日本機械学会論文集 B編
Online ISSN : 1884-8346
Print ISSN : 0387-5016
74 巻, 742 号
選択された号の論文の32件中1~32を表示しています
  • 菱田 公一
    2008 年 74 巻 742 号 p. 1218-1225
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    This paper presents mainly a review of experimental study on the turbulent structure of dispersed two-phase flow employing advanced laser techniques such as Shadow Doppler Velocimetry and Particle Image Velocimetry combined with Laser Induced Fluorescence. Shadow Doppler Velocimetry has been developed for particle sizing of arbitrary shaped particle, i.e. non-spherical particle. For the bubbly flow, combined shadow image and DPIV techniques allow us to acquire the detailed information of two-dimensional bubble motion and velocity vectors very close to the bubble. Microscale structures of turbulence associated with dispersed phase motion are certainly obtained by these Laser measurement techniques. Furthermore, PIV measurements in micro channel flow with sub-micron solid particles evaluated electroosmotic flow from particle motion in an applied electric field.
  • 越塚 誠一
    2008 年 74 巻 742 号 p. 1226-1231
    発行日: 2008/06/25
    公開日: 2011/08/16
    ジャーナル フリー
  • 川原 顕磨呂, 佐田富 道雄
    2008 年 74 巻 742 号 p. 1232-1238
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    The flow characteristics of the two-phase flows in a 100μm circular horizontal microchannel have been investigated experimentally and analytically. In the experiments, nitrogen gas and one of four liquids (distilled water and 4.8, 49, 100 wt% ethanol in water) were injected through a T-junction type mixer to the microchannel, having smaller diameter than that of the mixer. Both quasi-homogeneous flow and quasi-separated flow was observed depending on gas and liquid flow conditions. Furthermore, the data on void faction, frictional pressure drop and interfacial friction force were found to be larger in the quasi-homogeneous flow than the quasi-separated one. In the analysis, empirical correlations of the liquid-wall friction force and the gas-liquid interfacial friction force were developed respectively for the quasi-homogeneous and the quasi-separated flows. By substituting these correlations into an analytical code based on a one-dimensional two-fluid model, we calculated the void fraction. The calculations reasonably agreed with the data irrespective of the quasi-homogeneous and the quasi-separated ones.
  • 井手 英夫, 木村 龍二, 川路 正裕
    2008 年 74 巻 742 号 p. 1239-1246
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    An optical measurement system was developed to investigate the flow phenomena of gas-liquid two-phase flow in a circular microchannel with the diameter of 100 μm. From the output wave signals which correspond to the passages of the gas and the liquid by using multiple optical fibers and photodiodes, void fraction was measured successfully. The presence of a large compressible gas volume upstream of the mixing chamber had a significant effect on the two-phase flow characteristics in the microchannel, typified by the void fraction data. The flow patterns of bubbly flow, slug flow and ring film flow were observed. The characteristics of optical signal waves corresponding to these flow patterns have been described. The time averaged value of the optical signal wave agreed well with the space averaged value of the volume fraction of the gas from video image.
  • 鈴木 佳那子, 青木 一司, 菱田 公一, 児玉 良明
    2008 年 74 巻 742 号 p. 1247-1256
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    The phenomenon of the drag reduction effect with microbubble has been studied experimentally. We revealed the drag reduction effect by using two types of bubbles which are generated in tap water and that with surfactant. We have approached by wall shear stress measurement and flow visualization by using Highly Magnifying PTV with telecentric lens. In both bubble flows, the experiments have been carried out with the Reynolds number ranging from 10 000 to 50 000 and void fraction up to 0.04. In condition of drag reduction effect observed, injecting bubble diameter was 0.6-1.3 mm and the ejection and sweep event were reduced by bubble injection and Reynolds stress was decreased.
  • 渡辺 博典, 光武 徹, 柿崎 禎之, 高瀬 和之
    2008 年 74 巻 742 号 p. 1257-1262
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    The electro-void fraction meter (Capacitance type meter) was applied to high void fraction measurement with various shapes of flow conduits such as round, rectangular and rod-bundle geometries. The principle of the meter is that the electrical capacitance of a gas-liquid two-phase flow changes with the void fraction. High-frequency power supply enables to measure the electrical capacitance of the ion-exchanged water with even though conductivity as low as 1 μS/cm.It was confirmed by the air-water and steam-water boiling two-phase flow experiments that void fraction can be obtained in real time way. Void fraction ranging from 0% to 90% at maximum was successfully measured under steam-water boiling two-phase flow conditions of 2 MPa through 18 MPa pressure.
  • 実現性確認試験と性能予測
    佐田富 道雄, 川原 顕磨呂, 木村 隆直, 中尾 淳一
    2008 年 74 巻 742 号 p. 1263-1269
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    An advanced micro-bubble generator with a spherical body in a flowing water tube was invented by Sadatomi in 2003. In the present paper, as an industrial application of the micro-bubble generator, a bubble-jet-type air-lift-pump also invented by Sadatomi in 2005 has been presented together with the results of its feasibility test. In the test, effects of particles size, submergence ratio (=the riser length submerged in water divided by the total riser length), and water and air supply rates to the bubble-jet generator on the pump rerformance have been studied. Yoshinaga-Sato model for predicting water and particles discharge rates has been modified and tested against the present experimental data to confirm its validity. The results of such experiments and analyses are reported in this paper.
  • 松山 史憲, 佐田富 道雄, 川原 顕磨呂, 深町 健太郎
    2008 年 74 巻 742 号 p. 1270-1277
    発行日: 2008/06/25
    公開日: 2011/08/16
    ジャーナル フリー
    Sadatomi invented a micro-bubble generator with a spherical body in a flowing water tube. In the generator, when pressurized water is supplied to the tube, air is automatically sucked through numerous small holes drilled on the periphery of the tube behind the body, and is broken into a number of micro-bubbles by a highly-shear flow of water around the body. In the present study, in order to develop a large-flow-rate mist generator, pressurized air is spplied to the same generator and water is automatically sucked. Experiments were conducted to study the effects of parameters, such as the diameter ratio of the spherical body to the tube, on the hydraulic performance, and the data on the mist flow rate, the pressure at the generator inlet and the distribution of mist diameters were obtained by changing the air supply rate. In the analyses, an analytical model is proposed to predict the mist flow rate and the pressure at the generator inlet at a given air supply rate. In order to validate the model, a comparison is made between calculation and experiment. Results of the experiments and the comparison together with the model are presented in this paper.
  • 吉田 啓之, 永吉 拓至, 張 維忠, 高瀬 和之
    2008 年 74 巻 742 号 p. 1278-1286
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    Thermal-hydraulic design of the current BWR is performed by correlations with empirical results of actual-size tests. Then, when the reactor of new design is developed, an actual size test is required to confirm or modify the correlations. Development of a method that enables the thermal-hydraulic design of nuclear reactors without these actual size tests is desired, because these tests take a long time and entail great cost. For this reason we developed an advanced thermal-hydraulic design method for BWRs using innovative two-phase flow simulation technology. In this study, detailed two-phase flow simulation code using advanced interface tracking method : TPFIT is developed. In this paper, the TPFIT code was applied to simulation of two-phase flow in modeled 2 subchannels of BWRs rod bundle, and the existing two-phase flow correlation for fluid mixing is evaluated using detailed numerical simulation data.
  • 数値流動解析と可視化計測
    大森 修一, 奈良林 直, 岡本 孝司, 岩城 智香子, 森 治嗣
    2008 年 74 巻 742 号 p. 1287-1296
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    A steam injector (SI) is a simple, compact and passive pump and also acts as a high-performance direct-contact compact heater. This provides SI to apply as a direct-contact feed-water heater that heats up feed-water by using extracted steam from the turbine. To develop high performance compact feed-water heater, it is necessary to quantify the characteristics between physical properties of the flow field. We carried out the analysis and visualization study. The analysis was conducted by using CFD code embedded separate two-phase flow models and confirmed that the steam has a high-performance direct-contact heater that was suitable for compact feed-water heater. To visualize the water jet behavior inside the SI, we used the Dynamic PIV system. The Dynamic PIV system consists of the high-speed camera and lasers. In this study, 384×180 pixel resolution with 30 000 fps camera is used to visualize the flow. For the illumination CW green laser with 300 mW is applied. To view inside the SI, relay lens system is set at the SI wall. Very high speed water jet during the starting up of SI had been clearly visualized with 30 000 fps. The wave velocity on the water jet had been analyzed using PIV technique. The instability of the water jet is also detected.
  • 阿部 豊, 河本 雄二郎, 岩城 智香子, 奈良林 直, 森 治嗣, 大森 修一
    2008 年 74 巻 742 号 p. 1297-1302
    発行日: 2008/06/25
    公開日: 2011/08/16
    ジャーナル フリー
    The supersonic steam injector, one of the innovative technologies has been developed as a candidate of the most important component for next-generation nuclear reactors. The supersonic steam injector has functions of a passive pump without a large motor or turbo-machinery and a high efficiency heat exchanger. The performances of the supersonic steam injector as a pump and heat exchanger are dependent on direct contact condensation phenomena between a supersonic steam and a subcooled water jet. In the present study, the supersonic steam injector, which is made of visible transparent material and equiped with the measurement instrumentations for both axial/vertical temperature and velocity, is used to obtain the axial pressure distributions, the spatial temperature and velocity distributions in the supersonic steam injector. The visual observation on the interface of a water jet steam was made by a high-speed movie. The observation results reveal that there exist the condensation shock wave at the throat, the water jet surface fluctuation, and that the entrainment occurs on the water jet surface. The radial temperature and velocity distributions exhibit that the temperature and the velocity in the water jet are mostly symmetrical and higher at the downstream.
  • 永武 拓, 功刀 資彰
    2008 年 74 巻 742 号 p. 1303-1309
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    There are several methods of tracking gas-liquid interface of multi-phase flows (MF). In these methods, the MARS (Multi-interfaces Advection and Reconstruction Solver) developed by one of the authors has been successfully applied to many problems, because of the accurate volume/mass conservation of fluid. But the MARS was developed on a structured gird system, and it is difficult to get the results with high accuracy for the complex geometry of the solution domain. On the other hand, the usage of an unstructured grid system in the computational fluid dynamics is now to be a popular manner for handling the complex geometry of the computational domain. In the present stydy, we have developed an interface-volume tracking algorithm on the unstructured grid system for the MF numerical simulation based on the MARS. This paper describes the interface-volume tracking procedure based on the MARS for the unstructured grid system, and discusses on the accuracy of the reconstruction of the interfaces and also discusses on the conservation of the volume of fluid through the advection process.
  • 米本 幸弘, 功刀 資彰
    2008 年 74 巻 742 号 p. 1310-1317
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    The Young's equation describes the interfacial equilibrium condition of a liquid droplet on a smooth solid surface. This relation is derived by Thomas Young in 1805. It has been discussed until today after his work. In general, the Young's equation is discussed from the viewpoint of thermo-dynamics. However, there is no answer which elucidates the normal force balance σlg sin θ in the Young's equation. From the hydrodynamics point of view, there is a momentum jump condition at a gas-liquid interface. This jump condition is derived based on mechanical balance by using mathematical procedure such as Stoke's theorem and the differential geometry. In this study, we reconsider the Young's equation from this momentum jump condition point of view. Finally, we dynamics. However, there is no answer which elucidates the normal force balance σlg sin θ in the Young's equation. From the hydrodynamics point of view, there is a momentum jump condition at a gas-liquid interface. This jump condition is derived based on mechanical balance by using mathematical procedure such as Stoke's theorem and the differential geometry. In this study, we reconsider the Young's equation from this momentum jump condition point of view. Finally, we derive the revised Young's equation in which there is the normal force term (σlg sin θ). Then, we evaluate the revised Young's equation by comparing the analytical solution with the experimental data reported by Amirfazli. Moreover, we discuss on the line tension and the contact angle for a lens
  • 山本 和弘
    2008 年 74 巻 742 号 p. 1318-1323
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    Diesel engines have been used in a wide variety of commercial vehicles. However, several problems must be solved. One of the major concerns is that diesel exhaust gas has more particulate matters (PM) including soot, which are suspected to be linked to human carcinogen. Then, more strict diesel emissions standards are being set in many countries, and diesel particulate filters have been developed to reduce PM in the after-treatment of exhaust gas. In this study, we conduct Lattice Boltzmann simulation on combustion in metal honeycomb filter, where metal obstacles with square shape are inserted in 2-D duct flow with the porosity of 0.8. To examine the filter properties, we change the arrangement and size of metal obstacles in the filter. Results show that the combustion reaction is well simulated to discuss the burning rate of soot particles in the exhaust gas.
  • 内山 知実, 成瀬 正章
    2008 年 74 巻 742 号 p. 1324-1331
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    This study proposes a two-dimensional grid-free simulation method for gas-particle two-phase flow. The method is based on a vortex method, in which the vorticity field is discretized by vortex elements. The behavior of vortex element and the particle motion are simultaneously computed by the Lagrangian approach. Four square cells are allocated around each particle. In each cell, the change in the circulation of gas-phase due to the particle motion is calculated, and it is considered through the change in the strength of vortex element. The grid-free method is applied to simulate the particulate jet generated by small glass particles falling from a slit orifice into an unbounded quiescent air. It is shown that the simulated distribution of air velocity is favorably compared with the measurement. It is also confirmed that the entrained air flow rate agrees well with the prediction by an analytical model. These results suggest the validity of the method.
  • 酒井 幹夫, 越塚 誠一
    2008 年 74 巻 742 号 p. 1332-1339
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    Discrete element method is an effective approach for evaluating the particle behavior in granular flows, whereas it is hardly used in investigating the design and the operation conditions in industries. This is due to the fact that the number of particles is restricted by the limit of computer memories. Consequently the original discrete element method is difficult to be applied to the real-scale systems, where a large number of particles are dealt with. In our previous study, a new discrete element modeling for large-scale particle systems was proposed where a large-sized particle represents a crowd of original particles. The model which is called the coarse grain model was verified by a two-dimensional fluidized bed simulation. In the present study, the coarse grain model is applied to a three-dimensional plug flow in a horizontal pipeline. Plug length, the cycle and stationary layer area occupation are compared between the coarse grain model and the original particle system. The results show that the coarse grain model can simulate the original particle behavior in the system.
  • 東 隆平, 鹿園 直毅, 岩田 博
    2008 年 74 巻 742 号 p. 1340-1346
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    In the present study, a compact gas-liquid separator using micro grooves is proposed and its performance is evaluated by air-water experiment. The gas bubbles are forced out from the liquid flow at the expanding section by the minimization effect of excess gas-liquid interface free energy, while the liquid phase remain confined inside the micro grooves. Two major limits of gas-liquid separation, i.e., (1) flooding limit at high liquid flow rate, and (2) entrainment limit at high gas flow rate are found and investigated by flow visualization. Finally, dimensionless correlations for predicting gas-liquid separation limits are proposed. Furthermore, guidelines to design a high-performance and compact gas-liquid separator are discussed.
  • 水谷 恒一郎, 山本 悟
    2008 年 74 巻 742 号 p. 1347-1353
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    A simple computational algorithm for solving flows over an arbitrary-shaped 3D geometry is proposed. This algorithm is based on the Immersed Boundary (IB) Method. A surface mesh for the object is generated by 3DCG software as a set of triangle polygons. A 3D Cartesian grid is used for the flow field. The velocity field near the object is modified by the present IB method along each grid line separately. In this paper, the present method is applied to an incompressible Navier-Stokes solver based on SMAC method using the staggered grid. Some practical flow problems assuming low Reynolds number are calculated and the results are compared with the experimental and the numerical results. Also, the present method is applied to flows over a moving object. Finally, the performance of the simple IB method applied to flows over 3D objects is discussed.
  • 松井 純
    2008 年 74 巻 742 号 p. 1354-1359
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    The rarefied Couette flow between two walls with triangular surface grooves is simulated by Direct Simulation Monte Carlo method. The groove is set on the stationary wall only, whose depth is h and angle is α. The average flow speed is reduced by the groove, whose effect becomes large on large α and large Knudsen number Kn. The depth of groove has relatively small effect on the average flow. The area with strong disturbed flow made by grooves becomes largest at α=10 degree. When the Kn becomes 0.1, the disturbance becomes smaller. And at large Kn and large distance between walls, H, the area with disturbed flow becomes almost same.
  • 第2報, 乱流場
    宇都宮 浩司, 松山 哲也, 中西 助次, 大坂 英雄
    2008 年 74 巻 742 号 p. 1360-1367
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    The flow past the manipulator ring with permeability in a fully developed turbulent pipe flow was investigated by measuring the turbulent flow field. The manipulator ring with permeability has a rectangular cross section and a height 0.14 times the pipe radius. The experiments were performed under four conditions of the open area ratio β for Reynolds number of 6.2×104. The results indicate that the response of the turbulent flow field to the manipulator ring was delayed as compared with that of the mean velocity field, and that difference increased with β. The values of turbulence intensities and Reynolds shear stress profiles near the reattachment point increased in the region near the wall as β increased, while those peak values that were taken at the locus of the manipulator ring height decreased as β increased. Considering the change of η defined in this paper, the separated shear layer was systemically attenuated as β increased. The increase of β with the manipulator ring in this study was a small influence in the turbulence quantities profiles near the reattachment point as compared with the case of the external flow.
  • 前川 宗則, 宋 明良, 細川 茂雄, 冨山 明男
    2008 年 74 巻 742 号 p. 1368-1375
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    Effects of inlet bubble diameter on void and bubble size distributions in poly-dispersed bubbly flow in a rectangular bubble column under high gas volumetric flux conditions are experimentally investigated. Three types of gas distributors are used to form bubbly flows with different inlet bubble diameters at a constant gas flow rate. The conclusions obtained are as follows : (1) the bubble size distribution reaches an equilibrium state at which the birth rate of bubbles belonging to a bubble group due to bubble breakup and coalescence is equal to the death rate at high gas volumetric flux, (2) distributions of void fraction and bubble diameter are not affected by inlet bubble diameters except for the region close to the air diffuser, and (3) the elevation at which the bubble size distribution reaches the equilibrium state becomes lower as the gas volumetric flux increases.
  • 鷲尾 誠一, 高橋 智, 村上 健二, 多田 達誠, 出口 真次
    2008 年 74 巻 742 号 p. 1376-1385
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    A contact motion between two solids in liquid can give birth to a cavity. To investigate the phenomenon, processes of cavity generation in a liquid between two walls making accelerated relative motions in their normal and tangential directions have been observed in detail, using microscopes and high-speed video cameras. Generation and subsequent expansion of a cavity are dominated by such various factors as the thickness of a liquid film, the acceleration of motion, the initial pressure, the liquid viscosity and the contact area. On the other hand the air solubility in oil influences, not the generation but the size of a bubble remaining after the process is over. The pressure in a liquid film between two parallel walls normally separating with a constant acceleration has also been theoretically analyzed, providing the basis for occurrence of tensile stresses in liquid films. Finally, the following idea has been proposed as a mechanism of the phenomenon; a tensile stress occurring in a liquid film breaks the liquid-solid interface, producing a rift which can develop to a visible cavity. Considering liquid machines have many parts of solid-solid contact in liquid, it should be pointed out that some of the cavitations occurring in them can start from these cavities.
  • 第1報, 実験と数値解析の比較
    西 泰行, 松尾 信明, 福富 純一郎
    2008 年 74 巻 742 号 p. 1386-1394
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    Sewage pumps are designed with a wide flow channel by, for example, sacrificing some efficiency and reducing the number of blades, in order to prevent plugging with foreign bodies. Authors have been proposing a new type of sewage pump impeller designed to further improve pump efficiency and performance in passing foreign bodies. This sewage pump impeller has a structure in which the suction flow channel of closed type non-clog pump is wound in a helical spiral. The focus of this research was to investigate internal flow in this single blade sewage pump impeller. The results clearly indicated the following facts. As a result of having compared experimental results by LDV with calculated results by CFD, there is the difference about the radial component of absolute velocity, but agrees about pump performance and the tangential component comparatively well. A flow to circulate through in the impeller again is accepted by an experiment, and the sign is accepted by CFD in a specific impeller position.
  • 第2報, 切欠き配列迎え角の影響
    巽 和也, 松崎 慎太朗, 中部 主敬
    2008 年 74 巻 742 号 p. 1395-1402
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    The effects of the attack-angle of the fin notch array against the main flow and size of the clearance at the fin-tip on the heat transfer and pressure loss performances of a channel with cut-fins (parallel fins with square notches) mounted on the bottom wall were evaluated in the present article. Three-dimensional numerical simulations and heat transfer experiments employing a modified single-blow method were conducted to discuss these characteristics. Larger reduction of pressure loss ratio was obtained under smaller clearance conditions, while a smaller thermal resistance ratio was achieved with larger clearance by the cut-fins compared with fins without notches. A maximum peak, therefore, appeared in the overall performance in relationship to the clearance size. In the attack-angle effect case, larger heat transfer coefficients were obtained with smaller angles in both experimental and numerical results, particularly under larger Reynolds number conditions. A spanwise flow was generated in the area adjacent to the notch by inclining the notch array that effectively produced a longitudinal vortex like secondary flow and renewal of the thermal boundary layer at the trailing edge of the notch.
  • 大嶋 元啓, 米田 有紀子, 富永 浩二, 中尾 基, 清水 哲夫, 千田 二郎, 石田 耕三
    2008 年 74 巻 742 号 p. 1403-1410
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    The authors proposed a novel chemical vapor deposition system, flash boiling spray CVD (FS- CVD) to improve several kind of problem such as decomposition of precursor at supply line and evaporator. In this method, liquid precursors are supplied directly to vacuum chamber through an injector, just like fuel for an automobile engine, without any vaporizers, so as to induce an unsteady and intermittent flash boiling spray in the chamber. However, it is necessary to keep the lowest ambient pressure because the saturated vapor pressure of precursor is very low. Thus, it is very useful to modify the saturated vapor pressure of precursor. The technique to improve the vaporization of precursor is proposed by mixing a higher saturated vapor pressure organic solvent. In this paper, as a first step to ascertain FS-CVD principle, SiO2 film was formed on the Si substrate. Tetraethyl orthosilicate (TEOS) and n-pentane mixed solution was used as the mixing solution. Using this method, film thickness distribution of SiO2 film on 100 mm diameter Si wafer was ranged as +/-4%. Furthermore, this method enables us to control the film with various thicknesses by optimizing the injection period, cycle and frequency.
  • 近藤 千尋, 川那辺 洋, 小堀 誠也, 塩路 昌宏
    2008 年 74 巻 742 号 p. 1411-1418
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    Distributions of velocity and concentration of turbulent gas jets with various densities from helium to carbon dioxide against ambient air are measured by using particle image velocimetry and laser induced fluorescence methods. The turbulent transport of the jet fluid is directly investigated to analyzing the distributions of jet-fluid concentration and its vortex motion. The result shows that the self-similarity exists between profiles of scalar flux and Reynolds stress along the radial direction. Furthermore, several subgrid scale scalar-flux models for large eddy simulation are discussed. Based on the scattering plots of model values of subgrid scale scalar-flux against the measured values, the characteristics of each model are basically similar for every density conditions. Also, the Favre-averaged scale similarity model performs well for wide various densities.
  • 大内田 聡, 長谷川 達也, 中村 正則
    2008 年 74 巻 742 号 p. 1419-1426
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    A steady state modeling and simulation of refrigeration cycle for air conditioning is performed. The numerical model consists of a constant rotational speed compressor, a condenser, an evaporator, a capillary tube and connecting tubes. Modeling effort is based on deriving governing equations for local thermal flow together with overall conservation of charged refrigerant. After all, the model developed here considers choking event as well as effect of refrigerant charge that are typical problems in cycle simulation of refrigeration. Solution procedure of these equations requires rather complicated iteration since those governing equations cannot be explicitly solved from input parameters. Simulation example is introduced for typical model that uses R 22 as refrigerant. Calculation is conducted from low refrigerant charge to high refrigerant charge with other parameters fixed and the obtained results show qualitatively good agreement with reported experimental data.
  • 長谷川 亮, 阪田 一郎, 柳原 弘道, Bengt JOHANSSON, Alaa OMRANE, Marcus ALDEN
    2008 年 74 巻 742 号 p. 1427-1432
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    A new technique based on phosphor thermometry, for measurements of two-dimensional gas-phase temperature in combustion was established as a new laser diagnostic. The temperature calibration of Dy : YAG phosphor was taken at a surface of solid. The validation for applying gas-phase with line-intensity ratios method was evaluated with lifetime method and thermocouple data in a steady flow. These data showed the good agreements. Phosphor thermometry with single-shot was examined in turbulent combustion in an engine. The reasonable temperature deviation and the agreement with calculated data within 5% precision were achieved in the ignition process of compression ignition engine. The influence factors such as chemical luminescence and intrusion in combustion were discussed.
  • 飯島 晃良, 吉田 幸司, 庄司 秀夫
    2008 年 74 巻 742 号 p. 1433-1442
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    In this study, spectroscopic techniques were used to investigate the effects of the residual gas state and fuel octane number on ignition characteristics of a Homogeneous Charge Compression Ignition (HCCI) engine. Spectroscopic measurements were made of light emission spectra and of light absorption spectra. The results revealed that varying the fuel octane number and the residual gas state changed the cool flame magnitude and the duration of the low-temperature reaction period, which substantially altered the ignition characteristics of HCCI combustion. Specifically, when a low-octane fuel was used, the heat release rate waveform for HCCI combustion showed cool flame, which was clearly observed in the light emission spectra and light absorption spectra. The level of absorbance at a wavelength corresponding to the cool flame reaction decreased when the fuel octane number was increased. Additionally, the level of absorbance also decreased when residual gas was applied to HCCI combustion of a low-octane fuel and approached that seen for HCCI combustion of a high-octane fuel. With the application of residual gas, the low-temperature reactions showed less reactivity when low-octane fuels were used, and the reactions were less sensitive to changes in the octane number of the fuel. As a result, the ignition timing tended not to change in relation to variation of the fuel octane number.
  • 荒木 幹也, 岸本 秀雄, 中島 邦明, 前原 充宏, 志賀 聖一, 中村 壽雄, 小保方 富夫
    2008 年 74 巻 742 号 p. 1443-1450
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    Performance of a 2 stroke cycle engine fuelled with CNG (Compressed natural gas) using intermittent fuel injection from a scavenging port is investigated experimentally. The test engine is a 2 cylinder, 398 cm3, 2 stroke cycle spark ignition engine. Gaseous fuel injectors are attached at the cylinder block, and a CNG is injected into the scavenging passage through a fuel injection pipe. The fuel injection pressure is set at 0.255 MPa, and the fuel is injected intermittently during the scavenging process. The length and tip geometry of the fuel injection pipe are varied, and the effect on the engine performance is investigated. Using the scavenging port fuel injection, the BSFC is reduced by 25%, and the lean burn limit extends from λ= 1.2 to 1.46, at the maximum. The peak of the NOx emission shifts to leaner side, and the THC emission is reduced by 47 % at the maximum. It is_considered that the intermittent fuel injection from a scavenging port is effective to achieve stratified combustion and reduction in fuel short circuiting through the cylinder.
  • 植田 裕, 木下 英二, 田島 博士, 浜崎 和則
    2008 年 74 巻 742 号 p. 1451-1457
    発行日: 2008/06/25
    公開日: 2011/08/16
    ジャーナル フリー
    In order to reduce the pour point of palm oil biodiesel, palm oil butyl ester (PBE) is made with 1-butanol by transesterification. As a result, the pour point of PBE is 5.0°C and it is lower than that of palm oil methyl ester (PME), 12.5°C. The combustion characteristics and exhaust emissions of PBE are investigated using a direct injection diesel engine, and are compared with PME, rapeseed oil methyl ester (RME) and JIS No. 2 gas oil. The thermal efficiency of PBE is almost the same as those of the other test fuels. PBE has good ignitability as PME. Although HC, CO and smoke emissions of PBE are slightly higher than that of PME, PBE has lower exhaust emissions compared with the gas oil. Also, smoke emission of PBE is almost the same as that of RME. It is concluded that PBE is a good alternative diesel fuel.
  • 井上 誠司, 井上 哲, 三枝 弘, 小林 敬幸
    2008 年 74 巻 742 号 p. 1458-1459
    発行日: 2008/06/25
    公開日: 2011/03/03
    ジャーナル フリー
    An adsorption refrigerator is effective device to reduce the global warming. However it is necessary to down size the adsorber to make it into wide use. To reduce the size of adsorption refrigerator, it is important to make simulation model which can calculate the performance of adsorber. In the simulation model, some parameters of the layer (thermal conductivity, gas diffusion coefficient and so on) have to be estimated from experimental data. In this paper, gas diffusion coefficient was measured using minute glass beads from those parameters. Then the data was compared to simulation results, and an equation that indicates the gas diffusion coefficients was derived.
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