JSME International Journal Series B Fluids and Thermal Engineering
Online ISSN : 1347-5371
Print ISSN : 1340-8054
ISSN-L : 1340-8054
Volume 39 , Issue 1
Showing 1-28 articles out of 28 articles from the selected issue
  • Takashi TAMARU
    1996 Volume 39 Issue 1 Pages 1-9
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    A super/hypersonic aircraft is expected to be realized in the 21st century. Ramjet engines with subsonic flow combustion may be used for its propulsion up to the flight speed range of Mach 6, in combination with other accelerating propulsive systems. Much research has been conducted on combustion problems related to this engine, but new and additional technologies are still needed to cope with the problems encountered in the advanced ramjet engine. By reviewing past work on flameholding techniques, the author will introduce recent research results in an attempt to resolve the problems involved in realizing super/hypersonic vehicle engines.
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  • Hideo OSAKA, Chiharu FUKUSHIMA
    1996 Volume 39 Issue 1 Pages 10-18
    Published: February 15, 1996
    Released: February 18, 2008
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    A vortical structure within a turbulent boundary layer and spanwise variation of turbulent flowfield have been investigated for further understanding of the development of the turbulent boundary layer interacting with the spanwise periodic longitudinal vortex arrays which are artificially generated in a free stream. One of the parameters, spanwise periodicity of longitudinal vortices L/S (L denotes the spanwise distance between neighboring airfoils, S the airfoil span), rules both magnitude and streamwise path of secondary vortices caused within the turbulent boundary layer. As a result, whether the turbulent quantities show linear or nonlinear interaction significantly depends on the value of L/S. Therefore, in cases where L/S < 1, although the spanwise distortion of turbulent quantities in the outer region is not marked, those spanwise periods change in the streamwise direction due to the rapid vortex diffusion following corotating merging vortices. However, in cases where L/S &gsim; 1, turbulent quantities show a noticeable spanwise periodic variation corresponding to the arrangement of airfoil elements, and these spanwise periods are strictly maintained. Comparing the spanwise variations of the turbulent flowfield with those of the mean flowfield, mechanisms of spanwise variation of the turbulent boundary layer are discussed.
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  • Koichi SADA
    1996 Volume 39 Issue 1 Pages 19-27
    Published: February 15, 1996
    Released: February 18, 2008
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    The temperature of a flat wind tunnel floor was increased almost uniformly to 80°C to simulate an unstable atmospheric boundary layer. The velocity, temperature and surface temperature heat flux on the wind tunnel floor were measured using a laser Doppler anemometer, a resistance thermometer and a thin-film-type heat flowmeter. The tracer gas was released from continuous point sources located in the simulated unstable boundary layer, and its spatial concentration was measured by flame ionization detectors. The measured turbulent flow and tracer gas concentration characteristics such as turbulence intensities and plume spreads showed good agreement with those obtained from field experiments and water tank experiments when normalized by the convective velocity. The universal functions for velocity and temperature profiles were applied and the empirical constants were optimized. The length scales of turbulent motion were estimated by means of the universal functions. It appeared that the convective velocity and convective temperature could be applied as the similarity parameter for the flow and tracer gas diffusion when considering the corresponding equivalent atmospheric conditions.
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  • Takahiko TANAHASHI, Yoshiatsu OKI
    1996 Volume 39 Issue 1 Pages 28-35
    Published: February 15, 1996
    Released: February 18, 2008
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    In this paper, we present a new hybrid-streamline-upwind finite-element method, which is based on the finite analytic method developed in the field of the finite difference analysis. In order to obtain an optimal shape function, we introduce an adjoint differential operator to the differential operator for a steady advection-diffusion equation. The shape functions which satisfy these differential operators are mutually dual. One of them accurately interpolates the functions appearing in convection-dominated flows, and the other becomes a hybrid-streamline-upwind weight function. Furthermore, we define a discrete del operator for the reduction of memory storage in computers. As a result, we achieve simplicity of formulation and high-speed calculation in the finite-element method.
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  • Sei-ichi IIDA, Kakuji OGAWARA
    1996 Volume 39 Issue 1 Pages 36-43
    Published: February 15, 1996
    Released: February 18, 2008
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    The 5-equation model which represents weakly nonlinear two-dimensional thermal convection with various boundary conditions at the top and bottom walls has been constructed. Although the present system includes two control parameters of competing instabilities, the second parameter is fixed at unity, since the aim of this work is to obtain a model which is realistic compared with the Lorenz model but which maintains comparable simplicity. Examination of bifurcation structures of the present model obtained by increasing Rayleigh number as a parameter shows that there is a definite range of parameters in which the structures of orbits are strongly dependent on the boundary conditions such as slip/slip, slip/no-slip and no-slip/no-slip at respective top/bottom walls. In particular, a unique pattern for an inverse transitional region, which seems to be a "twin period-doubling bifurcation, " has been found for the first time in the case of no-slip/no-slip conditions.
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  • Susumu KYOMEN, Tateo USUI, Michio FUKAWA, Munekazu OHMI
    1996 Volume 39 Issue 1 Pages 44-50
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    It is well known that free convection is caused by the buoyancy forces of a laminar steady flow in a heated pipe. However, this experimental investigation shows that free convection occurs when the temperature differences between air in a room and water in an unheated pipe are large. Under such experimental conditions, the cross-sectional distributions of axial velocities are obtained for water with ReRa (Re: Reynolds number, Ra: Rayleigh number) as a parameter. Furthermore, a numerical analysis is also presented, and the calculated results are qualitatively compared with the above experimental data of axial velocities and those reported previously for air.
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  • Seiichi WASHIO, Satoshi TAKAHASHI, Satoshi YAMAGUCHI
    1996 Volume 39 Issue 1 Pages 51-56
    Published: February 15, 1996
    Released: February 18, 2008
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    Column separation and subsequent rejoining in an oil hydraulic line usually result in tensile waves and consequent ruptures in an oil column. In order to investigate these phenomena in more detail, it is essential to precisely measure transient flow rates in column separation and rejoining. The aim of the present work is to attain this objective : a method based on the theoretical relation of the flow rate change in a pipe with a kinetically induced pressure difference between the two separate sections. Instead of a conventional differential pressure transducer, two individual pressure gauges are used to measure pressures at the two sections and find the difference between them by subtraction. Theoretically predicted stepwise decreases of the flow rate until the column rejoining have been accurately measured, showing the effectiveness of the method. It is also pointed out that the successive calculus proposed by Zhao et al., which is expected to substantially economize the procedure to obtain flow rates from differential pressure data, may give unrealistic results.
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  • Yoshihiko SUGIYAMA, Tadakazu KATAYAMA, Eiji KANKI, Masakatu CHIBA, Kaz ...
    1996 Volume 39 Issue 1 Pages 57-65
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    This paper concerns a beam-type flutter of vertical pipes containing a flowing fluid and having the lower end immersed in fluid. The effect of surrounding fluid on motions of the pipe is assumed as a mass added to the immersed part of the pipe. The equivalent added mass is estimated using Morison's formula. The effects of the immersed length of the pipe on the critical flutter velocity are investigated. It is predicted theoretically that the lower end immersed in fluid may exert a considerable destabilizing effect, except in the case where the lower end is only slightly immersed in fluid and the mass ratio is as high as 0.75. Experiments with silicone-rubber tubes conveying water were conducted to check the theoretical predictions. It was confirmed that for sufficiently high flow velocities the tube was subject to violent flutter, and that the critical flutter velocity decreased with increasing immersed length of the lower end.
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  • Karel BALATKA, Sadanari MOCHIZUKI, Akira MURATA
    1996 Volume 39 Issue 1 Pages 66-71
    Published: February 15, 1996
    Released: February 18, 2008
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    An experimental study has been conducted on the flow behavior in an annular-conical passage. Experiments are carried out for three different cone apex angles (β=60°, 90°, 120°). For each apex angle two cases of different passage spacing are studied. The emphasis is placed on the transition from laminar to self-sustained oscillating flow regime in which the critical Reynolds number is investigated in relation to the apex angle and passage spacing. It is found that the critical Reynolds number depends on both the cone apex angle and passage spacing. For the self-sustained oscillating regime the Strouhal number is evaluated also with respect to both the passage spacing and cone apex angle and the dependence of the Strouhal number on the Reynolds number is determined.
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  • Jun ISHIMOTO, Masaaki OKUBO, Hideya NISHIYAMA, Shinichi KAMIYAMA
    1996 Volume 39 Issue 1 Pages 72-79
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The mechanism of pressure rise in a gas-liquid two-phase pipe flow of a magnetic fluid under a nonuniform magnetic field is investigated in detail both theoretically and experimentally. First, the governing equations of a one-dimensional gas-liquid two-phase flow of a magnetic fluid are presented and numerically solved. Next, the pressure distribution in a nonuniform magnetic field region is measured in the cases of two-phase flow, single-phase flow and the stationary state using a new experimental apparatus for the flow system. From the numerical and experimental results, the magnitude of the pressure components which contribute to the total driving force is accurately estimated. These results on the pressure distribution will contribute to the development of a new energy conversion system using a gas-liquid two-phase magnetic fluid flow.
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  • Junji OCHI, Kyozo AYUKAWA, Genta KAWAHARA
    1996 Volume 39 Issue 1 Pages 80-85
    Published: February 15, 1996
    Released: February 18, 2008
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    A two-phase critical flow with phase change through a converging nozzle is investigated and discussed in terms of the applications of three-layer model analysis which has already been reported for a case of two-component two-phase flow by Ochi and Ayukawa. In the theoretical analysis of a single-component two-phase flow during rapid phase change, there are some difficulties arising from the modeling of a complicated flow pattern at the interface. The calculated results using our proposed model are in good agreement with experimental data of the flow rate and the pressure of carbon dioxide or steam-water mixture flows. The flow properties in each layer through the channel are discussed in comparison with the completely separated flow or the homogeneous flow model. It is found that the three-layer model is a useful method for single-component two-phase flow undergoing rapid change of state in variable-area channels.
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  • Koji TAKAHASHI, Shojiro KAJI
    1996 Volume 39 Issue 1 Pages 86-94
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Aerodynamic acoustic problems near plate edges are treated by a new method based on the linear theory. For sound radiation and generation problems, we can calculate one of the half acoustic fields divided by semi-infinite plates by determining the distributions of the acoustic monopoles. Some numerical calculations confirm the validity of this distributed monopole method. Applying this method, we can impose the Kutta condition explicitly at the trailing edge and explain the feedback mechanism in terms of sound wave effects on the flow field. The generation of vorticity waves at the trailing edge due to the incident sound wave is calculated and the possibility of self-excited tones between the trailing edge and the leading edge is verified. The relationship obtained is the same as that of the edge tone phenomenon, and the necessary amplification of the vortex during its convection for the sound to become self-excited is quantified.
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  • Tomohide NIIMI, Tetsuo FUJIMOTO, Nobumasa TAOI
    1996 Volume 39 Issue 1 Pages 95-100
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    In this study, the flow fields of two, three or four interacting parallel supersonic free jets are studied by flow visualization using planar laser-induced fluorescence of iodine molecules seeded in carrier gas. Centers of orifices are set linearly and on vertices of a triangle or square. The flow fields are visualized on the plane including jet centerlines and in cross sections vertical to the centerlines, and are analyzed using various visual images for each geometrical arrangement of the orifices. Three-dimensional structures of the flow fields do not tend downstream to the structures expected from the arrangement of the orifices.
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  • Michael ZEUTZIUS, Alfred E. BEYLICH, Shigeru MATSUO, Toshiaki SETOGUCH ...
    1996 Volume 39 Issue 1 Pages 101-111
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The feasibility and performance of a gas dynamic thrust vector control for advanced space planes using wall bleeding were investigated experimentally in the form of a parameter variation. In these studies, attempts were made to minimize the required control mass flows taken from the forebody boundary layer or intake. Furthermore, a semiempirical method for the design of the bleeding channel and geometry is presented, as well as a possible application of the results to flight mechanics.
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  • Hirofumi MIYAMOTO
    1996 Volume 39 Issue 1 Pages 112-118
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    High-polymer aqueous solutions show various interesting flow phenomena in their liquid motions, e.g., non-Newtonian viscosity, the Toms effect, Johnson effect, and effect on jet breakup and elastic effects. Visualization and observation of the polymer chain orientation or alignment under external stress in a fluid flow region are very important in the basic research for the clarification of these phenomena. In this work, polyethylene oxide is used as the polymer additive, and a steady Couette flow region is formed with a rotating disk and a fixed wall. The sample is a thin piece of ice adhered to the end of a round brass base, which is supercooled by liquid nitrogen and fixed into the rotating disk, keeping the end of the surface flush with the disk surface. The ice sample is dehydrated by the freeze-drying method and observed under a microscope. Polymer molecules form a network structure as bundles of polymer chains, and this network state changes with flow shear rate, molecular weight and the concentration of polymer.
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  • Shinichi YOKOTA, Hisashi SOMADA, Hirotugu YAMAGUCHI
    1996 Volume 39 Issue 1 Pages 119-124
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Flow rate pulsation through pipelines due to hydraulic components is one of the most common sources of vibration and noise in hydraulic control systems. Among the flow rate pulsations caused by hydraulic piston pumps, which are commonly called fluid-borne noise, low-frequency pulsation can be easily absorbed and reduced by a passive element such as an accumulator. However, it is difficult to effectively reduce the high-frequency pulsation such as pulses using only passive elements. This paper concerns an active accumulator which is proposed and newly fabricated. It is driven directly by multilayered PZT devices to reduce the flow rate pulsation produced by hydraulic components in the high-frequency region. The active accumulator has the potential to actively reduce and cancel the variation in the high-frequency flow rate pulsation due to hydraulic piston pumps by producing and using inverse-phase flow by making use of fast-acting piezo-actuators.
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  • Etsuo MORISHITA, Yoshihisa KITORA, Kiyonori TOKUMITSU, Mitsuhiro NISHI ...
    1996 Volume 39 Issue 1 Pages 125-133
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The scroll compressor is now becoming extremely popular in air conditioning and refrigeration in conjunction with the adoption of the heat pump, especially in North America and in Japan. This is primarily due to its higher efficiency and its low noise/vibration characteristics. The scroll compressor technology can be applied in many ways. The authors have developed a scroll vacuum pump using the corotating principle. Although the scroll corotation mechanism is widely known, this is the first attempt at using and developing it for commercial use. Two scrolls rotate around their own axes and no crank mechanism is necessary. The compliant sealing mechanism can also be employed with this vacuum pump. In the present paper, the authors describes the characteristics of the corotating scroll vacuum pump which can be operated in wet and other harsh physical environments, i.e., with contamination, rust, and high suction pressure.
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  • Seong Won NAM, Hideya NISHIYAMA, Shin-ichi KAMIYAMA
    1996 Volume 39 Issue 1 Pages 134-140
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    A numerical analysis is conducted on the heat transfer and fluid flow of a plasma spraying process under the DC-RF hybrid electromagnetic field. Plasma flow is analyzed using Eulerian approach and the equation of particle motion is simultaneously solved using a trajectory analysis with a lumped-heat-capacity model. Axisymmetric two-dimensional electromagnetic fields governed by Maxwell's equations are solved based on a vector potential concept. The effects of the RF electromagnetic field on the temperature and velocity fields of the turbulent plasma flow are clarified. Control characteristics of phase changes and dispersed features of particles by applying the RF electromagnetic field are also clarified in an attempt to improve the plasma spraying process.
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  • Chi-Chuan HWANG, Jaw-Ren LIN, Rong-Fuh YANG
    1996 Volume 39 Issue 1 Pages 141-148
    Published: February 15, 1996
    Released: February 18, 2008
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    We apply the Brinkman-extended Darcy model to analyze the hydrodynamic lubrication of long porous slider bearings. The solutions are obtained and compared with those based on the Darcy model. The results show that the effects of viscous shear given by the Brinkman-extended Darcy model lead to a higher load capacity and a lower friction parameter. It is found that a thicker porous bearing gives a greater effect of viscous shear on load capacity and friction parameter.
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  • jose Javier GIL, Hiromu SUGIYAMA, Takakage ARAI, Norio TAKAKURA, Jin T ...
    1996 Volume 39 Issue 1 Pages 149-155
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The investigation described in the present work was intended to observe the behavior of lubricating oil film between a single pair of wet clutch plates used in automatic transmissions, taking account of the porous facing on one disk. Film pressure measurements and the most representative engagement characteristics, along with simultaneous visual recordings of the process, were obtained using a high-speed video system. The results clarified the variation of oil film pressure during the engagement process. Moreover, cavitation bubbles appearing over the porous plate surface were observed in the study.
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  • Yojiro ISHINO, Toshiaki KOJIMA, Norio OIWA, Shigeki YAMAGUCHI
    1996 Volume 39 Issue 1 Pages 156-163
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    In previous work, it was shown that acoustic excitation of a plane diffusion flame enhanced the periodicity and intensity of organized-eddy-controlled combustion. The main objective in this work was to examine phase characteristics of the excited eddy flames with high periodicity. A computer-aided phase-locked averaging method was employed to obtain graphical 2 D contour maps of the instantaneous profiles of temperature and CH emission. Both maps of eight consecutive phases indicated clearly not only the periodic behavior of the organized eddy flame, but also the gas dynamic properties peculiar to those flames with coherent structure. The profiles of local contribution of the sound field to the combustion process were also examined by calculating the 2 D distribution of the local Rayleigh index. The latter showed that the organized eddy flames are highly sensitive to sound, and play an important role in sound-flame interaction.
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  • Yukio SAKAI, Katsuyuki KONISHI, Atsushi ISHIHARA
    1996 Volume 39 Issue 1 Pages 164-170
    Published: February 15, 1996
    Released: February 18, 2008
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    Tip opening and burning intensity of Bunsen flames diluted with nitrogen have been experimentally investigated. Methane-air and propane-air flames were used in the experiment. The tip opening limit was mapped as a function of the equivalence ratio φ and added nitrogen ratio χ, and the tip temperature was measured. Results show that the burning at the tip was more intense in rich flame for methane and lean flame for propane. The maximum allowable dilution by nitrogen also occurs in rich flame (φ=1.05) for methane and lean flame (φ=0.94) for propane. The tip temperature decreases steeply with increasing χ if the methane flame is lean or the propane flame is rich, while it decreases gradually if the methane flame is rich or the propane flame is lean. These results at the tip were due to the preferential diffusion and nonunity Lewis number resulting from negative stretch induced by flame curvature. The flame responses presented here to preferential diffusion and Lewis number are the reverse those of positively stretched stagnation flames.
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  • Yoshisuke HAMAMOTO, Eiji TOMITA, Sadami YOSHIYAMA
    1996 Volume 39 Issue 1 Pages 171-175
    Published: February 15, 1996
    Released: February 18, 2008
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    A thick burning zone including unburned and burned gas is observed in turbulent premixed flames. In this study, the burning rate and the ion current in the burning zone were investigated in propane-air turbulent flames in a spark-ignition engine cylinder and a constant-volume combustion chamber. The main results are as follows: (1) in propagating turbulent flame, the rate at which mass is burned is not equal to the rate of mass entrainment to the flame front; (2) the ratio of the combustion rate per unit area of turbulent flame front to that of laminar flame, Z=(MbT/AT)/(MbL/AL), is a reasonable expression of the effect of turbulence on the combustion of propagating flame; (3) the ion-current signal has multiple peaks in turbulent flame. The average number of ion current peaks increases with the enlargement of burning zone and the value of Z.
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  • Norimasa IIDA, Shinji HOSONUMA, Ken'ichi YOSHIMURA, Shigehisa TAKASE
    1996 Volume 39 Issue 1 Pages 176-184
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    When methanol is used as fuel for internal combustion engines, formaldehyde and unburned methanol emissions can be a problem. To overcome this shortcoming, an engine with the active thermo-atmosphere combustion (ATAC) system was proposed, along with improvements in heat-insulating performance and the realization of high-temperature combustion by using ceramics for the combustion chamber walls. The combustion and emissions characteristics of this ceramic low heat rejection (LHR) methanol ATAC engine were investigated. Combustion performance was compared between operation with methanol and gasoline. When methanol was used, it was seen that the ATAC operation region was widened considerably. Also, a reduction in aldehyde emissions was achieved, due to the high-temperature operation of the combustion chamber. However, efficiency deteriorated at times due to early self-ignition timing. This was overcome by the use of lean fuel-air ratios, which resulted in both a reduction of NOx and an improvement in fuel consumption. With a premixed fuel supply system, wall surface ignition was unavoidable for combustion chamber surface temperatures greater than 800 K (527°C). Wall surface temperature swing and instantaneous heat flux increased substantially with ATAC operation under these conditions.
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  • Masahiro ISHIDA, Hironobu UEKI, Noboru MATSUMURA, Masanori YAMAGUCHI, ...
    1996 Volume 39 Issue 1 Pages 185-192
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The proposed two-zone model of diesel combustion consists of a burned zone and an unburned zone, and the thermodynamic process is independent and adiabatic in each zone except that the air is entrained from the unburned zone to the burned zone under a specified condition of the excess air ratio during the combustion period. The excess air ratio in the diffusion combustion period is assumed to be constant in the present model. The calculated time histories of the burned-zone gas temperature and the cumulative soot formation were compared with the measured time histories of the flame temperature and the KL value based on the infrared two-color method. The calculated results agree qualitatively and partly quantitatively with the experimental results except for the swirl effect. As a result, it is shown that the present two-zone model analysis is very useful and effective in evaluating the combustion process in a DI diesel engine.
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  • Hiroyuki NAGAKI, Koji KOREMATSU
    1996 Volume 39 Issue 1 Pages 193-201
    Published: February 15, 1996
    Released: February 18, 2008
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    In both spark ignition engines and diesel engines, the exhaust gas recirculation (EGR) system is well known as an effective technique to reduce nitrogen oxides emissions. However, wear of piston rings and cylinder liners is sharply increased by EGR. It is widely considered that sulfur dioxide contained in exhaust gas is strongly related to wear. In order to clarify the sole effect of sulfur dioxide in recirculated exhaust gas on wear of piston rings and cylinder liners, we performed an experiment where sulfur dioxide was added to the intake air. Furthermore, we compared the amount of wear, which was measured experimentally, with the amount of sulfur dioxide absorbed by a lubricating oil film, which was estimated by a numerical model. Consequently, sulfur dioxide absorbed by a lubricating oil film plays an important role on wear of piston rings and cylinder liners.
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  • Kazuo ONDA, Ken KATO, Yasuhiro KASUGA
    1996 Volume 39 Issue 1 Pages 202-210
    Published: February 15, 1996
    Released: February 18, 2008
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    It has been reported that SO2 and NOx in flue gas can be removed by corona discharge and that pulsed corona discharge is as energy-efficient as electron-beam treatment. A large amount of data is required, however, to assess the industrial application of the corona discharge method to the removal of SO2 and NOx from combustion flue gas. In this study experiments of SO2 and NOx removal from actual and simulated combustion gas have been performed on a laboratory scale, where combustion gas composition, temperature, residence time in the discharge duct, and the polarity of high-voltage electrodes are changed for DC and pulsed corona discharge. The following experimental results are obtained: (1) the increase in H2O and O2 concentration improves SO2 and NOx removal rate, (2) dendritic (NH4)2SO4 powders tend to deposit on high-voltage electrodes, and (3) the electrode polarity has a nominal effect on the removal rate under our experimental conditions.
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  • Kouichi KAMIUTO, Reiichiro ITOH, Kensei HIGASHI, Hironobu YANO
    1996 Volume 39 Issue 1 Pages 211-215
    Published: February 15, 1996
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    A constrained multispectral transmittance method, where the optical properties of soot are assumed to be known, is used to determine in situ soot size distributions and volume fractions in six solid-, liquid- and gas-fueled diffusion flames. The resulting soot volume fractions range from 0.97×1O-6 for propane to 1.1×1O-7 for acetone, and all soot size distributions indicate that the most probable radius is less than O.1μm. In addition, it is found that in the visible region, the relationship between the spectral extinction coefficient kλ (cm-1) and the soot volume fraction fv can be well represented by kλ=(7.33×104λ-0.989)fv, irrespective of the kind of soot. Here, λ denotes the wavelength of radiation in units of μm.
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