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Technical Paper

New Concept on Lower Exhaust Emission of Diesel Engine

1995-09-01
952062
One of countermeasures for exhaust emissions from a diesel engine, especially, DI diesel engine, is the use of a super high pressure injection system with a small hole diameter. However, the system needs greater driving force than that with normal injection pressure, and its demerit is increase in NOx, although soot is decreasing. Then, authors propose the new concept on the simultaneous reduction of NOx and soot. The concept is that the utilization of flash boiling phenomenon in a diesel engine. The phenomenon can be realized by use of the injection of fuel oil with CO2 gas dissolved. Flash boiling facilitates the distinguished atomization of fuel oil and CO2 gas contributes to realizes the internal EGR during combustion. Fundamental information on the characteristics of a flash boiling spray of n-tridecane with CO2 gas dissolved is described in this paper, as a first step.
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

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

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

The Structure Analysis of Evaporative Diesel Spray

2002-03-04
2002-01-0498
This paper analyzes heterogeneous distribution of branch-like structure at downstream region of the diesel spray. The liquid and vapor phase of the spray are obtained by a 35mm still camera and CCD camera in order to investigate spray structure of evaporative diesel spray. The many previous studies about diesel spray structure have yet stayed in the analyses of 2-D structure, and there is little information which is concerned with 3-D structure analysis of evaporative spray. The heterogeneous distribution of droplets in inner spray affects the mixture formation of diesel spray, and the combustion characteristics of the diesel engines. In this study, the laser beam of 2-D plane was used in order to investigate 3-D structure of evaporative spray. The incident laser beam was offset on central axis of the spray.
Technical Paper

CO2 Mixed Fuel Combustion System for Reduction of NO and Soot Emission in Diesel Engine

1997-02-24
970319
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.
Technical Paper

Detection of Luminescence from Pre-Autoignition Reaction Zone in S.I. Engine

1997-02-24
970508
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.
Technical Paper

Characteristics of Free and Impinging Gas Jets by Means of Image Processing

1997-02-24
970045
A transient gas jet seems to be a model of a diesel spray because it has no vaporization process. Recently, CNG is utilized in a diesel engine. In the case of diesel engine, sprays or jets have the free state in some cases, and they are impinging surely on the piston surface in the other cases. The 2-D image of acetylene gas with tracer particles was taken by high-speed photography. In both jets, the outer shape was measured on the images and the characteristics of the internal flow was obtained by particle image velocimetry. Then, the physical models of these jets were constructed by use of experimental results.
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.
Technical Paper

OH Radical Generation and Soot Formation/Oxidation in DI Diesel Engine

1998-10-19
982630
OH radical generated in a DI diesel engine has a close relationship to soot oxidation. To clarify this fact, the distribution of the natural emission of OH radical was captured by means of an interference filter system and that of soot was detected by the simultaneous application of a laser induced incandescence (LB) and a laser induced scattering (LIS). The experiments were carried out in a small sized high-speed DI diesel engine installed with an optical access view. The generation of OH radical and the formation/oxidation of soot are discussed by using both images.
Technical Paper

Investigation on the Characteristics of Diesel Fuel Spray

1980-09-01
800968
The authors carried out a basic and systematic investigation on diesel combustion processes using three different experimental apparatuses. This paper summarized the experimental results obtained from the three devices. Among the data contained in this paper are; (1) The structure and shape of diesel spray, the air movement around diesel spray and the spatial and temporal distributions of the size of droplets in diesel spray injected into the high pressure and room temperature charge. (2) The shape of diesel spray injected into the high pressure and high tempertaure charge. (3) The characteraistics of flame, and illumination delay, and ignition delay in the high pressure and high temperature charge.
Technical Paper

Vizualization of Evaporative Diesel Spray Impinging Upon Wall Surface by Exciplex Fluorescence Method

1992-02-01
920578
A single diesel spray of n-decane which was miscible with a small quantity of exciplex dopants was injected from a hole nozzle into a quiescent high-temperature and high-pressure atmosphere of nitrogen, and was impinged in a normaldirection upon a flat wall with elevated temperature. This experiment was to serve as a simplified model of the actual state in a combustion chamber of diesel engines. When a thin sheet of laser light from Nd:YAG laser is passing through the cross section of this spray containing its central axis, it is able to generate fluorescent emissions from vapor and liquid phases in this evaporating spray. Then, clear 2-dimensional images concerning the concentration distributions of vapor and liquid phases were obtained simultaneously, by an exciplex fluorescence method using an image-intensifier and a CCD camera system. The dispersion processes of vapor and liquid phases in this impinging spray near the wall were analyzed with an image analyzer.
Technical Paper

Atomization of Spray under Low-Pressure Field from Pintle Type Gasoline Injector

1992-02-01
920382
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.
Technical Paper

Knocking Phenomena in a Rapid Compression and Expansion Machine

1992-02-01
920064
In this study, a rapid compression and expansion machine(RCEM) with a pancake combustion chamber was designed to investigate fundamentally on the knocking phenomena in spark ignition(S.I) engines. This RCEM is intended to simulate combustion in an actual engine. The homogeneous pre-mixture of n-pentane and air was charged into a quiescent atmosphere of the chamber. Then, the combustion field become simpler in this machine than it in a real S.I. engine. Also, the combustion phenomena, that is a cylinder pressure history, the behavior of flame propagation and so on, with high reproducibility are realized in this machine. The phenomena caught in this experiment were so-called low speed knocking. And, this knocking characteristics such as a knock intensity and a knock mass fraction were revealed by the cylinder pressure analysis varying the charge pressure and the equivalence ratio of the mixture, a compression ratio and an ignition timing.
Technical Paper

Combustion in a Small DI Diesel Engine at Starting

1992-02-01
920697
It is unavoidable that a DI diesel engine exhausts a blue and white smoke at starting, especially in the cold atmosphere. In the experiments presented here, a small DI diesel engine started under the conditions of coolant and suction air whose minimum temperatures were 255 K and 268 K, respectively. The flame was photographed by high-speed photography, the temperature of flame and the soot concentration were measured by two-color method, and CO2 concentration was detected by luminous method. The engine cannot be started over several cycles when the coolant temperature is 255 K and suction air temperature is 268 K. As the temperature of coolant and suction air are decreasing, the maxima of the cylinder pressure, the flame temperature, the soot concentration and CO2 concentration are decreasing. Luminous small dots or small lumps of flame become scattered in the piston cavity.
Technical Paper

Characteristics of Combustion in an IDI Diesel Engine with a Swirl Chamber Made of Ceramics

1992-02-01
920696
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.
Technical Paper

Characteristics of a Diesel Spray Impinging on a Flat Wall

1989-02-01
890264
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.
Technical Paper

Similarity Law of Entrainment into Diesel Spray and Steady Spray

1990-02-01
900447
The surroundings around the diesel spray are entrained during the growth of the spray. The mixing process between the evaporated fuel oil and the entrained surroundings, that is, the entrainment, has a significant meaning for the combustion diesel engine. It is difficult to detect the movement of the entrainment because the diesel spray is the gas-liquid two-phase flow and the unsteady phenomenon within a few milliseconds. Then, in order to clarify and to generalize the movement of entrainment, following three experiments were done. 1)Two-dimensional steady water spray -flat spray- injected into the ambient atmosphere, using tuft and hot wire method. 2) Unsteady water jet injected into water, using tracer. 3)single diesel spray injected into the atmosphere with high pressure at room temperature, using smoke wire.
Technical Paper

Characteristics of Transient Gas Diffusion Flame

1997-10-01
972965
CNG is one of the future fuel for a CI engine. Recently, the general tendency is the use of the high pressure injection system over 100 MPa in a CI engine for the near future severe regulation. Combustion phenomenon in a CI engine with such injection system is like a transient gas diffusion flame. The flow in a gas diffusion flame was investigated by the particle image velocimetry on its 2-D images, the relative soot concentration, the temperature and the relative CO2 concentration was detected in the experiments. And the model of transient gas diffusion flame was constructed by use of experimental data.
Technical Paper

Characterization of Fuel Vapor Concentration Inside a Flash Boiling Spray

1997-02-24
970871
For current passenger vehicles, multi-point injection (MPI) systems are extensively employed for gasoline engines due to ease of control and rapid response. In these systems, the pressure within the intake manifold to which the injectors are installed can fall below the saturated vapor pressure of some hydrocarbon components present in the fuel. Such a condition leads to an atomization process in which flash boiling occurs. In the present work, the atomization process under flash boiling conditions has been characterized both experimentally and theoretically. The experimental investigation has been carried out with a spray test facility consisting of a variable pressure chamber equipped with a pintle type fuel nozzle. Infrared Extinction/Scattering (IRES) is utilized to provide temporal and spatially resolved distribution of the fuel vapor concentration within the spray.
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