The characteristics and differences in the two approximations. i.e., the additivity of forces and the additivity of velocities, on which Stokesian dynamics methods are based, have been investigated. To do so, Stokesian dynamics simulations of a ferromagnetic colloidal dispersion have been carried out for a simple shear flow, and the aggregate structures and the averaged viscosities have been evaluated, From the results of aggregate structures in equilibrium, the results obtained by the additivity of forces are quantaively different from those by the approximation of ignoring hydrodynamic interactions, although a qualitative agreement is recognized. The results obtained by the additivity of velocities give medium characteristics between the two above approximations. This difference in characeristics between the two additivity approximations and that of ignoring hydrodynamics becomes clearer as the influences of the shear flow dominate those of magnetic forces more significantly. From the results of transient characteristics from an initial state, the results of the additivity of velocities agree well with those of the additivity of forces. In contrast, the results without hydrodynamic interactions deviate from those of the two additivity approximations at a time step when a nearly particle particle touching situation starts to appear.

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This paper presents numerical analysis of the growth process of silicon (Si) single crystal. The technique applied is MCZ method. In MCZ method, two magnetic fields positioned facing each other is called cusp magnetic field. The cusp magnetic fields used for the analysis are outside magnetic field, surface magnetic field and inside magnetic field. In addition, the analysis was made using direct magnetic field. The results from our analysis and Watanabe's experiment were compared. And the examination and comparison of the calculation results were performed to the velocity field, temperature field and electromagnetic field. Each case was further examined centered on the degree of stirring, shaft symmetry and flow stability. Our examination drew us to conclude that the cusp magnetic field that satisfies these conditions in the inside magnetic field. The reason is that the flow of silicon was well controlled by the specific characteristics of the cusp magnetic field

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The purpose of the study is to investigate practical advantages, a potential for low computer time and fast convergence as well as accuracy to a steady state solution, of a lower upper symmetric Gauss-Seidel implicit relaxation method using overset grid technique and develop an efficient parallel computational algorithm with a data structure by one dimensional array. This method is applied to viscous turbulent flows around multi element airfoils. Almost linear performance of the speedup ratio in parallel computing is attained up to 16PEs on the Hitachi SR2201 computer. Comparison of the numerical result with available experimental data shows good agreement.

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The unsteady flow characteristics caused by the wake vortices generated from an isolated flat plate blade in a uniform flow were theoretically investigated with the discrete vortex method for elucidating the aeroacoustic source of the discrete frequency noise (DFN). We assumed that the DFN generated from the blade is originated by time fluctuation of the lift force caused by Karman vortex shedding. This calculation shows that the frequency and the intensity of velocity fluctuation in the wake can calculate accurately, and the half width of the wake is an important characteristic length to specify the periodic phenomena. The surface pressure, differentiated with respect to time, along the blade surface is closely related to the source, which gathers to the trailing edge. Then the chord wise correlation length calculated by integrating the distribution of the surface pressure data always conserved a constant value in all blades. The predicted DFN level agrees well with the experimental results.

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Effect of the body force in the finite difference lattice Boltzmann method (FDLBM) is studied. Inertial waves in a rotating field are calculated by FDLBM, the 3D15V lattice BGK model with introducing the Coriolis force in the local equilibrium distribution function of the collision term. The phase velocity and the group velocity of the inertial wave are compared with the theoretical one obtained by the dispersion relation of an incompressible inviscid fluid, and both agree well.

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The turbulent flowfield of a turbulent air jet issuing from a quasi two-dimensional nozzle with a rectangular notch at the midspan, has been measured using linearized constant temperature anemometers. The aim of this study is to examine the streamwise variation of the turbulent quantities and the turbulent scales, and to clarify the asymptotic process of the present jet toward the two-dimensional jet. Throughout this experiment, Reynolds number based on the nozzle width and the exit velocity, was kept constant 13000. From this experiment, in the upstream region of the quasi two dimensional jet, it is revealed that the development of the turbulent kinetic energy is suppressed by means of the rectangular notch. In the far downstream region, the decreasing rate of the turbulent velocity scale at the jet center region approaches to that of the two-dimensional jet. Furthermore, the turbulent kinetic energy flux in the interactive region takes the minimum value at the section of x/d=15 due to the inward secondary flow.

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When a constriction is formed inside a blood vessel, a self-excited oscillation of the blood flow and the vessel surface may occur. Numerical investigation has been conducted for incompressible viscous flows through a 2D channel with a flexible upper wall and a rigid lower wall. The flexible wall possesses mass, surface tension and a dumping factor. An obstacle modeled after the constriction was placed close to the inlet on the lower wall. The interactions of the internal flow and the deformation of the upper wall were elucidated for Reynolds numbers ranging from 800 to 5000. Steady solutions were obtained for Reynolds number below 1000 and unsteady solutions above this value. It was found that at the Reynolds number above 2500, a squeezing motion of the upper wall periodically occurs just behind the obstacle and propagates downstream. The flow rate at the outlet periodically varies due to the unsteady motion of the upper wall. The dimensionless period and the amplitude of the flow rate oscillation increase with increasing Reynolds number.

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This paper describes a model experiment of sootblower jets which have been used to remove fire side deposits of boiler tubes. A circular cylinder is used instead of a boiler tube. Flowfield around the circular cylinder placed in correctly expanded jets from a supersonic nozzle with a design Mach number of 2.0 and 2.4 is studied. Visualization by schlieren method and measurement of pressure on a cylinder are performed to diagnose the flowfield. The pressure coefficient on the cylinder is found smaller than that obtained by potential flow theory around a cylinder, especially, when the cylinder is located in the potential core region of the jets. The velocity distribution on the cylinder strongly depends on the flow Mach number just downstream of the shock wave generated in front of the cylinder.

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Experimental investigations on the discrete frequency noise and flow around a flat plate were carried out. Each cross section of the leading and tail edges of the flat plate was a semi-circle and tripping-wires (T. W.) were set on the both surfaces. The length and thickness of the flat plate was 80mm and 10mm. respectively. The diameter of the tripping wire was 2mm. The Reynolds number based on the thickness ranged from 1.2×(10)⁴ to 3.1×(10)⁴. The effect of the position of the tripping wires on the discrete frequency noise and the fluid flow around the flat plate was investigated. It was found that : the discrete frequency noise was reduced by T. W., and Γf (Γ : circulation, f : vortex shedding frequency) is one of the control factors of the discrete frequency noise.

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Ferrofluids show a magnetic field response. Magnetic particles in ferrofluids make aggregations by the own magnetic moment. Magnetic particles in ferrofluids are usually covered with surfactants, and dispersion ability of ferrofluids is high. Therefore, the aggregation does not become a problem under no magnetic fields. However, the aggregation cannot be disregarded in the strong magnetic field because the magnetic moment of magnetic particles is orientated in the direction of magnetic field. Therefore, the rheological characteristics also show complex behavior in the magnetic field. In this research, the aggregate structure in the state of equilibrium under the uniform magnetic field is analyzed. And we do a research on the aggregate structure from the view point of the "microscopic system." Results obtained are as follows. (1) A cylindrical structure in a strong magnetic field is shown when the saturation magnetization of particles is small. And, a plate structure is shown when the saturation magnetization is large in a strong magnetic field. (2) The particles in the cylindrical aggregation move violently in comparison with particles in the plate aggregation. (3) The aggregation does not move as pulsing and the translational velocity of the particle is constant when the system considered is the state of equilibrium in spite of microscopic system. (4) There exists a metastable area in the aggregation of ferrofluids.

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Ferrofluids make aggregations under a strong magnetic field. Therefore, the rheological property becomes complex and nonlinear. In this research, the numerical analysis of the aggregation of ferrofluids under the strong uniform magnetic field and simple shear flow field was made by the Stokesian dynamics method. Results obtained are as follows. (1) The aggregate structure can be classified into four types : the cylindrical structure type, the layered structure type, the diagonal structure type and the corrupt structure type. (2) The apparent shear viscosity by magnetic force shows a characteristic peculiar to each aggregate type. (3) The apparent shear viscosity by magnetic force decreases as the shear rate increases. (4) The apparent shear viscosity by magnetic force increases as the saturation magnetization of magnetic particles increases.

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This paper presents velocity profile measurements of an oscillatory pipe flow of magnetic fluid by Ultrasonic Velocity Profile (UVP) method. Experiments are performed at Reynols number Rc=367, defined by mean velocity amplitude and a pipe diameter, and non dimensional angular frequency W=4.76. It is shown that velocity amplitude increases in the center of a pipe and decreases in the near wall region under non-uniform magnetic field. The comparison of measured data under non magnetic field with those obtained from the theory of Newtonian-fluid reveals that noticeable discrepancies exist between them.

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A lifting line theory of a wing in exponential shear flow is presented. The governing equation due to Chen et al. is reduced to two ordinary differential equations by separation of variables, and a general solution is obtained by linearly combining the fundamental solutions. Induced attack angle is derived from the general solution and the condition of far downstream, and relation of lift force to effective attack angle is described by the Taylor series expansion in the vicinity of geometrical attack angle. From the induced attack angle and the lift force, a lifting-line equation is derived, and solved by Gaussian elimination method. By applying the theory to supercavitating hydrofiol, the effects of shear parameter, cavitation number and aspect ratio are clarified through some numerical calculations.

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The objective of the present work is to establish a vector field imaging system using a PIV technique with an optical fiberscope for applications of closed vessels such as a reactor, power plant, chemical plant, or combustor. A distribution of correlation coefficients employed to find particle displacements has inadequate peak of the correlation pattern by a fiberscope array itself in a coventional PIV technique, so that in the present study, the pattern of the fiberscope array was eliminated by subtracting an reference image pattern of the array provided byaveraging and the erroneous vectors could be reduced. Further the improvement of accuracy was achieved to obtain vectors using a particle streak tracking method. The optical fiberscope PIV with a high-powered pulse controllable laser diode system makes it possible to thoroughly investigate inside vessels and further, the physical compactness was achieved.

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Fluttering conditions are analyzed for webs with a simplified basic configuration with both leading and trailing edges fixed in a uniform flow by the method proposed in a previous study by one of the authors. The predicted flutter limits are expressed in terms of a ratio of fluid force to tension (σ^*) and a ratio of tension to bending stiffness (τ^*). Three regions for τ^* are seen to form characteristic zones of behavior. For τ^* greater than 1×(10)³ and less than 1×(10)⁶, σ^* and reduced frequency are of nearly constant values, respectively. For τ^* less than 1×(10)³, effect of bending stiffness appears and divergence-like instabilities having lower frequencies occur before the flutter. For τ^* greater than 1×(10)⁶, σ^* tends to become drastically lower and the reduced frequency becomes higher, with oscillation modes changing into higher order ones. Experimental flutter limits obtained in the wind tunnel, though scattered much, are seen on the average to conform to the expected ones in the limited range of τ^* of 1×(10)³-4×(10)⁴.

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To develop a better car engine, many design specifications are required because they would affect intake/exhaust system performance. Such specifications have to be found out by trial and error through many experiments and analysises. Therefore the automated multiobjective design optimization is desirable to reduce technical, schedule, and cost risks. Exhaust air has to be led from piston chambers to the exhaust pipe smoothly to increase the engine's power. It also needs to keep high temperature in the exhaust pipe because the catalyst located at the end of exhaust pipe will absorb more pollutant in higher temperature conditions. The design optimization has multiple objectives. This paper presents the development of the optimization code using Multi Objective Genetic Algorithm (MOGA).

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As an augmentative means of forced convective heat transfer, relationships between the heat transfer and the flow behavior were experimentally investigated when the longitudinal vortex was artificially generated by single vortex generator in a pipe. The formation of vortices and then flow spiraling downstream were visualized by means of fluorescein and smoke as tracer of water and air flow, respectively. The velocity components were also measured using an inclined hot wire probe in three flow directions. The vortices rings being accompanied with longitudinal vortex as a kind of shear vortex gradually closed to the wall surface. It was found that the local heat transfer coefficients was mainly increased depending on the circumferential velocity component. Furthermore, a law of non-analogy between heat and flow was discussed about some locations taking accounts of both heat transfer coefficients and skin friction factors.

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This paper describes a response of ice-layer formation to the time-varying cooling temperature at the top of the water-filled rectangular vessel, whereas the lower boundary is kept at 8°C. All the vertical side walls are insulated. The cooling temperature is varied periodically with several different conditions of amplitude and frequency. The corresponding ice-front movements are recorded accordingly. For a set of amplitude of the cooling temperature and ice-layer thickness, the critical frequency beyond which the ice-front movement is negligible (below 0.5mm) is determined. A time-lag of the front movement relative to the time-varying cooling temperature is also measured. A simple one-dimensional analysis is carried out in order to explain the above-mentioned critical frequency and time-lag. The PIV technique is also employed for studying convection flow structure in the liquid phase and the resulting ice-front deformation.

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The nonazeotropic binary mixtures such as, methanol-water, ethanol-water and ammonia-water, have variable boiling and dew points, depending on the mixture components and those concentrations. It is expected to have a higher coefficient of performance as a result of decreasing the thermodynamically irreversible loss, when there is a relevant concentration. Therefore, ammonia-water mixture is used as working fluid in small temperature difference power generation cycles and absorption refrigeration cycles. However, few experiments were carried out for measuring heat transfer coefficient for ammonia-water mixture in the world. Therefore, an experimental study has been carried out to measure boiling heat transfer coefficient of an ammonia-water mixture on a horizontal heated surface at low pressure of 0.2, 0.4 and 0.7MPa and at low concentration of 0<C<0.5 and at high pressure 0.7, 1.0, 1.5MPa and at concentration of 0.5<C<1.0 and at heat flux under critical heat flux the heat trasfer coefficient are compared with existing correlations prediction and a revised correlation can be proposed to predict them well.

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In an entrained flow coal gasifier, the gas temperature in the combustor or combustion region higher than the ash fluidizing point in order to discharge the mineral matter in the coal as molten slag. Following coal combustion, the gas temperature decreases as the gasification reactions proceed, eventually to below the ash softening point at the exit of the gasifier. This study focuses on the relationship between the ash melting characteristics and the ash deposition characteristics at temperatures below the ash softening point in the gasifier. Ash fusibility tests were conducted with DTA and ash liquid phase ratios were calculated as continuous ash fusibility index. The deposition tests were conducted using a drop-tube furnace for five types of coal. It was shown that the deposition characteristics have a close relationship with the ash liquid phase ratio and the difference of the ash deposition characteristics among coal types was explained by the ash liquid phase ratio. Furthermore, it was obvious that initial ash deposition phenomena at temperature below ash softening point are greatly influenced by Ca and Fe-aluminosilicate melts.

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The phenomenon of coal ash deposition on the walls is observed in an entrained-flow coal gasifier. The deposits interfere with heat transfer, and if they are heavy, they not only interfere with operation but also cause unplanned shutdowns of a gasifier. In order to commercialize IGCC power plant, ash adhesion behavior in a coal gasifier should be predicted when operational conditions of a gasifier or coal types might be changed. CRIEPI has been conducting study on the predicting technique of mineral matter deposition behavior in a coal gasifier. In this study, ash sticking/rebounding discrimination model based on ash liquid phase ratio was evolved. This model was introduced into numerical simulation code which had been developed by CRIEPI. Numerical simulation of ash behavior has been conducted for a 2/day coal gasifier and the ash deposition tendencies in a gasifier were evaluated. Numerical analysis results were in good agreement with experimental results of ash deposition tendency in a 2/day coal gasifier.

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A new concept slagging gasifier is tested in a 200kg/day scale facility. The new slagging gasifier is the pebble bed gasifier, which contains a fixed ceramic ball bed under an entrained bed. Gasification medium is high temperature air of about 1000°C added with steam. The gasification pressure is atmospheric. Pulverized Datong coal and crushed Skyline coal were respectively gasified in this facility. The gasification performances were evaluated by the cold gas efficiency and the carbon conversion rate. In the pulverized Datong coal gasification test, the achieved calorific value of the syngas was 4.970MJ/Nm³ (1187kcal/Nm³), where the cold gas efficiency as high as 78% was demonstrated.

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The thermal oxidation of acetone mixture, highly diluted with argon, has been observed in the mixtures of 0.02-0.5% acetone and 0.04-10% oxygen using UV absorption and IR emission. The experiments were performed behind reflected shock wave at temperatures 1200 1700K and at densities (2-9)×(10)⁵mol/cm³. The time histories of absorption intensity at 270nm and emission at 3.4μm due to CH₃COCH₃, absorption intensity at 310nm due to OH, emission intensity at 4.2μm due to CO₂, and emission intensity at 4.7μm due to CO and CO₂ were followed. The oxidation scheme CH₃COCH₃&roarr;CH₃CO&roarr;CH₃&roarr;(C₂H₆)&roarr;C₂H₄&roarr;CH₂O (H₂C₂O)&roarr;CO&roarr;CO_2- was obtained by comparing the experimental profiles with the profiles of computer simulation. The rate of acetone decomposition influenced the induction period of the oxidation.

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To evaluate the promotion of turbulent mixing, the time-average and fluctuation of fuel concentration were measured in a mixing channel with triangular plates using Rayleigh scattering method. Based on the obtained results, the deviations of fuel distribution were calculated at some crosssections, and also probability density functions were estimated by comparing with measured deviation and predicted ones from turbulence-mixing model. Furthermore, the effect of mixture heterogeneity on NO concentration in a burnt gas was demonstrated, and the trade-off relation between a mixing evolution and an increase in pressure drop was exhibited.

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For a reduction of period of piston development, it is very important to estimate the piston defects such as slap-noise and -vibration and skirt seizure induced by piston secondary movement and the difference of thermal expansion between piston and cylinder in engine running condition at the desktop stage. This paper describes the numerical simulation for prediction of the three dimensional skirt contact pressure and deformation in consideration of piston secondary motion. In this analysis, the iterference of piston skirt and cylinder was calculated by the geometrical consideration and reaction forces from cylinder was computed using stiffness matrix obtained in the experimental study. The validity of the results was verified by the comparison of the experimental results reported in the previous paper. After TDC firing, thrust side of the skirt was highly deformed by the piston slap.

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Effect of gravity level on the flickering motion was experimentally investigated for the propane and propane-hydrogen jet diffusion flames. A centrifuge was used for quantitative measurement of gravity effect, and frequency analysis was performed for the flickering flames. From the result of measurements under various gravity levels, it was clarified that the flickering frequency increased with an increase in the gravity level and it was correlated with two relationships expressed by the Strouhal number and the Froude number. One relationship was St∝Fr^-0.41 for high Froude numbers (Fr&ge;100), and the other was St∝Fr^-0.50 for low Froude numbers (Fr&le;100). It meant that the Froude number gave the criterion of the flickering behavior and that flickering frequencies expressed by these two equations were affected by buoyancy in different ways. From the frequency analysis, it was found that oscillations of a flickering flame and a thermal convection around the flame were linked, but the characteristic of each flickering motion was different in the stability of periodicity.

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The microexplosion occurrence in droplet combustion of miscible binary-fuel droplets has been studied experimentally and theoretically. In experiments, the burning droplet was injected upward, and the induction time for microexplosion occurrence was obtained. Results show that microexplosion induction time is distributed over the quasi-steady vaporization period. The maximum frequency of microexplosion induction time and the occurrence probability of microexplosion increase with the initial droplet diameter. The microexplosion occurrence was modeled considering homogeneous bubble nucleation rate. The present stochastic model well demonstrated the experimental results. The theory shows that these stochastic characteristics of microexplosion occurrence depend on the fifth power of the initial droplet diameter. The bubble nucleation leading to microexplosion depends on the time scale and the superheated liquid volume. The time scale in droplet combustion is proportional to the second power of the initial droplet diameter, and the volume of superheated liquid is proportional to the third power of the initial droplet diameter.

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An experimental study was performed of the extinction characteristics of counterflow diffusion flames in which polydisperse n-heptane sprays carried by a nitrogen stream from the lower duct, burnt in oxidizer streams from the upper duct. The distance between the ducts was varied to vary the strain rate with constant fuel flow rate, so that the upstream spray characteristics were independent of the strain rate. The burning behavior of the spray is observed and the oxygen concentration at extinction was determined as a function of the strain rate. The flat blue diffusion flame was observed between two ducts, which is supported by vaporization of small droplets. Relatively large droplets penetrate the flat blue flame and continue to burn on the oxidizer side with an envelope flame surrounding each single droplet. The burning behaviors and extinction characteristics were discussed based on the characteristic time scales such as the droplet response time to the flow and the vaporization time.

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A series of experiments was performed to investigate the effect of a new combustion technique, named doublet flows, on the extension of jet diffusion flame blowoff limits. Doublet flows were formed in a concentric annulus, in which fuel jet was ejected from a nozzle set at the center of the annulus and air was sucked into an outer cylinder encompassing the nozzle. Visualization of various changes of flame morphologies triggered by doublet flows and measurement of flame lift off heights were achieved by means of normal video recording as well as image processing and treatment devices. Results showed that the blowoff limits could be extended dramatically by an increase in air-suction flow rates. The limits could be further extended by an increase in rim thickness of the nozzle. Frequent flame lift-off and reattachment occurred only in the interim of doublet flow application.

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Blowoff characteristics of methane-air and propane-air edge flames are experimentally investigated by using the newly proposed burner that utilizes the stagnation region of an axisymmetric impinging jet. In the burner, "edge flame without premixed flame" can be formed as a hole in the diffusion flame, and, by changing the hole diameter as a parameter, the diffusion flame can be gradually turned from a pure diffusion flame to the diffusion flame with a hole. In the present study, the observation of flame shapes and the blowoff processes, and the measurements of the blowoff and separation limits have been performed. As a results, it is found that the blowoff and separation limits of the diffusion flames with a hole show qualitatively same tendencies with a pure diffusion flame, that is, the flames with a hole have critical stagnation velocity gradients for blowoff and separation phenomena, beyond which the flame can never be stabilized or existed. Especially, the critical stagnation velocity gradient for blowoff of "edge flame without premixed flame" decreases as the hole diameter is increased, and always shows lower value than that of a pure diffusion flame. Finally, it is clarified that Peclet number which is a ratio of the characteristic diffusion time to the characteristic convection time, is an important parameter for edge flame's blowoff process, and the transition of the blowoff process from blowoff without separation to blowoff with separation occurs at a constant Peclet number.

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Heat transport characteristics of a non-premixed turbulent flame formed in a curved rectangular duct (180° bend) are investigated experimentally. Key turbulence quantities of velocity and thermal fields such as Reynolds stress components and turbulent heat fluxes are measured using a combined LDV and fine-wire thermocouple technique. These measurements show direct evidence of the occurrence of counter-gradient heat transport, which can be ascribed to the existence of a strong pressure gradient in the radial direction of the curved duct. The schlieren photography for visualizing the density field reveals totally different behavior of the burned gas parcels between the high- and the low-pressure sides of the flow, and the observations may help us explain the mechanism of the occurrence of the counter-gradient heat transport in turbulent flows with combustion.

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Propagation characteristics of a spherical premixed flame in a constant volume bomb after spark ignition were investigated by analyzing pressure histories and the time dependency of the flame radius was examined using methane-air and propane-air mixtures over a wide range of equivalence ratio from lean to rich. The dependency was interpreted in terms of the effects of positive flame stretch on the laminar burning velocity. In order to estimate the sensitivity of the laminar burning velocity to the flame stretch, which is characterized and described by Markstein number, the mass burning velocity was calculated by analyzing the pressure profiles. The results obtained were compared with those reported by many researchers. Comparison of the results for methane-air mixture with those for propane-air mixture exhibited contrastive behavior, being typical of the flame propagation of lighter and heavier hydrocarbon fuels.

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Lattice Gas Automata (LGA) is an alternative approach for simulating fluids. The scheme of this discrete model is simple and easy for parallel computing. In this work, we simulate combustion filed by this LGA model. Two particles of reactant and product are used, which have properties of the unburned and burned gases. The model includes convection, diffusion, and reaction. The degree of reaction is expressed with reaction probability depending on the local temperature. We focus on the counter flow premixed flames. The flow, temperature, and concentration fields are determined by collective behavior of particles. It is concluded that combustion field can be simulated by this two component LGA model.

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A new concept compact boiler using high temperature air is proposed and experimental demonstration is done. In the boiler, high temperature air combustion is realized. Fuel can be efficiently burned by high temperature preheated air of about 800°C&acd;1000°C under low oxygen content (&acd;5%). The temperature distribution in the furnace is very uniform and there is no hot spot, so that low NO_x emission (&acd;40ppm) and relatively high average temperature in the furnace can be achieved. Thermal efficiency of more than 90% is accomplished including waste heat recovery of exhaust gas. This boiler is useful to partial load operation, because the response of thermal output is linear. This boiler is also suitable for low calorific value gas derived from gasification process of coal and wastes with no dioxin emission. Simulated low calorific value gas made from natural gas diluted with argon can be burned with low NO_x emission.

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Restraining the initial combustion, promoting the diffused combustion and reducing the cyclic combustion variation are of utmost importance to improving the fuel economy, exhaust gas emissions, and noise of the methanol fueled indirect injection (IDI) diesel engine. The author closely studied methanol fuel combustion in a high speed diesel engine (swirl-chamber system and single cylinder of 82.5mm bore and 92mm stroke), using different ignition systems, such as the spark-assisted method, glow-assisted method, and diesel fuel pilot injected method, to evaluate the engine performance and combustion characteristics. The methanol-fueled engine used in the study had a new combustion chamber with a refined jet passage for the optimum air discharge coefficient as well as for improved diffusion and penetration of jet in the main chamber. The engine cylinder was equipped with a miniature throttle nozzle for improved fuel injection characteristics. The new methanol-fueled combustion system was found to outperform the diesel-fueled conventional combustion system as regard the fuel consumption, smoke emission, and NO_x emissions, regardless of which ignition system were employed.

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In the previous studies, we proposed a two stage plasma-chemical process for control of NO_x gas emitted from electric power plants and factories. This process consists of a plasma process to oxidize NO to NO₂ with low electric power and low byproducts, and a chemical process to reduce NO₂ to N₂ using Na₂SO₃. Almost 100% NO_x removal efficiency was achieved for simulated exhaust gas using this hybrid method. In the present study, this method was first applied to a real exhaust gas from a diesel engine and the removal characteristics of NO_x were examined. As a result, the plasma reactor could oxidize nearly 100% of NO to NO₂ with the 50% load in the diesel engine. The NO oxidation decreased with increase in gas temperature and humidity. Using the plasma-chemical hybrid method, a 87% NO_x removal efficiency was obtained with the specific energy density. 140J/L.

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Considering the CO₂ problem, regenerated vegetable oil methyl esters have many advantages as an alternative fuel for diesel engines. However, operating with them increases NO_x emissions as compared with the gas oil. The present work is concerned with emulsified vegetable oil methyl esters characteristics and the effects of emulsified vegetable oil methyl esters on the exhaust emissions of a DI diesel engine. Increasing the water mass fraction of emulsified fuel decreased NO_x and smoke emissions simultaneously below the 15% water mass fraction. It was suggested that the optimum water mass fraction was 15% with regard to the engine performance and exhaust emissions, and emulsified vegetable oil methyl esters can be used as an alternative fuel of petroleum diesel fuels.

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The power response is a very important characteristic for the aircraft engine. Especially for the helicopter, engine power response is essential to the safety at an emergency condition. Here, a new idea of increasing the power response dramatically, with the combination of centrifugal compressor and variable inlet guide vanes, is studied and the verification test results using a small turbo shaft engine is described.

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