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Viewing 1 to 30 of 44
2004-03-08
Technical Paper
2004-01-0542
Nobuyuki Kawahara, Eiji Tomita, Daisuke Kasahara, Takashi Nakayama, Mamoru Sumida
Experimental investigations of fuel breakup very close to nozzle of practical high-pressure swirl injector, which is used in gasoline direct injection (GDI) engine, were carried out. In GDI engines, fuel is directly injected into cylinder therefore the spray characteristics and mixture formation are of primary importance. In this research, visualizations of primary spray formation process were demonstrated using a high-speed video camera (maximum speed: 1Mfps) with a long-distance microscope. Initial state and development of the spray were discussed under the different injection pressure condition. During the injection period, the length and thickness of the liquid sheet, which is produced from the nozzle exit, were measured using Ar-ion laser sheet and high-speed camera. Primary spray structure and behavior of liquid sheet, especially surface wave of liquid sheet, at nozzle exit were discussed using obtained images.
2004-03-08
Technical Paper
2004-01-1353
Atsushi Nishiyama, Nobuyuki Kawahara, Eiji Tomita, Masahiro Fujiwara, Naohiro Ishikawa, Kazuhiro Kamei, Keiichi Nagashima
In this study, a spark plug sensor for in-situ fuel concentration measurement was applied to a port injected lean-burn engine. Laser infrared absorption method was employed and a 3.392 μm He-Ne laser that coincides with the absorption line of hydrocarbons was used as a light source. In this engine, the secondary valve lift height of intake system was controlled to obtain appropriate swirl and tumble flow in order to achieve lean-burn with the characteristics of intake flow. For such in-cylinder stratified mixture distribution, the fuel concentration near the spark plug is very important factor that affects the combustion characteristics. Therefore, the mixture formation process near the spark plug was investigated with changing fuel injection timing. Under the intake stroke, the timing that fuel passed through near the spark plug depended largely on the fuel injection timing.
2004-06-08
Technical Paper
2004-01-1919
Sadami Yoshiyama, Eiji Tomita, Nobuo Tabuchi, Kenji Matsumoto, Katsunori Matsuki
In order to reduce the exhaust emission and the fuel consumption in a spark ignition engine, the combustion diagnostics had been developed. However, there are few sensors which can detect the combustion quality for the individual cycle and cylinder in production engines. In previous study, the new technique using a gasket ion sensor for measuring the combustion quality has been proposed. In present study, the flame propagation pattern in a spark ignition engine was detected by using a gasket ion sensor with a circular electrode. The waveforms of ion current obtained from a circular ion sensor were compared with the flame propagation pattern obtained from multiple ion sensors. When the mixture was ignited in offset center of the cylinder, the flame propagation pattern was distorted from the spherical pattern. Then the waveforms of ion current from the circular ion sensor were varied from the waveform for a center ignition.
2004-06-08
Technical Paper
2004-01-1946
Akihiko Kakuho, Koichi Yamaguchi, Yutaka Hashizume, Tomonori Urushihara, Teruyuki Itoh, Eiji Tomita
An investigation was made into two approaches to air-fuel mixture formation in direct injection SI engines in which charge stratification is controlled by swirl or tumble gas motions, respectively. Particle image velocimetry (PIV), laser-induced fluorescence (LIF) and air-fuel ratio measurement by infrared absorption were used to analyze fuel transport from the fuel injector to the spark plug and the fuel vaporization process. The results obtained were then compared with measured data as to combustion stability. As a result, the reason why the effects of injection timing on combustion stability were different between the two approaches was made clear from the standpoint of the mixture formation process.
2011-08-30
Journal Article
2011-01-2003
Mithun Kanti Roy, Nobuyuki Kawahara, Eiji Tomita, Takashi Fujitani
Hydrogen spark-ignition (SI) engines based on direct-injection (DI) promise significant advantages in terms of thermal efficiency and power output, as well as a means of overcoming problems related to knocking, backfiring, and pre-ignition. In a DI hydrogen engine, the fuel/air mixture is formed by injecting a jet of hydrogen into the air inside the combustion chamber. An Ar-ion laser beam was used as a light source to visualize the hydrogen jet in a constant-volume chamber. This allowed us to study the structure of the jet in addition to other physical processes resulting from hydrogen gas injection. Combustion experiments were conducted in a single-cylinder SI optical research engine equipped with a DI system to detect the early kernel growth assisted by the spark, as well as flame propagation. Various equivalence ratios and fuel injection timings were analyzed to identify the effects on combustion.
2011-08-30
Technical Paper
2011-01-1764
Ulugbek Azimov, Eiji Tomita, Nobuyuki Kawahara
The objective of this study is to investigate the performance and emissions in a pilot-ignited supercharged dual-fuel engine, fueled with different types of gaseous fuels under various equivalence ratios. It is found that if certain operating conditions are maintained, conventional dual-fuel engine combustion mode can be transformed to the combustion mode with the two-stage heat release. This mode of combustion was called the PREMIER (PREmixed Mixture Ignition in the End-gas Region) combustion. During PREMIER combustion, initially, the combustion progresses as the premixed flame propagation and then, due to the mixture autoignition in the end-gas region, ahead of the propagating flame front, the transition occurs with the rapid increase in the heat release rate.
2011-08-30
Technical Paper
2011-01-1769
Robert Kiplimo, Eiji Tomita, Nobuyuki Kawahara, Shiyu Zhou, Sumito Yokobe
Effects of injection parameters on combustion and emission characteristics of diesel PCCI engine operating on optical and test engine was investigated. PCCI combustion was achieved through slightly narrow included angle injector, low compression ratio coupled with exhaust gas recirculation. Analysis based on diesel spray evolution, combustion process visualization and analysis was carried out. Spray penetration was evaluated and related to the exhaust emissions. Advancing the injection timing and EGR extended the ignition delay, decreased NOx emissions and increased HC, smoke and CO emissions. Higher injection pressure led to low emissions of NOx, smoke, HC and comparable CO. Optimum spray targeting position for minimum emission was identified. Impingement on the piston surface led to deterioration of emissions and increased fuel consumption while spray targeting the upper edge of Derby hat wall showed improvement in emission and engine performance.
2005-04-11
Technical Paper
2005-01-0644
Yuji Ikeda, Atsushi Nishiyama, Nobuyuki Kawahara, Eiji Tomita, Shigeyuki Arimoto, Akira Takeuchi
An in-spark-plug flame sensor was developed to measure local chemiluminescence near the spark gap in a practical spark-ignition (SI) engine in order to study the development of the initial flame kernel, flame front structure, transient phenomena, and the correlation between the initial flame kernel structure and cyclic variation in the flame front structure, which influences engine performance directly. The sensor consists of a commercial instrumented spark plug with small Cassegrain optics and an optical fiber. The small Cassegrain optics were developed to measure the local chemiluminescence intensity profile and temporal history of OH*, CH*, and C2* at the flame front formed in a turbulent premixed flame in an SI engine. A highresolution monochromator with an intensified chargecoupled device (ICCD) and spectroscopy using optical filters and photomultiplier tubes (PMTs) were used to measure the time-series of the three radicals, as well as the in-cylinder pressure.
2015-09-01
Technical Paper
2015-01-1946
Yungjin Kim, Nobuyuki Kawahara, Eiji Tomita, Hiroshi Oshibe, Koichi Nishikawa
Bio-gas as an internal combustion (I.C.) engine fuel has many advantages such as cheaper fuel cost, low emission levels and especially the neutral recirculation loop of carbon dioxide, which is one of the principal factors in global warming. In this study, positive potentialities of bio-gas were investigated using a micro co-generation engine. The mixing ratio of methane (CH4) and carbon dioxide (CO2) was changed to simulate various types of bio-gases. Intake air and fuel flow rates were controlled to change the equivalence ratio. The engine load condition could be changed with the electric output power used. Base on the result, the higher CO2 content rate slowed down the engine speed in the same load condition and the combustion speed generally decreased under the same load condition with maintaining the engine speed. However thermal efficiency increased with lean burn conditions and NOX emission decreased with higher CO2 mixing rates.
2015-09-01
Technical Paper
2015-01-1792
Cagdas AKSU, Nobuyuki Kawahara, Kazuya Tsuboi, Shun Nanba, Eiji Tomita, Morio Kondo
A single cylinder, supercharged dual fuel gas engine with micro-pilot fuel injection is operated using methane only and methane-hydrogen mixtures. Methane only experiments were performed at various equivalence ratios and equivalence ratio of 0.56 is decided as the optimum operating condition based on engine performance, exhaust emissions and operation stability. Methane-hydrogen experiments were performed at equivalence ratio of 0.56 and 2.6 kJ/cycle energy supply rate. Results show that indicated mean effective pressure is maintained regardless of hydrogen content of the gaseous fuel while thermal efficiency is improved and presence of hydrogen reduces cyclic variations. Increasing the fraction of hydrogen in the fuel mixture replaces hydrocarbon fuels and reduces carbon monoxide and hydrocarbon emissions.
2015-11-17
Technical Paper
2015-32-0748
Nobuyuki Kawahara, Shota Hashimoto, Eiji Tomita
The objective of this study is to investigate the initial flame propagation characteristics of turbulent flame in an engine cylinder through time-series analysis of radical emissions. A spark plug with optical fiber was developed in this study. The plug sensor is M12 type that makes it possible to mount in practical engine. The spark plug sensor can detect radical emissions in time-resolved spectra through time-series spectroscopic measurement. In this spectra, some kinds of radical emissions such as OH*(306nm), CH*(431nm) and C2*(517nm) based on principle of chemiluminescence are observed. In this study, the spark plug sensor was applied to both compression-expansion machine (CEM) and practical engine. As a result of CEM with bottom viewed high-speed camera, three kinds of spectra could be detected.
2007-10-29
Technical Paper
2007-01-4052
Sadami Yoshiyama, Eiji Tomita, Masatoshi Mori, Yuji Sato
Homogeneous charge compression ignition (HCCI), has the potential to improve the fuel economy and to reduce NOx emission significantly. Spark plug in SI engine and fuel injector in diesel engine can be used directly to control the start of combustion and the combustion period. However, the combustion of HCCI engine is controlled by the chemical kinetic mainly due to the temperature histories in the cylinder. Therefore the combustion process of HCCI engine cannot be directly controlled. Ion sensors such as a spark plug or a gasket are useful to detect the combustion information in production engines. In this study, the ion current was measured in an HCCI engine with the heated charge mixture of fuel and air without EGR when the charge temperature, equivalence ratio and fuel were varied. Simultaneously in-cylinder pressure was measured and the rate of heat release was calculated. The relationship between the rate of heat release and the ion current is mainly discussed.
2007-10-30
Technical Paper
2007-32-0049
Nobuyuki KAWAHARA, Eiji TOMITA, Hidenobu Yasuda
This paper describes the development and application of a spark plug sensor using an infrared absorption technique to quantify the instantaneous residual gas concentration near the spark plug. The residual gas fraction inside engine cylinder is assumed to be proportional to CO2 concentration. The relationship between CO2 concentration and absorption strength of CO2 was determined for various pressures and temperatures in advance using a constant volume vessel with electric heating system. The spark plug sensor for in-situ CO2 concentration measurement was applied to a compression-expansion engine and also to a port injected motorcycle SI engine. It was possible to qualify the CO2 concentration inside residual gas during the compression stroke using the developed optical system with new spark plug sensor in compression-expansion machine.
2009-06-15
Technical Paper
2009-01-1957
Nobuyuki Kawahara, Eiji Tomita, Takuya Kadowaki
In this study, fuel concentration measurements in a spark-ignition (SI) engine with ethanol blended gasoline were carried out using an optical sensor installed in the spark plug with laser infrared absorption technique. The spark plug sensor for in-situ fuel concentration measurement was applied to a port injected SI engine. The molar absorption coefficients of ethanol blended gasoline were determined for various pressures and temperatures in advance using a constant volume vessel with electric heating system. Ethanol blended gasoline with high volumetric ratios shows lower molar absorption coefficients due to lower molar absorption coefficients of ethanol. The molar absorption coefficients of ethanol blended gasoline can be estimated by considering the molar fraction of each component.
2009-06-15
Technical Paper
2009-01-1773
Nobuyuki Kawahara, Eiji Tomita, Mithun Kanti Roy
Investigation of knocking combustion in a hydrogen spark-ignition engine is one of the major challenges for future vehicle development. The knock phenomenon in a Spark-Ignition (SI) engine is caused by autoignition of the unburned gas ahead of the flame. The explosive combustion of the end-gas creates a pressure wave that leads to damage of the cylinder wall and the piston head of the engine. We observed autoignition in the end-gas region due to compression by the propagating flame front using a high-speed colour video camera through the optically accessible cylindrical quartz window on the top of the cylinder head. Moreover, a high-speed monochrome video camera operating at a speed of 250, 000 frame/s was used to measure the pressure wave propagation. The goal of this research was to improve our ability to describe the effect of the autoignition process on the end-gas and propagating pressure wave during knocking combustion with the help of a high-speed video camera.
2009-06-15
Technical Paper
2009-01-1848
Murari Mohon Roy, Eiji Tomita, Nobuyuki Kawahara, Yuji Harada, Atsushi Sakane
This study investigated the effect of some pilot fuel injection parameters, like injection timing, injection pressure and injection quantity on engine performance and exhaust emissions of a supercharged producer gas-diesel dual fuel engine. The engine has been tested to be used as a co-generation engine and its power output is an important matter. Experiments have been done to optimize the injection timing, injection pressure and injection quantity for the maximization of engine power. At constant injection pressures, there is an optimum amount of pilot injection quantity for that maximum engine power is developed without knocking and within the limit of maximum cylinder pressure. Above or below of that amount engine power is decreased. Higher injection pressures generally show better results than lower ones. However, good results can also be obtained with lower injection pressure, if maximum power timings can be selected.
2005-04-11
Technical Paper
2005-01-0646
Nobuyuki Kawahara, Eiji Tomita, Kenji Ohnishi, Kazuhiro Goto
A heterodyne interferometry system with a fiber-optic sensor was developed to measure the temperature history of unburned gas in a spark-ignition engine. A polarization-preserving fiber and metal mirror were used as the fiber-optic sensor to deliver the test beam to and from the measurement region. This fiber-optic sensor can be assembled in an engine cylinder head without a lot of improvements of an actual engine. Adjustment system in the sensor was revised to face the distributed index lens with metal mirror. Before the flame arrived at the developed fiber-optic sensor, measured temperature was almost same with the temperature history after the spark, assuming that the process that changes the unburned gas is adiabatic. In situ unburned gas temperature measurements before knocking in a commercially produced SI engine can be carried out using developed fiber-optic heterodyne interferometry system.
2005-04-11
Technical Paper
2005-01-0645
Nobuyuki Kawahara, Eiji Tomita, Akira Takeuchi, Shigeyuki Arimoto, Yuji Ikeda, Atsushi Nishiyama
A small Cassegrain optics sensor was developed to measure local chemiluminescence spectra and the local chemiluminescence intensities of OH*, CH*, and C2* in a four-stroke spark-ignition (SI) engine in order to investigate the propagation characteristics of the turbulent premixed flame. The small Cassegrain optics sensor was an M5 type that could be installed in place of a pressure transducer. The measurements could be used to estimate the flame propagation speed, burning zone thickness, and local air/fuel (A/F) ratio for each cycle. The specifications of the small Cassegrain optics sensor were the same as those used for previous engine measurements. In this paper, measurements were made of several A/F ratios using gasoline to fuel the model engine. The performances of two Cassegrain optics sensors were compared to demonstrate the advantages of the new small sensor by measuring the local chemiluminescence intensities of a turbulent premixed flame in the model engine.
2007-07-23
Technical Paper
2007-01-1872
Changhee Lee, Eiji Tomita, Kihyung Lee
Emissions remain a critical issue affecting engine design and operation, while energy conservation is becoming increasingly important. One approach to favorably address these issues is to achieve homogeneous charge combustion and stratified charge combustion at lower peak temperatures with a variable compression ratio, a variable intake temperature and a trapped rate of the EGR using NVO (negative valve overlap). This experiment was attempted to investigate the origins of these lower temperature auto-ignition phenomena with SCCI and CAI using gasoline fuel. In case of SCCI, the combustion and emission characteristics of gasoline-fueled stratified-charge compression ignition (SCCI) engine according to intake temperature and compression ratio was examined. We investigated the effects of relative air/fuel ratio, residual EGR rate and injection timing on the CAI combustion area.
2007-07-23
Technical Paper
2007-01-1849
Nobuyuki Kawahara, Eiji Tomita, Yutaka Tanaka
In this study, residual gas fraction measurements in a spark-ignition engine were carried out using an optical sensor installed in the spark plug with infrared absorption method. The residual gas fraction inside engine cylinder is proportional to the CO2 concentration. Infrared absorption method was applied and an infrared lamp and optical filter (center wavelength: around 4.3 μm) that coincides with the absorption lines of CO2 was used as a light source.The molar absorption coefficient of CO2 is discussed and compared to results in the HITRAN database. The effect of water vapor absorption doesn't affect the absorption of CO2. The absorption characteristics of CO2 were determined in advance using a constant volume vessel. Molar absorption coefficient depends on the CO2 concentration and ambient pressure and temperature, and wavelength of absorption line.
2007-07-23
Technical Paper
2007-01-1848
Changhee Lee, Nobuyuki Kawahara, Eiji Tomita, Kenji Inoshita
Non-intrusive measurement of transient unburned gas temperatures was developed with a fiber-optic heterodyne interferometry system. Using the value of the Gladstone-Dale constant for DME gas and combustion pressure we can calculate the in-cylinder temperature inside unburned and burned region. In this experimental study, it was performed to set up a fiber-optic heterodyne interferometry technique to measure the temperature before and behind the combustion region in a DME-HCCI engine. At first, measured temperature was almost the same as the temperature history assuming that the process that changes of the unburned and the burned are polytropic. In addition, we measured the temperature after combustion which of condition was burned gas with DME-HCCI combustion. The developed heterodyne interferometry used the spark-plug-in fiber-optic sensor has a good feasibility to measure the unburned and burned temperature history.
2006-04-03
Technical Paper
2006-01-0182
Nobuyuki Kawahara, Eiji Tomita, Atsushi Nishiyama, Kenta Hayashi
This paper describes the development and application of a spark plug sensor using a 3.392 μm infrared absorption technique to quantify the instantaneous gasoline concentration near the spark plug. We developed an in situ laser infrared absorption method using a spark plug sensor and a 3.392 μm He-Ne laser as the light source; this wavelength coincides with the absorption line of hydrocarbons. First, we established a database of the molar absorption coefficients of premium gasoline at different pressures and temperatures, and determined that the coefficient decreased with increasing pressure above atmospheric pressure. We then demonstrated a procedure for measuring the gasoline concentration accurately using the infrared absorption technique. The history of the molar absorption coefficient of premium gasoline during the experiment was obtained from the established database using measured in-cylinder pressures and temperatures estimated by taking the residual gas into consideration.
2005-10-24
Technical Paper
2005-01-3872
Sadami Yoshiyama, Eiji Tomita, Shunsuke Kitawaki, Keizo Kamada
Recently, in order to warm up the catalyst temperature rapidly, the retard ignition management has been developed. However, the excess retard of ignition causes the combustion instability and misfire. In this case, the ion sensor has been used for detecting the combustion quality for the late burned cycle under the idling condition. Several researchers have focused on the potential of ion-current measurement for the retard ignition management. However, the interpretation of ion-current during the exhaust process under the idling condition is not clear. In this study the source of ion-current for the late burned cycle during the exhaust process is focused. In order to measure the flame propagation process in the cylinder and the exhaust pipe, the single-cylinder test engine was used instead of production engine. Several ion probes were mounted on the cylinder head gasket, the piston head and the exhaust pipe for detecting the flame front.
1995-02-01
Technical Paper
950056
Eiji Tomita, Yoshisuke Hamamoto, Hiroyuki Tsutsumi, Sadami Yoshiyama
A path line method utilizing a CCD random shutter camera and a laser light sheet was applied for obtaining the air mass entrained into a transient gas jet. Large, light weight particles and fine particles were used for scattering the path lines of the surroundings and visualizing the approximate shape of the jet, respectively The jet configuration and the entrainment process could be visualized simultaneously, and this path line method was found to be very useful for estimating the air mass entrained because of the good agreement with the value obtained using LDA data. The spatial and temporal change of the ambient air entrainment into the jet was approximately clarified.
2000-10-16
Technical Paper
2000-01-2828
Sadami Yoshiyama, Eiji Tomita, Yoshisuke Hamamoto
In order to investigate the relation between ion current and combustion characteristics, the ion current signal from a spark plug as an ion probe, pressure history and flame development were measured in a homogeneous propane-air mixture in closed combustion chambers. The flame propagation was measured by Schlieren photography technique. When negative bias is applied to the central electrode of the spark plug, the ion current flows only due to an early flame kernel existing near the spark plug. When positive bias is applied to the central electrode, the ion current flows from the central electrode to the combustion chamber wall and to the ground electrode. Consequently, the ion current is dominated by the contact area between the flame and the combustion chamber wall. The appearance period of ion-current is related to the combustion duration. This method was applied to the combustion analysis of the spark ignition engine.
2000-06-19
Technical Paper
2000-01-1940
Eiji Tomita, Sadami Yoshiyama, Yasuhiro Ohkura, Hiroshi Tabuchi, Yoshisuke Hamamoto
The structures of the turbulent premixed flame in the engine cylinder under lean burn conditions were investigated using ion probe method. The flow fields were measured with an LDA for two tumble ratios and two compression ratios. And ion-current signal was analyzed to discuss the interaction between the turbulence and the flame structure. The effects of turbulence and equivalence ratio on the characteristic values of the turbulent flame, that is to say number of ion-current peaks, thickness of flame front and thickness of burning zone of the flamelet, were investigated. In normal combustion, the structure of the turbulent flame front is almost the same as the laminar flame. In the lean limit, the flamelet is broken and stretched and then the structure may change.
2003-05-19
Technical Paper
2003-01-1801
Sadami Yoshiyama, Eiji Tomita, Nobuo Tabuchi, Kenji Matsumoto, Katsunori Matsuki
A new technique for combustion diagnostics of a spark ignition engine was developed. In this method the ion sensor with the circular configuration was installed into the cylinder head gasket. This sensor is expected to be applied for production engine. The signal measured by the ion sensor was similar with that of cylinder pressure. The peak timing of ion current was consistent with the peak timing of pressure. There was a strong correlation between IMEP and the peak timing of ion current. This sensor is available to detect combustion quality in a spark ignition engine.
2003-05-19
Technical Paper
2003-01-1799
Nobuyuki Kawahara, Eiji Tomita, Mitsuru Ichimiya, Kouji Takasu, Naoki Tsuchida, Kazuhiro Goto
A heterodyne interferometry system with a fiber-optic sensor was developed to measure the temperature history of unburned gas in an engine cylinder. A polarization-preserving fiber and metal mirror were used as the fiber-optic sensor to deliver the test beam to and from the measurement region. This fiber-optic sensor can be assembled in the engine cylinder or the cylinder head without a lot of improvements of an actual engine. The feasibility of our system was sufficient to be applied to temperature history measurement of an unburned gas compressed by flame propagation in an engine cylinder. The resolution of the temperature measurement is approximately 0.7 K, and is dependent on both the sampling clock speed of the A/D converter and the length of the measurement region.
2003-05-19
Technical Paper
2003-01-1828
Nobuyuki Kawahara, Eiji Tomita, Hisashi Kagajyo
Homogeneous Charge Compression Ignition (HCCI) combustion with dimethyl ether has been carried out in a single cylinder engine with a transparent piston. The engine was operated at 800 rpm with a wide-open throttle. The intake-premixed mixture was preheated with an electric heater to promote auto-ignition. HCCI combustion with dimethyl ether indicates multi-stage heat releases. Investigations were conducted with visualization of combustion in the cylinder and detailed and temporal spectroscopic measurements using spectrometer. In order to understand reaction mechanism of auto-ignition and combustion mechanism in HCCI engine, spectrum analysis of chemiluminescence was carried out.
2003-03-03
Technical Paper
2003-01-1109
Atsushi Nishiyama, Nobuyuki Kawahara, Eiji Tomita
This study measured the fuel concentration near a spark plug using a laser infrared absorption method. An IR spark plug sensor with a double-pass measurement length was developed. A He-Ne laser with a wavelength of 3.392 μm, which coincides with the absorption line of hydrocarbons, was used as the light source. In order to confirm the measurement accuracy, the concentrations of a methane-air mixture were measured in a compression-expansion engine. Then, the IR spark plug sensor was used for measurements in a 4-stroke spark-ignition engine fuelled with isooctane. The air/fuel ratio measured using this system clearly agreed with the mean air/fuel ratio.
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