The squeal generation mechanism in disk brakes is clarified by measuring the stiffness between the disk and pad in the contact region (contact stiffness) and performing an analysis using the surface contact analysis model. The results of a squeal test using a squeal testing machine with a simple structure show that the squeal frequency becomes higher as the thrust pressure for braking becomes larger. Since we thought that the contact stiffness depends on the thrust pressure and influences the squeal frequency because the vibration characteristics of the disk do not change with thrust pressure, we measured the contact stiffness under squeal generating conditions. The pad was given constant pressure and excitation force generated by random noise with the squeal bandwidth. Measurement results show that the contact stiffness depends on the thrust pressure and is different for each pad. To clarify the influence of contact stiffness on squeal, the disk-pad-caliper system was analyzed by using the surface contact analysis model, which connects the disk with the pad via distributed springs (contact stiffness). The analytical results show that squeal is easily generated and its frequency easily changes when the dependence of contact stiffness on thrust pressure is large.

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A hot-water supply system was constructed to utilize wasted heat of an air-conditioning system with HFC134a refrigerant. A desuperheater was equipped ahead of the condenser of an air-conditioning machine to extract thermal energy of compressed high-temperature refrigerant. HFC134a was selected as refrigerant because its pressure was relatively lower at higher temperature. The required refrigerant charge was investigated and performance of the air conditioning system with/without a desuperheater was compared to assess the effect of installing a desuperheater. It was concluded that the required refrigerant charge increased by installing a desuperheater, and that the ability of cooling heat exchange was similar for both with/without a desuperheater with required refrigerant charges. It was also shown that cooling COP decreased 15% by installing a desuperheater, because the work done by the compressor increased, but the overall energy efficiency including cooling and hot-water supply increased 34%.

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This paper deals with the radiated noise of strain wave gearing, which is a kind of K-H-V type planetary gears having features of light weight and high reduction ratio. The vibration of the Flex Spline (F/S), which is an element of strain wave gearing shaped like a thin circular cup, is considered to be a main cause of the noise. Theoretically, the magnitude of sound power is expected to increase in proportion to the square of the amplitude of the displacement of the F/S in the radial direction. The displacements in 3 models are calculated using FEM. The vibration of the F/S and the sound power are measured using the fixed-F/S experimental apparatus. It is confirmed that the relationship between the vibration of the F/S and the sound power agrees well with the theory, and that the vibration of the F/S is the main cause of radiated noise. Moreover, the radiated noise with various rotary speeds, loaded torques and assembly errors is measured and examined. The influences of rotary speed and torque are explained by the noise-generation mechanism on the basis of the velocity amplitude of the F/S. The noise becomes large with the increase of assembly error, but the amplitude of displacement is not increased. This is confirmed by the resonance between the F/S and experiment apparatus.

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In order to develop effective combustion and gasification system of waste plastics, thermal decomposition and combustion characteristics of plastics compounds containing flame retardant were investigated. Polypropylene (PP) with flame retardant, which was composed by Al(OH)₃ or (NH₄PO₃)_n, was decomposed in an image furnace. Mass reduction during thermal decomposition and combustion was measured by an electric micro-balance. The gas components produced by the thermal decomposition and combustion were analyzed with a gas analyzer. Soluble organic fraction (SOF) components in a condensable emission during the decomposition process were analyzed with a PM analyzer. SOF and solid carbon in the remains after the thermal decomposition were also analyzed by the PM analyzer. The oxygen concentration was changed from 0% to 21% and the content of flame retardant was changed from 0% to 50%. It was found that flame retardant had small effect on the thermal decomposition temperature. Gas components produced by thermal decomposition and combustion were changed corresponding to the content of flame retardant.

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In the development of vehicles such as automobiles, it has recently become increasingly important to consider not only flow dynamic performance but also aerodynamic noises produced while driving. To evaluate and reduce the surrounding aerodynamic noises, it is necessary to use closed-circuit-type 3/4 open-jet wind tunnels, which include a comparatively large open measuring section and are known as 3/4 open-jet aeroacoustic wind tunnels or simply 3/4 open-jet wind tunnels. In these wind tunnels the same wind conditions as those around vehicles being driven can be simulated. Because the open measuring section has a nozzle, a floor and a collector, each of which generates their own aerodynamic noises, their reduction is necessary to measure the aerodynamic noises around a vehicle without interference. On the other hand, because of the pressure loss in the open measuring section, a large and powerful fan is necessary to provide the large flow required for 3/4 open-jet wind tunnels used for actual vehicles. Therefore, the authors have distinguished differences between the techniques of reducing aerodynamic noises in 3/4 open-jet wind tunnels and those in conventional open-jet aeroacoustic wind tunnels and have newly investigated appropriate conditions for reducing both aerodynamic noises and total load in 3/4 open-jet wind tunnels by various techniques, such as the use of pile-fabric materials, entrainment systems and large collectors, on the basis of experimental data obtained from various models of wind tunnels. In this paper, the details of this investigation are described with explanations of the aerodynamic noise phenomena in 3/4 open-jet wind tunnels.

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Aeroacoustic wind tunnels, which consist of large measuring sections, such as anechoic rooms, and open jets, are generally applied as test facilities to measure aerodynamic noise generated around vehicles. In aeroacoustic wind tunnels, it is easy to generate flow-induced low-frequency fluctuations resulting in pressure fluctuations or velocity fluctuations associated with vortices or turbulence in the open jet. These low-frequency fluctuations are generated by various flow-induced phenomena, such as swaying that occurs in various elements of the circuit, fluctuations propagated from the shear layers or mixing layers of the open jet, and the acoustic resonances of the whole circuit, which often become serious problems, generally called pulsations, at particular wind speeds. Because these low-frequency fluctuations may affect the measured pressure and velocity of a flow around vehicles in measuring sections, we should aim to reduce or control them when designing aeroacoustic wind tunnels to ensure measurement with high reliability. In this study, we investigate the generating mechanisms and techniques for reducing these low-frequency fluctuations in aeroacoustic wind tunnels by performing experiments on a model wind tunnel. In particular, new techniques for reducing acoustic resonance components such as by installing an acoustic opening in the circuit are proposed and verified by simulations and experiments. Using these techniques for reducing low-frequency fluctuations, the fluctuations of pressure and velocity in the measuring section are markedly decreased over the entire wind speed range.

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In this paper, the numerical simulation of flows in Lake Biwa with real configuration is presented in order to predict the large circulating currents. The effects of flow rate of inflow rivers and thermal convection on the large circulating currents are investigated. The observational flow rate and temperature data of inflow rivers are considered. First, the simulation of 2D epilimnion model is carried out, so that the results show that the large circulating currents are sensitive to the flow rate of inflow rivers. Next, the 3D flows with real configuration are simulated. The numerical results without thermal effect show that the precise large circulating currents are formed in summer, but the large circulating currents develop until winter. Finally, the 3D simulation with thermal convection is carried out. As a result, the horizontal circulating currents become larger than the simulation without thermal effect in summer, and the vertical circulating currents are formed in winter. Therefore, the present numerical simulation with thermal convection can reproduce the actual circulating currents in Lake Biwa qualitatively.

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Some ceiling-mounted ventilators have a sound-attenuating function due to the resonant effect that takes place within a chamber that consists of a rectangular outer cover and a cylindrical fan unit. In order to control the resonant properties in a reactive manner and maximize the sound-attenuation effect of this resonant system, the chamber is separated by a partial shutting plate, called a "separator," located at the end of an inner cylinder—modeling a fan unit—into two spaces that are expected to approximate a Helmholtz resonator with two degrees of freedom. Variations in resonant properties are shown, experimentally obtained by modulating the dimension of the separator. In this model, the second resonance frequency can be widely changed depending on the clearance between the two spaces, without attenuation of the resonant effect. This is meaningful because the second resonance frequency can be shifted into a frequency range that corresponds to the main component of the radiated sound from an actual ventilator. In addition, it is indicated that the resonance frequencies can be approximated by a simple analytical approximation. Furthermore, detailed considerations of sound fields of relatively delicate models concerned are provided using numerical calculation (BEM) and the effectiveness of the chamber is summarized.

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Environmental chamber is widely used for testing the performance of the equipment with all kinds of natural ambient parameters. In this study, water droplet generated from ultrasonic humidifier is ascertained by laser diffraction measurement technology. The accurate droplet size and distribution is offered to CFD simulation as the initial condition. Humidity distribution with different initial conditions is studied by both experiment and CFD simulation. Comparisons show that the proposed CFD method can provide reliable results in simulation on the humidity distribution. The numerical and experimental results indicate that as the increase of inlet temperature, fluctuation of relative humidity (RH) at each point decrease with the time. Under the inlet condition with low-humidity, the deviation of average RH is decrease with inlet temperature. On the other hand, under the high-humidity condition, the difference of average RH is getting larger with the increase of inlet temperature. Compared with the mean value, the fluctuation of the humidity is big but the RH at measuring points is close to the inlet RH value under the inlet condition with low humidity.

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The influence of gas diffusion layer (GDL) design parameters on the performance of a polymer electrolyte fuel cell (PEFC) was evaluated using a test apparatus in which the clamp pressure on the cell could be accurately controlled. The PEFC performance varies significantly depending on the humidity of the supplied gas. Under moderate humidity, the PEFC performance is enhanced when using an untreated GDL with high air permeability. Under high humidity, improved performance is achieved using a GDL with PTFE hydrophobic treatment. A microporous layer (MPL) coated GDL significantly reduces flooding on the electrode, resulting in a decrease in the concentration overpotential. This enhances the PEFC performance at high current densities. A substrate with high air permeability for the MPL coated GDL enhances the ability of the MPL to prevent flooding. Under low humidity, the MPL is also effective to prevent drying-up of the membrane electrode assembly (MEA), resulting in enhanced performance. A substrate with low air permeability for the MPL coated GDL is effective for the prevention of drying-up.

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Human voices originate from the vibration of vocal folds in the larynx. In most previous studies on voice generation, a planar sound source was assumed for a laryngeal sound source and the effects of airflow in a larynx were neglected. However, no direct in vivo measurement of human glottal velocity has been reported. Therefore, detailed study of this airflow is necessary to elucidate mechanisms of human phonation. In the present study, airflow just above the glottis was experimentally analyzed to clarify the phonation mechanism and seek better modeling of vocal folds. This experiment focused on direct measurement of the airflow velocity by means of a tiny hot-wire probe and simultaneous observation of vocal fold movement by means of a high-speed digital camera. Experimental results show that the periodic change in the airflow velocity occurs out of phase with the opening of the glottis, although both have the same fundamental frequency. This is important because it provides crucial information to create better simulation models of the phonation mechanism.

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The proposed technology is a new concept that aims at energy-efficient drying and cleanup for general purposes by the use of liquefied DME (dimethyl ether) gas. Large amounts of energy are required for the cleanup of the ground since the water contained in the soil hinders the extraction processes that use hydrophobic organic solvents. Therefore, we focus on the use of liquiefied DME, which is eco-friendly, as an extractant. The saturated pressure of DME is moderate—0.51 MPa at 20°C and 0.68 MPa at 30°C. Liquefied DME resolves high volume organic contaminants and water. Moreover, water can be easily separated from DME by flash distillation. This technology reduces the energy required for water-removal to half the latent heat of water. We almost completely removed water and other oily materials by using DME. DME was completely recycled and none of it remained in these materials. The world's first prototype of a DME deoiling/dewatering process is shown. The capacity of this system is 10 L. Because of the low normal boiling point (-25°C) of DME, it does not remain in the soil and it can thus be reused as an extractant. In this presentation, we show the general purpose deoiling and dewatering processes for several materials.

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Authors have been proposing a new type of sewage pump impeller designed to further improve pump efficiency and performance in passing foreign bodies. And pump performance, internal flow and behavior of the radial thrust have been clarified by LDV measurement and CFD analysis. However, hydraulic design of pumps is integral calculus operation whereas flow analysis is differential calculus operation. Therefore, even if complicated internal flow was clarified by CFD analysis, it is difficult to improve pump performance if the cause and outbreak mechanism of each hydraulic loss were not clarified. This paper proposes loss analytical method of this pump equipped with a single blade impeller. As a result of having compared experimental values and CFD analysis values with loss analysis values about the head curve, they almost matched in a wide range of flow rates. When the flow flows backward to the impeller from the volute casing, the hydraulic loss becomes small in an appearance, but the power loss becomes excessive and the pump efficiency decreases.

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This paper describes fundamental characteristics of a small organic Rankine cycle (ORC) system to be used for power generation from low temperature heat sources such as waste heat and solar energy. The aim of the study was to develop an ORC system with a small power output of less than 1 kW with a hot source with temperature ranging from 60 to 100°C and a cold source with temperature ranging from 10 to 30°C. An ORC system with a potential to produce a turbine/expander power of 250 W was built and its fundamental characteristics were elucidated. A turbine/expander was not actually installed but was simulated by controlling two expansion valves. First, steady-state energy balance of the system was examined and the required turbine/expander efficiency was estimated in consideration of pump power of the working fluid. Then, the relationship between the expansion ratio and thermal efficiency was elucidated. The most important result of the study was that for maintaining high thermal efficiency in the case that the temperature difference between hot and cold sources varies during operation, it is indispensable to employ a variable expansion mechanism by which the expansion ratio of the turbine/expander can be adjusted to fit the optimal ratio at the operating temperature level.

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This study focuses on gasification technology of carbonaceous materials in molten carbonates since this gasifier can gasify those fuels catalytically and in-situ clean up the gasified gas at high temperature simultaneously. This gasification system has such advantages that alkali metal compounds have catalytic function for the gasification reactions, the molten alkali compounds can absorb sulfur compounds and the molten media can capture ash and un-reacted particles produced. The molten carbonate employed in this study is an eutectic salt with the compositions of 43 mol% Na₂CO₃ and 57 mol% K₂CO₃. CO₂ is selected as a gasification agent. Before the gasification experiments, the optimum gasification and desulfurization temperature is evaluated by the chemical equilibrium calculations. Fundamental gasification and desulfurization experiments were conducted, by using an electrically heated reactor. As a result, the main compositions of the gasified gas are CO, H₂ and CH₄. H₂S and COS gases in the product can be absorbed almost completely by the molten alkali carbonates. These results suggest that this gasifier can gasify the carbonaceous materials and desulfurize even at high temperature inside the furnace simultaneously.

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Hydrogen has a potential alternative to conventional hydrocarbon fuels, because no carbon dioxides (CO₂) is emitted from hydrogen combustion and it is able to make hydrogen by an electrolysis of water as renewable energy resources are used. This study aims to obtain stable auto-ignition and combustion of hydrogen when hydrogen is applied to a direct-injection compression ignition engine. In this study, influences of various ambient conditions such as temperatures, coexistence species etc. on auto-ignition and combustion behaviors of hydrogen jets were investigated with a rapid compression and expansion machine (RCEM). To be able to obtain the stable auto-ignition of hydrogen, in this study, first an ambient temperature in the cylinder of RCEM was raised by adding argon (Ar) gas, which has low specific heat capacity, and secondly the temperature was raised through chemical reactions of a little of di-methyl ether (DME), which was added into intake gas before the start of compression stroke. And effects of intermediates generated during the chemical reactions with DME on auto-ignition of hydrogen jet were also evaluated by both chemical kinetic analysis and experimental investigation.

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The present study was conducted as part of a series of R&D of gasification and reforming technologies aimed at creating a new energy recovery technology from biomass waste. Special emphasis was placed on the production of hydrogen-rich synthesis gas from waste wood via gasification and sequential reforming technology using catalysts. Experiments were conducted employing three types of commercially available nickel-based steam reforming catalysts. Waste wood was supplied as the raw material and the reactor temperature was set at 1023 K (750°C). The results obtained were as follows: (1) Hydrogen generation can be significantly promoted by using nickel catalysts in the reforming process, as well as by supplying steam directly to the gasification process. (2) Nickel catalysts were also found to reduce the quantities of tar and toxic materials deleterious to gas utilization, such as hydrogen sulfide. (3) A nickel catalyst containing CaO was verified to exhibit superior catalytic performance, with the synthesis gas having a maximum hydrogen content of 57vol% and the lowest tar level converted from the wood material when the catalyst was utilized at 1023 K.

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The identification of external force acting on a machine or a structure is important for the diagnosis. One of the force identification methods is based on the frequency response function. The method is very useful although it requires the knowledge of location of force acting. In this study, an identification method is proposed for the case of unknown excitation points. The method is firstly the external forces, whose amount is same as the one of sensors, are assumed at every candidate location, and the amplitudes of forces are identified. Then the exact location of external force is determined by the classification of all identified results. The method is numerically checked and it was shown that the method was useful using the data with noise. Moreover the experimental results showed that the method was feasible when the location and amplitude are separately identified.

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This paper verifies the representation of power input and subsystem energy in terms of modal density of subsystems in Statistical Energy Analysis (SEA) by means of FEM calculations. First, vibration response in the modal form is used to derive the representations. It is shown that the utilization of values averaged over space and frequency for the power input and the subsystem energy of the subsystem can be represented in terms of the modal density. Furthermore, the coupling loss factor between plate subsystems is also analytically estimated by using the wave theory and is determined on the basis of the modal density. In order to verify these representations, FEM calculations are performed to compare subsystem energies, power inputs and coupling loss factors of three types of structures with different subsystem shapes and the same modal densities. The estimations obtained with analytical SEA are also compared with the FEM calculation results.

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Recently, the use of the wind turbine generator has rapidly spread as the one of the clean energy resources, and its size is becoming larger. Because of the difficulty of the maintenance of such a large wind turbine generator, the vibration analysis and clarification of the dynamical characteristics of the wind turbine generator are important. However, the conventional researches aimed at the fluid engineering in order to gain higher efficiency, and only several investigations have been reported in the area of the vibration analysis and its suppression. The wind turbine is a special type of rotating machinery: It has a long heavy blade which rotates in the vertical plane under the action of the gravitational force, and the wind power acting on the wind turbine blade varies periodically because the wind power increases as the function of the height. Therefore, it requires the original point of view in the dynamical analysis. This paper investigates the fundamental vibration characteristic of the wind turbine blade by using a rigid blade model. The gravitational force causes the effect of parametric excitation on the blade system. The interaction effect of the gravitational force and the wind force on the vibration of the turbine blade is investigated, and the occurrence of super-harmonic resonance is clarified. Also, the occurrences of the unstable vibration ranges are indicated. Furthermore, these results are validated experimentally.

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