LES (Large-eddy simulation) of swirling cold-flows in a pulverized coal combustion furnace is performed and validated by comparing with experiment and RANS (Reynolds-Averaged Navier-Stokes) simulation with the standard k-ε model. Unstructured grids and energy-conserving scheme are employed to obtain robust and accurate solutions at high swirl numbers. The results show that the LES is in good agreement with the experiment in terms of the recirculation flow, though the RANS simulation overestimates it. This is considered due to the capability of prediction of turbulent mixing. The effect of secondary and tertiary swirler vanes' angles on the behavior of the recirculation flow are also well predicted by the LES. The recirculation flow affects the flame stabilization and combustion efficiency related to the particle residence time in the furnace. It can be said, therefore, that the LES is strongly recommended for the accurate prediction of the strong swirling flows in such furnaces.

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We have been developing small-scale gasification and power generation systems utilizing solid wastes. These systems employ dual-fueled diesel engines, which do not accept condensable tar content in the produced fuel gas. This paper describes a newly developed measurement method for small amount of light-weight tar (light tar) content in the fuel gas in a short time which is appropriate for usage in commercial plants. Furthermore, by employing this measurement method, the technical feasibility of removal of the light tar content in the fuel gas was showed by utilizing sawdust filter or activated carbon filter in the laboratory scale experiment and in the commercial plant.

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This paper reports on the pyrolysis and CO₂-gasification of various biomass materials in a pressurized thermobalance. In particular, the primary yields of total volatiles, tar and non-condensable gases, together with the composition of non-condensable gases, are measured as a function of temperature at 1 atm and 10.8 ata. The use of a high-intensity infrared heating source, in conjunction with a non-absorbing carrier gas (viz. argon), is reported to reduce the significance of secondary gas-phase pyrolysis reactions. Linear trends with atomic H/C ratio are observed in the tar yield, CH₄ yield and total volatile yield during pyrolysis. The gasification kinetics of biomass chars (pyrolysed to 700°C at a medium heating rate) have also been measured by measuring the rate of weight loss during reaction with CO₂, as a function of temperature. First-order kinetic rate constants are then determined by fitting the weight loss data using a random pore model. The results indicate that the gasification rate of biomass char increases as pressure increases.

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The most part of energy losses in power system such as fuel cells is due to the heat released by the exhaust gas to atmosphere. The exhaust gas consists of non-condensable gas and steam with sensible and latent heat. As a lot of latent heat is included in the exhaust gas, its recovery is very important to improve the power system efficiency. Based on the previous basic studies, a thermal hydraulic prediction method for latent heat recovery exchangers was proposed. For the condensation of steam on heat transfer tubes, the modified Sherwood number taking account of the mass absorption effect on the wall was used. Two kinds of compact heat exchanger with staggered banks of bare tubes of 10.5 or 4mm in outer diameter was designed with the prediction method. The more compactness was obtained with the smaller tubes at a designed heat recovery. The thermal hydraulic behavior in the compact heat exchangers was experimentally studied with air-steam mixture gas. In the parametric experiments varying the steam mass concentration, the temperature distributions of cooling water and mixture gas were measured. The experimental results agreed well with the prediction proposed in this study and the more compactness with the smaller tubes was proved.

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By installing HFC134a on the air-conditioning machine designed for HCFC22, it was proved that a more efficient heat pump system could be operated without changing mineral lubricant oil. The circulation mechanism of mineral oil with HFC134a was investigated in comparison with that of HCFC22. It was shown by the flow visualization that the mineral oil was not solved in condensed HFC134a, but droplets of mineral oil were transported with condensed HFC134a at the outlet of condenser. The circulation of mineral oil with HFC134a was also confirmed by extracting the working fluid from the tubing of the air-conditioning machine under operation.

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The fatigue strength of weld surfaces on truck frames has been estimated according to the fatigue limit diagram in JIS E 4207, General Rules for Design of Truck Frames for Railway Rolling Stock. However, it is not possible to predict actual fatigue life using this diagram. This study demonstrates the possibility of fatigue life estimation for welds on truck frames based on a modified Miner's rule. In order to estimate fatigue life, three factors are needed: the S-N diagram assumed from the allowable stress in JIS E 4207 or the JSSC fatigue design curve, the relationship between crack occurrence and running distance, and the stress frequency distribution caused by service loads.

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To develop a technology that can efficiently convert dewatered sewage sludge cake into solid fuel, we experimentally investigated the effects of the hydrothermal treatment on dewaterability and carbon distributions. Dewatered sewage sludge cake with a water content of about 80 wt% could not be dewatered by increasing the pressure of a mechanical press. However, after hydrothermal treatment, the sewage sludge cake could be dewatered with a mechanical press. Moisture content was negatively correlated with treatment temperature at temperatures below 473K but stayed about the same at temperatures above 473K in the range studied. Carbon contents in the residual solid after treatment with a mechanical press were negatively correlated with the reaction temperature of the hydrothermal treatment owing to the solubilization of part of the volatile carbons in the dewatered sewage sludge cake. On the basis of the above results, we proposed a novel solid fuel production system composed of the following processes: hydrothermal treatment, mechanical press treatment, concentration, and drying. The optimum operating temperature of hydrothermal treatment was 473K in the range studied, and at this temperature, we estimated that the energy input to obtain dry sewage sludge using the proposed system would be about two-thirds that of a conventional drying process.

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A new sensory test method is proposed in this paper. These days, users are demanding both amenity value and comfort in products. To provide comfort, it is necessary to measure the human senses. Various sensory test methods have been developed. Scheffe's paired comparison is one such widely used sensory test method. Nakaya's method was developed based on Scheffe's paired comparison. It estimates human senses and makes it possible to add a score to the samples. Nakaya's established method can separate the main effect, individual effect, and the combined effect. If there are any other factors that affect the samples' assessments, they will be neglected. Therefore, the main effect - if it is significant - also tends to be neglected with Nakaya's method when there are multiple environmental factors. The method proposed here solves these problems while still maintaining the merits of the established methods. Our proposed sensory test method uses multiple factors in its model. Therefore this method enables us to separate many environmental factors, the effects are detected correctly and circumstantially. Furthermore, this method is sensitive to the main effect because many environmental factors are considered. The proposed method was applied in an assessment of the psycho-acoustics of loudspeakers, and was found to be useful in sensory tests when differences were small and when there were only a few subjects.

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In this article, a vehicle dynamics integrated control algorithm using an on-line nonlinear optimization method is proposed for 4-wheel distributed steering and 4-wheel distributed traction/braking systems. The proposed distribution algorithm calculates the magnitude and direction of tire forces that satisfy constraints corresponding to the target resultant force and moment of vehicle motion and also minimizes the maximum μ rate (= tire force / friction circle) of each tire. The convexity of this problem is shown, and so global optimality of the convergent solution of the recursive algorithm is guaranteed. This implies that the theoretical limited performance of vehicle dynamics integrated control is clarified. The proposed algorithm is based on SQP (Sequential Quadratic Programming) and the steepest gradient algorithm. Calculation performance of the proposed algorithm is compared that of the primal-dual interior-point method, which is a representative optimization method. Furthermore, the effect of this vehicle dynamics control is demonstrated by a simulation and experiment comparing various vehicle dynamics integrated control methods.

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Evaluation of the natural frequency and the natural mode of vibration of a bolted joint is particularly important to avoid the failure of the structure due to the resonance. The vibration characteristics of a bolted joint are largely influenced by such factors as the surface roughness of contact surfaces, the magnitude of axial bolt force, the arrangement of claming bolts, etc. In this paper, natural frequencies of the bending vibration of a bolted joint with simple configuration are measured with strain gages mounted on the surface of test specimen, and the effects of surface roughness, axial bolt force and bolt position are systematically investigated. Then, a numerical procedure is proposed to analyze the free vibration problem of a bolted joint, where the effect of interface stiffness due to surface roughness is incorporated into the finite element formulation. It is also presented that the computation efficiency for solving the eigen value problem can be fairly improved by introducing selective reduced integration (SRI) scheme. The effectiveness of the numerical procedure proposed here is validated by experimental measurements of the natural frequencies of the first mode.

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One of the main challenges of HCCI engine research is developing a system to control the combustion phasing to achieve a stable operation. Though some HCCI combustion control systems have been suggested, they are heavy in weight and complex in mechanism. In this study, a simple combustion control system and an algorithm for a lightweight small-sized handy electrical generator HCCI engine fuelled with DME were developed and evaluated experimentally. In this system, the ratio of stoichiometric DME/air pre-mixture, Hot EGR gas and Cold EGR gas were adjusted by throttles. The experimental results showed that combustion phasing can be controlled through adjusting the mass-averaged in-cylinder gas temperature at intake valve closure timing by changing the ratio of Hot EGR gas and Cold EGR gas. Moreover, IMEP was PI (Proportional and Integral) feedback controlled by fuel flow rate, while the combustion phasing and equivalence ratio were PI feedback controlled by throttles. As a result, it is possible for these parameters to follow their set values.

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Composite materials consisting of peanut hulls and polylactic acid (PLA) resin were developed by a compression molding method. The density, water absorption properties and flexural properties of the composite materials were evaluated. The density of the composite materials was lower than the theoretical density, which was calculated by the peanut hull density, PLA resin density and peanut hull weight content because these materials have many voids. The saturated water absorption rate and mass diffusivity increased with the increase in peanut hull weight content. Especially, the saturated water absorption rate and mass diffusivity of the composite material with a peanut hull weight content of 75% were approximately 15 times and 2.4 times higher, respectively, than those of PLA resin. As a result of 3-point flexural tests, the flexural modulus of the composite materials improved as the peanut hull weight content increased up to 50%. At the peanut hull weight content greater than 25%, the flexural strength degraded as the peanut hull weight content increased. Furthermore, the cost performance of the composite materials based on flexural rigidity, material cost and thickness was discussed.

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Mussels living in the ocean adhere to shore reef and each other with byssus formed by insolubilization of adhesive proteins, whose application to the new bio-adhesion material has been expected. Their adhesive strength has not been accurately measured because peel test method is not established since the contact areas between a plaque and the substrate are less than 1 mm². Present paper attempts to measure adhesive strength of the plaques using original simple peel test method and investigates the influence of environmental change on the adhesive strength and the change of the adhesive strength in the lapse of time. The results show that the adhesive strength of the plaques decrease with the change in the environment by transferring mussels from the beach to an experimental environment and the adhesive strength changes along with the elapsed time after the plaques are secreted.

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There is increasing concern about the health effects of particulate pollutants such as the SARS virus, influenza and diesel emission particles; moreover, restrictions on them are becoming stringent. In this study, particle motions and flows around a human with periodic breathing are numerically solved to predict the gas-particulate two-phase flows. Since the targeted particles are bacteria and viruses, the particle sizes are selected as 1 μm and 100 nm in diameter with a density of 10 kg/m³, respectively. Three-dimensional numerical simulation was employed using the Lagrange approach for particle motion and the standard k-ε model for flows. In the human breathing cycle, inhalation flow exists in the vicinity of the human face within a small area. Exhalation flows exists below the inhalation flow and is spread across a larger area. Downward streams coming from the upper region to the region near the nose are observed not only at the maximum inhalation time but also at the maximum exhalation time. With these downward streams, particles always move downward when inhalation occurs. Motions of particles away from the human body with right-left unsymmetrical vortexes are observed. Particles reach the human nose when the source distance is less than 30 cm. A maximum of 9.9 % of the nanoparticles are captured. When the source distance L is 10 cm, smaller particles of d = 100 nm tend to have high captured efficiency. On the other hand, more 1 μm particles are captured when the source distance is 20 cm or greater.

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A polygon motor consists of several mirror faces and it is one of the core components for laser beam printers and copiers. Under high-speed rotation, aeroacoustic noise with a peak frequency of rotational speed times the number of mirror faces and its harmonics is prominently generated from a polygon motor covered with a casing. This paper describes a method to predict such noise that is generated from the flow, between the rotating mirror and stationary casing that propagates through the casing and is radiated into the ambient air. The unsteady flow is first computed by large-eddy simulation. The computed pressure fluctuations on the inner wall of the casing are then fed to structural analysis based on a dynamic explicit finite element method that computes the propagation of the elastic waves in the casing. Resulting external surface velocities are finally used for the computation of the acoustical field. A good correlation between the computed and measured results has been observed both in terms of velocity spectra on the casing and the spatial distribution of sound pressure level. The proposed method thus seems a promising engineering tool for predicting and identifying the generation mechanism of such noise that is generated from unsteady flow that propagates through solid walls and is radiated to ambient air, in general.

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With the minimum Gibbs energy of the system by computer simulation and experiments, the activity of activated coke (AC) and V₂O₅/AC was studied by the main components change in the system of flue gases activation. The results of calculating and experiments show that the change of value of carbon monoxide concentration in the system can be used to estimate the desulfurization activity of AC and V₂O₅/AC, and to find fitting flue gases. When the temperature of activation is 800°C, the carbon monoxide concentration increases as the amount of V₂O₅ in the AC rise, the V₂O₅ in the AC can be changed into V₂O₃ when there is carbon monoxide in the system. When the amount of V₂O₅ is greater than 5% of the AC, the increase trend of concentration of carbon monoxide will gradually weaken If there is air or O₂ in the desulfurization process, the V₂O₃ in the AC will be changed into V₂O₄, and then to active V₂O₅. The active V₂O₅ in porous AC has a higher catalytic activity than V₂O₅. In the temperature range of 150~200°C, the catalyst V₂O₅/AC shows good performance for SO₂ removal and is gradually deactivated at temperature above 200°C.

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Biomass resources are one of the attractive alternative fuels. It is effective to use such fuel in distributed power generation system with gas engine because it disperses. However, its calorific value is low, and the gas composition is affected by the source material, gasification method and gasifying conditions, causing it to change momentarily during engine operation. The gas engine must be stable and capable of high-thermal-efficiency operation under such fluctuations. The objective of this study is to develop a small gas engine system for biomass gaseous fuel. In this study, the effect of fuel composition on combustion was clarified by an engine experiment with low-calorific-value gaseous fuel. Diluted fuel exhibited longer combustion duration and lower thermal efficiency, but not necessarily a lower calorific value. It was also confirmed that spark timing control against fuel composition fluctuation was effective for maintaining high thermal efficiency even at a fixed speed engine. Fuels containing H2 also have lower calorific values, but they allow stable engine operation and higher thermal efficiency with respect to a shorter combustion duration.

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This paper describes the fluid force acting on a square cylinder of finite length in the lock-in region. The experiment was carried out in an N.P.L. blow-down type wind-tunnel with a working section of 500mm×500mm×2000mm at Reynolds number of 1.25×10⁴. The cylinder was forced to oscillate sinusoidally in the lift direction. The power spectrum of the fluctuating velocity in the wake behind a square cylinder was measured to show the lock-in region in the present experiment. The time-mean pressure distribution and fluctuating pressure distribution on the square cylinder were measured for the displacement in the vibration. Consequently it was found that the mean drag and fluctuating lift increase and become maximum in the lock-in region, while the base pressure in the rear surface of the cylinder becomes low and attains minimum.

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In this paper, basic studies on the high temperature steam gasification system which is named as HyPR-MEET system were carried out using the Japanese cedar and pure polyethylene (PE) particles as feedstocks. First, the characteristic of steam gasification is investigated. With each feedstock, the hydrogen concentration increases as the gasification temperature rises, but the increase rate of the hydrogen concentration decreases over the temperature of 1073K for Japanese cedar and 1173K for PE. The increase of the steam/carbon molar ratio also increases the hydrogen concentration. Second, the effectiveness of the Ru/Al₂O₃ catalyst for steam reforming of tar components is investigated. With use of this catalyst, tar components can be reformed at the temperature of 973K, while the temperature of 1173K is required without use of any catalysts. Furthermore, light hydrocarbon gases are also reformed with this catalyst, and the hydrogen concentration in the reformed gas can reach the value of 55% for Japanese cedar, and of 68% for PE.

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A surface contact analysis model was developed to investigate the dependence of the sound pressure level and squeal frequency on the thrust pressure in contact region. This dependence was hypothesized to be caused by the dependence of the contact stiffness between the disk and pad on the thrust pressure. To examine the influence of contact stiffness on squeal, the surface contact analysis model uses distributed springs (creating contact stiffness) to connect the disk and pad. The dependence of the contact stiffness on the thrust pressure causes coupling of the disk and pad motions, and instability in this coupling generates squeal. The analysis results are in good agreement with experimental observations that the disk has translational motion while the pad has both translational and rotational motions. The contact stiffness increases along with the thrust pressure, the rotational rigidity of pad increases. As a results, the squeal frequency increases. This report clarifies that the dependence of contact stiffness on thrust pressure cause both squeal generation and dependence of squeal frequency on thrust pressure.

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