Seiichi Shiga

Gunma University, Maebashi, Gunma, Japan

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Publications (86)36.01 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Electric-drive and lightweight vehicles can reduce CO2 emissions in road passenger transportation. However, maximum reductions are limited by the extent of their diffusion. A vehicle fleet stock turnover model was developed to study the impact of powertrain electrification, vehicle size reduction and lightweight materials substitution on light-duty vehicle fleet energy consumption, CO2 emissions and cost; and used in the case of Japan. Vehicle types included internal combustion engine vehicles, hybrid electric vehicles, battery electric vehicles, and fuel cell hybrid electric vehicles; using two glider types, conventional and lightweight; available in three vehicle size classes, normal, compact and mini-sized vehicles. Diffusion of mini-sized lightweight battery electric vehicles has the largest potential for tank-to-wheel energy consumption and CO2 emissions reductions, 70.6 and 92.2%, compared to the 2050 baseline values; with a net cash flow larger than zero until 2045. In contrast, diffusion of mini-sized lightweight fuel cell hybrid electric vehicles has the lowest net cash flow by 2050, with negative values from 2033 and potential tank-to-wheel energy consumption and CO2 emissions reductions of 55.4 and 82.9% compared to the 2050 baseline values. Lightweighting reduces significantly the capital cost of battery electric vehicles and fuel cell hybrid electric vehicles, favoring their deployment.
    No preview · Article · Dec 2015 · Energy
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    ABSTRACT: The behavior of the noises sources in the exhaust jet issuing from a rectangular hypersonic nozzle operating at takeoff condition were investigated experimentally The working gas was cold air, and the NPR was set at 2.70. By use of schlieren optics, the density gradient fluctuation in the jet and its acoustic field were detected as the variation of the light intensity. In the data obtained with the schlieren optics, intensive fluctuation of the light intensity is observed in the entire region of the jet. By use of cross-correlation analysis between the light intensity fluctuation and the far-field noise, a relatively large cross correlation is obtained. From the local maximum cross correlation, it is considered that, both at the ramp and cowl sides, the major source for the far-field noise at downstream angles exists in the upper shear layer of the initial free jet region because of the rapid mixing due to the steep velocity gradient. Regarding the cowl side, a relatively large cross correlation for the sideline microphones is also observed in the semi-confined jet region on the ramp.
    No preview · Article · Mar 2015 · AIAA Journal
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    ABSTRACT: This paper presents the performance and combustion characteristics of a spark-ignition gas engine power generation system fueled with a real biogas produced through a low-temperature biomass gasification process. The biomass resource was wood chips, which produce real biogas containing hydrogen, methane and carbon monoxide as fuels together with carbon dioxide and nitrogen as diluents. Real biogas operation gives much lower cyclic variability than that with natural gas. The maximum brake thermal efficiency was more than 30 %, even at the Brake Mean Effective Pressure less than 0.4 MPa. Thus, it is shown that the biogas is a suitable fuel for lean burn with dilution, which verifies the results obtained previously even quantitatively.
    Preview · Article · Jan 2015 · Journal of the Japan Institute of Energy

  • No preview · Article · Jan 2015 · Nihon Kōkū Uchū Gakkai ronbunshū = Journal of the Japan Society for Aeronautical and Space Sciences
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    ABSTRACT: Effects of a slit injection (SI) on exhaust noise from a rectangular hypersonic nozzle were investigated experimentally. In the Japan Aerospace Exploration Agency (JAXA), the pre-cooled turbojet (PCTJ) engine specified for a hypersonic transport is under development. In this study, a 1/100-scaled model of the rectangular hypersonic nozzle for the PCTJ is manufactured. The main jet (MJ) is injected to the atmosphere through the nozzle. The total pressure of the MJ was set at the takeoff condition of the vehicle. From slit shaped converging nozzles mounted at the end of the ramp, air is injected to the MJ. The sound pressure level (SPL) around the nozzle was measured with microphones. Using the SI, especially in the ramp direction, the SPL was decreased by 1 to 2dB at wide frequencies up to 50kHz. At the same time, the Overall SPL (OASPL) decreased monotonously with the increase in the momentum ratio of the SI and the MJ. It is considered that the governing parameter of the SI is the momentum ratio. The growth rate of the shear layer was estimated from Pitot pressure distribution. It is implied that the shear layer growth rate is linked to the acoustic radiation.
    No preview · Article · Jan 2013 · Nihon Kōkū Uchū Gakkai ronbunshū = Journal of the Japan Society for Aeronautical and Space Sciences
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    ABSTRACT: Thrust measurement of a rectangular hypersonic nozzle employed in the precooled turbojet engine under development in the Japan Aerospace Exploration Agency is carried out using an inclined baffle plate. A 1.0%-scaled model of the nozzle was manufactured, and its gross thrust was investigated. The hypersonic nozzle has a variable throat and an external ramp to compensate the drastic change in the nozzle pressure ratio through the operation. At takeoff, an intensive jet noise is expected due to the high-speed exhaust jet, and in the present study, the impact of aerodynamic-tab jet noise suppressors on the thrust vector of the nozzle is investigated. Because of the simplicity, a baffle plate, which basically provides an on-axis force measurement, is applied to a simultaneous measurement of the magnitude and angle of the thrust vector by giving an angle to the impact surface relative to the jet. It is shown that the magnitude of the thrust vector is kept constant regardless of the aerodynamic-tab mass fraction, which implies that a lossless mixing between the main jet and aerodynamic tab can be assumed. It is also shown that the thrust angle changes with the increase in the aerodynamic-tab mass fraction because of the deformation of the jet cross section.
    No preview · Article · Nov 2012 · Journal of Propulsion and Power
  • Lei Chen · Seiichi Shiga · Mikiya Araki
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    ABSTRACT: This paper presents further results of the study on fundamental combustion characteristics of gaseous fuels simulated for a biogas produced through a biomass gasification process with a catalyzer. The main work focuses on combustion characteristics of H2–CO blended fuel and the effect of CO2 dilution on it in a spark-ignition engine under the condition of WOT, MBT and a constant speed of 1500 rpm. Equivalence ratio were limited to lower than 0.8 in order to avoid excessive high combustion temperature to damage the engine, and lean conditions were maintained during the experiment to get acceptable economy and emissions. The results show that the BMEP decreases with an increase in dilution rate. The COV of IMEP is lower than 10% under most conditions, while H2 and CO2 have the opposite influence on brake thermal efficiency. CO2 dilution combustion could induce to remarkable decreasing in NOx emission with little decrease in brake thermal efficiency, which benefits for biomass gaseous fuel application. If 500 ppm of NOx emission and 26% of brake thermal efficiency could be viewed as accepted level, the accepted operation range of H2–CO mixture have been obtained.
    No preview · Article · Oct 2012 · International Journal of Hydrogen Energy
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    ABSTRACT: Noise reduction performance and feasibility of aerodynamic-tab (AT) jet noise suppressors in an actual hypersonic nozzle operating under takeoff conditions are investigated experimentally. Two kinds of AT nozzle geometries are applied, and it is shown that wedge ATs are more effective in terms of jet noise reduction. The AT nozzle position is varied every 1.0 mm in the y direction, and for wedge ATs, the AT position is defined as the center of gravity of their nozzle exit. It is considered that, due to the confinement of flow, distortion of the shock train by a large-scale structure in the shear layer, which contributes to shock associated acoustic radiation, is suppressed. It is considered that, near the shear layer, the effect of AT injection saturates since the AT working gas is injected out of the main jet (MJ) boundary and no longer contributes to the distortion of the MJ.
    No preview · Article · Mar 2012 · AIAA Journal
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    ABSTRACT: This paper presents studies of spray characteristics and controlling mechanism of fuel containing CO2. Using diesel fuel containing CO2 gas, experiments were conducted on diesel hole-type nozzles and simple nozzles. The steady spray and transient spray characteristics were observed and measured by instantaneous shadowgraphy, high-speed photography, phase Doppler anemometry (PDA) and LDSA respectively. The effects of CO2 concentration in the fuel, the injection pressure, the nozzle L/D ratio, surrounding gas pressure and temperature on the atomization behavior and spray pattern were evaluated. The results show that the injection of fuel containing CO2 can greatly improve the atomization and produce a parabolic-shaped spray; and the CO2 gas concentration, surrounding gas pressure, temperature and nozzle configuration have dominant influences on spray characteristics of the fuel containing CO2. New insight into the controlling mechanism of atomization of the fuel containing CO2 was provided.
    No preview · Article · Mar 2012 · Frontiers in Energy
  • H T C Machacon · S Shiga · K Fukino
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    ABSTRACT: In a previous paper, the authors built a neural network model to recognize Japanese sign language syllabary or yubimoji. One of the problems encountered in that study was the accurate digital representation and distinction of similar yubimoji gestures, i.e. gestures with the same finger flexure positions but with different hand/finger orientations. This study focuses on these yubimoji gestures. Using data from a glove interface with bend sensors and accelerometers, a neural network was built, trained and tested. The network performed well and good results were obtained.
    No preview · Article · Feb 2012 · Journal of Medical Engineering & Technology
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    ABSTRACT: This paper presents operation and the characteristics of electric power generation of a spark-ignition engine fuelled with biogas produced through a low-temperature biomass gasification process. The biomass resource was mixture of pig manure and wood chips. Two kinds of load was connected to the generator, one was electric resistance and the other is Ni-MH battery manufactured by Kawasaki Heavy Industry Co. The engine was successfully operated at the maximum BMEP (Brake Mean Effective Pressure) of 0.38 MPa which was 65% of the original gasoline. The generation efficiency was more than 26%, which was even higher than that of gasoline. The power could also be charged to the battery, but the BMEP and generation efficiency were 0.19 MPa and 15%, respectively, which were pretty lower than those of resistance.
    No preview · Article · Jan 2012 · Journal of the Japan Institute of Energy
  • L. Chen · R. Shiina · N. Araki · H. Nakamura · S. Shiga · T. Obokata
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    ABSTRACT: This paper presents further results of the study on basic combustion characteristics of gaseous fuels simulated for a bio-gas produced through a biomass gasification process with a catalyzer. CO2 dilution effect was examined for the individual fuel component of CH4, CO and H 2 in a single-cylinder spark-ignition engine under the condition of WOT, MBT and a constant speed of 1500 rpm. For these three kinds of fuels, until a certain level of CO2 dilution, the thermal efficiency does not vary, since the combustion duration increase is very small, which might have given negligible change in the indicated thermal efficiency or the degree of constant volume combustion. Thus, there is an operating condition under which acceptable level of deterioration of thermal efficiency was obtained with satisfactorily low level of NOx emission.
    No preview · Article · Oct 2010
  • M. Araki · A. Ebata · T. Inoue · S. Shiga
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    ABSTRACT: Feasibility of a newly developed size determination method for sub-micron particles using multiwavelength polarized lights is investigated, experimentally. According to the Mie's theory the polarization ratios of scattered lights are calculated numerically, which is a function of the particle diameter, the refraction index, and the wavelength of the incident light. Polystyrene particles are used as the test particles, which are suspended in purified water. The arithmetic mean diameters of them are varied from 0.356 to 0.77 μm, which is measured with a centrifugal sedimentation method. In order to extend the measurement range of convestional polarization ratio methods, three kinds of He-Ne lasers, whose wavelengths are 543.5, 594.1, and 632.8 nm, are used. The laser beams passes through the particles, and the scattered images are acquired with a digital CCD camera set in parallel and perpendicular directions to the polarization plane of the incident light. The polarization ratios of the scattered lights are estimated from these scattered light images, and the acquired data are compared with the analytical values. It is shown that, by use of the multi-wavelength polarization ratio method, the measurement range of the particle size can be extended up to the order of 1 urn, and that the accuracy of the results lies from 0.1% to 7.6%, when compared with the results of a centrifugal sedimentation method.
    No preview · Article · Oct 2010
  • H T C Machacon · S Shiga
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    ABSTRACT: Effective communication with the hearing and speech impaired often requires at least a basic working knowledge of sign language gestures, without which a memo pad and pen, or a mobile phone's notepad is indispensable. The aim of this study was to build a neural network that could be used to recognize static finger-hand gestures of the yubimoji, the Japanese sign language syllabary. To build the network, signal inputs from a data glove interface were taken for each of the static yubimoji gestures. The network was trained and tested 10 times using a multilayer perceptron model. Overall, only 18 of the 41 static gestures were successfully recognized. One of the reasons was attributed to the inability of the data glove to measure gesture directions particularly for yubimoji gestures with similar finger configurations. Future work will focus on these problems as well as the inclusion of dynamic yubimoji gestures.
    No preview · Article · Feb 2010 · Journal of Medical Engineering & Technology
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    ABSTRACT: Effects of nozzle scale, total temperature, and an afterburner on jet noise characteristics from a pre-cooled turbojet engine are investigated experimentally. In JAXA (Japan Aerospace Exploration Agency), a pre-cooled turbojet engine for an HST (Hypersonic transport) is under development. In the present study, 1.0%- and 2.4%-scaled models of the rectangular plug nozzle (Nozzles I and II) are manufactured, and the jet noise characteristics are investigated under a wide range of total temperatures. For Nozzle I, no air-heater is utilized and the total temperature is 290K. For Nozzle II, a pebble heater and an afterburner (AB) are utilized upstream of the nozzle model, and the total temperature is varied from 520K (pebble heater) to 1540K (pebble heater + AB). The total pressure is set at 0.27 and 0.30MPa(a) for both nozzle models. Jet noise is measured using a high-frequency microphone set at 135 deg from the engine inlet, and normalized jet noise spectra are obtained based on AUjn law and Helmholtz number. For cases without afterburner, the normalized spectra agrees well regardless of the nozzle scale and total temperature where the velocity index lies from n = 7.7 to 9.2, and the correlation factor between the two facilities is shown to be about 1dB. For the case with afterburner, the normalized spectrum does not agree with other conditions where the velocity index n seems to be about 4.
    No preview · Article · Jan 2009
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    ABSTRACT: In a boat two-stroke two-cylinder engine, SC-port fuel injection of CNG was applied at running condition in comparison with the fuelling with a gas-mixer. Three methods of tests were employed; operation at a test-bench, at an anchored condition and on a running boat. In a lower engine speed, the beneficial effect of higher thermal efficiency was obtained, while in higher engine speed range especially at the running condition, it has the inverse effect of lower thermal efficiency. It is based on the limited range of lower injection rate of the fuel injectors, and thus the fuel injection rate of this type of fuel injectors has a key role of developing the technology of the SC-port injection.
    No preview · Article · Jan 2009
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    ABSTRACT: This paper presents basic combustion characteristics of a spark-ignition engine fuelled with three kinds of gaseous fuels ; H2, CO and CH 4. A single-cylinder engine was operated under WOT at 1 500 min -1 condition, CO gas gives lower thermal efficiency than H 2 and CH4, since the energy of the fuel can not be transferred to the pressure or the work, although it gives higher combustion temperature which makes the higher exhaust gas temperature and much higher NOx emissions than those for CH4. H2 gives upper limit of flammability due to the occurrence of backfire and almost comparable thermal efficiency with that for CH4 at its stoichiometric condition.
    No preview · Article · Dec 2008 · Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B
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    ABSTRACT: Effects of fuel atomization on cold starting of a 4 stroke cycle spark ignition engine were investigated experimentally. Two kinds of ultrasonic fuel injectors using a micro nozzle array (MNA injectors) were applied, whose nozzle diameter d=4 and 6 μm, respectively. A conventional port fuel injector (PFI injector) was also used for comparison. The Sauter mean diameters (SMDs) of the sprays were 15 μm (MNA, d = 4 μm), 23μm (MNA, d = 6 μm), and 59 μm (PFI), respectively, An air cooled, single cylinder, 4 stroke cycle, spark ignition engine was used. The first ignition cycles and the cumulative fuel amount were investigated at a wide range of the air fuel ratio. For the MNA injector (d = 4μm), the first ignition cycle became much earlier when compared with the PFI injector. The cumulative fuel amount during cold starting reduced by about 30%. It is shown that, by use of the MNA injector, the unburned hydrocarbon emissions during cold starting could be reduced.
    No preview · Article · Aug 2008 · Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B
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    ABSTRACT: Performance of a 2 stroke cycle engine fuelled with CNG (Compressed natural gas) using intermittent fuel injection from a scavenging port is investigated experimentally. The test engine is a 2 cylinder, 398 cm3, 2 stroke cycle spark ignition engine. Gaseous fuel injectors are attached at the cylinder block, and a CNG is injected into the scavenging passage through a fuel injection pipe. The fuel injection pressure is set at 0.255 MPa, and the fuel is injected intermittently during the scavenging process. The length and tip geometry of the fuel injection pipe are varied, and the effect on the engine performance is investigated. Using the scavenging port fuel injection, the BSFC is reduced by 25%, and the lean burn limit extends from λ = 1.2 to 1.46, at the maximum. The peak of the NOI emission shifts to leaner side, and the THC emission is reduced by 47% at the maximum. It is considered that the intermittent fuel injection from a scavenging port is effective to achieve stratified combustion and reduction in fuel short circuiting through the cylinder.
    No preview · Article · Jun 2008 · Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B
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    ABSTRACT: Injection rate of a gaseous fuel injector was calculated by measuring the needle valve lift history. In our lab, a gaseous fuel injection rate meter using 1-dimensional pipe flow was developed. In the present study, the measurement accuracy of the injection rate meter was examined by comparing the theoretical injection rate estimated from the needle valve lift history. The needle valve lift was measured using an optical method. A small beam cut plate is attached to the needle valve of the gaseous fuel injector. A laser beam passes through the beam cut plate, and the variation of the beam intensity was measured with a photo sensor. From the beam intensity, the needle valve lift history was estimated. One-dimensional, compressible, inviscid, adiabatic flow was assumed, and the instantaneous mass flow rate through the needle valve sheet, the injector sack, and the injection hole was estimated. The estimated injection rate was compared with that obtained with the gaseous fuel injection rate meter. The estimated and measured injection rates agree relatively well even at transient duration. It is shown that the injection rate meter has high reliability and accuracy.
    No preview · Article · Mar 2008 · Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B