Showing papers on "Blade pitch published in 1982"

Theoretical and experimental power from large horizontal-axis wind turbines

Abstract: A method for calculating the output power from large horizontal-axis wind turbines is presented. Modifications to the airfoil characteristics and the momentum portion of classical blade element-momentum theory are given that improve correlation with measured data. Improvement is particularly evident at low tip-speed ratios where aerodynamic stall can occur as the blade experiences high angles of attack. Output power calculated using the modified theory is compared with measured data for several large wind turbines. These wind turbines range in size from the DOE/NASA 100 kW Mod-0 (38 m rotor diameter) to the 2000 kW Mod-1 (61 m rotor diameter). The calculated results are in good agreement with measured data from these machines.

Fixed pitch rotor performance of large horizontal axis wind turbines

Abstract: Experimental fixed pitch wind turbine performance data is presented for both the DOE/NASA Mod-0 and the Danish Gedser wind turbines. Furthermore, a method for calculating the output power from large fixed pitch wind turbines is presented. Modifications to classical blade element momentum theory are given that improve correlation with measured data. Improvement is particularly evident in high winds (low tip speed ratios) where aerodynamic stall occurs as the blade experiences high angles of attack.

Dynamics and Stability of Wind Turbine Generators

Abstract: This paper describes the dynamic and stability properties of wind turbine generators connected to power systems. Both synchronous and induction generators are considered. A comparison is made between wind turbines, steam, and hydro units. The unusual phenomena associated with wind turbines are emphasized. The general control requirements are discussed, as well as various schemes for torsional damping such as speed sensitive stabilizer and blade pitch control. Interaction between adjacent wind turbines in a "wind farm" is also considered.

Predicted motion wind turbine tower damping

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 ##EQU1##

Motion responsive wind turbine tower damping

Abstract: An accelerometer (1) disposed on the support tower (12) of a wind turbine electric generating system in the vicinity of the rotor (10, 16) thereof provides a signal (1) indicative of acceleration of the tower in the direction of the rotor rotational axis. The signal (2) is passed through a band-pass filter (4) for summation (9) with a torque/power controlled (100) blade pitch angle reference rate signal (98), the integral (104) of which provides a blade pitch angle reference signal (40) to control the pitch angle of the rotor blades (10) through a pitch change mechanism (38), thereby to provide additional, positive aerodynamic damping to the tower while modulating blade angle for constant torque/power in response to wind turbulence.

Rotor system for horizontal axis wind turbines

Abstract: A rotor system for horizontal-axis wind turbines is provided having compound coning and a sweep angle to improve the rotor system's yaw responsiveness and stability and to reduce vibration and stress. To further improve wind turbine performance and rotor durability blades with the load-bearing function and airfoil function separated are disclosed and are particularly useful in rotor systems having compound coning or compound coning and sweepback. The load-bearing function and support function of the rotor hub are separated to improve rotor system durability and to provide a rotor hub for use with a pitch change mechanism for altering the pitch of rotor system blades.

Wind turbine rotor control system

Abstract: In a pitch control system for a wind turbine, a mechanical control system changes pitch angle of the rotor blades collectively in response to blade pitch moment. The control system is designed to be used with a downwind constant speed two-bladed horizontal axis teetering hub wind turbine. Pitch placement controls torque for a synchronous alternator connected to the electrical power grid. The pitch control system is manually lockable from the ground in run or shutdown modes. An automatic shutdown mode provides fullfeathering for protection from large amplitude vibrations or loss of the electrical grid.

Evaluation of wind tunnel performance testings of an advanced 45 deg swept 8-bladed propeller at Mach numbers from 0.45 to 0.85

Abstract: The increased emphasis of fuel conservation in the world and the rapid increase in the cost of jet fuel has stimulated a series of studies of both conventional and unconventional propulsion systems for commercial aircraft. The results of these studies indicate that a fuel saving of 15 to 30 percent may be realized by the use of an advanced high-speed turboprop (Prop-Fan) compared to aircraft equipped with high bypass turbofan engines of equivalent technology. The Prop-Fan propulsion system is being investigated as part of the NASA Aircraft Energy Efficient Program. This effort includes the wind tunnel testing of a series of 8 and 10-blade Prop-Fan models incorporate swept blades. Test results indicate efficiency levels near the goal of 80 percent at Mach 0.8 cruise and an altitude of 10.67 km (35,000 ft). Each successive swept model has shown improved efficiency relative to the straight blade model. The fourth model, with 45 deg swept blades reported herein, shows a net efficiency of 78.2 at the design point with a power loading of 301 kW/sq meter and a tip speed of 243.8 m/sec (800 ft/sec.).

Helicopter individual blade control system

Abstract: The pitches of the several blades in a helicopter rotor assembly are controlled by individual blade control subsystems. Those blade control subsystems respond to the output signals from accelerometers mounted on the blades. The signals from the accelerometers are used to control the pitch of the blades on which the accelerometers are mounted as well as the pitch of other blades. By appropriate orientation of any accelerometer and filtering within a particular feedback subsystem, each subsystem is designed to correct particular modes of blade motion to the exclusion of other modes of motion by varying lift.

A New Approach for Active Control of Rotorcraft Vibration

Abstract: A state-variable feedback approach is utilized for active control of rotorcraft vibration. Fuselage accelerations are passed through undamped second-order filters with resonant frequencies at N/rev. The resulting outputs contain predominantly the N/rev vibration components, phase shifted by 180 deg, and are used to drive the blade pitch to cancel this component of fuselage vibration. The linear-quadratic-gaussian (LQG) method is used to design a feedback control system utilizing these filtered accelerations. The design is based on a nine-degree-of-freedom linear model of the Rotor System Research Aircraft (RSRA) in hover and is evaluated on a nonlinear blade-element simulation of the RSRA for this flight condition. The system is shown to essentially eliminate vibrations at N/rev in all axes. The required blade-pitch amplitude is within the capability of conventional actuators at the N/rev frequency.

Effects of Rotation and Blade Incidence on Properties of Turbomachinery Rotor Wake

Abstract: An experimental investigation of the effects of the speed of rotation on a turbomachinery rotor blade wake was conducted using a fan rotor in incompressible flow. Measurements were made at two different rotational speeds (1753 and 1010 rpm) with the same blade incidence angle. The blade incidence angle was also varied to discern the effect of blade loading. A three-sensor hot-wire probe mounted in a stationary frame of reference was used for the measurements made at several radial and axial stations in the near- and far-wake regions. The three-dimensional mean velocity and turbulence profiles, the wake defect, wake decay rate, turbulence intensities, and turbulence stresses are appreciably altered when the speed of rotation and the blade loading are changed. The wake defect is reduced and the radial velocity increased when the rotation speed is increased.

Experimental Verification of Propeller Noise Prediction

Abstract: Results of experimental measurements of the sound fields of 1/4-scale general aviation propellers are presented and experimental wake surveys and pressure signatures obtained are compared with theoretical predictions. Experiments were performed primarily on a 1C160 propeller model mounted in front of a symmetric body in an anechoic wind tunnel, and measured the thrust and torque produced by propeller at different rotation speeds and tunnel velocities, wakes at three axial distances, and sound pressure at various azimuths and tip speeds with advance ratio or tunnel velocity constant. Aerodynamic calculations of blade loading were performed using airfoil section characteristics and a modified strip analysis procedure. The propeller was then modeled as an array of point sound sources with each point characterized by the force and volume of the corresponding propeller section in order to obtain the acoustic characteristics. Measurements are found to agree with predictions over a wide range of operating conditions, tip speeds and propeller nacelle combinations, without the use of adjustable constants.

Helicopter rotor with blade trailing edge tabs responsive to control system loading

Abstract: A helicopter rotor having blade trailing edge tabs which are actuated in response to control rod loading to reduce or cancel the blade pitching moments imposed upon the blade and hence the control rods by blade aerodynamic and inertial loads, or other loads, encountered during rotor operation.

Injection molded propeller

Abstract: An inexpensive injection molded propeller for mounting on a drive shaft. The drive shaft is attached to the hub of the propeller by a chemical and thermal shrink fit and by deformation due to the rotational forces of the propeller thereby producing a positive locking hub on the drive shaft. The propeller may be used, not only for remote piloted missiles and aircraft, but can also be used with different types of boat inboard and outboard drives, vehicles and equipment requiring a propeller having a positive locking system for securing the propeller or the like to the drive shaft.

Control of rotor blade stroboscopic display

Abstract: The invention concerns method and apparatus to obtain accurate tracking of rotor blades, as for example helicopter rotor blades, despite the existence of conditions transiently altering rotor angular velocity.

Performance of a droplet separator with multistage rows of flat blades

Abstract: The performance and separation mechanism of mist separators, which consist of multi-stage rows of narrow flat plates, are experimentally studied. The effects of stages, blade inclination angle, air velocity, blade pitch and lateral blade dislocation on partial collection efficiencies and on pressure loss are described. The beat design has 30° blade inclination angle and 5 to 7 stages, under conditions of constant pressure loss and of constant blade pitch.

Control design for a wind turbine-generator using output feedback

Abstract: The modeling and approach to control design for a large horizontal axis wind turbine (WT) generator are presented. The control design is based on a suboptimal output regulator which allows coordinated control of WT blade pitch angle and field voltage for the purposes of regulating electrical power and terminal voltage. Results detailed nonlinear simulation tests of this controller are shown.

Method of making an injection molded propeller

Abstract: A method of making an inexpensive injection molded propeller for mounting on a drive shaft. The drive shaft is attached to the hub of the propeller by a chemical and thermal shrink fit and by deformation due to the rotational forces of the propeller thereby producing a positive locking hub on the drive shaft. The propeller may be used, not only for remote piloted missiles and aircraft, but can also be used with different types of boat inboard and outboard drives, vehicles and equipment requiring a propeller having a positive locking system for securing the propeller or the like to the drive shaft.

The optimum design configurations of Savonius wind turbines

Abstract: This paper describes results of a systematic wind tunnel study aimed at development of an optimum configuration of Savonius rotor wind mill. Model tests were conducted in a wind tunnel on a number of Savonius rotor configurations in wind speed of 4 - 12m/s. The variables tested were blade aspect ratio, blade overlap, blade separation gap, profile of the rotor blade cross-section and the effect adding the guide vane. From this study, the power coefficient of the basic Savonius rotor is relatively low value of 0.15-0.20, with optimum blade configuration and guide vane, a maximum value of power coefficient of 0.34 was obtained and the results appears quite encouraging. Moreover, a special study was made of the flow visualization in a water channel to confirm the inference for the air flow patterns round and through the rotor.

Propeller for ship

Abstract: In a propeller for use in a ship of the type comprising 4 or more even number blades, at least one of two adjacent blades is inclined forwardly or rearwardly or one inclined forwardly and the other rearwardly so as to make different the rake angles of the two blades. The pitch angle of the rearwardly inclined blade is made larger than that of the forwardly inclined blade. With this construction the mutual interference between adjacent blades is efficiently utilized to prevent decrease in the efficiency even when operating conditions and the diameter of the propeller vary.

Rotor, particularly for rotary wing aircraft

Abstract: 1. A rotor more especially of a rotary-wing aircraft, having radially outwardly directed rotor hub arms (2) each for holding a respective rotor blade (3), which has a blade neck portion (3.2), which is torsionally pliant at least for blade pitch movements, between the blade wing and the blade root, in which the blade pitch control is effected by means of control members arranged in the rotor hub by way of a control shaft (7), introduced so as to be movable through a rotary angle into the respective rotor hub arm and coaxial with the blade angle axis, and a blade control lever (10) connected thereto in a torsionally-fast manner and to a torsionally rigid sheat (6) which surrounds the blade neck portion in a contact-free manner and which is securely connected radially outwardly therefrom to the rotor blade, and in which the torsionally rigid sheat (6) is a fibre composite material body having a structure which is flexible in relation to beat and swivel movements as well as elongation under centrifugal force of the rotor blade (3).

Blade pitch control in rotatable bladed devices for vehicles

Abstract: A rotatable bladed device for vehicles, such as especially a helicopter rotor, which has its blade pitch controlled by a setup which includes a swash plate setup controlled by a set of hydraulic actuators and the particular swash plate setup position and attitude in turn controls the blade pitch by a plurality of rods pivoted together at one end at one particular point movable longitudinally of the rotor axis, one of which rods has its other end pivoted at a point on the pitch arm by which it controls pitch and another of which rods is also pivoted at a point fixed by the rotational position at any particular time of the rotor hub

Aeroelastic analysis for helicopter rotors with blade appended pendulum vibration absorbers. Mathematical derivations and program user's manual

Abstract: Mathematical development is presented for the expanded capabilities of the United Technologies Research Center (UTRC) G400 Rotor Aeroelastic Analysis. This expanded analysis, G400PA, simulates the dynamics of teetered rotors, blade pendulum vibration absorbers and the higher harmonic excitations resulting from prescribed vibratory hub motions and higher harmonic blade pitch control. Formulations are also presented for calculating the rotor impedance matrix appropriate to these higher harmonic blade excitations. This impedance matrix and the associated vibratory hub loads are intended as the rotor blade characteristics elements for use in the Simplified Coupled Rotor/Fuselage Vibration Analysis (SIMVIB). Sections are included presenting updates to the development of the original G400 theory, and material appropriate to the user of the G400PA computer program. This material includes: (1) a general descriptionof the tructuring of the G400PA FORTRAN coding, (2) a detaild description of the required input data and other useful information for successfully running the program, and (3) a detailed description of the output results.

Blade pitch automatic control type windmill

Abstract: PURPOSE:To make it possible to obtain effective rotating speed even during weak wind as well as resist against high speed revolution during strong wind by constituting pitch angles for a blade to the direction of wind so that the pitch angle may be automatically variable. CONSTITUTION:Any number of spokes 8 and 8' are projected in a radiating and symmetrical arrangement from the circumferential faces of flanges 7 and 7' and communicated to a circular-shaped limb 9. An elevated part 12 of a blade 11 is loosely fitted to the lower end of a pin 10. A shaft piece 13 at the lower end of the blade 11 is loosely fitted into a bore of the flange 7. A coil spring fitted to the upper end of each pin 10 is fastened to the blade 11 on one end, and fitted to the end of bolts 15 on the other end of the coil spring 14. During no wind condition, the pitch angle of the blade 11 is zero (90 deg. to the direction of wind) by the elastic force of the coil spring 14. When receiving wind, each blade is subject to the wind pressure and is gradually opened to the leeward side, resisting against the elastic force of the coil spring 14, that is, the force of bias and obtains the pitch angle in proportion to the wind force and then rotates with a selected pitch angle.

Wind power plant

Abstract: Wind power plant having a rotor consisting of a main rotor and auxiliary rotor and in the rotor hub of which there is provided a mechanism, controlled by a centrifugal governor, for adjusting the rotor blade or blades, which are mounted such that they can be adjusted in the hub about its longitudinal axis. The drive energy for the mechanism is supplied by the auxiliary rotor.

Oil hydraulically tightened propeller assembly

Abstract: PURPOSE:To freely and steplessly change a blade pitch, by detachably engaging a blade mounting part to a blade mounting hole with an opening of its oil groove. CONSTITUTION:To mount a propeller blade 7 to a boss 1, a blade mounting part 8 is firstly press fitted to a mounting hole 2. Then in a press fitting state, if an oil hydraulic pump is operated to press feed pressure oil into an oil groove 3, inner surfaces of the boss 1 are expanded by a pressure rise in the enclosed oil groove 3, under this condition the blade 7 is rotated so as to be in a prescribed pitch angle and performed its positioning, simultaneously the blade moounting part 8 is further deeply fitted. And then if the oil hydraulic pump is reversely rotated to discharge the pressure oil in the oil groove 3, the inner surfaces of the boss 1 are contracted to the original state, thus the blade 7 can be firmly fixed to the mounting hole 2 of the boss 1.

Rotor head for single blade rotor of wind power systems

Abstract: The invention describes a rotor head for single blade rotors of wind power systems with tubular rotor middle section and a mounting for the middle section, which is designed as a pivot joint mounting, which by adjustment of the joint adjusts the setting angle of the rotor blade. The rotor head according to the invention therefore surprisingly manages without large antifriction bearings with a diameter, for example, of approximately 4 m, in that only small movable connections are needed at the location of the pivot joints of the pivot joint mounting.

Propeller propulsion for ships

Abstract: A propulsion propeller for ships which has blades, the wake side or rear of which is supplied with air. The air-outlet openings are provided between the blade feet and in the vicinity of the rear of the blade, in the cylindrical casing of the propeller hub or of a ring which is coaxial to the propeller shaft.