A friction-based passive control technique to mitigate wind induced structural demand to wind turbines

2021 ◽  
Vol 232 ◽  
pp. 111744
Author(s):  
Moira Di Paolo ◽  
Iolanda Nuzzo ◽  
Nicola Caterino ◽  
Christos T. Georgakis
Keyword(s):  
Wind Turbines ◽  
Passive Control ◽  
Control Technique ◽  
Structural Demand

scholarly journals Sensitivity Study of the Influence of Blade Sectional Stiffness Parameters on the Aeroelastic Response of Wind Turbines

2021 ◽  
Vol 9 ◽  
Author(s):  
Cheng Chen ◽  
Tongguang Wang ◽  
Long Wang
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Stiffness Matrix ◽  
Passive Control ◽  
Beam Theory ◽  
Torsional Stiffness ◽  
Control Technique ◽  
Stiffness Parameter ◽  
Blade Section ◽  
Coupling Stiffness

With the development of wind turbines as a result of large-scale and offshore trends, the wind turbine size is becoming increasingly larger. The passive control technique is used to alleviate the increasing loads on the blade for the sake of improving the durability of the wind turbine. The ply design of shells considering the coupling effect of bending and torsion is one of the passive control techniques. The bending torsion coupling stiffness is one of the parameters of the blade section stiffness matrix. In order to fully understand the influence of each blade stiffness parameter on the aeroelastic responses of wind turbines and to consider the influence of structural characteristics on the aeroelastic responses in blade design, the influences and sensitivity of each stiffness parameter in the 6 × 6 stiffness matrix of the blade sections on the aeroelastic responses of the wind turbines are systematically studied under steady wind condition. The aerodynamic forces in the aeroelastic model are calculated by an AeroDyn module based on blade element momentum theory, and the structural dynamic responses of the blade are calculated using generalized Timoshenko beam theory and geometric exact beam theory. The NREL baseline 5 MW wind turbine and blade properties are used in this study, where the diagonal stiffness parameters and non-diagonal stiffness parameters of the matrixes of each blade section are scaled according to certain principles. The results show that the axial stiffness, the flap-wise stiffness, and the torsional stiffness in the diagonal are sensitive to the root loads and tip displacement of the blade. The flap-wise bending torsion coupling stiffness, the flap-wise shear-torsion coupling stiffness, and the edge-wise shear-torsion coupling stiffness in the non-diagonal are also sensitive to the aeroelastic responses. For completeness, the effects of other stiffness parameters on the aeroelastic responses are also analyzed and discussed.

An innovative passive control technique for industrial precast frames

2010 ◽  
Vol 32 (4) ◽  
pp. 1123-1132 ◽  
Author(s):  
Paolo Martinelli ◽  
Maria Gabriella Mulas
Keyword(s):  
Passive Control ◽  
Control Technique

scholarly journals Theoretical and Experimental Study of the Vibration Dynamics of a 3D-Printed Sandwich Beam With an Hourglass Lattice Truss Core

2021 ◽  
Vol 7 ◽  
Author(s):  
Zhenkun Guo ◽  
Guobiao Hu ◽  
Jingchao Jiang ◽  
Liuding Yu ◽  
Xin Li ◽  
...  
Keyword(s):  
Theoretical Model ◽  
3D Printing ◽  
Passive Control ◽  
Sandwich Beam ◽  
Control Technique ◽  
Sandwich Beams ◽  
Element Analysis ◽  
Printing Technology ◽  
3D Printing Technology ◽  
Truss Core

3D printing (also known as additive manufacturing) has been developed for more than 30 years. The applications of 3D printing have been increasingly extended to a variety of engineering fields in recent years. The sandwich material with a high strength and overall low density is a kind of artificial material that has been extensively used in various industrial and daily life applications. This paper presents a comprehensive vibration analysis and passive control technique for a cantilevered sandwich beam with an hourglass lattice truss core fabricated with 3D printing technology. The governing equation of the beam is established by using a homogenized model and the Hamilton's principle, from which the natural frequencies are determined. The theoretical model is verified by the results from the existing literature and the finite element analysis. The frequency response of the sandwich beam measured experimentally further validates the proposed model. Subsequently, a non-linear energy sink (NES) is proposed for being employed to passively suppress the vibration of the sandwich beam. A parametric study based on the theoretical model confirms the viability of using NES to effectively control the vibration of the sandwich beam. This work presents a good demonstration of using 3D printing technology for fabricating sandwich beams with a complicated lattice core. More importantly, some guidelines regarding the dynamic analysis of sandwich beams are provided. In addition, the analytical method presented in this work provides a potential means to theoretically explore the advantages of using sandwich beams for energy harvesting in the future.

Suppression of Acoustic Resonance in Rectangular Cavities Using Spanwise Control Cylinder

2015 ◽  
Author(s):  
Ahmed Omer ◽  
Atef Mohany
Keyword(s):  
Shear Layer ◽  
Vortex Shedding ◽  
Passive Control ◽  
Acoustic Resonance ◽  
Control Technique ◽  
Resonance Excitation ◽  
Base Case ◽  
Detached Eddy Simulation ◽  
Free Shear Layer ◽  
Aspect Ratios

Flow over cavities can be a significant source of noise in many engineering applications when a coupling occurs between the flow instabilities at the cavity mouth and one of the acoustic cross-modes in the accommodating enclosure. In this paper, a passive noise control technique using a spanwise cylinder located at the cavity upstream edge is investigated experimentally for two different cavities with aspect ratios of L/D = 1.0 and 1.67, where L is the cavity length and D is the cavity depth. The effect of both the location of the cylinder and its diameter on the flow-excited acoustic resonance is investigated in air flow with Mach number up to 0.45. This passive control technique is found to be effective in suppressing the acoustic resonance excitation when compared to the base case where no cylinder is attached. It is observed that using the optimum cylinder location and diameter reduces the acoustic pressure to less than 140 Pa, compared to the base case with values exceeding 2000 Pa. Moreover, a shift in the onset of acoustic resonance to higher velocities is observed. Localized hot-wire measurements of the free shear layer at the cavity mouth during the off-resonance conditions reveal that attaching a spanwise cylinder at the cavity upstream edge reduces the spanwise correlation of the free shear layer which, in turns, reduces its susceptibility to acoustic excitation. To further understand the interaction between the cylinder’s vortex shedding and the free shear layer at the cavity mouth, a numerical simulation of the flow field using a detached eddy simulation (DES) model has been carried out. The simulation shows that the suppression occurs due to a disturbance of the cavity shear layer by the vortex shedding from the cylinder which results in altering the impingement point at the downstream edge of the cavity, and thereby weakening the feedback cycle that controls the acoustic resonance excitation.

Passive Control of Two-Phase Flow Thermal Instabilities in a Vertical Tube Evaporator

2016 ◽  
Vol 8 (4) ◽  
Author(s):  
Ghazali Mebarki ◽  
Samir Rahal
Keyword(s):  
Heat Transfer ◽  
Void Fraction ◽  
Passive Control ◽  
Two Phase Flow ◽  
Tube Wall ◽  
Vertical Tube ◽  
Control Technique ◽  
Control Element ◽  
Phase Flow ◽  
Two Phase

Passive heat transfer techniques are considered to be one of the most important means to enhance heat transfer in heat exchangers that allow also reducing their size and manufacturing cost. Moreover, this passive technique can also be used to control the thermal instabilities caused by the two-phase flow in the evaporators. The thermal instabilities are undesirable because they can lead to a tube failure. For this purpose, a numerical study of the two-phase flow with evaporation in a vertical tube has been performed in this work. The volume of fluid (VOF) multiphase flow method has been used to model the water vapor–liquid two-phase flow in the tube. A phase-change model, for which source terms have been added in the continuity and energy equation, has been used to model the vaporization. The numerical simulation procedure was validated by comparing the obtained results with those given in the literature. The passive control technique used here is a ring element with square cross section, acting as a vortex generator, which is attached to the tube wall at various positions along the tube. Instabilities of temperature and void fraction at the tube wall have been analyzed using fast Fourier transforms (FFTs). The results show that the attachment of the control element has a significant influence on the value and distribution of the void fraction. Higher positions of the control element along the tube allow reducing the magnitude of void fraction oscillations.

On Dynamic Modelling of Compressed Air Engine With Connecting-Rod-Crank to Control Angular Position of Oscillating Rotation

2016 ◽  
Author(s):  
Alexandre C. Alves ◽  
Jose M. Balthazar ◽  
Angelo M. Tusset ◽  
Rodrigo T. Rocha ◽  
Atila M. Bueno
Keyword(s):  
Active Control ◽  
Passive Control ◽  
Angular Position ◽  
Dynamic Modelling ◽  
Rigid Bodies ◽  
Compressed Air ◽  
Control Technique ◽  
Connecting Rod ◽  
Nonlinear Dynamic Model ◽  
Linear Quadratic

In this work is examined the dynamic behavior and the controllability of a compressed air engine with a connecting-rod-crank. The pneumatic motor is composed by a monocylinder, a connecting-rod and a control crank to the oscillating rotation. For the obtainment the nonlinear mathematical model was considered the Lagrange’s method and the components of the physical system in the model are considered as rigid bodies with unilateral restriction. Numerical analysis of the application of the passive control position by a nonconservative pneumatic force with pilot valves in the cylinder showed that it was not possible an exact control to the angular position desired for the output crank. To solve this problem, it is proposed an active control by the Linear Quadratic Regulator method (LQR), to the control of the connecting-rod-crank mechanism. In addition, the robustness of the proposed control technique is tested considering noise measurement in pneumatic external excitation. The numerical simulation results showed the efficiency of the proposed control to the nonlinear dynamic model of the connecting-rod-crank and the sensibility analysis for parametric errors to the control of the oscillating angular positions, demonstrating so that the proposed active control is adequate for this system.

Controller Design to Reduce Mechanical Fatigue in Offshore Wind Turbines Affected by Ice and Tide

2011 ◽  
Author(s):  
Katherine Faley ◽  
Mario Garcia-Sanz
Keyword(s):  
Wind Turbines ◽  
Controller Design ◽  
Weather Conditions ◽  
Offshore Wind ◽  
Control Technique ◽  
Offshore Wind Turbines ◽  
Mechanical Fatigue ◽  
New Strategy ◽  
Equivalent Mass ◽  
Stiffness And Damping

This paper presents a novel control structure to mitigate the mechanical fatigue in towers of onshore and offshore wind turbines. A general wind turbine dynamic model for both, (1) onshore and (2) offshore systems with the effects of ice and tide is included. These weather conditions further contribute to the uncertainties in the model, most importantly, in the values of tower equivalent mass, stiffness, and damping and increase the amplitude of the velocity of tip-tower vibrations at some particular frequencies, which creates greater mechanical fatigue. A novel control technique to attenuate such a mechanical fatigue is presented in the paper. It is based on the variation of the generator torque in the above rated wind speed region. The control strategy, designed by using Quantitative Feedback Theory (QFT), decreases the velocity of the nacelle movement due to the wind turbulences, thus reducing the associated mechanical fatigue. The new strategy is validated with a realistic nonlinear simulator under a set of different input scenarios and a Monte Carlo method for the uncertainty selection.

scholarly journals Optimal Control of Hydrostatic Drive Wind Turbines for Improved Power Output in Low Wind-Speed Regions

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5001
Author(s):  
Ammar E. Ali ◽  
Majid Deldar ◽  
Sohel Anwar
Keyword(s):  
Optimal Control ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Power Output ◽  
Energy Production ◽  
Energy Output ◽  
Control Technique ◽  
Offshore Wind Turbine ◽  
Production Scale ◽  
Low Speed

World wind energy output is steadily increasing in both production scale and capacity of harvesting wind. Hydrostatic transmission systems (HTSs) have been used mostly in offshore wind turbine applications. However, their potential has not been fully utilized in onshore wind turbines, partially due to concerns related to hydraulic losses. In our prior work, it was shown that the annual energy production from a hydrostatic wind turbine can match or exceed that of a mechanical drive wind turbine with appropriate optimal control techniques. In this paper, we present an optimal control technique that can further improve energy production of a hydrostatic wind turbine, particularly in low speed regions. Here, the overall loss equation of the HTS is developed and used as a cost function to be minimized with respect to system model dynamics. The overall loss function includes the losses due to both the aerodynamic efficiencies and the hydrostatic efficiencies of the motor and pump. A nonlinear model of HST is considered for the drive train. Optimal control law was derived by minimizing the overall loss. Both unconstrained and constrained optimization using Pontryagin’s minimum principle were utilized to derive two distinct control laws for the motor displacement. Simulation results showed that both the controllers were able to increase power output with the unconstrained optimization offering better results for the HTS wind turbine in the low speed regions (3 m/s–8 m/s).

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