This paper describes the validation of Virtual Flux Method (VFM) to forced convection flows. The method, one of Cartesian grid methods, can sharply capture boundaries. The method is also designed to calculate flows inside and outside boundaries seamlessly, while many Cartesian grid methods are not. This method is applied to forced convection flows around a circular cylinder and a pair of circular cylinders. The results are well compared with other available numerical results and experiments. Also, heat/fluid flow fields inside and outside a circular cylinder where a heater is placed at the center of the cylinder are seamlessly calculated. These results indicate the reliability of VFM for forced convection flows.

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The behavior of an incompressible homogeneous turbulence in a rapidly rotating system is investigated. Linearized equations based on Rapid Distortion Theory (RDT) are used to analyze the rotating turbulence. In the rotating system without mean velocity-gradients, it is shown that the trace, which is defined by the phase space of the Fourier spectrum of the velocity fluctuation and the time-derivative of the Fourier spectrum of the velocity fluctuation, has an elliptic trajectory-the system has periodicity. Such a rotating system involves the conservation of the sum of the Reynolds stress tensor and the tensor composed of the vector streamfunction gradient correlation. The latter tensor describes the large-scale structure of vorticity field [for example, Reynolds et al., Phys. Fluids, 14 (2002), 2485-2492]. The tensors were calculated numerically with various initial anisotropic conditions using the solutions derived from the linearized equations. The results were found to substantiate the conservation relation under various conditions.

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This paper is focused on the high velocity tongue beneath the longitudinal vortices downstream of a pair of active vortex generators (AVG) with common flow up configuration. An active control of turbulent boundary layer separation is one of the most interesting projects. It is important to achieve a smart control system based on the detailed information of time depended characteristics of the longitudinal vortices. Phase averaged mean velocity is measured by a newly developed rotating X-array hot-wire anemometer. The high velocity tongue shows rapid response to the height of the AVG at the final-stage of up-phase compared with the early-stage of down-phase. The transportation of high velocity fluid beneath the longitudinal vortices plays an important roll on the response of longitudinal vortices.

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This paper is focused on the time depended characteristics of Reynolds shear stresses-u'v' and -v'w' of longitudinal vortices downstream of a pair of active vortex generators (AVG) with common flow up configuration. The measurements of Reynolds stresses within the longitudinal vortices are conducted by using a newly developed rotating X-array hot-wire anemometer which can measure full components of turbulent properties. Time depended characteristics of Reynolds stresses are discussed. Also, the production mechanism in the Reynolds shear stress -u'v'and -v'w'transport equation at the final-stage of up-phase is presented.

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The paper presents the flow mechanism of a reattachment process over a backward facing step with vortex generator jets (VGJs). The spanwise arrays of VGJs upstream of the step introduces the corotating longitudinal vortices in a separating shear layer. The measurement of the longitudinal vortices by the hot wire anemometer is made to clarify the spanwise structure in the separating shear layer downstream of the step. The particular emphasis is placed on understanding of the effect of the jet injection pitch on the shear layer development. The spanwise structure in the case of the injection pitch of 20 times jet diameter shows two-dimensional feature at the bottom of the separating shear layer as in the distribution of forward flow fraction near the reattachment region.

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The paper presents the turbulent flow characteristics of a separating shear layer associated with the corotating longitudinal vortices introduced by the vortex generator jets (VGJs) over a backward facing step. The turbulent flow structure is measured by the hot-wire anemometer. The two-dimensional time averaged velocity profile in the separating shear layer downstream of the step is observed, while the turbulent kinetic energy and Reynolds stress have the spanwise structure depending on the VGJ injection location. VGJ produces the primary and secondary vortices. The behavior of the primary and secondary vortices in the separating shear layer is also discussed.

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A rapid expansion of moist air or steam in a supersonic nozzle gives rise to non-equilibrium condensation. If the latent heat released by condensation exceeds a certain quantity, the flow becomes unstable and a periodic flow oscillation occurs. In the present study, a numerical simulation of moist air flows in a supersonic nozzle was carried out for a special short duration supersonic wind tunnel, called a Ludwieg tube. As a result, the effect of non-equilibrium condensation on the flow field in the nozzle was clarified numerically for case with occurrence of the non-equilibrium condensation in the unsteady expansion wave upstream of the nozzle.

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The single supersonic free jet discharging from a nozzle or an orifice has been often employed in various industrial processes. A number of studies have been done to detail the major features (Mach disk, barrel shock wave and the jet boundary configuration) of the supersonic jets. In the present study, the numerical computations were performed to investigate the effect of initial degree of supersaturation of moist air at reservoir condition on under-expanded jet structures and the total pressure loss behind the Mach disk. As a result, it was found that the position of Mach disk in the under-expanded moist air jets was almost the same as that in dry air jets. However, the Mach disk diameter increased slightly as the initial degree of supersaturation of moist air increased. Furthermore, the total pressure loss behind the Mach disk for moist air jet changed largely in comparison to that for dry air jet.

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The High Velocity Oxy-Fuel (HVOF) thermal spraying is a technique to make a coating on a solid surface. The gun consists of a supersonic nozzle followed by a straight passage called barrel. In this study, the internal flow of HVOF gun was analyzed by the theory of Fanno flow and the flow patterns are classified depending on barrel length and chamber pressure. The analytical results were evaluated by the experimental results including pressure distributions in the gun and schlieren photographs of jet. The analytical results show good agreement with the experimental results except for the condition that shock train stays inside the barrel.

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The authors conduct numerical and experimental investigations about the three-dimensional thermal convection in a cubic cavity heated below in the gravitational field. Frequency responses are analysed numerically concerning global quantities such as spatially-averaged kinetic energy, spatially-averaged internal energy and the Bejan number. We assume incompressible fluid with a constant Prandtl number Pr=7.1 (water) and Pr=130 (silicone oil). Tested Rayleigh number Rais varied from 1.0×10⁴ to 7.0×10⁴. A set of the full Navier-Stokes equations with the Boussinesq approximation and an energy equation are solved by a finite difference method based on the MAC method with a staggered computational grid. As a result, the authors find the existence of one optimum frequency where we get the maximum frequency response, and find the relation between the optimum frequency and Ra. In addition, experimentally, the authors check their computation, using thermo-graph technology at Pr=2500 (silicone oil).

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The present aim is to clarify the wake structure of a ring with rectangular cross sections, which is immersed perpendicularly to the main flow. In a wind tunnel, the authors carry out flow visualisation and the measurement using a hot-wire anemometer, synchronously. Flow is visualised by a smoke-wire method, and the authors take consecutive picutures using a high-speed camcorder. Analyses of these pictures by a PIV bring us flow-field informations, namely, velocity vectors and vorticity contours. Tested ranges are Re=5.0×10³, d/w=3.0-8.0 and t/w=0.28-1.30, where Re, d, w and t are the Reynoids numbor, mean diameter, cross-section Width and cross-section thickness of the ring, respectively. Consequently, the authors reveal the corresponding wake structures with four flow modes. In particular for two axi-symmetrical modes, the authors discuss the effect of t/won the development, the diffusion and the advection of ring vortices in near wake.

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This paper presents the technique of digital holographic particle image velocimetry (DHPIV) with a spatio-temporal derivative method for the velocity measurement in 3D space and the evaluation results on it's measurement accuracy. In this technique, hologram patterns are observed as a digital image by an electronic camera such as CCD or CMOS and image reconstruction is carried out on a personal computer. Since in-line observation system is utilized in the conventional digital holography, numerical reconstructed image is much enlarged in depth direction and its depth resolution is extremely poor, hence the measurement accurahy in depth is not accurate in the digital holographic measurement. To overcome this difficulty, we apply a spatio-temporal derivative method to this technique for the detection of particle displacement along z-axis. In numerical simulation, measurement accuracy is evaluated for multi particle model and cubic cavity flow model. Furthermore, we examine the effect of noise on displacement measurement accuracy for noisy hologram patterns numerically constructed.

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The purpose of this study is to clarify flow characteristics and drag reduction of a wettability spherical surface. A three-dimensional laminar flow past a sphere were numerically simulated by applying a new wet boundary condition for a hydrophobic surface. These results suggest that the wet boundary condition proposed in this paper is valid for the hydrophobic surface. The evolution of a gas-liquid interfaces at the hydrophobic spherical surface has been clarified. The simulation results of the hydrophobic spherical surface showed drag reduction.

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Drag reduction is achieved by using a hydrophobic surface with fluid slip. Fluid slip is closely related to a gas-liquid interface formed as a solid surface with many fine grooves. The friction generated by the solid boundary is modified considerably because the gas-liquid interface provides a zero-shear stress boundary condition. The purpose of this study is to experimentally clarify flow patterns and drag reduction of a hydrophobic surface sphere by visualizing flow and measuring the drag. The flow visualization results showed that the Vortex Loop was not exist at Re<400 in the hydrophobic surface sphere and the separation point moved downstream. The maximum drag reduction ratio was 28.5% at Re=7.2.

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This study investigated the characteristics of flow-induced vibrations of two circular cylinders in tandem arrangement. The response characteristics on elastically supported two circular cylinders were examined by a free vibration test in this study. Also, the behavior of the shear layers separated from the two circular cylinders was investigated on the basis of the visualized flow patterns. The measurements were performed by changing the spacing ratio L/D (L is the gap spacing between two circular cylinders, D is the diameter of cylinder). The main findings were that (i) the response characteristics of flow-induced vibrations were classified into five patterns in the region of L/D≤3.2, (ii) the flow-induced vibrations of the two cylinders depended strongly on the fluctuating lift forces of the two cylidners, (iii) the phase difference between the response of the two cylinders was proportional to distance between two cylinders, (iv) there were two kinds of vibration patterns at critical spacing of L/D=0.6 and 2.7, and (v) there exsisted the hysteresis phenomenon on two cylinders caused by acceleration and deceleration of the free-stream velocity.

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This paper describes the influence of attack angle on the flow past a flat plate of finite width placed vertically on ground plane. The experiment was carried out in the 800 mm diameter Eiffel type wind tunnel having the working section of 1.5m length at Reynolds number of 5.1×10⁴ mainly. The surface pressure distributions on the flat plate and on the ground plane around the flat plate were measured, and the drag coefficient and lift coefficient were determined from them. The power spectrum of the X component of fluctuating velocity was measured to check the arch vortices shedding behind the flat plate. The vortices generated in the flow field around a flat plate have also been observed by flow-visualization. Consequently, it is found that the disappearance of shedding arch vortices is in the range of α≥45°for W/H=2 and 4, while the drag coefficient decreases and lift coefficient attains maximum near α=45°for W/H≥4.

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Pressure drop and velocity profile for a micro tube were investigated on laminar flow of distilled water and dilute polymer solutions. It is the range of 50.2-251.8μmin diameter, and the value of l/d is about 340. By a pressure drop measurement it is shown that the experimental data agree with Hagen-Poiseuille equation in the case of Newtonian fluids. And the flow rate of the dilute polymer solutions increased comparing with that of distilled water at the low Reynolds number range. The increase ratio of the flow rate is about 15% in maximum in the case of d=251.8μm. For the result of micro PIV measurement, there are few differences between the velocity profile of distilled water and Peo 5 ppm solution.

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We investigated experimentally the unsteady flow in a counter-type T-junction. The T-junction was modeled by a mixing tee with square cross sections, in which the mixing channel was connected with the main and counter channels at right angles. Detailed distribution of velocity data have been measured using PIV. Reynolds number of the main-channel flow was fixed at 3 500, and the flow ratio of the counter-channel flow to main one was changed from 1.0 to 5.0. To identify the coherent flow structures, the proper orthogonal decomposition (POD) analysis was applied to the fluctuating velocity field in the mixing channel. Based on the data, the unsteady vortical motion along the shear layer and the wobbling motion of the interface between the main-channel and counter-channel flows are discussed.

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An Ultrasonic Velocity Profile monitor (UVP) measurement was performed to measure the averaged liquid velocity field in front of, around and behind the large bubble rising in stagnant water in a round pipe of inner diameter D=54 mm in order to obtain fundamental information for the gas liquid two-phase slug flows. Two ultrasonic transducers were used for the measurement to get velocity vectors. The measured results are presented and compared with some existing studies on the corresponding phenomena. In the liquid film near the bubble nose, velocity profiles are presented and compared with existing studies. The different of D may affect some features. The parameter z/D is found more dominant than z for this phenomenon. In the liquid phase behind the bubble tail or the wake region, a large ring vortex is recognized. The effect of bubble length on the vortex is also discussed. The upward velocity at the pipe axis agrees well the predicted results by an existing prediction.

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In order to clarify the propagation phenomenon of the bubble collapse induced during cavitation breakdown generating around a circular cylinder, pressure measurement on the cylinder surface, high speed video camera and Particle and Bubble image velocimetry observation were carried out. The bubble collapse process is that, in first, the inflow yields toward into the cavity accompanying with the weak bubble collapse. In second, when the inflow is impinging against the cavity boundary, the strong bubble collapse pressure is induced. In finally, the surrounding bubbles collapse successively inducing new collapse pressures and this chain-reacting bubble collapse propagates toward the upstream cylinder along the cavity boundary. The propagation velocity of the chain-reaction is extremely low in the range from about 10 m/s to 20 m/s compared with the sound velocity of two phase fluid of gas and liquid.

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While a supercavitating propeller is put to practical use, a supercavitating machinery like pump or turbine is not so many. One of the causes is that an interaction in supercavitation between the flow around the rotor or stator and the casing or hub is not clarified. It seems that the interaction is unsteady and the flow behavior is very complex, but in this paper, unsteady inviscid incompressible and small disturbance flow are assumed. An internal flow of axial flow machine is modeled into a flow between paralled plane walls and a velocity distribution is assumed to be the Karman-Prandtl 1/n power law of turbulent flow. Under these assumptions, three-dimensional characteristics of supercavitating hydrofoil between parallel plane walls are analyzed.

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Guide vanes are installed in the Wells turbine in order to improve its efficiency, self-rotating characteristics and off design performance with stall. This work attempts to explain the role of these guide vanes on the basis of momentum theory. A design method for guide vanes is suggested based on experimental data and potential theory. Experimental studies were carried out by the author to confirm the theory proposed.

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The pumping characteristics of an inscribed trochoid gear pump are investigated experimentally. The paper deals with viscosity-dominant conditions, i.e. low Reynolds number performances less than 5000 in order to develop a miniaturized pump. The test pump of 4 mm in the inner basic radius is designed for the experimentation. The volume flow rate and the pressure rise of the pump are measured using a test loop with two different liquids. Volumetric efficiency, dimensionless pressure rise, and pump's power efficiency are obtained as function of Reynolds number. The present results support the previous theoretical study, that is, the lower Reynolds number the higher performance the trochoid gear pump has. This implies an advantage toward miniaturization. On the other hand, the pump's power efficiency is obtained as only a few % because of significant increment of wear caused in six parts of gear clearance, which should be discussed as the next step of the research.

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An experimental study has been conducted to understand characteristics of transient heat transfer during quenching a hot cylindrical block with an impinging water jet. The experiment was done at atmospheric pressure for the following condition : an initial block temperature of 250 and 400°C, a subcooling of 20-80 K, a jet velocity of 3-15 m/s, and a nozzle diameter of 2 mm. The surface temperature and heat flux are estimated by applying two-dimensional inverse solution to the measured temperatures in the block during the quench. The surface heat flux is greatly influenced by the position of the wetting front. It reveals that the maximum heat flux appears slightly far from the wetting front and its value decreases with a distance from the jet. The experiment shows that the maximum heat flux in the quecnching is smaller than the critical heat flux (CHF) in the corresponding steady condition depending on a cooling situation, but the trend is similar between the maximum heat flux and the CHF. An equation is proposed to predict the maximum heat flux on a basis of the CHF correlation.

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By using an experimental apparatus to examine the performance in the heat and mass transfer between water and air through the porous plate having extremely small pores, effects of thermal conditions of fluids and geometrical conditions of experimental apparatus on mass transport were investigated. It was shown that the effects of water temperature and height of air channel on mass transport were noticeable. However, effect of the air temperature at the channel inlet on mass transport is slight. Moreover, in order to evaluate the degree of humidity absorption of air, the humidity absorption rate was introduced as a parameter of effectiveness. It was shown that the humidity absorption rate decreases with the increase of the air velocity, and hardly varies with water temperature.

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This paper describes the flow and heat transfer characteristics of the mixed convection in a horizontal square duct with heated and cooled side walls by the three-dimensional numerical analysis. The working fluid is water and the temperature dependence of kinetic viscosity and thermal conductivity of water is considered. The SIMPLE procedure and QUICK scheme are used to solve the governing equations through a control volume. Three-dimensional spiral flow appears along the longitudinal direction of the duct and swirl flow pitch is shortened with increases of Richardson number Ri (= Gr/Re²). The recirculation flow appears on the upper and bottom wall edges near the starting point of the heat transfer section. The size of the recirculation flow depends on Ri and the positions. The pumping power due to swirl flow is about 6-11 % larger than that of forced convection. In addition, high heat transfer and low pressure drop area exists the thermal performance.

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A “Vapor Chamber” is used as a novel heat spreader to cool high-performance MPUs (micro-processor units). The vapor chamber is placed between small heat sources and a large heat sink. This paper describes the effect of heat source size on the heat transfer characteristics of the vapor chamber. First, by the experiments, the effect of heat source size on the temperature distribution of the vapor chamber is investigated, and the validity of the mathematical model of the vapor chamber is confirmed. Secondly, by the numerical analyses, the effect of heat source size on the thermal resistances inside the vapor chamber is discussed. It is found that the heat source size greatly affects the thermal resistance of the evaporator section inside the vapor chamber. Although the thermal resistance is hardly affected by the heat generation rate and the heat flux of the heat source, it increases as the heat source becomes smaller.

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Natural convection heat transfer of suspension in a rectangular vessel heated from a vertical wall and cooled from the opposite one was investigated. The suspensions were mixtures of water and SiO₂ fine particles of 3 or 6 μm in mean diameter. The particle size distributions were narrow. The temperature and particle concentration distributions in the suspension and the average heat transfer coefficient on the vertical wall were measured under various conditions : temperature difference between the heat transfer walls, initial particles concentration, the mean diameter of particle and the width of the vessel. Comparing Nusselt number of the suspension to that of water, it was found that sedimentation of particles affected strongly the natural convection of suspension. Then the natural convection was classified into three types according to the intensity of convection. Effects of the experimental parameters on the natural convection phenomena and the Nusselt number were clarified.

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A passive cooling enhancement method is proposed, verified with simple model measurement and validated with numerical analysis. The multi channels built in an enclosure is a promising method to enhance the effectiveness of passive dissipation with dissipation with maintaining the surface temperature as its upper limit. To prove, the simplest two channel wall with copper plate and heater, which provides the uniform heat, is prepared. The PIV method is used for velocity distribution in a channel and temperature is measured in the same setup as well. The numerical analysis carried out with a model following the experimental setup. The comparison between the observations is discussed with fundamental analytic model. The results provide a strong evidence for the previous analytic optimization work, which suggested four fold improvements.

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The viscosity is one of the very important thermophysical properties for food industry and it is required to develop a new technique which is possible to measure significantly changing viscosity by single apparatus. In the present study, we have developed a new viscometry based on a laser-induced capillary wave technique by using a pulsed CO₂ laser as a heating source. The detected signals for several Newtonian liquids such as acetone, toluene, water, ethanol, 1-hexanol, decanol, ethylene glycol, glycerol, JS 100, JS 1000 and JS 14000 having wide range of the viscosity (10^-1-10⁴ mPa·s) agreed well with the theoretical calculations. It is also confirmed that in the viscosity range 10¹-10³ mPa·s, the viscosity can be determined by calculating decay time constant of detected signals. We have demonstrated that the application of the laser-induced capillary wave technique has considerable potential for the measurement from low to high viscosity liquids.

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Accurate prediction of the lifetime of a plasma ash melting furnace is essential for planning the timely repairs of it, as well as improving its design and operation. In this study, we took account of the slag temperature, the basicity of the ash and the ash feeding ratio to estimate the wear rate of the refractory material based on the mechanism of diffusion of SiO₃^2- in the slag. The experiment using an electric furnace indicated clear relationship among the refractory wear, the slag temperature and the basicity of ash. The relationship between the refractory wear and the ash feeding ratio was found based on the data obtained from the furnace under commercial operation. The validity of this estimation method is demonstrated because the estimated amount of the refractory wear agreed well with the amount of the refractory wear measured in the plasma ash melting furnace after three month operation.

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The purpose of this study was to understand the optimum operation condition of magnetic refrigerator at room temperature for direct air cooling. The basic components of the target system were a magnetic circuit including two permanent magnets, a test section, an air blower, and an associated instrumentation. The test section consisted of ten test cells which enclosed gadolinium chips as a magnetic working substance in prescribed packing factor. In order to change the applied magnetic field from 0 to 0.9 T, the magnetic circuit was installed on an electric slider which generated reciprocating motion. The system performances were widely investigated both experimentally and analytically for the variety of operation conditions such as a volumetric flow rate of air, a packing mass of magnetic working substance, and a heat exchange cycle. The results reveal that the maximum value of the cooling capacity of the present magnetic refrigerator is obtained in a certain operating condition.

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The installation to the individual house of the PEM fuel cell cogeneration with heat pump is considered. The electric power and the heat power output characteristics of the system differ from each other with the control variables of system-control devices. Then, the operation actions of the system were analyzed using the electric power load pattern accompanied by short-time random fluctuations. As a result, the transient response characteristics of the system are good by changing the control variables of controllers with the values of electric power load and heat power load. Furthermore, generation efficiency falls, so that electric power load and load fluctuations become large. The electric power consumption of heat pump is influenced by the values of the exhaust heat of a fuel cell stack and a reformer. When adding the same heat load as the system, the electric power consumption of heat pump decreases, so that electric power load and load fluctuations are large. Therefore, if a PEM fuel cell system is introduced into load patterns with large fluctuations in a short time of electric power load with little heat demand, it will be predicted that the advantageousness of the system decreases.

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Real time analysis on impedance spectroscopy in PEFC (Polymer Electrolyte Fuel Cell) was tried using FFT (Fast Fourier Transform) method to diagnose its running conditions. PEFC is simulated to equivalent circuit model with four resistances and three capacitances, and effects of running conditions on those were analyzed by the experiments. Results show that the voltage drops at each resistance correspond to over voltage calculated by conventional method and indicate distinctive characteristics according to deterioration of running condition. The logic is established to real time diagnosis of PEFC running conditions by classifying these voltage drops and to trace the flow chart. This method has capability of on-board diagnosis and control of fuel cell system vehicle.

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Until now, perfluorinated proton exchange membrane (PEM) has been widely used as the electrolyte for PEMFC. As long as the perfluorinated PEM is used for the electrolyte, both the cell performance and durability of PEMFC strongly depends on the water content in its electrolyte, since the high conductivity of electrolyte is presented only at the sufficient hydrated state. On the other hand, pre-humidification of fuel and oxidant gases complicates the PEMFC system and prevents it from cost reduction. Therefore, in order to achieve simultaneously the high performance, durability and cost reduction of PEMFC, it is though to be a best way that both the anode and cathode catalyst layers will be highly humidified only by the water produced through an electrode reaction without pre-humidification of fuel and oxidant gases. Although the management of the vapor permeation rates through gas diffusion layers will be most effective for such a self-humidified PEMFC, it isn't so easy to achieve it in the wide range of current density. In this study, by using the cell simulation method for PEMFC, we calculated numerically the vapor permeation rates through anode and cathode gas diffusion layers which enabled the self-humidified PEMFC without pre-humidification or with low pre-humidification of fuel and oxidant gases.

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This paper presents mapping method to show characteristics of cogeneration systems (CGS) for the reduction of carbon dioxide emission and economy. In this mapping method, effects of CGS can be consolidated into rated reduction ratio, relative reduction ratio map, demand repetition map and weight map. These are without recourse to building size or installed capacity. By lapping these maps, it can be easy to evaluate compatibility with each building types and optimal installed capacity. Variation of effects of CGS for different conditions can be evaluated visually from variation of maps. Analyzed charts are useful to evaluate quantitative effects of CGS for various areas and price rates of electric/gas from average annual demand of electricity and heat. Applicable scope of these charts depends on weighted center and dispersion of demands on the demand map.

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In this paper, the pyrolysis characteristic of waste paint dregs has been invistigated by comparing with wood chips at 500°C, 700°C and 900°C with a laboratory-scale reactor. The results showed that the gaseous yield significantly increased for waste paint dregs than that for wood chips with increase of pyrolysis temperature. Therefore, it is possible to gasify waste paint dregs like wood chips at high temperature to obtain efficient combustible gas for a dual-fueled engine. And the behaviors of heavy metals in the waste paint dregs were also investigated. It showed that Pb was volatile, Ti and Zn were non-volatile in the temperature range of 500°C-900°C.Then, demonstration gasification and power generation experiments were carried out by a plant of commercial scale, STAR-MEET, using waste paint dregs and wood chips. The results agreed with the laboratory experiments, namely the heating value of pyrolysis gas produced from waste paint dregs increased with increase of gasification temperature, while that produced from wood chips didn't increase significantly with increase of gasification temperature. Pb was also volatile as in the laboratory experiment. The power generator efficiency of the diesel engine was 34% when the energy input ratio of fuel gas produced from waste paint dregs was 60%.

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The adsorption refrigerator is effective for improvement in energy efficiency in order to make waste heat an useful energy source. Since the performance of an adsorption refrigerator will be greatly influenced by the cooling temperature of adsorbent, a performance will deteriorate under the highly ambient temperature. We devised a new system which makes it possible to bring out useful performance even under the high ambient temperature by using multistage adsorbers. The performance of the new device was studied by the experiment and the simulation.

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The flow loss in the regenerator mainly depends on fluid friction through the regenerator matrix, but it is also generated by sudden expansion and contraction flow at the regenerator ends. The entrance areas at the regenerator ends of typical Stirling cycle machines are smaller than the cross-sectional area of the regenerator matrix. So, the gas flow in the matrix becomes a flow field with non-uniform velocity distribution accompanying the expansion and contraction flow. In this paper, the geometry of a tapered flow passage between the regenerator ends and the matrix to produce more uniform flow in the matrix, is examined experimentally using steady single-blow equipment to model a regenerator with a narrow flow passage at the ends. Additionally, the effects of the flow passages are analyzed using CFD. The effect of the tapered flow passage, in producing more uniform flow, is greater than that of the gap.

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Relevant to Self-propagating High-temperatuzre Synthesis (SHS) process for Mo-Si system, burning velocity and range of flammability are examined not only experimentally but also theoretically, by varying Mo particle size in a relatively wide range, as well as mixture ratio of Mo-to-Si, degree of dilution by MoSi₂, and initial temperature. Although effects of the mixture ratio, degree of dilution, and initial temperature on the burning velocity are the same as those for other representative systems, the particle size effect has turned out to be quite different from those for these systems. It is found that with decreasing Mo particle size, the burning velocity first increases gradually, reaches a plateau, and then decreases steeply. The promoting effect of this burning behavior can be attributed to an increase in the heat generation rate, caused by an increase in the total particle surface that participates in the reaction; while the suppressing effect can be attributed to dilution by oxides, the portion of which in the particle increases with decreasing particle size. By the same token, it is found that the range of flammability for steady combustion is restricted, due to the heat loss from the flame. In order to further elucidate effects of dominant parameters on the burning velocities, range of flammability, and/or limit of steady combustion, theoretical study has also been conducted, based on the heterogeneous theory for the SHS flame propagation, with oxide-layer thickness over Mo particles taken into account in the formulation. It has turned out that the theoretical result for the burning velocity fairly represents the experimental result. Furthermore, range of steady combustion is found to be bounded by limits, upper one of which is due to suppression of the heat generation rate by increasing particle size, and lower one of which is due to dilution by the oxide-layer over Mo particles. It is also demonstrated that fair degree of agreement exists between the experimental and theoretical results, as far as the trend and approximate magnitude are concemed.

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Combustion behavior of pulverized coal has been observed with flash pyrolizer. Produced gas emission behavior has been investigated by high-speed continuous analysis with FTIR. The following results are acquired. (1) Coal combustion behavior is divided into volatile matter combustion and char combustion, and they are checked clearly. (2) The difference of the volatile matter combustion time by kind of coal is hardly seen, and combustion time of pulverized coal is determined by the time of char combustion. (3) The char combustion domain of coal combustion and char combustion are mostly coincident. (4) The burnout time of coal becomes large in proportion to a fuel ratio.

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Cavitation and internal flow in the nozzle of a liquid injector are known to affect the atomization of a discharged liquid jet. In the present study cavitation in a two-dimensional (2D) nozzle and the injected water jet were visualized using an ultra high-speed camera. As a result, the following conclusions were obtained : (1) The behavior of cavitation in the 2D nozzle and liquid jet agreed qualitatively with the previous observations of cylindrical nozzles. (2) When the cavitation number σ was1.18, the inception of small cavitation bubbles was observed near the nozzle inlet apart from the side wall. (3) The number of cavitation bubble clouds increased with decreasing of σ (0.75≤ σ<1.18), and the streamwise length of the cavitation region increased toward the middle of the nozzle (developing cavitation). The bubble clouds were clearly observed to recirculate in the separated boundary layer. In the case a wavy jet was observed with no significant effects of cavitation on liquid jet atomization. (4) With a slight decrease of σ from0.75, the cavitation region suddenly extended to the nozzle exit (super cavitation). The shape of the cavitation region near the inlet became smooth, which imply the formation of a long cavitation bubble near the inlet. At the downstream half of the nozzle, clouds of cavitation appeared and collapsed intermittently within the nozzle. In the case atomization was promoted to form spray with ligaments and droplets.

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Cavitation and internal flow in the nozzle of a liquid injector are known to affect the atomization of a discharged liquid jet. In order to obtain the knowledge on the mechanism how cavitating flow in a nozzle enhances the liquid jet atomization, liquid velocity distributions of cavitating flows in a two-dimensional transparent nozzle were measured using a Laser Doppler Velocimetry (LDV) system. As a result, the following conclusions were obtained : (1) The inception of cavitation occurs near the outer edge of the separated boundary layer (SBL), where the mean local velocity takes the highest value and the mean pressure is lower than the vapor saturation pressure. (2) When the cavitation number σ≥0.78 (No Cavitation or Developing Cavitation), the reattachment of SBL occurs in the middle of the nozzle. A large velocity fluctuation, which appears in and just downstream of SBL, decreases near the nozzle exit. This may be the reason of the wavy jet. (3) Whenσ≤0.65 (Super Cavitation), the lateral flow from the core region toward the side walls just upstream of the nozzle exit may be the major cause of the increase in spray angle and a drastic promotion of liquid jet atomization. The strong turbulence just upstream of the exit may also play a role on the formation of ligaments at liquid jet interface.

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Injection rate measurement of a gaseous fuel injector was carried out by use of one-dimensional pipe flow. A production gaseous fuel injector for an NGV (Natural gas vehicle) was used, which is for an intake port fuel injection. The injection pressure was set at 255 kPa, and the injection duration was varied from 3.4 to 20 ms. Nitrogen gas was used as the test gas. The test gas was injected into a pipe from the injector, and the static pressure history was acquired with a piezoelectronic pressure transducer. One-dimensional, compressible, inviscid, adiabatic flow was assumed, and the instantaneous mass flow rate inside the pipe was estimated. By integrating the injection rate during the injection duration, the total amount of mass flow per one stroke was calculated. Caliburation test was carried out by use of a pressure vessel, from which the total mass flow during one stroke was estimated. Both data are compared, and it is shown that the injection rate measurement was carried out with an error of about 10%.

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In order to obtain strategies for controlling ignition timing and heat release rate in direct-injection PCCI combustion, a fundamental study was carried out using a constant volume vessel. Effects of injection quantity, injection pressure, nozzle orifice diameter and ambient oxygen concentration were investigated under PCCI-like ambient conditions. The results show that a low oxygen concentration reduces increase in peak heat release by increase in injection pressure and equivalence ratio. Enhanced mixing causes rapid heat release at higher overall equivalence ratios and an usual oxygen concentration ; however, it brings about delayed and reduced heat release at lower overall equivalence ratios or a lower oxygen concentration.

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This paper investigates the effects of the injection timing, injection pressure, and compression ratio on low oxygen diesel combustion with ultra-high EGR. The resuts showed while increases in ignition delays by advanced or retarded injection timings can effectively reduce smoke emissions, advanced injection timings have the advantages over retarded injection timings for maintaining thermal efficiency and preventing misfiring. To establish smokeless combustion it is essential that ignition occurs after the end of fuel injection. Although the smoke emissions decrease with increasing injection pressure in the oxygen content range 10-21%, the oxygen content that realizes smokeless emissions is lower than 10% regardless of injection pressure. Reductions in compression ratios are effective to increase ignition delay, to reduce the in-cylinder temperature, and to expand the smoke-less range for EGR and IMEP while the thermal efficiency deteriorates with excessively low compression rations.

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The utilisation of the oxygen storage capacity of TWC is recently focused on for the improvement of emission purification and the purification of an engine exhaust gas is achieved fairly high level. However, the control system is seemed to be complicated to use such ability. For the simple utilisation of this ability, a new air fuel ratio control system and algorithm was investigated. The fuel injection mass was modulated periodically and the air excess ratio was detected at the TWC outlet by an oxygen sensor. As the output signal of an oxygen sensor was switching type, the signal value was filtered by a moving average method for translation to an analog value and the moving average value was used for the periodic modulation control as the control value. Furthermore, the two feed forward control system were equipped for fast response and stability of the fuel control. This simple control system was operated at transient state in many driving conditions, and compared with other control systems. The proposed control system can cut the emissions of NO_x and THC concurrently and the reduced amount were larger than other control system.

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A heat transfer correlation was proposed for inline-arranged high-finned tubes. This correlation was based on the Bell-model, where two stream assumption is used, the primary stream and the bypass stream. In the proposed correlation, the actual heat transfer coefficient between fin and the primary stream was assumed to be predicted by the generally accepted correlation for staggered arrangements, and a correction factor was introduced, which corrects the bypass flow effect. Comparing existing experimental data, the correction factor was determined as a function of the ratio of fin spacing to fin height and of the Reynolds number. The proposed correlation showed good agreements with experimental data of plain and also serrated fins.

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