High power generating cost is an important problem in a sustainable energy. In order to reduce the cost for the power generation, passive power control using elastic turbine blade made of composites is adopted. In this study, the performance evaluation system with fluid-structure interaction analysis and water tank tests has been developed to design the passive power control property and evaluate its performance. First, we made rigid blade models and elastic blade models to compare the calculated deformation by fluid-structure interaction analysis. The deformation of blade is measured by a noncontact optical stereo camera. Consequently we confirmed that we can predict the deformation with fluid-structure interaction analysis. By using some numerical optimization methods, we try to design elastic turbine blade in actual sea condition.

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We have developed the sewage sludge drying and pelletizing process that transforms sewage into low water content (less than 10%) and spherical pellet. This report introduces the description of the sewage sludge drying and pelletizing process, quality of dried sludge pellets, the basic results of the co-firing test of dried sludge pellets with coal in pulverized coal-fired furnace and municipal solid waste incinerator. It is concluded that dried sludge pellets had low water content and about 1/2～2/3 of heat value of coal. Also, co-firing of dried pellet results in good operation in pulverized coal-fired furnace and municipal solid waste incinerator.

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In this study, a continuation high-impact pulverizing vibration mill, which replaces the ball medium with a ring shape medium called tandem ring was developed for effective pretreatment of lignocellulosic biomass to produce the bio-ethanol. The pulverizing effects of the mill were investigated through a repeatedly pulverizing examination of Japanese cedarwood on its particle size distribution, moisture content and enzymatic saccharification efficiency. As the results, average particle size was reached around 22μm at the ten times pulverization at 1600cpm. An enzymatic saccharification efficiency of holocellulose was reached over 50% at the twenty times pulverization. Additionally its power consumption was one-third as large as the conventional the batch-type high-impact pulverizing vibration mill. Therefore the continuation high-impact pulverizing vibration mill had a better pulverizing performance for lignocellulosic biomass pretreatment.

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Bio-ethanol production from Japanese cedarwood using an enzyme and yeast cells was investigated. Japanese cedarwood was pulverized into powder by a high impact-pulverizing mill called inner power ring mill. The enzymatic saccharification examinations were carried out on solids concentrations of 13.5, 18, 22.5 and 27w/v% using acetic buffer solution of 200ml, a powder pulverized into 20μm in average diameter and an enzyme dosage of 5wt% per solids of powder. Ethanol fermentations with three fermentation states as fermentation without residual solids, fermentation with residual solids and simultaneous saccharification and fermentation (SSF) were carried out by yeast of Saccharomyces cerevisiae on the enzymatic saccharification liquid. As the results, the bio-ethanol yield of SSF was reached a high yield in a short time in this study.

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Autoignition and combustion characteristics of biomass gas and city gas 13A mixed fuels in a HCCI engine were investigated. A mock biomass gases consisting of H₂, CH₄, CO, N₂ and CO₂ were used assuming woody pyrolysis gases. Using a modified gas engine with high compression ratio pistons and an inlet air heating system, experiments were carried out. Influences of mixing ratio of two fuels on heat release and indicated thermal efficiency were investigated. Higher city gas 13A content make maximum value of rate of heat release lower at a constant equivalence ratio and a constant IMEP. The mixed fuel obtains higher indicated thermal efficiency and lower cyclic variation than biomass gas or city gas 13A only. Effects of H₂ and CO contents of biomass gas were also investigated. It is clarified that H₂ has a big influence on rate of heat release but CO does not.

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Supposing the design of ethanol steam-reforming reactors, the authors conduct experiments for Cu/ZnO/Al₂O₃ catalyst. Using a household-use-scale reactor with well-controlled temperature distributions, the authors compare experimental results with chemical-equilibrium theories. It has revealed by Shinoki et al. (2011) that Cu/ZnO/Al₂O₃ catalyst shows rather high performance with high hydrogen concentration C_H2 at low values of reaction temperature T_R. So, in the present study, the authors reveal the influences of liquid-hourly space velocity LHSV upon concentrations such as C_H2, C_CO2, C_CO and C_CH4 and the influence of LHSV upon the ethanol conversion X_C2H5OH, in a range of LHSV from 0.05 h^-1 to 0.8 h^-1, at S/C = 3.0 and T_R = 520 K. And, the authors reveal the influences of the thermal profile upon C_H2, C_CO2, C_CO, C_CH4 and X_C2H5OH, for several LHSV's. To conclude, with well-controlled temperatures, the reformed gas can be close to the theory.

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The authors develop a small and simple steam-reforming reactor in a home-use size for n-dodecane as a heavy-hydrocarbons fuel. Under the thermal condition controlled by electric heaters and a gas burner with a thermal diffuser, the authors measure the inside-temperature profile and the hydrogen-molecule ratio (concentration) R_H2, together with the molecule ratios R_CH4, R_CO and R_CO2 of other main gas components such as CH₄, CO and CO₂, respectively. As a result, the authors successfully achieve suitable inside-temperature profiles. And, the effects of the liquid-hourly space velocity LHSV and of the temperature T inside the reactor upon the molecule ratios are revealed, as well as the LHSV effect upon the conversion ratio. The comparison with the thermal-equilibrium theory indicates that the temperature at the catalyst-layer-bed downstream end could be regarded as the reaction temperature.

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Microgrid is noticed as the system that can reduce CO₂ emission from residence area. Microgrid can absorbs the fluctuation of electricity power which might be originated with several kinds of renewable energy, therefore it doesn't negatively affect the stability of utility grid. In addition, microgrid has a capability to control the heat-and-power ratio in demand and supply by optimizing the combination of several kinds of high efficiency residential devices in the area. However, here are few researches on this optimum combination of the eco-system devices. Therefore in this report, microgrid was evaluated in consideration for regional characteristics; those are 12 kinds of demand patterns and 3 kinds of electricity CO₂ emission coefficient. As a result of analysis, the region that has high heat-to-power ratio, large demand, and large capacity of photovoltaics makes much advantage of microgrid relating to CO₂ emission reduction.

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For the global warming prevention, attention has been paid to the renewable energy, such as heat pump, solar energy and so on. The heat pump with the low global warming potential (GWP) refrigerant is more needed, while the heat pump with currently much used refrigerant, such as R410A, contributes to the global warming prevention. The carbon dioxide (CO₂) refrigerant is one of the low GWP refrigerants. But, it has the problem with low refrigerating performance on physical properties. To solve it, we have investigated the ABSorption/CO₂ compression hybrid heat pump. In hybrid heat pump, efficiency of the CO₂ heat pump is improved by ABSorption heat pump that uses solar thermal energy for heat source. In this paper, the constitution of hybrid heat pump system and the downsizing of ABSorber are presented in detail. It is obtained through calculation that the volume of ABSorber is decreased by 30% than original one after downsizing process, which will be verified by experiment afterward.

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This paper reports application study of newly developed turbo heat pump for 130 °C water for an industrial process in an actual factory. The heat pump is characterized by high efficiency and large heat output, by using a state-of-the-art turbo compressor. The heat pump requires a low temperature heat source. The heat demand is for several drying furnaces in the factory, which requires producing hot air of 120 °C. The heat exchanger was designed to produce the hot air. Experiments were conducted to confirm the performance of the heat exchanger with a reduced size of the heat exchanger. Low temperature heat sources are from both exhaust gas of the drying and annealing furnaces. The heat exchangers were also designed to recover heat of the exhaust gas. As a result, it was confirmed that the heat pump was able to satisfy the present heat demand while retaining high efficiency.

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A cascade thermoacoustic engine that can lower the critical onset temperature was suggested recently. It has been reported that critical onset temperature was successfully lowered with multistage amplification. However, a cascade thermoacoustic engine that uses multiple regenerators needs installation of regenerators not only at the peak of acoustic impedance distribution in real part, and therefore is generally inefficient. In this report, we calculated the configuration of the cascade-type double-loop thermoacoustic refrigerator, and then calculated the temperature ratio of the refrigerator and its efficiency when the temperature ratio of the prime mover is changed. The cascade-type double-loop thermoacoustic refrigerator realized oscillation atΔT=159.5K, which is equivalent to industrial exhaust heat, and the entire apparatus showed 11% of Carnot efficiency. The result shows that low temperature drive and high efficiency can both be achieved with a cascade thermoacoustic engine.

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Laser beam welding is one of the jointing processes by irradiating laser beam on the material surface locally and widely used at various industrial fields. Toshiba has developed various laser-based maintenance and repair technologies and already applied them to several existing nuclear power plants. Laser cladding is a technique to weld the corrosion resistant metal onto a substrate surface by feeding filler wire to improve the corrosion resistance. Temper-bead welding is the heat input process to provide the desired microstructure properties of welded low alloy steels without post weld heat treatment, by inducing proper heat cycle during laser welding. Both laser welding technologies would be performed underwater by blowing the shielding gas for creating the local dry area. In this report, some evaluation results of material characteristics by temper-bead welding to target at Reactor Coolant System nozzle of PWR are presented.

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In order to evaluate the effects of flow field on flow accelerated corrosion (FAC), the flow field downstream from a globe valve was measured using laser Doppler velocimetry (LDV) and particle image velocimetry (PIV) and was simulated by unsteady RANS (URANS). The globe valve was a cage guided type and a column between cage windows was placed perpendicular to the flow direction. The diameter of a downstream pipe was 50 mm, and mean cross-sectional velocity was about 2 to 6 m/s. Swirl flow with twin vortices was visualized by PIV and simulated by CFD in the cross section downstream from the globe valve. The flow-directional velocity profiles measured by LDV and simulated by URANS under different velocity conditions coincided with each other when profiles were normalized by the mean velocity. It indicated flow structure downstream from the globe valve did not depend on the flow velocity. Predicted wall shear stress and turbulent kinetic energy adjacent to the wall were higher on the lower wall than those on the upper wall.

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Flow Accelerated Corrosion (FAC) is one of the issues to be noticed considerably in plant piping management. For the integrity and safety of the plant, the wall-thinning and thinning rate due to FAC should be clearly predicted in pipe wall inspection. In this paper, we study FAC from the view point of flow dynamics. The mass transfer coefficient is measured by the electrochemical method behind the orifice. Changing the orifice size, the peak location of mass transfer coefficient and its maximum value is evaluated by the flow condition and orifice parameter. The future problems are briefly summarized.

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Nuclear energy is fascinating on various points: enormous amount of energy, securing fuels, possibility of solving the global warming, etc. However, it's known that using nuclear energy involves dangerous and safety of nuclear power plant (NPP) is required. Study about NPP safety has been conducted by many researchers. In addition, concern for NPP safety has increased in resent years because of happening of some NPP accidents and newly establishment of NPP. In this paper, detection method of core abnormal phenomena is considered. They are: construction of this method, sensitivity analysis of transient phenomena, and examination for the validity of this method. Transient phenomena dealt with this study are: (A) small break and leak, (B) change in feedwater flow rate, (C) loss of feedwater heating. As a result, this method shows some validity to (B) and (C) but doesn't show to (A).

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In the design study for Japan Sodium-Cooled Fast Reactor (JSFR), fully natural circulation system is adopted as the decay heat removal system. We have been developing a new evaluation method of core hot spot in transition from rated operation to natural circulation decay heat removal conditions. Since the method is currently based on conservative assumptions and data, there is room for further rationalization of the safety margin which can be achieved by conducting best estimate analyses with confidence and with quantified uncertainty of results. This paper describes a development of PIRT (Phenomena Identification and Ranking Table) for JSFR under natural circulation decay heat removal operations and the sensitivity analyses of the uncertainties in the event of loss of external power as the first step to improve the core hot spot evaluation method.

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An analysis of JOYO MK-II natural circulation test has been performed to evaluate the applicability of the fast reactor plant dynamics code super-COPD to natural circulation decay heat removal phenomena. The analysis domain is set from the reactor core to the intermediate heat exchanger (IHX) so as to focus on the simulation accuracy of natural circulation behavior in the primary system and we compared the numerical results with experimental measurement. The inlet coolant temperature and the flow rate at the secondary side of IHX were the boundary conditions and the measured data were provided. As a result, it was found that natural circulation behavior is much influenced by the coolant mixing regime in the upper plenum of the reactor vessel. The predicted transient changes of the core outlet coolant temperature and the primary flow rate showed good agreement with the test results by using a variable mesh partitioning method and by setting appropriate mixing volume in the upper plenum region which can include the effect of thermal stratification phenomena on the natural circulation behavior.

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There are a lot of earthquakes in Japan. For this reason, it is very important to evaluate the soundness of piping of a nuclear power plant for adequate safety of seismic design. Additionally, piping in nuclear power plant confronts the effect of aging. The object of this study is to clarify relations between damping characteristics of piping and several conditions of pipe. In this study, thickness of pipe test, support type test, damaged pipe test and double pipe-filled glass bead test were conducted with impact system. The results obtained through the study are as follows; (1)Pipe thickness and support type contribute to the damping characteristics of pipe.(2)Damaged pipe don't affect the damping, but the frequency of pipe decrease as damage grew. (3)Double co-axial pipe has high damping ratio. Especially, the damping ratio when glass bead are filled between the inner pipe and outer pipe is about 10%.

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For the purpose of elucidating the mechanism of the sodium-water surface reaction in a steam generator of sodium-cooled fast reactors, kinetic study of the sodium (Na)-sodium hydroxide (NaOH) reaction has been carried out by using Differential Thermal Analysis (DTA) technique. The parameters, including melting points of Na and NaOH, phase transition temperature of NaOH, Na-NaOH reaction temperature, and decomposition temperature of sodium hydride (NaH) have been identified from DTA curves. Based on the measured reaction temperature, rate constant of sodium monoxide (Na₂O) generation was obtained. Thermal analysis results indicated that Na₂O generation at the secondary overall reaction should be considered during the sodium-water reaction.

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In a sodium-cooled fast reactor (SFR), liquid sodium is used as a heat transfer fluid because of its excellent heat transport capability. On the other hand, it has strong chemical reactivity with water vapor. One of the design basis accidents of the SFR is the water leakage into the liquid sodium flow by a breach of heat transfer tubes. This process ends up damages on the heat transport equipment in the SFR. Therefore, the study on sodium-water chemical reactions is of paramount importance for security reasons. This study aims to clarify the sodium-water reaction mechanisms using an elementary reaction analysis. A quasi one-dimensional flame model is applied to a sodium-water counter-flow reaction field. The analysis contains 25 elementary reactions, which consist of 17 H₂-O₂ and 8 Na-H₂O reactions. Temperature and species concentrations in the counter-flow reaction field were measured using laser diagnostics such as LIF and CARS. The main reaction in the experimental conditions is Na+H₂O→NaOH+H, and OH is produced by H₂O+H→H₂+OH. It was demonstrated that the reaction model in this study well explains the structure of the sodium-water counter-flow diffusion flame.

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High temperature measurement system is presented. This system employs the ultrasonic buffer rod and pulsed Doppler method. The buffer rod has a cooling jacket to use the high efficiency room temperature transducer. For considering ultrasonic velocimetry method in the molten borosilicate glass, the temperature dependency of sound velocity at the temperature of 1000°C to 1200°C is obtained using cross-correlation technique, and its difference is within plus-minus 5%. A numerical simulation is also applied to design the optimised buffer rod, and its result shows good agreement with an experiment. Using this technique, the velocity, especially the speed of relative moving wall is obtained, and its error is within plus-minus 4% when a value remained in measurable velocity.

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The purpose of the present study is to reveal the influence of CO₂ hydrate on the flow of liquid CO₂ injected in a packed bed as simulating seabed. In order to reveal the influence of CO₂ hydrate, differential pressure and temperature are measured under both condition of CO₂ hydrate generation and no-generation. As the result, under the condition of the hydrate generation, differential pressure at the inlet of the packed bed become large compared with that under the condition of no-generation. As a result of estimating the amount of the hydrate, it is suggested that the amount of the hydrate decreased with the increase in the flow rate. Friction factor is also estimated. As the result, in the upstream part of the packed bed, the difference of the friction factor between the hydrate generation and no-generation condition become small with increase of Reynolds number.

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In order to realize of CO₂ ocean sequestration, it is important to reveal the knowledge of CO₂ hydrate film thickness which forms on the interface between CO₂ and water. However, knowledge of CO₂ hydrate film thickness under various parameter conditions such as temperature, flow velocity on CO₂ hydrate film, and elapsed time from hydrate formation is little. The objective of the present study is to investigate the influence of temperature and flow velocity on CO₂ hydrate film thickness. CO₂ hydrate film thickness is measured under differential temperature and flow velocity conditions. In this study, CO₂ hydrate film thickness is measured with laser interference method. And, CO₂ hydrate film thickness is estimated based on duality of CO₂ saturated solubility under CO₂ hydrate formation condition. As the result, the measured CO₂ hydrate film thickness decrease with increase in temperature and flow velocity. And, the estimated CO₂ hydrate film thickness denotes the same tendency of measured CO₂ hydrate film thickness.

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We have invented a new power-saving device for ship drag reduction using microbubbles in order to reduce CO₂ emissions from ships. The new device, which consists of angled hydrofoils with air introducers, has been installed on a coaster and helps achieving ～10% net power saving. This device utilizes a low-pressure region produced above the hydrofoil as the ship moves forward, which drives atmospheric air into the water. Emissions can be reduced by about 87 million CO₂ ton/year if international shipping uses this new device, with 10% net-power reduction. We present the principal and optimization of this device on the basis of laboratory experiments on hydrofoils moving close to a free surface. In particular, we discuss free surface deformation and entrainment process using hydrofoils.

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Progressive ultrasonic waves cause acoustic streaming in a liquid. Although theoretical and experimental studies on acoustic streaming for liquid phase have been carried out, the acoustic streaming for a solid-liquid mixture dose not seems to be investigated. The purpose of this study is to clarify the velocity distribution of acoustic streaming in a solid-liquid mixture. An ultrasonic wave with a frequency of 485 kHz was irradiated on tap water or tap water with aluminum particles in a cylindrical container with a diameter of 120 mm whose orientation was kept horizontal; the acoustic streaming velocities were measured with the irradiation time of ultrasonic wave, particle concentration, and particle shape as the parameters. The followings were obtained: (a) The higher the particle concentration is, the faster the acoustic streaming velocity of solid-liquid mixture becomes; (b) When ultrasonic waves were irradiated on a liquid with heavier solid particles, the acoustic streaming velocity of the solid-liquid mixture decreases with irradiation time to a certain extent.

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The three-dimensional (3-D) density distribution of unsteady flow field was observed by using Laser Interferometiric Computed Tomography (LICT) measurement. A diaphragmless shock tube was used to produce shock waves with high reproducibility. In our previous study, density distribution of flow field was reconstructed by ART (Algebraic Reconstruction Technique). In this paper Hybrid ART is applied to LICT measurement to reduce the artifact of reconstructed image. In our case, a computational fluid dynamics (CFD) simulation is applied to the 3-D flow fields as a CFD. Hybrid ART is the combination of CFD and ART. The reconstructed 3-D density distribution from CFD is used as the initial condition of ART. As the results reconstructed images by Hybrid ART are compared with ART, together with the precise discussion. In reconstruction results by Hybrid ART, it is confirmed influence of the density distribution interpolated initial distribution.

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A pulsating turbulent pipe flow has been experimentally examined for the energy saving. The rotating speed of a centrifugal pump was periodically changed for generating the pulsating flow. The cycle-averaged friction Reynolds number is set to be 110 for comparison with the previous data of direct numerical simulation (DNS) by Sasou et al.⁽¹⁶⁾. In the acceleration period, the drag reduction rate increases with decreasing the amplitude of the mean pressure gradient in the acceleration phase with the longer acceleration period. As for the deceleration period, the drag reduction rate increases with larger negative mean pressure gradient in the deceleration period with the shorter deceleration period. The maximum cycle-averaged energy saving and drag reduction rates are respectively 58% and 63% when the cycle period normalized by the friction velocity and the radius is 10 and the mean pressure gradients in the acceleration and deceleration phases are respectively 4.1 and -0.93 times as large as the cycle-averaged pressure gradient.

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We experimentally investigate the unstable behavior of a large scale hollow-type streamwise vortex which has a solid-rotation type distribution of vorticity existing only in an annular region initially, focusing on how the large scale vortex breaks down into small scales downstream. With increasing the intensity of the initial vorticity, the large scale hollow vortex undergoes significant transition from a steady-state to nonlinear stages governed by coherent vortices through the primary linear instability. When the periodic motions due to the primary instability grow and redistribute the vorticity, a rotating vorticity field of polygonal shape begins to develop. This is an important precursor to the nonlinear evolution of the instability of hollow-type streamwise vortex. The flow structures we obtained in this work allow the fluid mixing to be significantly enhanced even under low Reynolds numbers. The present study also shows that the ratio of maximum azimuthal velocity to mean axial velocity is important as a governing flow-similarity parameter. This finding is reasonable as the cited swirl velocity ratio is directly proportional to the ratio of vortex Reynolds number to axial flow Reynolds number.

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The characteristics of a two-dimensional turbulent jet in the flapping motion are investigated by simultaneously measuring the velocity and pressure. The simultaneous measurements are performed by using a combined probe that consists of an X-type hot-wire probe and a static pressure tube. The measurement data are analyzed by using a conditional sampling technique and the ensemble-averaging technique, on the basis of an intermittency function. This function is used to determine whether the jet is in the flapping motion or not. The measurement results of two hot-wire probes set in the self-preserving region of the jet are analyzed by performing a wavelet transform. The experimental results show that the ensemble-averaged velocity field during the flapping motion shows a good agreement with the measurement result obtained by Sakai, et al. (2006) through multi-point simultaneous measurement of velocity. Further, the ensemble-averaged static pressure field during the flapping motion indicates the pressure of a vortex coherent structure, interpreted as a combination of flapping and puffing motions in the self-preserving region of the jet. In addition, the estimation of the turbulent energy budget shows that the turbulent energy production and its transportation from the inner region to the outer region of the jet by the diffusion are enhanced during the flapping motion. In particular, this enhancement of the turbulent energy transportation is caused by the combination of the increasing of the turbulent diffusion to the outer region of the jet and the decreasing of the pressure diffusion to the inner region of the jet.

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The simultaneous measurement of the velocity and pressure in a plane jet has been performed by using a combined probe that consists of an X-type hot-wire probe and a static pressure probe. Firstly, the conditional ensemble averaged statics are investigated on the basis of the intermittency function obtained from the velocity signal by the hot-wire sensor set in the intermittent region of a plane jet. Secondly, the validity of the models for a turbulent and pressure diffusion term is investigated. The measurement results show that the cross-streamwise profile of the diffusion term in the turbulent energy transport equation differs significantly, according to the state of the flow (turbulent or non-turbulent flow) in the intermittent region. By decomposing the diffusion term into two terms, i.e., the turbulent diffusion term and the pressure diffusion term and estimating each term separately, it is found that the cross-streamwise profile of the pressure diffusion term is virtually the same, irrespective of the state of the flow in the intermittent region. This indicates that the difference in the cross-steramwise profile of the diffusion term is cause by the difference in the turbulent diffusion term. In addition, the evaluation of the two kinds of gradient diffusion models of the Reynolds stress transport equation shows that the model constants become constant and the validity of these models can be confirmed except for the region near the jet centerline and intermittent region. Finally, it is shown that both slow-part and rapid-part of the velocity-pressure correlation term must be modeled appropriately to predict the velocity-pressure correlation correctly.

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The internal flow and noise-generating mechanism in a muliti-blade fan were investigated by using a computational fluid dynamics analysis. Additionally, particle image velocimetry was used to interrogate the passing flow between the blades in order to validate the computational flow fields. The results of computational fluid dynamics show that a large static pressure fluctuation was taken place near the leading edge on suction side of z/b=0.5. It was confirmed that this region was a boundary which was constituted between the main flow near the hub and vortical flow near the shroud and the flow near this boundary was very unstable. Furthermore, a sound pressure level between 400～700Hz was high in this region. The near-field downstream of the leading edge at suction side showed a high correlation each other. So, it is concluded that this region was seemed to be a strong noise source. Comparing the flow pattern and the static pressure fluctuation, it was found that a pulsating inflow into the blades induced the aerodynamics noise.

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CFD simulations were performed for the leakage flow in the gap between the casing and the shroud of a centrifugal impeller. The effects of swirl brakes equipped in the casing on the leakage flow were numerically investigated. The leakage flow swirling due to impeller rotation was trapped inside swirl brakes and interacted with the walls of the swirl brake, generating a very complex flow and a vortex structure inside. By the interaction with swirl brakes, the leakage flow rapidly lost its angular momentum mainly in the outer region of the swirl brake. The loss of swirl resulted in a decrease of the pressure difference in the radial direction due to the centrifugal force effect. The radial distribution of pressure in the gap between the casing and the shroud was largely modified, and thus the axial thrust force on the impeller was changed as well. The thrust balance of the impeller can be adjusted by an appropriate design of swirl brakes and the instability of rotating shaft can be reduced by decreasing the swirl of the leakage flow.

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Dynamic response of the fluid force acting on an axially oscillating balance piston was numerically investigated. The balance piston of a rocket engine turbopump was modeled and forced to oscillate in the axial direction. The flow field around the rotor was simulated using unsteady CFD simulation changing the oscillation frequency. By using the simulation results, the fluid force acting on the balance piston was found to be described by the equation of motion with the additional mass, the additional damping coefficient, and the additional stiffness coefficient. From the analysis of these coefficients, the fluid force on the balance piston in the present model was also found to work to stabilize for the axial oscillation.

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In recent years, pollution of the water in eutrophic lakes and marshes become an important problem. To improve this situation, we developed the water purification system by using the wind energy. In the present system, the Savonius wind turbine with the guide vane was used and the micro bubble was generated by this wind turbine to purify the quality of water. The most important characteristic of this system is to possess the wind energy conservation apparatus. That is, the wind was converted into the water pressure by using the accumulator to make the most use of the weak wind energy. To clarify the effectiveness of the present system, the field test was carried out. Test results showed that the micro-bubble was generated intermittently even in relatively low wind velocity condition, and the generation frequency of the micro-bubble was in proportion to the cube of the wind velocity.

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Direct numerical simulation was performed for air turbulent flows and heat transfer in a channel with square ribs attached to one wall. The spatially advancing cases and the fully advanced cases were both treated for the bulk Reynolds number of about 4,560. The rib height, H, was kept constant at 0.2 times the channel half-width, whereas the rib pitch was changed from Pi = 2H to 16H. The heat transfer performance was evaluated using the ratio between the mean Nusselt number of the ribbed case and that of the smooth case requiring the same pumping power. This ratio was maximized at Pi/H = 9 for the fully advanced cases, but at Pi/H = 2 or 4 for the advancing cases. The mechanisms leading to this difference were discussed through turbulence statistics and their visualization. The thin thermal boundary layer in the advancing region was shown to increase heat transfer on the extended surface of Pi/H = 2 and 4, resulting the higher heat transfer performance than the case of sparse ribs.

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The linear stability is studied for the Bénard-Marangoni convection in a diamagnetic liquid layer sustained by surface tension around a cylinder in the absence of gravitational force. A surface of the cylinder is kept at a constant temperature while a liquid surface is heated or cooled. An azimuthal magnetic field generated by an electric current through the central axis of the cylinder is considered. A combined convection takes place owing to the radial magnetic buoyancy force as well as the Marangoni effect acting at the liquid surface. It is shown that the convection of diamagnetic liquid can be enhanced or suppressed by the use of magnetic field.

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Polymer nanocomposites are one of the most promising applications of carbon nanotubes (CNTs). In order to improve their thermal properties, it is important to understand their heat conduction characteristics from a microscopic viewpoint. In this study, we have investigated the heat conduction of CNT/polyethylene composites by using molecular dynamics simulations. We particularly focused on the thermal boundary conductance across CNT/polyethylene interfaces and thermal conductivity of CNT in polyethylene matrix, which govern the overall thermal conductivity of CNT/polyethylene composites. We found relatively low thermal boundary conductance across CNT/polyethylene interfaces (～10 MWm^-2K^-1) and a moderate but non-negligible thermal conductivity reduction of CNT in polyethylene matrix (22 %). By the mode-dependent phonon transport analysis, the thermal conductivity reduction was identified to be mainly due to scattering of low frequency CNT phonons by polyethylene. The results obtained through an effective medium approximation model give overall thermal conductivity of the CNT/polyethylene composite that is in agreement with experiments.

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Oxygen molecule (O₂) in a flame is a critical molecule for the formation and oxidation processes of polycyclic aromatic hydrocarbon (PAHs) and particulate matter (PM). Then, it is important to know a spatial distribution of O₂ concentration in a flame. In this study, a laser-induced O₂ fluorescence technique was proposed. Oxygen molecule concentration was obtained with O₂-LIF signal from O₂ molecule excited by an ArF excimer laser. Excitation wavelength for maximizing O₂-LIF signal from a flame was optimized experimentally. Relationship of O₂ concentration regarding O₂-LIF signal and flame temperature was derived from a calibration experiment using hot air thermometry. In order to validate the technique, a spatial distribution of O₂ concentration in a propane diffusion flame was measured by the present technique and an oxygen analyzer via a gas sampling. Oxygen molecule concentration obtained with O₂-LIF technique showed good correlation as compared with that of oxygen analyzer measurement.

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Numerical calculation based on large eddy simulation was carried out to investigate mixture formation process in a spray formed by injecting n-heptane into a constant volume vessel under high-temperature and high-pressure conditions. Liquid phase of fuel was described by discrete droplet model. The results show that the shape of spray is similar to that of visualized image and spray tip penetration corresponds well to experimental results. In addition, distributions of fuel concentration and local non-homogeneous distribution were discussed by comparing the calculation results with the mixture distributions measured using planer laser induced fluorescence technique. The local distributions were well described except around downstream spray boundary. Calculations were also carried out for lower injection pressure condition and smaller nozzle orifice diameter condition. Although fuel concentration in a spray does not quantitatively reproduce the experimental results, the effects of the injection conditions qualitatively agreed with the experiments. Furthermore, ignition and combustion processes were investigated using Schreiber's model for calculating the progress of oxidation reactions.

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The cellulosic liquefaction fuel (CLF) was made from woods by the direct liquefaction process. Coconuts-oil Methyl Ester (CME) of 5 wt.% was used to mix CLF and diesel fuel, because CLF was not completely mixed with diesel fuel. To clarify a desirable CLF fraction for the diesel engine, CLF was divided into two fractions by the distillation: 200 to 250 °C (CLF1) and 250 to 300 °C (CLF2). The weight mixing ratio of CLF in blended fuel was varied until 20 wt.% to analyze ignition characteristics and performance of diesel fuel-CLF-CME blends. The brake thermal efficiency of both CLF mixed fuel was almost equal to diesel fuel, however high NOx was emitted at a high load. This is because the combustion gas temperature was increased by a rapid combustion pressure rise. The smoke concentration of CLF mixed fuel was lower than that of diesel fuel. When CLF1 or CLF2 is mixed with diesel fuel by using 5 wt% of CME and the weight mixing ratio of CLF is up to 20 wt%, CLF mixed fuels have almost no influence on engine performance. For both CLF1 and CLF2 mixed fuel, it is possible to operate diesel engine without any remarkable deterioration of engine performance. When 5 wt.% CLF was mixed to diesel fuel with CME, diesel engine could be continuously operating for 8 hours without any deterioration. The ignition timing of CLF1 mixed fuel was slightly earlier than that of CLF2 at any mixing ratios, therefore CLF1 was suitable for diesel engine.

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In recent years, there has been a demand for the development of a high-efficient heat exchanger for the purpose of saving energy and resources. A two-phase closed thermosyphon is a heat exchanging device which operates with no external power in a closed system and transports a large heat amount with a very small temperature difference between the ends of the pipe. Therefore, a thermosyphon is extremely effective at solving energy and environmental problems. In this study, the heat transfer characteristics of the dropwise condensed thermosyphon and the influence of condensation forms on the heat transfer characteristics is theoretically investigated. As a result, the change ratio of the heat transfer characteristics of the thermosyphon by the difference of the condensation form was able to be estimated by this proposed theoretical calculation method.

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Micro grid system is attracting attention from the viewpoint of reduction of CO2 emission. Micro grid is composed of uncontrollable fluctuating power generation (e.g. photovoltaics and wind power generation) and controllable power generation (e.g. fuel-cell cogeneration system and gas engine cogeneration system). Micro grid can complement the variation in power from photovoltaics. And micro grid can raise the operating rate of co-generation system because of transmitting electricity between consumers mutually. However, operating rate of co-generation system is cut when photovoltaics are installed on micro grid system on a large scale. Hence we installed heat pump water heater on micro grid to adjust the electricity demands. We used a simulation to determine the reduction of CO2 emission at micro grid. In the simulation, we changed conditions: number of co-generation system, heat pump water heater and capacity of photovoltaics. We observed that micro grid has the optimal component ratio of cogeneration system and heat pump water heater.

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A high-temperature wide-range humidity sensor has been developed using wetted material temperature measurement. A porous ceramic is used as a sensing element; it has a small tube for supplying water to maintain a wetted surface. However, the water supplied to the elements can affect the surface temperature. In this study, we experimentally investigate the accuracy of the developed sensor and its contributing factors-convective heat transfer, evaporation, radiant heat, and the water supplied to the wetted material-under the conditions of a gas flow temperature of 200 °C, gas flow velocity of 3 or 5 m/s, flow rate of supplied water of 0.01-0.05 g/s, and steam mole fraction of 0.03-1.00. Further, we calculate the heat flux and the surface temperature using a one-dimensional heat transfer model to clarify the effects of the each of the abovementioned factors. Consequently, we conclude that the supplied water strongly affects the accuracy of the developed sensor. We also improve the measurement error of the steam mole fraction from 0.07 to 0.03 by the controlling the flow rate of the supplied water.

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This paper describes a calculation method of moisture flow discharge coefficient for designing wet-steam turbines. The flow discharge coefficient in wet-steam conditions is different from that in dry-steam conditions, because the former is affected by supersaturation phenomenon and wetness fraction. An accurate prediction of the flow discharge coefficient is required for flow-pattern design in turbine stages. The developed calculation method is divided four models according to the wetness levels in the nozzle & bucket rows, and defined by the functions of wet-steam properties, such as saturated & supersaturated isentropic exponents, wetness fraction, and pressure ratio in the nozzle & bucket rows. The calculation method is applied to a full-size & a model test turbine data for the prediction of the moisture flow discharge coefficient. As a result, the developed calculation method is found to be very effective for estimating the moisture flow discharge coefficient in a wide range of wetness fractions.

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