Showing papers on "Blade pitch published in 1985"

Propeller system with electronically controlled cyclic and collective blade pitch

Abstract: A plurality of blades extend radially from a hub which is rotated by a motor about a drive axis. Each blade has a root which is rotatably connected to the hub so that it can be independently twisted to vary the pitch thereof relative to the drive axis. A plurality of electromagnets are annularly positioned adjacent the hub so that permanent magnets connected to the roots of corresponding blades can be attracted and/or repelled to induce twisting motion in the blades as the hub rotates about its drive axis. A control circuit receives input commands for a manual control device and causes predetermined electrical signals to be applied to the electromagnets for simultaneously varying the pitch of the blades. The pitch of the blades can be varied cyclically and collectively in accordance with any real continuous function, and not just sinusoidally as in the case of prior mechanical linkages employing swash plates. A vessel equipped with the propeller system at the fore and aft ends thereof can be precisely maneuvered in six degrees of freedom.

Wind energy conversion system

Abstract: The wind energy conversion system includes a wind machine having a propeller connected to a generator of electric power, the propeller rotating the generator in response to force of an incident wind. The generator converts the power of the wind to electric power for use by an electric load. Circuitry for varying the duty factor of the generator output power is connected between the generator and the load to thereby alter a loading of the generator and the propeller by the electric load. Wind speed is sensed electro-optically to provide data of wind speed upwind of the propeller, to thereby permit tip speed ratio circuitry to operate the power control circuitry and thereby optimize the tip speed ratio by varying the loading of the propeller. Accordingly, the efficiency of the wind energy conversion system is maximized.

Blade pitch angle control for large wind turbines

Abstract: A blade pitch angle control system for a wind turbine includes an improved control means (95) for providing a minimum pitch angle reference signal indicative of desired blade pitch at wind velocities less than rated The control means includes means (35 and 30) for providing signals indicative of generated (output) power or torque and the rotational frequency of the wind turbine rotor The output and rotor speed signals are input to a function generator which, in response to such signals, provides a signal indicative of the minimum pitch angle

Ram air turbine control system

Abstract: A blade pitch control mechanism for a ram air driven turbine blade mounted for rotation on a hub assembly having a central axis. A governor control member, including a seat, is mounted on a portion of the hub assembly for reciprocation along the central axis. A first spring acts on the governor control member in a first axial direction. A governor slide member is mounted for reciprocation along the central axis. The blade is in mating engagement with the governor slide member. A second spring acts between the governor slide member and the seat of the governor control member for biasing the slide member opposite the first axial direction. This causes the blade to assume a course pitch when the blade and hub assembly are in storage and to allow the blade to move to fine pitch during start-up. A flyweight is mounted on the hub assembly and engages the governor control member for acting against the first spring to control blade pitch and govern turbine speed after start-up.

The use of active controls to augment rotor/fuselage stability

Abstract: The use of active blade pitch control to increase helicopter rotor/body damping is studied. Control is introduced through a conventional nonrotating swashplate. State variable feedback of rotor and body states is used. Feedback parameters include cyclic rotor flap and lead-lag states, and body pitch and roll rotations. The use of position, rate, and acceleration feedback is studied for the various state variables. In particular, the influence of the closed loop feedback gain and phase on system stability is investigated. For the rotor/body configuration analyzed, rotor cyclic inplane motion and body roll-rate and roll-acceleration feedback can considerably augment system damping levels and eliminate ground resonance instabilities. Scheduling of the feedback state, phase, and gain with rotor rotation speed can be used to maximize the damping augmentation. This increase in lead-lag damping can be accomplished without altering any of the system modal frequencies. Investigating various rotor design parameters (effective hinge offset, blade precone, blade flap stiffness) indicates that active control for augmenting rotor/body damping will be particularly powerful for hingeless and bearingless rotor hubs.

Blade gearing and pitch changing mechanisms for coaxial counterrotating propellers

Abstract: A lightweight counterrotatable propeller system driven by a rotatable shaft is disclosed. The system includes first and second counterrotatable propellers, each propeller including a plurality of blades mounted on first and second hubs, respectively. Each blade is attached to the hub by means of a ball screw which converts centrifugal force on each of the rotating propeller blades into a pitch changing force. Gearing means for operatively connecting the shaft with each propeller are located between the propellers with a carrying member for one of the propellers forming an outer wall which radially bounds the gearing means. Additionally, non-rotating actuating means for changing propeller pitch are operatively connected to the blades of each of said first and second propellers through first and second thrust bearings, respectively.

Electric air-driven helicopter

Abstract: A helicopter has a low profile electric motor mounted in each of the rotor blades to drive a cross-flow fan which draws air in through a slot at the leading edge of the blade and forces it out through an opposing slot adjacent the trailing edge of the blade to provide the thrust for rotating the rotor blade. An engine is located in the fuselage of the helicopter for driving an electric generator to produce the electricity supplied to the motors mounted in the blades. In addition, yaw control is achieved without the necessity of tail structure or a tail rotor using a small electric motor driving or absorbing power from the main rotor shaft. Both the yaw control motor and the main rotor shaft tilt together as a rigid unit. Pitch and roll control is achieved without the necessity of aerodynamic surfaces by movement of the main rotor support mast about a gimbal bearing support located above the center of gravity of the helicopter.

Power trowel with cam-actuated blade pitch adjustment mechanism

Abstract: An engine-driven trowel includes a handle, a set of blades rotated within a single plane, a blade pitch control unit having a swash plate, a swash plate actuator arm and a pivot pin for pivotally coupling the actuator arm to the trowel. A blade pitch adjustment mechanism includes a lever-actuated cam assembly which engages and deflects the outboard end of the swash plate actuator arm. Up and down movements of the lever rotate the cam and displace the swash plate actuator arm to change the pitch of the trowel blades.

Noise radiation patterns of counter-rotation and unsteadily loaded single-rotation propellers

Abstract: In order to understand the effects of installation on propeller noise, numerous measurements are required to define the directivity of the noise as well as the level. An experimental study was designed to map the noise radiation pattern for various single-rotation propeller (SRP) installations and one counter-rotation propeller (CRP) installation covering an area ± 60 deg from the propeller disk plane and ± 60 deg laterally. The configurations considered included an SRP at angle of attack and in tractor and pusher operations and a CRP. A firstprinciples linear theory was validated for the SRP tractor operation over the angle range mentioned above. The increases in noise that arise from an unsteady loading operation such as an SRP pusher or a CRP exceed 15 dB and depend on the observer location. In particular, the majority of the additional noise from the unsteady loading appears to radiate in the axial directions.

Propeller for windmill

Abstract: PURPOSE:To aim at enhancing the strength of an air-foil cross-section shape propeller blade of a windmill and at enhancing and stabilizing the performance of the blade which is improved in the air stream thereof, by providing an auxiliary blade on the rear surface side of the air-foil cross-sectioned shape main blade of a propeller for a windmill, so that the auxiliary blade extends in parallel with the main blade with a predetermined space therebetween. CONSTITUTION:An auxiliary blade 1B is attached to the rear side surface of an air-foil cross-sectioned shape propeller blade 1 for a windmill with a predetermined distance therebetween through the intermediary of a rib 1A so that the auxiliary blade extends in parallel with the main blade 1. Therefore, the bending rigidity of the main blade is enhanced to eliminate a risk in strength thereof, and further, the pattern of air streams around the main blade 1 is improved so that it is possible to enhance the performance of the blade.

Helicopter gust alleviation, attitude stabilization, and vibration alleviation using individual-blade-control through a conventional swash plate

Abstract: The novel active control system presented for helicopter rotor aerodynamic and aeroelastic problems involves the individual control of each blade in the rotating frame over a wide range of frequencies (up to the sixth harmonic of rotor speed). This Individual Blade Control (IBC) system controls blade pitch by means of broadband electrohydraulic actuators attached to the swash plate (in the case of three blades) or individually to each blade, using acceleratometer signals to furnish control commands to the actuators. Attention is given to IBC's application to blade lag, flapping, and bending dynamics. It is shown that gust alleviation, attitude stabilization, vibration alleviation, and air/ground resonance suppression, are all achievable with a conventional helicopter swash plate.

Application of Quasi-Continuous Method to Unsteady Propeller Lifting-Surface Problems

Abstract: The Quasi-Continuous Method (QCM), originally applied to the steady planar thin wing problems, possesses advantages of both continuous and discrete loading methods. It has been successfully applied to steady propeller problems and in the work described here, is extended to unsteady propeller problems. First, explanations are made on unsteady two-dimensional wing problems for the evaluation of the validity of numerical methods and then a numerical procedure to solve unsteady propeller problems is described in detail. It is then shown that the fluctuating thrust of one blade and propeller vibratory shaft forces calculated by the present method agree well with experiments. A sample calculation is shown for pressure contours on a blade surface with varying angular position in a nonuniform flow.

Predicted Changes in Advanced Turboprop Noise with Shaft Angle of Attack

Abstract: Advanced turboprop blade designs and new propeller installation schemes motivated an effort to include unsteady loading effects in existing propeller noise prediction computer programs. The present work validates the prediction capability while studing the effects of shaft inclination on the radiated sound field. Classical methods of propeller performance analysis supply the time-dependent blade loading needed to calculate noise. Polar plots of the sound pressure level (SPL) of the first four harmonics and overall SPL are indicative of the change in directivity pattern as a function of propeller angle of attack. Noise predictions are compared with newly available wind tunnel data and the accuracy and applicability of the prediction method are discussed. It is concluded that unsteady blade loading caused by inclining the propeller with respect to the flow changes the directionality and the intensity of the radiated noise. These changes are well modeled by the present quasi-steady prediction method.

Variable pitch marine propeller

Abstract: The pitch of a blade of a marine propeller can be varied by relative rotation between a propeller shaft 14 and an inner shaft 30 co-axial therewith. Under normal driving conditions, drive from a motor shaft 19 is transmitted via gears 15, 17 to the shaft 14 which transmits drive via a gear 42, gears 44, idler gear (or spinner) 46, and gears 55 to a gear (54) mounted on the shaft 30. To vary blade pitch a housing 50 can be rotated by a chain drive engaging a sprocket 60 thus rotating the axis of rotation of the gears 55 relative to that of the gears 44 and causing relative rotation of the shafts 14, 13 superimposed upon their driven rotation. Such relative rotation is transformed into pitch change by means of a worm 36, worm wheels 38 and helical gears 25A, 25B secured to the blades 22.

Apparatus for adjusting and locking pitch of a variable pitch propeller on a ship

Abstract: Apparatus for adjusting and locking the pitch of a variable pitch propeller. Within a propeller shaft, a hydraulic piston is provided which drives a rod, a plate, and levers to rotate the propeller blades in, and with respect to, the hub of the propeller. The root of the propeller within the hub has a conical portion which has a mating conical ring thereabout. This conical ring is engaged and locked into place with the conical portion of the propeller root and the propeller hub by hydraulic oil pressure, once the optimum pitch of the propeller blades is determined.

Pitch control apparatus

Abstract: The apparatus for a turbine having a bladed rotor, whose rotational speed or torque depends on the blade pitch, comprises an elongate threaded control member 2 linear movement of which controls the pitch, the control member being driven via a reversible power transmission path including electric motor 10, gearing 8,9 and ball nut 5, such that in the case of failure of the normal power supply to the pitch control apparatus, the rotational energy of the rotor acts through this path to effect blade feathering.

Variable pitch device for a propeller

Abstract: The pitch of the propeller blades is adjusted by an adjusting motor (1), a transmission (27) and an adjusting spindle (21). The power supply to the adjusting motor (1) is provided via a generator (2) whose rotor (3) with the current-conducting conductors rotates with the hub (4), while the stator (5) of this generator is arranged with the magnetic field on the non-rotating parts (6) of the bearing of the hub (4). By controlling the magnetic field of the stator, it is possible to control the generator so that the required two directions of rotation of the adjusting motor (1) are maintained.

Analysis of the free-tip rotor wind-tunnel test results

Abstract: The results from a wind tunnel test of a small scale free-tip rotor are analyzed. The free-tip rotor has blade tips that are free to weathervane into the tip's relative wind, thus producing a more uniform lift around the azimuth. The free-tip assembly, which includes the controller, functioned flawlessly throughout the test. In a test of the free-tip's response after passing through a vertical air jet, the tip pitched freely and in a controlled manner. Analysis of the tip's response characteristics showed the free-tip system's damped natural frequency to be 5.2 per rev. Tip pitch angle responses to the local airstream are presented for an advance-ratio range of 0.1 to 0.397 and for a solidity weighted rotor lift coefficient range of 0.038 to 0.092. Harmonic analysis of the responses showed a dominance by the first harmonic. As a result of the tip being free, forward flight power requirements were reduced by 8% or more. More power reduction was recorded for high thrust conditions. In addition to the power reduction, flatwise blade bending moments were reduced by as much as 30% at the inboard blade stations.

Rotor for wind power stations

Abstract: The invention relates to a rotor for wind power stations or the like, and aims to provide a rotor which has a cost-effective and simple design and which, above all, manages without all the trouble-prone adjusting mechanisms for the rotor vanes. According to the invention, it is proposed for this purpose to mount the rotor wings inclined opposite to the wind direction on the axis of rotation or the rotor hub and to arrange tensioning or clamping devices mounted on the rotor wings eccentrically with respect to the rotor wing axes between the free end of the rotor hub, which is likewise extended opposite to the wind direction, and the rotor hubs.

System for producing angular displacement

Abstract: A system for producing angular displacement about a first axes (A) of an output member (9) which is also angularly displaceable about a second axis (B) transverse to the first axis comprising a drive motor (27) having a stator (29) on a frame (11) and a rotor (31) on a drive transmission member (15) mounted for rotation about the second axis (B) and coupled to the output member (9) to alter its angular position about the first axis (A). A first pick up means (41) senses the angular position of the output member (9) about the second axis (B) with respect to the frame (11) and a second pick up means (39) senses the angular position of the transmission member (15) about the second axis (B) with respect to the frame (11), and a servo loop (47) responsive to the pick up outputs and an angular displacement demand signal drives the motor (27). One particular application of the system is for helicopter rotor blade pitch control, the first axis then being the rotor blade pitch axis and the second axis the rotor rotation axis.

Driving arrangement for watercraft

Abstract: A driving arrangement for a watercraft includes a propeller and a freely pivoted guide wheel arranged subsequently to the propeller. The guide wheel which has a higher blade number and a smaller rotational speed than the propeller is provided with sectionized blades. One segment of each blade is propeller blade-like and extends outside the stream generated by the propeller and the other segment is turbine bucket-like and extends within the propeller stream. Upon equal rotational speed of the propeller and the guide wheel, the pitch of the respective segments is such that the pitch of the one segment which is outside the propeller stream is essentially constant in radial direction while the pitch of the other segment steadily increases radially from the one segment towards the hub on which the guide blade is arranged.

Method and apparatus for the performance testing of the engine of a ship while the engine is installed in the hull of a ship

Abstract: A method and apparatus for the performance testing of a ship's engine while the ship is moored in a harbor, and even when the ship is being refitted or before the ship is completely built. To facilitate stationary testing of the ship's engine, a zero-thrust controllable-pitch propeller substitute, designed in the manner of a water-braking device, is installed. The propeller substitute attaches to the propeller shaft of the ship and replaces the regular controllable-pitch propeller during testing. The water-braking device has controllable a drag which can be adjusted to correspond to the engine output, and is preferably designed to accept the controls and fittings of the regular propeller. The water-braking device produces substantially zero thrust on the propeller shaft and the hull of the ship at all speeds of operation thereof, thereby producing far less currents at the site of the mooring of the ship during testing than the prior art methods.

Minimizing fan energy costs

Abstract: Minimizing fan energy costs and maximizing fan efficiency is the subject of this paper. Blade design itself can cause poor flow distribution and inefficiency. A basic design criterion is that a blade should produce uniform flow over the entire plane of the fan. Also an inherent problem with the axial fan is swirl -- the tangential deflection of exit-flow caused by the effect of torque. Swirl can be prevented with an inexpensive hub component. Basic efficiency can be checked by means of the fan's performance curve. Generally, fewer blades translate into higher axial-fan efficiency. A crowded inboard area creates hub turbulence which lessens efficiency. Whether the pitch of fan blades is fixed or variable also affects energy consumption. Power savings of 50% per year or more can be realized by replacing fixed-pitch, continuously operating fans with fans whose blade pitch or speed is automatically varied.

Rotor for rotorcraft

Abstract: of EP00893811. A rotor, more especially for a rotary-wing aircraft, with a connection of the individual rotor blade to rotor hub (1) by way of a tension element (9), which is torsion-soft for the blade pitch angle movements, along with rotary-angle-movable support of the rotor blade by way of a sleeve, acting on blade root (2) and coupled with a control rod (13), in a rotor hub arm (1.1) which is directed radially outwardly in the form of a blade angle bearing sleeve on the rotor hub (1), in which respect the tension element (9) extending in the blade root sleeve (5) blocks this, in the effective direction of the centrifugal force of the blade, with its bladeroot-side end by way of an interpolated bush (7), characterised in that the bush (7) is lengthened by an extension (7.1), coupled in the rotor hub (1) with control rod (13), to form a control shaft which is rotary-angle-movable relative to the blade root sleeve (5) and which is, on the other hand, connected in a torsionally-fast manner to a lever (15) which justs out radially from the blade root sleeve (5) and which is secured thereto so as to be adjustable in the direction of rotation.

Varying pitch propeller for ship

Abstract: PURPOSE: To reduce the generation of radiation noise, by a method wherein a propeller is formed such that a pitch is gradually increased from a vane root toward a vane end. CONSTITUTION: Since the pitch of a propeller vane 1 is formed such that it is gradually increased from a vane root toward a blade end, an angle of eleva tion of the propeller blade with a flow in the vicinity of the blade end is prevented from becoming negative under a low speed sailing condition. Thus, since face cavitation is prevented from occurring, the generation of radiation noise is sharply reduced. Since the pitch of the propeller vane 1 is gradually increased toward the blade end, a pitch angle βG of the propeller blade 1 is always kept, even under a low speed state, at a state in that it is higher than a pitch angle β of a flow to the propeller blade 1, shown by a curved line e'. This prevents an angle of elevation α=βG-β of the propeller blade with a flow. Further, a curved line shows distribution of a pitch angle of the propeller angle. COPYRIGHT: (C)1987,JPO&Japio

Effect of angular inflow on the vibratory response of a counter-rotating propeller

Abstract: This report presents the results of a propeller vibratory stress survey on the Fairey Gannet aircraft aimed at giving an assessment of the difference in vibratory response between single and counter-rotating propeller operation in angular inflow. The survey showed that counter-rotating operation of the propeller had the effect of increasing the IP response of the rear propeller by approximately 25 percent over comparable single-rotation operation while counter-rotating operation did not significantly influence the IP response of the front propeller.

Aircraft with a retractable variable pitch propeller or a fluid motor driven multi propeller aircraft

Abstract: An aircraft has a pair of wing portions with propellers of a propeller pair which are driven and synchronized by a fluid transmission between the power plant and the propellers. A fluid line structure keeps most components of the craft together and consists preferredly of three pipes which are also utilized to carry the driving fluid to and from the motors, to hold the motors and to hold the wings. The take over of a plurality of functions by the interior pipe structure reduces weight and secures safe and economic operation of the craft. In the type of the aircraft where this application deals with, a variable pitch propeller may be applied which operates with variable pitch at flight to obtain its best efficiency at the respective speed of flight while the propeller is set with its chord parallel to the chord of the wing or tail when it is retracted into a slot in the wing or tail when another propeller drives the craft forward in leveled flight. This arrangement makes it suitable to apply a plurality of propellers for short way or vertical take off and landing while those propellers which are not needed or would reduce the efficiency at forward flight can be retracted to reduce drag at high speed forward flight.

Low-speed wind-tunnel tests of an advanced eight-bladed propeller

Abstract: As part of a research program on advanced turboprop aircraft aerodynamics, a low-speed wind-tunnel investigation was conducted to document the basic performance and force and moment characteristics of an advanced eight-bladed propeller. The results show that in addition to the normal force and pitching moment produced by the propeller/nacelle combination at angle of attack, a significant side force and yawing moment are also produced. Furthermore, it is shown that for test conditions wherein compressibility effects can be ignored, accurate simulation of propeller performance and flow fields can be achieved by matching the nondimensional power loading of the model propeller to that of the full-scale propeller.