The Rayleigh-Benard convection occurs, if the fluid between the parallel plates is heated from the bottom plate and cooled from the upper plate above the critical temperature difference. The Rayleigh-Benard convection is seen in the blast furnace. Particularly, the lower Prandtl fluid like the fused metal tends to be time dependence flow. This flow disturbs the pressure field and temperature field, and hinders the formation of the metal with the good crystal. The Lorentz force by DC magnetic field can control this flow. By this way, the time dependence flow changes to laminar flow and the three dimensional structure changes to the two dimensional roll structure. In this thesis, the computations have been performed for Rayleigh-Benard convection in the three dimensional cubic cavity, using GSMAC-FEM with φ method. From the solution, the author investigated the effect of magnetic field to the flow and temperature field and the two dimensional roll structure.

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A new method for computation which make an analysis of flow field around an arbitrary shaped body with elastic deformation by fluid force have been developed. Non-linear simultaneous equations are derived from governing equations of flow field and elastic deformation, and then the non-linear simultaneous equations are solved using Nowton-Raphson method. An independent variable is only fluid force in the equation of elastic deformation. The flow field is defined as implicit function of the fluid force acting on an elastic boundary. The number of the unkown quantity in Newton-Raphson method decreases substantially. The velocity field and the pressure field are computed after the fluid force acting on an elastic boundary is obtained. In this paper, we explain the principle of the computational method, and then two examples of numerical simulation are shown. One is the flow-induced oscillation of three-dimensional circular cylinder that is supported elastically and another is the computation of flow around an elastic wing with pitching motion.

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Previous studies say that the dynamic Smagorinsky's model of Germano et al. using lower order finite difference method tends to overestimate the statistics of the streamwise mean velocity and streamwise turbulent intensity. The objective of our research is to develop an isotropic eddy viscosity model which mitigate this tendency as an alternative to Smagorinsky's model. The procedure proposed by Yoshizawa et al. was utilized and more consistent eddy viscosity model for the dynamic procedure was obtained. The proposed model was tested in plane turbulent channel flow at Re_t=180 and 590 normalized by friction velocity and channel half width and predicted better statistics than those of Smagorinsky's. The new model was also found to be less sensitive to the discretized filtering operation than Smagorinsky's. We investigated the organized eddy structures near the wall and revealed that the overstimation of the eddy structures by Smagorinsky's model was clearly mitigated by using the proposed model, which shows the validity of the improvement of the statistics by the new model.

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In our previous research, the modified Galerkin method was proposed as one of the most efficient methods for convection-diffusion analysis and viscous fluid flow analysis. In the modified Galerkin method, the inertia term is considered explicitly, so only symmetrical matrixes appear. Then an artifical viscosity is introduced through an error analysis approach to improve its accuracy and stability. In this paper, this modified Galerkin method is applied to the thermal fluid analysis using the Semi-Implicit Method for Pressure-Linked Equations Revised formulation and the natural convection problems in a three-dimensional cavity are simulated up to the Rayleigh number of 10⁸. Authorts confirmed that out proposed method gives reasonable results for these problems comparing with other research works.

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An axi-symmetrical direct simulation Monte Carlo program for analyzing rarefied gas flow in a vacuum chamber with downstream-pressure and gas-flow-rate was developed. Rarefied gas flows with radicals and etching-products in microwave-plasma etching reactors were calculated using this simulator. The results show that the flow patterns in the plasma chamber strongly depend on the Knudsen number and the gas-supply structure. The ventilation of the etching products in the plasma chamber was found to be improved for higher Knudsen numbers, and in the gas-supply structure of down-flow type compared with that of radial flow type or upward flow type.

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A direct numerical simulation(DNS)was conducted for a particle-laden turbulent flow in a vertical channel. Particular attension was focused on the turbulence modulation through the Reynolds stress, rather than the wake-induced perturbation. We simulated downward flow as well as upward flow to observe the influence of the direction of particle forces to the mainstream. Comparison between our calculation with a corresponding experiment showed qualitatively reasonable agreement. Reynolds shear stress was increased in a downward flow while reduced in an upward flow according to the momentum balance change due to the particle-induced force. As a result, the production of turbulence energy was increased/decreased in a downward/upward flow. It was also affected by particle distribution. We therefore suppose the turbulence modulation without vortex shedding from particles could be predicted if the momentum exchange between two phases and the distribution of particle concentration were given accurately.

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The aim of this study is to elucidate experimentally the effect of chemical reaction on the diffusion process in a turbulent liquid jet. The chemical reaction in this study is a competitive-consecutive reaction(A+B→R, R+B→S)which kinetics is well known. The instantaneous concentrations of two reactive species (R and S)and a non-reactive dye(Y) were measured simultaneously by the light absorption spectrometric method. From the above measurements, the instantaneous concentrations of species A and B, which we have not been able to measure before, can be determined by the conserved scalar theory. To ascertain the validity of the concentration measurements, we compared the present measurement results with those for one non-reactive dye Y and two reactive species R and S. It was found that the concentrations of non-reactive dye Y and reactive species R and S can be measured accurately by the present measuring system.

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The diffusion field with a competitive-consecutive reaction(A+B→R, R+B→S)in a turbulent liquid jet has been experimentally investigated. The water solution of species B and non-reactive dye Y is issued into the main flow including species A. The instantaneous concentrations of two reactive species(R and S)and a non-reactive dye(Y)were measured simultaneously by the light absorption spectrometric method. The instantaneous concentrations of species A and B were determined by the conserved scalar theory. Since the reaction rate constant of the primary reaction is much larger than that of the secondary reaction, the species R starts to be produced efficiently from the neighborhood of the nozzle exit, while the species S is mainly produced in the downstream region. The skewness of the concentration PDF of reactants A and B on the jet axis show the positive values in the downstream region, while those products R and S show the negative values.

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When the propagating shock wave reaches at the open-end of a tube, the impulsive wave discharges to the surrounding area. A new technique of passive control that augments the magnitude of an impulsive wave is proposed in this study. Experimental and numerical studies are carried out to examine the effects of new technique of the passive control that alter the exit geometry of a straigit tube to a flare and a cup. The effects of geometry parameter of a flare and a cup at the tube exit on the magnitude of the impulsive wave were investigated over the range of Ms from 1.01 to 1.1. The results were compared with those of the straight tube and showed that the present technique of passive control enable augment the magnitude of the impulsive wave.

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A computational investigation has been made, concerning the interaction between a vortex ring, generated by starting a shock wave with Mach number 1.4, and plane shock waves with various shock Mach numbers. It is shown that a self-intensification of the shock wave takes place due to a mechanism of wave convergence by interaction of the shock wave and the vortex. In order to evaluate the strength of the intensification, the mean values of the maximum pressure and density for the time of the interaction are computed for the various shock Mach numbers. A remarkable feature is found in the computation that the strength increases, then achieves to some constant value, and finally decreases as the shock Mach number increases. These results show typical features for interaction such as the weak shock-strong vortex ring, med shock-med vortex ring and strong shock-weak vortex ring.

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Axial wall pressure distribution caused by the flow through a contraction was investigated by experiment and numerical analysis. By using various contraction with different lengths and diameters, downstream wall pressure were measured at low Reynolds number in the contraction. By the difference of the characteristics of measured pressure distributions, two flow modes, corresponding to laminar and transient flow condition, were distinguished in each contraction condition. In laminar condition, the distribution had well known smooth and unimodal shape. And transient condition, the wall pressure showed large and pseudoperiodic change at the site within a local region. The shape of temporally averaged pressure distribution was unimodal with acute peak. From the numerically calculated pressure distributions, a model expression for determining the location and the value of their peaks, with contraction conditions as parameters, was derived. Moreover a method for giving an approximate pressure distribution was established and verifird by comparing it to the measurement results.

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Experimental studies on the lift acting on a disk levitated by a circular impinging jet with confining wall were carried out. The diameters of upper and lower disks were 100 mm and 75 mm, respectively. The pressure distributions on the both disks were measured in the range of the space between the two disks from 0.5 to 6 mm at the flow rate 251/min, and the surface oil-flow patterns on the both disks were visualized. The conclusions obtained are as follows : The impinging jet rebounds and reattaches on the upper disk, and a separation bubble is formed on the upper disk. Then, the vena contracta occurs by the existence of the separation bubble, and a large pressure drop arises. After all, a large lift is established. This is the main reason for the levitation of the disk.

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Flow of viscoelastic fluid is commonly analyzed by using constitutive equations. In this paper, bead-spring-damper macro model is proposed as an alternative to analyze viscoelastic flow. The tetrahedral structure of beads, springs and dampers models a gathering of intertwined polymer chains. Behavior of the bead-spring-damper structure is computed under simple shear flow condition. Shear-thinning of shear viscosity and the mechanism of second normal stress difference generation are investigated. The results show that the phase lag of the tension, caused by the damper element, is the mechanism of second normal stress difference generation, and that the bead-spring-damper macro model can express characteristics of viscoelastic fluid consistently.

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This paper describes the numerical analysis on the generation mechanism of discrete tone noise radiated from a two-dimensional wing immersed in uniform flow. Linearized approximate equation of the small perturbation of the boundary layer flow is introduced to the interactive dynamical model between the perturbed flow on the suction side of an airfoil and the sound near field emitted from the trailing edge. The numerical solution of the Green function of the Fourier-Laplace transformation of the perturbed flow variables is derived given the mean velocity profile of the boundary layer. The solution estimates well the configuration of the perturbed flow development.

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A staggered array of closely packed rigid tubes has been tested, by varying the flow velocity in a wind tunnel, to study the conditions under which acoustical resonances occur. The items which have been studied are : the Strouhal numbers at which flow periodicities occur ; the relation between these Strouhal numbers and those at which acoustical resonances occur ; the effects of the Reynolds number and the longitudinal tube spacing on the occurrence of acoustical resonances. This investigation has shown that the acoustical resonance can be excited at a frequency well apart from that of vortex shedding. The results also show an evidence that both phenomena exis simultaneously at different frequencies. On the basis of these findings and those from a similar investigation into vortex induced tube vibration it is proposed that tube vibration and acoustical vibration can be treated as different mechanisms. Hence the guidelines presented in this paper should be followed to avoid the occurrence of acoustical vibration.

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The performance of active feedback control of edge tone phenomenon by the control flow is investigated experimentally and the mechanism is discussed. It is found that the pressure fluctuations over the edge surface are reduced by this control roughly to those of the free jet. The optimum conditions for the phase lag and amplitude of the control flow are obtained quantitatively for various edge distances from the jet nozzle. These results show that the present control technique is very effective for weakening the flow oscillation of the jet-edge system. The flow visualization study suggests that the control mechanism is due to the cancellation of pressure fluctuations created at the edge by the imposed velocity fluctuations.

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Supercavitation hydrofoil applied to high-speed marine propeller or hydro-machinery blade runs into unsteady behaviors such as cavitation breakdown and hydraulic flutter in some operation range. The hydrofoil performance was experimentally estimated and compared with the wedge performance using the cavitation tunnel and the torsional vibration apparatus with three component load cells. This experiment was carried out at several angles of attack in the region from subcavitation to supercavitation. At a general steady state but including some cavitation breakdowns, the hydrofoil has the most superior time mean lift/drag ratio about 6<C_l/C_d<8 at in all cavitation regions. But, the ratio drastically decreases as the angle of attack increases. Fluctuating lift coefficient C^'_l due to the cavitation breakdown reaches up to about 10% of time mean lift coefficient C_l. At the hydrofoil pitching motion, the torsional flutter margin of the hydrofoil extends to higher reduced frequency side as the angle of attack increases and has the nearly same margin of the wedge in all cavitation regions.

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Rising speed of a spherical gas bubble near a plane wall was measured experimentally. We developed an experimental apparatus in which a CCD camera with a microscope follows the rising bubble and used it to precisely estimate the change of the rising speed due to the plane wall below Reynolds number of 50. We also proposed the equation for estimating the effect of a plane wall on the drag force by modifying the analytical solution obtained under the Ossen approximation and compared with the experimental results. The results show that the Stokes solution including the wall effect is in good agreement with the experimental results for the Re<0.1. And they also show that the proposed equation agrees well with the experimental results and can be applied for estimating the wall effect on the rising speed up to the Re of 50.

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Magnetic fluids are known as a typical example of functional fluids in the magnetic field. Fundamental studies are conducted to develop engineering devices, in which the motion of magnetic fluid column is utilized. Since the oscillating characteristics should be crucial for the device performance, the motion of the liquid column in a U-tube is observed using step response method. In the experimental work, the effects of the magnetic field strength and the position of the column surface on the damping characteristics are examined for a variety of conditions. The damping ratio that is used in the case of forced vibration increases with the magnetic field strength. The natural frequency with damping oncreases with the magnetic field intensity and with the rise of the fluid column position. Numerical calculation is also carried out using conditions similar to the experiment. The predicted results agree qualitatively with measured values.

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The authors have proposed a new technique to suppress successfully the rotating stall in the vaneless diffuser. By positioning the completely rough wall between R=1.2 and 1.6 on the hub side diffuser wall alone, the flow rate of rotating stall inception was decreased by 42% at a small pressure drop less than 1% of the blower pressure rise. This is based on that the local reverse flow occurs firstly at the hub side in most centrifugal blowers with backswept blade impeller mainly depending on the distortion of tangential component of inlet main-flow velocity. The 3-D boundary layer calculation shows that the local reverse flow is decreased remarkably by an increase in wall friction, and it disappears if the friction coefficient is 0.01 about twice of the smooth wall. By analyzing the effect of wall friction and turbulence induced by the rough wall, it is clearly shown that the rough wall positioned in the limited region, where the wall-limiting streamline flow angle shows the negative maximum, is quite effective to suppress the rotating stall at a small drop of the diffuser pressure recovery.

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A numerical analysis of two-and three-dimensional separated and reattached flow and heat transfer in an enlarged channel is presented in this paper. Numerical calculations of Navier-Stokes equations and energy one are carried out using the finite difference method. The results of three-dimensional calculations are compared with the two-dimensional ones and show the effects of aspect ratio. The transition from symmetric to asymmetric flow is caused at lower Reynolds number with increasing the aspect ratio. The details of local heat transfer characteristics accompanying two different separated flow regions on two downstream walls are clarified. Two-dimensionality of the flow and heat transfer is disappeared at the aspect ratio considered.

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Direct numerical simulations have been performed to clarify the sound generation mechanism in a two-dimensional chemically reacting compressible mixing layers. The effects of heat release on the mechanism of sound generation are investigated. The dominant acoustic source term in Lighthill's equation is entropy component, while the Reynolds stress component and viscous component are considerably small. The maximum pressure fluctuation in the far-field increases with the increase of heat release parameter and Damkohler number, which suggests that the characteristics of sound are mainly determined by the heat release in reacting mixing layers. The far-field sound computed by DNS is compared with the predictions based on the acoustic analogies derived by Powell and Lighthill. Both analogies fail to predict the far-field sound in the reacting mixing layer. Lighthill's analogy gives quite large pressure fluctuation and Powell's analogy gives lower pressure compared with DNS. In this study, an analogy including Powell's source term entropy term is prmoposed. The pressure fluction predicted by the proposed analogy shows a good agreement with the DNS results.

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A correction factor for the theorectical fin efficiency of serrated fins was derived from an experiment. This correction factor compensates the influence of the assumptions made in the analytical model used for evaluating the fin efficiency, which has been derived theoretically in the 1st report of our atudy and has been expressed as an approximate equation in the 2nd report. Using this correction factor together with the theoretical fin efficiency, the actual fin efficiency can be estimated for serrated fins of various fin geometries, including plain or solid fins.

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Heat transfer coefficients of air-cooled fins which located on outer surface of a totally enclosed induction motor were measured. It was found that heat transfer coefficient decreases with fin distance. And it was also found that increasing the axial length of the fan cover(i.e., so that the fan cover overlaps the fin)effectively increases the average heat transfer coefficient of the outer fins. Internal flow induced by the rotor fan inside a bracket coincides with the rotational speed of the rotor fan. Flow between the stator coil end and the housing in the motor is small, so a cooling structure with an inside ventilation passage for air flow effectively increases the heat transfer of the stator coil. The effect of resin(varnish)between the stator and the motor housing on the thermal-contact conductance was also investigated by using an actual motor. The thermal-contact conductance of the motor with resin was 1.58 times higher than that of the motor without resin.

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Heat conduction during contact between a heat transfer surface and fluidizing particles, which is one of the effective heat transfer mechanisms in a gas-solid fluidized bed, has been empirically investigated. The temperatures of the fluidizing particles during the contact period are visualized by an infrared imager. This visualization reveals that the particles have been considerably heated in the thermal boundary layer on the heat transfer surface before the contact. Based on the visualized temperature of the particles, the contact conductance between a fluidizing particle and the heat transfer surface was estimated by an inverse analysis, and using the evaluated contact conductance, the contributions of the conductive heat transfer to the total heat transfer are also evaluated.

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Heat transfer for flow-boiling of water and Critical Heat Flux(CHF) experiments in the half-circumferentially heated round tube under low pressure condition were carried out. In order to clarify the flow patterns in the heated section the experiments in the round tube under the same condition were also carried out, and their results were compared. The experiments were conducted with atmospheric-pressure water in the test sections with inner diameter D=6mm, heated length L=360mm, inlet water subcooling △T_in=80K and mass velocity G from 0 to 2000kg/(m²·S)for the half-circumferentially heated tube and from 0 to 7000kg/(m²·S)for the full-circumferentially heated tube. The experiment data demonstrated that the wall temperature near the outlet of the half-circumferentially heated tube continued almost the same until CHF. And it was found that the burnout occurred when the flow regime changed from churn flow to annular flow, and the liquid film on the heated wall dried out nevertheless the liquid film on the unheated wall remained.

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Pressure drop and heat transfer of arrays of in-line circular blocks on the wall of parallel channel were measured. The diameter and height of the block were 40 mm and 18 mm, respectively. The effects of the pitches of the blocks, the number of line and row and the other factors on the pressure drop, △p, and heat transfer were clarified. The pressure drop coefficient, ζ, is given by the sum of the pressure drop of three regimes : the inlet, intermediate and outlet part. And the coefficient ζ can be formulated and the recommended equation agrees with the experimental data within ±10%. The average Nusselt number of the block of 1st row is 10% lower than that of 2nd row. Those of 1st to 5th rows, Nu_mican be approximately expressed within ±10% by the following equation : Nu_mi=0.118(Re/β)^0.75where β is the opening ratio. The average Nusselt number of 2nd to 5th rows was also correlated by using the pumping power, P_w, within 5% as follows : Nu^^^-=190P^0.25_w, where P_w=△pU_mA_o, U_m is the mean velocity and A_o is the cross-sectional area in a duct. Finally, the Nusselt number is represented by the non-dimensional expression as follows : Nu^^^-=0.134(ζ^1/3Re)^0.75.

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This paper deals with air flow around the inner pipe in annular space of a double-pipe, induced by corona discharge.A discharge electrode, made of a thin wire of 0.14 mm in diameter, is set in the annular space, in parallel to each axis of both pipes, and at the same and shortest distance from the internal surface of the outer pipe and the external surface of the inner pipe, which are used as collecting electrodes. As the external surface of the inner pipe approaches to the internal surface of the outer pipe keeping above geometric condition, circulating flow around the inner pipe is observed. Details of the flow, such as the relation between the inner pipe position and the pattern of flow are made clear by use of visualization technique and by measurement of flow velocity.

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Destabilization process of the vapor film formed around a hemispherical heated surface made of copper or stainless steel rod of 30 mm in diameter and immersed in R 113 is investigated experimentally. The vapor film is destabilized by an external pressure wave, which is produced by a magnetic hammer, and the configuration is taken photographes. The pressure change in the vapor film when the external pressure wave is supplied is measured by a small pressure transducer set at the stagnation point of the copper rod. The induced pressure change in the film is analyzed theoretically and is shown to be in good agreement with measured data. A sharp pressure pulse, which has a higher peak value than that of supplied external wave, is confirmed to generate in the vapor film. The maximum pressure in the vapor film is in proportion to 1.6 power of that of the external pressure wave.

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Water has an anomalous relationship between temperature and density. When water is cooled by two horizontal cooling tubes placed vertically in a rectangular enclosure, both downward and upward convection interfere with each other between the two tubes. The flow pattern of this convection is influenced by the tube separation distance and the cooling rate. We studied the effects of these factors by laser measurement techniques and numerical calculation, and some interesting relations were acquired. The tube separation distance has the great effects on the development of the density inversion flow, the release of supercooling, and the heat transfer characteristics. In this paper, we mainly discuss about these effects of the tube separation distance, and attempt to clear the cooling and freezing behavior of the water in this type cooling system.

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In the present paper, an attempt is made to develop an effective EHD enhancement technique for condensation heat transfer of steam around a horizontal finned tube. The main idea in the present study is to reduce the power consumption by using a partially coated electrode, and the experimental data of heat transfer coefficients and flooding angles are presented. The result indicates that, by using such an electrode, the enhancement ratio keeps almost the same level with that of a bare electrode but the power consumption can be markedly decreased. Within the present experimental range, the condensation heat transfer coefficient on the finned tube with the partially coated electrode reaches a value about 3 times larger than that without electrode. In addition, a model in presented for the EHD effect on the flooding angle and it is confirmed that the prediction from the model is in good agreement with the experimental data.

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A system that uses magnetic force can be effective for treating sewage water because it can rapidly separate solids from liquid. We are developing such a system that uses a superconducting magnet that consumes little power but produces a strong magnetic field. The system also uses rotating magnetic filters and can be operated continuously. We constructed a prototype and tested it using sewage water. The system successfully removed 90% of BOD(biochemical oxygen demand ; the BOD in the effluent for this system was less than 0.22 μm)and 97% of SS(suspended solids). This means that the total space required for a sewage treatment facility might be reduced when such a system is used.

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For further improvements on thermal efficiency of steam injected gas turbine, Partial Regenerative Dual Fluid Gas Turbine System(PRDF)is proposed. In this paper, parametric performance analysis of the new cycle gas turbine is carried out. The thermal efficiency of the PRDF is compared with other three kinds of gas turbine systems, that is, Steam Injected Gas Turbine, Regenerative Gas Turbine and Regenerative Steam Injected Gas Turbine. Results of the analysis show that the PRDF can realize higher efficiency than other two systems, in the range of such usual pressure ratio as applied in actual gas turbines. Effect of injection steam pressure on thermal efficiency of the PRDF is also evaluated.

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Rich-lean rapid two-stage combustion was attempted to reduce NO_x from the diesel engine. The effect of the mixture concentration and its history on NO formation was evaluated using a thermo-chemical three-zone model. The experimental study was also carried out using a small direct-injection diesel engine with high turbulent combustion system. Fuel-rich mixture was formed by two small cavity combustion chambers. Dimethyl Ether was used to form uniform rich mixture and to avoid smoke formation. The results show that NO_x can be reduced in the heavy load when the mixture concentration shifts to lean from rich condition in a short period.

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In this study, we measured pyrolysis and combustion characteristics of wood with a view to make clear premix and ignition mechanism of backdraft. Cone calorimeter was used to measure heat release rate(HRR)curves and mass loss rate(MLR)curves for 18 mm thick Lauan woods at an incident heat flux of 50 kW/m². Lauan has two peaks in the HRR and MLR curve. First sharp peak comes soon after ignition and a second peak appears near the end of the flaming combustion period. We also measured MLR curves and oxygen concentration curves for 18 mm thick Lauan woods in constant temperature, low oxygen concentration furnace. In low oxygen condition, MLR was de-creased because heat feedback from flame was decreased. In order to explain the second peak observed in the HRR and MLR curve, a simple calculation was carried out by considering wood and char properties and wood pyrolysis rate. It was found that the second peak is the result of a rapid rise in the bulk temperature of the remaining wood. The second peak is primarily dependent on the un-exposed face conditions.

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Lifting phenomena caused by vortex-flame interactions have been investigated about diluted-propane jet diffusion flames forced by a speaker installed at the bottom of a fuel tube. Open jet diffusion flames were formed on a co-flow burner composed of the inner fuel tube and an outer air tube. Two type nozzles of rim thickness of 1 mm and 0.2 mm were set at the end of the fuel tube for each experiment and the effects of the rim thickness on the flame stability were investigated. Artificial vortices were imposed in the fuel flow through the speaker excitation to make clear vortex-flame interactions. The schlieren and OH radical imaging techniques were employed to unveil the interactions. Experiments in terms of the difference of rim thickness revealed that the ratio of the rim thickness to the quenching distance is important for lifting criteria as proposed by Takahashi and Schmoll, because the ratio of unity determines the limitation of whether the end of the flame base being in or out the recirculation zone behind the rim. Moreover, it revealed that the vortex-flame interactions are able to become the trigger of lifting, though the effect to lifting was questionable so far.

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In an attempt to elucidate formation and disappearance processes of droplet clusters in spray flames, simultaneous measurements consisting of laser tomography and flame chemiluminescence detection are applied to a premixed-spay burner. The smart combination of measurements provides time-series data-set serving for better understanding of spray flames, which essentially contains inhomogeneity in space and time. It is revealed that referential flame propagation through a premixed-spray stream plays a significant role in creating droplet clusters and that droplet clusters formed in this manner evanesces from their outer boundaries. Those observation confirms that the premixed-spray flame comprises both premixed-mode flame in upstream region and diffusion-mode flame in downstream region, respectively, i.e, two-stage flame structure previously reported for spray flames stabilized in either counter or stagnation flows.

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When CVT was equipped with the 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. Though fuel consumption becomes economical at transient state by Engine-CVT consolidated control, accurate control of transient air fuel ratio(A/F)also becomes important issue under such control. And then, keeping A/F within the window around the stoichiometric A/F ratio is important for treatment of transient exhaust gas. In these case, SI-SO system was used to control the transient A/F. However, through A/F consists from induction air and fuel behavior, MI/MO system is seemed to be suitable for accurate A/F control for transient state. From such point of view, investigation was carried out about transient A/F control for Engine-CVT consolidated control.

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The possibility of low compression ratio (CR) for dimethyl-ether (DME) diesel engines was investigated experimentally.The CR was altered by changing the top clearance volume from the original 17.7 CR to 10.16.The main results are summarized below:(1) The lowest CR for easy start and stable combustion is around 12.(2)At CRs from 17.7to12.36, the brake thermal efficiency of a DME engine is almost the same.(3) The aggravations of THC, CO emissions and noise of DME engine are extremely low.(4) The high combustion efficiency and the increased degree of constant volume of DME engine within the above CR range enables operation with high brake thermal efficiency.

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The auxiliary port injection system was built up using low pressure injectors installed on a commmon rail. Methanol/water blend was injected into each suction port of a four cylinder turbocharged DI diesel engine by controlling the injection timing and duration electronically. The optimum conditions of the injected amount of methanol/water blend and the blending ratio of methanol and water were investigated to obtain simultaneous reduction in both NO_x and smoke without increasing fuel consumption. In the theoretical study, the effect of methanol/water blend on combustion and NO formation was analyzed by using the two-zone model. The proposed auxiliary port injection of meth anol/water blend combined with the pilot fuel injection could be a feasible countermeasure.

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