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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.

In this study, the authors analyze the concentration distribution of an evaporative spray mixture with LIEF (Laser induced exciplex fluorescence) method, which is a type of optical measurement. LIEF method is one of the optical measurements for obtaining the spray concentration distribution for separating vapor/liquid phases based on the fluorescence characteristics. In this paper, a quantitative concentration distribution analysis method for wall impingement spray in heterogeneous temperature field has been proposed. Then, a series of experiments were performed in varying injection pressure and ambient density. As a result, a two-dimensional concentration distribution was obtained for the free spray and wall impingement spray.

Research on alternative fuels is necessary to reduce CO2 emissions. Hydrotreated Vegetable Oil (HVO) of light fuel physically improves spray and combustion characteristics. Fatty Acid Methyl Ester (FAME) is an oxygenated fuel and its combustion characteristics are chemically improved, although its spray characteristics such as penetration and atomization are deteriorated. The purpose of this study is to understand the effects of blending HVO, which has carbon neutral (CN) characteristics, with FAME, which also has CN characteristics, on spray and combustion characteristics, and to further improve emission such as THC and Smoke. This report presents the effect of the combination of improved spray characteristics and oxygenated fuel on emissions. Spray characteristics such as penetration, spray angle and spray volume were investigated by shadowgraph photography.

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.

Bio-hydro fined diesel (BHD) oil is known as a second generation oil made from bio hydro finning process. Biodiesel in the first generation is made from transesterification process and it has several disadvantages such as high density and increased the viscosity that can cause operational problems because can make some deposits in the engine. To overcome this, the second generation process of biodiesel has been modified from the first generation oil. BHD is made from the waste cooking oil by using the hydro finning process without the trans-esterification process. The results of BHD oil has nearly the same with diesel oil. BHD oil has low viscosity and high oxidation stability. Therefore, BHD oil can be used in the diesel engine without making any modifications in the engine. In this study, the comparison of performance and emissions characteristics from BHD oil, waste cooking oil, and diesel oil are investigated.

In previous study, the model for flash-boiling spray of multicomponent fuel was constructed and was implemented into KIVA code. This model considered 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. These numerical results using this model were compared with experimental data which were obtained in the previous study using a constant volume vessel. The spray characteristics from numerical simulation qualitatively showed good agreement with the experimental results. Especially, it was confirmed from both the numerical and experimental data that flash-boiling effectively accelerated the atomization and vaporization of fuel droplets. However, in this previous study, injection pressure was very low (up to 15 MPa), and the spray characteristics of high pressure injection could not be analyzed.

The CO2 gas dissolved fuel for the diesel combustion is effective to reduce the NOx emissions to achieve the internal EGR (Exhaust Gas Recirculation) effect by fuel. This method has supplied EGR gas to the fuel side instead of supply EGR gas to the intake gas side. The fuel has followed specific characteristics for the diesel combustion. When the fuel is injected into the chamber in low pressure, this CO2 gas is separated from the fuel spray. The distribution characteristics of the spray are improved and the improvement of the thermal efficiency by reduction heat loss in the combustion chamber wall, and reduce soot emissions by the lean combustion is expected. Furthermore, this CO2 gas decreases the flame temperature. Further, it is anticipated to reduce NOx emissions by the spray internal EGR effect.

The flash boiling by fuel heating is a useful method to control the time spatial spray characteristics such as atomization of droplets, vaporization and air-fuel mixture concentration. It is one of the important phenomena for a direct injection gasoline engine (D.I.S.I) as a next generation powertrain. This report focuses on flash boiling spray using fuel heating. The purpose of this study is to understand its physical phenomena with scattered light method, schlieren photography, and Super High Spatial Resolution Photography (SHSRP). Fuel is iso-octane and injectors are a single hole nozzle and a multi hole nozzle. These are used for the basic phenomenon analysis. The influence on spray shape can be shown by schlieren photography. Spray droplet diameter and spray dispersion at the nozzle exit are observed by super high spatial resolution photography that is our original development technique. This is the first time that this SHSRP is applied to the measurement of the heating spray.

The atomization structure of the fuel spray is known to be affected by flow conditions and cavitation inside the nozzle hole. In this paper, the cavitation phenomena inside the nozzle hole was visualized by using large-scale transparent nozzles, as well as the effect of length-to-width ratio (l/w ratio) of the nozzle hole on cavitation and on the behavior of injection liquid jet. In addition, various flow patterns inside the nozzle hole same as experimental conditions were simulated by the use of Cavitation model incorporated in Star-CCM+, which was compared with experimental results.

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.

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.

In this study, it is purpose to make clear the effect of cavitation phenomenon on the spray atomization. In this report, the cavitation phenomenon inside the nozzle hole was visualized and the pressure measurements along the wall of the nozzle hole were carried out by use of 25-times enlarged acrylic nozzle. For the representatives of regular gasoline, single and two-component fuels were used as a test fuel. In addition, various cavitating flow patterns same as experimental conditions were simulated by use of Barotropic model incorporated in commercial code of Star-CD scheme, and compared with experimental results.

Methyl butanoate (MB) and methyl decanoate (MD) are surrogates for biodiesel fuels. According to computational results with their detailed reaction mechanisms, MB and MD indicate shorter ignition delays than long alkanes such as n-heptane and n-dodecane do at an initial temperature over 1000 K. The high ignitability of these methyl esters was computationally analyzed by means of contribution matrices proposed by some of the authors. Due to the high acidity of an α-H atom in a carbonyl compound, hydroperoxy radicals are generated out of the equilibrium between forward and backward reactions of O₂ addition to methyl ester radicals by the internal transfer of an α-H atom in the initial stage of an ignition process. Some of the hydroperoxy methyl ester radicals can generate OH to activate initial reactions. MB has an efficient CH₃O formation path via CH₃ generated by the β-scission of an MB radical which has a radical site on the α-C atom to the carbonyl group.

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.

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.

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.

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.

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).