This paper deals with an experimental study on the unsteady performance in the cylindrical choke of the oil hydraulic. Experiments are carried out under an unsteady flow in which the outlet pressure p₂ of the cylindrical choke takes the form of a trapezoid varying with time, keeping the inlet pressure p₁ constant. It is found that as the absolute value of the rates of pressure change dp₂/dt increases, the incipient cavitation number k_ci shows a tendency to decrease, and the desinent one, k_cd, shows a tendency to increase under two geometric parameters: diameter and length of the choke. As the larger absolute values of dp₂/dt further increase, the hysterisis between k_ci and k_cd becomes larger for each combination of the cylindrical choke.

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Incipient cavitation in a contoured-plug valve flow is studied both in a high-inlet-pressure range of 3∼5MPa and in a low-pressure range of around 0.4MPa. The argument is focused on features of a string bubble cavitation on schlieren photography. In a range of the intermediate and large valve openings, such bubbles occur intermittently before the usual fixed cavitation appears on the plug surface. The string bubble is induced in a pressure-reducing section of a vortex core which extends from the valve inlet chamber to the outlet, and a vortex instability splits off a spherical bubble from the top end of the string in the process of the pressure recovery. Then a shock wave and a light "pop" sound are generated by the bubble collapse. The inception and the scale effect of valve size between 2 and 6 inches are discussed in a semiempirical manner by utilizing a vortex flow model. A practical method of suppressing the bubble generation is briefly mentioned.

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A numerical analysis is performed for clarifying flow characteristics on a bubble elimination system, which consists of a circular body for a tangentially supplied swirled flow with a valve for discharging bubbles. At first, the steady laminar flow field is sought numerically through the incompressible Navier-Stokes equation, assuming that the fraction of bubble quantity is sufficiently small. Then, a bubble released in the system is traced by integrating the equation of motion for the bubble. As a result, the pressure distribution on the axis of the circular body obtained numerically is found to be in good agreement with experimental ones. In addition, according to the behaviour of bubbles contained, the larger the bubble size may be or the faster the mean velocity in the circular body may be, the easier the elimination of bubbles will be.

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Although there are many reports which present the performance of the Karman vortex shedding flowmeter, few reports discuss the features of vortex shedding in a pipe flow. In this study, the vortex shedding from a circular cylinder in a pipe was observed with the aid of the laser light sheet technique which is based on the tracer method, in the range of Reynolds numbers (based on mean flow velocity and diameter of a pipe) from 810 to 20000. As a result of the experiments, in the Reynolds number range of 1000 to 4600, two typical patterns of vortex shedding were observed, one of which is a type of Karman vortex shedding and the other, a type of twin vortex shedding. It was known that the two configurations of vortex shedding appear intermittently and alternatively in the pipe flow. The relationship between Strouhal and Reynolds numbers was examined.

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The structure of the mixing layer in an axisymmetric round free jet was investigated on the basis of the two-dimensional instantaneous photographs of turbulent eddies, which were taken using a laser-light sheet method with a YAG pulse laser and a 35-mm still camera. Eddies were successfully visualized by titanium dioxide particles seeded in the flow for nitrogen, helium and carbon-dioxide jets having different kinematic viscosities. The observation of the coherent structure of air entrainment eddies shows that the turbulent eddies have unexpectedly coarse spatial distribution and their scale in the horizontal plane is almost identical with that in the vertical one. This suggests that three-dimensional structure is established at the upstream position. It is also shown that in the helium jet having a larger kinematic viscosity and a lower density, eddies of a larger scale are formed and retard mixing with the surrounding air. In addition, we present a detailed discussion of the structure of mixing eddies, based on the formation of the elliptic and hyperbolic points in the shear flow.

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A liquid oxygen turbopump has been developed for the main engine (LE-7) of the H-II rocket. The turbopump requires a high-flow and high-pressure liquid oxygen main pump. Because the LE-7 engine does not use a low-speed and low-pressure pump ahead of the main pump which is applied to the space shuttle main engine, it is very important to operate the main pump at higher speed for smaller size and lighter weight of the turbopump. The operational speed was restricted by the suction performance of the main pump inducer with the present turbopump. This paper shows both the design and test results of the inducer. In particular, a problem of supersynchronus shaft vibrations and its suppression method are described in more detail. The shaft vibration is considered to be closely related to rotating cavitation in the inducer.

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The paper presents the cold flow measurements in a two-dimensional dump diffuser. The laser Doppler velocimeter was used for the measurements of mean velocity components and its fluctuation in order to clarify the flow regimes in a sudden expansion region. Wall friction velocity on the outer wall was also measured by a wall flow sensor. The rolling up of flow from the outer wall is observed in a sudden expansion region near the reattachment point. Such behavior contributes to the favorable characteristics on the flow rate distribution to the branched channels, while it produces turbulence energy which causes a large pressure loss in the dump diffuser. Wall friction velocity and its fluctuation in a sudden expansion region decrease toward the base of the prediffuser.

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An experimental investigation was carried out on the varying properties of void fraction averaged over a tube cross section in an isothermal fully developed air-water two-phase mixture flowing in a horizontal capillary tube of 1.0mm, 2.4mm and 4.9mm inside diameter, using the constant current method. The flow pattern was observed by video and photograph with streak flashing. Calibration of the void meter was performed using a nonconductive plastic model in bubbly flow, intermittent flow and annular flow. It was found that the scatter of the data of the void fraction was within 20% in each flow region. We obtained correlations between (1) void fraction and gas volume flow rate quality, (2) bubble volocity and total volume flux, (3) lengths of slugs and gas-liquid flow ratio and (4) mean liquid film thickness and pipe diameter

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A numerical study is made to investigate fully developed laminar flow characteristics in a curved square duct of finite curvature ratio. It is shown that, above critical Dean numbers, a pair of Dean vortices due to centrifugal instability appears near the center of the outside wall in addition to the secondary flow vortices. A stability diagram is given in the domain of Dean number and curvature ratio. On the basis of a similarity consideration, we propose new nondimensional expressions of flow characteristics that represent a whole range of parameters inclusively. Two friction factors are proved to be different for small curvature ratio, and a correlation is developed.

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This paper presents a refined momentum equation for unsteady one-dimensional flow in a collapsible tube. The available momentum equations for such flow cases are not suitable to handle a situation in which the cross-sectional area of the tube changes rapidly with time. In order to overcome this, the present equation is derived taking into account the energy loss due to flow separation with good accuracy than the conventional ones. Then applying this equation to a flow in a two-dimensional channel made of a pair of elastic membranes, numerical calculations are performed. The predicted oscillations show that the separation point is almost located at where the channel width is the smallest, and that the oscillatory waves traveling on the membranes become predominant compared to those predicted by the conventional model.

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It is well known that a cyclic Karman vortex street is periodically thrown out from a cylinder whose axis is vertical to the bulk flow. When the cylinder is vibrated at a frequency close to that of the Karman vortex street, the frequency is locked in to that of the cylinder. While there are many experimental studies of this phenomenon, analytical studies by numerical calculation are few. In this study, a new algorithm for a moving boundary problem is proposed, and a simulator, which can deal with this phenomenon is developed. The simulator is based on the boundary-fit method and MAC method. This lock-in phenomenon is analyzed by it and the following results are obtained. The lock-in phenomenon is confirmed to exist by this simulator. The bandwidth of the frequency in which it is locked in coincides with that from experimental results. For the near-wake of the cylinder, the velocity profile corresponds to the experimental one.

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Introducing a turbulent flow fully developed in a straight parallel-plate channel into a two-dimensional curved channel with a radius ratio of 0.92, measurements were made in the entrance section on the time-mean velocity, nonzero components of kinematic turbulent stress and other one-point multiple velocity correlations. No significant steady Taylor-Gortler vortices are found and the flow field is completely two-dimensional throughout the entire region of the entrance section. When arranged with wall variables, the time-mean velocity and turbulent stress distributions in the vicinity close to the walls are slightly affected by the wall curvature, while the skewness and flatness of the velocity fluctuation are strongly affected by it. Triple velocity correlations follow a complicated progress to arrive at fully developed states. The results obtained can be used as a data base to verify various types of turbulence models.

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A new near wall k-ε model has been proposed, which includes the Prandtl number effect. Modeling was made from the statistical theory developed by A. Yoshizawa. The model was compatible with near wall limiting behavior for turbulent energy and Reynolds stress. Using this model, a numerical calculation was carried out for turbulent heat transfer in a fully developed turbulent flows. The results were in good agreement with the experimental data and some another models.

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The accuracy of the direct simulation of turbulent flow is discussed on the basis of the numerical results of two-dimensional homogeneous isotropic turbulent flow. Four cases of calculation have been carried out by pseudospectral methods with/without removal of aliasing error and by finite difference methods with/without consistency between pressure and continuity equation. The grid resolution is required to be finer than 1/4 of the turbulence microscale for the full turbulence simulation. In that case, the finite difference method of more than the 4th order provides a result comparable with that obtained by means of the pseudospectral method. The reduction of the aliasing error is indispensable in the pseudospectral scheme. For the finite difference scheme for the pressure term using the regular mesh, higher accuracy for the Poisson equation is recommended rather than consistency with the continuity equation.

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Direct numerical simulations of three-dimensional homogeneous isotropic turbulence with temperature diffusion were performed by using a spectral method with 64³ Fourier modes. Temperature fluctuation was not so large, so we assumed that temperature is a passive scalar. We simulated two cases with Prandlt numbers of 0.71 and 0.20. During the decaying period, the turbulent kinetic energy dissipation rate decayed exponentially with time and the microscale Reynolds number changed from 30 to 17. Spectral distribution of the passive scalar fluctuation spread more widely than that of velocity fluctuation in the case of a Prandtl number of 0.71. In the case of a Prandtl number of 0.20, spectral distribution did not spread as widely, but two-point autocorrelation of the temperature fluctuation showed a negative value at large distance, which shows predominancy of the low wave number components.

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Numerical experiments have been performed to study accuracy and stability of a deterministic particle method for the diffusion equation. The diffusion velocity introduced in our method is defined as the velocity which is proportional to the density gradient and the diffusion coefficient ν, and inversely proportional to the density. The one-dimensional case is considered using the Gaussian distribution for the shape function, and the Forward-Euler scheme for solving the ordinary differential equations. The effect of the shape parameter σ, the time step Δt and the particle number on numerical erros is investigated. It is found that the stability depends not on the distance between the particles, but on the non-dimensional time step νΔt/σ², and that numerical errors of stable solutions are almost constant in spite of the variation of νΔt/σ². Criteria for obtaining the stable solutions and accurate density distribution are also given.

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The purpose of this study is to clarify the jet tip velocity and mixing process between the jet and its surrounding fluid. The analysis was made with the time history of injection velocity which monotonously rises up just after the opening of injection valve and is steady later. The jet is injected into quiescent ambient air. The jet tip velocity first increases, then decreases, increases and last decreases with time lapses from injection. Therefore, the growing process of the jet is composed of four periods from the standpoint of the jet tip velocity. The jet tip velocity is maximum at the time boundary between the first and second growing periods, when the rate of increase of the injection velocity is maximum. The mixture between the jet and surrounding fluid is very active at this time. The growing period between the first period to the initiation of the fourth period corresponds to the unsteady period of injection velocity.

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The annular jet has been characterized by a doughnutlike recirculating flow formed just at the downstream end of the annular nozzle. The behaviour of the recirculating flow governs the flow field when placing two annular nozzles in opposition, according to a distance L between the annular nozzles. In this study, first, the flow field was divided into three regions, varying the distance. Second, fundamental characteristics of these regions were studied using air and water as working fluids. The flow field in the region of small L was stable and an impinged surface was formed. That in the region of intermediate L was unstable and that in the region of large L was out of the scope of interest for the authors. It was ascertained that the flow fields of the annular opposed jets were closely correlated with that of an annular impinging jet.

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Basic studies of a magnetic fluid viscous damper are carried out theoretically and experimentally to clarify the effect of an applied magnetic field on the characteristics of a vibrating spring-mass system in the magnetic fluid. Experimental study shows that the application of magnetic field is effective reducing the resonance characteristics of the system. Theoretical analysis which is conducted by taking into account the aggregate of magnetic particles shows reasonable agreement with the experimental data.

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The buoyancy-driven motion of an encapsulated liquid drop in liquid-liquid-gas systems was analyzed experimentally and theoretically. To investigate the accelerated motion of the encapsulated drop in detail, the optical measuring device for the local upward velocity was designed. Furthermore, a simplified effective theory based on the experimental data was proposed for the rectilinear accelerated motion of the spherical encapsulated drop produced from the compound jet in the systems. The effects of drop radius and liquids, physical properties on the accelerated motion were clarified numerically. The drag components, which were composed of the steady drag term, the added mass term and the Basset history integral term, were also analyzed. The numerical results of the upward velocity quantitatively agreed with the experimental results in the intermediate Reynolds numbers; Re∼O(100).

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The effect of surface roughness on the solid-liquid wetting behavior was investigated experimentally. For the solid test piece on which regular surface grooves with various inclination angles φ were manufactured by a NC lathe, the advancing and receding contact angles θ_YA and θ_YR of water and ethanol-water solution were measured using a photograph. The experimental results showed that θ_YA (θ_YR) increased (decreased) linearly with φ, which agrees with the theoretical model obtained by Johnson and Dettre, and Eick et al. The magnitude of the contact angle hysteresis (i. e., the difference between θ_YA and θ_YR) was expressed well by the equation in which the effect of infinitesimal roughness smaller than the regular grooves was taken into consideration.

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An efficient numerical simulator for calculating the unsteady transonic cascade flows and for visualizing these numerical data is developed. The authors have already developed a numerical method, in which an implicit time-marching finite-difference scheme for solving the unsteady Euler and Navier-Stokes equations in general curvilinear coordinates and several numerical techniques have been applied in order to simulate the unsteady flows having shocks and their induced boundary layer separations such as the flow through a transonic or supersonic compressor cascade. With regard to a system developed by us, a graphics work station having the power of the super-minicomputer was connected with an image recorder which can control a 16mm movie camara, and we have developed a computational code with the UNIX System which can calculate any flow and make the visualized film from the results at the same time. In particular, we can make an animation visualizing the unsteady transonic cascade flow within a half-day at most with no effort, Therefore, we should emphasize that the present system is one of the most effective tools for simulating unsteady flows.

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Wake-induced unsteady aerodynamic responses of mistuned compressor cascades, in which blade pitch is purposefully made nonuniform, are investigated by means of the cascade superposition method developed in the previous paper. Numerical calculations are performed in focus, mainly on the effect of the blade pitch nonuniformity which is defined by the off-set level of the cascade superposition. It is consequently found that in most cases, unsteady lift on the compressor blade tends to increase in magnitude according to the off-set level, and it is also found that the reduction effect of the unsteady lift cannot be obtained by the simple mistuning of the blade pitch considered in this paper.

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The presence of water droplets in the low-pressure stage of a steam turbine leads to erosion of moving blade, especially of an advanced long blade, because of the larger blade tip speed and higher wetness. This paper describes the effect of the separation of water film through suction slits on the blade pressure surface. By assuming a linear velocity distribution with water film, the mass flow and film thickness of water moving on the blade pressure surface were calculated in order to determine the location of slits. Water flow separated through suction slits was measured in a wet steam tunnel under the same conditions of a low-pressure steam turbine. Droplet size and velocity were also measured for dispersed water droplets in the wake of the blade with and without suction slits by means of a fiber laser Doppler velocimeter (LDV). Test results indicated that the water separation coefficient is strongly affected by the location of slits and pressure difference between cascade inlet and drain separator. Finally, the flow rates of dispersed water droplets in the wake of the blade with suction slits are 30∼40% lower than those in the wake of the blade without suction slits.

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Horlock proposed the rapid calculation of the off-design performance of turbo machines, but the method gives inadequately accurate solution for the axial compressor. In this paper, the method is improved by introducing the representative characteristic curve and Mach-number of the compressor, and gives good agreement with the experimental data near the design point. The method may be of use in preliminary design studies of multi-stage compressors.

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In stationary hydraulic systems, a hydraulic pump is usually driven by an induction motor. The electric current density in windings of a motor is limited to a small value because of the heat generated. The aim of this study is to augment the output power density of an electromotor-driven hydraulic power source by cooling the inside of an induction motor by hydraulic oil and by operating at higher torque than the rated torque and at high speed using an inverter. In this study, an induction motor, whose specification of windings is altered for high-speed use, is manufactured. The maximum hydraulic output power reached in the experiment when driven by the manufactured, oil-cooled motor is about seven times as large as that reached at the rated operating condition of a conventional, air-cooled motor with the same size as the manufactured motor. The effect of oil-cooling restricts the temperature rise of windings to 10°C even at the maximum output power.

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Using the lumped parameter Greitzer model, most compressor surge behaviors (for classic or deep surge) can be estimated. However this model is too simple, since, in general, the rotor flow passage length is longer for high-pressure compressors than that for low-pressure ones, and modern high-pressure compressors have a strong axial pressure gradient distribution in the flow passage. Dealing with the above, this paper is aimed towards suggesting a multielement model to which is applied Greitzer model for each element, and explaining the relations between the surge behavior and compressor flow field time constant, by comparing the results of Greitzer model and the experiments of the aircraft gas turbine with a relatively high-pressure compressor.

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This paper reports a correlation of dew- and bubble-point curves for seven binary refrigerant mixtures of engineering importance. The present correlations have been established based upon the reliable measurements of dew- and bubble-points by the present authors and others using a constant volume method. We have made the present correlation by calculating the differences between the experimental values and the calculated values due to Raoult's law. After correlating these differences ΔPd or ΔPb with temperatures, we represented these temperature terms in terms of the composition x₁ of the first Components which have lower critical temperature in binary components. It was confirmed that the present correlations for seven binary refrigerant mixtures were effective to model the dew- and bubble-point curves for any mixtures with an arbitrary composition, and to reproduce the dew- and bubble-point pressures even in the neighborhood of the critical points where the SRK equation did not reproduce the measured vapor-liquid equilibrium.

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A cylindrical capsule in which two insoluble materials are packed is proposed as a thermal energy storage method. Using n-octadecane and ice as phasechange materials (PCM), phase change characteristics are examined experimentally under such conditions as that either of the PCMs changes its phase. A method of analysis applying natural convection heat transfer within a concentric horizontal cylindrical annulus is presented. The analytical results show good agreement with the experimental data. It is found that the phase-change process of a two-PCM-capsule is about 1.7 time as rapid as that of a single-PCM capsule.

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On the basis of the PVT, specific heat, and saturated-liquid-density data measured by our group, and other available experimental data, an equation of state for HFC-134a (1, 1, 1, 2-tetrafluoroethane, CH₂FCF₃) was developed. It is a nondimensionalized virial equation of state which has 25 terms and is effective in the range of pressures up to 15MPa, temperatures from 240 to 480K, and densities from 0 to 1400kg/m³. The equation represents reliable PVT measurements within ±0.5% in pressure in the superheated gaseous and supercritical fluid phases, while within ±0.5% in density in the compressed liquid phase. The reliability of the derived properties from the equation of state including specific heats, speed of sound, and so on, was confirmed by comparison with reliable experimental data. Speed-of-sound data in the gaseous phase reported by Goodwin and Moldover are reproduced within ±0.1%, and most of the isobaric specific heat data by Saitoh et al. are reproduced within ±1% by this equation of state.

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

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Experimental studies have been made for heat transfer during nucleate pool boiling on a horizontal platinum wire in nonazeotropic binary mixtures of R12+R113 and R134a+R113 at pressures from 2 to 8 bar and at heat fluxes below 1.0×10⁵W/m². The substances employed were chosen such that the pure substances have a large difference in saturation temperatures. A correlation was derived by improving J. R. Thome's correlation, predicting the heat transfer coefficients for mixtures with a large difference in saturation temperatures within an accuracy of ±20%. It is also shown that the correlation is applicable for mixtures with small differences in saturation temperatures within the same accuracy. The heat transfer coefficients using the mixtures are smaller than those using the pure substances over the entire concentration range. The heat transfer coefficients for the mixtures depend on the pressures of the system and the heat fluxes at a lesser extent than for the pure substances

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Natural convection heat transfer in a saturated porous matrix whose permeability is anisotropic is analyzed by a finite-element method. A specific problem involves the convection in a square box heated from below. The Rayleigh number is defined at vertical permeability, according to Kvernvold and Tyvand. The calculated critical Rayleigh numbers agree well with the linear stability theory. Variations of the Nusselt numbers with the Rayleigh numbers for various values of the x-to-y permeability ratio and cell number are calculated. It is found that the ratio and cell numbers have a great effect on the properties of natural convection heat transfer and the number of convection cells realized in a square space. Unsteady temperature distribution and Nusselt number changes in the transient state are also calculated.

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An experimental study has been performed to investigate the de-icing heat transfer characteristics along a horizontal cylinder immersed within a cold forced air flow with spraying seawater. Experiments were carried out under a variety of experimental parameters such as air velocity, air temperature, droplet diameter, and spraying liquid content. The location of onset of the ice pieces was observed to change markedly according to the condition of droplet size and air stream. It was also found that the heat-transfer characteristics along the cylinder under de-icing conditions were mainly affected by sensible heat values of the impinging droplets.

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An experiment was carried out to confirm the an effect of electric field on the onset of instability of a liquid surface. A static electric field was applied between the liquid surface and a horizontal planar electrode placed over the surface. The applied electric voltage was raised gradually until the liquid surface became unstable. The critical voltages were measured for different distances between the electrode and the liquid surface and for different liquids. Instability criteria were derived theoretically using a modified Rayleigh-Taylor instability equation and it was found that the theoretical results agreed very well with the experimental data. Also, consideration was given to clarify the mechanism of the EHD enhancement of the evaporation of a drop which was reported previously.

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This paper describes extenive computer-based analytical studies on the offset fin compact heat exchanger, which could assist thermal designers. In order to simulate the fin efficiency affected by the heat conduction from the condenser pipe to the fin, the numerical analysis was applied to a quasi-3-dimensional problem, using the 1 dimensional heat conduction analytical solution as a boundary condition. Using this calculation method, the heat transfer behavior of the offset fin heat exchanger for various fin numbers was examined.

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A. C. impedance measurement on the alkali metal thermoelectric converter (AMTEC) has been conducted under D. C. polarized conditions in the temperature range from 890-1123K. The obtained data have been analyzed in the complex impedance plane in terms of an equivalent circuit for the AMTEC system. The charge transfer resistance at the interface between the beta"-alumina solid electrolyte (BASE) and porous molybdenum electrodes has been evaluated and approximated by the introduced electrochemical model. The calculated current-voltage curves including the effect of the charge transfer resistance show good agreement with the measured data. The generating characteristics of the AMTEC can be completely predicted by this method, which may be useful for further studies on more efficient AMTEC cells. The contributions of BASE ionic conduction, contact resistance and mass transport through the porous electrode are also discussed.

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Transient methods such as those with pulse- or stepwise heating have often been used to measure thermal diffusivities of various materials including layered materials. The present study aims to derive an analytical solution of the temperature rise in a multilayered material, the front surface of which is subject to pulse- or stepwise heating. The Laplace transformation has been used to obtain the analytical solution. This solution is expected to enable us to establish the appropriate measuring method of thermophysical properties of the multilayered material. It is also shown that the present solution can be extended to that of the functionally gradient material (FGM), in which thermophysical properties as well as compositions change continuously.

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In measuring thermal conductivities of liquids by a transient line source technique, one of the main error factors involved is the "edge effect" owing to the heat flow from the hot wire to the electrode through the wire edge. In this report, analytical investigation is performed concerning the edge effect on the measured thermal conductivity considering two basic cases; in the first case, a hot wire is directly connected to the electrode; and in the second case, a ringwise projection having a square cross section is attached at the connection of the hot wire to the electrode. Then the effectiveness, using a Wheatstone bridge circuit where two hot wires of different lengths are set to cancel and minimize the edge effects, is discussed analytically. As a result, the edge effect cannot be negligible even when using the bridge circuit, depending on the size of projection.

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Thermal characteristics are discussed for a roof snow melting system equipped with a heat exchanger to extract the thermal energy from the well water pumped up from the aquifer where the waste heat from a cooling tower for the air conditioning of the station building during summer is retrieved and stored. And also a water heat-source heat pump, a thermal storage tank, and a conventional water heater set at Nagaoka station of Joetsu Shinkansen Line are discussed. The field experiments indicated that a heat reclamation efficiency in the aquifer thermal energy storage was 40% and that a coefficient of performance of the water heat-source heat pump was 7.5. The system utilizing natural energy for the roof-snow melting is quite promising because of its high energy-saving performance of up to 26%.

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A new hot-wall-type rapid thermal diffusion furnace was developed for the semiconductor manufacturing process. A high-temperature furnace of about 1000°C was composed of parallel plate heaters. The heaters were divided into four zones. Two wafers were inserted vertically from the bottom of the furnace and heated for about 3 minutes. The temperature of the wafers in the furnace was measured by means of a pyrometer. In order to heat wafers uniformly the temperature of the lower zone of the heater was set higher than that of the center zone, considering heat rejection through the entrance and the effect of the wafer holder. The temperature of the wafers reached the heater temperature about one minute after insertion. The effective heating temperature distribution in the wafers was within ±1°C when the heating power of the four zones of the heaters was properly controlled. Invading air accompanying the wafers was reduced by controlling the flow rate of the process gas. When the developed furnace was used to oxidize silicon wafers at 950°C for 3 minutes, the oxide film thickness was 5nm and the distribution of the thickness was within ±0.2nm.

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An infrared radiometer were used for measuring and analysing the radiation temperature of the material in many fields. The present paper shows the charateristics of the radiation temperature and its related radiosity coefficient of gray body materials. Furthermore, the space-dependent variation of the radiation temperature and the radiosity coefficient were derived by the two-dimensional CRT image of the infrared radiometer.

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An experimental investigation was conducted on the structure of hydrogen turbulent diffusion flames stabilized on a bluff body. A coaxial jet diffusion flame was formed using a cylindrical nozzle with an extremely thick rim, which works as a bluff body. In the present study, special attention was paid to the effect of combustion on the aerodynamic processes. The following results were obtained. (1) The combustion remarkably enhances the penetration of the central fuel jet. (2) The laminarization phenomenon, reported in simple jet diffusion flames, was observed more conspicuously also in this combustion field, and it was supposed to exert an important influence on the flame structure. (3) An accelerating flow field often exists in complicated flow fields with a reverse flow, where turbulence generation terms containing Reynolds normal stress become negative. This phenomenon sometimes exerts considerable effects on the turbulence behavior.

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It is well known that the characteristics of ion current depend on the flame configuration and movement. Therefore, it is expected that the flame configuration can be examined by analyzing the ion current record. In the present study, an attempt has been made to elucidate the dependence of the characteristics of ion current on the local flame curvature and its path. It is shown that even though the local flame curvature is constant, the ion current changes its profile significantly as the flame path changes. As the angle between the flame front and the probe axis increases, the maximum ion current decreases and the half value period increases. As the distance from the center of flame curvature to the midpoint of a probe sensor increases, the half value period increases.

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Laser Rayleigh scattering was applied for the remote, nonintrusive point probing of the fuel vapor concentration and its fluctuation near the spark plug of a motored spark ignition engine, which was caused by the intermittent injection of Freon-12 vapor into an intake port. The theoretical analysis showed that the instantaneous fuel vapor concentration can be split into three components which were the ensemble-averaged mean concentration, the cyclic variation of temporal mean concentration and the temporal concentration fluctuation in a specific cycle. This paper concentrates on the measurements of the ensemble-averaged mean concentration and the cyclic variation of temporal mean concentration. The results show that both the ensemble-averaged mean concentration and the cyclic variation of temporal mean concentration increased and reached a peak, after which they decreased during the intake and compression strokes. Moreover, they were strongly affected by the air fuel ratio, engine speed, injection duration and injection timing.

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Laser Rayleigh scattering was applied for remote, nonintrusive point probing of the fuel vapor concentration and its fluctuation near the spark plug of a motored spark ignition engine, which was caused by the intermittent injection of Freon-12 vapor into an intake port. The theoretical analysis showed that the instantaneous fuel vapor concentration could be split into three components; the ensemble-averaged mean concentration, the cyclic variation of temporal mean concentration and the temporal concentration fluctuation in a specific cycle. This paper concentrates on the measurements of the ensemble-averaged concentration fluctuation and the cyclic variation of temporal concentration fluctuation. The results show that the cyclic variation of temporal concentration fluctuation was too large to be neglected, and both the ensemble-averaged concentration fluctuation and the cyclic variation of temporal concentration fluctuation increased and reached a peak after which they decreased during the intake and compression strokes. They were strongly affected by the air fuel ratio, engine speed, injection duration and injection timing.

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The purpose of this study is to investigate fuel-air mixture formation during the ignition delay period and to clarify its effect on the initial combustion process. Thermal decomposition of fuel injected into hot compressed air or nitrogen was studied by detecting gaseous hydrocarbons, with a rapid compression machine and a total gas sampling device. The results show that the ambient temperature is a very important factor affecting the fuel decomposition process. If the temperature is sufficiently high, a considerable amount of injected fuel can be gasified even in the delay period when much oxygen is not yet supplied into the spray. When fuel is injected into very low-temperature air, the ignitability deteriorates because an adequate mixture to ignite exists in only the limited area in the combustion space. At very high temperature, residual fuel in the later stage of combustion is severely cracked into unburned gas and soot, because of the insufficient mixing until ignition.

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A detailed observation of the intermittent spray injected through diesel injection nozzle was made by adopting a double-exposure method using a delay system equipped with an optical fiber. The results are as follows: the atomization in the early stage of the intermittent spray is clarified, various forms of fuel jets appear immediately after injection from the nozzle, and in the next moment, small fuel droplets are dispersed radially. These phenomena suggest that the following fuel jets collide with a leading part of the jets decelerated by static ambient air, and the fuel jets are atomized. In addition to the shearing interaction between the fuel jets and the ambient air, this atomization mechanism turns out to play an important role in the early stage of the intermittent spray.

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An experimental study was carried out on the effects of swirl flow on the formation of a combustible mixture before and after ignition. The concentrations of gaseous hydrocarbons were traced for sprays injected into air or nitrogen under various swirl velocities, using a rapid compression machine and a total gas sampling device. The results obtained suggest that the strong swirl flow advances the commencement of fuel oxidation after fuel injection starts due to its ability to supply much oxygen into the spray, though it reduces the temperature of the surrounding air. At very low ambient temperature, the strong swirl tends to cause misfire. But at the high temperature, it greatly increases the fuel-air mixing rate and can almost perfectly oxidize lighter hydrocarbons, giving a very rapid combustion.

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The spray characteristics in the vicinity of an atomizer are very important for ignition and flame holding in spray combustion, but they remain largely unknown because the spray measurements are very difficult to perform by conventional methods alone due to small drop size, high drop velocity and high spray concentration. In this paper, the spray characteristics in the vicinity of the air blast atomizer and the liquid disintegration mechanism were investigated using the phase/Doppler particle analyzer, a contact probe method and photographs. The liquid disintegration mechanism can be classified into three types by the contribution of ligaments to the breakup of liquid. The maximum drop size decreases and small drops increase as one moves downstream. The drop velocity increases as axial distance increases, and as radial distance increases in the region near to the spray axis. The radial distribution of the number density of spray drops has a sharp peak in the region near to the atomizer, and it becomes flat as it moves downstream.

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