In this study, the factors affecting the occurrence of submerged vortices and their formation mechanism were clarified with reference to flow pattern and vortex position for various dimensions. The experiments indicate that (1) the flow pattern in the proximity of the pump suction bell and the formation pattern of vortices depend on the ratio of bell clearances against the rear and side walls in the sump, (2) submerged vortices are generated on the back wall when the edge of the bell is close to the back wall and occur on the side wall when the bell is located at a larger distance, and (3) critical velocity for vortex occurrence is affected to a great degree by the bottom clearance.

抄録全体を表示

The author has shown a new phenomenon. A three-dimensional, rectangular or round shaped jet oscillates periodically when it is issued into a suddenly enlarged flow passage. A suitable configuration of the rectangular or round nozzle features a smaller height than the one of the flow passage. Using this phenomenon, a new hydraulic oscillator-type flowmeter without control port and feedback loop can be constructed. This paper presents an entirely new method to measure the flow rate of a gas-liquid bubble flow in a vertical pipe using the above-mentioned new hydraulic oscillator-type flowmeter. The gas and liquid flow rates can be obtained by measuring the oscillatory frequency of a gas-liquid jet flow and the pressure loss of the flowmeter.

抄録全体を表示

Partial differential equations are discretized on a triangulated random mesh in two dimensions. As a first example to test our discretizations, a Laplace's equation with Dirichlet's boundary conditions on a square area is solved on two types of triangulated mesh. The results are compared with those of the regular sguare mesh. The second example is a discretization of Navier-Stokes equations for a standard cavity problem of incompressible viscous flow. For the region of low Reynolds number, the unsteady equations are iterated on two types of triangulated random mesh and a regular square mesh, as in the first example. Our tentative conclusion is that for many problems, our finite difference method on a triangulated random mesh can lead to the same results as those obtained by the use of a regular square mesh.

抄録全体を表示

A new numerical technique for two-dimensional incompressible flow problems combining the finite element method, which is best fitted to the flow analysis in an arbitrarily shaped flow geometry, and the finite difference method, which is advantageous in computing time and computer storage, is presented, aiming at realizing large-scale flow analysis inevitable for a detailed three-dimensional flow analysis and applying it to flow analysis around moving bodies. A modified ABMAC method is used as the basic algorithm, to which a sophisticated time integration scheme proposed by the present authors is applied. Numerical results including a moving boundary problem show good agreement with the experimental results.

抄録全体を表示

Mass, momentum and energy equations for a molten liquid flow of two chemical constitutions including their solidified particles were derived by the average method. Continuum model equations for the fine particles were also derived under the approximation of the locally homogeneous field. The present theory suggests that the energy equation should have energy transport terms accompanying heat conduction, migration of particles and diffusions of chemical constitution. As the representative examples, these energy transports were evaluated quantitatively for the binary molten salt and the liquid alloy. The results showed that the energy transport term for the migration of particles should be considered in the modeling of the molten liquid multiphase flow.

抄録全体を表示

The effect of a homogeneous magnetic field on the flow resistance of a magnetic fluid whose solid particles possess intrinsic magnetic moments is investigated. Flow resistance is tested in a two-dimensional channel in which the component of a liquid flow vorticity can be precisely evaluated. The increase of a flow resistance under the effect of magnetic field is analysed with the aid of the Shliomis equation in regard to the interaction between magnetic field and vortical flow. As a result, the mechanism of the flow resistance of a magnetic fluid is clarified.

抄録全体を表示

In the present paper, a new finite-element method for incompressible electrically conducting fluid flow is presented. This new method satisfies the conservation laws of mass, magnetic flux and electric current. The main algorithm of the GSMAC (generalized simplified MAC) method is employed in order to satisfy solenoidal conditions of both magnetic and electric current fields. Flows between two parallel plates driven by electromagnetic force are calculated to verify this method. Numerical results obtained here agree with other numerical results or exact solutions. M-shape axial velocity profiles are clearly simulated near the electrode between two parallel plates.

抄録全体を表示

Numerical solutions of the Navier-Stokes equations for viscous shear flows past a circular cylinder are obtained for the range of Reynolds numbers, Re, 2≤Re≤40 and a shear parameter, ε, 0.01≤ε≤1.0. The outer boundary values and the initial ones of numerical calculations are determined by our previous analytical solutions⁽¹⁾ utilizing Oseen's approximation, and numerical calculations are carried to be single-valued throughout the field of flow in the process of repetition. The flow patterns, drag, lift, moment and pressure distributions on a circular cylinder are compared with the results calculated in the same methods under the fixed boundary conditions and ones of other papers. From these comparisons, it is seen that the values of some properties are fairly affected by the outer boundary conditions, and also the present boundary values are favorable in comparison with the previous ones.

抄録全体を表示

The behavior of an approximate solution of the steady boundary layer equations for two-dimensional incompressible flows is clarified. The moment equations are derived from boundary layer equations as an improvement of the Karman-Pohlhausen method. By means of these results, a simple procedure to construct the boundary layer flow field (including separation flow) with an arbitrarily given retarded outer flow is proposed.

抄録全体を表示

The vorticity-stream function formulation is extended and the velocity potential is introduced for calculating viscous flows along multiple bodies. The governing equations are, therefore, composed of the vorticity transport equation, the Laplace equation for the velocity potential and the Poisson equation for the stream function. The computational method is composed of the method of lines. The spatial discretization is carried out by the centered difference, and the time integration is dealt with by the rational Runge-Kutta method. The domain decomposition method is used for calculating flows along multiple bodies. It is shown that the inlet flow in a plane channel and the flows past a bank of cylinders as well as along a pair of cylinders are successfully calculated by the present method. Results shows an excellent agreement with calculations using the MAC method and the finite-element method.

抄録全体を表示

The blood flow in the ascending aorta comes to rest after the aortic valve closure until the next ejection phase starts, and the flow in the aortic arch is close to an intermittent flow rather than an oscillatory flow. In order to reveal the nature of turbulence in the aorta, the measurements of turbulence in the intermittent air flow in a straight tube were made by a hot-film anemometer. The periodically intermittent flow was generated by the piston connected with a step-rod. The resting period was varied in a range of between 0.3 and 10 sec, but the velocity wave patern of the piston was fixed. The turbulence intensity, skewness and kurtosis for the intermittent flow depend entirely on the resting period. For the resting period of 0.3 sec, the nature of turbulence resembles that of pure oscillatory flow. As the resting period becomes larger, a significant intermittence of turbulence appears in the longer range of phase. The turbulence in the intermittent flow with a relatively long resting period turns out to be close to that in the ascending aorta.

抄録全体を表示

A new numerical scheme based on the method of lines is presented for two-dimensional backward-facing step flows. The formulation is based on the vorticity-stream function representation. The spatial discretizations are carried out by the modified differential quadrature (MDQ) method which is of arbitrary orders of spatial accuracy. For the time integration scheme, the fourth-order Runge-Kutta-Gill (RKG) method is used. The Poisson equation is solved by the point Jacobi method for adaptability to vector computers. Additionally, the multi-grid method is used in order to accelerate the convergence. In the first place, laminar flow calculations are carried out to verify the accuracy of the present method. The computed reattachment length shows excellent agreement with other results. The influence of the grid number and the order of spatial accuracy on the numerical solution is also investigated, and the present method is proved to be sufficiently accurate. Next, the turbulent simulation is carried out. It is found that the recirculating vortex splits into several vortices in the reattachment zone, and the chaotic flow which forms the irregular vortex streets occurs behind the reattachment zone.

抄録全体を表示

Among the problems in the application of the high-water-content fluid, erosion induced by a cavitating jet is an important and complex one. A high-velocity jet accompanying cavitation can be observed in hydraulic valves and hydraulic pumps. This paper treats erosion induced by a cavitating jet flowing out from a triangular notch. A pair of test pieces is used in each experiment. The first test piece has a triangular notch from which the fluid flows out, forming a jet. The jet impinges to the second test piece. A nondimensional parameter defined by the ratio of the eroded mass and the impinged fluid mass is used to express the strength of the erosion. The relation between the eroded mass of each test piece and the mass of the expelled fluid is studied by statistical method. The influences of the shape of the notch and the distance between the notch and the wall upon the erosion are also discussed.

抄録全体を表示

Three components of mean and fluctuating velocities have been measured in a gas-jet impinging normally onto a solid surface. Measurements are made by the technique of rotating a probe with an inclined hot wire under the Reynolds number of 60000. Distributions of the mean velocity, the turbulence energy and the Reynolds stress are shown in the impingement region of the jet. Also, the static pressure in the jet and the surface pressure are calculated by using the measured results, and the validity of the calculating method is confirmed by comparing the experimental results.

抄録全体を表示

An underexpanded annular impinging jet is visualized using a Mach-Zehnder interferometer and is also simulated solving compressible Navier-Stokes equations. A turbulence model developed by Coakley is used in the present simulation. It is shown that the calculated density distribution in the jet agrees fairly well with the measured distribution. Both the visual observation and the simulation show that the characteristics of the underexpanded annular impinging jet depend significantly on the distance H between the nozzle exit plane and the impinged flat plate. The annular impinging jet diverges in the downstream direction provided H is smaller than the critical value H_c. However, for H>H_c, the stream lines issuing from the inner edge of the annular nozzle join at a point near the nozzle exit.

抄録全体を表示

The flow vertically issuing from a circular pipe under gravity is measured by a laser Doppler velocimeter. The flow which is bound on the wall inside the pipe is released at the pipe exit and forms a free surface. First, the jet surface profiles were measured and then, the velocity distributions close to the exit were measured in both pipe and jet. From these experimental data, it is concluded that the profiles of the jet surface and the flow quantities can be expressed appropriately by simple formulas consisting of combinations of three dimensionless numbers: the Reynolds number, the Froude number, and the Weber number.

抄録全体を表示

Measurements of the plane wall jet under the self-preserving pressure gradient were made to investigate the effect of the ratio of the maximum velocity to the free stream velocity on the time mean properties. In the present experiments the value of U_m/U_e was set at three cases over the range of 2.0 to 4.0. Mean velocity and the local skin friction coefficient have been measured with the pitot tube and preston tube, respectively. The mean flow is closely self-preserving in the range of 57<x/S₁<162. However, the similar velocity profiles for each case may differ from one another depending on the difference of the velocity ratio. The value of the constants in the log law is found not to be similar to those in the boundary layer. The inner layer thickness increases with decreasing velocity ratio; conversely the half-width decreases. The skin friction coefficient is not in agreement with the formula adopted by previous investigators.

抄録全体を表示

Flows of silane in a model of a low-pressure chemical-vapor-deposition (CVD) reactor are analyzed by simulating the molecular motion. The model is a circular pipe having an array of substrates. The pressure, which is constant between each two substrates, is seen to decrease stepwise in the downstream direction. The growth rate of silicon film is proportional to the pressure.

抄録全体を表示

The centerline development of a turbulent boundary layer flow through a gap in an isolated wall-mounted roughness element has been studied experimentally. The effect of gap size was examined at a Reynolds number of 3300, based on obstacle height and free stream velocity. The magnitude of the distortion produced by the gap varies with gap size, but the downstream tendency of the mean velocity profile is almost similar, independent of gap size. Mean flow properties show maximum distortions at about four gap sizes downstream of the gap. Well downstream of the gap, it is shown that all three centerline flows are similar, and are different from that of undisturbed flow.

抄録全体を表示

A turbulence transport mechanism of a stratified flow was studied analytically by using a third-order upwind difference method for the Navier-Stokes equation without any turbulence average modelling. A stably stratified shear flow was analyzed where two parallel streams of water with different densities moving at different velocities were merged at the entrance to the channel. Regular arrays of the cross-flow vortices and fluid mixing were calculated at the interface where the analytical grid transformation method was used for concentration of the mesh size at the interface without losing any discretization order. Non-dimensional distributions of density and velocity at a vertical cross section agreed with experimental data. Turbulent mass diffusivity became negative at the upper side of the mixing layer, where dissipation of buoyancy had a large effect.

抄録全体を表示

The rotors and stators of turbomachinery operate in various types of shear flow such as wall boundary layers, jets and wakes. This paper aims firstly to propose a singularity method for thin aerofoil with thickness in exponential shear flow by introducing the fundamental solutions found by Ichikawa-Hirano, and secondly to clarify the effects of shear parameter on the characteristics, especially the pressure coefficient distribution in that shear flow.

抄録全体を表示

An existing lifting-line theory for a supercavitating hydrofoil in spanwise shear flow between parallel plane walls is applied to partial cavitation in the same condition. A lifting-line equation is derived from an assumption holding two-dimensional at any spanwise position, and the method of solution of the lifting-line equation is applied, in which an eigenvalue problem of the Sturm-Liouville type should be solved. The method to obtain the cavity spanwise distribution, in which the solution of type lifting-line equation is used, is also applied. The wing for the numerical example is flat in section, rectangular in planform, and 5 degrees in attack angle. Effects of the main stream velocity profile, aspect ratio and cavitation number on local lift coefficient, total lift coefficient and induced drag coefficient for force characteristics, and on spanwise distribution in cavity length and its three-dimensional effect for cavity characteristics are clarified.

抄録全体を表示

To improve the reliability on the performance of hydraulic machinery, especially at large angles of attack near stall conditions, the lift-and-drag performance of a symmetric hydrofoil was measured in the wide region from a noncavitating state to a supercavitating state in relation to the corresponding cavitation aspects. The noncavitating flow around the hydrofoil in the stall condition was also computed by directly solving the N-S equation. The spectra of lift fluctuation in noncavitating states are similar to those in states of the cavitation violent vibration. This means that the shedding of large-scaled coherent vortices corresponds well to the shedding of bubble clouds in the cavitation violent vibration.

抄録全体を表示

Suppression methods for rotating stalls in low-specific-speed centrifugal compressors with vaneless diffusers are experimentally studied. Using a low-solidity vaned diffuser, the aerodynamic performance is improved and the rotating stall is suppressed. The main parameter which affects the suppression is the ratio of the diffuser vane leading edge to the impeller tip radius. The suppression is large where the leading edge radius ratio is less than the radius ratio at which flow begins to reverse as calculated by axisymmetric boundary layer flow analysis. For rotating stalls in vaned diffusers, the stall cell tends to be equal to 1.

抄録全体を表示

Experiments for water flows using flow visualization techniques and for air flows using some conventional instruments were conducted on the vaneless diffusers. The rotating stall cells were confirmed in the region of lower flow rates in the vaneless radial diffuser, and the flow characteristic parameters of existence of the rotating stall cells were attained for various space widths between the impeller open face and lower diffuser side wall. The relationships between the variations in pressure and the traveling speeds of the stall cells were also shown. The pressure distributions in the vaneless diffuser can be represented by an empirical relation for the outer range of normal operating flow rates.

抄録全体を表示

Thin-film formation on a rotating disk during the spin-coating process is analyzed. In the experiments for a solution of PMMA (polymethyl methacrylate) solute and chlorobenzene solvent, the final film thickness of dry film formed on silicon wafers for integrated circuits is measured with an ellipse thickness meter. Also, the transient film thickness during the entire film formation process on a rotating optical glass is measured using a laser displacement meter. A numerical calculation considering heat and mass transfer such as solvent evaporation is performed using a one-dimensional complete model proposed by the authors for each phase of liquid film and adjacent gas phase. Satisfactory agreement is obtained between these numerical and experimental results and the effect of various process parameters, e.g., spinning speed and initial film thickness, is clarified by this study.

抄録全体を表示

The problem under consideration is the axisymmetric unsteady potential flow past a slender body of revolution capable of arbitrary radial deformations in a tube which also performs wavy deformation, where the mean radius of the tube wall is the same order as that of the body. In the analysis, the Stokes stream function is introduced and the method of matched asymptotic expansions is used. The flow is examined for two different time parameters. As a result, unsteady contributions to the flow generated by a deformable slender body and tube are obtained up to the second-order approximation, and effects of various parameters on the axial force coefficients are examined in two cases.

抄録全体を表示

The dependence of the small-signal gain coefficient of a supersonic flow CO chemical laser on the area ratio of nozzles is measured using a shock tunnel facility. It is shown that the increase of the Mach number of O₂ raises the peak of the gain and shifts the location of the peak gain to the upstream direction. On the other hand, the increase of the Mach number of the dissociated products of CS₂ decreases the peak gain and shifts the location of the peak gain to the downstream direction. A theoretical model which was developed previously is used to examine this interesting phenomenon and it is shown that the presence of the base relief between a CS₂ nozzle and an O₂ nozzle has great effects on the mixed stream.

抄録全体を表示

The digital image processing techniques of particle tracking velocimetry (PTV) have been developed rapidly, because they can realize the real-time and contact-free measurement of instantaneous two- or three-dimensional velocity fields. The measurement accuracy by these techniques is still insufficient. In the present study a new simplified double-check method is proposed to correct mismatched particle pairs which are found in the results of velocity vectors when applying a cross-correlation method. As a result, almost all mismatched particle pairs are replaced by correct ones, and the accuracy of the velocity field measurement can be improved. Some suggestions are given as to proper particle size and particle distribution density.

抄録全体を表示

The purpose of the present study is to propose a new method of particle identification in three-dimensional particle-tracking velocimetry (3D PTV) using binary image data. It is based on the necessary condition for particle identification and the 3D cross-correlation method for evaluating the similarity of particle distribution patterns in two spaces. Computer simulations are carried out to investigate the effects of particle size, search subregions and identification subregions on the performance of particle identification. The method has two key advantages: One is a quick and high efficiency particle identification performance and the other is that the computer memory required for the computation of particle identification is generally smaller compared to the other methods.

抄録全体を表示

A search was attempted for the noise source of a multiblade fan by measuring the acoustic intensity using a sound transmittable scroll, and by investigating the state of flow in detail by measuring three-dimensional flow and turbulence at the outlet of an impeller with the aid of a small-sized hot wire probe. As a result, it was clarified that the principal noise sources of a standard multi blade fan are roughly divided into the main flow zone at around 30% from the hub surface of the impeller, and the separation zone near the shroud surface. The former is the noise generated by the turbulence near the blade suction surface in the main flow zone where the blade passage velocity is large. The latter is the noise generated by the turbulence near the blade in the separation zone of the inlet flow.

抄録全体を表示

Output of horizontal axis wind turbine is improved by tip vane. This paper describes the results when the taper blade are used to the wind turbine. Comparing 1st report with 3rd one, the power coefficient on the turbine with the taper blade is more larger than that on one with the equi-chord length. The maximum power coefficient reaches to 0.48 in case of the taper blade. Also, this paper describes the effects of setting angles of tip vane to the tip main blade.

抄録全体を表示

At the first stage of a water power survey of a river, it is important to select the optimal water power site. The most important condition to be satisfied is to determine the optimal site where the greatest and most economical amount of water energy can be obtained. This paper presents a new method in which the optimal arrangement of the water power stations is determined by a computational operation using discrete data at points along the river such as the drainage area, altitude and distance along the river channel as obtained from topographical maps, instead of drawing on engineers' experiences and the intuition of experts. The results obtained by this method are then compared with data on existing water power stations and the results planned by expert engineers to show that this new computational method is superior.

抄録全体を表示

A mechanism for large-scale mantle convection is proposed on the basis of a new asymptotic solution to steady, two-dimensional, free convection at large Rayleigh and infinite Prandtl numbers. In the conventional asymptotic solution the isothermal core flow is mainly driven by the plume buoyances, yielding the Nusselt number proportional to one-third power of the Rayleigh number and inversely proportional to the cell aspect ratio. This solution is valid only for small-scale convection with nearly unit aspect ratio. The new solution which is revealed in the present paper describes the core flow which is mainly driven by the horizontal thermal boundary layer buoyances, and gives a favorable property to base large-scale mantle convection. The predicted Nusselt number is proportional to one-fourth power of the Rayleigh number and inversely proportional to the square root of the aspect ratio.

抄録全体を表示

A new enhancing technique was developed for a natural convection adjacent to a vertical, heated plate. In order to enhance the heat transfer, V-shaped diverter plates of which the edges faced upstream, were attached onto the vertical plate in a staggered layout. These plates work not only as the extended surface but also as the heat transfer promoter. The overall heat transfer coefficients of the above enhanced surface were measured and compared with the nontreated, flat surface and the conventional finned surface. The results show that the highest heat transfer performance is achieved for the present surface and that the heat transfer coefficient becomes 40% higher than that of the conventional finned surface with the same total surface area and fin height.

抄録全体を表示

In this paper, the heat transfer of natural convection along a vertical flat plate was investigated experimentally. Heat transfer coefficients were first measured in a wide variety of projection arrangements. The results showed that heat transfer coefficients were about 1.6∼1.8 times as large as those for a smooth wall. Then, various wall temperature patterns were also visualized by a liquid crystal sheet. It was noted that low-temperature streaks appeared on the wall, and that they played a significant role in heat transfer.

抄録全体を表示

The budgets of turbulent energy, Reynolds shear stress, mean square scalar variance and turbulent heat fluxes have been evaluated in a thermally driven boundary layer in air along a vertical flat plate. In the near-wall region, the velocity-gradient correlation plays an important role in turbulent energy production, and thermal energy is directly converted into kinetic energy through this correlation. Consequently, Reynolds shear stress and streamwise turbulent heat flux near the wall, which are normally considered to be closely related to the energy production process, behave differently from those in the ordinary turbulent boundary layers. On the other hand, the energy transfer in the outer region of the boundary layer becomes a process similar to that observed in the usual boundary layer.

抄録全体を表示

Heat transfer results were presented for the combined forced and natural convection around a heated cylinder placed in the downward flow of water. Local heat transfer coefficients were measured in the range of Reynolds and modified Rayleigh numbers of 100<Red<2500, 1.5×10⁶<Ra^*_d<4×10⁸. The result demonstrates that the heat transfer rates increase at the lower half of the cylinder with an increase in wall heat flux. Thus, the average Nusselt numbers for the combined convection become 20% higher than those estimated from the pure forced or natural convection. This result is rather different from the results by other workers. The enhancement of the heat transfer rates is explained by the recession of the separation point. Furthermore, the average Nusselt numbers of the combined convection correlate well with the parameter Gr^*_d/Nu_dRe²_d, and the combined convection region corresponds to the value of this parameter as 0.1< Gr^*_d/Nu_dRe²_d<10².

抄録全体を表示

This paper is an experimental study dealing with the basic boiling heat transfer for a solar-powered absorption chiller. Three kinds of surface-worked heat transfer tubes were tested in bulk liquid or in narrow spaces under several reduced pressure conditions, and the saturated boiling heat transfer characteristics were determined. The obtained data were compared with the data on smooth surface tubes of the same conditions. The experimental results show that the surface-worked tubes in bulk liquid do not get a greater boiling heat transfer promotion than that in the case of the smooth tube, but the surface-worked tubes with narrow spaces get considerable heat transfer enhancement in comparison to the than case without narrow spaces, and a new correlation equation is proposed.

抄録全体を表示

The augmentation effect of electrohydrodynamically (EHD) induced flow disturbance on forced-convection heat transfer in a channel was experimentally investigated. This study was carried out with the unique point that the flow near the wall is disturbed actively and controllably by applying electric fields between the wall and array of wire electrodes installed near the wall along the main stream. The liquid mixture of refrigerant R113 (96wt%) and ethanol (4wt%), called Fronsorubu AE, was selected as a working fluid. Heat transfer was found to be promoted intensely in the trubulent flow as well as in the laminar flow, up to a factor of about twenty-three in the case of laminar flow. It is noteworthy that the rate of increase in heat transfer coefficient is larger than that in the pressure drop. From the measurement of velocities by a laser Doppler velocimeter, it was clarified that the electrohydrodynamically induced flow disturbance brings about large heat trasfer coefficients.

抄録全体を表示

Experiments have been performed to investigate melting heat-transfer characteristics along a horizontal heated cylinder immersed in a liquid ice. A mixture of ice particles and ethylene-glycol aqueous solution was utilized as the testing liquid ice. The experiments were carried out for a variety of parameters such as heat flux, heated-tube diameter, and initial concentration of aqueous binary solution. Attention was mainly focused on visual observation of the melting feature. The results revealed that the melting front of the current liquid-ice layer might advance, in general, rather horizontally, unlike the normal melting observed in pure ice and PCM.

抄録全体を表示

The method of cool energy storage using heat transfers of direct contact boiling and condensation between refrigerant as a working medium and water as a PCM in an enclosure was proposed in the previous report. It was also shown that the efficient storage and release of cool energy were achieved for small height of water up to 50mm. In this report, the effect of height of storage material, the rate of heat storage and release and the heat transfer characteristics using same method were investigated under large height of storage material up to 517mm. HCFC142b and water or 2% n-butanol-water solution were used as a working medium and a storage material, respectively. Heat of chemical reaction of gas hydrates of HCFC142b and water was utilized. As a result, an efficient cool energy storage and release was achieved for large height of storage material. In particular, high rate of heat storage was maintained for all heights of the storage material for n-butanol solution.

抄録全体を表示

The heat transfer surface used in the experiments was a chrome-plated smooth brass pipe of 28mm in diameter and 1400mm in length. The film Reynolds numbers were varied in the range of 40-400, which includes the range of real machines. The average absorption mass flux is compared with the numerical results derived from the laminar flow model proposed in the previous paper. The agreement is good up to 100 in Re_f, but the experimental values are far higher above 200. This may be attributed to the wave motions on the film surface. Pictures show that the film is completely smooth only below 20. Beyond 20, ring-shaped waves appear, but the surfaces between the waves are relatively smooth for Re_f below 200. The measurements of film the thickness show that its minimum is constant at about 0.38mm, but its maximum thickness increases for Re_f beyond 60.

抄録全体を表示

Measurements of sound pressure level and frequency analysis were carried out for the control of oscillation noise due to the condensation of vapor injected from submerged various orifices into subcooled water. The phenomena were observed by means of shadowgraphy using a still camera. Peak frequency and amount of the oscillaoion noise caused by the condensation of vapor were dependent on subcooling and shapes of injecting orifice. The effect of bulk temperature in a water tank and difference among a single-orifice, a multi-orifice, a prous-disc-orifice and the other orifice were discussed and good predictive results for the visualization in a quiescent subcooled water envirnoment.

抄録全体を表示

A compression-type metal hydride heat pump system has been constructed which utilizes the exothermic and endothermic characteristics of hydrogen storage alloy during its absorbing and desorbing reaction with hydrogen. The system is composed of two identical heat exchanger units, a hydrogen compressor, a cooling/heating fluid circulating system, and a control unit. Four effects on the system performance were examined: (1) hydrogen mass in the system, (2) fluid mass in the reservoir, (3) switch-cycle timing, (4) flow rate of the fluid. Under the optimal parameters, the output of the system was 1.65kW and the coefficient of performance (COP) was 3.7

抄録全体を表示

The turbulent structures in the reattachment region of backward-facing step flow were investigated by using the crosscorrelations between velocity fluctuations of three-dimensional field and wall-pressure fluctuations. The sequential contour maps of crosscorrelation values were calculated from the simultaneous measurements in order to display the change and travelling of turbulent structures three-dimensionally. Two kinds of flow field were measured for comparision with the characteristics of the turbulent structures. It is found that the turbulent structures affected by the wall-pressure fluctuation at the measuring point move to the wall-pressure measuring point, and after the collision, the turbulent structures move downstream, staying near the wall. From the visualization results of the real-time two-dimensional wall-pressure fluctuation, these structures were brought about at various points simulataneously, which produced the three-dimensionality in the reattachment region.

抄録全体を表示

The transient temperature distribution in a row of wafers heating in a vertical diffusion furnace was numericaly calculated as the heating power of the furnace was PID controlled. Radiation heat transfer was combined with axisymmetric unsteady conduction in wafers and the furnace. When the feed forward control of the heating power was used, which meant that the heater temperature was set higher than a given heating temperature during insertion of the wafers into the furnace, the temperature of the wafers reached the heating temperature rapidly. Radiative properties of silicon wafers changed from semi-transparent to opaque at a temperature of 500°C, and the effect of the properties on the temperature distribution in the wafers were calculated. The possibility of occurrence of thermoplastic deformation of the wafers during a withdrawal period was higher than that during an insertion period.

抄録全体を表示

A single CWM droplet was suspended in a hot air stream by a fine R-type thermocouple. The surface temperature of this evaporating and burning droplet was measured by a radiation thermometer. The emissivity of the CWM droplet surface was kept at around 0.98 until the char combustion of the droplet proceeded to its middle stage. In the later stage of the char combustion, the emissivity decreased gradually to 0.82. Several degrees of temperature difference between the center and the surface of the droplet remained at the dry-up time, even when the diameter of the droplet was reduced to 2mm. The surface temperature at the start of char combustion was 700K when the droplet was exposed in surroundings of less than 900K. However, the surface temperature at the start increased from 700K in surroundings where it's temperature exceeded 900K. When the surroundings were 650K, the surface temperature at the char combustion start was 700K and higher than the surroundings, and the center temperature of the droplet was higher than that of the surface, which suggested that slow exothermic reactions in the droplet were already initiated before the char combustion started.

抄録全体を表示

The combustion state in a furnace may appear stable, eventhough an oscillating combustion potential may exist. A new index, called "the resonance factor", is proposed to quantitatively estimate the degree of the combustion oscillation potential, and a measurement technique to display it is developed. The resonance factor is defined as the root meansquare of the ratio of a power spectrum value at a resonant frequency to the mean square value of pressure fluctuation in a furnace. Applying this technique to a combustion test furnace with a single gas burner, it is shown that the resonance factor is useful in clarifying the combustion state where the lower the resonance, the more stable the combustion.

抄録全体を表示

The term "film combustion" means the diffusive combustion of fuel gas evaporated from a condensed fuel surface with an oxidizer gas flowing along the surface. The present study aims to gain a fundamental understanding of the effects of separated flow created by an obstacle on stabilization and structure of the diffusion flame. As an obstacle, a rod with diameter d is placed upstream of the fuel surface with its axis perpendicular to the flow direction. The distance L from the fuel surface to the axis of the rod as well as the main stream velocity U_∞ is varied to change the effects of the separated flow on the fuel surface. It is found that under appropriate conditions, a flame moves forward from the fuel surface and is stabilized behind the rod. A map is obtained which describes the state of flame stabilization in the U_∞ plane. Distributions of temperature and main species concentration are measured to elucidate the heat and mass transfer processes in the flame.

抄録全体を表示