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Technical Paper

Improvement of Spray and Combustion Process by Applying CO2 Gas Dissolved Fuel

2017-11-05
2017-32-0046
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.
Technical Paper

Reduction of Reaction Mechanism for n-Tridecane Based on Knowledge of Detailed Reaction Paths

2016-10-17
2016-01-2238
n-Tridecane is a low boiling point component of gas oil, and has been used as a single-component fuel for diesel spray and combustion experiments. However, no reduced chemical kinetic mechanisms for n-tridecane have been presented for three-dimensional modeling. A detailed mechanism developed by KUCRS (Knowledge-basing Utilities for Complex Reaction Systems), contains 1493 chemical species and 3641 reactions. Reaction paths during ignition process for n-tridecane in air computed using the detailed mechanism, were analyzed with the equivalence ratio of 0.75 and the initial temperatures of 650 K, 850 K, and 1100 K, which are located in the cool-flame dominant, negative-temperature coefficient, and blue-flame dominant regions, respectively.
Technical Paper

Artificial Control of Diesel Spray and Flame Feature by using Dual-component Fuel

2015-09-01
2015-01-1916
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.
Journal Article

Simultaneous Reduction of Pressure Rise Rate and Emissions in a Compression Ignition Engine by Use of Dual-Component Fuel Spray

2012-10-23
2012-32-0031
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.
Journal Article

Modeling of Auto-Ignition and Combustion Processes for Dual-Component Fuel Spray

2011-09-11
2011-24-0001
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.
Technical Paper

Effects of Mixedness and Ignition Timings on PCCI Combustion with a Dual Fuel Operation

2011-08-30
2011-01-1768
A dual fuel operation with different reactivity fuels has the possibility of optimizing performance and emissions in premixed charge compression ignition engines by controlling the spatial concentration and distribution of both fuels. In the present study, n-heptane and i-octane were independently injected through two different injectors. In-cylinder pressure analysis and emissions measurement were performed in a compression ignition engine. Injection timings, fuel quantity ratio between the injections were changed for the two cases, in which one fuel was injected using a port fuel injection system while the other was directly injected into the cylinder, in order to drastically vary mixture distributions and ignition timings. In addition, an optical diagnostic was performed in a rapid compression and expansion machine to develop an understanding of the ignition processes of the two mixtures.
Technical Paper

Demonstrating the Potential of Mixture Distribution Control for Controlled Combustion and Emissions Reduction in Premixed Charge Compression Ignition Engines

2009-04-20
2009-01-0498
The objective of this study is to explore the relation among mixture distribution condition, chemical character of fuel, combustion processes, and emissions characteristics with premixed charge compression ignition (PCCI) operation. The present experiment employs two fuel injectors which are capable of port injection and direct one. The former was used to supply a highly-homogeneous mixture and the latter with late injection timing was employed to control the mixture heterogeneity. Thus, these sets of injection equipments are capable of setting a wide variety of mixture heterogeneity. Furthermore, two primary reference fuels were used in order to know the influences of chemical character. The experiments were conducted in order to clarify the combustion and emissions characteristics through engine tests. Optical diagnostic was also performed to gain additional insight into the combustion processes for a wide variety of mixture distribution.
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

Large Eddy Simulation of Diesel Spray Combustion with Eddy-Dissipation Model and CIP Method by Use of KIVALES

2007-04-16
2007-01-0247
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.
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

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

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

Detailed Kinetic Modeling and Laser Diagnostics of Soot Formation Process in Diesel Jet Flame

2004-03-08
2004-01-1398
This work investigates the soot formation process in diesel jet flame using a detailed kinetic soot model implemented into the KIVA-3V multidimensional CFD code and 2D imaging by use of time-resolved laser induced incandescence (LII). The numerical model is based on the KIVA code which is modified to use CHEMKIN as the chemistry solver using Message Passing Interface (MPI). This allows for the chemical reactions to be simulated in parallel on multiple CPUs. The detailed soot model used is based on the method of moments, which begins with fuel pyrolysis, followed by the formation of polycyclic aromatic hydrocarbons, their growth and coagulation into spherical particles, and finally, surface growth and oxidation of the particles. The model can describe the spatial and temporal characteristics of soot formation processes such as soot precursors distributions, nucleation rate and surface reaction rate.
Technical Paper

Flame Structure and Combustion Characteristics in Diesel Combustion Fueled with Bio-diesel

2004-03-08
2004-01-0084
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).
Technical Paper

Effects of Ambient Gas Conditions on Ignition and Combustion Process of Oxygenated Fuel Sprays

2003-05-19
2003-01-1790
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.
Technical Paper

Numerical Simulation of Multicomponent Fuel Spray

2003-05-19
2003-01-1838
Fuel design for internal combustion engines has been proposed in our study. In this concept, the multicomponent fuel with high and low volatility fuels are used in order to control the spray and combustion processes in internal combustion engine. Therefore, it is necessary to understand the spray and combustion characteristics of the multicomponent fuels in detail. In the present study, the modeling of multicomponent spray vaporization was conducted using KIVA3V code. The physical fuel properties of multicomponent fuel were estimated using the source code of NIST Mixture Property Database. Peng-Robinson equation of state and fugacity calculation were applied to the estimation of liquid-vapor equilibrium in order to take account for non-ideal vaporization process. Two-zone model in which fuel droplet was divided into droplet surface and inner core was introduced in order to simply consider the temperature distribution in fuel droplet.
Technical Paper

Soot Kinetic Modeling and Empirical Validation on Smokeless Diesel Combustion with Oxygenated Fuels

2003-05-19
2003-01-1789
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.
Technical Paper

Fuel Design Concept for Low Emission in Engine Systems 4th Report: Effect of Spray Characteristics of Mixed Fuel on Exhaust Concentrations in Diesel Engine

2003-03-03
2003-01-1038
In this study, the novel fuel design concept has been proposed in order to realize the low emission and combustion control in engine systems. In this fuel design concept, the mixed fuels with a high volatility fuel (gasoline or gaseous fuel components) and a low volatility fuel (gas oil or fuel oil components) are used in order to improve the spray characteristics by flash boiling. In our previous papers on this study, the fundamental characteristics of spray and its combustion of mixed fuel were reported. In this paper, heat release and exhaust emission (smoke, NOx and THC) characteristics of single cylinder diesel engine operated with the mixed fuels were investigated under each load. The exhaust performance of diesel engine could be improved using mixed fuel, because fuel properties and spray characteristics were controlled by changing mixing fraction of the mixed fuel.
Technical Paper

Analysis of Visualized Fuel Flow inside the Slit Nozzle of Direct Injection SI Gasoline Engine

2003-03-03
2003-01-0060
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.
Technical Paper

Effects of Flame Lift-Off and Flame Temperature on Soot Formation in Oxygenated Fuel Sprays

2003-03-03
2003-01-0073
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.
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