Showing papers on "Turbine blade published in 2011"

3D simulation of wind turbine rotors at full scale. Part II: Fluid–structure interaction modeling with composite blades

Abstract: In this two-part paper, we present a collection of numerical methods combined into a single framework, which has the potential for a successful application to wind turbine rotor modeling and simulation. In Part 1 of this paper we focus on: 1. The basics of geometry modeling and analysis-suitable geometry construction for wind turbine rotors; 2. The fluid mechanics formulation and its suitability and accuracy for rotating turbulent flows; 3. The coupling of air flow and a rotating rigid body. In Part 2, we focus on the structural discretization for wind turbine blades and the details of the fluid-structure interaction computational procedures. The methods developed are applied to the simulation of the NREL 5MW offshore baseline wind turbine rotor. The simulations are performed at realistic wind velocity and rotor speed conditions and at full spatial scale. Validation against published data is presented and possibilities of the newly developed computational framework are illustrated on several examples.

3D simulation of wind turbine rotors at full scale. Part I: Geometry modeling and aerodynamics

Abstract: In this two-part paper we present a collection of numerical methods combined into a single framework, which has the potential for a successful application to wind turbine rotor modeling and simulation. In Part 1 of this paper we focus on: 1. The basics of geometry modeling and analysis-suitable geometry construction for wind turbine rotors; 2. The fluid mechanics formulation and its suitability and accuracy for rotating turbulent flows; 3. The coupling of air flow and a rotating rigid body. In Part 2 we focus on the structural discretization for wind turbine blades and the details of the fluid–structure interaction computational procedures. The methods developed are applied to the simulation of the NREL 5MW offshore baseline wind turbine rotor. The simulations are performed at realistic wind velocity and rotor speed conditions and at full spatial scale. Validation against published data is presented and possibilities of the newly developed computational framework are illustrated on several examples. Copyright © 2010 John Wiley & Sons, Ltd.

Comparison and analysis of non-destructive testing techniques suitable for delamination inspection in wind turbine blades

Abstract: Wind turbine blades are one of the key components of a complete wind turbine system due to their significant effect in the overall performance of the system. They are fabricated with composite materials with polymeric matrices and the current manufacturing processes are still highly manual resulting in different types of defects. Thus, non-destructive testing (NDT) techniques that provide surface and internal information of the blade are necessary. In this paper, the detection capabilities and performance of ultrasonic, shearography, thermography and X-ray CT techniques for the inspection of wind turbine blades with delamination defects have been analyzed. To this end, two specimens of E-glass/polyester and E-glass/epoxy with several teflon inserts have been fabricated and the necessary inspections with the NDT techniques under study have been performed. Finally, the efficacy of each NDT technique has been analyzed and a comparison among their capabilities for such application has been carried out.

The Sandia 100-meter All-glass Baseline Wind Turbine Blade: SNL100-00

Abstract: Sandia National Laboratories (SNL) Wind Energy Technologies Department, as part of its ongoing R&D efforts, creates and evaluates innovative large blade concepts for horizontal axis wind turbines to promote designs that are more efficient aerodynamically, structurally, and economically. Recent work has focused on the development of a 100-meter blade for a 13.2 MW horizontal axis wind turbine, a blade which is significantly longer than the largest commercial blades of today (approximately 60 meters long). This report documents the development of the Sandia 100-m All-glass Baseline Wind Turbine Blade, which employs conventional architecture and fiberglass-only composite material reinforcement. Follow-on studies for this baseline will include a variety of innovations targeting reductions in weight and improvements in structural and aerodynamic performance. The report begins with a review of several large utility-grade machines (3-6 MW). Available 5 MW turbine models (with 61.5 meter blades) are identified and described. Geometric scaling of these models is performed to produce aeroelastic turbine models with 100-meter blades, which are analyzed to demonstrate the important effects of scale for large blades. Based on these preliminary analyses, we proceed to develop the Sandia 100-m all-glass baseline blade model. A detailed composite layup and geometry are provided. Analyses of the baseline model for design loads from international standards are presented to demonstrate acceptance of the design with respect to strength, fatigue, deflection, and buckling. In future work, it is envisioned that this model will provide a starting point for consideration of blade innovations with potential performance and cost improvements and will be targeted toward the offshore environment.

Control of flapwise vibrations in wind turbine blades using semi-active tuned mass dampers

Abstract: The increased size and flexibility of modern multi-Megawatt wind turbines has resulted in the dynamic behaviour of these structures becoming an important design consideration. The aim of this paper is to study the variation in natural frequency of wind turbine blades due to centrifugal stiffening and the potential use of semi-active tuned mass dampers (STMDs) in reducing vibrations in the flapwise direction with changing parameters in the turbine. The parameters considered were the rotational speed of the blades and the stiffness of the blades and nacelle. Two techniques have been employed to determine the natural frequency of a rotating blade. The first employs the Frobenius method to a rotating Bernoulli-Euler beam. These results are compared with the natural frequencies determined from an eigenvalue analysis of the dynamic model of the turbine including nacelle motion, which is developed in this paper. The model derived considers the structural dynamics of the turbine and includes the dynamic coupling between the blades and tower. The semi-active control system developed employs a frequency-tracking algorithm based on the short-time Fourier transform technique. This is used to continually tune the dampers to the dominant frequencies of the system. Numerical simulations have been carried out to study the effectiveness of the STMDs in reducing flapwise vibrations in the system when variations occur in certain parameters of the turbine. Steady and turbulent wind loading has been considered. Copyright © 2010 John Wiley & Sons, Ltd.

Control method for a wind turbine

Abstract: The invention relates to a method of controlling a wind turbine having a rotor with pitchable wind turbine blades and a generator for producing power, where a pitch reference value for the wind turbine blades is determined, and an operational parameter representing a loading on the wind turbine rotor exerted by the wind is measured at time intervals. A variation parameter reflecting a variation of the operational parameter over time is determined and used in the determination of a minimum pitch limit value of the pitch reference value. The wind turbine is then controlled according to the pitch reference value only if the pitch reference value is above or equal to the minimum pitch limit value, and otherwise according to the minimum pitch limit value. The invention further relates to a method of controlling the change in the operational parameter as measured in two successive time steps is determined and the turbine then being controlled according to a safety control strategy if the difference between the operational parameter change and the variation parameter is above a certain alert threshold. The invention further relates to a control system configured to perform the above control method, and a wind turbine comprising such system.

Simulating the aerodynamic performance and wake dynamics of a vertical-axis wind turbine

Abstract: The accurate prediction of the aerodynamics and performance of vertical-axis wind turbines is essential if their design is to be improved but poses a signifi cant challenge to numerical simulation tools. The cyclic motion of the blades induces large variations in the angle of attack of the blades that can manifest as dynamic stall. In addition, predicting the interaction between the blades and the wake developed by the rotor requires a high-fi delity representation of the vortical structures within the fl ow fi eld in which the turbine operates. The aerodynamic performance and wake dynamics of a Darrieus-type vertical-axis wind turbine consisting of two straight blades is simulated using Brown’s Vorticity Transport Model. The predicted variation with azimuth of the normal and tangential force on the turbine blades compares well with experimental measurements. The interaction between the blades and the vortices that are shed and trailed in previous revolutions of the turbine is shown to have a signifi cant effect on the distribution of aerodynamic loading on the blades. Furthermore, it is suggested that the disagreement between experimental and numerical data that has been presented in previous studies arises because the blade–vortex interactions on the rotor were not modelled with sufficient fidelity.

Efficient wind turbine blades, wind turbine blade structures, and associated systems and methods of manufacture, assembly and use

Abstract: Wind turbine systems and methods are disclosed herein. A representative system includes a wind turbine blade having an inner region that has an internal load-bearing truss structure, and an outer region that has an internal, non-truss, load-bearing structure. In particular embodiments, the truss structure can include a triangular arrangement of spars, and/or can include truss attachment members that connect components of the truss without the use of holes in the spars. Spars can be produced from a plurality of pultruded composite members laminated together in longitudinally extending portions. The longitudinally extending portions can be connected at joints that interleave projections and recesses of each of the spar portions. The blades can include fan-shaped transitions at a hub attachment portion, formed by laminated layers and/or a combination of laminated layers and transition plates.

Improved non-dominated sorting genetic algorithm (NSGA)-II in multi-objective optimization studies of wind turbine blades

Abstract: The non-dominated sorting genetic algorithm (NSGA) is improved with the controlled elitism and dynamic crowding distance. A novel multi-objective optimization algorithm is obtained for wind turbine blades. As an example, a 5 MW wind turbine blade design is presented by taking the maximum power coefficient and the minimum blade mass as the optimization objectives. The optimal results show that this algorithm has good performance in handling the multi-objective optimization of wind turbines, and it gives a Pareto-optimal solution set rather than the optimum solutions to the conventional multiobjective optimization problems. The wind turbine blade optimization method presented in this paper provides a new and general algorithm for the multi-objective optimization of wind turbines.

Development and Verification of a Computational Fluid Dynamics Model of a Horizontal-Axis Tidal Current Turbine

Abstract: This paper describes the development of a computational fluid dynamics (CFD) methodology to simulate the hydrodynamics of horizontal-axis tidal current turbines (HATTs). First, an HATT blade was designed using the blade element momentum method in conjunction with a genetic optimization algorithm. Several unstructured computational grids were generated using this blade geometry and steady CFD simulations were used to perform a grid resolution study. Transient simulations were then performed to determine the effect of time-dependent flow phenomena and the size of the computational timestep on the numerical solution. Qualitative measures of the CFD solutions were independent of the grid resolution. Conversely, quantitative comparisons of the results indicated that the use of coarse computational grids results in an under prediction of the hydrodynamic forces on the turbine blade in comparison to the forces predicted using more resolved grids. For the turbine operating conditions considered in this study, the effect of the computational timestep on the CFD solution was found to be minimal, and the results from steady and transient simulations were in good agreement. Additionally, the CFD results were compared to corresponding blade element momentum method calculations and reasonable agreement was shown. Nevertheless, we expect that for other turbine operating conditions, where the flow over the blade is separated, transient simulations will be required.Copyright © 2011 by ASME

Instrumented component for wireless telemetry

Abstract: A telemetry system for use in a combustion turbine engine (10) having a compressor (12), a combustor and a turbine (16) that includes a sensor (50, 74) in connection with a turbine blade (18) or vane (22). A telemetry transmitter circuit (210) may be affixed to the turbine blade (18) with a first connecting material (52, 152) deposited on the turbine blade (18) for routing electronic data signals from the sensor (50, 74) to the telemetry transmitter circuit (210), the electronic data signals indicative of a condition of the turbine blade (18). An induction power system for powering the telemetry transmitter circuit (210) may include a rotating data antenna (202) affixed to the turbine blade (18) with a second connecting material (140) deposited on the turbine blade (18) for routing electronic data signals from the telemetry transmitter circuit (210) to the rotating data antenna (202). A stationary data antenna (184) may be affixed to a static seal segment 180 adjacent the turbine blade (18) for receiving electronic data signals from the rotating data antenna (202).

Wind turbine rotor blade components and methods of making same

Abstract: Structural preform layers of multiple rigid unidirectional strength elements or rods are constructed and arranged for use in fabricating load-bearing support structures and reinforcements of wind turbine blades. Individual preform layers include multiple elongate unidirectional strength elements or rods arranged in a single layer along a longitudinal axis of the preform layer. Each preform layer includes one or more fibrous carrier layers to which the multiple strength elements or rods are joined and arranged in the single layer. Each strength element or rod is longitudinally oriented and adjacent to other elements or rods. Individual strength elements or rods include a mass of substantially straight unidirectional structural fibers embedded within a matrix resin such that the elements or rods have a substantially uniform distribution of fibers and high degree of fiber collimation. The relative straightness of the fibers and fiber collimation provide strength elements or rods and the preform layers with high rigidity and significant compression strength.

Transonic Turbine Blade Tip Aerothermal Performance With Different Tip Gaps—Part I: Tip Heat Transfer

Abstract: A closely combined experimental and computational fluid dynamics (CFD) study on a transonic blade tip aerothermal performance at engine representative Mach and Reynolds numbers (Mexit=1,Reexit=1.27×106) is presented here and its companion paper (Part II). The present paper considers surface heat-transfer distributions on tip surfaces and on suction and pressure-side surfaces (near-tip region). Spatially resolved surface heat-transfer data are measured using infrared thermography and transient techniques within the Oxford University high speed linear cascade research facility. The Rolls-Royce PLC HYDRA suite is employed for numerical predictions for the same tip configuration and flow conditions. The CFD results are generally in good agreement with experimental data and show that the flow over a large portion of the blade tip is supersonic for all three tip gaps investigated. Mach numbers within the tip gap become lower as the tip gap decreases. For the flow regions near the leading edge of the tip gap, surface Nusselt numbers decrease as the tip gap decreases. Opposite trends are observed for the trailing edge region. Several “hot spot” features on blade tip surfaces are attributed to enhanced turbulence thermal diffusion in local regions. Other surface heat-transfer variations are attributed to flow variations induced by shock waves. Flow structure and surface heat-transfer variations are also investigated numerically when a moving casing is present. The inclusion of moving casing leads to notable changes to flow structural characteristics and associated surface heat-transfer variations. However, significant portions of the tip leakage flow remain transonic with clearly identifiable shock wave structures.

Review of aeroelasticity for wind turbine: Current status, research focus and future perspectives

Abstract: Aeroelasticity has become a critical issue for Multi-Megawatt wind turbine due to the longer and more flexible blade. In this paper, the development of aeroelasticity and aeroelastic codes for wind turbine is reviewed and the aeroelastic models for wind turbine blade are described, based on which, the current research focuses for large scale wind turbine are discussed, including instability problems for onshore and offshore wind turbines, effects of complex inflow, nonlinear effects of large blade deflection, smart structure technologies, and aerohydroelasticity. Finally, the future development of aeroelastic code for large scale wind turbine: aeroservoelasticity and smart rotor control; nonlinear aeroelasticity due to large blade deflection; full-scale 3D computational fluid dynamics (CFD) solution for dynamics; and aerohydroelasticity are presented.

The Impact of Ice Formation on Wind Turbine Performance and Aerodynamics

Abstract: Wind energy is the world's fastest growing source of electricity production; if this trend is to continue, sites that are plentiful in terms of wind velocity must be efficiently utilized. Many such sites are located in cold, wet regions such as the Swiss Alps, the Scandinavian coastline, and many areas of China and North America, where the predicted power curves can be of low accuracy, and the performance often deviates significantly from the expected performance. There are often prolonged shutdown and inefficient heating cycles, both of which may be unnecessary. Thus, further understanding of the effects of ice formation on wind turbine blades is required. Experimental and computational studies are undertaken to examine the effects of ice formation on wind turbine performance. The experiments are conducted on a dynamically scaled model in the wind turbine test facility at ETH Zurich. The central element of the facility is a water towing tank that enables full-scale nondimensional parameters to be more closely matched on a subscale model than in a wind tunnel. A novel technique is developed to yield accurate measurements of wind turbine performance, incorporating the use of a torquemeter with a series of systematic measurements. These measurements are complemented by predictions obtained using a commercial Reynolds-Averaged Navier―Stokes computational fluid dynamics code. The measured and predicted results show that icing typical of that found at the Guetsch Alpine Test Site (2330 m altitude) can reduce the power coefficient by up to 22% and the annual energy production (AEP) by up to 2%. Icing in the blade tip region, 95―100% blade span, has the most pronounced effect on the wind turbine's performance. For wind turbines in more extreme icing conditions typical of those in Bern Jura, for example, icing can result in up to 17% losses in AEP. Icing at high altitude sites does not cause significant AEP losses, whereas icing at lower altitude sites can have a significant impact on AEP. Thus, the classification of icing is a key to the further development of prediction tools. It would be advantageous to tailor blade heating for prevention of ice buildup on the blade's tip region. An "extreme" icing predictive tool for the project development of wind farms in regions that are highly susceptible to icing would be beneficial to wind energy developers.

Optical Non-contacting Vibration Measurement of Rotating Turbine Blades II

Abstract: Identifying the structural dynamics of rotating components can be difficult. Often times, structural dynamic measurements are obtained while the structure is in a static configuration. There are differences that exist in the structural behavior when comparing these statically performed tests and the dynamic characteristics when in operation. In order to evaluate the actual system while in operation, slip-rings are used during testing with measurements made at only a very few selected points. But this slip-ring configuration can be problematic, suffer from measurement noise and the attached sensors can obscure the true dynamic response due to mass loading and aerodynamic effects. 3D digital image correlation (DIC) has been used to capture the out-of-plane motion on the surface of a small scale rotating fan blade. This work extends prior efforts, by quantifying the performance of the optical measurement on a 46 in (1.17m) diameter, rotating wind turbine. The optical measurements are made using DIC (10,000+ measurement points) and dynamic photogrammetry (providing dozens of effective measurement locations). The motion of the turbine as measured using DIC, photogrammetry and accelerometers is compared at several discrete points. The proposed measuring approaches via DIC and dynamic photogrammetry enable full-field dynamic measurement and monitoring of rotating structures in operation.

Wind turbine blade

Abstract: A wind-turbine blade that prevents foreign matter from entering the inside thereof during transportation and that can be efficiently assembled in good condition is provided. A wind-turbine blade includes a skin that forms a long and hollow shape, and a main spar that extends in the longitudinal direction and reinforces the skin from the inside thereof. The main spar is divided into a blade-root-side main spar and a blade-tip-side main spar in the longitudinal direction; the blade-root-side main spar and the blade-tip-side main spar have connection sections that are connected to each other; the skin is divided into a connection-section skin, located at a position corresponding to the connection sections, a blade-root-side skin, and a blade-tip-side skin; and openings formed in the blade-root-side skin and the blade-tip-side skin are blocked off by blanking plates.

Effects of Contact Interface Parameters on Vibration of Turbine Bladed Disks With Underplatform Dampers

Abstract: The design of high cycle fatigue resistant bladed disks requires the ability to predict the expected damping of the structure in order to evaluate the dynamic behavior and ensure structural integrity. Highly sophisticated software codes are available today for this nonlinear analysis, but their correct use requires a good understanding of the correct model generation and the input parameters involved to ensure a reliable prediction of the blade behavior. The aim of the work described in this paper is to determine the suitability of current modeling approaches and to enhance the quality of the nonlinear modeling of turbine blades with underplatform dampers. This includes an investigation of a choice of the required input parameters, an evaluation of their best use in nonlinear friction analysis, and an assessment of the sensitivity of the response to variations in these parameters. Part of the problem is that the input parameters come with varying degrees of uncertainty because some are experimentally determined, others are derived from analysis, and a final set are often based on estimates from previous experience. In this investigation the model of a commercial turbine bladed disk with an underplatform damper is studied, and its first flap, first torsion, and first edgewise modes are considered for 6 EO and 36 EO excitation. The influence of different contact interface meshes on the results is investigated, together with several distributions of the static normal contact loads, to enhance the model setup and, hence, increase accuracy in the response predictions of the blade with an underplatform damper. A parametric analysis is carried out on the friction contact parameters and the correct setup of the nonlinear contact model to determine their influence on the dynamic response and to define the required accuracy of the input parameters

Grain Selection in Spiral Selectors During Investment Casting of Single-Crystal Turbine Blades: Part I. Experimental Investigation

Abstract: Spiral grain selectors are used to grow single-crystal (SX) turbine blades during investment casting. Competitive growth in the spiral selectors leads to the selection of a single grain that subsequently grows to form the blade. In this study, the effect of spiral design on grain selection during investment casting was investigated through a series of experiments. It is found that the spiral design can effectively reduce the grain number but is not able to optimize axial grain orientations during solidification, the effectiveness of grain selection is strongly dependent on the spiral “take-off” angle, and spirals with smaller take-off angles are most potent. It is proposed that grain selection in the spiral is controlled by the geometry of the spiral via a “geometrical blocking” mechanism.