Showing papers in "JSME international journal : bulletin of the JSME in 1987"

Flow in curved pipes.

Abstract: This paper brings together recent information on flow in curved pipes. As to fully developed laminar flow, the appearance of additional vortices for curved pipes of particular cross-sectional forms, existence of dual solutions, and effects of the pitch on the flow in a helically coiled pipe are presented. In the case of developing laminar flow in a curved pipe, fascinating behavior of the separation of the secondary flow boundary layer near the inner wall is shown. Flow in a rotating curved pipe and a periodically curved pipe are also discussed. Different hydrodynamic conditions at the inlet greatly affect the flow in the bend ; a strong swirl is created downstream of two 90° bends in combination according to the combination angles. A brief description of the discharge coefficients for bend flowmeters, and unsteady flow in curved pipes are also given.

Magnetic and Gravitational Natural Convection of Melted Silicon—Two-Dimensional Numerical Computations for the Rate of Heat Transfer : Heat Transfer, Combustion, Power, Thermophysical Properties

Abstract: The two-dimensional natural convection of fluid under both a magnetic and a gravitational field was modeled by conservation equations. Sample computations were carried out for the fluid in a square enclosure for Rayleigh number of from 104 to 106, for Hartman number of from 1 to 103 and for Prandtl number equal to 0.054, equivalent to melted silicon. The numerical computations converged successfully and the Nusselt numbers obtained were correlated to give an empirical equation for the rate of heat transfer. The steady state solutions were graphically visualized. At Ha=103 and Ra=106, the point at which the temperature profile was almost linear, the flow was almost suppressed and elongated in a regime with high wave numbers.

Laminarization of Turbulent Flow in the Inlet Region of an Axially Rotating Pipe : Fluids Engineering

Abstract: This paper describes the laminarization phenomenon of the flow in an axially rotating pipe when a fully developed turbulent flow is introduced into it. The rotating boundary layer is initially strongly stabilized by the centrifugal force due to the rotating velocity component, resulting in a laminarization of flow. This flow laminarization has been found to be more remarkable in the inlet region where a non-rotating inner core exists in the pipe section. The laminarized flow tends to be unstable as the flow goes downstream, and bursts of turbulence appear, which was also confirmed by the use of a flow visualization technique.

Nonlinear Responsed of Sloshing Based on the Shallow Water Wave Theory : Vibration, Control Engineering, Engineering for Industry

Abstract: Based on the shallow water wave theory, the basic equations to describe the nonlinear responses of sloshing are derived, and a numerical method is presented to simulate sloshing phenomena in a rectangular tank which is oscillated horizontally. As the dispersion relation of the free surface wave plays an important role in the stable calculation of resonant responses, it should thus be taken into consideration. In this study, it is implicitly replaced by the dispersion relation produced by the discretization of the basic equations. Numerical results are in good agreement with those of experiments. In cases of shallow water depths, stable progressive waves are observed both in experiments and in numerical calculations, and the various nonlinear characteristics of sloshing, such as the hardening restoring forces and the jumping phenomena in resonant responses are well-simulated by the basic equations and the calculation method presented in this paper.

Analysis of Ultra-thin Gas Film Lubrication Based on the Linearized Boltzmann Equation : Influence of Accommodation Coefficient

Abstract: A generalize Reynolds-type lubrication equation valid for both arbitrary Knudsen numbers, defined as the ratio of the molecular mean free path to the film thickness, and arbitrary accommodation coefficients at boundaries, is derived form a linearized Boltzmann equation. Numerical analyses of lubrication characteristics through the equation for high Knudsen numbers reveal that, if the accommodation coefficient is less than 1, that is, if not all the molecules reflect diffusely as is the case with real gases, load carrying capacities are smaller than those for diffuse reflection.

Critical Heat Flux and Flow Characteristics of Subcooled Flow Boiling in Narrow Tubes

Abstract: The critical heat flux (CHF) of subcooled flow boiling in narrow tubes and its flow characteristics were investigated, and the bubble boundary layer concept was discussed. For subcooled flow boiling in narrow tubes of 1 mm inside diameter, the void fraction was estimated to be several ten percent smaller than the predicted by the subcooled void fraction correlations for large-inside-diameter tubes. This caused the CHF in the narrow tubes to increase and the friction pressure drop multiplier to decrease. The Tong CHF correlation based on the bubble boundary layer separation model was examined. Considering the dependence of pressure on the empirical parameter C in the Tong correlation, a modified correlation was proposed.

Modified k-ε Model for Turbulent Swirling Flow in a Straight Pipe : Fluids Engineering

Abstract: Turbulence models applicable to turbulent swirling flow in a straight pipe have been developed. Two models, the standard k-e model with higher order terms in Reynolds stress equation are applied, and a modified k-e model with an anisotropic representation of turbulence is proposed. The comparisons between the computed flow distributions and the experimental data show that the modified k-e model predicts complex flow fields successfully. The magnitudes of the viscosity tensor components in the modified k-e model are discussed in detail.

Measurements of Vapor Pressure, Vapor-Liquid Coexistence Curve and Critical Parameters of Refrigerant 152a : Heat Transfer, Power, Combustion, Thermophysical Properties

Abstract: Forty-four vapor pressures of Refrigerant 152a (CH3CHF2: 1, 1-difluoroethane) between 273 K and 386 K have been measured in the range of pressures from 0.26 MPa to 4.48 MPa. Ten saturated liquid densities and eleven saturated vapor densities near the critical point have also been measure in the range of temperatures from 370 K to the critical temperature which corresponds to a density variation of 153 kg·m-3 to 635 kg·m-3. The experimental uncertainties of temperature, pressure and density measurements have been estimated within 10 mK, 0, 8 kPa and 0.55%, respectively. On the basis of these results, the critical temperature, critical pressure and critical density of R 152a have been determined to be 386.44K, 4.5198 MPa and 368 kg·m-3, respectively, in consideration of the meniscus disappearing level as well as the intensity of the critical opalescence. In addition, the correlation of vapor pressure and the vapor liquid coexistence curve have also been proposed.

Adhesive Tensile Strengths of Scarf and Butt Joints of Steel Plates (Relation Between Adhesive Layer Thicknesses and Adhesive Strengths of Joints) : Solid-Mechanics, Strength of Materials

Abstract: For the study of fracture criteria, adhesive tensile strengths (σY) of scarf joints with a scarf angle of 30° and butt joints bonded by a brittle epoxy adhesive A and a ductile epoxy adhesive B have been measured at adhesive layer thicknesses (h) from 0.05 to 5.0mm, and three-dimensional elastic finite element analyses have been performed. σY of each joint decreased with an increasing value of h. A brittle fracture occurred on the scarf and butt joints bonded by adhesive A and the butt joints bonded by adhesive B. The fracture of scarf joints A and B satisfied a maximum principal stress criterion and the von Mises criterion, respectively. Gradients of σY-h curves for butt joints A and B were greater than those predicted from the results of stress analyses. The location of fracture initiation and fracture modes of adhesive layers observed with and optical microscope agreed with those expected from the results of experiments and stress analyses.

A Study of HC Emission from a Spark Ignition Engine (The Influence of Fuel Absorbed into Cylinder Lubricating Oil Film) : Heat Transfer, Combustion, Power, Thermophysical Properties

Abstract: The effect of the cylinder lubricating oil film on unburned hydrocarbon (HC) emissions from a spark ignition engine was investigated. A lubricant-free piston ring and cylinder were employed to study the interaction between the fuel and the oil film. Absorption and desorption of fuel vapor into and from the oil film was found to account for about 25-30 percent of the total unburned HC emissions. The variation of the concentration of combustion gases and unburned hydrocarbons in the combustion chamber and exhaust port were also studied, during the combustion, expansion and exhaust strokes, by means of high speed sampling valves. The HC concentration in the combustion chamber was found to increase during the expansion and exhaust strokes.

Mechanisms and mechanics of short fatigue crack propagation.

Abstract: The present paper reviews state of the art of theoretical and experimental studies of both the propagation and non-propagation of short fatigue cracks. The limitation of the conventional ΔK-based fracture mechanics approach to short crack growth is clarified, and several useful, alternative mechanical approaches proposed are discussed on the basis of crack growth mechanisms. The significance of short crack studies is emphasized in relation to fatigue-life prediction, fatigue-limit determination, and alloy microstructure design. Possible future developments are suggested.

A Study of Grippers with Multiple Degrees of Mobility : Vibration, Control Engineering, Engineering for Industry

Abstract: The number and dimensional syntheses of mechanical grippers with multiple degrees of mobility are presented systematically. Several types of contacts of fingers with a grasped body are considered as kinematic pairs, and number conditions for grasping a body are derived by applying Grubler's mobility equation to the gripper-body kinematic system. A number synthesis of a gripper with one input and three degrees of mobility, as an example, is carried out, and dimensions of parameters of such a gripper are determined by considering action forces and transmissibilities. Moreover, the graspable size of a circular cylinder by such a gripper is obtained, and is compared numerically to that with the use of a conventional parallel-two-finger-type gripper. Also, characteristics such as shapes, sizes, and masses of the bodies are obtained with respect to a circular cylinder, a regular square prism, and a hexagonal prism.

Flow Characteristics of Condensate on a Vertical Column of Horizontal Low Finned Tubes

Abstract: Experiments were performed to study the flow characteristics of condensate on a simulated bank of horizontal low finned tubes. Two or three tubes arranged in a vertical column were set in a stationary vapor. The top tube had a longitudinal slit at the upper end through which the test liquid was fed uniformly on the tube surface. Cooling water was passed through the lower tubes. The test fluids used were R-113, methanol and normal propanol. Four major flow modes: droplet, column, column-sheet and sheet, were observed as the liquid flow rate was increased. Experimental data on the number of instantaneous falling sites, the proportion of surface area covered with the falling liquid and the flooding angle below which the inter-fin sp. ace was flooded with condensate were obtained for a range of liquid flow rates. Theoretical considerations were given to the effect of liquid flow rate on the flow mode transition and on the measured quantities.

The Nonstationary Rondom Vibration of an Elastic Circular Cylindrical Liquid Storage Tank in Simulated Earthquake Excitation : Straightforward Analysis of Tank Wall Deformation : Vibration, Control Engineering, Engineering for Industry

Abstract: The nonstationary response of an elastic circular cylindrical tank, partially filled with liquid, to lateral earthquake excitation is investigated by modeling the earthquake acceleration as an amplitude modulated nonwhite random process. The differential equation governing the displacement of the tank wall due to the finite amplitude liquid surface oscillation is solved directly and the results are compared with those obtained by Galerkin's method reported previously. A fairly good agreement is found between the previous and the present results.

Method of Estimating Equivalent Mass of Multi-Degree-of-Freedom System

Abstract: To attain the optimum design of vibration controllers to suppress the many resonance peaks of machine structures, it is necessary to know the equivalent mass at the location at which the controller is mounted. This paper shows two ways of estimating equivalent mass, one is a modal analysis method, and the other is called the mass response method which utilizes the change in natural frequency of a structure when an additional mass is attached. The first method is useful for identifying a modal mass having a physical meaning, while the other method is more suitable for application to experimental analysis. The accuracy of these methods are compared by applying them to three kinds of mechanical structure.

Film Boiling Heat Transfer and Minimum-Heat-Flux (MHF)-Point Condition in Subcooled Pool Boiling : Heat Transfer, Power, Combustion, Thermophysical Properties

Abstract: The minimum-heat-flux (MHF) -point condition and film-boiling heat transfer in subcooled pool boiling of water were experimentally investigated by using a horizontal cylinder and a sphere. First, collapse behavior of vapor films was observed, and it was found that collapse modes can be classified into coherent and propagative collapses. Second, the relation between the MHF-point temperature and the propagation rate of film collapse was experimentally obtained, and the MHF-point temperature at which coherent collapse occurred was defined as its true value. The experimental data obtained show that the true MHF-point temperature is not strongly dependent on liquid subcooling and it does not exceed the liquid's maximum, metastable superheat temperature even at large subcoolings. Finally, using the experimental data of subcooled film-boiling heat transfer for various liquids, a prediction technique based on Hamill's correlation was developed.

Monitoring System for Cutting Tool Failure Using an Acoustic Emission Sensor : Vibration, Control Engineering, Engineering for Industry

Abstract: Failure of a cutting tool is one of the most serious problems in machining systems. Therefore, several methods have been proposed so far to detect cutting tool failure. However, most of them have some problems from the viewpoint of practical application. In this study, an acoustic emission sensor is used to detect cutting tool failure and a monitoring system which has high reliability is developed. The failure of single-point as well as multipoint cutting tools is successfully detected with the monitoring system developed in this study.

Void Signal Analysis and Gas-Liquid Two-Phase Flow Regime Determination by a Statistical Pattern Recognition Method : Fluids Engineering

Abstract: A statistical pattern recognition method was applied to the analysis of the signals of a cross-sectional mean void fraction for discriminating gas-liquid two-phase flow regimes. The analysis and discrimination were carried out based on six key flow patterns: bubble, cap-bubble, plug, froth (FI and FII), and annular flow. For each flow condition, 100 void signals with a recording dimension of 1 second were used and transferred to discrete data, the sampling frequency of which was selected as 100 Hz by comparison with correct recognition rates obtained from different frequencies. The magnitude of the time-averaged void fraction was partly employed supplementary to the pattern recognition method. The boundaries between the six flow regimes were determined corresponding to a correct recognition rate of 80% and were drawn on a superficial gas-liquid velocities diagram. These flow boundaries were also compared with those available in the literature.

Interfacial Instability of Magnetic Fluids in a Rectangular Container : Fluids Engineering

Abstract: An experimental and theoretical study is presented for the interfacial instability of magnetic fluids in rectangular containers subject to magnetic fields. Experiments were performed to determine the critical field intensity for incipient instability and to observe the growth of instability waves. Magnetic fluids used in the experiments were water-base ferricolloid W-35 and its dilution with distilled water. It was found that interfacial instability appeared when the field intensity exceeded the threshold value and grew in amplitude with the field intensity. It was also found that the wave number for the instability depended upon the field intensity and the dimensions of the container. The possible equilibrium configuration was analyze theoretically by minimizing the total energy. The experimental results can be explained well by the theoretical analysis.

The Influence of Tool Geometry on Axial Hole Deviation in Deep Drilling : Comparison of Single- and Multi-Edge Tools : Vibration, Control Engineering, Engineering for Industry

Abstract: The influence of tool geomtry on hole deviation is investigated using four types of deep hole drilling tools, i.e. a normal type gundrill, a standard type BTA tool, a double-edge gundrill and a multi-edge BTA tool. Two types of workpieces are uned to make their influence clear: one has an unsymmetric wall thickness on the right or left side and the other is made up of two materials where the hardness of the bonded plate is lower than that of the base metal. Experimental and theoretical results show that balanced cutting forces on the tool head contribute to decreased hole deviation. However, to some extent, an unbalanced condition of forces generates a slightly oversized hole.

Studies on MHD Pressure Drop and Heat Transfer of Helium-Lithium Annular-Mist Flow in A Transverse Magnetic Field : Heat Transfer, Power, Combustion, Thermophysical Properties

Abstract: Pressure drop and heat transfer coefficient of helium-lithium annular-mist flow in a rectangular duct were investigated experimentally under a transverse magnetic field at system pressure of 0.2 MPa. A ratio of MHD pressure drop to that of non-magnetic field increases with magnetic flux density and a mass flow rate ratio of lithium to helium in low helium velocity region. However, as increasing the helium velocity, the increment of MHD pressure drop with the magnetic flux density is much reduced and then becomes almost zero. At this condition, the MHD pressure drop of the annular-mist flow becomes much smaller than that of lithium single phase flow with the same lithium mass flow at the high magnetic flux density. Heat transfer coefficient ratio of the helium-lithium annular-mist flow to helium single phase in the non-magnetic field is well correlated by a ratio of the mass flow rate of lithium to helium. The heat transfer coefficient in the magnetic field increases with the magnetic flux density and then terminates at a certain value depending on the mass flow rate ratio and the helium velocity. These characteristics of the MHD pressure drop and the heat transfer in the magnetic field suggest that the helium-lithium annular-mist flow is effectively applicable to cooling of the high heat flux wall in a strong magnetic field like a first wall of a magnetic confinement fusion reactors.

Root Stress of Thin-Rimmed Internal Spur Gear Supported with Pins : Vibration, Control Engineering, Engineering for Industry

Abstract: This paper reports on a study on the root stress of a thin-rimmed internal spur gear supported with pins. Root stress analyses by the finite element method (FEM) for internal spur gears of various rim thicknesses supported with pins were carried out. The effects of constraint conditions for gear models on the root stresses and the deformation of the rim are discussed, and the relations between the root stresses, the deformation of the rim and the position of the loaded teeth are indicated. The effects of the number of pins and the rim thickness on the root stresses are clarified to a considerable extent.

Tribology on Reciprocating Internal Combustion Engines

Abstract: In the development of reciprocating engines, the objectives have included the simultaneous improvement of the power, fuel and lubricant economy, and engine durability. To achieve these objectives, many tribological problems have had to be solved with regard to pistons, piston rings and cylinders, which are particularly crucial and complicated. Some of these problems are reviewed, and their main points of concern are listed as follows: (1) temperatures of the piston and the cylinder and their influences, including methods to keep them below critical values, (2) relations between the piston-ring motion, blow-by gas and oil consumption, (3) piston friction loss and its characteristics, (4) effects of multi-grade oil and friction modifiers on friction of the piston and cam, and (5) capability of the two-ring package to reduce piston friction, piston weight and engine height.

Design and Manufacture of Gear Cutting Tools and Gears with an Arbitrary Profile : Vibration, Control Engineering, Engineering for Industry

Abstract: The authors introduced a new method (element removal method) for calculating the profiles of the tools (hob, form grinding wheel, etc.) used for finishing gears with an arbitrary tooth profile. Because this method simulates exactly the metal removing process in the gear tooth profile generation, it is possible to calculate the generated tooth profile when interference occurs between the cutting edge and the finished tooth profile. Using this method, the authors calculated the exact wheel profile which can produce and involute tooth profile with a tip relief at a transverse section of the involute helical gears. The wheel profile was generated by a single point diamond dresser using a universal NC milling machine with an attachment made by the authors. The tooth flank and root of test gears were ground at the same time to prevent a step (notch), which is apt to be produced at the boundary of ground and unground surfaces. The accuracy of the form ground test gears was in the zero class of JIS and the surface roughness was in the range of 0.5 to 1.0 μm Rmax.