Gas-liquid two-phase flow and mixture systems are encountered in various industrial apparatuses and applications. The systems can be categorized as the following four : (a) the systems with heat transfer and with the flow of both gas and liquid, like boiling two-phase flow in heat exchangers, (b) the systems without heat transfer but with the flow of both gas and liquid, like adiabatic two-phase flow in oil pipe line systems, (c) the systems with heat transfer but without the flow of one of gas and liquid, like pool boiling, and (d) the systems without heat transfer and without the flow of one of gas and liquid, like aeration in chemical reaction and water purification systems. Of these, the first two categories are mainly dealt here and the relating papers reported in “Transactions of the Japan Society of Mechanical Engineers, Series B” and in “JSME International Journal, Series B” since January 2004 to August 2006 are reviewed to seek the future studies in the field of the gas-liquid two-phase flow and mixture systems.

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Synchronous rotating cavitation is known as one type of cavitation instability, which causes synchronous shaft vibration or head loss. On the other hand, cavitation in cryogenic fluids has a thermodynamic effect on cavitating inducers because of thermal imbalance around the cavity. To investigate the influence of the thermodynamic effect on synchronous rotating cavitation, we conducted experiments in which liquid nitrogen was set at different temperatures (74 K, 78 K and 83 K). We clarified the thermodynamic effect on synchronous rotating cavitation in terms of cavity length, fluid force, and liquid temperature. Synchronous rotating cavitation occurs at the critical cavity length of Lc/h≅0.8, and the onset cavitation number shifts to a lower level due to the suppression of cavity growth by the thermodynamic effect, which appears significantly with rising liquid temperature. Furthermore, we confirmed that the fluid force acting on the inducer notably increases under conditions of synchronous rotating cavitation.

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Flow-induced vibration often becomes a cause that damaged in a structure and causes a serious accident like the case of “Monju”. Therefore, the research of mechanism of flow-induced vibration is very important subject. Moreover, many structures have three-dimensional shape with sharp edge in span-wise direction. Therefore we investigated the three-dimensional flow structure about flow-induced vibration of a circular cylinder with finite span-wise length by numerical simulation. An analysis object is three kind of span-wise length, L=2.5D, 5D and 8D, where D is a diameter of circular cylinder. The range of simulated reduced speed is 1.5 to 4.0, in which shows 'in-line oscillation'. A reduced mass-damping parameter sets to zero. We assumed that the flow field is unsteady and laminar because Reynolds number which is defined by uniform flow velocity U and D, is 10³. We inspected simulated results in detail and investigated the relation between the fluctuation of fluid forces and flow pattern. As a result, at small span-wise length, because cylinder is largely affected by the flow, which rolls up from the tip, vortex shedding is restrained. On the other hand, as larger span-wise length, the flow interference between tip and wake, so the flow pattern and flluid forces affected to cylinder is more complex.

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In the present study flow patterns around pitching airfoils such as a NACA 65-0910 and BTE have been visualized by three kinds of dyes in a water tunnel at low Reynolds number region, Re=4.0×10³.Moreover, the dynamic lift and drag acting on them have been measured by a six-axes sensor.At the angle of attack α=16±6 deg., where the separation occurs under the stationary condition, and at higher non-dimensional pitching rate, the vortex with clockwise rotation shed from the leading edge reattaches on the suction surface and the re-circulation region was formed on the suction surface. It interferes with the other vortex with counter clockwise rotation shed from the trailing edge. They form a cloud of vortices behind five chords length distant from the trailing edge.The dynamic lift is much higher than the stationary one because of the re-circulation region on the suction surface. The dynamic behavior of vortices on the suction surface influences the dynamic lift strongly.

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Flow-induced in-line oscillation of two tandem circular cylinders has been experimentally studied by free-oscillation tests in a wind tunnel. Only one cylinder composed of two tandem cylinders was elastically supported easily to move in the in-line direction for reduced mass-damping parameter Cn≈1 and the other of the tandem cylinders was fixed to the tunnel sidewalls. The gap distance ratio between upstream and downstream cylinders was changed from 0.3 to 3. We measured the response amplitudes of the oscillatory cylinder in the in-line direction and the vortex-shedding frequency in the wake. The flow around the tandem cylinders was visualized by the smoke-wire method. The results of in-line oscillation of an upstream cylinder are as follows, there was a wide excitation region of reduced velocity, Vγ=1.5 to 2.5 in all ranges of gap ratio of 0.3 to 3. This excited oscillation was mainly induced by symmetric vortex shedding;the other excitation of Vγ= 2.8 to 3.5 at wide gap distance ratios of 1.75 to 3, was induced by alternate Karman vortex shedding, as in the case of the in-line oscillation of a single cylinder. The downstream cylinder had an excitation region in a wide range of Vγ=2 to 4 for the narrow gap distance ratios of 0.3 to 0.75. which seems to be induced by alternate Karman vortex shedding. The other excitation regions due to symmetrical vortices were limited to the region of gap distance ratio of 0.75 to 2. Furthermore, the downstream cylinder oscillated as a buffeting phenomenon influenced by wake-fluctuation of the upstream cylinder, when gap distance ratio was greater than 2.5.

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In this study, we developed a code which can calculate three-dimensional micro multi-phase flow using Moving Particle Semi-implicit method. Surface tension which dominates the fluid motion in micro flow also makes the time steps very small and the simulation time becomes very long. We employed a sub-time steps algorithm that enable us stable and efficient calculation of micro fluid with strong surface tension. Using developed code, micro droplet generation in y-shaped micro channel is calculated. We could realize micro droplet generation in our calculation as the same as experiment. In our calculated results, we measured droplet size. The measured droplet size quantitatively agrees with experimental ones. We also visualize flow inside of droplet when a droplet is generated in the calculated results.

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Mixing performance of optical micro rotors with 3, 4 and 5 paddles has been studied by computational simulations. First, the relation between laser power and optical torque acting on the rotors is analyzed. Second, fluid torque which consists of pressure and sheer stress acting on the rotors, and mixing rate of two kinds of fluids are calculated by solving the three dimensional Navier-Stokes equations. It is found that the optical torque caused by a laser beam is proportional to laser power and paddle number, that the fluid torque is proportional to the rotation speed of the rotor and increases with the paddle number, and that 3-paddle rotor shows the best mixing performance for fixed laser power among these three rotors.

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After studying forms of convection in governing equations for compressible fluid flow, a new and useful skew-symmetric form was proposed. This leads to quadratic conservative schemes of convection for low-Mach number compressible fluid flow simulations. Then, commutable divergence, advection and skew-symmetric forms of convection were indicated for standard finite difference method in regular and staggered grid systems. Also, convection schemes for compact finite difference method in regular and staggered grid systems were indicated. In order to check the quadratic conservation property of the schemes, a numerical test was done on a three-dimensional periodic inviscid flow. The computational results have shown that the commutable convection schemes for standard finite difference method have quite good conservative property. For compact finite difference method, only the schemes with the proposed skew-symmetric form have acceptable conservative property.

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A new treatment of no slip boundary condition on complex geometry in a lattice Boltzmann method is proposed. We developed Space-Time Bounce-Back (STBB) method, which evaluate distribution functions in the vicinity of the solid boundary whose geometry described in the scale less than the lattice size. The STBB method is based on not only the spatial distribution but also the temporal distribution of distribution functions, in order to satisfy both the complete reflection on the solid boundary and the second order accuracy in the spatial discretization. Two-dimensional channel flow is calculated by using the proposed method, and both the accuracy and the stability are examined by comparing with the analytical solution.

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The mechanism of a bubble production method using controlled gas pressure fluctuation, originally developed by Kariyasaki and Osaka [Trans. JSME, Series B, Vol. 68, No. 674, (2002)], is further investigated using high-speed photography. We found out more appropriate pressure fluctuation than that of Kariyasaki and Osaka in producing single bubble. The radius of bubbles can be varied from about 0.3 to 0.8mm with extremely small standard deviation of less than 1 μm. Shrinking motion of a capillary bridge connecting a bubble and a nozzle was observed in detail. Force balance on a growing bubble which is based on a spherical bubble formation model is also estimated. As a result, we reveal that when gas pressure is decreased the capillary bridge is sucked down into a nozzle and upward added mass force is applied on a bubble, both of which cause the detachment of a bubble from a nozzle.

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A direct numerical simulation (DNS) of turbulent channel flow with high Reynolds number has been carried out to show the effects of magnetic field. In this study, the Reynolds number for channel flow based on bulk velocity u_b, kinematic viscosity ν, and channel width 2δ was set to be constant ; Re_b=2δu_b/ν=45818.A uniform magnetic field was applied in the direction of the wall normal. The Hartman number was Ha=2δB₀√σ/ρν=32.5 and 65. Turbulent quantities such as the mean flow turbulent stress, and the turbulent statistics were obtained by DNS. Although the influence of the magnetohydrodynamic dissipation terms in the turbulent kinetic energy budget was small, large-scale turbulent structures, such as vertical structures, low-speed streaks, ejection, and sweep, disappear at the central region of the channel. Consequently, the difference between production and dissipation in the turbulent kinetic energy decreases with increasing Hartmann number at the central region and large-scale structures at this region disappear.

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A ring vortex shedding phenomenon observed in the confined swirling flows of polyacrylamide (PAA) solutions whose concentrations were 0.5wt% and 1.0wt% was investigated using particle image velocimetry (PIV) system. It was found that the fluid within the ring vortex formed near the rotating disc rorates with semi-rigid rotation, where the angular velocity of ring votex was about 0.9times that of the rotating disc. The high shear layer was found to exist at the boundary between the ring vortex and the outer large-scale secondary flow. After the ring vortex was shed, the surrounding large-scale secondary flow moved into near the rotating axis, so that the strong axial flow was observed near the rotating axis. Periodic azimuthal and radial velocity fluctuations with considerably large amplitude, in which their correlation varied with the radial locations, were seen for the nonaxisymmetric ring vortex which was observed for the higher Reynolds number compared to that of the axisymmetric ring vortex.

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Direct numerical simulation of a zero-pressure gradient drag-reducing turbulent boundary layer of viscoelastic solutions was performed using constitutive equation models such as the Oldroyd-B and Giesekus models. First, the streamwise variations in boundary layer parameters such as the shape factor and friction coefficient were clarified. Next, mean velocity profiles and turbulence statistics at the different streamwise locations were discussed using both inner and outer scaling. The maximum drag reduction ratio for the Oldroyd-B model, which has the higher elongational viscosity, is larger than that for the Giesekus model. The distinct difference in turbulence statistics near the wall between the Oldroyd-B model and Newtonian fluid is observed, as reported in the drag-reducing turbulent channel flow, while the difference between the Giesekus model and Newtonian fluid is slight in this study. On the other hand, in the outer region, distributions of mean velocity and turbulence statistics for both the Oldroyd-B and Giesekus models are similar to those for Newtonian fluid.

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Energy transfer and turbulence structures in a zero-pressure gradient turbulent boundary layer of a drag-reducing viscoelastic solution were investigated using the direct numerical simulation (DNS) data with the Oldroyd-B and Giesekus models. This work is an extension of the first report, in which mean velocity profiles and turbulence statistics have been investigated. It is found that the contribution to turbulent kinetic energy transfer due to the polymer stress work term is not negligible for the Oldroyd-B model, whereas it is negligible for the Giesekus model. The polymer diffusion term for both the Oldroyd-B and Giesekus models is negligible. For the Oldroyd-B model, we can see that quasi-streamwise vortices are weakened and become larger in the streamwise direction, compared to Newtonian fluids. On the other hand, quasi-streamwise vortices for the Giesekus model are similar to those for Newtonian fluid.

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The motion of a conducting fluid with an externally-applied magnetic field at the low magnetic Reynolds number is important in Magnetohydrodynamic (MHD) applications. For example, magnetic field is applied to control turbulent flow in the manufacturing process of the industrial products. The characteristic of the MHD turbulence is the anisotropic energy dumping. In order to understand the characteristic, we focus on different behavior of the diagonal components of the Reynolds stresses. The purpose of our study is show the process of energy distribution in the MHD turbulence at low magnetic Reynolds number using the transport equation for the Reynolds stresses. We take the case of homogeneous turbulence in a conducting fluid which is exposed to a uniform external magnetic field. In order to elucidate the anisotropic process, it is important to understand the characteristic of the Lorentz force. In this study, we clarify it and derive the transport equation for the Reynolds stresses, which is based on the characteristic. We show the mechanism of anistropic energy transfer in the physical space and the cause of the difference in the diagonal component of the Reynolds stresses.

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Unsteady flow in a baffled stirred tank of which Reynolds number based on the tip velocity and the radius of tank is 45000 has been simulated by solving numerically Navier-Stokes and continuity equations. LES model were used for sub-grid scale flows. Calculated results show unsteady flow fields in the whole region of the tank during about 16 complete impeller revolutions. As the results we present the occurrence and the disruption of large vortices, and the generation of many small eddies which are nearly homogeneous. The calculated visualized flow field, time-averaged velocity and turbulent intensity distributions are fairly in good agreement with the experimental data. It indicates that the present simulation procedure and results are applicable to describe the flow field in the real high Reynolds number baffled stirred tank. The calculated results also show the role of the baffle plate which blocks the tangential flow and induces the complicated flows that increase the stirring effect. The present results elucidate the unsteady flow mechanism in a high Reynolds number baffled stirred tank.

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In an attempt to control an axisymmetric jet using multiple “moving delta-tabs” having triangular shapes, an experimental investigation was performed. Computer-controlled five delta-tabs, which can be driven independently, were installed at the skimmer. Two modes were tested : in the first case, all delta-tabs were stationary (i.e. conventional way) and in the second case, delta-tabs were oscillated in phase at the frequency of 4 Hz. A rake of 21 I-type hot wires was used to measure instantaneous velocities. The results were compared with a canonical axisymmetric jet without tabs. The results show that turbulence quantities such as mean and rms velocities, skewness, kurtosis, probability density function, power spectra are significantly altered by the stationary and moving delta-tabs. The effects of the oscillation of the delta-tabs were found to modify the large-scale structures in the near field of the jet. The results suggest the active control of an axisymmetric jet using moving delta-tabs.

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In the present study, to reveal the air entrainment mechanism into a suction pipe in a suction sump, the authors conduct flow-velocity measurements by UDM (Ultrasonic Doppler Method). Here, we consider the simplest geometry as a suction sump, that is, a straight channel with rectangle-cross section and a simple suction pipe near the end of the channel. Ultrasonic transducers are fixed outside the side, bottom and back walls with right/near-right angle and, we get three-dimensional time-mean velocity distributions and equi-vorticity contours. At first, measurement accuracy is checked by comparing velocity profiles by UDM with hydrogen bubble method. As a result, the authors show typical flow fields in the sump, and show the relation between flow pattern and the air entrainment. Especially, we compare two cases where the air entrainment is often observed.

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Recently, Temperature/Pressure Sensitive Paint (T/PSP) has been promising as a 2-dimentional quantitative optical measurement, because T/PSP is a very simple system with high spatial resolution. However, PSP depends generally on temperature as well as pressure. It is, therefore, necessary to eliminate temperature sensitivity in spite of having still pressure sensitivity. In this study, a mixed dye system ; Pyrromethene 546 and Ru (dpp) ₃Cl₂, is proposed as a temperature-independent PSP. Temperature variation of this system was experimentally found to be reduced to 95% in comparison with that of single PSP dye ; i.e. Ru (dpp) ₃Cl₂, because these dyes have opposite temperature dependencies in the same spectral band. Furthermore, the spectrum of the mixed dye system can be separated in respective spectral bands, which can be employed as temperature-independent and pressure-independent band. We constructed a dual emission imaging system ; i.e. 2-camera system, which was able to simultaneously capture images under both spectral bands. Consequently, it was verified that, using this system with proposed mixed P/TSP dye, temperature and pressure distribution can be independently measure at the same time.

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This paper describes the complicated flow associated with the three-dimensional surface-mounted square cavities. The experiment was carried out in two types of wind tunnels and a water channel. The effect of the aspect ratio (cavity length to depth : L/D=1-8) of the cavity has been investigated in terms of the overall cavity drag increment, the surface pressure distribution and the velocity profiles in the flow inside the cavity. The flow pattern inside the cavities was observed by the flow visualization. The three-dimensionality of the primary vortex in the cavities have been estimated from location of the centre along the span of the cavity. Consequently it was found that (i) a remarkable decrease of the drag occurs at L/D=4, and (ii) two cells structure for L/D=4 and three cells structure for L/D=8 exist in the velocity profile inside the cavity.

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This paper describes the flow past an inclined flat plate of finite width with the attack angle placed on a ground plane. The experiment was carried out in the 800 mm diameter Eiffel type wind tunnel having the working section of 1.5m length at Reynolds number of 5.1×10⁴ mainly. The surface pressure distributions on the flat plate and on the ground plane around the flat plate were measured, and the drag coefficient, lift coefficient and side force coefficient were determined from them. The power spectrum of the X component of fluctuating velocity was measured to check the arch vortices shedding behind the flat plate. Consequently, it is found that the appearance of shedding arch vortices is in the range of 45°≤β≤120° for W/H=2 and β=90° for W/H=4 when α=30°, while the drag coefficient attains maximum near β=90° and the lift coefficient decreases for W/H=2, 4 and 7, as β increases from 30°to 135°.

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The purpose of this study is to reduce cavitation noise occurring around a butterfly valve. The main cause of cavitation occurrence is an abrupt decrease of the fluid pressure behind a valve. To recover the pressure behind the valve in our experiment, the pipe was partly enlarged from just ahead of the valve shaft forward downstream. From the results of the noise measurement and visualization, the size of the ditch was determined and it was found that the effect of noise reduction was greatest when the length and the depth of the ditch were 1 and 0.2 times the width of the duct, respectively. The effect of the ditch was very clear in the experiments using an actual valve and piping. It was confirmed that the sound pressure level can be reduced by about 8 dB even with severe cavitation. When a partly enlarged pipe was used, secondary cavitation occurred from the edge of the ditch. It was found that the effect of the noise of secondary cavitation was about 2 dB to 4 dB. However, this noise could be eliminated by changing the shape of the ditch.

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Noise reduction performance of aerodynamic tabs in an under-expanded supersonic jet is investigated experimentally. From a converging round nozzle, air is injected into the atmosphere (Main jet) at a pressure ratio of 2.25 (M_j=1.14). The nozzle exit diameter D=8.0mm. From small nozzles mounted in the main jet nozzle wall, air is injected in the normal direction to the main jet (Secondary jet). The nozzle exit diameter d=1/8D and 1/16D, and the number of nozzles is varied from 1 to 8. The average total pressure of the main jet decreases with the increase in the total mass flow rate of the secondary jets. The secondary jet penetration is estimated from the momentum flux ratio and the secondary jet nozzle exit diameter. Equivalent secondary jet penetration is introduced to consider the effect of the number of secondary jet nozzles. The screech SPL decreases monotonously with the increase in the equivalent secondary jet penetration. The OASPL, which represents the broadband noise level, also decreases with the increase in the equivalent secondary jet penetration, and takes the minimum value where the screech is removed.It i§ shown that the jet penetration is one of the most important criteria of the noise reduction performance of aerodynamic tabs.

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The present study performed numerical simulations of bioconvection generated by chemotactic bacteria in a shallow chamber, and examined influences of Rayleigh number upon the bioconvection. The present results are in good agreement with the previous linear theory in stationary flow field. At the small Rayleigh number, the bioconvection does not occur, and the bacteria cells collect near the free surface. The difference between the numerical result and the linear theory appears with an increase of the Rayleigh number owing to the influence of the non-linearity. At the critical Rayleigh number, the cell near the free surface becomes unstable by the Rayleigh-Talor instability, and the bioconvection is formed in the center of the chamber. The bioconvection grows with further increase of the Rayleigh number. The bacteria are active near the bottom of the chamber because the oxygen is supplied by the diffusion from the free surface. When the Rayleigh number increases, the convective transport becomes dominant by reason of the generation of the bioconvection as compared with the oxygen diffusion and bacteria swimming.

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Numerical flow simulations are useful for understanding pressure wave propagation in circulatory systems. Our one-dimensional numerical model, which encompasses the effect of unsteady viscosity and the generalized viscoelasticity of tubes, has previously indicated that the tube's viscoelasticity plays an important role in the wave propagation. In the present study, in order to investigate the relationship between changes in the viscoelastic properties of the tube and periodic blood pressure wave propagation. A one-dimensional numerical model of wave propagation in a silicone tube was validated quantitatively and the approximation error of the model was estimated. By analyzing the calculated results using these models with the parameter change of a viscoelastic property of the tube, we can make the following conclusions. The pulse wave velocity and the pulse pressure increase from increasing of the viscoelasticity of the tube. The tube viscoelasticity also plays an important role in the periodic blood pressure wave propagation, and the arterial stiffness index affect by the blood vessel viscoelasticity.

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A cross-flow wind turbine near a structure was tested for the performance. The results showed that the performance of a cross-flow wind turbine near a structure was about maximum 30% higher than the case without a structure and these effects were remarkable especially in lower wind speed case. At 4m/s low wind speed, the performance curves got higher value at the start (in lower tip speed ratio) and the range of tip speed ratio for the high power coefficient was wider. In addition, we tried to get higher performance of a cross-flow wind turbine by using an Inlet Guide Structure on the edge of a structure. In this case, a cross-flow wind turbine showed about 4 to 17% higher value in maximum power coefficient than the case without Inlet Guide Structure.

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In air-conditioning systems, it is desirable that the liquid-solid phase change temperature of a cool energy storage material is approximately 10°C from the perspective of improving coefficient of performance (COP). Moreover, a thermal storage material that forms slurry can realize large heat capacity of working fluids. Since the solid that adheres to the heat transfer surface forms a thermal resistance layer and remarkably reduces the rate of cold storage, it is important to avoid the adhesion of a thick solid layer on the surface so as to realize efficient energy storage. Considering a harvest type cooling unit, the force required for removing the solid phase from the heat transfer surface was studied. Tetra-n-butylammonium Bromide (TBAB) clathrate hydrate was used as a cold storage material. The effect of the scraper shapes on the scraping force for detachment of adhered solid of TBAB hydrate to the heat transfer surface was examined experimentally. The TBAB hydrate solids were categorized broadly into two kinds of solids. The scraping force of the TBAB hydrate solid on the heat transfer surface was different for the two kinds of the TABA hydrate solids. And the scraping force of the TBAB hydrate solid formed after scraping was improved by the modifying the scraper shape.

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A technique for measurements of time-space distribution of convective heat transfer has been developed using a test surface fabricated from a thin conductive film heated electrically. The fluctuating temperature on the test surface can be measured using infrared thermograph having high frame-rate, if the heat capacity of the test surface is sufficiently low. In this work, the frequency-response of the heat transfer from the test surface was investigated by solving the heat conduction equations by considering the heat losses. Also, the spatial resolution due to the lateral conduction through the test surface was investigated. The upper limit of the fluctuating frequency and the lower limit of the spatial wavelength, which is detectable using infrared thermography, are found to be uniquely decided for each test surface as a function of (T_w-T_O) Δh/ΔT_IRO, where (T_w-T_O) is the mean temperature difference between the wall and freestream, Δh is time or spatial amplitude of the heat transfer coefficient, and ΔT_IRO is a temperature difference equivalent to noise of infrared measurements for the black body.

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An experiment of heat transfer characteristics in a two-phase thermosyphon with an adiabatic connecting pipe of inner diameter D_p=2 to 8mm and of length L=250, 500 and 1000mm has been carried out at atmospheric pressure employing water as an operating substance. As the heat is loaded into the thermosyphon, the temperature of heated surface starts fluctuating at a heat flux at which unstable vapor-liquid counter current flow is generated in the connecting pipe. A feature of bubbles at the upper end of the connecting pipe was photographed when the temperature fluctuation starts. It was found that the heat flux at the onset of the temperature fluctuation is increase with an increase in D_p and then can be predicted well by the Wallis equation with C_w=0.7 for 5≤D_p≤8mm. Furthermore, we clarified that the cause of this fluctuation comes from the inlet effect of the connecting pipe using a bell mouth, which is placed to either bottom end or both ends of the connecting pipe.

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The interaction between gaseous molecules and a rectangular hole with adherent molecules was calculated by the classical molecular dynamics method in order to invistigate fundamental behaviors of adhesion and passage in a nanometer scale filter with adherent molecules. The adherent molecules affected the passage of gaseous molecules. Gaseous molecules passed through the center of filter hole as the increase of volume ratio of adherent molecules in the rectangular hole. The flow regime in the hole was affected by a kind of gaseous molecules passing through the hole. When the interaction between the surface of the hole and gaseous molecules was small, the gaseous molecules moved far from the surface of the hole and most of them passed through the hole. On the other hand, when the interaction between them was large, the gaseous molecules moved near there and most of them were adherent there. Therefore, the flow velocity in case of large interaction was lower than that in case of small interaction under the same pressure difference.

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Atomization characteristics of an ultrasonic fuel injector using a micro nozzle array were investigated experimentally. Micro nozzles whose exit diameter is d =3, 6 and 9μm are mounted on a thin metal film.The number of the micro nozzle is 2.0×10⁴. Using an ultrasonic oscillator, gasoline is periodically pushed out from the micro nozzles at the frequency of 63.6kHz.A disk-type PZT is used as an ultrasonic oscillator, and the oscillation is amplified using a step-type horn.The input voltage is varied from 0 to 200 V.At the natural frequency, the oscillation amplitude of the horn is about 10μm.The droplet diameter and velocity are measured with a phase Doppler analyzer at 15 mm downstream from the micro nozzle array.For d=3μm, the Sauter mean diameter (SMD) is about 10μm, and the fuel flow rate is 0.023 cc/s. The SMD is much smaller when compared to conventional port fuel injectors.For d=6μm, the SMD is about 10 to 18μm, and the fuel flow rate is 0.055 cc/s.For d=9μm, the SMD is about 16 to 28μm, and the fuel flow rate is 0.41 cc/s.It is shown that, using the micro nozzle array, a uniform-diameter steady spray can be obtained without high-pressure fuel pump and nozzle type injectors.

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We have evaluated resistances under the channel and rib of the separator in a polymer electrolyte fuel cell (PEFC) from the change of overpotentials by removing the gas diffusion layer (GDL) under the channel. As a result, we find that contact resistance between the GDL and electrode under the channel amounts to twelve times larger than that under the rib, leading to electron transfer rate limited reaction under the channel. Accordingly, the current ratio under the rib is calculated to be more than 90%. The ratio increases as the total current density increases when the current density is small, and it becomes almost constant as the current densiy becomes larger. The large current ratio under the rib suggests that the vapor produced in the electrode under the rib transfers toward that under the channel and accumulate there. Thus the major part of the vapor is probably carried away through the MPL and GDL base material under the channel by the cathode gas flow in the channel.

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High efficiency pulverized coal power plant technology, especially the system simulation and design for high temperature steam turbines, is discussed. It is believed that a 700-deg C class steam turbine system will be realized with Ni-based super alloys. The super alloys are more expensive than current materials like 12%Cr steels though its high temperature strength is excellent. In addition, the size of the alloys is limited for the current design. Therefore, it is necessary to study new design concept to utilize the super alloys. The key concept is the optimized combination of steam turbine cooling and the super alloys. In this paper, the development of a simulation technique and the application of the gas turbine cooling technique to the high temperature steam turbine design are discussed. The simulation software is specially designed to integrate the entire system simulation and the detailed design of components to evaluate the system performance with the cooled steam turbines. The results of calculation are assessed by taking the other calculations with a similar steam condition into consideration

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