Some kinds of slurry fuels, which are comprising about 70% coal, oil pitch, vacuum residue (asphalt) or biomass such as wood chips, and about 30% water containing small amount of chemicals. were investigated in terms of fuel properties and combustion characteristics. Those slurry fuels have wide particle size distribution of sub-micron to 500μm, heating values of 20000 to 28000 kJ/kg, viscosities of 200 to 800 mPa·s@20°C and sulfur of 0.1 to 4wt%, depending on properties of raw feedstocks. From combustion tests using the pilot scale combustion furnace, steady flame and good combustion were observed for coal water mixture (CWM) and asphalt-residue water mixture (As-RWM), on the other hand, a few sparkles and long period combustion of char were observed for pitch-residue water mixture (Pi-RWM). Such different combustion characteristics, depending on slurry oils, were elucidated in terms of microexplosion, combustion characteristic times, and thermal decomposition by the combustion of a single droplet in the electrically heated furnace and the thermo-gravimetric analysis (TG/DTA). In order to obtain fundamental data in prediction of practical furnace combustion for biomass slurry fuel (BSF), the combustion behavior of BSF droplets was obsrved in the electric furnace and its combustion characteristics time was discussed in comparison with those of CWM, As-RWM, and Pi-RWM.

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This paper reports on the pyrolysis and CO₂-gasification of various biomass materials in a pressurized thermobalance. In particular, the primary yields of total volatiles, tar and non-condensable gases, together with the composition of non-condensable gases, are measured as a function of temperature at 1 atm and 10.8 ata. The use of a high-intensity infrared heating source, in conjunction with a non-absorbing carrier gas (viz. argon), is reported to reduce the significance of secondary gas-phase pyrolysis reactions. Linear trends with atomic H/C ratio are observed in the tar yield, total volatile yield and CH₄ yield during pyrolysis. The gasification kinetics of biomass chars (pyrolysed to 700°C at a medium heating rate) have also been measured by measuring the rate of weight loss during reaction with CO₂ as a function of temperature. First-order kinetic rate constants are then determined by fitting the weight loss data using a random pore model. The results indicate that the reactivity of the biomass materials is intermediate between lignin and cellulose and that they are much more reactive than a black coal char.

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For suppressing NO_x and smoke simultaneously, an alternative diesel combustion strategy is required to avoid local over-rich regions in the mixtures at EGR conditions. In the present study, a variable valve timing (VVT) mechanism is applied in a light duty HSDI diesel engine. By means of lowering effective compression ratios, compressed gas temperatures near the top dead center are lowered, thereby preventing too early ignition and increasing ignition delay to enhance fuel-air mixing. At the same time, the expansion ratio is kept constant to ensure thermal efficiency. It is recognized that the optimum control of EGR and effective compression ratios can simultaneously reduce NO_x and smoke.

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We have succeeded to extinguish a diffusion flame formed over a PMMA plate using laser ablation. When a pulsed laser beam is focused tightly on a solid surface, laser ablation occurs and a hemispherical blast wave and a high-speed flow behind its wave front are generated. Flame base which dominates the stability of a diffusion flame, can be blown out by the blast wave and high speed flow due to laser ablation. A single mode, Q-switched Nd : YAG laser (wavelength : 532 nm) is used, and produces a laser pulse with energy of 200 mJ. The laser beam is focused on a PMMA surface with a 100 mm-focal-length lens. We have investigated the characteristics of the laser-ablation extinguishment of a diffusion flame spreading over a PMMA plate. Probability of success of laser-ablation extinguishment is measured by varying flame base width and flame height of the diffusion flame. From the results, the laser extinguishment limits for flame height and flame base width, in which the spreading diffusion flame is blown out perfectly by the laser ablation are clarified.

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In the present study, a sooting flame was formed in a reduced-pressure combustion chamber with a premixed flame of methane and oxygen for the surrounding flame and premixed flame of toluene and oxygen for the center flame. Collected soot samples were analyzed using the high performance liquid chromatography and a gas chromatography to determine the fullerene and the total PAH contents and 22 species of PAHs under various conditions. Effects of the chamber pressure, the equivalence ratio of totluene and oxygen, the flow velocity and the chamber length to yield of soot and contents of PAHs and fullerenes were discuseed. When the chamber pressure increases, the contents of PAH and fullerene decreased with keeping a constant soot yield. There were optimal equivalence ratio and flow rate of the center flame for fullerene formation whereas flow rate of the outer flame and chamber length were not essential for fullerene formation. Such chemical species as acenaphthene, fluorene, phenanthrene, fluoranthene and phyrene accounted for large content in total PAHs.

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Square shape notches were applied to a parallel fin array, referred to as “cut-fin”, for the purpose of enhancing the fluid mixing and heat transfer, and also reducing the pressure loss penalty. Three-dimensional numerical simulation, velocity measurement and heat transfer experiment were carried out for a rectangular channel with cut-fins mounted on the bottom wall, and the notch size and spanwise fin pitch effects on the fin performances were evaluated under laminar flow condition. In the cut-fin case, although the heat transfer area was reduced, a comparable heat transfer performance to the notch-less plain-fin case was obtained. The notch size did not largely affect the overall heat transfer performance due to the trade-off problem between the heat transfer coefficient at fin sidewalls and the extended heat transfer area. Reduction of the friction loss was also achieved in this case, indicating an increase of the total performance. An optimum value of the fin pitch in minimizing the fin thermal resistance was found and the value of the cut-fin case was smaller than that of the plain-fin case. As the Reynolds number, Re, was increased in the range of 1000≤Re≤2000, heat transfer coefficient remained constant in the plain-fin case but increased in the cut-fin case.

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This study deals with flow-structure coupled analysis of cerebrovascular arteries with an aneurysm of realistic geometry. Analysis models are constructed from 3D-Computed Tomography data. The flow-structure coupled analysis employs commercial solvers CFX and ANSYS to calculate unsteady movement of the artery wall subjected to pulsatile blood flow. The data transfer between the two solvers is performed by UNIX shell script. Non-Newtonian properties of blood flow is taken into account in this simulation by use of the Carreau-Yasuda viscosity model. In this study, the arterial wall of the analysis model consists of a number of shell elements with linear elasticity. The results show a close relationship between wall shear stress and blood flow during one cardiac cycle. In addition, this study investigates non-Newtonian effect for realistic model.

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In “Japan Clean Air Program” (JCAP) project, we are developing air quality simulation model which reproduces real world air quality. In Japan, the existence of high-emitters has not been recognized, and thus has never been considered in air quality model simulation. To consider the effect of high-emitters on air quality, we have investigated real world vehicle emissions using a Remote Sensing Device (RSD), and determined the percentage and emission level from high emitter gasoline vehicles. Our investigation on gasoline vehicles showed that approx. 5 to 15% of gasoline vehicle fleet in urban areas was high emitters, and their emission levels were about 4 to 8-fold higher than normal emitter gasoline vehicles. By our estimation using air quality model, in view of the existence of high emitters, the percentage of emissions from high emitters in emissions from gasoline vehicle fleet in the specified area for Kanto NO_x/PM Laws accounts for about 25% for CO, 30% for HC and 50% for NO_x in 2000, and would reach about 80% for NO_x in 2015. Our investigation and determination of the percentage and emission level from high emitter gasoline vehicles would help improvement in reproducibility of the air quality model, and would contribute to cleaner air quality. We will determine the percentage and emission level from high emitter diesel vehicles in the next step.

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Mixing two liquids and generating a concentration gradient in a microchannel are important in biochemistry. In a microchannel, mixing is limited by molecular diffusion due to the constraints of the laminar flow. Therefore, it is important to reduce the length of the mixing path for a quick mixing. One of the techniques for reducing the mixing path is sequential segmentation. A concentration gradient is generated by producing a wave-like pattern along the microchannel direction. In this technique, the high frequency vibration of the liquid-liquid interface is generated to form a wave-like pattern for mixing along a short channel length. High frequency switching of the fluid flow is achieved by employing the newly developed microvalve using tailor-made multilayer piezoelectric actuators (TAMPA) that is compact and low-cost yet produces large displacements and forces. This paper details the concept for the concentration gradient generation method. Next, a microvalve (20×15×15mm) was designed and produced using TAMPA (8.5×10×10mm), Finally, a concentration gradient in two-layered flow was generated with the microvalve. As a result, the generation of a concentration gradient in two-layered flow with active mixing was achieved in a high-speed fluid (120 mm/s, Re = 14.4). Moreover, the concentration gradient was controlled by adjusting the input voltage to TAMPA.

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We have analyzed the time-dependent behaviors of the rheological properties of a dilute colloidal dispersion composed of the ferromagnetic spherocylinder particles influenced by the external magnetic field. A series of basic equations is derived for the orientational distributions of the particles in steady three dimensional flow by using the perturbation expansion method. Exact solutions of the basic equations are obtained theoretically. By using the solutions, we have discussed the viscosity induced by the external magnetic field. The viscosity is mainly described by the simple fractional functions of the magnetic field. The coefficients of the fractional functions make a classification of the behaviors of the viscosity. The reference time obtained from the rate of the convergence to the steady state of the viscosity is shorter for the stronger magnetic field, because the orientations of the particles are arranged by the strong magnetic fields. We have derived the condition to generate the viscosity by the magnetic field, and the condition to increase the viscosity with the increased magnetic field.

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To evaluate the effect of pipe wall surface wettability on flow characteristics in a vertical upward gas-liqid two-phase flow, a visualization study was performed using three test pipes : an acrylic pipe, a hydrophilic pipe and a hydrophobic pipe. Such basic flow characteristics as flow patterns, pressure drop and void fraction were investigated in these three pipes. In the hydrophilic pipe, the slug flow to churn flow transition boundary was shifted to a higher gas velocity at a given liquid velocity, whereas the churn flow to annular flow transition boundary was shifted to a lower gas velocity at a given liquid velocity. In the hydrophobic pipe, an inverted churn flow regime was observed in the region where the churn flow regime was observed in the acrylic pipe, while a droplet flow regime was observed in the region where an annular flow regime was observed in the acrylic pipe. At a high gas flow rate, the mean void fraction in the hydrophobic pipe was higher than in the acrylic pipe. The effect of surface wettability on frictional pressure loss was confirmed to be insignificant under the present experimental conditions.

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The effects of fetch on mass transfer across the wind-driven air-water interface was investigated through laboratory experiments in a large wind-wave tank. The CO₂ transfer coefficient on the liquid-side, k_L, was measured by applying the flux-profile method to the vertical distributions of wind velocity and CO₂ concentration in air. The surface-renewal frequency f_s that dominates mass transfer across the air-water interface was measured by applying the VITA method to the streamwise velocity fluctuation in water. The results show that both k_L and f_s are well correlated with free-stream wind velocity U_∞ irrespective of fetch, whereas k_L and f_s are poorly correlated with the velocity at the center of entrance U_∞. Furthermore, k_L measured in both small and large wind-wave tanks is well correlated with U_∞ whereas k_L is poorly correlated with air friction velocity u^*_a.These results suggest that an outer parameter is a more suitable parameter for correlating k_L.

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Three-dimensional direct numerical simulations (DNS) are applied to turbulent boundary layers over the wavy walls, which imitate sheared air-water interfaces (wind-waves) with swells, and the effects of parallel and oblique swells on the turbulence structure and drag forces are investigated. The results show that the oblique swell increases the turbulence intensities and the Reynolds stress over the wavy wall, whose trends are similar to those of the parallel swell. The oblique swell also increases the pressure drag and decreases the friction drag on the wavy wall, and consequently increases total drag because of the remarkable increase of the pressure drag. These effects are smaller for the oblique swell than that for the parallel swell. The predictions suggest that the oblique swell supresses the mass transfer across the air-water interface, but the effect is weaker than that for the parallel swell.

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Experiments have been performed for a turbulent channel flow obstructed with a triangular cylinder. Two kinds of triangular cylinders with different front edge angle are used. Three clearances between the wall and the triangular cylinder of 1, 2 and 5 mm are tested. The local heat transfer coefficient, the wall static pressure and the wall shear stress are measured. The particle image velocimetry (PIV) has been applied to measure the fluid flow around the triangular cylinder. When the flow field is unsteady because of the existence of the periodically shed vortices, a phase-averaged measurement is carried out. When the clearance is small, the reattachment flow effectively enhances the heat transfer. On the other hand, at large clearance the heat transfer coefficient takes a high value in the location where a large periodic fluctuating motion appears.

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An experimental study was performed on the effects of the distance between heat transfer plates on free convection heat transfer in a stably stratified fluid between vertical plates. The stratified layer was formed using a sucrose aqueous solution, and was heated from one sidewall at constant heat flux and cooled from the other sidewall at constant temperature. The experiments were conducted for the distance between the heat transfer platesl=10 mm, 20 mm, 40 mm and 60 mm. As a result, it was found that the average heat transfer coefficient deceases with an increase in the distance between the heat transfer plates, when the cellular convection layers do not fully develop and heat conduction prevails in the heat transfer. On the other hand, it was found that after the cellular layers have fully developed, the average heat transfer coefficient becomes great in the case of the thickness of the cellular layer being close to the distance between the heat transfer plates.

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In recent years, heat dissipation rates in personal computer, power devices and laser diodes have been increasing, and water-cooling technique is becoming to be used in electronic equipment cooling. When fins cannot be mounted on the heated base plate surface in the liquid channel because of manufacturing constraint, turbulence promoter is usually used in the liquid channel. We developed a heat sink with a wavy turbulence promoter facing heated base plate as a thermal enhancement technique in the liquid channel. The heat transfer coefficient of the base plate facing wavy turbulence promoter was 20000-30000W/ (m²·K). The heat transfer performance of the heat sink with a wavy turbulence promoter facing heated base plate was 3 or 4 times larger than the smooth surface channel.

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The sliding angle of liquid drops on inclined plates were investigated in order to evaluate the characteristics of SAMs (Self-Assembled Monolayers) surfaces. The contact angles and sliding angles for two kinds of test liquids, i.e., BCA and Ethylene glycol, were measured on 4 kinds of SAMs surfaces made by the immersion method with different immersion times. The contact angle hysteresis became minimum on the standard film, i.e., the most homogeneous surface. The experimental sliding angles φ agreed well with the theory discussed in the preceding report. Using the small drop (1μL), the difference of φ between the standard film and others could be made larger than that of the contact angle hysteresis. The film characteristics can be evaluated from rather simple measurement of sliding angles. The 3-dimensional drop profile on the inclined plate was discussed from an approximate theory. Assuming circle and ellipse as the attached surface profile, the drop configuration was calculated from the approximate Laplace equation. The results agreed well with the experimental profiles.

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The flooding, especially in gas diffusion layer (GDL), is one of the critical issues to put PEMFC to practical use. However, the experimental data of the flooding in GDL is so insufficient that the optimization design to solve the flooding problem in GDL has not established until now. In this study we show a method to estimate the water saturation, namely the liquid water ratio for unit volume in GDL. We fabricated a simple interdigitated cell where the supply gas is enforced to flow under rib. This structure made it possible to capture the water droplet in GDL with the measurement of differential pressure through the cell. We operated the cell and measured the differential pressure, and succeeded in estimating the water saturation, which largely changed with changing cell operation condition. In addition to deferential pressure measurement, we measured the ionic resistance in polymer electrolyte membrane by AC impedance method. We evaluated the effect of the water saturation on the decrease of cell voltage.

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Experimental study was made to investigate the propagation and extinction characteristics of a stretched cylindrical flame undergoing periodic fluctuation of equivalence ratio near the lean limit. With a lean methane-air and a lean propane-air mixture, burning velocity, flame luminosity and flame stretch rate were measured or evaluated for the fluctuation frequencies of 5 Hz and 20 Hz. The results were summarized as follows : (1) In some part of a period, burning velocity and flame luminosity of the dynamic flame near the lean limit were possible to become lower than those at the lean flammability limit of the static flame. (2) At the high frequency of 20 Hz, the burning velocity took a negative value in a certain time range. In spite of this loss of propagation ability, the flame was not extinguished but sustained, indicating the recovery of the flame intensity due to the dynamic effect of fluctuating flame. (3) Flame recovery phenomenon could occur more easily for the methane flame which was strengthened by the Lewis number effect than the propane flame which was weakened by that effect.

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A two-dimensional numerical simulation is applied to spray flames formed in a laminar counterflow, and soot formation behavior is studied in terms of equivalence ratio and radiation in detail. N-decane (C₁₀H₂₂) is used as a liquid spray fuel, and the droplet motion is calculated by the Lagrangian method. A one-step global reaction is employed for the combustion reaction model. A kinetically based soot model with flamelet model is employed to predict soot formation. Radiation is taken into account using the discrete ordinate method. The results show that the soot is formed in the spray diffusion flame region and its radiation emission increases with increasing the equivalence ratio of the droplet fuel. This trend is in good agreement with that of the luminous flame behavior observed in the experiment. The radiation is found to strongly affect the soot formation behavior. Without the radiation model, the soot volume fraction is fatally overpredicted.

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In order to use waste vegetable oil as an alternative burner fuel, the fuel properties, combustion characteristics and exhaust emissions of waste vegetable oil methyl ester (WME) are investigated using an agricultural warm air furnace. The rapeseed oil methyl ester (RME) and the bunker A are also used for the comparison. From the experimental results, the fuel properties of WME are almost the same as that of RME expect for diglyceride content. Although the heating output of WME is lower than that of bunker A, the thermal efficiency of WME is almost the same as the bunker A with the same excess air ratio. WME has lower Smoke, NO_x and SO₂ emissions compared with the bunker A. WME has almost the same heating output, thermal efficiency and exhaust emissions as RME expect for CO emission. It is concluded that WME can be used as a burner fuel.

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