日本機械学会論文集 B編
Online ISSN : 1884-8346
Print ISSN : 0387-5016
60 巻, 570 号
選択された号の論文の54件中1~50を表示しています
  • 田中 敏雄, 肥田 久史, 田中 栄一, 小里 泰章
    1994 年 60 巻 570 号 p. 351-356
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    An experimental study has been made on deflection and reattachment of a radial turbulent jet (main jet) discharged from a cylindrical nozzle onto an adjacent disk plate in the presence of a lateral control flow from an annular nozzle. Three parameters : the nozzle width of the control flow, the control flow rate and the nozzle distance between two nozzles, which describe the control flow, can be combined in one parameter, namely a control momentum flux. The relations between the deflection angle of the main jet, the reattachment position on the side wall and the control momentum flux for each step height were obtained. Also, the deflected and reattached jet flow properties for various experimental conditions were investigated.
  • 中川 順達, 竹中 俊夫
    1994 年 60 巻 570 号 p. 357-365
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    A water hammer in collapse of a cooling cavity is modeled and formulated by making well-connections between the water hammer in liquid pipelines and the thermodynamics in the cavity, as a combination of the rigid column theory with the piston-cylinder system and in consideration of the gas in the cavity as moist air. Transient responses of the variables are calculated numerically, including the equation of energy and the term of heat transfer, with a correction for the area of heat transfer to the cavity shape and the identification of the coefficient of heat transfer on the basis of numerical stability. The high-damping waveforms of pressure fluctuation recorded in the experiment, which are not reproducible in the case of using only pipe friction and valve loss, are simulated adequately. Some physical interpretations for the numerical solutions are given and the dependency of solutions on the initial air concentration in the cavity is discussed.
  • 飯田 誠一, 小河原 加久治
    1994 年 60 巻 570 号 p. 366-372
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    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 held to unity, since the aim of this paper is to obtain a realistic model compared with the Lorenz model but still maintaining comparable simplicity. Examination of bifurcation structures of the present model obtained by increasing Rayleigh number as a parameter shows that there is a definite parameter region 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 newly found only in the case of (no-slip/no-slip) conditions.
  • 福田 和磨, 菱田 公一, 前田 昌信
    1994 年 60 巻 570 号 p. 373-380
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    The transition of an initially laminar two-phase confined jet has been studied experimentally and analytically. Time series velocity data of both phases were measured by LDV with particle size discrimination. The spectral evolution was discussed to clarify the transition mechanism, Two-phase jet properties were also analyzed using a new mathematical model based on the linear stability theory wherein the interaction force by solid particle motions was taken in account. The resulting eigenvalue problem of the modified Orr-Sommerfeld equation was solved numerically using expansions of Chebyshev polynomials and the modified LR matrix eigenvalue algorithm. The experimental results showed the energy transferred from the mean flow to the disturbance was suppressed in the two-phase flow and as a result, the transition to turbulence was delayed. The numerical analysis indicated that the temporal growth rate of disturbances decreased, and the stability of the flow was enhanced with increasing particle loading ratio.
  • 河原 源太, 鮎川 恭三, 越智 順治, 渡部 哲也
    1994 年 60 巻 570 号 p. 381-387
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    Streaky structures have been studied in a fully developed turbulent square-duct flow by using combined dye flow visualization-LDV velocity measurement techniques. Velocity fluctuations were characterized both by topological properties of low-speed streaks, such as coalescing and branching, and by the transverse location λ of the visually identified low-speed streaks. Near-wall coherent structures are discussed for each topological type of low-speed streak in terms of the dependence of the most probable values of the velocity fluctuations on λ. It is shown that without coalescing and branching, a spanwise symmetric pair of counter-rotating quasi-streamwise vortices is, statistically speaking, associated with one low-speed streak. However, upstream of the coalescing point and downstream of the branching point of low-speed streaks, an asymmetric single quasi-streamwise vortex may be associated with one low-speed streak.
  • 二宮 尚, 笠木 伸英
    1994 年 60 巻 570 号 p. 388-394
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    In the previous study an axisymmetric free jet was measured with the aid of a three-dimensional particle tracking velocimeter, and a database of the turbulent statistics was constructed. In this study, by using the database, the budgets of the turbulent kinetic energy and the Reynolds normal and shear stresses are calculated. The dissipation term of the turbulent kinetic energy is estimated as a residual of its budget neglecting the pressure diffusion term. The pressure terms in the budgets of the Reynolds stresses are also obtained as closing terms of each budget equation in which the dissipation term is calculated with an assumption of local isotropy. The mechanism of energy exchange among the stresses is revealed, i.e., the mean flow energy is first fed to the streamwise normal stress through the Reynolds shear stress and then redistributed to the radial and azimuthal normal stresses via the pressure term. The production terms in the budgets of the radial and azimuthal stresses are found to be negative around the flow axis.
  • 粥川 尚之
    1994 年 60 巻 570 号 p. 395-400
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    Turbulent magnetohydrodynamical correlations between the conductivity and the electric field σ'E' and those between the current density and the electric field J'·E' in the mean MHD governing equations were evaluated using simulated fluctuation data of the velocity and temperature. The instantaneous electrical equations were solved in the cross section of a Faraday-type MHD channel driven by a combustion plasma in chemical equilibrium. It was clarified that both σ'E'y and J'yE'y are large values in the vicinity of electrodes. Therefore, they might play an important role in the mean boundary layer phenomena and arc behavior. However, they hardly affect the gross output characteristics of the generator, because the mean electrical conductivity is enhanced by the temperature turbulence. We also showed that the mean correlations σ'E'x, σ'E'z, J'xE'x and J'zE'z are negligiblly small.
  • 三宅 裕, 中島 正弘
    1994 年 60 巻 570 号 p. 401-408
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    Measurements of a turbulent flow in a wavy channel of high aspect ratio, one wall being sinusoidal and the other flat, are described in this report. Attention is focused on the flow in the near field of the flat wall. Mean flow and major statistical quantities of turbulence such as turbulence intensity. Reynolds stresses and skewness factors are included. The near-wall region was influenced largely by periodical pressure variation and the viscous sublayer was thickened. In the mean time, the core region was little affected and the velocity defect law was little modified. As for the turbulence property, it was revealed that acceleration of flow vitalized the turbulence in the layer very close to the wall and deceleration attenuated it. These disturbances were reflected quickly in the turbulence intensity and turbulent energy production, but slowly in the shear stress. However, it turned out that the effect of the pressure gradient on the turbulence behavior could be explained in terms of flow structure.
  • 定岡 紀行, 梅垣 菊男
    1994 年 60 巻 570 号 p. 409-416
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    A new approach to simulate flow-induced vibration is introduced. A fully coupled analysis of fluid-structure interaction has been realized in a turbulent flow field using the following calculational steps : a) solving turbulent flow by a direct simulation method where the ALE (arbitrary Lagrangian-Eulerian)-type approximation is adopted to take account of structural displacements ; b) estimating fluid force on structures by integrating fluid pressure and shear stress ; c) calculating dynamic response of structures and determining the amount of displacement ; d) re-generating curvilinear grids for new geometry using the boundary-fitted coordinate transformation method. Vortex-induced vibration of a circular cylinder in a cross flow were successfully simulated and the synchronization phenomena between Karman-vortices and cylinder vibrations were clearly observed.
  • 西田 正浩, 吉村 康輔, 谷下 一夫
    1994 年 60 巻 570 号 p. 417-424
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    Axial gas transport has been investigated experimentally in an oscillatory flow through a single symmetrical bifurcating tube with lung-like geometry. The dispersion coefficients were determined by measuring the solute gas which was pulse-injected at the divider section, and the propriety of the method of measurement was evaluated considering the flow states which were measured using a laser Doppler velocimeter. As a result, the axial dispersion coefficient in a bifurcating tube slightly increased compared with the laminar solution in a straight tube.
  • 黒川 淳一, 高城 邦彦, 紺野 大介, 相吉沢 俊一
    1994 年 60 巻 570 号 p. 425-431
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    The optimum dimensions of spiral-grooved thrust bearings are determined for both incompressible and compressible fluids, together with the relationships between the optimum dimensions and the steady-state flow characteristics. The Reynolds equation and the modified Reynolds equation are numerically solved by the finite-element method, taking into consideration the wall slip condition. The calculated results reveal that the through-flow rate takes the maximum at the optimum dimensions, and that the optimum spiral angle is larger and the optimum groove depth is smaller in incompressible fluid than in compressible fluid. It is also revealed that the inclination of the bearing plate causes little change in the bearing load capacity in spite of considerable nonaxisymmetricity of pressure distribution.
  • 清水 昌幸, 木谷 勝, 望月 修, 井門 康司
    1994 年 60 巻 570 号 p. 432-437
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    The leading-edge separation bubble of a blunt circular cylinder aligned with the main flow was forced by bimodal disturbances at Reynolds numbers of 0.69×105 and 1.38×105. The bimodal disturbances consisted of two sinusoidal components with different frequencies : one has the frequency F at which the minimal reattachment length was achieved by the single-frequency forcing, and the other has subharmonics or higher harmonics of this frequency. The reattachment length was found to most significantly depend on the phase difference between the two sinusoidal components for a particular combination of the frequencies F and 2F.
  • 古口 日出男, 関根 健生, 矢田 敏夫
    1994 年 60 巻 570 号 p. 438-445
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    When we fill the narrow gap between two parallel plates with a viscous fluid, the meniscus of the free surface forms a concave shape due to capillary action. Air enters the gap with the movement of the viscous fluid when the gap between the two plates is increased at a certain speed. In this paper, the appearance of a moving meniscus is simulated by the boundary element method for two situations : two-dimensional flow and axisymmetric flow. First, the solutions obtained as fundamental solutions satisfying the Stokes approximation equation were quantitatively compared with experimental results with respect to the tip of the moving meniscus. Second, a new fundamental solution for the axisymmetric boundary element method was used for the direct evaluation of a singular integral. Numerical results showed a good agreement with experimental ones.
  • 祖山 均, 大山 信, 阿部 淳平, 砂山 良彦, 山部 正博, 大場 利三郎
    1994 年 60 巻 570 号 p. 446-451
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    In order to reduce the drag of the hydraulic elements, we attempt numerical simulations of a typical hydrofoil using the QUICK method because the computational fluid dynamics are very useful in precisely simulating the details of the local flow characteristics concerning the vorticity and the flow separation around a hydrofoil. In our previous paper, our computational results agree well with the experiments for the power spectra of the lift-and-drag fluctuation of the hydrofoils, as well as the time-averaged values of the lift and the drag. The flow characteristics, therefore, are investigated around the hydrofoil in steady inflow, in particular the characteristic of fluctuating vortex shedding, which concerns the leading-edge-and trailing-edge-shape of the hydrofoil, since these shapes are associated with the separation and are very important factors of the drag and lift. The behavior of the relation between the fluctuating vortex in the separation bubble and the vortex shedding from trailing edge is clarified.
  • 門田 茂, 川口 清司, 鈴木 昌彦, 松井 数馬, 菊山 功嗣
    1994 年 60 巻 570 号 p. 452-457
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    In order to design a low-noise multiblade fan, there have been earnest demands for detailed analysis of the flow pattern between the fan blades. However, the flow between the fan blades is unsteady and three-dimensional in nature, thus it is too complex to analyze theoretically. In the present study, a spark tracing method was employed to visualize the detailed three-dimensional flow between fan blades at a high speed. A Petchan prism and drum camera were used to convert the rotational images observed from the axial and radial directions into static ones, enabling visualization of the three-dimensional flow between the blades for a desired blade cross section.
  • 川口 清司, 門田 茂, 鈴木 昌彦, 松井 数馬, 菊山 功嗣
    1994 年 60 巻 570 号 p. 458-463
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    Multiblade fans have been widely used for car air-conditioning systems because of their high flow rates and high pressure as compared to their size. These fans, however, cause a comparatively high noise level due to their high rotational speed and the complex flow pattern inside the blade passages. This paper concerns the pressure fluctuation on the blade surfaces and the flow pattern inside a multiblade fan for car air-conditioning systems. As uneven flow distribution between shroud and hub was found to cause a large pressure fluctuation on the blade surfaces, resulting in the generation of high-level turbulent noise.
  • 須藤 浩三, 高見 敏弘
    1994 年 60 巻 570 号 p. 464-472
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    Three components of mean velocities and wall static pressure have been measured in swirling flows through a circular-sectioned 90°bend with a curvature radius ratio of 4.0 under the Reynolds number of 60000. The complicated correlation between internal flow behavior and wall pressure distribution has been clarified from a region of upstream straight pipe through a bend to a down-stream one. Also, the shift of axial flow, the movement of the swirl center and the streamwise decay of swirl intensity have been investigated.
  • 楊 基明, 小野寺 収, 高山 和喜
    1994 年 60 巻 570 号 p. 473-478
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    In order to generate weak shock waves with repeatability of better than 99%, a shock tube was constructed which, instead of rupturing conventional diaphragms, utilizes 0.5 mm to 1.0 mm thick rubber membrane to separate the driver and driven gases. Sudden leakage of the high-pressure gas which bulged the rubber membrane subsequently drove a weak shock wave into the low-pressure channel within a relatively short formation length. The rubber membrane was operated within its elastic limit and moved very quickly, giving good repeatability. With identical initial conditions for a series of experiments, the scatter of shock Mach number was found to be at most ±0.25% for shock Mach number ranging from Ms=1.02 to 1.55 throughout more than 100 runs.
  • 平塚 和人, 浦井 隆宏
    1994 年 60 巻 570 号 p. 479-483
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    At present, nozzle-flapper-type servovalves are capable of being used for a wide range of flow rate control and quick response control systems for many fluid power applications. However, the users must always keep contamination levels low, due to first-stage flow leakage which has a detrimental effect upon these valves. The DDV (direct-drive servovalve) utilizing a GMM (giant magnetostrictive material) has no first-stage leakage. This paper describes the FEM (finite-element method) analysis and experimental results of a magnetic bias of the GMM, using permanent magnets to produce linear operation under an AC field. Furthermore, it is shown that the DDV exhibits high performance as a new servovalve.
  • 横田 眞一, 杣田 久志, 山口 博嗣
    1994 年 60 巻 570 号 p. 484-490
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    The pulsation of flow rate through pipelines caused by hydraulic components (e.g., piston pumps) is one of the most common sources of vibration and noise in hydraulic control systems, particularly in pipelines between pumps and actuators. Among the flow rate pulsations caused by hydraulic piston pumps, which is 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 the passive elements. This paper deals with an active accumulator which is proposed, newly fabricated and is driven directly by multilayered PZT devices to reduce the flow rate pulsation produced by hydraulic elements in the high-frequency region. The active accumulator has the potential to actively reduce and cancel the variation of high-frequency pulsating flow rate (from 500 Hz to 1 kHz frequency) with hydraulic piston pumps by producing and using the inverse-phase flow by making use of fast-acting piezo device actuators. An active control method is proposed to simultaneously reduce several targeted frequency components of the pulsation without influencing on the other components. The validity and the effectiveness of the method are ascertained experimentally.
  • 橋本 成広, 冨永 誠一, 吉田 実, 佐々木 康順
    1994 年 60 巻 570 号 p. 491-495
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    A new membrane oxygenator combined with a reciprocating pump was designed to shorten the extracorporeal circulation circuit and to increase the efficiency of oxygenation. At a polycarbonate cylinder, 1700 silicone tubes were bundled and packed among elastic silicone filler. In both inflow and outflow sides of the cylinder, ball valves were equipped. The total available area of the membrane was 8.8×10-2 m2. The membrane was pneumatically driven with a reciprocating pump in performance tests, in which 100% oxygen circulated in the gas side. The mock test shows that the partial pressure of oxygen increases from 1.57×104 Pa at the inlet to 4.72× 104 Pa at the outlet of the oxygenator when 2.0×10-7 m3s-1 saline solution is pumped. The performance has been maintained in animal tests.
  • 小原 拓, 相原 利雄
    1994 年 60 巻 570 号 p. 496-503
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    A molecular dynamics (MD) study was performed on water over a wide range of temperature and density. The vapor-liquid coexistence region and near-critical region were intensively studied. The Carravetta-Clementi (CC) potential function was applied, and simulation for a system of 256 molecules was performed for 97 state points. Dependence of cluster size and its probability distribution on temperature and density were analyzed in detail.
  • 松永 直樹, 堀 守雄, 長島 昭
    1994 年 60 巻 570 号 p. 504-507
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    The mutual diffusion coefficients of CFC12, HFC134a, CFC113, CFC114 and CFC115 into air have been measured at 0-180°C and at atmospheric pressure by the Taylor method. The experimental uncertainty was estimated to be ±2%. The present results can be represented by the following equations : CFC12-air, D=4.77×10-10 T1.75 ; HFC134a-air, D=5.04×10-10 T1.75 ; CFC113-air, D=2.75×10-10 T1.80 ; CFC114-air, D=3.97×10-10 T1.75 ; CFC115-air, D=4.03×10-10 T1.76, where D is the mutual diffusion coefficient in m2/s and T is the temperature in K.
  • 鶴田 隆治, 加藤 裕二, 安信 強, 増岡 隆士
    1994 年 60 巻 570 号 p. 508-514
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    The purpose of the study is to obtain the experimental data on condensation coefficient for a future molecular-scale clarification of the mechanism of vapor-liquid phase transformation. Condensation coefficients of ethylene glycol and water were investigated by the dropwise condensation method based on the fact that the heat-transfer coefficient depends on an interfacial heat-transfer coefficient. Assuming the value of condensation coefficient, the heat-transfer coefficient can be calculated for the measured drop-size distribution. It should coincide with the actually measured heat-transfer coefficient, so that the condensation coefficient can be determined. To improve measurement accuracy, the effects of constriction resistance and of Knudsen number on the heat-transfer coefficient are considered. It is concluded that the condensation coefficients are 0.17∼0.45 for ethylene glycol at pressures between 0.24 and 1.57 kPa and 0.35∼0.7 for water between 1 and 3.5 kPa.
  • 齋藤 武雄, 中村 慎, 五味 達彦
    1994 年 60 巻 570 号 p. 515-522
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    In this paper, a super time-saving method (Time-space method : TSM) for general transient flow and heat transfer problems was proposed. In the proposed TSM, the timewise coordinate is incorporated into one of the spatial coordinates, thereby transforming usual transient 2-D(or 3-D)problems into steady 3-D(or 4-D) spatial problems. The initial and future equilibrium conditions are treated as the boundary conditions. The TSM has an outstanding feature that it can eliminate the so-called numerical instability since time integration is not necessary, which has been the biggest problem in the principal numerical methodologies in the past. Namely, no error propagation in the timewise direction occurrs for the TSM. The TSM is applicable to almost all the transient heat transfer and flow problems including 3-dimensional freezing/melting, global warming, urban warming, large scale atmospheric and ocean circulations. The TSM will be also effective for other problems in the field of solid mechanics and so on. The computer running time will be drastically reduced to only 1/100 th∼1/1000 th of the existing schemes for 2-D or 3-D problems. The sample calculations were presented for a two-dimensional melting problem in a square cavity and the validity of the present method was examined.
  • 佐々木 世治, 増田 英俊, 日向野 三雄, 佐々木 博志
    1994 年 60 巻 570 号 p. 523-529
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    The specific heat c and total hemispherical emissivity εh of iron and constantan have been measured using the simultaneous-measurement method proposed in our previous report to verify the accuracy in the measurement. Cylindrical specimens, whose geometrical shape is presumed to be more appropriate than those in the previous report, are used as the compound specimens necessary for the method. To obtain more accurate results, an expression for the temperature versus time curve has been developed ; this expression is highly accurate over the entire temperature range. For iron, the measured c- and εh-values are compared with c-values recommended in CINDAS Data Series and with εh-values previously measured by H. Masuda and M. Higano, respectively. For constantan, empirical relations between c and T (temperature) and εh and T are obtained. Errors in the present results are analyzed and the total errors in the results are estimated.
  • 牧野 俊郎, 蔵田 秀敏
    1994 年 60 巻 570 号 p. 530-536
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    For heat transfer problems, radiation scattering characteristics of particles of various sizes should be investigated. A significant percentage of such particles is larger than the wavelength of the radiation considered, and have micro-geometrical structures on the surfaces. The scattering characteristics can be affected strongly by the surface structure. This paper presents a new technique for modelling a flake-type metal particle with a rough surface, which has a three-dimensional self-similar micro-structure. We describe the scattering by the particle on the basis of an electromagnetic wave theory. The behavior is characterized by three factors : wavelength of radiation, size of the particle and size of micro-structure of the particle surface. It is shown that the scattering characteristics change from the particle scattering-type to the surface scattering-type with an increase in the particle size. It is emphasized that the size parameter range, in which the conventional theories of particle scattering are directly applicable, is restricted.
  • 遠藤 哲也, 長谷川 英治
    1994 年 60 巻 570 号 p. 537-544
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    The problem of close-contact melting of a cylindrical solid body of a phase-change material is studied analytically. Relative orders of magnitude for various terms are examined using the dimensionless governing equation, taking into account the temperature distribution in the cylindrical heated body. It is found that the unsteady terms can be neglected. The governing equation approximated is solved using a Fourier series. The relationship between the squeezing force due to the weight of the phase-change material and the melting velocity is determined as a function of the aspect ratio of the heated body. The critical condition above which a steady melting phenomenon exists is shown in the plane of aspect ratio and dimensionless applied temperature difference. If the aspect ratio is very small, this relationship tends to that derived by Moallemi in which the temperature in the heated body is assumed to be constant. In the case that the aspect ratio is comparatively small, its effect on the melting velocity is very strong. Convection in the melting fluid layer makes the range of steady melting narrow.
  • 小泉 安郎, 吉成 考正, 植田 辰洋, 松尾 輝之, 宮下 徹
    1994 年 60 巻 570 号 p. 545-551
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    Boiling heat transfer experiments were conducted to examine dry-out phenomena in a two-phase natural circulation system of R-113. This work followed closed two-phase thermosiphon experiments and was performed with the same heating sections. The dry-out heat fluxes were much higher than those of the closed thermosiphons. The results showed that the dry-out heat flux rose as the circulation flow rate increased, and was little affected by the heating surface configuration. Dry-out was observed near the exit end of the heating section under an annular flow state. The relationship between the dry-out heat flux and the liquid film flow rate was analyzed and a correlation to predict the dry-out heat flux was proposed based upon the present results and data obtained using a forced upflow boiling system.
  • 世古口 言彦, 古川 徹
    1994 年 60 巻 570 号 p. 552-559
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    Experimental data are presented on the liquid lump velocities in vertical upward gas-liquid two-phase flow. The liquids used in this experiment are water and glycerol solutions, and the kinematic viscosity of these liquids ranges from 1.0×10-6 to 15.5×10-6 m2/s. Flow regimes concerned herein cover plug flow, huge wave flow and annular flow. Velocities of liquid lumps, such as liquid slugs, huge waves, disturbance waves or ephemeral large waves, are determined using two sets of signals of time-varying cross-sectional mean liquid holdups which are electrically detected at two axially separated locations in the test tube. It is first described, from the observations of liquid holdup signals, that the liquid viscosity affects the formation of liquid lumps or the appearance frequency of the same kind of liquid lump under the same gas and liquid flow rates. Next, the mean values of liquid lump velocity and their standard deviations are discussed with attention paid to the effect of liquid viscosity.
  • 小泉 博義, 細川 巖
    1994 年 60 巻 570 号 p. 560-565
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    This research aims at controlling the convective flow of a horizontal rectangular duct heated from below by properly setting the sidewall temperature profile, to provide a uniform spatial thickness distribution of the film deposited in a thermal chemical vapor deposition (CVD) reactor. The experiment is performed using the naphthalene sublimation technique, which deals with the inverse phenomenon to deposition, at a Rayleigh number of about 3.4×105 and Reynolds numbers below 220. In the case of an unsteady flow with time-averaged horizontally uniform temperature, the time-averaged mass transfer rate on the bottom wall becomes almost uniform both in the spanwise and streamwise directions.
  • 木村 文義, 北村 健三
    1994 年 60 巻 570 号 p. 566-573
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    The natural convection over an upward-facing horizontal plate was investigated experimentally. Special interest was directed at high-Rayleigh-number flow ranging up to Ra*=1015. Test plates of 850 mm and 1500 mm width were adopted to attain such high Rayleigh numbers and they were heated with uniform heat fluxes. Water was used as the working fluid. The fluid flow over the plate and the surface temperatures of the plate were visualized with dye and liquid crystal thermometry, respectively. Local heat-transfer coefficients of the plate were also measured. The result shows that the following four regions appear over the plate at the distance x from the plate edge : 1) the laminar boundary layer region, 2) the streaky, transitional flow region, 3) the turbulent region and 4)impinging flow region. It is found that the second region covers a considerable portion of the plate and that the local heat-transfer coefficients there decrease monotonously with x. Thus, the overall heat-transfer coefficient of the plate still depends on the width of the plate even for the highest Rayleigh numbers.
  • 許 正憲, 加藤 豊文, 鎌田 佳伸, 柏木 孝夫
    1994 年 60 巻 570 号 p. 574-581
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    In the previous paper, it was clarified that a cell model theory is sufficiently effective for the derivation of the drag coefficient in slow flow through porous materials. In this paper, this cell model theory is applied to the heat flow problem, that is, the thermal conductivity of composite foam is determined. The theoretical results are compared with the experimental ones of syntactic foam and neoprene foam. The cell model theory is also applied to the prediction of the temperature changes inside a closed container covered with the neoprene foam, under high hydrostatic pressure. It is confirmed that the cell model is appropriate for this apprication.
  • 一宮 浩市, 片山 將希, 鈴木 祐二
    1994 年 60 巻 570 号 p. 582-586
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    A contraction fin, which plays the role of an extended surface, the acceleration effect and the wall jet, is proposed in the present study. The local heat transfer was examined experimentally on a heated surface with and without fins. The effects of the fins depend on contraction angle and the ratio of fin occupation across the section. Thermal performance of this fin was compared with those of other fins. Flow visualization was also performed for corresponding to the local heat transfer, by the smoke wire method.
  • 北村 健三, 梅田 秀樹
    1994 年 60 巻 570 号 p. 587-593
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    Heat transfer results were presented for combined forced and natural convection around a heated cylinder placed in a cross-flow of water. Local heat transfer coefficients were measured in the range of Reynolds and modified Rayleigh numbers as 40<Red<1600, 3.0×106<Rad<2×108. The result demonstrates that the heat transfer rates increase on the rear side, and decrease on the front side of the cylinder with an increase in wall heat flux. The average Nusselt numbers for the combined convection become 20% higher than those estimated from the pure forced or natural convection. The enhancement and the retardation of the heat transfer rates are explained in terms of the local variation of the lower separation point due to buoyancy force. Furthermore, the average Nusselt numbers of the combined convection correlate well with the parameter Gγd/NudRed2, and the combined convection region corresponds to the value of this parameter of 0.1<Gγd/NudRed2<20.
  • 佐藤 英明, 三長 崇, 田川 正人, 長野 靖尚
    1994 年 60 巻 570 号 p. 594-602
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    Turbulent structures in the outer intermittent region of a thermal boundary layer were experimentally investigated. To distinguish accurately two unique thermal states related to the inside or the outside of the thermal boundary layer, we have modified a previous method by simultaneous use of the instantaneous temperature and the time derivative of temperature fluctuation. The theoretical probability density function (p.d.f.) of an intermittent turbulent quantity, e.g., t and ∂t/∂x, has been obtained from the intermittency-factor-weighted sum of two p.d.f.s inside and outside the thermal boundary layer. The distributions of the p.d.f.s and statistical quantities remain similar in the thermal entrance region. The conditionally-sampled weighted p.d.f. of the wall-normal turbulent heat flux and the wavelet transform of velocity and temperature fluctuations clearly show that ejection-type fluid motion dominates the heat transport or thermal-field entrainment in the outer region of a thermal boundary layer.
  • 角口 勝彦, 深野 徹, 恵美 洋一
    1994 年 60 巻 570 号 p. 603-608
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    A heat pipe with a working fluid of binary mixture is a more advantageous heat transfer device than a gas-loaded variable-conductance heat pipe controlling the temperature of the electric devices which is important in the recent industrial field. In the present study heat transfer characteristics of a closed two-phase thermosyphon, a gravity-assisted wickless heat pipe, was experimentally and analytically investigated. The working fluid was the mixture of ethanol and water. The axial temperature distribution at the heating wall obtained experimentally was very different from that in the case of a one-component (pure) working fluid. This is due to the axial distribution of the concentration of ethanol (the more volatile component). In order to estimate these concentration and temperature distributions, an analytical model was introduced, in which we took the vapor-liquid phase equilibrium of the binary mixture and the mass conservation of ethanol into consideration. The calculated results agreed well with the experimental data.
  • 熊谷 哲, 佐野 佳洋, 鎌田 長幸, 鈴木 伸寿, 久保 良
    1994 年 60 巻 570 号 p. 609-613
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    Most of the studies of boiling heat transfer to an impinged jet have paid attention only to the area near the stagnation region. However, in the case of cooling a massive body by a jet, heat transfer outside the stagnation region and temperature profile inside the body are important, as well. In this paper, transient boiling heat transfer rate to a two dimensional impinged water jet was measured at each point on the whole surface of a 20×150 mm rectangle, during cooling from about 400°C to 100°C. Local surface temperature fell rapidly when the temperature at that point reached the temperature corresponding to its high heat flux region of transition boiling. The rapid cooling line on the surface progressed from the impinging region toward the outer ends of the surface, in accordance with the progress of boiling peak heat flux line. Temperature profiles inside the body were also calculated at respective times with the measured transient surface heat flux distribution as the boundary condition. Cooling rate was very sensitive to the jet impinging velocity.
  • 内山 篤, 山本 雅洋, 志沢 高朗, 本阿弥 眞治
    1994 年 60 巻 570 号 p. 614-619
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    The present paper describes the behavior of the cooling jet on the flat surface in the lateral injection in film-cooling. Simultaneous velocity and temperature measurements were made by the double-wire probe. The test surface was also covered with an encapsulated temperature-sensitive liquid crystal. The surface temperature distributions were obtained by the image-processing system of the liquid crystal. The tests were conducted at three mass flux ratios. The laterally injected jet has an asymmetric structure with a large scale of vortex motion on one side caused by the interaction with the primary stream. Asymmetry is promoted with increase of the mass flux ratio, resulting in low film-cooling effectiveness.
  • 新 隆之, 畑田 敏夫, 大黒 崇弘
    1994 年 60 巻 570 号 p. 620-626
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    A high-performance air cooling system unifying the heated plates temperature distribution is investigated. The plates are arranged in series and cooled by serial air flow. As a result of the investigations, fins with projections and a multiflow air duct system have been developed by the authors. The fins have inclined rows of minute projections on the surface and can improve the cooling performance. The multiflow air duct system can promote unification of the plate temperature distribution bypassing fresh, low-temperature air onto the lower plate.
  • 西尾 茂文, 張 〓民
    1994 年 60 巻 570 号 p. 627-633
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    In the present paper, the optimum conditions are investigated for development of the oscillation-controlled heat transport tube (the so-called dream pipe). First, it is shown that the effective thermal diffusivity reaches a maximum at the tube radius under fixed frequency and amplitude conditions. A correlation equation between the tube radius and frequency for the optimum condition is developed. The relationship between the tube radius and frequency for the optimum condition gives a transition frequency on the frequency characteristic curve of the effective thermal diffusivity for a fixed tube radius. Next, a concept of heat transport efficiency accounting for oscillation power is presented, and it is shown that the efficiency also reaches a maximum at the optimum condition for effective thermal diffusivity.
  • 海野 紘治
    1994 年 60 巻 570 号 p. 634-640
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    A method of predicting the relationship between the similarity function and the heat release fraction has been proposed and applied to the solidification process of an annulus-type storage unit. The concept of this method has been derived from analysis under the quasi-steady approximation. The prediction should be performed in two separate stages of the solidification process individually. In the first stage-prior to completion of the freezing of phase change material-the similarity function vs. frozen fraction curve can be transformed in accordance with the fact that the heat release fraction is approximately proportional to the frozen fraction. In the second stage after the completion of freezing, where all heat is released as sensible heat, the heat flow rate maintains a linear relation with the heat release fraction. Thus, the similarity function defined in terms of the heat flow rate can be directly correlated with the heat release fraction. The results predicted are in good agreement with numerical calculations.
  • 實原 定幸, 池上 康之, 上原 春男
    1994 年 60 巻 570 号 p. 641-648
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    In order to build a high-performance OTEC (ocean thermal-energy conversion) plant and operate it efficiently, it is necessary to optimize design conditions, such as velocities of cold sea water and warm sea water passing through heat exchangers, working fluid temperatures for evaporation and condensation, and warm and cold sea water temperatures. In this paper, the total heat exchanger area per annual net power is used as an objective function. Calculated results are shown for a 1000 kW OTEC plant. Ammonia is used as the working fluid. Okinawa is selected as the construction site.
  • 山本 康之, 大江 太郎, 成瀬 一郎, 大竹 一友
    1994 年 60 巻 570 号 p. 649-655
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    Ignition characteristics and its mechanisms in pulverized coal combustion are experimentally studied by using a swirling-flow turbulent pulverized-coal combustor, a thermogravimeter and a low-pressure coal pyrolysis reactor. In the ignition experiment, the released combustion gases are analyzed, and the composition of burning particles is measured by means of the proximate and ultimate analyses. The changes of specific surface area and surface structure are also measured by a BET method and a SEM, respectively. As a result, it is found that ignition characteristics and its mechanisms in coal are influenced by the volatile matter content, its evolution rate and mechanism, and the chemical species of released volatile matter. The evolution rate and mechanism of volatile matter determine whether coal particles ignite homogeneously or heterogeneously. During the ignition process, an H-component is released faster than a C-component. The composition of low-temperature volatile matter consists of the mixture of CH4, H2, CO and C2H6. The composition strongly affects the coal ignition.
  • 栗原 昇, 池田 裕二, 中島 健
    1994 年 60 巻 570 号 p. 656-661
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    In this paper, we describe experimental results of the spray of an industrial oil burner obtained using phase Doppler anemometry. The burner is a gun-type burner whose flame is stabilized by a baffle plate. The measurements were carried out near the burner throat in the cold condition. The purposes of this study are to elucidate the interaction between turbulent air flow and spray, and to present basic data for numerical modeling. Two-dimensional distributions of velocity vectors, dispersion, droplet Reynolds numbers and mass flux were obtained in the experiments. The results show that the behavior of the droplets in the spray can be classified into three patterns by the droplet diameters. The particles with diameter smaller than 30μm show fluid motion and the particles with diameter larger than 50μm penetrate the turbulent air flow. The spray with droplets larger than 70μm in diameter forms a hollow cone distribution, which induces shear flow along the spray. Then the shear generates turbulence and the small droplets are drawn inside the hollow cone.
  • 伊藤 献一, 伊東 弘行, 藤田 修
    1994 年 60 巻 570 号 p. 662-667
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    The behavior of soot particles was investigated under the microgravity condition using a 490 m (10 second microgravity duration) drop shaft. A butane jet diffusion flame was formed above a burner tube with 6 mm inner diameter. The fuel velocity and the oxygen concentration of surroundings were varied. Generated carbon particles were sampled and their detailed structures were observed using the electron microscope. The results showed that characteristic soot clusters were formed in the flames under microgravity. It was found that the generated soot particles in the flames under microgravity were agglomerated and grew to about 200-500 times as large as one generated under normal gravity.
  • 津江 光洋, 川岡 嗣尚, 角田 敏一
    1994 年 60 巻 570 号 p. 668-674
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    An experimental study was conducted on the structure of a propane jet diffusion flame discharged normal to a free stream of air with uniform velocity profile. Attention was paid to the effect of the ambient gas motion on the structure of the flame. The temperature and velocity profiles in the flame were measured using a fine thermocouple and forward-scattering laser Doppler velocimeter, respectively. A gas chromatograph was provided to measure the concentration profile of the major species in the flame. A photographic observation was also made to determine the flame configuration. The results showed that the increase in the cross-flow velocity caused a kidney shape of the contours of constant axial component velocity, temperature and concentration in the transverse cross section normal to the jet axis of the flame.
  • 張 福榮, 若林 慎也, 徳岡 直静
    1994 年 60 巻 570 号 p. 675-680
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    The drop size, velocity and volume flux and their distributions were measured to clarify the spray structure from a swirl atomizer. A inner region of a spray consists of smaller drops which are entrained by induced air. In outer region, larger drops with larger momentum traject at straight from an atomizer. The region between them consists of drops with the characteristics of the inner region and of the outer region. From those results, a structure model of a spray from a swirl atomizer was proposed. A spray consists of a disintegration region, a main flow region, and a stagnated flow region along the axis. The main flow region can be divided into two regions, an entrained flow region inner and an sheath region outer.
  • 張 福榮, 寺嶌 浩章, 徳岡 直静
    1994 年 60 巻 570 号 p. 681-686
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    The relationship between swirl atomizers of different flow characteristics and structure of sprays formed by them was clarified experimentally. The injection pressure is varied up to 3.0 MPa and water is used as injection liquid. The mean drop size, spray angle, flow rate of entrained air and the entrained air velocity into the spray decrease with the increase in characteristics factor K(=m· d02/(de. di)). Where m is the inlet hole number of swirl chamber, d0 is the inlet hole diameter of swirl chamber, di is the diameter of swirl chamber and de is the orifice diameter. The mean drop size, spray angle and flow rate of entrained air increase with the flow factor B(=2·m1/2·d0/di). When the d0 decreases or the di increases, the K and B decrease simultaneously. The effects of K and B on drop size, drop velocity and spray angle are canceled. Therefore, the change of spray characteristics is smaller than that incurred by changing K or B individually. The drops of spray concentrate on the sheath relatively and the thickness of the sheath region decreases when the injection pressure increases.
  • 森棟 隆昭, 塚越 孝徳
    1994 年 60 巻 570 号 p. 687-692
    発行日: 1994/02/25
    公開日: 2008/03/28
    ジャーナル フリー
    In a previous study, it was shown by Hilliard and Weinberg and the present authors that pollutants such as nitrogen oxides (NOx) and soot can be destroyed by nitrogen atoms generated by N2 plasma. In this study, a small-size, light-weight, simple-structure arc plasma generator is designed for practical applications. It has been examined by the authors that NOx removal efficiency has a maximum value in the range of low electrical power input to the plasma operated under stable conditions. In order to improve plasma stabilization, argon gas is added to N2 plasma, and the rate of production of N atoms is estimated by injecting the nitrogen monoxide (NO) gas into a plasma jet. It is concluded that NO removal by use of the (N2 + Ar) mixing plasma is possible under low voltage (12∼16 V) and power (500∼580 W) conditions.
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