著者

Takashi SAIKA Mitsuhiro NAKAMURA Tetsuo NOHARA Shinji ISHIMATSU

出版者

社団法人 日本機械学会

雑誌

JSME International Journal Series B Fluids and Thermal Engineering (ISSN:13408054)

巻号頁・発行日

vol.49, no.1, pp.78-83, 2006 (Released:2006-08-15)

参考文献数

14

被引用文献数

10 18

---

Carbon-free fuel is effective in preventing global warming. Hydrogen has no carbon and can be made also from nuclear energy or reproducible energies other than fossil fuels. However, hydrogen lacks portability because of its difficulty in liquefying, but ammonia can easily be liquefied at a room temperature and dissociated into high-content hydrogen and nitrogen using a suitable catalyst. An ammonia dissociation system for fuel cells is proposed in this paper. The residual ammonia by 13ppm or more in the dissociated gas (H2+ N2) causes a decrease in the output of fuel cells. To separate residual ammonia, it should be sent to an ammonia separator and then to an ammonia distiller. In the experiment, the authors examine the concentrations of ammonia after dissociation at various temperatures, pressures and space velocities. The ammonia separator uses the fact that ammonia dissolves well in water. Then the ammonia water is distilled in the distiller. Thereby, the authors have proposed an ammonia circulation system that is a clean energy system.

著者

Tie LI Keiya NISHIDA Yuyin ZHANG Tuyoshi ONOE Hiroyuki HIROYAU

出版者

社団法人 日本機械学会

雑誌

JSME International Journal Series B Fluids and Thermal Engineering (ISSN:13408054)

巻号頁・発行日

vol.48, no.4, pp.687-694, 2005 (Released:2006-05-15)

参考文献数

9

被引用文献数

5 19

---

The effect of split injection on the mixture characteristics of DISI (Direct Injection Spark Ignition) engines was investigated firstly by the Laser Absorption Scattering (LAS) technique. Through splitting the fuel injection process, two possible benefits were found: 1) High density liquid droplets piling up at the leading edge of the spray can be circumvented, subsequently the reduction of the spray tip penetration; 2) The quantity of “over lean” (φv<0.7, φv: equivalence ratio of vapor) mixture in the spray can be significantly reduced. These are believed to contribute to the reduction of the engine-out smoke and HC emissions. In order to clarify the mechanism behind the effect of the split injection, the spray-induced ambient air motion was investigated by the LIF-PIV technique. The strong ambient air entrainment into the tail region of the spray and a counter-vortex structure were found in both the single and split injections. In the case of the single injection, the spray develops in extending its length, subsequently a larger volume results and thus it is diluted to “over lean” by the ambient air entrainment. In contrast, in the case of split injection, the second spray is injected into the tail region of the first spray and its evaporation is promoted by the ambient air motion induced by the first spray. Hence the replenishment of the liquid fuel into the leading edge of the first spray is reduced. As a consequence, the high density liquid droplets piling up at the leading edge is avoided. Furthermore, a more compact spray results so that the ambient air motion plays a positive role on evaporating the spray into “more combustible” (0.7<φv<1.3). This is especially true in the tail region of the spray and the region where the counter-vortex motion is occurring.

著者

Yuyin ZHANG Keiya NISHIDA Takuo YOSHIZAKI

出版者

社団法人 日本機械学会

雑誌

JSME International Journal Series B Fluids and Thermal Engineering (ISSN:13408054)

巻号頁・発行日

vol.46, no.1, pp.100-108, 2003 (Released:2004-06-25)

参考文献数

17

被引用文献数

2 10

---

Recent experimental studies have shown that with split injection strategy, the soot and NOx emissions from a diesel engine can be reduced significantly in comparison with a conventional non-split injection. To understand the mechanism of emissions reduction, it is essential to clarify the process of mixture formation in the diesel spray. For characterizing the droplets and vapor concentration distributions inside a fuel spray, a dual-wavelength laser absorption-scattering technique (LAS) was developed by using the 2nd harmonic (532nm) and the 4th harmonic (266nm) of an Nd: YAG laser and using dimethylnaphthalene as a test fuel. By applying the ultraviolet-visible LAS imaging technique, the distributions of droplets and vapor concentrations in the spray, which was injected into a high-temperature and high-pressure nitrogen ambient in a constant volume vessel by a common-rail diesel injection system, were measured and quantitatively analyzed. The effect of injection mass ratio of double-pulse injections on distributions of equivalence ratios of vapor and droplets in the sprays was examined.

著者

Jiro SENDA Takatsugu ASAI Bungo KAWAGUCHI Hajime FUJIMOTO

出版者

社団法人 日本機械学会

雑誌

JSME International Journal Series B Fluids and Thermal Engineering (ISSN:13408054)

巻号頁・発行日

vol.43, no.3, pp.503-510, 2000-08-15 (Released:2008-02-18)

参考文献数

14

被引用文献数

5 11

---

A new injection system using mixed fuel dissolved with liquefied CO2 is proposed in this paper. Liquefied CO2 is mixed with n-Tridecane under pressure in order to promote spray atomization and evaporation due to the effect of the flash boiling phenomenon during fuel injection, and to control the combustion process due to the effect of the internal exhaust gas recirculation (EGR) effct of CO2 gas. Therefore, a simultaneous recduction of soot and NOx is achieved effectively using this injection system. In this study, the characteristics of diesel fuel spray dissolved with liquefied CO2 are investigated quantitatively by several optical measurements. The spray characteristics are revealed by analyzing the chemical thermodynamics. As a result, it is determined that atomization of this fuel is promoted by flash boiling much more than in n-Tridecane, which is normal reference fuel, and the spray structure is considerably different from that of the normal fuel. Moreover, the numerical analysis of atomization and vaporization processes are carried out, based on the flash boiling spray model.

著者

Jun Daesu Ishii Kazuaki Iida Norimasa

出版者

一般社団法人日本機械学会

雑誌

JSME international journal. Ser. B, Fluids and thermal engineering (ISSN:13408054)

巻号頁・発行日

vol.46, no.1, pp.60-67, 2003-02-15

被引用文献数

1

---

Homogeneous charge compression ignition (HCCI) is regarded as the next generation combustion regime in terms of high thermal efficiency and low emissions. It is difficult to control autoignition timing and combustion duration because they are controlled primarily by the chemical kinetics of fuel-air mixture. In this study, it was investigated the characteristics of autoignition and combustion of natural gas in a 4 stroke HCCI engine. And also, to clarify the influence of n-butane on autoignition and combustion of natural gas, it was changed the blend ratio of n-butane from 0 mol % to 10 mol % in methane/n-butane/air mixtures. Autoignition strongly depends on incylinder gas temperature. Autoignition of natural gas occurs when in-cylinder gas temperature reaches in a range of 1 000 ± 100 K under this experimental condition. To realize high thermal efficiency and low CO emissions, it is necessary to prepare operation conditions that maximum cycle temperature is over 1 500 K. Autoignition temperature is 25 K lower by increasing n-butane blend ratio of 10%. As the blend ratio of n-butane increases, the maximum cycle temperature increases, and THC, CO emissions reduce.

著者

Takada Naoki Tomiyama Akio

出版者

一般社団法人日本機械学会

雑誌

JSME international journal. Ser. B, Fluids and thermal engineering (ISSN:13408054)

巻号頁・発行日

vol.49, no.3, pp.636-644, 2006-08-15

被引用文献数

7 24

---

For interface-tracking simulation of incompressible two-phase fluids with high density ratios, a new numerical method was proposed by combining Navier-Stokes equations with a phase-field model based on a van der Waals-Cahn-Hilliard free-energy theory. The method was applied to several benchmark problems. Major findings are as follows: (1) The volume flux derived from a local chemical potential gradient in the Cahn-Hilliard equation leads to accurate volume conservation, autonomic reconstruction of gas-liquid interface, and reduction of numerical diffusion and oscillation. (2) The proposed method gave good predictions of pressure increase inside a bubble caused by the surface tension force. (3) A single liquid drop falling in stagnant gas and merging into a stagnant liquid film was successfully simulated.

著者

Keizo WATANABE YANUAR Hiroshi MIZUNUMA

出版者

The Japan Society of Mechanical Engineers

雑誌

JSME International Journal Series B Fluids and Thermal Engineering (ISSN:13408054)

巻号頁・発行日

vol.41, no.3, pp.525-529, 1998-08-15 (Released:2008-02-18)

参考文献数

4

被引用文献数

51 55

---

A real fluid does not slip at the surface of a solid boundary. Most experimental results of a Newtonian fluid satisfy with this condition. If a real fluid can slip freely over the surface of a solid boundary, how can we deduce the slip velocity. The purpose of this study is to experimentally clarify fluid slip velocity of Newtonian fluids at the duct wall. Velocity profiles of tap water and 20 wt% glycerin solution flowing in a square duct with a highly water repellent wall were measured by means of a conical hot film anemometer. Consequently, the velocity profile with the slip is measured, and the laminar drag reduction phenomena and the friction factor formula for a square duct with fluid slip at the wall have been obtained.

著者

Yuya BABA Fumiteru AKAMATSU Masashi KATSUKI

出版者

The Japan Society of Mechanical Engineers

雑誌

JSME International Journal Series B Fluids and Thermal Engineering (ISSN:13408054)

巻号頁・発行日

vol.47, no.4, pp.750-760, 2004 (Released:2005-05-15)

参考文献数

22

---

The numerical methods of CIP (Cubic Interpolation Pseudo-particle/Propagation) and C-CUP (CIP Combined Unified Procedure) are appropriate and numerically robust even in the direct simulation of turbulent combustible flows. Although these methods have many advantages in the numerical procedure, their accuracy and characteristics have not been evaluated in detail. In the present study, the ability of CIP was firstly examined by comparing it with classical methods in a direct numerical simulation of incompressible turbulent flow. Secondly, C-CUP was evaluated by direct simulations of a compressible-fluid, single-vortex convection problem and of the Aeolian tone. In the first cases, CIP was inferior to the classical method in the vortex shape reproduction. In the latter case, C-CUP showed an advantage in suppressing unrealistic pressure increase and satisfactorily simulated the sound pressure distribution. Furthermore, CIP and C-CUP were applied to numerical simulation of spray combustion in conjunction with applying classical methods in order to compensate the inferior points of CIP.

著者

Sudarmanto Budi NUGROHO Akimasa FUJIWARA Junyi ZHANG

出版者

The Japan Society of Mechanical Engineers

雑誌

JSME International Journal Series B Fluids and Thermal Engineering (ISSN:13408054)

巻号頁・発行日

vol.49, no.1, pp.8-18, 2006 (Released:2006-08-15)

参考文献数

17

被引用文献数

2 2

---

Jakarta city has serious air pollution problems which largely affected by transportation activities. In this paper, a comparative analysis of ambient roadside air pollution patterns in Jakarta city was conducted by using time series data at the existing roadside monitoring stations in 2003. The complex cause-effect relationships between meteorology and pollutants, thus, differ from one season to another. This paper attempts to apply structural equation models with latent variables, which represents the above-mentioned cause-effect relationships. The effectiveness of the established models is empirically confirmed that the goodness-of-fit indices are 0.783 for the weekday wet, 0.845 for the weekday dry, 0.775 for the weekend wet, and 0.822 for the weekend dry. The models give us a better way to analyze urban air pollution due to the results of the significant interactions among meteorological factors, wind and primary pollutants, and also their different influences on surface ozone for each season.

著者

Takeo KAJISHIMA Satoshi TAKIGUCHI Hiroyuki HAMASAKI Yutaka MIYAKE

出版者

The Japan Society of Mechanical Engineers

雑誌

JSME International Journal Series B Fluids and Thermal Engineering (ISSN:13408054)

巻号頁・発行日

vol.44, no.4, pp.526-535, 2001 (Released:2002-09-27)

参考文献数

24

被引用文献数

164 215

---

Turbulence modulation in particle-laden flow, especially the influence of vortex shedding, was investigated by means of the direct numerical simulation. To this end, we developed a finite-difference scheme to resolve the flow around each particle moving in turbulence. The method was applied to the flow around a sphere and the accuracy was confirmed up to the Reynolds number range with vortex shedding. The agreement between our 4th-order central finite-difference method and spectral method for turbulent channel flow without particles was also fine. Then, we simulated upward flow in a vertical channel including solid particles. The velocity and vorticity fluctuations as well as Reynolds shear stress were strongly affected by wakes from particles. The shed vortices were elongated in the mainstream direction by the velocity gradient and resulted in the hairpin vortices. They increased the energy production rate in couple with production due to particle-turbulence correlation.

著者

Masaaki MOTOZAWA Yoshiyuki MATSUMOTO Tatsuo SAWADA

出版者

The Japan Society of Mechanical Engineers

雑誌

JSME International Journal Series B Fluids and Thermal Engineering (ISSN:13408054)

巻号頁・発行日

vol.48, no.3, pp.471-477, 2005 (Released:2006-02-15)

参考文献数

14

被引用文献数

4 4

---

Experimental results for the properties of ultrasonic propagation velocity in kerosene-based and water-based magnetic fluids are reported. Ultrasonic wave frequencies of 1MHz, 2MHz and 4MHz are used and the measurement scheme is based on the pulse method. The external magnetic field intensity is varied from 0mT to 550mT and the angle between the magnetic field direction and the direction of ultrasonic wave propagation is varied from 0° to 90°. The ultrasonic propagation velocity in magnetic fluids is dependent on temperature, elapsed time of applying the magnetic field, and magnetic field intensity. Hysteresis and anisotropy of ultrasonic propagation velocity are observed. These interesting results seem to be related to chain-like cluster formation in the magnetic fluids and the characteristic period of Brownian motion of the magnetic particles.

著者

Hwang Jaeho Yoon Tae-Seok Lee Dong-ho LEE Soo-Gab

出版者

一般社団法人日本機械学会

雑誌

JSME international journal. Ser. B, Fluids and thermal engineering (ISSN:13408054)

巻号頁・発行日

vol.44, no.3, pp.451-464, 2001-08-15

参考文献数

18

被引用文献数

21

---

In order to study unsteady flowfield around high speed trains passing by each other, a three-dimensional inviscid numerical method based on three types of domain decomposition techniques is developed. Roe&rsquo;s FDS scheme is used for the space discretization, and LU-SGS method is adopted for the time integration. After validation of the code to a single track train/tunnel interaction problems with three dimensional tunnel configuration, the numerical simulations of the trains passing by on the double-track are performed for the 5 different cases using 3 basic parameters; e.g. nose shape, existence of tunnel, and train length. After the parametric study, variational parametric studies are carried out to understand the effects of the velocity of the train, the gap between the train and the blockage ratio. Firstly, train/tunnel interaction problems for double track railway system are investigated and aerodynamics loads histories during the crossing events&mdash;train/train interaction problem&mdash;are presented and discussed.

著者

Lee Hsing-Juin Chang Chih-Luong

出版者

一般社団法人日本機械学会

雑誌

JSME international journal. Ser. B, Fluids and thermal engineering (ISSN:13408054)

巻号頁・発行日

vol.44, no.4, pp.658-667, 2001-11-01

参考文献数

27

被引用文献数

2 3

---

The kinetic power and efficiency equations for general jet propulsion systems are classically given in a much cursory, incomplete, and ununified format. This situation prohibits the propulsion designer from seeing the panorama of interrelated propulsion parameters and effects. And in some cases, it may lead to an energy-inefficient propulsion system design, or induce significant offset in propulsion performance as demonstrated in this study. Thus, herein we attempt to clarify some related concepts and to rigorously derive the associated generalized equations with a complete spectrum of physical parameters to be manipulated in quest of better performance. By a highly efficient interweaved transport scheme, we have derived the following equations for general jet propulsion systems: i.e., generalized total kinetic power, generalized kinetic power delivered to the jet propulsion system, generalized thrust power, generalized available propulsion power, and relevant generalized propulsive, thermal, and overall efficiency equations. Further, the variants of these equations under special conditions are also considered. For taking advantage of the above propulsion theories, we also illustrate some novel propulsion strategies in the final discussion, such as the dive-before-climb launch of rocket from highland mountain on eastbound rail, with perhaps minisatellites as the payloads.

著者

Radu Rosca Edward Rakosi Comsa Iulian-Agape RADU Gaiginschi

出版者

一般社団法人日本機械学会

雑誌

JSME international journal. Ser. B, Fluids and thermal engineering (ISSN:13408054)

巻号頁・発行日

vol.44, no.4, pp.634-640, 2001-11-01

参考文献数

4

被引用文献数

2

---

The paper presents the application of a three component model to the theoretical study of the combustion process of a Diesel engine fueled with sunflower oil and sunflower oil-Diesel fuel mixtures. The model assumes that the working fluid consists of three components: the fresh air, the flame and the burned gases.<BR>The combustion model uses the energy conservation equation:<BR>v<SUB>c</SUB>·Q<SUB>c</SUB>·dξ<SUB>α</SUB>=dU<SUB>α</SUB>+dL<SUB>α</SUB>+dQ<SUB>wα</SUB>, [1]<BR>where v<SUB>c</SUB> is the fuel cyclic dose, Q<SUB>c</SUB> is the fuel heating value, ξ<SUB>α</SUB>=v<SUB>cα</SUB>/v<SUB>c</SUB>, v<SUB>cα</SUB> is the quantity of burned fuel up to the moment α, U<SUB>α</SUB> is the internal energy of the working fluid, Q<SUB>wα</SUB> is the heat exchanged through the cylinder walls and L<SUB>α</SUB> is the mechanical work.<BR>The heat release law was assumed to be a Vibe type one:<BR>ξ<SUB>α</SUB>=R<SUB>c</SUB>·[1−exp(−6.9·A<SUP>m</SUP><SUB>P</SUB><SUP>p+1</SUP>)]+(1−R<SUB>c</SUB>)·[1−exp(−6.9·A<SUP>md+1</SUP>)], [2]<BR>where:<BR>·A<SUB>p</SUB>=(α−α<SUB>d</SUB>)/(α<SUB>P</SUB>−α<SUB>d</SUB>) and A=(α−α<SUB>d</SUB>)/(α<SUB>F</SUB>−α<SUB>d</SUB>);<BR>·α<SUB>d</SUB>-start of combustion angle;<BR>·α<SUB>f</SUB>-end of combustion angle;<BR>·α<SUB>P</SUB>-end of rapid combustion angle.<BR>Using Eqs. [1] and [2] we have obtained the cylinder pressure during combustion, for the vegetable fuels taken into account; the peak values were confirmed during the experiments.

著者

Takahisa YAMAMOTO Koshi MITACHI Takashi SUZUKI

出版者

社団法人 日本機械学会

雑誌

JSME International Journal Series B Fluids and Thermal Engineering (ISSN:13408054)

巻号頁・発行日

vol.48, no.3, pp.610-617, 2005 (Released:2006-02-15)

参考文献数

13

被引用文献数

16 24

---

The Molten Salt Reactor (MSR) is a thermal neutron reactor with graphite moderation and operates on the thorium-uranium fuel cycle. The feature of the MSR is that fuel salt flows inside the reactor during the nuclear fission reaction. In the previous study, the authors developed numerical model with which to simulate the effects of fuel salt flow on the reactor characteristics. In this study, we apply the model to the steady-state analysis of a small MSR system and estimate the effects of fuel flow. The model consists of two-group neutron diffusion equations for fast and thermal neutron fluxes, transport equations for six-group delayed neutron precursors and energy conservation equations for fuel salt and the graphite moderator. The following results are obtained: (1) in the rated operation condition, the peaks of the neutron fluxes slightly move toward the bottom from the center of the reactor and the delayed neutron precursors are significantly carried by the fuel salt flow, and (2) the extension of residence time in the external-loop system and the rise of the fuel inflow temperature show weak negative reactivity effects, which decrease the neutron multiplication factor of the small MSR system.

著者

Ujita Hiroshi Ikeda Takashi Naitoh Masanori

出版者

一般社団法人日本機械学会

雑誌

JSME international journal. Ser. B, Fluids and thermal engineering (ISSN:13408054)

巻号頁・発行日

vol.45, no.3, pp.607-614, 2002-08-15

参考文献数

14

被引用文献数

5

---

SAMPSON is the integral code for severe accident analysis in detail with modular structure, developed in the IMPACT project. Each module can run independently and communication with multiple analysis modules supervised by the analysis control module makes an integral analysis possible. At the end of Phase 1 (1994 - 1997), demonstration simulations by combinations of up to 11 analysis modules had been performed and physical models in the code had been verified by separate-effect tests and validated by inegral tests. Multi-dimensional mechanistic models and theoretical-based conservation equations have been applied, during Phase 2 (1998 - 2000). New models for Accident Management evaluation have been also developed. Verificaton and validation have been performed by analysing separate-effect tests and inegral tests, while actual plant analyses are also being in progress.

著者

Tokumasu Takashi Matsumoto Yoichiro

出版者

一般社団法人日本機械学会

雑誌

JSME international journal. Ser. B, Fluids and thermal engineering (ISSN:13408054)

巻号頁・発行日

vol.43, no.2, pp.288-295, 2000-05-15

---

In our 3rd report, we introduced a Lennard-Jones (LJ) potential parameter based on the potential obtained by ab initio calculation and collision cross section from the Wang-Chang, Uhlenbeck and Taxman's theory and molecular dynamics (MD) simulation. In the present study, we have improved the dynamic molecular collision (DMC) model to callculate the property of MD simulation better than the previous model. To confirm its validity we calculated the equilibrium state, the transport coefficient (viscosity coefficient and heat conductivity) at various temperatures and the normal shock wave by the direct simulation Monte Carlo (DSMC) method using the DMC model and compared the results with other theoretical and experimental results. Consequently, we found that the diatomic rarefied gas flows could be simulated very well using our model. These results were compared with those obtained by the Larsen Borgnakke model. It was found that this model was more efficient than the previous model.