Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 1970"

Hydrodynamic Lubrication of Journal Bearings by Pseudo-Plastic Lubricants : Part 2, Experimental Studies

Abstract: Few experimental investigations on the relation between the nonlinearity of lubricants and the performance of bearings have been published. Theoretical analysis of the relation was presented in the first paper, and experimental analysis of this problem is conducted in this paper. The initial viscosity and the coefficient of pseudo-plasticity are given by the investigation of the flow rate of pseudo-plastic fluids obtained by adding polyisobutylene to spindle oils. The coefficient of pseudo-plasticity is a scale to indicate the behavior of this lubricant. Analyzing the experimental results of the performance of bearings using this lubricant, it is found that the film pressure and the load capacity of pseudo-plastic fluids are smaller than those of Newtonian fluids whose viscosity is equal to the initial viscosity. These values become smaller with an increase in nonlinear factor and eccentricity ratio of bearing.

Study of the Pass Schedule in Conventional Simple Spinning

Abstract: This paper deals with the decision of pass schedule of roller in conventional simple spinning. It is important to control the deformation mode of blank by an excellent pass schedule of roller, lest the sheet metal should be wrinkling or fracturing. At first, the authors attempt to draw in sheet metal by four fundamental types of template, namely-linear shape template (revolved and inside shifted type) and circular shape template (outside and inside shifted type). From the experimental results of these types, an involute curve is proposed for the profile of template. According to the test result of the new involute template, it is evident that the height of spun cups can be controlled freely by the alteration of working conditions, and the limit drawing ratio is best improved. The authors obtain the drawing ratio of 2.5 when t0/d=1.25.

Analysis of Stress Intensity Factors for Plates Containing Random Array of Cracks

Abstract: This paper presents a general method of stress analysis of cracked wide plates subjected to plane stresses at infinity. Geometric and other parameters may be arbitrarily specified, including the number, locations, directions and lengths of the cracks as well as the stress parameters. The stress function is first assumed as the sum of stress functions having singulariteies within the cracks and at infinity, and the unknown parameters are determined from the boundary conditions using a perturbation technique. Then the stress intensity factors at all the crack tips are given by power series formulae, and they are considered to give practivaly exact values so far as the enclosing circles of all the cracks are not so close to each other. Numerical examples are given for several typical cases of practical importance.

A Study of Pseudo-Shock : 2nd Report, X-Type Pseudo-Shock

Abstract: The X-type pseudo-shock was investigated, which appeared at comparatively high Mach number, and was compared with the λ-type pseudo-shock reported in the previous paper. The similarity and difference between them were discussed. At the duct center, the shock loss by the leading shock wave is smaller for the X-type pseudo-shock than for the λ-type one, but near the wall and in the subsonic region, the flow conditions are similar. The over-all total pressure loss is affected by the mixing of the flow near the wall with the main stream and the so-called shock loss is rather small. the effect of the boundary layer and the wall friction force on the static pressure rise of the pseudo-shock is also made clear. The simple model for the mechanism of the pseudo-shock is presented in the appendix.

Natural Convection Heat Transfer from Vertical Rectangular-Fin Arrays : Part 2, Heat Transfer from Fin-Edges

Abstract: As a sequel to the previous report of this series, the author has this time taken up the fin-edge as one component surface composing a fin array and experimentally studied natural convection heat transfer from the fin-edges in air. The effect of fin geometry and temperature on the respective heat transfer coefficients for the upper, vertical, and lower edges of fin arrays has been clarified. Furthermore, empirical formulas for the respective average Nusselt numbers are obtained. It is found that the heat transfer coefficients for the lower and vertical edges show fairly high values, e.g. 20∼30kcal/m2hr°C.

An Experimental Study of the Stabilizing Effect of Floating-Bush Journal Bearings

Abstract: While floating-bush bearings have been used in high-speed turbomachinery in recent years, there have been few investigations of the dynamic performances of such bearings. Experiments on the stability of a rotor with floating-bush journal bearings were carried out in this study. It was found that although the floating-bush would hardly rotate until the shaft speed reached the point where the oil-whirl occurred, the floating-bush stabilized the rotor system in a higher speed range. The stabilizing effect of the floating-bush bearing was conspicuous when the ratio between inner and outer clearance and the absolute clearance were large. It was also seen that the bush speed depended on its dimensions, particularly on the inner clearance and approached a nearly constant value as the shaft speed increased.

Analysis of Unbalance Vibration of Rotating Shaft System with Many Bearings and Disks

Abstract: A method is presented for calculating the unbalance vibration of a rotating shaft system consisting of variable cross sections, disks, journal bearings and unbalances. Property of oil film bearing is assumed to be that of the springs and dampers including those which give resistance to the change of inclination angles and velocities of inclination angles. These latter springs or dampers will be called "rotational" springs or dampers. These coefficients of cylindrical journal bearings are derived from the short bearing approximation. It is concluded that the property of rotational springs and dampers of oil film in the bearing cannot be neglected, and that the calculated results obtained by means of this method agree very well with most of the experimental results for the case of rotating shaft systems with two or three cylindrical journal bearings, that of an overhung shaft system, and that of a shaft system with distortion.

Studies on the Heat Transfer of Impinging Jet : 1st Report, Mass Transfer for Two-Dimensional Jet of Air Impinging Normally on a Flat Plate

Abstract: An investigation on the mass transfer for a two-dimensional jet of air impinging normally on a flat plate was undertaken. Results are summarized as follows. (1) Sherwood numbers at the stagnation point obtained experimentally are about twice those predicted by theory. This fact is due to the turbulence of jet itself. (2) By assuming the flow field on a plate simulated by the wall jet having an imaginary slot at the stagnation point and by applying Myer's theory concerning the heat transfer of the wall jet, we obtained the theoretical prediction for local Sherwood numbersm which agree well with experimental data. (3) Gardon's postulate that mean Sherwood number is correlated by the arrival Reynolds number was checked by the present experiment and discussed under the theoretical background.

Effects of Turbulence on Flame Propagation in Closed Vessel

Abstract: The effects of turbulence on the flame propagation in the propane-air mixture in a closed vessel were investigated by analyzing the high speed motion pictures of flame, the ion-currents due to combustion and the change of the gas compositions in combustion zone. In the combustion chamber, the uniform turbulent conditions were produced by moving suddenly a perforated plate which was driven by the spring and the electro-magnetic control system. The main results are as follows: (1) The combustion zone of turbulent flame may be composed of a lot of flame elements which are similar to laminar flame, and the apparent burning velocity is increased by enlargement of combustion zone due to turbulence. (2) during the early stage following ignition, the flame speed is affected by both factors of mixture strength and intensity of turbulence. with further development of the flame, however, the intensity of turbulence becomes a dominant factor determining thee flame speed.

The Acoustic Resonance in a Tube Bank

Abstract: In this investigation experimental studies on the acoustic resonance are undertaken. In the first place the effect of the pitch of tubes on Strouhal number or the nondimensional acoustic resonance frequency is studied in a wind tunnel test using many model banks. According to the result the Strouhal number increases with a decreasing pitch of tubes. In the second place a two-dimensional model basin test is undertaken and putting together the theory on the single tube in a flow previously reported and the observation result on the model basin test, a self-iduced vibration theory for the acoustic resonance is proposed.

Laminar Swirling Flow in the Entrance Region of a Circular Pipe

Abstract: Treated in this paper is the laminar swirling flow in the hydrodynamic entrance region of a circular pipe, in which the entering flow has uniform axial-and linearly varying tangential-velocity components The analysis is carried out within the framework of the boundary layer theory, the solutions being obtained by means of an extended form of the finite difference method invented by Leigh and Terril the following results are obtained from the analysis: (1) The entrance length is significantly increased by the presence of swirl at the entrance section (2) The additional pressure drop based on the center-line pressure at the entrance section is considerably decreased as the swirl is increased (3) If the wall temperature is constant, the local Nusselt number is increased by a few percent at a certain distance downstream from the entrance section when Prandtl number is taken as 072 (4) The damping coefficients of the swirl show an exponential decay shortly after the entrance section However, in the immediate neighbourhood of the entrance section, the damping of the swirl is a little faster than the exponential decay

Natural Convection Heat Transfer from Vertical Rectangular-Fin Arrays : Part 4, Heat-Transfer Characteristics of Nonisothermal-Fin Arrays

Abstract: A method is presented for predicting the characteristics of practical nonisothermal-fin arrays from the results of the previous reports on isothermal ones. According to this method, the effects of the fin-geometry, thermal conductivity, and temperatures on the heat-transfer characteristics have been quantitatively clarified. A heat-transfer experiment on a fin array with the fin efficiency of about 80% and the hemispherical emissivity of 0.67 has verified the validity of the present method of prediction.

Entrance Loss for Turbulent Flow without Swirl between Parallel Discs

Abstract: This paper is concerned with the investigation on the entrance loss which occurs in a radial turbulent flow between parallel discs. Because the theoretical determination of the entrance loss is almost impossible, the author has constituted an empirical equation by using nondimensional quantities - the space between the discs, the radius of rounded corner at entry boundary etc.- which have large influences on the entrance loss. This equation will be usefull for the solution of practical problems.

Vibration of a Combination of Circular Plates and Cylindrical Shells : 2nd Report, A Cylindrical Shell with a Circular Plate in the Intermediate Section

Abstract: The present paper is primarily devoted to the study of the vibrations of a cylindrical shell with a panel or a flange of a circular plate in the intermediate section. Frequencies and displacements are determined by means of minimizing the total Lagrangian. The numerical calculations are restricted to the cylindrical shell having both ends built-in and three displacement waves along the circumference. Frequencies, displacements and bending moments are shown in the figures. In a certain narrow range of frequency, the magnitude of displacement of vibrating circular plate becomes large almost independently of the length of the shell and the position of the panel, while that of the cylindrical shell gets very small. Except the above case, in general, vibrations of a cylindrical shell of the same dimension freely supported or clamped in the same section with the panel, and then the displacement of the panel is small compared with that of the cylindrical shell.

A Study of Squish in Open Combustion Chambers of a Diesel Engine

Abstract: In the Diesel engine with an open combustion chamber, the utilization of gas motion produced in the chamber is important to improve engine performance. As the first step to finding the relation between the shape of combustion chamber and the formation process of squish, squish velocity has been measured with a velocity detector of solenoid type by motoring a model engine, and then investigated theoretically. The measured squish velocity is not much different from the ideal one calculated under the condition without any loss. Through theoretical considerations, it is confirmed that the decrease of velocity due to both the heat loss to the wall and the leakage of charged air through the piston rings is remarkable in the period after 20 deg. before t.d.c. and becomes maximum at top dead center. However, the absolute value of decrement seems to be too small to affect seriously the squish velocity.

Bending Deformation of U-Shaped Bellows

Abstract: The Problem of bending deformation of U-shaped bellows has not been treated hitherto except by an approximate energy method, and the presentation of the data for this problem is being looked forward to by the designers in piping engineering at the present time. In this paper, the numerical method proposed by B. Budiansky and P.P. Radkowski for problems of unsymmetrical bending of axisymmetric shells, is applied to the problem mentioned above, and the design data for it are presented.

Chatter Vibration in Centerless Grinding : Research 1, Work-Rounding Mechanism under the Generation of Self-Excited Vibration

Abstract: The work-roundign mechanism by centerless grinding under a stable working condition is studied so far mostly from a geometrical point of view. Recently, Dr. Gurney and Rowe applied the regenerative theory to the case of centerless grinding and pointed out the existence of unstable grinding regions. In these papers, however, the work-rounding mechanism as well as other phenomena in an unstable region are not made clear yet. In the present paper, are made clear, taking the regenerative effect due to work-surface waviness into consideration, the generation mechanism of self-excited vibration that the given grinding condition which is stable geometrically transits to an unstable region as a result of work-surface regeneration and system dynamic characteristics, and the mechanism that the vibration is kept at a steay state. That is, analyzing the stability criterion as for a grinding system by the help of vector loci, the work-rounding mechanism under the self-excited vibration is clarified. Then, it is confirmed experimentally that there is a case where the self-excited vibration is not generated even though the given grinding condition is situated in an unstable region according to the solution by Gurney and others.

Thermal Stresses of the Elastic Plane with a Circular Hole, Including One Heat Source

Abstract: The thermo-elastic solutions for the case of one heat source near a circular hole in an infinite elastic plate are given in the steady-state condition using the thermal expansion displacement for "zero stresses". It is assumed that the temperature along the edge of this hole is held at zero degree always. Numerical calculations are done for the temperature distributions near the hold and the stresses along x and y axes.

Study on Ignition Lag and Flame Propagation in Spark Ignition Engines

Abstract: The ignition lag in the spark ignition engine was determined by detecting the ion current through the spark plug itself, which was caused by the ions produced by the combustion immediately after the ignition spark. The influences of mixture ratio of fuel and air, electrode spacing and dilution with incombustible gas on the ignition lag of propane-air mixture in the closed vessel were made clear by this technique. In a two-stroke cycle gasoline engine, the ignition lag and the subsequent flame propagation and cycle-to-cycle variations in them were investigated. The results are as follows : (i) The cycle-to-cycle variations of ignition lag are hardly affected by the mixture ratio, the content of residual gas and by the engine speed. (ii) The cycle-to-cycle variations of the flame propagation and the maximum pressure in the cylinder are hardly affected by the cycle-to-cycle variation of ignition lag.

On the Non-Uniform Deformation of Material in Axially Symmetric Compression Caused by Friction : Part 1, Comparsion of Results of Analysis Using Calculus of Variations with Experiments Concerning Compression of Cylinder

Abstract: Formerly, the authors analyzed non-uniform plastic deformation of a cylinder that was caused by friction on cylinder-tool interface in axial compression, using the calculus of variation. In this report, shape of bulge, deformation in the body, load, distributions of vertical pressure, of tangential stress and of friction coefficient on the cylinder-tool interface, etc. are calculated again, improving the former method of calculation. Next, various experiments are performed to prove the theoretical results, and to get further knowledge about friction. The experimental results agree qualitatively with the theoretical ones. As the result, it becomes clear that double bulge yields when height of the cylinder is large, that distribution of pressure is much affected by its height, that friction coefficient increases from the center to the edge, that friction coefficient can be investigated both by oblique type pin method, by measuring contact ratio of the surface, etc.

A Numerical Method for Solving Elastic-Plastic Problems of Rotationally Symmetric Shells

Abstract: This paper contains the derivation of the basic differential equations which govern the elastic-plastic behaviours of rotationally symmetric shells. Geometrical nonlinearity is considered in the same degree as in the nonlinear theory of thin elastic shells derived by E. Reissner. Using the assumption of plane stress, the Euler-Bernoulli hypothesis, and the Prandtl-Reuss equations for stress-strain relations in the plastic region, the basic differential equations are expressed in terms of the increments of the variables. These differential equations are approximated in finite difference forms and they are solved by an elimination method. These solutions relating to the increments are integrated numerically, and the final states of shells are obtained. As an example of the numerical analysis a U-shaped bellows loaded by an axial force is discussed, and it is ascertained that our results coincide well with the solutions obtained by another method for the elastic problem.

Relation between Scavenging Flow and Its Efficiency of a Two-Stroke Cycle Engine

Abstract: There has been few investigations of the relation between scavenging flow of a two-stroke cycle engine and its efficiency. To investigate the relation, the process in which the water in a transparent cylinder was scavenged by injection of a colored salt solution was photographed. By measuring the specific gravity of contents in the cylinder after scavenging, scavenging efficiency was calculated, and the results were compared with theoretical scavenging characteristic curves. These experiments were carried out on a two-dimensional scavenging flow in a model with a fixed piston and on a three-dimensional scavenging flow in a model with a movable piston. It is concluded that, (1) scavenging efficiency varies continuously with delivery ratio, (2) vortex motion of scavenging does not appear within the delivery ratios of engines which are in practical use, and (3) the deterioration of scavenging efficiency is caused mainly by the pure short-circuiting loss.

Analysis of Axi-Symmetric Extrusion

Abstract: In the present paper, the axi-symmetric extrusion of the Tresca's solid is analysed by means of the semi-inverse method under the Haar-von Karman hypothesis. At first, the stress field is constructed by assuming the distributions of the pressure and the frictional stress on die surface. Then, the velocity distribution in the slip line field is calculated with the boundary conditions of the velocities of the rigid regions. Here, an arbitrary stream line is considered as the die surface, and the stress and the velocity fields obtained above become the solution of the problem of certain peculiar frictional condition, which is different from the given one. Several iterations of this procedure make the difference sufficiently small. From the numerical calculations, the lower and the upper bounds of the extrusion forces are obtained, which are much better than the usual solutions, and the mean extrusion pressures are found to be 10%∼30% larger than those of the plane strain extrusions. Then the strain distributions are compared with the experimental results analysed by the moire and the gridwork methods.

Pipe Flows of Dilute Aqueous Polymer Solution : Part 1, Experimental Study of Pipe Friction Coefficient

Abstract: Pipe flows of dilute aqueous polymer solution are studied experimentally. Measurement is made for two different pipe-sizes using 0.5 to 70 wppm solutions of polyethylene oxide of approximate molecular weight of 6×106. The results show : 1) the friction coefficient is dependent, under a certain condition, on a heading tank water level and this phenomenon is not due to pressure : 2) the Toms effect is promoted at relatively small Reynolds number by decreasing the pipe diameter, increasing the concentration and /or the heading tank level : 3) an unusual pressure drop occurs upstream immediately before the orifice plate : and 4) interesting behavior of dye filaments in pipe flow is observed in the transition and turbulent flow regions.

Wear of Metals in Corrosive Environments

Abstract: The wear of carbon steel in corrosive environments has been observed under the potential controlled conditions, and the mechanism of wear and friction in corrosive environments is discussed. In the wear of metals in corrosive environments, the fracture of adhesion points, the fracture by thermal fatigue, the rubbing off of corroded layer and the damage by corrosion fatigue are observed in accordance with the variety of corrosive agents, the corrosion intensity, the type of friction, the rubbing velocity and the contact load. In the oxidizing neutral media, the lubrication due to the corrosion products plays an important role in the behavior of wear, the minimum wear rate being obtained under the mild corrosiveness in the type of face contact. In the reducing acid media, the lubrication of corrosion products is not found because of their dissolution. In the corrosive wear of metals, the wear rate is much affected by the dissolution rate of metals because of the great effect of corrosion fatigue. The cathodic potential sufficient to protect the static corrosion is not adequate to the members under friction in corrosive environments, owing to the increase of the surface activity of metals. However, the protection from corrosion is not always expected to decrease the wear rate as is mentioned above.