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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

Heat Release Rate and Cylinder Gas Pressure Oscillation in Low and High Speed Knock

2015-09-01
2015-01-1880
One of the authors has proposed to use the decay rate of EHRR, the effective heat release rate, d2Q/dθ2 as an index for the rapid local combustion [1]. In this study, EHRR profiles and the cylinder gas pressure oscillations of the low and high speed knock are analyzed by using this index. A delayed rapid local combustion, such as an autoignition with small burned mass fraction can be detected. In the cases of the low speed knock, it has been agreed that a rapid local combustion is an autoignition. Although whether the cylinder gas oscillation is provoked by an auto ignition in a certain cycle or not is an irregular phenomenon, the auto ignition takes place in almost all of the cycles in the knocking condition. Mixture mass fraction burned by an auto ignition is large. A small auto ignition may induce a secondary auto ignition, in many cases, mass burned by the secondary auto ignition is extremely large.
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.
Technical Paper

Reaction Zone Propagation by Spark Discharge in Homogeneous Lean Charge after Low-Temperature Oxidation

2015-04-14
2015-01-0820
The interaction between spark discharge and low-temperature oxidation (LTO) was investigated using an optical compression and expansion machine fueled with n-C7H16 or i-C8H18 for an equivalence ratio of 0.33. Charge pressure was adjusted so that the compression stoke could induce LTO for n-C7H16, but could not lead to high-temperature reactions. A spark was discharged in the field before, during, or after the LTO for n-C7H16 or in the field without LTO for i-C8H18. Reaction zones were induced in the field after the LTO, whereas no reaction zones were induced in the fields before the LTO and without LTO. Local ignitions were induced in the areas surrounding the propagating reaction zones. The reaction zone propagation with the low equivalence ratio must be a different phenomenon from conventional flame propagation. The reaction zones can compress or heat the surrounding areas containing H2O2 and CH2O, and accelerate an H2O2 regeneration loop in the pre-reaction zones.
Journal Article

Ignition Characteristics of Ethane and Its Roles in Natural Gas for HCCI Engine Operation

2015-04-14
2015-01-0811
The ignition characteristics of each component of natural gas and the chemical kinetic factors determining those characteristics were investigated using detailed chemical kinetic calculations. Ethane (C2H6) showed a relatively short ignition delay time with high initial temperature; the heat release profile was slow in the early stage of the ignition process and rapid during the late stage. Furthermore, the ignition delay time of C2H6 showed very low dependence on O2 concentration. In the ignition process of C2H6, HO2 is generated effectively by several reaction paths, and H2O2 is generated from HO2 and accumulated with a higher concentration, which promotes the OH formation rate of H2O2 (+ M) = OH + OH (+ M). The ignition characteristics for C2H6 can be explained by H2O2 decomposition governing OH formation at any initial temperature.
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.
Technical Paper

Chemical Kinetics Study on Effect of Pressure and Fuel, O2 and N2 Molar Concentrations on Hydrocarbon Ignition Process

2012-04-16
2012-01-1113
Ignition process chemistry was analyzed using a detailed chemical kinetic model of n-heptane generated by KUCRS (Knowledge-basing Utilities for Complex Reaction Systems), wherein pressure-dependent rate constants of the O₂ addition to alkyl radicals and hydroperoxy alkyl radicals and the thermal decomposition of ketohydroperoxides have been introduced. Then, the effect of the initial pressure and the individual effects of the initial fuel, O₂ and N₂ molar concentrations on a relationship between the initial temperature and the ignition delay were discussed. When the initial temperature increases, the branch of C₇H₁₄OOH removal into the second O₂ addition and the decomposition into C₇H₁₄cyO and OH is more sensitive to the pressure and the O₂ concentration, and thus, the LTO preparation phase is more affected by the pressure and the O₂ concentration. The LTO phase terminates mainly by the OH removal by intermediate species.
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

Visualization of the Cavitating Flow inside the Nozzle Hole Using by Enlarged Acrylic Nozzle

2011-08-30
2011-01-2062
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.
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

Lumped Chemical Kinetic Model Based on the Detailed Analysis of Hydrocarbon Fuel Ignition

2011-08-30
2011-01-1782
A systematic chemical lumping method has been proposed, based on the detailed kinetic analysis of hydrocarbon fuel ignitions. The model constructed by using this method contains two reaction sets, RO2 and fragment reaction package. The ignition characteristics of each fuel can be reflected by only adjusting several rate parameters in RO2 reaction package. From the comparison with detailed model, it was confirmed that this simplified model well reproduces the results of detailed one without missing the kinetics of hydrocarbon ignitions. We concluded that this new lumping approach has the possibility to be applicable to every hydrocarbon fuels.
Technical Paper

Universal Rule of Hydrocarbon Oxidation

2009-04-20
2009-01-0948
Hydrocarbon thermal ignition in internal combustion engines is controlled by the balance of heat release rate by chemical reactions and internal energy formation or removal rate by adiabatic compression or expansion. Heat release rate can be described by a simple “Universal Rule”, that the heat release rate during the thermal ignition preparation period is determined by H2O2 loop composed of four elementary reactions. This rule was validated by sensitivity analysis and response analysis to perturbation of intermediate species concentrations. The rule was applied to clarify several subjects with experimental backgrounds, such as ignition characteristics of higher octane number fuels, an old and well-known knocking model and the influence of H2 addition.
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

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

Particulate Matter Emission in steady state operation and transient operation from Direct Injection (DI) Off-Road Diesel Engine

2005-09-11
2005-24-017
For protecting human health and preserving the clean environment, current regulations stipulate acceptable levels of particulate emissions based on the mass collected on filters obtained by sampling in diluted exhaust. Such regulations will be imposed not only on-road engines but also off-road engines. From the point of view of human health [1], so-called nano-particle (d<50nm) is thought to be nuisance because it could reach deeper lung tissue. So, many researches have been done in this research field [2]. A series of experiments were conducted on an off-road general purpose direct Injection (DI) diesel engine using EEPS (Engine Exhaust Particle Sizer) to make real time particle size distribution measurements possible. The data presented covers whole operating conditions including the operating modes of off-road diesel engine emission test (C1mode). Additionally, PM emissions in transient (NRTC test cycle) engine operation were examined.
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

On-Board Measurement of Engine Performance and Emissions in Diesel Vehicle Operated with Bio-diesel Fuel

2004-03-08
2004-01-0083
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.
Technical Paper

Modeling Atomization and Vaporization Processes of Flash-Boiling Spray

2004-03-08
2004-01-0534
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.
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