Concerning the Karman vortex flowmeter, an experimental investigation was performed on the resistance of a vortex shedder in a turbulent flow through a circular pipe. The shedders are cylindrical bodies having various cross sections. The open ratio β ranged from 0.660 to 0.915 and the Reynolds number based on the diameter of the pipe and the mean velocity of the flow ranged from 1.9×10⁴ to 2.47×10⁵. The resistance coefficient K is given as follows regardless of the Reynolds number : K=C(1-β)/β². The constant C is proportional to the drag coefficient, C_D, of the shedder in a uniform flow, that is, C=0.8 C_D.

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Similarity between the fully developed laminar flows in a curved pipe and an orthogonally rotating pipe is discussed. Two nondimensional parameters are obtained properly for each flow. When the second parameters become large, it is shown that friction factors for these two flows are in accord with each other and flow characteristics become very similar.

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The characteristics of gas-liquid two-phase flow in a cyclone separator are experimentally studied in order to determine the performances of separating gas and the optimum configuration of a cyclone separator. The flow patterns are classified for the cases of no separation and gas separation. The measured velocity and pressure distributions reveal that the gas separation depends mainly upon the swirl of the flow and the decay of vortex.

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Numerical calculations by a finite-difference method have been made for a steady three-dimensional flow induced by a rotating disk with radial slits enclosed in a cylinder, and the results were compared with those for the nonslitted condition. The main conclusions obtained from the calculations are summarized as follows: (1)Considerable radial flows are generated inside the slits of the disk, resulting in a flow pattern quite different from that induced by a disk without slits and an increase of the momentum exchange. (2)With the increase in the Reynolds number the torque transmitted to the slitted disk is increased more due to the angular momentum exchange compared with that of the nonslitted disk.

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Low-density gas flow through a slender channel was analysed by one-dimensional flow approximation based on integrated boundary layer equations. In order to reveal the discharge characteristics of the slender channel in the region from continuum to slip flow, the present approximation method was applied to a 2-dimensional nozzle shaped by two parallel cylinders with the same radius. The calculated discharge coefficients agreed well with the experimental results in wide ranges of Reynolds numbers, including the slip flow region. Correlation equations of the discharge coefficient proposed from the calculated results well approximate the experimental results for not only the present nozzle but also the conventional DeLaval nozzle.

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Pulsatile laminar flow is examined experimentally in a two-dimensional furrowed channel with varying flow parameters. We present flow diagrams in which five flow modes are classified in terms of the Womersley number and oscillatory fraction of the flow rate for each net flow Reynolds number, on the basis of the process of vortex formation, growth and subsequent disappearance. A striking feature of pulsatile flow in the wavy-walled channel is that after the vortex ejects from the furrow, the vortex does not always disappear in the mainstream, but reattaches to the wall and eventually disappears under certain conditions, in contrast to oscillatory flow. We also show the transition to three-dimensional flow and a new flow structure in which a wave appears in the mainstream during the flow deceleration phase due to a shear layer instability.

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The algebraic stress model for high Reynolds number is extended to the near-wall region of low Reynolds number. In developing the model, convection and diffusion terms are approximated to take viscous effect into consideration by applying Rodi's proposal. The pressure strain term and dissipation term of the Reynolds stress equation are modified by introducing the invariant function. The transport equations for turbulent energy and the dissipation are standard two-equation models adopted for the near-wall region. To examine the proposed model, numerical analysis has been performed on a fully developed turbulent flow in a square duct. Calculated results are compared with the experimental data available and the calculated results obtained by using an algebraic stress model for high Reynolds number. The proposed model can predict more precisely wall shear stress and normal stress in the mean flow direction than can the model for high Reynolds number, but the results of normal stress in the secondary flow direction are slightly different from the experimental data.

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The particle tracking method using the Kalman filter has been improved in the expansion of its dynamic range of measurable velocity. This method becomes more responsive to variation in the particle velocities by observing not only particle positions but also the information related to the particle velocities. Once the absolute values of velocities of particles are obtained from the length of particle paths on images, the senses of velocity vectors are determined automatically. When the observed positions have sufficient precision, it is possible to improve the accuracy of the velocity measurement even if the errors in the observed absolute values of velocities are significant.

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In this paper, it will be shown that the concentration distribution in a plume is multifractal-like if we choose the measure as the integral of concentration over a finite time interval in the recorded concentration data. This kind of multifractality is most possibly due to that of the kinematic energy dissipation field. Some phenomenological explanation is given to this multifractality through the use of the binomial multiplicative process model and the so-called random dilution coefficient model. It will also be shown that both models give lognormality of the pdf of concentration, which is an empirical result of experimental studies. Moreover, by processing the experimental data, the f(α) spectra are obtained for the concentration field of the plume, and it is found that the distortion of flow due to the sphere appears to reduce the maximum singularity exponents α_max.

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A clear design principle has not been established for powder surface modification technology by mechanical and physial methods, such as microencapsulation. In this paper, the transport equations of polar fluids proposed by the authors in a previous report are applied to microencapsulation. Using the functional analysis, we show mathematical properties of mixed problems under perfect absorptive barrier boundary condition. The unique existence theorem of a weak solution to mixed problems is obtained by a priori evalution and a successive approximation method. Since this weak solution tends to be a sufficient classical solution, these mixed problems are wellposed in the sense of Hadamard.

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In a previous report, we proposed a statistical theory for powder surface modification technology by means of a mechanical method using the transport equations of polar fluids with infinitesimal particle surface deformation. In this paper, we demonstrate the unique existence theorem for a weak solution on a mixed problem under imperfect reflective barrier boundary conditions (∥M_B∥<1) by a priori evalution and the successive approximation method. We consider the relationship between weak solutions and other improper solutions, such as strong solutions and almost-everywhere solutions. The positive-valued property and the comparison theorem for weak solutions are proven by positive operators to assign the physical meaning to improper solutions.

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This research aims to clarify the characteristics of the axisymmetric point-source plume which develops in the turbulent flow distorted by a sphere. Here reported are mainly results on the probability density function and the auto correlation function of the concentration field. The data are summarized by imagining a striation structure of a diffusing plume. The effects of the distortion of flow on the concentration detecting frequency and the molecular diffusion have been quantitatively estimated with a simple theory and compared with the experiment. The results obtained back up a conclusion : a striation structure exists in the plume, and the striae of the diffusing matter appear to slim and merge with each other principally due to the distortion of the mean flow and the molecular diffusion near the stagnation point. Some comments are also given on the limitation of resolution of the measuring probe.

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A mathematical model is presented for numerical simulation of the fluid transients in the return line during the decompression operation of any hydraulic system. Particular attention has been paid to clarification of the influence of gas diffusion on the fluid transients because part of the separation cavity consists of a gas-liquid two-phase flow containing a number of minute gas (air) bubbles in such a system. Experiments, using sump oil and deaerated oil as a test fluid, showed that the generation mechanism of the separation cavity and the fluid transients are significantly affected by the gas diffusion. Values calculated from the proposed "bubble-diffusion model", which takes into consideration the effects of gas diffusion as well as the amount of gas bubbles released from the liquid flowing out of the valve before column separation occurs, a change of state of gas and the surface tension applied to the gas bubble, agreed well with the measured values over a wide range of tests.

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With regard to inverse design problems, numerical integration of the first-order partial derivatives given on discrete points in n-dimensional spaces is demanded occasionally, for example, to obtain a velocity field satisfying the velocity gradients given in the field. In this paper, such numerical quadratures are proposed by the use of the shape function for finite element methods or the finite difference approximation, based on a least squares method. Applicability of these methods is confirmed by applying them to a two-dimensional problem, and the characteristics of computational accuracy and the CPU time necessitated are discussed.

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The experimental study of three dimensional turbulent flow in a distorting duct was made using a laser-Doppler anemometer. To make clear the relationship between mean strain and structure of turbulence is of fundamental importance in all turbulent shear flows. The purpose of this work is to analyze the flow in a distorting duct by comparing present experimental data with published data. The obtained experimental data was compared the other data of Tucker-Reynolds measured by hot wire anemometer and the numerical results using Reynolds stress model. The present experimental data of decay for normal stresses along the center line was close to the calculated results. Separated flow was observed in outlet corner region of a distorting duct by laser-Doppler anemometer and flow visualization technique. Numerical method was also able to predict this separated flow. The three dimensional turbulent flow in a distorting duct is analyzed more clearly by the present experimental data.

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Detailed studies are again conducted to investigate the characteristics of the transitional boundary layer on the flat plate which is subjected to wakes generated by rotating circular cylinders with diameters larger than those in the 1st report. In this paper, the 2nd report, the focus is on the modification of the previously proposed model of the intermittency factor of the transitional boundary layer influenced by the wakes. It is consequently found that the newly developed model, taking account of the effect of wake duration, yields better predictions of the time-averaged heat transfer for the wide range of wake conditions covered in this study. Furthermore, it is confirmed that the forced transition may begin near the instability point of the laminar boundary layer.

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The effects of area ratio on electrical and fluid-dynamical properties in a disk magnetohy-drodynamic (MHD) generator have been experimentally investigated. The experimental results have shown that for a generator with a large area ratio, the wall static pressure is kept lower than that of the small area ratio generator. It is observed that high values of the Hall field are obtained at the downstream part of the channel which has a large area ratio. The stagnation pressure at the exit of the disk MHD channel was measured and compared with the results of one-dimensional calculations. It is found that in pressure loss processes a strong Lorentz force becomes quite significant relative to the wall friction which plays a major part in the pressure loss mechanism in the absence of MHD interaction.

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A low-solidity circular cascade, conformally transformed from a high-stagger linear cascade of double-circular-arc vanes with solidity 0.69, was tested as a part of the diffuser system of a transonic centrifugal compressor, and the blade loading of the cascade was investigated by means of pressure measurement around the vane. The experimental data for the lift-coefficient of the vane were almost on a single straight line when plotted against angle-of-attack for a wide range of Mach numbers and flow angles. The maximum lift-coefficient reached about 1.5 and the vane functioned well even near the surge condition of the compressor.

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A method to determine the shock loss of an adjustable blade runner with the incidence angle is presented by analyzing the on-cam hydraulic performances of a bulb turbine. The shock losses are investigated with two model bulb turbines having discharge specific speeds n_SQ of 158 and 171. The results obtained are summarized as follows : The shock loss can be predicted by the shock loss coefficient and shock velocity head. The values of the shock loss coefficient are approximately 0.85 (n_SQ=158) and 0.95 (n_SQ=171) in the case of the positive incidence angle, and 1.6∼1.9 (n_SQ=158) and 1.9∼2.1 (n_SQ=171) for negative angle.

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Experimental investigations into an affinity law of cross flow fans have been conducted using three fans with different dimensions but good geometrical similarity, and peculiar scale effects appearing on the performance curves have been shown. The results obtained have been confirmed with a series of additional experiments which examine the effects of errors in geometrical configurations of tested fans, as well as effects of the flow turbulence and velocity distortions of the inlet flow into the fans. The critical Reynolds number based on the chord length and tip speed of the rotor is as small as (1∼1.5) × 10⁴. The performance curves represented in a usual nondimensional form are affected by Reynolds number as well as the fan dimensions, which shows that the performances of cross flow fans never simply obey the conventional fan law, but it is essential to introduce the fan dimensions to represent the performance curves in a universal form.

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Performance tests were conducted for centrifugal compressors of CFC11 having vaneless diffusers whose flow passage widths decrease linearly from near the outlet to the outlet. The beginning point of reduction in diffuser width was selected appropriately and its reduction ratio was optimized experimentally. The optimum value of the width reduction ratio was 0.5. The surge margin was improved and the compressor adiabatic efficiency was improved over wide range of flow rates, as compared with a compressor without a width reduction region at the diffuser outlet. At surge inception, the static pressure difference between the hub and shroud walls of the diffuser inlet decreased as the width reduced at the diffuser outlet. The pressure difference between the hub and shroud walls of the diffuser inlet at surge inception was characteristic constant value independent of the conditions of inlet guide vane opening. Therefore, surge inception can be predicted by measuring the pressure difference between the two walls of the diffuser inlet.

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Three-dimensional two-phase flows in a centrifugal pump have been analyzed numerically by the authors on the basis of a so-called bubbly flow model. The local void fractions obtained, however, seem to amount to somewhat higher values than the applicable range of the model. In this paper, a revised model is proposed to extend the applicability under the assumptions that the bubbles in high void fraction regions adhere to the impeller walls just as in a fixed cavity, and this model is applied to the analyses for a radial-flow pump. When the inlet void fraction exceeds a critical one, the fixed cavity obtained expands rapidly from the shroud to the hub in the section just after the impeller inlet and fills the section. When the pump is operated under a two-phase flow condition, it loses its function at nearly the same inlet void fraction due to the blockade of the entrained air. This model is thus applicable to the prediction of the limit of pumping activity.

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In order to enhance the efficiency of the screw compressor, it is necessary to study the effect of the number of teeth on the rotor profile. With the aim of developing an oil-flooded high-efficiency profile, we generated data, including the stroke volume and seal area, with a computer program. The increase in pressure and temperature inside the rotor groove was simulated on the basis of the results obtained, and performance as a function of the number of teeth was computed. Based on the results of this computation, a trial model using a new rotor profile was prepared, and its performance was compared with that of the conventional profile. The results of our analysis are explained in this report.

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A radiator cooling axial fan is one of the major sources of noise in an engine room, and many efforts have been made to reduce the noise emitted by the fan. In this study asymmetric distributions of the acoustic intensity (AI) and blade-to-blade velocities were studied when the fan was located downstream of the radiator, off its center. Higher values of the Reynolds shear stress component, v'w', in the θ-z plane were found to be distributed randomly between the blades in the local low-noise region. In the high-noise region, however, they were shifted toward the suction side of the blades, which caused the increase in the noise of discrete frequencies.

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Shock wave and transient flow induced by thermal release such as combustion, detonation or electric discharge are of special interest in research on combustion phenomena of gas turbines and shock wave propagation in gas laser oscillators. In MHD power generation, excessive Joule heat due to Faraday and Hall current, and abnormal phenomena such as arc discharge disturb supersonic flow in the generator. In this paper, numerical simulation of compressible flow involving thermal release is executed by means of the Euler implicit method, in which Neumann-type artificial viscosity is appended in order to calculate the behavior of physical discontinuities such as shock waves in pressurized gas. In terms of gas pressure and energy density, the Mach number of the shock wave due to arc discharge is investigated here, where the pressurized gas is argon (Ar) at room temperature. Furthermore, the behavior of the thermal wave as the boundary of the high-temperature region, which follows after a shock wave with a velocity much lower than that of the shock wave, is also clarified.

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A combined numerical and experimental study is reported of a reactional melting of snow into solutions of sodium chloride, calcium chloride, and magnesium chloride. The numerical results are successfully validated through temperature decreases in the melting system. It is found that the temperature in the system quickly falls in a few seconds, and keeps an uniform temperature which denotes thermodynamical equilibrium. Although the maximum melting mass per unit volume of snow M_max is dependent on initial concentration C_mi and initial temperature T_i, M_max is not largely influenced by initial porosity or dry density of snow. Simple relationships are proposed to conventionally obtain the dimensionless maximum melting mass for each binary aqueous solution.

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Time-spatial measurements were carried out on the thickness of liquid film falling inside a vertical tube. It was examined how both locations of initiation in waviness and coalescence-separation of waves depend on liquid film Reynolds number. Fractal analysis of time-series signals of liquid film thickness reveals that wavy characteristics of falling film are a deterministic random phenomenon, i.e., a chaos. Comparison between fractal dimension, waviness in falling film and power spectral density of film thickness suggests that waves including higher-frequency components roughly correspond to larger values of the fractal dimension. Two different types of axial variations in fractal dimension and standard deviation of liquid holdup were found. The boundary of these on a map of axial distance vs. film Reynolds number is simply specified by a wave behavior transition film Reynolds number of 200∼350.

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An apparatus for the measurement of the diffusion coefficient of supercritical fluid has been constructed based on the Taylor dispersion dispersion method. The apparatus uses a 1.2m-long straight capillary tube for the diffusion tube, which has two concentration detectors with no dead volumes, and a position-sensitive detector with a He-Ne laser in order to detect the solute concentration. The diffusion coefficients of the acetone-CO₂ system and alkane (C₅H₁₂-C₁₄H₃₀)-CO₂ systems have been measured at 299.15-308.15 K and 9-10.5 MPa. The accuracy of the present results was estimated to be ±3%. In the results for acetone at low enough solute concentrations, it was found that the experimental data of Sassiat et al. by the Taylor dispersion method which had a 9.5m-long diffusion tube and single concentration detector was consistent with the present values. For C₅H₁₂-C₁₄H₃₀, the temperature dependence was found to be positive and concave near the critical temperature. The molecular-weight dependence of the diffusion coefficients was negative and convex, and the diffusion coefficient of C₅H₁₂ was about 1.4 times as large as that of C₁₄H₃₀ at the same conditions.

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In nucleate and transition boiling, the wettability of a heated surface plays an important role. Up to now, the contact angle has been a common measure of surface wettability. But because of contact angle hysteresis, measuring it from the shape of a liquid droplet on a horizontal solid surface may have almost no meaning. In this study, the hysteresis is studied theoretically and effects of surface energetics, roughness and temperature on wettability are investigated experimentally by measuring contact angle under various conditions. As a result, a new measure of solid surface wettability is proposed.

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Natural convection heat transfer in a square cavity filled with a saturated anisotropic porous medium has been investigated analytically. One vertical wall is kept at a constant temperature which is higher than that of the other. Top and bottom walls are insulated. All boundaries are assumed to be nonpenetrable for the fluid. The temperature and stream function are expanded about Ra, the Rayleigh number of the system. The series solutions are then substituted in the governing equations. Equating terms of equal power of Ra, a number of sets of the homogeneous or nonhomogeneous linear systems are generated. The linear systems are solved by Fourier series. Anisotropy of both permeability and thermal conductivity is considered in the process of solving these linear systems. The degrees of anisotropy of fluid permeability K_x/K_y and of thermal conductivity k_x/k_y are varied from 0.1 to 100 and from 0.01 to 100, respectively. The effect of both anisotropy of permeability and thermal conductivity on the overall heat transfer is found to be equally significant. It is also found that the anisotropy of a porous medium produces similar effects on flow and temperature patterns as does the geometric aspect ratio of the rectangular cavity.

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Boiling of n-pentane, CFC-113 and water under microgravity were studied, utilizing parabolic flight maneuvers with a Caravelle aircraft. The experimental apparatus was constructed so as to permit simultaneous video recording of the side view of vapor bubbles, generated on a Joule-heated, transparent indium-oxide film plated on a glass substrate, and the backside view through the substrate. The heat transfer to n-pentane or CFC-113 in the nucleate-boiling regime deteriorated slightly under microgravity, while the critical heat flux was lowered to two-fifths of the corresponding terrestrial value. In contrast, the heat transfer to water significantly deteriorated under microgravity. The difference in the degree of heat transfer deterioration thus observed is presumably ascribed to a considerable difference, between the former two liquids and water, in the bubble behavior in the vicinity of the heater surface, which in turn must depend on the surface tension of each liquid and the wettability of the heater surface with the liquid.

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An experimental study is reported on convective boiling heat transfer for HFC134a, HCFC22, CFC114 and CFC12 inside a horizontal smooth tube. The test evaporator is of the double-tube type in which the heating water flows in the outer annulus, and the local heat transfer coefficients are measured for both counter and parallel flow. Based on the supposition of Chen that the total heat flux q is represented as the sum of forced convective contribution q_cv and nucleate boiling contribution q_nb, a general correlation is developed for the data in the annular flow regime. The mean deviation between the calculated and measured heat transfer coefficients is 12.2% for the present experimental data and 9.5% for available data collected from previous research. According to the proposed correlation, nucleate boiling is not suppressed even in the high-quality region in the case of counter flow, while two-phase forced convection has been recognized as predominant in the high-quality region with uniform heat flux conditions.

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Numerical analysis has been conducted for evaporating annular two-phase flow of nonazeotropic binary mixtures flowing upward in a vertical tube. The equations of continuity, momentum, energy and mass transfer for each phase have been solved numerically by a finite volume method. The model expressing the interfacial wave effect on momentum, heat, and mass transfers has been applied to the analysis. The computational results of the local heat transfer coefficient agree fairly well with experimental data previously reported by others for the evaporation of R11-R113. Therefore, the validity of the present method is confirmed. The present analysis can also predict the local evaporation rate of each component. From the results of numerical study for three types of binary mixtures, R11-R113, R22-R114 and R22-R11, it is confirmed that the greater the difference between the bubble-point and dew-point curves, the more noticeable is the effect of the low rate of mass diffusion, which causes a decrease in heat transfer efficiency.

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The following unsteady local properties were measured simultaneously around a horizontal heated circular cylinder in a gas-solid fluidized bed for three kinds of particles with different diameters; (1) the heat transfer coefficient, (2) wall pressure and (3) the discrimination between emulsion and void phases. The unsteady signals were analyzed statistically. The arrival frequency of bubbles on the cylinder surface, the mean contact time of the emulsion and bubbles with the cylinder surface, the rate of contribution of the emulsion and bubbles to the heat transfer coefficient, the contact heat transfer coefficient of emulsion with the cylinder surface, etc., were obtained. On the basis of these characteristics, the effects of the diameters of the particles were estabished quantitatively. Moreover, a new model of heat transfer around a circular cylinder, considering the effect of the sliding emulsion, was applied to the experimental results, and the validity of the model and the dominant mechanism of heat transfer were clarified.

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A local maximum appears in the distribution of Nusselt numbers of the axisymmetric confined jet with a cylindrical ring. It has been confirmed by flow visualization and the measurements of velocity fluctuation and its spectrum that the large-scale vortices shedding from the ring bring about heat transfer enhancement at some downstream region of the ring. In the cases of the velocity ratio of the jet and circumferencial flows U_j/U_s≤1.5, the periodically shed vortices attach directly to the pipe wall. On the other hand, the vortices are entrained into the jet due to the intense shear rate in the case of larger velocity ratio, and the high-intensity turbulence produced during the collapse of the vortices can be considered to increase the heat transfer coefficient.

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Rapid quenching of thin horizontal platinum wires (0.3 and 0.5mm in diameter) was studied experimentally using pure water as a quenching liquid. The cooling curve was measured in the ranges of water temperature of 0 to 50°C, falling velocity of the wire of 0.1 to 1.5 m/s, and initial wire temperature of 600 to 1400°C. The boiling curve for the rapid quenching process was obtained from the cooling curve. The degree of superheat at the minimum heat flux point was around 350 K irrespective of the water temperature, the falling velocity and the wire diameter. The heat flux in the film, transition and nucleate boiling regions increased with increasing degree of subcooling and falling velocity. A numerical analysis of transient film boiling on a horizontal cylinder with upward liquid flow was performed. The measured heat flux was about 30% higher than the calculated value at the forward stagnation point.

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Natural convection in a heated horizontal fluid layer have been studied experimentally and theoretically for many years. In industrial components such as boilers or reactors, heat and mass are sometimes transferred through a horizontal fluid layer, including the internal structures. The heat transfer characteristics was experimantally studied in the horizontal water layer, including honeycombs of different flow area reduction ratios. Large eddy motion was reduced with the honeycomb but the heat transfer rate through the layer could not be affected, even at the flow area reduction rate of 0.09. Further reduction of the flow area resulted in the nonuniform temperature distribution of the central fluid layer and depression of the heat transfer rate.

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Microscopic structure of turbulent diffusion flames is studied by a time-resolved planar video picture system obtained by a laser Rayleigh scattering (LRS) method and a single-point LRS measurement. The microscopic temperature is measured by using a two-dimensional LRS signal and image processing. Coaxial turbulent diffusion flames at moderate Reynolds numbers, which exhibit typical diffusion flame structures, are formed on laboratory-scale burners. It is found that the flame can be divided into four typical regions characterized by the distribution of macroscale of temperature fluctuations. These four regions are visualized by the two-dimensional LRS pictures. The turbulent heat transfer mechanisms in these four regions are discussed in terms of the two-dimensional LRS and the power spectral density of temperature fluctuations, in terms of one-point LRS. A cluster of temperature inhomogeneity is observed by cluster analysis in Regions I and III. It is found that different structures of microscopic inhomogeneity in the mixing region of Taylor's dissipation length scale appear, corresponding to the characteristics of mixing and combustion mechanisms in each region.

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Flame-front propagation in a densified condensed medium of Ti and C is studied experimentally. Effects of mixture ratio, diameters of particles, relative density, and degree of dilution on burning velocity are investigated. Burning velocity has been defined as the flame-front velocity normal to its surface through the adjacent unburned condensed medium. Results shows that there exist flammability limits, over which flame-front propagation occurs, and outside of which the flame cannot be self-sustained. The diameter of carbon particles is found to exert great influence on the burning velocity, while that of Ti particles has no remarkable effects when particle sizes are smaller than the thickness of the combustion region. Dilution with the combustion product is also shown to be effective in controlling the burning velocity while there exists a dilution limit beyond which the flame front ceases to propagate.

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Deflagration in a densified condensed medium is studied theoretically to investigate the basic nature of combustion synthesis. On the basis of an analogy to spray combustion, governing equations are obtained for the combustion system of premixed combustibles with a nonpremixed process of dispersed nonmetal particles in liquid metal. The analysis is reduced to a problem of obtaining an eigenvalue which is related to burning velocity. Calculated results show that the eigenvalue depends on the Lewis number, the surface Damkohler number, the initial temperature, the mixture ratio of nonmetal to metal, and the degree of dilution by the combustion product. The range of flammability is also predicted. Fair agreement is demonstrated between the predicted results and the experimental data in the literature, as far as the trend and the approximate magnitude are concerned.

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The laser Rayleigh scattering method was applied for the time history measurements of local gas temperatures in a methane-fueled spark-ignition engine. Transient temperatures were measured at three different points in the combustion chamber under various operating conditions of the engine. Results showed that the gases at the respective points were subjected to nearly the same temperature history with the highest temperature just after flame arrival, followed by gradual decrease as the process proceeded. A simulation model, which was developed to predict gas temperatures under the relevant engine operations, revealed that the temperatures measured corresponded fairly well with the predicted ones. The Rayleigh scattering method was found to be an effective means of time- and space-resolved temperature measurement in an actual engine.

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The characteristics of prechamber lean burn were researched by using high-speed, small singlecylinder engines. The prechamber system can run at leaner mixture than the open chamber because the ignition lag of the prechamber and combustion period are very short and keep constant in spite of changing A/F. Without supplying gas to prechamber the main chamber is relatively effected by the combustion. However, while gas is supplied into the prechamber, the effect of the main chamber is relatively small. The strong squish decreases the combustion period, but NO.x, is reduced. Then, THC is decreased by large squish area and high swirl.

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The influence of fuel properties on the combustion and emissions of a D. I. diesel engine was analyzed, providing independent descriptions of the distributions of distillation temperature, kinematic viscosities, ignitabilities, and aromatic contents. The results showed that smoke increased with increase in the kinematic viscosities, shorter ignition lags, and increase in the aromatic content, especially at high equivalence ratios. This NO_x was reduced slightly with increase in kinematic viscosity and with the decrease in aromatic content. The content of unburnt HC increased with increases in the ignition lags and kinematic viscosities. The only substantial effect of aromatic content on particulate matter was an increase in dry soot at high equivalence ratios. However, the dry soot decreased at high equivalence ratios and SOF increased at all equivalence ratios with lengthening ignition lags caused by the increases in the aromatic content and so on. The distribution of distillation temperatures had very little influence on exhaust gas emissions and engine performance.

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Sauter mean diameter and air entrainment characteristics of nonevaporating unsteady dense sprays are measured by means of an image analysis technique, which uses an instantaneous shadow picture of the spray and injected fuel amount. Influences of injection pressure and ambient gas density on Sauter mean diameter and air entrainment are investigated parametrically. An empirical equation for the Sauter mean diameter is proposed based on a dimensionless analysis of the experimental results that Sauter mean diameter decreases with an increase in injection pressure and with a decrease in ambient gas density. It is also shown that the air entrainment characteristics can be predicted by the quasi-steady jet theory.

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The effect of induction swirl on the combustion of a D. I. diesel engine with deep bowl chamber was studied for both standard and retarded fuel injection timings by the analysis of exhaust gas and engine output characteristics as well as the composition distribution of burnt gas along the exhaust procedure. As a result, the following was revealed: The burning characteristics of the engine are principally controlled by the swirl velocity. The optimum swirl velocity for combustion increases with retarding of the fuel injection timing. Under the optimum swirl velocity, the distribution patterns of fuel and burnt products in the cylinder hardly change irrespective of a remarkable change in the fuel injection timing. This assures that without any increase in soot and imperfect combustion products, a significant reduction of the exhaust No_x is possible, provided that the swirl velocity is optimized for the retarded phase of the burning period.

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It is well known that the turbulent flow in an engine cylinder affects the combustion. The turbulent air flow with tumbling motion was measured with a laser Doppler velocimeter. The measurements were performed in two kinds of intake systems with one or two valves. In order to determine the cycle-resolved turbulence characteristics, such as turbulence intensity and integral time scale the flow velocity data were analyzed by the Butterworth digital filter method. The cycle-to-cycle variations in the turbulence intensity and the mean velocity were also investigated in changing the cut-off frequency. Furthermore, the isotropy of the turbulence near top dead center of the compression and expansion stroke was discussed.

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The cooling characteristics are theoretically investigated in the case of a return-flow type of gaseous-cooled gas turbine rotor blade. The blade model is intended for the application of a closed-circuit gaseous coolant system. An analytical method based on one-dimensional fluid flow and heat transfer is proposed for calculating temperatures of the blade metal, incoming coolant, and outgoing coolant at various spanwise positions, and also pressure losses of the coolant at each cooling passage. The numerical analysis is carried out for a steam-cooled rotating blade under reasonably selected gas turbine operating conditions. In comparing both cooling characteristics of the blade with and without rotation, it is shown that the pumping effect on the cooling performance and pressure loss is relativery small in this study.

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Effects of surface roughness on the unsteady cavitating flow around a two-dimensional circular cylinder were experimentally considered. Detailed results are presented at Reynolds numbers from 1.36×10⁵ to 1.78×10⁵. Two patterns of surface roughness were investigated. One was the double-cut and another the single-cut pattern. For some roughness parameters tested, the length of the cavity exhibits an extreme decrease. In the particular case of the double-cut pattern, it is found that there exists the minimum cavity behind the circular cylinder.

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The scour around bridge piers and its prevention have been studied in a wind tunnel with a sand stratum bed. The final scour depth H^* and length L^* are proportional to the DU^2.4, where D is the diameter of the cylinder and U is the flow velocity. These are correlated with the following expression : L^*/D=1.33×(H^*/D-0.1). The scour can be prevented by arresting the formation of horseshoe vortex, and in the case of the disk larger than 2.5D in diameter located at the position of the cylinder less than 0.2D from the sand surface, the scour is completely prevented.

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An experimental study was carried out on vortices issued from a thin symmetrical airfoil with angle of attack under rotational oscillation of small amplitude. The experiments were conducted in a hydraulic flume using Laser Doppler Velocimetry (LDV) and ensemble averaging technique to map the unsteady velocity field about the vortex generating region. From this study, transitional characteristics of vortices issued from a body which creasts asymmetric flow field became clear. Especially, the reducing mechanism of circulation due to different flow characteristics between the upper and lower vortices became clear from investigation of time variation of the vorticity and shear velocity distributions.

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