日本機械学会論文集 B編
Online ISSN : 1884-8346
Print ISSN : 0387-5016
57 巻, 539 号
選択された号の論文の45件中1~45を表示しています
  • 富山 明男, 宋 明良, 南川 久人, 坂口 忠司
    1991 年 57 巻 539 号 p. 2167-2173
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    In order to examine the feasibility of direct simulation of bubbly flows, the applicability of the VOF (volume of fluid) method to the analyses of a single rising bubble was examined in this study. Calculated bubble shapes and terminal velocities under wide ranges of Eotvos number and Morton number were compared with the experimental data summarized by Grace et al. Except for the cases when bubble shapes are spherical-cap and skirted, the VOF method could predict them well by assigning only eight cells to the bubble diameter. Hence, it was confirmed that some modification of this method will enable us to simulate bubbly flows directly under a wide-range of flow conditions. Moreover, the relation between a bubble shape and velocity distribution was examined within the ranges in which the VOF method is valid. It was found that the secondary vortex appearing in wobbling bubbles induces the velocity component normal to the bubble interface, and this velocity is one of the causes of the wobbling shape of the bubble.
  • 宮崎 啓, AHMED Shemy M., 大場 利三郎
    1991 年 57 巻 539 号 p. 2174-2179
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The term "hard erosion" means erosion harder than ordinary erosion of two figures or more. We carefully observed the cavitation aspects of several types and the corresponding eroded surfaces in typically accelerating erosion tests on a typical material of 304 stainless steel by means of high-speed and SEM photography under a specified condition of uniform cavitation-nuclei-size distribution. The hard erosion is clearly resulted from the very high shock pressures accompanied by collapsing massive bubbles.
  • 橋本 弘之, 川野 聡恭
    1991 年 57 巻 539 号 p. 2180-2185
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    A new sequential production equipment of solid shells was designed. This method using liquid-liquid-gas systems is very simple comparing the previous method using chemical reactions or annular nozzles. For the first step to investigate the performance of the equipment, a molten salt (HTS)-turbine oil-air system was used. It was found that relatively large and thin solid shells could be produced and the diameter could be controlled easily. The geometric figures of solid shells produced here were of good spherical shape. Furthermore, the diameter, size distribution, shell thickness, aspect ratio and production frequency were measured for the wide injection gas conditions. Useful suggetions for the development of sequential solid shell production were presented.
  • 戸嶋 正美, 岡村 共由, 佐藤 譲之良, 宇佐美 賢一, 田辺 誠一
    1991 年 57 巻 539 号 p. 2186-2191
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    Damage due to the coupled action of silts abrasion and cavitation erosion was experimentally studied using water channel in which artificial silt (Al2O3) were included. It was confirmed that the incipient cavitation number in silt laden water increased by 10-15% compared with that in tap water. It was shown that the magnitude of impact pressure measured by the pressure detecting films and casing vibration-acceleration had good correlation with the cavitation erosion intensity but not with the abrasive wear intensity. The damage patterns on aluminum specimens were greatly affected by the cavitation occurrence, but the amount of damaged volume was almost constant with and without cavitation. A ploughing type of abrasive wear was mainly observed on the damaged surface by scanning electron microscope.
  • 越塚 誠一, 岡 芳明, 肖 国強, 志田 孝二
    1991 年 57 巻 539 号 p. 2192-2196
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    As a verification problem for computation techniques on complex geometry, such as BFC or FEM, backward-facing step flow has been investigated by varying the step geometry. Reattachment length has been measured as a main parameter. Inlet mean flow velocity and turbulence energy profiles have been measured, which will be available to the computation as an inlet boundary condition. The experiment has been carried out with five geometries and two inlet boundary conditions. The experimental results show that the reattachment length becomes shorter for a smoother step. This tendency is strong in the case of the large inlet turbulence.
  • 江崎 秀司, 深野 徹, 安藤 康博, 木之下 博文
    1991 年 57 巻 539 号 p. 2197-2202
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    An experimental study was made on the methods to control the distribution of flow rate into branch tubes in a multitube heat exchanger. The distribution of flow rate was strongly dependent upon the direction and the dynamic pressure of the water jet from an inlet nozzle. In this experiment, a circular plate or a flat plate with a large circular or rectangular hole was set downstream from the nozzle to modulate the dynamic pressure of the water jet. The results show that the properly determined dimensions and position of the circular or the rectangular plate were useful to render the flow rate distribution uniform. Also, a circular plate with many small holes had a better effect.
  • 山口 隆平, 矢野 徳康, 山口 隆美
    1991 年 57 巻 539 号 p. 2203-2208
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The wall shear stress and the flow pattern in a 45 degree unsymmetrical branch model in steady flow have been studied experimentally. The model, made of Plexiglas, consists of the parent tube (D0=24mm) and the daughter tube (D1=14mm). The curvature of the outer wall in the daughter tube and of the flow divider was RD=3.5D0 and Rc=D0/8, respectively. The wall shear stress was measured using an electrochemical method at the Reynolds number of 500, 800 and 1200, and the flow pattern was visualized by dye injection. Approximately 150 electrodes were embedded in the median plane of a branch tube. The ratio of the flow rate in the daughter tube to the total flow rate in the upstream parent tube is about 0.25, which corresponds to the ratio of the cross-sectional area downstream. The flow through this branch was characterized at the outer wall of the daughter tube, at the outer wall of the parent tube and near the flow divider. In particular, at the outer wall of the daughter tube, flow separation did not occur although the helical flow appeared.
  • 林 農, 吉野 章男, 若 良二
    1991 年 57 巻 539 号 p. 2209-2216
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    This report presents the contribution of the characteristic values to the lift acting on a circular cylinder with a tangential blowing jet immersed in a uniform shear flow. The characteristic values include the angle and the pressure coefficient of the stagnation point, separation points, minimum pressure and back pressure. A series of experiments was made for seven shear parameters K=0, ±0.03, ±0.045, ±0.15 and Reynolds number 6×104. All variable characteristics with increasing lift coefficient were clearly distinguished into three categories of which one was influenced only by the shear parameter, another was influenced only by the location of the tangential blowing jet, and the third was influenced by both parameters.
  • 小濱 秦昭, 大場 利三部, 太田 福雄, 大山 信, 寺田 嘉之
    1991 年 57 巻 539 号 p. 2217-2224
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    Systematic flow measurements were performed around a typical propeller strut of 13.8% in thickness ratio, designed for a high speed-boat engine, in a low turbulence wind tunnel as well as a cavitation tunnel, and also around a real strut equipted for an engine at sea. A relatively small drag coefficient CD≠0.02 was obtained in the wind tunnel, indicating a strut having reasonable hydpodynamic performance. We also discussed the state of the boundary layer, the thickness distribution, the velocity distribution, the behavior of the following wake and cavitation performance.
  • 伊藤 和巳, 高橋 浩爾, 井上 淳
    1991 年 57 巻 539 号 p. 2225-2232
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The steady axisymmetric laminar flow in a poppet valve is analyzed using a conventional finite difference method (ψ-ω method). After obtaining the numerical results for stream function ψ and vorticity ω on the cylindrical coordinate system, a streamline coordinate system (φ, ψ) is applied to compute pressure distributions because good pressure distributions cannot be obtained using the cylindrical coordinates. The pressure on the valve body surface is experimentally measured. The numerical results for pressure distributions are in good agreement with the experimental ones.
  • 新美 智秀, 藤本 哲夫, 原 豊, 井嶋 健一
    1991 年 57 巻 539 号 p. 2233-2238
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The structures of two opposed supersonic argon free jets with different source pressures are studied by flow visualization using laser-induced fluorescence of iodine molecules seeded in argon. The ratio between source pressures is kept at 2.0. Experiments are carried out for various source pressures and various ratios of the source pressure to the pressure of the expansion chamber. Characteristic structures of the flow field are classified roughly into four types depending on the condition of the source pressures and the pressure of the expansion chamber. Specifically, an unstable flow in the interacting region is found. The pressure condition is examined for each type of flow field.
  • 蒔田 秀治, 松元 毅, 朝倉 忠裕
    1991 年 57 巻 539 号 p. 2239-2246
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The coherent structure dynamics was experimentally investigated in a two-dimensional jet. The fundamental velocity fluctuation modes, i.e., the symmetrical and antisymmetrical modes, were excited acoustically in the jet. Conditional sampling was employed and vorticity contours were calculated from ensemble-averaged velocity components, and the mean velocity at the center of the vortex, the peak value of vorticity, and trajectory of the coherent vortex were educed. The peak position of the coherent vorticity component moved almost parallel to the jet axis in both cases of the excited jets. The convection velocity of the vortex was almost constant throughout the linear interaction and the nonlinear interaction regions independent of the local mean velocity at the center of the vortex . Furthermore, the convection velocity was larger than the local mean velocity throughout the linear interaction regions.
  • 牧 博司, 新本 實美, 鈴木 敏雄, 小川 信夫, 塙 康弘
    1991 年 57 巻 539 号 p. 2247-2253
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    When viscoelastic fluids are extruded through the nozzles and the flow velocity exceeds a critical velocity, it is widely known that the fluids flow out with anomalous shapes, so called melt fracture. This paper deals with geometrical dimensions of extruded polyethylenes with roughly regular shapes in order to verify fundamental causes of occurrence for those anomalous phenomena among melt fracture, so called the "spiraling" and the "wrinkling". It was found, as a result, that one of the causes of the wrinkling was due to fluctuation of the flow rate yielded by the mixing pins usually installed on ohe downstream end of the screw shaft. It was also found that the spiraling had two kinds of phenomena, one was extruding with small pitch like the triangular thread and the other large, and this anomalous phenomena occurred at the same working condition.
  • 古口 日出男, 丸山 博幸, 矢田 敏夫
    1991 年 57 巻 539 号 p. 2254-2260
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    In the present paper, the authors develop a time-dependent numerical algorithm using the boundary element method to simulate the behavior of the free surface of a thin liquid film between two parallel circular plates in negative squeeze motion. A nonlinear evolution of fingers on the free surface is numerically simulated in order to examine the validity of the criterion for meniscus instability on the basis of the linear instability theory and to confirm the validity of the formulation in the boundary element method. Several types of disturbances were imposed at the free surface as an initial perturbation in the simulation. Consequently, when the disturbances with the wavelength distributed at random around the most unstable wavelength given by our theory were applied, finger patterns similar to those formed in the experiment were formed in the simulation.
  • 菊山 功嗣, 西堀 賢司, 前田 太佳夫, 野村 哲
    1991 年 57 巻 539 号 p. 2261-2268
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    Effects of the centrifugal force by streamline curvature and the Coriolis force by system rotation on a turbulent boundary layer along a convex surface are studied experimentally using a curved rectangular channel which rotates about an axis perpendicular to the main flow. In addition to the stabilizing effects due to the streamline curvature, system rotation has a large effect on the stabilization or destabilization of turbulent motion in the boundary layer. The flow tends to be laminarized in the suction side due to the stabilizing effects of both system rotation and surface curvature. The Monin-Oboukhov formula modified for the curved rotating channel does not hold for the boundary layers on the convex surface. Experimental results are also compared with those on the concave surface of the same channel.
  • 杉山 均, 秋山 光庸, 平田 賢, 上野 智志
    1991 年 57 巻 539 号 p. 2269-2276
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    A numerical analysis has been made on a three-dimensional distorting duct using a Reynolds stress equation model and transport equation model for heat flux. It is important to examine the validity of an anisotropic turbulent model for the flow with complex configuration because we do not know the worth of the anisotropic turbulent model until we apply it. We compared the calculated results with the published experimental data and made clarified that the present method was able to predict the mean flow field, but it is necessary to modify the convective and diffusion terms of a Reynolds stress equation.
  • 柏木 孝夫, 李 東浩, 黒沢 茂吉, 野呂 奉弘, 小俣 康二
    1991 年 57 巻 539 号 p. 2277-2284
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    In most commercial machines, absorption enhancement has been done by adding small amounts various kinds of surfactants, thereby reducing the surface tension of the absorbent solution and generating Marangoni convection near the solution surface during the refrigerant vapor absorption process. This paper clarifies the most effective conditions of surfactant addition for absorption enhancement in the process of refrigerant vapor absorption into a vertical falling absorbent film. H2O/LiBr and n-octanol were used as the refrigerant/absorbent combination and the additive. Experiments were carried out by using the LiBr aqueous solution with and without n-octanol dissolution. Moreover, n-octanol vapor was supplied to the absorber in order to clarify the effect of additive on the absorption enhancement. The results of these experiments reveal that the presence of dropwise n-octanol in the surface of the absorbent falling film contributed greatly to the generation of violent and irregular Marangoni convection.
  • 高山 和喜, 小野寺 収, 小原 哲郎, 桑原 正明, 北山 修
    1991 年 57 巻 539 号 p. 2285-2292
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    This is a preliminary report of an application of underwater shock wave focusing to the so-called extracorporeal shock wave lithotripsy, ESWL. Underwater spherical shock waves were initiated by microexplosions at one of two focus points of an ellipsoidal cavity. Consequently, the reflected shock waves were focused at the second focus point outside the ellipsoidal reflector, and high pressure was generated for a few microseconds. To the shock wave propagation, human tissue has a character very similar to that of water, and we can generate high pressure inside the human body by shock wave focusing sufficient to disintegrate human calculi. This paper reports an experimental and numerical approach of determining the most effective shape of ellipsoidal reflector for the lithotriptor and clarifying the mechanism of focused high-pressure generation by microexplosions. It was found that a half-ellipsoidal shape having a major and minor axis ratio of about 1.4∼1.5 was very suitable for the lithotriptor.
  • 浜井 祐治, 渡辺 正五, 長谷川 泰明, 大田 英輔
    1991 年 57 巻 539 号 p. 2293-2300
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    A two-dimensional computer simulation study is developed to obtain efficient understanding of unsteady flow behaviors during the intake-compression stroke of a rotary engine. Emphasis is put on describing swirling flow features as a function of the rotor geometry and operating conditions. The system of the compressible N-S equations is solved by applying the Beam and Warming method with the DD-ADI algorithm. Second and fourth-order nonlinear artificial dissipation terms are added in the scheme with minmod-type limiters. Since the convective acceleration of the gas is considerably weak, a special treatment for the pressure description is required along the rotor boundary wall. Various flow patterns are presented satisfactorily, which are constituted of vortices generated in the intake process and secondary vortices developed by the rotor movement. Their features agree well with the experimental observations made separately by the authors, and a prospective view to design more efficient engines is obtained.
  • 青木 克己
    1991 年 57 巻 539 号 p. 2301-2306
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The most practical combustor is considered to be the continuous combustion type with swirling flow. With this type, it is easier to control combustor and reduce pollutants. In this study, swirling nonreacting flows are investigated in an axisymmetric test section with expansion ratio of D/d=2, sidewall expansion angle α=180°and swirl vane angle 45°, which can be equipped with contraction nozzles of area ratios C={1-(Dc/D)2: Dc : contraction nozzle diameter, D: test section diamerter} 0.0, 0.54, 0.74 and 0.89, and its contraction nozzle locations, Lc/D=1.5, 2.0 and 2.5. From these results, the present study has clarified the mechanism of recirculation zone and the characteristics of flow pattern for a contraction nozzle and the location of the contraction nozzle. Other characterestics such as the intensity of turbulence and power spectra in these zones are also clarified.
  • 鈴木 宏尚, 長谷川 英治, 松藤 久良
    1991 年 57 巻 539 号 p. 2307-2314
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The unsteady motion of small particles which are initially uniformly distributed in a square chamber with a pulsating inlet velocity is studied numerically. The force between the particle and fluid is assumed to be proportional to the relative velocity. The problem considered is governed by four parameters: the Reynolds number, the dimension ratio (which characterizes the particles to be coarse or fine), the period and the amplitude of the pulsating inlet velocity (which are made dimensionless). The motion of the particles is classified into three types: the exhaust type, in which the particles are exhausted through the outlet; the circulation type, in which the particles circulate in the chamber; and the adhesion type, in which the particles adhere to the wall of the chamber. The effects of the period and the amplitude of the inlet velocity on the ratio of the number of particles of each type to the total number of particles are examined taking the Reynolds number and the dimension ratio as parameters. The suitable ranges of the period and the amplitude of the inlet velocity, in which the number of the exhausted particles increases and the number of the circulating particles decreases, are found taking the dimension ratio as a parameter. The mechanism on the exhausting of the particle is qualitatively clarified on the basis of the relation between the stream line and the trajectory of the particles.
  • 笹口 健吾, 野口 尚志, 森山 芳生
    1991 年 57 巻 539 号 p. 2315-2322
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    Experiments for solidification have been conducted using aqueous ammonium chloride (NH4Cl-H2O) as a binary mixture. Effects of the initial concentration and the initial superheat of the solution, the orientation and the temperature of a cold surface, and attached brass plates to the cold surface on the solidification process have been systematically examined from observations of timewise variation of the solidification morphology and from measurement of temperature distributions. It has been shown that these parameters considerably affect the strength of the thermal driven and/or solutal driven buoyancy flows, and the solidification morphology largely changes with the variations in the parameters. In particular, the effect of the orientation of the cold surface is significant, and various solidification morphologies appear with the variation in the orientation.
  • 閔 敬春, 佐古 光雄, 菊地 義弘
    1991 年 57 巻 539 号 p. 2323-2328
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    An experimental study was conducted to investigate the process of evaporation of water droplets on hot metals (silver or stainless steel) whose heat transfer surface was coated with a low thermal conductivity material. The coating thickness was varied from 0 to 0.13mm. The initial diameter and temperature of a droplet were 2.70±0.05mm and 20±3°C, respectively. The coating widened the range of the surface temperature, in which the lifetime of the droplet was shorter than 1 s and also increased the Leidenfrost temperature. This tendency was more accentuated with thicker coating. The better wettability of the coating spread the boiling droplet more widely on the heated surface and caused the lifetime of the droplet shorter. In the superficial nucleate boiling region, the time-averaged heat flux from the heated surface to a droplet increased with superheating of the heated surface. The maximum time-averaged heat flux was observed in a higher temperature region with increasing coating thickness, but its value was approximately 107W/m2 for every coating thickness.
  • 越後 亮三, 花村 克悟, 高橋 義憲, 奥山 正明, JUGJAI Sumrerng, 萩原 明房, 宇佐美 優, 船橋 信之
    1991 年 57 巻 539 号 p. 2329-2335
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    A numerical analysis has been performed extensively on a two-dimensional tubular methane-steam reformer with a porous radiative converter by means of a proposed quasi-multidimensional analytical model, in which a two-dimensional energy equation is integrated and averaged along the direction perpendicular to the flow, and the divergence of radiation for a participating gas is also averaged after the rigorous three-dimensional treatment relating to the radiative transfer. The results disclose that the proposed method is beneficial for heat transfer problems including gas radiation compared with a uniform gas temperature method or a two-dimensional analytical method; the numerical results show a reasonable agreement with experimental results and exhibit much the same precision as those of a two-dimensional analytical model, and further, the CPU time for the proposed method is about half that for the two-dimensional method.
  • 山崎 晴幸, 坂元 健, 中武 良二, 上野 善人
    1991 年 57 巻 539 号 p. 2336-2341
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    A U-bend coolant supply was applied to transformer windings in an attempt to eqaulize the flow rate in the horizontal coil ducts and to cool windings uniformly. The U-bend supply, which distributes coolant uniformly, is used in heat exchangers. Using a two-dimensional coil cooling model with ten coils, the velocity distribution in the coil ducts and the temperature rise distribution of the coils are measured for the U-bend supply and the Z-shaped supply (baffle plate type). Experiment proves that the cooling characteristics of the U-bend supply are superior to those of the Z-shaped supply at a low flow rate. Computational programs were developed for the U-bend supply and the Z-shaped supply to estimate flow and heat transfer characteristics in the windings. The programs accurately predict the velocity distribution in the coil ducts and the temperature rise distribution of the coils.
  • 平松 道雄, 石丸 典生, 大河内 隆樹
    1991 年 57 巻 539 号 p. 2342-2348
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The purpose of this study is to improve the performance of inner-fins for intercoolers use for automotive turbocharger engines. Since these intercoolers are used at high flow velocities, unlike other automotive heat exchangers, analytical treatment needs to be unsteady manner. In this paper, a numerical analysis was made, considering flow instability, to know determine the fluctuation in the flow of fin wake effects the efficiency of heat transfer of each rear fin. It was ascertained that the heat transfer enhancement of the fin is related to each fin space and Reynolds number, and high heat transfer is obtained when the fin space is greater than three times the fin thickness.
  • 大久保 英敏, 西尾 茂文
    1991 年 57 巻 539 号 p. 2349-2354
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The effects of cooling rate and thermal conductance of a heat transfer plate on the heat transfer coefficient of mist cooling are experimentally investigated in the high-temperature region. Experiments are conducted for horizontal upward facing surfaces made of silver, stainless steel and fused quartz. The experimental conditions of mist flow are as follows: the air velocity is Va=20m/s, the temperature of the water droplet is Tl=21°C, and the volumetric-droplet-flow-rate is D=0.00043-0.00472m3/m2s. It is found that, in the case where the horizontal surfaces face upward, thermal conductance of the surface material does not significantly affect the heat transfer coefficient, but the cooling rate of the surface affects the heat transfer coefficient if the heat capacity of the surface decreases to less smaller than a critical value.
  • 坂下 弘人, 熊田 俊明
    1991 年 57 巻 539 号 p. 2355-2362
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    A new correlation consisting of heat flux q, superheat ΔTsat, density of nucleation sites n and a group of physical properties is proposed for the coalesced bubble region, based on a model where the heat conduction and the liquid flow induced by bubble growth are dominant mechanisms in the heat transfer. The new correlation of heat transfer arranges well the experimental data from the isolated bubble region to the coalesced bubble region obtained for various combinations of liquids and heating surfaces of upward flat plates at pressures of 0.04MPa to 0.1MPa. The correlation is used to calculate the relations of n-ΔTsat from the experimental data of q-ΔTsat. The generalized correlation consisting of n, ΔTsat, Physical properties and surface characteristics is derived and combined with the new correlation of heat transfer in order to predict boiling curves. The predicted results agree well with the experimentally obtained boiling curves from various sources for a wide range of boiling conditions.
  • 中島 忠克, 中山 恒, 大橋 繁男, 桑原 平吉
    1991 年 57 巻 539 号 p. 2363-2368
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The device considered in this paper is a porous stud having a net of microchannels, designed to enhance boiling heat transfer from the electronic component at the stud base to the pool of FC-72. The two-step approach was taken to clarify the effects of geometrical parameters on the critical heat load on the porous stud. In the first step, the attention was focused on the burn-out condition in a confined space, using a pair of thermal chips to simulate the geometry of microchannels. The data were obtained by changing the microchannel gap in a range of 0.1∼5mm; and based on these data, the correlation was derived for the critical heat flux vs. the microchannel size. In the second step, the heat conduction analysis was performed assuming the critical state at the stud base and using the experimentally determined correlations of boiling heat transfer for the rest of the stud zone. Finally, it is shown that there exist optimum sizes of microchannels that maximize the alowable heat load within a certain set of geometrical constraints.
  • 木村 照夫, 竹内 正紀, 宮永 俊晴
    1991 年 57 巻 539 号 p. 2369-2376
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The effects of the inner body on the heat transfer phenomena in an inclined rectangular enclosure have been studied numerically. The calculations were carried out for Pr=10 and Grw=5×102-5×105 (Raw=5×103-5×106). The aspect ratio of the enclosure H/W was 2 throughout the study. The size (Wi/W, Hi/H) and the aspect ratio Hi/Wi of the nonconducting inner body were changed parametrically. The flow and temperature fields were shown in detail and the heat transfer coefficient was discussed from the results. It is clarified here that the average Nusselt number (Nuw)^^- largely depends on the size of the inner body in the case where the inclination angle γ is larger than 0°, and there are instances where Nuw for the enclosure with the inner body is larger than that for the enclosure without inner body.
  • 高松 洋, 小山 繁, 池上 康之, 屋良 朝康, 喜多村 稔, 藤井 哲
    1991 年 57 巻 539 号 p. 2377-2382
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The performance of a vapor compression heat pump system is tested using R22/R114 mixtures as the working fluid. Double pipe heat exchangers, where the refrigerant flows inside the inner tube with grooved internal surface and water flows countercurrently in the outer annulus, are used for the condenser and evaporator. Experimental results are compared with those for the same system with a smooth tube condenser and the evaporator presented before. The effect of the superheating of the refrigerant at the exit of the evaporator on COP is also discussed. A trial calculation based on the experimental results shows that the COP of the mixture becomes larger than that of the pure refrigerant in the case of a large change in the water temperature only if the heat transfer surface area is large enough and the superheating of the refrigerant is quite small at the exit of the evaporator.
  • 城戸 裕之, 北川 敏明, 中島 健四郎, 金 俊孝
    1991 年 57 巻 539 号 p. 2383-2390
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    A formerly proposed spectral model of turbulent mass burning velocity is refined in regard to the following three points: (1) a small modification of the characteristic spectrum of mixture, (2) consideration of varying turbulence spectrum shape with turbulence intensity and (3) a new idea of the upper limit of the integral which is strongly related to the small-scale structure of turbulent flame. Predictions of turbulent mass burning velocity were made by this spectral model. The predicted velocities were compared with the measured turbulent mass burning velocities, where laminar burning velocity, laminar flame thickness and turbulence intensity were varied extensively and independently with each other under a stoichiometric mixture condition. As the result of comparison, the quantitative accuracy of the refined model was confirmed.
  • 白羽 陸宏, 藤井 健一, 原田 英一, 野添 浚平, 鈴谷 信吾, 平尾 元亮, 高野 英樹
    1991 年 57 巻 539 号 p. 2391-2398
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    Exploratory activity has been conducted to develop a "Coal Partial Combustor" for the conversion from gas/oil firing to coal firing under the sponsorship of MITI since 1984. One application includes the use of CPC as a simple coal gasifier. Development of a coal gasifier was carried out by using a 36 T-coal/D pilot plant in 1989. The gasifier is characterized by five types (1) atmospheric, (2) oxygen-enriched air-blown, (3) cyclone slagging type, (4) with char recycle, and (5) compact. This paper presents the test results on the characteristics of coal gasification and the means of data analysis. Test results indicated that the overall performance of the gasifier such as the heating value of the product gas and cold gas efficiency can be predicted by the stoichiometric ratio of the product gas. One-through carbon conversion efficiencies were determined under several operation conditions. The use of oxygen-enriched air and char recycle help to increase the heating value of the product gas and the cold gas efficiency.
  • 福場 秀和, 守田 栄之
    1991 年 57 巻 539 号 p. 2399-2403
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    When an automobile has a continuous variable transmission (CVT), it is possible to reduce the fuel consumption by controlling both throttle valve angle and CVT gear ratio simultaneously. The main reason for this is that the fuel consumption of the engine becomes tolerably economical when it runs with an operating condition of low speed and high torque rather than high speed and low torque. But changing the value of the throttle valve angle or CVT gear ratio naturally affects the automobile speed. Therefore control theory such as decoupling control or multi-input output control becomes necessary. Reported here is the optimization fuel consumption control using a decoupling control theory. Also, modelling of the relevant system (engine∼CVT∼load system) was performed for designing the decoupling control system and for simulation studies. The experiments achieved the expected results.
  • 後藤 雄一
    1991 年 57 巻 539 号 p. 2404-2409
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    Ultralean combustion (air-fuel ratio is more than 20) is known to be effective in point of combustion improvements such as clean exhaust gas and high thermal efficiency. Yet, there are unsolved problems such as combustion instability. Swirl is an effective method of stabilizing lean combustions, and it is important from a combustion stability standpoint to understand the relationship between swirl and wall temperature or between swirl and flame. This paper presents measurement methods of two-dimensional visualization on hemisphere chamber wall temperature and three-dimension like flame speed in spark-ignition engine ultralean combustion by means of an image intensifier.
  • 雪竹 次太, 相馬 憲一, 小豆畑 茂, 高久 豊
    1991 年 57 巻 539 号 p. 2410-2415
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The fluctuations of excess air factor in a combustion chamber of a spark ignition engine have been measured with an optical diagnostic technique. The excess air factor was estimated by the ratio of light emission intensities of two different wavelengths, 431nm (CH radical) and 517nm (C2 radical). The experimental data showed that, in one combustion cycle, the excess air factor at the beginning of combustion was higher and gradually decreased, and that the fluctuation of an excess air factor obtained by stoichiometric flame was smaller than under other combustion conditions. Furthermore, two types of fuel injectors were evaluated from the viewpoint of fluctuation of the excess air factor. The Probability density function (PDF) showed that the injector, whose mean droplet size was 50μm, provided smaller variance of the excess air factor than another injector, which had a larger mean droplet diameter of 200μm.
  • 吉田 肇, 新井 雅隆, 廣安 博之, 横谷 昌道
    1991 年 57 巻 539 号 p. 2416-2420
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    High speed schlieren movies were taken for detailed observation of the physical structure of flames propagating in propane-air mixtures containing kerosene spray. Effects of an overall equivalence ratio and a mixture ratio of propane/kerosene to the total fuel on the structure were examined. Fractal analysis of the flame structure was also attempted. As a result, two typical flame structures were observed, into which flame structures were classified according to propane concentration. One consisted of droplets ignited successively, the other consisted of flame front propagating in the interdroplet propane-air mixture. In the latter, flame front had fractal character and its fractal dimension increased and decreased with the flame propagation velocity.
  • 榎本 良輝, 大矢 利博, 石井 光教, 榎本 謙二郎, 北原 伸浩
    1991 年 57 巻 539 号 p. 2421-2427
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    Instantaneous heat flux flowing into wall surfaces of combustion chambers was used for analysis according to waveforms of instantaneous temperatures measured by thin film thermocouples. Such analyses, however, were in fact done using known fixed values of the thermophysical properties. In this study, the instantaneous heat flux has been studied by means of numerical analysis using differential equations (which had an added heat storage term) taking account of the temperature dependency of the thermophysical properties. In addition, related measured values in the previous paper have also been studied again. As a result, it has been concluded that the temperature dependency of the thermophysical properties should be considered when analyzing instantaneous heat flux.
  • 横田 源弘, 伊藤 幸雄, 青木 八郎
    1991 年 57 巻 539 号 p. 2428-2433
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    Cavitation characteristics of multihole diesel-fuel nozzles, especialy on the effects of static pressure, oil temperature and nozzle shape, were systematically investigated in high-speed oil fiows under several hydrodynamic conditions. Practical diesel nozzles, 110°∼160°in hole angle, 0.20∼0.35mm in hole diameter, 5.5∼6.5 in hole length/diameter ratio, and 5∼9 in number of holes, were tested in typical gas-oil flows in a wide range of cavitation number σ from a subcavitating state to a supercavitating state. Marked cavitation effects on the flow coefficient and the critical cavitation number are also shown in detail.
  • 矢加部 久孝
    1991 年 57 巻 539 号 p. 2434-2441
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The control methods of a gas engine are presented using response waveforms of an O2 sensor through three-way catalysts under dynamic operation. Zirconia O2 sensors were used to measure the response of three-way catalysts following stepchange in the engine air/fuel ratio. The concentration measurements at the catalysts' inlets and outlets were made by using the successive exhausts analyzers. In the dynamic behavior of three-way catalysts, the lean-to-rich or rich-to-lean step response of the O2 sensor had a time lag. This time lag depends on the controlled condition of air/fuel ratio. Taking advantage of this response characteristic, the stable control of the air/fuel ratio and the low NOx, CO, CH4 emissions were achieved. The results of the control experiments demonstrate the availability of the new control methods.
  • 梶谷 修一, 澤 則弘, 林 重信, 久保田 譲
    1991 年 57 巻 539 号 p. 2442-2448
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    A direct fuel-injection two-stroke cycle engine operated with neat methanol was investigated. The engine performances, combustion and exhaust gas characteristics were analyzed experimentally and were also compared with the results of operations with a carburetor, EFI injection at the intake manifold, and EFI injection at the scavenging port. As a result, the power and the brake thermal efficiency of the direct fuel-injection engine were higher than those of engines operated with a carburetor and the above two EFI methods. The exhausted unburned fuel of the direct fuel-injection engine was lower than that with operation with a carburetor, and holmaldehyde and CO concentration were of the same level as the operations with the carburetor and EFI methods. The NOx concentration of the direct fuel-injection was half the level of the result of carburetor operation. Because a stratified charge using direct fuel-injection activated the combustion of the lean mixture which increases working gas temperature, therefore, the vaporization of injected fuel was promoted by the elevated temperature of the residual gas.
  • 関谷 弘志, 寺田 房夫
    1991 年 57 巻 539 号 p. 2449-2456
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    In order to predict and evaluate the performance of the Vuilleumier (VM) cycle machines in research and development, numerical analysis using the computer is significant. It must include a technique for the 3rd-order method, particularly in the case of the detailed analysis of performance and the design optimization. This paper describes our simulation model for the VM cycle machines, which is based on such a method. The working space is divided into thirty-eight control volumes for our prototype VM heat pump, and the fundamental equations are derived rigorously by applying the equations for the conservation of mass, momentum, and energy to each control volume using a staggered mesh. These equations are solved simultaneously by the Adams-Moulton method. Then, our prototype VM heat pump is investigated as to the fluctuations of the working gas pressure and temperature, the energy flow, and the performance. The calculated results are inspected in comparison with the experimental ones.
  • 関谷 弘志, 松栄 準治
    1991 年 57 巻 539 号 p. 2457-2464
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    For the purpose of predicting and evaluating of the Stirling engine performance in detail, the cycle simulation code requires a technique for the 3rd-order method. The first paper presented our code which was useful in the research and development of our Stirling engine NS 30 S. In the second paper, a comparative study of working gases (helium and hydrogen) was carried out, and the effect of the test conditions of temperature was investigated. In addition, the calculated results were inspected in comparsion with the experimental ones This paper describes the test conditions of pressure and the cylinder volume and the piston phase angle affecting the Stirling engine performance and design. Then, the particulars of heat exchangers are evaluated as to design optimization. As a result, it is verified that our code is an available tool for optimizing the Stirling engine design.
  • 関谷 弘志, 中里 孝
    1991 年 57 巻 539 号 p. 2465-2472
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    The double-acting Stirling engine needs a pressure balancing system (PBS) in order to drive it stably, but the PBS decreases the engine power and the thermal efficiency. Accordingly, it is important that how the PBS affects engine drive is clarified by virtue of design and evaluation of the Stirling engine. We have already presented the cycle simulation code of the Stirling engine based on the 3rd-order method, which was useful to study and develop our double-acting Stirling engine, NS30S. In this paper, by numerical analysis using our code, the differences of fluctuations with the PBS operating and not operating are manifested with regard to quantities of state and rates of mass flow, heat flow, and work, and the effects of the PBS on the working gas behavior and the engine performance are investigated in detail. In addition, the calculated results are inspected in comparison with the experimental ones as to fluctuations of pressure and pressure drop.
  • 多田 幸生, 松本 隆一, 岡本 勝, 外川 一郎
    1991 年 57 巻 539 号 p. 2473-2478
    発行日: 1991/07/25
    公開日: 2008/03/28
    ジャーナル フリー
    Flow of a polymer in the plasticizing process of an injection molding machine is analyzed. A polymer in the heat barrel of the machine is regarded as an imaginary non-Newtonian fluid irrespective of melting. Its mathematical model is solved by FEM based on the adjoint variational principle. In order to obtain initial states in the entire analyzed area, the steady-state problem is first solved. Next, using its results as initial values, the original nonsteady problem is analyzed. Moreover, the boundary conditions are also considered.
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