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Technical Paper

Mechanism of NOx Reduction by Ethanol on a Silver-Base Catalyst

2001-05-07
2001-01-1935
Since there is a trade-off relationship between NOx and particulates in exhaust gas emitted from a diesel engine, simultaneous reduction of the amounts of NOx and particulates in a combustion chamber is difficult. However, the amount of particulates produced in the combustion process could be reduced in a state of almost complete combustion, and the amount of NOx produced during the combustion process could be reduced by the use of a catalyst and reducing agent in the exhaust process. It has been demonstrated that the use of ethanol as a reducing agent on a silver-base catalyst in the presence of oxygen is an effective means for reducing NOx, although the mechanism of the reduction has not been elucidated. Therefore, in the present study, an NOx-reduction apparatus was conducted, and model experiments on NOx reduction were carried out in an atmosphere simulating exhaust gas emitted from a diesel engine and at the same catalyst temperature as that in a combustion chamber.
Technical Paper

A Study on In-Cylinder Injection of Low Pressure Natural Gas for Performance Improvement of Small Sized Two-Stroke SI Engines

2001-05-07
2001-01-1959
Small two stroke SI engines supplied with natural gas in the intake port are advantageous for low maintenance and low cost when used in co-generation systems for residential use. However in the engines with port injection systems, the unburned HC emissions are higher and thermal efficiency is lower than with 4 stroke engines. To overcome these disadvantages, an in-cylinder injection with a special low pressure injection nozzle system was attempted. The results showed that improvements in unburned HC emissions and thermal efficiency are possible due to the remarkable reduction in scavenging loss and the lean combustion.
Technical Paper

A Study of Lean Burn of a 4 Stroke Gasoline Engine by the Aid of Low Pressure Air Assisted In-Cylinder Injection - Part II

1999-10-25
1999-01-3689
Lean-burn engines now being developed employ in-cylinder injection which requires high pressures and so necessitates expensive injection equipment. The injection system proposed here is an air assisted in-cylinder injection system which is injecting a mixture of air and fuel in the cylinder during the intake stroke and allowing atomization at lower injection pressures than those necessary in compressing fuel with a usual solid injection. This time, the experiments used a testing engine of a 4 stroke gasoline OHV type replacing the Side Valve type. Performance with a small depression in the main combustion chamber was investigated with a spark plug and reed valve installed in the depression. The engine was operated then following the same method as last year (SAE 982698). As a result, the lean burn method employed here was possible over a wide range of engine speeds and loads. Moreover, it was also shown that this operation was possible with a fully opened throttle valve.
Technical Paper

An attempt at Lean Burn of a4 Stroke Gasoline Engine by the Aid of Low Pressure Air Assisted In-Cylinder Injection

1998-10-19
982698
Lean burn engines now being developed employ in-cylinder injection which requires high pressures and so necessitates expensive injection equipment. The experiments reported here used air assisted in-cylinder injection, and injected a mixture of air and fuel during the intake stroke, so allowing atomization at lower injection pressures than those necessary in compressing fuel with solid injection. The experiments confirmed that operation in this manner resulted in similar output and fuel consumption as with a carburetor. Next, a divided combustion chamber was installed and connected to the main combustion chamber and air assisted in-cylinder injection from a reed type injection nozzle was attempted. With this arrangement, stable idling operation was possible to air-fuel ratios (A/F) of 70. Lean burn at A/F = 22 to 35 was also achieved at maximum rated outputs (3.7 kW at 4200 min-l) of 6 - 18 %.
Technical Paper

Study on Exhaust Control Valves and Direct Air-Fuel Injection for Improving Scavenging Process in Two-Stroke Gasoline Engines

1996-02-01
960367
A critical factor in improving performance of crankcase-scavenged two-stroke gasoline engines is to reduce the short-circuiting of the fresh charge to the exhaust in the scavenging process. To achieve this, the authors developed a reciprocating exhaust control valve mechanism and direct air-fuel injection system. This paper investigates the effects of exhaust control valve and direct air-fuel injection in the all aspect of engine performance and exhaust emissions over a wide range of loads and engine speeds. The experimental results indicate that the exhaust control valve and direct air-fuel injection system can improve specific fuel consumption, and that HC emissions can be significantly reduced by the reduction in fresh charge losses. The pressure variation also decreased by the improved combustion process. CRANKCASE SCAVENGED two-stroke gasoline engines suffer from fresh charge losses leading to poor fuel economy and it is a reason for large increases of HC in the exhaust.
Technical Paper

Simultaneous Reductions of Smoke and NOx from a DI Diesel Engine with EGR and Dimethyl Carbonate

1995-10-01
952518
Extensive experiments were conducted on a low emission DI diesel engine by using Dimethyl Carbonate (DMC) as an oxygenate fuel additive. The results indicated that smoke reduced almost linearly with fuel oxygen content. Accompanying noticeable reductions of HC and CO were attained, while a small increase in NOx was encountered. The effective reduction in smoke with DMC was maintained with intake charge CO2, which led to low NOx and smoke emissions by the combined use of oxygenated fuel and exhaust gas recirculation (EGR). Further experiments were conducted on an optically accessible combustion bomb and a thermal cracking set-up to study the mechanisms of DMC addition on smoke reduction.
Technical Paper

Analysis of NO Formation Characteristics and Control Concepts in Diesel Engines from NO Reaction-Kinetic Considerations

1995-02-01
950215
This paper uses NO Reaction Kinetic to determine NO formation characteristics in diesel engines. The NO formation was calculated by Extended Zel'dovich Reaction Kinetics in a diffusion process. The results show that the NO formation rate is independent of the mixing of the combustion gas, and that internal EGR (combustion gas mixing in a cylinder) has no effect on NO reduction. The paper also shows the potential of two stage combustion, and its effect strongly depends on the time-scale of mixing. Additionally the paper investigates the mechanism of increased NOx emissions in high pressure fuel injection.
Technical Paper

Theory and Experiments on Air-Entrainment in Fuel Sprays and Their Application to Interpret Diesel Combustion Processes

1995-02-01
950447
This paper presents a theory and its experimental validation for air entrainment changes into fuel sprays in DI diesel engines. The theory predicts air entrainment changes for a variety of swirl speeds, number of nozzle holes, nozzle diameters, engine speeds, injection speeds and fuel densities. The formulae of the theory are simple non-dimensional equations, which apply for different sized engines. Experiments were performed to compare theoretical predictions and experimental results in six different engines varying from 85 to 800mm bore. All results showed good agreement with the theoretical predictions for shallow-dish piston engines. However the agreement became poor in the case of deep cavity piston engines. With the theory, it is possible to interpret a variety of combustion phenomena in diesel engines, providing additional understanding of diesel combustion processes.
Technical Paper

An Investigation on the Simultaneous Reduction of Particulate and NOx by Controlling Both the Turbulence and the Mixture Formation in DI Diesel Engines

1993-10-01
932797
This paper presents experimental results of the reduction of both particulate and NOx emitted from direct injection diesel engines by a two stage combustion process. The primary combustion is made very rich to reduce NOx and then the particulate is oxidized by strong turbulence generated during the secondary combustion. The rich mixture is formed by low pressure fuel injection and a small cavity combustion chamber configuration. The strong turbulence is generated by a jet of burned gas from an auxiliary chamber installed at the cylinder head. The results showed that NOx was reduced significantly while maintaining fuel consumption and particulate emissions. An investigation was also carried out on the particulate reduction process in the combustion chamber with the turbulence by gas sampling and in-cylinder observation with an optical fiber scope and a high speed camera.
Technical Paper

Catalytic Reduction of NOx in Actual Diesel Engine Exhaust

1992-02-01
920091
Copper ion-exchanged ZSM-5 zeolite catalyst, which reduces nitrogen oxides (NOx) in the presence of oxygen and hydrocarbons, was applied to actual diesel engine exhaust. Copper ion-exchanged ZSM-5 zeolite effectively reduced NOx by 25% in normal engine operation, and by 80% when hydrocarbons in the exhaust were increased. Water in the exhaust gas decreased the NOx reduction efficiency, but oxygen and sulfur appeared to have only a small effect. Maximum NOx reduction was observed at 400°C irrespective of hydrocarbon species, and did not decrease with space velocity up to values of 20,000 1/h. THE PURPOSE of this paper is to evaluate the possibilities and problems in catalytic reduction of NOx in actual diesel engine exhaust. Here, a copper ion-exchanged ZSM-5 zeolite (Cu-Z) catalyst was applied to diesel engine exhaust to examine the dependency of the NOx reduction efficiency on temperature and space velocity. The effects of oxygen, water and hydrocarbons were also examined.
Technical Paper

Combustion Similarity for Different Size Diesel Engines: Theoretical Prediction and Experimental Results

1992-02-01
920465
This paper presents a theoretical and experimental study on the possibility of combustion similarity in differently sized diesel engines. Combustion similarity means that the flow pattern and flame distribution develop similarly in differently sized engines. The study contributes to an understanding and correlating of data which are presently limited to specific engine designs. The theoretical consideration shows the possibility of combustion similarity, and the similarity conditions were identified. To verify the theory, a comparison of experimental data from real engines was performed; and a comparison of results of a three dimensional computer simulation for different engine sizes was also attempted. The results showed good agreement with the theoretical predictions. THE PURPOSE of this research is to determine the possibility of the existence of combustion similarity in differently sized diesel engines, and to propose conditions for realizing model experiments.
Technical Paper

Reduction of Smoke and NOx by Strong Turbulence Generated During the Combustion Process in D.I. Diesel Engines

1992-02-01
920467
This paper presents results of experiments to reduce smoke emitted from direct Injection diesel engines by strong turbulence generated during the combustion process. The turbulence was created by jets of burned gas from an auxiliary chamber installed in the cylinder head. Strong turbulence, which was induced late in the combustion period, enhanced the mixing of air with unburned fuel and soot, resulting in a remarkable reduction of smoke and particulate; NOx did not show any increase with this system, and thermal efficiency was improved at high loads. The paper also shows that the combination of EGR and water injection with this system effectively reduces the both smoke and NOx.
Technical Paper

A Quantitative Analysis of Schlieren Photography for an Internal Combustion Engine Diagnostics

1991-02-01
910730
This report describes the possibility of quantitative analysis of Schlieren photographs as an internal combustion engine diagnostic. Using a recently developed photographic analysis system, it was attempted to analyze Schlieren photographs. Results showed simple integration calculations produced significant distortion in the analyzed results. To eliminate the distortion, some correction techniques were developed in this research. Accuracy of the analyzed results were evaluated roughly with uncertainty analysis. The results showed that this analysis technique can be one of the approximate diagnostics for the measurement of fuel vapor and density distribution in internal combustion engine research. SCHLIEREN photography is one of the most popular visualization techniques in the research of internal combustion engines. Although the photographs have density information in themselves, they are used mainly for the purpose of qualitative visualization.
Technical Paper

The Microcrystal Structure of Soot Particulates in the Combustion Chamber of Prechamber Type Diesel Engines

1990-09-01
901579
To clarify the microcrystal structure of soot particulate in the combustion chamber, we examined sampling methods which freeze the reaction of sample specimens from the combustion chamber and collected the soot particulates on microgrids. We investigated the microcrystal structure with a high resolution transmission electron microscope. The results were: the particle size distribution and the microcrystal structure of the soot particulates is little different for the cooled freezing method and room temperature sampling. The typical layer plane structure which characterizes graphite carbon is not observed in the exhaust of diesel engines, but some particulates display a somewhat similar layer plane structure. The structure of soot particulate is a turbostratic structure as the electron diffraction patterns show polycrystals. The soot particulates in the combustion chamber is similar to exhaust soot particulates.
Technical Paper

W/O Emulsion Realizes Low Smoke and Efficient Operation of DI Engines without High Pressure injection

1989-02-01
890449
To improve engine performance parameters such as smoke, NOx, and BSFC in a DI diesel engine, water-in-gas oil emulsified fuel was used without high pressure or high injection rate. It was confirmed that when compared with high pressure and high injection rate operation with gas oil, emulsified fuel gives significant reductions in NOx concentration, improved fuel economy, and reduced smoke density at ordinary injection pressure and retarded timings.
Technical Paper

Characteristics of Diesel Soot Suppression with Soluble Fuel Additives

1987-09-01
871612
Experiments on a large number of soluble fuel additives were systematically conducted for diesel soot reduction. It was found that Ca and Ba were the most effective soot suppressors. The main determinants of soot reduction were: the metal mol-content of the fuel, the excess air factor, and the gas turbulence in the combustion chamber. The soot reduction ratio was expressed by an exponential function of the metal mol-content in the fuel, depending on the metal but independent of the metal compound. A rise in excess air factor or gas turbulence increased the value of a coefficient in the function, resulting in larger reductions in soot with the fuel additives. High-speed soot sampling from the cylinder showed that with the metal additive, the soot concentration in the combustion chamber was substantially reduced during the whole period of combustion. It is thought that the additive acts as a catalyst not only to improve soot oxidation but also to suppress soot formation.
Technical Paper

Effects of Combustion and Injection Systems on Unburnt HC and Particulate Emissions from a DI Diesel Engine

1986-09-01
861232
This paper is a systematic investigation of the effects of combustion and injection systems on hydrocarbon(HC) and particulate emissions from a DI diesel engine. Piston cavity diameter, swirl ratio, number of injection nozzle openings, and injection direction are varied as the experimental parameters, and the constituents in the soluble organic fraction (SOF) of the particulate were analyzed. The results show that the emission characteristics of deep dish chambers greatly differ from those of shallow dish chambers varying with the number of nozzle openings, the injection direction, and swirl intensity. The HC analysis shows mainly low carbon number gaseous HC constituents, and there is a tendency towards increasing polynucleation of polynuclear aromatic hydrocarbon(PAH) in SOF with increasing soot formation.
Technical Paper

Effects of Super Heating of Heavy Fuels on Combustion and Performance in DI Diesel Engines

1986-02-01
860306
This paper is concerned with the effects of temperature of heavy fuels on combustion and engine performance in a naturally aspirated DI diesel engine. Engine performance and exhaust gas emissions were measured for rapeseed oil, B-heavy oil, and diesel fuel at fuel temperatures from 40°C to 400°C. With increased fuel temperature, mainly from improved efficiency of combustion there were significant reductions in the specific energy consumption and smoke emissions. It was found that the improvements were mainly a function of the fuel viscosity, and it was independent of the kind of fuel. The optimum temperature of the fuels with regard to specific energy consumption and smoke emission is about 90°C for diesel fuel, 240°C for B-heavy oil, and 300°C for rapeseed oil. At these temperatures, the viscosities of the fuels show nearly identical value, 0.9 - 3 cst. The optimum viscosity tends to increase slightly with increases in the swirl ratio in the combustion chamber.
Technical Paper

The Effects of Flash Boiling Fuel Injection on Spray Characteristics” Combustion, and Engine Performance in DI and IDI Diesel Engines

1985-02-01
850071
This paper deals with the effects of flash-boiling injection of various kinds of fuels on spray characteristics, combustion, and engine performance in DI and IDI diesel engines. It is known that spray characteristics change dramatically at the boiling point of fuel. When the fuel temperature increases above the boiling point, the droplet size decreases apparently and the spray spreads much wider. At higher fuel temperatures, above the boiling point, the apparent effects are a lower smoke density and improved thermal efficiency at higher loads, resulting from the shorter combustion duration; it is thus possible to obtain a markedly improved engine performance in engines with a low air-utilization chamber. Remarkable changes in heat release with the increase in fuel temperature are; an increase in premised combustion quantity and shortening of the combustion duration. The changes in smoke emission and thermal efficiency for different engine types are also considered in this paper.
Technical Paper

Description and Analysis of Diesel Engine Rate of Combustion and Performance Using Wiebe's Functions

1985-02-01
850107
Two laboratory engines, one direct, injection and one indirect injection, were operated for a range of speeds, loads, injection timings, fuels, and steady and transient conditions. Rate of combustion data were derived and analyzed using a double Wiebe's function approximation. It is shown that three of the six function parameters are constant for a wide range of conditions and that the other three can be expressed as linear functions of the amount of fuel injected during ignition lag. Engine noise, smoke, and thermal efficiency correlate with the parameters describing the amount of premixed combustion and diffusive combustion duration. These characteristics may be optimized by reducing the quantity of premixed combustion while maintaining the duration of diffusive combustion to less than 60°CA.
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