著者

段 智久 高岸 佐代 大石 直己 千田 二郎 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.62, no.599, pp.2867-2873, 1996-07-25 (Released:2008-03-28)

参考文献数

14

被引用文献数

2 5

---

This study deals with the effect of the viscosity of the ambient gas on the atomization process of a diesel spray. The liquid fuel is injected through a single-hole nozzle (ln/dn=0.75 mm/0.25 mm)with the injection differential pressure of 16.2 MPa inside a constant-volume vessel under a high-pressure field at room temperature. In practical combustion chambers of diesel engines, the viscosity of the ambient gas varies mainly with its temperature. In this experiment, various gases (CO2, N2, Ar, Ne, and Ar+Ne) were utilized for the ambient atmosphere in order to change the ambient gas viscosity. The vaporization of fuel drops was negligible. This study, revealed that the higher the viscosity, the more the spray spreads in the radial direction, thus the spray angle increased and tip penetration decreased. The droplets became smaller and were distributed in the inner region of the cold-state diesel spray under high ambient viscosity conditions. Further more, it was found that processes of ligament formation in the liquid jet and initial atomization were affected by kinematic viscosity ratio between the liquid fuel and ambient gas, and the spray dispersion and mixing process in the downstream region was affected only by the ambient gas kinematic viscosity.

著者

井門 敦志 小濱 泰昭

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.703, pp.817-824, 2005-03-25 (Released:2011-03-03)

参考文献数

8

被引用文献数

4 4

---

As a train runs at higher speeds, the aerodynamic drag increases. On long train-sets such as those of Shinkansen, the aerodynamic drag is mainly generated by intermediate vehicles. In previous researches, we proved that smoothing the under-floor surface reduces the aerodynamic drag. To investigate the mechanism of this effect, we performed wind tunnel tests with train models consisted of three vehicles, each representing a head, intermediate and tail vehicle, and measured the aerodynamic drag and pressure distributions on the intermediate vehicle. We divided the aerodynamic drag of the intermediate vehicle into the components at different parts of the carbody and clarified the effect of smoothing the under-floor surface to decrease the aerodynamic drag.

著者

井門 敦志

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.69, no.685, pp.2037-2043, 2003-09-25 (Released:2008-03-28)

参考文献数

8

被引用文献数

1 1

---

In our previous researches, we estimated the reduced quantity of aerodynamic drag of trains by smoothing under-floor construction. However, we did not compare the results of wind tunnel tests with those of on-track tests, or verify the accuracy of wind tunnel tests for the aerodynamic drag of trains. In this research, we estimated the aerodynamic drag of a train-set by wind tunnel tests. Regarding the reduced quantity of the aerodynamic drag of trains, we compared the results of wind tunnel tests with those of on-track tests. These test results show that the reduced quantity of the aerodynamic drag of trains by wind tunnel tests approximately agrees with that by on-track tests.

著者

寺地 淳 津田 剛 野田 徹 久保 賢明 伊東 輝行

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.710, pp.2581-2587, 2005-10-25 (Released:2011-08-16)

参考文献数

13

被引用文献数

1

---

Combustion in IC engines involves very complicated phenomena, which are strongly affected by engine speed, load and turbulence intensity. The aim of this study was to develop a flame propagation model and a knock prediction technique applicable to various engine oparating conditions. A new flame propagation model (UCFM) has been developed that improves the Coherent Flamelet Model (CFM) by considering flame growth both in terms of the turbulent flame kernel and laminar flame kernel. A knock prediction model was developed by implementing the Livengood-Wu integral as the autoignition model in the flame propagation model. The combined model allows evaluation of both where and when autoignition occurs in a real shape combustion chamber. The three-dimensional calculation results indicate the general tendency for the pressure history and the location where autoignition occurs in the combustion chamber.

著者

吉田 正武

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.617, pp.305-311, 1998-01-25 (Released:2008-03-28)

参考文献数

8

被引用文献数

1

---

The author had previously reported that work done by a power stroke of 4-stroke gasoline engine is expressed as a function of engine factors (ignition timing, combustion period, heat release diagram and so on.) using an approximate pressure diagram of a cylinder, which is an approximate solution of the energy conservation equation. In this report, the author examined the effects of combustion period and heat release diagram on the work done by a power stroke. The results show that (1) the factors mentioned above have little effect on the thermal efficiency at the optimum ignition timing (MBT) ; (2) When combustion period is decreased, MBT shifts from advanced crank angle to retard crank angle in proportion to the decrease of combustion period ; and (3) The idea that a short combustion period improves thermal efficiency does not apply in the case of non-adiabatic engines.

著者

小島 晋爾 勝見 則和 宮川 浩 奥村 猛 植田 貴宣

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.65, no.638, pp.3523-3529, 1999-10-25 (Released:2008-03-28)

参考文献数

9

被引用文献数

2 1

---

The slant-shaped squish chamber recently developed by our company improves charging efficiency and raises compression ratio of its gasoline-engines. We clarified its knock suppression mechanism using rapid compression-and-expansion machine, autoignition simulation, and 3-dimensional turbulent flame propagation simulation. The results indicate the following: 1. Timing of flame acceleration is a key of knock suppression, that is, optimum timing of flame acceleration exists in the latter half of combustion, because expansion stroke suppresses the temperature rise in the end gas. This universal mechanism improves knock-limited ignition timing and compression ratio of the above engines. 2. A cause of the flame acceleration in the slant-shaped squish chamber is strengthened turbulence occurring in front of the flame and in reverse squish flow which separates at the squish lip. 3. The reverse squish flow, which is well known to be induced by the suction due to the larger expansion ratio of squish region than the other region of combustion chamber, is enhanced by the thermal expansion of burning mixture.

著者

高田 洋吾 荒木 良介 野々垣 元博 海老田 一章 石井 利長 脇坂 知行

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.764, pp.650-659, 2010-04-25 (Released:2017-06-09)

参考文献数

20

被引用文献数

3 2

---

Polymer electrolyte fuel cell (PEFC) is expected to applications for various usages such as a power source for small robots and personal computers because PEFC has high energy density and can generate electric power under low temperature environment. As the application, swimming fish robots with PEFC are useful for various usages such as ecological investigation in water etc. In the case that rechargeable batteries are used for supplying electricity to robots, they are not able to continue swimming for a long time because of low energy density of the batteries. Therefore, a small and ultra-light passive-type polymer electrolyte fuel cell called "Power Tube" has been developed. On the basis of this fuel cell technology, the authors have created low energy consumption small fish robots powered by Power Tubes on a float or a buoy. The fish robot with a float swims for approximately 50 minutes by only Power Tubes with a voltage booster and the other fish robot with a submersible system can also swim for about 50 minutes by a hybrid system of a lithium polymer battery and Power Tubes.

著者

森西 洋平

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.62, no.604, pp.4106-4112, 1996-12-25 (Released:2008-03-28)

参考文献数

14

被引用文献数

4 5

---

In this report, numerical tests of the conservation properties of finite difference schemes are performed. Inviscid flow simulations in a two-dimensional periodic domain are performed using several finite difference schemes that are discussed in the first and second reports. The momentum and kinetic energy are conserved when the proper schemes in regular and staggered grid systems are used. The defect of the finite difference schemes in a collocated grid system is emphasized in the simulation. In addition, plane channel flows at Re=180 and 2000 are simulated using the proper fourth-order accurate finite difference scheme in a staggered grid system and the results are better than those of the second-order accurate algorithm and an existing fourth-order accurate scheme.

著者

田中 宗信 佐藤 忠教 阿川 薫

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.484, pp.4084-4093, 1986-12-25 (Released:2008-03-28)

参考文献数

5

---

An experimental study on the reforming characteristics of five different catalysts for methanol fuel was conducted and the endurance of each catalyst was examined using a fixed type reformer. A reformer utilizing the heat of exhaust gas was also designed and constructed, and the effect of blending the reformed methanol fuel to gasoline was studied in the combustion process of a spark ignition engine. Analyses of the indicator diagram show that the increase of the ratio of reformed gas and gasoline results in (1) an increase of speed and stability of combustion characteristics, (2)the extension of the lean limit of the air-fuel ratio, (3) an increase in the thermal efficiency, (4) a decrease in the cycle-by-cycle fluctuation of the combustion process, and (5) quick achievement of stability for abrupt changes in the throttle position. In view of three results, the optimum operating conditions are proposed.

著者

宋 載翼 吉田 正武 小栗 康文 五味 努

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.54, no.508, pp.3572-3578, 1988-12-25 (Released:2008-03-28)

参考文献数

13

---

It has been reported in many papers that the humidity in a mixture causes a lower S. I. engine output because of the decrease of combustion heat and flame speed. However, the reason for and the extent of the above-mentioned effect have not yet been elucidated. In order to clarify the effect of humidity on S. I. engine output, the author applied the relationship between the humidity and combustion period to the analytical model of an S. I. engine which formulates the work done on a piston as a function of ignition timing. The result shows that (1) humidity decreases S. I. engine output by about 4.5% at constant spark advance, but at optimum spark advance the reduction is about 1.2%, and (2) the rate of flame speed reduction as a result of humidity in a engine is the same as the rate in burner.

著者

白鳥 敏正 松平 晏明 小西 奎二 桜井 忠一

出版者

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.58, no.546, pp.182-187, 1992-02-25

---

Scale model experiments were made to investigate the steady and unsteady airflow characteristics in an underground railway station. The experimental apparatus consists of a scale model of a two-layer underground railway station and train wind generators that simulate the steady and unsteady airflow caused by trains. The steady and unsteady airflows were measured with hotwire anemometers at several points of the station for several cases. The unsteady airflow patterns were almost identical to the estimated airflow patterns obtained from steady values. The method of reducing the train wind effect in a station by means of tunnel ventilation dynamic control was considered and its effectiveness was confirmed through experimentation.

著者

高橋 易資 野村 友和 石間 経章 小保方 富夫

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.706, pp.1694-1701, 2005-06-25 (Released:2011-03-03)

参考文献数

17

被引用文献数

2 4

---

A computational fluid dynamics (CFD) code with partial cells in Cartesian coordinate (PCC) method has been developed. The merit of this method is that input data preparation time is extremely short because computational mesh data are separated from geometry data. However, a general Cartesian coordinate method has a big subject in calculation accuracy. One of the factors is precision in geometry expression around the complicated shape, and another is a turbulence model near the wall because mesh is independent from the boundary and not fitted with it. Therefore, discretization equations were derived based on Finite Volumetric Method, and a combination of the wall function and a low Reynolds number k-ε turbulence model was proposed here. This paper describes implementation of this method and shows the results compared with experimental data by particle image velocimetry (PIV) at the steady flow in the cylinder of a 4-valves S.I. engine. The comparison results of velocity vector maps show good agreement between CFD and PIV.

著者

伊藤 献一 矢野 利明 永坂 玲

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.48, no.428, pp.803-810, 1982-04-28 (Released:2008-03-28)

参考文献数

18

---

単筒エンジンをメタノールで運転し,排気管に沿う未燃燃料とCH2Oの変化を調べた.400℃以上で未燃メタノールは排気管中で酸化のため減少するのに対し,CH2Oは減少せず希薄運転では増加することを見い出し,両者の成因は異なることを指摘した.この原因は,CH2Oがメタノールの酸化に伴い生成されることにあり,排ガス温度が400~600℃において,CH2O濃度は増加現象を示すことを,定温度場における反応実験により裏づけた.

著者

鈴木 博 長島 昭

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.408, pp.1574-1582, 1980-08-25 (Released:2008-03-28)

参考文献数

15

被引用文献数

3 4

---

最近,海水は従来より広い温度・圧力の範囲で利用される機会が増した.冷却水としての利用,海洋温度差発電,淡水化あるいは深海での機器の伝熱などがその例である.本研究では従来のデータのない30℃以上を含めて,0℃から80℃までそして400bar程度までの高圧域で,海水の粘性係数を閉回路式の高圧用毛細管式測定装置によって実験研究を行った.試料としては,標準海水を用いた.得られた結果から,純水の粘性係数に対する海水の値の比を広い範囲で表す実験式を作成した.

著者

沢田 雅 中村 雅英 鎌田 信

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.51, no.471, pp.3743-3747, 1985-11-25 (Released:2008-03-28)

参考文献数

3

被引用文献数

2 2

---

For the purpose of clarifying the mechanism of rotation of Savonius rotors, ones which have two semicylindrical blades are studied experimentally. The force acting on a blade is measured in a water two tank for both cases where a rotor is at rest and rotated. The flow around a rotor is observed by using aluminum powder floating on the water surface. Although the Savonius rotor is classified into a resistance type, the lift produces the torque in a pretty wide range of angle relative to the flow.

著者

辻村 真治 飯田 雄章 長野 靖尚

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.67, no.659, pp.1762-1769, 2001

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In the Earth's atmosphere, zonal currents with a vertical velocity gradient are induced under the action of rotation and horizontal temperature gradient. These currents satisfying the so-called "thermal wind equation" generate the cyclones and anticyclones through the baroclinic instability, and hence have serious effects on the global circulation. In this study, the generation and development mechanisms of vertical vortices associated with the cyclones and anticyclones are investigated by using direct numerical simulation of the thermal wind. By imposing the stable density stratification in the vertical direction, the effects of the stable stratification and the Reynolds number are studied in detail. As a result, we have found the distinct effects of stable stratification on the anisotropy of the flow field and the generation of the vortical structure. It is also found that the cyclone becomes dominant in comparison to the anticyclone at a relatively low Reynolds number under the weak stable stratification. At a higher Reynolds number, both cyclonic and anticyclonic vortices are enhanced by the nonlinear vortex stretching term, and hence the asymmetry between them becomes negligible. The intensive stable stratification attenuates the nonlinear vortex stretching and contributes to the occurrence of the asymmetry in the vortices even at the higher Reynolds numbers

著者

青山 絢子 中島 求

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.73, no.734, pp.2018-2026, 2007

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The objective of this study was to investigate the stability during freefall in skydiving, in which the diver has to take various body position in order to control precisely their distance, velocity, and direction relative to the other divers for the group performance. For this objective, the state equation for a simple elliptic cylinder model was firstly derived, considering its equations of motion and the fluid force characteristics. Next, using the form of state equation derived for the elliptic cylinder and the input/output data obtained from the developed simulation method for the body behavior of the skydiver, the state equations of skydiver were identified for various body positions. Finally, roots of the state equations were obtained to investigate the stability. As the results, the causes of instability such as spin and spiral phenomena were clarified as an unstable natural modes, and the stable limit of body position was obtained as a value of parameter which is related to the arch magnitude of the diver's body.

著者

山内 庄司 中西 重康 石谷 清幹

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.47, no.416, pp.693-702, 1981

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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

鳴尾 丈司 溝田 武人 下園 仁志

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.70, no.697, pp.2371-2377, 2004-09-25 (Released:2011-03-03)

参考文献数

8

被引用文献数

1 1

---

A device to rotate a real golf ball at a maximum of 10 000 rpm in the wind with a maximum speed of 80 m/s was developed. Aerodynamic forces and torque acting on the ball were measured under various flight conditions in a wind tunnel flow. As a result, it was found that drag, lift, and torque coefficients under the real conditions depended on the spin parameter but were independent of the Reynolds number. Using the measured aerodynamic force coefficients and a ball initial condition measured by ejection experiments, mathematical calculation of trajectory equation was made by time integral calculus. Ejection experiments were conducted by a robot. The correctness of the trajectory analysis and measured aerodynamic force was verified by comparing the calculated results with measured results.

著者

松井 健太 山本 和弘

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.765, pp.896-902, 2010

参考文献数

21

---

Since particulate matters (PM) emissions including soot from diesel cars do harm to our health, a diesel particulate filter (DPF) has been used in the after-treatment of exhaust gas. It is reported that DPF filling with PM causes higher back-pressure and more fuel consumption, and continuously regenerating PM trap system is needed. Then, we have focused on the diesel exhaust gas perfect burning system (DEGPBS) developed by COTEC, Ltd., where soot is trapped and burned by the heater. However, the phenomena in the system are not well understood, because it is difficult to conduct the measurement inside the filter. In this study, we simulated soot combustion and deposition by the lattice Boltzmann method to observe the combustion field in the filter. The inner structure of the filter was obtained by a 3D X-ray CT technique. Results show that the heat and mass transport in DEGPBS are well visualized. It is found that temperature of the filter and oxygen concentration are important factors to burn soot in exhaust gas.