A self-induced flip-flop flow phenomenon in diamond-shaped cylinder bundles has been disclosed in previous studies by the authors. The flip-flop flow oscillation promotes fluid mixing and thus contributes to an enhancement in convective heat and mass transfer when the cylinder bundles are used as heat and mass exchanger equipment. An experimental study was performed to disclose the occurrence of flip-flop flows in diamond-shaped cylinder bundles. Velocity and pressure fluctuations in divergent-flow region inside diamond-shaped cylinder bundles were measured by LDV and piezo-meter, respectively. The difference in the oscillations of flip-flop flows and von Karman vortex streets is disclosed quantitatively. The mechanisms that cause the reciprocating bubble migration in network ducts of diamond-shaped cylinders are explained.

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Wind turbines operate in strong wind conditions, which are generally irregular and unsteady. The previous paper reports a study on two wind turbine generator systems having different types of control methods at a site. It discusses the characteristics of these wind turbines with respect to their control methods by clarifying the relationship between wind parameters and various electric parameters under steady wind conditions. Wind behavior can change drastically, particularly in the transition of output power, for instance when a wind turbine starts up or stops. Therefore, understanding the transient behavior of various electric parameters is beneficial in comprehensively evaluating the performance of a wind turbine generator system. This paper further reports on the same two wind turbine generator systems. Their electric parameters when the output power of the turbines is changed are measured and their performances during their transient state are also discussed.

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Effective prevention from the leakage of Polychlorinated Biphenyls (PCBs) requires the rapid analysis with on-line detection, but conventional methods require extensive analytical time (several days per sample) and are thus unsuitable. The objective of the research reported here was to develop the Laser Ionization / Ion Trap Storage / Time of Flight Mass Spectrometry (LI-IT-TOFMS) capable of monitoring PCBs within 1 min/sample, as applied to exhaust gas and the atmosphere of the disposal work environment. The achievable PCBs sensitivity for on-line measurement was found to be in the pptV range (< 0.01 mg/m³_N) by means of comparison with conventional gas sampling and gas chromatograph - mass spectrometry (GC-MS). A satisfactory proportional relationship was confirmed between laser-based and conventional results for PCBs. We measured the exhaust gas in a PCBs treatment plant (hydrothermal decomposition and container treatment processes) by using the PCBs monitoring system, confirming that PCBs monitoring is possible without interference from either the main gas composition or minor coexisting substances. Accordingly, the LI-IT-TOFMS method is a useful method for the trace analysis of PCBs in exhaust gas.

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Based on an indication in the previous research that there is an ocean bacterium which can reduce iron red rust to magnetite extracellularly, it is attempted to develop a new recycling process employing such kind of bacteria. Two methods for producing very fine magnetite powder from red rust are presented by making up an artificial environment and shown to be successful. Bacteria participating in magnetite production are examined in detail, and are found to be microaerobic ammonia-oxidizing bacteria (coccus and bacillus), regarded as new types different from the GS-15 bacterium reported earlier. Their role is clarified and a mechanism of magnetite formation is presented.

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It is important to predict the environment around the breathing human because inhalation of virus (avian influenza, human influenza, SARS) is recently severe worldwide problem. And air pollution caused by diesel emission particle (DEP) and asbestos attracts a great deal of attention, and their restrictions are becoming tight. In the present study, three-dimensional numerical simulation is carried out to predict the gas-particulate two-phase flows around breathing human and how suspended particulate matter (SPM, diameter ∼ 1 μm) reaches the human nose in inhalation and exhalation using Lagrange approach for particle motion and k-ε model for flows. Our research is a unique dealing with micro particle motions. Such small particles have great ability to affect our health in some case. In the calculation, the authors find out the smaller breathing angle and the closer distance between human nose and pollutant region are effective in the inhalation of SPM.

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The mechanical deformation of a human fingertip pressed on a flat plate was numerically analyzed using a three-dimensional human fingertip model based on CT images of a human index finger. The fingertip model consisted of three components: the distal phalanx, the nail, and the soft tissue composed of skin and subcutaneous tissue. The analyses were performed for seven different values of Young's moduli in the range 34 to 200 kPa, and for five different values of Poisson's ratios in the range 0.3 to 0.5. The numerical results obtained were compared with reported experimental data for a human fingertip. The numerical results showed that the deformation around the nail and the distal fingertip was generated subsequent to the generation of a large deformation of the pulp. The numerical deformation results showed a similar pattern as the experimental data. Using the numerical results, we calculated the length of the contact area from the lateral view and the width of the contact area from the axial view in order to qualitatively estimate the deformation. By comparing the numerical and experimental results, we found that there were no unique values of Young's modulus and Poisson's ratio for expressing the experimental results. These results suggest that the epidermal, the dermal, and the fat tissue constituting the soft tissue may influence the mechanical deformation by different amounts.

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In this paper, experiments on the motion of a tethered system with large deformation and large displacement are discussed. A tethered subsatellite in space environment is a well-known example of this system. However, even fundamental experiments on the motion of the tethered system have not been conducted. Also, from the viewpoint of flexible multibody dynamics, it is expected that simple experiments for the motion of a very flexible body should be completed first in order to verify the validity of the proposed approach. In this study, the tethered system consists of a very flexible body and a rigid body. First, we conducted an experiment on the fundamental motion of a very flexible body with an attached mass in gravity space. We selected steel and rubber as tether materials. In the experimental results, the characteristics of the complex motion of a very flexible body were obtained. Second, an experiment in microgravity space was done. The coupled motion between the very flexible body and rigid body was investigated. It was verified that the motion of the system with large deformation is excited in microgravity space, and there is the coupling motion between the deflection of the very flexible body and the rotation of the rigid body.

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The lateral vibration of elevator ropes for high-rise buildings, which is forcibly excited by the displacement of the building induced by wind force, is numerically analyzed, and a new practical method of reducing rope vibration by using vibration suppressors is proposed for relaxing the restricted elevator operation. Finite difference analyses of rope vibration with/without vibration suppressors are performed. The advantage of using vibration suppressors for reducing lateral vibration of the rope is demonstrated through numerical calculation: The resonant position of a rope with vibration suppressors greatly depends on the position of the vibration suppressors. When the vibration suppressors are uniformly installed along the full length of the rope, the maximum rope deflection becomes smaller as the number of vibration suppressors is made greater. It is also shown that the calculated results of the reaction force from the vibration suppressor are in fairly good agreement with the experimental results.

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Elevator rope for high-rise buildings is forcibly excited by the displacement of the building induced by wind force. An exact solution to the forced vibration of a rope with time-varying length is presented, on the assumption that the rope tension and the moving velocity are constant, and that the damping coefficient of the rope is zero. Virtual sources of waves that can be assigned to reflecting waves are used for obtaining the exact solution. Finite difference analyses of rope vibration are also performed to verify the validity of this exact solution. The calculated results of the finite difference analyses are in fairly good agreement with the calculated results of the exact solution.

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Energy loss due to the wall skin friction in a turbomachinery impeller is directly related to the mechanical efficiency. Generally, the flow is modeled as a flow around an enclosed rotating disk, and we can estimate the energy loss of the impeller by applying the analytical or experimental results of the friction moment for a rotating disk. Several analytical and experimental studies have been performed in order to examine the friction moment and reduce the skin friction drag. The flow behavior of the boundary layer on the rotating disk surface is strongly affected by the vortices that are formed the spiral streak for the disk rotation stationary. In order to reduce the drag caused by disk friction, the behavior of the vortices in the boundary layer must be controlled. In the present study, the drag reduction phenomena of an enclosed rotating disk were clarified experimentally using a disk with several fine spiral grooves made by a wet etching process. Experiments were carried to measure the frictional moment of a disk having 120∼160 fine spiral grooves, the depths of which ranged from 100∼200 μm, in Newtonian fluids. The shape of the grooves was obtained by referring to spiral streaks in the boundary layer. The Reynolds number range is 4×10⁴ < Re < 6×10⁵. The maximum drag reduction ratio is approximately 15%, and the phenomena depend on the number, the spiral angle, and the depth of the grooves. The experimental results for the velocity profile and the flow visualization clarified that the fine spiral grooves control the secondary flow of the boundary layer on the disk surface and delays the generation of local turbulence in the transition range.

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In order to clarify the laminar drag reduction and the slip velocity on a hydrophobic surface, the pressure loss of a rectangular duct was measured while applying various types of wall surface qualities to the duct inner wall. Test wall surfaces were classified into three types according to surface characteristics, which were a hydrophobic coating surface, a fine rectangular groove surface, and a fine rectangular groove with a hydrophobic coating. The directions of the fine rectangular groove are parallel, vertical, and random in the flow direction, and the widths are 5 and 10 μm. For fine rectangular grooves with a hydrophobic coating surface, it was clarified that the laminar drag reduction occurred in the Reynolds number range of 150 < Re < 770. The maximum drag reduction ratio is approximately 13% at Re = 649. The Reynolds number range in which the drag reduction occurred increased with decreasing width of the groove, and the direction of the grooves did not affect the drag reduction effect.

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Helical compression mechanism is the newly developed one that can compress gas by using helical components. As helical shape has uneven pitch, the volume of each chamber becomes smaller along the rotation, and the gas is transferred and compressed continuously. This mechanism was designed in 1987, and the compressors with lubricant were developed and manufactured for refrigerators first in the world in 2000. And oil-less air compressors using helical mechanism were also developed and manufactured in 2003. This oil-less helical compressor doesn't contain oil at all. To achieve high performance and reliability in oil-less compressor, gas sealing, wear durability, and cooling are usually major problems, because contribution of oil to these functions can not be expected. This study focuses on the performance related to these problems, and investigates flow performance at variable motor speed, and compression process of oil-less helical compressor by measuring P-V diagram.

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Combustion characteristics of a prototype micro gas turbine combustor fueled by kerosene were investigated. In order to enhance a recirculation in a primary combustion zone, a swirler was set between the primary and secondary combustion zones. Primary combustion air was introduced through the swirler and forced to flow upward to the combustor bottom, from which the fuel spray was supplied through a nozzle. Fundamental combustion characteristics such as lean combustion limit, flame luminosity etc. showed that this prototype combustor had a high potential for lean combustion and wide flame holding. Since a strong forced recirculation flow was induced by the upward swirl, lean and non-luminous flame was maintained in the primary combustion zone. Further, burned gas recirculation and highly turbulent shear flow in the primary combustion zone, both of which were caused by the upward swirl, resulted in the low NOx emission characteristics.

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Recently a great deal of waste PET bottles has been accumulated in the stock yards without any processing. In the ceramic kiln industries, commercial grade LPG is generally employed as a gaseous fuel and used simply as a heat source. It is therefore very useful and necessary for replacing a part of gaseous LPG with an alternative fuel, such as PET-resin powder, from the view point of energy saving and low environmental impact. The proposed twin-fueled burner is then designed to burn PET-resin powder as an auxiliary fuel, while gaseous propane is employed as a main fuel. Some improvements are introduced to a commercial ceramic burner, in order to enable retro-fitting the proposed burner to various types of established burner systems. By taking into account of fusible properties of PET-powder, some auxiliary but indispensable devices are made to the construction and dimensions of the ceramic burner for preventing not only PET-powder from melting in the supply pipe, but also dissolved PET-resin from adhering to the burner wall. By varying the overall equivalence ratio under a constant combustion loading, combustion behaviors of the proposed ceramic burner are examined and analyzed experimentally, based on both optical observations of the flames and measurements of temperature and exhaust gas compositions at the exit of the model furnace.

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To burn plastic-resin powder as an auxiliary fuel and to realize clean and effective thermal recycling of a great deal of recycled plastic resin, fundamental elucidation of physical and chemical characteristics of a plastic-resin particle subjected to sudden heating is extremely important and necessary. In this case, it is indispensable to measure the temperature history in a micro plastic resin particle under abrupt heating and to get quantitative knowledge of its life time. However, the diameter of micro plastic particles is so small that measurement of the temperature history within it is found to be extremely difficult. In this paper, therefore, the spherically symmetric analysis is applied to the abrupt heating process of a micro spherical plastic resin particle. Variations of the temperature history and the life time with the ambient temperature and the initial particle diameter are numerically estimated, by dividing the entire heating process into four independent periods; the solid heating period, the melting period, the liquid heating period, and the thermal decomposition period. Effect of Nusselt number on the life time is also discussed.

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To examine the possibility of thermal recycling of waste PET bottles, a commercial LPG-fueled ceramic burner has been first improved to burn PET-resin powder as an auxiliary fuel and the combustion characteristics have been investigated by varying the median diameter and the mass flow rate of PET-powder. According to the results, the proposed burner realized reasonable combustion performance comparable to the original LPG-fueled ceramic burner, being reliable experimental certification to the possibility and availability of the proposed idea. The use of PET-resin powder as one of the alternative fuels in the ceramic kiln furnace was also found to be efficient from the viewpoint of saving energy resources and attaining low environmental impact. In this paper, under the fixed conditions of a total heat input of 11.6 kW and an overall equivalence ratio of 0.8, the combustion characteristics of the improved burner are experimentally investigated in the model furnace by varying the replacement rate and the mass median diameter of PET-powder. Brief qualitative discussion on the behavior of unburnt PET particles is also made by transforming the mass-based histograms to the profiles of particle number fraction of virtual spherical particles.

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Characteristics of a micro bubble generator using a strong swirl jet were studied experimentally and numerically. Experiments were conducted by changing the nozzle diameter, the inflow pressure and the gas flow rate, systematically. For measurements of the bubble distribution function of PDF, a simple method using a light transmission was proposed. Principle of the method was based on changes of the light transmission due to the bubble rising to the surface of water. The bubble distribution measured by the method agreed well with that by a usual backlight method. In this study four non-dimensional parameters governing the micro bubble generation were adopted, that is, Weber number for the average diameter of bubbles, Reynolds number, the ratio of flow rate and the velocity ratio for the swirl jet. It was found that the relationship between Weber number and Reynolds number could be arranged with each velocity ratio as a parameter. An approximate experimental expression for the average diameter showed that the micro bubble diameter strongly depended on the axial flow velocity and the rotational speed of the swirl jet.

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Low air-ratio combustion has become the major subject with enormous attention as a measure to reduce the amount of substances with environment impact from the waste incineration process, and to make the most effective use of energy. However, it has been thought that there would be considerable difficulty in utilizing low air-ratio combustion on the classic grate furnace due to fundamental problems in its process, which treats the wide range and heterogeneity of waste materials. The application of high temperature air combustion technology for enhancing sound combustibility provided solutions to these problems. In practice, a mixture of high-temperature air and flue gas is injected at high velocity from both sides of the furnace walls to form a stable high-temperature zone in the combustion initiation region above the waste. This prevents fluctuations or localized extinguishing of the flame, while heating the waste directly with the flame to promote gasification at the same time. A practical study was conducted at a 105-ton/day municipal solid waste stoker type incineration plant. The test demonstrated that stable low excess-air combustion operation is possible at a combustion air stoichiometry of 1.3 with EGR (Exhaust Gas Recirculation) and high temperature air combustion technology resulting in a 17% decrease in flue gas flow, an energy efficiency improvement of 10%, and more than 50% reduction in NOx emissions when compared with an air stoichiometry of 1.6.

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This paper describes the effect of a thin plate as a static controlling device to suppress cavity noise when it is inserted vertically into a cavity. Experiments using small and large wind tunnels are carried out to investigate the size effect of the cavity model. As a result, it is shown that there are two optimum plate locations for the noise reduction. One is near the upstream edge and the other is just in front of the downstream edge. By comparing the experiments at small and large wind tunnels, it is found that in the large wind tunnel, noise reduction is not so effective as in the small one.

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A questionnaire survey was conducted regarding two appliances, a vacuum cleaner and hairdryer, using the contingent valuation method to estimate the value added to products with improved sound quality. For each appliance, two machinery noises, one causing an unpleasant impression and one causing a pleasant impression were presented to participants based on the assumption that the former sound was emitted from the original product and the latter from a product with improved sound quality. The participants were asked how much extra they would pay for the improved product in addition to the price of the original product. The questionnaire items also included the personal attributes of each participant, including age, income, and having the experience of being distracted by the noises emitted from a vacuum cleaner or hairdryer. In addition, buying preferences were checked with respect to product performance, appearance, and price, etc. Logistic regression analysis was applied to the questionnaire results with the probability that participants would buy the product with improved sound quality as the dependent variable. The independent variables were the personal attributes and the amount of extra money that would be paid for the improved product. Results showed that the variables of price, with regard to the things considered before purchase, previous experience of being distracted by machinery noise, and the extra amount that would be paid were statistically significant. Furthermore, for both two appliances, the estimated added values of the improved sound quality were equivalent to 12% of the price of the original product.

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