The role of the disturbance waves for transferring liquid toward the top of a horizontal tube wall to cope with the drainage due to gravity is investigated by the direct numerical simulation (DNS) which is based on the continuity equation and Navier-Stokes equations in three-dimensional cylindrical coordinate system. The level set method is used for capturing the, interface between gas-liquid two fluids. Developing flow from a separated to an annular flow is simulated by using this numerical technique, and the liquid film formation is reproduced. It is demonstrated by this calculation result that liquid is transferred in the circumferential direction as the liquid film by the pumping action of disturbance waves which has been proposed by one of the present authors. And the pressure gradient in the circumferential direction plays an important role for the formation in a horizontal annular flow.

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The Free Mesh Method (FMM) is a kind of meshless method modified from the conventional finite element method. In this method, the global equations can be constructed without element-node connectivity information, coordinates and boundary information only are required as input data. We applied the FMM to the interaction problems of incompressible viscous fluid and structure. The Arbitrary Lagrangian-Eulerian (ALE) method and the staggered method were employed here. As the example, we calculated the motion of the pitching-bending wing, which resulted in higher propulsion than that of the pitching wing without bending.

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A novel model of the finite difference lattice Boltzmann method (FDLBM) is presented. One term related the viscosity is added to the discrete Boltzmann equation, and the relationship between the kinetic viscosity and the relaxation parameter is changed. The time increment can be chosen much larger than that of the ordinary FDLBM, and the stability of the scheme is much improved. Characteristics of the model are also clarified by calculations of typical benchmark test, i.e. 2 D Couette flows and square cavity flows.

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An experimental study has been made on the jet-like flow induced by an elastically vibrating plate. In order to clarify the effects of configuration of the plate on the induced flow, time-averaged velocity decay along the center line of the jet has been measured by using a hot-wire anemometer. As a result, the flow filed was found to be categorized into three regions defined by characteristics of the axis velocity decays. By introducing a method similar to that applied to jets issuing from rectangular nozzles, measured velocity decays have been normalized. The normalized velocity decays obtained were found to he independent of both amplitude and frequency of vibration and showed geometrical similarity for the various plate configurations tested. Therefore the diagrams for normalized velocity decay are useful means to estimate the flow field induced by an elastically vibrating plate with various configurations.

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In order to investigate the diversity of the development of near-field of a round jet found in experiments and in numerical simulations by different authors, we applied a global instability analysis to a secondary instability of the near-field region of a round jet. The secondary instability takes place in a braid region between neighbouring vortex rings after the primary instability generating vortex rings, and streamwise vortices due to the secondary instability is a key issue in a decay process of a spatially developing jet. They consist of various modes with a non-uniform concentration in the azimuthal direction in a spatially devoloping jet. The analysis demonstrates that the small difference in receptivity of each unstable mode causes locally different speed of the growth of disturbances. This non-uniform receptivity in the secondary instability causes diverse process of decay of vortex rings in spatially developing jets.

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A long circular cylinder with the diameter of 20 mm was placed in an air jet, issuing from a rectangular orifice with the short side, h, of 3 mm and the aspect ratio of 10. The cylinder was settled on the symmetrical plane of the jet flow along the long side of the exit. The impinging distances between the jet exit and the front surface of the cylinder, xi, were varied within fifty times of the short side length. The jet exit velocity was kept constant at 24 m/s and the Reynolds number, based on the short side length, was about 4 900. It was found that the mean and fluctuating(rms) pressure profiles around the circular cylinder showed remarkable changes with the impinging distance and the position along the cylinder axis, z. The value of fluctuating pressure at the stagnation, being different from that of fluctuating velocity of the free jet, was large even at the vicinity of the jet exit. The negative pressure region, formed on the front surface of the cylinder, alone diminished clearly at a position of z over the impinging distance of xi/h<5. The saddle-backed velocity profiles for the orifice jet as well as the diminshment of the negative pressure region along z-axis might result in the off-axis distributions of the drag per unit width. The drag per unit width at z/h=3.3 of xi/h=5 was increased up to 2.4 times of the drag at z/h=0. The coefficient of total drag on the cylinder was estimated 1.16 at the jet exit and 0.76 at xi/h=50.

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If separation occurs in a flow field, it makes a large pressure loss and thus aerodynamic performance is largely reduced. A wall jet (i.e. tangential blowing) is one of control techniques for such a flow field. However, the verification of turbulence models for a wall jet in compressible flow is insufficient. In the present study, we examine the predictive performance of five typical turbulence models (Spalart-Allmaras 1 eq. model, Lam-Bremhorst, Myong-Kasagi and Shimada-Nagano k-ε 2 eq. models and Craft-Launder-Suga k-ε-A₂ 3 eq. model) for 3 cases of wall jet. In the results, the k-ε models show a relatively good predictive performance and little difference of distributions among the models. On the other hand, Spalart-Allmaras and Craft-Launder-Suga models indicate the inclination to overestimate a separation region.

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Atmospheric boundary layers were simulated in a laboratory wind tunnel by regulating parameters of a turbulence shear flow generator. The generator could control turbulence characteristics ; mean velocity U=0∼8 m/s, turbulence intensity u'/U_∞=1∼13% and integral scale L_ux=0.02∼1.9 m. The maximum turbulence Reynolds number reached about 650 at U_∞=8 m/s and the spectrum had a wide inertial subrange comparable to those in natural atmospheric boundary layers. When the turbulent boundary layers with δ∼0.4 m were realized on a smooth surface, they maintained the power law profile of U∼Y¹/7 until downstream region. On a rough wall, the velocity profiles changed into U∼Y¹/3 and vertical distributions of u', v' and -uV^^^- gave fairly good approximation to the actual conditions of surface boundary layers. Flow visualization around an architecture suggested that precise simulation of turbulence phenomena in atmospheric boundary laers required experimental turbulence fields afforded by large scale turbulence characteristics comparatively sufficing actual wind conditions on the ground.

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In this study, Direct numerical simulation (DNS) of wind-driven turbulent flow at the Reynolds number is about 3 300 based on the gas layer height and the free stream velocity, was conducted by the direct numerical solution procedure (MARS method) for a coupled gas-liquid flow. As the results, completely mass conservation was kept during the all calculation time and the capacity of MARS method as the method for DNS of multiphase turbulent flow indicated. In wind-driven turbulent flow, local friction coefficient in gas side was 15% decreased compared with the wall turbulent flow. Near free surface, large horizontal scale shaped the water surface wave motion supplied the velocity fluctuations to the fluid motion. But, vertical component of turbulent intensity was constrained by the water surface existence as well as turbulent open-channel flow at low Froude number. In both gas- and water-side, high and low speed streaky structures were observed and these structures and surface wave motion was interacted each other. It seems that relationships between wave height and turbulent boundary layer thickness was one of the important factors in wind-driven turbulent structure.

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Active control of wavelength of the velocity fluctuation pattern along the spanwise direction in the flow over a cavity using thin piezo-ceramic actuator pieces is tried out. The aim of the flow control is to reduce the aerodynamic noise coming out from the cavity. Eight actuator pieces attached at the upstream-edge of the cavity are used in the laminar boundary layer case, and four pieces are used in the turbulent boundary layer case. Judging from the velocity fluctuation patterns obtained by the hotwire measurements, it is shown that this system is capable of controlling the flow field structure. In addition, the dominant noise generated at the cavity is successfully reduced in both, laminar and turbulent boundary layer case.

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The effects of ultrasound on turbulent mixing and chemical reaction were experimentally investigated in reacting and non-reacting liquid mixing-layer flows downstream of a turbulence-generating grid. The experiments were carried out under the condition that the ultrasound hardly causes acoustic cavitation. Instantaneous velocity and concentration were simultaneously measured using a combination of a laser-Doppler velocimeter and a laser-induced fluorescence method. The results show that both turbulent mixing and chemical reaction are promoted by high-frequency ultrasound. The ultrasound can be regarded as a better tool for promoting turbulent mixing and chemical reaction than mean shear, because turbulent mass transfer at smaller scales is more enhanced by ultrasound compared to the sheared case.

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A study was performed to characterize the behavior of the flow moving past an oscillating circular cylinder and the interactions between the flow velocity fluctuation and the cylinder oscillation. The oscillations of the cylinder had three distinct regions : two instability regions separated by a stability region. The flow velocity fluctuation was measured using built-in electromagnetic flow meters. The velocity data showed that the flow velocity fluctuations : a) had two frequency components in both the stability region and the second instability region ; the first dominant frequency matched the dominant frequency of the in-line oscillation and the second dominant frequency was induced by the alternate vortices. b) had phase estimations that : 1) indicated the effect of the alternate vortices on the cylinder gave different timings for the stability region and the second instability region. 2) confirmed the energy transfer between the flow and the cylinder occurred at the dominant frequency of the in-line cylinder oscillations. 3) indicated the flow velocity fluctuations induced by the alternate vortices were the antiphase at the opposite of the cylinder and 4) showed the flow velocity fluctuation at the dominant frequency of the in-line oscillation was stable for the two instability regions and unstable for the stability region.

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This paper aims to propose a concise and precise method of solution for a three-dimensional cascade in shear flow between two parallel plane walls. The equation of motion with respect to disturbance pressure is reduced to two differential equations by separation of variables. One of the differential equations is transformed into a simultaneous integral equation and the other is the equation for the Sturm-Liuville type of eigen value problem. The former is solved by using the Fourier analysis according to Schlichting, and the latter is solved by the analytical method according to Honda. Effects of main stream velocity distribution, pitch chord ratio and stagger angle on pressure coefficient distributions, lift coefficients, induced drag coefficients and local lift coefficients of hydrofoiles with ogival section, circular arcs and flat plates are clarified concretely.

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Taking into account of the serious greenhouse effect of the Earth, drastic proposal which presents the Carbon Dioxide emission from transportation system must be done. In Japan, over 20% of the Carbon Dioxide is emitted from transportation system. Aero-Train is the new zero-emission high speed vehicle which we are proposing. Wing in ground effect is introduced to obtain highest lift to drag ratio and highest payload. Because of its high efficiency, Aero-Train can be run using only natural energy existing in the space where the vehicle runs. First phase of the present investigation has been done using a running model pushed by a car in the guideway located at the Miyazaki Research Center of RTRI. Results showed that the model successfully floated over 70 km/h around 30 seconds. Best lift to drag ration was 20. Present concept seems to be quite plausible for next generation zero-emission high speed vehicle.

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The transient processes of rotating stall evolution were investigated experimentally in a low-speed axial compressor stage with three stator-rotor gaps. The pressure traces at 8 circumferential locations on the casing wall near the rotor leading edge were analyzed by the wavelet transforms, which is useful to look into the behavior of disturbances with various length scales. In addition to this, the pressure field traces on the casing wall covering the rotor region were examined to imagine the transient event in the stalling process. The experimental results show that the evolution process of these disturbances depends on the stator-rotor gap. For the large and middle gap, the stall is initiated by a spiky short length-scale disturbance, and the number of spiky waves increases to generate the high frequency waves. These high frequency waves become the short length-scale cells for large gap, while they turn into a big stall cell with growth of a long length-scale disturbance for the middle gap. For the small stator-rotor gap, the stalling process is identified with 'long wavelength stall inception'.

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The effect of pulsating gas injection on the flow pattern was studied numerically. Discrete element method was applied to the solid-phase calculation. To examine the effect of particle condition, two case of solid particles were considered : one is Group B particles in Geldart's classification and the other is Group D particles. The multiple bubbling state without pulsation was chosen as the basis gas-flow condition. In order to characterize quantitatively the effect of the gas pulsation on the flow pattern, we analyzed power spectra of the distributions of void fraction and solid velocity. The results of the present simulations suggests that the gas pulsation largely modifies the solid flow patterns in a low frequency range. Especially in the case of Group B particles, the pattern of bubbles tends to be ordered by applying the gas pulsation.

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Ferrofluid has the property that responds to the change in the magnetic field. The aggregate structure of magnetic particles has an effect on the rheological properties. For example, the effective shear viscosity increases with the intensity of magnetic field. We are studying the aggregate structure of ferrofluids by the Stokesian dynamics simulation except for Brownian motions. In this paper, we discuss the aggregate structure of ferrofluids from the viewpoint of "mesoscopic system" that consists of some calculation cells, for the purpose of understanding the whole aggregation state. Results obtained are as follows. (1) The aggregation of magnetic particles is parallel to the direction of magnetic field. (2) The aggregation diameter increases with reduction of the magnetic moment. The aggregation is thin at a small magnetic moment. (3) The aggregation of magnetic particles forms the uniform hexagonal structure on the plane perpendicular to the direction of magnetic field at a large intensity of magnetic field and magnetic moment.

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The movement of magnetic particles in a micro-separation channel with a cross-section of 0.5×5 mm was investigated for the purpose of improving the separation efficiency. Since it is hard to observe the particles (diameter : about 3 μm) movement sideways because the separation channel is shallow, a sheath flow chamber specialized for microscopic-flow visualization was developed. It can make the flow velocity profile in the chamber similar to that between the upper and bottom walls in the separation channel. In addition, to check the velocity vector of the particles, a stroboscopic illumination with two sub-micro-second pulse lights was combined with the chamber. This combined system clearly showed the particle movement in the small gap between the channel walls. Moreover, the particles were captured closer to the bottom of the chamber, but conglomerated and piled tip at the front of the magnet position as flow speed decreased.

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It is of great importance to improve the accuracy of the diverter to achieve high accuracy liquid flow measurements by using static gravimetric systems with flying start and finish. A new system with the double diverting wing has been developed in order to reduce the diversion timing error that dominates the uncertainty for the calibration of flowmeters. The diversion timing error has been estimated with a small prototype in a water flow circuit in order to make a comparison between the performance of the new system and those of previous system with the single diverting wing. The results show that the jet flow condition has little effect on the timing error estimated by the double wing method, although the error with the single wing is dependent on the liquid flow rate. Therefore, the triggering of the timing system can be easily adjusted over a wide range of flow rate by using the new diverter system.

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Flutter characteristics of flexible webs affected by several influential factors are investigated by the analytical method described in a previous study. The factors include the following : (1) mass ratio, (2) fluid surface friction, (3) presence of nearby wall (s), and (4) web movement. In the region of medium tension/bending-stiffness where progressing waves of lower-order modes dominate, mass ratio and fluid friction have little effects on the flutter speeds and conditions. The web movements, however, have a significant effect in lowering the flutter speeds. Presence of nearby walls causes considerable changes in the flutter speeds and conditions particularly for the ratio of gap to web length below 0.3.

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Unsteady stress of 4-bladed inducer blades was measured with and without inlet flow distortion at the blade root near the leading edge. The following results were obtained : (1) Without the inlet flow distortion, and with the alternate blade cavitation at intermediate cavitation number, the mean stress of the blade with shorter cavity is lower than that with longer cavity. At lower cavitation number, the stress fluctuation occurs caused by the cavitation instabilities such as rotating cavitation and cavitation surge, which is one of the major causes of stress fluctuation of inducers. (2) The magnitude of stress fluctuation due to the interaction with the inlet flow distortion basically decreases as we decrease the cavitation number. With inlet flow distortion, the occurrence ranges of alternate blade cavitation and cavitation instability shift toward the lower cavitation number. Under the alternate blade cavitation, the fluctuation of longer cavity causes the stress fluctuation of the adjacent blade with shorter cavity. The stress fluctuations caused by the rotating cavitation and cavitation surge are neary the same level as those in case without inlet flow distortion.

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The present numerical analysis has been performed for obtaining the heat transfer characteristics of microencapsulated solid-liquid phase change material and water mixed slurry flow in a circular tube heated with constant wall heat flux. The energy equation was formulated by taking into consideration of the heat sink due to melting process and the heat transfer enhancement induced by the motion of microcapsules. The heat source function in the energy equation was derived from solutions for melting in a spherical latent heat material. The governing parameters were found to be latent heat material concentration, pipe diameter. microcapsule diameter, heat flux, and the slurry velocity. The numerical results revealed that mean heat transfer coefficient for latent microcapsule slurry was about 1.3∼1.8 times greater than that for the single phase of water.

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In this paper, numerical and experimental investigation on natural and mixed convection heat transfer in a vertical duct with asymmetric side-wall heating has been carried out. The present study is triggered by a possible thermal insulation created on the cold wall in a vertical duct via an upward forced flow. We discuss how the velocity and temperature of forced flow influences the cold-wall average Nusselt number. It was found that two critical values of Reynolds number exist. One is associated with flow structure (Re^FS_cr), and causes the disapperance of natural convection cell. The other gives the critical value on heat transfer (Re^HT_cr), which makes cold-wall effectively insulated. The latter is found independent of Ra and only dependent of aspect ratio scaled as Re^HT_cr &vprop; A².

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This paper investigates dynamic responses of ice-layer growth when water is cooled from the top boundary with time-varying cooling temperature. One-dimensional and two-dimensional numerical models, both of which consider convective heat transfer at the ice-water boundary, are formulated respectively. The Stefan number, the modified Rayleigh number and the cooling temperature are identified as the key parameters of solidifying process. The results of dynamic responses of ice-layer formation from the two models agree well, and this proves the usefulness of one-dimensional model at high Rayleigh number regime, where direct numerical simulation of convective flow is impossible.

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In recent years, calorific power of semiconductor has been increasing. So more compact cooling unit for high power control panel compared with air-forced aluminum fin is desired. We have been developing the new counter flow type cooling unit having inclined radiation fins. In this paper, we have found the shape of the heat exchanger and the layout of the fin for higher cooling performance by using the simple numerical analysis. Further we clarified the reason that the cooling performance of the new cooling unit was better than the conventional cooling unit.

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We studied the feasibility of using rectangular vortex generators (Fig. 1) to improve the heat-transfer performance of heat exchangers in air conditioners. Using the ratio of the heat-transfer coefficient to the pressure drop, we determined the optimum height of a vortex generator mounted between parallel plates. We determined that was about 50% of the distance between the parallel plates.

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Accurate and simple measurement method for the thermal diffusivity of high-conductivity thin film is required for the design of very densely packed integrated circuits such as ULSI. In order to measure the thermal diffusivity of high-conductivity thin film such as graphite and diamond, a new apparatus based on a dynamic grating radiometry (DGR) has been developed. In DGR method, a sample surface is heated by interference of two pulsed laser beams, and the decay of temperature at a spot on the thermal grating is monitored by an infrared detector. In the ideal case where the grating period is much smaller than the light absorption length, the thermal diffusivity parallel to the surface can be determined from the decay constant and the grating period. To consider the two dimensional problem, the anisotropy of the thin film is detected by DGR. In this paper, the theory which can calculate the thermal diffusivity perpendicular to the plane is presented. The validity of DGR is discussed through the preliminary measurement for Zr foil and Graphite Sheet.

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This paper presents a comparison among various vehicles when using fossil fuels and renewable energy. In case of using fossil fuel, we compared 5 key factors among the fuel cell electric vehicle (FCEV), internal combustion engine (ICE) vehicle (gasoline or diesel), battery-powered and hybrid vehicles. Comparison factors are cruising range, carbon dioxide (CO₂) emissions, waste heat rejection, air pollutants and running noise. According to this comparison, hybrid, battery-powered and fuel cell electric vehicle have better potentials than ICE vehicles. In case of utilizing renewable energy, EV will become the mainstream among vehicles. In addition, FCEV will play an important role until that age. Moreover, we designed a high efficiency FCEV for the purpose of fuel effective utilization. This vehicle has not only fuel cell, but also various energy utilization and storage systems, for example battery, flywheel and PV cell. This vehicle has excellent fuel economy more than 90 km/l.

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Thermal management is the crucial issue for polymer electrolyte fuel cells (PEFCs). This demands two challenging tasks for the system performance and the reliability; the membrane temperature must be kept within a certain range, and the generation of a hot spot must be avoided. In order to tackle this problem, a novel theoretical approach must be developed that considers both the electrochemical and the heat transport processes. In this study, the coupling phenomena of electrochemical reaction and heat transport in PEFC have been analyzed by using a newly developed simulation model. Effects of the various parameters on the thermal characteristics have been studied, and the mechanism of the hot spot generation on the membrane has been discussed. The validity of the present model has been confirmed by comparing with experimental results. It has been revealed that sufficient humidification and low utilizing rate of oxygen are effective to avoid the hot spot generation and to establish the uniform membrane temperature in the longitudinal direction.

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The objective of this study was to estimate the optimization of fuel cell electric vehicle systems by the driving simulation that we developed. The results of the driving simulation showed the power of fuel cell, battery and motor for a 1 500 cc class sedan is 12, 18 and 15 kW at the condition of 10-15 mode of the minimum fuel consumption. The fuel consumption of the series driving system of FCEV was more than the parallel because of the heavier vehicle weight of the series compared to the parallel. The numerical analysis showed that the FCEV performance is affected by the regenerative brake and the fuel consumption of the FCEV with the regenerative brake systems is 23% less than without them.

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The effect of flame instabilities on the flame surface of spherical premixed flames at various Lewis numbers has been studied experimentally using laser tomography technique. For laminar flames at low Lewis numbers, what appear to be cracks, which might also be regarded as cusps, in the flame surface were observed. For turbulent flames, flame surfaces were found to be corrugated by turbulence indeed. At the same time, the cracks were also observed for low Lewis number mixtures. The Laser tomography technique enabled unstable wave number associated with cracks observed to be measured for both laminar and turbulent flames. The results are compared with the theoretical framework of the stability analysis of Bechtold and Matalon. As a result, it has been found that turbulent flames at low Lewis numbers are affected not only by turbulence but also by flame instability.

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In order to elucidate the enhancement mechanisms of turbulent flame propagation, it is indispensable to examine and clarify the detailed process of vortex-flame interaction. This is because that it constitutes one of the key processes to promote flame propagation velocity. In this investigation a series of large scale organized eddies formed in the plane propane-air premixed shear flow are selected as an objective eddy-field. Two ingenious techniques are introduced and combined with each other ; one is the acoustic excitation of the shear layer, the other is the divided-double-beam high-speed schlieren photography. The former makes the organized eddy formation extremely regular and enables synchronized spark ignition with a single high-speed video camera, while the latter gives the chance to analyze two different directional views of a same propagating flame. In this paper a spark-ignited flame, which is initiated at the center of an organized eddy and propagates in the vortex tube, is optically observed and analyzed by using the proposed technique. According to the results, it is found that two kinds of effects of neighboring eddies on the enhancement processes of flame propagation.

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To examine the premixed flame structure in highly turbulent flow, by a cyclone-jet combustor, we have examined the flow field both in cold flow and in combustion field using LDV system. The turbulence scale has been obtained by Slot-Correlation method. The experiments have been conducted from the flamelet regime (U_m=10 m/s) to the distributed reaction zone regime (U_m=30 m/s) in combustion diagram. Results show that, in combustion filed, the mean axial velocity does not decrease as much and rms fluctuation velocity is lower along the center axis, compared with those in cold flow. It could be explained with the flow expansion in combustion. That is, the turbulence transport is reduced due to the existence of low-density gas in shear layer at the flame front, which leads to a longer potential core in combustion field than that in cold flow. Flame generated turbulence is observed in radial velocity distribution. The integral length scale becomes larger at the flame zone due to the flow expansion.

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We verified through experiments that dioxins and related compounds formation through an incineration process of the refuse which contains chlorides and aroma can be disturbed by sulfur component addition. According to the experimental results, the dioxin reduction efficiency is two order higher when solid sulfur, which is contained in refuse, is supplied than when gaseous sulfur is supplied. These experiments were carried out by using 205 mm diameter, 4 000 mm length fluidized bed furnace. Sample refuses are basically made of wood saw dust, poly vinyl chloride or sulfur including coal is added respectively. The effect of dioxins and related compounds reduction by sulfur addition were evaluated under the condition changing molar ratio of S/Cl, keeping furnace gas temperature and residence time constant.

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A catalytically assisted combustor for a gas turbine was designed to achieve low NO_x emission. This combustor is composed of a burner and a ceramic liner. The burner consists of an annular preburner, 6 catalytic combustor segments and 6 premixing nozzles, which are arranged in parallel and alternately. In this combustor system, catalytic combustion temperature is controlled under 1 000°C, premixed gas is injected from the premixing nozzles to the catalytic combustion gas and lean premixed combustion over 1 300°C is carried out in the ceramic liner. This system was designed to avoid catalyst deactivation at high temperature and thermal shock fracture of the ceramic honeycomb monolith of the catalyst. The combustor of 1 MW class was tested under high pressure conditions using LNG fuel. As a result, NO_x emission was approximately 4 ppm (at 16% O₂) at adiabatic combustion temperature of 1 350°C and combustor inlet pressure of 1.33 MPa.

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Premixed lean diesel combustion was performed in a condition that a fuel injection timing was near top dead center. To promote fuel-air mixing a micro-hole nozzle (nozzle hole diameter is 0.08 mm) and high pressure injection (up to 250 MPa) were used. Low cetane number fuel was used for main injector mounted at the bore center to make ignition delay. Small quantity of high cetane number fuel was supplied from two side injectors to control the ignition timing. As a result, low NO_x combustion was realized in an operating codition when the ignition started after several crank angles from injection end. Important factor to realize this combustion is to complete the fuel injection and vaporization before ignition.

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The control of ignition and combustion behavior in a premixed charge compression ignition engine was investigated and ultra low NO_x and smokeless combustion was achieved with direct in-cylinder injection of water as a reaction suppressor. The reaction suppressing effect increased with advancing injection timings of the suppressors, resulting from greater decreases in charge temperature as compression progressed. However, as the in-cylinder temperature was less than the water boiling point before 60° CA BTDC, water vaporization was delayed with too early injection timing and the suppressing effect decreased. Therefore, the optimum timing in terms of the suppressing effect was found at 60° CA BTDC thereabouts when the in-cylinder gas temperature reached the boiling point of water. The water injection significantly reduced the heat release at cool flame, which suppressed the increase in charge temperature after the cool flame and the rapid combustion caused by the hot flame.

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Effect of cetane number on ignition delay and ignition location of disesel spray was experimentally investigated. Five kinds of fuels, which had different cetane numbers of light fraction and heavy fraction of fuel, were used. As a result, the ignition delay was not so affected by the change of cetane number, however, the ignition location was strongly affected by a cetane number. When the light fraction cetane number was low, the ignition was not observed near the nozzle. And when the heavy fraction cetane number was high, the ignition was observed at the position far from the nozzle. Ignition position had an effect on flame development. When the ignition occurred near the nozzle, flame development rate was slow. When the ignition occurred at the position far from the nozzle, flame development rate was fast. In case of the ignition position was far from the nozzle, effect of the cetane number on flame development was remarkable.

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When a CVT (Continuously Variable Transmission) is equipped with an engine, fuel consumption can be reduced by controlling the throttle valve angle and the gear ratio of CVT simultaneously. If the engine is operated with lean air-fuel ratio (A/F), it is also effective for fuel economy. A simple control method is required because the input-output relations are coupled complicatedly. In the previous study, a decoupling control theory had been applied to this Engine-CVT-A/F consolidated control. However, fast response had been instifficient. From such point of view, investigation was carried out about the application of model following control to the Engine-CVT A/F consolidated control for realizing fast response and well-decoupled control such as a Single-Input-Single-Output system. As a consequence, Good experimental results were obtained.

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