Showing papers on "Rotational speed published in 2006"

Surgical machine and method for operating a surgical machine

Abstract: To improve a surgical machine with an electric motor comprising a rotor and a plurality of motor windings, and with a motor controller for controlling and/or regulating the electric motor so that, in particular, the efficiency of the electric motor can be optimized essentially over the entire rotational speed range, it is proposed that the entire rotational speed range of the surgical machine be divided into at least one lower rotational speed range for low rotational speeds and at least one upper rotational speed range for higher rotational speeds than those in the at least one lower rotational speed range, that the motor controller be so designed that a first controlling and/or regulating method for controlling and/or regulating the electric motor is performable in the at least one lower rotational speed range, and that a second controlling and/or regulating method for controlling and/or regulating the electric motor is performable in the at least one upper rotational speed range.

Method and apparatus to control an electro-mechanical transmission during shifting event

Abstract: A method and system for executing a shift from a first fixed gear to a second fixed gear in a powertrain system comprising a two-mode, compound-split, electro-mechanical transmission operative to receive a speed input from an engine is described. It includes deactivating an off-going clutch, and generating a time-based profile for rotational speed of an oncoming clutch. The input speed is controlled based upon the rotational speed of the oncoming clutch and an output of the transmission. The oncoming clutch is actuated, preferably when the input speed is synchronized with a rotational speed of an output shaft of the transmission multiplied by a gear ratio of the second fixed gear, preferably after a predetermined elapsed period of time in the range of 500 milliseconds.

The influence of the ratio of “rotational speed/traverse speed” (ω/v) on mechanical properties of AZ31 friction stir welds

Abstract: The influence of different parameters such as welding pressure, rotational speed, and traverse speed on the weld properties has been evaluated earlier but there are some important parameters yet to be thoroughly investigated. In this study, an effort has been made to determine the influence of different ratios of rotational speed/traverse speed on mechanical properties of different zones of friction stir welded AZ31 magnesium alloy. Mechanical properties of different zones were determined by a shear punch test. It was found out that increasing the aforementioned ratio leads to a slight decrease in yield and ultimate strength of the stir zone and the transitional zone. It was also observed that increasing rotational/traverse speed ratio increases the weld nugget size and decreases the incomplete root penetration.

Manufacture of large uniform droplets using rotating membrane emulsification.

Abstract: A new rotating membrane emulsification system using a stainless steel membrane with 100 μm laser drilled pores was used to produce oil/water emulsions consisting of 2 wt% Tween 20 as emulsifier, paraffin wax as dispersed oil phase and 0.01–0.25 wt% Carbomer (Carbopol ETD 2050) as stabilizer. The membrane tube, 1 cm in diameter, was rotated inside a stationary glass cylinder, diameter of 3 cm, at a constant speed in the range 50–1500 rpm. The oil phase was introduced inside the membrane tube and permeated through the porous wall moving radially into the continuous phase in the form of individual droplets. Increasing the membrane rotational speed increased the wall shear stress which resulted in a smaller average droplet diameter being produced. For a constant rotational speed, the average droplet diameter increased as the stabilizer content in the continuous phase was lowered. The optimal conditions for producing uniform emulsion droplets were a Carbomer content of 0.1–0.25 wt% and a membrane rotational speed of 350 rpm, under which the average droplet diameter was 105–107 μm and very narrow coefficients of variation of 4.8–4.9%. A model describing the operation is presented and it is concluded that the methodology holds potential as a manufacturing protocol for both coarse and fine droplets and capsules.

A turbine driven electric power production system and a method for control thereof

Abstract: A turbine (2) driven electric power production system (1), - said turbine (2) arranged for being driven by a fluid (3) having a fluid speed (v) varying in time, - said turbine (2) connected to a hydrostatic displacement pump (6) further connected to a hydrostatic displacement motor (8) as part of a closed loop hydrostatic transmission system (7), - said motor (8) arranged for driving an electrical generator (9) supplying AC power (10) at a frequency (fg) near a given desired frequency (fdes), characterized by a closed loop system arranged for controlling a volumetric displacement (13) of the hydrostatic motor (8), comprising - a fluid speed meter (11m) arranged for producing a speed signal (11s) representing a speed (v) of said fluid (3), and - a rotational speed meter (12m) arranged for providing a rotational speed signal (12s) representing a rotational speed measurement (ω) of said turbine (2), - a motor displacement control system (15) for continuously receiving said speed signal (11s) and said rotational speed signal (12s) and arranged for calculating a control signal (16), - a volumetric displacement control actuator (17) on said hydrostatic motor, arranged for receiving said control signal (16) for continuously adjusting a volumetric displacement (d) of said hydrostatic motor (8) for maintaining a set turbine tip speed ratio (tsrset) and thereby providing an improved power efficiency of the power production system (1) during fluctuations in said fluid speed (v).

Methods and apparatus for controlling rotational speed of a rotor

Abstract: A method for controlling a rotational speed of a rotor having at least one rotor blade, a rotor shaft, and an electrical generator coupled thereto. The method includes controlling a torque of the rotor shaft by controlling a torque of the electrical generator, alternating between changing an angle of pitch of the at least one rotor blade and maintaining the angle of pitch of the at least one rotor blade substantially constant, and maintaining a substantially constant rotational speed of the rotor during variable wind speeds above a predetermined rated wind speed.

Microstructure and Mechanical Properties of Friction Stir Welded AA2024-T3 Aluminum Alloy

Abstract: AA2024-T3 Aluminum alloy plates of 3 mm thickness were friction stir butt welded at a constant welding speed of 50 mm/min and rotation speeds of 400, 600, 800, 1000, 1250, and 1500 min � 1 . Effects of rotation speed on microstructures, hardness distributions, and tensile properties of the joints were investigated. Equiaxed grain size increased with increasing rotation speed till 1000 min � 1 of rotation speed. Increase of rotation speed more than 1000 min � 1 brought about no significant increase of grain size in the stir zone. Also, increasing rotation speed resulted in finer and more homogenous distributions of second phase particles in the stir zone. Hardness increased both in the stir zone and thermo mechanically affected zone as the rotation speed increased and reached to that of base metal. Kissing bond-free joints were fractured at the heat affected zone on the retreating side and a maximum tensile strength of the joints was 402 MPa which was achieved at 1250 min � 1 of rotation speed. The joint efficiency was 88%.

Simulation of unsteady flow and runner rotation during shut-down of an axial water turbine

Abstract: The paper describes a novel method for prediction of water turbine characteristics during transient operating regimes It is based on numerical flow simulation with finite volume method The whole axial turbine flow-passage is considered in the computation During the observed time interval, the runner grid rotates and both the distributor vanes and runner blades simultaneously change their positions The rotational speed of the runner is dependent on computed flow field Rotational speed, axial force and pressure at selected points are predicted and compared to prototype measurement data Convergence of results has been shown by using better influential computational parameters The method was applied on an industrial case to show that it is useful for engineering practice

Performance and Internal Flow Characteristics of a Very Low Specific Speed Centrifugal Pump

Abstract: In very low specific speed range (n,<0.25), the efficiency of the centrifugal pump designed by the conventional method becomes remarkably low. Therefore, positive-displacement pumps have been widely used for long. However, the positive-displacement pumps remain associated with problems such as noise and vibration and they require high manufacturing precision. Since the recently used centrifugal pumps are becoming higher in rotational speed and smaller in size, there appear to be many expectations to develop a new centrifugal pump with high performance in the very low specific speed range. The purpose of this study is to investigate the internal flow characteristics and its influence on the performance of a very low specific speed centrifugal pump. The results show that large reverse flow at the semi-open impeller outlet decreases absolute tangential velocity considerably which in turn decreases the pumping head.

S shape of a granular pile in a rotating drum

Abstract: The shape of a granular pile in a rotating drum is investigated. Using discrete elements method (DEM) simulations we show that the ``$\mathsf{S}$ shape'' obtained for high rotation speed can be accounted for by the friction on the end plates. A theoretical model which accounts for the effect of the end plates is presented and the equation of the shape of the free surface is derived. The model reveals a dimensionless number which quantifies the influence of the end plates on the shape of the pile. Finally, the scaling laws of the system are discussed and numerical results support our conclusions.

Method for Controlling a Blood Pump

Abstract: A blood pump is temporarily operated at a low rotational speed lying below the design speed, resulting in a risk of thrombogenesis as burbling may occur on the impeller blades of the rotary blood pump. The rotational speed of the pump is temporarily increased to the design speed in order to eliminate deposits on the impeller. Alternatively, the pump is alternately operated at the design speed and at a lower speed, and said pulsed operation is synchronized with the heart rate.

Method of controlling exhaust gas purification system, and exhaust gas purification system

Abstract: In regeneration control, when the catalyst temperature index temperature (Tg2) using the temperature of the oxidation catalyst (12a) as an index is below a predetermined first determination temperature (Tc1), the rotation speed of idling is brought to a predetermined first target rotation speed (Neil) which is higher than the rotation speed of idling (Nei0) in the ordinary operation, and, further, multi-injection is carried out. On the other hand, when the catalyst temperature index temperature (Tg2) is the predetermined first determination temperature (Tc1) or above, the rotation speed of idling is brought to a predetermined second target rotation speed (Nei2), which is lower than the predetermined first target rotation speed (Nei1) and is higher than the rotation speed of idling (Nei0) in ordinary operation, and, further, post injection is carried out, followed by raising of the temperature of an exhaust gas flown into a DPF apparatus (12b) to a predetermined second determination temperature (Tc2). According to the above constitution, in the regeneration control of the DPF apparatus (12b) in an internal combustion engine (10), the regeneration can be forcibly carried out with high efficiency while enhancing the temperature raising efficiency of the exhaust gas, and, at the same time, excessive rise in the exhaust temperature, a deterioration in fuel consumption, and the occurrence of noise are suppressed.

A New Proposal for Explicit Angle Calculation in Angular Contact Ball Bearing

Abstract: In order to optimize the mechanical behavior of high speed rotors, it is useful to know the load-displacement law of the angular-contact ball bearing. The relationship between preload, speed, and contact angle is studied and a new analytical approach is proposed, giving explicitly and with good precision the contact angle versus preload and rotational speed for the special case of elastically preloaded high speed angular-contact ball bearing.

Design optimization of an 8 W, microscale, axial-flux, permanent-magnet generator

Abstract: This paper presents the design optimization and characterization of a microscale, permanent-magnet (PM) generator, capable of supplying 8 W of dc power to a resistive load at a rotational speed of 305 000 rpm. The generator is a three-phase, axial-flux, PM machine, consisting of a stator with Cu surface windings and a multi-pole SmCo PM rotor. Optimization of the machine geometries has enabled a 30% improvement in power density (for the same rotational speed) over a previously reported machine. Furthermore, these design improvements, in combination with higher rotational speeds, have enabled a >7x improvement in total output power and a net power density of 59 W cm -3 .

Motor vehicle and control method of motor vehicle

Abstract: During a starting operation or a low-speed drive of a vehicle on a slope, the drive control of the invention sets a gradient-corresponding rotation speed N? as a rotation speed of an engine to output a required driving force against a longitudinal vehicle gradient ?fr (step S110), and sequentially sets a low-µ-road correction rotation speed Nlow upon identification of a low-µ-road drive condition, a vehicle speed difference-compensating rotation speed Nv based on a vehicle speed V, and a brake-based correction rotation speed Nb based on a brake pressure Pb (steps S120 through S250). The drive control sets a target engine rotation speed Ne* based on these settings (step S260) and subsequently sets a target throttle opening THtag (step S270). The operation of the engine is controlled with the greater between the target throttle opening THtag and a required throttle opening THreq corresponding to an accelerator opening Acc (step S290). This arrangement effectively prevents an unexpected slide-down of the vehicle along the slope.

One-Dimensional Modeling of Rotor Stator Interaction in Francis Pump-Turbine

Abstract: A one-dimensional hydroacoustic model is set up to perform the numerical simulation of the rotor-stator interaction of a Francis pump-turbine scaled model. The numerical results enable to identify both rotating diametrical modes in the vaneless gap between the 20 guide vanes interacting with the 9 rotating impeller blades and the standing waves in the spiral casing. Moreover, the simulations enlighten the interaction between these rotating diametrical modes and the standing waves. Finally, the parametric study of the influence of the guide vane thickness, the wave speed and rotational speed emphasizes the predominant role of the eigen frequencies of the hydraulic system.

Film Cooling Effectiveness on the Leading Edge Region of a Rotating Turbine Blade With Two Rows of Film Cooling Holes Using Pressure Sensitive Paint

Abstract: Detailed film cooling effectiveness distributions are measured on the leading edge of a rotating gas turbine blade with two rows (pressure-side row and suction-side row from the stagnation line) of holes aligned to the radial axis using the pressure sensitive paint (PSP) technique. Film cooling effectiveness distributions are obtained by comparing the difference of the measured oxygen concentration distributions with air and nitrogen as film cooling gas respectively and by applying the mass transfer analogy. Measurements are conducted on the first-stage rotor blade of a three-stage axial turbine at 2400 rpm (positive off-design), 2550 rpm (design), and 3000 rpm (negative off-design), respectively. The effect of three blowing ratios is also studied. The blade Reynolds number based on the axial chord length and the exit velocity is 200,000 and the total to exit pressure ratio was 1.12 for the first-stage rotor blade. The corresponding rotor blade inlet and outlet Mach numbers are 0.1 and 0.3, respectively. The film cooling effectiveness distributions are presented along with discussions on the influence of rotational speed (off design incidence angle), blowing ratio, and upstream nozzle wakes around the leading edge region. Results show that rotation has a significant impact on the leading edge film cooling distributions with the average film cooling effectiveness in the leading edge region decreasing with an increase in the rotational speed (negative incidence angle).

Synchronous electrorotation of nanowires in fluid.

Abstract: We demonstrate electrorotation of metal nanowires phase-locked to a driving alternating current electric field. Field rotation was accomplished by a low-frequency signal that modulates the amplitude of the high-frequency field. Steady, synchronous rotation of the nanowires was observed for frequencies up to a maximum rotational frequency, which depends on the magnitude of the applied electric field. A locally two-dimensional nanowire fluid flow model was developed to calculate the viscous fluid drag torque, including drag contributions due to the proximity of the floor. Synchronicity and phase-lock angle predicted by equating the calculated fluid drag and electrical driving torques is in good agreement with experimentally determined values, which provides support for the model. Synchronous electrorotation allows for precise control of nanowire rotational speed and orientation for frequencies as low as a fraction of 1 Hz. Potential applications include reconfigurable polarization filters, microfluidic valves, and stirring devices.

Speed control structure and method for work vehicle

Abstract: A load control structure for a work vehicle comprises: set rotation speed detection device for detecting a set rotation of an engine of the work vehicle; actual rotation speed detection device that senses an actual rotational speed of the engine; continuously variable speed change device that receives power from an engine of the work vehicle; speed change position detecting device for detecting a speed change operation position of the continuously variable speed change device; operating device for speed-shifting the continuously variable speed change device; control device for controlling the operation of the operating device; wherein the control device calculates a drop amount of the actual engine rotation speed from the set rotation speed based on the detected information from the set rotation speed detection device and the actual rotation speed detection device, and sets a limit operation position for the continuously variable speed change device based on the calculated drop amount and a correlation data that correlates the actual engine rotation speeds with operating positions of the continuously variable speed change device, and controls the operating device such that the operating position of the continuously variable speed change device moves to the limit operating position based on the set limit operating position and detected information from the speed change position detecting device, and wherein the control device has command device for commanding a change of the correlation data.

Method for engaging the starter pinion of a starter with the starter ring gear of an internal combustion engine during the running-down of the internal combustion engine

Abstract: A method is provided for engaging a starter pinion of a starter with a starter ring gear of an internal combustion engine during the running-down of the internal combustion engine, which internal combustion engine has an arrangement for determining rotational speed and rotational direction of a crankshaft. The starter pinion is engaged with the starter ring gear when the following conditions are satisfied: a) the speed of the internal combustion engine is below a maximum speed and above a minimum speed; and b) the rotational direction corresponds to the forward rotational direction of the crank shaft.