In order to study on disappearance phenomena of velocity fluctuation in the laminar-turbulent transition of spherical Couette flow with only an inner sphere rotating, we measured azimuthal component of velocity fluctuation at the equator for various clearance ratios β=0.06∼0.206, and considered the evolution of correlation dimension d, maximum Lyapunov exponent λ and power spectra of the azimuthal velocity component with an increase of the rotating Reynolds number Re for each β. Consequently, the following conclusions were obtained. The disappearance phenomena occur only for β≒0.13∼0.17. Even though d≒2, no T² torus appears in the case of λ>0. The kinetic energy of disturbance increases with Re in the range of higher frequencies in the case of β where the disappearance phenomena do not occur, but decreases to almost zero in the case where they occur.

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In the spherical Couette flow with only an inner sphere rotating, relaminarizing flow in the laminar-turbulent transition process has been investigated by the introduction of infinitesimal disturbances from the external into the supercritical flow modes with a pair of toroidal Taylor-Gortler (TG) vortices. Normal and reverse bifurcations are discussed. The onset Reynolds numbers of toroidal TG vortices, spiral TG vortices and traveling waves as well as the onset Reynolds number of the relaminarization are influenced by the external disturbances, although the critical Re of the primary instability is not influenced. Influence of the external disturbances on rms values of velocity fluctuations is greater in the relaminarizing Re-region than in the lower Re-region. Fundamental frequencies of disturbances are not influenced by the external disturbances.

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The disintegration process of a radial liquid sheet due to laminar-turbulent transition is investigated by LDV measurement. Radial liquid film flow is generated by a water discharge through a small gap formed between the end of a nozzle and the flat surface of a disk. The liquid film flow spreads radially on the disk, flowing from the disk edge into the still air as a liquid sheet. Sudden laminar-turbulent transition occurs in the liquid sheet when the Reynolds number exceeds a critical value, resulting in the perforation and the disintegration of the liquid sheet: the configuration of the liquid changes from the liquid sheet into ligaments and drops in the disintegration process. In order to identify the liquid configuration, a laserbeam through the liquid sheet is detected using a photo sensor. LDV measurement synchronized with photography and photo-sensing reveals that while small drops are formed as satellite drops at low Reynolds number, they are done by separations from microprojections, which exist on the ligaments and the edges of perforations, at high Reynolds number.

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Transition from steady thermal convection to unsteady convection in a square channel heated from below is predicted by means of the secondary instability analysis. In the presence of a through flow, longitudinal roll is realized for the Reynolds number and the Rayleigh number above the critical values. It is steady and two-dimensional, and aligns along the channel. Linear stability of the longitudinal roll with respect to unsteady three-dimensional disturbances is examined numerically. Stability boundaries of the longitudinal roll are specified for the Prandtl number Pr=7 and for two kinds of thermal boundary conditions on the sidewalls. For the perfectly conducting sidewalls, the longitudinal roll is predicted to become unstable as a result of two kinds of instabilities. For the perfectly insulating sidewalls, the longitudinal roll is found to be stable for a wide range of the Reynolds number and the Rayleigh number, while additional two kinds of instabilities are found.

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Stability of thermal convection in an inclined slot which is differentially heated is examined. The temperature dependence of the viscosity, thermal conductivity and density is taken into account as non-Boussinesq effects. As a result of the linear stability analysis, oblique modes are predicted not to become critical, and either longitudinal mode or transverse mode gives the critical condition. We specify the existence regions of the longitudinal mode, the transverse shear mode, and the transverse buoyancy mode in a parameter space involving the inclination angle of the slot.

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The laminar-turbulent transition of spherical Couette flow between two independently rotating concentric spheres for the gap ratio 0.14 where the Taylor instability occurs for the fixed outer sphere has been investigated by simultaneous spectral and flow-visualization measurements. Rotation frequencies (phase velocities) of periodic disturbances do not so much depend on the ratio of the outer-to the inner-sphere rotating Reynolds number if they are non-dimensionalized by the mean rotation frequency of both spheres. Traveling azimuthal waves on only an inflow boundary of toroidal Taylor-Gortler (TG) vortices and herring-bone waves appear for the case of co-rotating spheres, while spiral vortices and twists in toroidal TG vortices appear for the case of counter-rotating spheres. Flow regimes and their occurrence-regions in the plane of the inner- and outer-sphere rotating Reynolds numbers differ depending on the Reynolds-number history.

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Boundary layer suction is applied to a turbulent boundary layer through a short strip of perforated wall to examine the development of near-wall coherent structures downstream of the suction area. Low-frequency fluctuations, which are markedly suppressed near the wall during relaminarization due to the boundary-layer suction, start to grow algebraically downstream of the suction area, leading to retransition to wall turbulence. The algebraic growth of near-wall low-frequency fluctuations in the retransition process is found to be due to appearance and development of near-wall low-speed streaks, which are responsible for by-pass boundary-layer transition caused by high-intensity background turbulence.

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A difference method of spatially fourth order accuracy on the staggerd mesh points is applied to study the transition of natural convection in a cubic box heated from below with insulating side-walls. Special attentions are paid to the sensitivity of the solution on the degree of spatial resolution and transformation way of the coordinate variables to concentrate mesh points near the boundaries. As a preliminery study, numerical solutions of the cavity flow are computed. The present results agree with those ohtained by the methods with high accuracy reported in the previous paper. It is found that the natural convection which initially grows symmetrically with respect to the vertical center line, changes to a lateral single roll as time proceeds. The critical Rayleigh number is about 6 050 slightly smaller than 6 798 which has been obtained for the fixed boundary condition by use of the linear stability analysis (Mizushima et al. 1997).

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By-pass transitions of the plane Poiseuille flow originated from the various initial disturbance are simulated directly on a parallel computer. The simulations are started with initial flows given by the basic flow plus small disturbances with different amplitudes for various Reynolds numbers. It is found from the simulations that when an amplitude of the disturbance velocity is greater than the threshold value, which depends on -1.7 power of the Reynolds number, the by-pass transition of the flow is triggered by the instability of streamwisevortex components in the disturbance. From the visualization of the vortical structures in the transitional flow, we obtain that fine streamwise vortices are excited in the flow at early linear instability period and then, they are amplified to turbulent spots at nonlinear instability period. Finally, the flow breaks down to turbulence.

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It is important to investigate a pressure profile when a diffracted shock wave interacts with a reflector from a safety point of view. Because the diffracted shock waves are often generated by the explosions of combustible gases to cause serious damages against human race and surrounding buildings. The maximum pressure behind reflected shock wave is one of the most important parameter and this report is concerned with the evaluation of maximum pressure, which might be a function of Mach number of the shock wave, distance from a source of the shock wave, initial pressure of the gas, and initial diameter of the shock wave, etc. In this study, a detonation-driven shock tube of 14 m long and 50 mm diameter is used to generate a strong shock wave of propagating Mach number M_S=3.0∼5.2. The shock wave is diffracted from an open end of the shock tube of 25 mm diameter and reflected from a cylindrical reflector of 50 mm diameter. These phenomena are observed using color-schlieren optical techniques and the pressure histories at the stagnation point of the reflector are simultaneously measured. As a result, (i) The behaviors of the diffracted shock wave and complicate flow-fields behind reflected shock wave are observed. (ii) An empirical equation to calculate the maximum pressure behind reflected shock wave is estimated by the results of experimental and numerical simulation.

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Three-dimensional numerical simulations in the large-scale CZ method are carried out to investigate the complicated melt flow. Large Eddy Simulation (LES) is adopted to calculate unsteady, turbulent buoyancy-driven flow fields. When the crucible and the crystal keep static, the melt flow becomes non-axisymmetrical as the temperature of the crucible wall increases because of the instability of the potential energy, and finally it turns out to be turbulent. The oscillation of velocity in the circumferential direction is also observed near the free surface, and it causes the mode transition in the temperature field. On the other hand, when the crucible and the crystal rotate constantly, the natural convection driven by the buoyancy is greatly suppressed because of the large magnitude of Coriolis' force, and the forced convection dominates the flow field.

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Numerical simulation studies on the removal of contaminants in the conducting fluid using the electromagnetophoresis are presented. Applying the high-frequency electromagnetic fieled to the conducting liquid, two vortices are induced in a cylindrical pipe. The upstream vortex conveys the contaminants from the center to near the wall. In the region near the surface opposite to the induction coil high Lorentz force acting on the liquid results in the electromagnetophoresis of contaminants toward the wall. With the increase in the current of coil the removal efficiency increases. There exists the optimum frequency to the efficiency because of the compensation of the electromagnetic coupling and the skin effect. The removal efficiency also increases with the coil width.

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This paper presents drag reduction in a pipe flow with riblet. The experiment was carried out in the pipe flow apparatus with test section of inner diameter D=492 mm and length 4 000 mm. The parameters were selected 5 kinds, in order to investigate the details of drag reduction for the shape and size of the isosceles V groove riblet. The velocity profiles, static pressure and flow rate were measured for each experiment in the range of Re=3.0×10⁵∼8.0×10⁵. Consequently it was found that (i) the friction drag reduces in the range of non-dimensional riblet height h⁺≤20 and the maximum drag reduction attains almost 8% at h⁺=11.4, and (ii) the optimum shape and size of riblet were shown for the maximum drag reduction in a pipe flow.

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Numerical study was conducted for vertical flow of magnetic fluid in a partly heated pipe wall. It was assumed that the magnetization of magnetic fluid changed linearly to the imposed magnetic field and temperature. As the results of the calculation, the total heat transfer coefficient as well as the local one were obtained for various magnetic, temperature and flow conditions. It was yielded that the heat transfer characteristics were affected by the magnetic field dynamically and the total amount of heat transfer from the heated wall was increased with magnetic field and Reynolds number.

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The streamwise rotational vibration of the skinplate of Tainter gates induces an excessive push-and-draw pressure. The potential theory developed for dissipative wave radiation problems was applied to analyze the push-and-draw pressure, where the circular-arc skinplate was replaced by a vertical, flat and rigid weir plate so that theoretical calculations could be made. This paper presents theoretically derived dimensionless equivalent added mass and the wave-radiation damping coefficients due to the rotational vibrations of the vertical, flat, and rigid weir plate. The theoretical push-and-draw pressure was applied to derive the equation of motion of the flow-induced rotational vibrations. Nondimensionalization of these equations of motion yielded the equivalent added mass and the wave-radiation damping coefficients in dimensionless form. Model experiments for free vibration tests of a vertical, flat and rigid weir plate model, both in air and in water, were performed to measure the equivalent added mass and the wave-radiation damping coefficients. Experimental results compared favorably with the theoretical predictions, thus validating the theoretical analysis of the equivalent added mass and wave-radiation damping coefficients as a prediction tool for flow-induced vibrations.

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When circular cylinders are moved in still water, it is known that fluctuating lift exhibits nonrecursive characteristics even if the cylinder is repeatedly towed or swung under the same conditions. In this study, the cylinder is operated near a wall in towed or swung motion to investigate the effects of interaction with the wall on the nonrecursive characteristics of fluctuating lift. The effects of the interaction were evaluated by standard deviation of ensembly collected lift data at each towed distances or swung angles. The results obtained by this study will be applied to the development of manipulator arms operated in water where the effects of mechanical vibrations are insignificant in comparison of those of fluctuating fluid forces associated with vortex formation and the wall interaction.

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The purpose of the present paper is to examine experimentally the drag reduction of square prisms with the cutout of rectangular shape at their edges. The drag and lift coefficients, the base-pressure, the Strouhal number and pressure distribution are measured for various angles of attack from 0° to 90°. The present experiment shows: (1) The drag coefficient of the square prism with a cutout is smaller than that without the cutout. (2) For the case of angle of attack small, the drag coefficient of the square prism with the cutout is approximately constant against the change of the angle of attack and it is smaller than that of a circular cylinder. (3) The minimum pressure coefficient on the front cut surfaces is smaller than base pressure coefficient, in the case where the drag coefficient becomes minimum value, 0.8.

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This paper describes the gas-liquid interface shape and the internal flow field of a liquid bridge that is placed to bridge the cross-section of a horizontal narrow rectangular converging channel made of glass with a gap size of 1.2 mm and a converging angle of 2.97°. Such a liquid bridge is moved to the smaller cross-section by surface tension. Liquid bridge are observed and transported in semi-scale channels and also in gas-liquid separator under a microgravity condition. Thus, it is important to understand the liquid bridge behavior from point of view of semi-scale flows dominated by surface tension. In the present study, a liquid bridge made of ethyl alcohol or mixture of water and ethyl alcohol as the liquid was viewed from the top and the side. (1) The internal flow fields of the liquid bridge in the side view were quantitatively measured by the brightness distribution cross-correlation method, i.e. PIV (Particle Imaging Velecimetry). (2) The gas-liquid interface shape was expressed using Fourier factors, and the feature was clarified. (3) Effects of various parameters on the liquid bridge behavior were examined.

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Recently, there are great requirement for ultra fine powder in IT industry. Especially, the request of the diameter control of ultra fine powder is increasing. Pneumatic type ultra fine powder separator or classifier, is one of the equipment which meet the request. But, there is no study which makes clear the flow condition quantitatively and qualitatively. The purpose of this study comes out of a check of being the inner flow which can give a large centrifugal force to all particles. The flow of pneumatic classifier is investigated by flow visualizations in tuft grid and oil dot methods, and measurement of gas velocity. As the results, this classifier has a large revolution velocity of flow to be able to classify ultra fine particle in high accuracy.

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The bubble-bubble interaction in a swarm of wall-sliding bubbles is experimentally investigated using an image processing measurement. At first, the drag coefficient of a vertically sliding bubble is measured for the range of Reynolds number from 2 to 9. Secondly, the two-dimensional pattern of the bubble-bubble interaction in a layer of wall sliding bubbles is detected by using particle tracking velocimetry (PTV). The evolution of relative coordinates and the relative velocity vectors of the bubbles are clarified by the statistical data analysis. Also, hydrodynamic mechanism of the bubble-bubble interaction is discussed with the present data comparing literatures on twin bubble interactions.

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Three-dimensional separation of the flow over a slender body at high angles of attack is difficult to model and still a challenging problem. The singularity of the flow, such as large sideforces and yawing moments, is caused by mutual interactions of three-dimensional separation and separated vortices. In this study, the flow in the cross-flow separation region of an axisymmetric paraboloid at 40 and 50 deg angles of attack has been investigated experimentally by smoke visualization technique and hot wire anemometer. Reynolds numbers are 9.0×10³ and 1.8×10⁴ referred to the base diameter. The process of the change from symmetric to asymmetric vortices and vortex breakdown has been identified on the basis of the visualization results. It was suggested that the relations between separated vortex and the other flow regions, such as primary separated flow region, reattachment flow region and external flow region, are estimated calculating two-points velocity cross-orrelation in various cross-sections.

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The ceramic gas turbine for cogeneration system is operated under its high temperature; the flow Reynolds number falls. Because the fluid temperature rises, the viscosity increases. The flow around the turbine blade involves complex flow, for example a separation. LES (Large Eddy Simulation) calculations are performed. Smagorinsky and Structure Function models are selected for the turbulent model. An identification method for the turbulent structure around the turbine blade based on Q is shown. The Q is defined as the second invariant of velocity gradient.

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Numerical analysis has been performed for three-dimensional developing turbulent flow in a curved pipe with contraction inlet by using an algebraic Reynolds stress model. Special attention is paid for the developing turbulent flow in curved pipe under the condition that the intensity of fluctuating velocity is low value at the inlet cross section of curved pipe. Such developing turbulent flow plays an important role in several engineering fields as well as a fully developed turbulent flow. In calculation, algebraic Reynolds stress model is adopted in order to predict preciously Reynolds stresses and boundary fitted-coordinate system is introduced as the method for coordinate transformation to set boundary conditions along complicated shape of curved pipe. Calculated results are compared with the experimental data in order to examine the validity of the presented numerical method and turbulent model. As for the comparison of mean velocity, the calculated results are relatively good agreement with the experimental data and are able to reproduce characteristic features observed in developing turbulent flow. By contrast to the comparison result of mean velocity, it is found that the present calculation has a tendency to overestimate the value of turbulent energy in a curved pipe region. Adding to this, it is pointed out as a characteristic feature that the region with high intensity is generated near inner wall region which phenomenon is also recognized in mean flow field.

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The objective of the present study is to elucidate the mechanism of interaction between global and local structure of turbulence, especially the influenced of inter-bubble spacing on the microscopic flow structure in bubbly flow. We explored the flow structure in the vicinity of the bubble in conjunction with bubble deformation by PIV/LIF and a shadow image technique respectively. The experiment consisted of a fully developed vertical upward channel flow with 0.5% and 1.0% void fraction. We used a small quantity of 3-Pentanol as surfactant to control the bubble diameter and number density of bubble. Our main conclusion is that not only the void fraction but also the distribution of the bubble diameter serves as characteristic spatial parameters of the turbulent structure of bubbly flow. Enstrophy contours characterizing turbulent modulation were derived from velocity data measured by PIV/LIF. The high intensity of enstrophy was distributed around the large bubble and in the narrow inter-bubble spacing. The spatial scale of enstrophy was almost the same as the vorticies induced by these large bubbles.

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Direct numerical simulations of fully developed Couette-Poiseuille type turbulent flow are performed. The velocity law of this flow depends on the Reynolds number and two non-dimensional parameters of the shear stress gradient. We pay a particular attention to the effect of the shear stress gradient on the velocity distribution on the Couette-type flow. Computational results are dependent on the three non-dimensional parameters and are compared with theoretical laws and existing experimental data. The law of the mean velocity profile for Couette-Poiseuille type turbulent flow is considered in the regions characterized by 1/2-power law and velocity defect law. In particular, it is shown that the influence of turbulent diffusion from the opposite wall appears in the flow with large shear stress gradient and 1/2-power law is restricted to narrow region.

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The surge inception of a centrifugal compressor is studied by investigating the attractor behaviors in the phase portraits. The pressure time traces measured at the exit plenum of a compressor system are reconstructed on the phase portraits and the deformations of the attractors occurred preceding surge are shown. The possibility of detecting the surge inception by the proposed method is suggested.

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The Liquid Droplet Radiator (LDR) has an advantage over comparable conventional radiators in terms of the rejected heat power-weight ratio. Therefore, the LDR has attracted as an advanced radiator for high-power space systems that will be prerequisite for large space structures. In this study, the performance of a droplet emittor under microgravity condition has been investigated from the viewpoint of operational space use of the LDR in the future. From experiments, it is considered that the droplet emittor can produce uniform droplet streams under microgravity condition in the non-dimensional wave number range from 0.215 to 0.490. In this range, the droplet diameter and the spacing range are from 204 to 285 [μm] and from 445 to 1 160 [μm] respectively. And it is concluded that these diameter and spacing can be estimated by the equations based on the law of conservation of mass in the process of generating droplets.

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The internal flow in a centrifugal pump with semi-open impeller is visualized and measured by PTV method. In this pump, the design type number is 0.244 of low specific speed. The experimental results of two impellers whose outlet angles are 30 and 90 degree are compared. At the outlet of impeller, most of the quantity of fluid flows out along the pressure side of the vane, but some climbs over the top of the vane and flows into the suction side through the tip clearance. When the total quantity is changed, the meridian velocity distribution changes only near the tongue area, and in other area the meridian velocity is almost same. When the quantity becomes small, large vortices are produced between vanes, and this vortex reduces the tangential velocity at the outlet of impeller. This causes the reduce of theoretical head and instability in the performance curve.

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This paper deals with an experimental study on the generation of sink-mark and residual stress in a press formed glassware. Since both phenomena appear in the cooling process after pressing, it is considered that they were related with the growth of solidification layer on the press-formed surface. In this paper, the growth of solidification layer in a glassware and the generation of residual stress due to non-uniform shrinkage of glass, i.e. the generation of thermal tempering stress were numerically predicted, and the mechanism dominating the generation of sink-mark and residual stress frozen in a press-formed glassware was discussed by comparing the numerical results with those measured in actual glassware, which were press-formed in this study. The obtained results can be summarized as follows: (1) With elongating the pressing duration, both the sink-mark depth and the compressive residual stress at the pressed surface decrease while temperature at the pressed surface are little affected by the pressing duration. (2) The pressing-duration dependency of the sink mark and residual stress at the pressed surface is qualitatively explained well by a hypothesis that the thermal tempering stress starts to appear in the glass just after the deformation of the pressed surface, i.e. the generation of sink-mark stops due to the rigidity of solidification layer, and that the switchover timing becomes later as the pressing duration is elongated. (3) The compressive residual stress at the pressed surface is considered to consist of the thermal tempering stress due to non-uniform shrinkage of glass and the bending stress in the solidification layer due to sink mark generation.

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An experimental study was performed on the effects of heating conditions and the initial temperature of a fluid T₀ on free convection heat transfer in a stably stratified fluid. The stratified layer was formed in a rectangular container using sucrose aqueous solution, and was heated laterally from one side at temperature T_h with constant heat flux and cooled from the other side at constant temperature T_c. The experiment was conducted for both cases of T₀=T_c and T_c< T₀< T_h. From a comparison with previously reported results for constant heating temperature it has been found that the constant heat flux condition tends to create uniform convection layers, and that the effects of the initial temperature on the heat transfer are limited to the early stage of heating. A relation between the thickness of a convection cell and the heat transfer coefficient was also clarified in the preset study.

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An experimental study was performed on free convection heat transfer in a stably stratified fluid between coaxial cylinders. The stratified layer was formed using a sucrose aqueous solution, and was heated from the inner cylinder at constant heat flux and cooled from the outer cylinder at constant temperature. As a result of generation of cellular convection layers in the stratified fluid the local heat transfer coefficient at the heating surface becomes larger in the upper part and smaller in the lower part, since the heating surface is below in the former case but above in the latter case. This distribution of the local heat transfer coefficient is quite different from that for a nonstratified fluid, where the local heat transfer coefficient decreases in the upward direction. The transient characteristics of the heat transfer and flow in the stratified fluid was also clarified comprehensively in the present study.

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This paper presents discussions on predicting turbulence and heat transfer by a version of the two-component-limit (TCL) second moment closure. It is a realizable low Reynolds number turbulence model originally developed at UMIST. For turbulent heat flux, a higher order version of the generalized gradient diffusion hypothesis (GGDH) is applied. Encouraging results have been obtained in turbulent channel, backward step, and square sectioned duct flows. It has been confirmed that the TCL second moment closure produces sufficiently reliable results for all flows tested. For the heat transfer prediction, it has also been shown that the use of the higher order GGDH heat flux model improves the results of the standard GGDH model.

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This study is concerned with the method of control of thermal convection in a vertical fluid layer by utilizing a shape memory screen consisting of a row of shape memory alloy plates with two-way shape memory effects. Numerical and experimental results show that the shape memory screen, which brings about the temperature dependency of flow resistance, can suppress the formation of temperature stratification in the vertical direction. It is found that the shape memory screen can reduce the average Nusselt number.

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We have developed a method of cooling high-power-density CPU modules within a bending duct. The method uses a jet-duct system made of an air duct and axial fans. This system has slit orifices upstream from the CPU modules. Pressure drops in this system are calculated as four values: wringing loss in the chamber, friction loss in the duct, extrusion loss from the duct, and wringing loss in the slit orifice. These loss values agree with the experimentally measured losses to within an error of ±10%. The calculation showed that when the duct width is small, the wringing loss in the chamber account for the major part of the total loss. Experiments in a wind channed show that a CPU module can be cooled by a volumetric flow rate of more than 0.32m³/min and a velocity in front of the CPU module of more than 2m/sec. These results show that the jet-duct system has good cooling performance and redundancy.

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In this paper the effect of rotational degree of freedom on the properties of liquid is analyzed by the Molecular Dynamics (MD) Method. Oxygen is assumed as the liquid and molecules are assumed as both monatomic and diatomic one. Lennard-Jones (LJ) potential is used as the intermolecular potential for monatomic molecule and 2 center Lennard-Jones (2CLJ) potential is assumed for diatomic molecules. Simulations are performed at various combinations of density and temperature and an Equation of State (EOS) of each liquid is obtained by using these results. The parameters of each potential are determined so that the critical temperature and density are consistent with each other. The properties of liquid such as spinodal line, latent heat, specific heat, thermal conductivity and surface tension are compared with each other and the effect of rotational degree of freedom on the properties of liquid is investigated.

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The verification test of flow induced vibration (FIV) in U-bend tube bundles of steam generator (SG) have been carried out using model steam generator, equipped with the large scale U-bend tube bundles, in a freon two-phase flow loop. The objectives of this program are to confirm the margin of FIV of SG U-bend and to advance the evaluation techniques of Thermal-hydraulic flow and FIV for SG U-bend. This report (Part 1) shows the experimental facilities which is included the modeling of a steam generator and the results of thermal-hydraulic test which is included the results of analysis. Another results are shown in Part 2 and Part 3 report. The conclusion of this paper is that void fraction and velocity profile of U-bend tube bundle are obtained in detail and analysis code (FIT-III) is verified very well by using these data. Therefore, it is considered that the results of FIT-III are valid for evaluation of flow induced vibration in actual SG.

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For an enhancement of power generating system, the CH₄/O₂ fired gas turbine that is one kind of CBC (Closed Brayton Cycle) and the CH₄/O₂ fired steam turbine are proposed as a solution of high performance and non-CO₂ emission into the environment of atmosphere. The combined plant of these two closed cycle systems results in the generating efficiency of 60.1% HHV at 1 350°C of firing temperature and 61.8% HHV at 1500°C. The CH₄/O₂ fired gas turbine can supplant a conventional open cycle gas turbine in a combined cycle power plant. On the contrary, the CH₄/O₂ fired steam turbine can be used with a conventional open cycle gas turbine. These two applications are expected as the modification of conventional combined cycle to achieve the reduction of CO₂ emission or repowering.

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There are two kinds of main pollutants (NO_x and Dioxins) which can be controlled by municipal refuse combustion procedure improvements. The reduction phenomena of both of them are completely different, so that appropriate combustion condition must be considered separately. The basic theory to decrease NO_x is to make self de-NO_x combustion area and to maintain longer residence time in this area by decreasing primary combustion air supply. Also it is required for low dioxins combustion to maintain high furnace temperature and longer residence time in this area by decreasing combustion gas volume and well mixing of unburned combustion gas and air. We present in this paper the experimental results to determine the lower limit volume of primary combustion air, using over fire air and/or recirculated combustion gas injection into furnace and oxygen enriched primary combustion air supply. The best result would be presented by actual scale municipal refuse incineration test. The combination of oxygen enriched primary combustion air, recirculated combustion gas injection into lower furnace and overfire air injection into upper furnace can decrease NO_x and dioxins simultaneously.

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Characteristics of homogeneous charge compression ignition (HCCI) combustion using dimethyl ether and methanol-decomposed gas were experimentally analyzed. This research controlled ignition timing in HCCI combustion by varying a ratio of a high cetane number fuel and a high octane number fuel. Dimethyl ether was employed as the high cetane number fuel and methanol-decomposed gas, mixture of 67% hydrogen and 33% carbon monoxide, was as the high octane mumber fuel. Both dimethyl ether and methanol-decomposed gas can be reformed from methanol in endothermic reactions using exhaust heat of engines. The experiments were made with several equivalence ratio, proportions of the fuels and compression ratio. The results show that the HCCI combustion with dimethyl ether and methanol-decomposed gas has high thermal efficiency over a wide operational range.

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Effects of droplet diameter, liquid and vaporized fuel concentration on the ignitability of fuel spray were investigated. A large number of ignition trials of various methanol liqui/vapor/air mixture were carried out. As a result, ignition probability increases with the increase of the liquid and vaporized fuel concentration and decreases with the increase of droplet diameter. The particular condition exists which fuel spray is not always ignited successfully even if the total fuel concentration is higher than that of lean ignition limit of vaporized fuel. In addition, simple probabilisticignition model that based on the fluctuation of spray concentration is applicable for macroscopic evaluation of ignition phenomenon. However, from the result of instantaneous liquid fuel concentration measurement, the assumption of probabilistic model, i. e., ignition is deterministic by the instantaneous liquid fuel concentration just befor ignited, is not adequate for microscopic evaluation.

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A reactant gas seal is one of critical issues to achieve the reliability of the MCFC stack which is a key equipment in MCFC power plant. The wet-gas seal with carbonate melted at operating temperature (650°C) is generally expected to be suitable for such a seal. We develop the wet seal configuration composed of thin sheet metal parts to be cost-competitive with other power plants. In this report, the proposed configuration of wet-gas seal using thin sheet metal parts is produced for trial, which is assembled in single cells. The leak rates from wet seals were examined under the condition of MCFC operating temperature. Then, the superior seal performance was found and it is confirmed that the wet seal configuration composed of thin sheet is reliable.

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This paper covers our investigation into a decline in Fuel Cell performance resulting from hydrogen fuel containing CO. Here, we had several investigations into CO poisoning on dependence of types of catalyst between Pt and Pt-Ru alloy. The results are summarized as follows: 1) The poisoning prediction formulas and the poisoning estimation coefficient to predict and estimate the FC performance were derived theoretically. 2) The actual process of CO poisoning was scrutinized by focusing on adsorption of CO and desorption of CO₂ molecules, and changing of several polarizations of FC caused by CO poisoning were estimated. 3) Investigations into the relationship between the CO concentration, operating pressure, operating temperature and the CO poisoning were carried out. If FC underwent at a high CO concentration, no significant improvement could be expected by operating at increased pressure, and effects of the operating temperature is almost the same between two types of catalyst.

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Extinction and flame front behavior of ultra lean premixed flames of propane/air and methane/air mixtures formed in opposite turbulent flow have been studied experimentally. Extinction limits, velocity profiles and time series flame front movement in the near extinction limits have been measured and the extinction mechanism has been discussed. The distance of hot and cold boundaries between the upper flow and the lower flow are increased due to turbulent burning velocity. Furthermore, the flame stretch duo to flame wrinkling as well as the turbulent flame motion also affect to the flame extinction. Therefore, the extinction limit increases with increase in the turbulence. Extinction limits of the propane-air flame depend on the more concentrated burner condition regardless of the less concentrated burner condition. The methane-air ultra lean mixture could be react impinging to the high temperature burnt gas and the stable region extends to the lower fuel concentration zone. The characteristics of hot and cold boundary movement remarkably change with the concentration of the premixed gas even when the turbulence conditions of the approach flows are equal.

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In order to clarify flame base structure of turbulent lifted diffusion flame, two flames (Re=4 200 and 6 700) have been experimentally investigated in the configuration of a coflow nozzle. Fuel is methane/hydrogen mixture. These flames were visualized by the schlieren method and OH radical luminescence was also captured by an ICCD camera to characterize the flame bases. Quantitative argumentation of the flame bases has been done on the temperature fields measured by the Rayleigh scattering method; especially, on the temperature dissipation rate and the scalar dissipation rate. Flame bases of turbulent lifted diffusion flames are exposed to small-scale turbulence and emit the light from OH radicals strongly. Both of the vortex-flame interaction and the partial premixing are possibly related to the phenomenon. On the other hand, the scalar structure of the flame base seems to be close to the conventional flamelet structure to show lognormal probability density distributions of the scalar dissipation rate.

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There are many advantages in using emulsified fuels. The emulsified fuels with secondary atomization can enhance the transformation efficiency of fuels, and more importantly they can reduce NO_x emission and particulate matter. In this paper, the secondary atomization is observed when an emulsified fuel droplet is heated by an electric furnace. The secondary atomization of the fuel droplet has been classified into micro-explosion and puffing by the high-speed photography. In addition, it is proposed that the A. E. (Acoustic Emission) technique is used for the judgment of the generation of micro-explosion. It is confirmed to judge the generation of micro-explosion by the sound pressure or its FFT analysis.

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For developing internal combustion engines best suited to needs in the market, it is necessary to keep a suitable balance among performance, reliability, manufacturing costs and so on targetted in the stage of initial planning. Since engine mass is closely related to engine manufacturing costs, it is desirable to establish suitable target values of engine mass in this stage. For this purpose, the authors developed the method of simulation for estimating and evaluating the mass of two-stroke cycle, low-speed diesel engines before, and papers on this method were presented in the several transactions. This time the authors developed the method of simulation for estimating and evaluating the mass of four-stroke cycle, medium-speed, V-type diesel engines, based on the way of thinking similar to the above. This paper reports the contents of this simulating method.

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