Kazuhiko Madokoro

Daihatsu Motor Co., Ltd., Ōsaka, Ōsaka, Japan

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Publications (17)16.94 Total impact

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    ABSTRACT: Influences of space velocity and engine output power on the plasma particulate matter (PM) removal with a dielectric barrier discharge (DBD) reactor have been investigated. The PM removal ratio without plasma discharges is approximately in inverse proportion to space velocity. The PM removal ratio with plasma discharges has been found to be less susceptible to space velocity than that without plasma discharges. As a cause of this result, it is suspected that active oxygen species produced by the plasma discharges transfer with the floating PM within the DBD reactor and then react with the floating PM. The PM removal ratio decreases with the increase in the engine output power and the more pronounced declination has been found to be observed with the higher discharge electric power. This result is not explained only by the increase in space velocity arising from increasing engine output power. The factors, PM size, PM concentration and reaction temperature, increasing with engine output power are considered to reduce the effects of plasma discharges on the PM removal.
    No preview · Article · Dec 2009
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    ABSTRACT: The scale-up of an uneven type of dielectric barrier discharge (DBD) reactor driven by a positive-negative pulse power supply for the removal of particulate matter (PM) from a diesel engine has been carried out. The scale of the uneven DBD reactor was changed by using three kinds of reactors consisting of 20, 30, or 50 pairs of uneven alumina and stainless steel plates. In this study, relations of energy injection into the above DBD reactors, PM removals, PM removal efficiencies with pair numbers have been investigated. The parameters in the kinetic model used to describe the PM removal are given.
    No preview · Article · Jan 2009 · International Journal of Chemical Reactor Engineering
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    ABSTRACT: An uneven dielectric barrier discharge (DBD) reactor of 21 electrode pairs that can improve the energy efficiency for the removal of particulate matter (PM) from a diesel engine is characterized. Ninety percent of PM (about 0.48 g/h) is removed by plasma discharges at an energy injection of 90 W into an exhaust gas (40 Nm3/h with PM emission rate 0.53 g/h). The discharge properties and relations of PM removal and energy efficiency with energy injection are given. The fuel penalty due to the use of the uneven DBD reactor is estimated. Comparison with other types of DBD reactors is carried out. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
    No preview · Article · Jan 2009 · Asia-Pacific Journal of Chemical Engineering
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    ABSTRACT: The influence of polarity and rise time of the pulse voltage on the removal of particulate matter (PM) emitted from a diesel engine was investigated using a dielectric barrier discharge reactor. Four kinds of pulse voltage waveforms (positive, negative, positive–negative and negative–positive) were used. It was found that the energy efficiency for PM removal is just a function of energy injection and that there are no obvious influences on PM removal and energy efficiency within the voltage waveforms except the negative pulse voltage of a peak voltage below 8kV. A comparison of PM removals using various kinds of pulse voltage waveforms and different types of plasma reactors is given.
    No preview · Article · Jul 2008 · Plasma Chemistry and Plasma Processing
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    ABSTRACT: The removal properties of diesel exhaust particles (DEP) were investigated using an engine exhaust particle size spectrometer (EEPS), field emission-type scanning electron microscopy (FE-SEM) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). DEP were treated using a dielectric barrier discharge (DBD) reactor installed in the tail pipe of a diesel engine, and a model DBD reactor fed with DEP in the mixture of N(2) and O(2). When changing the experimental parameters of both the plasma conditions and the engine load conditions, we obtained characteristic information of DEP treated with plasma discharges from the particle diameter and the composition. In evaluating the model DBD reactor, it became clear that there were two types of plasma processes (reactions with active oxygen species to yield CO(2) and reactions with active nitrogen species to yield nitrogen containing compounds). Moreover, from the result of a TOF-SIMS analysis, the characteristic secondary ions, such as C(2)H(6)N(+), C(4)H(12)N(+), and C(10)H(20)N(2)(+), were strongly detected from the DEP surfaces during the plasma discharges. This indicates that the nitrogen contained hydrocarbons were generated by plasma reactions.
    No preview · Article · Mar 2008 · Analytical Sciences
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    ABSTRACT: Recently, a great deal of attention has been paid to the innovative plasma technology for the removal of diesel particulate matter (PM). The authors have developed a plasma PM removal system. In order to estimate the contribution of active oxygen species to PM oxidation,
    No preview · Article · Jan 2008 · International Journal of Automotive Technology
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    ABSTRACT: In order to successively remove particulate matter (PM) from exhaust emissions of diesel engines, a non-thermal plasma (NTP) system is under development for practical use. In the NTP system, a dielectric barrier discharge (DBD) reactor driven by high-voltage pulses has been mainly investigated. A newly designed electrode has been developed in order to remove PM efficiently in a transient mode that the volume of exhaust gases and amounts of PM change frequently. This electrode shows wide discharge space and has a function of temporary trap, different from partial or full trap such as a dicscl particulate filter (DPF). PM removal properties of the plasma reactor with developed electrodes were evaluated in the Japanese JC08 test mode using a virtual vehicle simulator system with 2-cycle diesel engine (1.2 L). It was confirmed that PM emission was reduced to 0.038 g/km below the Japanese post new long-term emission regulation (JP 2009) or Euro5 level by the plasma reactor using discharge power of only 210 W. The plasma reactor showed high removal capability for soot which is not easily oxidized with catalytic reaction. PM removal by using the plasma reactor was achieved effectively even under the low temperature of below 170°C. Also, the plasma reactor showed lower pressure drop below 3.2 kPa during JC08 mode by comparison with conventional DPF systems. This NTP system without precious metals such as platinum group metals (PGM) is expected to be the promising technology for dicscl emission control, and to be one of the solutions for not only emission control but also PGM resources problems.
    No preview · Article · Jan 2008
  • Shuiliang Yao · Kazuhiko Madokoro · Chihiro Fushimi · Yuichi Fujioka
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    ABSTRACT: The removal of diesel particulate matter (PM) is experimentally carried out using two types of uneven dielectric barrier discharge (DBD) reactors driven by positive–negative pulse voltage power supplies. One uneven DBD reactor is fed with exhaust gases from a diesel engine at the exhaust gas temperature and another uneven DBD reactor is fed with PM dispersed in a gas mixture of oxygen and nitrogen at room temperature, where PM was collected from the exhaust gases of the diesel engine. PM emission rates, PM sizes, and PM oxidation products are measured using a PM emission rate monitor, a particle size spectrometer, and a gas chromatograph at various discharge energy densities. It has been found that most of PM is oxidized completely into gaseous products of CO and CO2 under plasma discharge conditions. © 2007 American Institute of Chemical Engineers AIChE J, 2007
    No preview · Article · Jul 2007 · AIChE Journal
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    ABSTRACT: An uneven type of dielectric barrier discharge (DBD) reactors driven by a positive?negative pulse power supply is studied for diesel particulate matter (PM) removal by pulsed corona discharges. More than 90% of PM from a diesel engine operated at 1220 rpm rotation speed and 3 kw power output could be removed at an energy injection higher than 140 w if the uneven DBD reactor of 50 layers of alumina plates was used. PM removal efficiency per layer could be presented simply using a function of energy injection per layer, thus this will be useful for the scale-up of the DBD reactor. The adsorbed PM could inhibit the pulsed corona discharges. This is an abstract of a paper presented at the 2007 AIChE Annual Meeting (Salt Lake City, UT 11/4-9/2007).
    No preview · Article · Jan 2007
  • S. Yao · C. Fushimi · K. Madokoro · Y. Fujioka
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    ABSTRACT: Recently, the authors have developed a non-thermal plasma system for the removal of harmful particulate matter from diesel engines. In this paper, the characterization of such a non-thermal plasma system (typically including a dielectric barrier discharge (DBD) reactor and a pulse power supply) is carried out electrically and optically using a discharge waveform measurement system of a voltage probe, two current transformers, and an oscilloscope, a high dynamic range streak camera combined with a spectroscope, and a high speed camera. The pulse voltage is applied to the DBD reactor at a fixed value and a frequency of 100 Hz. The rise time, positive width, and peak value of the pulse voltage are, respectively, 3.5 μs, 6 μs, and 13.2 kV. The discharge time duration is 14 μs. The optical emission from the discharge gap lasts for 14 μs. The emission lines are found within 300 - 410 nm and 620- 770 nm. The discharges are generally of an individual micro-discharge property as reported elsewhere.
    No preview · Article · Oct 2006
  • Source
    S. Yao · C. Fushimi · K. Madokoro · K. Yamada
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    ABSTRACT: Uneven dielectric barrier discharge (DBD) reactors driven by positive–negative pulse plasma discharges were investigated for particulate matter (PM) removal from a diesel engine. Two kinds of uneven alumina plates and three kinds of uneven stainless steel plates were used to assemble six kinds of uneven DBD reactors of discharge gaps 0.4–1.0mm. The experimental results show that PM from diesel engines can be removed using the uneven DBD reactors. The maximum PM removal was 67% at 300W energy injections using the DBD reactor of 0.4mm gap distance. PM removal increased with decreasing gap distance. The energy efficiency using the uneven DBD reactor of a shorter gap distance was higher than that using the uneven DBD reactor of a longer gap distance as the uneven DBD reactor of a shorter gap distance has a higher PM deposition rate. The energy efficiency was typically in a range of 3–10.6g/kWh at an energy density of 2–16J/L. A comparison of this study with reports given by other research groups is given.
    Full-text · Article · Sep 2006 · Plasma Chemistry and Plasma Processing
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    ABSTRACT: Worldwide emission regulations on diesel particulate matter (PM) into the atmosphere have become more stringent. In Japan, a new vehicular emission regulation, so called "post new long term regulation", will be introduced since 2009. In this regulation, PM emission rate should be < 0.005 g/km. An uneven type of dielectric barrier discharge reactor, which consists of uneven alumina plates and uneven stainless steel plates, was developed to comply with the regulation. The rise in the number of the pairs substantially increases the ratios of PM removal and its energy efficiency by the increase of discharge area and residence time. The maximum PM removal ratio reached 94% at 250 w. The pressure drop increases with time, indicating that the adsorbed PM is accumulated on the surface of alumina or stainless steel plates. The energy efficiency of PM removal is inversely proportional to the ∼ 1.6 power of the space velocity and that the pressure drop is proportional to the 1.2 power of space velocity. This is an abstract of a paper presented at the 2006 AIChE Annual Meeting (San Francisco, CA 11/12-17/2006).
    Full-text · Article · Jan 2006
  • S. Yao · K. Madokoro · C. Fushimi · K. Yamada
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    ABSTRACT: A new DBD reactor made of uneven alumina and stainless steel plates has been developed for particulate matter (PM) removal from a diesel engine using pulsed plasma discharges. PM removal using 24 pairs of uneven alumina and stainless steel plates is the same as that using 32 pairs of flat alumina plates and mesh metal electrodes that we previously reported. A disturbed discharge uniformly has been obtained in spaces between the uneven alumina plates and stainless steel plates; however, it is difficult to get a uniform discharge using flat alumina plates and mesh metal electrodes. The discharge energy efficiency is 3.6 g/kWh at maximum, which is under improvement for an actual application. © 2005 American Institute of Physics
    No preview · Article · Oct 2005

  • No preview · Chapter · Jan 2005
  • S. Yao · M. Okumoto · K. Madokoro · T. Yashima · E. Suzuki
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    ABSTRACT: A dielectric barrier discharge (DBD) reactor, driven by a pulsed corona surface discharge (PCSD), was developed for the removal of particulate matter (PM) in an undiluted exhaust gas of a diesel engine. The DBD reactor consisted mainly of alumina (Al2O3) plates and metal meshes covered on the surfaces of Al2O3 plates. The PCSD was carried out with a pulse power supply at atmospheric pressure and the temperature of exhaust gases. The energy efficiency for PM removal was 26.5 μg/J at maximum and 1 μg/J with 42% PM removal. The construction of the DBD reactor that promoted PM deposition on Al2O3 surfaces improved energy efficiency. The constants in PM removal model were given. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1901–1907, 2004
    No preview · Article · Aug 2004 · AIChE Journal
  • S. Yao · M. Okumoto · T. Yashima · J. Shimogami · K. Madokoro · E. Suzuki
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    ABSTRACT: A pulsed corona surface discharge (PCSD) system was established for particulate matter (PM) and NOx removals from a diesel engine. The PCSD was carried out with a dielectric barrier discharge (DBD) reactor and a pulse power supply at atmospheric pressure and room temperature. The DBD reactor consisted mainly of an alumina (Al2O3) tube and a stainless steel rod (cathode) inserted in the alumina tube, and an aluminum coil (anode) wound on the outside surface of the Al2O3 tube. Pulse voltage was applied to the outside Al coil and stainless steel rod. PM was removed at a rate of 89% at maximum with 40% NOx removal. Relations of pulse voltage and frequency to PM and NOx removals were investigated. PM was oxidized by NO2 and other kinds of active oxygen species, such as O and O3 from plasma discharges. A surface adsorption/desorption and PM oxidation model of PM removal was established. The kinetic equations and their constants were given. © 2004 American Institute of Chemical Engineers AIChE J, 50:715–721, 2004
    No preview · Article · Mar 2004 · AIChE Journal
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    ABSTRACT: For reducing amount of CO2 emitted by acetylene production, a research on energy efficient plasma technologies for converting methane to acetylene was conducted, resulting in development of a tubular circle-to-plate (CTP) type of reactor. The CTP reactor driven by a pulsed plasma converted mixture of methane and CO2 to acetylene, ethylene, ethane, carbon monoxide, higher hydrocarbons such as C-3 and C-4, and hydrogen. CO2 was used mainly for stabilizing the plasma discharge, though it also reacted with methane yielding CO and hydrogen. A maximum energy efficiency of 4 mmol/kJ, which was obtained at a pulse frequency of 625 Hz, indicated a potential to reduce CO2 emission from the acetylene production. The energy efficiency decreased at a pulse frequency above 625 Hz with the CTP reactor, which differed from results with co-axial cylindrical (CAC) and point-to-point (PTP) type reactors. Acetylene selectivity was 62% at maximum at 8 kHz. The plasma technology would also be useful for relocating conventional fossil fuel dependent acetylene production to the sun-belt where solar thermal power, which is relatively inexpensive among renewable energies, can be utilized to generate plasma. Such relocation accompanied by replacement of fossil energy with renewable energy would result in reduction of global CO2 emission.
    No preview · Article · Apr 2003 · Journal of chemical engineering of Japan