Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 1966"

The Unsteady Laminar Flow between Two Parallel Discs with Arbitrarily Varying Gap Width

Abstract: A theoretical analysis is presented for the unsteady laminar flow of an incompressible fluid in a narrow gap between two parallel discs of which gap-width h (t) varies arbitrarily with time. An infinite set of the non-dimensional time-dependent parameters [numerical formula], …… is introduced providing that the function h (t) is continuously differentiable, and the exact solutions of the Navier-Stokes equations and the thermal energy equation are obtained as the "multifold"series of these non-dimensional parameters. As an application, a detailed numerical study has been made of the fundamental case when the walls perform reciprocating harmonic oscillations with finite amplitudes {h (t)=h0 (1+asinωt)}. The flow characteristics are governed by the two non-dimensional parameters a and Rω=(h02ω)/υ. As compared with the sinusoidal velocity of the gap-width change, (dh)/(dt)=aωh0cosωt, the varying hydrodynamical force acting on the wall surface becomes more distorted in wave form as a increases, and becomes more advanced in phase as Rω increases. Heat is generated in the fluid between the walls through viscous friction : when the fluid is cooled by only one wall surface the fluid temperature becomes very much higher than when the cooling is done by both the two walls.

Convective Heat Transfer in an Annulus with an Inner Rotating Cylinder

Abstract: This paper presents a detailed study of the heat transfer between concentric cylinders with an inner heated cylinder rotating and an outer cooled cylinder stationary. The heat transfer in the case of zero axial flow of fluid in the annuli was carefully measured for air, water, iso-buthyl alcohol and spindle oil with varying rotational speeds and annular gap widths. The heat transfer in the laminar plus Taylor vortices type of flow is analyzed with the assumption of constant physical properties. The heat transfer data confirm the existence of the critical Taylor number obtained theoretically for isothermal flow. The Nusselt number increases suddenly at the modified critical Taylor number and the theoretical results show a comparatively good agreement with the experimental ones. The simple empirical equation to fit well the heat transfer data over a wide range of Taylor numbers has been presented.

The Flow of a Viscous Fluid through a Porous Wall into a Narrow Gap : A Consideration of the Slip of Fluid on a Porous Wall Surface

Abstract: An exact theoretical analysis is presented for the axi-symmetric flow of a viscous fluid through a porous wall into a narrow, uniform gap. In this analysis, the two equations of motion, one for the flow in the gap and the other in the porous medium, are solved under the generalized condition that the fluid may flow radially in the porous medium and as the result may slip on the porous wall surface. The important conclusions confirmed through this research are as follows. The flow characteristics are governed by the two non-dimensional parameters, [numerical formula] and [numerical formula] (k : permeability of the porous medium, h : gap width, ν0 : constant normal velocity component at the porous wall surface). Except the limiting case λ→0, the flow generally has a tangential velocity component at the porous wall surface, and especially for the flow with large values of R, the no-slip assumption which has been made customarily to date, becomes invalid even when λ is very small. For the flow of boundary-layer type the slip of fluid may usually be ignored, but for the flow through a porous wall into a narrow gap, such as in the porous gas bearing, it is necessary to take account of the new phenomena found by the present research.

Nucleate Boiling at Low Liquid Levels

Abstract: Experiments of nucleate pool boiling were carried out on three kinds of heating surfaces and five kinds of liquid in the range of liquid level from 1mm to 30mm. As a result, the following facts were disclosed. It was found invariably in each liquid that coefficient of boiling heat transfer remains nearly constant at the liquid level higher than that which is inherent in each liquid and that it increases as the liquid level becomes lower than that value. The slope of boiling characteristic curve in such a low liquid level is different from that of usual liquid level. The effect of liquid level on boiling heat transfer coefficient depends on the liquid properties and heat flux and becomes more conspicuous as heat flux decreases. According to the dimensional analysis based on the facts mentioned above, coefficient of heat transfer was succesfully correlated.

The Experiment on the Skewed Boundary Layer on a Rotating Body

Abstract: When a body of revolution rotates in an axial stream, skewed boundary layers develop on the body surface. Experiments are carried out on the skewed boundary layers over a body of revolution with streamlined nose. Measured velocity profiles differ a little from the quasi-collateral condition, that is, a velocity component perpendicular to the streamline appears in a layer near the wall with thickness of 1.5 mm. The magnitude of this velocity component is about 5% of the main stream velocity. Measured boundary layer thickness is compared with two theories which use the momentum integral equations. Although there is some difference in the assumed velocity profiles between the theoretical and experimental results, their agreement is fairly good.

Deformation Modes and Wrinkling of Flange on Shear Spinning

Abstract: It is important to investigate the deformation modes of the outer flange portion of the blank during shear spinning operation, in order to know an optimum working condition or spinnability of sheet metal. According to the measurement of the radial and cirumferential strains and the periodic variation of curvatures on the flange portion, the magnitudes of these strains and curvatures change considerably at the contact point between the roller and the blank, and do not distribute uniformly on the flange. Then, though the radius of the blank is not changeable on shear spinning, collapse into waves or wrinkles occurs, when the thickness of the blank is small. The conditions of wrinkling can be simplified by using the ratio of displacement of z direction and blank thickness t0, and flange width ratio w/r. The deformation of the flange portion is influenced mostly by feed of roller, roller diameter and blank thickness among the many working conditions, but the other conditions scarcely affect the deformation of the flange portion.

Experimental Study of Transition Boiling on a Vertical Wall in Open Vessel

Abstract: Water in an open vessel was brought to the transition boiling from the outer surface of a vertical copper tube heated from inside with saturated steam. By analyzing the oscillograph record of the surface temperature and the steam film detecting probe, it was concluded that the transition boiling is a particular phenomenon in which the boiling surface gets alternately wet and dry. It was found that the boiling characteristic curve is smooth and continuous throughout the nucleate and the transition boiling, and a particular type of boining was observed in the vicinity of the maximum heat flux and was termed the burnout boiling.

Turbulent Boundary Layers on Wire-Screen Roughnesses

Abstract: Experiments were carried out on the boundary layer along plates artificially roughened by both wire-screens and also by sand. The flow was incompressible with zero pressure gradient, in the range of 2.3×103

On a Semi-Infinite Thin Plate with a Circular Inclusion under Uniform Tension

Abstract: In this paper, we consider the problem of a semi-infinite thin plate subjected to uniform tension and having a circular hole which is filled with the elastic inclusion of another material. The analysis is treated by applying the bipolar co-ordinates with help of a method of perturbation. Numerical calculations about the stress distribution along main parts of the semi-infinite plate and the inclusion are also carried out, in order to clarify the effect of an inclusion.

X-Ray Investigation on Fatigue Fracture of Notched Steel Specimen : Observation of Fatigue Phenomena of Annealed Low-Carbon Steel by X-Ray Microbeam Technique

Abstract: It was successful to apply the X-ray microbeam technique for observing fatigue phenomena of annealed low-carbon steel. The following conclusions were obtained : (1) Misorientation and lattice strain increase quickly in the early period of fatigue process, and subsequently they continue to increase till initiation of a crack. Formation of subgrains proceeds relatively slowly in the early period, and it becomes thereafter a main process of fatigue. Formation of subgrains is not observed for fatigue below fatigue limit. (2) Density of excess dislocation of one sign in subboundaries for fatigue is much smaller than those for uniaxial tension and rolling. (3) It is considered that the reason why the half-value breadth increases during fatigue is not the formation of subgrains but is mainly the increase of lattice strain. (4) Schematic diagram of deformation in a grain for fatigue is suggested. The formation of subgrains is closely related to fatigue fracture.

The Stress and Strain Distribution at the Neck of a Tensile Specimen

Abstract: Some approximate solutions to the problem of stress distribution at the neck of a tensile specimen have been developed by Bridgman, and Davidenkov and Spiridonova, assuming the following conditions : (1) The elastic strain can be neglected. (2) The strains are uniform over the cross section of the neck. (3) The yielding stress, therefore, is constant over the cross section of the neck. The strains of the surface of the minimum section were measured from the elongations of circumferential lines drawn finely by a diamond tool. By these measurements, it has been made clear that the axial strains over the minimum section are considerably different. It will be reasonable, therefore, to consider that the yielding stress is not constant over the minimum cross section. Using the obtained strains, we calculated the stress distribution over the minimum section, considering the difference of strain hardening over the minimum section.

An Analysis of Combustion Knock in a Diesel Engine

Abstract: The present work theorizes the phenomenon of rapid combustion in a diesel engine by introducing a concept that the ignition delay of the injected fuel element varies from time to time according to the changes in temperature and pressure of the charge. In this process the rate of heat release is multiplied by the rate of shortening of the ignition delay, thus causing an explosive combustion. In this paper, a theoretical analysis was conducted to establish the course of the changing delay and thereby the physical and chemical features of the process were described by simultaneous differential equations. Discussions were made on the influences of the following factors on the maximum rate of heat release ; namely, ignition delay, injection rate, pilot injection and vaporization velocity of fuel. The results show that the present theory can successfully describe the qualitative nature of the combustion knock in a diesel engine.

Investigation of Surface Film Boiling under Free Convection : (1st Report, An Experiment on Small Wires)

Abstract: The experimental study on film boiling was undertaken to clarify how the behavior of bubble formation on the liquid-vapor interface depends upon the degree of subcooling and the size of heating surface, and to determine the influence of the stirring action of bubbles on film boiling heat transfer. The ranges of the experiment are as follows. Heating surface : horizontal platinum-wire of 0.5, 0.7 and 1.0 mm in diameter Test fluid : H2O, CCl4 Heat flux : (20∼80)×104 kcal/m2hr for H2O, (8∼50)×104 kcal/m2hr for CCl4 Degree of subcooling : 0∼15°C From the experiment performed, the following facts were found : (I) the assumption of smooth liquid-vapor interface, as often adopted in the theoretical analysis, can not be applied for low degree of subcooling ; (II) the behavior of bubble formation is affected by the size of heating surface ; (III) the distance between the bubble formation sites is larger than the critical and dangerous wave length determined by Taylor's instability ; and (IV) the effect of the size of heating surface on heat transfer coefficient can be correlated in a unified law by introducing the concept of equivalent Prandtl number.

Strength of U-Shaped Bellows : 5th Report, Fatigue Strength under Axial Loading

Abstract: In this paper the fatigue strength of U-shaped bellows under axial loading is studied. Fatigue tests of bellows in the elastic and plastic ranges are carried out by using the fatigue testing machine designed for this research, and the results are compared with the fatigue strength of test pieces made of the same material as bellows. From experimental data a formula for estimation of the life of U-shaped bellows made of stainless steel is proposed, i.e. [numerical formula] where N is cycles to failure and σ is the maximum stress value calculated from the design formula or charts in the 1st or 2nd report. This formula is compared with M.W.Kellogg's formula which is nowadays usually employed.

Calibration Test for a Photo-Rheological Method of Stress Analysis in the Plastically Flowing Body

Abstract: Formerly, a method for analysing the stress state in the plastically flowing transparent plane model by using the stress birefringence was proposed as a model test for studying the metal forming process or creep deformation. In this paper, the values of constants contained in the fundamental relations of the method are determined by the calibration test with a softened celluloid specimen. From the results of calibration test, it becomes clear that the value of principal stress difference in the plastically flowing body may be estimated from the fringe order appearing in it within a few percent of error independent of the values of stress rate and principal stress ratio as far as the latter value is negative.

A Study on the Scavenging Air Flow through the Scavenging Ports

Abstract: To examine the characters of the scavenging air flow through the scavenging ports in two-stroke engines, the inlet flow pattern through the model ports has been observed by a high speed motion camera, using a single cycle test apparatus. In general, the scavenging air flow is not coincident with the designed direction of the scavenging port at comparatively slight opening, and the efflux direction changes with the piston displacement. In a small crankcase-scavenged two-stroke engine cylinder, to keep the scavenging air flow close to the direction of the scavenging port it is effective to make the scavenge air guide long and to incline the scavenge air passage between the crankcase and the cylinder axially along the circular surface of the cylinder. In a large loop scavenged engine cylinder, to make the scavenging air flow coincide with the direction of the scavenging port in the early stage of scavenging, it is effective to set the guide plate inside the scavenging port.

Fluctuation of Void Ratio in Two-Phase Flow : (3rd Report, Absolute Velocities of Slugs and Small Bubbles, and Distribution of Small Bubbles in Liquid Slugs)

Abstract: This paper has presented the formulas to calculate the absolute velocities of the gas slug (Taylor bubble) wB, the small bubbles in the liquid slug section wS, the liquid in the liquid slug ww and the liquid film around gas slug wF by the mean void ratio and gas time ratio. The experimental values of the absolute velocities are expressed by the following empirical formulas for air-water two-phase upward flow in 27.6 mm I.D. tube. wB=1.25(wwo+wdo) ; wS=1.10 (wwo+wdo) ; wW=0.96(wwo++wd0) Also the absolute velocity of the gas slug has been directly measured. The distribution characteristics of the small bubbles in the liquid slugs have been presented. It has been estimated on the results that the axial pitch is longer than the radial pitch, namely the small bubbles do not distribute isotropically.

On the Forced Vibrations of the Shaft Carrying an Unsymmetrical Rotor : Forced Vibrations Having the Circular Frequencies Differing from the Rotating Angular Velocity of the Shaft

Abstract: When the unsymmetrical rotor with angular velocity ω is excited by a periodic external force having frequency ω0, two forced vibrations of frequencies ω0 and ω0'=2ω-ω0 take place simultaneously. Depending on the circumstances, the amplitudes of the vibration of frequency ω0'become remarkably larger than the amplitudes of the harmonic oscillation, i.e., the forced vibration of frequency ω0. Thus the idea generally accepted for the forced vibrations, that"the frequency of the forced vibration is equal or relates to that of the external force"is not always applicable for the forced vibrations of the shaft carrying an unsymmetrical rotor. In the present paper the response curves, the amplitude ratio between two forced vibrations, the effects of the damping forces are discussed analytically, and the obtained results are ascertained through the experiments.

The Flexure-Torsion Flutter of Aerofoils in Cascade : 1st Report, Computation and Experiment of Unsteady Aerodynamic Derivatives

Abstract: Theoretical and experimental investigation of"the flexure-torsion flutter of aerofoils in cascade"are presented. In this first report are shown a computational method and computed results of unsteady lift, drag and moment acting on the vibrating aerofoils in cascade, and some experimental results of these unsteady aerodynamic forces and moment. In computation are included the effects of stagger angle, solidity, attack angle (or steady circulation), inter-blade phase angle of vibration and camber of blade (or distribution of steady circulation). Each aerofoil constituting the cascade is considered to have two degrees of freedom of translational vibration (not necessarily normal to blade chord) and torsional vibration about elastic axis. Agreements between computational and experimental results are satisfactory. The effects of cascade parameters on critical flutter speed of binary flutter analyzed using the aerodynamic derivatives developed in this 1st report are shown in the 2nd report.

Swirling Flow in Suction Pipe of Centrifugal Pumps : 2nd Report, Distribution of Shearing Stress

Abstract: For the swirling flow created in the suction pipe of centrifugal pumps at partial discharges, the authors evaluated the distribution of shearing stresses by using measured velocity and pressure and compared it with strain velocity. The stress tensor at any point within the pipe is verified to be in proportion with the rate of strain velocity. Although the absolute value of the radial component of velocity exceeds hardly one hundredth that of the axial or rotational component, it contributes considerably to the stress tensor and can not be neglected. Eddy kinetic viscosity of the flow near the pipe wall ranges from 20 to 70 times the kinetic viscosity due to molecular causes.

On a Method of Calculating Characteristics of Exhaust Gas Turbo-Charged Two-Stroke Diesel Engine

Abstract: The matching of exhaust turbo-charger with diesel engine has important effects on the performance of exhaust gas turbo-charged diesel engine. To determine the matching conditions we presented a method of computation by an electronic digital computer based on the characteristics of exhaust gas turbine and turbo-blowers which were obtained from each experiment. The calculated results for the cycle in the cylinder, the variation of exhaust manifold pressure and temperature and the performance of engine were much the same as the results obtained on the practical engines. It was also made clear that the optimum turbine nozzle area varied with the total efficiency of turbo-charger.

Bending Fatigue Strength of Gears

Abstract: In this paper, the authors investigated the mechanisms of bending fatigue breakage of gears in one side and reverse loading conditions by examining the change in microstructure and in magnitude of residual stress with the number of load cycles and proposed Na-Np diagram, in which the number of load cycles after reverse Na is plotted against the number of load cycles before reverse Np, to indicate the bending fatigue properties of various gears such as annealed carbon steel gears, case-hardened gears etc. Moreover, the bending fatigue properties of shot-peened gears which had residual compressive stresses of considerable magnitude were investigated and it was made clear that there exists the optimum shot-peening conditions for the bending fatigue strength. The results obtained in this paper indicate some points which must be taken into consideration in the practical strength design of gears.

Self-Excited Standing Wave Generated in Subcooled Boiling

Abstract: An investigation is carried out on the self-excited standing wave which is frequently observed in a boiling channel when subcooled boiling occurs in it. At first, the properties of the self-excited standing wave are made clear experimentally, and then the mechanism of excitation of the standing wave is studied by introducing the effects of collapsing void. As the result, the following facts are found. The self-excited standing wave occurs only in the case of subcooled boiling. It is generated most easily when the heater is located at the loop of the pressure wave. Collapsing voids cause some phase lead in the variation of the exsisting void volume as compared with that in the case of the conservative system. Then the work done to the water column in the channel per cycle of vibration becomes positive and so the vibration grows.

Elasto-Plastic Bending of Thin Annular Plates

Abstract: This paper is concerned with the analysis of the elasto-plastic bending of thin annular plates based on Mises' yield condition and Hencky's stress-strain relations The fundamental equations for the purely elastic range are obtained from the usual ones by introducting a new variable representing the appearance of plastic state on the surface of plate, and the elastoplastic range is analysed by using the corresponding VV Sokolovsky's equations Numerical calculation is performed for several combinations of edge conditions, loading conditions and the ratios of inner and outer radii Propagation of the plastic range in the meridian section and distributions of the deflection and th components of bending moments for various magnitudes of load intensity are obtained for each case

Thermal Performances of Radiative and Convective Plate-Fins with Mutual Irradiation

Abstract: In using radiative and convective fins on heat exchangers, space radiators or nuclear fuel elements for heat release at high temperature, there are cases when the surface of the fins emits radiative and convective energy with mutual irradiation. Most of analyses studied thus far have been carried out for an isolated fin and have neglected the mutual irradiation. In this paper, thermal performances of radiative and convective plate-fins are systematically analysed on the basis of a derived steady-state integro-differential equation. This has been solved for a wide range of values of the normalized parameters. Lastly, the relation between the cases when there is mutual irradiation and when there is not is formulated.

The Elastic Plane with a Circular Insert, Loaded by a Concentrated Moment

Abstract: The problem treated is that of a plate of unlimited extent containing a circular insert and subjected to a concentrated moment. The elastic properties of the insert are generally different from those of the plate, and a perfect bond case and a smooth joint one are both treated. The solutions for the perfect bond case and for the identical materials of a smooth joint case, are in closed forms in terms of elementary functions. Explicit formulas are given for the stress components in Cartesian coordinates, and also in polar coordinates at the circumference of the insert.

The Stress in a Helical Corrugated Tube under Axial Tension

Abstract: This paper deals with the stress in a helical corrugated shell subject to axial tension. In order to describe the form of such a shell, the corrdinate system (γ, θ, φ) is used, where coordinates γ, θ are those in cilindrical corrdinates (γ, θ, z), and φ is the length in z direction measured from the base helix. Because this is a skew system, an orthogonal system (λ, μ, n) is used together with it. The stress and strain are expressed referring to the system (λ, μ, n), and the position of the point is represented by the system (γ, θ, φ). Using these two systems, the problem treated now becomes a boundary value problem of ordinary differential equation. This equation is numerically integrated by electronic computer. The result shows that the weakest part of the helical corrugated tube is the trough, and the value of stress is close to that of the shell of rotational symmetry.