Heat transfer characteristics of a dilute surfactant/water solution in a two dimensional channel has been experimentally investigated. It is known that surfactant solutions do show a large sensitivity of their drag reduction and heat transfer reductlon effectiveness on temperature. In the present experiment, the heat transfer at fixed Reynolds number increased three times when temperature increases only 3 deg. Temperature profile measurements in the thermal boundary layer were also made. It was found that high diffusivity layer exists near the wall in the drag reducing thermal boundary layer. The relation with high difussivity layer and heat transfer coefficient is discussed.

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Flow of surfactant solution (C₁₄ TABr and ARQUAD) through a sudden expansion pipe is studied experimentally from measurements of pressure distribution, velocity profile, and flow visualization. Two acrylic pipes with inside diameters of 15 mm and 30 mm are joined and the test section with 5.4 m length is used. Velocity profiles are measured by LDV. In the case of surfactant solution, loss coefficient of sudden expansion is lower than that for water at low Reynolds number. Pressure recovery length and reattachment length for surfactant solution increase remarkably compared with the case of water. In the sudden expanded pipe, fluid near the center of the pipe is very fast, while reverse flow appears near the wall. This flow becomes more remarkable for surfactant solution than for water.

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Transition in pipe flow of drag reducing surfactant solution (C₁₄TABr) has been studied experimentally. Two stainless pipes with inside diameter of 3.03 mm and 2.04 mm are used and the measurements of pressure drop and pressure fluctuations are carried out. In the case of surfactant solution, turbulence appears at higher Reynolds number than that for water and the flow is stabilized. In contrast to the flow of polymer solution, critical Reynolds number for surfactant solution doesn't decrease even in the case of smooth inlet condition, except for the case of high concentration solution. With an increase in the concentration of solution, critical Reynolds number becomes to be unaffected by the pipe inlet conditions. When the surfactant solution is used, frequency of pressure fluctuation becomes higher and amplitude of it becomes less than that for water.

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We have investigated flow behavior of viscoelastic fluid in half-spherical gap between two coaxially rotating spheres. Numerical analysis was carried out, using constitutive equation of the Giesekus model, which characterizes a viscoelastic fluid with both the shear-thinning and the elasticity. Numerical solutions were obtained for flow field and its associated torque and thrust characteristics in the transient process by using the finite difference method.

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It is important to fluid mechanics and bio-fluid mechanics to understand an interaction among deformable surface, its surface, its surrounding flow field and hydrodynamical forces. In order to clarify this interaction by experiments, we have been using several cylinder models having an elasto-flexible surface in uniform water flow. The hydrodynamic forces were measured by a three-component force balance. The deformation of the surface and the flow field around it were visualized using a laser light sheet method simultaneously. The experimental results showed that the time-averaged hydrodynamical drag was approximately 20% lower than that of the rigid cylinder when the continuously occurring wave appeared on the surface. In the case of the drag reduction occurrence, the power spectra of the lift fluctuation were broadened and had several peaks. In particular, the prominent frequency of power spectrum was about 45% lower than the frequency in the cases of the rigid cylinder and of no drag reduction occurring. The visualization results suggested that the strength of the Karman vortex shed from the cylinder was decreased compared with that from the rigid cylinder and this decrease was responsible for the above mentioned drag reduction.

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It has been shown that there exists large longitudinal vortical structure in the core region of turbulent plane Couette flow and they are meandering quasi-periodically. In this paper, we study the fluctuating velocity properties in the core region using power-spectrum and wavelet analysis. Power spectrum in the core region of Couette flow demonstrates the existence of a periodic component in the velocity fluctuation. This periodic component has low-frequency amplitude modulation over the turbulent motion. It is shown that the modulation is caused by the meandering motion of the large longitudinal vortical structure. This meandering motion raises another fluctuating velocity in the core region. The velocity fluctuation component due to the meandering motion does not contribute to Reynolds shear stress. In the Couette flow, sweap motion is more dominant than in Poiseuille flow even near the wall. For the Couette flow, the power spectrum in the core region has ω^-1 distribution.

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When hydraulic machinery start to operate, the flow around the blades has to be transient, so that hydraulic losses have to come out within very specified regions transiently. To clarify such behavior of the losses, we take up a typical vortical flow around a highspeed hydrofoil and numerically simulate such transient behavior of the losses arisen around the foil, especially near the stagnation point, the backward separation region and the trailing edge. Even within the transient : range, the boundary layer develops on the entire foil surface and the starting vortex sheds off from the trailing edge, in the manner of pseudo-potential response. The losses limitedly appear around the above-mentioned regions, but the wake accompanying with Karman vortices scarcely appears.

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Heat transfer in a channel of rough wall is simulated in this work. Two kinds of roughness are considered ; i. e., one assumes sand-grain roughness based on roughness model which is just for the profile drag, not implementing thermal effect and the other, regularly arranged two-dimensional ribs which is treated rigourously. For the sake of computational load, one wall is assumed to be smooth and the global Reynolds number Re_τ based on global mean friction velocity and half channel width is 150. Mean flow property of velocity and thermal fields are found to be little influenced by the property of roughness elements but depends on total drag, except for in the layer close to the wall where direct interference with roughness elements manifests itself. Similarity of thermal field with velocity one is confirmed for the low Prandtl number flows considered in the work. The mixing is found to be controlled by large scale motion which is inherent to the logarithmic layer, getting closer to the wall.

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With an aim to clarify the effects of leading edge sweep on unsteady cavitation, four inducers with backward/forward leading edge sweep were examined. It was found that the cavity length at the tip is made shorten by both backward/forward leading edge sweep, and cavitation performances are also improved. In addition, the shape of leading edge affects the development of the blade cavitation at inner radial location. With forward sweep, the blade cavitation at the mid-span occurs considerably, which begins at the leading edge. On the contrary, with backward sweep, no blade cavitation develops at the mid-span. For unsteady cavitation, backward leading edge sweep is very effective in suppressing the unsteady cavitation, and an inducer with strong backward sweep could totally suppress the rotating cavitation, although the inlet backflow occurs more easily. On the other hand, an inducer with strong forward leading edge sweep suffers from various types of unsteady cavitation including backward rotating cavitation, although the head breakdown occurs at significantly smaller cavitation number.

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This study aimed at clarifying unsteady flow near the delivery port of winnowing fans using CFD technology, the commercially available flow analysis software FLUENT/UNS, and the visualization software AVS. Both standard impellers and forward-inclined impellers were studied for comparison purposes. The results of this investigation demonstrate that forward-inclined impellers have better performance in terms of producing uniform flow. They develop many points where the static pressure is low, and from where large and unstable three-dimensional vortexes are produced. It was also demonstrated that a characteristic of winnowing fans is that they produce a balance between the swirling now after the suction port and that after the delivery port. This means that the flow after the impeller can be made uniform within a short distance.

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We have improved the numerical scheme based on the boundary element method combined with the finite volume method. Heat transfer inside the bubble is taken into account in this sheme. We apply unstructured adaptive grids inside the bubble, which are generated by Delaunay triangulation, to analyze the temperature field inside the collapsing bubble with the very large deformation. We compare the present numerical results with one-dimensional results for a spherical bubble and numerical results for a nonspherical bubble where the structured grids are used to calculate the heat transfer inside the bubble. The results show that the present method has sufficient accuracy to deal with thermal boundary layers both for spherical and nonspherical bubble collapses. It is also shown that the present scheme is effective for the analysis of a tiny bubble in which the thermal boundary layer near the bubble wall is relatively thick to its radius.

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By using numerical analysis in the present study, we found that the size of formed bubble increased with air-flow rate and pressure in a solid-gas pressurized fluidized bed. But frequency of production was almost kept a constant without changing pressure. Calculation were based on DEM code where have taken a new approach concerning the air void rate and accuracy of convergence. To verify the bubble behavior, the experimental observation on the shape and flow characteristics of the formed bubble was carried out in the distributor with a single nozzle in the pressurized solid-gas fluidized bed. Experimental data were obtained from the visualized image of the bubble using the shadow-graph method and later were analyzed. Those results indicate that the size and rising velocity of the bubble increased with added rate of nozzle flow and these bubble behaviors directly correspond to increase of pressure in the bed. Also the growth rate of first produced bubble was agreed with the previous works in theoretical and experimental.

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This paper concerns with flow visualization and image measurement of bubbly flows around several shapes of obstacle. Coaxially confined twin rectangular tanks are constructed in order to provide a wide two-dimensional uniform bubble distribution upstearm of the obstacle. The experiments show that a quite large two-phase convection is induced by inserting the obstacle into the bubbly flow. Spatial scale of the two-phase convection depends on the shape of the obstacle as well as its arrangement. Measurement results of void fraction, bubble velocity and liquid phase flow, which are obtained by PIV and PTV, explores the detailed mechanism of generating the convection. Especially, the interaction between accumulated bubbles in upstream the object and downward liquid flow behind the object determines the scale of the two-phase convection.

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This paper presents the hybrid finite element and boundary element method (FEM-BEM) with a level set method (LSM) for the analysis of a free surface deformed in the alternating current magnetic field. Three-dimensional numerical simulations In the floating zone (FZ) method under microgravity are carried out to investigate the deformation process of a silicon liquid bridge with two types of coil positions, the upper case and the middle case. The results clearly show the deformation processes. The liquid parts which are the same position as each coil yield to pressure caused by strong Lorentz force and both ends swell out. This phenomenon conforms well to behavior of melt in the real growing process qualitatively.

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MHD flow behavior and the performance of an experimental nonequilibrium subsonic disk MHD generator driven by a shock-tube facility have been examined with time-dependent γ-z two-dimensional and γ-θ-z three-dimensional numerical simulations. In the subsonic MHD generator with two throats, the choking position is found to depend on the strength of MHD interaction. For optimal or high load operations, the flow chokes at the downstream throat and the subsonic flow is maintained in the generator channel. For low load operations, on the other hand, the flow chokes at the upstream throat and the flow becomes supersonic. In the generator under the subsonic flow condition, the relation between enthalpy extraction ratio and isentropic efficiency can be described as a function of Mach number at the anode for a fixed Mach number at the cathode. When the magnetic flux density is low, the inlet stagnation pressure should be decreased to achieve high enthaply extraction ratio and isentropic efficiency. The proper fluid flow and discharge structure can be realized under the optimal load resistance. Under the low resistance, however, shock-waves and ionization instability can occur and the generator performance can be deteriolated.

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A novel polarized-type phase Doppler method is proposed for simultaneous measurements of particle size, velocity and refractive index on the basis of. the phases of two polarized Doppler beat signals in a single scattering direction. Light scattered by a moving particle in a certain direction is divided into two rays, which are then detected with different polarization angles to transmit dominantly reflected or refracted rays. Signal phases of these two rays are measured with respect to the phase of beat signal obtained by the reference detector. The particle diameter can be determined from the phase of reflected ray, whereas the particle refractive index can be obtained from the phase ratio of reflected and refracted rays. We carried out numerical computations and experiments to confirm the usefulness of the proposed method for simultaneous measurements of the particle size and refractive index.

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This paper deals with a novel process for separating mixed plastics such as found in industrial waste by utilizing unsteady heat transfer to the plastics and so-called melt-sticking between the plastics and a heated solid surface. First the concept of the novel separation process was proposed, and then the feasibility of the concept was experimentally examined by using an experimental setup, in which particles of various types of plastics were pressed against a heated plate. The results clearly showed that the heated plate temperature at which the melt-sticking between plastic particles and the heated plate takes place markedly varies with the types of plastics, and that the temperature is also influenced by the materials of the heated plate. These results suggest that the melt-sticking phenomenon can be applied for separating mixed plastics. Based on a hypothesis that the melt-sticking phenomenon takes place when the interface temperature between the heated plate and plastic particles exceeds a certain temperature, which varies with the types of plastics, and by using a theoretical solution of unsteady heat conduction between two semi-infinite bodies, the heated plate temperature at which the melt-sticking occurs was successfully estimated for various types of plastics and heated plate materials, and separation ability of this process was discussed.

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The effects of an acoustic excitation and shear layer instability on heat transfer in circular jet impinging upon a heated plate are studied experimentally for jet velocity u = 10 m/s with corresponding Reynolds number 18 800 and acoustically excited condition 40 Hz, 1 W/m². It is found that average heat transfer with significant acoustic excitation effect can be correlated by impinging length H/d≤4. Flow visualization data suggest qualitatively the heat transfer mechanisum and the associated flow stracture in the near wall region.

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In order to pursue the effectiveness of an ultra-fine structure surface for the enhancement of mist cooling heat transfer, detailed experiments have been conducted on the evaporation of a droplet (distilled water and fluorocarbon KPF-72) formed on circular heated surfaces, which are ultra-fine structure surface and smooth surface. The ultra-fine structure surface was made from corroded the uni-directionally solidified alloy (Al-5.7 wt%Ni) with an alkaline solution. On the case of ultra-fine structure surface, it was observed that the deposited droplet instantly permeated into the structure layer and spreaded to radial direction. The reduction of the contact angle and an increase of the wetted area was also confirmed from an optical measurement. The evaporation time of droplet deposited on this surface was almost an order of magnitude lower than that on the smooth surface.

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To make full use of the cold heat of LNG, two new style heat exchangers were studied that exchange heat between combustible LNG and air. Channels of each fluid are structurally independent with each other to improve the safety. Heat flow, pressure loss and effectiveness of air coolers for an liquid air enegy storage system were calculated. As for the Parallel Tube heat exchanger, thermal resistance due to the fin depends mainly on the ratio of the fin pitch to the fin thickness. When the ratio was 10, thermal resistance due to the fin was below 20% of total thermal resistance. In the case of the Double Tube heat exchanger, thermal resistance due to the double tube depends mainly on the ratio of the groove pitch to the contact width. When the ratio was 6, thermal resistance due to the double tube was about 20% of total thermal resistance.

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Heat extraction rate from porous media saturated with water using a vertical type heat exchanger has been studied experimentally and analyzed numerically. The unsteady heat extraction characteristics are presented, and the effect of the flow rate of the heat extraction medium of water in a heat exchanger and that of the Rayleigh number on heat extraction rate are discussed. The present computed results predict comparatively well the heat extraction rate from porous media saturated with water in the range of the parameters covered.

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A large number of terrestrial experiments have been conducted on Marangoni convection in a liquid bridge to date. The limitation in the terrestrial experiments lies in the maximum size of the bridge and thus in the maximum attainable Marangoni number under the normal gravity. In the present study, a series of experiments was performed in a low temperature environment in order to realize a large temperature difference between the both ends of the bridge to attain a high Marangoni number in spite of a small size of the bridge while suppressing the evaporation of the fluid. The test fluid was silicone oil of 1, 2 and 5 cSt. The temperature difference ΔT was increased gradually and a critical point of transition from steady to oscillatory flow was obtained. With increase of ΔT, a pulsative oscillatory mode and then a rotational one became discernable. In this series of experiments a wide range of aspect ratio of the bridge was concerned and thus flow structures with mode number m=1, 4, 5 and 6 were realized. The product of the mode number and the aspect ratio was found to be approximately unity as often pointed out.

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It is important for energy saving to use the waste heat efficiently. An absorption cycle is effective equipment for the thermal utilization. In order to improve the performance of absorption cycle for the various operating conditions, it is important to analyze the exergy loss in each component and evaluate not only the quantity but also the quality of heat flow. In this paper, the evaluation of exergy loss in the absorption process and an exergy analysis of the single-and double-effect LiBr-water absorption refrigerating cycles whose heat source is a saturated steam at the pressure of 800 kPa were carried out, and the exergy loss in each component were obtained. As a result, it was shown that the exergy coefficients and the COP of the single-effect absorption cycle were about 17% and 80%, and those of the double-effect cycle were about 30 and 140%, respectively.

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Removal of acetaldehyde (CH₃CHO) and ammonia (NH₃), which is the main odor components in cigarette smoke, was investigated using two different types of nonthermal plasma reactors. One is the barrier-type packed-bed plasma reactor (BPPR), the other is the barrier-type multi-layer plasma reactor (BMPR). As the experimental results using the BPPR, more than 95% of CH₃CHO removal efficiency was obtained under dry air environment. As for NH₃ removal, almost 100% removal efficiency was obtained with negligible reaction byproducts in dry air. On the other hand, approximately 90% of CH₃CHO and 100% of NH₃ removal efficiency was obtained using the BMPR with 33 W. As the experimental results of the removal of the real cigarette smoke, NH₃ was completely removed. However, removal of CH₃CHO was somewhat difficult because of its low concentration and the co-existence of other constituents.

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In space station, short-circuit of electric wiring is thought as one of the factors responsible for firing. For crews' safety, we need to investigate combustion characteristics of electric wire insulation burning under micro-gravity condition and establish a criterion for material selection. In electric wire burning under micro-gravity condition, the copper wire with very large heat conductivity is considered to play an important role. The mechanism of electric wire insulation burning is supposed ; to consist of the following two processes. (1) At the coating-burned-out wire part, the spherical, flame contacts with the copper wire and heats it and intensive gasification occurs at the edge of coated wire part. (2) The gasified fuel diffuses radially to meet oxygen, forming a spherical flame. Our calculations confirm that the heat feedback via copper wire is very crucial to whether selfsustained burning is attained or not after the cease of heating, and that it brings about phenomena that are peculiar to electric wire insulation burning under micro-gravity condition.

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A new method for measuring local equivalence ratios in hydrocarbon mixture fields was established with an application of LIBS, Laser-Induced Breakdown Spectroscopy. Gas molecules of the mixture were separated to excited atoms by introducing the focused lights of Nd, YAG laser, to obtain atomic emissions from the excited atoms. The emission peaks of H, O, and N were observed at different wavelengths. The wavelengths for their representative peaks include 656 nm, 777 nm, and 871 nm respectively. The ratios of the emission intensity from H and O, F_H/F_N, or from H and N, F_H/F_N had a good correlation to the equivalence ratios, regardless of the laser power. The experimental results showed that local equivalence ratios above 0.01 thereabout were measured instantaneously and with high accuracy for propane-air mixtures.

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A new technique for observing a local flame-front structure using local chemiluminescence measurements is proposed, and its performance is demonstrated. Local chemiluminescence measurements of OH*, CH* and C₂* were carried out at the flame front of premixed turbulent propane/air flames (Re=14000, u'/S_L<1.0, φ=1.1) to study details of the reaction zone and characteristics of turbulent flame-front structure. Cassegrain optics were developed to detect of these chemiluminescent emission intensities to obtain flame spectroscopic data for a local point. PIV was also applied to measure combustion flow characteristics. In this study, time-series signals of OH*, CH* and C₂* were measured to understand those profile at the flame front with/without Cassegrain optics. These time-series data was analysed to understand turbulent characteristics in comparison with velocity data. The structure of the flame front can be characterized by the duration of the chemiluminescence intensity peak and by the patterns of its occurrence, which were found to correspond to the flame thickness and the Damkohler number. The relationship between turbulence scale and flame thickness at the flame front was investigated by simultaneous measurement of the three chemiluminescences and LDV. It was found that local chemiluminescence can provide useful information on the flame-front structure and its characteristics.

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The thermal expansion of gases due to heat release across the flame front of turbulent premixed flames modifies the turbulence. The present study has been performed to examine velocity changes and changes in turbulence across the flame front at different positions In the turbulent flame brush. The measurements employ an electrostatic probe with three identical sensors and a two-color, four-beam LDV. The LDV measures axial and radial components of the local gas velocity, while the electrostatic probe measures two dimensional movement of the flame front in the plane of the LDV velocity components. The component of the local gas velocity normal to the flame front tends to increase in passing through the flame front. The flame front thereby can generate anisotropy in initially isotropic turbulence. They also produce difference in turbulent spectra conditioned on unburnt or burnt gas. Local modification of turbulence by the flame front are demonstrated experimentally. The modifications are different at different Positions in the turbulent flame brush. On the centerline, inclination angle of the flame fronts are relatively small, and turbulence is enhanced manly in the axial direction, while off axis the flame fronts are more nearly vertical, and the enhancement is mainly in the radial direction.

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Numerical analysis is made on the H₂/N₂-air nonpremixed laminar counterflow diffusion flames with positive or negative stretch rate induced by locally sucking flow from fuel and air side. Adjusting the suction velocity forms typical three flames of flat shape and concave or convex curvature. Numerical computations taking into account detail chemical kinetics and multi-conponent diffusion makes it clear the effects of negative stretch rate on the flame structure and characteristics. In addition, the effects of preferential diffusion In relation to the flame curvature under the negative stretch are discussed. The results show that (1) Temperature increases with decreasing the stretch rate, and the tendency is the same even in the negative stretch rate. (2) H. concentration due to the preferential diffusion and excess enthalpy due to nonunity Lewis number effect becomes relatively significant with decreasing the stretch rate. This is one of the reasons of (1). (3) Temperature increasing due to the negative stretch rate depends on the flame curvature. (4) The maximum flame temperature cannot be rationlized by local stretch rate, and changes widely depending on the preferential diffusion in relation to flame curvature.

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The local reaction rate and the diffusion rate are important parameters which dominate combustion phenomena in a turbulent diffusion flame, but they cannot be directly measured. Then, in the previous study, the present authors developed the method to obtain the reaction rate and the diffusion rate by numerical calculation using measured values for a hydrogen jet diffusion flame. In the present study this method was applied to a CO jet diffusion flame where the chemical reaction is comparatively simple and preferential diffusion may not be influential. The following results were obtained. (1) Effective diffusion coefficients D_C, D_O and D_N, which are obtained using respectively C, O and N elements as tracers, were almost the same to each other in the whole region of the flame. This seems to mean that, because the turbulent diffusion rate is sufficiently larger than the molecular diffusion rate, effective diffusion rates are nearly the same to all chemical species. (2) Then, the assumption, that Lewis number is 1 in the conserved scalar approach, is applicable to this CO flame. The present data may be useful in the examination of modeling methods of turbulent diffusion flames.

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Flame tip oscillation of a Bunsen type premixed flame with burner rotation is experimentally investigated. Methane/air mixture and Propane/air mixture are used to take into account the effect of Lewis number. Cross sectional images of unburnt mixture are visualized by a laser tomographic technique. Time variations of flame tip location, flame curvature and thermodiffusive zone thickness are measured from visualized images. As the flame tip is oscillated, the flame curvature and the preheat zone thickness along the centerline are varied periodically. Furthermore, it is shown that values of the flame curvature at the same location of the flame tip are different whether the flame tip moves upward or downward. In other words, the flame tip oscillates with a hysteresis. This suggests that the instantaneous burning intensity at the flame tip varies periodically with the hysteresis, which results in the periodical oscillation.

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To clarify the effect of water content on combustion characteristics of watery materials, combustion test of a high water-permeable balsa wood was performed using a thermogravimetric furnace. The furnace temperature is between 650°C and 1000°C, and water contents in the small balsa pieces (0.3g) were varied up 70 wt%. Mass reduction during pre-heating, volatile matter combustion and char combustion were measured with a microbalance. Also, the variations of flame temperature and center temperature of the test piece during combustion process were measured. On the combustion of high water-contained balsa, it was found that ignition started before the water was evaporated completely. It means that two proceses, devolatilization of volatiles and vaporization of remaining water, are proceeding simultaneously during the volatile matter combustion. Ignition delay and retention time of volatile matter combustion increased with increasing the water content. The increases of flame temperature and center temperature of the test piece were prevented by the latent heat of water vaporization. The combustion rate of volatile matter was drastically reduced in proportion to the water content. Also, it was confirmed that a part of char burned during the latter stage of volatile matter combustion. The effect of water content on char combustion rate was small. From this study, it was concluded that the water content over 50 wt% affected remarkably to the volatile matter combustion.

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Jet ignition method by hydrogen oxygen flame is proposed to control the combustion of lean mixtures. Hydrogen flame jet is supplied from the cavity whose volume is less than one percent of main chamber volume through a nozzle. Generally, the heat loss of the jet ignition method at the chamber wall is thought to be bigger than conventional ignition. In this report, the heat flux at the cavity wall are measured. The heat flux in the cavity is larger than that in the main chamber. The leaner the mixture in the main chamber is, the smaller the heat flux is. When hydrogen oxygen mixture is used in the cavity, the heat flux is much bigger than that using hydrogen air mixture. The smaller the nozzle diameter is, the bigger the heat flux becomes. The heat flux depends on the velocity of the flame in the cavity.

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Stratified mixture was formed in the constant volume bomb by the injection of gaseous fuel. The structure of the transient fuel jet was visualized by the laser tomography and the combustion characteristics of the stratified mixture was investigated. Combustion pressure and the amount of unburned fuel were affected strongly by the ignition timing. The unburned fuel was caused mainly by the bulk quenching in the over lean region. Secondary flame came out in the burned region after the initial flame had propagated through the fuel jet in the condition that the mixture was ignited during the fuel injection. The shape of this flame was quite different from that in the condition that the ignition timing was after the termination of the injection. Fuel remained in the burned region and injected fuel after ignition burned gradually mixing with surrounding air.

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This study was aimed at reducing Soot and NO_x. by uniform and lean distribution of fuel in diesel spray using high-pressure fuel injection and a micro-hole nozzle. But this injection system made ignition delay shorter. So that, it couldn't completely make uniform and lean distribution of fuel in diesel spray. Then, in addition to this injection system, using low cetane number of fuel, which can not easily ignited, we made ignition delay longer, and attempted to make complete uniform and lean distribution of fuel in diesel spray. The combustion event was observed by high-speed direct photography, ignition and combustion was analysed by the combustion chamber pressure history, and KL values and a flame temperature was analyzed by the two-color method from the two-dimensional flame image.

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Investigation on diffusion process is required in variety of field such as chemical reaction, combustion, and environmental studies. However, there is no appropriate index for analyzing degree of homogeneity and scales of the clouds in diffusion field. This paper pressents Entropic Method for determining the homogeneity degree and the scale of the heterogeneous clouds based on the statistic-entropy concept. The results of the investigation on the performance and characteristics of the method showed good correspondence between the analyzed results and the states of the tested pictures. A method for determining a mean effective diffusion-coefficient from the pictures is also discussed. The paper proposes an analitical method available for the study on diffusion phenomena.

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In order to increase the brake thermal efficiency and reduce NO_x emissions of a stationary diesel engine, a direct injection (DI) combustion system, which consists of a combustion chamber with a high compression ratio and a fuel injection system with a high injection pressure, was installed in a single cylinder diesel engine with a 240 mm bore, and it was tested to investigate its potential and fundamental characteristics. The high compression ratio was proven to have a potential of high brake thermal efficiency and become advantageous on the point of the brake thermal efficiency and NO_x emissions at the retard of fuel injection timing. The high injection pressure by means of small nozzle hole diameter restrained the initial combustion, promoted the diffused combustion and increased the effective combustion efficiency. The high compression ratio and high injection pressure with the retard of fuel injection timing improved the brake thermal efficiency and NO_x emissions.

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The aim of this study is to investigate the influence of lean combustion on the formation of combustion chamber deposit in a two-stroke cycle engine. The contribution of fuel and lubricant oil to the deposit formation was discussed in this paper. The results obtained were as follows : (1) With making the mixture lean from the rich side, the weight of combustion chamber deposit derived from the lubricant oil was increased, but that derived from gasoline was decreased. (2) The contribution ratio of gasoline to the total weight of deposit was below 5% in the lean side, however, that was 10 to 30% in the rich side. (3) Most of the combustion chamber deposit derived from the lubricant oil was formed from the detergent dispersant added to the lubricant oil, and the metallic detergent formed a larger amount of combustion chamber deposit than the ashless dispersant.

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Fuel-spray patterns are critical to stable combustion. As a result, a DI fuel injector in which the fuel-spray pattern can easily be controlled is essential to design an in-cylinder configuration. Our main goal was to develop a fuel-spray pattern control method that takes into account the influences of ambient and fuel pressures. A swirl-type DI fuel injector with an L-cut orifice nozzle (L-step nozzle) is newly designed. Experimentally and numerically we investigate the influences of its nozzle geometry on the spray angle and penetration length. In our experiments, fuel spray was injected inside a pressure chamber by using the new injector. The resulting spray patterns were visualized by using a YAG-laser sheet and recorded by using CCD cameras. These experiments showed that our L-step nozzle produces an inclined and split fuel-spray pattern. The fuel was well atomized by using our new nozzle. A CFD was performed to analyze the mechanism for inclining fuel spray pattern. Comparing the experimental and numerical results showed that the code accurately predicted the spray angle. The spray angle was found to be dependent on the air void geometry inside the orifice. We also found that the fuel-spray pattern could be controlled by changing the depth of the orifice.

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The automatic transmissions of automobiles are composed of a torque converter and a planetary type peduction gear sets, and it has a grate benefit of so-called easy drive ability or two-pedals action. However, ATF Oil Slipping behaviour inside the torque converter makes the converter efficiency worse. In order to improve the efficiency, it is necessary to minimise the slip. For this, Drive By Wire (DBW) technology was applied in this paper. Not only the efficiency, but also the dashing performance must be considered as well. Therefore, the tuning of the DBW makes a compromise of the two performances in actuality.

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When CVT was equipped with an engine, fuel consumption of the car becomes economical while the throttle valve angle and the gear ratio of CVT were controlled simultaneously. If the engine was operated with a lean air-fuel ratio (A/F), it is also effective for fuel economy and low level emission. Therefore, combining A/F control with the simultaneously control of the throuttle valve angle and the gear ratio becomes more important method for controlling the powertrain of a car. However, though these input-output relations were coupled complicatedly, the adequate and convenient control method was required for the simple powertrain control. From such point of view, investigation about appilication of decoupling control theory for Engine-CVT-A/F consolidated control was carried out experimentally. Good experimental results were obtained.

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The binary turbine system that employs steam as the primary working fluid has used R11 as the secondary working fluid because R11 has good characteristics as a working fluid in power plants. However, substitute LBMs (low boiling-temperature mediums compared with water) are being developed because of the destruction of the ozone layer by CFCs. In this paper, modeling and experimental investigations into the dynamics of a directly combined binary turbine system using R123 instead of R11 are described. The system consists mainly of a steam-and an R123-turbine, an R123 vapor generator, and an AC generator. The dynamic behavior of the system is similarly discussed from the viewpoint of the network theory with the previous report. The validity of the model was proven through comparison with our experimental results, which are the frequency responses examined with respect to generator load changes. In addition, the effects of the thermodynamic property of the secondary medium on the steady and dynamic characteristics of the system are also described.

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