In this study, TiO₂ nanotube arrays were prepared by anodization. The photocatalytic activity was measured. The influence of diameter and length of the TiO₂ nanotubes on the activity was discussed. The activity relates with the length, and the activity increases with the length to 9 μm. The reduction treatment in carbon powder was performed for TiO₂ nanotube arrays. The activity was enhanced and visible light response of TiO₂ nanotube arrays was obtained by the reduction treatment.

In this study, TiO₂/TiC and TiO₂ photocatalyst balls were prepared by MCT and heat treatment in carbon powder or in air. TiO₂/TiC photocatalyst balls have photocatalytic activity under UV light and visible light irradiation. However, TiO₂ photocatalyst balls have photocatalytic activity only under UV light. A measuring the water splitting experimental setup was proposed. The set-up is very simple and can measure the volume of the generated gas from water splitting by photocatalysts. TiO₂/TiC photocatalyst balls have water splitting activity.

Normally, lubrication in linear motion guides is performed by spreading the lubricant over the entire load area by means of rolling elements supplied with lubricant during long strokes. However, during small strokes, the rolling elements cannot pass through the end plates at both ends of the carriage, so the lubricant cannot be supplied to the entire load area, which leads to wear and fatigue of the rolling elements. Therefore, the gap between the carriage and the rails can be utilized. By enlarging the gap by machining and adding porous material, we thought we could supply lubricant to the entire load area even during small strokes. For the experiment, the carriage was cut in half and a porous material was installed. As a result, it was found that the larger the rotation angle, the better the diffusivity, and the larger the number of rolling elements to be fed, the easier it was to supply grease to the entire load area.

The purpose of this study is to investigate the effect of the kinematic viscosity of the lubricating oil on the load-carrying characteristics of the bush chain. In the previous study, the lubricating oil was penetrated in the bush chain at the room temperature. In this case, the lubricant may not enough penetration in the friction surface. Therefore, in this study, heating the lubricating oil reduced the kinematic viscosity, making it easier for the lubricant to penetrate the bush chain. Then comparing with the previous study, we found the following; (1) In the case of lubricating oil was heated, since the penetration amount increased due to the heating lubricant, the experimental results showed that the bulk temperature rise decreased. (2) The coefficient of friction for bush chain were estimated via Matsumoto’s formula, it is necessary to obtain f_L and f_S considering real contact condition between pin and bush.

Nowadays, the small generators are widely used as a primary power supply to protect family health care and infrastructure while the cut-off happens at extreme weather or disasters. However, the stabilizing fuel supply is a problem under that situation. It is urgency to looking for renewable substitute fuel. From these viewpoints, this study focused on the exhaust characteristics of small power generation engines with alternative fuel as alcohol fuel and investigated the influence of water addition ratio in ethanol aqueous on engine performance and emission characteristics.

In recent years, to realize a sustainable society, internal combustion engines are required to reduce carbon dioxide emissions by using new energy such as hydrogen and artificial methane fuel, and to improve the efficiency of existing engines. As one of the improvement methods of the latter, the authors have been studying the multi-stage impinging injection method, which is a combination of multi-stage injection and impinging spray. The multi-stage impinging injection method is a method in which fuel is injected in multiple stages from two facing fuel nozzles. By using this method, it is possible to reduce unburned components due to spray collision in the center of the combustion chamber and to improve combustion by promoting pre-evaporation by early injection before ignition. It has been suggested that combustion can be improved by the accelerating effect ^{(1), (2), (3)}. In this study, as the next step, to improve the combustion improvement effect of the impinging injection method, we investigated the influence of pre-evaporation and fuel properties due to changing the impinging injection timing on combustion characteristics.

A spectroscope is used to measure emission intensity for each wavelength in Laser-Induced Breakdown Spectroscopy (LIBS), therefore its measurement system is large. However Laser-Induced Plasma Spectroscopy (LIPS) can measure distributions of concentration and temperature of the atoms and molecules by taking the plasma images only through optical filters. In this study, emission spectra from H, O atoms and CN, C₂ molecules were calculated and these concentration and temperature measurements by LIPS were simulated from the calculated spectra.

Recently, hydrogen has been attracting attention in the field of shipping from the viewpoint of global warming prevention and environmental protection. Liquified hydrogen, which is one of the hydrogen storage methods, has high transportation efficiency and is suitable for use in ships. On the other hand, boil-off gas (BOG) from liquified hydrogen is generated and leads to unstable for system operation due to the large temperature difference with the outside air, and it is an issue that needs to be addressed. To come up with an effective method for dealing with the problem, the use of metal hydrides (MH) for fuel cell system, which can reversibly adsorb and desorb hydrogen, can be a solution to this problem when the ship is stationary or cruising. However, the system operation of fuel cell ship driven by liquified hydrogen as power source has not been reported so far. Therefore, this study aims at clarifying the dynamic characteristics of the liquid hydrogen supply system using MH. In this paper, we conduct numerical simulations using mathematical models of the system components to evaluate the system response on load variation of fuel cell. As a result, it is revealed that the fuel supply system can be operated stably against the load variation by suggested control system.

The objective of this study is to find the optimum operating time for a double effect adsorption refrigeration cycle with adsorption heat recovery. Adsorption refrigerators are used to utilize low-temperature heat to produce cooling. In this study, an experimental equipment was made to examine the performance of the double effect scheme with adsorption heat recovery. Heat from the adsorbent FAM-Z02 is transferred to silica gel bed for the desorption process. The behavior of the cycle was observed experimentally which indicates the regeneration of the adsorbent worked successfully with the adsorption heat at the heat source temperature of 85℃. Furthermore, the effect of adsorption / desorption time on the cooling performance was investigated, which reveals there is an optimal time to maximize COP.

An increase of turbine blade loading by increasing blade turning angle is an effective method to improve the performance of a gas turbine, which also enables to reduce a gas turbine in size and weight. However, it inevitably intensifies the secondary flows due to the increase of pitchwise pressure gradient. The application of a fillet at the leading edge-endwall junction (LEF) is known to be effective for reducing the horseshoe vortex which is a predominant secondary flow. Since the pressure side-leg of the horseshoe vortex and the passage vortex have same sence of rotation and merge with each other, the LEF may also reduce the passage vortex. In this study, the LEF was applied to the ultra-highly loaded axial turbine linear cascade (UHLTC) with the allowable maximum turning angle of 160 degrees. The effectiveness of the LEF on the UHLTC was verified by performing the internal flow measurement and the oil flow visualization.

In this study, the influences of the shape of scroll passage on the flow behavior at the inlet of turbine rotor of turbocharger with the variable geometry system were investigated by using commercial CFD code. The computations were performed for the simplified model which is composed of the inlet duct, the scroll, the vaned nozzle and the exhaust pipe without the turbine rotor. The computed results clarified that the tongue and the overhang shapes of the scroll deteriorated the circumferential uniformities of the physical quantities such as the flow angle and the total pressure loss at the nozzle inlet. However, the nozzle vane installed in the nozzle passage improved the circumferential uniformity at the nozzle outlet by its straightening effect. Moreover, the overhang shape of the scroll increased the total pressure loss at the nozzle outlet due to the deflection of the main flow toward the hub side wall at the nozzle inlet.

Centrifugal pumps with semi-open impellers are indispensable for the cleaning process of electrical components such as semiconductors and printed circuit boards. To improve the productivity of these products, it is required to improve the head performance of these impellers. This report proposes five types of impellers with different blade outlet angles, clarifies the hydraulic loss by applying experiments and loss analysis methods based on the results of three-dimensional computational fluid dynamics for each head performance. As a result, it was clarified that the impeller with a blade outlet angle of 30[deg.] has a lift performance improved by 5[%] or more compared to the conventional design method. Furthermore, it was clarified that as the blade outlet angle increased, not only the other losses other than the friction loss of the volute casing increased, but also the total head increased.

In a centrifugal compressor which is a main component of turbocharger, instability phenomena such as surge and rotating stall occur at low flow rate conditions. These phenomena degrade the performance characteristics of compressor and may damage the compressor system. Nozzle injection system is one of the effective methods to suppress the instability phenomenon and composed of the injection nozzle and the bypass tube. A part of air compressed by the compressor is extracted from the scroll outlet and injected into the impeller inlet by the nozzle installed on the inner wall of suction pipe through the bypass tube. It has been already clarified that the most effective circumferential location of injection was located around the opposite side of the scroll tongue against the rotational axis of impeller. In this study, the effect of the increase of rotational speed on the effect of injection nozzle for the surge suppression was investigated in detail. The results showed that the increase of rotating speed enhanced the effectiveness of nozzle injection system and enlarged the effective circumferential region of the injection nozzle.

It was reported previously that applying unsteady Reynolds stress to the right-hand side of the equation of motion had the effect of delaying the divergence of the flow analysis in the circular tube. By changing the value of the Reynolds number to a small value in and around the cell where the value of the unsteady Reynolds stress term applied to the right side exceeded a certain value, the solution no longer diverged and a solution consistent with the conventional experimental results of circular tube turbulence was obtained. Therefore, tube turbulence could be calculated without the use of experimental knowledge.

Aerogels have recently been widely used as a capture medium for solid particles impacting at high velocity in space. In order to estimate impact conditions of the solid particles captured in aerogels, it is necessary to better understand physics of the collection mechanism inside the aerogel. In this study, the particle collection mechanism by aerogel was studied using a combination of numerical calculations and laboratory experiments. The relationship between the velocity and size of particles impacting on the aerogel and the length and diameter of the impact tracks created inside the aerogel was clarified. By assuming that the aerogel behaves fluidly during the particle impact, the track length is approximately proportional to the particle size and velocity in low to medium velocity regions which are below sound velocity of the aerogel. These results will be applied to estimate the impact conditions of solid particles that actually impact onto the aerogel at hypervelocity in space.

In recent years, the precision machines and mechanical parts have become more and more complicated, therefore, it is necessary to develop a cleaning technology for narrow area, that is environment friendly. In this study, the effect of the presence or absence of a narrow space on the cleaning effect experiments was clarified using two-dimensional and three-dimensional specimens with ultrasonic cleaning, microbubble-filled cleaning, and microbubble-filled cleaning combined with ultrasonic cleaning on the back and narrow space. The results showed that microbubble filling combined with ultrasonic cleaning in narrow area had an advantage over ultrasonic cleaning in that the amount of residual oil was higher, but the surface of the specimen was cleaned evenly.

In this research was performed an evaluated heat transport characteristic of simulated semiconductor heat flux conditions in thin plate type parallel tube heat transport device by using alcoholic solutions, in order to investigate the relationship between heat transport characteristics and internal fluid flow, it was conducted heat transfer experiment and internal flow visualization. As a result, heat input and heating location changes, the internal flow pattern changes, affecting the heated wall temperature.

Previous researches found that acoustic wave enhanced the adsorption speed of Silica gel by experiments and low frequency oscillating flow also would enhanced the adsorption speed by simulations. The objective of this study is to construct low frequency oscillating flow generator and to confirm the effect of low frequency oscillating flow on the adsorption. Two blowers are involved to create oscillating flow with reverse flow, which is necessary for the adsorption enhancement. The adsorption amount was measured with steady flow and with the oscillating flow. According to the results, it was observed that the oscillating flow increased the adsorption by 1.35 for the velocity amplitude ratio U*=4.7.

In this study, we focus on wet clutches, which are widely used in automobile transmissions, and compare the behavior of gas-liquid two-phase flow of oil and air between narrow flat plates simulating wet clutches by experiment and numerical analysis to clarify the mechanism of drag torque generation because of fluid friction caused by the increase in rotation speed between clutch plates. In the numerical analysis, the VOF (Volume of Fluid) method is used to track the gas-liquid two-phase interface, and the SST k-omega, which solves the two-equation RANS shear stress transport equation, is also used to incorporate turbulent flow phenomena. In this paper, the causal relationship between the vortex generation on the surface distribution and the drag torque will be rigorously checked. In addition, the behavior of the drag torque curve and the interface distribution at 50[℃] and 80[℃] were clarified by using temperature as a factor. As a result, the drag torque curve could not be reproduced perfectly, but it was found that the drag peak occurred earlier in the experiment than in the analysis at every 200 [rpm] of the rotation speed with and without temperature change. In addition, the downward slope in the gas-liquid two-phase region could be reproduced because the air mixture after the drag peak was well removed. In addition, it was found that when the interface was at 50[℃], the oil was cut cleanly from the periphery, while at 80[℃], the oil was cut in a spiral shape due to the decrease in oil viscosity, and air was mixed in.

Cavitation is a phenomenon that occurred due to ultrasonic vibration or when liquid go through a low-pressure section which induced the formation of vapor bubbles. Cavitation was a common phenomeon in a Venturi tube which were then utilized to generate microbubbles. These microbubbles were used in many industriess and research were done to find optimum parameters to produce them. However, most research focused on cavitation occurring in a single-phase flow. Therefore this study aim to investigate effects of cavitation on bubble breakup phenomena under multiphase flow condition for two different throat diameter. Flow inside the Venturi tube was observed and pressure for 17locations along the tube was recorded for different flow conditions. Cavitation number calculation and bubbles distribution results suggest that flow with lower cavitation number produce more bubbles but throat diameter play a bigger role although having slightly higher pressure loss.

In this experiment, single crystal sapphire and quartz glass are used for the heat transfer surface, and the liquid is cooled by a liquid jet with a two-dimensional temperature field fluctuation over time by a non-contact type temperature measurement using an infrared radiation thermometer and a high-speed video camera. We tried to measure the membrane behavior.In single crystal sapphire, the dependence of each liquid subcool degree on the MHF point temperature at the center of the superheated surface is qualitatively consistent with the value given by the Dhir-Purohit equation for each liquid flow velocity up to a liquid subcool degree of 20 K. In quartz glass, it was confirmed that the liquid subcooling degree of 40K has the strongest correlation with the Dhir-Purohit equation.The heat transfer coefficient of both single crystal sapphire and quartz glass improves as cooling progresses. At the same liquid flow rate at liquid subcool degrees of 10k, 20k, and 40k, the higher the liquid subcool degree, the better the heat transfer coefficient. At 10k, 20k, and 40k, the higher the liquid flow velocity, the better the heat transfer coefficient.The temperature at the tip of the liquid film when using quartz glass decreases as the liquid film progresses, and the liquid subcooling degrees 0K and 20K show close values. At 40K and 60K, the cooling water flow rate may affect the temperature at the tip of the liquid film.

The heat transport performance enhancement in a pulsating heat pipe (PHP) was experimentally evaluated using a microencapsulated phase change material (MEPCM; melting point 60 °C). In these experiments, a one-turn U-shaped PHP with a square channel formed on a copper plate was used as the test channel. Ethanol with and without MEPCM were used as the working fluid. The mass fraction of MEPCM particles dispersed in ethanol was 0.5 wt.%. Experiments were conducted for various heater input power, and the wall temperature distributions and the relationships between the heat transport rate and the wall temperature difference between the heating section and the cooling section (heat transfer characteristics) were obtained for the working fluids (ethanol with and without MEPCM). The results indicated that MEPCM in the working fluid can enhance the heat transport performance of PHP.

In recent years, the use of plant factories has been attracting attention as a type of agricultural form. There are two types of plant factories, artificial light type, and sunlight type. The sunlight type has the advantage of using the sun and other natural resources, which reduces costs. The author controls the Vapor Pressure Deficit (VPD) using the fog cooling system in sunlight type plant factory. This is because controlling VPD can promote plant growth. The current problem is that the control model of the fog cooling system has not been clarified. The sunlight type is controlled in a semi-closed environment, so it is difficult to clarify the control model by measurement. In addition, since it is practically impossible to understand and model all the conditions that affect the fog cooling effect, numerical methods are also difficult. Therefore, we propose a method to reveal the control model using data assimilation. Data assimilation is the statistical combination of observed values and numerical results to obtain more plausible values close to the true value. The purpose of this study was to investigate whether the fog cooling effect can be predicted under the assumed conditions by using data assimilation. If predictions can be made, the control model can be estimated using past observation data and numerical analysis. As a result, we were able to predict the fog cooling effect on days with meteorological conditions close to those on which the observed data were obtained.

Oscillatory flow through pipe can be an important cause in improving the heat transfer of fluids in a variety of engineering fields’ applications. For instance, improvement of cooling performance of electronic equipment is a highly desired problem. In this study, investigations of fluid dynamics of oscillatory flow at three values of low range frequencies (0.10 [Hz], 0.15 [Hz], 0.20 [Hz]) with three different oscillation amplitudes (39.9 [mm], 55.9 [mm], 89.9 [mm]) over narrow horizontal pipe is carried out experimentally. The purpose of this research is to investigate the effective thermal conductivity of the oscillatory flow in the horizontal pipe between the heat source and heat sink. Here, the heat transport performance produced inside the smooth pipes or so called dream pipes is calculated. At higher frequencies with great amplitudes, effective thermal conductivity usually enhances. In general, the increment and decrement in the heat transfer depended chiefly on the oscillation amplitude, oscillation frequency and temperature difference.

Effective cooling technologies are essential to use energy efficiently. Recent results of large eddy simulation by authors’ group has found that channel flow pulsation is effective for improvement of heat transfer performance on a channel wall with teardrop-shaped dimples. In this study, effects of flow pulsation on overall heat transfer performance over dimpled surface were experimentally investigated by transient technique with compensation of three-dimensional heat conduction. Seven different surface geometries were examined, by changing the angle of the dimples to the flow direction and dimple arrangement (inline and staggered). Strouhal number based on the dimple diameter of 0.15, pulsating flow amplitude of 10% and 15% of mean velocity, and bulk Reynolds number of 2.5×10⁴ were considered for the pulsating flow conditions. With flow pulsation, Nusselt number became 12.7% and 10% larger than that without pulsation for the cases of 30 deg and 60 deg inclined dimpled surface of inline arrangement respectively. However, friction coefficient became 86% and 67% larger than that without pulsation for the cases of 30 deg and 60 deg inclined dimpled surface respectively.

To realize Mo-99 production method using an accelerator, an optimal cooling design of gamma-ray converter is necessary. Generally, designers sample the design variables and calculate the temperature distribution by multiphysics analysis repeatedly to obtain an optimal design. However, this process takes high calculation cost to achieve the optimal result because of the increase in the number of finite elements and poor convergence. We have proposed more efficient design technique that divide the analysis model into upstream and midstream sections. First, the inlet boundary condition of the midstream section was optimized by response surface method, to find an optimal flow velocity distribution which minimize the maximum temperature of the converter. Second, the upstream section was designed to obtain the optimal flow velocity distribution. The results demonstrate that venturi structure can control the flow and efficiently cool the case section of the converter, which is the possible bottleneck.