Journal of Environment and Engineering
Online ISSN : 1880-988X
ISSN-L : 1880-988X
Volume 6 , Issue 1
Showing 1-20 articles out of 20 articles from the selected issue
Papers
  • (1st Report: Impacts of Gas Flow Rate at Inlet and Gas Channel Pitch of Separator on In-Plane Temperature Distribution and Power Generation Performance)
    Akira NISHIMURA, Kenichi SHIBUYA, Atsushi MORIMOTO, Shigeki TANAKA, Ma ...
    2011 Volume 6 Issue 1 Pages 1-16
    Published: 2011
    Released: January 19, 2011
    JOURNALS FREE ACCESS
    To clarify the mechanism of combined phenomena of heat, mass and electric charge transfers in a single-cell polymer electrolyte fuel cell (PEFC), it is necessary to measure in-plane temperature distribution of a single-cell PEFC when it is run, i.e., generating power. The measurement by thermograph assists to investigate the influence of gas flow rate at inlet and gas channel pitch of separator on in-plane temperature distribution and power generation performance. As a result, the higher temperature region is observed near the outlet of cell when the excess ratio of gas flow is set due to the convective heat transfer by excess oxygen flow in gas channel at the cathode. When the gas flow is set at stoichiometric, in-plane temperature distribution becomes even and high power generation performance can be achieved. The other observation is that the total voltage is increased and temperature in observation area is dropped with decreasing gas channel pitch of separator irrespective of gas flow rate.
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  • Tatsumi KITAHARA, Toshiaki KONOMI, Hironori NAKAJIMA, Masato KAZAMA
    2011 Volume 6 Issue 1 Pages 17-27
    Published: 2011
    Released: January 19, 2011
    JOURNALS FREE ACCESS
    Gas diffusion layers (GDLs) coated with a microporous layer (MPL) have been commonly used to improve water management properties of polymer electrolyte fuel cells (PEFCs). However, the appropriate pore diameter, thickness and hydrophobicity of the MPL remain unclear. In the present study, the influences of MPL design parameters on permeability and PEFC performance were evaluated. A decrease in the pore diameter of the MPL reduces through-plane permeability significantly, but reduces in-plane permeability only slightly. Under high-humidity conditions, a decrease in the MPL pore diameter is effective for preventing flooding, enhancing PEFC performance. However, when the pore diameter becomes too small, PEFC performance tends to decrease. Reducing the MPL thickness improves in-plane permeability, enhancing the ability of the MPL to avoid flooding. Under low-humidity conditions, a decrease in the MPL pore diameter is effective for preventing drying-out of the MEA. Increasing the MPL thickness is also effective for maintaining the humidity of the MEA. However, when the MPL thickness becomes too large, the transport of oxygen to the electrode through the GDL is deteriorated, lowering PEFC performance.
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  • Shigeo YANABE, Makoto ENDO, Masanobu NAKANISHI
    2011 Volume 6 Issue 1 Pages 28-40
    Published: 2011
    Released: January 19, 2011
    JOURNALS FREE ACCESS
    The present study treats a paper wrinkle appearing in a fixing roller unit of printers or copiers with electro-photographic process. An experiment shows that a wrinkle always occurs, when an A4-sized paper is tilted by 3 degrees against a horizontal fixing roller unit without a heating devise and is fed to a roller nip. The wrinkle appears in the middle of the paper width. Computer simulations were carried out to illustrate this wrinkle occurring process. The simulation model consists of a rigid cylindrical driving roller, a driven rubber roller, a paper, and a guide plate. The paper is assumed to be an isotropic elastic-plastic body. The results reveal the following wrinkle occurring process. When the tilted paper is fed to the rollers, the center part of the paper leading edge firstly enters the roller nip and is pulled by friction forces in the nip. Then paper wavy bending deformations appear in front of the nip. A steep slope of the deformation is crushed and yielded in the nip. After this, a neighbor area of the yielded point gathers together and a folded wrinkle is formed. Further, this type of wrinkle is liable to occur when the paper tilt angle, Young's modulus, or coefficient of friction is large, or when the paper yield stress is small.
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  • Katsuyuki KONISHI, Yukio SAKAI, Atsushi ISHIHARA
    2011 Volume 6 Issue 1 Pages 41-52
    Published: 2011
    Released: January 19, 2011
    JOURNALS FREE ACCESS
    A new model of spray combustion with a flame boundary and two NO formation regions was developed in order to predict NO emission from large marine diesel engines. The basic prediction characteristics were studied by using the actual engine specifications and several parameters such as a droplet initial diameter, a fuel injection period, and a flame angle. The simulation could show the change of chemical species composition in the inside and outside of a spray during their combustion. As a result, it was found that this model predicts that the NO formation is frozen after the end of combustion, and the flame angle influences the NO exhaust rate and the thermal efficiency more sensitively than the other parameters.
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  • Junichiro YAMABE, Hirotada FUJIWARA, Shin NISHIMURA
    2011 Volume 6 Issue 1 Pages 53-68
    Published: 2011
    Released: January 19, 2011
    JOURNALS FREE ACCESS
    In order to clarify the influence of high pressure hydrogen gas on mechanical damage in a rubber O-ring, the fracture analysis of the O-ring used for a sealing material of a pressure hydrogen vessel was conducted. The O-ring was exposed twenty cycles to hydrogen gas at 100 MPa. All the cracks observed in this study emanated from the interior, which can be classified into two types, type 1 and type 2, from the viewpoint of the location of crack initiation and the direction of crack growth. The type-1 cracks started from the center of the O-ring, while the type-2 cracks started from the sites near the surface of the O-ring. It is implied that tensile stress by compression influenced crack initiation and growth of the type-1 cracks. The mechanical damage by the type-1 cracks was more serious than that by the type-2 cracks. Stress analysis was conducted by the nonlinear FEM; then fatigue crack initiation of the O-ring was evaluated in terms of the maximum principal strain criterion, which has been widely employed for the evaluation of fatigue strength of rubber materials. The strain generated by compression was considerably smaller than fatigue fracture strain although the increase in the strain due to swelling was considered. It is considered that the type-1 cracks initiated and grew due to strain concentration caused by bubbles which were formed from supersaturated hydrogen molecules after decompression in addition to the strain due to compression and swelling.
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  • Hiromitsu HAMAKAWA, Kouichi MURAOKA, Eiichi NISHIDA, Tohru FUKANO
    2011 Volume 6 Issue 1 Pages 69-80
    Published: 2011
    Released: January 19, 2011
    JOURNALS FREE ACCESS
    This paper focuses on the vortex shedding from tube banks with closely mounted serrated fin. The tube banks were installed rigidly in the test section of a wind tunnel. We measured the mean velocity, the velocity fluctuation spectrum, and the gap velocity in the model tube banks that had the same pitch ratio as a boiler heat exchanger. We found two types of vortex shedding with different Strouhal numbers St of 0.40 and 0.20 in the case of Reynolds numbers Re in the range 2.8 × 104 to 6.2 × 104. Strouhal numbers were calculated by using the measured values of the vortex shedding frequency, the gap velocity, and the equivalent diameter. The vortex shedding for St = 0.40 was mainly formed within the finned tube banks and the other vortex shedding for St = 0.20 was in the wake of the finned tube banks. The Strouhal number of the vortex shedding inside the finned tube banks changed from 0.40 to 0.32 for Re = 6.2 × 104. The applicability of the equivalent diameter, obtained from a single circular cylinder with a serrated fin, to the finned tube banks was examined. The calculated Strouhal number of 0.32 agreed with a Strouhal number of 0.30 obtained from Fitz-hugh’s map for bare-tube banks. The Strouhal number of 0.20 is similar to that for vortex shedding from a circular cylinder.
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  • (Deposit Accumulation on Wick during Wick Combustion)
    Kazuhiro HAYASHIDA, Katsuhiko HAJI, Hiromi ISHITANI, Masataka ARAI
    2011 Volume 6 Issue 1 Pages 81-89
    Published: 2011
    Released: January 19, 2011
    JOURNALS FREE ACCESS
    Effect of fuel properties of kerosene on deposit accumulation was studied experimentally. Five types of kerosene, which distillation and composition properties were different, were used as the test fuel. Deposit accumulation processes were investigated by using wick combustion burner. Deposit accumulation rate was estimated from the mass of deposit which accumulated on wick and the fuel consumption. As the results, it was confirmed that the deposit accumulation rate increased with the content of aromatic hydrocarbons and naphtheno benzenes. Main component of the deposit was heavy hydrocarbons formed by thermal decomposition and polycondensation of the fuel within the wick. To estimate the effect of peroxide on deposit accumulation, test fuels which contain peroxide generated by sun exposure were used. The peroxide-containing fuels significantly increased the deposit mass than normal fuels.
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  • (Fluid-Dynamic Oscillations)
    Hiroshi YOKOYAMA, Chisachi KATO
    2011 Volume 6 Issue 1 Pages 90-106
    Published: 2011
    Released: January 19, 2011
    JOURNALS FREE ACCESS
    Fluid-acoustic interactions in fluid-dynamic oscillations of a flow over a two-dimensional cavity were investigated by directly solving the compressible Navier-Stokes equations. It was assumed that the upstream boundary layer is turbulent and the depth-to-length ratio of the cavity is 0.5. To clarify the effects of the freestream Mach number on the fluid-dynamic oscillations, the computations were performed for two freestream Mach numbers, i.e., 0.15 and 0.3. The oscillations occur with the Mach number of 0.3, while they do not occur with the Mach number of 0.15. For the Mach number of 0.3, phase-averaged flow fields show that large-scale vortices form in the shear layer. When the large-scale vortex collides with the downstream wall, the low-pressure region spreads along the downstream wall. As a result, a local pressure gradient induces a local downstream velocity, causing the upstream fluid to expand and an expansion wave to propagate to the outside of the cavity. To clarify the mechanism for the formation of the large-scale vortices, backward-facing step flows with an artificial acoustic source were also computed. These computations clarify the reason that oscillations do not occur in the cavity flow with Mach number of 0.15.
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  • Hiroyuki IWAMOTO, Nobuo TANAKA, Akira SANADA
    2011 Volume 6 Issue 1 Pages 107-118
    Published: 2011
    Released: January 27, 2011
    JOURNALS FREE ACCESS
    This paper is concerned with an active noise control for an enclosed sound field. It is the purpose of this paper to present an active wave control method of a three dimensional rectangular cavity and to clarify fundamental properties of the control system. Firstly, a transfer matrix method for the target system is newly introduced to describe the wave dynamics in the enclosure. This is followed by the derivation of feedforward control laws for absorbing reflected waves or eliminating transmitted waves. In the proposed method, the control laws are including the modal actuation scheme for uncontrolled direction. Then, from a viewpoint of numerical analyses, basic properties of the proposed method are verified. It is found that the transmitted wave eliminating control enables the generation of silent zone, and the reflected wave absorbing control enables the inactivation of acoustical modes in the controlled direction.
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  • Tomoaki NAMIOKA, Yoshiaki MOROHASHI, Kunio YOSHIKAWA
    2011 Volume 6 Issue 1 Pages 119-130
    Published: 2011
    Released: January 27, 2011
    JOURNALS FREE ACCESS
    To evaluate malodor reduction by means of the hydrothermal torrefaction, concentrations of the main malodorous compounds in odor samples from solid products before and after treatment were measured using gas chromatography. The concentrations of the sulfur-containing compounds were decreased by this treatment. To elucidate the mechanisms of this malodor reduction, odor distributions were analyzed with an odor-measuring device. The odor intensities in the odor sample from the solid product were lower than those from the dewatered sewage sludge (DSS), whereas the odor intensities in samples from liquid and gaseous products were as high as or higher than those from the DSS. Therefore, we conclude that one of the main malodor reduction mechanisms is reactive distillation: malodorous compounds are separated from the solid product by the inherent thermal effect of the hydrothermal torrefaction. In addition, the masking effect of odorous compounds produced as by-products in this treatment process and the sterilization of microbes in DSS probably play important roles in malodor reduction as well.
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  • -Ratchet Type Drive System with Self-Drive Rotational Valve-
    Kenji KANEKO, Kazuki ENOMOTO
    2011 Volume 6 Issue 1 Pages 131-139
    Published: 2011
    Released: February 02, 2011
    JOURNALS FREE ACCESS
    This research aims at developing the heat engine system using Shape Memory Alloy (SMA) wires, which work by alternating supply of hot/cold water through the newly developed automatic valves. The SMA wire is connected to the chain and sprocket system having the ratchet type bearing and the spindle with the flywheel. The valves for supplying hot/cold water to the SMA wires are driven by the flywheel, so no outside power is necessary. Output power of the developed heat engine with two φ 0.3 mm SMA wires is 0.1W at 30∼40 rpm. The SMA wire used in the developed heat engine was produced by the Furukawa Electric Co., Ltd.. The wire shows the fatigue life of more than 105 cycles under conditions of 150 MPa in loading and heating/cooling cycle rate of 0.5 Hz in the cyclic transformation fatigue tests. The heat engine system works without any adjusting process of a length of SMA wire and water supplying timing. The stress of the SMA wire is kept to be rather higher during working because that the engine has no crank system. So, the developed heat engine system is hopeful to use in recovering energy from waste hot water.
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  • Toshihiko KOMATSUZAKI, Yoshio IWATA
    2011 Volume 6 Issue 1 Pages 140-149
    Published: 2011
    Released: February 02, 2011
    JOURNALS FREE ACCESS
    In general, the sound waves propagate spherically in free space, which accordingly makes the global attenuation difficult. Using ordinary loudspeaker as a control source may cause interfered sound field with both attenuated and amplified regions. On the other hand, the recent development of high-directional loudspeakers based on new sound production theory known as 'parametric array' has allowed sound transmission within a narrow range of acoustic space. In the present paper, a numerical model of parametric array based on the quasi-linear approach of Westervelt is studied, and the calculated results are compared with the measured fields. The spherically spreading noise in space is mitigated either by a normal or a parametric loudspeaker as control source, and it is known that the suggested ANC system can mitigate sound locally but cause less influence on circumferential field.
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  • Akira AOKI, Yoshitaka MARUMO, Ichiro KAGEYAMA
    2011 Volume 6 Issue 1 Pages 150-164
    Published: 2011
    Released: February 04, 2011
    JOURNALS FREE ACCESS
    This paper presents theoretical research in the fundamentals on the directional stability and controllability of multi-articulated vehicles. Analyses and numerical calculations are conducted by using models incorporating vehicle side-slipping and yawing. Two vehicle combinations are examined with regard to straight running stability, as well as steering sensitivity and off-tracking in steady-state turning. Type I is a tractor and two semitrailers; type II is a tractor, semitrailer, and full-trailer. The following conclusions are drawn. (1) The criterion of non-oscillatory stability of types I and II is a function of the stability factor as well as that of tractor and semitrailer combinations. (2) Type I is more stable than type II in oscillatory modes. (3) Type I differs slightly from type II regarding non-oscillatory stability, steering sensitivity, and off-tracking in steady-state turning.
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  • Akira SADAMOTO, Seiji SHIRAHAMA, Yasuhiro ANDO
    2011 Volume 6 Issue 1 Pages 165-177
    Published: 2011
    Released: February 04, 2011
    JOURNALS FREE ACCESS
    The quietness of a ceiling-mounted ventilator consisting of a rectangular outer cover and a cylindrical fan unit is investigated. In order to confirm the sound-attenuation effect using a space between the cover and the fan unit, several properties of a chamber having a simplified symmetrical shape, which models an actual ventilator, have been investigated. In a previous study, in which the chamber was located in an infinite duct, the chamber was separated into two domains by a partially shutting plate to control the chamber performance. In the present study, this chamber is attached to one end of a duct and the properties of the sound radiated from the duct end into free space are investigated experimentally and numerically using the boundary element method. The effect of the chamber is similar when located at a duct end and in an infinite duct. In a certain low-frequency range, however, the chamber has an adverse effect in the duct-end case. Fortunately, this is not serious for an actual ventilator because the corresponding frequency range is not dominant for the sound radiated from an actual ventilator. Although the sound pressure in the chamber is quite different between the two chamber locations, the sound pressure ratio of the two domains is the same. Although the chamber performance depends on the chamber location, the physical aspect of the chamber as a resonator can be said to be independent of its location. When the opening connecting the two domains is moderately narrow, the chamber behaves approximately as a Helmholtz resonator having two degrees of freedom.
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  • Hisanori ABIRU, Akira YOSHITAKE
    2011 Volume 6 Issue 1 Pages 178-186
    Published: 2011
    Released: February 04, 2011
    JOURNALS FREE ACCESS
    In this paper, a hydroelectric power generation system able to extract the water flow energy from the hydroelastic response of an elastically supported rectangular wing is experimentally investigated. Except for a vertical wing, supported in the manner of a cantilever, the generator has no other parts submerged in water. An electric motor is used to excite pitching oscillations of the wing. Both the wing and the electric motor are supported by leaf springs which are designed to work both as a linear guide for the sway oscillations and as elastic elements. The wing mass in sway direction necessary to achieve a hydroelastic response is obtained by using a mechanical snubber mechanism. The appropriate load to generate electricity is provided by magnetic dampers. By employing the linear potential hydrodynamic theory, a theoretical analysis was performed to model the water channel tests on the power generation system and to determine its structural and hydrodynamic features. Tests revealed that the proposed power generation system is feasible and able to work with an efficiency of 32-37%.
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  • Daniel FUENTES DEL RÍO, Takeo KAJISHIMA
    2011 Volume 6 Issue 1 Pages 187-198
    Published: 2011
    Released: February 04, 2011
    JOURNALS FREE ACCESS
    This paper reports on numerical simulations of the flow of hot gases released vertically from a chimney into a crosswind with velocity and temperature ratio corresponding to an experiment. The use of a weak compressible scheme, which is capable of taking into account thermal expansion at low Mach number is proposed in order to improve the simulation of the flow. Simulations with 3 different temperature ratios were performed using the proposed method and the incompressible scheme with the Boussinesq approximation. For the isothermal case, both schemes predicted similar trajectories and had good agreement with experimental data. For high temperature ratios, our method showed better agreement with experimental data than the simulations with the method based on the Boussinesq approximation. It was found that the density changes due to thermal expansion near the nozzle exit act against buoyancy, diminishing the vertical velocity over the chimney affecting the trajectory of the flow, also modifying the areas where buoyancy has a considerable effect.
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  • Shijie GUO, Rentaro KATO
    2011 Volume 6 Issue 1 Pages 199-209
    Published: 2011
    Released: February 04, 2011
    JOURNALS FREE ACCESS
    Dynamic dampers are usually made of rubber and rigid mass elements. They are widely used for cutting the resonance of mechanical structures. In this research, modification was made to a traditional damper by introducing small chambers, channels (orifices) and fluid into the rubber. By using the resonance of the fluid, a two-degree-of-freedom damper was developed with a slight weight increase. Its characteristics and vibration reduction effects were formulated and investigated experimentally. It was demonstrated that the damper works in a broad frequency range as compared to traditional dampers and can cut two resonance peaks simultaneously.
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  • Osamu IMAMURA, Bo CHEN, Kiyotaka YAMASHITA, Shunsuke NISHIDA, Mitsuhir ...
    2011 Volume 6 Issue 1 Pages 210-219
    Published: 2011
    Released: February 14, 2011
    JOURNALS FREE ACCESS
    Flames are affected by external electric fields because they contain ions and electrons. The movement of ions and electrons affects the external electric field owing to their charge. In this context, this paper discusses the change in the electric field on the basis of experimental results obtained at different electrode distances. Employing one-dimensional (1D) steady-state analysis, we assume that if the electric field is changed spatially, the effect of the electric field on combustion behavior is aligned with V2/L3, where V is the applied voltage between the electrodes and L is the distance between the electrodes. Because a flame deforms to a cathode owing to electric body force in an electric field, the change in the flame shape of burning ethanol droplets observed in a vertical DC electric field and the electric current during combustion are measured as flame characteristics. The results reveal that applied electric voltage exists where the flame becomes vertically symmetrical to balance the buoyancy due to the electric body force. The relationship between m and n of Vm/Ln for flame symmetry is around n/m = 1.5. On the basis of these results, all experimental results for different electrode distances are rearranged with εV2/L3, which is a representative electric body force, and it is proved that the use of parameter εV2/L is effective. These results indicate that the change in the electric field due to the existence of a flame should be considered when examining the effect of an external electric field on combustion behavior.
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  • Yoshihiko KANOTO, Kenichiro NAGAI, Tsunemichi KAWA, Norimasa IIDA
    2011 Volume 6 Issue 1 Pages 220-232
    Published: 2011
    Released: February 14, 2011
    JOURNALS FREE ACCESS
    In recent years, higher thermal efficiency and lower emissions are required on a reciprocating engine development and therefore cycle-to-cycle combustion control is necessary. Especially it is a key factor to control HCCI combustion engine. In HCCI engine, one of the most promising combustion methods to achieve high thermal efficiency, the ignition timing strongly depends on the mass-averaged temperature of charged gas and residual gas and very precise combustion phase control is required. Therefore it is important to detect the changes of cycle-to-cycle intake air flow rate, EGR gas flow rate and as well as residual gas in each cycle. The traditional laminar flow meter has too low responsivity to measure cycle-to-cycle flow rate. In this study, the fast-response laminar flow meter was developed in order to measure cycle-to-cycle dynamical flow rate. The availability of the fast-response laminar flow meter for cycle-to-cycle intake air flow rate measurement of the HCCI engine is shown in this paper.
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  • Yoshitoshi SAITO, Andy INGRAM, Xianfeng FAN, Jonathan Peter Kyle SEVIL ...
    2011 Volume 6 Issue 1 Pages 233-241
    Published: 2011
    Released: February 23, 2011
    JOURNALS FREE ACCESS
    Wet granulation in high shear mixer is important in reducing potential environmental and safety hazards. A complex mechanism dominates high shear mixer granulation because there is an enormous range of geometries and designs for the mixer. This study is the first report of the effects of blade design on wet granulation in high shear mixer. In this study, two designs of blade were used to compare the granulation, and it was determined that the flat blade resulted in no granule or lump formation, while the beveled blade resulted in good granule formation. Positron emission particle tracking was used in order to investigate the effects of different impeller designs in wet granulation in a high shear mixer. These results should prove useful in improving process design in order to optimize the final granules, and in improving the quality of the resultant product.
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