scispace - formally typeset
Search or ask a question

Showing papers on "Blade pitch published in 2005"


Patent
Dan Keith Mccoin1
18 Feb 2005
TL;DR: A wind energy conversion system includes upper and lower wind turbines having counter-rotating blade assemblies supported for rotation about a vertical rotation axis, with each blade assembly carrying a rotor for rotation past a stator to produce an electrical output as mentioned in this paper.
Abstract: A wind energy conversion system includes upper and lower wind turbines having counter-rotating blade assemblies supported for rotation about a vertical rotation axis, with each blade assembly carrying a rotor for rotation past a stator to produce an electrical output. The wind turbines are supported by a tower at an elevated position above the ground. Each wind turbine produces torque, and the wind energy conversion system provides for balancing the torques to avoid a net torque on the tower. Adjustment mechanisms are provided for adjusting blade pitch and for adjusting the size of an air gap between a stator and a rotor that comes into alignment with the stator as the rotor rotates therepast. The wind energy conversion system provides a hood for supplying intake air to a wind turbine and an exhaust plenum for exhausting air from the wind turbine, with the hood and the exhaust plenum being directionally positionable.

273 citations


01 Jan 2005
TL;DR: The main results of the numerical optimisation of the control parameters in the pitch PI-regulator performed in Chapter 6 are the following: • Numerical optimization can be used to tune controller parameters, especially when the optimization is used as refinement of a qualified initial guess.
Abstract: The three different controller designs presented herein are similar and all based on PI-regulation of rotor speed and power through the collective blade pitch angle and generator moment. The aeroelastic and electrical modelling used for the time-domain analysis of these controllers are however different, which makes a directly quantitative comparison difficult. But there are some observations of similar behaviours should be mentioned: 1) Very similar step responses in rotor speed, pitch angle, and power are seen for simulations with steps in wind speed. 2) All controllers show a peak in power for wind speed step-up over rated wind speed, which can be almost removed by changing the parameters of the frequency converter. 3) Responses of rotor speed, pitch angle, and power for different simulations with turbulent inflow are similar for all three controllers. Again, there seems to be an advantage of tuning the parameters of the frequency converter to obtain a more constant power output. The dynamic modelling of the power controller is an important result for the inclusion of generator dynamics in the aeroelastic modelling of wind turbines. A reduced dynamic model of the relation between generator torque and generator speed variations is presented; where the integral term of the inner PI-regulator of rotor current is removed be-cause the time constant is very small compared to the important aeroelastic frequencies. It is shown how the parameters of the transfer function for the remaining control system with the outer PI-regulator of power can be derived from the generator data sheet. The main results of the numerical optimisation of the control parameters in the pitch PI-regulator performed in Chapter 6 are the following: 1) Numerical optimization can be used to tune controller parameters, especially when the optimization is used as refinement of a qualified initial guess. 2) The design model used to calculate the initial value parameters, as described in Chapter 3, could not be refined much in terms of performance related to the flapwise blade root moment (1-2 %) and tilt tower base moment (2-3 %). 3) Numerical optimization of control parameters is not well suited for tuning from scratch. If the initial parameters are too far off track the simulation might not come through, or a not representative local maximum obtained. The last problem could very well be related to the chosen optimization method, where more future work could be done. (au)

267 citations


Proceedings ArticleDOI
12 Jun 2005
TL;DR: In this article, the authors proposed a pitch angle control strategy based on the average wind speed and standard deviation of wind speed, and pitch angle was controlled using a generalized predictive control in all operating regions for wind turbine generator.
Abstract: Effective utilization of renewable energies such as wind energy is expected instead of the fossil fuel. Wind energy is not constant and windmill output is proportional to the cube of wind speed, which cause the generated power of wind turbine generators to fluctuate. In order to reduce fluctuating components, there is a method to control pitch angle of blades of windmill. We have proposed the pitch angle control using minimum variance control in a previous work. However, it is a controlled output power for only rated wind speed region. This paper presents a control strategy based on average wind speed and standard deviation of wind speed, and pitch angle control using a generalized predictive control in all operating regions for wind turbine generator. The simulation results with using actual detailed model for wind power system show effectiveness of the proposed method.

141 citations


Patent
10 May 2005
TL;DR: In this paper, a turbine control system for a variable speed electrical generator in a wind turbine mounted atop a support tower is described, which includes a turbine support tower position sensor and may also include other tower acceleration and velocity sensors.
Abstract: A turbine control system for a variable speed electrical generator in a wind turbine mounted atop a support tower. The wind turbine converts wind energy into a driving torque applied to the generator. The control system includes a turbine support tower position sensor and may also include other tower acceleration and velocity sensors. A wind flow estimator uses the measured motion, generator rotation rate and blade pitch angle to predict wind flow over the swept area of the turbine's rotor, and the tower motion. The predicted wind flow and motion is used in the turbine control system to properly adjust its operating point, to tune the controller, to control the rotor rotation rate, and to damp tower oscillations.

114 citations


Patent
Enno Eyb1, Rainer Arelt1
15 Dec 2005
TL;DR: In this paper, a rotor blade for a wind turbine includes a flange section configured to connect the rotor blade to a rotor hub, which is formed from a hybrid material including glass fibers and carbon fibers embedded in a matrix material.
Abstract: A rotor blade for a wind turbine includes a flange section configured to connect the rotor blade to a rotor hub. The flange section is formed from a hybrid material including glass fibers and carbon fibers embedded in a matrix material. The carbon fibers are oriented substantially parallel to a longitudinal axis of the rotor blade.

78 citations


ReportDOI
01 Dec 2005
TL;DR: In this paper, a finite-element code that provides dynamically coupled modes for a beam can be used to provide accurate modeling of major flexible components for modal-based aeroelastic codes such as FAST (Fatigue, Aerodynamics, Structures, and Turbulence).
Abstract: This guide explains data preparation and execution with BModes, a finite-element code that provides dynamically coupled modes for a beam. The beam can be a rotating or non-rotating rotor blade or a tower, and it can have arbitrary distribution of structural properties and geometry along its length. A coupled mode implies presence of coupled flexural, axial, and torsion motions in a natural mode of vibration. Knowledge of flap-lag-torsion-axial coupled modes is crucial to several applications. Examples are: accurate modeling of major flexible components for modal-based aeroelastic codes such as FAST (Fatigue, Aerodynamics, Structures, and Turbulence), validation of flexible component models using experimental data, modal-based fatigue analysis, and interpretation of aeroelastic-stability behavior of turbines. Our plan is to eventually integrate BModes with FAST to provide tower and blade modes as rotor speed and blade pitch control settings change during a simulation. This guide provides step-by-step instructions on how to prepare input files (specify blade geometry, section properties, and finite-element discretization), how to execute the code, and how to interpret the outputs.

70 citations


Patent
17 May 2005
TL;DR: In this paper, a pitch controlled wind turbine blade (5) consisting of a pressure surface side (14) and a leeward surface side(13), where the surfaces (13, 14) established a leading edge and a trailing edge (7).
Abstract: The invention relates to a pitch controlled wind turbine blade (5) comprising a pressure surface side (14) and a leeward surface side (13), where the surfaces (13, 14) established a leading edge (6) and a trailing edge (7). The blade (5) comprises turbulence generating means (10) wherein said means are placed on the leeward surface sides (13) of the wind turbine blade (5) and at the outer section (OS) of the wind turbine blade (5) in direction of the blade tip (8). The invention further relates to a wind turbine (1) comprising at least two pitch controlled wind turbine blades (5) and pitch controlling means for pitching the blades (5). The blades (5) comprise turbulence generating means (10) wherein said means are placed on the leeward surface sides (13) of the wind turbine blades (5) and at the outer section (OS) of the wind turbine blades (5) in direction of the blade tips (8).

67 citations


Patent
09 Sep 2005
TL;DR: In this paper, a method for limiting loads in a wind turbine by using measured loads or wind speed to increase the minimum pitch angle for extended periods was proposed, allowing turbines to capture more energy by operating in higher wind speeds or utilizing larger rotors without additional loss of fatigue life.
Abstract: A method for limiting loads in a wind turbine by using measured loads or wind speed to increase the minimum pitch angle for extended periods. The minimum pitch angle will be allowed to relax down to the default when load excursions diminish. The method will allow turbines to capture more energy by operating in higher wind speeds and/or utilizing larger rotors without additional loss of fatigue life.

65 citations


Patent
26 Apr 2005
TL;DR: In this paper, a method for reducing load and providing yaw alignment in a wind turbine including measuring displacements or moments resulting from asymmetric loads on the wind turbine is proposed, and the pitch of each rotor blade is adjusted in accordance with the determined pitch to reduce or counter asymmetric rotor loading.
Abstract: A method for reducing load and providing yaw alignment in a wind turbine includes measuring displacements or moments resulting from asymmetric loads on the wind turbine. These measured displacements or moments are used to determine a pitch for each rotor blade to reduce or counter asymmetric rotor loading and a favorable yaw orientation to reduce pitch activity. Yaw alignment of the wind turbine is adjusted in accordance with the favorable yaw orientation and the pitch of each rotor blade is adjusted in accordance with the determined pitch to reduce or counter asymmetric rotor loading.

63 citations


Patent
Anton Bech1, Gerry Madden1
05 Jul 2005
TL;DR: In this article, a wind turbine (1) comprising at least two pitch controlled wind turbine blades (5), each blade comprises pitch bearings (9) including two or more bearing rings (24, 25, 26, 26), and pitch controlling means for pitching the blades by means of the bearings.
Abstract: The invention relates to a wind turbine (1) comprising at least two pitch controlled wind turbine blades (5). Each blade (5) comprise pitch bearings (9) including two or more bearing rings (24, 25, 26), and pitch controlling means for pitching the blades (5) by means of the bearings (9). The blades (5) are mounted on a hub (7) via the pitch bearings (9) and the pitch bearings (9) comprise separate flexibility enhancing means (10, 11, 12, 14, 19, 20, 28) for controlling loads in the bearings (9). The invention further relates to a use hereof.

50 citations


Proceedings ArticleDOI
23 May 2005
TL;DR: In this paper, a three-bladed Gamesa G58 wind turbine with a rotor diameter of 58 m and a tower height of 53.5 m was evaluated using 152 microphones mounted on a horizontal wooden platform (15 by 18 m 2 ).
Abstract: Acoustic array measurements were performed on a three-bladed GAMESA G58 wind turbine with a rotor diameter of 58 m and a tower height of 53.5 m. The goal was to characterize the noise sources on this turbine, and to verify whether aerodynamic noise from the blades is dominant. In order to assess the effect of blade roughness, one blade was cleaned, one blade was tripped, and one blade was left untreated. The acoustic array consisted of 152 microphones mounted on a horizontal wooden platform (15 by 18 m 2 ), which was positioned about 58 m upwind from the rotor. In parallel to the acoustic measurements, a number of turbine parameters were monitored, such as wind speed, power, turbine orientation, RPM, and blade pitch angle. In total more than 100 measurements were taken at wind speeds between 6 and 10 m/s. Two array processing methods were used to characterise the noise from the turbine. First, the noise sources in the rotor plane were localised using conventional beamforming. These results clearly show that, besides a minor source at the rotor hub, practically all noise (radiated to the ground) is produced during the downward movement of the blades. The noise is produced by the outer part of the blades (but not by the very tip), and blade noise levels scale with the 5 th power of the local flow speed. The second processing method employed rotating scan planes to localise the noise sources on the individual blades. It turns out that the tripped blade is significantly noisier than the clean and untreated blades, which is a strong indication of trailing edge noise (rather than inflow turbulence noise). The similar noise levels for the clean and untreated blades suggest that the untreated blade was aerodynamically clean.

Proceedings ArticleDOI
06 Mar 2005
TL;DR: In this article, control algorithms and implementation issues for a wind turbine simulator are presented for realistic emulation of variable characteristics of wind and rotor blades using a lab-scale motor and generator set.
Abstract: Control algorithms and implementation issues for a wind turbine simulator are presented for realistic emulation of variable characteristics of wind and rotor blades using a lab-scale motor and generator set A randomized wind speed pattern is generated with given average speed and turbulence coefficient Aerodynamic characteristics of rotor blade are considered as a real-time function of rotating speed and wind speed Periodic pulsations of torque are also included as a tower effect In addition, arbitrary size of inertia can be emulated instead of actual rotor blade inertia using the proposed algorithm of electronic inertia compensation Proposed algorithms are verified by the computer simulations and experiments using a hardware-in-loop wind turbine simulator

Patent
28 Apr 2005
TL;DR: In this paper, a method for reducing at least one of loads, deflections of rotor blades, or peak rotational speed of a wind turbine includes storing recent historical pitch related data, wind related data or both.
Abstract: A method for reducing at least one of loads, deflections of rotor blades, or peak rotational speed of a wind turbine includes storing recent historical pitch related data, wind related data, or both. The stored recent historical data is analyzed to determine at least one of whether rapid pitching is occurring or whether wind speed decreases are occurring. A minimum pitch, a pitch rate limit, or both are imposed on pitch angle controls of the rotor blades conditioned upon results of the analysis.

Patent
07 Dec 2005
TL;DR: In this paper, the transducers are incorporated in or laminated to wind blades and electrically connected to a self-powered electrical circuit to improve the response to changing wind conditions by reducing loads, at least until the turbines pitch axis system can alter the lie of the blades.
Abstract: The transducers are incorporated in or laminated to wind blades and electrically connected to a self-powered electrical circuit. The transducers in combination with the self-powered electrical circuit improve the wind blades' response to changing wind conditions by reducing loads, at least until the turbines pitch axis system can alter the lie of the blades. Thus, when there is a change in wind conditions, the resultant twisting or bending of the wind blade during the impact of the wind (gust) on the wind blade is used to extract energy from the transducers. This energy is then transferred to the electrical circuit which in turn sends a signal back to the transducers to actuate them so as to resist the imposed load.

Patent
18 Mar 2005
TL;DR: In this paper, a method of using the rotor axial force to actively counter the motions of a floating power plant is described, where rotational forces about the vertical axis (12) of the tower (4) are controlled and countered by cyclic variation of pitch angles and associated forces on the individual rotor blade.
Abstract: A method which continuously reduces the variations of the rotor axial force and thus reduces fatigue loads on rotor blades and tower, whilst the resultant output to the generator is not significantly affected or is maintained within acceptable limits in relation to limitations of the drive gear, generator and power grid. A method of using the rotor axial force to actively counter the motions of a floating power plant. The method of using the rotor axial force to actively counter the motions of a floating power plant. The method also describes how rotational forces about the vertical axis (12) of the tower (4) are controlled and countered by cyclic variation of pitch angles and associated forces on the individual rotor blade. The method also describes how the aerodynamic force variation on each individual blade as a consequence of different wind velocities at different heights (vertical wind shear) and in the horizontal direction parallel to the rotor plane (horizontal wind shear) can be reduced.

Patent
06 May 2005
TL;DR: In this article, the pitch control of individual rotor blades of a helicopter is controlled to reduce control loads, vibration and noise in or from the rotating rotor control elements, the system generates blade dynamics signal representing dynamic forces acting on either or both of the rotating and noon-rotating elements of the helicopter.
Abstract: Controlling the pitch of individual rotor blades of a helicopter to reduce control loads, vibration and noise in or from the rotating rotor control elements, The system generates blade dynamics signal representing dynamic forces acting on either or both of the rotating and noon-rotating elements of the helicopter, including rotor blades of a rotating assembly. The system extracts information representing at least one dynamic force, generates a dynamic force compensation output that represents a compensation for the dynamic force, and generates, from flight control signals and the dynamic force compensation output, a compensated pitch actuator cntrol signal for each rotor blade wherein the compensation factor of the pitch control signal compensates for the dynamic force.

Journal ArticleDOI
TL;DR: In this paper, a method for predicting transonic rotor noise, which is more computationally efficient than previous methods and which furthermore offers physical insight into the noise generation, is developed, which can be used to make it of potential use to helicopter rotor designers.
Abstract: Helicopter noise is an increasingly important issue, and at large forward-flight speeds transonic rotor noise is a major contributor. A method for predicting transonic rotor noise, which is more computationally efficient than previous methods and which furthermore offers physical insight into the noise generation, is developed. These benefits combine to make it of potential use to helicopter rotor designers. The permeable surface form of the Ffowcs Williams-Hawkings (FW-H) equation is used to express the sound field in terms of a distribution of monopole and dipole sources over a permeable control surface and a distribution of quadrupole sources over the volume outside of this surface. By choosing the control surface to enclose the transonic flow regions, the noise from the quadrupole distribution becomes negligible. Only the more straightforward surface sources then need be considered, making the acoustic approach computationally efficient. By locating the control surface close to the blade subject to enclosing the transonic flow regions, efficiency in the computational-fluid-dynamics (CFD) approach is also attained. To perform noise predictions, an Euler CFD method to calculate the flowfield was combined with an acoustic method incorporating the retarded time formulation of the FW-H equation. Several rotor blades in hover and steady forward flight were considered, all of which involved transonic flows but for which shock delocalization did not occur. The predictions showed very good agreement with experimental data and with predictions obtained using more computationally intensive methods.

Patent
10 Oct 2005
TL;DR: In this article, a method for operating a wind turbine with at least one blade with an active flow control actuator configured to increase an angle of attack range in which the blade or blades can generate torque without flow separation is presented.
Abstract: A method for operating a wind turbine with at least one blade includes providing at least one blade with an active flow control actuator configured to increase an angle of attack range in which the blade or blades can generate torque without flow separation, and using the flow control actuator to adjust this angle of attack range in accordance with load.

Proceedings ArticleDOI
12 Dec 2005
TL;DR: In this paper, the authors investigated different approaches to the design of the controller for the tower speed feedback loop and found that the flap mode has a central role in determining whether this approach is effective since there is a strong interaction between the blade flapwise mode and the tower fore-aft mode.
Abstract: With the increase in size of wind turbines, there is increasing interest in exploiting the pitch control capability of variable speed turbines to alleviate tower fatigue loads. The most direct method is to modify the blade pitch angle in response to a measurement of tower acceleration. It is shown that the flap mode has a central role in determining whether this approach is effective since there is a strong interaction between the blade flap-wise mode and the tower fore-aft mode. Several different approaches to the design of the controller for the tower speed feedback loop are investigated.

Patent
13 May 2005
TL;DR: In this article, a wind power installation consisting of a rotor, a generator for generating electric power, at least one rotationally mounted rotor blade that can be displaced about its longitudinal axis in order to adjust the angle of attack and an auxiliary generator was described.
Abstract: The invention relates to a wind power installation comprising a rotor, a generator for generating electric power, at least one rotationally mounted rotor blade that can be displaced about its longitudinal axis in order to adjust the angle of attack and an auxiliary generator for generating electric power for at least one consumer. The invention is characterized in that the auxiliary generator generates electric power in a rotational speed range that is lower than in normal operating mode for the control mechanism controlling rotor blade adjustment and for a drive mechanism for adjusting the angle of attack of the at least one rotor blade, wherein the control mechanism controls or adjusts the angle of attack for permanent operation in the rotational speed range.

Patent
10 Feb 2005
TL;DR: A rotor blade of a wind power installation in which the rotor blade, in particular in the central region of the rotor, the so-called main board, has a lift-drag ratio which in the region of about ± 2° from the optimum pitch angle has a value of more than 80%, preferably 90% and more of the maximum value of the lift-rate.
Abstract: A rotor blade of a wind power installation in which the rotor blade, in particular in the central region of the rotor, the so-called main board, has a lift-drag ratio which in the region of about ±2° from the optimum pitch angle has a lift-drag ratio value of more than 80%, preferably 90% and more of the maximum value of the lift-drag ratio.

Patent
03 May 2005
TL;DR: In this article, a collective blade pitch control is configured to collectively control pitch of only one of the upper rotor and the lower rotor and not another rotor and lower rotor; and create an unbalanced torque force which acts on the rotorcraft and which enables a yaw attitude control input through said collective blades pitch control.
Abstract: A control system for a coaxial rotorcraft comprises a coaxial rotor set, further comprising an upper rotor actuated by a first drive shaft and a lower rotor actuated by a second drive shaft, the lower rotor having a direction of rotation counter to a direction of rotation of the upper rotor. A collective blade pitch control is configured to: collectively control pitch of only one of the upper rotor and the lower rotor and not another of the upper rotor and the lower rotor; and create an unbalanced torque force which acts on the rotorcraft and which enables a yaw attitude control input through said collective blade pitch control.

Patent
14 Apr 2005
TL;DR: A rotary wing vehicle includes a body structure having an elongated tubular backbone or core, and a counter-rotating coaxial rotor system having rotors with each rotor having a separate motor to drive the rotors about a common rotor axis of rotation as mentioned in this paper.
Abstract: A rotary wing vehicle includes a body structure having an elongated tubular backbone or core, and a counter-rotating coaxial rotor system having rotors with each rotor having a separate motor to drive the rotors about a common rotor axis of rotation. The rotor system is used to move the rotary wing vehicle in directional flight.

Journal ArticleDOI
TL;DR: In this paper, an experimental study is performed on a three-bladed rotor model in two water tanks, showing the development of both short-wave and long-wave instabilities on the helical vortices in the wake.
Abstract: : An experimental study is performed on a three-bladed rotor model in two water tanks. The blade pitch, rotational velocity, descent angle, and descent speed are all varied in order to simulate a wide range of rotorcraft operating states, focusing on descent cases where the rotor is operating in or near vortex ring state--an area in which there is currently very little available data. Flow visualization is done by injecting air bubbles and fluorescent dye tangentially from the blade tips to mark the vortex core, showing the development of both short-wave ("sinuous") and long-wave ("leapfrogging") instabilities on the helical vortices in the wake. Strain gages are used to record transient loads, allowing a correlation between the rotor thrust performance and the development of the vortex wake. Reynolds numbers are of order 105 and test runs are performed for extended periods--up to 500 rotor revolutions-- demonstrating the repeatability of the patterns of thrust variation. The data indicate that as the instabilities develop, adjacent vortices merge and form thick vortex rings, particularly during descent. Periodic shedding of these rings from the wake associated with vortex ring state is observed, resulting in peak-to-peak thrust fluctuations of up to 95% of the mean and occurring at regular intervals of 20-50 rotor revolutions, depending on flow parameters.

Proceedings ArticleDOI
12 Dec 2005
TL;DR: In this paper, it is shown that due to the strong coupling between blade edgewise motion and drive train torsion, the fundamental frequency associated with the drive train's torsional motion can vary significantly across the range of blade pitch angles observed in practice.
Abstract: Given the prohibitive costs of replacement of damaged gearboxes, damping drive train osillations is of immense significance in large wind turbine control design. The Drive Train Damper (DTD) is an important constituent of the power production control routine in variable-speed, pitch-regulated large wind turbines. The DTD is used to mitigate fatigue loading of drive train components. This paper motivates the need for scheduling the parameters of the damper based on blade pitch angle. It is shown that due to the strong coupling between blade edgewise motion and the drive train torsion, the fundamental frequency associated with the drive train's torsional motion can vary significantly across the range of blade pitch angles observed in practice. If left unaccommodated, this variation in fundamental frequency is shown to adversely affect the performance of the DTD.

Proceedings ArticleDOI
08 Jun 2005
TL;DR: The linearized dynamics of the map from blade pitch to tower top fore-aft deflection in horizontal-axis wind turbines are studied to show that the mass and stiffness distribution of the blades at certain operating conditions determine the presence of a right half-plane zero in the transfer function of interest.
Abstract: Most commercial large wind turbines use blade pitch action to mitigate structural loads in high wind velocity conditions. In this paper, we study the linearized dynamics of the map from blade pitch to tower top fore-aft deflection in horizontal-axis wind turbines. We show that the mass and stiffness distribution of the blades at certain operating conditions determine the presence (or absence) of a right half-plane zero in the transfer function of interest. We conclude that blade design can impose constraints on the achievable tower fore-aft oscillation mitigation through collective blade pitch control. Consequences of this result to wind turbine design are discussed.

Patent
30 Mar 2005
TL;DR: In this paper, a rotor for mounting on a helicopter drive shaft is described, comprising a hub (23) for location on the shaft and a plurality of blades (16) mounted to and extending out from the hub.
Abstract: A rotor (10) for mounting on a helicopter drive shaft (32) is disclosed, comprising a hub (23) for location on the shaft (32) and a plurality of blades (16) mounted to and extending out from the hub (23), wherein a pitch angle (ϕ) of at least one of the blades (16) is controllable with respect to each other blade (16) by an electrical stepper motor mechanism (18) arranged at the hub (23). Also disclosed is a method for determining a pitch angle (ϕ) of the blades (16) of the rotor (10), a computer program arranged to, when loaded onto a computing system, utilise an algorithm for determining blade pitch angle (ϕ) values for the blades (16), an alternator for providing power to motors (18) that control the pitch of the blades (16) and a control method for implementation by a computer in controlling the pitch of the blades in real time.

Journal ArticleDOI
TL;DR: In this article, a vortex lattice method is used to evaluate the performance and the time-dependent pressure distribution on the blade surface in a non-uniform flow, while efficient optimization algorithms are used to modify the blade sections.
Abstract: A new method for designing propeller blade sections is presented. A vortex lattice method is used to evaluate the performance and the time-dependent pressure distribution on the blade surface in a non-uniform flow, while efficient optimization algorithms are used to modify the blade sections. Two different designs were carried out in this study. The first was a design to realize a target pressure distribution in a rotating three-dimensional flow. A two-dimensional wing theory was used to obtain the target pressure distribution. The predicted increase in efficiency and the reduction in the cavity volume were confirmed by model experiments. The second was a design to maximize the propeller efficiency. By this method, the propeller efficiency was improved by 1.2% under the constrains of constant thrust and a prescribed margin for face cavitation.

Patent
16 Nov 2005
TL;DR: In this article, a method of operating a rotor aircraft involves measuring an airspeed of the aircraft and a rotational speed of the rotor, and a controller determines a Mu of the helicopter rotor based on the airspeed and the rotor speed.
Abstract: A method of operating a rotor aircraft involves measuring an airspeed of the aircraft and a rotational speed of the rotor A controller determines a Mu of the rotor based on the airspeed of the aircraft and the rotational speed of the rotor The controller varies the collective pitch of the rotor blades in relationship to the Mu, from an inertia powered jump takeoff, through high speed high advance ratio flight, through a low speed landing approach, to a zero or short roll flare landing In addition as the rotor is unloaded and the rotor slows down, the controller maintains a minimum rotor RPM with the use of a tilting mast

Patent
11 Nov 2005
TL;DR: In this article, the tip parts of the propeller blades of a horizontal-shaft windmill are tilted in the front direction of the blades to form inclination parts, and the inclination angle of the tilted parts is set within the range of 25 to 50° relative to the longitudinal direction of propeller motion.
Abstract: A propeller, wherein the tip parts of the propeller blades (3) of a horizontal-shaft windmill are tilted in the front direction of the propeller blades (3) to form inclination parts (3c). The inclination angle of the tilted parts (3c) is set within the range of 25 to 50° relative to the longitudinal direction of the propeller blades (3).