Seiichi Shiga

Gunma University, Maebashi, Gunma Prefecture, Japan

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Publications (29)16.01 Total impact

  • 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.
    International Journal of Hydrogen Energy 10/2012; 37(19):14632–14639. · 3.55 Impact Factor
  • AIAA Journal 03/2012; 50(3):751-755. · 1.08 Impact Factor
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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.
    Journal of The Japan Society for Aeronautical and Space Sciences. 01/2009; 57(663):148-154.
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    ABSTRACT: Effects of the nozzle geometry and intermittent injection of aerodynamic tabs on exhaust noise from a rectangular plug nozzle were investigated experimentally. In JAXA (Japan Aerospace Exploration Agency), a pre-cooled turbojet engine for an HST (Hypersonic transport) is planned. A 1/100-scaled model of the rectangular plug nozzle is manufactured, and the noise reduction performance of aerodynamic tabs, which is small air jet injection from the nozzle wall, was investigated. Compressed air is injected through the rectangular plug nozzle into the atmosphere at the nozzle pressure ratio of 2.7, which corresponds to the take-off condition of the vehicle. Aerodynamic tabs were installed at the sidewall ends, and 4 kinds of round nozzles and 2 kinds of wedge nozzles were applied. Using a high-frequency solenoid valve, intermittent gas injection is also applied. It is shown that, by use of wedge nozzles, the aerodynamic tab mass flow rate, necessary to gain 2.3dB reduction in OASPL (Overall sound pressure level), decreases by 29% when compared with round nozzles. It is also shown that, by use of intermittent injection, the aerodynamic tab mass flow rate, necessary to gain 2.3dB reduction in OASPL, decreases by about 40% when compared with steady injection. By combination of wedge nozzles and intermittent injection, the aerodynamic tab mass flow rate significantly decreases by 57% when compared with the conventional strategy.
    Journal of The Japan Society for Aeronautical and Space Sciences. 01/2008; 56(659):590-595.
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    ABSTRACT: Effects of aerodynamic tabs on exhaust noise from a rectangular plug nozzle were investigated experimentally. In JAXA (Japan Aerospace Explanation Agency), a pre-cooled turbojet engine for the 1st stage propulsion of a TSTO (Two stage to orbit) is planned. In the present study, a 1/100-scaled model of the rectangular plug nozzle for the pre-cooled turbojet engine is manufactured and the exhaust noise characteristics were investigated. Compressed air is injected through the rectangular plug nozzle into the atmosphere. The nozzle pressure ratio was set at 2.7, which corresponds to the take-off condition of the vehicle. Aerodynamic tabs were installed at the ramp end (Upper AT), the cowl end (Lower AT) and the sidewall end (Side AT). The SPL (Sound pressure level) was measured with a high-frequency microphone. Without AT, the sound spectrum has a broadband peak at which the SPL is around 105dB. For Lower and Side ATs, the OASPL (Overall SPL) of the exhaust noise decreases, especially around ramp end. At the maximum, the OASPL was reduced by 2.4dB with about 2% loss of the main jet total pressure at the cowl exit. It is shown that the aerodynamic tabs are effective in noise reduction in a rectangular plug nozzle.
    Journal of The Japan Society for Aeronautical and Space Sciences. 01/2008; 56(651):149-156.
  • AIAA Journal 01/2006; 44(2):408-411. · 1.08 Impact Factor
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    ABSTRACT: This paper aims to investigate the steady spray characteristics of kerosene and diesel fuel containing dissolved methane. The spray pattern images were captured using a digital camera at the nozzle exit, and the spray droplet sizes were measured using a particle size analyzer (LDSA 1300A) based on the narrow-angle forward-scattering theory. Six types of the straight-hole nozzles with different length/diameter ratios (L/D) were employed in the study. The concentration of methane in liquid fuel was controlled by the dissolving pressure of methane, and the flashing phenomenon produced by the separating dissolved methane was utilized to improve the atomization of the spray. Meanwhile, the parameters, including the spray angle, the Sauter mean diameter, and the discharge coefficient were measured, and the droplet size distribution was fitted using the Rosin−Rammler distribution function. Furthermore, comparison of the spray characteristics between kerosene and diesel fuel with dissolved methane was made. The study reveals that, for a given L/D ratio nozzle, there is the corresponding critical value of methane concentration. When the methane concentration in liquid fuel is larger than the critical value, the liquid fuel atomization is found to improve, whereas below the critical value, the atomization would be suppressed. Moreover, spray angles of liquid fuel containing dissolved methane give smaller values compared to that of pure liquid fuel under lower concentration of methane, but it will increase dramatically when the concentration is over a certain value. Due to low viscosity, the flashing atomization of kerosene can be improved remarkably with the dissolved methane in fuel compared to that of diesel fuel containing dissolved methane in the case of high methane concentration.
    Energy & Fuels 05/2005; 19(5):2050-2055. · 2.85 Impact Factor
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    Z. Huang, S. Shiga, T. Ueda
    Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering 11/2003; 217(11):1031-1038. · 0.58 Impact Factor
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    ABSTRACT: A basic study on the ignition position of natural gas direct injection super-lean combustion was studied by using a rapid-compression machine. The
    Combustion Science and Technology 08/2003; 175(5):965-992. · 1.01 Impact Factor
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    ABSTRACT: A visualization study of natural gas direct injection combustion was carried out by using a high speed video camera. The results show that the distribution of the stratified mixture di ers with the injection mode, with parallel and single injection tending to form a higher degree of mixture stratification than opposed injection. Flame propagates toward the downstream direction in the cases of parallel and single-injection combustion, and flame propagates outward from the centre of the combustion chamber in the case of opposed injection combustion. A characteristic of turbulent combustion with a wrinkled flame front is presented in natural gas direct injection combustion. Super-lean combustion can be realized owing to the formation of an ignitable stratified mixture with the optimum setting of the fuel injection timing.
    Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering 08/2003; 217(8):667-676. · 0.58 Impact Factor
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    Z. Huang, S. Shiga, T. Ueda
    Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering 06/2003; 217(6):499-506. · 0.58 Impact Factor
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    Z. Huang, S. Shiga, T. Ueda
    Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering 05/2003; 217(5):393-401. · 0.58 Impact Factor
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    ABSTRACT: The concentrations of NO, NO2 and NOx for direct injection (DI) combustion were analysed on the basis of experimental data by using a rapid compression machine fuelled with compressed natural gas (CNG) and gasoline. The analysis showed that the maximum values of NO and NO2 for stratified combustion would shift to a smaller overall equivalence ratio than that of homogeneous mixture combustion, and this phenomenon was more obvious for gasoline stratified combustion. The NOx concentration drops to a very low level at the stoichiometric equivalence ratio but still remains relatively high at an equivalence ratio of 0.6 in the case of stratified combustion. The ratio of NO2/NOx increased with decreasing equivalence ratio. A high ratio of NO2/NOx was observed in the constant-volume combustion experimental study which differs from that of an engine. This was caused by the long residence time of NO at high temperature after combustion, leading to the conversion of more NO into NO2.
    Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering 01/2003; 217(10):935-941. · 0.58 Impact Factor
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    ABSTRACT: The characteristics of natural-gas direct-injection combustion under various fuel injection timings were studied by using a rapid compression machine. Results show that natural-gas direct injection can result in combustion that is much faster than homogeneous combustion while shortening the time interval between injection timing and ignition timing can markedly decrease the combustion duration. Unburned hydrocarbon would increase over a wide range of equivalence ratios, shortening the time interval between injection timing and ignition timing can decrease the value to that of homogeneous-mixture combustion. The NOx level is high but the CO level is low over a wide range of equivalence ratios and is little affected by fuel injection timing. High values of pressure rise due to combustion can be realized and it is insensitive to the variation in fuel injection timing. High combustion efficiency can be achieved, which is also independent of injection timing.
    Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering 01/2003; 217(5):393-401. · 0.58 Impact Factor
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    Z Huang, S. Shiga, T. Ueda
    Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering 01/2003; 217(10):935-942. · 0.58 Impact Factor
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    ABSTRACT: A study on the correlation of ignitability with fuel injection timing for direct injection combustion fuelled with natural gas and gasoline was carried out by using a rapid compression machine. The injection pressure of natural gas is 9 MPa and the injection pressure of gasoline is 7 MPa. The study results show that natural gas direct injection possesses higher momentum than that of gasoline, and this is beneficial to the combustion enhancement since a higher intensity of turbulence could be induced. Correlation of ignitability with injection timing shows better behaviour in natural gas direct injection, and this correlation is insensitive to injection modes in the case of natural gas. Thus, natural gas direct injection would have better engine applicability under cold-start conditions. The lean burn limits of natural gas and gasoline direct injection can extend to extremely low equivalence ratio when the ignitable stratified mixture exists around the spark electrode gap by optimizing the injection timing.
    Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering 01/2003; 217(6):499-506. · 0.58 Impact Factor
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    ABSTRACT: The effect of fuel injection timing relative to ignition timing on natural gas direct-injection combustion was studied by using a rapid compression machine (RCM). The ignition timing was fixed at 80 ms after the compression start. When the injection timing was relatively early (injection start at 60 ms), the heat release pattern showed a slower burn in the initial stage and a faster burn in the late stage, which is similar to that of flame propagation of a premixed gas. In contrast to this, when the injection timing was rela-tively late (injection start at 75 ms), the heat release rate showed a faster burn in the initial stage and a slower burn in the late stage, which is similar to that of diesel combustion. The shortest duration was realized at the injection end timing of 80 ms (the same timing as the ignition timing) over a wide range of equivalence ratio. The degree of charge stratification and the intensity of turbulence generated by the fuel jet are consid-ered to cause this behavior. Early injection leads to longer duration of the initial com-bustion, whereas late injection leads to a longer duration of the late combustion. Early injection showed relatively lower CO concentration in the combustion products while late injection gave relatively lower NO x . It was suggested that early injection leads to com-bustion with weaker stratification, and late injection leads to combustion with stronger stratification. Combustion efficiency was kept at a high value over a wide range of equiva-lence ratio.
    Journal of Engineering for Gas Turbines and Power-transactions of The Asme - J ENG GAS TURB POWER-T ASME. 01/2003; 125(3).
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    ABSTRACT: The basic characteristics of direct injection (DI) combustion fuelled with compressed natural gas (CNG) and gasoline was studied using a rapid compression machine. The characteristics of stratified combustion and emission of natural gas and gasoline direct injection at the optimum injection settings over a wide range of equivalence ratios were investigated. The results showed that, similar to premixed combustion, natural gas stratified combustion was of shorter duration than gasoline DI combustion. In contrast to this, the heat release pattern for gasoline DI combustion was similar to that of diesel combustion, which seems to have both a premixed phase and a diffusion phase. This phenomenon tends to be more obvious at a lower overall equivalence ratio, which suggests that fuel and charge stratification have a great influence on DI stratified charge combustion. Thus, this faster burn for natural gas promotes extremely lean combustion and a higher pressure rise. However, natural gas DI stratified combustion produces more hydrocarbons (HC) than gasoline DI stratified combustion at a low overall equivalence ratio. Combustion effciency is at the same level for the two fuels, and natural gas DI combustion was shown to have a slightly leaner combustion capability than gasoline DI combustion, which suggests the better feasibility of natural gas stratified combustion.
    Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering 01/2003; 217(11):1031-1038. · 0.58 Impact Factor
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    ABSTRACT: The objective of the present study is to determine the characteristics of combustion and emissions of compressed-natural-gas (CNG) direct-injection combustion using a rapid-compression-machine which has a compression ratio of 10 and a disc-shaped combustion chamber. Combustion and emission characteristics are compared for three types of fuel injection (single side, parallel side and opposed side injection) and a homogeneous mixture. The results show that with fuel injection, the fuel could be burned up to an equivalence ratio φ of 0.2 with sufficiently high combustion efficiency except for the case of φ = 1.0, while with a homogeneous mixture, the lean burn limit was only φ = 0.6 with poor combustion producing higher unburned CH4 By adjusting the location of the spark plug and fuel injectors, the combustion limit was extended to φ = 0.02. The Combustion efficiency of the injection modes is over 0.95 except for φ = 1.0 and φ < 0.06 which gave a lower combustion efficiency. Incomplete combustion in the stratified rich zone reduced the combustion efficiency at large values of φ, and possible occurrence of bulk quenching resulted in the lower combustion efficiency for very lean mixtures. Combustion efficiency for the homogeneous mixture decreases greatly with leaner mixtures, which is probably due to the thicker quenching layer near the wall. Combustion duration with fuel injection was insensitive to φ and was much shorter than for the homogeneous mixture. It was also shown that the number and location of the injectors and the injection rate had little influence on the combustion and the exhaust emissions including NOx. The pressure rise due to combustion in the case of fuel injection is higher compared to that of homogeneous mixture combustion due to the lower heat loss to the combustion chamber walls resulting from a short combustion duration. Thus it is shown that stratified-combustion with extremely lean burn capability can be realized with CNG direct injection.
    Combustion and Flame. 01/2002;
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    ABSTRACT: A basic characteristics of compressed natural gas direct-injection (CNG DI) combustion was studied by using a rapid compression machine. Results show that comparing with homogeneous mixture, CNG DI has short combustion duration, high pressure rise due to combustion, and high rate of heat release, which are considered to come from the charge stratification and the gas flow generated by the fuel injection. CNG DI can realize extremely lean combustion which reaches 0.03 equivalence ratio, φ. Combustion duration, maximum pressure rise due to combustion and combustion efficiency are found to be insensitive to the injection modes. Unburned methane showed almost the same level as that of homogeneous mixture combustion. CO increased steeply with the increase in φ when φ was greater than 0.8 due to the excessive stratification, and NOx peak value shifted to the region of lower φ. Combustion inefficiency maintains less than 0.08 in the range of φ from 0.1 to 0.9 and increases at very low φ due to bulk quenching and at higher φ due to excessive stratification. The combustion efficiency estimated from combustion products shows good agreement with that of heat release analysis.
    JSME International Journal Series B 01/2002; 45(4):891-900. · 0.15 Impact Factor