Search Results

In order to clarify the trend of PM emission characteristic caused by fuel change, we propose a fundamental flame research method using a small pool flame system. Characteristics such as size distribution and formation rate of PM from laminar diffusion flames of gasoline fuels (JIS No.1 and No.2) were investigated by an electric microbalance and a SMPS (Scanning Mobility Particle Sizer). PM exhaust from flame of surrogate gasoline fuels and hydrocarbon fuels of various chemical structures were also measured. As the result, it was found that both of exhaust-PM concentration and PM number peak size increased with increasing of alkene and aromatic compositions in fuel.

An experimental study on emission formation processes, such as these of nitric oxide, particulate and total hydrocarbon in a small direct injection (D.I.) diesel engine was carried out by using a newly developed total in-cylinder sampling technique. The sampling method consisted of rapidly opening a blowdown valve attached to the bottom of the piston bowl, and quickly transferring most of the in-cylinder contents into a large sampling chamber below the piston. No modification of the intake and exhaust ports in a cylinder head was required for the installation of the blowdown apparatus. The sampling experiment gave a history of spatially-averaged emission concentrations in the cylinder. The effects of several engine variables, such as the length-to-diameter ratio of the nozzle hole, the ratio of the piston bowl diameter to the cylinder bore and the intake swirl ratio, on the emission formation processes were investigated.

In this study, compositions, size distributions and activation energy in oxidation of diesel PM were investigated. Benzene (C6H6) was mixed to diesel fuel as a promoter of PM formation, and further, ferrocene (Fe(C5H5)2) was added as a promoter for oxidation processes during in-cylinder combustion and after-treatment. The effect of those additions on the PM characteristics was discussed on the basis of measured results such as SOF and dry-soot ratio in PM, primary and aggregate particle size distributions of PM, activation energy of PM oxidation, and PM components with elemental analysis. As a result, it was shown that ferrocene had special effect on the PM size distribution and the activation energy.

The formation mechanism of Particulate Matter (PM) in a flame and fuel effect on this mechanism, are still under unclear problems. In this study, a fundamental pool combustion flame of diesel fuel was formed and PM emission from the flame was analyzed. As a result, though emission of soot from the flame was not observed, significant number of nuclei mode PM was emitted. From a flame of incomplete combustion, aggregate mode particles increased and nuclei mode particles reduced drastically. When a little mount of lubricant oil was contaminated into diesel fuel, number concentration of nuclei mode particle increased.

Characteristics of PM and its compositions inside and outside of flame were required to develop reduction technologies for combustion origin PM. In this paper, relationship between PM size distribution and compositions such as soot and soluble organic fraction (SOF) of PM sampled with filter were investigated. Number distributions of PM (30 nm-10 μm) were measured using an ELPI (Electrical Low Pressure Impactor). Dry-soot and SOF in PM that was captured an individual stage of ELPI were analyzed using a combustion type PM analyzer (MEXA-1370PM). It was clarified that nuclei mode particle included more SOF than accumulation mode particle. PM characterization showed that there were many differences between in-flame PM and out-flame PM. In-flame PM contained much of low boiling point SOF and dry-soot composition was thermally unstable. Further, similarities between SOF in PM sampled with filter and gaseous hydrocarbons passing through PM filter were discussed.

For diesel vehicles, NOx aftertreatment systems have become increasingly important, since the emission legislations continuously tightened. However, particulate matters (PM) and NOx aftertreatment systems have an impact on the engine operation and fuel penalties. Therefore, it is necessary either to find some auxiliary systems to decrease this impact or to find some brand new deNOx aftertreatment systems. In the literature, most research works concerning NOx and PM emission elimination using non-thermal plasma was conducted by employing either a dielectric barrier discharge (DBD) reactor alone or a plasma-assisted catalysis working under high temperature condition (over 150°C). Although there have been evidences that non-thermal plasma decomposes diesel PM but its mechanism is still not clear. In this paper, the simplified model for laboratory experiments consists of a wire-to-cylinder DBD reactor combined with a DPF was used to investigate NOx removal characteristics.

New empirical equations to represent the Sauter mean diameter of a spray injected by a diesel nozzle are presented in this paper. In order to determine the new equations, drop sizes of a diesel spray were analyzed by a laser diffraction technique. Liquids with different viscosities and different surface tensions were tested to obtain the generalized empirical equations. The maximum injection and maximum ambient pressures were 90 MPa and 3.0 MPa respectively. Both the minimum value of the injection pressure to produce a fine spray and the Sauter mean diameter increase the greater the viscosity and the surface tension of the liquid. At a high injection velocity, the Sauter mean diameter increases with an increase in ambient pressure, but it decreases when ambient pressure is increased at a low injection velocity.

The effects of engine parameters, such as spray characteristics and combustion chamber geometry on performance and exhaust emissions in a small D.I. diesel engine were investigated to find out the optimum way of improving the engine. Diesel spray injected into a high-pressure vessel was photographically analyzed to guess the spray behavior in a firing diesel engine. The ratio of hole length to the diameter of a nozzle (L/D) was varied from 3 to 7 as the main parameter of the nozzle. Piston cavity diameter and intake swirl were chosen as the other parameters. The effect of the above parameters was investigated in terms of brake specific fuel consumption (BSFC), exhaust smoke, nitric oxides (NOx) and total hydrocarbon (THC). The L/D of the nozzle is concluded to be of major importance in terms of BSFC and THC emission. Smaller piston cavity diameters lead to lower exhaust smoke, but to a higher level of NOx emission.

A six-stroke DI diesel engine proposed by the authors had second compression and combustion processes which were added on a conventional four-stroke diesel engine. This engine had the first and second power strokes before the exhaust stroke. Numerical predictions and experiments previously carried out had shown that this six-stroke diesel engine could reduce NO exhaust emission. Further, the ignition delay of the second combustion process could be shortened by a high temperature effect in the second compression stroke. This advantage of short ignition delay could be utilized for an ignition improvement of a fuel with low cetane number. In the engine system reported here, a conventional diesel fuel was supplied as the fuel of first combustion process, and in the second combustion process, methanol was supplied.

In this study, formation behaviors of soot in laminar diffusion flames of diesel fuel with fatty acid or fatty acid methyl ester (FAME) were investigated. Oleic acid and oleic acid methyl ester were selected as fatty acid and fatty acid methyl ester. Combustion gas emitted from the laminar diffusion flame was sampled, and PM composition in the gas was analyzed. Laser induced incandescence (LII) and laser induced fluorescence (LIF) techniques were applied to measure soot and polycyclic aromatic hydrocarbon (PAH) distributions in the laminar diffusion flames. As the results, soot emission and soot incandescence distributions were decreased by the addition of fatty acid or fatty acid methyl ester. Moreover, PAH concentration in the closed flame became high by addition of fatty acid or fatty acid methyl ester.

The main component of PM (particulate matter) formed in the combustion field is soot. Soot is formed by pyrolysis, polymerization and partial oxidation of hydrocarbon fuel. In this experimental research, the effects of temperature and oxygen on PAHs (polycyclic aromatic hydrocarbons) and PM formed from benzene-oxygen mixture were investigated by independent control of temperature (Tf = 1,073 K, 1,173 K, 1,273 K, and 1,338 K) and oxygen concentration (ϕ = ∞, 6.2, and 2.8). In order to investigate the growth processes of PAHs, mass concentrations of naphthalene, biphenyl, phenanthrene, anthracene, and pyrene were measured. As the result, it was found that mass concentration of biphenyl (two-ring PAH, nC = 12) was higher than naphthalene (two-ring PAH, nC = 10) under benzene-N2 mixture condition (without oxygen condition:ϕ = ∞). Mass concentrations of biphenyl and naphthalene were almost same levels under ϕ = 6.2 condition.