Showing papers on "Blade pitch published in 1983"

Ship propulsion unit with a main and an auxiliary propeller

Abstract: 1. Ship's propulsion system which is driven from a main machine, preferably a Diesel engine or a gas or steam turbine, and consists of a main propeller and a fixedly installed tandem propeller between main propeller and rudder or of a main propeller and a rudder which is constructed as active rudder with or without jet or as a pivotable propeller with of without gear nacelle and which for improvement of the overall propulsion efficiency and the rudder effect permanently corotates as counterpropeller, characterized thereby, that a part of the total mechanical output is taken off by a synchronous generator (5) arranged at the end face of the main machine (2) or in the shafting (3) and conducted by way of an electrical shaft to a polyphase alternating current motor which drives the tandem propeller (6, 16), that the generator (5), during starting and reversing and in derivation from the travel command generator signal, receives shock excitation until the polyphase alternating current motor has started or reversed and the excitation is regulated towards U/f = constant.

Model helicopter rotor high-speed impulsive noise: Measured acoustics and blade pressures

Abstract: A 1/17-scale research model of the AH-1 series helicopter main rotor was tested. Model-rotor acoustic and simultaneous blade pressure data were recorded at high speeds where full-scale helicopter high-speed impulsive noise levels are known to be dominant. Model-rotor measurements of the peak acoustic pressure levels, waveform shapes, and directively patterns are directly compared with full-scale investigations, using an equivalent in-flight technique. Model acoustic data are shown to scale remarkably well in shape and in amplitude with full-scale results. Model rotor-blade pressures are presented for rotor operating conditions both with and without shock-like discontinuities in the radiated acoustic waveform. Acoustically, both model and full-scale measurements support current evidence that above certain high subsonic advancing-tip Mach numbers, local shock waves that exist on the rotor blades ""delocalize'' and radiate to the acoustic far-field.

Pitch control system for variable pitch propeller

Abstract: A propeller pitch control system having a mechanical low pitch stop which includes an electrical backup therefor. The backup comprises an electrically operatable means (245) to effect blade pitch adjustment toward feather under conditions of failure of the low pitch stop indicated by propeller operation at pitch angles in the range of beta operation, but power settings in the range of normal engine speed governor pitch control. Such operating conditions actuate a pair of switches (190 and 195) connecting the means (245) to a voltage source to increase blade pitch toward feather, thereby preventing overspeed operation of the propeller.

Collective and cyclic in-mast pitch control system for a helicopter

Abstract: A compact, rugged, streamline, stiff, pitch control system is devised in a helicopter by concentrically nesting a cyclic pitch control tube and collective pitch control tube within the drive shaft and stationary mast of a helicopter rotor system. The collective pitch control tube terminates in an upper inclined flange which engages a stationary swashplate by means of a bearing member disposed in an inclined bearing raceway in the stationary swashplate. The stationary swashplate in turn is rotatably coupled through a universal joint to the cyclic pitch control tube. Relative rotation of the cyclic pitch control tube with respect to the collective pitch control tube adjusts the stationary swashplate to a selected inclination with respect to the longitudinal axis of the control tubes and of the helicopter mast. A rotating swashplate is rotatably coupled to the stationary swashplate and transmits the angular orientation of the stationary swashplate to the pitch case of each rotor blade as appropriate. The cyclic pitch control tube and collective pitch control tube are rotatably coupled to each other to permit relative angular rotation, but otherwise can be displaced vertically in the direction of the mast as a collective unit, thereby vertically displacing the stationary swashplate and hence the rotating swashplate to effect collective pitch control for all of the blades of the rotor system.

A horizontal axis wind energy conversion system with aerodynamic blade pitch control

Abstract: The horizontal axis wind tubrine converts wind into electrical energy and includes a pitch control vane with a flyweight mechanism on each rotor blade to provide aerodynamic efficiency at operating wind velocities, near constant speed and zero lift pitch of the rotor blades when speeds exceed the design speed of the system. A gravity neutralization means composed of a bevel gear and pinions couples the blades together while a flyweight arrangement connected to the bevel gear acts to neutralize centrifugal torque on the blades.

Helicopter rotor control system with integrated hub

Abstract: A rotor control system for a helicopter in which the conventional swashplate is eliminated and the rotor hub is integrated to include an actuator for each rotor blade. Two arrangements are employed, each of which utilizes a hydraulic circuit. One arrangement is a hydromechanical arrangement with stick control, while the other arrangement is an electro-hydraulic fly by wire arrangement. The latter does not employ a swashplate, while the former employs a modified swashplate. The controls, like the actuators, are mounted in the rotor hub, and the hydraulic lines and fiber optics pass through the rotor drive shaft to the rotor hub.

Helicopter engine torque compensator

Abstract: The blade angle controlling pitch beam servo (26) of a helicopter tail rotor (22) is responsive to a signal manifestation (76) indicative of free turbine engine (20) gas generator speed (78) to provide torque compensation so that the helicopter airframe will not counter-rotate under the main rotor (10) of a helicopter as a consequence of the torque provided thereto by the airframe-mounted engine (20), or in the absence thereof. A trimming embodiment (Fig. 2) provides only sufficient blade angle command (82a) to compensate for that provided by fixed, collective/tail mixing (110-114). Torque compensation tail rotor blade angle commands may be applied through existing stability and autopilot actuators (30-32) or through an additional torque servo (120, Fig. 3).

Wind turbine with gale protection

Abstract: A wind turbine with a single rotor blade drives an alternator whose output is connected to an a-c network to supply same with power when the alternator acts as a generator under the driving force of the wind. The network establishes a synchronous speed for the alternator which corresponds to a rotor speed so chosen that a certain laminar flow along the blade will be maintained even at high wind velocities. Changing the pitch of the blade allows a wide range of wind velocities to be accommodated.

Engine speed control in propeller pitch control systems

Abstract: In a propeller pitch control system, a selector 10 isolates engine (42) speed control in one of two engine governor (175 and 300) systems. The selector is input with fluid pressure signals from a pair of pilot valves (215 and 325), each operated by a corresponding one of the governors. The selector passes the signal of lowest magnitude to an actuator 40 which sets blade pitch in accordance with the magnitude of the signal whereby the governor providing such signal (through its associated pilot valve) controls engine speed independently of the other governor.

The control of variable-speed wind turbine generators

Abstract: The problem of smooth control of electrical power from a large wind turbine generator to an electrical utility system grid is discussed. A control system is proposed which is applicable to either induction or synchronous machines asynchronously coupled to the grid through a controllable DC current link. A power limiting strategy is developed which spills powers at high wind velocities without recourse to blade pitch control mechanisms.

Methods of Reducing Wind Power Changes from Large Wind Turbine Arrays

Abstract: Previous results have [1,2,3] been concerned with establishing (1) whether operating problems could exist when WECS generation is significant and (2) the proper modification of unit commitment, regulation, and economic dispatch required to provide sufficient system security and alleviate the operating problems caused by WECS generation changes. This paper discusses methods of reducing the WECS generation change through selection of the wind turbine model for each site, selection of an appropriate siting configuration, and wind array controls. An analysis of wind generation change from an echelon and a farm for passage of a thunderstorm is presented to establish the factors concerning the wind turbine model and ; siting configuration that contribute to these variations. Detailed simulation results indicate more. precisely how these factors can be exploited to. minimize the WECS generation changes observed. Reduction of the wind generation change over ten minutes is shown to reduce the increase in spinning reserve, unloadable generation and load following requirements on unit commitment when significant WECS generation is present and the farm penetration constraint is satisfied. Controls on the blade pitch angle of all wind turbines in an array or a battery control are shown to reduce both the wind generation change out of an array and the effective farm penetration in anticipation of a storm so that the farm penetration constraint may be satisfied.

Wind motors and aerogenerators

Abstract: An aerogenerator or wind motor comprises a variable pitch propeller rotor. It comprises compensation means (13) which are sensitive to the deceleration of the rotor to automatically exert on each blade (3), in case of deceleration of the rotor, a force which is substantially equal and opposed to the perturbating force generated by the kinetic energy of the rear or unbalanced mass of the blade.

Apparatus for the control of an aerial propeller

Abstract: Apparatus for controlling the pitch of the blades of a variable pitch, governor controlled, aerial propeller of which the pitch of the blades is variable between a coarse pitch limit and a fine pitch limit to match the torque of its prime mover has holding means (A) to maintain a forward thrust-generating blade pitch angle greater than the fine pitch limit with the prime mover idling as when an aircraft propelled by the propeller is taxi-ing whereby the propeller rotates more slowly, and hence more quietly, than it would otherwise. Preferably the holding means is effective by actuating a lock pitch solenoid valve (21) and an autofeather valve (18).

Adjustable propeller for marine vessel drive

Abstract: The adjustable propeller has an adjusting mechanism for adjusting the pitch of the individual propeller blades. The adjusting mechanism comprises an actuator and a correction mechanism for each propeller blade for cyclically adjusting the pitch angle of a related propeller blade under the control of a control device.

Wind Turbine Speed Control by Automatic Yawing

Abstract: A yaw dynamics analysis was developed for a two-bladed horizontal axis wind turbine with passive cyclic pitch variation achieved by letting the blade pair freely oscillate about a common axis with which the blades formed a small prelag angle. This type of rotor was found capable of high yaw rates without imposing vibratory hub moments and without producing noticeable flapping amplitudes. Experiments were conducted with a tail vane stabilized 7.6-m-diam wind rotor driving a three-phase alternator tuned and loaded to produce a rotor torque proportional to the square of the rotor speed. Two yaw control systems which replaced the usual blade feathering controls were investigated: an active yaw control system using a hydraulic rotor speed governor, and a passive system responding to a combination of rotor thrust and torque. During strong gusts both systems limited rotor speed quite accurately. The passive system appeared to be more promising because of its greater reliability and because of the greater ease of adapting it to larger size wind turbines.

Vortex flow blower

Abstract: PURPOSE:To reduce the noise of a blower by differentiating the relative position of each blade of two impellers mounted on the same shaft to casing partitions, between these impellers and arranging the phases of the sound of blades caused by these impellers to be different mutually by 180 deg. CONSTITUTION:In a double-shaft swirling blower, the position of each blade 3A' and 3B' of impellers 3A and 3B mounted on the same shaft is mutually differentiated by half the blade pitch theta when mounting. When operating, there is a difference between the blades 3A' of the impeller 3A and the blades 3B' of the impeller 3B in their timing of passing through partitions (not shown in the figure) of a casing by an amount corresponding to theta/2, which results in a phase difference corresponding to half the wave length in the sound of blade between the both impellers 3A and 3B. Accordingly, the sound of blades of both impellers will mutually interfere as reverse phases and the level is lowered thereby reducing the noise.

Optimum Propeller Wind Turbines

Abstract: The Prandtl-Betz-Theodorsen theory of heavily loaded airscrews has been adapted to the design of propeller windmills which are to be optimized for maximum power coefficient. It is shown that the simpler, light-loading, constant-area wake assumption can generate significantly different ''optimum'' performance and geometry, and that it is therefore not appropriate to the design of propeller wind turbines when operating in their normal range of high-tip-speed-to-wind-speed ratio. Design curves for optimum power coefficient are presented and an example of the design of a typical two-blade optimum rotor is given.

Windmill, rotor, rotor blade and mast for the same and method of manufacturing said rotor blade

Abstract: A windmill whose mast formed by a lower vertical part (1) and a rotatable inclined upper part (4) to which is connected the rotor (5) formed by at least two blades (6) so as to be rotatable about a horizontal rotor axis A-A, wherein each blade (6) made of parallel extruded profiles (10) is coupled with a blade carrier so as to be tiltable about an axis parallel to said blade (6) and extending beyond the centre of gravity Z thereof, the axis of tilt crossing the rotor axis A-A at a distance therefrom, whilst means for resetting the blade towards the rotor plane are arranged on the carrier, whereby the blades will be urged out of the rotor plane at an increase in wind load so that the wind pressure on the blade decreases to an extent such that the same torque is ensured with a speed of rotation remaining the same.

Wind-force turbine system for electric power generation

Abstract: Damping of the primary bending mode of a tower (12) mounting a wind turbine having a control (36) for providing a pitch blade angle reference signal (40) to modulate the pitch of the turbine blades (1) through a pitch change mechanism (38) for constant power is provided by generating the pitch blade angle reference signal as the integral (104) of the summation (266) of a torque/power controlling blade pitch angle reference rate signal (98) with an estimated acceleration signal (255) generated by filtering (250, 252, 254) the blade pitch angle reference signal (40) with the following transfer function

Acoustic measurements of a full-scale coaxial hingeless rotor helicopter

Abstract: Acoustic data were obtained during a full-scale test of the XH-59A Advancing Blade Concept Technology Demonstrator in the 40- by 80-Foot Wind Tunnel. The XH-59A is a research helicopter with two coaxial rotors and hingeless blades. Performance, vibration, and noise at various forward speeds, rotor lift coefficients and rotor shaft angles of attack were investigated. The noise data were acquired over an isolated rotor lift coefficient range of 0.024 to 0.162, an advance ratio range of 0.23 to 0.45 corresponding to tunnel wind speeds of 89 to 160 knots, and angles of attack from 0 deg to 10 deg. Acoustic data are presented for seven microphone locations for all run conditions where the model noise is above the background noise. Model test configuration and performance information are also listed. Acoustic waveforms, dBA, and 1/3-octave spectra as functions of operating condition for selected data points and microphones are presented. In general, the noise level is shown to increase with rotor lift coefficient except under certain operating conditions where significant impulsive blade/vortex interactions increase noise levels.

A study of helicopter gust response alleviation by automatic control

Abstract: Two control schemes designed to alleviate gust-induced vibration are analytically investigated for a helicopter with four articulated blades. One is an individual blade pitch control scheme. The other is an adaptive blade pitch control algorithm based on linear optimal control theory. In both controllers, control inputs to alleviate gust response are superimposed on the conventional control inputs required to maintain the trim condition. A sinusoidal vertical gust model and a step gust model are used. The individual blade pitch control, in this research, is composed of sensors and a pitch control actuator for each blade. Each sensor can detect flapwise (or lead-lag or torsionwise) deflection of the respective blade. The acturator controls the blade pitch angle for gust alleviation. Theoretical calculations to predict the performance of this feedback system have been conducted by means of the harmonic method. The adaptive blade pitch control system is composed of a set of measurements (oscillatory hub forces and moments), an identification system using a Kalman filter, and a control system based on the minimization of the quadratic performance function.

Blade pressure distribution for a moderately loaded propeller

Abstract: : A new theoretical procedure has been developed modifying the existing analysis for a marine propeller operating in a nonuniform inflow field by considering the radially varying mean wake and mean propeller induction. In addition, the selection of a new reference surface around which the perturbation analysis is developed is based on the nonlinear form of the Bernoulli equation together with an appropriate kinematic condition existing at the propeller operational condition. A flow field closer to the propeller operating condition is achieved thereby and the linear theory requirement of small perturbation quantities is reinforced. The approach is thus applicable to moderately to heavily loaded propellers immersed in the stronger wakes of hulls of large block coefficient, although it can be used for lightly loaded propellers as well. (Author)

Wind energy converting device

Abstract: Die Erfindung betrifft einen Windenergiekonverter mit Einblattrotor (4), durch den ein Generator (7) angetrieben ist. Um eine moglichst einfache und doch leicht regelbare und sturmgesicherte Ausfuhrung zu erreichen, ist vorgesehen, das der Generator (7) im Netzverbund betrieben wird und fur hohere Leistung zur Leistungsregelung durch Abris der Stromung am Rotorblatt (4) ausgelegt ist. In besonderer Ausfuhrungsform kann fur den Zweck des Anfahrens und zur Sturmsicherung eine Zwei- oder Dreipunktsteuerung des Blattanstellwinkels (E) vorgesehen sein.

A new generation controllable pitch propeller

Abstract: Modern design techniques and numerical tools have been employed in the design of a new generation of controllable pitch propellers. Research and development work at Lips has been concentrated on calculation of blade spindle torque, hub design incorporating non-mechanical pitch feed back and optimisation control of the fuel system.