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宮倉 秀人, 大場 利三郎, 池田 隆治, 五十嵐 三武郎
1988 年 54 巻 504 号 p.
1879-1884
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
In order to make clear the mechanism of dissolved gas-content effects on cavitation in this report, the author precisely analyzed statistically the acoustic pressure pulses generated from cavitation in a typical orifice flow and simultaneousely observed the cavitation aspect within the near-desinent cavitation range, for various dissolved CO
2-gas contents in air-undersaturated water. The CO
2 gas was forcibly dissolved in water under the same cavitation-nuclei distribution. Since both the aspect and the corresponding stochastic behavior of the pulses change considerably in comparison with the air-saturated water counterparts, it is concluded that the dissolved gas is not necessarily dircetly related to the cavitation inception. However, if the water is saturated by air or if it has many weak micro air bubbles, the dissolved gas becomes a dominant factor through a typical process, by which the very small nuclei rapidly grow to the well-grown breeded nuclei.
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大島 亮一郎
1988 年 54 巻 504 号 p.
1885-1890
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
In order to find a simple practical rule of cavitation inception in butterfly valves, the inception was carefully investigated for various sizes of model valves and a full scale valve of 1500 mm in diameter. Predominantly, there is a kind of vortex cavitation within the vortex core downstream from the test valve, so I define a new cavitation number K based on the local pressure drop within the core, and find a simple rule of inception, such as the inception cavitation number K
i is almost constant for butterfly valves.
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西山 哲男, 大柳 英樹, 井殿 幸則
1988 年 54 巻 504 号 p.
1891-1897
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Time-series analysis were performed for the measured cavity length, back surface pressure and lift of the ogival section oscillated in pitch about midchord. The notable features were clarified through some typical stochastic functions obtained ; that is, (i) flow patterns consist of two kinds of cavitation, static and dynamic ones, their ranges of occurrence of which are shown with respect to cavitation coefficient and oscillation frequency and (ii) hysteresis characteristics are discussed for the cavity length and lift in each cavitation coefficient to which partial, transient and super cavitation correspond.
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中村 育雄, 戸谷 順信, 山下 新太郎, 植木 良昇
1988 年 54 巻 504 号 p.
1898-1905
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Various steady flow fields of Taylor vortex flow between concentric cylinders have been investigated by means of a flow visualization technique. The experiments have been made on an apparatus of particular small aspect ratio Γ, with the aim of comparing the Taylor vorticies between asymmetric and symmetric end conditions, that is, the cell structure, cell formation processes, and variation of cell heights relative to Reynolds number Re. In the asymmetric case the cell structure has mainly odd number cells, and also even number cells in the limited range of Γ and Re. For even number cells in the asymmetric case, curious facts are revealed as anomalous modes which have flow direction near the end and outward, that is, opposite to the primary flow direction. And in the symmetric case the cell structure has only even number cells. The formation process which depends symmetric case the cell structure has only even number cells. The formation process which depends on the Γ and end condition, has three types in the asymmetric case and only one in the symmetric case.
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石橋 幸男, 富田 幸雄, 進邦 紀夫
1988 年 54 巻 504 号 p.
1906-1912
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
In this paper, the influence of various factors on the behavior of the meniscus and the drop shape are experimentally examined in a uniform drop formation region in which ink-drops are released very regularly from a capillary nozzle. For that purpose, the applied voltage and flow rate are varied, and in addition, liquids having different values of physical properties are used. Then, the relations among the various factors governing the behavior of the meniscus are found by using dimensional analysis.
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吉田 一徳, 山田 豊
1988 年 54 巻 504 号 p.
1913-1919
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The flow characteristics in a tube composed of numerous ring plates of uniform size at an interval of the same clearance are investigated experimentally. The friction coefficients and the radial distributions of the velocity are reported for fully developed flow with different clearances and wall taper angles. The friction coefficient is calculated from the momentum and the static pressure gradient of the flow. The results show that the mean velocity decreases with the axial distance exponentially, and that the wall taper angle at which the friction coefficient is minimum for various clearances is 2°. The radial distributions of the velocity agree with the logarithmic law of rough tubes for an angle of 2° and over.
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石川 勝也, 中村 育雄
1988 年 54 巻 504 号 p.
1920-1928
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
To obtain the best performance and optimum geometries for a wide range of diffuser geometries, experiments have been performed on many conical diffusers having a uniform inlet flow outside the thin inlet boundary layer and free discharge using air flow. Performance data for diffusers are presented comprehensively in a pressure pecovery and effectiveness chart including optimum geometry lines. A comparison of present results with those in references related to the problems shows that the contours of the performance chart and optimum geometry lines do not conform among respective investigations under similar inlet and outlet conditions. The present performance chart and optimum lines approximately give average values of the results obtained by other investigators. For geometries of cone angle 2α between 6.8° and 30° the effectiveness may be expressed with a fair degree of accuracy by the relationship, η
p=1-0.0415α, when the area ratio is larger than 3.
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高曽 徹, 西野 友太良, 栗山 勝志, 妹尾 泰利
1988 年 54 巻 504 号 p.
1929-1937
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The conditional average and spectrum of turbulent intermittency were determined experimentally in order to study the large-scale structure in a fully developed region of a jet at Re≒4×10
4. Turbulent intermittency functions, which were derived from hot-wire signals using a turbulent/non-turbulent decision, were used to obtain the zone average velocity and spectrum of intermittency. An interesting observation that the tips of turbulent bulges in far edge regions flowed slower than the co-flowing stream is attributed to the large-scale eddy motions in the intermittent region. As the time period in the turbulent intermittency functions correspond to the spatial length in the turbulent/non-turbulent interface, the spectra of intermittency functions are assessed to examine the length scale distributions of the large-scale structure. Walsh spectral analysis, which is suitable for the intermittency functions, reveals that the large-scale motions have no predominant scale but rather have many length scales longer than several-times the velocity half width.
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蒔田 秀治, 大谷 秀雄, 石角 勝利
1988 年 54 巻 504 号 p.
1938-1945
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Acoustic excitation of velocity components was experimentally examined in a two-dimensional plane jet with a parabolic velocity profile with respect to its symmetrical or anti-symmetrical fluctuation mode. Fluid dynamical features of the excited jets were inspected using hot wire anemometers with respect to mean velocity profile and distributions of turbulence intensities and Reynolds stress. The turbulent quantities of the excited jets were compared with those of the natural jet without excitation. The acoustic excitation method proved useful for distinguishing the differences more clearly with respect to the fundamental characteristics of the flow field about the jet and the aspects of its transition into turbulence. The present results suggest a good possibility to regulate jet structure by sound wave with these two modes.
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蒔田 秀治, 大谷 秀雄, 石角 勝利
1988 年 54 巻 504 号 p.
1946-1952
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
A plane jet was acoustically excited at its symmetrical and anti-symmetrical excitation frequencies. Effects of the excitation were elucidated by measuring spectral profiles. Velocity vector plots were also obtained around the jet to distinguish the difference in the flow pattern due to the excitation modes. When the jet was acoustically excited, it demonstrated clearer symmetrical or anti-symmetrical eddy arrangement than a natural jet without excitation. The symmetrical eddy arrangement in the linear interaction region of the symmetrically excited jet was not quite stable and began to make flapping motions in its non-linear interaction region. When the sound wave of the anti-symmetrical mode was introduced, the jet demonstrated an eddy arrangement with largest scales and most rigid construction in the non-linear interaction region, and its width was observed to spread outward most rapidly as it flowed downstream.
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鷲尾 誠一, 小西 忠孝, 植田 俊明, 大熊 昭二
1988 年 54 巻 504 号 p.
1953-1961
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Flow pulsation often causes vibration and noise in piping systems, and therefore has been a nagging concern for fluid system engineers. As is known in acoustics, a branch pipe can act as a low-impedance element for harmonic waves of specific frequencies. The present report deals with an attempt to reduce pulsation in oil hydraulic lines using branch pipes alone. Attention in paid particularly to the effects of viscosity on their behaviors as a band-elimination filter. The availability of branch pipe filters is experimentally examined in a test to reduce prominent pulsation created by a gear pump. Finally a combination of branch pipes, which is called a 'π-shape filter', has been proved to absorb the pulsation so thoroughly that it can take the place of accumulators which are conventinally used for this purpose.
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平井 秀一郎, 高城 敏美, 東谷 輝義
1988 年 54 巻 504 号 p.
1962-1969
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Numerical predictions are compared with the experiments of turbulent swirling flow in a stationary pipe. Two kinds of turbulence models, the k-ε two equation model and the stress equation model, are applied in the present calculations. The applicability of the turbulence models is tested. The characteristics of axial and tangential velocity profile in the presence of the swirl can be predicted by applying the stress equation turbulence model, whereas the k-ε two equation model fails to predict this. The comprehensible interpretations of the phenomena, especially the retardation of the turbulent transport of momentum due to the swirl, are presented. The suppression of the transport of axial momentum in the radial direction is caused by the additional production term, including the tangential velocity component .The anisotropy of Reynolds normal stresses has the effect of transporting the tangential momentum towards the central axis.
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小林 康徳, 松本 毅
1988 年 54 巻 504 号 p.
1970-1976
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
An analytical model of upward condensing vapor flow in the presence of non-condensable gas in the condenser region of a gravity assisted thermosyphon was developed. The main objective is to examine the interfacial layer generated in such vapor-gas mixing regions influenced by the gravity. The model was derived from conservation equations of incompressible steady flows including transport effects of binary diffusion and of concentration inequalities in the flow field caused by gravity force. Numerical results such as density, temperature and vapor velocity distributions obained by this model were compared with those of a flow visualization experiment. The agreement was fairly good qualitatively, indicating that the model is describing the basic feature of the flow field, although it needs further finalization for quantitative discussion.
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石井 徳章, / 今市 憲作, 佐柳 恒久, Tsunehisa SANAGI
1988 年 54 巻 504 号 p.
1977-1984
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
To study the flow-induced small-amplitude vibration of long-span gates with small gate openings which are inclined toward the downstream side, this study presents an analytical method to derive the dimensionless parameters of the added mass and fluid damping coefficients induced by fluid motion. The equation of motion of long-span gates includes the integral fluid term which describes the effects of the added mass and fluid damping. In the calulation of the integral fluid term for a periodic gate vibration, it is reduced to a superposition of the acceleration and the velocity terms. Thus, the added mass and fluid damping coefficients are derived in the form of a series summation. They are calculated numerically and the major characteristics of added mass and fluid damping are revealed and discussed. Based on the calculated fluid damping effect on the gate vibration, the tendency of long-span gates to vibrate as a result of flow-induced vibrations is discussed.
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加藤 健司, 藤田 秀臣, 佐々木 英治
1988 年 54 巻 504 号 p.
1985-1993
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The purpose of this study is to investigate the mechanism of wetting from a macroscopic viewpoint. The liquid meniscus formed under a conical solid surface is chosen as the subject of the theoretical analysis. The meniscus configuration is obtained by solving the Laplace equation numerically, and using this result, the total energy of the system is calculated. In the case of the half vertical angle of the cone φ=90° (horizontal plate), the system shows thermodynamic instability when the meniscus attaches to the solid surface at the contact angle. This fact, unlike a popular view, explains the wetting phenomena observed in this report. On the other hand, when 0°<φ<90°, the system shows thermodynamic stability at the contact angle. However, when the solid cone is held at a position higher then the critical height from a static liquid surface, the system becomes unstable. It is possible to measure the contact angle easily using this unstable phenomenon.
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鳴海 明, 柏木 孝夫, 佐藤 公治, 坂田 成則
1988 年 54 巻 504 号 p.
1994-2001
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The laser speckle photography technique has the advantage of obtaining a whole instantaneous two-dimensional velocity distribution as the vector quantity. However, there have been few reports on the measuring accuracy of this technique. Furthermore, most of these reports employed a high-power laser, e.q. an argon laser or a ruby pulse laser, as a light source. In this study, a He-Ne gas laser is employed in order to enhance the validity of the technique. This technique is applied to the coaxial cylindrical Couette flow to discuss the measuring accuracy of the velocity vector, especially the velocity direction. The measuring results agree with the analytical solution within ±10 % at the local scalar quantity of the velocity ν
θ(γ)=0.01∼0.40 m/s, and within ±2 degrees in the velocity direction.
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藤田 秀臣, 広田 真史, 横沢 肇, 長谷川 昌雄
1988 年 54 巻 504 号 p.
2002-2009
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
An experimental study was conducted on a fully developed turbulent flow through a rectangular duct of aspect ratio 2:1, one of whose long-side walls was roughened. Detailed and reliable results of such quantities as the secondary-flow velocities and the turbulent shear stresses were obtained by using a well-devised technique of the hot wire anemometry developed by the authors. The secondary-flow pattern in the rough duct was remarkably different from that in the smooth duct. Only one large longitudinal vortex appeared in the vicinity of each short-side wall. on the other hand, in quite a large region near the core, the secondary-currents proceeded from the smooth long-side wall to the rough one along the midplane of the rough wall. Furthermore it was found that the production and convection terms in the vorticity equation, which had been believed to balance, did not balance in the rectangular rough duct.
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媚山 政良, 松本 尚雄, 小林 茂, 佐藤 雄一, 村上 忠幸
1988 年 54 巻 504 号 p.
2010-2016
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The utilization of natural snow and ice was investigated and the conserving of them for a long term period was found to be possible with simple means. The authors thought that if they could transport natural snow or ice from the highlands to living quarters using simple means, it might be of benefit to people living in dry or massed regions nearby the highlands to obtain not only cold heat but also water. In this paper, the possibility of long distance transportation of ice and water mixture through a pipe using only gravity drive was investigated. The theoretical analysis cleared the possibility of transportation for few hundred kilometers and some characteristic features.
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田中 和博, 田口 孝司, 池尾 茂
1988 年 54 巻 504 号 p.
2017-2022
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Screw centrifugal pumps are of non-clog type and they are used to transport slurries, rainwater and sewage as well as solids. The impeller has a three-dimensional spiral blade. The pump combines the characteristics of both positive displacement pump by screw action in suction cover and a centrifugal pump by centrifugal action in volute casing. The radial thrust of the impeller was measured and the followings were proved ; (1) The time-averaged component of the radial thrust is much influenced by pressure distribution in volute casing, so that the three-dimensional effect of screw part is small. (2) The time-varying component is caused by the peripheral unbalance of the blade area in volute casing. (3) The radial thrust could be estimated easily by measuring the pressure at the surface of volute casing.
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山部 正博, 田辺 誠一, 川本 一俊, 人見 一郎
1988 年 54 巻 504 号 p.
2023-2030
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
In a previous paper, it was described that turbine step characteristics occured in runners which had a low ratio of exit diameter to entrance diameter and a large entrance angle. A new runner of extremely low specific speed, however, does not show the characteristic in contrast to the result of the paper .Then, the relation between the shape of many runners and the characteristic is studied. As a result, it is clarified that, (1) whether the characteristic occurs or not depends on the relation between the ratio of the exit diameter to the entrance diameter D
2/D
1 and the ratio of outlet clearances to the entrance diameter δ
2Z/D
1, where δ
2 is an outlet width between vanes, and Z is the number of vanes, and (2) decreasing δ
2Z/D
1 and an entrance angle, and increasing D
2/D
1 and the spiral angle of a vane are effectively in suppression of the occurrence of the characteristic.
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宇野 美津夫, 松永 成徳, 飛田 二雄, / 宮沢 英智, 古河 嘉之, 塚本 寛, Hiroshi TSUKAMOTO
1988 年 54 巻 504 号 p.
2031-2037
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Hydraulic losses of mixed-flow pump impellers with four different specific speed impellers were measured near the respective best efficiency point .The measured radial variations of the hydraulic loss at the impeller exit were compared with those calculated y the two-dimensional boundary layer calculation procedure under the support of the quasi three-dimensional potential flow analysis. The calculated hydraulic losses at the impeller downstream section showed good agreement with the measured ones in the case of good agreement between the calculated and measured velocity distributions at the impeller inlet. In addition, the measured data were rearranged to get the information on the reasonable choice for the casing and hub cone angle as well as blade loading.
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菊山 功嗣, 長谷川 豊, 前田 太佳夫
1988 年 54 巻 504 号 p.
2038-2046
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Fluctuations of pressure in the impeller caused by the interactions between a centrifugal impeller and a volute casing were examined experimentally. By using a Fourier analysis, the phase-lock averaged pressure was found to have its maximum amplitude of fluctuation on the pressure surface of the midpoint of the impeller passage and have different phase angles between the pressure and suction sides of a blade. The resultant force exerted on a blade at every circumferential position was calculated from the pressure distribution on the blade and was found to undergo a drastic change at off-design operating flow rate when the trailing edge of the blade passed by the volute tongue.
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鄭 材錬, 京極 啓史, 中原 網光
1988 年 54 巻 504 号 p.
2047-2054
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Measurements of the dynamic internal pressures near the vane of a pressure balance type of an oil hydraulic vane pump with intravanes have been made to provide essential information for the study of the pump dynamics and control, the pump design and the analysis of tribological problems in the sliding components. The influences of the discharge pressure and rotating speed of the vane on the dynamic pressure in four chambers surronding a vane have been investigated. The results indicate that the surge pressures of the chambers at the instant of the start of discharge and closure are affected by the rotating speed, and the pressure in the intravane chamber maintains approximately constant values with marked effect of pulsating discharge pressure.
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峯村 吉泰, 西垣 緑, 田中 清英
1988 年 54 巻 504 号 p.
2055-2060
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Pneumatic servo systems with the use of air cylinders have lately been put to practical use in relation to robots or factory automations. These systems usually employ an electropneumatic valve to control the pressure in proportion to the input electric current. This paper is concerned with the theoretical analysis of the valve to simulate and improve its characteristics. The numerical results obtained are confirmed by the experiments.
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瀬戸 邦聰, 松岡 宗治
1988 年 54 巻 504 号 p.
2061-2066
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
In order to increase the noise-reducing effect of a porous tube, we investigated the change in the acoustic characteristics due to the variation of porosity, the diameter of the aperture and the porous pattern of the tube. We found that the noise-reducing characteristics are changed by the attachment of a shroud to each porous tube especially in the range of low pressure ratios. We showed the preferable combination of a porous tube and shroud to effectively reduce the noise level for a variety of pressure ratios. Furthermore, we discovered experimentally that the combination of a shroud and porous tube can increase the thrust (momentum) of the jet flow through it, especially in the range of higher pressure ratios.
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木村 照夫, 竹内 正紀, 田中 数則
1988 年 54 巻 504 号 p.
2067-2074
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The natural convection heat transfer of fluids with two-layer stratification in an inclined enclosure was investigated by numerical analysis of F.E.M.. Two kinds of combination of stratified fluids were used to describe the heat transfer rate, and the flow and temperature fields in detail in the range of Raw<1.2x10
4. The inclination angle of the enclosure was varied from 32° to 148° and the aspect ratio (height/width) of the cross-section of the enclosure was 2. It was shown that the quantity of heat Q
B transferred through the boundary surface of the two stratified fluids varied widely with the inclination angle and the Rayleigh number of each fluid. And the quantity of heat through the hot and the cold walls was influenced significantly by the quantity of heat Q
B.
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木村 照夫, 竹内 正紀, 田中 数則
1988 年 54 巻 504 号 p.
2075-2082
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Natural convection heat transfer of fluids with two-layer stratification in an inclined rectangular enclosure was studied. The experiments were carried out for stratified fluids such as spindle oil-pure water for the Rayleigh numbers in the range of Raw
I (spindle oil)=8.1X10
6-3.5X10
7 and Raw
II (pure water)=3.8X10
7-1.6X10
8, and an aspect ratio H/W=2. The velocity and the temperature fields and the heat transfer coefficient were investigated at several inclination angles of the enclosure. It was clear for the inclined enclosure that the configuration of each fluid region, varying with the inclination angle, significantly effects the heat transfer coefficient.
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三角 利之, 北村 健三
1988 年 54 巻 504 号 p.
2083-2089
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Natural convective heat transfer from a vertical plate with a horizontal partition plate has been investigated experimentally. The expemiments were carried out with water, for modified Rayleigh numbers ranging from 6.0×10
7 to 10
11, and for various heights of partition plates in the range of 0-70 mm. The flow and temperature fields are visualized. The results show that the three dimensional flow appears behind the plate when the height of the partition plate, H, exceeds a certain value. The transition to turbulence is found to occur at higher values of H. The local heat transfer coefficients are measured to examine the effect of the partition plate. It is revealed that the heat transfer rates decrease in the upstream region of the partition plate when compared with those for the no partition plate. On the other hand, the heat transfer rates behind the partition plate increase significantly at high values of H.
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竹内 正紀, 木村 照夫, 東川 佳晴
1988 年 54 巻 504 号 p.
2090-2098
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The effects of the width of a rectangular thermosyphon passage on the natural convection heat transfer in an open thermosyphon with uniform temperature and adiabatic surfaces were investigated numerically and experimentally. The numerical analyses were excuted by the finite difference method for the Prandtl number Pr = 5 in the range of the Grashof number G
rH=10
3∼10
5 and the aspect ratio of the passage W/H (width/length) = 0.05∼1.0. The experiments were carried out for pure water in the range of G
rH = 3.7x10
7∼1.2x10
10 and W/H = 0.025∼0.20. It was found that the overall Nusselt number (Nuw)^^
- for both of the numerical and experimental results were correlated with the Rayleigh number Raw by the following empirical equation. (Nuw)^^
- = 0.0021 Raw·(W/H)·{1-exp[ -300 (Raw(W/H))
-3/4 ]} [2x10
2 <Raw (W/H) < 1X10
6]
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中山 顕, 石代 哲也, 児山 仁
1988 年 54 巻 504 号 p.
2099-2106
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The local similarity solution procedure was successfully adopted to investigate non-Darcian flow and heat transfer through a boundary layer developed over a horizontal flat plate in a highly porous medium. The full boundary layer equations which consider the effects of convective inertia, solid boundary and porous inertia in addition to the Darcy flow resistance, were solved using novel transformed variables derived from a scale analysis. The results from this local similarity solution are found to be in good agreement with those obtained from the finite difference method. The effects of the convective inertia term, boundary viscous term and porous inertia term on the velocity and temperature fields are examined in detail. Furthermore, useful asymptotic expressions for the local Nusselt number were derived in consideration of possible physical limiting conditions.
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檜和田 宗彦, 松原 功治, 熊田 雅弥, 馬淵 幾夫
1988 年 54 巻 504 号 p.
2107-2113
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The overall and local heat-transfer characteristics on the circular cylinder set near a plane surface at t he subcritical Reynolds number range (Re=4×10
4) have been clarified by changing the turbulent boundary layer thickness (δ/d=0.4∼1.5) and the clearance (C/d<1.0), where C is the distance between the circular cylinder and flat plate and d is the cylinder diameter. At C/d<0.3, where the vortex shedding from the circular cylinder ceases, the flow structure close to the cylinder surface is proposed on the basis of the detailed flow measurements, and the local heat-transfer characteristics have been explained by this flow structure.
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河村 隆雄, 田中 誠司, 熊田 雅弥, 馬淵 幾夫
1988 年 54 巻 504 号 p.
2114-2120
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
A distribution of instantaneous heat transfer coefficients around the flow reattachment region behind a two-dimensional backward-facing step was accumlated as time-continuous data, in order to clarify the heat transfer mechanism at that region. For this purpose, ten heat flux meters based on a constant temperature method were arrayed on the bottom surface of the step. The ensemble-averaged heat transfer coefficients were calculated on the condition that the maximum instantaneous heat transfer coefficient appeared at a specified heat flux meter. The position, where the peak in the ensemble-averaged distributions shows the maximum, located a about a one step height upstream of the time-averaged reattachment point. In general, the position of the maximum instantaneous heat transfer coefficient moves downward and appears discontinuously near the time-averaged reattachment point.
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稲田 茂昭, 宮阪 芳嘉, 佐久本 政和, 茂木 郁男
1988 年 54 巻 504 号 p.
2121-2127
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The present report aims at presenting basic data to prove the wetability of a heated surface contaminated by scale adherence by comparing the behaviors of a water droplet on a contaminated surface and a glossy surface polished by emery paper. A water droplet (2.3 mm in dia. ) of about 18°C is dropped from a height of 20 mm above the heated surface and the evaporation behavior on the heated surface is photographed by a high speed camera. The initial temperatures of the heated surface are in the range of 140-220°C. At temperatures of the heated surface above 200°C, in the case of a fresh surface, the residence time of a drop on the heated surface is about 13 ms. While in the case of a contaminated surface, even if the drop is about to rebound from the heated surface, its root is so firmly contacted with the heated surface through the thin liquid film that the residence time is longer than that of the fresh surface. This fact proves that the surface with scale has a high wetability.
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本田 博司, 野津 滋, 武田 泰仁
1988 年 54 巻 504 号 p.
2128-2135
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
A previously proposed theoretical model of film condensation on a single horizontal low finned tube is extended to the case of a horizontal tube bundle with negligible vapor shear. Based on the flow characteristics of condensate on a vertical column of horizontal low finned tubes, two major flow modes, the column mode and the sheet mode, are considered. It is shown that the present model can predict the heat transfer coefficient satisfactorily for available experimental data including four fluids and five tube columns. Sample calculations show that the effects of the fin spacing and the number of vertical tube rows on the heat transfer performance are significant for R-12 with small values of σ and Δh, while these effects are small for steam with large σ and Δh values.
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笹口 健吾, 吉田 正道, 中島 秀司
1988 年 54 巻 504 号 p.
2136-2143
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Effects of the configuration of a finned tube on the heat transfer characteristics of latent heat storage have been studied experimentally and theoretically. As a result, it has been shown that the performance of the latent heat storage unit is almost the same for finned tubes having the same surface area even if the fin configuration is different. Calculated results of heat fluxes for two types of finned tube have been in good agreement with the experimental values, and the validity of the calculations has been indicated.
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大島 信徳, 渡里 望
1988 年 54 巻 504 号 p.
2144-2149
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
In treating problems of thermal conduction in dispersive media, it is necessary to calculate the effective thermal conductivity instead of analyzing the detailed thermal field. The present paper aims to estimate the effective thermal conductivity of two-dimensional media with regularly dispersed materials by applying the boundary element method. Media with parallel cylinders dispersed at square lattice points are considered. It is assumed that two-dimensional thermal conduction takes place in the plane normal to these cylinders. In the case of regularly arranged circular cylinders, the present authors have also developed an exact analytical method. The present method is compared with the previous one by carrying out numerical calculation and the result is satisfactory. The method is also applied to analyze the case of cylinders of square cross section.
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恩田 和夫
1988 年 54 巻 504 号 p.
2150-2158
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The first (P
1) and the third (P
3) spherical harmonics approximations of a radiative transfer equation in rectangular enclosures containing anisotropically scattering media are studied with boundary conditions of the diffusely emissive and reflective wall, the diffuse irradiation of known intensity from outside and the transparent boundary. Inhomogeneties in the radiative properties of the medium, as well as in the radiation characteristics of the boundaries, are allowed for to take into account the real condition of radiative heat transfer. The governing differential equations and the boundary conditions are systematically displayed for the one-, two- and three- dimensional Car-tesian coordinates, correcting errors and misprints in the previous studies. The P
3 approximation may be considered to be the optimal choice as far as accuracy and computational efforts are concerned, because it may yield accurate heat flux predictions for optical thicknesses greater than unity and is compatible with the finite difference schemes required for flow and temperature field calculations.
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高橋 一郎, 菅原 章, 三舩 英伸, 藤倉 秀明
1988 年 54 巻 504 号 p.
2159-2166
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The final goal of this study is to develop a multi-purpose measurement system, which can simultaneously obtain thermal conductivity, total hemispherical emittance, thermal diffusivity, thermal expansion, and specific heat, by a direct electrical heating method. In this report, the principle of the newly developed methods for measuring thermal expansion and specific heat are described. Rod samples of silver (purity 99.99%) and JIS SUS304 (austenitic stainless steel), which are coated with a black refractory-paint of 0.01 mm in thickness, are used in order to verify the applicability of these methods. It becomes clear that the coating film is useful for accurately measuring these thermophysical properties. Effect of the film thickness on the accuracy in obtaining the specific heat is revealed by theoretical analysis.
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藤井 照重, 赤川 浩爾, 石田 紀久, 久保 雅英
1988 年 54 巻 504 号 p.
2167-2174
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Experiments on single-phase natural circulation were conducted for five cooler configurations in the loop-type PWR for marine applications. The loop consisted of a heating box, a cooler, and connecting pipes. The transient circulation velocity and transient temperatures at different locations after pump tripping were obtained at atmospheric pressure by holding the heater input constant (Q=0.25 kW to 4 kW). The flow stability maps are shown for heat input and elevation difference, and the effects of the cooler configurations on the flow stability are clarified. In parallel with the experiments, a one-dimensional nonlinear analysis was carried out and the results were compared with the experimental results. Both agreed well qualitatively and quantitatively. Further, the effects of parameters such as overall heat transfer coefficient and pressure losses on the flow stability were obtained by this analytical simulation.
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吉澤 善男, 越後 亮三, 富村 寿三
1988 年 54 巻 504 号 p.
2175-2182
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
This study aims to develop a high-performance radiant heater which would be able to convert almost all energy released by combustion into thermal radiation. A compact radiant heater was produced, which was an application of the effective energy conversion method from flowing gas enthalpy to thermal radiation emitted from the porous medium of an appropriate optical thickness placed in a duct of high-temperature gas. It consists of a porous medium energy converter and a quartz window. It is also equipped with a convective heat exchanger between the burnt and unburnt gases. The thermal radiation emitted from the porous medium energy converter is taken out in the opposite direction to the burnt gas flow. The temperature profiles in the heater were examined and the energy balance of the heater has been elucidated. The results shows that 80 to 90% of the energy released by combustion is converted into thermal radiation.
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佐藤 定男, 垣原 光喜, 部谷 正明
1988 年 54 巻 504 号 p.
2183-2191
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The geometry of blades and cascades for a single-component, two-phase flow with a high void ratio was optimized to design an axial-impulse-type two-phase flow turbine suitable for recovering geothermal and/or industrial waste heat. The dissimillar performances of scaled cascades as well as the strong dependence of a cascade's performance on vapor density were predicted by a simple theoretical model. These were confirmed by the measured thrust conversion efficiency of a blade cascade located within a two-phase jet emerging from a nozzle. The nozzle expands the hot, saturated water at 510 K into a chamber where the pressure varies between 15 kPa and 0.45 MPa.
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吉澤 善男, 林 昭彦, 越後 亮三
1988 年 54 巻 504 号 p.
2192-2198
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
A new concept of a reactor for methane steam reforming has been proposed, which is an application of a high-performance radiant heat exchanger composed of a couple of porous media energy converters. One of the porous media also works as the support for the catalyst on which the endothermic reaction takes place. Therefore, the heat is transferred directly to the place where it is consumed as the heat of reaction. A numerical model is developed describing a one-dimensional model of the reactor, and the basic operation characteristics, such as the profiles of temperatures and concentrations in the reactor, the local and the total energy balances and overall yield, have been discussed and clarified extensively for a wide range of operating conditions of the reactor.
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稲村 隆夫, 永井 伸樹, 松永 易
1988 年 54 巻 504 号 p.
2199-2206
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Highly concentrated coal-water mixture (CWM) has attracted special interest as a substitute fuel for petroleum, and various types of twin-fluid atomizers have been developed for spray combustion. However, it will not be easy to atomize CWM finely at small air/fuel ratios, because CWM is highly viscous and has the complicated properties. This study intends to apply flash-boiling atomization to the practical burner instead of twin-fluid atomizers in order to improve the spray performances. The general disintegration mechanisms and spray characteristics were investigated and compared with those of water. Flash-boiling of CWM is strongly influenced by the degree of superheat and begins at a lower superheat than that of water. Vapor bubbles are mainly generated at the interface between coal particles and water. A solid-cone type of spray is formed by flash-boiling, relatively large liquid droplets are dispersed throughout, but smaller ones almost in the center of the spray.
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花村 克悟, 吉野 真一, 吉澤 善男, 越後 亮三
1988 年 54 巻 504 号 p.
2207-2213
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
This paper describes the structure and burning velocity of a methane-air premixed flame stabilized one-dimensionally in a spongy highly porous medium. The combustion gas enthalpy is effectively converted into thermal radiation emitted from the porous medium at the downstream side of the reaction zone. On the other hand, the thermal radiation incident from the downstream side is absorbed by the porous medium and is effectively converted into an enthalpy increase of the mixture at the upstream side. As a consequence, it is demonstrated that the burning velocity in the porous medium is increased by energy recirculation created from radiation heat transfer by as much as three times compared with that of a gas-phase flame. Further, the amount of radiation heat loss from the upstream end of the porous medium was measured accurately. his plays an important role in the characteristics of the flame holding. As a result, it is also demonstrated that a flame can be held in the porous medium over a wide range of flow velocities and equivalence ratios of the mixture.
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浜本 嘉輔, 泉 政明, 冨田 栄二
1988 年 54 巻 504 号 p.
2214-2218
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The characteristics of roughness of a turbulent flame front in a disc-type combustion chamber were determined with high-speed schlieren photography and image analyzing. The correlations between the characteristics of roughness of the turbulent flame front and the turbulence characteristics or turbulent burning velocity were discussed. The main results are as follows: (1) the RMS value "a" and integral scale "L
f" of the flame front roughness are dependent on the turbulence intensity and integral spatial scale, (2) the power spectrum of the flame front roughness is similar to that of turbulent flow, and the microscale of the flame front roughness is close to the Taylor microscale of turbulence and (3) under the condition of very low turbulence, the ratio of turbulent burning velocity and laminar burning velocity, S
T/S
L, is proportional to √(1+(2a/L
f)
2).
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水谷 幸夫, 佐伯 孝敏, 中部 主敬
1988 年 54 巻 504 号 p.
2219-2227
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
The technique developed by Mizutani and his co-workers (Trans. JSME 52-476B (1986), 1931), in which the self-emission images of radicals were obtained by the image processing technique using a system composed of optical interference filters, an image intensifier and a video camera, was improved. As a result, the time averaged emission images of OH and CH radicals with a high S/N ratio and a high accuracy became obtainable for both luminous flames and nonluminous ones. In addition, for nonluminous flames, not only the time averaged images of OH, CH and C
2 radicals but also their instantaneous images of ca. 1 ms exposure became obtainable.
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塩路 昌宏, 紀本 孝, 岡本 昌章, 池上 詢
1988 年 54 巻 504 号 p.
2228-2235
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
A picture processing technique is applied to study the flame motion in a direct-injection diesel engine. From the high-speed photographs, two-dimensional cross-correlation coefficients of flame luminosity between two successive frames are obtained. The location and value of the maximum coefficients give us the mean and fluctuating velocities of the flame, respectively. The results show that the fluctuating velocity obtained in a wide region is almost independent of measuring position and size in the middle and later stages of combustion, indicating that the turbulent flow field is almost uniform and isotropic over the space. Furthermore, the effects of the swirl and chamber geometry on the flame behavior are discussed in detail.
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清水 正則, 新井 雅隆, 廣安 博之
1988 年 54 巻 504 号 p.
2236-2244
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
This paper deals with an experimental study on the disintegrating processes of a high speed liquid jet injected into the various ambient pressures from a cylindrical nozzle. The effects of the diameter and the shape of the nozzle on the breakup length were investigated by an electrical resistance method. The close dependence between the internal flow in the nozzle and the disintegrating process of the jet were observed using a photographic method. The disintegrating process was divided into six kinds of form. When the disturbance of the liquid flow in the nozzle was very small, the spray flow could not be formed even if the injection velocity was very high at the reduced ambient pressure condition. If both the strong disturbance and the strong interfacical force were given to the liquid jet, the jet could be broke up to the spray flow.
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鈴木 豊彦, 藤本 義雄, 落合 義孝, 藤村 一郎
1988 年 54 巻 504 号 p.
2245-2251
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
Piston slap phenomena in diesel engines were numerically studied by a method which can deal with pistons and cylinders with arbitrary profiles. The effects of piston skirt profile and piston clearance were discussed. The results showed that a piston with a curved profile such as a barrel type piston is more advantageous than a piston with a constant radius for the reduction of piston slap impact.
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藤本 元, 斎藤 昌弘, 箕浦 章, 千田 二郎
1988 年 54 巻 504 号 p.
2252-2259
発行日: 1988/08/25
公開日: 2008/03/28
ジャーナル
フリー
In the experiments presented here, a single diesel spray was impinging on a flat plate at a normal angle, in a high pressure of atmosphere 1.5 MPa at room temperature. The temporal and spatial droplets density was measured by the laser extinction method. The data was processed statistically, applying the model of a concentric circle for this spray. Also the Sauter mean diameter was calculated from these data, under the some assumptions. Then the droplets density is increased, and its profile peaked at the spray edge, as the measuring point went nearer the plate. The Sauter mean diameter is about 30 μm and is not so much different from that of free diesel spray.
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