To make clear the effects of throat lengths on cavitation characteristics arising in very small "long orifices, " the cavitation aspects and the discharge characteristics were carefully and systematically investigated in two-dimensional high-pressure oil flows through very small "long orifices" by means of high-speed photography for several throat lengths and cavitation numbers. It is shown here that the cavitation aspects, the cavitation characteristics and the jet appearances are considerably affected by the throat length.

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Noncircular jets were investigated experimentally by manipulating the vortical structures under controlled excitation, and the effects of the mixing enhancement were discussed in relation to the dynamics of vortical structures. The experiments were carried out for the air jets issuing from sharp-edged circular, square, triangular and rectangular orifices. The jets were excited at two modes of the stable vertical structures: the deformation mode and the interaction mode. The mean-velocity contours measured by the hot-wire anemometer exactly correspond to the vertical structures. The jet diffusion increases significantly by enhancing the noncircular vertical structures especially at the interaction mode. The results suggest that the intense stretching and the splitting of the vertical structures are key mechanism to enhance entertainment and mixing in the noncircular jets.

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This paper uses a new finite-element method for incompressible electrically conducting fluid to present transient and steady entrance flows. The GSMAC method is employed as the main algorithm of calculation to satisfy both the conservation laws of mass and magnetic flux. Entrance flows between two parallel plates under a constant magnetic field are calculated to verify this method. Meanwhile, entrance length can approximately be expressed as an explicit function of Hartmann number, using the Oseen approximation and the momemtum integral method. Numerical and theoretical results obtained here agree with other numerical results or exact solutions.

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The characteristics of turbulent flow and heat transfer around a square prism in a turbulent boundary layer have been experimentally investigated, which simulated one of the ribbing inside the ribbed tubes for an enhancement of heat transfer in a heat exchanger. Three-dimensional flow measurements were performed by combining a 2-color 4-beam LDV and a conventional 2 beam LDV probes which were miniaturized by using optical fibers. Local flow characteristics such as the mean velocity and turbulence intensity in three components were presented to clarify the flow behavior. The heat transfer coefficient has a peak value behind the rib near the reattachment region. It has been pointed out from the results that the feature of heat transfer coefficient was closely related to the turbulent flow characteristics.

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Constitutive equations regarding interfacial transports for a multiphase flow consisting of solidified particles and molten material were thermodynamically derived under the condition of the local quasi-equilibrium. The basic equations including the conservation equations and the constitutive equations for the multiphase flow were expressed in dimensionless form. The theory developed here confirmed that the temperature fields closely depended on the Lagrangian derivative of solid fraction accompanying the latent heat effect, and was characterized by the Stefan number. It was also suggested that the simplified basic equations considering the phase equilibrium diagram were useful in analysis of the multiphase flow with solid-liquid phase change.

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It is simulated numerically by the MAC method how a flow pattern evolves in a curved duct as the Dean number increases and then decreases. The duct has an aspect ratio of 2 and a curvature ratio of 8. Fully developed and unsteady flows are calculated by the condition that pressure gradients are made to fall and then kept constant, and by the initial condition that they were suddenly given to move fluid in a stationary state. The flows agree with them asymptotically as the pressure gradients are given to the stationary state. The flows become a pair of vortices and stabilize. The fix point which corresponds to the flow attracts orbits starting from the other points on a phase plane of velocity. No hysteresis is found near the Hopf bifurcation point. For this reason, the calculation shows that the Hopf bifurcation is supercritical.

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This paper provides an efficient numerical method on supercomputers for two-dimensional incompressible unsteady viscous flows. The unsteady vorticity-velocity Navier-Stokes equations are discretized by means of the Crank-Nicholson formula and the resulting elliptic system of equations is solved by the parabolic multigrid method with the group explicit relaxation scheme. Application of the method to oscillating flows and impulsively started flows around a circular cylinder shows high computational efficiency on a parallel processor. The computed results are in good agreement with other numerical and experimental results and those based on the vorticity-stream function equations.

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This paper is the second one by the authors, which clarifies the effects of flow distortion by a sphere upon the statistics of a point-source diffusing plume evolved in grid-generated turbulence. In the preceding paper, only the results on the forward stagnation streamline was given. Here, various statistics of the whole concentration field around the sphere are investigated. It is found that the conditioned mean concentration has almost the same level everywhere but in the wake recirculation region, but the conditioned concentration fluctuation rms values show a slight drop near the surface of the sphere in the non-recirculation flow region. And, except for the wake recirculation region, the conditioned probability density for near-zero concentration shows slight drop, while that for the higher concentration increases slightly as the sphere is approached. Furthermore, from the spectra, the intermittency and the probability density distribution, it is rationally concluded that only in the region next to the surface of the sphere, has the molecular diffusion fully advanced and the concentration fluctuation dropped to nearly zero.

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The flow in and around two-dimensional right-angled intake has been studied both experimentally and numerically. Pressure distributions on the intake surfaces are measured at various velocity ratios of the intake flow to the main flow, and the basic intake performances, such as the total pressure loss, the cavitation and the drag, are evaluated. It is shown that they are reproduced well by the numerical results with a standard k-ε model of turbulence, while the agreement becomes poorer as the velocity ratio becomes large. It is also demonstrated by the smoke-wire visualization study that the recirculating region formed upstream of the intake flow is reduced as the velocity ratio increases, contributing to the relative decrease in the total pressure loss at large velocity ratios.

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A suitable simulation scheme for simulating the internal flow of a cross-flow fan was developed. In this scheme, the impeller is treated as an actuator disk which restricts the flow direction and supplies vorticity to the flow. The continuous vorticity distribution is replaced by a finite set of point vortices and calculated by the CIC (clouds-in-cells) method which is combined with FEM instead of FDM (finite-difference method) so that nonstructual meshes can be used. We applied this scheme to simulate the internal flow of a room air conditioner incorporating a cross-flow fan, and the results show good agreement with the experimental data. It is of particular interest that this model is effective to simulate the secondary vortex which sometimes appears at the position opposite to the main vortex on the impeller.

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This paper presents the effects of a finite-length yawed circular cylinder in a uniform flow on the spanwise pressure distribution in cases with and without end-plates. This study demonstrates that for a free stream Reynolds number of 2×10⁴ and yaw angles varying from 0 to 30 degrees, stagnation pressure coefficients obey the independence principle and are distribute a almost uniformly along the axis of the yawed circular cylinder. Base pressure coefficients differ from the value expected by this law, however, and these spanwise distributions have a gradient along the axis. The measured pressure distribution on the surface of the yawed circular cylinder is also compared with the results of a numerical calculation.

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The purpose of the present study is to clarify the points to be overcome for applying the molecular dynamics method to flow phenomena, especially a flow past an obstacle. For this purpose, we here focus the investigation on a subsonic flow of a rarefied gas around a sphere. The results of the simulations show that the influences of the boundary condition can be neglected, and that the drag coefficient agrees well with the analytical value of the free molecule flow if the simulation region is sufficiently large. However, since the CPU times roughly increase in proportion to the square of the mumber of molecules with enlargement of the simulation region, we meed some new techniques for the successful application of the molecular dynamics method to a flow around an obstacle: a new boundary condition which does not distort the flow field even if a small simulation region is used; a new algorithm where the speeding-up techniques used in simulations of liquids are applicable.

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The effect of the Reynolds number, the boundary layer thickness and the gap ratio on the beginning of the periodic vortex-shedding from a circular cylinder in a laminar boundary layer was experimentally investigated. The Reynolds number Re, which was defined in terms of the cylinder diameter (d) and the free stream velocity (U₀), ranged from 40 to 1000. The range of the boundary layer thickness (d/δ) was from 0.08 to 0.38. The gap ratio defined by the circular cylinder (d) and the clearance between the circular cylinder and the wall (g) was varied from 0.38 to 3.0. As a result, the frequency of the vortex-shedding from the circular cylinder in the laminar boundary layer can be determined by the gap ratio, but it does not depend on the Reynolds number and the boundary layer thickness.

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A new scheme of the thermo anemometer was designed on simplified formulations. The reliability of the thermo anemometer in actual measurements was improved. Its calibration process was greatly simplified. The cold-wire thermometer has two automatic phase compensators and they are able to immediately respond to change in the wire's time constant. The frequency response of temperature signals was compensated up to about 5.0kHz. Velocity signals were correctly compensated up to the temperature difference of about ΔT=140°C for U₀=1.8m/s∼12m/s.

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An experimental study of the turbulent flow due to a rotating disk in an infinite quiescent fluid was conducted. Using a single normal- or inclined-type hot wire, mean velocities and all the six components of the Reynolds stress were measured for various local Reynolds numbers Re_L. The circumferential velocity profiles, normalized by the wall variables, in the semilogarithmic plot show a linear variation in the fully turbulent region. When Re_L=1.0×10⁶, this profile is in close agreement with that for the flat-plate boundary layer. The circumferential component of the turbulence intensity reaches a maximum value in the buffer region. All components of the turbulence intensity, normalized by the friction velocity, were found to be considerably smaller than those for the flat-plate boundary layer except very near the wall. The values of the structure parameter a₁ are smaller than those for the flat-plate boundary layer.

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The cellular automaton method, which can generate the Navier-Stokes equation, is utilized for simulating fluid motion numerically. This method has the advantage of examining the statistical property involved in the macroscopic variables, since the elementary process is described by the stochastic process. The present paper demonstrates that an automaton solution of the Poiseuille flow results in turbulent behavior of a Reynolds number of 3200. After careful review of the calculated intensity of turbulence and correlation function of this solution, it may be concluded that this method serves as a reasonable alternative for examining the turbulent flow, in addition to the LES the and k-ε methods.

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The variation of turbulence structure and the relaxation process of turbulence quantities to the equilibrium state for the d-type rough wall boundary layer disturbed by a cylinder rod have been investigated experimentally. The rod was positioned at two distances of y_c/δ₀=0.14 (inner layer) and 0.92 (outer layer). The quantities measured are three component turbulent intensities and Reynolds shear stress. From the results, each turbulence quantity of the present rough wall flow disturbed by the rod virtually recovered over a shorter distance for y_c/δ₀=0.14 than that for y_c/δ₀==0.92. For y_c/δ₀=0.92, the turbulent intensities of the three components and the Reynolds shear stress profiles most possibly reach the equilibrium state differed from that of the undisturbed flow at the farthest downstream station. The influence of the disturbance was found to appear as the enlargement of the v component turbulent intensity profile for both cases. The Reynolds shear stress profile exhibited the negative value near y/δ=0.6 in the region of y_c/δ₀≤3.3 for y_c/δ₀=0.92. The relaxation process to the equilibrium flow was examined by evaluating the streamwise variation of turbulent kinetic energy flux.

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The space-time correlations and power spectra of velocity fluctuations are measured in two-dimensional turbulent flows through curved and straight channels. Noticeable differences are found between the experimental results of the two channels. While the effective power spectrum in the straight channel has only one maximum, that in the curved channel has two maxima on both sides of a wave number corresponding to the dissipation length. The spanwise correlation of radial velocity fluctuations in the curved channel takes a large negative maximum at a distance of about half the channel width. The streamwise integral length scales in the outer-wall side of the curved channel increase by about ten times those in the straight channel. These results indicate that intensive large-scale eddies which are unsteady but resemble Taylor-Gortler vortices exist in the curved channel.

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This experimental study aims at investigating the flow characteristics on turbulent diffusion flames at the low Reynolds numbers of 2000 and 3000 at the nozzle exit. Measurements were made of velocity and temperature by means of a LDV and a fine thermocouple under flows of three equivalence ratios (6, 24, ∞) to each Reynolds number. The mass flux distribution along the flame axis shows three separate flow regions, that is, potential core, free jet and buoyancy regions. The maximum temperature position on the axis xp was the point where combustion was almost completed. This position was a representative length of flame derived from not noly fluid dynamic characteristics but also chemical characteristics. Both temperature and mass flux distribution against the normalized axial distance x/x_p have good similarity up to the free jet flow region. The local Froude number defined in the buoyancy region gradually approached small constant values for each flow condition. These results show that x/x_p is one of the important parameters in the expression of the flow characteristics of relative temeprature and mass flux in turbulent diffusion flames.

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This paper presents an analytical study of a coupled vibration of two discs which face with each other in a fluid-filled annular vessel. Simple theoretical formula are obtained by assuming that the discs have a small width compared with the outer diameter of the annular vessel. In this case, the motion of the disc is approximated to be uniform in the radial direction. It is assumed that the fluid has no viscosity, no compressibility and no flow through the gap between the disc and the vessel wall. This paper discusses only the vibration of diametral modes with identical node number in the two discs. The formulae obtained show that two coupled frequencies appear for each number of the node. The effects on the frequencies of the disc thickness and the fluid layer are discussed in detail.

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A numerical technique for the computation of two-dimensional unsteady turbulent flows through an oscillating cascade is presented. To consider the interblade phase angle, a time phase shifted boundary condition is introduced on the periodic boundaries. A finite volume method is used to obtain the spatially discretized governing equations, while the second-order accurate Adams-Bashforth method is employed for the time integration. In the present analysis, a two-equation model of turbulence is introduced to estimate the turbulence effect. In order to assure the effectiveness of the present method, computations are carried out for the flow through cascades of flat plate blades (inviscid flow analysis), lens-type blades and compressor blades. The present method gives unsteady periodic flow fields including the aerodynamic forces and moments acting on the blade clearly, and the negative damping force is obtained from the computational result of flat plate cascade flow.

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Aerodynamic analysis based on the double linearization theory has been combined with a structural analysis by a finite element method to study the unsteady aerodynamic response of a rotating subsonic annular cascade composed of twisted blades undergoing three-dimensional elastic vibrations with chordwise displacements and flexible deformations. Numerical results are presented to demonstrate the unsteady pressure difference distributions on blade surfaces, aerodynamic works, three-dimensional effects and flutter boundaries for two kinds of cascade blades. In particular, it is found that the second elastic vibration mode can be most unstable for a turbine-type cascade with small camber operating at a subsonic Mach number.

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Up to the authors' previous reports on the oscillation of the circular shock waves, the investigations have been concerned with situations where the upstream flow is uniform, and oscillation and deformation were induced by only downstream conditions. But in the centrifugal diffuser of a centrifugal compressor, the flow into the diffuser becomes nonuniform due to the impeller wake and the stall in the upstream impeller, which causes deformation and oscillation of the shock wave. Here, the above effects are considered, and the upstream disturbance is generated by cylindrical bars. The imperfect circular shock wave was induced by the effect of the wake, and the oscillation state, along with the oscillation modes caused by forced oscillation, is investigated experimentally. It was found that the basic mode of the oscillation is predominant and that the oscillation is weaker than in the case of uniform upstream.

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In order to investigate the accuracy of finite difference methods for weak shock waves, comparisons for the reflection and the diffraction of weak shock waves around wedges and corners between simulations and analyses are made. Analytical solutions are obtained for the wave equations by employing the conical flow method of Keller and Blank. Finite difference simulations are conducted by applying such finite difference methods as the total variation diminishing (TVD) method, the flux-corrected transport (FCT) method, the flux vector splitting (FVS) method and the method of Roe to numerically solve the Euler equations. Computed flow fields by the finite difference methods are almost equivalent to each other in the present investigation. The approximate solutions obtained from finite difference calculations deviate from the analytical exact solutions near the apexes of the wedges or the corners that are singular points in grid systems. The weaker the shock waves passing through the apexes, the more noticeable numerical errors originating from the singular points. Among the finite difference schemes examined in the present investigation, the TVD method is the most reliable because of its stability and smooth results. The FVS method is almost comparable to the TVD method. In the results of the FCT method, small noises are observed to be superposed. In the results of Roe's method, shock waves are simulated most sharply, but instabilities near the singular points are observed to be great.

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A three-level one-stage Runge-Kutta scheme has been proposed for time integration of the incompressible Navier-Stokes equations. This scheme contains three free parameters and includes the conventional one-stage schemes, forward Euler scheme and Adams-Bashforth scheme, as special cases. The novel feature of the scheme is that the stability region can be extended further than that of the conventional one-stage scheme, and time accuracy can be controlled up to second order by tuning parameters. Numerical solutions for the transient Poiseuille flow and the two-dimensional lid-driven cavity flow are presented and compared with the analytical solution and those of the one-stage schemes. It is shown that the present scheme allows a larger time step and requires less computing cost than does the conventional one-stage scheme.

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The performance of compressors used for automotive air conditioners is affected greatly by leakage which flows through a clearance between a rotor face and a sideplate. There are some studies which analyze distributions of pressure and velocity on the rotor face under a certain boundary pressure distribution on the rotor circumference. In this study we analyzed the leakage flow through the clearance on the rotor face by using a more realistic boundary condition which considers that pressure on the rotor circumference changes periodically with rotation of the rotor. Because of less influence of inertial force than that of viscous force, the pressure and velocity distribution at each moment can be evaluated under a quasi-steady condition with an instantaneous pressure distribution on the rotor circumference. On the other hand, the average flow field on the rotor face must be analyzed under a boundary condition that pressure at each angular position on the rotor circumference is equal to the time average of pressure in a compression chamber which is facing that position.

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The mechanisms of low-cycle system oscillation whereby reverse flow including cavitation repeats periodical emergence and dissipation in the suction pipe, are discussed. The effects of cavitation on the characteristic frequency of a pump-pipe system and the dynamic behaviour of the reverse flow were investigated experimentally. It was found that the dynamic response of reverse flow versus fluctuating inlet flow rates play key roles in the onset of oscillation.

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A simple method of measuring thermophysical properties has been developed. Two square plates of a specimen are heated stepwise for a few seconds by a film heater which is placed between the plates. The resulting temperature history of the opposite surface, to which an aluminum foil is attached to make it have high thermal and electric conductivities, is measured by pressing separated C-A thermocouple wires against the surface. From a comparison between the measured and theoretical temperature histories, the thermal diffusivity, the specific heat and the thermal conductivity of the specimen can be determined automatically in a few minutes by a personal computer. To confirm the accuracy of this method, the specific heat and the thermal conductivity of Pyrex 7740 glass were measured and compared with the reported values. The results showed that the present method can be applied with reasonable accuracy of no more than 10%.

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Experimental results on heat transfer of straight pipe flow with internal freezing of water are presented. This study covers the range of Re_D=200-10000, T^*_w=3-10 and L/D=20-80. The Pr number is fixed to 11.2. Referring to the steady pressure drop data and observation of internal ice layers, data of mean Nusselt number at steady state are categorized into four regions: L-region (low Re_D and smooth ice surface), S-region (low Re_D and ice layer with a step), T-region (high Re_D and very thin ice layer) and I-region (intermediate region between L-and T-region or intermediate region between S-and T-region). Experimental formulae of Nu_m for each region are presented. Transient behaviors of Nu_m, pressure drop and the location of the step on the ice surface are also shown.

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After prolonged experiments and theoretical studies on the condensation phenomena of the specially characterized mixture of carbon tetrachloride and water on inclined cooled plates, the area of interest has been shifted to the development of a heat transfer model whose characteristics correlate with the analytical and experimental results. The attached report consists of a critically analyzed model which is considered to be a good proposition for a mixed condensation consisting of water adherent drops and the organic liquid flow. The model has been developed with facing into consideration given to the sweeping effect of sliding drops. The predictions by the model agree well with the experimental results.

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In order to clarify the condensation heat transfer mechanism of binary vapors of immiscible liquids, experimental and theoretical studies have been performed on condensation of a nonazeotropic mixture of R113 and water on a cooled vertical flat plate. The condensation rate and the dynamic characteristics of droplets of water, i. e., the critical diameter and frequency of departure droplets, were measured for several concentrations of mixture. Considering the diffusion layer developing along the liquid layer and the sweeping effect by falling drops, we proposed a heat transfer model. The predictions of this model agree well with the experimental results for the mixed condensation heat transfer phenomena consisting of the water adherent drop and the organic liquid film.

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The possibility of radiation heat transfer control by a combined model of an active thermal insulation system and a radiative converter was investigated. A semitransparent porous layer was placed between a high-temperature region and a low-temperature region, and gas was injected through the layer in the positive and negative directions. The mechanism of heat transfer is completely different for the positive and negative mass flux. By changing mass flux of air between -0.1 and 0kg m^-2s^-1, dimensionless radiative flux at the back face can be controlled between 2×10^-4 and 0.1. In this region, the porous layer behaves as the active thermal insulation system, and the mechanism of the radiation heat transfer control is similar to that of a triode.

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Experiments on critical heat flux (CHF) were conducted to clarify the enhancement effects of twisted tapes. The swirled tube is made of stainless steel (6mm in inside diameter, 0.25mm in thickness, and 100mm in heated length) and equipped with a twisted zirconia tape (about 1.2mm in thickness and 5.4mm in width). Twisted tape ratios y (value of tube inside diameter to complete 180 degree twists of tape insert) are about 2.7, 4.0, 9.0, and ∞. Swirl-flow CHF increased in proportion to the one-third power of (y^-1) at small y or of the tangential velocity at the inner tube wall at large centrifugal force. An empirical CHF correlation for swirl flow was proposed by applying the tangential non dimensional centrifugal acceleration at the wall as a parameter. It was verified that this correlation gave accurate predictions at nearly atmospheric pressure.

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A numerical analysis is presented for laminar free-convection condensation of saturated vapors of water and carbon dioxide on a vertical flat surface in the reduced temperature range T_s/T_c=0.990∼0.999. The heat transfer coefficient in the region T_s/T_c<0.998 can be correlated by using Nusselt's equation for constant physical properties when the representative physical properties are evaluated at the film temperature. The reduction of condensation mass flux or the heat flux at the vapor-liquid interface due to the convection term in the film is expressed as a function of the phase change number with the average isobaric specific heat.

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A similarity curve proposed by Shamsundar was examined as to whether or not it is an appropriate chart to clarify the configuration effect on the thermal performance of a latent heat energy storage unit. The unit consisting of concentric circular tubes with longitudinal fins in the annular space was analyzed numerically for the solidification process by means of the ADI method. A similarity rule was found to be valid in application to this unit as well as to an unfinned unit, while it suffered somewhat with increasing number of fins. The differences among similarity curves for the different numbers of fins were so remarkable that the configuration effect was able to be discussed according to this chart. Heat exchanger effectiveness evaluated from the similarity curve was compared with existing experimental data and shown to be in good agreement within a sufficient degree of accuracy.

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The blow-off velocity of a flame stabilized in recirculating flow of a backward-facing step in a two-dimensional air duct is obtained experimentally. The fuel injection slit is located at the down-stream of the step whose heights are 0, 10 and 20mm. The fuels employed are methane, propane, hydrogen and city gas, and the air velocity can be changed from 1 to 60m/sec. The results show that the backward-facing step extends the blow-off velocity with increase in the velocity of fuel, and that this effect is more remarkable in the higher step height. The blow-off velocity nondimensionalized by the burning velocity can be expressed in a uniform manner, i. e., independent of fuel, by the heat release flux. Furthermore, it is ascertained experimentally that heat loss across the combustor wall apparently does not influence the blow-off velocity in this configuration. Also, the velocity fields are measured by LDV.

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The emission problem of a catalytic combustor using methanol mixture arises during the start-up condition. A modified quasi-steady-state model is used to analyze the transient behavior of the catalytic combustor. Parameters considered in this study were air-fuel ratio, preheat temperature of the catalyst, space velocity, heat input, catalyst length, combustion efficiency and heat loss coefficient. From the numerical computation, the range of operating parameters of the catalytic combustor during transient condition can be predicted with sufficient accuracy. The transient combustion efficiency was found to be greatly affected by the space velocity, preheat of the catalyst and air-fuel ratio. At a condition of the air-fuel ratio and heat input, the required catalyst length to achieve a certain combustion efficiency can also be predicted.

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Heat and mass transfer characteristics from air with high water vapor content on a spirally finned tube heat exchanger were experimentally investigated. The experimental results are summarized as follows. The convective heat transfer coefficient with condensation of the water vapor is almost same as that without condensation. The mass transfer coefficient is enhanced by increasing the water vapor content in the air, and is different from that evaluated by means of analogy between the haat and mass transfer. This means that the analogy does not hold for the finned tube heat exchanger. It was found that the effect of the water vapor content is caused by the difference of the wet fin surface on which the mass transfer occurred.

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We have been studying a new automobile air conditioner that controls the thermal sensation of the occupants. We believe that in air conditioners, the most important controlling factor is not air temperature but the thermal amenity of occupants. For control of thermal amenity, it is necessary to quantitatively evaluate the thermal sensation of the occupant. We had proposed that the thermal sensation of an occupant corresponds well with skin temperature in previous work, but this relationship is not always linear. The proposed method to quantitatively evaluate the thermal sensation of the occupant is based on the neural networks which have often been applied to those concerning nonlinear problems⁽¹⁾. The input data are the occupant's skin temperature and the passenger compartment air temperature; the output is the thermal sensation of the automobile occupant. We make the neural networks learn the relation between skin temperature and thermal sensation by back-propagation. The effect of the number of hidden cells is also shown. The results show that the accuracy is within 1.0 for the voting scales used. This accuracy is sufficient to control our new air conditioner.

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A new technique for particle shape measurements has been examined using a LDV optical system for nonspherical particles. The principle of the present measuring system is based on the phase Doppler technique. Fringe pattern reflected to the backwards direction is captured by CCD camera and is processed to detect the spatial distortion of fringes, which enables us to estimate the local curvature of nonspherical particles. Calibration has been carried out by metal spheres of several sizes and nonspherical particles with an ellipsoidal revolution. The accuracy of ellipsoidal particle sizing could be estimated within 7 percent for the radius of local curvature.

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The turbulence has a significant effect on the combustion process in an internal combustion engine. It is very important to separate the gas flow in the engine cylinder to the turbulence and the mean flow. The turbulence is defined as higher-frequency components in the turbulent flow. In this study, some methods of frequency filtering for distinguishing the turbulence components in the flow were investigated. The characteristics of four kinds of frequency filtering methods, that is to say, both digital and analog filters of Butterworth types, running-averaged and stationary time-averaged methods, were compared. These methods were applied to an unsteady jet similar to the flow in the engine cylinder, and the turbulence characteristics obtained were discussed.

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In the consolidated control, so-called "drive by wire", for an automobile engine power train system, there are two manipulated variables: throttle valve angle (θ) and CVT gear speed ratio (R_m). These two manipulated variables both affect the automobile speed (n_v). Therefore, in order to keep the desired engine operating condition under the n_v commanded by the driver, the control theory such as the decoupling control on multi variable input-output control is necessary. On the other hand, there are two pairs of reference and controlled variables because of the existence of these two manipulated variables. This means that there are two subsystems inside the power train system. One of the pair must be n_v itself. As the other pair, R_m or engine speed (n_e) is most considerable. Reported here is the comparison of the consolidate control performances of 3 combinations of the adopted control theory and another pair of variables. Results showed that decoupling control with n_e was excellent.

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It is said that the fuzzy feedback control system has an excellent characteristics of the robustness against the non-linear object. Therefore, to apply the fuzzy control for the field of an internal combustion engine is suitable because of its non-linearity. Here, Diesel engine governor was adopted as a concrete control subject, and the experimental engine operations using the fuzzy control algorithm were carried out as well as simulation studies. Beside the comparison of robustness or other control performances were investigated among the best tuned PI, LQI and this fuzzy controller. Result showed that the fuzzy controller showed the best characteristics for robustness.

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Characteristics of three dimensional LDV, consisting of a single focus lens, two colors and five beams, as a tool of in-cylinder flow velocity measurement were investigated by simulation and experiment. In this type of 3D-LDV, the on-axis velocity component is feasible to accept a false value when a center beam is deflected slightly from the optical on-axis direction. The more unstableness of cycle period of doppler burst signal gives rise to the higher on-axis velocity turbulence than the other velocity component in a counter type signal processor being used. Under the higher fluctuation of velocity, the larger count-cycle number and the lower shifting frequency, however, the on-axis velocity turbulence is more suppressed. In a conventional dual beam LDV, turbulence measurement errors would be observed under the particular conditions. Through in-cylinder velocity measurement, the on-axis velocity turbulence and its correlation with the other component were clarified to reveal higher and certified by the simulation.

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The reduction of friction and wear of cam/tappet interfaces in the valve gear mechanism is effective to improve the performance and reliability of internal combustion engines. Lightweight, antiwear materials such as ceramics seem applicable to the tappet, so it is necessary to study the tribological characteristics. In the present study, the frictional force between the cam and tappet is directly measured using a load sensor installed in a test rig, and the following is carried out. Firstly, the changes of friction with valve spring load, camshaft revolution speed and oil temperature are examined for current materials and CD-level oil of diesel engines, and their empirical relations with the coefficient of friction or frictional mean effective pressure are investigated. Secondly, the influence of oil contamination is examined for the oil used. Lastly, the friction characteristics of the ceramic tappet of silicon nitride, silicon carbide and sialon are obtained, and the influence of surface roughness and the running-in effect of rubbing are clarified.

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