When a high-speed train enters a tunnel equipped with branches, pressure waves are radiated from the portals of the branches as well as from those of the main tunnel. They can cause wayside environmental problems for high-speed railways, especially in urban areas. In this study, we investigated a countermeasure against the pressure waves radiated from the portals of the branches. It has been shown that a branch with an inside partition which divides the inside of the branch into two parts in the vicinity of its portal with the end of one part closed, can be effective in reducing the magnitude of the micro-pressure wave.

抄録全体を表示

Brownian dynamics simulations for entangled polymer systems were carried out using a reversible network model, which represents the network structure of polymers as a suspension of elastic dumbbells that have two states, i.e. active and dangling. The effects of both shear rates and entanglement strength on the orientation behavior of polymers were analyzed. Polymers generally tend to align well in the flow direction and the degree of orientation increases with increasing the shear rate. However, the dependence of the degree of orientation on the shear rate is not monotonic because of the active/dangling transition. The change in the ratio of active/dangling dumbbells remarkably affects the orientation behavior. Furthermore rheological properties of the present system were investigated. This system shows shear-thinning viscosity and positive N₁ and negative N₂.

抄録全体を表示

We experimentally investigated the effects of operational conditions and liquid properties on the formation and breakup of ligaments from a high-speed rotary bell cup atomizer. Glycerin ethanol solutions and glycerin water solutions of different viscosity and surface tension were supplied. The rotational speed of bell cup ranged from 8000 rpm to 30000 rpm. The liquid volume flow rate was varied from 150 mL/min to 600 mL/min. We observed by photography with 180 nsec flash exposure, the shape of the liquid film divided by grooves and breakup behavior of ligaments ejected from a bell cup. From pictures obtained, we quantitatively evaluated by image processing based on edge detection, the width of liquid film divided by groove, the diameter and length of ligaments and the diameter of droplets generated. The results are summarized as follows: (1) The ligament diameter at bell cup edge increased with the increase in liquid volume flow rate and liquid viscosity. (2) The ligament diameter decreased rapidly for ligament axial length l < 300 μm, but more slowly for l > 300 μm. (3) The breakup distance of ligament increased with the increase in liquid volume flow rate and liquid viscosity. (4) The droplet diameter was determined by both the diameter of ligament at the front tip and the wavelength of capillary wave. (5) The gamma distribution well described the experimentally obtained droplet size distribution with the shape factor n of approximately 20.

抄録全体を表示

We intend to develop a laser Doppler velocimetry (LDV) system for in-vivo imaging that can measure blood flow velocity, that can generate tomograph of blood vessels with information in the depth direction and that has a high spatial resolution to enable individual microvessels. The present system evolved from a multipoint LDV (MLDV) that we developed for performing simultaneous multipoint measurements of water flow in transparent artificial flow channels. In this paper, we suggest an optical component of advanced MLDV for in-vivo and a method to determine the blood flow velocity from the sampling data. We measured microvessels of an experimental mouse, and succeeded in imaging the blood flow velocity in microvessels as 2 or 3 dimensional images. Finally, we demonstrate that using MLDV of blood vessels is useful for diagnosing malignant melanomas by comparison with visual diagnosis by dermoscopy.

抄録全体を表示

Contaminated soil washing test was implemented in Fukushima for the purpose of performance verification and set-up of engineering database for construction of contaminated soil washing plant. Chemical interface controlled dispersion approach and high-speed shearing washing techniques were applied to wash the contaminated soil over 10,000 Bq/kg and the following results were obtained in this first field test. (1) Dispersion of the radioactive contaminated soil over 10,000 Bq/kg was enhanced in alkalized washing solution at base equilibrium point of pH=10.1～10.5. (2) Remarkable washing performance was achieved under the combination of dispersion and high-speed shearing washing conditions with bead cracking technique in the particle grain size over 0.5 mm and enhanced by ceramic bead addition. (3) Rapid and slow clearing process for surface locking over the coarse grain soil caused by clean-up of very fine contaminated soil particle and strong affinity particles were observed in the relationship between washing rate and operation time. (4) Remarkable well-ordered structural refinement and cumulation of the contaminated soil particle groups with strong FP confinement were observed at the particle size of 0.5～10 μm after washing the contaminated soil particle grain size under 0.5 mm, and sieve classification technique can be applied for elective elimination of this soil particle groups. (5) Filter pressing technique is effective for solidification of the eliminated high ordered contamination soil groups. (6) No contamination in washing solution and machines applied in present field test was observed after these operation.

抄録全体を表示

In this study, we investigated combustion characteristics and flame structure of a multiple port nozzle burner. We measured combustion products of soot and NOx. The multiple port nozzle burner has 4 fuel nozzles and 9 air nozzles, where one air nozzle is located at the center (inner) of the burner, surrounded by four fuel nozzles and eight air nozzles outside of the fuel nozzles. Several diffusion flames are formed in the boundary of fuel and air flows. Fuel was methane or propane. A laser-induced incandescence (LII) technique was used to detect soot regions in the luminous flame zone. For comparison, a so-called jet diffusion flame in a co-axial burner was also examined. Results show that, as inner or outer air flow velocity is increased with fixed fuel flow velocity, the flame height becomes smaller. At the critical air flow velocity, the inner and outer flames are lifted. There are three flame configurations. Namely, attached flames, inner lifted/outer attached flames, and twin lifted flames. When the flame is lifted, the maximum soot concentration and NOx emission are decreased. Interestingly, the soot concentration of the multiple port nozzle burner is much smaller than that of the co-axial burner, although the NOx emission of both burners is almost the same.

抄録全体を表示

The objective of this research is to investigate the effect of the EGR guide, employed to generate a strong in-cylinder thermal stratification, on the recharged EGR gas flow into the cylinder in a gasoline HCCI engine equipped with the blowdown supercharging (BDSC) system. The recharged EGR gas flow was visualized using an optical access engine. A steady gas flow and an unsteady gas flow in motoring from the exhaust port into the cylinder were visualized via PIV method. The effect of the pressure difference between the exhaust port and the cylinder and the geometry of the EGR guide on the recharged gas flow was investigated. The results indicate that the flow field pattern is largely affected by the EGR guide height, and that an increase in the EGR guide height is effective to generate a strong in-cylinder thermal stratification. And then, the reduction of maximum pressure rise rate (dp/dθ) was investigated with a larger EGR guide height. Also, the in-cylinder thermal stratification was investigated by numerical simulation. The results indicate that thermal stratification gets stronger by a higher EGR guide. However, it was found that the reduction of maximum pressure rise rate takes a peak at a height of EGR guide.

抄録全体を表示

Oxygen (O₂) in a flame is one of the important substances for formation and oxidation of soot. Then it is necessary to investigate the effect of O₂ concentration in a flame on soot formation for clarification of soot formation mechanism. In this study, soot formation and soot oxidation mechanism inside propane laminar diffusion flame were focused. O₂ concentration of ambient air was adjusted as 21% and 18%. Laser induced fluorescent (LIF) method and laser induced incandescent (LII) method were applied to measure O₂ concentration and soot concentration distribution inside the flame. PM size distribution inside the flame was analyzed using scanning mobility particle sizer (SMPS). As the results, according to comparison between soot LII signal and O₂ concentration along flame center, the LII signal was detected in a region of more than 2% O₂ concentration. It means that soot was not generated under O₂ concentration less than 2%. Inside the flame, number concentration of PM at 21% O₂ condition was larger than that at 18% O₂ condition. The difference of in-flame PM number concentrations between 18% and 21% O₂ conditions became small with increasing distance from a nozzle, and at outside of the flame, number concentration of PM at 21% O₂ condition became smaller than that at 18% O₂ condition.

抄録全体を表示

Semiclathrate hydrate consists of cage structures composed of water molecules and ionic large guest molecules, which distinguish semiclathrate hydrate from normal clathrate hydrate. Semiclathrate hydrate is stable under atmospheric pressure condition and at near room temperature. This is the reason semiclathrate hydrate is expected to be used in various novel technologies, for example use as a cool-energy storage agent and gas separator. However, there is little knowledge about thermophysical properties of semiclathrate hydrate. Up to the present, few experimental data on its thermal conductivity have been reported. Thermal conductivity is necessary for the evaluation of industrial formation process of semiclathrate hydrate and heat transfer performance of semiclathrate hydrate used as cool-energy storage agent. The present paper reports measurements of the thermal conductivity of Tetra Butyl Ammonium Bromide (TBAB) hydrate by the transient hot-wire technique using a newly developed Parylene-coated probe, in which a metallic wire is coated with a thin electrical insulation layer formed by a chemical vapor deposition of poly-para-xylyene polymer. In order to confirm the reliability of the probe, we have performed check measurements on the thermal conductivity of toluene and water. We have measured the thermal conductivity of TBAB hydrate in the temperature range from 193 to 282 K with the uncertainty of ±2 %. It is found that the thermal conductivity of TBAB hydrate is less than 17 % of that of ice with almost no temperature dependence and its absolute value is lower than that of normal clathrate hydrate such as methane hydrate.

抄録全体を表示

The gas turbine system known as AHAT (Advanced Humid Air Turbine) has been drawing attention. AHAT employs a humidification tower to increase the air mass flow at the compressor outlet. A dynamic simulator of an AHAT plant was developed to determine the control method of the system. This paper outlines the dynamic simulator which is based on simultaneous differential equations considering heat and mass equilibrium of humid air, feed water and turbine exhaust gas. Physical values calculated using the simulator were compared to operational values obtained from trial operations of the 4MW-class AHAT pilot plant. The calculation errors of the humidification tower model, a main component of this simulator, were 0.60% for air outlet mass flow and 0.73% for air outlet absolute humidity. The developed simulator was then applied to determine the feed water control method for the humidification tower startup operation. Increasing absolute humidity affected fluctuations of the automatically controlled fuel flow rate. These fluctuations were influenced by water feeding rate, and were estimated to decrease from 59% to 58% when starting humidification in 4 minutes and to decrease from 59 % to 52% in 2 minutes.

抄録全体を表示

An experimental study has been made of the behavior of flame spread along linear arrays of emulsion droplets suspended on quartz fibers in slow air flow. Emulsions consisting of base fuel, water and a small amount of surfactant were tested. Two types of surfactants were used for changing the state of the emulsions; one was used for producing a water-in-oil emulsion and another for an oil-in-water emulsion. The base fuel was n-dodecane. The effects of the emulsified state, initial water content, droplet spacing in the array and forced air flow velocity on the flame spread were examined. Two modes were observed for the flame spread. The mode changed at certain values of the droplet spacing and the flame spread velocity showed a peak around the mode transition. The flame spread velocity increased with the air co-flow velocity. The oil-in-water emulsion showed slightly higher flame spread velocities than the water-in-oil emulsion in the opposing forced air flow or without forced flow. The flame spread velocities for the water-in-oil emulsions turned to exceed those for the oil-in-water emulsions in the air co-flow. The droplet spacing at the peak velocity of the flame spread showed an increasing trend with the air co-flow velocity. The flame spread velocity decreased with increasing the initial water content. Reduction of the velocity was comparable to that of the water content. The difference in the velocity between the emulsified states was reduced with higher water content. The oil-in-water emulsion reached the spread limit at smaller water content without forced flow.

抄録全体を表示

３件の誤植がありましたので訂正いたします．

抄録全体を表示