Showing papers on "Blade pitch published in 1997"

Key Results from a Higher Harmonic Control Aeroacoustic Rotor Test (HART)

Abstract: In a major cooperative research program within existing US-German and US-French Memoranda of Understandings (MoU's) a comprehensive experimental study was conducted with a 40-percent geometrically and dynamically scaled BO-105 main rotor operated in the open-jet-anechoic test section of the German-Dutch Wind Tunnel (DNW). The objectives of the program were to improve the physical understanding and the mathematical modelling of the effects of the higher harmonic blade pitch control technique on blade-vortex interaction (BVI) impulsive noise and vibration reduction. A unique set of acoustic, dynamic, dynamic response, performance, and rotor wake data were acquired with a pressure and strain gauge instrumentedblade and by application of non-intrusive measurement techniques. This paper is focused on the experimental part of this research program, termed Higher-harmonic-control Aeroacoustic Rotor Test (HART) which was jointly performed by researchers from the.

Helicopter with a gyroscopic rotor and rotor propellers to provide vectored thrust

Abstract: A model helicopter creates lift using rotor propellers mounted to the rotor arms of a gyroscopic rotor assembly. A controller converts front-back, and left-right inputs into speed control signals used to vary the speeds of the rotor propellers at selected positions of the rotor assembly as it rotates. The varying speed of the rotor propellers at selected rotor positions produces thrust vectors at those positions. The resultant thrust vector determines the direction of the helicopter's flight and enables it to pitch and roll in response to the front-back and left-right inputs. The rotor assembly can have two or more rotor arms, each with a propeller. The helicopter provides left-right yaw control with a yaw propeller on the helicopter body. Electric motors, or motors using other conventional power and speed control methods, can be used to drive the rotor and yaw propellers. Power and speed control signals can be transferred to the rotor motors via commutators on the helicopter body and rotor assembly that make electrical contact as the rotor assembly rotates.

Oscillating air jets for helicopter rotor aerodynamic control and BVI noise reduction

Abstract: An active control system for reducing blade-vortex-interaction (BVI) noise generated by a rotor blade. The active control system includes a pressure sensor assembly, a device for changing a lift generated by the rotor blade, and a controller for activating the device upon a detected change in air pressure by the sensor assembly. The sensor assembly is disposed in close proximity to the rotor blade, and is adapted to detect a change in air pressure on a surface of the rotor blade near a leading edge of the rotor blade. The device is adapted to be activated by the controller, to thereby change a lift of the rotor blade. The controller activates the device to change a lift of the rotor blade in order to introduce a compensating pressure onto the surface of the rotor blade. This compensating pressure attenuates the magnitude of the change of air pressure. The device for changing a lift generated by the rotor blade can include at least one aperture on the rotor blade and a diaphragm in the interior of the rotor blade. The diaphragm can be activated and moved between a first position and a second position at a frequency. Movement of the diaphragm from the first position to the second position pushes air out of the at least one aperture, and movement of the diaphragm from the second position to the first position draws air into the at least one aperture.

Hydraulically controlled riding trowel

Abstract: A high performance, multiple rotor riding trowel for finishing concrete and hydraulic controls therefor, enabling complete hand control to the operator of steering, propulsion, and blade pitch. A rigid trowel frame mounts two or more downwardly-projecting, bladed rotor assemblies that frictionally engage the concrete surface. The rotor assemblies are tilted with double acting hydraulic cylinders to effectuate steering and control. Double acting hydraulic cylinders also control blade pitch. A joystick system enables the operator to hand control the trowel with minimal physical exertion. The joystick system activates solenoid control valves that in turn energize the various hydraulic cylinders that tilt the rotors and alter blade pitch. The rotor gearboxes are mounted to tiltable, pivot steering boxes secured to the frame within suitable mounting regions bounded by rigid frame elements. The rotor assembly blades contact plastic concrete to finish the surface while supporting the trowel.

Rotor blade swashplate-axis rotation and gyroscopic moments compensator

Abstract: An apparatus for compensating for spatial phase angle phase errors in the flapping angle oscillations of a rotor blade is disclosed. The apparatus receives a measured aircraft roll and a measured aircraft pitch. Gyroscopic moments resulting from these measured rolls and pitches are determined, and compensating gyroscopic moments are then generated and summed with commanded pitch and roll accelerations. Flapping angle phase lags of the rotor blade swashplate are added to the summed signals to cancel any flapping angle phase leads, caused by changes in aircraft or rotor blade speed caused by installation configurations of the rotor blade swashplate.

Different Wings Flowfields Interaction on the Wing-Propeller Coupling

Abstract: A high-portability numerical technique based on the method of free wake analysis (FWA) is described that analyzes the interference between an aircraft propeller and a wing having different planforms and computes the influence of the wing aerodynamic field on the propeller performance. For an isolated propeller and wing, the models employed are based on the FWA and Prandtl theory, respectively. The performance of the propeller in the presence of the wing is related to the wing angle of attack and to the variation of wing circulation and the corresponding induced velocity at the propeller disk. A numerical model, previously and successfully used, was implemented to account for the effects of a wing on the wing- propeller coupling. To test the robustness of the method, the available experimental data obtained on a scale model of an isolated propeller are used. In a correlation study, the results, when wing and propeller are coupled, show the sensitivity of thrust, power, and efficiency to inflow conditions and blade pitch, as well as to the wing planform

Bulldozer blade pitch control method and controller for the same

Abstract: A bulldozer blade (10) is automatically reset to a predetermined excavating pitch while the bulldozer (20) is traveling backwardly after it has completed an operation of excavating, carrying, or dumping earth. The bulldozer blade (10) can be set to an excavating pitch, a carrying pitch, or a dumping pitch when excavating, carrying, or dumping earth while the bulldozer is traveling forwardly, the bulldozer blade being attached to the leading ends of frame members (15A, 15B) which are pivotally mounted on opposite sides of the vehicle body (20a) in such a manner that the bulldozer blade can swing longitudinally. The rotational angles of left and right lifting cylinders (21A, 21B), which are attached to the bulldozer blade, are detected by first detectors (23a, 23b) while the bulldozer is traveling backwardly after it has completed an operation of excavating, carrying, or dumping earth, and the bulldozer blade is automatically reset to a predetermined excavating pitch from the carrying pitch or the dumping pitch in response to a command issued by a controller (50) which receives detection signals from the first detectors.

Design and testing of a 1/12th-scale solid state adaptive rotor

Abstract: A new approach to helicopter flight control through active blade pitch manipulation is presented. By using piezoceramic directionally attached piezoelectric (DAP) torque plates mounted between the rotor shaft and the blade root, the pitch angle of the helicopter rotor blades may be adjusted as the blades sweep the azimuth. Analytical models based on classical laminated plate theory for steady torque-plate deflection are presented. To verify the models, a 1/12th-scale two-bladed experimental test article was constructed. The test article was Froude scaled with a 122 cm total diameter and a 5.5 cm chord. Static and dynamic testing showed that blade pitch deflections could be controlled from -4 through with good correlation between theory and experiment. Dynamic testing demonstrated that the first natural frequency in pitch was greater than 2.5 with a maximum power consumption of 194 mW under the most extreme conditions, thus making it feasible for control of collective, longitudinal and lateral cyclic. Whirl-stand testing at up to 600 RPM showed that the rotor could generate thrust coefficients ranging from -0.0046 through +0.014 with little sensitivity of blade deflection to increases in rotor speed.

Actuation system for a gas turbine rotor blade

Abstract: An actuation system which includes apparatus for transferring control signals for varying the blade pitch from a non-rotating member to a rotating member of a gas turbine engine is described. In one embodiment, the engine includes a main disk containing a row of blades, and the disk is coupled to a main shaft which rotates about the engine axis. An actuating disk, or cone, rotates with the main disk, and the torque required to rotate the actuating cone is transmitted through ball splines attached to the main shaft. The ball splines allow transmission of torque between the disk and the cone and at the same time enable the disk and the cone to move axially relative to each other without binding. The actuating cone is supported at one end by the ball splines and at its other end by ball thrust bearings. The ball thrust bearings are pre-loaded to enable the bearings to withstand axial loads in opposite directions. The outer races of the bearings are supported by a ring, and the ring is connected to an actuator through a connecting cone. In addition to the actuating system, a blade support system is provided wherein the load of the blade is transferred from a blade "button" head to the main disk through a load transfer ring, a bearing inner race support, and a thrust bearing. A nut retains a crank of the actuating system on the blade spindle. To rotate the blade about its radial axis, the ring is moved axially by the actuator. Such axial movement of the ring imparts axial motion to the rotating actuating cone, which rotates a crank attached to the blade. The thrust bearings allow the actuating cone to rotate about the centerline of the actuator and to move axially when actuated.

Helicopter rotor blade control device

Abstract: In a helicopter having three or more rotor blades, and with mechanical actuation of the rotor blades by a swash plate and a superimposed electrohydraulic active control system, in addition to three regulating units (18) is an actuator (4) between a rotatable part (9) of the swash plate and a rotorblade mount (2) of each rotor blade. This arrangement allows for the safe actuation of individual blades in helicopter noise reduction, and increased efficiency at a modest constructional effort.

A toy more difficult to control than the real thing

Abstract: Standard helicopters use the propeller angle to alter the aerodynamic force and have been shown to be feedback linearizable with the pitch, yaw and roll angles being the flat outputs. In this work, a-two-degree-of-freedom, laboratory-scale helicopter-like system (termed the toycopter), where the aerodynamic force is manipulated using the propeller speed, is considered. For such a system the yaw and pitch angles are not flat outputs contrarily of the real helicopters. Moreover, the system does not seem to be flat and is shown to admit at most a one dimensional defect. Various properties of this system are investigated to illustrate the difficulties that arise in the control of the toycopter.

Drive for angular displacement of wind-power generator rotor blades

Abstract: The drive (11) for resetting the blade has an energy store which is fully independent of the normal drive supply for adjusting the rotor blade. It requires no electrically powered components for converting the stored energy into a rotor blade torque. The torque, amplified by a mechanical gear system, is sufficient to produce a rotary movement of the blade in a braking direction. The energy store can be a spring, the shaft of which on failure of the power supply is coupled to the motor shaft and released to drive the rotor blade

Method and device for reducing the effect of the vibration generated by the driveline of a helicopter

Abstract: Method for reducing the effect of the vibration generated by the driveline of a helicopter. The helicopter includes at least one rotor, the collective pitch of the blades of which can be controlled by a control system. The values of at least one parameter representing the effect of the vibration generated by the driveline are measured. A control signal for the collective pitch of the blades of the rotor is directly formed from the measured values of the parameter. The control signal to the system for controlling the collective pitch of the blades of the rotor generates a set of forces and of moments which oppose the effect of the vibration generated by the driveline. The control signal thus formed is applied to the system for controlling the collective pitch of blades of the rotor.

Power trowel with counterbalanced trowel blade pitch adjust assembly

Abstract: A power trowel incorporates a counterbalanced blade pitch adjust assembly that is relatively easy to manufacture and to install (and hence that can be retrofitted onto an existing power trowel machine) and that is easy to operate. The blade pitch adjust assembly includes 1) a blade pitch adjustment mechanism, 2) a pivotable control lever assembly that is coupled to the adjustment mechanism by a cable or other tension element, and 3) a counterbalancing mechanism such as a torsion spring. The counterbalancing mechanism imposes a force on the control lever assembly that is significantly lower than the resistive force imposed on the control lever assembly by the tension element to avoid potentially dangerous control lever snap-back and to provide the operator with a sense of feel as he or she adjusts blade pitch. A latch mechanism is incorporated into the system that releases automatically when the operator applies a pivotal force to the control lever assembly--thereby obviating the need to effect a secondary release operation. The orientation of the control lever assembly also can be adjusted to meet the needs of the operator.

Method of adjusting rotor blade of wind generator

Abstract: The method involves turning rotor blades simultaneously about their longitudinal axis, so that the rear blade edges are turned into the wind. Each blade is then turned back separately into a flag position, while the rotor is braked by the remaining blades, so that no excessive rotor speed is reached. The remaining blades are then turned back one after the other in the same way. The beginning of the turning back is synchronised with the rotor position.

Wind force device

Abstract: PROBLEM TO BE SOLVED: To provide a cross flow shaped wind force device which is easy to change blade pitch by a simple constitution. SOLUTION: The center E of a link pin 28 revolves by synchronizing with revolution of a blade 7 with the center O' of an eccentric core cam 18 as a center. Therefore, the center C of a pitch changing pin 34 can be moved between points H to I by a link 30 and can be changed by one reciprocation during one revolution of an angle along the tangent of a rotary disc 23 of the blade 7. This eccentric core center can be changed with a fixed point O as a center by revolving an eccentric core shaft 17 by relating a wind direction. When the blade 7 is on the right side of a shaft 15, the center line of the blade 7 is in D to I states, when the blade 7 is just above or just under the shaft 15, the center line of the blade 7 in B to C states and when the blade 7 is on the left side of the shaft 15, the center line of the blade 7 becomes B to H states. Therefore, when wind blows from the left side, upward force is generated when the blade 7 is on the left side of a fixed shaft 15 and downward force is generated when the blade 7 is on the right side of the fixed shaft 15, and force becomes rotational force. COPYRIGHT: (C)1999,JPO

Twin engine, coaxial, dual-propeller propulsion system

Abstract: A twin engine, coaxial, dual-propeller propulsion system employing a unique transmission having two independent drive trains. The first of the two engines exclusively drives a first drive train, which in turn rotates a forward multi-bladed propeller assembly. The second engine exclusively drives a second drive train, which in turn rotates an aft multi-bladed propeller assembly. Thus, the propellers of this propulsion system, even though coaxial, are driven by separate engines. The propulsion system also enjoys the increased propulsive efficiency of a coaxial dual-propeller design as the first drive train rotates the forward propeller assembly in a first rotational direction and the second drive train rotates the aft propeller assembly in the opposite direction. Further, the propulsion system employs pitch change control mechanisms which independently control the respective pitch of the blades of the two propeller assemblies. Specifically, a first pitch change controller exclusively controls the pitch of the blades of the forward propeller assembly and a second pitch change controller exclusively controls the pitch of the blades of the aft propeller assembly.

Influence of Pitch, Twist, and Taper on a Blade’s Performance Loss due to Roughness

Abstract: The purpose of this study was to determine the influence of blade geometric parameters such as pitch, twist, and taper on a blade`s sensitivity to leading edge roughness. The approach began with an evaluation of available test data of performance degradation due to roughness effects for several rotors. In addition to airfoil geometry, this evaluation suggested that a rotor`s sensitivity to roughness was also influenced by the blade geometric parameters. Parametric studies were conducted using the PROP computer code with wind-tunnel airfoil characteristics for smooth and rough surface conditions to quantify the performance loss due to roughness for tapered and twisted blades relative to a constant-chord, non-twisted blade at several blade pitch angles. The results indicate that a constant-chord, non-twisted blade pitched toward stall will have the greatest losses due to roughness. The use of twist, taper, and positive blade pitch angles all help reduce the angle-of-attack distribution along the blade for a given wind speed and the associated performance degradation due to roughness. 8 refs., 6 figs.

The Noise from Piston Engine Driven Propellers on General Aviation Airplanes

Abstract: Analysis of extensive flyover noise data from piston engine powered propeller aeroplanes (General Aviation Aeroplanes) revealed the occurrence of - at first sight quite unexplainable - additional noise components which were, however, clearly related to propeller operation. It turns out that such "excess" propeller noise is a direct result of a nonuniform rotation of the piston engine crank- shaft which causes unsteady aerodynamic propeller blade-loadings. Associated propeller noise characteristics were determined in the framework of wind tunnel tests for a number of full-scale piston- engine/propeller combinations. The subject noise type was found most pronounced at low helical blade-tip Mach numbers and in the forward and the rear arc directions. Azimuthal noise directivity was no longer omnidirectional. Moreover, overall A-weighted propeller noise levels were found to increase by more than 5 dB as a result of such RPM-nonuniformity vs. that of a propeller.

Influence of Shaft Angle of Attack on Sound Radiation by Subsonic Propellers

Abstract: The formulation to account for effects of propeller angle of attack on acoustic radiation by propellers is presented. A propeller operating at an angle of attack presents a nonuniform ine ow situation that is known to have a pronounced ine uence on noise. Noise predictions, based on this new formulation, are compared with measured wind-tunnel data. Predictions for observers e xed in the propeller plane are also included to assess the ine uence of shaft angle of attack. Nomenclature c0 = ambient speed of sound f = function dee ning blade surface l = local force per unit area of blade acting on e uid lr = component of loading vector in direction of radiation vector, liri M = source Mach number Mr = component of source Mach vector in direction of

An examination of loads and responses of a wind turbine undergoing variable-speed operation

Abstract: The National Renewable Energy Laboratory has recently developed the ability to predict turbine loads and responses for machines undergoing variable-speed operation. The wind industry has debated the potential benefits of operating wind turbine sat variable speeds for some time. Turbine system dynamic responses (structural response, resonance, and component interactions) are an important consideration for variable-speed operation of wind turbines. The authors have implemented simple, variable-speed control algorithms for both the FAST and ADAMS dynamics codes. The control algorithm is a simple one, allowing the turbine to track the optimum power coefficient (C{sub p}). The objective of this paper is to show turbine loads and responses for a particular two-bladed, teetering-hub, downwind turbine undergoing variable-speed operation. The authors examined the response of the machine to various turbulent wind inflow conditions. In addition, they compare the structural responses under fixed-speed and variable-speed operation. For this paper, they restrict their comparisons to those wind-speed ranges for which limiting power by some additional control strategy (blade pitch or aileron control, for example) is not necessary. The objective here is to develop a basic understanding of the differences in loads and responses between the fixed-speed and variable-speed operation of this wind turbine configuration.

Blade Section Lift Coefficients for Propellers at Extreme Off-Design Conditions

Abstract: : The Propeller Force Module (PFM) code developed by Analytical Methods Inc. (AMI) for calculating propeller side forces during maneuvering simulation studies requires inputs of propeller blade sectional lift, drag, and moment data. A set of steady two-dimensional foil force data for NACA profiles is normally used by PFM as input. Wake survey data show that the propeller blade sections will encounter large spatial variations in angle of attack during maneuvers. A literature search is conducted to review the effect of unsteady angle of attack fluctuations on two-dimensional hydrodynamic forces. Methods to calculate unsteady hydrodynamic loads are evaluated, and a method selected for use with the PFM code.

Method and apparatus for calculating helicopter airspeed

Abstract: A method or apparatus for determining the airspeed of a helicopter, comprises establishing at least one cyclic pitch trim curve relating lateral and longitudinal cyclic blade pitch angle of the main rotor to airspeed, establishing the position of the centre of gravity of the helicopter relative to a datum position and using this to modify the trim curve to account for the offset, measuring the lateral and longitudinal cyclic pitch of the rotor blades and determining the airspeed from the modified trim curve using these angles. The pitch angles of the rotor blades may be determined by direct measurement at the blades or by measurement of the cyclic control stick position. The airspeed determined by the method may be displayed on an instrument showing both direction and magnitude. The method may be particularly useful at low speeds and near sea level. Compensation may be made for pitch and roll rates and accelerations.

Helicopter rotor blade pitch control swash plate

Abstract: The rotating star (14) is rotated integrally with the rotor by a driving device (31) with two rigid driving tracks (32b). Each track engages with one of two driving pegs (34) rotating integrally with the rotating star and diametrically opposite to it. The track has two flanges (33) between which the peg is engaged so as to follow a rectilinear trajectory parallel to the rotor axis (Z-Z) and a circular arc trajectory centered on this axis for variation of collective and cyclic pitch respectively.

Helicopter rotor blade pitch control swash plate with non rotating star stop peg

Abstract: The non-rotating plate is held to rotate around the rotor axis by a stop arm and a stop track, this track cooperating with a stop finger fixed to the plate. The track has two flanges between which the finger follows a rectilinear and curved trajectory to compensate for collective or cyclic pitch variations. The non-rotating star (16) is held to rotate around the rotor axis (Z-Z) by a stop arm (31) with an axially extending rigid stop track (31b) integral with the helicopter structure (24). The track engages a stop peg (33) integral with the non rotating star to retain it rotation. The peg is engaged between has two track flanges (32) so as to follow a rectilinear trajectory parallel to the rotor axis (Z-Z) and a circular arc trajectory centered on this axis in the event of variation collective and cyclic pitch respectively. The stop peg includes a runner (34), sliding between the two flanges, articulated around its attachment axis (X'X) on the non rotating star.

Partially immersible propeller

Abstract: The propeller comprises a propeller shaft mounted so that its position in relation to the ship's hull can be varied both at stopovers or in transit. The propeller shaft carries propeller blades of such a configuration that, while going into the water, they position their face sides normally to the longitudinal center plane of the ship. According to the invention the propeller blades can change position relatively to the longitudinal center plane or to the midship section plane or simultaneously to both the planes, thereby increasing speed, maneuverability, efficiency, and safety.

A Study on the Structural Behavior for the Design of the Small Aircraft Composite Propeller Blade by Considering Bird Strike Impact

Abstract: The development of aircraft composite propeller is necessarily required because recently changing metal propeller to composite propeller is a global tendency due to the improvement of composite manufacture technique and good characteristics of composite materials. The composite propeller blade must be safely designed about static and dynamic loads. The structural stability of composite propeller blades in this study was analyzed by the Finite Element Method. When the static load was acted on the composite propeller, linear and nonlinear analysis was performed with the three different types of blade structure. In order to analyze the problem of the dynamic impact load acted on the blade of shell-spar-foam structure by bird strike, Newmark method was used for linear direct transient analysis. And the Campbell diagram was drawn as the result of eigenvalue problem analysis about the composite propeller. The Natural frequencies of the shell-spar-foam blade were compared with the forced frequencies by engine rotational speed and it was found that the resonance phenomenon did not occurr in the blade. The results of the above structural analysis will be used as technical data fer the design optimization of composite propeller blade.