Passive Pitch Control Research Articles

Model-scale experiments of passive pitch control for tidal turbines

Tidal currents are renewable and predictable energy sources that could prove fundamental to decrease dependency from fossil fuels. Tidal currents, however, are highly unsteady and non uniform, resulting in undesirable load fluctuations on the blades and the drive train of turbines. A passive morphing blade concept capable to reduce the load fluctuations without affecting the mean loads has recently been formulated and demonstrated with numerical simulations (Pisetta et al., 2022). In this paper, we present the first demonstration of this morphing blade concept, through experimental tests on a 1.2-m diameter turbine. We show that fluctuations in the root-bending moment, thrust and torque are consistently reduced over a broad range of tip-speed ratios. This work also highlights some critical design aspects of morphing blades. For instance, it is showed that the friction resistance can substantially decrease the effectiveness of the system and thus must be minimised by design. Overall this paper demonstrates for the first time the effectiveness of morphing blades for tidal turbines, paving the way to the future development of this technology.

Nonlinear Attitude Control of a Spherical Underwater Vehicle.

In this work, we present the design, implementation, and testing of an attitude control system based on State Feedback Linearization (FL) of a prototype spherical underwater vehicle. The vehicle is characterized by a manifold design thruster configuration for both locomotion and maneuvering, as well as on a novel pendulum-based passive pitch control mechanism. First, the mechanical design and onboard electronics set up of the spherically shaped hull are introduced. Afterward, a high-fidelity dynamic model of the system is derived for a 6 degree-of-freedom (DOF) underwater vehicle, followed by several experiments that have been performed in a controlled environment to compare the performance of the proposed control method to that of a baseline Proportional-Integral-Derivative (PID) controller. Experimental results demonstrate that while both controllers were able to perform the specified maneuvers, the FL controller outperforms the PID in terms of precision and time response.

Study on fatigue life of bend-twist coupling wind turbine blade based on anisotropic beam model and stress-based fatigue analysis method

Bend-twist coupling (BTC), also called aeroelastic tailoring or passive pitch control method, is often utilized to reduce the fatigue loading on wind turbine blades. With BTC, the blade can twist as it bends, this alleviates the aerodynamic force due to the decrease in the angle of attack when the load is increased suddenly. In this research, the stress-based method is employed to investigate the fatigue load due to the BTC effect under different wake conditions. To begin with, the one-dimensional anisotropic beam model is adopted in aeroelastic simulation. Next the static and modal analyses for the NREL 5 MW wind turbine blade with different fiber orientations are performed to verify the anisotropic beam model. Finally, the stress history of each element on each cross section is reconstructed using DTU BECAS. The fatigue life of different materials in each cross section under different wake conditions has been analysed. The results show that the predicted fatigue life of NREL 5 MW wind turbine blade (26.0187 years) is very close to the design life (20 years). The fatigue effect has an impact on the life of wind turbine blades, which can be affected by the layout of wind turbines and alleviated by BTC effect.

EFFECTS OF BEND-TWIST COUPLING DEFORMATION ON THE AERODYNAMIC PERFORMANCE OF A WIND TURBINE BLADE

Comprehensive research exists on passive pitch control of wind turbines using bend-twist coupling property of composite materials. Blades with bend-twist coupling deformation can increase energy capture, improve dynamic stability, or reduce aerodynamic loads. The objectives of this work are to apply bend-twist coupling into an existing blade design and to investigate the resulting aerodynamic performance. The 41.25-meter blade was based on GE 1.5 GLX wind turbine. Aerodynamic loads were calculated using Blade Element Momentum (BEM) theory and Computational Fluid Dynamics (CFD) simulation. The resultant thrust and torque from both methods agree well. However, only the CFD can provide details of pressure distribution over the complex blade surface. Three levels of bend-twist coupling were designed for the Glass/Epoxy blade skins i.e. no coupling, low coupling, and high coupling. From Finite Element Analysis (FEA), the deflections of the three blades were slightly different while the twist angles were considerably different. The deformed geometries of the blades were then used to produce new three dimensional (3D) models for the prediction of the power coefficient (CP) by CFD. The results show that the proper bend-twist coupling laminate can improve the performance of the blade. At low wind speed, the CP is higher than the baseline blade. At wind speed greater than rated speed, however, the blades twist two much and the CP decreases below the baseline blade. Simulation of 3D blade models can help in the design of a bend-twist coupling level suitable to the blade shape and wind speed.

Cavitating response of passively controlled tidal turbines

The use of passive pitch control in marine hydrokinetic turbine (MHK) blades has been shown to provide structural and performance improvements over similar systems with non-adaptive blades. Recent work has demonstrated such advantages as increased lifetime energy capture, reduced hydrodynamic instabilities, and improved efficiency, load shedding, fatigue behavior, and structural integrity. Additionally, passively adaptive blades have been shown to delay cavitation and decrease cavitation volume for marine propellers. For MHK turbines, a reduction in cavitation susceptibility could increase effectiveness of the turbine and reduce the rate of fatigue on the system. In this work, a previously validated, coupled 3-D boundary element method-finite element method solver is used to model two adaptive blades and a non-adaptive reference blade under both uniform and non-uniform inflow conditions. A numerical investigation of the onset of sheet cavitation on an MHK turbine blade and the structural response of a blade under cavitating conditions is presented. Results show that passive control can be used to delay cavitation and decrease cavitation volume under normal operating conditions. Cavitation is shown to increase the rate of fatigue on the system and has the potential to lead to unanticipated failures if proper cavitation analysis is not integral to the MHK turbine design process.

副翼を利用したパッシブ・ピッチ制御方式プロペラ型風車の 実験的研究・開発

副翼を利用したパッシブ・ピッチ制御方式プロペラ型風車の 実験的研究・開発

Experiments on the Performance of Small Horizontal Axis Wind Turbine with Passive Pitch Control by Disk Pulley

The present work is to design a passive pitch-control mechanism for small horizontal axis wind turbine (HAWT) to generate stable power at high wind speeds. The mechanism uses a disk pulley as an actuator to passively adjust the pitch angle of blades by centrifugal force. For this design, aerodynamic braking is caused by the adjustment of pitch angles at high wind speeds. As a marked advantage, this does not require mechanical brakes that would incur electrical burn-out and structural failure under high speed rotation. This can ensure the survival of blades and generator in sever operation environments. In this paper, the analysis uses blade element momentum theory (BEMT) to develop graphical user interface software to facilitate the performance assessment of the small-scale HAWT using passive pitch control (PPC). For verification, the HAWT system was tested in a full-scale wind tunnel for its aerodynamic performance. At low wind speeds, this system performed the same as usual, yet at high wind speeds, the equipped PPC system can effectively reduce the rotational speed to generate stable power.

Fluid–structure interaction analysis of a morphing vertical axis wind turbine

There has been much recent interest in the development of Vertical Axis Wind Turbines (VAWTs), especially for use in off-grid or off-shore electricity generation, due to inherent advantages over the more popular horizontal axis types. Although there have been a number of recent attempts to increase efficiency of VAWTs using active and passive blade pitch control strategies, these designs come at an increased upfront cost, detracting from the simplistic allure of the VAWT design. This study investigates the feasibility of a flexible bladed (or morphing) VAWT, wherein individual blades are able to passively adapt to local flow conditions and serve as a pitch control mechanism to increase rotor efficiency. Using a finite volume fluid–structure interaction algorithm, a rigid VAWT is simulated with good agreement with existing experimental data, then compared to several other geometrically identical morphing designs with varying material flexibility. All simulated flexible rotors achieved higher efficiency than the standard (rigid) one, with efficiency gains up to 9.6% for the VAWT geometry investigated herein. The results suggest that the morphing rotor design can have significant advantages over the rigid design particularly in part-load scenarios, and is also likely to increase the self-starting abilities of the VAWT.

신규 익형 KA2가 적용된 풍력 블레이드의 공력 하중에 대한 동특성 해석

This paper proposes a novel airfoil named KA2 for the blade of the wind turbine systems. Dynamic loads characteristics are analyzed and compared using aerodynamic data of ten airfoils including the proposed airfoil. The blade is divided into the sixteen elements in the longitudinal direction of the blade for applying the Blade Element Method Theory (BEMT) method, and in each element, torque, thrust, and pitching moment are calculated using turbulent time varying wind speed and aerodynamic data of each wing. Additionally, each force and torque is accumulated in the whole region of the blade for the estimation of representative values. The magnitude of such forces is comparatively analyzed for different airfoils. The angle of attack is constant below the rated wind speed due to the fact that the tip speed ratio is kept at the constant value, and it increases in the region of over rated wind speed as the tip speed ratio decreasing with constant rated rpm and increasing wind speed. Such increase in the angle of attack causes the changes of the force acting on the airfoil with different characteristics of lift and drag in the stall region of each different airfoil. Even though the mean wind speed is in the rated speed in a given time, because of the turbulence, it has either the over rated or under rated speed most of the time. Furthermore, the dynamic properties of each force are analyzed in this rated wind speed in order to objectively understand the dynamic properties of the blades which are designed based on the different airfoils. These dynamic properties are also compared by the standard deviation of time varying characteristics. Moreover, the output characteristics of the wind turbine are investigated with different airfoils and wind speeds. Based on these investigations, it was revealed that the proposed airfoil (KA2) is well applicable to the blade with passive pitch control system.

Experimental and Fluid Structure Interaction analysis of a morphing wind turbine rotor

Active control of blade pitch for wind turbines is known to increase efficiency, especially for part and over-load operation. An unfortunate consequence of this practice is added upfront and maintenance costs, making these schemes economically viable only in large scale applications. This study investigates a novel concept for wind turbine design, in which the blade is purposefully built of a flexible material which can passively adapt its geometry according to local wind conditions. This design concept therefore acts as a low cost, simplistic passive pitch control mechanism. Using a finite-volume fluid–structure interaction solver, the aeroelastic response of such a turbine is analyzed and compared to experimental data collected from wind tunnel tests as part of this project. The results indicate that the flexible rotor is markedly superior to a geometrically identical rigid one in terms of the size of its operational envelope as well as average and maximal torque production. Using post-processing tools, the performance improvements are attributed to passive deflection of the airfoil, which act to delay blade stall and drastically change surface pressure distribution to improve turbine performance.

Emerging trends in vibration control of wind turbines: a focus on a dual control strategy.

The paper discusses some of the recent developments in vibration control strategies for wind turbines, and in this context proposes a new dual control strategy based on the combination and modification of two recently proposed control schemes. Emerging trends in the vibration control of both onshore and offshore wind turbines are presented. Passive, active and semi-active structural vibration control algorithms have been reviewed. Of the existing controllers, two control schemes, active pitch control and active tendon control, have been discussed in detail. The proposed new control scheme is a merger of active tendon control with passive pitch control, and is designed using a Pareto-optimal problem formulation. This combination of controllers is the cornerstone of a dual strategy with the feature of decoupling vibration control from optimal power control as one of its main advantages, in addition to reducing the burden on the pitch demand. This dual control strategy will bring in major benefits to the design of modern wind turbines and is expected to play a significant role in the advancement of offshore wind turbine technologies.

10kW 급 풍력 블레이드의 수동형 피치제어 모듈의 설계를 위한 여러가지 익형의 공력 특성에 관한 연구

풍력터빈 블레이드의 가변 피치제어는 풍력발전기의 과풍속 영역 설계에 있어 중요한 요소로 알려져 있으나 원가문제 때문에 소형 풍력터빈에는 적용되지 못하고 실속제어가 많이 적용되고 있다. 하지만, 블레이드 주변의 난류 때문에 설계된 실속이 구현되지 않는 실속지연 현상이 종종 발생되고, 이에 따른 풍력 블레이드의 과회전과 발전기의 과출력 위험이 발생하고 있다. 이에 따라 블레이드에서 발생되는 공력으로 피치가 변하고 스프링의 복원력으로 복귀되는 수동형 피치제어 모듈이 주목 받고 있다. 본 연구에서는 회전하는 블레이드의 익형에서 발생되는 양력과 항력을 이용하여 회전면으로 작용되는 토크와 블레이드의 Flap 방향으로 작용되는 추력을 계산하는 방법을 제시하고, 이러한 힘들의 크기를 여러 가지 익형에 대해 비교하였으며, 블레이드의 피치모멘트를 정량적으로 산출하여 수동 피치제어 모듈의 설계자료로 활용될 수 있도록 하였다.

The Design and Analysis of Passive Pitch Control for Horizontal Axis Wind Turbine

The purpose of this thesis is to design and analysis of passive pitch control. Design a mechanics to control different revolution of blade's pitch angle. The use of small wind turbines gradually popularization, but how to overcome the low wind speed start-up and the operation under high wind speed, that is the difficult problems encountered by designers. In order to extend the use and the safe of wind speed, this design is required. This paper is focus on the mechanism design of the passive pitch control for the small horizontal axis wind turbine (HAWT). When the wind speed is fast, the rotation speed is also faster and faster. The system uses centrifugal force to make Pulley disk driven the pitch angle of the blade. It can achieve the effect of passive pitch control. The mechanism is our laboratory's patent. Through the experiments in wind tunnel, it can be observed the variation of the performance curve when the pitch rotation. This system not only successfully operates under high wind speed but also has better performance at low wind speed.

Passive control of marine hydrokinetic turbine blades

Marine hydrokinetic (MHK) turbine blades are generally constructed from fiber reinforced polymer composites and are subject to large, highly dynamic fluid forces. The bend-twist deformation coupling behavior of these materials can be hydroelastically tailored to improve system performance over the expected life of the turbine by way of rapid, passive pitch control that can increase lifetime power generation, reduce hydrodynamic instabilities, and improve load shedding and structural performance. There are practical concerns, however, that make the design of these devices complex. Constraints on system components such as the rated power of the generator system, maximum rotational speed, or material degradation can affect the extent to which passive control can enhance performance. Using a previously validated boundary element method-finite element method solver, this paper examines the capabilities of passive pitch adaptation under both instantaneous and long-term variable amplitude loading to better describe potential benefits while considering practical design and operational restrictions.

Study on Output Characteristics of H.A.W.T. by Passive Pitch Control Units by means of Sub-Blades

Study on Output Characteristics of H.A.W.T. by Passive Pitch Control Units by means of Sub-Blades

Study on Output Regulating Characteristics of H.A.W.T. by means of Passive Pitch Control of Sub-Blade

Study on Output Regulating Characteristics of H.A.W.T. by means of Passive Pitch Control of Sub-Blade

Theoretical & Experimental Study on the Aerodynamic Characteristics of H. A. W. T. and on an Approach to Avoid from Gale/Blast by a Passive Pitch Control Mechanism using to Sub-Blades.

Theoretical & Experimental Study on the Aerodynamic Characteristics of H. A. W. T. and on an Approach to Avoid from Gale/Blast by a Passive Pitch Control Mechanism using to Sub-Blades.

Implementation of bending-torsion coupling in the design of a wind-turbine rotor-blade

An investigation is performed on the implementation of bending-torsion coupling of a composite wind turbine rotor blade to provide passive pitch-control. Limited passive torsion deformation is realised with a structural coupling between flapwise bending and elastic twist of a constant speed rotor-blade. The blade and skin laminate configuration are analysed with a FEM program, in which a complete blade with spar webs is modelled. This conventional blade configuration has some disadvantages. Therefore alternative design concepts are reviewed, where the coupling plies are restricted to a load-bearing spar, while a softer skin provides for the aerodynamic shape. From additional analysis, it is found that, while for the two alternative design concepts the stress concentrations at the leading edge joint are bypassed, the bending-torsion coupling response is lower. An experiment was performed to validate the calculation methods. The experimental results show good correlation with theoretical predictions. It is recommended to investigate further the fatigue life properties of a glass/carbon hybrid FRP with off-axis fibre orientations.

96/00621 Design criteria for passive pitch control of wind turbines using self-twisting blades

96/00621 Design criteria for passive pitch control of wind turbines using self-twisting blades

Design criteria for passive pitch control of wind turbines using self-twisting blades

SYNOPSIS A simple model of blade twisting was used in conjunction with a wind turbine rotor performance model to predict the ability of a self-twisting blade to regulate the speed of a small wind turbine. The results were used in order to establish guidelines for some of the design choices for such a turbine, particularly with regard to blade shape.