著者

須賀 一彦 Timothy J. CRAFT Hector IACOVIDES

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.71, no.711, pp.2725-2733, 2005-11-25 (Released:2011-03-03)

参考文献数

21

被引用文献数

1

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This paper reports the development of a refined wall-function strategy for the modelling of turbulent flows over smooth and rough surfaces. In order to include the effects of fine-grain surface roughness, the present study extends a more fundamental work on the development of advanced wall functions of general applicability. The presently proposed model is validated through comparisons with data available for internal flows through channels, pipes and for external flows over flat plates with both smooth and rough surfaces. Then, its further validation in separating flows over a sand dune and a sand-roughened ramp as well as a smooth ramp is discussed. The validation results suggest that the presently proposed form is successfully applicable to a wide range of attached and separated turbulent flows over smooth and fine-grain rough surfaces.

著者

田中 正暁 佐郷 ひろみ 岩本 幸治 江原 真司 小野 綾子 村上 貴裕 早川 教

出版者

The Japan Society of Mechanical Engineers

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.78, no.792, pp.1392-1396, 2012

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A study on flow induced vibration in the primary cooling system of Japan Sodium cooled Fast Reactor (JSFR) consisting of large diameter pipe and pipe elbow with short curvature radius ("short-elbow") has been conducted. Flow-induced vibration in the short-elbow is an important issue in design study of JSFR, because it may affect to structural integrity of the pipe. In this paper, unsteady flow characteristics in the JSFR short-elbow pipe related to the large-scale eddy motion were estimated based on knowledge from existing studies for curved pipes and scaled water experiments and numerical simulations for the JSFR hot-leg piping.

著者

池田 博和 松浦 文生 越塚 誠一 岡 芳明

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.64, no.624, pp.2431-2437, 1998-08-25 (Released:2008-03-28)

参考文献数

13

被引用文献数

2 7

---

Fragmentation of liquid metal takes place as basic processes of vapor explosions. This leads to rapid evaporation on the stretched interface. To date, a number of models explaining the fragmentation mechanisms have been proposed. However, few evidence has been obtained from the experiment because the phenomena are rapid. In Moving Particle Semi-implicit (MPS) method, grids are not necessary so that fluid fragmentation as well as multi-fluid thermal hydraulics can be analyzed. A numerical model of evaporation is developed for the present study. Impingement of water jets on a liquid metal pool is analyzed using the MPS method to investigate two typical models explaining the fragmentation mechanisms : Kim-Corradini and Ciccarelli-Frost models. Penetration of the water jet, which is assumed in Kim-Corradini model, is not observed in the calculation results. A filament of the liquid metal is observed between two water jets as assumed in Ciccarelli-Frost model. The filament appears when the jet density is smaller than the pool density, while the penetration appears when the jet density is hypotheticaly larger. The usual combinations of densities in vapor explosions are in the region of Ciccarelli-Frost model.

著者

佐藤 智明

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.76, no.762, pp.359-361, 2010-02-25 (Released:2017-06-09)

参考文献数

1

被引用文献数

1

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In this paper, as a new application of Stirling cycle, it is proposed to apply the Stirling cycle to heat speaker which amplifies sound vibration by means of the thermal energy. The heat speaker is composed of a pressure vessel whose capacity is variable, a displacer to which a voice coil is attached, a vibration board attached to the pressure vessel and a permanent magnet placed around the vessel. The displacer with voice coil is vibrated by the magnetic force which is generated by electric current of sound signal flowing in the voice coil. The vibrating displacer makes the air come and go between the hot side and the cold side in the pressure vessel. The air temperature goes up and down, and then the pressure follows it. The capacity of the vessel repeats expansion and shrinkage by the pressure change of the air. The moving vessel vibrates the vibration board and it yields the sound.

著者

中島 求 面田 雄一

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. B編 (ISSN:03875016)

巻号頁・発行日

vol.73, no.734, pp.2010-2017, 2007-10-25

被引用文献数

1

---

The objective of this study was to develop a simulation method for analysis of body behavior in skydiving freefall and to clarify the most stable body position during the freefall. The details of the developed simulation method were firstly described. Using the simulation method, we conducted an optimizing calculation to maximize an objective function with respect to the stability in the freefall. It was found that the most stable position became arched one. In order to clarify the reason why the most stable position became arched, optimization with respect to a simple shaped object which consists of 20 cylinders was conducted. Then the angle to maximize the restoring moment for each cylinder element was analytically calculated and compared with the optimized angle. From the results, we conclude that the most stable position becomes arched mainly since the restoring moment at each part itself becomes maximum at that angle. We also conclude that the magnitude of the arch in the most stable position is determined by the ratio of the normal and tangential drag coefficients.

著者

長谷川 豊 菊山 功嗣 谷本 正信 Gerard J. W. van Bussel

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. B編 (ISSN:03875016)

巻号頁・発行日

vol.63, no.608, pp.1297-1304, 1997-04-25

被引用文献数

6

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We describe a method of calculating yawed inflow effects on horizontal axis wind turbine rotors. Yawed inflow brings about asymmetric induced velocity distributions on the rotor plane due to an inclined vortex wake construction. For the calculation of yawed inflow phenomena, an inviscid aerodynamic model based on pressure distributions is adopted. Under the assumptions of an incompressible inviscid irrotational flow, the pressure perturbation satisfies the Laplace equation and acts as an acceleration potential function. The rotor blades are represented by spanwise and chordwise pressure distributions composed of analytical first-order asymptotic solutions to the Laplace equation. Integration of the accelerations determines the velocities in the rotor plane. With these velocities the aerodynamic loads can be calculated. An advantage of this model is that evaluation of the relatively complicated unstationary effects from the vorticity in the wake is not necessary in the calculation procedure.

著者

太田 有 大田 英輔 田島 清〓

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. B編 (ISSN:03875016)

巻号頁・発行日

vol.54, no.500, pp.890-899, 1988-04-25

被引用文献数

5

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Fan noise data are categorized into source characteristic terms and a frequency response term expressing attenuation in the propagation passage. These terms are determined by sweeping the fan speed from 1000 to 4500 rpm. The fan specific speed and the impeller diameter are 42 and 460 mm. The blade number is 12. By setting the exponent in a power law relationship of sound pressure level versus frequency as 3, two factors describing the source level are determined with simple relationships to the scroll cut-off location. By selecting the distance, the noise level is possibly reduced by more than 10 dB without influencing fan performance. The frequency response if satisfactorily presented by introducing a one-dimensional linear wave model, where the key passage is blade passages selectively determined by the noise wavelength. By choosing the blade number or the inlet duct length so that a frequency of the maximum attenuation is achieved, a noise reduction of 10 dB is again expected.

著者

近藤 卓 飯尾 秀一 昼間 勝 古濱 庄一

出版者

一般社団法人日本機械学会

雑誌

日本機械学会論文集. B編 (ISSN:03875016)

巻号頁・発行日

vol.63, no.610, pp.2209-2214, 1997-06-25

参考文献数

4

被引用文献数

1

---

In order to facilitate practical application of hydrogen fueled engines with external mixture formations. it is necessary to determine the cause of backfire and to identify appropriate countermeasures. It has been found in our study that one of the causes of backfire is attributed to the electric discharge which occurs after the ignition of the spark plug when the pressure in the cylinder becomes low enough to discharge the electric charge remaining in the ignition system. The electric charge in the plug cable remains much longer when hydrogen is used as the fuel than when gasoline is used. In other words, the number of ions produced from hydrogen-air combustion after the ignition of the spark plug is less than that from gasoline-air combustion, so it is difficult for the ion current to flow out through the gap of the spark plug. It has been found in our experiments that backfire takes place when the electric discharge occurs during the intake stroke and that engine operation could be performed up to an excess air ratio of λ=1 without any backfire at a low engine speed when the ignition system was modified such that no electric charge remained in the spark plug cable.

著者

井上 雅弘 金子 賢二 瀬戸口 俊明 猿渡 哲郎

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. B編 (ISSN:03875016)

巻号頁・発行日

vol.53, no.496, pp.3691-3698, 1987-12-25

被引用文献数

6

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A Wells turbine operating under irregular wave conditions has been analyzed theoretically. It is shown that the turbine performance depends on a unique parameter, including characteristic parameters of the irregular wave, turbine speed and dimensions of the turbine and air chamber. In order to obtain the optimum value of this parameter, a model test has been performed using a computer-controlled wind tunnel, which can simulate arbitrary oscillating flows based on spectra of irregular waves. From this value a set of optimum dimensions of a Wells turbine system can be determined. Furthermore, starting and running characteristics of the Wells turbine have been obtained by a computer simulation. It is possible to predict the optimum value of the parameter and behavior of the output coefficient by computer simulation.

著者

橋本 健 古畑 朋彦 新井 雅隆

出版者

日本機械学会

雑誌

日本機械学會論文集. B編 = Transactions of the Japan Society of Mechanical Engineers. B (ISSN:03875016)

巻号頁・発行日

vol.72, no.721, pp.2323-2329, 2006-09-25

参考文献数

8

被引用文献数

1

---

Six-stroke diesel engine proposed here has six processes in one cycle, i.e. intaka, 1st compression, 1st combustion, 2nd compression, 2nd combustion and exhaust. By the effect of direct EGR in the 2nd combustion process, NO concentration could be expected to decrease. However, by a weak mixing in the 2nd combustion process, much soot was exhausted and NO concentration was hardly decreased compared with the conventional four-stroke diesel engine. To improve the fuel/air mixing at the 2nd combustion process, high pressure injection with common rail system was applied to the engine. As the result, NO concentration was increased owing to the increase of premixed combustion of 1st combustion process, although soot was reduced. Therefore, the 1st injection timing was extremely advanced to control the 1st combustion process. It changed 1st combustion process into HCCI-like combustion, and NO concentration was greatly decreased. Moreover, soot was reduced with no increase of NO concentration in the 2nd combustion process. As the result, trade-off curve of NO and soot was improved compared with the conventional four-stroke diesel engine. But CO concentration was increased.

著者

鈴木 健二郎 林 哲郎 SCHUERGER Matthew J. 西原 淳夫 林 政克

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. B編 (ISSN:03875016)

巻号頁・発行日

vol.55, no.516, pp.2457-2464, 1989-08-25

被引用文献数

2

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The interruption of a fin surface causes renewed boundary layers starting from the leading edge of each interrupted fin. This results in boundary layer thinner in the average over entire length of fin surfaces compared to the uninterrupted case. Therefore, a higher degree of interruption is normally expected to lead to a higher degree of heat transfer. However, to realize this expectation actually, care must be taken of the geometrical allocation of each fin in an array so as to avoid other undesirable effects relating to the fin geometry. Numerical computation of flow and thermal fields have been made for two-dimensional models of two types of parallel louver fins and an offset fin. Heat transfer characteristics of parallel louver fins are discussed in comparison with those of an offset fin based upon the results obtained from the performed numerical computation. It is demonstrated that a cartain type of parallel louver fin has a higher heat transfer performance than that obtained with an offset fin.

著者

千田 二郎 錦織 環 北條 義之 塚本 時弘 藤本 元

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.60, no.578, pp.3551-3555, 1994-10-25 (Released:2008-03-28)

参考文献数

13

被引用文献数

3

---

In this study, the influence of the flash boiling phenomenon on the fuel spray characteristics was in vestigated using both experiments and model analysis. Pure liquid fuel of n-Pentane or n-Hexane is injected into a vessel under quiescent gaseous atmosphere at room temperature through a pintle-type injector. Fuel sprays are observed by taking photographs for variation of ambient back pressure. In particular, changes in spray characteristics with back pressure are examined in detail. The results show that the saturated vapor pressure of fuel is the most significant factor and the spray characteristics can be varied with the pressure difference between the back pressure and saturated vapor pressure. Furthermore, flow field of the fuel inside the nozzle is estimated with regard to bubble initiation inside the film flow.

著者

山内 庄司 中西 重康 石谷 清幹

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. B編 (ISSN:03875016)

巻号頁・発行日

vol.47, no.416, pp.693-702, 1981-04-25

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蒸発管内密度波振動(流れ逸走を含む)の安定限界に対し, 各種因子が及ぼす効果について, 広範囲に解析的に検討した. 圧力降下一定の均一加熱管を対象に, 均質流モデルを用いて解析し, 7個の無次元パラメータによるスケーリングが可能であることを示した. また, 基礎式を線形化, ラプラス変換して得た特性方程式を用いて, ラプラス平面の虚軸をパラメータ空間に写像(ネイマルクのD分割法)することにより, いくつかのパラメータ平面で安定限界の形状を示した. 特に線形パラメータ面上では, D分割境界線の形状に双曲線状のものとだ円状のものがあり, 前者では, 安定限界は対応する漸近線にほぼ一致することを示した. また蒸発管内流動時間と安定限界振動数との関係についても検討し, 奇数次の振動が可能なこと, 本モデルでは極端な例を除いて基本振動が最不安定であることなどを示した

著者

千田 二郎 山田 耕司 藤本 元 三木 英雄

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.53, no.485, pp.176-182, 1987-01-25 (Released:2008-03-28)

参考文献数

19

被引用文献数

1 2

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The purpose of this paper is to obtain fundamental information concerning the heat transfer process and breakup behavior characteristics of individual small droplets impinging upon a hot surface. A uniform sized water droplet array at room temperature under atmospheric pressure was produced by the vibratory method to impinge upon a heated flat copper surface. And then, heat transfer from a surface to the droplets is assessed by a transient technique. Further, the deformation and the breakup behavior owing to the impingement of the droplet is observed by means of a drum camera recording high-speed microscopic photographs. Heat transfer effectiveness in a low temperature range of less than 125°C decreases as droplet impingement frequency increases because of interference between the impinging droplet and the remaining liquid film on a surface. It is possible that heat transfer per droplet is transfermed into a heat transfer coefficient by use of droplet residence time and film contact area on a surface. And Variations in the heat transfor coefficient for a droplet array with surface temperature are measured by difference calculus of the one dimensional unsteady heat conduction equation.

著者

佐藤 泰生 佐田富 道雄 堀田 圭之助 中里 見正夫 世古口 言彦

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.46, no.409, pp.1790-1796, 1980-09-25 (Released:2008-03-28)

参考文献数

8

被引用文献数

1 2

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第1報で提案した管内気ほう流の運動量と熱輸送の理論を実験値をもとに検討した.運動量輸送に関しては液相速度分布と摩擦圧力損失,熱輸送に関しては液相温度分布と熱伝達係数のそれぞれについて予測値と実験値を比較した結果,いずれもよい一致がみられ,理論の妥当性が確かめられた.本理論により摩擦圧力損失と熱伝達係数の断面ボイド率分布への依存性が定量的に明らかになった.

著者

佐藤 泰生 佐田富 道雄 川原 顕磨呂 朝倉 信次

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.57, no.538, pp.1979-1984, 1991-06-25 (Released:2008-03-28)

参考文献数

10

被引用文献数

2 2

---

The purpose of this work is to propose an experimental method of a two-dimensional (2-D) two-phase gas-liquid flow. A test channel in which a nearly 2-D, uniform two-phase flow can occur was made. This channel was a vertical, narrow gap space made up of two large concentric pipes. A two-phase air-water flow around a body mounted in the channel was recorded consecutively by a high-speed TV camera, and its void fraction distribution was determined using image processing. Several results for flows around a flat plate, and flows along a straight wall and flows between parallel walls were obtained.

著者

古川 徹 世古口 言彦

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.52, no.473, pp.199-207, 1986-01-25 (Released:2008-03-28)

参考文献数

13

被引用文献数

1

---

環状流路内を垂直に上昇する空気-水系二相流の相分布に関する調査を行った。実験には半径比の異なる3種類の環状流路を用いた。まず,環状流路における流動様式について述べ,次いで,断面内ボイド率分布を提示し,流路幅が及ぼす影響について論ずる。調査の対象とした流動様式は気泡流,スラグ流,フロス流およびフロス流領域に近い環状流である。最後に断面平均ボイド率の整理式を導出した結果について報告する。

著者

白羽 陸宏 藤井 健一 原田 英一 野添 浚平 平尾 元亮

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.57, no.542, pp.3513-3519, 1991-10-25 (Released:2008-03-28)

参考文献数

11

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The slag flow rate and heat flux through a combustor wall were measured in a 24 T/D pilot plant of a coal partial combustor, which is one kind of slagging cyclone combustor. Results of computer analysis on the slag behaviour and the heat transfer were compared with good agreement to the test results. The computer model predicted the following characteristics. (1) The slag flow rate showed rapid increase or sudden decrease when combustion conditions were changed. (2) The effects of various factors were evaluated, including the firing rate, combustor stoichiometry, ash content, flux additive, air preheat temperature, enriched oxygen concentration, refractory thickness, cooling-wall temperature and the reactivity of coals.

著者

木村 俊哉 川崎 聡 島垣 満 内海 政春 後藤 公成

出版者

The Japan Society of Mechanical Engineers

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.78, no.787, pp.576-587, 2012

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CFD simulations were performed for the leakage flow in the gap between the casing and the shroud of a centrifugal impeller. The effects of swirl brakes equipped in the casing on the leakage flow were numerically investigated. The leakage flow swirling due to impeller rotation was trapped inside swirl brakes and interacted with the walls of the swirl brake, generating a very complex flow and a vortex structure inside. By the interaction with swirl brakes, the leakage flow rapidly lost its angular momentum mainly in the outer region of the swirl brake. The loss of swirl resulted in a decrease of the pressure difference in the radial direction due to the centrifugal force effect. The radial distribution of pressure in the gap between the casing and the shroud was largely modified, and thus the axial thrust force on the impeller was changed as well. The thrust balance of the impeller can be adjusted by an appropriate design of swirl brakes and the instability of rotating shaft can be reduced by decreasing the swirl of the leakage flow.

著者

和栗 雄太郎

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. B編 (ISSN:03875016)

巻号頁・発行日

vol.65, no.634, pp.1859-1861, 1999-06-25