When a partial differential equation is solved numerically, it is conventional to discretize the calculating domain into many elements by elaborate handwork. For this discretization we devised a new method with which the three-dimensional domain can be automatically divided into Voronoi polyhedron elements enclosing arbitrary nuclear points. The present report describes this method in detail giving an example. When the Voronoi polyhedron elements are used, various types of differential equations can be easily transformed into simultaneous algebraic equations for each of the nuclear points, and parallel processing can be achieved more quickly and accurately. Moreover, the Voronoi polyhedron element table has possibilities for future development : it can be used not only as a direct analytical method of solving a partial differential equation, but also, after being transformed, as an ordinary tetrahedron element table.

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A simple finite-element method for unsteady incompressible viscous flow is presented. This method is a simplified version of the GSMAC (generalized simplified marker and cell) finite-element method, and it is applicable to large systems. Navier-Stokes equations in rotational form and the equation of continuity are employed as the governing equations. A time-dependent solution is obtained by the following procedures. (1) Prediction of velocity field by explicit time advancement. (2) Correction of both velocity and the Bernoulli function by simultaneous relaxation satisfying the equation of continuity. Unsteady flow in a lid-driven cubic cavity at the Reynolds number of 5000 is numerically investigated to verify the present method. Velocity profiles in the cavity are in good agreement with the experimental results of Prasad and Koseff. The present method is stable in three-dimensional analysis, and nonphysical pressure oscillations are not observed.

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An experimental investigation on the distribution of the entrainment flow rate in a horizontal annular two-phase flow was conducted. In this experiment, the isokinetic sampling probe technique was used for the measurement of the entrained droplet flow rate. It was demonstrated that the distribution of the entrained droplet flow rate was sensitive to the flow configuration, the total entrained droplet flow rate in the gas core was smaller than that of the vertical upward flow and the correlation of the entrainment flow rate proposed by Paleev et al. was superior to that by Wicks et al. Furthermore, a new correlation for the critical flow condition of the onset of droplet entrainment was proposed.

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In this paper, the numerical analyses on the behavior of a heavy monoatom beam are presented. Some numerical methods for the analysis of rarefied gas flow have been proposed thus far, which have been successfully applied to the flow of Kn<1, such as in the semiconductor manufacturing processes and other vacuum technologies. However, since the atomic number density of the beam is extremely low, the flow here is categorized as molecular (Kn>1), in which the atomic free path is rather large compared with the representative scale of the beam. Hence, the probability density function of the atomic free path in the nonequilibrium field was taken into account in the numerical simulation of the beam propagation. Consequently, the calculated results of the beam diffusion due to mutual atomic scattering agreed well with the measured data obtained using gadolinium vapor.

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Basic study is conducted on the oscillating motion of a magnetic fluid plug and a piston in a U-tube with an exciting periodic magnetic field as a simple example of the magnetic fluid plug actuator. Under the assumption that the effect of a magnetic field on pipe friction is constant, frequency response curves for the displacement of the piston are obtained by numerical calculation. Furthermore, an experimental study is carried out for comparison with the theoretical analysis. The theoretical analysis shows good agreement with the experimental results of the resonance frequency. However, prediction of the maximum amplitude requires the correction of piston seal friction.

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A flow rate control valve using a piezoelectric element has been investigated. The valve has a horn and a ball (diameter : 4mm) which are vibrated by the piezoelectric element. The liquid flow rate is controlled by the valve-opening time. The element is effective for decreasing the time required for valve open in order to supply a voltage when the pulse width is increased. Flow rate increases linearly when the pulse width is increased. The minimum pulse width is 0.4ms, which is smaller than the 1ms-width minimum for a valve using a solenoid coil.

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Liquid lump velocities were experimentally determined for vertical upward gas-liquid two-phase flow under a wide range of pressures from near atmospheric pressure to a highly elevated pressure, about 20MPa. The liquid lumps dealt with here are the liquid slug, huge wave, disturbance wave and ephemeral large wave. Velocities were determined using two sets of signals of time-varying cross-sectional mean liquid holdup which were electrically detected at two axially separated locations of the test tube. The effects of flow parameters such as gas and liquid flow rates as well as pressure on liquid lump velocities are described. The initiation of the transition from plug flow to huge wave flow is also discussed in the presentation of the results.

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The motion of a single measure of a gas slug in a vertical tube using a closed loop filled with stagnant liquid was studied to investigate the influence of the system pressure under a wide range from near atmospheric pressure to highly elevated pressure, e.g., 20MPa. One purpose of this study was to investigate the influence of pressure on the rising velocity of the gas slug. The experimental equation was presented for rising velocity of the gas slug. The other purpose was to study the phenomenon of the liquid film around the gas slug as pressure increased. It was found that when liquid waves with liquid film around the gas slug appear, there are many bubbles with small diameters in the wake of the gas slug. The correlation of smooth liquid film length around the gas slug was presented.

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An efficient numerical method based on the double porosity model is proposed in order to analyze heat and fluid flows in fractured rock formations. The specific problem to which the present numerical method is applied assumes a single vertical or horizontal fracture that drains heat from neighboring blocks of homogeneous and isotropic impermeable rock. The outlet temperature history is monitored to evaluate the amount of heat extraction from the rock. The numerical results are favorably compared with the available analytical data. The present method is proven to be ten times more efficient than a conventional algorithm that requires a fine grid network along the fracture. The method can be extended to three-dimensional space or complex fracture networks.

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The enhancement of heat transfer caused by the presence of a single vortex generator in a laminar boundary layer was experimentally investigated. The local heat transfer coefficients just downstream of the vortex generator and the mean and fluctuation components of velocity were measured. A substantial increase in the heat transfer was noted, with a maximum improvement of the heat transfer coefficient of 80%, even in regions where the laminar structure was clearly predominant. It was observed that the heat transfer coefficient presented two peaks in the spanwise direction. These peaks were found to be associated with the downward motion of the mean vortex and the corner vortex, which arose in the generator's front corner. The influence of the height, angle of attack and geometry of the vortex generator on heat transfer was also investigated.

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The purpose of this study is to improve the performance of innerfins for intercooler use for automotive turbocharger engines. Since these intercoolers are used at high flow velocities, unlike other automotive heat exchangers, analysis of their unsteady nature is necessary. In this paper, a numerical analysis was conducted, taking into account flow instability, to determine how the fluctuation in the flow of the fin wake affects the efficiency of heat transfer of each rear fin. It was ascertained that the heat transfer enhancement of the fin is related to each fin space and Reynolds number, and that high heat transfer is obtained when the fin space is greater than three times the fin thickness.

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Experimental studies were conducted on the flame stability and combustion characteristics of the twin-flame matrix burner which is composed of a number of counterflow burners arranged in a regular matrix. The burner consists of two opposing burner matrices which form the combustion chamber with two side plates and a bottom plate. The stability limits of the matrix flames, the profiles of temperature and the concentrations of some stable species were measured for methane flames at atmospheric pressure. Although the characteristics of the flames vary gradually toward the exit of the combustion chamber, the counterflow twin flames are established within a wide range of ejection velocity and equivalence ratio of the mixture. It is found that the turn-down ratio of this burner reaches 11, which is 3∼4 times larger than that of usual domestic appliances.

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The formerly proposed spectral model of turbulent mass burning velocity is refined for practical use. The model is expressed by an integral form of the product of two independent functions. One is the turbulence energy spectrum and the other is the characteristic spectrum solely related to the mixture properties, such as laminar burning velocity and laminar flame thickness. Refinements are made in regard to the following three points : (1) a small modification in the characteristic spectrum of the mixture, (2) consideration of turbulence spectrum shape variation with turbulence intensity and (3) a new idea regarding the upper limit of the integral which is strongly related to the small-scale structure of the turbulent flame. The predicted velocities for stoichiometric mixtures are compared with the measured turbulent mass burning velocities, where the laminar burning velocity, laminar flame thickness and turbulence intensity are varied extensively and independently with each other. The comparison shows fairly good quantitative consistency.

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A three-dimensional computer model of a swirling fired-type furnace in which pulverized petroleum coke and ASTM No. 6 heavy oil are fed from two opposite side walls is presented. The predicted results are compared with measurements of exhaust NO concentration in an operating 125 MW(e) boiler with and without air introduced tangentially from the bottom of the furnace (below the lower burners) to convert H₂S to SO₂ effectively. Agreement between predicted and experimental data is quite satisfactory. Both show that the unburned ratio decreases with an increase in the fraction of the flow of tangential air to that of secondary air and with an increase of NO concentration. Our prediction also shows that when the tangential air is introduced from the bottom, a reduction in the H₂S formation rate is successfully effected in low-grade high-sulfur-content fuels such as heavy oil and petroleum coke.

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This paper presents a unique approach for two-dimensional visualization and measurement of chamber wall temperatures in ultralean combustion engines. It also includes a three-dimensional measurement method for flame speed in the lean combustion of spark-ignited engines. Ultralean combustion, which is characterized by an air fuel ratio of more than 20, has proven to be effective for combustion improvements such as emission gas cleaning and thermal efficiency. However, combustion has inherent difficulties such as instability. Swirl is an effective method of stabilizing lean combustion. It is important from a combustion stability standpoint to understand the relationship between swirl and wall temperature and between swirl and flame. Wall temperature distribution and three-dimensional flame speed in ultralean combustion are clearly observable by use of the visualization method. The relationship between wall temperature distribution and three-dimensional flame speed is investigated.

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In order to study the optimization control for the fuel consumption ratio (be) of the engine∼continuously variable transmission (CVT)∼load system, a method employing consolidated control was attempted. This means that the throttle value angle (θ) of the engine and variable ratio of the CVT are controlled simultaneously under the conditions satisfying the desired speed (n_v) of the CVT output shaft. In this case, it is well known that some countermeasure must be taken against the interaction between θ and R_m to n_v. A countermeasure based on decoupling control theory was applied. Also, modelling of the objective system, which was necessary for the procedure of designing the control system, was carried out taking into account the nonlinearity and CVT actuator speed R_m. The investigation was carried out experimentally as well as theoretically, and a desirable be-result was obtained with an excellent n_v time response.

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In order to measure the pressure under an apex seal and the related temperatures, the Mazda rotary engine was modified to operate as an overhanging eccentric shaft-type single-rotor research rig. This rig permitted the exposed center of the rotor to drive a multichannel packaged slip ring through a helical spring absorbing the eccentricity of the rotor. The pressure was measured with an inductance-type diaphragm pressure sensor by compensating the change in the gain due to the heat of combustion by the use of the measured sensor temperature. The effect of the seal configuration on the pressure has been analyzed by comparing the measured pressures with apex seals of 3mm and 6mm thicknesses with the theoretically calculated pressures, treating the vicinity of the apex seal as a labyrinth passage.

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In the absorber of most absorption refrigerating machines, an aqueous solution of lithium bromide at high concentration is irrigated on the horizontal tubes which are cooled by cooling water. To make the mechanism more compact, a spray-type absorber can be considered. The process by which water vapor is transformed into absorbent drops of small size placed in the steam flow is analyzed numerically as a first step towards evaluating performance. From the analysis it is shown that the distributions of temperature and concentration in a droplet are considerably influenced by the circulatory motion which is caused by the contact with the steam flow. The absorption rate increases by about several tens of a percent compared with that for the stagnant droplet, although the increase rate depends upon the Reynolds number and the lapse of time.

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A U-bend coolant supply was applied to transformer windings in an attempt to equalize the flow rate in the horizontal coil ducts and to cool windings uniformly. The U-bend supply, which distributes, coolant equally, is used in heat exchangers. With the use of a two-dimensional winding model with ten coils, the velocity distribution in the horizontal ducts between each of two coils and the temperature rise distribution of the coils are measured for the U-bend supply and the Z-shaped supply (baffle plate type). Experiments prove that the cooling characteristics of the U-bend supply are superior to those of the Z-shaped supply at a low flow rate. Computational programs are developed for the U-bend and Z-shaped supplies to estimate flow and heat transfer characteristics in the windings. The programs accurately predict the velocity distribution in the coil ducts and the temperature rise distribution of the coils.

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