Showing papers on "Blade pitch published in 1995"

Air driven turbine including a blade pitch control system

Abstract: An air driven turbine having variable pitched blades is provided that includes a pitch change mechanism and associated control circuits for automatically adjusting the pitch of the blades during either rotating or non-rotating operational modes of the air driven turbine. The pitch control mechanism includes a resettable overspeed protection device which is directly actuated by an overspeed condition of the turbine and operates independently from the pitch change mechanism to move the blades to a failsafe, feathered, or coarse pitch, low speed position. The pitch control mechanism utilizes a linear actuator in the form of an acme screw drive. The air driven turbine includes a ball ramp thrust bearing for attaching the blades to a hub of the turbine in such a manner that during rotation of the turbine actuation loads on the pitch change mechanism are reduced. The control circuits utilize simple on-off switching circuits for controlling blade pitch, thereby eliminating the need for more complex PID type control functions.

Inlet acoustic mode measurements using a continuously rotating rake

Abstract: Comprehensive measurements of the spinning acoustic mode structure in the inlet of the advanced ducted propeller were obtained using a unique method that was first proposed by Sofrin. A continuously rotating microphone system was employed. Three inlet configurations with cut-on as well as cut-off stator vane sets were tested. The cut-off stator was designed to suppress all modes at the blade passing frequency. Rotating rake measurements indicate that several extraneous circumferential modes, possibly due to the interaction between the rotor and small interruptions in the casing tip treatment, were present. The cut-on stator produced the expected circumferential modes plus higher levels of the unexpected modes seen with the cut-off stator. HE next generation of fan engines will likely employ a marriage of turbofan and propeller technologies to achieve significant noise and fuel consumption reductions. The ad- vanced ducted propeller (ADP) model used in this investi- gation was designed and built by Pratt and Whitney, a Di- vision of United Technologies, and tested in the NASA Lewis 9- by 15-ft Anechoic Wind Tunnel. Typical of propeller tech- nology, the ADP allows for the in-flight adjustment of the blade pitch angle. This provides reverse thrust and optimum performance over a wide range of conditions. The duct pro- vides the noise suppression advantage of a conventional fan engine. Since future engines are expected to use still higher bypass ratios, fan noise is likely to be the dominant engine source. One of the most important features of fan tone noise is its modal structure. Knowledge of these spinning modes helps to identify the generation mechanism, control duct propa- gation (thus, mode knowledge is needed for acoustic treat- ment design) and control far-field radiation. Previous at- tempts at direct mode measurements1'3 have faced formidable practical difficulties such as: very large axial and circumfer- ential arrays of wall microphones that are not practical for the short ducts of ultrahigh bypass engines, and radial mea- surements upstream of the fan that introduce a wake that interacts with the rotor, thus causing extraneous modes. A continuously rotating microphone technique first proposed by Sofrin4 overcomes the problem of wake-generate d modes, reduces the number of microphones and the duct length re- quired. This technique has been implemented for the first time in this investigation. Two important features of this tech- nique are as follows:

Inlet acoustic mode measurements using a continuously rotating rake

Abstract: Comprehensive measurements of the spinning acoustic mode structure in the inlet of the advanced ducted propeller were obtained using a unique method that was first proposed by Sofrin. A continuously rotating microphone system was employed. Three inlet configurations with cut-on as well as cut-off stator vane sets were tested. The cut-off stator was designed to suppress all modes at the blade passing frequency. Rotating rake measurements indicate that several extraneous circumferential modes, possibly due to the interaction between the rotor and small interruptions in the casing tip treatment, were present. The cut-on stator produced the expected circumferential modes plus higher levels of the unexpected modes seen with the cut-off stator. HE next generation of fan engines will likely employ a marriage of turbofan and propeller technologies to achieve significant noise and fuel consumption reductions. The ad- vanced ducted propeller (ADP) model used in this investi- gation was designed and built by Pratt and Whitney, a Di- vision of United Technologies, and tested in the NASA Lewis 9- by 15-ft Anechoic Wind Tunnel. Typical of propeller tech- nology, the ADP allows for the in-flight adjustment of the blade pitch angle. This provides reverse thrust and optimum performance over a wide range of conditions. The duct pro- vides the noise suppression advantage of a conventional fan engine. Since future engines are expected to use still higher bypass ratios, fan noise is likely to be the dominant engine source. One of the most important features of fan tone noise is its modal structure. Knowledge of these spinning modes helps to identify the generation mechanism, control duct propa- gation (thus, mode knowledge is needed for acoustic treat- ment design) and control far-field radiation. Previous at- tempts at direct mode measurements1'3 have faced formidable practical difficulties such as: very large axial and circumfer- ential arrays of wall microphones that are not practical for the short ducts of ultrahigh bypass engines, and radial mea- surements upstream of the fan that introduce a wake that interacts with the rotor, thus causing extraneous modes. A continuously rotating microphone technique first proposed by Sofrin4 overcomes the problem of wake-generate d modes, reduces the number of microphones and the duct length re- quired. This technique has been implemented for the first time in this investigation. Two important features of this tech- nique are as follows:

Initial Results from the Higher Harmonic Control Aeroacoustic Rotor Test (HART) in the German-Dutch Wind Tunnel.

Abstract: In a major cooperative research program within existing US-German and US-French Memoranda of Understanding (MoU's), a comprehensive 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, aerodynamic,dynamic response, performance, and rotor wake data were acquired witha pressure and strain gauge instrumented blade 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 US Army Aeroflightdynamics Directorate (AFDD) and NASA Langley, the DNW, and the French and German Aeropace Research Establishments ONERA and DLR. The applied test procedures and obtained key results are presented.

Tail rotor authority control for a helicopter

Abstract: An apparatus for interconnection in a helicopter tail rotor control linkage (32) for changing the pitch of the tail rotor blades (36) in response to predetermined inputs is provided. The apparatus comprises a linkage member (46) having a variable geometry, an actuator (54), and a control unit (56). In a preferred embodiment, the control unit (56) utilizes a microcontroller (216) to monitor inputs corresponding to ambient air condition and automatically vary the maximum tail rotor pitch so as to provide maximum tail rotor authority over a range of altitudes.

Wind power generator with automatic regulation of blade pitch in response to wind speed by means of spring mounted blades

Abstract: A wind power generator having a plurality of wind mill blades whose pitch angles stably vary depending upon the wind power. A plurality of spokes radially extend from a horizontal power shaft. A plurality of protrusions respectively projecting from the spokes and the wind mill blades are paired with opposite protrusions by connector shaft. Each blade is rockable within a range from an extremely inclined position to a plane perpendicular to the power shaft to neary 90 degrees to the plane. One side of the wind mill blade strikes on the spoke at the above extremely inclined position. A plurality of blade springs are sandwiched in a compressed state between the spokes and the wind mill blades, surrouding the connector shafts respectively. Thus, each blade is biased toward the closing direction relative to the plane. If the wind is not so strong, each blade faces it to rotate the power shaft. If the wind is too strong, the blade is aligned to the direction of the wind against the blade spring, thereby preventing damage to the blades.

Cyclic pitch control having torsion spring system

Abstract: A pitch control system for a vertically launchable and recoverable winged aircraft includes a collective and cyclic pitch control system, a drive yoke and a rotor hub. The collective and cyclic pitch control system is operably connected to two proprotor blades to cyclically control the pitch of each proprotor blade, so that the aircraft is capable of controlled helicopter mode flight when the aircraft body is pointed in a generally upward direction. Proprotor blade flapping caused by applying cyclic pitch control results in teetering of the rotor hub with respect to the drive yoke. Torsion bar springs are used with suitable mechanical linkages to resist this teetering motion and generate the hub moment which is transmitted to the airframe and used to maneuver the aircraft.

Air driven turbine having a blade pitch changing mechanism including overspeed protection

Abstract: An air driven turbine having variable pitched blades is provided that includes a pitch change mechanism for adjusting the pitch of the blades during either rotating or non-rotating operational modes of the air driven turbine. The pitch control mechanism includes a resettable overspeed protection device which is directly actuated by an overspeed condition of the turbine and operates independently from the pitch change mechanism to move the blades to a failsafe, feathered, or coarse pitch, low speed position. The pitch control mechanism utilizes a linear actuator in the form of an acme screw drive. The air driven turbine includes a ball ramp thrust bearing for attaching the blades to a hub of the turbine in such a manner that during rotation of the turbine actuation loads on the pitch change mechanism are reduced.

Wind power rotor blade adjuster in light wind

Abstract: Wind speed (V) and direction (BETA) are measured relative a spatially fixed system of coordinates so the control computer etc. (E) can produce positional commands for blade alignment reference a rotor-fixed coordinate system so the mechanical blade adjusters on the leeward side of the blade trajectory set blades at right angles to the wind compared with the upwind side which now lines up with the wind. The blades are adjusted continuously round their trajectory on the basis of a control function from the control unit. The blades are adjusted so the increasing rotor speed is measured on starting and the resulting fluctuating oncoming wind flow allowed for in the control unit so the blades round part of all of the trajectory adopt their airfoil position. The control uses the adjusters to bring the blades radial to the rotor axis at maximum wind speed and thus halt the rotor.

Controllable pitch propeller for propulsor and hydroturbine

Abstract: A controllable pitch propeller for application principally to sailboats employing electric auxiliary power. The design addresses a highly efficient approach to performing four basic functions desirable on sailing vessels that have electrical, or internal combustion, auxiliary power and onboard electrical systems typically employing batteries. The design employs no external nor remote actuator means; instead, blade position (nominal pitch) is inherently "controlled" by the direction of shaft rotation and whether the propeller is acting as a propulsor or a turbine. The four basic functions, or configurations, performed by the design are 1) forward propulsion, 2) reverse propulsion, 3) efficient power generation as a turbine, and 4) feathering for no-power minimum drag. The propeller includes a cambered blade configured with a cross section that would purposely act efficiently with fluid inflow impinging on either edge, depending upon the function being performed.

The multi-unit rotor blade system integrated wind turbine

Abstract: The described wind turbine has a set of propeller type wind force collecting rotor turbines which is comprised of an up-wind auxiliary rotor blade turbine, being disposed on the front end of the combined bevel-planet gear assembly, and a down-wind main rotor blade turbine. These rotor blades rotate in opposite directions with respect to one another, and the extender enables the main turbine to be activated by normal wind speed without any aerodynamic wake turbulence effects created by the movement of the auxiliary rotor blade. The super-large scale, integrated, multi-unit rotor blade wind turbine has four sets of wind force collecting rotor blade turbines composed of an auxiliary down-wind rotor turbine and three up-wind rotor turbine units evenly spaced around a central pivotal rotor hub on extenders which are the same length as the radius of the auxiliary turbine blade. The above described wind turbines are provided with a microprocessor pitch control system thereby achieving high efficiency operation and to stall for storm control.

Helicopter rotor blade of glass fibre reinforced synthetic resin

Abstract: The rotor blade (2) has a profile at the tip of the blade which is rotated about the rotor blade longitudinal axis via actuators. The torsion skin (6) of the rotor blade is anisotropic at the blade tip, for providing a tension-rotation coupling and associated with a control actuator (8), extending in the longitudinal direction of the rotor blade. Pref. the control actuator provides a controlled normal force at the end face of the rotor blade tip and is pref. provided by a piezoactuator, extended in length for rotation of the blade tip in one direction and reduced in length for its rotation in the opposite direction.

A Guide to the Use of the Pressure Disk Rotor Model as Implemented in INS3D-UP

Abstract: This is a guide for the use of the pressure disk rotor model that has been placed in the incompressible Navier-Stokes code INS3D-UP. The pressure disk rotor model approximates a helicopter rotor or propeller in a time averaged manner and is intended to simulate the effect of a rotor in forward flight on the fuselage or the effect of a propeller on other aerodynamic components. The model uses a modified actuator disk that allows the pressure jump across the disk to vary with radius and azimuth. The cyclic and collective blade pitch angles needed to achieve a specified thrust coefficient and zero moment about the hub are predicted. The method has been validated with experimentally measured mean induced inflow velocities as well as surface pressures on a generic fuselage. Overset grids, sometimes referred to as Chimera grids, are used to simplify the grid generation process. The pressure disk model is applied to a cylindrical grid which is embedded in the grid or grids used for the rest of the configuration. This document will outline the development of the method, and present input and results for a sample case.

Actuator for a variable pitch propeller

Abstract: An actuator for varying the pitch of a plurality of propeller blades mounted on a propeller blade hub comprising an electric motor driving a drive gear, a reduction gear set driven by the drive gear and driving an externally threaded drive spool, an internally threaded pitch ring including a tangential slot, a pin received within the tangential slot and disposed on a blade hub to which the propeller blade is secured. Rotary movement of the drive gear, the reduction gear set, and the drive spool results in translational movement of the pitch ring. Translational movement of the pitch ring causes movement of the pin within the tangential slot, resulting in rotation of the propeller blade.

Modified propeller blade

Abstract: A plastic propeller for marine electric trolling motors modified to prevent the entanglement and build-up of weeds by the application to its surface of a thin sheet of metal formed in the shape and size of the blade and extending beyond the blade's leading edge.

Flow Field Investigation of a Rotating Helicopter Rotor Blade by Three-Component Laser-Doppler-Velocimetry

Abstract: The measurement of three dimensional local flow vectors of a blade tip vortex at positions near the helicopter rotor plane were performed with a three component laser-Doppler-velocimeter (3D LDV). A 'possition monitoring system' synchronized to the blade rotation gave access to blade motion parameters like lead-lag and pitching at the desired radial position of the blade. Mainly results concerning the structure of blade tip vortices were obtained. The measurements of a vortex generated at hover condition showed the correctness of 'time history' data acquisition, e.g. taking data during the time interval when one particular blade is passing the location of the measuring volume of the LDV.

Blade pitch change mechanism

Abstract: A pitch change mechanism for a plurality of fan blades (12) comprises adjustment device (60) to rotate the blades (12) about their longitudinal axes. A gear box (34) provides rotary power to drive the adjustment device (60) in response to a control signal. The gear box (34) is mounted in the fan shaft (30) and rotates therewith. An input shaft (33) to the gear box (34) is mechanically connected to a turbine shaft (32) so that the input shaft (33) rotates with the turbine shaft (32). The difference between the speeds of the fan shaft (30) and the turbine shaft (32) is used to drive an output shaft (39) of the gear box (34). The rotary power of the output shaft (34) drives the pitch adjustment device (60) via a plurality of gears (50).

Pitch angle control device of motor boat

Abstract: PROBLEM TO BE SOLVED: To stabilize the position of a hull relative to the lift of a stem which is varied according to various conditions. SOLUTION: A pitch angle sensor to detect the pitch angle of a hull 1 is fitted, the detected value by the pitch angle sensor is corrected according to the acceleration of the hull 1, and the angle of a flap 2 fitted by a cylinder 3 to a stem in an oscillating manner in the vertical direction is controlled from the corrected pitch angle and the target pitch angle obtained according to the ship speed. In the accelerating condition, the control frequency is increased to control the flap 2 according to the change in the pitch angle, while in the sudden deceleration, the control of the flap 2 is stopped. In addition, a plurality of target pitch angles can be set, and one of them can be selected.

A Contrarotating Propeller Design for a High Speed Patrol Boat with Pod Propulsion.

Abstract: : A contrarotating (CR) propeller design with a tractor pod for a high speed patrol boat is addressed In the current arrangement, a CR propeller is placed at the forward end of a pod which is aligned with the local inflow The powering and cavitation experiments show the performance prediction agree well with measurements Compared to the existing controllable pitch propeller with shaft and strut configuration, the pod-mounted CR propeller show a 28% reduction in power consumption at design speed with a 7 knot improvement in cavitation inception speed At full power, a larger pod is required, which will reduce the gain in power consumption

Effects of Nonuniform Blade Pitch on the Flow Through an Annular Turbine Nozzle

Abstract: This paper discusses flow measurement results both upstream and downstream of a transonic annular gas turbine nozzle with a nonuniform pitch. The downstream measurements are performed in the plane where the leading edge of the rotor blade is located in the gas turbine. The experiments were performed using total pressure probes and wall static pressure taps. The pitch variation modifies the flow field both upstream and downstream of the nozzle, although the experiments show that the effect is localized to the immediate neighborhood of the involved blades. The effects on the wakes and on the inviscid flow are discussed separately. The mean velocities show a strong sensitivity to the changes of the pitch, which is due to a potential flow effect rather than a viscous effect.

Application of a genetic algorithm to wind turbine design

Abstract: This paper presents an optimization procedure for stall-regulated horizontal-axis wind-turbines. A hybrid approach is used that combines the advantages of a genetic algorithm and an inverse design method. This method is used to determine the optimum blade pitch and blade chord and twist distributions that maximize the annual energy production. To illustrate the method, a family of 25 wind turbines was designed to examine the sensitivity of annual energy production to changes in the rotor blade length and peak rotor power. Trends are revealed that should aid in the design of new rotors for existing turbines. In the second application, a series of five wind turbines was designed to determine the benefits of specifically tailoring wind turbine blades for the average wind speed at a particular site. The results have important practical implications related to rotors designed for the Midwest versus those where the average wind speed may be greater.

Fluid type vibration damping device

Abstract: PROBLEM TO BE SOLVED: To provide a fluid type vibration damping device which can efficiently oscillate liquid by low power without discharging compressed air into the atmosphere in order to damp vibration. SOLUTION: A structure 9 carries thereon an acceleration sensor 10 and a U-like tank 1 which is a closed container incorporating left and right air chambers 2, 4 communicated with each other through an air pipe line 5, and charged therein with liquid 2. A blower having variable blades 6a, is provided in the air pipe line 5, and is rotated by a prime mover 7. A vibration control device 13 receives signals from an acceleration sensor 10, and pressure sensors 11, 12, and delivers an output signal to a blade pitch control device 8. The control device 8 adjusts the pitch angles of the variable blades 6a of the blower 6 so as to move the liquid 2 for damping vibration of the structure 9, up and down, and controls the air volume. The efficient damping of vibration is thus enabled without discharging compressed air.

Simple, adjustable pitch ship's propeller

Abstract: The pitch is adapted to different front travel modes of the propeller performance. A hub (2) is coupled to the propeller shaft (1) by a conical or cylindrical interference fit and has a bayonet-type recess for mounting, adjusting, and fixing of the adjusting blades in plug-rotary couplers (5) of the blade foot mounting on the hub. The couplers are located so that behind the hub interference fit an exchangeable and subsequently fittable pitch adjuster and fastener can be inserted in the rear section of the hub. This is adaptable to the operational requirements. The adjusting mechanisms are driven by an electric on hydraulic motor up to fine adjustment.

Cross flow fan and air conditioner using this fan

Abstract: PURPOSE:To realize a cross flow fan easy to assemble and improved so as to reduce air quantity fluctuation and a noise level, and an air conditioner compact with low noise using this face and contributing to saving resource and energy. CONSTITUTION:A small impeller 1 with plural blades 2 disposed at the same pitch into cylindrical shape around a rotary shaft is made a unit small impeller, and plural impellers 1, seven impellers 1a-1g, for instance, are connected in the direction of the rotary shaft. At the connecting time, the impellers 1 are connected by shifting the positions of the blades 2 of the adjacent small impellers 1 mutually by the specified quantity, avoiding the center position of the blade pitch. The shifted positions of the blades 2 are set by recessed parts, provided at the back face of each side plate 10 for connecting the blades 2, as positioning means. An air conditioner easily attaining the expected purpose can be realized by substituting an existing once-through fan.

Experimental Analysis of Tractor Propeller Effects on a Low Aspect Ratio Semi-span Wing

Abstract: A combination of a low aspect ratio semi-span wing model with a 4 bladed tractor propeller was investigated in the Delft University Low Speed Windtunnel. The nacelle could be disconnected from the wing to enable investigation of the propeller position effects. Two thrust conditions were tested to wit Tc=0.77 at Re=0.3*10{6} and Tc= 0.00 - 0.20 for Re=0.8*10{6}. The effects of the propeller slipstream on the overall aerodynamic coefficients of the propeller/wing configuration and the wing alone were determined. The experimental results reveal that substantial performance benefits can be obtained. The propeller angle of attack seems to have a dominant influence on the wing performance. Mounting the propeller at a negative (tilt down) angle with reference to the wing suggests a strong reduction of overall wing induced drag. Besides this, the wing efficiency is found to be strongly dependent on both the spanwise and vertical position of the propeller.

Cupped propeller test and analysis

Abstract: Cupping a propeller means to deform its blades near the trailing edge, thus increasing the profile camber. Gawn-Burrill propellers with z = 3, P/D varied from 0.8 to 1.6, AE/AO = 0.5, medium cupped, were tested in open water condition. Cavitation tests were performed for P/D = 1.0 The cupped propeller performance could be predicted from the Newton-Rader series by the virtual pitch concept with good accuracy both in cavitating and non-cavitating conditions. Suitable cupping could increase the effective pitch ratio and improve the cavitation performance, however with 5% less efficiency compared to the Newton-Rader series in non-cavitating condition. A numerical method for calculating the virtual pitch of cupped propeller is presented.

Anti-torque shrouded rotor with play-mounted blades

Abstract: The rotor consists of a hub (12) on a shaft, with blades (2) connected to the hub by arms (18) which can flex and turn about the blades' variable pitch axes. Each blade is mounted in bearings (8,9) and turned by a lever (23) which lies eccentrically relative to the blade axis. The blade pitch is controlled collectively by a plate (26) which turns with the hub and has a control lug (25) for each blade, connected to a lever. Each lug is connected to a lever by a rotary coupling engaging with an elongated aperture in a ring, having a greater amount of play in the lengthwise than in the transverse axis. Each aperture in the ring has two flat opposite edges lying parallel to its longer axis and symmetrically in relation to its centre. Each blade is mounted in its bearings by means of a sleeve (5) which carries the pitch control lever.

Blade Pitch Influence at the Exit Flow Field of an Axial Flow Fan

Abstract: Variable pitch axial flow fans are widely used in industrial applications to satisfy variable operating conditions. In this work, an experimental research on a fan of this kind has been carried out. The performance curves of the fan have been obtained and the flow field has been measured at the best efficiency point of each blade pitch tested and for a lower and higher flow rate, in a fixed plane downstream the rotor with a triple hot-wire probe. The radial and circumferential distributions have been obtained, and maps of the velocity components over a blade channel are shown for each operating condition. The flow structure, including the tip and hub blockage, the blade wakes and the main flow core, is characterized.Copyright © 1995 by ASME