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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.

Diesel sprays injected into a combustion chamber of a small sized high-speed CI engine impinge surely on a piston surface and a cylinder wall. As a consequence, their vaporization, mixture formation and combustion processes are affected by impingement phenomena. And the other important factors affecting on the processes is the injection pressure. Then, the distribution of the vapor concentration in a single diesel spray impinging on a flat and hot wall was experimented by the exciplex fluorescence method, as a simple case. The injection pressure was varied in the range from 55 MPa to 120 MPa. It is found that the distribution of the vapor concentration in this case is much leaner than that in the case of the low injection pressure of 17.8MPa.

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.

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.

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.

LES of non-evaporative diesel spray have been performed to investigate the effects of breakup models of Modified TAB, WAVE and KHRT model on computational results. KIVALES that is LES version of KIVA code was used for base code. In our KIVALES, CIP scheme was incorporated in order to suppress the numerical diffusion. Results showed that the breakup model is significantly affected on the calculated spray shape, because the droplet diameter determined by breakup models affects on the transmittance of the droplet momentum into the ambient gas, the evolution of the vortex structure in the gas phase and the droplet dispersion by the vortex structure.

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.

The Flame structure and combustion characteristics for two waste-cooking oils were investigated in detail. One fuel is the waste-cooking oil methyl esters. This fuel is actually applied to the 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 the 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. In the experiments, the used fuels were gas oil, i-BDF, B100 and B20. Spray characteristics and basic combustion properties were measured inside a rapid compression and an expansion machine (RCEM).

The maximum liquid-phase penetration and vaporization behavior was investigated by using simultaneous measurement for mie-scattered light images and shadowgraph ones. The objective of this study was to analyze effect of variant parameters (injection pressure, ambient gas condition and fuel temperature) and fuel properties on vaporization behavior, and to investigate liquid phase penetration for the single- and multi-component fuels. The experiments were conducted in a constant-volume vessel with optical access. Fuel was injected into the vessel with electronically controlled common rail injector.

Flash-boiling occurs when a fuel is injected to a combustion chamber where the ambient pressure is lower than the saturation pressure of the fuel. It has been known that flashing is a favorable mechanism for atomizing liquid fuels. On the other hand, alternative fuels, such as gaseous fuels and oxygenated fuels, are used to achieve low exhaust emissions in recent years. In general, most of these alternative fuels have high volatility and flash-boiling takes place easily in fuel spray, when they are injected into the combustion chamber of an internal combustion engine under high pressure. In addition, fuel design concept the multicomponent fuel with high and low volatility fuels has been proposed in the previous study in order to control the spray and combustion processes in internal combustion engine. It is found that the multicomponent fuel produce flash-boiling with an increase in the initial fuel temperature.

This study proposes a hybrid model which consists of modified TAB(Taylor Analogy Breakup) model and DVM(Discrete Vortex Method). In this study, the simulation process is divided into three steps. The first step is to analyze the breakup of droplet of injected fuel by using modified TAB model. The second step based on the theory of Siebers' liquid length is analysis of spray evaporation. The liquid length analysis of injected fuel is used for connecting both modified TAB model and DVM. The final step is to reproduce the ambient gas flow and inner vortex flow injected fuel by using DVM. In order to examine the hybrid model, an experiment of a free evaporating fuel spray at early injection stage of in-cylinder like conditions had been executed. The numerical results calculated by using the present hybrid model are compared with the experimental ones.

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.

In the actual spray combustion fields, coupled combustion process should be occurred, between the pre-evaporate fuel component and remaining liquid droplets. Therefore it is insufficient to clarify the fundamental spray combustion mechanism with use of only droplet or only premixed mixture analyze method. In this study, the premixed mixture - droplets coupled combustion field was focused as a model of the actual spray combustion field. In the experiments, the effect of the flame pattern and the combustion rate constant by the interference between the droplets were clarified with the variation of fuels used by droplets. Besides, the effect of the premixed gas surrounding the droplets was clarified by the experiment on coupled combustion. The experiments were carried out under the normal gravity field and the micro gravity field to estimate the effect of convection in combustion field

This work presents the ignition delay time characteristics of oxygenated fuel sprays under simulated diesel engine conditions. A constant volume combustion vessel is used for the experiments. The fuels used in the experiments were three oxygenated fuels: diethylene glycol dibutyl ether, diethylene glycol diethyl ether, and diethylene glycol dimethyl ether. JIS 2nd class gas oil was used as the reference fuel. The ambient gas temperature and oxygen concentration were ranging from 700 to 1100K and from 21 to 9%, respectively. The results show that the ignition delay of each oxygenated fuel tested in this experiments exhibits shorter than that of gas oil fuel for the wide range of ambient gas conditions. Also, NTC (negative temperature coefficient) behavior which appears under shock tube experiment for homogenous fuel-air mixture was observed on low ambient gas oxygen concentration for each fuel. And at the condition, the ignition behavior exhibits two-stage phase.

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.

It is unavoidable that a DI diesel engine exhausts a blue and white smoke at starting, especially in the cold atmosphere. In the experiments presented here, a small DI diesel engine started under the conditions of coolant and suction air whose minimum temperatures were 255 K and 268 K, respectively. The flame was photographed by high-speed photography, the temperature of flame and the soot concentration were measured by two-color method, and CO2 concentration was detected by luminous method. The engine cannot be started over several cycles when the coolant temperature is 255 K and suction air temperature is 268 K. As the temperature of coolant and suction air are decreasing, the maxima of the cylinder pressure, the flame temperature, the soot concentration and CO2 concentration are decreasing. Luminous small dots or small lumps of flame become scattered in the piston cavity.

There is a concept that the increase in the temperature of charge in a combustion chamber and the shield of heat transferred through a chamber wall can facilitate the oxidation of soot and reduce the discharge of soot from the engine. In the experiments presented here in, an IDI diesel engine was used to inspect the concept. The engine was installed a bigger sized cylindrical swirl chamber which was equipped with two flat quarts windows, in order to observe the combustion phenomena and to apply the optical measurement. The experiments were carried out using two types of divided chambers, that is, the swirl chamber made of ceramics and that made of steel, to examine the the effects mentioned above.

In this study, a rapid compression and expansion machine(RCEM) with a pancake combustion chamber was designed to investigate fundamentally on the knocking phenomena in spark ignition(S.I) engines. This RCEM is intended to simulate combustion in an actual engine. The homogeneous pre-mixture of n-pentane and air was charged into a quiescent atmosphere of the chamber. Then, the combustion field become simpler in this machine than it in a real S.I. engine. Also, the combustion phenomena, that is a cylinder pressure history, the behavior of flame propagation and so on, with high reproducibility are realized in this machine. The phenomena caught in this experiment were so-called low speed knocking. And, this knocking characteristics such as a knock intensity and a knock mass fraction were revealed by the cylinder pressure analysis varying the charge pressure and the equivalence ratio of the mixture, a compression ratio and an ignition timing.

This paper presents an atomization mechanism of a spray injected into the low-pressure field, as the subject of injection system in a suction manifold of gasoline engine. Pure liquid fuel, which is n-Pentane or n-Hexane is injected into quiescent gaseous atmosphere at room-temperature and low- pressure through pintle type electronic control injector. Fuel sprays are observed by taking photographs for variation of the back pressure and the changes in spray characteristics with the back pressure below atmospheric pressure are examined in detail. In particular, in the case of the back pressure below the saturated vapor pressure of fuel, the atomization mechanism is discussed from a viewpoint of flash boiling phenomena, those are bubble growth rate and so on.