A discrete vortex method combined with the source distribution method was applied to the flow analysis around a rectangular cylinder accompanied by through-flow. The effects of kinematic viscosity ν on drag coefficient and Strouhal number were investigated. The value ν of 0.00001m²/s was the most appropriate one under our conditions. The ratio of vertical to horizontal length of a rectangular cylinder was changed as a calculational parameter. The drag coefficient C_D was in agreement with the reported results. The calculations of the through-flow into the rectangular cylinder were carried out under the same conditions as those in the experiments in a two-dimensional water pool. The calculated and experimental values were satisfactorily in agreement. Consequently, it is shown that our numerical method is very useful in calculating the through-flow into the body.

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The effect of tripping wires on the unsteady cavitating flow past a two-dimensional circular cylinder is experimentally considered. Detailed experimental results are presented for Reynolds numbers Re from 1.33 × 10⁵ to 1.62 × 10⁵ and angles of tripping wires ± α from the forward stagnation point in the range from 25° to 55°. It is found that the development of cavitation is strongly controlled by changing α. At small angles of tripping wires, the cavity length becomes short and the cavity vanishes at α=35°. As a increases, the cavity length, in general, becomes longer. Distinctive variations of unsteady characteristics are detected by the tripping wires.

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The wall effects on a separated flow past an elliptic cylinder are numerically investigated by a method combining the discrete vortex method with the image one. Present results for the mean drag and lift coefficients and the pressure distribution are in fairly good agreement with previous experimental data. The mean drag and lift coefficients and the fluctuating lift coefficient increase with the increase of blockage ratio, but their increasing rates depend on the axis ratio of the elliptic cylinder and its angle of attack. The Strouhal number increases slightly with the blockage ratio, but its increasing rate is small compared to that of the rectangular cylinder.

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In the preceding paper, the axial flow of the liquid fillet generated by a paddle of a rotor was analyzed and compared with experimental data, where it was assumed that the cross section of the liquid fillet was a triangle. However, it was observed that the cross section was a trapezoid rather than a triangle if the width of the liquid fillet was wide, and a wide fillet was observed in the upstream zone when the flow rate was large. The critical width of the liquid fillet was experimentally related to the thickness of the fillet. By utilizing this relationship, the preceding analysis was generalized so that it could handle a trapezoidal liquid fillet for the case of a wide fillet exceeding the critical width. Good agreement of the prediction with experimental data was secured in a wide range of operating conditions.

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The paper presents two and three-dimensional flow separation within a supersonic intake at Mach number 3. Unsteady behavior of a separation bubble at the wedge base in the intake was clarified by using a micro flow sensor which can detect flow reversal in a separated flow. Flow visualization is made by a vapor screen and oil-film techniques. The secondary flow on the side wall and cowl surface involves a large scale of vortices due to the interaction of the oblique shock wave with the turbulent boundary layer.

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We carried out 2-D cascade tests of multiple-circular-arc (MCA) blades with a relatively high camber angle of 56 deg. in the region of inlet Mach number(M₁) 0.4≤M₁≤1.2, and with systematic variations of cascade geometry and incidence angle. Systematic data with respect to inlet Mach number characteristics of the cascade of MCA blades were obtained. The effect of stagger angle on inlet Mach number characteristics was discussed in the second report. In the present report, we discuss the following on the basis of experimental results. 1. the effect of inlet Mach number on the relation ship between incidence angle and parameters of cascade performance (incidence-angle characteristics). 2. the effect of stagger angle on incidence angle characteristics. 3. the relation ship between incidence angle and critical inlet Mach number. 4. the relation ship between stagger angle and stall incidence angle, reference incidence angle. 5. the relation ship between limit in the available range of operation of the incidence angle and inlet Mach number.

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The guide vanes and the impellers of turbomachinery operate in shear flow due to the wall boundary layer of the casing and the boss, and further operate in a supercavitating condition in the case of high-speed hydraulic machinery. This paper aims to propose an analytical method of solution for the three-dimensional supercavitating thin wing in shear flow between two parallel plane walls. An equation of motion and boundary conditions are formulated, and the problem is transformed into two problems in the same way as the existing noncavitating theory. The first problem is that of spanwise direction and has an analytical solution. The other is that of the section plane normal to the spanwise direction, and is reduced to a simultaneous integral equation which is solved by introducing the mode function method.

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The aim of this study is to clarify the streamwise vortical structure (ribs) in the two-dimensional vortical core region of a turbulent mixing layer. To achieve this purpose, the velocity fields of temporally growing turbulent mixing layers with initial random fluctuations were calculated numerically by using large eddy simulation, and vortical fields were investigated by using 3-dimensional graphics. The rib structure was observed, and the structure of these vortex tubes in the core region was made clear. From these studies, the following conclusions were obtained. (1) Ribs are formed in the blade region. (2) Ribs are connected in the core region.

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A turbulent flow in a two-dimensional channel with fluid injection from one wall has been numerically simulated by large eddy simulation (LES). The Reynolds number based on the channel width and bulk velocity is 4900. The total grid number used in the calculation is about 1.23 million, which allowed a highly resolved turbulent flow simulation. In the flow field, events of production, redistribution and dissipation of turbulence energy are observed in streamwisely separated locations. Therefore the LES data are instrumental in understanding the turbulence structure as well as in investigating turbulence models. The present result shows that the pressure-strain terms in Reynolds stress equations are related to the streamwise vortices with intensified pressure fluctuation, rather than to the direct isotropization.

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This paper analyzes an unsteady viscous incompressible flow between two parallel disks with a time-varying gap width and a central fluid source whose total pressure is arbitrarily varied with time. The theoretical results obtained in the authors' previous papers, which analyzed the case where the rate of flow from the source is forcibly varied with time, are utilized, and the flow is now solved under the boundary conditions of a given time-varying total pressure of the fluid source by the Houbolt method. Experiments were carried out for the special case where the gap width is varied sinusoidally with time, and the total pressure of the fluid source is kept constant by making a hole at the center of the upper disk. The theoretical results are in good agreement with the experimental ones over a wide range of the oscillatory Reynolds number and nondimensional amplitude of the gap width.

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A shock tube wall boundary layer of a dilute dusty gas is studied by a numerical analysis. Transverse motion of particles are taken into account by introducing the Saffman type lift force, which is induced in shear flows if a considerable slip of velocities exists between the gas and the particle motions. The result indicates that in case of large particles the boundary layer is constituted with a particle concentrated layer at a considerable distance from the wall, a clean gas layer on the wall, and a strayed particle layer between the two. While in case of fine particles, typically smaller than 10 μm diameter, the effect of the boundary layer mass sink is superior to the particle lift force, and the boundary layer takes a particle dispersed profile. In both cases, however, the wall heat transfer indicates monotonous change similarly to a clean gas heat transfer, since the process is almost determined in the clean gas wall layer.

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This paper deals with the pressure generated btween two flat disks in the fluid, one lower disk fixed and another upper disk moved perpendicular to the fixed lower one. Results obtained from the experiment are as follows :When the upper disk approaches the lower one, viscoelasticity of the fluid decreases the pressure below the pressure of corresponding Newtonian fluids, whereas in the case of separating the upper disk from the lower one, the pressure takes minus values of about - 3.5 × 10⁵Pa and the magnitude is increased by the viscoelasticity of the fluid used. This minus pressure is raised to a vacuum pressure by the cavitation inception inferred, the vacuum pressure holds constant for a duration and finally the pressure abruptly increases by the cavity extinction which accompanies pressure vibrations of high frequencies. These experimental results are qualitatively explained using the assumption of squeezing flow and the constitutive equation of the second order fluid.

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Two-dimensional incompressible Navier-Stokes equations in vorticity-velocity formulation and the energy equation for temperature have been solved using a method of lines approach. The spatial derivatives are discretized by means of the central finite differential approximation, and the resulting system of the ordinary differential equations in time is integrated by a rational Runge-Kutta (RRK)scheme. Poisson equations for velocity are solved by a Group Explicit Iterative (GEI) method, using the multigrid technique. The GEI method is a fully explicit scheme so it takes advantage of the supercomputer's architecture. As the verification of the scheme, the classical problem of natural convection in a square cavity of Boussinesq fluid has chosen. Numerical calculations are obtained at a Prandtle number of 0.71 corresponding to air and Rayleigh number up to 10⁸. The results of calculation essentially agree well with those of de Vahl Davis.

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Unsteady flows of natural convection in a square cavity are investigated numerically using the GSMAC (generalized and simplified marker and cell) finite-element method at high Rayleigh numbers(Ra =10⁶ - 10⁸). The present result at Ra = 10⁶ is compared with the bench mark solutions by de Vahl Davis and Saitoh-Hirose. Both results are in good agreement. The validity of BTD (balancing tensor diffusivity) suggested by Dukowicz and the multi-pass explicit algorithm suggested by Donea are discussed. As a result, it is found that the GSMAC method is very stable and accurate at high Rayleigh flows as at high Reynolds flows. The complex transient phenomena at high Rayleigh numbers are successfully observed.

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Power expended theorems or energy methods are generally used for structural analysis in materials science. These theorems are constructed from the standpoint of statics and most of them cannot be employed when dissipative phenomena are considered. In the present paper, a power expended theorem for compressible magnetic fluids is obtained for the first time considering both internal rotation and electrical conduction being based on the kinematic balance equations for conducting magnetic fluids assuming that suspended fine particles rotate rigidly and the velocity of fluids is much smaller than that of light. Developing this theorem, some useful information concerning both the flow field and the electromagnetic field in the flow of magnetic fluids can be expected to find.

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This paper deals with a real-time measuring method of the progressive wave of fluid velocity pulsation in a pipe, which is necessary for the development of an active attenuator of pressure pulsation in liquid piping systems. The principle of the present measurement is to obtain the fluid velocity (cross-sectional average velocity) signal by integrating the difference between signals produced by two pressure transducers spaced a suitable distance apart, on the basis of the momentum equation, and then to obtain the progressive wave component of fluid velocity pulsation from the pressure and velocity signals by a simple algebraic operation according to the plane wave theory. A general purpose digital signal processor (DSP) has been used for the high-speed calculation necessary for the real-time measurement. The measured values agree with the theoretical results within the experimental errors mainly due to the detection accuracy of the pressure transducer and the resolving power of the A/D converter of DSP, except for the frequency ranges of nearby resonant frequencies. The applicable limit of this measurement is the frequency range above about 15Hz mainly because of the detection accuracy of the pressure transducer.

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Gasoline fuel droplet size, velocity and spatially relative frequency were measured at an intake valve annular passage with an LDV, which has been equipped with a droplet size analyzer. The analyzer acquires the light intensity scattered by a droplet and the number of Doppler Burst waves. In this paper, the effects of fuel injector location on droplets at the valve passage, which play a great role in fuel mixture formation, have been investigated. Fuel was injected to a poppet valve near the valve, and in the other case, to the intake port 100mm upstream of the valve. The droplets enter from the confined valve periphery even in the upstream injection case. The SMD at the high frequency position is small in the upstream injection, but is large in the valve injection case. This is explained by the difference in airflow and droplet size. The delay time of droplet appearance at the valve passage from the injection start is different in these cases and drastically effects fuel mixture formation.

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The purpose of the present paper is to clarify the pumping effect obtained by a vibrating choke nozzle in a stationary liquid and to investigate the possibility of practical applications. The relation of liquid rise height to the vibration conditions was investigated experimentally. By the liquid velocity measurement, pressure measurement and the flow visualization, the flow mechanism was made clear and a suitable geometrical form for the vibrating choke nozzle was determined. It has been suggested that there is a good possibility of realizing practical transportation machinery by utilizing the pumping effect.

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In this report, the analytical method developed in the previous paper was refined to deal with the cascades with steady blade loading. The unsteady aerodynamic force acting on the linear oscillating cascades with tip clearance was calculated numerically by use of the vortex lattice method. Tip vortices were assumed to consist of linear vortex segments, and their paths were determined on the basis of experimental data measured with a 5-hole pitot tube. Calculated damping forces showed good agreement with the corresponding experimental data. The effect of tip clearances on the flutter boundary was also investigated, and it was revealed that the cascade flutter was suppressed owing to the presence of tip clearances. When the blade oscillation was destabilized, it was found that the unsteady aerodynamic force became the exciting force at the blade-tip side sooner than at the hub side.

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In order to improve the high-speed performance of outboard engines, we carefully observed cavitation aspects, especially those of clear attached cavities around a thick symmetric hydrofoil conforming to the profile of the engine strut. in a two-dimensional water flow when "violent" cavitation vibrations take place. The behavior and the associated vibrational accelerations were measured through stereo-high-speed photography, high-speed movies and an accelerometer. Such an attached cavity appears periodically on the foil back-surface, resulting in very unstable, abrupt cavity breakdown accompanied by periodical shedding of bubble clouds into the downstream. A reentrant jet appearing at the cavity trail plays an important role both in the breakdown and in the vibrations. Such vibrations usually result in a drastic change of flow pattern, so that highly erosive types of cavitation and/or a marked size change in many bubbles flowing into the wake often arise.

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This paper describes the relation between turbine efficiency and rotor blade loading parameters. Tests were carried out on the 12 kinds of rotors, which had the same velocity triangle and meridional contour, but different blade number (8-11) and blade length. Momentum thickness and shape factor of boundary layers obtained from the results of a quasi-three dimensional flow analysis were used as the rotor blade loading parameters. It was found that blade loading was evaluated by the shape factor of the mean stream surface, and the efficiency of turbines was influenced by the blade shape of an exducer.

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In the CO₂ gasdynamic laser (GDL), the mirrors, which make up the laser resonator, are usually set in the recesses of a duct to prevent damage or contamination of the mirrors. Consequently, a cavity is formed in the duct, and the gas flow is disturbed by the cavity. In this paper, two-dimensional numerical analysis which considered the cavity in the duct was carried out. From the numerical results and experimental data, the influence of the cavity on the small-signal gain was discussed. According to the numerical results, the small-signal gain decreases in the case which considered the cavity in the duct. This tendency was in good agreement with the experimental ones.

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Can fishes pass safely through the rotating runner of water turbine ? We have interest in this problem. If possible, many ultra low head water turbines will be set in the river and we will enjoy our life with many kinds of river fishes. In this paper, several conditions of safety pass in the rotating runner were investigated and several pictures were taken to demonstrate the fact that fishes can pass through the rotating runner from downstream to upstream.

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Rotating stalls in a centrifugal impeller/vaned diffuser system were studied experimentally. Experiments were carried out for various clearances between a 2-D impeller and 2-D vaned diffuser (a=20°: Z=18) to clarify the impeller and vaned diffuser interaction. The results showed that the interaction has large effects on rotating stalls of the impeller and/or the vaned diffuser. Various types of rotating stalls were observed: coupled rotating stall with smaller clearance, diffuser rotating stall with larger clearance, unstable diffuser rotating stall with intermediate clearance, and impeller rotating stall.

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Rotating stalls in a centrifugal impeller/vaned diffuser system were studied experimentally and analytically. In this report, the diffuser vane angle and the number of vanes are changed and it is shown that the impeller-diffuser interaction effects on rotating stalls are qualitatively unchanged by those parameters. Simple expressions of the results of 2D stability analysis are given for the cases of isolated impeller, impeller/vaned diffuser combination, vaned and vaneless diffusers. Comparison with the experimental results shows that the models can be used for the identification of principal origin of various rotating stalls observed.

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This paper discribes the operating characteristics of a mechanical governor installed for blade pitch control, rotor speed control and generator power control in a variable-speed wind turbine generator system (VWTG). The VWTG is equipped with a 2-bladed teetered rotor of 15-meter in diameter and a 22-kW generator. Since the centrifugal forces of the weight-elements of the governor are utilized as direct control forces, the control are performed firmly and rapidly. The operation data show that the governor works satisfactorily to regulate rotor rotational speed and the generator power within the designed range of operation.

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The Trans Tokyo Bay Tunnel is planned with longitudinal ventilation system equipped with a vertical shaft and electostatic precipitator(EP) stations. Because the tunnel will be excavated in terms of shield method, the EP stations have to be in the tunnel cross section, above the traffic room. The authors have established a theoretical consideration which gives pressure rise effect of an EP station. A simplified model is proposed based on Bernoulli's theorem and momentum theory. Scale model of 1/40 is constructed and experimentally tested. Pressure rise performance is measured under various disposal ratio of the EP station. The result is compared with the theoretical one, which gives rather good agreement except that some discrepancy caused by losses is observed. In addition to pressure characteristics velocity distribution is also measured. After the injection into the tunnel, the high speed region is observed to spread along the tunnel wall.

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The advanced absorption cycle with the circulation of the auxiliary refrigerant between the absorber and the evaporator has been studied to improve the efficiency and to utilize low-temperature heat sources. As an initial step, the 1st report focuses on the cycle simulation to verify the operating principles and the performance characteristics. In the cycle simulation, a counterflow-type heat exchanger was assumed for each component with the water/LiBr as the main refrigerant and absorbent combination. Since the auxiliary refrigerast should be immiscible with the main fluid pair, Pentanol was selected as the auxiliary refrigerant. Computer simulation was carried out based on these fluid combinations and the cycle performance was obtained. A comparison of COP between this cycle and conventional ones was made.

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Now a days, it is necessary to develop an advanced single effect absorption cycle which could reach the double effect efficiency, and keep the advantages of a single effect cycle for the viewpoint of effective utilization of energy, cost and miniaturization. In this study, authors proposed in the 1st. report a high performance absorption cycle with the circulation of an auxiliary refrigerant and expected performances were calculated by computer simulation. The purpose of this paper is to show the technical choice of auxiliary refrigerant which lays an important role on the efficiency of this cycle and to verify the principle of this absorption cycle. So authors made an experimental apparatus in order to clarify the performances of a real type experimental system in actual conditions, and tested the performances of this system. The results of these experiments was to clear the effect of chilled water and auxiliary refrigerant for this absorption cycle. Also the principle of this cycle was shown and authors verified the practicability and usefulness of this absorption cycle.

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Natural circulation of water was investigated in a rectangular loop by tripping the circulating pump of the loop, which is 2.03 m in height and 0.81 m in width and is equipped with a heater and three coolers. The plane including the loop path is situated vertically, and the cooler arrangement was changed. In our experimental conditions, flow boiling and the transition of flow pattern occurred in the riser depending on the variation of mass flow rates, which was accompanied by the oscillations of water temperatures and pressure drop in the downcomer. Three modes of the transition were distinguished for the present cooler arrangements. Irrespective of these flow instabilities, the mean values of mass flow rates were maintained at the level of the single-phase natural circulation. The photographs of flow patterns such as bubble and slug flows were analyzed by the image processing system.

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An optical method is used to estimate the variation in time of the thickness of a liquid film which is formed on a shock-tube endwall behind a reflected shock wave. The variation of the film thickness is compared with theoretical ones based on matched asymptotic expansions. The condensation parameter of ethanol vapour is deduced from the comparison between experiment and theory and is evaluated to be 0.05. This value is in rather good agreement with a theoretical one on the basis of chemical kinetics.

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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 component of velocity were measured. A substantial increase in the heat transfer was noticed, 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 presents two peaks in the spanwise direction, each one associated with different vortices. The corner longitudinal vortex, which arose in the generator's front corner, was found to be associated with one of these peaks. The effects on the heat transfer of varying the generator's size, angle of attack and geometry were clarified.

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Is this paper, heat transfer and fluid flow of natural convection around two horizontal cylinders are investigated experimentally. Heat transfer coefficients were first measured in a wide variety of interference aspect ratios H/D. The results showed that the heat transfer rates around two cylinders for 1<H/D<4 became larger than those for a single cylinder. On the contrary, the retardation of heat transfer for H/D<1 was observed. Then, the surface temperature patterns were also visualized by a liquid crystal sheet. It was revealed from the visualization that low-temperature streaks appeared on the heat transfer plate, and they played a significant role in heat transfer.

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Experimental and analytical studies were carried out to investigate the heat transfer performance in a so-called dream pipe where the heat transfer in liquid was enhanced by sinusoidal oscillation. The heat transfer process in the dream pipe was formulated using a simplified lumped-parameter model, and the effective thermal diffusivity was obtained analytically. The effective thermal diffusivity increased with increasing frequency and amplitude of the oscillation. The numerical simulation of heat transfer agreed with that of the experiment, and thus, the applicability of the presented model to the estimation of the transient behavior of the dream pipe was verified.

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A numerical analysis of two-dimensional vapor flow was conducted in the condenser region of a thermosyphon in the prerence of a noncondensable gas in that region. The governing equations are composed of three conservative equations of a vapor gas mixture including binary diffusion and that of species concentration. In the diffusion equation, two conditions of constant mass concentration and constant molar concentration are examined, and their results are discussed. The effect of a liquid film on the heat transfer rate of vapor condensation on the condenser wall is considered, with the assumption that a Clausius-Clapeyron relation holds at the film-vapor interface. A finite difference scheme is employed in the calculation, and the results are compared with those of the experiment. Agreement between the two is fairly good, which implies the validity of the numerical model in analyzing the mechanism of such a flow field.

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This paper presents a variational principle which connects solid and fluid temperature fields in the analysis of thermally coupled problems. The principle satisfies the equilibrium condition of heat flux on the boundary. The combination of this principle and a hybrid type virtual work principle for flow problems is applicable to the analysis of the thermally coupled problems between solids and fluids. This paper also formulates a finite element method (FEM) based on the combined principle. The FEM eliminates an iterative calculation to satisfy the equilibrium condition on the boundary. The FEM is applied to a heating problem for a vertical plate with a heat source. The use of the FEM gives good accurate results in comparison with experimental ones.

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The temperature has been measured in a field in which laminar hydrogen (6.0 m/s at the center of a burner exit) was injected into a co-flowing air stream (6.0 m/s) with some kinds of grid turbulence. It is shown that the ratio of a laminar flame length to the turbulent one is proportional to the turbulent Reynolds number, Re_ι, (integral scale is considered a characteristic length) in the measured extent (Re_ι≤1000), and therefore that the integral scale of a reactant flow is an important parameter for the flames in this paper. The width of a flame displacement is estimated from the temperature profiles when the flame is assumed to be a wrinkled laminar flamelet. The width is also measured directly by a flow visualization method. Both the widths obtained by the two different methods agree well with each other. This fact indicates that the turbulent flame in this paper can be treated as a wrinkled laminar flamelet.

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An improvement on the two-equation heat-transfer model developed by Nagano and Kim (1988)has been made in conjunction with an accurate prediction of near-wall scalar turbulence. The present model automatically reproduces the exact wall limiting behavior of turbulent quantities related to heat and momentum transfer under arbitrary wall thermal conditions. The proposed model was tested by application to turbulent boundary layers along a flat plate with a uniform wall temperature or a uniform wall heat flux. The results satisfied the exact physical requirements, and agreement with the experiment was generally good.

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A new-type compact heat exchanger has been suggested, and the fundamental heat transfer performance has been studied chiefly from experimental aspects. The design concept is based on the new principles for heat transfer enhancement, namely, "reducing the size of heat transfer surfaces" and "arranging a couple of turbulence promoters to cause drastic change in turbulence structure". To satisfy such requirements, the heat exchanger consists of fine tubes (o. d.- 1 mm) and woven threads (d.- 0.3 mm) : the latter play a combined role of both turbulence promoter and fin. The maximum heat transfer coefficient obtained in the experiment is fourteenfold larger than that around a cylinder without threads. Since the fin-effect contribution to the heat transfer enhancement is theoretically estimated to be less than tenfold, the turbulence-promoter effect is also considered significant. Owing to the combination of the woven threads and the very small characteristic length, the heat transfer coefficient per unit projected area is about 5 × 10³ W/(m²K), and that per unit volume reaches 3 × 10⁶W/ (m³K).

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The thermophysical properties of toner are required for temperature analyses and evaluations of fusing performance of the toner. However, the thermophysical properties have not been thoroughly observed. The effective thermal diffusivity and conductivity of the toner powder in standard atmosphere were measured. To solve the problem of preparing the specimen, an assumption of semi-infinite length for the specimen was employed. To obtain the measured value effective for the fixing process, irradiative heat flux was employed. In this manner, the following points were noted : the toner thermophysical properties are sensitive to air between the toner particles, toner particle diameter, quantity of carbon in the toner and molecular Weight of resin : and higher thermal diffusivity and conductivity raise toner-paper interface temperature.

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The formation of ice growth that occurs in branched pipes (branch angle θ=45° and 90°)containing water flow was investigated experimentally. The experiments were carried out under various experimental conditions over the range of Reynolds number (based on pipe i.d.) Re=420-12500 and cooling temperature ratios of the freezing parameter T(= T_f - T_w)/(T_∞ - T_f), T_f=0°C, T_w= cooling water pipe wall temperature, T_∞= flowing water temperature)=1.3-11.1. From the visualization of ice formation in the pipes, the branched pipe with flowing water was first blocked by ice formation : subsequently, the main pipe downstream of the branched portion was frozen off, and eventually the main pipe upstream of the branched portion was blocked by ice formation. As a result, freezing of the remaining water in the branched portion resulted in a pipe rupture at around the branched portion of the pipe. The transient behavior of ice formation, according to time proceeding, was expressed as a relationship between the pressure loss coefficient f and the Reynolds number Re for various cooling temperature ratios T. In addition, the critical condition of the complete ice blockage in branched pipes was obtained with experimental correlation equations in terms of T and Re.

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An experimental investigation was performed on predicting drypatch characteristics based on the transient heated surface temperature and static pressure characteristics, using a flat-plate-type obstacle in a rectangular channel. Three points were clarified. (1) A relationship was obtained between the drypatch occurrence and the transient heated surface temperature in the obstacle and its downstream side using a map of the drypatch occurrence around the obstacle. (2) The mechanism and places of drypatch occurrence were investigated using the Boiling number Bo on heat transfer and the steam Weber number We_υ on fluid flow as factors affecting drypatch phenomena. (3) There was a good correlation of drypatch occurrence between the steam Weber number and higher transient heated surface temperatures.

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Recently, treatment of the numerical heat transfer and fluid flow in airconditioning problems has become popular. Their solution may help to optimize the blowing direction from the air conditioner. In these problems, it is common that the grid line and velocity directions of the flow are not closely aligned, and the Peclet number of flow is large. A large error may result from the false diffusion when upstream differencing of convective terms in the conservation equations is used in that condition. Raithby introduced two new schemes for 2-D problems which reduced this error, but retained the advantages of upstream differncing: they are SUDS and SUWDS. In air-conditioning problems, multidimensionality is required. We propose two new schemes, SUDS-3D and SUWDS-3D, which extend Raithby schemes to 3-D problems. Solutions to some problems were obtained by our new schemes and compared with those obtained by conventional methods.

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Catalytic combustion is considered to be the best combustion method in order for a gas turbine to achieve lower NO_x levels. However, the disadvantage of this method is that the catalyst temperature would reach the same tomperature as hot gas or higher, and so the life span of the catalyst would not be sufficiently long for practical use with a gas turbine. A new method of catalytically ignited premixed combustion which will keep catalyst temperatures at favourable levels has been developed.

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Effects of various basic factors of combustion conditions and coal properties on thermal NO_x formation behaviors in pulverized coal combustion have been experimentally clarified, and a theoretical analysis for the flame structural change around a coal particle has been performed including full chemical kinetics of prompt NO_x formation. Thermal NO_x concentrations much higher than that predicted by the extended Zeldovich mechanism have been experimentally observed even in the usual pulverized coal combustion conditions. The contribution of thermal NO_x to the total NO_x rapidly increases with the increases of flame temperature and oxygen-fuel stoichiometric ratio especially for high volatile coals. Both the large amount of thermal NO_x formation and effects of various factors on it have been well explained by considering the prompt NO_x formation in the flame zone around each particle through HCN and NH formed by the reactions between N₂ in air and hydrocarbons in the evoluted volatile matter.

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In order to eliminate the counterflow phenomenon of flame at the combustion point of fuel as well as design a compact burner with high capacity, it is desirable that a centrifugal fan with the characteristic of high discharge pressure should be developed. On the design condition that impeller shapes are fixed, the relationship between the discharge performance and the various design factors of the casing was evaluated by systematic experiments. As a result, the most suitable casing shapes and new assembly parts to increase the disharge pressure were proposed, and an investigation of its effectiveness was performed.

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In the coal gasification combined-cycle power generation system, it is necessary to develop a high-temperature gas turbine combustor using coal-derived gaseous fuels, which has high thermal efficiency and low emission of pollutants. Combustion tests were conducted using a full scale combustor for a 150-MW-class gas turbine under atmospheric pressure. Furthermore, high pressure combustion tests were conducted by using a 20-MW-class gas turbine combustor. Main results are as follows : Thermal NO_x emission was very low in a combustion of coal derived low Btu gaseous fuel, and its emission level was 15 ppm under a full load condition at of the combustor exit gas temperature of 1300°C. The tested combustors were not designed for low fuel NO_x combustion. Therefore NO_x emission resulting from l000 ppmv of ammonia accounted for about 95 % of the total NO_x emissions, The ammonia conversion to NO_x decreased slightly with increasing of combustion pressure.

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The purpose of the present work is to study the possibility of removing the various pollutants contained in combustion flue gases by using energetic species produced by plasma injection. By feeding the gas mixture (N₂ + O₂ + CO₂ + NO + SO₂ + H₂O) into argon arc plasma, the effects of O₂, CO₂ and H₂O on the formations of nitrogen oxide NO and carbon monoxide CO were studied experimentally, and the possibility of removing NO and CO by injecting ammonia into the plasma, and the removal of SO₂ were discussed. Furthermore, plasma temperature was measured by means of a thermocouple, and the residence time of flue gas in the high-temperature region was obtained.

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A new combustion system called a jet-mixing-type combustor was designed to obtain a nonluminous blue flame of a kerosine spray. A spray was injected by a conventional-type swirl atomizer into the combustor and combustion air was introduced through a baffle plate with 16 inlet holes. The principle of this combustion method was revealed as a prompt mixing of the air and the spray, which was achieved by a high-speed air jet. The combustion characteristics such as combustion stability, temperature distribution and exhaust emissions were compared with a conventional swirler-type combustor. NO and THC emission levels exhausted from nonluminous kerosine flame were lower than those exhausted from the swirler-type combustor.

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The test results on the dynamic behavior of the free piston displacements, the hydraulic pressures and the gas pressure on the first cycle at the start of the engine at room temperature are reported in this paper. It becomes clear that the entire cycle consists of four processes, that is, the compression, expansion, bounce and damped oscillation processes. Dynamics of the free piston in these four processes are discussed in this paper. Furthermore, the value of the polytropic index on the compression process is obtained experimentally. The energy losses in the compression process are also discussed in this paper. It becomes clear that the main sources of energy losses are piston friction and pressure loss in the pilot-operated check valve. Finally, the firing operation is repeated every 0.5 or 1.0 second, and the free pistons stop after each operation.

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