To improve the efficiency of the compact centrifugal blower in the limitation of size, we developed two diffusers. The pressure loss of the return channel bending part accounts for about 20% of the internal flow loss of the blower. For high efficiency of the blower, it is necessary to minimize the pressure loss of the return channel bending part. By comparing the analysis results between original diffuser and developed diffusers using CFD (Computational Fluid Dynamics), it was revealed that the pressure loss of the return channel bending part was reduced up to 31% and the pressure loss of the static channel was reduced up to 4.7%. Furthermore, we confirmed that the amount of rise in static pressure of the blower increased up to 0.7% compared with the original diffuser by an experiment.

View full abstract

To facilitate the manufacture of impeller in an centrifugal blower, we developed a swaged 3D impeller using CFD (Computational Fluid Dynamics) and multi-objective optimization method. By visualizing the total efficiency coefficient distribution in the impeller, it was revealed that the total pressure loss in the impeller flow passage was reduced. Furthermore, we confirmed that the static pressure efficiency of the developed impeller increased by 1% compared with the baseline impeller by an experiment.

View full abstract

Large-scale detached eddy simulations (DES) have been conducted on the K computer, in order to elucidate the flow mechanism of the rotating stall inception in a multi-stage axial compressor for an actual gas turbine. In the present study, the front half stages of the 14-stage axial compressor used for a 30MW class industrial gas turbine were analyzed by taking advantage of data mining techniques, with which vortex structures were identified by the critical point theory and limiting streamlines were visualized by the line integral convolution (LIC) method. This paper describes unsteady flow phenomena in the compressor at stall inception, which were seen on the hub side not the tip side.

View full abstract

In order to reduce the fan power of a 4-way cassette type indoor unit of a packaged air conditioner, we developed the shape of air outlet nozzles reducing of the pressure-loss. The main cause of the pressure-loss was the flow separation area shaped in current air outlet nozzles. Therefore, we devised the shape for the control of the flow separation area. The shape was defined by two parameters, and the influence of parameters on the fan power reduction was surveyed by using the simulation technology with CFD (Computational Fluid Dynamics). We used the response surface which was made by results of CFD and approximate values with the Kriging-based method since the appropriate combination of parameters was efficiently searched from multiple parameters. As the result, the combination of parameters which reduces the fan power the most in the response surface was found. The shape adopted the combination of parameters can control the flow separation area. The fan power reduction by 9.9% in comparison with the current shape of air outlet nozzles was confirmed by the experiment.

View full abstract

Development of silent air-conditioners is one of the most important tasks in recent changes to life-styles, such as demands of silent office and home. Aerodynamic noise from fans contributes to a large percentage of the overall noise from air-conditioners. Therefore, the development of silent fans would contribute to reducing the noise levels of air-conditioners. In this study, flow fields in multiblade fan for the indoor units of air-conditioners were calculated with large eddy simulation (LES). The computational fluid dynamics (CFD) code employed throughout the LES was called FrontFlow/blue (FFB). The numbers of grid elements were approximately 80 million. In the computational aero-acoustics (CAA), the sound propagation equation of Lighthill was solved in the frequency domain. The number of mesh elements is approximately 12 million. We compared calculated and experimental results for validation. We confirmed that the static pressure rise and the shaft power reasonably agreed with the experimental results. The predicted sound pressure level agreed reasonably well with the experimental data in the frequency range from 1000 Hz to 2500 Hz. The tendencies of acoustic effects were captured near 1200 Hz and 2000 Hz. As a result, we confirmed that the calculated results captured main flow field structures and acoustic field, which played dominant roles with aerodynamic noise. Moreover, we confirmed that CFD and CAA in this study were useful tools for predicting the aerodynamic noise of multiblade fan.

View full abstract

Small-sized axial fan is used as air cooler for electric equipment. But there is strong demand for higher power of fan according to the increase of quantity of heat from electric devices. Therefore, higher rotational speed design is necessary, however it causes the deterioration of efficiency and increases the noise. Contra-rotating axial fan is smaller than conventional axial fan under the same rotational speed, and is effective for lower rotational speed design under the same diameter. So, the adoption of contra-rotating rotor for small-sized axial fan was proposed for the improvement performance. In the present paper, the unsteady numerical analysis was conducted to investigate the performance and flow field in contra-rotating small-sized axial fan rotors at the partial flow rates. Further, the ideal blade row distance of the contra-rotating small-sized axial fan was clarified with the unsteady numerical analysis results.

View full abstract

In the present paper, we have considered about a fundamental fluid machine having a screw fin. The screw type fluid machine can transport a fluid substantially with a very simple structure. It has been, therefore, used as a water pump. On the other hand, there is not the example which was applied to a blower because of low efficiency and not to be suitable for gas transportation. However, it can forecast the degree of freedom of installation and the noise reduction. Here, we have examined the optimum fin design by dividing the spiral fin into a circular elements to obtain the design guidance of the screw wing when I used the screw wing as a blower, and considered the optimum pitch angle using CFD.

View full abstract

This paper presents an aerodynamic design method for half-ducted axial flow fan using meridional viscous flow analysis and one-dimensional inverse method. The meridional viscous flow analysis which can take into account the mixing loss related to the vortices in the meridional flow field. A conventional half-ducted axial flow fan has been investigated by a three-dimensional Reynolds Averaged Navier Stokes analysis (3D-RANS) and the meridional viscous flow analysis. The 3D-RANS analysis result shows a flow separation on the suction surface near the trailing edge of the blade. In addition, the meridional viscous flow analysis results shows the high blade loadings near the trailing edge of the blade. The blade shape has been redesigned by the present design method with improved blade loading distributions which has lower blade loading near the trailing edge. The numerical result shows the flow separation is successfully suppressed as intended in the design concept. As a result, the aerodynamic performance in the designed blade is improved.

View full abstract

Mini turbo-pump is used in a wide range of fields, such as water-cooler for personal computer, fuel cells, and ventricular assist device. And there is demand for more compact and higher performance. However, the design method for the mini centrifugal pump is not established because the internal flow condition for these small-sized fluid machines is not clarified and conventional theory is not suitable for small-sized pumps. Then, the semi-open impeller for the mini centrifugal pump with 55mm impeller diameter was adopted for this research. It is important to clarify the suitable design parameters for the mini centrifugal pump with simple structure. Then, the influence of the blade outlet angle, blade number and volute casing size on its performance and internal flow condition were investigated. In the present paper, the high performance design of the mini centrifugal pump is discussed based on the experimental results.

View full abstract

When solid particles are included in the working fluid in various fluid machines, the machines may be damaged by solid particle erosion. Therefore, the prediction of the phenomenon is required from the viewpoint of safety of the machines. The authors have developed a method that reproduces the interaction between the change of gas-solid two-phase flow and the change of surface geometry. In this study, the authors improved the method and propose a robust and accurate computational approach for sand erosion simulation. Numerical simulation for 90-degree bend with a square cross-section were performed. The results showed that the proposed method reduced physically unrealistic effects due to smoothing and improved the eroded surface geometry.

View full abstract

To clarify the steady characteristics of torque converter against cavitation, numerical simulation of cavitation is carried out in several speed ratios of turbine to pump (0, 0.2, 0.4, 0.6, 0.8). The following relationships between the torque decrease and cavitation were found. All the speed ratios less than equal to 0.4, torque decreases because of decrease of mass flow by cavitation at stator. Second, at the speed ratio of 0.6, cavitation occurs at pump as well as at stator. Cavitation at pump changes meridional flow and causes increase of pump torque at certain pressure. Finally, speed ratios of 0.6 and 0.8, cavitation at pump would leads to sudden drop in torque.

View full abstract

Hydropower has been attracting attention as a renewable energy. As for the small-scale power generation for low-drop use were limited until now, the aim of application is the power generation by Darrieus-type hydro turbine in the small waterway. With the installing the guide plate at the rear of the water turbine, the effect of efficiency improvement is verified. Experiments in the test model and numerical analysis by two-dimensional models were carried out. As a result, when the guide plate at the rear of the water turbine is installed, performance improvement can be expected by attaching a tilt angle against waterways. In addition, torque improvement can be expected by installing the guide plate in the upstream side of water turbine rotational direction.

View full abstract

The effect of curvilinear element blade in open-type centrifugal impeller was examined in this research using numerical simulation. Four different open-type centrifugal impellers were compared. Two of them were linear element blade impellers, one had a positive tangential lean to the rotation at the outlet and the other had a negative tangential lean. The other two were curvilinear element blade impellers having different tangential lean profiles. Numerical simulation of steady flow was conducted in one-blade path model with inlet, impeller and vane-less diffuser regions. The simulation confirmed that impellers with negative tangential lean profiles improved the stage efficiency under the flow rate condition at the design point. The efficiency increase at the design point was obtained in the impeller region since the negative lean profile reduced the tip-leakage loss near the impeller outlet region.

View full abstract

The promotion of the utilization of renewable energy is being strongly demanded in order to prevent the progression of climate change due to the increase in greenhouse gas emissions. In this paper, a new generator which utilizes carbon dioxide (CO_2) gas hydrate is proposed. This generator is driven by a small-temperature difference of a heat source at near room temperature and it discharges no exhaust gases at all. In this paper, we model the proposed generator and report the power generation efficiency characteristics and the energy storage characteristics based on the relationship between the performance of the heat exchanger and the power loss by the heat medium circulation.

View full abstract

Although BiCuSeO has become of interest as a high-performance thermoelectric material, it is reported to be unstable in air above 548 K. However, about details of time dependence of thermoelectric ptoperties for BiCuSeO at high temperatures in air have not yet been determined. In this study, the time dependence of the thermoelectric properties for BiCuSeO in tair was investigated. The relationship between the temperature difference AT and the thermoelectromotive force E in air was measured using the large temperature difference method. Variations in p and a over time at 550 K were determined using the DC four terminals method and small temperature difference method. From the result of large temperature difference method, the thermoelectromotive force at 723 K was actually less than the value obtained at 673 K. The results of thermoelectric properties measurements over time showed that p abruptly increased between 135 and 182 min then decreased from 182 to 210 min, while the a exhibited a opposite tendency for p. The result of XPS and XRD suggested that BiCuSeO was pyrolyzed upon heating at 550 K for 6 h in air. In contrast, the risult of TG analysis demonstrated that BiCuSeO was stable below 800 K under an inert gas flow, thus the pyrolysis observed at 550 K was the result of reaction with atmospheric oxygen.

View full abstract

Generally, the NO_x (Nitrogen Oxides) density rises and the PM (Particulate matters) emission decreases when the combustion of the diesel engine is promoted. On the other hand, BDF (Bio Diesel Fuel) containing a lot of oxygen promotes the combustion of diesel engines, hence the improvement in thermal efficiency can be expected. However, the previous researches found out that the PM emission of the diesel engine using BDF increased compared with using gas oil. In this research, by using gas oil and BDF, the relationship between the fuel injection pressure and the operating characteristics was examined by testing the performance of the diesel engine with a common rail fuel injection system. As a result, it was clarified that the combustion characteristic of BDF was inferior to gas oil due to high kinematic viscosity, but the NO_x exhaust characteristic and other operating characteristics of the diesel engine could be improved by injecting BDF with high pressure.

View full abstract

In Japan, 7.50 million tons of rice straw was incinerated and plowed under soil. This abundant resource of rice straw is useful as alternative energy for recycling-based societies and also in possibly activating agriculture that is dependent on local production for local consumption. We aimed to effectively use unutilized rice straw by producing Bio-coke, which is a new briquette (in the rest of this document referred to as the BIC) with high density and hardness, and evaluated characteristics of rice straw BIC because the relationship between specific gravity and specific surface area of BIC is not well known. Additionally, it is seems that the specific gravity and specific surface area at the periphery of BIC may affect its combustion characteristics. In this study, one of the aims is that BICs are produced with various specific gravity and specific surface area as a parameter. It was confirmed to be able to produce BIC with different specific gravity and specific surface area at the periphery of BIC by changing manufacturing conditions of BIC and be led the relationship between the specific gravity and the specific surface area. After that, it was examined that difference of the specific gravity or the specific surface area at the periphery of BICs relates the ignition delay time as one of the combustion characteristics derived from burning BIC with different specific gravity. As a result, it was led that the relationship between the specific gravity or the specific surface area at the periphery of BICs and the ignition delay time was a direct proportional relationship.

View full abstract

Our society depends upon a variety of energy resources. From an environmentally friendly point of view, the reduction of carbon dioxide emissions that cause global warming and fossil fuel resource depletion are big problems and the Bio-coke, as a new self-sufficient energy in Japan, is being considered a solution. This study was carried out for the purpose of investigating the characteristics of Bio-coke made from EFB fiber as a substitute fuel for coal coke.

View full abstract

Amount of scale formed in the heat exchanger and its fouling factor are experimentally investigated. It is cleared that the increment of scale is proportional to the square of time. The amount of scale are closely relating to the composition melting in the hot spring water and the velocity. The increment of the fouling factor with time is valued with the amount of scale. At early step the fouling factor increases rapidly. And then the increment of fouling factor is gradually decreased. The fouling factor is fairly larger than the estimated value with the full filled scale.

View full abstract

Small hydropower generation is one of important alternative energy, and potential of small hydropower is great. Efficiency of small hydro turbines is lower than that of large one, and these small hydro turbine's common problems are out of operation by foreign materials. Then, there are demands for small hydro turbines to keep high performance and wide flow passage. Therefore, we adopted contra-rotating rotors which can be expected to achieve high performance and low-solidity rotors with wide flow passage in order to accomplish high performance and stable operation. Experimental apparatus of the contra-rotating small hydro turbine with 60mm casing diameter was manufactured and performance of it was investigated by an experiment. Efficiency of the contra-rotating small hydro turbine was high in pico-hydro turbine and high efficiency could be kept in wide flow rate range. In the present paper, performance of contra-rotating small hydroturbine with foreign vegetables materials, was investigated by an experiment. And, internal flow condition with foreign vegetable materials, and grasses, were investigated using a high speed camera and the causes of troubles related to the foreign materials were considered.

View full abstract

Most of the conventional hydraulic turbines have been used for those sites having the static head larger than around 1 m. To extensively utilize not only large hydro-power but small one, development of an energy conversion system being operable under an extremely low head stream is crucial. A flapping-foil micro hydroelectric generator which works based on the lift acting on the flapping foils in a stream is proposed. An experimental apparatus with symmetric foils of 150 mm chord and 400 mm span was designed to generate average power output of 25 W at a flow velocity of 1 m/s. Through the tests carried out in the circulating water channel, the performance of the generator was verified to satisfy the design specifications. Further, the demonstration field tests by using an irrigation stream performed for 16 months clarified the performance equivalent to that in the in-door water channel and the durability to a certain extent, and showed the applicability to the practical use of lighting the LED street lamp in a park during night.

View full abstract

Research has been conducted for carry out the tidal generation in the Tsugaru Current. However, the flow speed of Tsugaru Current is slower than the Kuroshio Current. The wind-lens technology is used to obtain a lot of energy. The brimmed diffusers for tidal generation are made to carry out the hydraulic experiments. The hydraulic experiments have shown that the brimmed diffusers obtain the speed increasing effect. Therefore we suggested the brimmed diffuser for tidal generation with integrated water turbine and power generation section supported by circumference. To investigate the velocity distribution for designing it, we carried out the wind tunnel experiments with brimmed diffusers. The wind tunnel experiments have shown that the diffuser length has significant influence on the speed increasing. And the longer the diffuser length, it more obtains the speed increasing effect. Also it obtains remarkable speed increasing effect near the wall. The brimmed height doesn't influence on the speed increasing effect clearly.

View full abstract

The aim of this study is to design and propose the size and layout of buildings which provide the better wind speed distribution for the higher power generation of wind turbine. A building model whose layout is like nozzle is proposed to obtain the acceleration of wind blowing through buildings due to contracted flow between buildings. In addition, the effect of the angle between two buildings on the power generation performance of the proposed building model is also investigated. For the feasibility check of installing the building model in some cities actually, the power energy output of wind turbine is investigated by considering the meteorological data such as wind speed and direction distribution for Fukushima city and Tsu city as an example. As a result, the proposed building models which have the angle between two buildings like nozzle of 90, 135 and 180 degree can provide the wind acceleration at the back of buildings for the wind blowing from the main wind direction and the angle of 135 degree is found to be the optimum building layout. In the case of installing the proposed building model in Fukushima city and Tsu city, the wind power energy output in winter is higher while that in summer is lower irrespective of the buildings angle. The interaction between the change in frequency distribution of wind speed direction through the year and the location of open tip of building model decides the power generation characteristics of the proposed building model.

View full abstract

The aim of this study is to design and propose the building model integrated with solar panel and wind turbine for the purpose of realizing the smart city. The number and angle of tilt of solar panel installed on the roof of the building are investigated considering the effect of shadow for some cities in Japan. The power generation characteristics of solar panel installed on not only the roof but also the wall of the building are also investigated assuming the building model to be installed in Tsu city. In addition, the power generation performances of the photovoltaic as well as the combined power generation of photovoltaic and wind turbine which are integrated with the buildings are compared with the power demand of the buildings. To estimate the power generation characteristics of the proposed model, the statistical meteorological data base is used. As a result, the optimum angle of tilt is 0 degree irrespective of investigated cities since the number of solar panel is the largest. Though the power energy generated by solar panel installed on the roof covers the most part of energy demand of the building, the addition of solar panel installed on the wall is effective to cover the energy demand through the year. The combined power generation of photovoltaic and wind turbine is effective when these power generation systems perform complementing the weakness of each system, e.g., the wind turbine covers the energy demand in night.

View full abstract

Floating offshore wind turbine-generator systems are expected to install in areas that have very deep waters. Vertical axis wind turbines possess great potential for floating offshore applications because they excel in stability of a floating platform due to a generator and gearbox installed near an oscillation center. To conduct a feasibility study on floating offshore systems using vertical axis wind turbines, a performance analytical model of vertical axis wind turbines under inclined axis conditions is developed by extending a conventional multiple streamtube model. Then, the impact of the inclined axis conditions on the performances of a straight-wing vertical axis wind turbine is analyzed. The calculation result reveals the mechanism of the slight increase in the maximum power coefficient under inclined axis conditions.

View full abstract

Gyromill wind turbines with two different blade profiles were investigated experimentally and numerically in order to verify the effect of the negative camber on aerodynamic performance. Experiments were carried out using a model turbine impeller with an axial length of 200 mm and a diameter of 200 mm. The performance of the model wind turbines with two blades were measured with a wind tunnel in a wind velocity of constant 4 m/s. The results showed that the maximum power coefficient was higher for the blade with negative camber by 5.0 percentage points than the one without camber. An unsteady numerical flow analysis around the wind turbine was then conducted using a commercial code employing the finite volume method. The results showed that the power coefficient of one blade had a maximum value in the second quadrant for the two tested wind turbines. The results also showed that the blades with negative camber were advantageous for obtaining high rotational torque in the position by examination of the pressure distribution on the blade.

View full abstract

We have clarified the power characteristics and the transient response of the power in a small type wind turbine at about 1.1 m diameter of wind receiving area having maple seed type blades in a great wind tunnel experimentally. We have proposed a new type of wind turbine blade having the possibility of easy producing the blades which are imitated the rotation of falling maple seed in the nature world. At the study, we used maple seed type blades made of CFRP because we kept the blades strength by becoming larger diameter of wind receiving area. In the present study, as a subsequent experiment, we conducted on the outdoor proof examination. By comparison of the accumulated power per day to the type of ordinal propeller wind turbine, we can obtain more power at the type of maple seed than that of propeller because that its transient response to the wind at the maple seed type blade is better than that at the ordinary propeller type blade.

View full abstract

There is tubercle structure at leading edge of humpback whale fin. The research of this structure is studied flourishingly . Now, in this research, I made the wind mill blade which has tubercle structure and the one which has no tubercle structure .and calculated that the difference of tubercle fin and no tubercle fin by ANSYS-CFX. I calculated the rise time of small wind mill blade at air force -kinematic coupled analysis . There is no large difference between the rise time of tubercle fin and the one of no tubercle fin. However, I confirmed the obvious differences in the pressure on blade and vortex near blade ,which are caused by tubercle structure

View full abstract

It is effective to estimate the rotor performance of large scale wind turbines such as 10 MW-class wind turbines using Computational Fluid Dynamics (CFD), since it is necessary to capture complex flow fields in order to estimate the performance precisely. The CFD analysis targeted small scale wind turbines has been conducted and the results are consistent with those of wind tunnel tests. When applying the analysis conditions used in the CFD analysis of small scale wind turbines to that of large scale wind turbines, the effect caused by the difference of Reynolds number should be considered. In this study, we executed CFD analysis targeted 10 MW-class wind turbine with the analysis conditions used in the analysis of small scale wind turbines, then we validated the applicability of the analysis conditions through the comparison of the results between CFD and Blade Element Momentum Theory (BEM). Consequently, the stability of CFD analysis using analysis conditions of small scale wind turbines and the possibility of capturing the properties of complex flow fields using CFD are shown.

View full abstract

The surface flow on rotor blade of Horizontal Axis Wind Turbine (HAWT) has complicated three-dimensional flow with span-wise velocity. Detail of flow around rotor blades are not clarified sufficiently, since the measurement of velocity including boundary layer on rotor blades are difficult to reveal precisely. This paper's aim is to clarify the flow field around wind turbine blades. As the method, the measurement was performed on a model wind turbine having three blades by using of Laser Doppler Velocimeter (LDV) in wind tunnel. This paper showed that two-dimensional relative velocity in the boundary layer outer edge accelerate in the blade leading edge, in the region of the boundary layer from the outer edge to the blade surface the flow on the rotor blade surface is decelerating toward the trailing edge from the blade middle part due to the influence of the adverse pressure gradient and three-dimensional flow in the blade root area is stronger than the blade tip area.

View full abstract

In recent years, size of the wind turbine has progressed in order to reduce energy costs. If further larger size of wind turbine is advanced, rather than the three blades wind turbine, two bladed wind turbine may become cost-effective. But load fluctuation of two-bladed wind turbine in a transient state, such as extreme wind direction change of inflow, has not been revealed. Therefore, in order to experimentally investigate the load fluctuation of two-bladed wind turbine for extreme wind direction change, the extreme wind direction change defined by IEC 61400-1 was caused, and the load fluctuation of two-bladed wind turbine for extreme wind direction change was measured using 6-component balance. This paper showed that without any specific transition for extreme wind direction change, the fluctuation of the mean value of thrust coefficient during extreme wind direction change was based on the thrust coefficient measured in each yaw misalignment angle in the steady inflow experiment.

View full abstract

In order to make an approach according to the dynamic characteristics of the two-bladed horizontal axis wind turbine, that is substantially unsteady and non-linear motion, the basic equations were derived by Lagrangian method on Eulerian coordinate system. The result shows some reasonable form corresponding to the practice.

View full abstract

The nacelle-mounted LiDAR has been attracted as the wind measurement instruments for the evaluation and the advance control of the wind turbines. Nacelle-mounted LiDAR can measure the wind speed in front of the turbine using the Doppler effect of the laser pulse. Using the measured forward wind speed, the inflow wind speed could be estimate more exactly than existing methods like an anemometer on the nacelle or of the metrological mast. However, it is reported the inflow wind slow down as the wind approaches the wind turbine, called Blockage effect, by the model experiments and the CFD simulations, affected by blades of the turbine. Moreover the wind measurement precision nacelle-mounted LiDAR could be affected by the yaw angle of the turbine since the LiDAR is attached on the turbine and the yaw angle of the LiDAR is connected with that of the turbine. In this paper, the blockage effect and the influence of the yaw error on the wind measurement was investigated using the measurement wind data by the nacelle-mounted LiDAR. The blockage effect was confirmed and made good agreement with the results of the model experiments and the CFD simulations. It is verified that the yaw error of the turbine also affected the wind measurements.

View full abstract

Two-bladed wind turbines are noticed because of reducing nacelle's weight on multi megawatt wind turbine size. However, two-bladed wind turbines have some issues such as increasing fatigue load and noise. Increasing noise is not so important when installing wind turbines in a sea area. So, to implement larger size of off-shore wind turbines, reducing fatigue load is important. As one of the methods that reduce fatigue load, a teetered-hub is noticed. A teetered-hub enables blades to rotate on a central axis of the hub like a seesaw. By this movement, the difference of aerodynamic load between two blades is balanced. In this study, blades behavior of teeter axis circumference and a blade root bending moment are analyzed by AIST-Realtime Aeroelastic Model (AIST-RAM). AIST-RAM is derived by Lagrange's method on Euler's coordinate system and is coded by The National Institute of Advanced Industrial Science and Technology using MATLAB/Simulink. By comparing AIST-RAM result with wind tunnel test result, confirming the validity of AIST-RAM.

View full abstract

We report on our efforts to measure the purity of RNA extracted from single cells via electrical lysis and ITP (isotachophoresis). We have developed a fluorescence microscopy to quantify absolute masses of RNA and protein focused at ITP interface with fluorescence dyes that specifically bind with RNA and protein, respectively. This quantification is performed without enzymatic amplification in less than 5 min. We demonstrate our technique using K562 single cells, for which we obtained an average of 12.1±1.6 pg and 43.8±8.8 pg of RNA and protein masses, respectively, and 36.3±4.9% of RNA purity.

View full abstract

Ionic responses in micro/nanofluidic channels have attracted significant attention in various research fields, where ionic currents have an important role to modulate electrophoretic behavior of electrically charged molecules. In order to manipulate target molecules, flow fields have to be accurately controlled. Some problems, however, have remained to figure out such difficulties. In this study, we have developed an experimental system to investigate a relationship between the spatial and temporal scales of ionic current responses. Using a pair of conical shaped electrodes to variably change the gap distance, we can measure unsteady ionic responses systematically and analyze the scales of phenomena. Based on a previous theoretical study, the validity of experimental results is confirmed. As a consequence, ionic responses that consist of electrophoresis and diffusion are revealed from both experimental and theoretical aspects.

View full abstract

In this paper, we proposed a sealing method of a degassed working fluid for a micro thermal diode. The micro thermal diode is one of the key components of a micro thermal device such as a micro refrigerator and a thermal energy harvester. A working fluid, which transfers heat energy by evaporation and condensation like a vapor chamber, is encapsulated in a cavity of the thermal diode. The working fluid is driven by wettability difference of condensation and evaporation parts, which makes a one-way fluid circulation. To work the thermal diode properly, non-condensable gas such as air should not be included in the cavity. Therefore, a fluid insertion method without mixing the non-condensable gas is proposed. The non-condensable gas in the device was removed by in situ freeze-degassing method and the working fluid was sealed by using gold-bump crushing method. The working fluid was successfully sealed and the pressure in the cavity was kept for more than 600 hours.

View full abstract

In recent, transport of electrically charged micro/nanoparticles in electrolyte solution has been widely studied. Some difficulties in accurate control techniques, however, have to be solved. For deeper understanding of the transport mechanism, the motion of particles should be divided into electrophoresis, electroosmosis, and electrohydrodynamic (EHD) flows. In this study, we experimentally observe ion transport phenomena that modulate the behavior of microparticles. Especially, by using ion-exchange membranes, highly polarized electrolyte solutions are prepared to make clear the transition of electrokinetic and hydrodynamic phenomena. In such a solution, cations, which highly concentrate around negatively charged microparticles, drag solvent molecules and drive liquid flows under externally applied electric fields. As a result, observed motions of charged particles gradually change from electrophoretic transport to EHD flows.

View full abstract

The scattering behavior of water molecules on silicon(100) surface was investigated by the molecular beam experiment and molecular dynamics (MD) simulation. We changed the incident energy between 35 and 130 meV which corresponds to the energy of thermal motion of gas molecules at the room temperature, and measured the scattering distribution and the mean translational energy of scattered molecules in each scattering angle. The experimental results indicated that the scattering distribution was diffusive and close to that of the cosine scattering due to the roughness of the silicon surface when the incident energy was 130 meV. Generally, incident molecules would accommodate with a surface when the incident energy is low. That is because the incident molecules would interact with atoms on surface longer. However, when the incident energy was 35 meV, the scattering distribution had a directivity toward a certain angle close to the specular reflection angle. In order to investigate the reason of this directivity, we are analyzing the motion of water molecules on the silicon surface using MD method.

View full abstract

Along with the development of micro- and nano-technologies, gas-surface interaction becomes important due to large surface area-to-volume ratio in micro-scale gas flows. In such flows, the Knudsen number (Kn) is often employed as a parameter of rarefaction of flows. When 0.01<Kn≦0.1, a flow is classified as the slip flow with a finite velocity slip at boundary. In this regime, the mass flow rate increases from the rate in the continuum regime because of the velocity slip. The mass flow rate depends on the combination of molecule and surface. In this study, we measured the mass flow rate of water molecules to investigate the characteristics on gas properties. The constant-volume technique was employed for measuring the mass flow rate through a micro channel. The obtained results suggested that the adsorption of water molecules on the measurement system influenced the accurate measurement of the mass flow rate.

View full abstract

Electrolydrodynamic (EHD) flow is known as a flow generated by external electric force. However, it requires at least tens of volts of applied electric potential to generate EHD flows. In our previous study, we successfully generated an EHD flow by applying a low voltage of 2.2 V by using a novel device that separated pass ways of both anion and cation via an anion-exchange membrane with a small pore. In this study, effects of the cross-sectional area of anion-exchange membrane are investigated by electrical measurements. Potential differences between both ends of a pore are measured for three different sizes of the membrane. As a result, the conductance of anion is improved and on the other hand, the resistance decrease in the pore causes to weaken EHD flows.

View full abstract

Gas flow in porous media is used in industrial processes such as dissociation reaction, desiccation, adsorption and reduction reaction. It is important to understand flow phenomena in porous media for improving of performance of devices including such processes. However, gas flow in nanoscale porous media is cannot treated as a continuum and the flow property is not yet clear. In this study, we analyzed the nanoscale gas flow in the porous media by using the DSMC simulations and proposed the model predicting the velocity of gas flow.

View full abstract

In this study, the performance of Knudsen pump which works by the use of thermal induced flow was studied experimentally. The driven force of the pump system presented in this study is thermal edge flow around laminated plates which one surface is black and the other is white. The thermal induced flow is generated by irradiating the infrared lamp to the laminated plates. The system was placed in a glass pipe which was connected to two vessels and irradiated by infrared. It was observed that the pressure ratio of the high pressure vessel and low pressure vessel was about 96% when the temperature difference between the black and white surfaces of the plates were about 40 degrees in the centigrade scale.

View full abstract

The aim of this study is to investigate the relation between the slip velocity at the gas-liquid interface and the rarefaction. We carried out the numerical simulation of the steady shear flow between the liquid slab and the solid wall with changing Knudsen number based on mean field kinetic theory. The simulation results showed that the slip velocity at the gas-liquid interface increases with the increase of Knudsen number. On the other hand, the slip velocity at the gas-solid interface is smaller than that at the gas-liquid interface in all cases of Knudsen number.

View full abstract

On the basis of the molecular gas dynamics analysis, we investigated the influence of non-condensable gas on non-equilibrium vapor condensation induced by reflected shock wave. In the present study, the governing parameters of this problem are initial number density ratio (ratio of the number density of non-condensable gas to that of vapor) and condensation coefficient including in the boundary condition for vapor molecules at vapor-liquid interface. From the present results, it is clarified that the condensation mass flux of vapor is affected by the non-condensable gas near the interface just after the instance when the shock wave reflects at the interface. Furthermore, as the initial number density ratio become larger, the condensation mass flux of vapor is suppressed more strongly, and also the condensation mass flux is not affected by the value of condensation coefficient.

View full abstract

The objective of this research is to clarify the condensation process of water droplets on nanostructured surfaces by means of the sequential visualization of droplets using an environmental scanning electron microscope (ESEM). So far, we observed the condensation process of submicron-scale droplets on silicon (100) surface, where the contact angle of millimeter-sized droplets is around 60°-70°. During visualization measurements, the pressure of water vapor inside the ESEM chamber and the temperature of the sample stage were 700 Pa and 1.2 ℃, respectively. We found that the condensation growth of a submicron-sized droplet is classified into two modes. In the first mode, the contact angle of individual droplets is smaller than the macroscopic contact angle (600-700), which is the contact angle observed for millimeter-sized droplets, and increases linearly with time until reaching the macroscopic contact angle. In the second mode, which starts after the contact angle reaches the macroscopic contact angle, the base diameter increases with time while the contact angle remains constant.

View full abstract

The collapse and rebound of a single spherical bubble with phase changes at the vapor-iquid interface are fundamental physical phenomena in the fields of industry and medicine. In this study, we propose a mathematical model of describing the dynamics of a spherical vapor bubble with phase changes (evaporation and condensation) at the vapor-liquid interface. To deal with evaporation and condensation phenomena at the interface precisely, we utilize the boundary condition of the interface derived from the molecular gas dynamics analysis. The calculation results of the mathematical model show that the maximum pressure inside a bubble due to the bubble collapse with phase changes becomes higher than that of the bubble collapse without phase changes.

View full abstract

Recently, application of hydrogen energy has been expanded. For more safe and efficient use of hydrogen, study of bubble nucleation in liquid hydrogen is necessary. Various studies already have reported the quantum nature effects on thermodynamic and transport properties. Therefore, it is expected that quantum nature also influences bubble nucleation. We reproduced quantum liquid hydrogen using path integral centroid Molecular Dynamics (MD) method and also simulated virtual classical liquid hydrogen with classical MD. First, we compared the energy barrier for bubble nucleation and the critical bubble size using Classical Nucleation Theory. Next, we investigated quantity of void in both fluids with local density function. In consequence, it is suggested that quantum nature affects bubble nucleation, and quantum hydrogen is difficult to create a bubble nucleus than classical hydrogen.

View full abstract

Nucleation and growth processes of cavitation bubble in water are simulated by molecular dynamics (MD) method. The water molecule is approximated by a particle with Lennard-Jones potential. The simulated model consists of a cube shaped decompression MD cell under periodic boundary condition. The gas and liquid phases are defined by number density. The growth process of cavitation babbles is visualized by the number density as a continuous quantity which is converted from the molecular configuration as a discrete quantity.

View full abstract

Mass transport in ordered structures of a liquid which are formed in the vicinity of a solid-liquid interface exhibits decidedly different characteristics from the ordinary diffusion. Using the PMF (potential of mean force) profile obtained from the number density of liquid molecules, the kinetic process model to describe the molecular mobility inside these ordered structures was developed in this study. From the result obtained from molecular dynamics (MD) simulations, it was found that the developed kinetic model can accurately predict the molecular mobility over the free energy barrier.

View full abstract