Small fans are especially used in information device for its cooling. Since packaging density has been increasing, requirements of not only performance improvement but also noise reduction arise strongly. An experimental research on small multi-blade fan was carried out in order to improve performance and reduce noise. In this report, effects of scroll angle, tongue clearance and inlet diameter on small multi-blade fan with impeller diameter of 100 mm were investigated. The optimal index efficiency and noise were found by making a scroll starting point radius and a scrool termination radius into a design index, instead of the scrool design by a conventional clearance and a scroll angle. In order to reduce noise, we found that we should set the radius of scroll beginning into about 0.65 times of the outlet diameter of the impeller. And for improving efficiency, we should set the radius of scroll end into about 0.9 times of the outlet diameter of the impeller.

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Flame colors in kerosene spray flames were quantitatively determined by the correlated color temperature. Detailed relations between the correlated color temperature and air ratio were investigated by using a water-cooled furnace. The heat input of an atomizing oil burner was 96 kW and the air ratio changed from 1.1 to 2.5. The results indicated that the correlated color temperature was useful to accurately express the change of flame color. The correlated color temperature ranged between 1 580 K and 2 290 K and its mean value decreased monotonously with the air ratio. Thus it was suggested that the mean value of the correlated color temperature was a good indicator of the air ratio and had the possibility to be a new information source for combustion diagnostics.

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We have developed a coupled numerical simulation of vortex method and particle trajectory tracking method, which is applicable to internal unsteady two-phase flows. It is a completely grid-free Lagrangian-Lagrangian simulation, which is able to simulate the interaction between solid particles and vortical flow. It can handle unsteady high Reynolds number flows. However, so far, no one has applied this kind of method to internal multiphase flows, though many industrial multiphase flows are internal. In this study, internal liquid-solid two-phase flows in a mixing tee had been analyzed by the new method, in which use of the vortex introduction model enables the simulation of the dynamic behavior of separation or reattachment. We simulated and measured particle motions, such as deposition or particle-wall collision, which change according to confluent flow rate ratio. Numerical results based on two-dimensional flow and one-way model showed good agreement with the experimental data. It has been shown that the present method can be useful in the design of industrial multiphase flows.

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A gas-liquid two-phase flow through vertical sudden contraction pipe is an area that still little is known and has been studied experimentally, visually and numerically. In this study, the flow characteristics of vertical upward gas-liquid two-phase flow through a sudden contraction pipe are examined experimentally and numerically, and a new simple method of flow control to reduce the flow fluctuation and resistance is shown. When mounting a ring-shaped step before the contraction, vortex formation at the contraction was reduced. That is, the flow is suggested by mounting a ring-shaped small obstacle before the contraction to lead to stabilized flow and drag reduction. The effects of Reynolds number, volumetric flow rate ratio of air to water and the ring position were examined. Numerical analysis using an incompressible tow-fluid model was conducted in order to understand the flow pattern well.

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The jet pump generally needs a long throat to mix the driving and induced fluids and transfer the momentum of driving fluid to induced fluid. Simultaneously, the energy loses when the fluids flow through the long throat because the friction loss occurs inside of the throat wall. Therefore, it is known that the throat length largely affects the jet pump efficiency. In this study, to obtain fundamental knowledge of the effect of surface roughness in the throat on jet pump performance, experimental studies were performed for a typical single nozzle jet pump using water at room temperature. It was revealed that surface roughness located nearer the throat inlet had a greatest effect on the jet pump efficiency because the local skin friction coefficient nearest the throat inlet is the largest. The best efficiency and its flow rate ratio decrease linearly as surface roughness increases. The frictional resistance coefficient in the throat for each roughness is made clear by fitting a one-dimensional theoretical prediction equation to the experimental results.

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In industries, a radial supersonic jet often occurs in valves of a pipe system and on a surface of a work on which a cooling jet impinges and so on. In order to clarify a flow pattern of such a jet, the radial underexpanded jet issuing from a curved slit nozzle was examined theoretically as well as numerically and experimentally. The flow field is analyzed by the numerical simulation under the assumption of an axisymmetric flow and the visualization using Shadowgraph method and Schlieren method. The slit nozzle consists of two tubes which are set face to face each other. The radial jet is underexpanded from the nozzle and the jet cells are formed in sequence. The cells become shorter as they are further downstream. Tam's theory for a rectangular jet is extended to the radial jet and applied to the analysis of a length of the 1st cell. The results obtained by the calculation and the experiment are compared to those by the extended theory. As a result, a quantitative agreement was found to be good between them.

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We have investigated the drag reduction phenomena on highly water repellent surfaces, which have micron to submillimeter order of projections. In the present study, the flow field is modeled as laminar flow between two walls and is solved only near-wall region with finite difference method. To derive the entire velocity profile and to evaluate drag reduction ratio, velocity of the center region is estimated as quadratic function of distance from wall with appropriate boundary condition. The numerical results show that 50 μm-width, 100 μm-pitch, 25μm-height square projections on the parallel plates at 2 mm distance gives 6.2% of drag reduction. Larger scale of microstructure or thinner micro-projections more drag reduction. On the other hand, air layer thickness or height of projections does not have significant influence on the degree of drag reduction.

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In this paper, a front-tracking (FT) method combined with a solver of interfacial transport of surfactant was proposed in order to resolve interfacial flows affected by contamination. In the FT method, because the interfaces are presented explicitly, advection-diffusion equation on the interface can be easily treated and can be solved highly accurately. In this study, a scheme which conserves the total mass completely was constructed and proposed. Numerical simulations of a water drop sinking in silicone oil were performed taking the Marangoni effect into account. The effects of three parameters, damping coefficient of interfacial tension, diffusion coefficient and total mass, were evaluated. Calculated results were compared with PTV measurements and were in very good agreement with them in the points of stagnant cap size, flow separation point, peak of shear stress and so on. So, we can expect that our simulations can estimate the conditions of surfactant on the interfaces, which is very difficult to be measured.

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The present paper provides the discussions on the unsteady characteristics of a restriction flow in a hydraulic line. By ingeniously creating sinusoidal flow at a fixed orifice in a pipe, the unsteady relationships between the pressure drop across and the flow rate through the orifice were properly measured. When being estimated using the experimental results, -the unsteady nonlinear pressure loss turned out to change against the flow rate describing a loop with a counter-clockwise hysteresis along the steady-state relation between the two. The finding, probably indicating that the structure of turbulence producing a nonlinear pressure loss in an orifice jet flow changes with a delay behind the change of flow rate, provides an answer to the long-pending question in acoustics ; why the acoustic impedance of orifice decreases its reactive part as an amplitude of oscillation increases. A hypothetical mathematical model incorporating the delay into the steady-state relation was proposed to simulate the behavior of an unsteady nonlinear pressure loss in an orifice flow. The impedance analytically obtained by the model explained the decrease of reactance with an increasing amplitude.

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Deformation of a small capsule in a flow field is an important phenomenon in many research fields such as a blood flow in a small artery. In this research, the deformation of a capsule is experimentally investigated under a low Re number simple shear flow condition. We used two kinds of capsules and changed their membrane visco-elasticity and the inner and outer viscosity. We also made a capsule with spheroid shape. The effects of the membrane visco-elasticity, the ratio of inner to outer viscosity and the initial aspect ratio on the deformation and the inclination of the capsule are discussed. The results show that the deformation of a spherical capsule can be described mainly by the Ca number. The inclination of a capsule increases with increasing the membrane viscosity and with decreasing the ratio of inner to outer viscosity. In the case of spheroid capsule, the deformation and the inclination oscillate with time. The oscillation is strongle affected by the initial aspect ratio, however, the time-mean values are not so affected. These results are compard with the former researches, and show good agreement.

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An aqueous solution of CTAB/NaSal forms wormlike micelles and shows viscoelastic properties. It also shows flow-induced structure and flow instability in high shear rate flows. In this study, the occurrences of flow-induced structure and flow instability in planar elongational flows in a 4-roll mill flow cell were examined. An empirical formula of planar elongation strain as a function of elapsed time was proposed by results of particle trace velocimetry technique. In the planar elongational flow, the fluid was observed to become turbid, caused by the structure change, beyond a certain elongation rate. Subsequently, the elastic recoil was observed and simultaneously the turbid region disappeared. The change of turbidity is closely related to the planar elongation strain and the occurrence of the elastic recoil is related with a certain critical elastic energy. Furthermore, both critical rate and critical strain of the occurrence of these phenomena are considerably low in the planar elongation flow as compared with the shear flow.

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In order to investigate the mechanism of noise generation by a train-car gap, which is one of the major noise sources of Shinkansen train, experiments were carried out in a wind tunnel by using 1/5-scaled model train. We measured velocity profiles of the boundary layer that approaches the gap, and it is confirmed that the boundary layer is turbulent. We also measured the power spectrum of noise and surface pressure frustrations around the train-car gap. Peak noise and broad band noise were observed. It is found that strong peak noise is generated when the vortex shedding frequency corresponds to the acoustic resonance frequency determined by the geometrical shape of the gap, and broad band noise is generated at the downstream edge of the gap where vortexes collide. It is estimated that the convection velocity of the vortexs in the gap is approximately 45% of the uniform flow velocity.

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An experimental investigation has been carried out for the flow-induced sound in a grooved circular pipe. The length of the pipe is 500 mm, the inner diameter is 23 mm and the groove pitch is kept at 8 mm. The velocity in the pipe is varied from 6 m/s to 66 m/s. In the region of the velocity smaller than 30 m/s, the frequency of the sound generated in the pipe increases in the shape of stairs with increase of the velocity, and then resonant sound of the pipe generates from the pipe. When the velocity becomes large, the frequency of the sound increases linearly to the velocity. The shape of change of the frequency can be explained from characteristics of a cavity flow and lock-in phenomenon by the resonant frequency of the pipe.

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An experimental investigation has been carried out for the flow-induced sound in a grooved circular pipe. The length of the pipe is 500 mm, the inner diameter is 23 mm and the groove pitch is changed from 4 mm to 20 mm. The velocity in the pipe varied from 6 m/s to 66 m/s. The characteristics of the sound generated from the pipe are classified into three patterns according to the groove pitch. In the case of the pitch changed from 6 mm to 10 mm, the resonance of the sound generated for the pipe length occurs by the lock-in phenomenon when the velocity is smaller than 30 m/s. Strouhal number based on the groove pitch and the frequency of the sound is summarized the same smooth line when the velocity is larger than 30 m/s. The output power of the sound is proportional to the 4 th power of the velocity regardless of the groove pitch.

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Flow characteristics by a Vibrating Elastic Plate Flow Generator (VEPFG) was investigated experimentally. The device was a plate made vibrated perpendicularly to itself at the leading edge. The flow was found to be generated for a narrow range of frequency around the resonance frequency, with its maximum at the resonance frequency. The induced flow rate and its efficiency were experimentally determined. The performances were relatively low compared with the analytically expected ones. The efficiency turned out to be of 10 per cent. On the basis of the visualized flow patterns, one of possible causes for the difference is attributed to the existence of unsteady large-scale discrete vortices at both the trailing edge and the side edges. The side-edge vortices are seen to reduce drastically the induced flow rate by the factor of more than two.

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Various micropumps are devised, researched and developed for the liquid supply systems in the fields of micro machine, medical engineering and biotechnology and so on. In the present study, a new viscous micropump with a cylindrical rotor in a duct was presented. A gate is devised and installed in the wall over the cylindrical rotor to control the pump characteristics, i.e. the flow field and the pressure performance. The model experiment and the numerical simulation are performed. In the model experiment, the low Reynolds number flow is realized by using glycerin as a working fluid for a centimeter-scale (non-micrometer-scale) pump model. In the numerical simulation, the commercial software STAR-CD is used. Qualitative and quantitative agreements between experimental and numerical results are obtained with respect to the flow field and the pressure performance. The installed gata changes the flow field and accordingly the pressure performance. Therefore, it can be said that the pump characteristics can be controlled by using the gate.

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Sewage pumps are designed with a wide flow channel by, for example, sacrificing some efficiency and reducing the number of blades, in order to prevent plugging with foreign bodies. However, the behavior of foreign bodies which actually flow into a pump is extremely complex, and there are questions about whether the presumed foreign matter will actually pass through. This paper proposes a new type of sewage pump impeller designed to further improve pump efficiency and performance in passing foreign bodies. This sewage pump impeller has a structure in which the suction flow channel of closed type nonclog pump is wound in a helical spiral. The focus of this research was to investigate pump performance and radial thrust in this single blade sewage pump impeller. The results clearly indicated the following facts. The developed sewage pump impeller had high efficiency and exhibited high efficiency over a wide range of flow rates. When experimental and calculated values of radial thrust were compared at the best efficiency point flow rate, both the radial thrust size and direction almost matched. It is effective to reduce radial thrust fluctuating component by added mass.

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Experimental investigations have been carried out for opposing mixed convective flows of air over uniformly heated plates. The experiments covered the ranges of the Reynolds and modified Rayleigh numbers as ; Re_L=7.2×10²-1×10⁴ and Re_L*=5×10⁶-8×10⁸, and the inclination angles as ; θ=15 to 75° from horizontal. The flow fields over plates were visualized with smoke. The results showed that a separation of forced boundary layer flow occurs first at the trailing edge, and then, the separation point shifts toward upstream with increasing the wall heat flux, and finally, reaches to the leading edge of the plates. It was also found that the separations at the trailing and leading edges are correlated well with the non-dimensional parameter as ; (Gr_Lθ*/Re_L^2.5) =0.35 and 1.0, respectively. The local heat transfer coefficients of the inclined plates were also measured and the results showed that minimum coefficients appear in the separation region. Moreover, it was revealed that the forced, natural and combined convective flows can be classified by the non-dimensional parameter (Gr_Lθ*/Re_L^2.5).

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In order to derive a possible path for developing a large eddy simulation (LES) applicable to high Reynolds-number turbulent flows with heat transfer, a hybrid approach connecting LES with the Reynolds-averaged Navier-Stokes (RANS) modeling in the near-wall region is studied. In this study, an advanced non-linear eddy-viscosity model and a higher-order extension of the generalized gradient diffusion hypothesis model are introduced to resolve the near-wall turbulence and turbulent heat transfer more correctly. To investigate the model performance in detail, the proposed model is applied to fully developed plane channel flows with various grid resolutions. The present model provides encouraging results for further development of this kind of hybrid LES/RANS model.

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High-powered satellites need larger heat rejection area. Deployable radiator is one of key technologies for high-powered satellite bus. Reservoir Embedded Loop Heat Pipe (RELHP) is a two-phase heat transfer device and constitutes the deployable radiator. RELHP has an evaporator core which is used as a liquid reservoir to enhance operational reliability. This paper presents the heat transport characteristics of RELHP under changing evaporator direction against gravity and charged ammonia weight by experiment and calculation. Liquid slug position in the reservoir has great influence on heat transport characteristics, and that is caused by changing heat transfer coefficient between returned liquid into evaporator and vapor in the reservoir.

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A behavior of a flame propagating through a narrow channel is of importance, since this phenomenon is concerned with a quenching of the flame when heat losses by convective heat transfer or radiative one to a wall of channel are dominant and temperature behind the flame is not enough to increase that of unburned gases. Since, this phenomenon is also related to a safety-engineering problem where combustible gaseous mixture is handled, a device applying a narrow channel in a pipe might be one of useful technique to prevent the flame from propagating. Experiments were conducted to investigate a behavior of the flame propagating through a narrow channel, which connects two rectangular combustion chambers. The behavior of the flame was visualized using schlieren optical technique with an aid of high-speed video camera. In this study, an equivalence ratio of methane-air mixture, initial pressure and a width of the channel were varied in order to investigate effects of these parameters on characteristics of the flame propagation. As a result, the behavior of the flame entering into the narrow channel was classified into two phenomena, i.e. (i) the flame was quenched inside the narrow channel and combustion wave was not propagated into the downstream chamber, which results in just an emission of burned gaseous jet to the downstream chamber, (ii) the flame was propagated through the channel without quenching, which produced a high-pressure at both chambers.

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The flame characteristics of confined flames are investigated for propane and hydrogen jet nonpremixed flames in cylindrical furnaces. Flame characteristics can be strongly dominated by the combination of the burner and furnace geometries. In the present study, the effects of the inner diameter of the cylindrical furnance D₁, the turbulence at the flame boundary, and the global equivalence ratio φ are examined in terms of the emission of NO_x. The emission index of NO_x, EINO_x, decreases roughly with these parameters. The decrease in EINO_x is thought to be related to the dilution of mixtures by the burned gas and the flame stretch. The dilution is attributable to vortices formed at the furnace bottom, and the flame stretch is attributable to the air velocity difference ΔU_a created by two air nozzles. The EINO_x characteristics are evaluated by the furnace Reynolds number Re, _c based on the inner diameter of the furnace reflecting the dilution and the strain rate S-Da^-1 based on the air velocity difference, where Da indicates the Damköhler number. The ENO_x is well characterized by the factor D₁U_FΔU_a, which is proportional to Re, _cDa^-1. This result indicates that the confined nonpremixed flame is characterized by the furnace volume, not the flame volume, which is related to the reaction rate of the jet nonpremixed flame with coflowing air based on the flamelet model. This may imply that the furnace combustion should be modified from the flamelet concept owing to the dilution.

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One-dimensional simulation of laminar diffusion flame is performed both in physical and mixture-fraction (Z) space, and the relation between their flamelets are investigated. The strain rate, which characterizes the flamelet behavior in physical space, is converted into scalar dissipation rate and the combustion properties are transfered to Z space. The results show that the behaviors of the flamelets under the assumption of unity Lewis number for Z space calculation are in general agreement with those for physical space calculation. For the Z space calculation, non-unity Lewis number condition leads to the expansion of the extinction limit and the decrease of the peak temperature. As a results, the distributions of the temperature and mass fractions with Z deviate from those for Z space calculation with unity Lewis number assumption and physical space calculation.

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In this study, a planar laser-induced Rayleigh scattering (PLIRS) was applied to unsteady gas jets to understand processes of jet development process and ambient gas entrainment in a relatively high pressure ambient. In the verification of PLIRS, Rayleigh scattered light intensities were in proportion as incident light intensities and molar number densities of scatterer. From the results of this study, it is clarified that dense mixtures occupy in the center part of the jet and large-scale vortices exist around the jet axis as a large-hole nozzle is used, that dense mixtures do not clearly appear as a small-hole nozzle is used, and that in volumetric concentrations in the steady portion of jets distribute according to a law of 3/2.

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Polymer electrolyte fuel cells, which have been developed for mobile equipment, are mainly direct methanol fuel cells (DMFC). From the standpoint of safety to a human body, it is desirable to use ethanol as fuel. In order to improve the performance of direct ethanol fuel cells (DEFC), it is necessary to investigate the fuel flow pattern in the anode flow channel with many sharp turn corners in the fuel cell, and to improve the channel shape. So, in this study, the velocity distribution of the water flow in a micro-channel was numerically analyzed using the authors' GTT code and the calculated results were verified by the velocity measurement with a line LDV system. For reducing the pressure loss in consideration of the suppression of flow stagnation in the channel, it was attempted to optimize the sharp turn corner shape by three-dimensional numerical flow analysis with a genetic algorithm (GA) and a shape with less pressure loss was found.

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Characteristics of flamelet in spray flames in a laminar counterflow are investigated by a two-dimensional DNS in terms of mixture fraction and scalar dissipation rate. The motion of spray droplets is calculated by the Lagrangian method without parcel model. The results show that large difference in the trends of temperature and mass fractions of chemical species in mixture fraction space between the spray flame and gaseous diffusion flame is observed. Especially the temperature in the spray flame is much higher than that in the gaseous diffusion flame. This is considered due to much lower scalar dissipation rate and co-existence of premixed and diffusion combustion in the spray flame. It is also revealed that for the spray flame, temperature and mass fractions of chemical species cannot be clearly identified by the mixture fraction and the scalar dissipation rate by themselves. The behavior becomes marked in lower strain rate conditions.

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Characteristics of flamelet in spray flames in a laminar counterflow are investigated by a two-dimensional DNS in terms of mixture fraction and scalar dissipation rate. The motion of spray droplets is calculated by the Lagrangian method without parcel model. Decane and heptane are targeted as a fuel. The results show that for both fuels, temperature and mass fractions of chemical species cannot be clearly identified by mixture fraction and scalar dissipation rate by themselves. This behavior is caused by the fuels' evaporation in the spray flame, and becomes marked in the smaller droplet size condition due to its higher evaporation rate and in the higher equilvalence ratio condition due to its larger evaporation amount.

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The dynamic of a micro-grid that consists of engine generator and sixteen fuel cells was clarified by the transfer function model using the actual data of power generators. The microgrid was composed from a 3 kW engine generator and 1 kW fuel cells, and the dynamic characteristics of the grid was analyzed using the energy demand model in February of cold region. As a result, the settling time (Time to converge on ±5% of limit of an output target) of a micro-grid is 15 seconds from 10 seconds. The control parameter of a fuel cell system influences in the settling time and overshooting of a micro-grid strongly. Since the excess and deficiency of electric power can be covered each other if two or more fuel cells are connected with a gird, the instant electric power demand load peak can be distributed. Compared with the number of fuel cells in the case of installing independently, the number of installation of a micro-grid system is reducible

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