographs varying the moment of exposure, the back pressure, and the ambient density. The results show that the mechanism of spray atomization is divided into 4 processes, and spatial distribution of breakup droplets and a droplet volume rate are assessed for the whole spray region. Total and local distributions of droplet size are expressed by empirical equations as a function of time elapsed from the moment of injection. It is confirmed that the uniformity of the distribution, Sauter mean diameter of droplets, and droplet production rate change with time. Mean droplet diameter is further described in relation to the pressure drop and the ambient density.

In a small high-speed DI diesel engine, injected fuel sprays impinge on the wall of piston cavity. Discussion and analysis of the combustion phenomena in the diesel engine demand the measurement of the characteristics of the impinging spray. In the experiments presented here, diesel fuel oil was injected into a high pressure chamber in which compressed air or CO2 gas at room temperature was charged. The single spray was impinged on a flat wall at a normal angle. The growth of the spray was photographed, not only with transmitted light but also with scattered light through a narrow slit. The temporal and spatial distribution of the droplets density in the impinging spray applying the concentric circle model was calculated using the data of the laser light extinction method. From these results, the detailed information concerning the droplets density in the impinging diesel spray was obtained.

We propose a new concept on simultaneous reduction of NO and soot emissions in Diesel engine exhaust by use of the diesel fuel oil (n-Tridecane) with liquefied CO2 dissolved. The CO2 dissolved component is expected to undergo flash boiling or gas separation when being injected into the combustion chamber, and improve spray atomization and mixing process both of which are primary factors to govern soot formation. Further, the internal EGR effect caused by CO2 component injected with the fuel is expected for NO formation. In order to assess this concept, spray dynamics measurement was conducted in the constant volume vessel with a variation of ambient pressure and temperature. Further, combustion experiments were carried out by using a rapid compression and expansion machine. Here, characteristics of the evaporative mixed fuel spray were examined by shadowgraph photography.