Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 1965"

Fluctuation of Void Ratio in Two-Phase Flow : 2nd Report, Analysis of Flow Configuration Considering the Existence of Small Bubbles in Liquid Slugs

Abstract: In this paper, the flow configuration of the two-phase slug flow, which contains small bubbles in the liquid slug has been analysed. The experiment has been carried out for air-water two-phase upward flow in 27.6 mm ID glass tube, using the electrode probe which indicates the void ratio fluctuation. The new parameters such as the ratios of the large bubble (Taylor bubble) volume (fdB) and of small bubbles volume in liquid slug (fdS) to a control volume, the void ratio in gas slug section (fd1) and the void ratio in liquid slug section (fd2) have been introduced. These parameters except fd1 are given experimentally as the funtion of mean void ratio fd only. They are as follows : fdB=fd1.8 fdS=fd(1-fd0.3) fd1= fd2=fd1.8

The Axi-Symmetric Laminar Flow in an Arbitrarily Shaped Narrow Gap : (2nd Report, Theoretical Analysis for the Downstream Region)

Abstract: This study is generally concerned with the laminar, meridional flow in an arbitrarily shaped narrow gap between two axi-symmetrically formed walls. In this paper, a momentumintegral method is used to obtain the solutions for the downstream region where the exact series solutions obtained in the first report are no longer valid. Together with the usual Pohlhausen's parameter ∧=δ2/νdU/(dx), a new shape factor Γ=h2/U(∂2u/(∂y2))y=k is introduced, which results in smooth changes of the hydrodynamical quantities from the inlet region to the filled region, and a rigorous theoretical expression of the pressure distribution containing both the inertia and the viscous effects of the fluid flow. As an example, detailed numerical calculations have been made for the radial outward flow between two parallel discs. The important conclusions are : the breadth of the separation region changes largely with the Reynolds number, and separation does not occur when the Reynolds number is less than a critical value Rcrc100 : in the downstream region where X={1+x/(r0)}22Rc0.5, the influence of the flow condition close to the entrance disappears practically.

Studies on Vortex Tubes : 2nd Report, Reynolds Number. The Effects of the Cold Air Rate and the Partial Admission of Nozzle on the Energy Separation

Abstract: The authors tried to explain the effects of the dimensions of a vortex tube (especially the rate of partial admission of nozzle) on the energy separation of gas flowing through it. They tried also to explain the influence of the cold air rate on the flow and thermal fields in a vortex tube with the optimum proportion of the total area of nozzle openings (Fn) to the cross-sectional area of main tube (Ft). From these researches the following results have been obtained : (1) The maximum efficiency of energy separation is obtained when Fn≒0.17Ft. (2) The values of turbulent diffusivity calculated from the tangential velocity profiles nearly coincide with the values computed from Keyes'empirical formula. Reynolds number of jet from the nozzle, Ret=(0.5∼3.0)×106. (3) For the case of large axial velocity, the modified formulae including the axial velocity terms (36) and (37) should be used to predict the stagnation temperature profile in the cross-section at the cold end of the tube.

Method of Measuring the Aerodynamic Drag of Trains

Abstract: The running resistance of a train is composed of two parts, i.e. mechanical resistance and aerodynamic one. The ratio of the latter to the former increases remarkably with train speed, so it is very important for the planning of high speed trains to estimate the aerodynamic drag accurately. We have, however, only insufficient knowledges about it so far. In the test using actual trains, only the total running resistance could be measured and aerodynamic drag could not be obtained separately. And also in the model test in a wind tunnel it was practically impossible, though possible in principle, to obtain quantitatively accurate data, because of the inevitable reduction of model size and of the difficulties of experiments using models with rolling wheels and moving ground. As such was the case, there was no way but to rely on unsatisfactory data. The author found that the aerodynamic drag is closely related with the pressure rise on the side surface of a train, when it rushes into a tunnel, and that the aerodynamic drag can be obtained from this pressure rise independently of mechanical resistance. The mean aerodynamic drag coefficient of streamlined trains obtained through this method can be expressed as follows : cD=0.12+0.0075x where x is the length of a train measured in meters.

Pressure Lubricated Deep Drawing : Conclusion

Abstract: Continued from the preceding research, the hydrostatic counter-pressure which actuated upon the material being drawn into the die chamber was investigated in detail and it was made possible to predict the pressure throughout a process. This prediction is necessary for a project of this process to be successful. Matters of importance as to the control of the pressure during a process were pointed out. Applicability of this process to an actual press work was ascertained by an equipment having an intermediate scale between a laboratory test and a press-shop practice.

Experimental Study of Shear Spinning

Abstract: Many researchers have done some work on the analysis of shear spinning process. But their works are limited to a certain extent. This paper deals with the experiment on the shear spinning process of aluminium to find out the fundamental characters in detail. The influence of the following working conditions is discussed ; roller position angle, clearance between roller and mandrel, feed of roller, cone angle, speed of rotation of mandrel, roller corner radius, roller diameter, blank thickness and blank diameter. In addition, the deformation theory of simple shear which is derived from the observation of the experiments, is checked about tangential force Pθ. It is said that there is an optimum blank thickness ts, of which the calculated values agree with the experiments, and if the blank thickness is smaller than ts, the theoretical value is overestimated, but underestimated, if it is the other way round.

Fundamental Characteristics of Single-Track Vehicles in Steady Turning

Abstract: In equations of equilibrium, amounts of the tyre tread radius, gyroscopic couples due to wheels and engine as well as special properties of conventional models which have a large angle of lean and a small steering angle in rounding a curve are taken into account. And both results of calculations and experiments are well agreeable with each other. The angle of lean is always greater than the balancing angle of gravitational and centrifugal force. This is due to effects of large tyre tread radius and low position of mass centre. Moreover, the gyroscopic effect of engine is considerably intensive, especially in lower gear. The main reason why the motor-cycle has the property of oversteering is in the geometrical relation of the steering system. The side slip angle of tyre in single-trackers takes a far smaller value than that of four-wheeled vehicles.

Vibrations of Air-Columns Excited by Heat Supply (1st Report)

Abstract: The phenomenon of "Singing Flame" or "Gauze Tone" is the vibration of an air-column in a tube excited by heat supply. As the temperature of the airflow changes at the hot heater in adverse phase to the air velocity variation, there occurs some phase lag in the airflow when passing through the heater. Then, according as the phase of the velocity variation at the heater is by a quarter period before or after the phase of the pressure variation, the vibration is encouraged or discouraged. The characteristic that according to its position the heater can be an exciting source or a damping source to the vibration, is thus explained.

Vibration of Rotor Based on Ball Bearing : 1st Report, Static Stiffness of Ball Bearing

Abstract: That a ball bearing forming a link of an oscillatory system presents a strange and complicated character, when seen as one of the springs, is quite probable from its mechanism, and some of its features have been already pointed out. The first step in the investigation of the vibration of the rotor supported on ball bearings is to know its spring property in detail, but there are few papers that have pursued that question sufficiently. Here is reported an analysis which is simple but effective for inspecting the character of spring due to Hertz contact of elements in the bearing. It proposes a simple method of estimation with some considerations on the effects of production and assembling accuracy, which were given little consideration as spring theory and an actual calculation on the case containing only two balls which is a simple but important model with which to penetrate the essential feature of this mechanism. The authors believe that this theory gives a key to the causes of vibration especially in the direction of revolving axis, which is a curious trouble among the rotors constructed comparatively rigid e.g. an induction motor.

Strength of U-Shaped Bellows : 1st Report, Case of Axial Loading

Abstract: At the present time the U-shaped bellows are used widely in many fields, but hitherto few papers on their strength have been issued. In this research this problem is treated by using the shell theory which was presented by the authors in the previous paper, and the design formulas and charts for the U-shaped bellows are given. In this first report, the case of axial loading is considered, and comparatively simple design formulas are obtained by making some assumptions to simplify the solution. The accuracy of this solution is checked up by the results of a more exact solution which will be described in detail in the second report.

Theoretical Study of Shear Spinning

Abstract: This paper deals with a theoretical study of shear spinning process, which was clarified by the experiments described in the previous report. Assuming that the deformation in shear spinning is divided into the three parts, which are redundant bending at the start line of contact, shearing, and bending on the contact surface between the roller and the blank, tangential force is evaluated from the total work of deformation in an infinitesimal time interval. The calculated results are checked not only by the experimental results of the previous report, but the data of Spincraft, Cincinnati and S.Kobayashi's reports. The state of contact between the roller and the blank is indicated numerically for several working conditions by introducing the contact factor m. In addition, it is shown that axial and radial force components can be estimated approximately by the optimum angles of frictional components νθ and νθ.

Studies on the Characteristics of Axial Plunger Pumps and Motors : 1st Report, Effects of Trapping Phenomena on the Characteristics

Abstract: In order to apprehend the characteristics of axial plunger pumps and motors, it is very important to investigate their trapping phenomena thoroughly. For this purpose this paper gives the formula to calculate the pressure change in a cylinder during a trapping period in which a liquid flow from a cylinder is considered, and makes clear the effect of relief grooves, shaft speeds and inertia of the liquid in a cylinder on the trapping pressure. Then the efficiencies of pumps and motors are defined in consideration of the compressibility of liquid, trapping and relief grooves. Using this definition, power losses due to trapping are estimated, and then it becomes possible to decide the relief groove which is effective to reduce not only vibrations and noises due to trapping but also power losses.

Strength of Mild Steel at High Strain Rate

Abstract: The compressive yield point and the flow stress to cause a certain amount of compressive strain of 0.03%C steel were obtained experimentally within the range of strain rates of 2∼200/sec. The ratio of dynamic yield point to static yield point is 1.6∼2.5 and the ratio of dynamic flow stress to static flow stress is 1.0∼1.6. The yield point and flow stresses begin to be affected evidently by the strain rate in the region of the strain rate of more than 1/sec. And the stresses increase rapidly in the region beyond the strain rate of 100∼200/sec. By the repetition of impacts, the strain increment caused by one blow decreases with the repeating of impact. But at low stresses, the early blows cause very small strain and the strain is produced appreciably thereafter.

A Fundamental Study of Super-High Speed Machining

Abstract: Super-high speed turning of medium carbon steel S45C was studied using tungsten carbide, titanium carbide and ceramic tools. Tool force, tool wear, tool life and surface finish were investigated at the cutting speed from 150 to 3000 m/min. It was found that a certain grade of ceramic tool has great possibility of being employed for super-high speed machining from the viewpoint of tool force and tool life. Super-high speed machining operation produced an excellent surface finish, increasing the productivity of finish operation. But the tool life at super-high speeds was short at the present stage. Application of cutting fluids in super-high speed machining improved surface finish a little, but decreased tool life.

Temperature Measurements of the Connecting Rod, Piston Pin and Crankpin Bearing of an Automobile Gasoline Engine

Abstract: The thermocouple wires were led from the connecting rod to the piston through in a coil which received a twisting stress only in the piston pin. From here the wires were led out by means of the"combustion chamber pass through and on the circular spring"method that had been used by the authors. From the measuring results, the followings were found. (i) The heat flow from the piston reaches to the middle part of the connecting rod, at the big end, however, this effect fade away. The temperatures of the crankpin and main bearing metal rise a certain extent above the surroundings by the friction. (ii) These temperatures are increased proportionately with the engine speed. (iii) An increasing the oil temperature increases the temperatures of the bearing-metals as same extent as it.

Strength of U-Shaped Bellows : 3rd Report, Case of Loading of Internal Pressure

Abstract: In the 1st and 2nd reports the elastic analyses of U-shaped bellows under axial loading were made, but in this 3rd report, the stresses and elongations of the U-shaped bellows subjected to uniform internal pressure are solved by applying the elastic theories of shells and plates. The appropriateness of the conclusions in this report is confirmed by comparing its theoretical results with experimental data and another investigator's conclusions. The numerical results of this report are expressed by several design charts, which are considered to be useful for practical designing.

Temperature Dependence of Carbon Deposit in a Diesel Combustion Chamber

Abstract: In order to prevent carbon deposits in the combustion chamber of a diesel engine, it is recommended to avoid direct impingement of fuel on the wall of combustion chamber, though it may sometimes be impossible. In this report, the present authors examined how the carbon deposits were dependent on the wall surface temperature of the combustion chamber in the case where fuel spray impinged directly on the wall. For this purpose, a probe on which the spray impinged was set in the prechamber of the testing engine and thereby the relation between deposits and wall temperature was determined. The test results are summarized as follows : The deposits increase with time at a constant rate at first and, when it exceeds a certain limit, the deposit lump is removed off the probe. With the fuel employed in the test, the deposit reached a maximum at 200°C. Above 550°C, the amount of the deposit is only about one thirtieth the quantity at 200°C. This is because inadhesive deposits are produced at a high wall temperature owing to thorough cracking.

The Experimental Investigation on the Transpiration Cooling

Abstract: In this paper, the effectiveness and the coefficient of heat transfer with the transpiration of distilled water and air across the porous plate are discussed The conditions selected for the experiments were as follows : Velocity of bulk flow is 5∼35 m/sec Temperature of bulk flow is 100∼600°C Mass flow ratio is 005∼10% From this investigation the following conclusions have been obtained : 1) Water is more excellent than air as coolant and the difference in cooling effect between air and water is considerable in the range of little mass flow ratio, 2) Nusselt number with transpiration of water is larger than that for solid plate and Nusselt number increases with the mass flow ratio in our experimental investigation, 3) Nusselt number with transpiration of water is nearly in proportion to R64/5 for the constant mass flow ratio

Heat Transfer by Radiation and Other Transport Mechanisms : 1st Report, Couette Flow with Simultaneous Radiation and Conduction

Abstract: In order to provide some insight into problems of heat transfer by simultaneous radiation and conduction, heat transfer in a Couette flow with a medium absorbing and emitting thermal radiation is investigated theoretically and experimentally. Numerical solutions are obtained for a radiant medium whose heat conductivity and absorption coefficient are linear with temperature. Approximate solutions for optically thin media are obtained by replacing the kernel of the radiation-integral term in the fundamental equation with a quadratic expression. The regions of the total heat flux where both radiation and conduction should be considered are shown in a figure by a curved surface in three-dimensional coordinates system and the total heat flux turns out to be approximately the sum of the heat flux due to radiation calculated by neglecting other mechanisms than radiation and that due to conduction calculated by neglecting radiation. Some experimental studies have been made by generating a Couette flow between two concentric cylinders with the inner cylinder rotating and heated, and the outer at rest and cooled, where carbon-dioxide is used as a radiant medium. Experimental results are in good agreement with theoretical ones.

A Study on the Flow Visualization by the Hydrogen-Bubble Method.

Abstract: In the investigations of both the steady and unsteady flow in turbomachines, it has been found to be highly successful to visualize the flow in ducts and around the bodies. Recently W. Clutter and O. Smith have presented a suitable technique for flow visualization using small hydrogen-bubbles produced by electrolysis of the working water itself. According to their experiments, unfortunately the method was not applied to the flow with higher velocity than about 0.6m/sec. In order to observe the stream lines flowing at about 5∼8m/sec in an axial-flow type testing water compressor, the authors improved the electric source and the working liquid in the hydrogen-bubble method, and developed several new probes which are inserted into the stream as cathodes for the electrolysis process and which consist of a straight or kinked platinum wire and fork-type brass stem. In a small water tunnel having a test section 60×200 mm and two observation windows on each side, direct current of high tension (2000volts) was charged between the probe and the tunnel duct and thereby the lines of hydrogen-bubbles generated from the probe wire were visible fairly well even in the higher velocity stream of about 7m/sec. Further, using the above mentioned method, some photographs of the rotating stalls occurring in the testing water compressor were taken successfuly as was expected.

Analysis of an Externally Pressurized Thrust Collar Gas-Bearing with Multiple Supply Holes

Abstract: An externally pressurized thrust gas-bearing with multiple supply holes, which has no recess, is investigated by use of the complex potential theory. Using a series of complex pontential functions, which satisfies the boundary conditions, the load capacity of this bearing can be calculated theoretically, and the volume rate of flow as well. Experimental pressure distributions coincide very well with theoretical ones especially for the case with low supply pressure and small bearing clearance. Experiments are also made to investigate theoretically the load capacity, yielding good agreement between experiments and theory, with consideration of secondary effects due to the compressibility of the fluid and pressure loss for the acceleration of the fluid at supply holes and for the change of the flow velocity profiles, whose effects are estimated by assuming a flow pattern.

The Effects of Impeller Vane Roughness and Thickness on the Characteristics of the Mixed-Flow Propeller Pump

Abstract: Effects of the impeller vane roughness and thickness on the flow conditions and hydraulic losses as well as on the overall performances of the mixed-flow propeller pump are presented. The vane roughness has a most harmful influence upon the optimum performances, and also has a marked effect on the peripheral component of the discharge velocity near the impeller tip. The change in hydraulic losses in the impeller due to the variation of vane roughness is equivalent to that of the flat plate. The effects of roughness at various parts on the vane surface are also discussed. The head-capacity curves with varying vane thickness may be calculated actually on assumption that the capacity varies proportionally to the space area between vanes while the head remains constant.

Strength of U-Shaped Bellows : 2nd Report, Case of Axial Loading-Continued

Abstract: In the previous report, the radial displacements in the annular plate sections of the bellows were neglected and the deformations of the concave parts and those of the convex parts were assumed to be symmetric with respect to the middle line of the width of the annular plate. But in this second report, these assumptions are removed, and this problem is analyzed as exactly as possible. The results of the analysis are presented as the design charts instead of formulas. These charts are readily available for design considerations.