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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.

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.

The slit nozzle in the fuel injection valve for a direct injection spark ignition gasoline engine forms a thin, fan-shaped spray. The fan-shaped spray is characterized by high dispersion, comparatively high penetration, and fine atomization. This enables it to form a stable air-fuel mixture. However, further improvement of engine performance requires that the spray characteristics (particularly the level of atomization) be improved. Since the spray characteristics are strongly influenced by the fuel flow within the nozzle, it was clarified this effect by visual analyses of the fuel flow inside the nozzle using enlarged acrylic slit nozzles. The results demonstrated that vortices that are formed within the nozzle sac are continuously propagated in a periodic manner within the sac and that they influence the streamline of fuel flow from the sac to the slit.

One of the most effective means of improving the thermal efficiency and the specific fuel consumption in spark ignition engines is the increase of the compression ratio. However, there is a limit to it because of the generation of knocking combustion due to the rise of temperature and pressure in the unburnt mixture. Also in turbo charged spark ignition engines, the ignition timing cannot be advanced until MBT in order to avoid the knocking phenomena. Generally speaking, it is very difficult to investigate the phenomena in an actual engine, because there are many restriction and the phenomena are too complex and too fast. According-ly, it is advantageous to reveal the phenomena fundamentally, including the autoignition process of the end-gas by using simplified model equipment. Therefore, a rapid compression and expansion machine (RCEM) with a pan-cake combustion chamber was designed and developed for the experiments presented here.

In the direct injection spark ignition gasoline engine (D-4), thin fan-shaped high-dispersion, high-penetration and high-atomization spray formed by the slit nozzle generates a stratified mixture cloud without depending on a strong intake air motion, subsequently realizing stable stratified charge combustion. To improve fuel economy further in actual traffic, the region of stratified charge combustion in torque-engine speed map must be expanded by improving spray characteristics. Since the fuel flow inside the nozzle has a large effect on the spray characteristics, it was clarified this effect by visual analysis of the fuel flow inside the nozzle using an enlarged acrylic slit nozzle of 10 magnifications. Consequently, it was found that vortices are generated frequently within a sac even in the case of steady state conditions. The effect on the spray characteristics is corresponding to the vortex scale.

Fuel design approach has been proposed as the control technique of spray and combustion processes in diesel engine to improve thermal efficiency and reduce exhaust emissions. In order to kwow if this approach is capable of controlling spray flame structure and interaction between the flame and a combustion chamber wall, the present study investigated ignition and flame characteristics of dual-component fuels, while varying mixing fraction, fuel temperature and ambient conditions. Those characteristics were evaluated through chemiluminescence photography and luminous flame photography. OH radical images and visible luminous flame images were analyzed to reveal flame shape aspect ratio and its fractal dimension.

Computational Fluid Dynamics (CFD) simulation is widely used in the development and validation of automotive engine performance. In engine simulation, spray breakup submodels are important because spray atomization has a significant influence on mixture formation and the combustion process. However, no breakup models have been developed for the fuel spray with plate-type multi-hole nozzle installed in port fuel injection spark ignition (SI) engines. Therefore, the purpose of this study is to simulate spray formation in port fuel injection precisely. The authors proposed the heterogeneous sheet breakup model for gasoline spray injected from plate type multi-hole nozzle. The novel breakup model was developed by clarifying the phenomenological mechanism of the spray atomization process. In this paper, this model was improved in dispersion characteristics and evaluated by the comparison of the model calculation results with experimental data.

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.

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.

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 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.

Knocking phenomenon in a spark ignition engine breaks out due to autoignition in the unburned gas region. Investigation on the pre-autoignition reaction, that is, the reaction of cool and blue flames happening before autoignition must be carried out in detail to control knocking. The reactions appear in an extremely short time before autoignition, so, much difficulties accompany an attempt to grasp the situation. In the experiments presented hear, progress situation of pre-autoignition reaction was made clear by visualized phenomena in a rapid compression and expansion machine (R.C.E.M), which had good reproducibility. Taken by two ultra high-speed video cameras. We determined the ignition delay time was caught by analyzing the emission of light from the combustion chamber before knocking occurrence.

Distribution of injected fuel droplets, total hydrocarbon concentration and soot concentration in the combustion chamber of a diesel engine with a swirl chamber have been measured microscopically with regard to the time and the space by means of optical method. As a result of this study, effect of the swirl flow on atomized droplet distribution, relation between the droplets and hydrocarbon concentration, and relation between the change in concentration gradient of hydrocarbon with the time and the velocity of the swirl flow, and effect of non-luminous flame on the time of heat release rate raising period have been obtained. And from spatial distributions of hydrocarbon concentration, soot concentration, and local temperature in the combustion chamber at each time, the locational characteristics of soot generation are clarified. Further, effects of hydrocarbon and local temperature on soot generation have been considered.

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.

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.

In this study, a numerical experiment using a 2D convective equation and LES of an evaporative diesel spray for different convective schemes has been performed to examine effects of convective schemes on a fuel-air mixture formation of the diesel spray simulation and to determine the convective scheme used in KIVALES. In addition to KIVALES original schemes, such as QSOU, PDC and IDC, CIP was incorporated into KIVALES in order to calculate the convective terms with low numerical diffusion. The numerical experiment using the 2D convective equation showed that the numerical diffusion of CIP scheme was lowest in the convective schemes used in present study. However CIP scheme used was not a monotone scheme completely due to the overshoot and the undershoot of the scalar provided near the boundary. Hence, CIP scheme was employed for only the convective term of the LES momentum equation, while the other convective schemes were calculated using QSOU, which is a monotone scheme.

In recent years, internal combustion engine using hydrogen gas, has attracted attention as one solution to the problem of global warming. Hydrogen gas has excellent combustion characteristics such as wide limits of inflammability and fast burning velocity because of high diffusion rate. Therefore, it has been made to obtain stable ignition and combustion by adding hydrogen with lean mixture in spark ignition engines using hydrocarbon fuels and to be attempted efficient operation by engine researchers. The purpose of this study is to reduce cooling loss in a gas engine using hydrogen gas and hydrogen Mixer system (Mixer) engine was remodeled to hydrogen Port Injection (PI) system engine. In this report, the heterogeneity of hydrogen mixture is clarified by comparing the combustion characteristics of the Mixer and the PI, and the effect of the difference in hydrogen supply systems on cooling loss is system. Ignition delay of the PI system is shorter than that of the Mixer.

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.

Considering the bell-shaped temperature dependence of soot particle formation, the control of flame temperature has a possibility to drastically suppress of soot formation. Furthermore, oxygenated fuels are very effective on soot reduction, and the use of these kinds of fuels has a potentiality for smokeless diesel combustion. In this paper, the effects of flame lift-off and flame temperature on soot formation in oxygenated fuel sprays were experimentally investigated using a constant volume combustion vessel which simulated diesel engine conditions. The diffusion flame lift-off length was measured in order to estimate the amount of the oxygen entrained upstream of the flame lift-off length in the fuel jet. This was determined from time-averaged OH chemiluminescence imaging technique. Also, the flame temperature and soot concentration were simultaneously evaluated by means of two-color method.

Soot formation process inside the combustion chamber of an DI diesel engine is focused as a phenomenological basic scheme by using several optical diagnostics technique for the improvement of diesel exhaust emission. We have conducted the series of optical measurement research for the clarification of combustion field in an DI diesel engine. Then, this paper is a kind of review by adding the fuel vapor properties and particle image velocimetry (PIV) analysis with focusing the soot formation process. The experiments were carried out in a small sized high-speed DI diesel engine installed with an optical access view. The spray characteristics and its flow field in 2-D field were measured by laser sheet scattering (LIS) method and PIV scheme.