Showing papers on "Rotational speed published in 2011"

Measurement of instantaneous shaft speed by advanced vibration signal processing - Application to wind turbine gearbox

Abstract: Condition monitoring of machines working under non-stationary operations is one of the most challenging problems in maintenance. A wind turbine is an example of such class of machines. One of effective approaches may be to identify operating conditions and investigate their influence on used diagnostic features. Commonly used methods based on measurement of electric current, rotational speed, power and other process variables require additional equipment (sensors, acquisition cards) and software. It is proposed to use advanced signal processing techniques for instantaneous shaft speed recovery from a vibration signal. It may be used instead of extra channels or in parallel as signal verification.

Air conditioner for vehicle

Abstract: An air conditioner for a vehicle equipped with a motor for driving the vehicle has a vehicle speed detecting unit, an electric compressor, an evaporator, an electric compressor rotation speed controlling unit, a controlling unit and a refrigerant pressure detecting unit. The controlling unit calculates a first candidate for a rotation speed upper limit value of the electric compressor based on a vehicle speed detected by the vehicle speed detecting unit, calculates a second candidate for the rotation speed upper limit value of the electric compressor based on a refrigerant pressure detected by the refrigerant pressure detecting unit, and decides a minimum value of the first and second candidates for the rotation speed upper limit value of the electric compressor, as the rotation speed upper limit value of the electric compressor.

Quad tilt rotor vertical take off and landing (vtol) unmanned aerial vehicle (uav) with 45 degree rotors

Abstract: A system and method to control the stability and direction of a quad tilt vertical takeoff and landing (VTOL) unmanned aerial vehicle (UAV) by manipulating the rotational speed of propellers at each rotor while simultaneously tilting the rotors in a 45 degree configuration related to a central axis for directional control. Each rotor is attached to a tilting mechanism configured to be symmetrically aligned at a 45 degree angle from a central axis to manipulate a directional angle of each rotor along a first and second axis. The first and fourth rotors are aligned on the first axis while the second and third rotors are aligned on the second axis. A controller includes a first control loop for manipulating the rotational speed of the propellers to control the aircraft balance and a second control loop for controlling lateral movement by tilting the rotors along the first and second axis.

Investigation of the High Speed Rolling Bearing Temperature Rise With Oil-Air Lubrication

Abstract: The oil-air lubrication system has been widely used for rolling ball bearing. However, as the rotation speed increases, the temperature rise will increase dramatically, resulting in shortening the service life of the ball bearing. The existing literature has offered valuable fundamental data about the oil-air lubrication of rolling bearing; however, there are still some problems that concerned the oil-air lubrication, which are not addressed. In this study, an experiment setup to investigate the oil-air lubrication for the high speed ball bearing has been developed, and performance tests of hybrid ceramic and steel ball bearings under the extensive operating conditions including oil-air supply pipe length, bearing preload, lube interval, oil type, oil viscosity, nozzle design, and rotation speed have been conducted. The test results show that the bearing has the lowest temperature rise with the pipe length of 1.5 m. For the steel ball bearing, the proper preload decreases with increasing of the rotating speed, and the temperature rise of the hybrid ceramic ball bearing is not sensitive to the axial preload. There exists a proper amount of lubricant for the bearing at each rotational speed; and a larger amount of lubricant is required for the bearing as the rotating speed increases. The tested bearings under different speeds have almost the same lowest temperature rise under the lubricant with the viscosity of 100 cSt; a higher or lower viscosity will increase the bearing temperature rises. The nozzle design is an important factor to affect the temperature rise of the ball bearing, and the suitable geometric parameter of the nozzle is closely related to the cage landing method of the bearing. The temperature rise of tested bearings increases with the increase in the rotation speed; and the hybrid ceramic ball bearing always has a lower temperature rise than that of the steel ball bearing at the same operating conditions.

Modelling and control strategy of PMSG based variable speed wind energy conversion system

Abstract: With the advance of power electronic technology, novel control strategies and new circuit topologies direct driven permanent magnet synchronous generators (PMSG) have increasingly drawn interests to wind turbine manufactures. In the proposed wind energy system, a PMSG is used as a variable speed generator. The generator model is established in the synchronous-rotating dq reference frame. The torque of PMSG is suitably controlled according to a generator speed and thus the power from a wind turbine settles down on the maximum power point by the proposed MPPT control without a wind speed detector. The speed control is realized through field orientation where the q-axis current is used to control the rotational speed of the generator according to the variation of wind speed and the d-axis current is set to zero. Active and reactive power can be controlled by direct and quadrature current components, respectively.

Vehicle drive device

Abstract: In a vehicle drive device, a response to a range change request, during which the drive wheels are rotated in a low or high range, can be smoothly and quickly completed without using a synchronous engaging mechanism. When the range change is requested when the drive wheels are rotated in the low range or in the high range, the control devices disengage a clutch sleeve from a currently engaged gear piece so as to establish a neutral range, and control an output rotational speed of the motor generator such that a difference between an input rotational speed and an output rotational speed of the transmission mechanism is set to be zero, or be equal to or less than a predetermined value. After that, the control devices cause a connection processor to slide the clutch sleeve to be connected to a connection target gear piece.

Investigation of the effects of critical process parameters of friction stir welding of polyethylene

Abstract: Friction stir welding is a solid-state method of joining thermoplastic materials. This paper studied the effect that varying process parameters (rotational speed, welding speed, and attack angle) h...

Numerical and experimental analyses of drills used in osteosynthesis.

Abstract: This paper presents the results of numerical analysis and experimental studies of the process of bone drilling using drills applied in osteosynthesis procedures. In the studies, two surgical drills with a diameter d = 4.5 mm and varying in drill point geometry 2κ were used. Thermal analysis based on FEM allowed determining the distribution of temperatures generated in the bone as a function of rotational speed of the drill. The results indicate that both drill point geometry and rotational speed of the drill have influence on temperatures generated in bone tissue. Additionally, the range was determined for possible values of rotational speed, which does not initiate the process of thermal necrosis of bone. The experimental studies of the process of drilling in a femur model showed the impact of drill point geometry on the values describing the cutting process. It was concluded that the highest values of torques and axial forces during cutting occur in the tools with angle 2κ₂ = 120°.

Experimental Investigations on Upper Part Load Vortex Rope Pressure Fluctuations in Francis Turbine Draft Tube

Abstract: The swirling flow developing in Francis turbine draft tube under part load operation leads to pressure fluctuations usually in the range of 02 to 04 times the runner rotational frequency resulting from the so-called vortex breakdown For low cavitation number, the flow features a cavitation vortex rope animated with precession motion Under given conditions, these pressure fluctuations may lead to undesirable pressure fluctuations in the entire hydraulic system and also produce active power oscillations For the upper part load range, between 07 and 085 times the best efficiency discharge, pressure fluctuations may appear in a higher frequency range of 2 to 4 times the runner rotational speed and feature modulations with vortex rope precession It has been pointed out that for this particular operating point, the vortex rope features elliptical cross section and is animated of a self-rotation This paper presents an experimental investigation focusing on this peculiar phenomenon, defined as the upper part load vortex rope The experimental investigation is carried out on a high specific speed Francis turbine scale model installed on a test rig of the EPFL Laboratory for Hydraulic Machines The selected operating point corresponds to a discharge of 083 times the best efficiency discharge Observations of the cavitation vortex carried out with high speed camera have been recorded and synchronized with pressure fluctuations measurements at the draft tube cone First, the vortex rope self rotation frequency is evidenced and the related frequency is deduced Then, the influence of the sigma cavitation number on vortex rope shape and pressure fluctuations is presented The waterfall diagram of the pressure fluctuations evidences resonance effects with the hydraulic circuit The influence of outlet bubble cavitation and air injection is also investigated for low cavitation number The time evolution of the vortex rope volume is compared with pressure fluctuations time evolution using image processing Finally, the influence of the Froude number on the vortex rope shape and the associated pressure fluctuations is analyzed by varying the rotational speed

System and method for controlling a single-spool turboshaft engine

Abstract: A controller receives a power-level command representative of a level of power to be transmitted by a single-spool turboshaft engine to a controllable load. A torque command determined responsive to a measure of inlet pressure, from a control schedule responsive to the power-level command, is representative of a level of torque to be transmitted by an element to drive the controllable load. Under some operating conditions, a rotational speed command provides for at least nearly minimizing a measure of associated fuel consumption when the transmitted torque is regulated to the level corresponding to the torque command by controlling one of the controllable load and a fuel flow to the engine, and the other of the controllable load and the fuel flow to the engine is controlled so as to regulate an associated rotational speed to a level corresponding to the rotational speed command.

Wind turbine generator and method of controlling the same

Abstract: An object of the present invention is to, if a frequency decrease has occurred in a power system, avoid a trip in a wind turbine generator and reliably contribute to recovery of the frequency of the power system. The present invention provides a wind turbine generator that, if a predetermined frequency decrease that requires PFR has occurred in the power system, calculates a marginal active power based on the difference between a predetermined rotational speed lower limit value, which is obtained by providing the parallel-off rotational speed with a predetermined margin, and a measured value of the shaft rotational speed, and generates an active power command value based on the marginal active power.

Temperature dependent single molecule rotational dynamics in PMA

Abstract: Temperature dependent measurements of the rotational diffusion of single dye molecules in the polymer poly(methyl acrylate) (PMA) are presented and compared to shear viscosity data and numerical simulations of the rotational diffusion process. It is found that single molecule rotational diffusion very accurately follows the Debye-Stokes–Einstein predictions for the shear viscosity without any additional parameter. We employ a simple model of dynamic changes of the rotational speed of a single molecule. This dynamic heterogeneity model is based on a Gaussian distribution of activation energies in a VFTH (Vogel-Fulcher-Tammann-Hesse) type temperature dependence of the polymer viscosity. The simulations explain all experimental details concerning the stretched exponential single molecule relaxation dynamics and the related distributions. They also reveal that the observed distributions are related to the intrinsic physical properties of the polymer but do not in general reflect the instantaneous spread of local viscous properties.

Slab Analysis of Ring Rolling Assuming Constant Shear Friction

Abstract: In this article, an analytic solution for ring rolling process based on the slab method theory is presented, in which the non-uniformity of the normal and shear stresses across the section of the deforming material throughout the plastic region is considered. The friction factor multiplied by the shear yield strength (s = mk) is used to present friction between the main roll and the ring. The influence of the process parameters such as friction factor, feed speed, main roll rotational speed, and radii of the main roll and mandrel on process outputs is investigated. Complete expressions for the ring rolling pressure, force, and torque are obtained, and the position of neutral point is predicted. Comparison of the analytic results of this model with the experimental results of other investigators and FEM analysis show that they are in good agreement.

Numerical Simulation and Cold Modeling experiments on Centrifugal Casting

Abstract: In a centrifugal casting process, the fluid flow eventually determines the quality and characteristics of the final product. It is difficult to study the fluid behavior here because of the opaque nature of melt and mold. In the current investigation, numerical simulations of the flow field and visualization experiments on cold models have been carried out for a centrifugal casting system using horizontal molds and fluids of different viscosities to study the effect of different process variables on the flow pattern. The effects of the thickness of the cylindrical fluid annulus formed inside the mold and the effects of fluid viscosity, diameter, and rotational speed of the mold on the hollow fluid cylinder formation process have been investigated. The numerical simulation results are compared with corresponding data obtained from the cold modeling experiments. The influence of rotational speed in a real-life centrifugal casting system has also been studied using an aluminum-silicon alloy. Cylinders of different thicknesses are cast at different rotational speeds, and the flow patterns observed visually in the actual castings are found to be similar to those recorded in the corresponding cold modeling experiments. Reasonable agreement is observed between the results of numerical simulation and the results of cold modeling experiments with different fluids. The visualization study on the hollow cylinders produced in an actual centrifugal casting process also confirm the conclusions arrived at from the cold modeling experiments and numerical simulation in a qualitative sense.

Dual input drive AGB for gas turbine engines

Abstract: A mechanical drive system of an aircraft gas turbine engine includes a tower shaft operatively connected to first and second shafts in an accessory drive gearbox. The first shaft rotates at a rotational speed lower than the rotational speed of the tower shaft and the second shaft rotates at a rotational speed equal to or higher than the rotational speed of the tower shaft.

The generalized Onsager model for the secondary flow in a high-speed rotating cylinder

Abstract: The generalizations of the Onsager model for the radial boundary layer and the Carrier–Maslen model for the end-cap axial boundary layer in a high-speed rotating cylinder are formulated for studying the secondary gas flow due to wall heating and due to insertion of mass, momentum and energy into the cylinder. The generalizations have wider applicability than the original Onsager and Carrier–Maslen models, because they are not restricted to the limit , though they are restricted to the limit and a high-aspect-ratio cylinder whose length/diameter ratio is large. Here, the stratification parameter . This parameter is the ratio of the peripheral speed, , to the most probable molecular speed, , the Reynolds number , where is the molecular mass, and are the rotational speed and radius of the cylinder, is the Boltzmann constant, is the gas temperature, is the gas density at wall, and is the gas viscosity. In the case of wall forcing, analytical solutions are obtained for the sixth-order generalized Onsager equations for the master potential, and for the fourth-order generalized Carrier–Maslen equation for the velocity potential. For the case of mass/momentum/energy insertion into the flow, the separation-of-variables procedure is used, and the appropriate homogeneous boundary conditions are specified so that the linear operators in the axial and radial directions are self-adjoint. The discrete eigenvalues and eigenfunctions of the linear operators (sixth-order and second-order in the radial and axial directions for the Onsager equation, and fourth-order and second-order in the axial and radial directions for the Carrier–Maslen equation) are determined. These solutions are compared with direct simulation Monte Carlo (DSMC) simulations. The comparison reveals that the boundary conditions in the simulations and analysis have to be matched with care. The commonly used ‘diffuse reflection’ boundary conditions at solid walls in DSMC simulations result in a non-zero slip velocity as well as a ‘temperature slip’ (gas temperature at the wall is different from wall temperature). These have to be incorporated in the analysis in order to make quantitative predictions. In the case of mass/momentum/energy sources within the flow, it is necessary to ensure that the homogeneous boundary conditions are accurately satisfied in the simulations. When these precautions are taken, there is excellent agreement between analysis and simulations, to within 10 %, even when the stratification parameter is as low as 0.707, the Reynolds number is as low as 100 and the aspect ratio (length/diameter) of the cylinder is as low as 2, and the secondary flow velocity is as high as 0.2 times the maximum base flow velocity. The predictions of the generalized models are also significantly better than those of the original Onsager and Carrier–Maslen models, which are restricted to thin boundary layers in the limit of high stratification parameter.

Experimental Investigation of the Viscous Effect on Two-Phase-Flow Patterns and Hydraulic Performance of Electrical Submersible Pumps

Abstract: Using a visualization prototype built from original electrical-submersible-pump (ESP) components and with minimal geometrical modifications, a pioneer experimental procedure was developed and conducted to address the viscous effect on liquid/gas two-phase flow through these types of pumps. Based on dimensionless groups that govern centrifugal-pump single-phase performance, two-phase experiments were conducted at different shaft speeds (15, 25, and 30 Hz), with nonslip void fractions (up to 5%), and viscosity values of 46 to 161 cp, while liquid rates were kept constant at 60% of the maximum rate at the defined shaft speed. High-speed video footage was taken from the entire impeller flow channel, and stage incremental pressure was measured. The authors identified four liquid/air flow patterns inside the impeller channels: agglomerated bubbles, gas pocket, segregated gas, and intermittent gas. By comparing the images with the differential-pressure data, it was concluded that the agglomerated-bubbles pattern is responsible for the initial head degradation and that the surging event coincides with the gas-pocket structure, indicating that this is an interface-instability problem. Another conclusion made was that the increase in viscosity caused surging to occur at lower void fractions, which could be compensated for by increasing rotational speed. The significance of this work is given by the fact that several authors hae investigated centrifugal-pump performance under two-phase flow; however, previous experiments have been conducted only with water as the liquid, thus neglecting the viscous effect on the two-phase-flow mixture. In most of the petroleum industry's applications, ESPs operate with oil and natural gas. The present work begins the task of addressing this knowledge gap between scientific research and field applications.

Neural rotational speed control for wave energy converters

Abstract: Among the benefits arising from an increasing use of renewable energy are: enhanced security of energy supply, stimulation of economic growth, job creation and protection of the environment. In this context, this study analyses the performance of an oscillating water column device for wave energy conversion in function of the stalling behaviour in Wells turbines, one of the most widely used turbines in wave energy plants. For this purpose, a model of neural rotational speed control system is presented, simulated and implemented. This scheme is employed to appropriately adapt the speed of the doubly-fed induction generator coupled to the turbine according to the pressure drop entry, so as to avoid the undesired stalling behaviour. It is demonstrated that the proposed neural rotational speed control design adequately matches the desired relationship between the slip of the doubly-fed induction generator and the pressure drop input, improving the power generated by the turbine generator module.

Motor control device and electrical equipment with motor controlled thereby

Abstract: A motor control device includes a current detecting unit detecting current flowing into a motor winding, a speed/electrical angle estimating unit estimating a rotational speed and an electrical angle of the motor, based on the current, a load torque estimating unit estimating load torque to be developed by a load, from a torque current obtained based on the current and the electrical angle, a motor constant and inertia moment of the motor inclusive of the load, a load torque phase calculating unit calculating a phase of periodic fluctuation indicated by the load torque, a torque-compensating current determining unit determining a sinusoidal torque-compensating current, based on the load torque phase, and an amplitude/phase adjusting unit detecting speed fluctuation of the motor to adjust amplitude and phase of the torque compensating current by increasing or decreasing the amplitude and the phase so that the speed fluctuation is reduced.

Shift control device for continuously variable transmission

Abstract: A requested cruise-control horsepower calculator obtains a requested cruise-control horsepower from a speed difference between a target cruising vehicle speed and an actual vehicle speed. A requested cruise-control torque calculator obtains a requested cruise-control torque on the basis of the requested cruise-control horsepower and an engine rotation speed. A cruise-control accelerator-opening calculator sets a cruise-control accelerator opening by referring to an engine torque map in which a cruise-control accelerator-opening characteristic curve is set along an equal horsepower line on the basis of the requested cruise-control torque and the engine rotation speed. A target primary rotation-speed calculator sets a target primary rotation speed by referring to a shift-line map on the basis of the cruise-control accelerator opening and the actual vehicle speed. A shift controller obtains a target gear shift ratio on the basis of the target primary rotation speed and the actual vehicle speed so as to perform shift control.