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

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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

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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

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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

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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

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

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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

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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

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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

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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

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

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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.