日本機械学会論文集 B編
Online ISSN : 1884-8346
Print ISSN : 0387-5016
71 巻, 712 号
選択された号の論文の35件中1~35を表示しています
  • 稲垣 昌英, 近藤 継男
    2005 年 71 巻 712 号 p. 2829-2836
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    The usage of a wall-damping function based on Kolmogorov velocity scale in large eddy simulation (LES) is investigated. To calculate Kolmogorov velocity scale, the dissipation rate of turbulent energy, ε, is needed. In LES, however, the dissipation rate is not solved unlike in the k-ε model, and we have to take the statistics of the calculated unsteady data to obtain it. Therefore, the usage of the wall-damping function in LES is not straightforward. In some studies, the dissipation rate of the subgrid-scale (SGS) turbulent energy, εSGS, is used instead of ε. However, since the SGS components contain only the turbulent components in the scale smaller than the grid-filter width, the damping effect becomes inappropriate and dependent on the grid resolution employed. To overcome this problem, we propose a method for estimating ε from εSGS, where the ratio of two length scales, one in LES and the other in the k-ε model, is used. The revised wall-damping function using the estimated ε is tested in canonical channel flows, and the results show that it gives proper near-wall damping effect in every case with considerably wide range of grid resolutions.
  • 第3報, 非定常問題に対する格子細分化非構造解適合格子形成法
    山川 勝史, 松野 謙一
    2005 年 71 巻 712 号 p. 2837-2842
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    A new adaptive mesh refinement method for unsteady compressible flow is presented in this paper. For unsteady flow problem, the solution-adapted grid is also dynamically changing its shape at every time step according to the flow change since the flow is non-stationary. For the present solution-adapted grid method, two grid cells are merged into one grid cell and one grid cell is divided into two grid cells according to a criterion of grid adaption in a time-dependent way in unstructured grid system. In this case, it is important to assure geometric conservation low as well as physical conservation low on such the grid system. Therefore, we adopt a finite volume method in which a control volume on the space-time unified domain for estimating numerical flux. The method is described and applied for two-dimensional unsteady compressible flows.
  • 渡辺 敬三, 小方 聡, 廣瀬 敦, 木村 彰宏
    2005 年 71 巻 712 号 p. 2843-2848
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    In order to clarify laminar drag reduction and the slip velocity on a hydrophobic surface, the pressure loss of a rectangular duct was measured applying the various kinds of the wall surface qualities to duct inner wall. Test wall surfaces were classified three types by the surface characteristics, which were hydrophobic coating surface, fine rectangular groove surface and fine rectangular groove with hydrophobic coating. Direction of the fine rectangular groove are parallel, vertical and random in the flow direction, and the widths are 5 and 10 mm. For fine rectangular groove with hydrophobic coating surface, it was clarified that the laminar drag reduction occurred in the Reynolds number range of 150<Re<770. The maximum drag reduction ratio is 12.6% at Re=649. The Reynolds number range in which the drag reduction occurred increased with decreasing the width of the groove, and the direction of the groove did not affect the drag reduction effect.
  • 渡辺 敬三, Budiarso, 小方 聡, 上村 圭吾
    2005 年 71 巻 712 号 p. 2849-2855
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    The purpose of this study is to obtain the new type of the drag reduction for the frictional moment of an enclosed rotating disk by using the fine spiral grooves on the disk surface. The experiments were carried out the measurement for the frictional moment of an enclosed rotating disk with fine spiral grooves, of which there were 120-160 in the number and 0.1-0.2mm in depth, respectively. The Reynolds number range is 4 × 104Re≤6×105. Test fluids are tap water and aqueous solutions of glycerin, It was seen that the drag reduction occurs in the turbulent flow range at the non-dimensional axial clearance (s/a) =0.011, 0.22 and 0.33, the maximum drag reduction ratio is approximately 15%. The drag reduction depends on the number, the angle and the depth of the grooves. The fine spiral groove has the effect which suppresses the development of the fluctuation of transition region, and which delays the generation of the local turbulence in the transition range.
  • 寺島 洋史, 藤井 孝藏
    2005 年 71 巻 712 号 p. 2856-2863
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    One criterion that determines time stepping size in the implicit time integration method is given for accurate and effective transonic flutter simulations. Transonic flows over two-dimensional forced oscillating airfoils with several reduced frequencies are first investigated for constructing a criterion for selecting the time stepping size, and then two and three-dimensional transonic flutter simulations are performed for evaluating the criterion. Results for the forced oscillating airfoil indicate that unsteady aerodynamic forces converge in a constant value as the time stepping size decreases and the time stepping size required the convergence of unsteady aerodynamic force depends on the reduced frequency. From these results, it turns out that 4000 integration steps during one cycle of airfoil oscillations are enough for the estimation of the unsteady aerodynamic forces at any reduced frequency. The time stepping size is automatically decided by setting 4000 integration steps during one cycle of airfoil oscillations. Results for two and three-dimensional transonic flutter simulations show that flutter boundaries can be accurately and effectively calculated based on the criterion.
  • 阿部 豊, 青木 一義
    2005 年 71 巻 712 号 p. 2864-2869
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    It is expected to manufacture new materials under the micro-gravity environment in space. Under the micro-gravity environment, holding technology of molten metal is important to manufacture new materials. There are previous studies about droplet levitation by the acoustic wave for the holding technology. However it is still unknown experimentally and analytically how the acoustic wave act on the levitated droplet. In the present study, the technology to handle the material in space by the ultrasonic wave is developed and the simulation technique to evaluate the acoustic wave field and the movement of the droplet in the acoustic field. Therefore the followings are the purposes of present study. At first, the characteristics of droplets holding by the ultrasonic standing wave under normal gravity environment and micro-gravity environment is investigated. Secondary, numerical simulation is conducted to clarity the characteristics of ultrasonic standing wave. Finally, the force committed to a droplet is investigated by reproducing a movement of the droplet.
  • 励起したフィルム流によるエントレイメント量の変化
    宮城 徳誠, 木村 元昭, 庄司 秀夫, 藤田 肇, 程谷 幸平
    2005 年 71 巻 712 号 p. 2870-2877
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    Active control of jet is applied at control of burner flame or air conditioning. In this study, secondary film flow is built on the outside of axisymmetric jet. And it is driven by the acoustic excitation for active jet control. Furthermore, the velocity ratios of mainstream and film flow and acoustic strouhal number were changed. The freestream velocities were measured by the LDV and jets were visualized by LLS for research of change in jet structure. As a result, axisymmetric jet is diffused in all condition by acoustic excitation vortices. In the case of VR=0.5, potential core is shortened by St=0.6. At VR=1.0 diffuses than at VR=0.5. Potential core is most short at VR=1.0, St = 0.6. Mainstream most mixes with film flow at VR=1.0, St=0.6 and film flow mixes with surrounding air at VR=1.0, St=0.3.
  • 舘林 康, 田中 和博, 小林 敏雄
    2005 年 71 巻 712 号 p. 2878-2883
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    Authors have been investigating the various characteristics as for a screw-type centrifugal pump, for example pressure fluctuation in the impeller, flow pattern in a volute casing and pump performance in air-water two-phase flow. During these investions, it was found from numerical results that three back flow regions existed in this pump. Among them, the back flow from the volute casing toward the impeller outlet was the most influential on the pump performance. The important factor for higher pump performance was to reduce the influence of this back flow. The trial was carried out by the restraint of the back flow in order to investigate its influence. A wall was attached at the trailing edge of the impeller blade. Its effects on the flow patterns and the pump performance were discussed and clarified by comparing the calculated results under the conditions between with and without the wall. From the obtained results, it was found that the wall avoided the congestion of solids and worked well for the suppression of this back flow. In addition, the improvement in pump performance was realized by this trailing-edge type wall. The pump head and the efficiency at BEP were improved by 10% and 3%, respectively.
  • 界面追跡法と流体粒子追跡法の統合
    迫田 健一, 冨山 明男, 宋 明良
    2005 年 71 巻 712 号 p. 2884-2891
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    A hybrid numerical method for solving dispersed multi-phase flows was developed. The method is the integration of an interface tracking method (ITM) based on a volume tracking scheme, a new fluid particle tracking method (PTM) based on a one field formulation (OFPT), a PTM based on the jump condition (BCPT) and a PTM based on volume averaging (VAPT). This hybrid integration made it possible to cover a wide range of spatial resolution within the context of continuum dynamics. The validity of OFPT was confirmed through comparisons of predicted bubble wake velocity distributions between OFPT and ITM. It was also verified through a simulation of two inline air bubbles and that of air-water bubbly flow in a duct that OFPT can seamlessly connect to ITM.
  • 第1報, 水平方向から鉛直方向に分岐する場合
    太田 淳一, 山本 司, 貝沼 洋介, 高木 邦雄
    2005 年 71 巻 712 号 p. 2892-2899
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    A solid-liquid two-phase mixture (water and aluminum particles) is horizontally led to a T-junction. The particle number densities (number of particles per volume) at the outlets are measured in the inlet concentration of (0.9-16.8) ×10-3%, at the velocity ratio of the outlet to the inlet as the parameter. The diameter of tube in the T-junction is 10 mm, Stokes number ranges with 0.14 to 6.6, and liquid Reynolds number ranges with 9300 to 13000. The relationship between the particle number densities in the two outlets is obtained by a one-dimensional model. We compare the measured particle number density in the branch with the concentration obtained by Nasr-El-Din whose inlet concentration is 3 to 26%. The followings are obtained. The one-dimensional model can express the relationship between the concentrations of the two outlets. The present distribution characteristics of the T-junction show the same tendency as Nasr-El-Din's. However, the gradient of particle number density with respect to velocity ratio for the low concentration at the inlet is greater than that for high concentration data.
  • 高垣 直尚, 小森 悟
    2005 年 71 巻 712 号 p. 2900-2906
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    The effects of rainfall on both mass transfer across the air-water interface and turbulence structure in the interfacial region were investigated through laboratory experiments in a turbulent open-channel flow. The CO2 absorption rate by rain droplets impinging on the free surface and turbulence quantities were measured. The results show that the rainfall enhances the turbulent mixing near the free surface on the liquid side and the CO2 transfer across the air-water interface. The mass transfer coefficient on the liquid side is well correlated by the mean kinetic energy of rain droplets impinging on the unit area of the air-water interface, KEF, and it is proportional to the square root of KEF. The maximum value of the mass transfer coefficient obtained in this study corresponds to that obtained in wind-driven turbulence with wind speed 15 m/s. This suggests that it is of great importance to consider the effects of rainfall on the CO2 exchange rate in a general circulation model for estimating the global warming.
  • 旋回の減衰に伴う角運動量の変化
    畠沢 政保
    2005 年 71 巻 712 号 p. 2907-2913
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    The swirl effects on the angular momentum distribution of turbulent swirling flow in a straight pipe are described. When the swirl strength increases, the axial velocity decreases in the central region and its distribution becomes constant in the annular region of the pipe, except in the boundary layer adjacent to the pipe wall. Tangential velocity induces the formation of a combined vortex similar to the Rankine vortex which is a solid vortex in the central domain and a free vortex in the annular region of the pipe. Although factors that affect flow, such as the contours of the swirling angle, axial and tangential velocities and fluctuation velocity, have been discussed previously by the authors, their analyses have not yet been conducted. The local angular momentum at radius, r, in the pipe is employed in this study. As a result, the local angular momentum downstream does not change in the central region but decreases in the annular region of the pipe. It is suggested that most of the swirl decay in a straight pipe depends on the viscous forces that occur either between fluids or between a fluid and the pipe wall in the annular region of the pipe.
  • 木原 直人, 花崎 秀史, 植田 洋匡, 水矢 亨
    2005 年 71 巻 712 号 p. 2914-2921
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    Characteristics of the airflow over a train of waves moving at a constant speed are investigated using a direct numerical simulation. We simulate the flow for various wave ages (c/u*=0, 4, 8, 10, 12, 16 and 20), where c is the phase speed of the wind wave and u* is the friction velocity on the wave surface. The results show that both the mean flow profiles and the turbulent statistics depend strongly on the wave age. For example, the mean-flow speed in the log layer generally decreases at small wave ages, i.e., when the wave growth rate is positive. Vertical profiles of the flow change significantly at the critical height zc, where the mean flow speed and the wave speed c agree. Then, the wave-induced vertical flux of the horizontal momentum is positive below zc, decreases rapidly near zc, and becomes negative above zc.
  • 榊原 洋子, 遠藤 正樹, 岩本 順二郎
    2005 年 71 巻 712 号 p. 2922-2927
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    A radial jet issuing from a slit nozzle is studied experimentally and numerically in this paper. It is a simple model of the wall jet for an axisymmetric jet when it impinges on a flat plate perpendicularly. The slit nozzle is a spacing between the open ends of two tubes placed face to face with each other. The air is choked at nozzle exit and radial underexpanded jet is formed around the tubes. Both of a front and a side view of the flow field are visualized simultaneously using the shadowgraph method. As the oblique shocks in the jet are formed surrounding the circular tubes, the ring-shaped shocks are visualized in the front view, the cell structure of the jet being in the side view. Oscillation of the flow field with many vortices and a feedback mechanism of density waves around the jet obtained experimentally and numerically are discussed.
  • 遠藤 正樹, 岩本 順二郎
    2005 年 71 巻 712 号 p. 2928-2933
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    If shock wave is discharged from an open pipe end, unsteady jet issues from it and a vortex ring occurs at an edge of pipe end. The vortex ring accelerates downstream and reaches a certain velocity at last. In the vortex ring going downstream, a core of vortex ring roles up a boundary of the unsteady jet so that a rearward-facing shock is formed in the vortex ring. The jet boundary interacts with the shock wave there, and then the weak pressure waves are scattered. The interaction is pointed out to be one of the sources of noise. As one of the examples, there is unsteady jet from an exhaust pipe of a reciprocating internal combustion engine or a reciprocating compressor. In order to clarify the mechanism that the shock-vortex interaction occurs, the unsteady jet from a circular pipe end is visualized by the shadowgraph method and analyzed.
  • 陳 恵青, 鷲尾 誠一, 高橋 智
    2005 年 71 巻 712 号 p. 2934-2940
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    When a liquid flow in a pipe is accelerated or decelerated, a differential pressure is kinetically induced between two separate sections of the liquid column. This fact has been utilized to measure an unsteady flow rate, and that way of measurement is called “Kinetic Differential Pressure (KDP) Method”. In the present paper, the KDP method is modified so as to find oscillatory flow rates, pressures and hydraulic impedances simultaneously at any section in pulsating pipe flows of oil from the pressure data detected at two fixed sections of the pipe. Through being applied to measurements of impedances of a pipe with a closed end and a Helmholtz resonator, the modified KDP method has proved effective enough for pratical use. In actual measurements, it turned out more recommendable from the viewpoint of accuracy to employ differential pressures obtained by electrical subtraction between outputs of the two pressure transducers than to rely upon pressure data alone.
  • 西海 孝夫, 加藤 博司, 原口 崇, 一柳 隆義
    2005 年 71 巻 712 号 p. 2941-2948
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    This paper presents the angular velocity control of a hydraulic motor by adaptive learning using the Neural Network, which is located in the feedback loop. This system features a precise steady performance, and has robustness. In the report, at first, the mathematical model is introduced from the basic equations on a servovalve and hydraulic motor. Based on this model, various measurement results of the static characteristic determine the design parameters that will be needed for the hydraulic servo control design. The open loop dynamic response experimentally reveals that the mathematical model is extremely appropriate. Furthermore, as it is necessary that the better performance will be accomplished, a Neural Network compensator is employed instead of the state feedback one. The experimental results demonstrate the effectiveness on robustness by means of the adaptive learning of Neural Network, even when the disturbances such as the leakage, additional torque, and supply pressure are intensively provided.
  • 梅田 眞三郎, 長谷川 盛三, Wen-Jei YANG
    2005 年 71 巻 712 号 p. 2949-2955
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    A self-induced flip-flop flow phenomenon in diamond-shaped cylinder bundles has been disclosed in previous studies by the authors. The flip-flop flow oscillation promotes fluid mixing and thus contributes to an enhancement in convective heat and mass transfer when the cylinder bundles are used as heat and mass exchanger equipment. An experimental study was performed to disclose the occurrence of flip-flop flows in diamond-shaped cylinder bundles. Velocity and pressure fluctuations in divergent flow region inside diamond-shaped cylinder bundles were measured by LDV and piezometer, respectively. The difference in the oscillations of flip-flop flows and von Karman vortex streets is disclosed quantitatively. The mechanisms that cause the reciprocating bubble migration in network ducts of diamond shaped cylinders are explained.
  • 第1報, 流量計測に対する不確かさ解析
    嶋田 隆司, 土井原 良次, 武田 一英, 寺尾 吉哉, 高本 正樹
    2005 年 71 巻 712 号 p. 2956-2963
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    The uncertainty of a new primary standard for hydrocarbon flow measurements has been evaluated analytically and experimentally in detail in accordance with the “ISO Guide to the expression of uncertainty in measurement”. The expanded uncertainty has been estimated to be 0.03% for volumetric flow rate and 0.02% for mass flow rate (coverage factor : k=2). This evaluation shows that the uncertainty of duration time when liquid is accumulated into the weighing tank is negligible by using the new diverter, and that the dominant sources of combined uncertainty of flow rate are the mass of oil accumulated in the weighing tank and the density of oil flowing through the flowmeter under test. In particular, the uncertainty in the low flow rate at the kerosene test rig using the 10t weighing system is quite larger than those at the other test rigs due to the loss of oil caused by oil mist and vapor discharged from the diverter and the weighing tank. Furthermore, the uncertainties of temperature measurements at the test meter and the density meter have large effect of the combined uncertainty of volumetric flow rate.
  • 佐伯 壮一, 兼田 幹也, 斉藤 俊, 西田 輝夫, 中村 和行
    2005 年 71 巻 712 号 p. 2964-2969
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    This paper presents a novel pH measurement technique for microfluidic devices; “2-Color Laser-induced Fluorescence”. In this technique, an undesirable influence of excitation light distribution can be eliminated by dividing one fluorescence image with the other one taken at the same time. This can simplify measurement procedure in terms of omitting fluorescence intensity normalization at a lot of image locations, and measure a scalar distribution more accurately than 1-color LIF. In this study, the proposed method was applied to neutralization chemical reaction in T-type microchannel. Using Fluorescein and Rhodamine B, the divided value of fluorescence intensities was calibrated with 7 different pH solutions. Spatial intensity error can be reduced to about 80 to 90% as compared with 1-color LIF image. As a result, pH distribution of neutralization reaction between acetic acid and ammonia hydroxide at T-junction was visualized quantitatively at some flow rate conditions.
  • T字形合流管における熱流動特性
    浅野 秀夫, 多田 勝義, 廣田 真史, 中山 浩, 浅野 太一, 平山 俊作
    2005 年 71 巻 712 号 p. 2970-2978
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    In this paper, experimental results are reported on turbulent mixing of hot and cold airflows in a T-junction, which models the HVAC unit used in an automobile air conditioning system. Experiments were conducted keeping Reynolds number and temperature of the main flow at 2.5×104 and 12°C, respectively, and the velocity of the branch flow (60°C) was changed for three velocity ratios of 0.5, 1, and 2. The influence of the channel aspect ratio on the flow characteristics was also investigated. The flow entering the main channel from the branch is separated at the edge of the T-junction and forms a large separation bubble. Longitudinal vortices are formed around this separation bubble, thus the flow field has a complex three-dimensional structure. In spite of such a complex flow field, the mean temperature of the airflow in the mixing layer shows quite uniform distributions in the spanwise direction of the channel. It was also found that the strong turbulence produced around the separation bubble does not work effectively to the thermal mixing of hot and cold airflows.
  • 第2報, 貯湯槽のモデル化とシステムの分析
    横山 良平, 清水 猛, 竹村 和久, 伊東 弘一
    2005 年 71 巻 712 号 p. 2979-2986
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    Heat pumps using CO2 as a natural refrigerant have been developed and are expected to contribute to energy saving in hot water supply. In residential applications, CO2 heat pumps are used in combination with hot water storage tanks. The objective of this series of papers is to analyze the overall performance of a hot water supply system composed of a CO2 heat pump and a hot water storage tank by numerical simulation. In the 2nd report, a simulation model of a hot water storage tank is created and the performance of a hot water supply system is analyzed. The performance calculated is compared with that measured, and the simulation model is validated. The trade-off relationship between the system efficiency and the volume of hot water unused through the operational condition on the inlet water temperature is clarified quantitatively.
  • パラメトリックスタディによる詳細熱設計ならびに実験的評価
    長野 方星, 大西 晃, 長坂 雄次, 森 康彦, 長島 昭
    2005 年 71 巻 712 号 p. 2987-2995
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    This paper describes a new passive thermal control device-a Reversible Thermal Panel (RTP), which changes its function reversibly from a radiator to solar absorber by deploying/stowing the radiator/absorber reversible fin. Parametric studies were conducted and the RTP configuration which satisfies the thermal requirements were determined. The RTP engineering model was fabricated using highly oriented graphite sheets, honeycomb base plate and shape memory alloy. The heat rejection performances and autonomous thermal controllability were evaluated by thermal vacuum tests. The test results show the excellent performances of heat rejection, absorption and autonomous thermal control for the RTP.
  • 単層カーボンナノチューブを用いた予備的測定
    田口 良広, 堀口 幸裕, 小林 三香子, 斎木 敏治, 長坂 雄次
    2005 年 71 巻 712 号 p. 2996-3002
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    It has been suggested in the past decade that nano-scale thermal properties play an important role in a thermal design of nano-devices. In order to measure the thermal conductivity and thermal diffusivity of nano-materials such as single-walled carbon nano-tubes and fullerenes, we have developed a new measurement technique based on near-field optics thermal nanoscopy (NOTN). NOTN targets spatial resolution better than 100 nm (up to 10 nm) which is beyond the diffraction limit of light, and is applicable to measure the thermal properties of nano-scale materials in situ. In NOTN, the sample surface is heated by sinusoidally modulated near-field light, and the temperature change on the sample surface is monitored as a thermoreflectance signal of near-field light. In this paper, to check the validity of developed setup, the distance dependence of near-field light is monitored. Moreover, a thermoreflectance signal of 150 nm-thick Al thin film is detected for nano-scale thermometry. Finally, the applicability of our detection scheme, to measure the thermal properties of nano materials, is discussed through the preliminary measurement for Al thin film and single-walled carbon nano-tube.
  • 谷本 浩一, 笠原 二郎, 鈴田 忠彦, 上田 剛史, 正森 滋郎
    2005 年 71 巻 712 号 p. 3003-3010
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    It is necessary to evaluate the temperature of a valve when a specification of a valve is decided in a branch pipe connected to a main loop with a constant flow. The evaluation methods have been established in the case of the horizontal branch pipe below the main loop, and the method is based on the stable thermal stratification. However, a thermal stratification behavior is unstable in the horizontal branch pipe above the main loop because the cold fluid due to a heat removal in the branch pipe is higher than the hot fluid carried into the branch pipe by a cavity flow. The natural circulation is caused by the temperature and height difference between the main loop and the branch pipe. Since the interaction between the cavity flow and the natural circulation affects the natural circulation, it is not clear whether the developed method is applied to the phenomenon or not. Therefore, the experiments were carried out in order to understand the effect of the cavity flow on the natural circulation. From the results, the behavior of the natural circulation depends on the intersity of the cavity flow. In addition, the applicability of the CFD to the phenomenon under the cavity flow was verified only for the weak cavity flow such as 0.07 m/s of the average fluid velocity in the main loop.
  • 管内連続製氷における閉塞条件の検討
    小山 祐嗣, 寺岡 喜和, 岡田 昌志, 松本 浩二, 川越 哲男
    2005 年 71 巻 712 号 p. 3011-3016
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    A dynamic-type of ice-making cold thermal energy storage system was investigated. Slurry ice was formed continuously by cooling water-silicone oil emulsion with silane-coupler agent in a heat exchanger. Experiments were carried out in order to clarify the conditions for continuous ice formation without choking in the heat exchanger. It was found that the choking occurred when the ice content of the emulsion flowing into the heat exchanger became lager than a critical value or when the oil content of the emulsion became less than a critical value. It was found that the freezing point of the emulsion rose gradually by aeration. Additionally, as the freezing point rose, the range of condition for the continuous ice formation became narrower. The ice formation system was improved as much as possible to avoid the exposure of the emulsion to air. It was confirmed that the improved system could hold a low freezing point.
  • 玉木 伸茂, 清水 正則, 廣安 博之
    2005 年 71 巻 712 号 p. 3017-3024
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    The purpose of this study is to develop a combustion burner for high-viscous liquid fuel such as waste oil, which is able to atomize high-viscous liquid using a little energy and is able to reduce pollutant emissions. The internal mixing twin-fluid atomizer developed in this study mixed waste oil and atomizing air with swirling flow in a mixing chamber. The effects of kinematic viscosity of liquid, geometric shapes and dimensions of the twin-fluid atomizer on spray characteristics were studied. The results indicated that atomization of high-viscous liquid was achieved with a little energy of atomizing air, and the spray with small droplets was obtained. Moreover, the atomizer, which the hole number of atomizer is single hole of N=1, the liquid supplying hole was multi holes of n=6 and the height of the mixing chamber is low of h=2mm, is suitable for atomization of high-viscous liquid and a large amount of liquid.
  • 開路及び閉路小電流域の内部漏洩電流
    許斐 敏明, 川上 淳, 立花 秀晃
    2005 年 71 巻 712 号 p. 3025-3030
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    Over voltages and internal leak current density in PEFC were analyzed by FFT impedance method. Results showed that the conventional coefficient of Butler·Volmer's equation was twice as theoretical one. The coefficient measured by FFT impedance method was corresponding to the theoretical one. Measured internal leak current density in PEFC is 7.5 mA/cm2, and it reduces output voltage from 3 to 13 mV. Sum of the over voltages by the leak current and the known is 20-30%lower than Nernstian theoretical potential. Analysis and improvement of the unknown over voltages such as mixed potential and so on, will make big performance increase in PEFC.
  • 林 明典, 稲毛 真一, 百々 聡, 伊藤 和行, 大塚 雅哉, 唐司 茂樹
    2005 年 71 巻 712 号 p. 3031-3037
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    Turbulent burning velocity under high pressure conditions were estimated. The turbulent burning velocity was measured by the angle of premixed flame. And, the effect of pressure on turbulent scale, which has strong effect on the burning velocity, was evaluated under the unburned condition. Using of the turbulent scale, the experimental turbulent burning velocity was compared with the theoretical model. The theoretical one was in good agreement with experimental one. Further, using of Kovasznay number defined by the turbulent scale, the relation of the turbulent burning velocity and the turbulent flame structure was discussed.
  • 予混合火炎構造を支配する物質量としての反応進行度とその勾配の妥当性
    加藤 敏宏, 林 直樹, 山下 博史, 中村 祐二, 山本 和弘
    2005 年 71 巻 712 号 p. 3038-3045
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    The flame structure of unsteady two-dimensional premixed flame is numerically simulated with elementary reaction mechanism. In order to investigate unsteady behavior, a sinusoidal fluctuation is added to the inlet velocity of methane-air premixed mixture as follows : u0= um {1+A·sin (2πky) · sin (2πft)}. The average velocity um is 1.25-2.00m/s, the amplitude A is fixed to 1.0, the frequency f is 100, 250, 500 Hz, and the wavenumber k is 0.1-0.4mm-1. The Smooke's skeletal mechanism is adopted as the elementary reaction mechanism. The equivalence ratio is fixed to 0.75. The unsteady behavior and flame structure of premixed flame are examined by using the progress variable defined with mass fraction of oxidizer Cq and its gradient (dC/dn) q at flame front. The obtained results are as follows : The total heat release rate, the temperature gradient, the maximum concentration of species are determined by Cq and (dC/dn) q. Consequently, they are the most important descriptors of premixed flame which dominate the flame structure of premixed flame. The unsteady behavior is classified by the flame curvature and the flame propagation direction, and the classified regions are related to Cq and (dC/dn) q.
  • 高橋 陽一, 末永 陽介, 北野 三千雄, 工藤 めぐみ
    2005 年 71 巻 712 号 p. 3046-3052
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    Response of a cylindrical premixed flame to periodic concentration fluctuation was investigated. The flame was formed in a porous cylinder by percolating the mixture uniformly through the cylinder wall. The burner used here was devised so as to fluctuate the mixture concentration (equivalence ratio) only in the radial direction of the flow (vertically to the cylindrical flame surface) without varying the flow field. With this burner the time variations of burning velocity, burnt gas temperature and flame luminosity were measured for the lean methane-air mixture in the range of fluctuation frequency from 3 Hz to 50 Hz, and the results were examined from the viewpoint of flame curvature effects. The results show that the variation width of the burning velocity of the dynamic flame is larger than that of the static flame corresponding to the concentration fluctuation. Burnt gas temperature and flame luminosity also exhibit similar tendencies. The magnification ratio of the variation width depends on the flame curvature and the large flame curvature makes the flame sustainable even for the mixture leaner than the flammability limit of the static flame.
  • 牧野 敦, 柴田 尚弘
    2005 年 71 巻 712 号 p. 3053-3059
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    Relevant to Self-propagating High-temperature Synthesis (SHS) process for Ti-Al system, burning velocity and range of flammability are examined theoretically. Use has been made of the heterogeneous theory for the SHS flame propagation, presented in the literature. It is found that effects of particle size, mixture ratio, degree of dilution, and initial temperature on the burning velocity and/or the range of flammability are the same as those for other representative systems. It has been confirmed that even for the Ti-Al system, a parameter defined as a product of the burning velocity and the particle size can be useful in correlating experimental results for the flame propagation. It has also been confirmed that a parameter defined as the square of particle size divided by the compact diameter can be useful in correlating experimental results for the flame extinction. In addition, it has been demonstrated that a fair degree of agreement exists between theoretical results and experimental data in the literature, as far as the trend and approximate magnitude are concerned.
  • 馬場 雄也, 赤松 史光
    2005 年 71 巻 712 号 p. 3060-3067
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    Numerical simulation of spray combustion in homogeneous isotropic turbulence was performed under realistic time and spatial scales. The simulation was realized by newly developed numerical methods which had a lot of advantage in simulation of unstable subjects. The method was preliminary examined in several situations to prove the method was able to be applied for direct numerical simulation. In non-combusting cases, we found liquid droplet followed typical “preferential effect” and number density fields of droplets showed homogeneous and heterogeneous distribution according to Stokes number. The effect appeared in both small and large structural turbulences. In combusting cases, flame formation also varied by the Stokes number in turbulence where large structure existed in flow field. On the other hand, in turbulence with small structure, the regimes became homogeneous regardless of the Stokes number. We defined “local group combustion number” which was different from existing one, however it was convenient to understand the combustion regime variation and it could explain how combustion was proceeded.
  • 田川 正人, 桂川 貴弥, 深津 光広, 太田 安彦
    2005 年 71 巻 712 号 p. 3068-3075
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    Spatio-temporal structures of the thermal field of a non-premixed turbulent flame formed in a curved rectangular duct and the relevant unburned-fuel emission characteristics were investigated experimentally. The combustion field was dominated by a pressure gradient in the radial direction of the duct curvature, which caused strong gradient diffusion in turbulent heat transfer on the inner-wall side of the flame and, conversely, counter-gradient heat transfer on the outer-wall side. Two-point correlation measurement of temperature fields revealed that, in the strong gradient-diffusion region, a spatial thermal pattern generated by turbulent mixing of high-and low-temperature fluid parcels was advected downstream with little diffusion. In contrast, the pattern was attenuated and rapidly diffused in the counter-gradient diffusion region. The behaviors of the unburned-fuel emission were also dominated by the pressure gradient and showed quite different characteristics between the inner- and outer-wall regions of the curved duct. In the downstream combustion field, the volume concentration of the unburned fuel remained much higher on the outer-wall side of the flame than the inner-wall side. This characteristic conforms closely to the turbulence structures of the thermal field.
  • 内田 浩二, 齊藤 弘順, 立石 又二
    2005 年 71 巻 712 号 p. 3076-3081
    発行日: 2005/12/25
    公開日: 2011/03/03
    ジャーナル フリー
    This paper revealed the reason of poor self-ignition quality of alcohol spray from the viewpoint of mixture formation considering fuel properties. Ignition characteristics of Ethanol and Diethyl Ether blended fuels were experimentally investigated with changing their blend ratio in order to clear the effects of fuel's physical and thermal properties on ignition. Experimental results and prediction of mixture formation of blended fuels showed that stoichiometric air/fuel ratio (Lth) and latent heat for vaporization (γ) were main parameters on ignition. Alcohol spray becomes lean situation faster than conventional diesel fuel such as Gas oil due to their smaller Lth. On the contrary, temperature rise of alcohol spray up to ignition point is slower than Gas oil caused by their larger γ.This causes poor self-ignition quality of alcohol spray. Namely, it is difficult for an alcohol spray to be a mixture of suitable mixing ratio and temperature for self-ignition at the same time and place.
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