Showing papers on "Rotational speed published in 1968"

Atomic Beam Source for the Energy Range of 0.2–45 eV

Abstract: An apparatus has been developed for producing an atomic beam of potassium in the energy range of 0.2 to 45 eV (1000–15 000 m/sec). The technique used here is cathode sputtering. With a velocity selector (spread, 6.7%; maximum rotational speed, 48 000 rpm), both the signal of a Pt‐W detector and an energy independent one are measured as a function of the velocity of the beam particles.

An Investigation of Steady and Unsteady Flow through a Napier Turboblower Turbine under Conditions of Full and Partial Admission

Abstract: The paper presents the results of tests on an axial-flow turbine and describes how they are obtained, in steady and unsteady flow. An analysis of turbine-test results obtained under the unsteady operating conditions is then given. It is shown that over a limited range of cyclic operation the mass flow and power output may be predicted by assuming that the turbine operates instantaneously as it would under steady-flow conditions (at the same expansion ratio and the same non-dimensional rotational speed) and integrating over the engine cycle. At high pressure ratios, pulse frequencies and rotational speeds, this ‘quasi-steady’ analysis gives a slight overestimate of mass flow and power output but the error in turbine efficiency is very small.

Press line synchronization

Abstract: Apparatus for controlling a line of power presses of the type including a flywheel driven by a direct current motor and having a clutch for selectively connecting the flywheel to its respective press drive shaft. The disclosed method comprises energizing the motors and rotating the flywheels while the clutches are disengaged. Thereafter, the speed of rotation of the flywheels is monitored and the excitation of the motors is varied to bring all flywheels to the same rotational speed. The crank or eccentric of each press is positioned at a location so that, considering the inertia of the driven parts of each press, simultaneous actuation of the clutches will cause each press to attain the same rotational speed at substantially the same position of rotation. With the presses rotating at the same rotational speed all the clutches are simultaneously actuated and, thereafter, the angular position of each press crankshaft is measured. After a predetermined time period, variation of the excitation of the motors in response to flywheel speed is discontinued and the excitation is varied in a manner to maintain the presses within a predetermined angular position relationship.

Improvements in radial-type hydraulic machines

Abstract: A radial-type hydraulic machine has a number of sets of hydraulically interconnected cylinders, each set consisting of four cylinders, and a cam with which pistons in the cylinders cooperate. The cam has a number of lobes equal to the number of sets of cylinders. Each lobe is divided in profile into two symmetrical halves, each half comprising in sequence a first circular section, a first parabolic section, a spiral section, a second parabolic section, and a second circular section. This configuration ensures that the sum of the linear speeds of those pistons which are at any instant travelling in a working stroke is constant, and in turn that the swept volume is constant throughout the operating cycle. In a motor, the torque and rotational speed are therefore constant for a constant-pressure, constant-volume supply of hydraulic fluid.

Improvements in machines for mixing or conveying material of a plastic dough-like consistency

Abstract: 1,112,390. Mixers; driving arrangements. BAKER PERKINS GRANBULL Ltd. 31 Aug., 1965 [7 Oct., 1964], No. 40901/64. Heading B1C. [Also in Divisions B5, B8 and F2] A screw conveyor 5 which may be associated with an extrusion or injection moulding machine, or a mixing machine, is driven at varying speeds with substantially constant torque by (i), a variable speed electric motor 33, whose power output is transferred to conveyor 5 via a cylindrical cage 17, pinions 22, sun wheel 14 and a shaft 10, and (ii), by a constant speed electric motor 29 whose output is transferred via worm gearing 26, 27, shaft 16, sun wheel 15, pinions 22, sun wheel 14 and shaft 10. In operation, sun wheel 15 remains stationary when motor 29 is not working, and when it is working the rotational speed of screw conveyor 5 is increased by a fixed amount. This allows a motor 33 to be chosen of reduced speed variation range and power output. The connection between shaft 16 and sun wheel 15 is arranged to break if a predetermined torque is exceeded and such a connection may be a shear pin (not shown). Preferably conveyor 5 and shafts 10 and 16, linked by a rotary coupling 34, are hollow to allow circulation of a cooling liquid and barrel 3 of screw 5 is provided with heaters 4. Motor 33 may be of the constant speed type and associated with either a mechanical or hydraulic gear or an electro-magnetic induction coupling. The invention is particularly applicable to the extrusion of PVC.

Free Convection in a Rotating Medium

Abstract: Numerical techniques have been used to study natural convection in a fluid subjected to axial rotation. Axisymmetrical flows were studied in two different geometries for a variety of rotational speeds. For case I (R1 = 1.0, R2 = 2.5, H = 3.0), the computed flow patterns were qualitatively compared with those which would be expected from the basic rules of physics, and good agreement was obtained. Rotational speeds between Ω = 0, and Ω = 20 were studied for a Grashoff number of 3000. Increased rotational speed was found to decrease the over‐all heat transfer rate. For case II (R1 = 1.0, R2 = 4.0, H = 1.0), rotational speeds of Ω = 0.0 to Ω = 40.0 were studied at a Grashoff number of 400. At low rotational speeds, a single convection cell was found, however, at higher rotational speeds, the single cell became unstable, and changed to a two‐celled pattern. This transition resulted in a slight increase in the over‐all heat transfer rate.

Improvements in or relating to tachometers

Abstract: 1,105,099. Measuring rotational speed electrically. SMITHS INDUSTRIES Ltd. Jan. 27, 1967 [Jan. 28, 1966], No.3847/66. Heading G1N. The rotational speed of the output shaft of an I. C. engine having a coil ignition system is determined by measuring the frequency of the pulses of current in the ignition system. A coil 11 of tape of a square loop, grain orientated, magnetic material is wound to form an annulus, carrying three windings 5, 12, 13, of which the primary windings 5, 12 are connected, one in series with the vehicle battery, and the other with the contact breaker 3, so that the annulus is saturated alternately in opposite directions. The current induced in the secondary coil 13 flows through a meter 16, in series with coil 13, only when the contact 3 is closed because of an avalanche diode 15 connected in series with the meter 16. As the coil 11 is saturated when the contact 3 is closed, the reading on the meter 16 is proportional to the frequency of the pulses in the ignition system and therefore to the rotation speed of the engine. A parallel arrangement of resistor 17 and thermistor 18 is also included in this circuit to compensate for effects of temperature changes.

The Characteristics of a Thin Liquid Film on a Spinning Disk.

Abstract: : An experimental study of thin liquid films on a spinning disk is described. Such films are characterized by large values of the ratio of interfacial area to liquid volume, can be formed in very small equipment compared to falling films, and their development is independent of surface orientation to the gravitational field. This makes them interesting for a number of energy and mass transfer processes. The paper summarizes the available numerical and analytical studies of the fluid-mechanical characteristics of spinning films and presents measurements of average film thickness as a function of radial position, liquid flow rate, and rotational speed. In spite of surface-tension phenomena (waves, dry spots, etc.) not accounted for in the theoretical study, the data indicate that the theory predicts the proper relative effects of the several variables. (Author)

On the Vibrations of Horizontal Shaft Supported in Oil Lubricated Journal Bearings

Abstract: Based on a pressure solution for an infinitely long journal bearing clarified in the previous paper, the vibrations of a rotating shaft which is supported in oil lubricated journal bearings is investigated theoretically and experimentally. The results are as follows : 1) A system in which a rigid shaft is supported in oil lubricated journal bearings has in general an angular natural frequency slightly less than ω/2 (ω is angular velocity of rotating shaft). Although the free vibration with angular frequency about ω/2 is stable at low rotational speeds, it becomes self-excited when the rotational speed increases to a high enough value. 2) In the case of a flexible shaft, the system has three angular natural frequencies, one of which is slightly less than ω/2 and the others are nearly equal to Ω (Ω is a fundamental angular frequency of flexural vibration of the shaft). Only one of the vibrations with frequency Ω becomes unstable when the rotational speed increases above about twice the critical speed of the shaft.

Optical measurements of mass density in a high- speed, confined, gaseous vortex

Abstract: An optical method based on light-deflection mapping has been developed and used to determine the radial variation of fluid density in a high-pressure ratio, high-speed, air vortex that was generated in a 3-in.-diam, 18-in.-long swirl chamber consisting of two symmetric halves. An intense, parallel, thin light beam was transmitted laterally through the vortex at various off-axis positions, and the small light deflections caused by the density field of the vortex were measured. From the variation of the deflection angle over the radius, the radial density profile was numerically calculated by assuming rotational symmetry and solving the resulting integral equation. The density profile of the vortex was determined in two cross sections, at various operating conditions of the chamber. The results show that the core region in which the fluid rotates like a solid body has a very uniform diameter corresponding to about half of the exhaust port diameter. The presence of slight axial density differences, which are related to the meridional flow movements, is clearly shown. The lowest density is found to occur at the vortex axis in the central portion of the chamber. From the density profiles and suitably corrected pressure profiles measured with probes, static temperature profiles were calculated; the temperature exhibits a very low minimum near the outer limit of the solid-body-type core. The fluctuations of the light-beam deflection angle shed some light on the nature of transient phenomena occurring in the vortex. In addition to acoustic resonance, considerable irregular density fluctuations were observed, especially at radii smaller than that of the exhaust opening. This is believed to be because of the existence of periodic fluctuations in the rotational speed of the vortex.