著者

池田 光優 三上 真人 小嶋 直哉

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.625, pp.3126-3132, 1998

被引用文献数

1

---

Attempts have been made to improve exhaust gas characteristics of the direct injection diesel engine under dual-fuel operation with gas oil and LPG. In dual-fuel operation with LPG as a sub-fuel, two kinds of LPG mixing methods can be employed. One is LPG mixing in gaseous state with the intake air, which is so-called "fumigation". The other is LPG mixing in liquid state with gas oil prior to injection. The experimental results show that the mixing method in liquid state is better than the fumigation method in terms of NO and THC emission and specific energy consumption. In the mixing method in liquid state, NO is reduced in comparison with the base engine without the increase in THC, smoke and specific energy consumption if a proper squish intensity is employed.

著者

三上 真人 嶺山 隆志 伊藤 勝幸 河野 通方

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.600, pp.3178-3184, 1996

被引用文献数

1

---

The droplet combustion of n-heptane, benzene and ethyl alcohol was investigated in acoustic fields. The frequencies of the acoustic waves used were around the characteristic frequencies of droplet combustion ; the residence frequency and the diffusion frequency. Under low frequency conditions (70-200 Hz), the experimental results can be interpreted by the mechanism of quasi-steady state combustion, which includes all types of droplet combustion ; the envelope name, wake flame and flame extinction. Under high frequency conditions (300-800 Hz), the combustion is possibly influenced by a diffusional mechanism which is induced by acoustic waves of such high frequency.igh frequency acoustic waves increase the flame luminosity, especially for benzene and n-heptane droplets. This suggests that the high frequency acoustic wave enhances radiant heat transfer from the flame zone to the droplet, and thus the burning rate constant increases.

著者

三上 真人 八木 孝 小嶋 直哉

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.2690-2695, 1998

被引用文献数

2

---

Occurrence behavior of microexplosion in droplet combustion of fuel mixtures is studied. Experiments were performed using unsupported droplets of n-alkane/n-hexadecane mixtures in normal gravity. It was found that the occurrence of microexplosion is stochastic and cannot be predicted by the classical criterion for microexplosion occurrence using the limit of superheat and the droplet temperature. An occurrence model for the microexplosion based on the homogeneous nucleation theory is presented and shows that the occurrence probability of the microexplosion is determined by the ratio of the liquid phase lifetime to the nucleation time during the quasi-steady vaporization period. The nucleation time is inversely proportional to the nucleation time is inversely proportional to the nucleation rate and superheated liquid volume. The relative value of the droplet temperature and the limit of superheat affects the occurrence probability through the nucleation rate. It can be well explained by the model that the occurrence probability has the maximum value for a certain initial concentration of the fuel mixture.

著者

三上 真人 加藤 秀輝 佐藤 順一 河野 通方

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.61, no.582, pp.731-737, 1995

被引用文献数

1

---

The effect of gravity on fuel droplets burning interactively has been studied experimentally. Experiments on two droplets aligned horizontally were conducted both in normal gravity and in microgravity. Results show that in normal gravity, oxygen starvation between the flames is not as severe as in microgravity. Natural convection, which supplies oxygen to the flame, is stronger at a smaller initial separation distance when two flames exist separately. The instantaneous burning rate for the same normalized droplet diameter has a maximum in normal gravity when the initial separation distance is changed and decreases monotonically in microgravity with decreasing initial separation distance, except for the initial period of burning. Thus, the effect of gravity, which decreases the burning lifetime, is greatest at a certain initial separation distance.

著者

武藤 昌也 坪倉 誠 大島 伸行

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:18848346)

巻号頁・発行日

vol.77, no.775, pp.781-792, 2011 (Released:2011-03-25)

参考文献数

14

被引用文献数

1

---

Flow characteristics and fluid force on a sphere rotating along with axis perpendicular to mean air flow were investigated using Large Eddy Simulation (LES) at two different Reynolds numbers Rep of 1.0×104 and 2.0×105. As a result of simulation, opposite flow characteristics around the sphere and displacement of the separation point were visualized depending on the Reynolds number even though rotation speed according to the Reynolds number is the same. When the sphere rotates at some specific rotation velocity and at Rep = 1.0×104, flow characteristics agree with the flow field explained in the Magnus effect. While sphere rotates at the same rotation velocity while increasing Rep to 2.0×105, separation point moves in opposite direction and wake appears in the different direction. The reason of the negative Magnus force was discussed in terms of the boundary layer transition on the surface.

著者

寺島 修 伊澤 精一郎 稲澤 歩 福西 祐

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:18848346)

巻号頁・発行日

vol.77, no.773, pp.56-65, 2011 (Released:2011-01-25)

参考文献数

19

被引用文献数

4 2

---

The streamwise interface of an isolated turbulent region in a laminar flat plate boundary layer is investigated by performing a wind tunnel experiment. In the experiment, bimorph-type piezoceramic actuators are used to generate a trapezoidal-shaped turbulent region that has a wide interface in the spanwise direction. With the use of the piezoceramic actuators, the interference of the spanwise interface with the streamwise interface of the turbulent region is eliminated. Therefore, the streamwise interface can be considered as an independent interface. The experimental results show that the rms value of the velocity fluctuation and the turbulent fluctuation rapidly changes at the leading edge of the turbulent region. On the other hand, the rms value of the velocity fluctuation remains high after the turbulent fluctuation disappears at the trailing edge of the turbulent region. It is also shown that the traveling speed of the trailing edge of the turbulent region is faster than the ensemble-averaged streamwise velocity at the trailing edge of the turbulent region near the wall (η≤1.3). In addition, the velocity profile at the trailing edge of the turbulent region indicates the existence of the acceleration of the turbulent fluid near the wall. From the above results, it is found that the inverse transition occurs at the trailing edge of the turbulent region near the wall due to the acceleration of the turbulent fluid.

著者

大橋 博志 門脇 敏

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:18848346)

巻号頁・発行日

vol.79, no.799, pp.477-481, 2013 (Released:2013-03-25)

参考文献数

8

被引用文献数

1 1

---

To investigate the front shape and fluctuation of cellular flames on a flat burner, we treated CH4/Air mixtures and two types of CH4/O2/CO2 mixtures. We obtained the front shape of cellular flames, i.e. the cell width and cell depth, by the planar laser-induced fluorescence of CH radicals (CH-PLIF) and measured the light emission to clarify the characteristics of fluctuation of premixed flames. As the flow rate of methane decreased, the cell width and cell depth became larger, and the size of attractors increased. Compared with CH4/Air mixtures, cellular fronts were observed at large flow rates of methane in CH4/O2/CO2 mixtures, and the trajectory of attractors was complicated. These were because of high intensity of diffusive-thermal instability resulting from the replacement of N2 with CO2.

著者

清水 幸丸 鈴木 利明 松崎 健 森 健次朗

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.625, pp.2844-2851, 1998

---

Sport science progresses step by step in the world. The paper describes, the first, the relationships between fluid drag for a model of woman swimmer and the flow around it. The flow around the model swimmer is very complicated, and includes, for example, wave, some kinds of vortices, hydraulic jumping and so on. The complicated flows are visualized by the surface tufts method and so on. Second, the possibility of the reduction of fluid drag for a woman athlete swimming suit is challenged. The boundary layer control is applied to reduce the fluid drag. The separation occurs around the breast of a woman swimmer. The separation can be suppressed by the boundary layer control. Many beads are distributed on the breast area of a woman swimming suit. As the result, it is found that the fluid drag for the model swimmer can be reduced in a range of 1.5%∼2% by the suit with the boundary layer control, which is carried out by many beads.

著者

平田 勝哉 中森 真志 谷川 和哉 片岡 福太郎 藤本 泰貴 篠木 俊雄 谷川 博哉 舟木 治郎

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:18848346)

巻号頁・発行日

vol.79, no.808, pp.2873-2884, 2013 (Released:2013-12-25)

参考文献数

15

被引用文献数

2 2

---

The authors develop a small and simple steam-reforming reactor in a home-use size for n-dodecane as a heavy-hydrocarbons fuel. Under such a well-controlled condition by a thermal diffuser as the reactor satisfies two target-temperature criteria, the authors measure the inside-temperature profile and the hydrogen molar fraction (concentration) CH2, together with the molar fractions CCH4, CCO and CCO2 of other main gas components such as CH4, CO and CO2, respectively, using a gas chromatograph. In addition, the authors conduct theoretical calculations based on the thermal-equilibrium theory, and reveal CH2, CCH4, CCO and CCO2, as well as experiments. As a result, the authors successfully achieve suitable inside-temperature profiles. The steam-reforming reaction becomes more active at the position where temperature T > 800 K. The effects of the steam-to-carbon molar ratio S/C upon CH2, CCH4, CCO and CCO2 are shown, experimentally and theoretically. The experimental results agree well with the theoretical ones. Besides, carbon balance and conversion ratio show high accuracy in experiments.

著者

川島 豪 星 絢也

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:18848346)

巻号頁・発行日

vol.78, no.789, pp.984-987, 2012 (Released:2012-05-25)

参考文献数

3

被引用文献数

1 1

---

It is necessary to examine what kind of vibration and swinging is comfortable, in order to develop the comfortable human-machine interface using vibration or swinging. This study is focusing on the fluctuation in the period on the rhythm produced by the human; especially the stroke interval of the air stick is examined. The air stick is a simple version of the devil stick which is a kind of street performance. First, the portable measuring system of the stroke interval is developed by sticking two strain gauges on each hand stick and putting a wired battery driven strain amplifier and a portable data recorder in a knapsack which the performer wears. Then, the fluctuation is measured and the power spectrum is examined. As the result, it is clarified that the power spectrum shows the downward-sloping tendency in the low frequency range, and it shows the relation of about 1/f averagely.

著者

小川 信夫 牧 博司 土方 邦夫

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.57, no.535, pp.935-942, 1991

---

From our previous reports, it is clarified that the fluctuations in the jet center have an important effect on opposed turbulent jet flow fields. In the jet center, where symmetrical flow fields are characterized, the turbulent structure will be different from those in other parts of the jet. In the turbulent opposed jet center, the fluctuating velocity plays role equal in importance to that of the mean velocity. The momentum which locates the impinging surface comprises three parts: that is, a mean velocity, a static pressure and a fluctuating velocity. The present paper deals with the influences of the variations of the fluctuating velocity, employing the turbulent lattice in the center of turbulent opposed jets, to the locations of the impinging surface.

著者

金子 暁子 野村 康通 高木 周 松本 洋一郎 阿部 豊

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:18848346)

巻号頁・発行日

vol.78, no.786, pp.207-217, 2012 (Released:2012-02-25)

参考文献数

14

被引用文献数

8 19

---

Microbubble has distinguished characteristics of large surface area to unit volume and small buoyancy. Recently microbubble generators with low energy and high performance are required to wide applications. In the present study, we propose one new effective technique to generate tiny bubbles with less than 200μm diameter utilizing a venturi tube under high void fraction condition. The objective of the present study is to elucidate the mechanism of bubble breakup phenomena in the venturi tube and to clarify the effects of parameters which are necessary to realize an optimum system experimentally. Under low velocity condition, bubbles which were observed with a high speed camera parted gradually in a wide region. On the contrary under high velocity condition, bubbles expanded after passing through the throat and shrank rapidly. Since the speed of sound in gas-liquid system is extremely lower than that of single-phase flow, the bubble breakup phenomenon in the venturi tube is explained as the supersonic flow in a Laval nozzle. With rapid pressure recovery in diverging area, expanding bubbles collapse violently. The tiny bubbles are generated due to the surface instability of shrinking bubbles.

著者

村瀬 英一 森上 修 橋本 英樹 松崎 伊生

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:18848346)

巻号頁・発行日

vol.79, no.805, pp.1839-1847, 2013 (Released:2013-09-25)

参考文献数

9

被引用文献数

1

---

Spark ignition of premixed gases was experimentally studied. Minimum ignition energy and initial burning velocity, which is a burning velocity at an initial stage of flame propagation, were measured and their dependences on equivalence ratio were discussed. Minimum ignition energy takes a minimum value when equivalence ratio is around 0.9 for methane/air mixtures, and around 1.5 for n-butane/air mixtures, which corresponds with the study of Lewis and von Elbe. A shadowgraph technique was used to observe the growth of the flame kernels. A burning velocity was measured from the images of the flame kernel, and initial burning velocity was defined as a burning velocity at the moment when the equivalent radius of the flame kernel is approximately 3.0mm. Initial burning velocity takes a maximum value when equivalence ratio is around 0.9 for methane/air mixtures, and around 1.5 for n-butane/air mixtures, while laminar burning velocity of well-grown flame takes a maximum value when equivalence ratio is around 1.1 for both mixtures as known well. This is caused by the curvature of flame surface at the initial stage. It is suggested that the equivalence-ratio dependence of minimum ignition energy is derived from that of initial burning velocity.

著者

佐藤 航

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:18848346)

巻号頁・発行日

vol.79, no.801, pp.1027-1037, 2013 (Released:2013-05-25)

参考文献数

18

---

I describe our study on a cooling device that is based on the electrocaloric effect (ECE). The ECE causes increases and decreases in the temperature of a dielectric material by changing the electric field. I used a multi layer ceramic capacitor (MLC) to demonstrate the temperature change based on the ECE. The temperature change of commercial MLCs can be controlled by applying a voltage to them and the maximum change is 0.55 K when using 300 V. However, these changes occurred sequentially by applying and removing the voltage. Therefore, it was difficult to apply this phenomenon to a cooling device. I used a heat pipe that had an anisotropic heat conduction feature in this study to separate the heating and cooling. I developed a cooling device consisting of MLCs and a heat pipe containing acetone as the working fluid. The MLCs were set in the bottom of the heat pipe as the cold side and the other side of the heat pipe was attached to a heat sink as the hot side. Only the heat of the ECE in this device was transferred to the heat sink. The temperature of the cold side decreased by applying and removing the voltage periodically. This device demonstrated that the temperature of an MLC dropped 0.49 K when using 300 V at 0.10 Hz frequency.

著者

野原 正寛 金子 雄大 萩原 俊輔 永田 晴紀

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:18848346)

巻号頁・発行日

vol.77, no.777, pp.1249-1258, 2011 (Released:2011-05-25)

参考文献数

6

---

The authors have been developing Cascaded Multistage Impinging-jet (CAMUI) type hybrid rockets. A CAMUI type hybrid rocket uses a fuel grain consisting of several cylindrical fuel blocks with two ports. To minimize both of c* loss due to O/F shifting and residual fuel weight after burning, an appropriate design of initial fuel grain shape is necessary. However, obtaining an optimum design of initial grain shape is not easy because there are many design variables influencing one another. To solve this problem, the authors employed Genetic Algorithm (GA) combined with a numerical model forecasting performance history of a CAMUI type motor. GA can acquire an approximate optimum solution for problems with a vast search space in practical time. The numerical model gives c* loss and residual fuel weight to evaluate the degree of performance of each initial fuel grain shape. A fuel grain design proposed by this method showed residual fuel weight as small as 6.36% of the initial weight and c* loss less than 1%.

著者

山本 昌平 坂口 大作 植木 弘信 石田 正弘

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:18848346)

巻号頁・発行日

vol.79, no.799, pp.380-389, 2013 (Released:2013-03-25)

参考文献数

16

被引用文献数

5

---

In order to realize a premixed compression ignition (PCI) engine by utilizing bio-alcohol, combustion characteristics of bio-alcohol blended with gas oil were compared between ethanol and n-butanol in a diesel engine. The effects of the ethanol blend ratio and the butanol blend ratio on ignition delay, premixed combustion, diffusion combustion, fuel consumption and exhaust emissions such as smoke density, nitrogen oxide (NOx) and so on were investigated experimentally. It is found that ethanol almost burns out together with low evaporation temperature composition of gas oil in the premixed combustion period and the heat release in the diffusion combustion is based on mainly high evaporation temperature composition of gas oil, then, soot is formed in the diffusion combustion of gas oil. On the other hand, a part of butanol burns in the diffusion combustion, and the combustion of butanol in the diffusion stage is not the cause of soot formation. Butanol is more useful in diesel engine compared with ethanol because butanol can be blended with gas oil without surface-active agent, and fuel consumption and smoke are almost equal in both blend fuels if the alcohol blend ratio is the same.

著者

佐藤 範和 竹内 伸太郎 梶島 岳夫 稲垣 昌英 堀之内 成明

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:18848346)

巻号頁・発行日

vol.79, no.803, pp.1219-1231, 2013 (Released:2013-07-25)

参考文献数

13

被引用文献数

1 1

---

A new discretization scheme of a Cartesian grid method for flow with heat transfer is proposed. The energy transport equation is discretized directly even in the boundary cells involving either the Dirichlet (isothermal) or the Neumann (iso-heat-flux/adiabatic) boundary conditions in order to ensure the energy conservation in those cells. The basic idea of this discretization is the same as the discretization scheme which is previously proposed by the present authors for boundary forcing in incompressible flow simulations. Moreover, the temperature gradients in both the normal and tangential directions at boundaries are required in the present method for representing the Neumann boundary condition on the Cartesian grids which do not necessarily coincide with the body geometries. The tangential components of the temperature gradients at boundaries are calculated by the extrapolations from the surrounding temperature field. Accuracy evaluations are conducted in a convective heat transfer problem in a flow between concentric cylindrical walls under the several different types of thermal boundary conditions applied at the inner and outer walls. It is confirmed that the present method significantly improves the accuracy orders for the temperature as well as the error magnitudes under both types of thermal boundary conditions. In particular, because the temperature gradients are correctly considered at the boundary cells where the Neumann boundary conditions are enforced, the same level of accuracy order is also maintained even in cases of non-uniformly distributed temperature at those boundaries.

著者

杉井 泰介 石井 英二

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:18848346)

巻号頁・発行日

vol.77, no.781, pp.1779-1790, 2011 (Released:2011-09-25)

参考文献数

23

---

We present a simulation of meso-scale fluid in a grooved channel conducted using the many-body dissipative particle dynamics (MDPD) method. The simulation system consists of a straight channel with a rectangular groove and a liquid that fills the channel. In the simulation, an instantaneous liquid interface was defined and the time-series variation of the angle between the channel wall and the interface was investigated. The calculated angle was found to satisfy the Gibbs' inequality condition when the interface passes the corner of the groove. We also investigated the behavior in which the liquid filled the groove by varying the contact angle between the liquid and the channel wall. The results show that the feasibility of filling the groove, which depends on the contact angles between the liquid and the grooved/non-grooved channel wall, qualitatively agrees with the geometrical analysis. We also showed that a smaller contact angle between the liquid and the grooved channel wall and a larger contact angle between the liquid and the non-grooved channel wall causes the liquid to fill the groove.

著者

甲村 圭司 中村 佳朗

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:18848346)

巻号頁・発行日

vol.79, no.804, pp.1489-1499, 2013 (Released:2013-08-25)

参考文献数

10

---

Aerodynamic noise with discrete frequencies is generated in an unexpected way from a slit between a flat plate, which is placed in parallel to the main flow, and a wedge that is placed normal to the flow. To study this phenomenon, we examined the discrete frequency noise generated by a subsonic air jet flow from a slit. It was found that the slit height and the plate length have considerable effects on the noise generation. In addition, the discrete frequency noise was generated only when the values of these parameters are within a limited range. Furthermore, it was found that the noise frequency is proportional to the jet velocity and is inversely proportional to the plate length. Finally, it was made clear from the present study that the interaction of the vortex, which is generated from the shear layer due to a wedge, with the wake of a flat plate is a major cause for the discrete noise due to a slit.

著者

鈴木 貴之 加藤 千幸

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:18848346)

巻号頁・発行日

vol.79, no.808, pp.2743-2758, 2013 (Released:2013-12-25)

参考文献数

15

被引用文献数

1 2

---

Over the past two decades, many types of homogeneous models have been proposed for the numerical simulation of cavitating flows. Homogeneous models represent cavitation by the media whose density continuously varies from the value corresponding to liquid to that to gas. Recent studies have, however, revealed that the present homogenous models are unable to predict the breakdown characteristics of cavitating hydrofoils. The objective of this study is to clarify causes of such inability of homogeneous models to predict breakdown characteristics of cavitating hydrofoil accurately. Theoretical analysis shows that the present cavitation models inevitably cause kinetic energy loss through expansion and contraction of the media. To illustrate this fact, we computed cavitating flows in a venturi and around a hydrofoil (NACA0015) with a homogeneous model and investigated the computed flow field in detail. It is shown that the expansion and contraction of the media based on the homogeneous model do in fact cause kinetic energy loss and as a result, a region of low velocity appears downstream of the cavity. This results in a decrease of lift force in a partial cavitation condition, which is not observed in the corresponding measurements.