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Viewing 1 to 30 of 37
1992-02-01
Technical Paper
920467
Mitsuru Konno, Takemi Chikahisa, Tadashi Murayama
Abstract 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.
1992-02-01
Technical Paper
920465
Takemi Chikahisa, Kazushige Kikuta, Tadashi Murayama
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.
1992-02-01
Technical Paper
920091
Mitsuru Konno, Takemi Chikahisa, Tadashi Murayama, Masakazu Iwamoto
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.
1992-10-01
Technical Paper
922212
Tadashi Murayama, Takemi Chikahisa, Jianwei Guo, Masaharu Miyano
Dimethyl ether (DME) can be converted easily from methanol in a catalytic reactor, and it has very good compression ignition characteristics. This paper presents experimental results on a compression ignition methanol engine with DME as an ignition improver. The results show that engine operation is sufficiently smooth with high efficiency without spark or glow plugs. In the experiments, two methods for DME introduction were investigated: an aspiration and a torch ignition method. The aspiration method introduces DME into the intake manifold, and is structurally simple but suffers from poor emission characteristics at partial loads, and a large amount of DME is required for ignition. With the torch ignition method, DME is introduced into a torch ignition chamber during the intake stroke, and significant reductions in both the necessary DME quantity and emissions were obtained. Engine operation was also attempted with DME-dissolved methanol fuel without ignition aids.
1993-10-01
Technical Paper
932799
Yasuhiro Fujiwara, Shigeru Tosaka, Tadashi Murayama
Exhaust Particulate emitted from diesel engines is a serious problem form the point of view of the environment and energy saving. Exhaust particulate is consist of dry soot and SOF (soluble organic fraction). To clarify the formation process of SOF in the combustion chamber of diesel engines, first lower temperature column condensed method was investigated. The gas from combustion chamber was collected to the sampling column using this method, and the cracked as well as the condensation polymerized components were analyzed with gas chromatography. The sampling condition of the low temperature column condensation method are length of condensation column 600mm, cooling temperature 198K, and dilution ratio 5. The diesel fuel injected into the combustion chamber, first cracks into lower boiling point hydrocarbons, this is followed by dehydrogenation and formation of benzene ring compounds through condensation polymerization. This is followed by the formation of PAH.
1993-10-01
Technical Paper
932797
Mitsuru Konno, Takemi Chikahisa, Tadashi Murayama
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.
1995-02-01
Technical Paper
950447
Takemi Chikahisa, Tadashi Murayama
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.
1995-02-01
Technical Paper
950215
Takemi Chikahisa, Mitsuru Konno, Tadashi Murayama
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.
1995-10-01
Technical Paper
952518
Tadashi Murayama, Ming Zheng, Takemi Chikahisa, Young-Taig Oh, Yasuhiro Fujiwara, Shigeru Tosaka, Masayoshi Yamashita, Hideya Yoshitake
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.
1996-02-01
Technical Paper
960367
Tadashi Murayama, Yoshio Sekiya, Bambang Sugiarto, Takemi Chikahisa
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.
1998-10-19
Technical Paper
982698
Shiyujii Hatakeyama, Mikiro Kondo, Yoshio Sekiya, Tadashi Murayama
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 %.
1976-02-01
Technical Paper
760552
Tadashi Murayama, Naoya Kojima, Yu Satomi
In the present work, an attempt was made to predict engine noise from the shape of the burning rate curve. Thus, the influence of the shape of the burning rate curve on engine noise, especially on combustion noise was studied in detail and clarification of the relationship was successfully made. At first, an approximation of burning rate curve using a function was attempted. And in second, the transfer rate from cylinder pressure to combustion noise was obtained. Then, the relation between the deciding parameters of burning rate curve and noise and performance of engine were studied.
1978-02-01
Technical Paper
780224
Tadashi Murayama, Minoru Tsukahara, Yasushi Morishima, Noboru Miyamoto
With the aid of static mixer and non-ionic emulsifying agent, a comparatively stable water-fuel emulsion was obtained. Engine performance in a 4 cycle direct injection engine using these fuels were studied. A large reduction of NOx concentration was obtained over the wide range of engine operation, in spite of increased ignition lag and rapid combustion. Furthermore, improvements of economy and reduction of exhaust smoke were obtained. The reduction of NOx concentration, fuel consumption and smoke were even more remarkable when compared with operating same engine with water fumigation.
1999-10-25
Technical Paper
1999-01-3689
Shiyuji Hatakeyama, Yoshio Sekiya, Tadashi Murayama, Hideyuki Tsunemoto
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.
2001-05-07
Technical Paper
2001-01-1959
Shiyuji Hatakeyama, Yoshio Sekiya, Tadashi Murayama, Shunsaku Nakai, Takahiro Sako, Hideyuki Tsunemoto
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.
2001-05-07
Technical Paper
2001-01-1935
Tadashi Noto, Tadashi Murayama, Shigeru Tosaka, Yasuhiro Fujiwara
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.
2001-05-07
Technical Paper
2001-01-2020
Hiroshi Kitagawa, Tadashi Murayama, Shigeru Tosaka, Yasuhiro Fujiwara
The blending of dimethyl carbonate (DMC), which contains 53% of oxygen, in diesel fuel is very effective to suppress the formation of exhaust particulates, however, the mechanism of the suppression has not been made clear. In this study, the comparison on the performance of gas oil and DMC mixture was achieved. The effect of the oxygen in DMC molecule has to suppress the formation of particulates was monitored by way of using thermal cracking analyzer under various conditions.
1989-02-01
Technical Paper
890449
Minoru Tsukahara, Yasufumi Yoshimoto, Tadashi Murayama
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.
1989-02-01
Technical Paper
890421
Shigeru Tosaka, Yasuhiro Fujiwara, Tadashi Murayama
Exhaust particulate in diesel engines are affected by fuel properties, especially the aromatic hydrocarbon content and distillation properties, but the reasons for this are not clear. The process of particulate formation has been reported to start with a thermal cracking of the fuel to lower boiling point hydrocarbons followed by condensation polymerization and production of benzene ring compounds; the formation of particulate takes place via polycyclic aromatic hydrocarbons. The fuel properties affect diesel engine particulate because the thermal cracking and condensation polymerization of various fuels are different.
1989-09-01
Technical Paper
891841
Minoru Tsukahara, Yasufumi Yoshimoto, Tadashi Murayama
Micro-explosions and vaporizing behaviors of droplets of various emulsified fuels were investigated to determine the influence of emulsified fuel properties such as water content, water particle size, and viscosity of base fuel on combustion in a diesel engine. The investigation used gas oil, A heavy oil, and B heavy oil mixed with water and evaporated on a hot surface under atmospheric pressure. The influence on the engine performance was also investigated. It was confirmed that the viscosity of the base fuel, the water content, and the water particle size influenced the droplet evaporation on the hot surface and the occurrence and intensity of micro-explosions. There were remarkable differences in the BSFC for emulsified fuels in or outside the range where micro-explosions occurred on the hot surface.
1990-09-01
Technical Paper
901579
Yasuhiro Fujiwara, Shigeru Tosaka, Tadashi Murayama
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.
1981-11-01
Technical Paper
811375
Takemi Chikahisa, Noboru Miyamoto, Tadashi Murayama
In order to obtain improved combustion of methanol in a dual fuel diesel engine, both methanol and gas oil as an auxiliary fuel were injected into a pre-combustion chamber. The effects of proportion and timing of the auxiliary fuel injection, and the main injection timing on the engine performance and on emissions were investigated. As a result, with methanol 95% of total energy input, combustion took place without misfiring or knocking. The combustion was smokeless, smoother, with lower NOx, and lower noise than for usual combustion with gas oil. The thermal efficiency was maintained at the same level as in conventional diesel operation.
1980-09-01
Technical Paper
800983
Noboru Miyamoto, Tadashi Murayama, Shin-ichi Gotoh
To get accurate indicator diagrams without the use of pressure transducers, the strain and the displacement of the various parts of engine structures that would have some relationship with the pressure variation in the cylinder were measured and analyzed mathematically. By measuring the strain of the cylinder head bolts, the horizontal displacement of the crank shaft end, and the vertical displacement of the intake valve stem, we realized that the indicator diagrams could be obtained easily without a passage from the interior to the outside of the combustion chamber. Accurate indicator diagrams were estimated by applying the pressure-strain diagram obtained from the static pressure test in the cylinder to the strain variation in the cylinder head bolts. On this occasion, the accuracy of the estimated indicator diagrams could be improved by providing the cylinder head system with a one degree freedom vibration system.
1980-09-01
Technical Paper
800966
Tadashi Murayama, Noboru Miyamoto, Toshio Tsuda, Masao Suzuki, Shun-ichi Hasegawa
In a four-cycle, naturally aspirated, pre-chamber diesel engine, the combustion characteristics such as the rates of fuel injection, the ignition lag, the rates of heat release, the combustion peak pressure, the maximum rates of pressure rise, and the smoke density, were investigated for over 70 consecutive cycles under acceleration, with the aid of an on-line data handling system developed for this experiment. The effects of operating conditions such as the fuel injection timing, the fuel spray angle, the wall temperature of the combustion chamber, and the coolant temperature, on the combustion characteristics were also investigated.
1986-02-01
Technical Paper
860306
Tadashi Murayama, Young-taig Oh, Akihiro Kido, Takemi Chikahisa, Noboru Miyamoto, Koichiro Itow
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.
1985-02-01
Technical Paper
850071
Nobuyuki Yamazaki, Noboru Miyamoto, Tadashi Murayama
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.
1985-02-01
Technical Paper
850107
Noboru Miyamoto, Takemi Chikahisa, Tadashi Murayama, Robert Sawyer
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.
1987-09-01
Technical Paper
871612
Noboru Miyamoto, Zhixin Hou, Akira Harada, Hideyuki Ogawa, Tadashi Murayama
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.
1986-09-01
Technical Paper
861232
Tadashi Murayama, Noboru Miyamoto, Takemi Chikahisa, Kohji Yamane
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.
1986-09-01
Technical Paper
861277
Shinichi Goto, Noboru Miyamoto, Tadashi Murayama
Remarkable progress has been made in recent years on pressure measuring techniques and apparatuses, yet they seem not necessarily successful in achieving accurate pressure diagrams at the high frequency range. The primary cause of difficulty lies in the occurrence of undesirable vibrations in the connecting passages which diminishes the accuracy of pressure diagrams. In order to prevent such vibration, the authors have attempted to increase the natural frequency in the connecting passages by enclosing heat resisting silicon oil, to analyse the frequency characteristics of the passages, and to ensure the propriety of the analysis through comparison with experiments. As a result, it is proved that the natural frequency of the silicon oil enclosed passage increases twice as high as that of the passage filled with working gas.
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