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Kazuyoshi TAKAYAMA
1989 Volume 55 Issue 513 Pages
1271-1276
Published: May 25, 1989
Released on J-STAGE: March 28, 2008
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Yukio ISHIBASHI, Yukio TOMITA, Toshio YOKOYAMA
1989 Volume 55 Issue 513 Pages
1277-1282
Published: May 25, 1989
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The purpose of this study is to investigate the basic properties of a ferrofluid jet in a nonuniform magnetic field. Using nozzles which have various diameters, the behavior, the liquid column deformation and the droplet formation of water-based ferrofluid jets in a nonuniform magnetic field being perpendicular to the flow direction are experimentally examined. Then, the factors influencing greatly the liquid column length and droplet spacing of ferrofluid jets ejected from capillary nozzles are found by using dimensional analysis.
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Kimitaka HIRANO, Masanori KIKUCHI, Tetsuo NISHIYAMA
1989 Volume 55 Issue 513 Pages
1283-1288
Published: May 25, 1989
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In a supersonic flow with a discontinuous surface of tangential velocity, a Mach wave from a supersonic source is reflected and refracted at the discontinuous surface. According to the image method, a reflected wave is expressed by an image source and a transmitted wave by a transmitted source. Further more, the image method is applied to reflection and transmission of a Mach wave in a supersonic flow with two different boundaries: a discontinuous surface and a solid wall. a lot of image and transmitted sources are introduced in a flow field as the interference between these boundaries. A flow disturbed by an aerofoil is discribed as a function of the original sources distributed on the upper and lower surfaces of an aerofoil and their image sources. We determined numerically the effect of two boundaries on the characteristics of a lens section and so on.
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Kimitaka HIRANO, Tetsuo NISHIYAMA, Masanori KIKUCHI
1989 Volume 55 Issue 513 Pages
1289-1295
Published: May 25, 1989
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When a vortex and a source are placed in a subsonic flow a discontinuous surface of tangential velocity, flow fields disturbed by these original singularities are derived by the image method. a system of an image singularity and a transmitted singularity is determined by linear boundary conditions on the discontinuous surface. Further more, this method is applied to original singularities in a flow with two discontinuous surfaces. In the thin aerofoil theory, original vortexes and sources are distributed on a chord to represent an aerofoil. an original source distribution is determined only by the thickness of an aerofoil. However, an original vortex distribution is affected by the interference between discontinuous surfaces and the aerofoil thickness. We determined numerically the effect of two discontinuous surfaces on the characteristics of a flat plate and a symmetrical aerofoil.
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Katsuhiro YAMAMOTO, Eisuke OUTA, Masashi OUTA, Toshio MIWA, Koichi OKA ...
1989 Volume 55 Issue 513 Pages
1296-1301
Published: May 25, 1989
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As an effective computational model, a vaporous cavity model, an air release model and a discrete free gas model have been developed to simulate transient cavity flows. In this report, the validity of these models is reexamined by employing a prototype horizontal pipeline with or without elevation points. In the vaporous cavity model and the discrete free gas model, fairly good results are obtained for the case of low void fraction becouse numerical instability appears to be small in the pressure responses using the characteristics method with linear interpolations. The air release model represents satisfactory results in the case of a relatively large void fraction, however such a model includes some unpredictable parameters and requires a more complicated algorithm than the other two models to get a solution. all the models discussed here are able to predict the maximum pressure profile along the pipeline for transient cavity flows up to at least 3% of void fraction.
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Toshio YOKOYAMA, Yukio TOMITA
1989 Volume 55 Issue 513 Pages
1302-1307
Published: May 25, 1989
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The behavior of jets of water and dilute polymer solutions issuing from curved pipes has been experimentally investigated. A jet column from a curved pipe is not disintegrated up to a larger Reynolds number as compared with a jet column from a straight pipe. It has been found that a particular region on the jet length exists between the laminar region and the transition one in the flow of solutions. The transition Reynolds number to this region has been formulated in terms of the Weber number, Weissenberg number and the ratio of curvature radius. Empirical formulas for jet length also have proposed in the laminar, the turbulent and the particular regions. Furthermore, it has been shown that there is a correlation between jet breakup length and disturbance in the flow.
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Katsutaka NAKAMURA, Yasutoshi SENOO
1989 Volume 55 Issue 513 Pages
1308-1311
Published: May 25, 1989
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In order to cure asymmetry of the flow field near the inlet and the exit of a conventional horizontal film evaporator, the following modifications were made. Liquid was supplied to the evaporator cylinder through a circumferential groove covered with a net. The circumference of the groove was divided into eight sections, each of which was connected to a different head tank so that liquid of almost equal head was supplied to all in spite of the different heights of the sections. The outlet was a simple circumferential groove. A net was installed on the rotor normal to the axis near the inlet. Experimental data showed that the circumferential variation of the liquid fillet was considerably reduced compared to the pattern observed in a conventional apparatus.
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Katsutaka NAKAMURA, Yasutoshi SENOO
1989 Volume 55 Issue 513 Pages
1312-1317
Published: May 25, 1989
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In a horizontal agitated thin-film evaporator, axial flow has to be induced according to the required flow rate. The axial driving force of liquid is the axial gradient of the pressure force on the cross section of the liquid fillet, and the gradient of pressure force is materialized by variation of the circumferential length of the fillet on the rotor blades. The axial driving force balances the axial component of the friction forces on the rotor and the stationary cylinder which are induced by the relative motion of liquid in the fillet and the thin film. the configuration of the liquid fillet varies depending upon the rotor speed and the flow rate as well as the viscosity of the working liquid. The relationship observed in a series of experiments was well predicted by the theory developed in this paper.
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Min Chi CHENG, Tadashi YANAGISAWA, Mitsuhiro FUKUTA, Takashi SHIMIZU
1989 Volume 55 Issue 513 Pages
1318-1323
Published: May 25, 1989
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A scroll compressor has a built-in volume ratio, and ideally it should be operated under a built-in pressure ratio condition that is a function of the built-in volume ratio. but in actual operation, the compressor shows its maximum efficiency at a pressure ratio that differs from the built-in pressure ratio. In this paper, theoretical performances are presented by analyses accounting of flow resistance at the opening of scroll warps and leakage through wrap clearances. The flow resistance at the discharge opening causes an over compression loss in a built-in pressure operation but reduces a undercompression loss in a high-pressure operation, which indicates that the optimum operating pressure ratio shifts to a pressure ratio higher than the built-in pressure ratio. Leakage accelerated the pressure rise during a compression process so that the optimum pressure ratio becomes lower than it would be in the absence of leakage. Increase in the compressor speed moderates the under compression loss and leads to a higher optimum operating pressure ratio.
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Nobuyuki TANIGUCHI, Chuichi ARAKAWA, Toshio KOBAYASHI
1989 Volume 55 Issue 513 Pages
1324-1328
Published: May 25, 1989
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In flow simulations with the finite different method or the finite volume method, it is a serious limitations that the calculating points must be ordered on the co-ordinates. Using the Voronoi diagrams for the cell division of the finite volume method creats a new discretization form which permits the arbitrary distribution of thee points. This paper constructs a new method for the flow simulations by Voronoi diagrams, and shows calculation results of the two-dimensional flows.
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Shigeru TADA, Yoshihiro MOCHIMARU
1989 Volume 55 Issue 513 Pages
1329-1333
Published: May 25, 1989
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The pressure gradient method using components of pressure gradients as dependent variables is applied to the simulation of two-dimensional transient natural convection in a horizontal circular cylinder, where fluid is initially at rest, and then the wall is subject to a step change of temperature. It is found that, at least in the case of a low Grashof number flow, relative errors of velocity, pressure, and temperature, produced by the present method are smaller than those produced by a primitive velocity-pressure variable method and that, over the wide range of a Grashof number, from 5×10
2 to 2×10
5, the prediction of the maximum of the magnitude of velocity at the center and of the time when the magnitude of the velocity at the center becomes maximum is in good agreement with the available experimental data.
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Akira MIZUKAMI
1989 Volume 55 Issue 513 Pages
1334-1337
Published: May 25, 1989
Released on J-STAGE: March 28, 2008
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With the wider use of vector-processing computers, much attention has come to be paid to the conjugate gradient method to solve a linear system of algebraic equations. However, in the case of finite element methods, it is rather difficult to tune up the computer program of the conjugate gradient method so as to make a big reduction in CPU time, because a coefficient matrix appearing in the finite element analysis is sparse and the nonzero components are irregularly located. In this paper, we present a vectorization technique for the conjugate gradient method by using element matrices only. The loop length attained by the present technique is as long as the number of elements and the rate of acceleration is very high.
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Hideki KAWAI, Teruyuki KAWASHIMA, Takahiko TANAHASHI
1989 Volume 55 Issue 513 Pages
1338-1344
Published: May 25, 1989
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The flow of an incompressible viscous fluid in a porous pipe has been considered by many investigators. but these studies have been performed under the assumption that the wall suction or the injection velocity are constant to the axis. It is natural that the filtration or the absorption velocity across the wall depends on the difference the hydorostatic pressure between the inner and outer wall (Starling's hypothesis). But analysis based on Starling's hypothesis has been difficult to calculate because of the feedback condition which causes numerical instability. In the present paper, this problem is improved by the penalty function method. We show here that flow in a porous pipe is controlled by the porosity or the pressure difference across the porous wall.
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Keisuke SUESADA, Mitsuhiko TAKEMURA, Takahiko TANAHASHI, Eiji KASAHARA
1989 Volume 55 Issue 513 Pages
1345-1350
Published: May 25, 1989
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A clean room has recently become indispensable equipment for various kinds of industries. In order to design a clean room, it is important to consider improvement of the working environment and energy conservation. The air flow of a clean room is very complex. It consists of recirculation flows, and the direction of mean air flow is changed locally. A method of numerical simulation have been developed to delineate a guideline for ventilation design of a clean room. This paper presents an improved finite element analysis for solving unsteady incompressible Navier-Stokes equations. This scheme is based on the algorithm of the HSMAC (Highly simplified marker and cell) method in SOLA and the general idea of orthogonal decomposition. It has actually been applied to the case of the lid-riven square cavity flow at Re=10 000, and of air flow in a conventional clean room. Unsteady flow simulations in terms of stream lines, equipressure lines, and equivorticity lines are obtained on a color graphic display.
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Ryuii FUJINUMA, Teruo NAKAMURA
1989 Volume 55 Issue 513 Pages
1351-1356
Published: May 25, 1989
Released on J-STAGE: March 28, 2008
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The rarefied gas lubrication was analyzed based on modefied Reynolds equation and a FEM formulation was adopted for the computation with a trial function separated locally. The air film under the slider has such a thin dimension as 1/3000 (depth/width) and flows in one direction. Therefore the distribution of the pressure in transversal direction is almost constant except the boundary region. Typical two dimensional FEM formulation is not adequate for this type of problem. Results presented in this report show the above perspective. The computational analysis was done for three types of sliders, that is, a tapered flat slider, a two rail slider and a zero load slider. All results reveal the applicability of the present method of computation.
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Manabu SANO, Tsutomu OOISHI, Noboru TAKANO
1989 Volume 55 Issue 513 Pages
1357-1361
Published: May 25, 1989
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The self-excited oscillation of a rectangular jet impinging on an edge is investigated experimentally. Cross-correlation functions between the pressure of fluctuation of the edge and those of measured points in the nozzle-edge span are calculated. Contour lines of cross-correlations and phase differences are depicted. Peaks from the edge to the nozzle exit are found in those contour lines; a connecting line with these peaks is assumed as a main path of feedback. The phase lags a bit and is positive. This suggests that the oscillation occurs by the positive feedback of the pressure fluctuation at the proximity of the edge to the nozzle exit. Furthermore, the existence of the feedback path is made visible by three-dimensional graphics of cross-correlation functions. It seems that there is a relation between the cross-correlation and the maximum magnitude of the pressure fluctuation.
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Hiroyuki HANIU, Hiroshi SAKAMOTO, Yoshitake SAKAI
1989 Volume 55 Issue 513 Pages
1362-1367
Published: May 25, 1989
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An experimental study was carried out on a turbulent jet with streamline curvature. The experiments were conducted in a hydraulic tank using Laser Doppler Velocimetry (LDV) with frequency shifters for the measurement of reverse flow. The measurements were made at the self preserving range namely 10≲s/D≲20, where s is distance along the curved jet center line and D is the width of the jet at exit. The results show the effects of streamline curvature on the turbulent quantities, such as shear stress and eddy viscosity. Especially the weak stabilizing effects of streamline curvature in the inner region and destabilizing effects of curvature in the outer region can be seen.
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Shusuke HARA, Toshiki SUZUKI
1989 Volume 55 Issue 513 Pages
1368-1371
Published: May 25, 1989
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The hydrodynamic forces generated by water-circular cylinder interaction have been investigated experimentally. Two kinds of circular cylinder models of 50 and 75 mm diameter and 200 mm span length, and six kinds of end-plates of 68, 100, 150, 200, 300 and 400 mm width were used. The cylinder supported by two end-plates was oscillated horizontally in standing water by mechanical oscillation machinery. Period parameters ranging from 0.2 to 2.6 and Reynolds numbers from 5 000 to 40 000 were covered in the investigation. The results have shown that the force amplitude coefficients based on the acceleration have a constant value of 1.0 at the end-plate dimensions of greater than four times the cylinder diameter, and the effects of end-plate dimensions on the force amplitude coefficient are not influenced by Reynolds number and Period parameter.
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Yoshikuni SHIRAHAMA, Kuniaki TOYODA
1989 Volume 55 Issue 513 Pages
1372-1376
Published: May 25, 1989
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The large-scale structure of a turbulent pipe jet has been studied measuring the stasistical properties of fluctuating pressure and velocity. The power spectral density of fluctuating pressure shows the large-scale vortical structure more clearly than that of fluctuating velocity. The jet response to excitation has been discussed in consideration of the effect by pipe resonance, suggesting that the most unstable mode occurs at the Strauhal number St=0.38. The space correlations of fluctuating velocities show the so-called "lobe" structure in the azimuthal direction of the large-scale structure.
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Masami SUZUKI, Chuichi ARAKAWA, Tetsuo TAGORI
1989 Volume 55 Issue 513 Pages
1377-1385
Published: May 25, 1989
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This is a report of a fundamental study on the design method that includes the interaction between air chambers and turbines, using the rule of similarity in the nondimensional form of governed equations. It is presented how to analyze the power absorbed in irregular waves by use of both their spectrum and probability. It is shown that the linear theory of water waves and the equivalent floating body approximation are applicable to the evaluation of the absorbed power in air chambers. Furthermore, in order to get good agreements with the experiments, losses of air chambers owing to the viscosity should be added in the analysis. Turbine performances in irregular waves are easily shown with the probability density distribution, that is, Gauss distribution. This paper also presents the design method that can predict the minimum cost in the constrution, which is now very important to develop these facilities in the society.
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Hideki YOSHITOMI, Tsutomu WADA, Tadao KOIZUMI, Kenichi MUROYAMA
1989 Volume 55 Issue 513 Pages
1386-1391
Published: May 25, 1989
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The investigation described in this paper was undertaken to obtain the design criteria of a fluidic pump with two vortex diodes. As the design parameters of the pump, we selected the pump head, driving pressure, passage areas of the suction and delivery diodes, diode characteristics, and resistances of the suction and discharge pipes. In the first stage, dimensionless performance factors were derived by analyzing the pump system to have the advantage of estimating the design parameter effects under any specified conditions. Then their effects were clarified by both theoretical calculations and experimental measurements. The optimum values were discussed for the dimensionless performance factors focusing on not only pump efficiency but also flowrate. From the results of this study, design guides to provide good performance pump are suggested.
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Yoshihiko HARAMURA
1989 Volume 55 Issue 513 Pages
1392-1396
Published: May 25, 1989
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A new technique is developed to measure the thickness of liquid film formed under a coalesced bubble in high heat flux nucleate boiling which is considered to play a major role in the restriction of heat transfer. Thickness of the film is determined by conservation of the heat. The liquid film is formed at the moment a coalesced bubble covers the whole of the surface, which is determined through high-speed photographic obsevation. The initial thickness of the film can be estimated when it dries before the bubble departs, assuming that it is dissipated only by vaporization and there is no liquid inflow. The heat transfer surface is 3.7mm×4mm and made o nickel foil, 5 μm thick, heated electrically to keep its temperature constant. it is surrounded by a copper block-heated surface to avoid liquid inflow. The thickness measured for saturated water at atmospheric pressure is about 15-20μm, which must be made reliable by accumulating a large amouat of data.
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Sadahiro NAMIE
1989 Volume 55 Issue 513 Pages
1397-1402
Published: May 25, 1989
Released on J-STAGE: March 28, 2008
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In order to apply the large heat capacity of a two-phase mist flow for the purpose of uniform and soft cooling of high-temperature surfaces, the effects of mass flow rate, mass flow quality, liquid droplet diameter and heat flux on an increase rate of the fluid temperature are investigated numerically in the tube. The results indicate that newly defined coefficient of temperature increase becomes small for a smaller droplet diameter than 200 microns and for thee low inlet quality. A simple expression of the relation between the coefficient and the above-mentioned parameters, including the effect of temperature dependence of fluid properties, is obtained for the thermally developed region of the tube. The initial values of gas temperature and relative velocity between the droplet and the gas phase influence the coefficient mainly at the entrance region of the tube.
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T. ITO, K. TANAKA, T. TAMARI
1989 Volume 55 Issue 513 Pages
1403-1409
Published: May 25, 1989
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An attempt is made to predict the augmentation performance of the nucleate boiling heat transfer at surfaces with a sintered layer of metal particles. The estimated performances are compared with experimental data collected under different combinations of the boiling liquid and the surface. The correspondence is found to be fairly good.
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Suguru YOSHIDA, Takashi MATSUNAGA, HONG Hai-Ping, Makoto MIYAZAKI
1989 Volume 55 Issue 513 Pages
1410-1417
Published: May 25, 1989
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Local heat transfer coefficients were experimentally investigated, with special attention paid to their values along a tube perimeter, for the flow of Refrigerant-22 with 0 to 6 percent by mass of oil contained inside horizontal evaporator tubes. The addition of the oil to the refrigerant produced an increase in the heat transfer coefficient over a wide range of quality at low mass velocities and in the low quality region at high mass velocities where the tube perimeter was not wholly wetted. This increase was attributed to an intensive foaming action which promoted tube wetting. The heat transfer coefficient at high mass velocities, where an annular liquid film was formed over the whole tube perimeter, decreased with increasing quality due to the formation of the oil-rich liquid film, which gradually expanded from the top toward the bottom of the tube.
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Kengo SASAGUCHI, Yoshinobu SAKAMOTO
1989 Volume 55 Issue 513 Pages
1418-1425
Published: May 25, 1989
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Many studies have been performed on the solidification and melting of a phase change material around a finned tube. Detailed information on the solidification process has been obtained experimentally and theoretically since heat conduction plays a main role in the process and the phenomenon is relative simple. On the melting process, however, no analytical studies have been presented so far because natural convection is important in this process, thus the problem becomes very complicated. In this study, numerical calculations have been performed for an elemental region around a tube with longitudinal fins in order to clarify the effect of natural convection on the melting process.
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Hiroshi YAMASHITA, Yan WANG
1989 Volume 55 Issue 513 Pages
1426-1431
Published: May 25, 1989
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The purpose of this report is to investigate the fluid flow and heat transfer in an opposed axisymmetric jet in a uniform stream, paying attention to the unsteady motions for jet velocity u^
-0=1045 m/s and uniform stream velocity U^
-=5=15 m/s. An air jet heated to a temperature of about twenty degrees above a uniform air stream issues from a nozzle 5.0 mm in diameter. Time histories and power spectra of velocity and temperature are measured by a hot-wire anemometer, a resistance thermometer and a FFT spectrum analyzer. These indicate that there are unsteady motions of low frequency and large scale, the frequencies of which are varied with the distance form the nozzle exit and velocity ratio u^
-0/U^
-. The results may be well rearranged in terms of jet-reached distance, that is, the distance between the nozzle exit and the flow stagnation point.
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Takehiko YANAGIDA
1989 Volume 55 Issue 513 Pages
1432-1437
Published: May 25, 1989
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This paper shows a calculating model of the heat transfer coefficients of IC packages in succession on a printed wiring board. Air temperature around any downstream package rises from the inlet air temperature by the thermal wake of the upstream packages. Therefore, the heat transfer coefficient of a downstream package decreases. The air temperature distribution behind a single package was shown in the previous report. By superposing the temperature rise behind the upstream packages, an equation used to predict the heat transfer coefficients of the packages is proposed. The predicted values agree well with the experimental results.
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Toshio OHARA, Toshihiro YAMAMOTO, Kosho MATSUZAKI
1989 Volume 55 Issue 513 Pages
1438-1443
Published: May 25, 1989
Released on J-STAGE: March 28, 2008
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Experimental investigations were made on boiling heat transfer using refrigerant-12, inside plate-fin-type evaporator tubes with a sharp 180-degree turn. The wall temperature distributions in a smooth tube and cross-ribbed tube were measured in detail. Experiments were conducted with the following conditions: (1) pressure of 0.29 MPa, (2) mass velocities of 44 to 132 kg/m
2s, (3) heat fluxes of 4.7 to 20 kW/m
2, (4) inlet quality of 0.3 to 0.85. Results show that the smooth tube has an uneven wall temperature distribution along the longitudinal and transverse directions. Wall temperatures of the near-inlet and near-outlet regions are higher than other regions. The cross-ribbed tube, contrary to the smooth tube, has however uniform wall temperature distributions along the longitudinal and transverse directions, which gives higher cooling performance and more uniform outlet air temperature.
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Yasushige UJIIE, Tatsuro TSUKAMOTO, Michikata KONO
1989 Volume 55 Issue 513 Pages
1444-1447
Published: May 25, 1989
Released on J-STAGE: March 28, 2008
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Two kinds of laser diagnostic techniques, the Rayleigh scattering and Raman scattering methods, were used to measure the temperature of the flame which propagates spherically in a spherical combustion chamber. First, the temperature of a stoichiometric methane-air flame was measured by the Rayleigh scattering method and the results were compared with the calculated values. It was found that the measured result agreed well with the calculated one for the temperature of the flame just behind the flame front, but the measured temperature was quite low compared with the calculated value in the final period of the combustion. Next, the Raman scattering method was used to measure the temperature of stoichiometric methane-air and propane-air flames. In this case, agreement between the measured temperature and calculated one is good. It was shown that the Raman scattering method is suitable for the temperature measurement of propagating flames.
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Satoshi KADOWAKI, Tatsuya HASEGAWA, Ko TERADA, Yasuhiko OHTA
1989 Volume 55 Issue 513 Pages
1448-1453
Published: May 25, 1989
Released on J-STAGE: March 28, 2008
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Unsteady motions of one-dimensional reacting flows in planar, cylindrical, and spherical coordinates were numerically simulated using the explicit MacCormack scheme and the Beam-Warming scheme. The preexponential term of the reaction rate was determined by theoretical analysis to compare the numerical results with the solution of the asymptotic method. The explicit MacCormack scheme was proved to be more appropriate in this subject than the Beam-Warming scheme; this included both the accuracy of solutions and the computational efficiency. The MacCormack scheme could well reproduce a fluid dynamic interaction of reflected pressure waves and a plane flame when simulating confined flame propagation.
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Yuji Ogawa, Shiro TAKI
1989 Volume 55 Issue 513 Pages
1454-1457
Published: May 25, 1989
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Experiments on the deflagration to detonation transition (DDT) in gas mixtures in open space are carried out. Turbulent flames are accelerated by several grids repeatedly placed on the bases of the idea of a positive feed back mechanism. This experimental technique makes us possible to control the flame propagation velocity. The flame acceleration in methane/oxygen mixtures are compared with those in ethane/oxygen systems to investigate the parameters on the sensitivity of DDT. It is found that the DDT in the methane/oxygen mixtures can be made even in the open space, although the flames have to be highly accelerated to form "shock + flame" structures. The mechanism of the acceleration of the methane flames are no different from those of the ethane flames. The small explosions appearing in the turbulent flames of the methane mixtures are fewer in number than those of the ethane mixtures which may be connected with the DDT sensitivity.
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Tatsuya HASEGAWA, Koji MIYAWAKI, Shigeki YAMAGUCHI, Norio OHIWA
1989 Volume 55 Issue 513 Pages
1458-1462
Published: May 25, 1989
Released on J-STAGE: March 28, 2008
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Iodine concentrations in a nitrogen cold jet were measured by the laser-induced fluorescence method. The fluorescence signal was found to depend on the jet velocity, but the dependency became negligible above 10m/s as the sampling volume became smaller than the volume of the focal point. Concentration measurements in a cold nitrogen jet were then performed at a velocity of 46.7m/s. The distrubution profiles of the average concentration along the jet axis showed familiar jet profiles. The transition to turbulence was recognized by the longitudinal decrease of the peak concentration. The distribution profiles showed self-similarities.
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Asumasa YOSHIDA, Takeshi KUNITOMO
1989 Volume 55 Issue 513 Pages
1463-1468
Published: May 25, 1989
Released on J-STAGE: March 28, 2008
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A two-dimensional numerical simulation is carried out for the unsteady heat transfer in a polluted urban boundary layer containing aerosols. The effects of aerosols upon the thermal structure over a region including an urban area are studied synthetically in full consideration of radiative heat transfer. The results indicate a strong interaction among the distribution of air temperature, wind velocity and aerosol concentration in connection with the scattering and absorbing characteristics of aerosols. When the scattering of solar radiation by aerosols is predominant, the air temperature in the urban area drops greatly, and the convergent flow to the urban area becomes weak, causing the aerosol concentration in the urban area to become high. when the absorption of solar radiation is predominant, the convergent flow to the urban area is not weakened. Air temperature drops near the earth surface, but the change in the upper air temperature is small.
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Kunio HIJIKATA, Hiromi HASEGAWA, Takao NAGASAKI
1989 Volume 55 Issue 513 Pages
1469-1476
Published: May 25, 1989
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Heat transfer characteristics of a variable conductance heat pipe, which uses a binary mixture of Freon R113 and R11 as a working fluid have been investigated. In a certain range of a heat input, the more volatile substance, R11, is gathered in the upper part of the cooling section, and condensation does not occur in this part. The length of this noncondensing region decreases with increasing the heat input, and a temperature difference between the heated and cooled wall is kept constant. The same characteristics are also observed in the case of the mixture of R113 and air. However, the mixture of R113 and R11 has a higher heat transfer rate and excellent performance for constant temperature operation. A theoretical model for the heat transfer in the cooling section of the heat pipe is proposed, and the calculated results well explain the experimental results.
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Kunio YOSHIKAWA, Susumu SHIODA
1989 Volume 55 Issue 513 Pages
1477-1484
Published: May 25, 1989
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A new triple combined cycle which is topped by closed cycle MHD and bottomed by gas and steam turbines is proposed for natural gas and gasified coal-fired plants. This triple combined cycle shows a potential for higher plant efficiency and lower NO
x emission level than a conventional gas turbine combined cycle. The optimum weight ratios of air to coal and stem to coal supplied to a gasifier are investigated for maximizing the plant efficiency and minimizing NO
x emission level in the gasified coal-fired triple combined cycle.
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Toshikazu KADOTA, Mitsunori HOSHINO, Osata SUMIDA, M.A. MEMON
1989 Volume 55 Issue 513 Pages
1485-1489
Published: May 25, 1989
Released on J-STAGE: March 28, 2008
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An experimental study was made of droplet behavior in the combustion chamber of an automotive spark ignition engine with multipoint fuel injection. The laser Mie scattering technique was applied for time-resolved measurements of the size of the liquid droplets in the combustion chamber which were caused by the intermittent injection of unleaded regular gasoline into an intake port during the intake stroke of the motored engine. In order to make the optical diagnostics accessible, the original engine was modified to permit installation of an extended transparent combustion cylinder and a piston. The results showed that the temporal variation of the droplet size during intake and compression strokes was slight. It was also found that the droplet size decreased with an increase in the intake valve temperature. Both engine speed and fuel injection timing did not have an appreciable effect on the drolet size within the range of experimental conditions.
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Tomio OBOKATA, Stefan BOPP, Cam TROPEA
1989 Volume 55 Issue 513 Pages
1490-1493
Published: May 25, 1989
Released on J-STAGE: March 28, 2008
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A simple adapter for a two-dimensional, backscatter, fiber-optic laser Droppler anemometer probe consisting of two glass plates has been developed to measure the spatial correlation of velocity fluctuations. A conventional two-color, four-beam LDA probe has been modified by reversing the placement of two of the fibers so that both the green and the blue control volumes measure the same velocity component. An adapter for beam separation is ten mounted behind the front lens to separate the two control volumes. In the present work, the measuring point separation was varied up to 3 mm in the lateral and vertical directions. By using only one glass plate 10 mm thick, it was also possible to achieve in-line (Axial) displacements of the control volumes of up to 3.5 mm. spatial correlations were performed in an intermittent jet flow in which the convective flow velocity could be deduced from the offset of the cross-correlation function.
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