The mechanism of secondary flow was discussed based on the result of an LES for the turbulence flow parallel to bundled rods. The LES was carried out in the Cartesian grid system using an improved immersed boundary method developed for accurate simulation of complex wall boundary of industrial interest. The method was verified by comparing the LES with a DNS of turbulence flow in a pipe. The LES for bundled rods reasonably reproduced the secondary flow of the second kind. We proposed a theoretical method to analyze the mechanism of the secondary flow. The result of the analysis indicated that the main source of secondary flow was the non-conservative component of Reynolds stress term as was the case for a square duct. The theory proposed that non-conservative force corresponds to the difference between the pressure gradient along the wall and the Reynolds stress term decreasing rapidly near the wall. The present theory will unify the understandings for the secondary flow of the first and second kinds. The present LES technique and theory is useful for investigating the physics in turbulence flow in complex walls.

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This paper describes a numerical solver of the Boltzmann equation which is originally developed for micro scale flow simulations. The convection terms are evaluated with an upwind gridless method, while the collision term is evaluated using a kinetic model collision term which correctly resembles the lower 13 moments of the Boltzmann equation. Validation of the solveris carried out for a supersonic flow over a circular cylinder at a free stream Mach number of 2.0 and several Knudsen numbers from 0.01 to 1.0. The numerical results are compared with those of the direct simulation Monte Carlo (DSMC) method and those of the compressible Navier-Stokes equations with slip boundary conditions. The comparison indicates that the results of the present Boltzmann equation solver are in good agreement with those of the DSMC method for the whole range of Knudsen number considered and the predictions of the slip Navier-Stokes equations are adequate if the Knudsen number is less than 0.1.

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An iterative partitioned coupling algorithm for fluid-structure interaction problems is implemented and its stability and efficiency are investigated in detail in this paper. The partitioned coupling algorithms, which can treat a structural problem and a fluid dynamics one independently, seem suitable for large-scale computation in parallel environments because the approaches can utilize existing parallel analysis codes. In this paper, an optimal selection of iterative partitioned coupling algorithm, which consists of dynamic control of relaxation factor, elastic predictor and consistent time integration scheme, was proposed, and numerical examples show its accuracy.

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The spatial structure of internal gravity waves and counter-gradient heat flux were investigated in a strongly stably-stratified mixing layer. Multi-point simultaneous measurement was made on its temperature and velocity fields by a rake of 7 cold-and hot-wire system. Streamwise change in temperature spectrum showed that the internal gravity waves developed in the mixing layer and suddenly collapsed in the downstream region. Vertical correlation between the temperature fluctuations became stronger as the internal gravity waves grew downstream. Coherence and phase difference between the temperature fluctuations showed that the collapse of the grownup internal gravity waves started from around the wave front. Nonlinear interaction between the resonant components and their higher harmonics generated negative heat flux by converting large potential energy contained in the waves to turbulent kinetic energy in the turbulence producing process.

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Propagation of pressure waves caused by a thermal shock in liquid metals containing gas bubbles is performed by a numerical simulation. The present study examined the influences of bubble radius and void fraction on the absorption of thermal expansion of liquid metals and attenuation of pressure waves. As the result of the calculation, since the large bubbles have a smaller natural frequency than small bubbles, the peak pressure at the heated region increases with increasing bubble radius. Contrary, the peak of propagated pressure wave to the wall decreases. But, when the bubble radii are around 500μm, the pressure wave propagates through the mixture not with the sonic speed of the mixture but with that of liquid mercury. And the peak of such pressure wave becomes higher than that of the pressure waves which propagate with sonic speed of mixture. On the other hand, decreasing the void fraction makes behavior of bubbles nonlinear and a collapse of bubble produces a high pressure wave. However, the calculation shows that the method of introducing micro gas bubbles into liquid metals is effective to prevent cavitation erosion on the wall.

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Experiments have been performed on turbulent channel flow with suction through a slit. The inclined angle of the suction is changed 30°, 60°and 90°at the main stream velocity 10m/s. The dimensionless suction flow ratio is varied nine steps in the range of 0.067-0.500. In order to investigate the relationship between fluid flow and heat transfer characteristics, local heat transfer coefficient, wall static pressure, wall shear stress, velocity profile and turbulence intensity are measured. In addition, the velocity profiles of the suction region are measured by the particle image velocimetry (PIV). Difference due to the inclined angle is not observed in the result of wall pressure and heat transfer coefficient. The heat transfer coefficient decreases as the suction flow ratio increases. The recovery mechanism of turbulence is greatly different between the lower side and upper side of the channel.

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A system for recovery of methane hydrate from the deep ocean floor has not been established. As one possible recovery system, a gas-lift system was investigating. Methane gas, which was generated from decomposition of methane hydrate in the recovery pipe, reduce the power consumption of gas-lift system. In the present paper, gas hydrate decomposition rate was measured by using HCFC141b hydrate. Methane hydrate decomposition phenomenon was simulated by gas hydrate decomposition model applied from lattice gas automata method. From the results of experiment and simulation, the formula which expressed the heat transfer around the lump of methane hydrate, was obtained as the relationship between Reynolds number and Nusselt number. Furthermore, methane hydrate decomposition quantity under recovery pipe condition was calculated from this formula. It was indicated that gas-lift effect generated from decomposition methane gas reduce the gas lift system for recovery of methane hydrate.

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Experimental investigations of the generation of resonant sound by flow in a pipeline containing two closely spaced orifice plates were performed. The frequencies of the tone generated were examined in detail when the velocity was increased from 3 to 25 m/s. In order to determine the convection velocity of vortices formed between the two plates, the measurements of the phase of fluctuating velocity were made using a hot-wire anemometer. The vortex shedding frequency is locked-in the pipe modes, but indicates a slight increase with an increase in the flow velocity. The ratio of the distance between the two orifice plates to the spacing of vortices is expressed by m+ε, where m is an integer and ε is a decimal part. It was found that the value of εdecreases with increasing flow velocity within the range from 0 to 0.5, and a change of the number of vortex or frequency jump occurs when ε reaches a limit value.

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The characteristics of large-scale coherent structures were investigated for a two-dimensional turbulent (Re=22000) jet undergoing self-sustained oscillations due to the interactions with the leading edge of a flat plate. The edge was placed 20 times the jet initial thickness away from the nozzle exit, x₁/b_e=20. The flow in this geometry was characterized by periodic oscillations, or edgetone, whose length scale reaches a distance between nozzle and leading edge. The X-probe hot wire data were filtered and phase-averaged to discriminate the periodic velocity fluctuation components from the steady and the non-periodic components. The spatial distribution of the vorticity derived from the periodic velocity components indicate clearly the generation of large-scale coherent structures at the frequency of the jet oscillations. Each coherent structure, or a fluid volume with a correlated vorticity, increased monotonically its lateral extent and the maximum magnitude of vorticity in it, as it was transported toward the edge. The contribution of the periodic velocity flucutuations to the Reynolds stress and the turbulence energy production by far overweighed that of the non-periodic fiuctuations in 10≤x₁/b_e≤30. The coherent structures indicated monotonic decay along the flat plate.

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It is well known that the airflow in the gas exchange bronchi in avian lung has a unidirectional nature. Since the direction of the flow is against the blood flow, the gas exchange efficiency of avian respiration is higher than that of mammalian counterpart. To clarify flow phenomena in avian lungs, oscillatory flow fields and concentration fields in a right angle branched tube, model bifurcation of avian trachea, were numerically studied. The three-dimensional incompressible Navier-Stokes equations were solved by SIMPLE method, while the convection equation of concentration was solved by CIP method based on the results of flow simulation. The results showed that separation vortex observed at the entrance of a side-daughter tube during inspiration drove the unidirectional net flow from the side-daughter tube to the daughter tube. Due to the convective inertia, unidirectional net flow persisted even in the expiration. It was clearly shown that the unidirectional net flow strongly enhanced axial mass transport. The effect of constriction just upstream of the bifurcation was also studied and increase in the magnitude of unidirectional net flow was observed in the case with constriction.

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Unsteady effect of rotor-stator interaction on turbine stage performance was investigated for two cases of axial spacings between stator and rotor, i.e. large and small axial spacings. Unsteady RANS simulations were performed to clarify several interesting features of the unsteady three-dimensional flow field in the turbine stage. Simulation results showed that the stator wake was convected from pressure side to suction side in the rotor. As a result, secondary flow was periodically generated by the wake passing through the rotor passage, and then the passage vortices in the rotor near the endwall were suppressed and fluctuated in the radial direction downstream of the rotor. It was found that turbine stage efficiency with the small gap was higher than that with the large gap because the wake entered the rotor before mixing.

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Reactor internal pumps (RIPs) are used in the advanced boiling water reactor (ABWR) nuclear power plants to circulate the reactor coolant in the reactor pressure vessel (RPV). Control rod drive housings (CRDHs) and control rod guide tubes (CRGTs) in the lower plenum were subjected to RIP discharge flow. Fluid force acting on those structures in the lower plenum must be evaluated in the next ABWR in which lower plenum structures are improved from the current design. Computational fluid dynamics (CFD) analysis is expected to evaluate the fluctuating fluid force acting on those structures. The 5 RIPs sector models of the reactor lower plenum were simulated to investigate the fluid force in the present study. Fluctuating fluid forces were calculated based on the velocity distribution obtained from the CFD analysis. Fluctuating fluid forces were applied to the structural models and those FIV stresses were calculated by the vibration analysis. As a result, flow in the lower plenum went along the RPV bottom and these flow characteristics were desirable for structures.

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A basic study of a gap flow in a closed piston-cylinder system of ER fluid was carried out. The purpose of this study is to elucidate flow behavior of ER fluid in the piston-cylinder system. The electric field is applied between inner wall of the cylinder and outer wall of the piston, and the pressure difference between upper and lower chamber of the piston is measured. Theoretical formula of pressure difference was obtained by the one-dimensional assumption of the flow in the gap of cylinder. Furthermore, simulation cord is developed in the present study based on the finite volume method (FVM) with moving boundary condition. In comparison with the theoretical approximation and experimental results, it was found that some difference occurrs in the case of the lower aspect ratio of the piston. However, when aspect ratio is large and piston speed is low, the theoretical approximation and experimental results show fair agreement. On the contrary the simulation results showed a good agreement with whole results in experiments.

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A method for aeroacoustic simulation, where the acoustic equations are split from the flow equations, is applied to calculate the acoustic field with a large solid surface. The acoustic equations employed here in this study can treat not only far fields, but also near fields. Specifically, the acoustic field around a rectangular cylinder on the ground surface is calculated. The calculation method is the finite volume method with the fourth order WENO scheme for values of the solution vector at cell interface as well as the two-stage Runge-Kutta scheme as time integration. This numerical method has been verified to provide reasonable results in complex acoustic fields. Comparison with experimental data shows that the acoustic field can be well predicted by the present method. Furthermore, the source location of acoustic waves is examined by visualizing the propagation path of those waves.

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In order to enhance the mixing and reaction yield in a microreator, an alternate pumping method has been investigated. As the visualization results of the flow patterns generated by the alternate pumping in several types of micro channel, the flow patterns were classified into five categories depending on the pumping conditions, which are the Reynolds number and the non-dimensional infusion time that are defined by the infusion flow parameters. One of the flow patterns which we observed is a layered structure and is able to contribute to enhancing the diffusion mixing, because the molecular diffusion time is proportional to the square of the diffusion length and the thickness of each layer in the layered structure can be taken thinner than the width of micro channels, which is the diffusion mixing length in the case of the convestional concurrent pumping. The most appropriate channel for creating the layered structure is a cross-shaped channel consisting of two inlets and two mixing channel. It is confirmed that the thickness of each layer is less than one-tenth of the mixing channel width, i.e. the mixing time is reduced to less than one-hundredth of that in the concurrent pumping with the same dimension.

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Bioconvection is a convection that is autonomously generated by the high-density suspension of some kinds of microorganisms. This study aims to apply the bioconvection to a power source of a micro mechanical system. For that purpose, the authors previously reported that a downward flow of bioconvection could be controlled by changing the electrical field. The construction of the experimental pool is that the bottom surface is covered with a positive electrode. A negative electrodes array is also installed at the top of the pool. In this paper, application system of electrical field was renovated to allow the application of any desired voltage to each electrode. Image processing system is installed to detect the position of the downward flow automatically. The configuration of the electrodes array is optimized to the shape that the width is 0.5 mm and that the gap between electrodes is 0.2 mm. Gaussian distribution is used to apply the electrical field by using plural electrodes. It was succeeded to locate the downward flow to any position. The maximum moving speed of downward flow is 0.14 mm/s. As an example of the mechanical application, it was also succeeded to drive a small seesaw automatically by the controlled downward flow with the reciprocating cycle 70-150 s.

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The adsorption refrigerator for automobiles reduces the impact on the environment, because it uses wasted heat of engine as its energy source. But the space for air conditioning devices in an automobile is not so enough in general that their volume must be very compact to assemble in a car. In this paper, the relationship between the specifications of the absorber and its volume was studied from simulations and experimental data. As a result, the necessary characteristics of the adsorbent and necessary specifications of heat exchanger were obtained.

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Motion of a nanoscale droplet on a solid wall with temperature gradient was numerically simulated by using the molecular dynamics method. The platinum (Pt) solid wall (fcc with surface of (1 1 1)) was composed, and the argon (Ar) droplet was formed on it. The number of Ar molecule was 1000, 2000, and 4000. The number of Pt atom was 8000 or 16000 for the semi-cylindrical droplet, and 32000 or 72000 for the hemispherical droplet. The mean wall temperature was 90 K, and the maximum temperature gradient was 2×10⁹K/m. On the isothermal wall, the droplet stayed around the initial location with some fluctuation. When the temperature gradient was applied to the wall, the droplet clearly moved toward the lower temperature side. In the hemispherical droplet case, the velocity was larger for the stronger fluid-solid interaction case, that is, the higher wettability and the lower contact angle case. On the other hand, the semi-cylindrical droplet case did not show a definite tendency in the effect of the fluid-solid interaction intensity on the velocity. Within the present computational conditions, the imposition of the temperature gradient did not make a distinct difference in the profile of the time-averaged interaction force exerted on the fluid molecules by the solid molecules, when compared between low and high temperature sides.

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An experimental study is performed on the effects of the inner cylinder diameter on free convection heat transfer in a stable stratified fluid between coaxial cylinders. The stratified layer is formed using a sucrose aqueous solution. and is heated from the outer cylinder (70mm I.D.) at constant heat flux and cooled from the inner cylinder at constant temperature. The experiment is conducted for the inner cylinder of 50.8mm O.D. and the results are compared with those for the inner cylinder of 30mm O.D., which are reported previously by the authors. As a result it is found that the size of the inner cylinder affects the heat transfer in the early stage of heating : the increasing diameter of the inner cylinder leads to a decrease of the distance between the heating and cooling surfaces and thereby reduces both the duration of heat conduction prevailing and the resulting temperature increase of the heating surface in the period. The increasing diameter of the inner cylinder also makes the characteristics of the heat transfer similar to those between vertical plates.

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To reduce friction loss in automotive reciprocating engine, it is required to know the lubricant oil film behavior. In the present study, a laser-induced fluorescence (LIF) and a particle image velocimetry (PIV) were applied to measure the oil film thickness and its velocity, independently. A model engine with a quartz glass cylinder was used. Using Rhodamine B, a linear relationship between oil film thickness and fluorescence intensity can be obtained in the range of 0 to 150 μm. The LIF measurements were performed under the 300 rpm of mortaring condition. The range of oil film thickness was from 10 to 25 μm on the piston rings. The crank angle variation of oil film thickness was demonstrated successfully. The PIV measurements were also carried out under the motoring speed of 100 rpm. The velocity vector map was obtained in the slit of piston ring. The oil velocity was almost the same as the piston speed near the oil ring. Velocity profiles in the slit were visualized according to the crank angle positions. The results suggested the possibility to analyze the oil film behavior under the combination of the LIF and the PIV measurements.

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The performance and over voltages of the polymer electrolyte fuel cells (PEFC) with paper and cloth type gas diffusion layers (GDL) were evaluated using a test apparatus in which the clamp load of a test cell could be changed. The contact pressure distribution of GDL was also evaluated using a pressure measuring film. Under moderate humidification condition, an increase in the clamp load is effective in reducing IR over voltage, and thereby improving the PEFC performance. The performance of the paper type GDL is higher than that of the cloth type GDL at all clamp loads. The GDL contact pressure has a peak at the center of the separator rib and has a bottom at the separator channel. The pressure distribution becomes more uniform when using the paper type GDL rather than the cloth type GDL. The GDL electrical resistance amounts to only about 20% of the overall IR resistance. The difference of the overall IR voltage between the paper and cloth type GDLs is more significant than that of the GDL electrical resistance. This is because the uniform pressure distribution obtained with the paper type GDL enhances the contact between MEA and GDL, thereby reducing the MEA resistance.

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A real-time monitorinsg method of local water content in polymer electrolyte membrane (PEM) is required to achieve higher current density operation of a polymer electrolyte fuel cell. Based on the T₂ relaxation measurement of nuclear magnetic resonance (NMR), the local water-content sensor consisting of the planar surface coil of 0.8 mm outside diameter and a permanent magnet of 1.0 Tesla was developed. In this research, T₂ (CPMG) relaxation time of PEM was measured by Carr-Purcell-Meiboom-Gill (CPMG) method. The measurement time of CPMG method is 1.1 s. It is found from the result using the solenoidal coil that the T₂ (CPMG) relaxation time of the membrane at 75°C increases with increasing a vapor concentration in N₂ gas.The accuracy of T₂ (CPMG) measurement by two small planar coils of 0.8 mm and 2.0 mm outside diameters was evaluated using CuSO₄ sulution with the concentrations of 0.1 and 1.2 mmol/l as standard samples. The average and coefficient of variation of T₂ (CPMG) measured by the planar surface coils were evaluated by comparing with the T₂ (CPMG) STAND measured by the standard solenoidal coil. In the case of 2.0 mm planar coil, the average of T₂ (CPMG) _{D=2.0 mm} was equal to T₂ (CPMG) _STAND within the accuracy of 6%, and the coefficient of variation was in the range of 0.11 to 0.13. In the case of 0.8 mm planar coil, the average of T2 (CPMG) _{D=0.8 mm} was longer than T₂ (CPMG) _STAND by the factor of 1.32 to 1.54 due to inhomogeneous perturbing magnetic field exposed from the small planar coil, and the coefficient of variation was in the range of 0.14 to 0.16. Furthermore, T₂ (CPMG) measurement of PEM by the planar surface coils was performed. Using the planar surface coil and the obtained relationship between T₂ (CPMG) and water content of PEM, the developed monitoring system can measured local water content in the membrane during 1.1 s.

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Mixture formation of diesel spray impinged on an extruded surface, which was a top of cylindrical column, was investigated experimentally. A diesel spray was impinged vertically to the extruded surface. The behaviors of impinged spray were observed using a high-speed drum camera. A spray volume was estimated from the photographs. Effect of cylindrical column diameter on spray behavior was investigated. Adhering fuel was measured by a primitive “wiping by paper and mass measuring” method under various conditions. Air-fuel ratio in spray was calculated from spray volume and adhering fuel. As the result, the behavior of diesel spray impinged on an extruded column was strongly influenced by the diameter of the extruded column. From the measured results, it is clear that the air-fuel ratio in spray in the extruded column diameter of 45 mm was larger than those in the other columns.

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The effects of fuel injection parameters, such as injection pressure and nozzle hole diameter, on NO_x formation in direct-injection Premixed Charge Compression Ignition (PCCI) combustion were investigated using a constant volume vessel and a total gas-sampling device. The results show that promotion of fuel-air mixing reduces final NO_x mass accompanying delayed hot flame. In this case, the NO_x reduction trend is enhanced by lowering oxygen concentration. Under a fixed nozzle hole size condition, final NO_x mass is reduced with increasing injection pressure, and smaller nozzle hole size promotes this effect. Enhanced mixing and reduced oxygen concentration provide longer mixing periods leading to lower NO_x mass per released heat NO_x/q_t, while promotion of mixing hardly affects NO_x/q_t when the quantity of injected fuel exceeds a certain level.

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Experiment and numerical simulation indicated that the large NO_x formation in diesel engine is due to the weak mixing intensity in the spray tip region, where the flow and turbulence structure is quite different from the continuous jet flames. The fact indicates that there is a possibility of reducing NO_x, from diesel engines by enhancing mixing intensity at the spray tip region to the level of continuous jet flame. As one of the attempts to make the velocity profile of diesel spray similar to the steady jet, an inert gas was injected prior to the fuel injection. With the pre-injection of inert gases, the flame apparently became less luminous, and the NO_x emission index decreased to two-thirds of the non pre-injection case. Numerical simulation showed that NO decreases with the increase of the pre-injection period, although the maximum temperatures are almost constant in all cases. This suggests that the NO_x reduction is not due to the temperature difference but due to the enhanced mixing and decreased time at high temperature by the pre-injection. The report presents the above results together with photographic analysis of enhanced mixing of spray tip region by pre-injection of water.

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A combined probability density function (PDF) /moment method has been developed to improve the accuracy of the Monte-Carlo method which is employed to simulate the evolution of PDFs in the PDF approach. The accuracy of Monte-Carlo method depends strongly on the number of Monte-Carlo particles and declines with the decrease in the PDF transport probability. The present method solves simultaneously a modeled PDF transport equation and moment equations of mean and variance. Both the mean and variance values obtained from the moment equations are just used as the reference values to match to the corresponding values of PDFs. In the frame of the conserved scalar concept, the usefulness of the present method is evaluated in the configuration of a turbulent jet diffusion flame, with a comparison with other methods; the PDF method and the flamelet model method. The results have showed good agreement between the present PDF method and the flamelet method, highlighting the improvement from the PDF method. Especially, the agreement in terms of PDF shape has verified that the beta function approximation in the flamelet model has high accuracy.

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The effects of oxidizer preheating and dilution levels of fuel and exygen on the extinction and structure of counterflow CH₄-O₂-Ar diffusion flame were investigated experimentally and numerically. The oxidizer temperature of both experiments and calculations were varied up to 1100 K. The oxidizer preheating significantly contributes to expansion of the extinction limits. The oxidizer preheating and the dilution levels are characterized by the magnitude of stoichiometric mixture fraction (F_st). The extinction limit curves can be roughly divided into two regions based on the magnitude of F_st. In the region about F_st<0.5 which the flame location is in the oxidizer flow side, the oxidizer concentration exerts dominant effect on the extinction, and the effects of preheating is clearly observed. In this region, the combustion reaction appears with oxidizer preheating from the upper of oxidizer side. On the other hand, the region about F_st>0.5, which the flame is located to the fuel flow, the expansion of reaction zone with preheating is almost small. Only small effects of the oxidizer preheating to the extinction limits are observed in this region. As the results, the flame location is quite important factor to understand the effects of dilution levels and oxidizer preheating on the extinction phenomena.

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To burn plastic-resin powder as an auxiliary or alternative fuel and to realize the effective thermal recycling of a great deal of recycled plastic-resin, some experimental investigations have been made on the overall combustion characteristics of plastic-powder in the industrial burner and those in the annular burner. According to these results, the basic elucidation of physical properties of an abruptly heated micro plastic-resin particle was found to be necessary and indispensable. In this paper, therefore, evaporating and burning processes of a micro plastic-resin particle, which has a diameter of about 200μm and is suddenly exposed to a hot oxidizing atmosphere, are observed and analyzed by combining the devised micro direct and schlieren system with a high-speed CCD video camera. The results show that there exist multiple internal micro boiling, micro explosions and micro diffusion flames, and that their existence exerts strong influences on evaporation characteristics of a micro plastic-resin particle. Also calculated is the burning rate constant of the micro plastic-resin particle.

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As a means for a stable premixed combustion, there is a so-called cyclone combustor, which consists of a cylindrical chamber and fuel nozzles installed tangentially on the side wall. In this combustor an extremely stable flame can be obtained in the swirl flow, formed along the inner wall of the combustor. The authors utilized this combustor as a flame holder, to burn a high velocity jet flowing axially in the central part, and named this combustor a cyclone-jet combustor. In the present study, experiments on the air preheated by the cyclone-jet combustor were carried out. The maximum air temperature is 700 K, and the propane was used for fuel. With the air flow rate changed, the effects of the turbulence on the NO_x formation were examined in non-premixed and premixed flames. It was shown that the increase of the air temperature increases the NO_x emission, while the increase of the turbulence reduces the NO_x, emission. The results suggest that the air preheated combustion using this combustor becomes very effective for the NO_x reduction and the low fuel consumption, particularly under the strong turbulence.

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The purpose of this research was to clarify the electric characteristics of diamond film synthesized by combustion flame and to synthesize a suitable diamond film for use in electroric device applications. When the film contains amorphous carbon, the dielectric loss increases, i.e., the electric characteristics of the diamond film become worse. To decrease the amorphous carbon in the diamond film we utilized three methods, the detection of the optimal equivalence ratio, the addition of hydrogen into synthesizing gas and heat treatment (annealing) of the diamond film. All of these methods can decrease the amount of amorphous carbon effectively, thus systematically changing the factors influencing the optimal synthesis for improving the film's electric characteristics. We have successfully developed a method for making high-quality diamond film with excellent electric characteristics, which has no dielectric loss in the wide frequency rage (10²-10⁸ Hz).

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Effects of the velocity and the air ratio of the mixture supplied into the boundary region between the rich and lean flames on the characteristics of flame stabilization of the rich-lean combustion were investigated in order to develop a new type of a domestic boiling water heater and a warm heater with low emission of NO_x and high TDR. The characteristics of stabilization of the rich-lean flames are substantially improved when the stoichiometric, the lean mixture and the air are supplied at the low velocity into the boundary region between the rich and lean flames, but not improved when the rich mixture is supplied into the boundary region between the rich and lean flames. The optimum velocity of the lean mixture supplied into the boundary region between the rich and lean flames exists for improving substantially the stability limits of the rich-lean flames. It is possible to develop the new type of burners with high performance of further low emission of NO_x and high TDR by controlling the velocity and the air ratio of the mixture supplied into the boundary region between the rich and lean flames.

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Over the past several years, much interest has been devoted to the study of thermal acoustic machines that achieve simplicity by eliminating moving parts such as pistons. This paper is concerned with the development of a numerical simulation to accurately predict the behavior of thermal acoustic machines. A nodal analysis model is employed in this study. Complete differential equations of continuity, momentum, energy and the state of the gas are derived. An implicit method is used to solve equations in the time direction. The simulation results of a typical thermal acoustic generator are presented and these include the frequency, pressure ratio and gas temperature versus the heater temperature using helium, argon and nitrogen as working gas. Experimental data are discussed to confirm the validity of the simulation model.

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By installing an additional condenser on the air-conditioning machine designed for HCFC22, a more efficient heat pump system could be operated with HFCI34a as well as HCFC22 without changing mineral lubricant oil. It was shown that COP for cooling operation was improved when operating with HCFC22 and HFC134a. It was also shown that this heat pump system could be operated at higher ambient temperature exceeding 50°C when operating with HFC134a.

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