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Technical Paper

Effect of Octane Rating and Charge Stratification on Combustion and Operating Range with DI PCCI Operation

2007-01-23
2007-01-0053
A single cylinder engine has been run with direct-injection premixed charge compression ignition (PCCI) operation. The operation is fueled with primary reference fuels for a wide variety of injection timing and equivalence ratio to investigate the effect of charge stratification and octane rating on PCCI combustion. The test results showed that although the change of the injection timing can gain the high combustion efficiency for a wide range of equivalence ratio, the combustion phasing where the high combustion efficiency is accomplished is not varied only by changing the injection timings. Therefore, the only change of injection timings does not improve the thermal efficiency which is influenced by the combustion phasing. On the other hand, at the fixed compression ratio, inlet air temperature and so on, the octane rating is useful in altering the combustion phasing.
Technical Paper

Spray and Combustion Characteristics of Reformulated Biodiesel with Mixing of Lower Boiling Point Fuel

2007-04-16
2007-01-0621
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.
Technical Paper

Controlling PCCI Combustion with Mixed Fuel - Application of Flashing Spray to Early Injection

2007-04-16
2007-01-0624
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.
Technical Paper

Study on Characteristics of Auto-Ignition and Combustion of Unsteady Synthetic Gas Jet

2007-04-16
2007-01-0629
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.
Technical Paper

Soot formation/oxidation and fuel-vapor concentration in a DI diesel engine using laser-sheet imaging method

2000-06-12
2000-05-0078
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.
Technical Paper

Mixing and soot formation processes in transient gas jet flame

2000-06-12
2000-05-0075
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.
Technical Paper

The Effect of a Longer Stroke on Improving Fuel Economy of a Multiple-Link VCR Engine

2007-10-29
2007-01-4004
Some automakers have been studying variable compression ratio (VCR) technology as one possible way of improving fuel economy. In previous studies, we have developed a VCR mechanism of a unique multiple-link configuration that achieves a piston stroke characterized by semi-sinusoidal oscillation and lower piston acceleration at top dead center than on conventional mechanisms. By controlling compression ratio with this multiple-link VCR mechanism so that it optimally matches any operating condition, the mechanism has demonstrated that both lower fuel consumption and higher output power are simultaneously possible. However, it has also been observed that fuel consumption does not reduce further once the compression ratio reached a certain level. This study focused on the fact that the piston-stroke characteristic obtained with the multiple-link mechanism is suitable to a longer stroke.
Technical Paper

Mechanism of Combined Combustion of Premixed Gas and Droplets

2002-10-21
2002-01-2843
In an SI engine with direct injection of gasoline (DGI), many small droplets disperse in premixed gas in the cylinder. In a CI engine, diesel spray is injected a cylinder, thus, the situation at the spray periphery is almost the same as that of DGI SI engine. From the standpoint it is useful for understanding the combustion phenomena in both engines to experiment the combined combustion of premixed gas where many small droplets exist. This paper describes this kind of combustion and it seems to be able to apply the results to the simulation of combustion in these engines.
Technical Paper

Fundamental Study of Single Droplet and Droplets Array Combustion with Premixed Gas

2002-03-04
2002-01-0648
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
Technical Paper

Experimental Analysis on Soot Formation Process In DI Diesel Combustion Chamber by Use of Optical Diagnostics

2002-03-04
2002-01-0893
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.
Technical Paper

Fundamental Research on Unsteady Pre-mixed Combustion in Non-Uniform Distribution of Fuel Concentration

2001-09-24
2001-01-3487
It is significant for understanding the phenomena in a stratified charge engine and an SI engine with direct injection system to carry out the fundamental research. The experiments were conducted in a constant volume chamber with atmospheric condition. The pre-mixed charge composed of ethylene and air was charged with various equivalence ratio, the second charge with the same composition was injected into the chamber, thereafter, the combustion started by a spark plug. The phenomena were analyzed by use of the experimental results of shadowgraph, [OH] natural emission, pressure history and NOx and UHC in the exhaust gas.
Technical Paper

Detailed Chemical Kinetic Modeling of Diesel Spray Combustion with Oxygenated Fuels

2001-03-05
2001-01-1262
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.
Technical Paper

The Effect of Fuel-Vapor Concentration on the Process of Initial Combustion and Soot Formation in a DI Diesel Engine Using LII and LIEF

2001-03-05
2001-01-1255
A phenomenological or empirical model based on experimental results obtained from various optical measurements is critical for the understanding of DI diesel combustion phenomena as well as for the improvement of its emission characteristics. Such a model could be realized by the application of advanced optical measurement, which is able to isolate a particular phenomenon amongst complicated physical and chemical interactions, to a DI diesel combustion field. The authors have conducted experimental studies to clarify the combustion characteristics of unsteady turbulent diffusion flames in relation to the soot formation and oxidation process in a small-sized DI diesel engine. In the present study, the effect of fuel vapor concentration on the process of early combustion and soot formation has been investigated using several optical measurements.
Technical Paper

Fuel Design Concept for Low Emission in Engine Systems 2nd report: Analysis of combustion characteristics for the mixed fuels

2001-03-05
2001-01-0202
In the present study, we have proposed a novel fuel design concept in order to achieve low emissions and combustion control in engine systems. The fuel design concept is based on the combustion control that could be realized by using a mixed fuel with a lower boiling point fuel, such as gasoline or gaseous fuel components and a higher boiling point fuel, such as gas oil or fuel oil components. According to the fuel design concept proposed in this work, the characteristics of vaporization during mixture formation process as well as of combustion can be reasonably improved due to the formation of two-phase region. The heat release analysis was conducted to compare the temporal history of heat release for both a mixed fuel and a single component fuel that has the same transport properties of mixed fuels. In addition, the two-color method, which simultaneously allows the measurements of temperature distribution and soot concentration, is applied to the combustion field for mixed fuels.
Technical Paper

A Fundamental Study on Ignition Characteristics of Two-Component Fuel in a Diesel Spray

2006-10-16
2006-01-3383
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.
Technical Paper

Soot Generation in Spray of Oxygenated Fuel

2006-10-16
2006-01-3371
One of the effective ways to cope with the very severe future regulation of soot exhausted through a CI engine is the use of oxygenated fuel. This paper describes the experimental results of the soot generation of six kinds of oxygenated fuel and n-heptane whose cetane number is the almost the same as that of the gas oil by means of time resolved LII (TIRE-LII) and the classical two color method. The experiments were carried out in a constant volume chamber. The main result is that the oxygen content of the fuel is the much significant factor to decrease in the soot.
Technical Paper

Large Eddy Simulation of Non-Evaporative and Evaporative Diesel Spray in Constant Volume Vessel by Use of KIVALES

2006-10-16
2006-01-3334
Large Eddy Simulation (LES) is applied to non-evaporative and evaporative diesel spray simulations. KIVALES, which is LES version of KIVA code, is used as the LES computational code. Modified TAB model is used as breakup model, and interpolated donor cell differencing scheme is employed to calculate convective terms. To validity LES simulation, LES results using KIVALES are compared with experimental results and simulated results with conventional RANS approach using KIVA3V res.2. The results show that the LES simulation of non-evaporative spray depends on the grid size in comparison with RANS simulation, and good agreement is obtained between experimental results and the LES results with fine grid (720,000 cells). Furthermore, asymmetric non-evaporative spray which has intermittency at the outer edge of sprays is simulated, since instantaneous turbulent flow field can be predicted directly in LES case.
Technical Paper

Exhaust Emission Through Diesel Combustion of Mixed Fuel Oil Composed of Fuel with High Volatility and that with Low Volatility

2004-06-08
2004-01-1845
The mixed fuel composed of two kinds of fuel oil whose boiling temperature is different each other forms the fine spray with minute droplets when its condition crosses over the two-phase region. It is expected that the fuel with low volatility dominates the ignition delay and that with high volatility does the generation of particulate matter. The experiments were carried out in a rapid compression and expansion machine and in an actual high-speed small sized diesel engine by use of this kind of fuel. The experimental results prove this expectation.
Technical Paper

Multicomponent Fuel Consideration for Spray Evaporation Field and Spray-Wall Interaction

2001-03-05
2001-01-1071
It is expected that the analysis of the evaporation process for multicomponent fuels such as actual fuels like gasoline and diesel gas oil could be performed to assess more accurately the mixture preparation field inside the cylinder of D.I.S.I engines and diesel engines. In this paper, we suggested the importance of this multicomponent fuel consideration relating to the mixture formation and combustion characteristics from the basis of their own fuel physical and chemical properties. Then, we introduce a treatment for the phase change of a multicomponent solution through the formation of two-phase regions with the basis of chemical-thermodymical liquid-vapor equilibrium. Next, we analyze the distillation properties of a multicomponent fuel as well as the evaporation process of a multicomponent single droplet by use of the chemical-thermodymical analysis.
Technical Paper

Visualization of Micro Structure in a Diesel Spray by Use of Photography with High Spatial Resolution

2008-10-06
2008-01-2465
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.
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