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Auto-ignition and combustion processes of dual-component fuel spray were numerically studied. A source code of SUPERTRAPP (developed by NIST), which is capable of predicting thermodynamic and transportation properties of pure fluids and fluid mixtures containing up to 20 components, was incorporated into KIVA3V to provide physical fuel properties and vapor-liquid equilibrium calculations. Low temperature oxidation reaction, which is of importance in ignition process of hydrocarbon fuels, as well as negative temperature coefficient behavior was taken into account using the multistep kinetics ignition prediction based on Shell model, while a global single-step mechanism was employed to account for high temperature oxidation reaction. Computational results with the present multi-component fuel model were validated by comparing with experimental data of spray combustion obtained in a constant volume vessel.

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.

The authors have explored the potential of fuel to control spray and its combustion processes in a diesel engine. Fuel has some potential for low emission and high thermal efficiency because its volatility and ignitability are one of the ultimate performing factors of the engines. In present study, the ignition process of mixed fuel spray was investigated in a constant volume combustion vessel and in a rapid compression and expansion machine, The ignition delay based on the diagram of rate of the heat release, the imaging of natural flame emissions and the numerical simulation were carried out to clarify the effect of the physical and chemical properties of mixed fuel on ignition characteristics.

Fuel design concept has been proposed for low emission and combustion control in engine systems. In this concept, the multicomponent fuels, which are mixed with a high volatility fuel (gasoline or gaseous fuel components) and a low volatility fuel (gas oil or fuel oil components), are used for artificial control of fuel properties. In addition, these multicomponent fuels can easily lead to flash boiling which promote atomization and vaporization in the spray process. In order to understand atomization and vaporization process of multicomponent fuels in detail, the model for flash boiling spray of multicomponent fuel have been constructed and implemented into KIVA3V rel.2. This model considers the detailed physical properties and evaporation process of multicomponent fuel and the bubble nucleation, growth and disruption in a nozzle orifice and injected fuel droplets.

This paper is concerned with the formation of Particulate Matter (PM) in direct-injection (DI) diesel engines. A system featuring an electromagnetically actuated sampling valve was used for sampling of gas directly from the combustion chamber. The concentrations of total particulate matter (TPM) and of its two components, the Soluble Organic Fractions (SOF) and the Insoluble Fractions (ISF), were determined at different locations in the combustion chamber at different sampling times (different crank angles). High concentrations of SOF were found at sampling positions along the spray flame axis. The concentrations of SOF and ISF were higher at sampling positions close to the wall than away from the wall. The results suggest that SOF formation is significantly affected by wall quenching. Also, the PM concentrations were much higher in the combustion chamber than in the exhaust.

CNG is one of the future fuel for a CI engine. Recently, the general tendency is the use of the high pressure injection system over 100 MPa in a CI engine for the near future severe regulation. Combustion phenomenon in a CI engine with such injection system is like a transient gas diffusion flame. The flow in a gas diffusion flame was investigated by the particle image velocimetry on its 2-D images, the relative soot concentration, the temperature and the relative CO2 concentration was detected in the experiments. And the model of transient gas diffusion flame was constructed by use of experimental data.

The particulate matters (PM) containing in the exhaust gas through a CI engine affects strongly the human health. Thus, it is very significant to measure the mechanism of PM itself generation for actualization of a clean CI engine. On the standpoint mentioned above, the authors carried out the experiments of the characteristics of PM generated from a small high speed DI CI engine with a single cylinder. The variables were the equivalence ratio, the injection timing, the EGR rate and the sort of fuel. As a result, the effect of experimental condition on the distribution of PM is clear through experiments.

Selected as an alternative diesel fuel based on consideration regarding the relationship between the fuel molecular structure and exhaust emission and criteria as alternative fuels, Dimethylacetal (DMA) was evaluated in both a direct injection (DI) diesel and a Direct Fuel Injection Impingement Diffusion Combustion Diesel (OSKA-D) engines. Since DMA with a 1% commercial-type cetane improver has 53 for the cetane number, no ignition-assist divice such as a spark plug is needed, unlike methanol. According to the DI diesel engine test, the NOx emission for DMA was almost equal to that for hydrocarbon diesel fuel, but smoke for DMA was much lower than that for diesel fuel. The OSKA-D engine test showed that NOx emission for DMA was much lower than that for diesel fuel and smoke emission for DMA was zero under all engine conditions.

A direct injection stratified charge engine using New Mixture Formation Technology (OSKA) has been developed. Experiments on a single cylinder engine, with methanol and gasoline fuels showed the following results: 1) With methanol, the maximum IMEP was 1.3 MPa and the best indicated thermal efficiency was 46 %. 2) With gasoline, the maximum IMEP was 1.16 MPa and the best indicated thermal efficiency was 43 %. Analysis of the cylinder pressure diagram showed the following results: 1) High indicated thermal efficiency was observed by low time loss. 2) A relatively short combustion duration was observed even if the engine was operated with an overall lean fuel-air mixture in the part-load condition. This fact suggests that a stratified charge was attained. 3) From observation of the heat release rate,it will be predicted that combustion is characterized by flame propagation.

Three-dimensional large eddy simulation (LES) has been conducted for a diesel spray flame using KIVALES which is LES version of KIVA code. Modified TAB model, velocity interpolation model and rigid sphere model are used to improve the prediction of the fuel-mixture process in the diesel spray. Combustion is simulated using the Eddy-Dissipation model. CIP method was incorporated into the KIVALES in order to suppress the numerical instability on the combustible flow. The formation of soot and NO was simulated using Hiroyasu model and KIVA original model. Three different grid resolutions were used to examine the grid dependency. The result shows that the LES approach with 0.5 mm grid size is able to resolve the instantaneous spray with the intermittency in the spray periphery, the axi-symmetric shape and meandering flow after the end of injection as shown in the experimental results.

A diesel engine operating in premixed charge compression ignition (PCCI) mode promises the reduction of engine-out emissions of NOx and particulate matter. A serious issue for PCCI operation with the early injection timing during the compression stroke is the difficulty of controlling the mixture formation process. In this study, a mixed fuel consisting of high volatility fuel and high ignitability one is applied in order to develop a control technique for the mixture preparation. In particular, we focuses on a flash boiling phenomenon of mixed fuel. For pure substance, the quality of flashing spray is dominated by the degree of superheat. In contrast, that of mixed fuel is affected much by low boiling point fuel.

Authors propose the reformulation technique of physical properties of Biodiesel Fuel (BDF) by mixing lower boiling point fuels. In this study, waste cooking oil methyl ester (B100), which have been produced in Kyoto city, is used in behalf of BDF. N-Heptane (C7H16) and n-Dodecane (C12H26) are used as low and medium boiling point fuel. Mixed fuel of BDF with lower boiling point fuels have lighter quality as compared with neat BDF. This result is based on the chemical-thermo dynamical liquid-vapor equilibrium theory. This paper describes fundamental spray and combustion characteristics of mixed fuel of B100 with lower boiling point fuels as well as the reformulation technique. By mixing lower boiling point fuel, lighter quality fuels can be refined. Thus, mixed fuels have higher volatility and lower viscosity. Therefore, vaporization of mixed fuel spray is promoted and liquid phase penetration of mixed fuel shortens as compared with that of neat BDF.

It is thought that the synthetic gas, including hydrogen and carbon monoxide, has a potential to be an alternative fuel for internal combustion engines, because a heating value of the synthetic gas is higher than one of hydrogen or natural gas. A purpose of this study is to acquire stable auto-ignition and combustion of the synthetic gas which is supposed to be applied into a direct-injection compression ignition engine. In this study, the effects of ambient gas temperatures and oxygen concentrations on auto-ignition characteristics of the synthetic gas with changing percentage of hydrogen (H2) or carbon monoxide (CO) concentrations in the synthetic gas. An electronically-controlled, hydraulically-actuated gas injector was used to control a precise injection timing and period of gaseous fuels, and the experiments were conducted in an optically accessible, constant-volume combustion chamber under simulated quiescent diesel engine conditions.

It is very much necessary for researchers and engineers whose work is the field of combustion in a CI engine to find the information of droplets in a diesel spray. The information is strongly required to construct the model of spray built in the numerical code for its simulation and to be used for the verification of the accuracy of the calculation. This paper describes the photographing system with high spatial resolution, the distribution of droplet size and the vortex scale caused by the droplets motion by means of this system.

A transient gas jet and its flame are the most fundamental phenomena of a transient spray and its flame breaking out in a CI engine and an SI engine with the direct injection system. In the case of CNG and LNG engines, the fuel itself is just gaseous state. The 2-LIF technique was applied to the transient gas jet to obtain the mixing process between the surroundings and it, and the simultaneous application of LII and LIS techniques were applied to the transient gas jet flame to obtain the soot formation process.

Four kinds of optical measurements were performed to investigate the process of soot formation and oxidation in a direct-injection (DI) diesel engine. Measurements were carried out in an optically accessible DI diesel engine that allows planar laser sheet for combustion diagnostics to enter the combustion chamber either horizontally or along the axis of the fuel jet. The temporal and spatial distribution of soot particles has been investigated using the laser- induced incandescence (LII) and high-speed direct photography. Fuel vapor concentration, which is directly linked to the soot formation process in diesel combustion, has been deduced from the images obtained by the measurements of laser shadowgraph and elastic Mie scattering. According to the experimental results, soot formation begins to occur near the injector nozzle in which a fuel-rich mixture is distributed with a homogeneous condition. LII signal is dominated by the fuel vapor concentration in initial combustion period.

In this study, the purpose is placed in analysis the structure of diesel spray and, especially, making clear the mixture formation process in the evaporative diesel spray. The liquid fuel was injected from a single-hole nozzle (1/d = 1.0 mm/0.2 mm) into a constant-volume vessel possessing phenomena visualization under high pressure and temperature field. As for measurement method, in order to investigate liquid and vapor-phase of injected spray, exciplex fluorescence method was applied in the evaporative fuel spray. And the interested view region in injected spray is the downstream spray. For the minute investigation of spray flow, the liquid and vapor-phase region is taken with 35 mm still camera and CCD camera, respectively.

The mixture formation by fuel spray impingement (OSKA system) was applied to a small direct-injection diesel engine in order to reduce the wall quenching- induced emissions, i.e., the emissions of THC and soluble organic fractions (SOF). Experiments were carried out using a single-cylinder engine, fitted with various piston cavity geometries, ran under a wide range of compression ratios and fuel injection specifications. The piston cavity was designed as a centrally located reentrant type. The combination of the high squish flow and the weak penetration of the OSKA spray was very effective in reducing harmful emissions. A short ignition delay, under the retarded fuel injection timing, was obtained because of the high compression ratio. The OSKA DI diesel engine showed reduced NOx, smoke, and THC emissions without deterioration of the fuel consumption compared to modern DI diesel engines used in automotive applications.

The premixed charge compression ignition (PCCI) combustion in a compression ignition (Cl) engine is one of countermeasures against the very much severe regulation for exhaust gas of engine out. The authors have been proposed to use the fuel mixed with high volatility component and low volatility component to actualize PCCI combustion. This kind of fuel injected forms a fine and lean spray by the flash boiling phenomena which depends on the pressure and the temperature. The role of the former fuel is to decrease in the generation of particulate matters (PM) and that of the latter one is to break out the ignition. Thus, it is very much significant to find the distribution of vapor concentration of both fuels in a spray. This paper describes both distributions in a single diesel spray by use of the technique of laser induced fluorescence (LIF) in a constant volume chamber with high temperature at high pressure as the fundamental research.

This paper describes the results of on-board measurement of engine performance and emissions in diesel vehicle operated with bio-diesel fuels. Here, two waste-cooking oils were investigated. One fuel is a waste-cooking oil methyl esters. This fuel is actually applied to a garbage collection vehicle with DI diesel engine (B100) and the city bus (B20; 80% gas oil is mixed into B100 in volume) as an alternative fuel of gas oil in Kyoto City. Another one is a fuel with ozone treatment by removing impurities from raw waste-cooking oils. Here, in order to improve the fuel properties, kerosene is mixed 70% volume in this fuel. This mixed fuel (i-BDF) is applied into several tracks and buses in Wakayama City. Then, these 3 bio-diesel fuels were applied to the on-board experiments and the results were compared with gas oil operation case.