Showing papers on "Rotational speed published in 2002"

High-speed machining of titanium alloys using the driven rotary tool

Abstract: Machining of titanium at high cutting speeds such as from 4 m/s to 8 m/s is very challenging. In this paper, a new generation of driven rotary lathe tool was developed for high-speed machining of a titanium alloy, Ti–6Al–4V. The rotary tool was designed and fabricated based on the requirements of compact structure, sufficient stiffness and minimal edge runout. Cylindrical turning experiments were conducted using the driven rotary tool (DRT) and a stationary cutting tool with the same insert, for comparison in the high-speed machining of Ti–6Al–4V. The results showed that the DRT can significantly increase tool life. Increase in tool life of more than 60 times was achieved under certain conditions. The effects of the rotational speed of the insert were also investigated experimentally. Cutting forces were found to decline slightly with increase of the rotational speed. Tool wear appears to increase with the rotational speed in a certain speed range.

Effects of rotational direction and rotation-to-revolution speed ratio in planetary ball milling

Abstract: The rotational direction of a pot in a planetary ball mill and its speed ratio against revolution of a disk were studied in terms of their effects on the specific impact energy of balls calculated from the simulation on the basis of the Discrete Element Method (DEM) and structural change of talc during milling. The specific impact energy of balls is measured as a significantly large value, and the structure of talc is transferred into an amorphous state quickly when the mill pot is rotated in the counter direction against the revolution. In both rotation–revolution relationships, the specific impact energy increases with an increase in the rotation-to-revolution speed ratio in the initial stage and then falls around the critical speed ratio, which can be calculated by the balance equation based on the centrifugal forces acting on a ball due to the combination of the rotation and revolution. The highest value in the specific impact energy of balls during milling can be achieved effectively around this critical speed. This critical speed would, therefore, be a key condition in milling for designing suitable and optimum mechanical milling performance.

Characteristics of flow over a rotationally oscillating cylinder at low Reynolds number

Abstract: Effects of rotary oscillation on unsteady laminar flow past a circular cylinder have been investigated in this study. Numerical simulations are performed for the flow at Re=100 in the range of 0.2⩽Ω⩽2.5 and 0.02⩽Stf⩽0.8, where Ω and Stf are, respectively, the maximum rotational speed and forcing oscillation frequency normalized by the free-stream velocity and cylinder diameter. Results show that the rotary oscillation has significant effects on the flow. The lock-on frequency range becomes wider as the rotational speed increases. In a non lock-on region, modulations in the velocity, lift and drag signals occur and the modulation frequency is expressed as a linear combination of the forcing frequency and vortex-shedding frequency. Also, the mechanism for the modulation phenomenon is presented in terms of the vortex merging process. Finally, it is found that the mean drag and amplitude of the lift fluctuations show local minima near the boundary between the lock-on and non lock-on regions.

Methods and apparatus for controlling a continuous flow rotary blood pump

Abstract: A control system for a continuous flow rotary blood pump is provided. A normal operating range of the blood pump is established. The normal operating range may comprise a normal pump flow range and a normal pressure head range. A target rotational speed of the pump is set in accordance with the normal operating range. A current operating condition of the blood pump is determined. The current operating condition may comprise a current pump flow, a current pressure head, and a current rotational speed of the pump. The current operating condition is compared with the normal operating range. An appropriate control algorithm is selected from a plurality of available control algorithms based on the comparison. The target rotational speed of the pump is adjusted using the selected control algorithm to maintain or recover the normal operating range.

Laminar flow past a sphere rotating in the streamwise direction

Abstract: Numerical simulations are conducted for laminar flow past a sphere rotating in the streamwise direction, in order to investigate the effect of the rotation on the characteristics of flow over the sphere. The Reynolds numbers considered are Re = 100, 250 and 300 based on the free-stream velocity and sphere diameter, and the rotational speeds are in the range of 0 [les ] ω* [les ] 1, where ω* is the maximum azimuthal velocity on the sphere surface normalized by the free-stream velocity. At ω* = 0 (without rotation), the flow past the sphere is steady axisymmetric, steady planar-symmetric, and unsteady planar-symmetric, respectively, at Re = 100, 250 and 300. Thus, the time-averaged lift forces exerted on the stationary sphere are not zero at Re = 250 and 300. When the rotational speed increases, the time-averaged drag force increases for the Reynolds numbers investigated, whereas the time-averaged lift force is zero for all ω* > 0. On the other hand, the lift force fluctuations show a non-monotonic behaviour with respect to the rotational speed. At Re = 100, the flow past the sphere is steady axisymmetric for all the rotational speeds considered and thus the lift force fluctuation is zero. At Re = 250 and 300, however, the flows are unsteady with rotation and the lift force fluctuations first decrease and then increase with increasing rotational speed, showing a local minimum at a specific rotational speed. The vortical structures behind the sphere are also significantly modified by the rotation. For example, at Re = 300, the flows become ‘frozen’ at ω* = 0.5 and 0.6, i.e. the vortical structures in the wake simply rotate without temporal variation of their strength and the magnitude of the instantaneous lift force is constant in time. It is shown that the flow becomes frozen at higher rotational speed with increasing Reynolds number. The rotation speed of the vortical structures is shown to be slower than that of the sphere.

Vehicle engine control device

Abstract: Escape running performance at the time of the occurrence of an abnormality in an electronic throttle control system is improved. At the time of the occurrence of a severe abnormality, an abnormality storage element is operated, and an electric supply load relay of a throttle valve driving motor is de-energized to return a throttle valve to the default, and further, an alarm display is actuated, and an upper limit engine rotational speed is suppressed by control of a fuel injection valve, and escape running is carried out. As a suppression rotational speed, a lower limit threshold at a stop, a rotational speed substantially in proportion to the output of an accelerator position sensor, a rotational speed substantially in inverse proportion to the output of a throttle position sensor, or a default threshold rotational speed is selected, and multiple escape running can be carried out.

System for estimating absolute boost pressure in a turbocharged internal combustion engine

Abstract: A system for estimating absolute boost pressure in a turbocharged internal combustion engine includes a pressure sensor producing a pressure signal indicative of the pressure of air entering a turbocharger compressor inlet, a temperature sensor producing a temperature signal indicative of the temperature entering the compressor inlet, a first speed sensor producing a first speed signal indicative of the rotational speed of the turbocharger, a second speed sensor producing a second speed signal indicative of the rotational speed of the engine, and a control computer estimating the absolute boost pressure as a function of the pressure signal, the temperature signal, the first speed signal and the second speed signal.

Nonlinear Dynamic Analysis of a Hydrodynamic Journal Bearing Considering the Effect of a Rotating or Stationary Herringbone Groove

Abstract: This research investigates the dynamic characteristics of a herringbone grooved journal bearing with plain sleeve (GJPS) and a plain journal bearing with herringbone grooved sleeve (PJGS) under static and dynamic load. FEM is used to solve the Reynolds equation in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors of a journal, such as orbit or rotational speed, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. Numerical results are validated by the experimental results of prior researchers. A GJPS produces less friction torque than a PJGS so that the GJPS consumes less input power than the PJGS. Under static load, the PJGS converges to the fixed equilibrium position, but the GJPS has a whirling motion due to the rotating groove even at the steady state, which produces the excitation frequencies corresponding to the integer multiple of the rotor speed multiplied by the number of grooves. The variation of rotational speed of a GJPS is always less than that of a PJGS due to less friction torque. Under the effect of mass unbalance, the excitation frequencies of the reaction force in a GJPS and a PJGS are the rotational frequency due to mass unbalance and its harmonics due to the nonlinear effect of fluid film. However, the GJPS has relatively big amplitude corresponding to the multiples of the number of grooves, in comparison with the amplitudes at the adjacent harmonics.

Device, system and method for on-line monitoring of flow quantities

Abstract: Measures of a torque (T) and rotational speed (n) of a pump or fan (12) are obtained, from which a mechanical input power (Pm) can be calculated. By further using predetermined relations (47) between mechanical input power (Pm) and flow rate (Q) through the pump or fan, a measure of the flow rate (Q) can be derived without use of in-line flow or pressure sensors. In preferred embodiments the torque (T) and/or rotational speed (n) is obtained by measuring the input current (51) and voltage (50) of a motor (20) driving the pump or fan (12) and using predetermined relations (54, 58) between on the one hand current (I) and voltage (U) and on the other hand torque (T) and rotational speed (n). Furthermore, also other flow properties, such as pump head, pump efficiency (hP) and total efficiency (hT) can be determined in this manner.

Vehicle drive system and vehicle controlling method

Abstract: A minimum needed power is computed by adding a reserve drive power to a target drive power, a best fuel cost-performance rotation speed is computed based on the target drive power and the best fuel cost-performance power characteristics of an engine ( 1 ), and a minimum needed rotation speed is computed based on the minimum needed power and the maximum power characteristics of the engine ( 1 ) The best fuel cost-performance rotation speed is compared with the minimum needed rotation speed, the larger is selected as a target input rotation speed of a continuously variable transmission ( 2 ), the speed ratio of the transmission ( 2 ) is controlled based on the driving axe rotation speed and target input rotation speed, and the torque of the engine ( 2 ) is controlled based on the engine rotation speed and target drive power

Display control device

Abstract: PROBLEM TO BE SOLVED: To make it possible, by a simple and intuitive operation, to arbitrarily select from a plurality of scroll modes and to use the selected scroll mode. SOLUTION: A track bar 15 is provided with a roller part that a user rotates and also a rotary encoder that detects the rotation of the roller part by one unit angle. A rotational speed calculating means 20a, when the track bar 15 is operated, calculates the rotational speed of the body of revolution on the basis of the output of the rotary encoder and the timer value of a timer 19. A scroll mode selecting means 20b, depending on which of 'low speed' range and 'high speed' does the calculated rotational speed fall into, sets the scroll mode to be either of line scroll mode and page scroll mode. Then, a scroll processing means 20c executes a screen scroll by the scroll amount responsive to the scroll mode selected responsive to the rotation by one unit angle of the roller part.

A study of the effects of polishing parameters on material removal rate and non-uniformity

Abstract: In this paper, experiments are conducted to reveal the effects of polishing parameters such as rotational speed, applied pressure, locations of nozzles for slurry, and flow rate of flurry on surface characteristics when polishing an aluminum based rigid disk. A double-sided polishing machine is used in these experiments and an inner pin ring is held still during the process, so that the removal rates of disks at different locations are different. It was shown that the removal rate for outer disks is less than that for inner disks. This phenomenon is in contrast to that predicted using the popular Preston equation. Although it was shown that the removal rate increases as the relative velocity or the applied pressure increases, it is not proportional to either the applied pressure or the relative speed as described by the Preston equation.

Control system for electric motor for driving electric vehicle

Abstract: A control system for an electric motor for driving an electric vehicle comprising lock state judgment means to judge that the electric motor is in a lock state when a state where a rotational speed of a brushless DC motor has a value equal to or less than a set lock start rotational speed while an opening degree of an accelerator is equal to or more than a predetermined judgment opening degree continues during predetermined judgment time and lock time drive current control means to perform such a control as to gradually reduce a drive current of the motor to a lock-time limit value Thus, when the rotational speed of the vehicle is lowered until the motor gets the lock state while the vehicle is driven in the state where the accelerator is opened with the opening degree being equal to or more than the judgment opening degree, the drive current is decreased whereby a temperature of armature coils is prevented from abnormally rising

Turning of glass with abrasive waterjet

Abstract: This article reports research results on abrasive waterjet (AWJ) turning of glass. Glass rods, 25 mm in diameter, were turned by using AWJ to investigate the effects of several process parameters on the surface quality of the machined glass surfaces. The parameters studied are rotational speed, stand-off distance, water pressure, nozzle traverse speed, and abrasive flow rate. The results were also compared with those obtained from conventional machining of glass. The results showed that higher traverse rates were associated with an increase in material removal rate and thus an increase in surface roughness and waviness values. The sensitivity of surface quality to rotational speed was more than that to the traverse speed. Good surface finish was achieved at lower traverse speeds and higher turning speeds. Higher stand-off produced rougher surface finish. The best finish was generated when the nozzle consumed 300 g min−1 of abrasives. Higher pressures did not produce smoother surface finish.

Brushless motor control method and controller

Abstract: In a brushless motor control method and a brushless motor controller in accordance with the present invention, a rotor rotation position detection means detects the time of the intersection of a detected induced voltage and an induced voltage reference value. In addition, a motor speed calculation means calculates the rotation speed of a brushless motor on the basis of the interval of the intersection times detected by the rotor rotation position detection means. Furthermore, a speed control means outputs a duty factor index on the basis of the deviation between the command speed and the rotation speed of the brushless motor. Still further, a switching signal generation means outputs switching signals to groups of switching devices on the basis of the rotation speed and the duty factor index at the time of the intersection.

Control system of hybrid driving device

Abstract: PROBLEM TO BE SOLVED: To provide a control system for a hybrid driving device for performing a power-off shift in a transmission for adding the torque of an assist motive power source to an output shaft without causing a delay and the deterioration of a shock. SOLUTION: This control system has an electric motor rotation speed control means (Step S04 and 09) for controlling an electric motor so that a rotation speed becomes a synchronous rotation speed after a shift or a target rotation speed set on the basis of the synchronous rotation speed in a state of maintaining the transmission torque capacity of a brake to a prescribed value or less in the shift by a shift mechanism in a state of not outputting torque to an output member by an electric motor and an engaging device control means (Step S11) for increasing the transmission torque capacity of an engaging device for setting a shift state after the shift after the rotation speed of the electric motor reaches the synchronous rotation speed after the shift or the target rotation speed. COPYRIGHT: (C)2004,JPO&NCIPI

Influence of rotational speed on effectiveness of rotary-type heat exchanger

Abstract: This paper analyzes the effect of rotational speed on the effectiveness of rotary-type heat exchangers. Numerical, analytical and experimental studies are carried out to investigate the influence of rotational speed, especially at low values. The governing partial differential equations for the regenerator are solved numerically with some assumptions. For a limiting case, two analytical solutions are also obtained with different assumptions. Based on the results of the numerical study and the experiments carried out using a laboratory-made rotary-type heat exchanger, an empirical equation that can be used even for very small rotational speeds is presented.

Control device for variable-geometry turbocharger

Abstract: In a control device for a variable-geometry turbocharger which allows adjustment of the opening of the nozzle in the turbine inlet, the basic opening target value of the nozzle is calculated on the basis of the actual engine rotational speed and load. The final opening target value of the nozzle is then calculated by adding a nozzle opening correction value VNta to this basic opening target value. In the calculation of this nozzle opening correction value VNta, the amount of variation ΔAc in the engine load is multiplied by a correction gain calculated on the basis of the engine rotational speed and pressure ratio, and a filter processing using a specified transmission function is performed on the resulting value ΔAc1. The amount of variation in load ΔAc2 following this filter processing is used as the input value for the calculation of the nozzle opening correction value VNta.

System and method for adjusting air flow in air seeding applications

Abstract: A system for maintaining an appropriate air flow in an air stream in an air seeder. A fan provides an air stream to carry agricultural materials for distribution across a width of a seeding implement. A tank contains a granular agricultural material and a metering device dispenses the material into the air stream. The system is calibrated such that a known weight of material is dispensed for each revolution of the metering device whereby the rotational speed of the metering device multiplied by the known weight per revolution results in a known per minute rate of agricultural material being dispensed into the air stream. A microprocessor is programmed to derive an appropriate fan speed for the per minute rate of agricultural material being dispensed and send a signal to a fan control to adjust the speed of the fan to correspond to the appropriate fan speed.

Slippage detection system and method for continuously variable transmutations

Abstract: A slippage detection system for a continuously variable transmission capable of continuously changing a ratio between a speed of rotation of an input member and a speed of rotation of an output member is provided. The slippage detection system calculates a correlation coefficient relating to the input rotation speed and the output rotation speed, based on a plurality of measurement values of the input rotation speed and a plurality of measurement values of the output rotation speed, and determines slippage of the torque transmitting member in the continuously variable transmission based on the calculated correlation coefficient.

Optical speed sensing system

Abstract: An apparatus for determining the rotational speed of an object returning diffuse reflections where no reflective singularity exists on the object or no clearly distinct light pulse is produced. A light source illuminates a target area on the object. An optical system receives the reflected light, selectively filters by wavelength, and focuses the light on a detector for signal processing. The reflected light signals may be a series of complex patterns that repeat once per revolution. A Fourier Transform with additional processing enhancements is performed on the signals and used as a basis to calculate the speed of the object The signal processing may be automated, resulting in a speed (RPM) solution being displayed for the operator of the device.

Development of high speed composite flywheel rotors for energy storage systems

Abstract: A composite flywheel rotor was developed. The rotor was designed, which was based on the finite element analysis, and fabricated to achieve the peripheral speed of 1300 m/s. The rotor consisted of a composite rim and aluminum alloy hub. The inner diameter of the rim was 340 mm, the outer diameter was 400 mm and thickness was 25 mm. The rim comprised press fitted multiple concentric rings(multi-ring) to prevent radial tensile failures at high rotational speed. Rings were fabricated by a filament winding process using high strength carbon fiber. The configuration of the hub was like a steering wheel with 4 spokes. The cross-section area of these spokes was changed to withstand a centrifugal force. Spin tests of flywheel rotors were performed, using an air turbine driven spin tester in a vacuum chamber. The rotor was spun to maximum peripheral speed at 1310 m/s, whose stored energy was 354 Wh, and the specific energy density was 195 Wh/kg.