A theoretical analysis is made on laminar open channel flows of magnetic fluid induced by a traveling magnetic field which is applied with a stator of a single-sided linear induction motor. The induced flows are mainly in the direction opposite to the traveling direction of the magnetic field and in proportion to the phase velocity of the magnetic field. The velocity profiles are greatly affected by dimensionless wave number k of the magnetic field. Near the bottom of the channel, the theoretical velocity distributions agree well with the experimental ones which are measured with a laser optical fiber velocity sensor. However, the experimental velocity distributions become larger near the free surface.

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The authors experimentally studied a shear flow of a water-based magnetic fluid between concentric annuli. The experiment was carried out by changing the roll accerelation of the outer cylinder, and the moment acting on the inner cylinder was measured. Experimental results were discussed in the following three ways. At first the magnetic fluid was treated as a Newtonian fluid, and a small difference in the flow curves was found. Next the power law theory was applied in order to explain these differences. Finally the authors examined this flow problem using the micropolar theory, which gives the theoretical relation between the moment acting on the inner cylinder and the roll accerelation of the outer one. In this relation, a coefficient denotes the micropolar effect. The authors measured this value and showed the effect of the substructure on the fluid.

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Torque characteristics are investigated experimentally for spherical Couette flow, using manetic fluids. Torque measurements were obtained for the situation where the inner sphere was rotating while the outer sphere was kept stationary. The magnetic field was imposed on the fluid, using a bar magnet which was situated in the inner sphere. There are two distinct regions before the onset of the turbulence flow regime. In the laminar flow regime the torque increases when the magnetic field is applied, indicating an increase in the effective viscosity. However, in the laminar transition regime, the effect of the magnetic field on the torque characteristics decreases as the rotation rate increases. The critical Reynolds number is observed to shift toward higher values.

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An experimental study is presented for the subsurface phenomena and the splashing produced by the impact of magnetic fluid drops against the target surface of various liquids under nonmagnetic and magnetic fields. Magnetic fluid used in the experiment as the projectile drop was water-based ferricolloid W-35. Kerosene and distilled water were used as the target liquids. High-speed movies were taken of the formation of the subsurface cavity and the sedimentation of magnetic fluid during the splash of a drop. Without applied magnetic fields, the sequence of events following the impact of a magnetic fluid drop was usually found to be similar to that of a water drop in the formation of the subsurface cavity and the Rayleigh jet. On the other hand, under the applied magnetic fields, the size of the subsurface cavity was very small, and the Rayleigh jet was also very small. The sedimentation velocity of magnetic fluid in distilled water under magnetic field was different from that in the kerosene target.

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The characteristics of oscillatory pipe flow driven by the reciprocating motion of a magnetic fluid column are examined mainly under the conditions where the waveform of the oscillating magnetic field is rectangular. The displacement of the fluid column for the rectangular waveform of the magnetic field is larger than that for the sinusoidal waveform. The phase difference between the magnetic field and the displacement of the fluid column increases with the frequency of the applied magnetic field in the lower frequency region. However, it decreases with the frequency in the higher frequency region, in contrast to the sinusoidal waveform. Experimental data on the vibrating characteristics agree qualitatively with the predicted results. The response of the fluid column to sudden change of the magnetic field strength is also examined.

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A new fluid-drive gas compressor using magnetic fluid and traveling magnetism is investigated. Its principle is as follows. Consider a cylinder equipped with a linear motor which generates successive magnetic fields traveling along the cylinder axis. At one end of the cylinder, magnetic fluid (MF) and gas flow alternately into it. Immediately after entering, the MF is formed into successive slugs by the magnetism of the linear motor, and each slug is drawn towards the other end. The gas between MF slugs can be thrust and thus compressed. In order to confirm the feasibility of this compressor, a simplified test was conducted by means of permanent magnets instead of the linear motor. The results of both this test and the comparison with the analytical model proposed here are presented and discussed.

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Electrorheological fluid (ER fluid) is a kind of two-phase fluid. It shows rheological behavior when an electric field is applied to it. Although numerous theoretical and experimental studies have been conducted at many laboratories and institutions, there is still an unsettling controversy regarding the fundamental mechanism involved in the ER effect. In this investigation, first, the effects of electric fields, shear rates and concentrations of dispersed particles on shear stress acting in the fluid were studied. Then, under various strengths for applied electric fields, the velocity profiles of ER fluid between electrodes were measured with a laser Doppler velocimeter. These measurements show that the fluid flow is divided into three layers : an almost-solid-state layer, two-phase layer and pure-liquid layer.

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The static yield stress of Electrorheological Fluid(ERF) was calculated. The result is in good accordance with the experiment. Using a particle chain model to estimate the interactions of particles, we solved Maxwell equation by the finite differential method, and calculated Maxwell stress directly. In this method, both multipole and manybody effects between particles, which were not included or were treated inappropriately before, were treated exactly. The relationship of the static yield stress to the electric field strength and the particle size is also derived from our model.

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In the present paper, the conservation laws for micropolar electrically conducting fluids with many small fine particles are discussed on the basis of a nonequilibrium thermodynamics relation which leads easily to precise expressions of the energy flux vector and the dissipation function of micropolar fluids. The thermodynamic pressure defined here is based on the local conservation laws of mass, momentum and entropy, which satisfies the mutually complemental relation with the sum of kinetic energy and internal energy. As a result we obtain Euler's thermodynamic relation as a homogeneous function in the first order of entropy, density and pressure. The above discussion takes into account the three parts of nonpolar fluid, polar fluid and micropolar electrically conducting fluid.

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The applications of MHD (magnetohydrodynamics) devices have been rapidly developed in recent years. Thermo-electrically conducting fluid has been increasingly used in the manufacturing process of semiconducting material such as silicon crystal. In the present paper, we propose a new GSMAC (generalized simplified marker and cell) finite element method coupling with the B method. The present scheme efficiently satisfies both conservation laws of mass and magnetic flux. In order to verify the present scheme, we discuss the natural convection of thermo-electrically conducting fluids in a square cavity under a constant magnetic field. The numerical results obtained here agreed well with the past experimental and numerical results. Moreover, we estimate the effect of the induced heating term on a temperature field.

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Effects of transversely applied magnetic fields on induced flow and frictional resistance of enclosed rotating disks have been studied. Torque data were obtained over a range of disk Reynolds numbers from l0⁵ to 2 * 10⁶ for axial clearance-disk radius ratios s/a from 0.025 to 0.15 for a constant radial tip clearance, and pressure and potential difference were measured for laminar and turbulent flows.

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In order to improve qualities of a single crystal, it is essential to understand thermal and hydraulic behavior of a melt flow during single crystal growth by the magnetic Czochralski method. Since flow and temperature distributions in the melt show non-axisymmetric flow patterns and temperature oscillations, an unsteady three-dimensional magneto-thermal-hydraulic simulation is necessary. Development of a numerical simulation code requires use of an effective algorithm in terms of memory usage and CPU time, because the simulation tends to become a large size problem. In the paper, the one-point integration method was applied, and the result showed reduction in memory usage and CPU time compared with the conventional Gauss-Legendre integration. Effects of the magnetic field on melt behavior were investigated by varying the magnitude and the direction of an imposed magnetic field.

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A plasma jet can be regarded as a multifunctional fluid, since it has high enthalpy, chemical reactivity and is easily controllable. Hence, it has been extensively utilized in plasma processing and in the new types of energy conversion systems. In these industrial applications, it is one of the effective and important methods for controlling precisely the characterization of plasma flow by applying the electromagnetic field. In the present study, a new numerical analysis of the continuum approach based on the two-temperature model for the description of a low-pressure plasma jet in the strong magnetic field is presented taking the temperature and pressure dependent and heterogeneous transport properties and the microscopic behavior of electrons into account. Numerical examples are shown to clarify the effect of the magnetic field on the thermofluid characteristics of heavy particles and plasma parameters such as electron number density and electron temperature in the nonequilibrium plasma jet. In addition, the effects of operating pressure and thermal boundary condition at the wall on the characteristics of the plasma jet are discussed.

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Effects of the spatiotemporal inhomogeneity of a plasma in thermal equilibrium on the local and output characteristics of a Faraday-type MHD generator were investigated using numerically modeled turbulence data of the temperature and the velocity. The conditions of Saha equilibrium in the range of the temperature level and the frequency were given. The mean conductivity formula was also given as a function of the rms fiuctuation. The average correlations between the electric field fluctuation and that of the conductivity in the mean Ohm's law were evaluated in terms of the mean electrical parameters. Rosa's G-factor was modified to include the spatiotemporal conductivity variance. It was shown that the 1D anisotropic model somewhat underestimates the effective plasma resistance of the turbulent MHD plasma with 2D anisotropy.

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The purpose of present paper is to report the experimental studies of the gas dynamic characteristics, especially those such as shock wave-boundary layer interaction, in a supersonic MHD generator with constant area channel. The plasma for MHD generator is produced by a shock tube. In order to obtain a clear and sharp image of shock wave-boundary layer interaction in MHD generator channel, the color schlieren method has been employed. The experimental results show that a pressure rise occurs through the shock wave. The schlieren photographs show the bifurcation of shock wave and the separation bubble due to the shock wave-boundary layer interaction in MHD channel. As a result of this interaction, the passing of the shock wave reduces the output current over an axial distance of several duct diameters downstream.

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MHD power generation experiments have been performed for disk-type generators with different channel shapes. The increase in the enthalpy extraction ratio due to enlargement of the area ratio has been shown experimentally and the highest enthalpy extraction ratio of 18.0% was achieved. The experimental results have shown that for a generator with a large area ratio, the wall static pressure in the MHD channel is kept lower than that for a small area ratio generator. These phenomena suggest that a high Hall parameter is obtained by enlargement of the area ratio. Furthermore, a swirl ratio at the channel exit was measured and was characterized by the ratio of the Hall current and the mass flow rate of the working gas.

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The vortex shedding frequency and the wake structure of a sphere in a uniform shear flow were experimentally investigated. The Reynolds number Re, which was defined in terms of the sphere diameter and approaching velocity at its centre, ranged from 200 to 3000. The shear parameter, which was the transverse velocity gradient of the shear flow nondimensionalized by the above two quantities, was varied from 0 to 0. 25. The critical Reynolds number beyond which vortex shedding from the sphere occurred was found to be lower than that for a uniform flow and decreased approximately linearly with increasing the shear parameter. Also, the Strouhal number St of the loop-shaped vortex which was discharged from the high-velocity side became larger than that for the uniform flow and increased as the shear parameter increased. Moreover. the formation and structure of the sphere wakes corresponding to each range of Reynolds number, which was classified into three regions, were examined on the basis of successive photographic evidence. It was found that the wake configuration did not differ substantially from that for a uniform flow.

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Theoretical and experimental studies of the behavior of a bubble near a plane rigid wall were made. A bubble was generated by focusing a ruby laser into water and the subsequent behavior was observed by means of high-speed photography. The experimental results were compared with the numerical predictions obtained from the boundary integral method as well as from the image theory and we found excellent agreement. A systematic investigation has been carried out on bubble migration and microjet formation, which are considered to be very important phenomena in relation to the impulsive pressure generation during bubble collapse.

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The MAC (Marker and Cell) method was applied to simulate a single rising bubble, in order to investigate the possibility of direct simulation of the motion and shape of a bubble. Bubble shapes and terminal velocities predicted from axially symmetric two-dimensional calculation were compared with the experimental data summarized by Grace et al. Except for the one case in which the bubble shape differed most from a sphere, the MAC method could predict motion and shape under wide ranges of Eotvos numbers and Morton numbers. Finally, the departure of a bubble including bubble splitting from a wall is analyzed, and detailed behavior of the bubble and single phase heat transfer was obtained. It is found that use of the MAC method could simulate the bubble motion satisfactorily, and some modification of this method will enable us to simulate nucleate boiling.

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Cavitation inception in control valves should be accounted for in terms of not only the time-averaged distribution of pressure but also the instantaneous structure of vortices formed in the flow, since the pressure of the vortex core can easily attain vapor pressure as velocity gradient of the shear layer increases. In a range of low and intermediate opening of contoured plug valves, instantaneous cavitation pictures indicate that the cavitation bubbles are first formed around the leading edge of the plug seating rim and then along the outer shear layer of the throttled jet. The inception of the cavitation bubbles may be related to formation and shedding of vortices in the flow immediately before the inception. Such cavitation-free structures of the valve flow, the growth rate of the vortex and boundary layer separation at the seating rim are studied by means of a 2-D numerical analysis of unsteady Navier-Stokes equations. By replacing the separation bubbles at the rim with Rankine vortices where the vapor pressure is first reached, a criterion of the cavitation inception is presented in a similarity law form in terms of the Strouhal number, the boundary layer thickness, and the valve discharge coefficient. The prediction of the inception agrees very well with the experimental data at valve inlet pressurs between 0.4 and 5 MPa for the valves of diameter between 2 and 6 inches.

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In order to clarify supercavitating hydrofoil performance numerically, especially in the base-vented state at a low incidence, we try to make numerical simulations for three typical thin super cavitating hydrofoils with pseudo-Kirchhoff noses by means of the QUICK method. The precise water-tunnel tests on the supercavitating steady lift- and drag-performance for the foils are examined, after the marked effects of leading edge and the peculiar behavior of disc drag have been clarified. We find that the analyses agree well with the experiments, especially in the base-vented flow at low incidences, showing several interesting facts.

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In this paper, we attempt to clarify the jet structure and the behavior of severely erosive cavitation clouds around a high-speed submerged water-jet, using a high-speed movie camera with a framing rate of ten thousand frames. The effects of the injection pressure and the nozzle geometry on cavitation are also investigated. The experiments are performed with both a free jet and an impinging jet. It is clearly found that the cavitation clouds are periodically discharged. The cavitation clouds are also closely related to downstream instability and to the impinging erosion.

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This paper proposes a method to analyze the flow field around a slender diamond cone traveling at hypersonic speed. We used the equivalence principle to analyze the problem. In order to apply the equivalence principle, we assumd that the flow field around a slender diamond cone traveling at hypersonic speed concides with the two-dimensional unsteady flow field around a diamond shape body expanding at a constant rate. Using conformal mapping, we solved the flow field to satisfy the boundary condition around the expanding body. Using this analysis, the velocity distribution and the streamline around the body became clear. Consequently, we obtained the flow field around a slender diamond cone traveling at hypersonic speed.

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Measurements were presented of the time-averaged and fluctuating fluid forces and the vortex shedding frequency on a square-section cylinder forced into rotary oscillation with constant frequency and amplitude. The cylinder's Reynolds number was 3.7×10⁴. The cylinder was forced into rotary oscillation at angular displacements up to α=±10°and the non-dimensional frequency F^*B/U (F : frequency of forced oscillating cylinder, B : width of cylinder, U : free-stream velocity) was varied from 0.04 to 0.23, in which the lock-in region was included. It is found that the frequency of vortex shedding from the oscillating cylinder tends to be equal to n times the cylinder oscillation frequency. Also, within the lock-in region in which the vortex shedding is perfectly synchronized with the forcing frequency F^* of the cylinder only, the time-averaged and fluctuating fluid forces are found to reach a maximum at a certain critical frequency. Furthermore, it is recognized that the fluctuating moment induces the generation of negative aerodynamic damping since the work done by the force is almost always positive in the lock-in region.

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This paper presents an experimental study of a turbulent cylindrical wall jet impinging normally on a flat plate. This type of jet flow may have properties including boundary layer separation on the cylindrical wall and reattachment on the impingement plate. The effect of the nozzle impingement distance on the mean flow properties of the jet before and after the impingement was investigated. The changes in the static pressure on the cylindrical wall surface, the maximum jet velocity and the boundary layer thickness were examined. Both the separation point from the cylindrical wall and the reattachment point on the impingement plate were divided into three trends depending on the nozzle impingement distance.

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With the use of the molecular beam method, scattering of argon and helium molecules from an Ag ion-plated stainless steel surface (SUS304) is studied experimentally. Time-of-flight (TOF) spectra of the scattered molecules are analyzed by means of superposition of two spectra ; one corresponding to the elastic or inelastic scattering process (the 1st spectrum) and one to the adsorption and desorption process (the 2nd spectrum). The mean energy of the scattered molecules, flux distributions and partial adsorption probability, which is defined based on the 2nd spectrum, are calculated from the TOF spectrum and compared with the results of the naked surface. From these results, the Ag ion-plated surface is verified to be adequate for use with vacuum technology.

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Constitutive equations of conducting magnetic fluids are derived using the principle of material frame indifference and the thermodynamical method based on the free energy and the dissipation function. The quasi-conservative part of the constitutive equations is determined by thermodynamical equations while their dissipative part is derived from the principle of maximal dissipation rate. The electric displacement and the magnetic flux density are treated as variables of electromagnetic fields. A new constitutive equation of magnetization is proposed. This constitutive equation includes terms related to the unsteady effect of the magnetic field and the rotation of suspended particles.

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The cyclone separator is widely used in industrial applications as a method for dust removal from gases. In this chamber, a very complex flow field is formed, involving the interaction between high-swirling velocity and turbulent stress field. The problem of predicting this kind of flow is solved by applying a Reynolds stress transport model. Furthermore, we perform a calculation using a K-ε model in order to compare with the predicted performance. It is shown that the predicted results obtained by the Reynolds stress model are in good agreement with those of measurements.

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A new energy spectrum of stratified shear flow has been proposed, which includes the flux Richardson number effect. Modeling was performed from the two-scale direct interaction approximation (TSDIA) theory by Yoshizawa. According to the present spectrum, the difference between stratified and isothermal shear flow was proportional to the -3rd power of the wave number. Such a behavior was compatible with the experimental results of Iwashige et al.

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Using direct numerical simulation (DNS) database for wall turbulence, we have performed critical assessment of representative dissipation-rate equations (i.e., ε-or ε-equations) for k-ε turbulence models and proposed a new dissipation-rate equation. The DNS data of mean velocity and turbulent kinetic energy are used as the known exact quantities for solving theε-or ε-equation. Thus, the obtained values ofεare the true solutions with no contaminants. The assessment indicates that, except for one recent model, the performance in predicting the exactε profiles is poor, irrespective of the model type. The proposed model constructed on the basis of the proposal of Nagano and Hishida (1987) provides a good performance, though the model formulation is very simple.

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In this paper, the shock waves propagating in a rectangular elbow were investigated numerically in order to clarify how the transmitted shock wave past the elbow is stabilized to the uniform shock and the flow field induced by the shock. The computations were carried out by solving the two-dimensional compressible Navier-Stokes equations by means of the TVD finite difference method. The calculations were performed for three incident shock strengths and three Reynolds numbers of the flow, and the flow fields were expressed by contour lines of pressure, density and the vorticity, velocity vectors, stream lines, pressure distributions and wave diagrams. The numerical results showed that the nonuniformity of the transmitted shock continued for a long distance and the attenuation of the transmitted shock was very slight, and the production of the vortex and the secondary shock wave and their development were observed clearly.

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The effects of uneven flow on the discharge coefficients and flow patterns of 90°-bend flowmeters with a square cross-section have been studied experimentally. Flows having a stepped velocity profile were introduced to the bend flowmeters with various radius ratios. The results obtained are summarized as follows : (1) The uneven flow patterns introduced in the straight duct become uniform within a distance of approximately 50 times the duct width. (2) The uneven velocity profiles caused upstream the inlet of flowmeters are largely deformed inside the bend correspondence to the coefficients of uneven parameter δ. (3) With decrease of the radius ratio R/a, the effects of the uneven flow through the bend flowmeter on discharge coefficients are also decreased.

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The overset grid technique is applied to simulation of 2-dimensional flows through a butterfly valve. The numerical simulation for valve openings of varying numbers of degrees can be carried out using the same grid system of a minor grid around the disk and a major grid in the channel. The rational Runge-Kutta scheme with implicit residual averaging and local time stepping techniques is employed as the time integration method. This time integration method is effective for obtaining a high convergence ratio to a constant solution, though it is an explicit scheme. The results are obtained for valve openings of 45°and 60°. The figures of the velocity vector show two vortices behind the disk. These typical flow patterns are in agreement with those of experiments. The loss coefficient obtained for each valve opening also agrees with those of experimental data.

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In the present report, simultaneous measurements of void fraction and temperature above a horiozontal surface in nucleate pool boiling were investigated using a thin optical fiber void sensor and a micro thermocouple sensor. As a result, the relationship of the bubble population density and heat flux with two kinds of surface roughness was obtained. It is shown that there is a cold spot around the center of the nucleation site in the superheated layer formed above the heating surface, and that there is an isolated hot spot about 0.3 mm in height apart from the nucleation site.

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Saturated pool boiling heat transfer of hexane-solvent magnetic fluid containing magnetite particles was investigated on a horizontal surface in a vartical magnetic field and field gradient. The heat transfer characteristics observed are qualitatively the same as those of the previous result for the toluene-solvent magnetic fluid ; i.e., in the absence of a magnetic field, the heat transfer was enhanced for the fluid with particles added dilutely, while it is reduced for a dense fluid. With increasing magnetic field, heat transfer of the dense fluid is enhanced significantly, but it is reduced above a certain transition heat flux. However, the transition heat flux and the heat transfer at high superheat region is higher compared with those of the toluene-solvent magnetic fluid.

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Saturated pool boiling heat transfer of toluene-solvent magnetic fluid with magnetite particles was investigated on a vertical cylindrical surface in the vertical magnetic field and gradient. The gradients of the boiling curves of pure toluene and magnetic fluid are much smaller than the previous results for a horizontal heater. The heat transfer of magnetic fluid is enhanced first in both the absence and presence of a magnetic field. However, with increase in heat flux it is reduced suddenly at a certain transition heat flux. The transition heat flux is higher with higher magnetic field gradient and lower magnetite concentration. The magnetic field gradient has no influence on the boiling heat transfer, and there is a hysteresis in the transition, which are much different results from the previous results for horizontal heater.

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This experimental study was conducted on the heat transfer around two-dimensional blocks in a parallel duct. The dimensions of the blocks were 10mm(H)×30mm(L). The duct height(B)and the gap between the blocks (b) were varied (B=20 ; 30 mm, b=10, 20, 30mm). The duct Reynolds number Re_B ranged from 1920 to 11500. Local heat transfer coefficients and the pressure drop of the duct flow were measured. As a result, it became clear that with a constant pumping power, the greatest performance of heat transfer was determined to be at the dimension of B=20mm and b=20mm. Additionally, we investigated the effects of the upper stream heat flux on the adjacent downstream block. The experimental equation which predicted the reduction of the heat transfer coefficient of the downstream block was established.

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The cavitation intensity and the heat transfer coefficient on the bottom surface of the object, by applying ultrasonic vibration, were measured experimentally. The object faced the ultrasonic generator adhered to the bottom of the water tank. The dimensions of the object were greater than the ultrasonic wavelength. Ultrasonic power of 600 W with a frequency of 40 kHz was used. The cavitation intensity was defined by the erosion loss of aluminum foil, whose thickness was 15 μm, when aluminum foil stuck on the bottom of the object was immersed into water in the ultrasonic field. The result was that the larger the cavitation intensity became, the more the heat transfer coefficient increased. With varying densities of objects, the greater the density was the larger the cavitation intensity.

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The characteristics of flow pattern, heat transfer and pressure drop in the case of evaporation of HCFC22 inside a horizontal tube are experimentally revealed. The experiment is conducted with a double-tube evaporator, where the refrigerant flows inside the inner tube and the heating water flows countercurrently in the surrounding annulus. The inner tube is an internally grooved copper tube having a 9.52 mm o. d. and an 8.72 mm mean i. d. The ranges tested for the refrigerant are as follows : the mass velocity of 110 to 220kg/m²s, vapor pressure of 0.4 to 0.65 MPa and the heat flux of 5 to 35 kW/m². The flow pattern observed through sight glasses changes from the wavy-annular type to the annular type and then to the mist flow type as the evaporation progresses along the tube. These transitions of flow patterns occur at much lower values of vapor qualities than those predicted from the Baker map modified by Scott for a smooth tube. The heat transfer coefficients in the wavy-annular and annular regions are about 2 to 4 times higher than those of smooth tubes, and are expressed as a simple function of Lockhart-Martinelli's parameter and a newly derived equation for the single-phase heat transfer coefficient. The empirical equation for the heat transfer coefficient in the mist flow region is also presented. The accuracy of these equations along with the value of the transition quality is confirmed in the comparison between design calculations and experimental data.

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The problem of steady melting of a solid body of a phase-change material in contact with a warm rigid body is theoretically studied in two-dimensional space. The phase-change material, always at the melting temperature, is assumed to melt upon contact with the downwards horizontal surface of the rectangular rigid body. The equations governing heat flow in the melted liquid and in the rigid body are simultaneously solved using the technique of Fourier analysis. The analytical procedure of determining the shape of the interface between the liquid phase and the solid one is explained in detail. The coefficients of the Fourier series are found in the analytically closed forms with two parameters, the aspect ratio and the Peclect number. The interface of the phase-change material melted from above is found analytically. The phenomenon of steady melting considered here connot arise if the temperature of heating does not accommodate the speed of melting. The critical conditions determining whether there exists a state of steady melting are found in an analytical form for the cases without and with convection. The effect of convection is discussed in terms of the difference in the heat flux on the undersurface of the rigid body and the interface.

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In order to develop new types of domestic heaters and burners for effective use of thermal energy and low emission of pollutants, characteristics of excess enthalpy flames stabilized in an axisymmetric stagnation flow established in a heat-recirculating burner were compared with thouse of ordinary flames stabilized by a non-heat-recirculating burner. The excess enthalpy flames can be stabilized at a low equivalence ratio and even in the stagnation flow with high velocity compared with the ordinary flames. The values of heat flux transferred from the excess enthalpy flames are about 1.5∼1.8 times as much as those transferred from the ordinary flames at the same flow rate of fuel. The flow rate of fuel for the excess enthalpy flame is about 40% of that for the ordinary flame under the condition of the same value of heat flux transfered from both flames. Then, carbon dioxide emitted from the excess enthalpy flame seems to be decreased by about 60% of that emitted from the ordinary flame. Therefore, the excess enthalpy flames are suitable for effective use of the thermal energy and low emission of carbon dioxide compared with the ordinary flames.

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Transpiration cooling effectiveness is influenced by the heat transfer coefficient on both surfaces and the thermal conductivity of the test plate. In the present paper, two circular air jets were perpendicularly impinged on the back surface of the test plate as coolant. Transpiration cooling effectiveness was measured for several values of the transpiration rate, the standoff of the jets, the thickness of the test plate and its thermal conductivity under steady conditions. Transpiration cooling effectiveness was significantly improved by impinging the coolant on the back surface. Also, a three-dimensional numerical study using the finite difference method was performed under the steady state, and transpiration cooling effectiveness was evaluated. The calculated results qualitatively agreed well with the experimental ones.

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A new methanol-steam reformer has been developed on the basis of the effective energy conversion method between flowing gas enthalpy and thermal radiation. The basic concept consists of a porous medium (heating side) and a porous catalyst (heated side), which are separated by a solid wall. The combustion gas is used to heat the system, and a methanol-water solution is supplied to the heated side. The evaporation rate of the solution is controlled by the radiant energy. The radiant energy is effectively converted into the endothermic reaction heat for the hydrogen production and the enthalpy increase in the flowing methanol-steam mixture in the porous catalyst.

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The efficiencies of binary mixture operated heat pumps are analysed by available energy method. Mixtures HCFC22+CFC114, HCFC22+HCFC142b and HCFC22+HFC134a are used as working fluids. One of the advantages of binary mixtures in heat pump applications is a higher coefficient of performance, which is caused by small temperature difference between the heat sink/source fluid and the refrigerant. The relations between the COP and the irreversibility are examined for various mixtures. The mixture, of which temperature change throught the cooling process is almost the same as the temperature increase of the heat-sink fluid, has a maximum of the COP. Available energy evaluation gives us an effective advice in choosing a suitable binary mixture for conditions of heat sink and source fluids.

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Experiments have been carried out to investigate the inhibitory effect on catalytic reaction of methane and the formation of formaldehyde in the presence of nitric oxide(NO). Catalysts used in the experiment were Pd, Pt, Rh, Pd/Pt/Rh loaded on γ-Al₂O₃ monolith. With all these catalysts, the presence of NO and NO₂ showed inhibitory effects on methane oxidation reaction and caused the formation of formaldehyde. In the absence of oxygen, however, formaldehyde was not produced in the catalytic reaction of methane and NO. Maximum formation of formaldehyde was about 0.6% in the presence of NO with the Pt, Pd/Pt/Rh or Rh catalysts. It was also found that N₂O was formed simultaneously with formaldehyde in the catalytic reaction of methane in the presence of NO.

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Under the knocking condition, luminous emission from the autoignition portion in actual S.I. engine is observed using optical fibers. The difference in emission intensity between the knocking and no-knocking conditions is mainly caused by the intensities of OH and C₂ radical emission. The emission intensity from these two species increases steeply at the occurrence of autoignition. In addition, emission intensity from C₂ radical in some cycles has two peaks. As the first peak is due to the autoignition reaction, the second peak is understood to be caused by the soot formation in some cycles under the knocking condition. This second peak corresponded to the shadowlike object under the expansion stroke which was taken by our high-speed shadowgraphy.

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Improving combustion of the spark ignition engines contributes largely to decreasing fuel consumption, especially under the conditions of medium or low speed and low load. In this paper, valve timing is evaluated from the viewpoints of swirl velocity as well as the volumetric efficiency, burned gas fraction in a fresh mixture charge, and pumping loss at intake stroke by using the predictions of the simplified simulation model. As a result, the timing of intake valve opening and closing is considerably affected by the swirl velocity. It is also confirmed that the mean swirl velocity controlled by the valve timing is higher than that controlled by the conventional throttling system under the same volumetric efficiency condition.

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The lean-burning characteristics of a spark-ignition engine homogeneously fueled with natural gas and propane are studied. It was shown that a higher swirl in a deep-bowl chamber significantly suppresses the cycle-to-cycle variation in peak pressure. There is a "window" of the equivalence ratio in which a very low concentration of oxides of nitrogen and an allowable degree of variation can be achieved over a range of loads, provided the ignition timing is correctly regulated with the operating conditions. Based on the test results, it is possible to establish a lean-burning gas engine without the supplementary treatments of a three-way catalyst or exhaust gas recirculation as an alternative to the diesel engine.

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