Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 1963"

On the Conditions of Incipient Subcooled-Boiling with Forced Convection

Abstract: Generally it is possible to start the boiling at the surface temperature of a heated wall somewhat exceeding the saturated temperature of the liquid, and the heat flux of initial boiling varies depending on the fluid temperature, liquid velocity, system pressure, surface condition of the heated wall, and so on. In this paper, an analytical consideration was tried to make clear the conditions of incipient subcooled-boiling with forced convection, and the equation to estimate the heat flux under that condition was determined. By comparing with the authors' data at atmospheric pressure or the experimental data of previous investigators at higher pressure, it is known that the analytical results agree very well with experimental ones. The relation to estimate the conditions of incipient boiling is as follows ; [numerical formula] where, A : heat equivalent of work, De : hydraulic diameter, Pr : Prandtle number, q : heat flux at incipient boiling condition, γ : latent heat, Ts : saturated temperature, ΔTsub : subcooling, u : velocity, v : specific volume, λ : thermal conductivity, ν : kinematic coefficient of viscosity, σ : surface tension. Suffix ; g : vapour, l : liquid, 0 : value of bulk temperature.

Convective Heat Transfer of the Rotational and Axial Flow between Two Concentric Cylinders

Abstract: This paper considers convective heat transfer to a flow in an annular gap with an axial flow between a rotating inner cylinder and a stationary outer cylinder The experimental results indicate that the heat flow from the surface of the inner rotating cylinder is the sum of the following two kinds of the heat flow : one by turbulent vortices induced by rotation instead of Taylor vortices and the other by the turbulent axial flow For turbulent vortices we have the empirical equation for the overall heat transfer coefficient when without an axial flow : [numerical formula] Moreover for the turbulent axial flow we have the empirical equation on the heat transfer coefficient [numerical formula] Here it is shown how this correlation of summing up the two heat flows is applicable to the wide regime of such mixed flow

Heat Transfer in an Open Thermosyphon

Abstract: In this report two sorts of experimental studies of free convection heat transfer in an open thermosyphon tube are described : One is carried out using an apparatus with a rectangular passage for observation of the flow pattern, and the other gives the exact heat transfer data, including the turbulent region using two sorts of apparatus with a circular passage. On the basis of such studies, the heat transfer mechanism of thermosyphon in both laminar and turbulent regions are explained. In the laminar region experimental data agree closely with analytical solution. As for the occurrence of turbulence, however, it may be probably originated at a boundary between up-flow and down-flow, where only the down-flow is disturbed at first, and there the heat transfer data are little different from those in the laminar region. When a turbulence occurs under the impeded flow regime, however, it spreads to all over the tube at once, affecting heat transfer data considerably, but they can be correlated by using Prandtl number and length-radius ratio as parameters. Finally the correlating equation for the heat transfer in an open thermosyphon tube is derived.

Load Distribution on the Contact Line of Helical Gear Teeth : Part 1 Fundamental Concept

Abstract: The load distribution along the contact line of helical gear teeth is studied. The deflection of gear teeth is characterized by the second kind integral equation of Fredholm, and the measurement of strain at the root of a gear tooth leads to the first kind of the same type equation. The load distribution can be obtained as the solution of any of the above equations. Since each of them can hardly be solved analytically, the numerical solution by a system of linear equations is introduced. The choice of numerical integration formula, the number of ordinates, the accuracy of the solution and the basic characters of the load distribution are investigated thoroughly in this paper, employing thin cantilever plates with large width. It is concluded that Gauss' formula of numerical integration is most suitable and is used conveniently for this problem.

Vibrations Caused by Dry Friction

Abstract: Self-excited vibrations caused by dry friction, which is generally expressed as a function of relative sliding velocities between two solid bodies, are analysed theoretically and observed experimentally. The characteristics of these vibrations are divided into two groups by the type of friction. One is experienced in the case of pure dry friction, where the amplitudes of steady vibration increase with the increase of sliding velocities and the frequencies are nearly equal to the natural frequency of the system. Another occurs in the case of boundary lubrication, where the amplitudes vary slowly with sliding velocities and the frequencies increase with the increase of sliding velocities. In the case of boundary lubrication, self-excited vibrations occur by hard excitation, even if the frictional force increases with the increase of relative velocities. Experimental results obtained from the case of dry friction show good coincidence with the theoretical results.

Thrust of the Disc Valves

Abstract: Clear knowledge on the thrust of valves is necessary to discuss the stability of valves which plays an important role concerning the stability of a pipe line. In order to have a general idea of relations between the thrust and the lift, and between the discharge coefficient and the lift of common valves, we studied the characteristics of the most simplified valve, that is, a circular disc valve. The flow between the valve and the valve seat is very complex. The pressure distribution over the valve surface and the lifting-force were calculated analytically for various types of the flow, and examined experimentally for three kinds of disc valve. Experimental results show the correlation between the lifting-force and the discharge coefficient.

The Theoretical Research on the Blanking of a Sheet Material

Abstract: In this paper, the author applied the theory of limit analysis to a theoretical investigation of the blanking process. In Part I, the statically admissible stress field in a sheet material was analysed on the assumptions : (1) The sheet material is a non-hardening plastic-rigid body. (2) The material near tool edges is approximately in the state of plane strain. (3) The stress field consists of several regions of constant stress separated by straight lines of discontinuity. In Part II, the deformation process of the sheet material was devided into four stages, and the kinematically admissible velocity field was analysed in each stage. Furthermore, comparing the solution of the stress field with that of the velocity field, an exact solution of the blanking force was obtained for blanking with smooth punch and die.

Photoelastic Investigation of the Stresses in Cemented Joints : 1st Report, Lap Bonding

Abstract: The stresses in cemented joints, specially lap joints, were studied photoelastically. The photoelastic mcdels were made of epoxy resin and epoxy rubber or epoxy resin and metal, namely, each material had its own elastic constant. The shapes of the adhesive joints are a rectangular type, with a fillet, with convex or concave semi-circular ends. According to the results of experiments, the fillet is more effective for reducing the high stresses in lap joints. The other result has revealed that the joint with concave semi-circular ends is best, one with rectangular ends is second best and one with convex semi-circular ends is worst of all so far as the stresses in lap joints are concerned.

The Effects of Runner Surface Roughness on the Performance of a Francis Turbine

Abstract: The effects of runner surface roughness on the performance of a Francis turbine have been studied experimentally. The performance data were obtained for seven various type roughnesses from 0.007 to 1.0 mm in protuberant height. Preliminarily, the frictional resistance of enclosed rotating disks with respective roughnesses was measured for laminar and turbulent flows, in order to relate these different roughnesses to hydraulic frictional resistance. Through these disk-friction tests, the roughness of these surfaces could be expressed by the equivalent Nikuradse sand-grain diameter. The following conclusions may be drawn from this experimental study. (1) The turbine efficiency dercreases in proportion to the frictional resistance of its equivalent sand roughness. (2) With an increasing roughness, the maximum efficiency point shifts to the lower speed and the lower discharge. (3) Concerning the admissible roughness, the Schlichiting's formula is in good agreement with this experiment.

Combination Tones of Summed Type in Nonlinear Vibratory Systems

Abstract: When two periodic disturbing forces with frequencies Ω1 and Ω2 excite a nonlinear vibratory system, combination tones having a frequency Ω=Ω1+Ω2 appear. In the present paper, the combination tones are discussed analytically and experimentally. For a small value of frequency ratio K=Ω2/Ω1 (Ω2lΩ1, Kl1), the response curves of combination tones are hard or soft spring type, and the magnitudes of amplitude increase with the value K and the value of the unsymmetrical nonlinearity. When the value K is somewhat large, peculiar response curves take place, and the amplitudes of harmonic oscillations become larger than those of combination tones. By introducing the conception of apparent external force, the back bone curves and the phase angles can be obtained, and further, the effects of unsymmetrical nonlinearity can be explained clearly. Generally, the amplitudes of combination tones are comparable to those of ultraharmonic oscillation.

Fundamental Study on Electrohydraulic Forming

Abstract: There were many studies on electrohydraulic forming in which the relationship between the deformation of metallic meterial and the stored electrical energy was investigated. It is necessary for us, however, to explain the correlation between the deformation resistance for each of these metals and the pressure pulse in order to analyze the deformation characteristic of metals. The experiments were carried out by means of pressure gage (BaTiO8) on deformation pressure and pressure pulse which were directly related to the deformation, and further, the shock wave energy was calculated. The efficiency of these apparatus was discussed. The clearance between the electrodes creating pressure was short-circuited with several kinds of fine wire, and the influences of the diameters and lengths of wires were presented. Also in the case when there existed water only between the electrodes, the influences of electrode diameters and clearances were presented. It is found from experimental results that cases where the clearance between the electrodes was short-circuited with a fine wire are superior to the case where water was the only pressure source between the electrodes, and the aluminum wire which had a low boiling point metal was effective. The rise time of pressure pulse is about 5μsec and its duration is about 15μsec. Such shapes of pressure pulse do not change up to 1000 joule charged energy. Shorter wires are better than longer wires as pressure sources, while the diameter of wires creating the largest pressure is limited by characteristic of apparatus and the charged energy.

Research on Externally Pressurized Circular Thrust Gas-Lubricated Bearings

Abstract: In externally pressurized gas-lubricated circurlar thrust bearings, the occurrence of depression in the pressure profile is observed under some working conditions. Following the previous paper on the theoretical investigation of pressure depression, this paper investigates theoretically the pressure distribution in externally pressurized circular thrust gas bearings with a circular recess by assuming the generation of a normal shock wave in the bearing recess. Good quantitative agreement is found between the analytical results and available experimental data except the case of small bearing clearance height or deep recess. In order to prevent the pressure depression just after the gas supply hole, it is effective to provide a round or tapered chamfer at the entrance edge of the hole to the bearing clearance or to make the recess tapered doubly. Through these alternations, the shape of pressure distribution becomes flatter so that the load capacity can increase remarkably.

A Study on the Exhaust Muffler of Internal Combustion Engine

Abstract: In this paper, it was studied on the exhaust muffler of an internal combustion engine. Generally, the theoretical analysis of the exhaust muffler of an engine contains various difficult factors. For example, almost all the recent reports are based on the presupposition that the tail pipe of a muffler has an infinite length. In this report, therefore, a theoretical formula of the attenuation was studied from the point of view that the tail pipe has a finite length. The formula was established by the application of the theory of electric transmission line, and the values calculated by the above formula have been found practically in good agreement with those obtained from the experiments. Moreover, many experiments were executed as to the influence of varying the various factors of the cavities and the tail pipes.

On the Tension of an Infinite Plate Containing an Infinite Row of Elliptic Holes

Abstract: Utilizing the physical meaning of interference of notch effects in two-dimensional elasticity, the author developed a method of calculating the stress in a plate due to the effect of interference of many notches. By this method, the stress concentration factors of an infinite plate containing an infinite row of elliptic holes subjected to tensile load were calculated. When the ellipses degenerate to circular holes, the stress concentration factors obtained by author's method are in close agreement with the exact values obtained by Howland and Isida.

Tension of a Semi-infinite Plate with a Circular Hole Connected to the Straight Edge by a Slit

Abstract: When there is a crack on the straight edge of a plate under tension, to prevent further development of the crack, a circular hole is drilled at the end of the crack. Considering the above case, the author has solved the problem of a semi-infinite plate with a circular hole connected to the straight edge by a straight and narrow slit subjected to uniform tension parallel to the straight edge. He has obtained stress distributions on the plate and the factors of stress concentration at the bottom of the circular hole.

Noise of Ball Bearing in Electric Motor

Abstract: There are many performances of electric motors equipped with rolling bearings, and one of the most important performances is running noise. Especially, for a small three phase a-c induction motor, quiet running is demanded. However, the component noises in the motor noise are not well known and the influences of ball bearing on the motor noise are not made clear. Therefore, to abate the motor noise, we must study it. So, in the first place, the noise of a small three phase a-c induction motor was divided into several component noises, and ones influenced by ball bearings were found out ; next, the influences of ball bearings were examined, lastly the causes of the influences were made clear in the present paper. As a result of the above studies, we could establish the most suitable treatment of ball bearings theoretically, and further obtain new knowledges on fitted ball bearing noise.

Vibration of a Circular Arc Bar in its Plane : Both Ends Built-in

Abstract: The Lagrangian in the vibration of a circular arc bar in its plane is discussed and the radial and tangential displacements are obtained in general forms. The frequency equations of a circular ring and a circular arc bar with hinged ends for the vibration in its plane are obtained and they are compared with the already known solutions. Then, the frequency equations of a circular arc bar with both ends built-in are obtained from the Lagrangian and the nondimensional frequencies are shown in figures. Also, for the vibration of a circular arc bar with free ends, the nondimensional frequencies are calculated and are shown in figures.

Fluctuation of Void Ratio in Two-Phase Flow : 1st Report, The Properties in a Vertical Upward Flow

Abstract: The remarkable characteristic of a two-phase flow is the pulsating phenomenon. In this study, the pulsation has been measured by an electrode probe as the pericdical fluctuation of the local void ratio to analyse the flow configuration quantitatively. The experiment has been carried out on the air-water two-phase vertical upward flow in a tube of 27.6 mm ID and 2595 mm length. This paper presents the period of the void ratio fluctuation, the pitch of the void ratio and the gas time ratio. And the empirical formulas of the average period and the average pitch are given. The behavior of the gas time ratio in this experiment agrees with that of the local void ratio which has been reported by other investigators. Thus, it is shown that the void ratio distribution reported before was the distribution of the time mean value of the local void ratio.

Stall-Flutter in Cascade : 1st Report, Translatory Vibration of Cascade Blades as Treated by Semi-Actuator Disc Method, Part 1

Abstract: In the 1st report fundamental equations for calculating the aerodynamic force acting on the cascading blades vibrating in a translatory mode were given This report shows the results of the calculation and gives the criterion for the flutter (the boundary of the region where the aerodynamic damping force cannot be negative)

Vibration of a Rotating Cylindrical Shell

Abstract: In this paper, the state of vibration of a circular cylindrical shell which is rotating about its axis with a constant angular velocity is discussed utilizing the fundamental differential equation introduced by the present author. The same problem has researched by G.H. Bryan(1) ; the utilization of his results, however, is very limited because of his assumption of inextensionality. In this paper, no such limitation is imposed and several problems which cannot be solved by Bryan's method are exhibited. The relations between the angular velocities of the nodes and those of the shells in various wave patterns are obtained, and in the particular case where the shell vibrates as a beam, the relation between the critical speed and the natural frequency is also discussed.

A Study of Viscoelastic Fluid Flow : 2nd Report, Extrudate Irregularities

Abstract: In the flow of molten high polymers through capillaries, an instability occurs at shear stresses 105∼108 dynes/cm2. The instability results in emerging streams of irregular shape. Several explanations of extrudate irregularities have been published up to the present, but they may be considered to be insufficient. In this paper, considering that the flow states of a viscoelastic fluid are governed by the elastic force, the viscous force and the inertia force, two dimensionless numbers Re* and NE are deduced. Then, it is verified by the experiment that the onset of instabilities in an extrudate of molten high polymers depends on these dimensionless numbers Re* and NE.

Heat Transfer of Slurry Flow with Internal Heat Generation : 3rd Report, Laminar Heat Transfer of Thermal Entrance Region in a Circular Tube for a Pseudo-Plastic Fluid

Abstract: This paper deals with an analysis to determine the heat transfer characteristics of thermal entrance region for the established laminar flow of a heat generating pseudo-plastic fluid through a circular tube with wall heat transfer. The conditions of wall heat transfer treated in this paper are for both cases of uniform wall heat flux and uniform wall temperature. In this analysis, the numerical calculations were done by means of a digital computer KDC-1. The results for no internal heat generation with uniform wall temperature which were analyzed as a special case agree very well with those by Bird et al(2). And the heat transfer characteristics in the case of uniform wall heat flux approach those of a fully developed region which were calculated by U. Grigull(5).

On the Steady-State Creep of Rotating Solid Disks

Abstract: Here is described an analytical method on the steady-state creep of a rotating disk with variable thickness and nonuniform temperature distribution. The numerical computation by this method is easy. Creep tests of rotating solid disks of forged 18-8 Mo stainless steel were carried out in a hot spin tester prepared by the author and his associates. At the same time, specimens were cut out from the various parts of the disks and put to creep tests and other material tests. The analytical results were compared with experimental ones. Mises criterion has shown better agreement with the test data.

On the Strength of Toroidal Shells : 1st Report, A Proposition on the Solutions

Abstract: A method for solving the fundamental differential equations for the symmetrical problems of toroidal shells is proposed in this paper. The perturbation method is used, and the solutions are obtained in such a form that the numerical values of the solutions may be easily found, if the values of the parameters are given. The ranges of the values of the parameters in which the solutions are available with satisfactory accuracy are checked.

On the Inlet-Flow Field for a Two-Dimensional Supersonic Cascade with Curved Entrance Regions

Abstract: This paper deals with an analytical study of the inlet-flow field for a two-dimensional cascade, where the axial flow is subsonic and the relative flow is supersonic. The case is considered as the flow model, where the suction surface of a blade is convex in the entrance region. By using this analysis, a complete inlet-flow field can be constructed, then the loss due to shock waves estimated. Two numerical examples for different circular entrance regions are given in the case where the Mach number is 1.6 at the end of the entrance region. The results in either case indicate that the pressure amplitude decreases gradually below about 4% of the dynamic pressure upstream at infinity in the place removed by more than about 1.5 blade space, and the loss due to shock waves is so small as to be negligible.

Experimental Study on Flutter in Cascading Blades : 1st Report, Measurement of the Aerodynamic Damping Force Acting on Cascading Blades Vibrating in Translatory Mode

Abstract: For the purpose of investigating the aerodynamic damping effects on vibrating cascade blades, the authors made a water tunnel with a linear cascade in which five blades vibrate in a translatory mode with arbitrary frequency and phase angle between the adjacent blades. A series of experiments were carried out on an isolated blade and on the cascades with the following conditions : Blades : NACA 65-(12) 10 (fixed : 8, vibrating : 5) chord : 30 mm span : 60 mm solidity : 1 stagger angle : 0°, 30° amplitude of vibration : 2 mm The experimental results were analyzed by comparing with the theoretical ones hitherto obtained and with the aid of the considerations about the quasi-steady force of vibrating blades.

The Lubrication of Bevel Gears

Abstract: In bevel gears, the behaviours of the oil in the gear box differ from those in spur gears, presenting conditions worse than the latter. In this paper, the mechanisms of the oil being supplied to the tooth surface and of the oil film formation between the teeth surfaces of pinion and gear are investigated. And it was made clear that jet lubrication is superior to bath lubrication in various points.

A Study on the Hydrodynamic Instability in Boiling Channels : 2nd Report, The Instability in Two Parallel Boiling Channels

Abstract: An investigation is carried out on the hydrodynamic instability in a system having two parallel boiling channels. The basic equations for the circulation flow rates and the driving heads are derived from the laws of conservation of mass, energy and momentum. The stability of equilibrium in a hydrodynamic system and the modes of vibration are discussed. As the result, the following facts are found. (a) A hydrodynamic system is always stable when the equilibrium of the system lies in the range of positive inclination of the characteristic curve for each channel and (b) always unstable when the equilibrium is in the range of negative inclination of the characteristic curve for each channel ; (c) when the equilibrium lies in the range of positive inclination for one channel and in one of negative inclination for the other channel, the system is either stable or unstable ; (d) there are two normal modes of vibration in the system having two parallel boiling channels. The first is a mode in which each channel vibrates in the same phase and the second is one in which each channel vibrates in the opposite phase ; (e) in the case of (b) the second mode is always unstable and a throttle or a pump in the downcomer is not effective to cause positive damping to the second mode, and (f) in the system with parallel channels there may be many equilibriums, so that non-uniform distributions of flow rates may occur.

Study on Sand Pump : 1st Report, On the Trajectories of Solid Particles in the Pump Impeller

Abstract: When solid particles flow through the impeller of a volute pump with water, the behavior of particles is not always clear. The writers recorded photographically the trajectories of solid particles in the impeller using a high speed camera. In this paper the experimental results are cited, especially those on the relative velocity and its direction at the impeller exit. Moreover the numerical method of calculating the trajectories is demonstrated.