Sample records for blade loading

  1. Blade loading and slip factor in centrifugal compressor impellers

    Oh, J.S. [Korea Institute of Machinery and Materials, Taejon (Korea)


    In the present numerical analysis, to investigate the effect of blade loadings from design shape on the slip factor variation, both the Eckardt radial bladed impeller and the back swept impeller were analyzed. In addition, a new design of the blade profile was arbitrarily attempted to generate a center-loading pattern in the original back swept impeller. Three dimensional compressible Navier-Stokes flow analysis with the Baldwin-Lomax turbulence model was applied to get the numerical slip factor at each impeller exit plane using the mass-averaging technique. The numerical slip factors are in good agreement with the experimental ones, and the Wiesner's slip factors deviate further from the numerical and experimental ones in both back swept Deviation angles and meridional channel loadings are found in no relation with the trend of change of the slip factor. Blade-to-blade loadings in midspan location are, however, found in direct relation, especially at the sections where maximum loadings are to be expected. That information can be utilized in establishing an improved expression for slip factor in the future. (author). 4 refs., 9 figs.

  2. Full scale test SSP 34m blade, combined load. Data report

    Nielsen, Per H.; Nielsen, Magda; Jensen, Find M. (and others)


    This report is part of the research project where a 34m wind turbine blade from SSP-Technology A/S was tested in combined flap and edgewise load. The applied load is 55% of an imaginary extreme event based on the certification load of the blade. This report describes the reason for choosing the loads and the load direction and the method of applying the loads to the blade. A novel load introduction allows the blade to deform in a more realistic manner, allowing the observation of e.g. transverse shear distortion. The global and local deformation of the blade as well as the blades' respond to repeated tests has been studied and the result from these investigations are presented, including the measurements performed. (Author)

  3. Structural investigation of composite wind turbine blade considering various load cases and fatigue life

    This study proposes a structural design for developing a medium scale composite wind turbine blade made of E-glass/epoxy for a 750 kW class horizontal axis wind turbine system. The design loads were determined from various load cases specified at the IEC61400-1 international specification and GL regulations for the wind energy conversion system. A specific composite structure configuration, which can effectively endure various loads such as aerodynamic loads and loads due to accumulation of ice, hygro-thermal and mechanical loads, was proposed. To evaluate the proposed composite wind turbine blade, structural analysis was performed by using the finite element method. Parametric studies were carried out to determine an acceptable blade structural design, and the most dominant design parameters were confirmed. In this study, the proposed blade structure was confirmed to be safe and stable under various load conditions, including the extreme load conditions. Moreover, the blade adapted a new blade root joint with insert bolts, and its safety was verified at design loads including fatigue loads. The fatigue life of a blade that has to endure for more than 20 years was estimated by using the well-known S-N linear damage theory, the service load spectrum, and the Spera's empirical equations. With the results obtained from all the structural design and analysis, prototype composite blades were manufactured. A specific construction process including the lay-up molding method was applied to manufacturing blades. Full-scale static structural test was performed with the simulated aerodynamic loads. From the experimental results, it was found that the designed blade had structural integrity. In addition, the measured results of deflections, strains, mass, and radial center of gravity agreed well with the analytical results. The prototype blade was successfully certified by an international certification institute, GL (Germanisher Lloyd) in Germany

  4. Combined wind turbine fatigue and ultimate load reduction by individual blade control

    If each blade of the wind turbine has individual pitch actuator, there is possibility of employing the pitch system to mitigate structural loads through advanced control methods. Previously, considerable reduction of blade lifetime equivalent fatigue loads has been achieved by Individual Blade Control (IBC) and in addition, it has also been shown the potential in blade ultimate loads reduction. However, both fatigue and ultimate loads impact on the design and life of wind turbine blades. In this paper, the design and application of IBC that concurrently reduce both blade fatigue and ultimate loads is investigated. The contributions of blade load spectral components, which are 1P, 2P and edgewise mode from blade in-plane and/or out-of-plane bending moments, are firstly explored. Four different control options for reducing various combinations of these load components are compared. In response to the different spectral peaks of both fatigue and ultimate loads, the controller has been designed so that it can act on different frequency components which vary with wind speed. The performance of the IBC controller on fatigue and ultimate load reduction is assessed by simulating a 5MW exemplar wind turbine. Simulation results show that with a proper selection of controlling inputs at different wind speed, the use of a single combined IBC can achieve satisfactory reduction on both fatigue and ultimate loads

  5. Loadings in thermal barrier coatings of jet engine turbine blades an experimental research and numerical modeling

    Sadowski, Tomasz


    This book discusses complex loadings of turbine blades and protective layer Thermal Barrier Coating (TBC), under real working airplane jet conditions. They obey both multi-axial mechanical loading and sudden temperature variation during starting and landing of the airplanes. In particular, two types of blades are analyzed: stationary and rotating, which are widely applied in turbine engines produced by airplane factories.

  6. Individual pitch control of NREL 5MW wind turbine blade for load reduction

    As the size of a wind turbine increases, the rotor diameter increases. Rotor blades experience mechanical loads caused by the wind shear and the tower shadow effect. These mechanical loads reduce the life of the wind turbine. Therefore, with increasing size of the wind turbine, wind turbine control system design for the mitigation of mechanical loads is important. In this study, Individual Pitch Control in introduced for reducing the mechanical loads of rotor blades, and a simulation for IPC performance verification is discussed

  7. Controller Design for Blade Load Reduction Using Synthetic Jets

    Soltani, Mohsen; Mirzaei, Mahmood


    strain gauges along the blade and the tower to estimate the contribution of each blade modal state to the vibration of the tower and the blades. The synthetic jet actuators are then controlled, such that the desired vibration modes are damped effectively. Designed estimator and controller are implemented...

  8. Calibration procedures for improved accuracy of wind turbine blade load measurement

    Dahlberg, J.Aa. [Aeronautical Research Inst. of Sweden, Bromma (Sweden); Johansson, Hjalmar [Teknikgruppen AB, Sollentuna (Sweden)


    External loads acting on wind turbine blades are mainly transferred via the hub to the rest of the structure. It is therefore a normal approach to measure the loads acting on the turbine by load measurements in the blade roots. The load measurement is often accomplished by measurements of strain on the surface of the blade or the hub. The strain signals are converted to loads by applying calibration factors to the measurements. This paper deals with difficulties associated with load measurements on two different wind turbines; one with strain gauges applied to a steel hub where a linear stress-load relationship is expected and the other with strain gauges applied to the GFRP blade close to the bearings where strong non-linearity`s and temperature effects are expected. This paper suggests calibration methods to overcome these problems. 2 refs, 11 figs

  9. Evaluation of Rotor Structural and Aerodynamic Loads using Measured Blade Properties

    Jung, Sung N.; You, Young-Hyun; Lau, Benton H.; Johnson, Wayne; Lim, Joon W.


    The structural properties of Higher harmonic Aeroacoustic Rotor Test (HART I) blades have been measured using the original set of blades tested in the wind tunnel in 1994. A comprehensive rotor dynamics analysis is performed to address the effect of the measured blade properties on airloads, blade motions, and structural loads of the rotor. The measurements include bending and torsion stiffness, geometric offsets, and mass and inertia properties of the blade. The measured properties are correlated against the estimated values obtained initially by the manufacturer of the blades. The previously estimated blade properties showed consistently higher stiffnesses, up to 30% for the flap bending in the blade inboard root section. The measured offset between the center of gravity and the elastic axis is larger by about 5% chord length, as compared with the estimated value. The comprehensive rotor dynamics analysis was carried out using the measured blade property set for HART I rotor with and without HHC (Higher Harmonic Control) pitch inputs. A significant improvement on blade motions and structural loads is obtained with the measured blade properties.

  10. Extreme Design Loads Calibration of Offshore Wind Turbine Blades through Real Time Measurements

    Natarajan, Anand; Vesth, Allan; Lamata, Rebeca Rivera

    Blade Root flap and Edge moments are measured on the blades of a 3.6MW offshore wind turbine in normal operation. Ten minute maxima of the measurements are sampled to determine the extreme blade root flap moment, edge moment and resultant moment over six month duration. A random subset of the...... measurements over a week is taken as input to stochastic load extrapolation whereby the one year extrapolated design extreme is obtained, which are then compared with the maximum extremes obtained from direct measurements over a six month period to validate the magnification in the load levels for the blade...... root flap moment, edge moment obtained by extrapolation. The validation yields valuable information on prescribing the slope of the local extrapolation curve at each mean wind speed. As an alternative to determining the contemporaneous loads for each primary extrapolated load, the blade root resultant...

  11. blades

    Shashishekara S. Talya


    Full Text Available Design optimization of a gas turbine blade geometry for effective film cooling toreduce the blade temperature has been done using a multiobjective optimization formulation. Three optimization formulations have been used. In the first, the average blade temperature is chosen as the objective function to be minimized. An upper bound constraint has been imposed on the maximum blade temperature. In the second, the maximum blade temperature is chosen as the objective function to be minimized with an upper bound constraint on the average blade temperature. In the third formulation, the blade average and maximum temperatures are chosen as objective functions. Shape optimization is performed using geometric parameters associated with film cooling and blade external shape. A quasi-three-dimensional Navier–Stokes solver for turbomachinery flows is used to solve for the flow field external to the blade with appropriate modifications to incorporate the effect of film cooling. The heat transfer analysis for temperature distribution within the blade is performed by solving the heat diffusion equation using the finite element method. The multiobjective Kreisselmeier–Steinhauser function approach has been used in conjunction with an approximate analysis technique for optimization. The results obtained using both formulations are compared with reference geometry. All three formulations yield significant reductions in blade temperature with the multiobjective formulation yielding largest reduction in blade temperature.

  12. Failure Test and Finite Element Simulation of a Large Wind Turbine Composite Blade under Static Loading

    Xiao Chen; Wei Zhao; Xiao Lu Zhao; Jian Zhong Xu


    This study presented a failure analysis of a 52.3 m composite wind turbine blade under static loading. Complex failure characteristics exhibited at the transition region of the blade were thoroughly examined and typical failure modes were indentified. In order to predict multiple failure modes observed in the tests and gain more insights into the failure mechanisms of the blade, a Finite Element (FE) simulation was performed using a global-local modeling approach and Progressive Failure Anal...

  13. Full scale testing of wind turbine blade to failure - flapwise loading

    Jørgensen, E.R.; Borum, Kaj Kvisgaard; McGugan, Malcolm; Thomsen, C.L.; Jensen, Find Mølholt; Debel, C.P.; Sørensen, Bent F.


    A 25m wind turbine blade was tested to failure when subjected to a flapwise load. With the test setup, it was possible to test the blade to failure at three different locations. The objective of these tests is to learn about how a wind turbine bladefails when exposed to a large flapwise load and...... how failures propagate. The report shows also results from ultrasonic scan of the surface of the blade and it is seen to be very useful for the detection of defects, especially in the layer between the skinlaminate and the load carrying main spar. Acoustic emission was successfully used as sensor for...

  14. Effect of blade flutter and electrical loading on small wind turbine noise

    The effect of blade flutter and electrical loading on the noise level of two different size wind turbines was investigated at the Conservation and Production Research Laboratory (CPRL) near Bushland, TX. Noise and performance data were collected on two blade designs tested on a wind turbine rated a...

  15. A Low Order Model for Analyzing effects of Blade Fatigue Load Control

    Kallesøe, Bjarne Skovmose


    A new low order mathematical model is introduced to analyse blade dynamics and blade load reducing control strategies for wind turbines. The model consists of a typical wing section model combined with a rotor speed model, leading to four structural degrees of freedom (flapwise, edgewise, and...

  16. Load consequences when sweeping blades - A case study of a 5 MW pitch controlled wind turbine

    Verelst, D.R.S.; Larsen, Torben J.


    The generic 5 MW NREL wind turbine model is used in Risoe's aeroelastic simulator HAWC2 to investigate 120 different swept blade configurations (forward and backward sweep). Sensitivity for 2 different controllers is considered as well. Backward sweep results in a pitch to feather torsional moment of the blade, effectively reducing blade twist angles under increased loading. This behaviour results in decreased flap-wise fatigue and extreme loads, an increase for edge-wise fatigue loading and status quo or slight decrease in extreme loads (depending on the controller). Tower base and shaft-end bending moments are reduced as well. Forward sweep leads to an increase in angle of attack under loading. For a pitch controlled turbine this leads to an increase in fatigue and extreme loading in all cases. A controller inflicted instability is present for the more extreme forward swept cases. Due to the shape of considered sweep curves, an inherent and significant increase in torsional blade root bending moment is noted. A boomerang shaped sweep curve is proposed to counteract this problematic increased loading. Controller sensitivity shows that adding sweep affects some loadings differently. Power output is reduced for backward sweep since the blade twist is optimized as a rigid structure, ignoring the torsional deformations which for a swept blade can be significant. (author)

  17. Full Scale Test SSP 34m blade, edgewise loading LTT. Extreme load and PoC_InvE Data report

    Nielsen, Magda; Roczek-Sieradzan, Agnieszka; Jensen, Find Mølholt;

    edgewise direction (LTT). The blade has been submitted to thorough examination by means of strain gauges, displacement transducers and a 3D optical measuring system. This data report presents results obtained during full scale testing of the blade up to 80% Risø load, where 80% Risø load corresponds to 100......This report is the second report covering the research and demonstration project “Eksperimentel vingeforskning: Strukturelle mekanismer i nutidens og fremtidens store vinger under kombineret last”, supported by the EUDP program. A 34m wind turbine blade from SSP-Technology A/S has been tested in...

  18. Evaluation of a Blade Force Measurement System for a Vertical Axis Wind Turbine Using Load Cells

    Morgan Rossander; Eduard Dyachuk; Senad Apelfröjd; Kristian Trolin; Anders Goude; Hans Bernhoff; Sandra Eriksson


    Unique blade force measurements on an open site straight-bladed vertical axis wind turbine have been performed. This paper presents a method for measuring the tangential and normal forces on a 12-kW vertical axis wind turbine prototype with a three-bladed H-rotor. Four single-axis load cells were installed in-between the hub and the support arms on one of the blades. The experimental setup, the measurement principle, together with the necessary control and measurement system are described. Th...

  19. Influence of Thermodynamic Effect on Blade Load in a Cavitating Inducer

    Kengo Kikuta


    Full Text Available Distribution of the blade load is one of the design parameters for a cavitating inducer. For experimental investigation of the thermodynamic effect on the blade load, we conducted experiments in both cold water and liquid nitrogen. The thermodynamic effect on cavitation notably appears in this cryogenic fluid although it can be disregarded in cold water. In these experiments, the pressure rise along the blade tip was measured. In water, the pressure increased almost linearly from the leading edge to the trailing edge at higher cavitation number. After that, with a decrease of cavitation number, pressure rise occurred only near the trailing edge. On the other hand, in liquid nitrogen, the pressure distribution was similar to that in water at a higher cavitation number, even if the cavitation number as a cavitation parameter decreased. Because the cavitation growth is suppressed by the thermodynamic effect, the distribution of the blade load does not change even at lower cavitation number. By contrast, the pressure distribution in liquid nitrogen has the same tendency as that in water if the cavity length at the blade tip is taken as a cavitation indication. From these results, it was found that the shift of the blade load to the trailing edge depended on the increase of cavity length, and that the distribution of blade load was indicated only by the cavity length independent of the thermodynamic effect.

  20. Design of fatigue loading monitoring system for wind turbine blades under dual-axes resonance mode

    Leian ZHANG


    Full Text Available In order to shorten fatigue test period of wind turbine blades, a fatigue loading method based on the dual-axes resonance driven by electricity is proposed. The method for detecting the speed and phase of the two loading sources is given, and the synchronization control strategy is formulated. The master-slave network framework mode is applied in the control system. The speed and phase of the two loading sources are measured by using high-speed pulse counting sensor, the blade amplitude is obtained by laser range finder, and the PC monitoring interface is developed by using Labview. Test results show that the speed, phase, blade amplitude of the loading sources and other characteristic parameters can be measured well by using the monitoring system, which provides a new test platform for dual-axis resonance fatigue test of wind turbine blades.

  1. Relevance of aerodynamic modelling for load reduction control strategies of two-bladed wind turbines

    A new load reduction concept is being developed for the two-bladed prototype of the Skywind 3.5MW wind turbine. Due to transport and installation advantages both offshore and in complex terrain two-bladed turbine designs are potentially more cost-effective than comparable three-bladed configurations. A disadvantage of two-bladed wind turbines is the increased fatigue loading, which is a result of asymmetrically distributed rotor forces. The innovative load reduction concept of the Skywind prototype consists of a combination of cyclic pitch control and tumbling rotor kinematics to mitigate periodic structural loading. Aerodynamic design tools must be able to model correctly the advanced dynamics of the rotor. In this paper the impact of the aerodynamic modelling approach is investigated for critical operational modes of a two-bladed wind turbine. Using a lifting line free wake vortex code (FVM) the physical limitations of the classical blade element momentum theory (BEM) can be evaluated. During regular operation vertical shear and yawed inflow are the main contributors to periodic blade load asymmetry. It is shown that the near wake interaction of the blades under such conditions is not fully captured by the correction models of BEM approach. The differing prediction of local induction causes a high fatigue load uncertainty especially for two-bladed turbines. The implementation of both cyclic pitch control and a tumbling rotor can mitigate the fatigue loading by increasing the aerodynamic and structural damping. The influence of the time and space variant vorticity distribution in the near wake is evaluated in detail for different cyclic pitch control functions and tumble dynamics respectively. It is demonstrated that dynamic inflow as well as wake blade interaction have a significant impact on the calculated blade forces and need to be accounted for by the aerodynamic modelling approach. Aeroelastic simulations are carried out using the high fidelity multi body

  2. Structural qualification testing and operational loading on a fiberglass rotor blade for the Mod-OA wind turbine

    Sullivan, T. L.


    Fatigue tests were performed on full- and half-scale root end sections, first to qualify the root retention design, and second to induce failure. Test methodology and results are presented. Two operational blades were proof tested to design limit load to ascertain buckling resistance. Measurements of natural frequency, damping ratio, and deflection under load made on the operational blades are documented. The tests showed that all structural design requirements were met or exceeded. Blade loads measured during 3000 hr of field operation were close to those expected. The measured loads validated the loads used in the fatigue tests and gave high confidence in the ability of the blades to achieve design life.

  3. Blade design loads on the flow exciting force in centrifugal pump

    Xu, Y.; Yang, A. L.; Langand, D. P.; Dai, R.


    The three-dimensional viscous flow field of two centrifugal pumps, which have the same volute, design head, design flow rate and rotational speed but the blade design load, are analyzed based on large eddy simulation. The comparisons are implemented including the hydraulic efficiencies, flow field characteristics, pressure pulsations and unsteady forces applied on the impellers to investigate the effect of the design blade load on hydraulic performance and flow exciting force. The numerical results show that the efficiency of the pump, the impeller blade of which has larger design load, is improved by 1.1%~2.9% compared to the centrifugal pump with lower blade design load. The pressure fluctuation of the pump with high design load is more remarkable. Its maximum amplitude of coefficient of static pressure is higher by 43% than the latter. At the same time the amplitude of unsteady radial force is increased by 11.6% in the time domain. The results also imply that the blade design load is an important factor on the excitation force in centrifugal pumps.

  4. Aerodynamic unsteady loads and vibrations of steam turbine L.P. blades

    In steam turbines, the aerodynamic sources of the blades vibrations for low pressure stages can induce a high stress level for some operating points. Therefore theoretical and experimental investigations are performed at E.D.F. They specially focus on the turbine rotor-stator interaction and the aerolastic rotor stability. A numerical method has been developed for predicting the aerodynamic damping of one cascade of profiles. The insteady flow calculation is based on the boundary element method, and is performed for the blade-to-blade surfaces. The results obtained on the first flexural mode for the L.P. blades of a 900 MW steam turbine, for several displacements and for several interblade phase angles, exhibits no instability of the rotor except low phase angles, but it is difficult to investigate these cases. The numerical results also support the relevance of the quasi-steady assumption. The same method has been used to calculate the rotor-stator interaction in the case of a potential flow. The main parameters are the gap between the two rows and the stator blade number/rotor blade number ratio (NR/NS). The results show that the dynamic loads strongly decrease with respect to the gap increase. Otherwise NR/NS = 2 (periodical pattern), which is a good approximation of the industrial value, provides slight unsteady loads on the rotor blades comparatively to other values

  5. A zero torsional stiffness twist morphing blade as a wind turbine load alleviation device

    This paper presents the design, analysis and realization of a zero stiffness twist morphing wind turbine blade. The morphing blade is designed to actively twist as a means of alleviating the gust loads which reduce the fatigue life of wind turbine blades. The morphing structure exploits an elastic strain energy balance within the blade to enable large twisting deformations with modest actuation requirements. While twist is introduced using the warping of the blade skin, internal pre-stressed members ensure that a constant strain energy balance is achieved throughout the deformation, resulting in a zero torsional stiffness structure. The torsional stability of the morphing blade is characterized by analysing the elastic strain energy in the device. Analytical models of the skin, the pre-stressed components and the complete blade are compared to their respective finite element models as well as experimental results. The load alleviation potential of the adaptive structure is quantified using a two-dimensional steady flow aerodynamic model which is experimentally validated with wind tunnel measurements. (paper)

  6. Ultimate Strength of Wind Turbine Blades under Multiaxial Loading

    Haselbach, Philipp Ulrich

    Modern wind turbine rotor blades are sophisticated lightweight structures, optimised towards achieving the best compromise between aerodynamic and structural design as well as a cost efficient manufacturing processes. They are usually designed for a lifetime of minimum 20 years, where they must...

  7. Method and apparatus for reducing rotor blade deflections, loads, and/or peak rotational speed

    Moroz, Emilian Mieczyslaw; Pierce, Kirk Gee


    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.

  8. Calculation and characteristics analysis of blade pitch loads for large scale wind turbines


    Based on the electric pitch system of large scale horizontal-axis wind turbines,the blade pitch loads coming mainly from centrifugal force,aerodynamic force and gravity are analyzed,and the calculation models for them are established in this paper.For illustration,a 1.2 MW wind turbine is introduced as a practical sample,and its blade pitch loads from centrifugal force,aerodynamic force and gravity are calculated and analyzed separately and synthetically.The research results showed that in the process of rotor rotating 360o,the fluctuation of blade pitch loads is similar to cosine curve when the rotor rotational speed,in-flow wind speed and pitch angle are constant.Furthermore,the amplitude of blade pitch load presents quite a difference at a different pitch angle.The ways of calculation for blade pitch loads are of the universality,and are helpful for further research of the individual pitch control system.

  9. Wind Turbine Load Mitigation based on Multivariable Robust Control and Blade Root Sensors

    This paper presents two H∞ multivariable robust controllers based on blade root sensors' information for individual pitch angle control. The wind turbine of 5 MW defined in the Upwind European project is the reference non-linear model used in this research work, which has been modelled in the GH Bladed 4.0 software package. The main objective of these controllers is load mitigation in different components of wind turbines during power production in the above rated control zone. The first proposed multi-input multi-output (MIMO) individual pitch H'' controller mitigates the wind effect on the tower side-to-side acceleration and reduces the asymmetrical loads which appear in the rotor due to its misalignment. The second individual pitch H'' multivariable controller mitigates the loads on the three blades reducing the wind effect on the bending flapwise and edgewise momentums in the blades. The designed H'' controllers have been validated in GH Bladed and an exhaustive analysis has been carried out to calculate fatigue load reduction on wind turbine components, as well as to analyze load mitigation in some extreme cases

  10. Optimum blade loading for a powered rotor in descent

    Ramin Modarres; David A. Peters


    The optimum loading for rotors has previously been found for hover, climb and wind turbine conditions;but, up to now, no one has determined the optimum rotor loading in descent. This could be an important design consideration for rotary-wing parachutes and low-speed des-cents. In this paper, the optimal loading for a powered rotor in descent is found from momentum theory based on a variational principle. This loading is compared with the optimal loading for a rotor in hover or climb and with the Betz rotor loading (which is optimum for a lightly-loaded rotor). Wake contraction for each of the various loadings is also presented.

  11. Ultimate Strength of Wind Turbine Blades under Multiaxial Loading

    Haselbach, Philipp Ulrich; Branner, Kim; Berggreen, Christian; Bitsche, Robert


    Modern wind turbine rotor blades are sophisticated lightweight structures, optimised towards achieving the best compromise between aerodynamic and structural design as well as a cost efficient manufacturing processes. They are usually designed for a lifetime of minimum 20 years, where they must endure a variety of weather conditions including uncontrollable, extreme winds without developing damage and fracture.The trend in the development of wind turbines is towards larger, more efficient win...

  12. Analysis of wind turbine blade behavior under static dual axis loads

    Son, Byung Jik [Korea Univ., Seoul (Korea, Republic of); Huh, Yong Hak; Kim, Dong Jin; Kim, Jong Il [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)


    For the assessment of the performance of a wind turbine blade, a simulated loading test may be required. In this study, the blade behavior was investigated through numerical analysis using a dual axis loading test, closely simulating the real operation conditions. The blade structure for the 100 kw class wind turbine system was modeled using the finite element (FE) program ANSYS. The failure criteria and buckling analysis under dual axis loading were examined. The failure analysis, including fiber failure and inter fiber failure, was performed with Puck's failure criterion. As the dual axis load ratio increases, the relatively increased stress occurs at the trailing edge and skin surface 3300-3600mm away from the root. Furthermore, it is revealed that increasing the dual axis load ratio makes the location that is weakest against buckling move toward the root part. Thus, it is seen that the dual axis load test may be an essential requirement for the verification of blade performance.




    Full Text Available With the aim to increase allowable blade loadings and enlarge stable operating range in highly loaded compressor, this work is carried out in order to explore the potential of passive control via slotted bladings in linear cascade configurations under both design and stall conditions. Through an extensive 2D-numerical study, the effects of location, width and slope of slots were analysed and the best configuration was identified. Based on the optimal slot, the 3D aerodynamic performances of cascade were studied and the influence of slotted blading to control endwall flow was investigated. Both 2D and 3D calculations are performed on steady RANS solver with standard k-epsilon turbulence model and low Mach number regime. The total loss coefficient, turning angle and flow visualizations on the blade and end-wall surfaces are adopted to describe the different configurations. The obtained results show, for 2D situation, that a maximum of 28.3% reduction in loss coefficient had been reached and the flow turning was increased with approximately 5°. Concerning 3D flow fields the slots marked their benefit at large incoming flow angles which delays the separation on both end wall and blade suction surface at mid span. However, at design conditions, the slotted blades are not able to control secondary flows near the wall and so, lose their potential.

  14. Analysis of aerodynamic load on straight-bladed vertical axis wind turbine

    Li, Qing'an; Maeda, Takao; Kamada, Yasunari; Murata, Junsuke; Kawabata, Toshiaki; Furukawa, Kazuma


    This paper presents a wind tunnel experiment for the evaluation of energy performance and aerodynamic forces acting on a small straight-bladed vertical axis wind turbine (VAWT) depending on several values of tip speed ratio. In the present study, the wind turbine is a four-bladed VAWT. The test airfoil of blade is symmetry airfoil (NACA0021) with 32 pressure ports used for the pressure measurements on blade surface. Based on the pressure distributions which are acted on the surface of rotor blade measured during rotation by multiport pressure-scanner mounted on a hub, the power, tangential force, lift and drag coefficients which are obtained by pressure distribution are discussed as a function of azimuthally position. And then, the loads which are applied to the entire wind turbine are compared with the experiment data of pressure distribution. As a result, it is clarified that aerodynamic forces take maximum value when the blade is moving to upstream side, and become small and smooth at downstream side. The power and torque coefficients which are based on the pressure distribution are larger than that by torque meter.

  15. Full Scale Test of SSP 34m blade, edgewise loading LTT

    Nielsen, Magda; Jensen, Find Mølholt; Nielsen, Per Hørlyk;

    This report is a part of the research project “Eksperimentel vingeforskning: Strukturelle mekanismer i nutidens og fremtidens store vinger under kombineret last” where a 34m wind turbine blade from SSP-Technology A/S has been tested in edgewise direction (LTT). The applied load is 60% of an...... unrealistic extreme event, corresponding to 75% of a certificated extreme load. This report describes the background, the test set up, the tests and the results. For this project, a new solution has been used for the load application and the solution for the load application is described in this report as...

  16. Full Scale Test of SSP 34m blade, edgewise loading LTT. Data Report 1

    Nielsen, Magda; Jensen, Find M.; Nielsen, Per H. (and others)


    This report is a part of a research project where a 34m wind turbine blade from SSP-Technology A/S has been tested in edgewise direction (LTT). The applied load is 60% of an unrealistic extreme event, corresponding to 75% of a certificated extreme load. This report describes the background, the test set up, the tests and the results. For this project, a new solution has been used for the load application and the solution for the load application is described in this report as well. The blade has been submitted to thorough examination. More areas have been examined with DIC, both global and local deflections have been measured, and also 378 strain gauge measurements have been performed. Furthermore Acoustic Emission has been used in order to detect damage while testing new load areas. The global deflection is compared with results from a previous test and results from FEM analyses in order to validate the solution as to how the gravity load on the blade was handled. Furthermore, the DIC measurement and the displacement sensors measurements are compared in order to validate the results from the DIC measurements. The report includes the results from the test and a description of the measurement equipment and the data acquisition. (author)

  17. The Effect of Mass and Web Spacing on the Loads and Structural Response of Increasing Wind Turbine Blade Size

    Bennett, Jeffrey


    The research presented considers the effect of varying shear web spacing and mass for two blades; a61.5m 5MW blade (based on the NREL5MW reference turbine) and a 100m 13.2MW blade (based onthe SNL100 blade). The variations are analyzed using HAWC2 aeroelastic simulations and Abaqus/CAE finite element simulations;and the effect of the variations is measured by comparing natural frequencies, loads, tip deflection,equivalent fatigue loads, material strength and buckling. Additionally, a tool was...

  18. Investigation of Maximum Blade Loading Capability of Lift-Offset Rotors

    Yeo, Hyeonsoo; Johnson, Wayne


    Maximum blade loading capability of a coaxial, lift-offset rotor is investigated using a rotorcraft configuration designed in the context of short-haul, medium-size civil and military missions. The aircraft was sized for a 6600-lb payload and a range of 300 nm. The rotor planform and twist were optimized for hover and cruise performance. For the present rotor performance calculations, the collective pitch angle is progressively increased up to and through stall with the shaft angle set to zero. The effects of lift offset on rotor lift, power, controls, and blade airloads and structural loads are examined. The maximum lift capability of the coaxial rotor increases as lift offset increases and extends well beyond the McHugh lift boundary as the lift potential of the advancing blades are fully realized. A parametric study is conducted to examine the differences between the present coaxial rotor and the McHugh rotor in terms of maximum lift capabilities and to identify important design parameters that define the maximum lift capability of the rotor. The effects of lift offset on rotor blade airloads and structural loads are also investigated. Flap bending moment increases substantially as lift offset increases to carry the hub roll moment even at low collective values. The magnitude of flap bending moment is dictated by the lift-offset value (hub roll moment) but is less sensitive to collective and speed.

  19. Flow separation control by using bowed blade in highly loaded turbine cascades

    YAMAMOTO; Atsumasa


    Due to the serious flow separations and centralized vortices,there are high secondary losses in highly loaded turbines.It is imperative to find measures to control the flow separation and vortices hence improve the turbine performance.This paper reports our recent progress on flow separation and vor-tices control in highly loaded turbine cascades by using bowed blades.Two sets of highly loaded tur-bine cascades with the turning angles of 113° and 160°,and each with 7 bowed blade angles 0°(straight),±10°,±20° and ±30° were experimentally investigated.Both internal flow field measurement and flow visualization on the blade surfaces were conducted,and the effects of blade bowing on the flow topology,distribution of vorticity and the flow energy loss were discussed.The results show that,for the cascade with the turning angle of 113°,the appropriately positive bow angle could reduce the flow energy loss;whereas for the cascade with the turning angle of 160°,the well selected negative bow angle can give the better aerodynamic performance.

  20. Flow separation control by using bowed blade in highly loaded turbine cascades

    TAN ChunQing; ZHANG HuaLiang; CHEN HaiSheng; DONG XueZhi; ZHAO HongLei; YAMAMOTO Atsumasa


    Due to the serious flow separations and centralized vortices, there are high secondary losses in highly loaded turbines. It is imperative to find measures to control the flow separation and vortices hence improve the turbine performance. This paper reports our recent progress on flow separation and vor-tices control in highly loaded turbine cascades by using bowed blades. Two sets of highly loaded tur-bine cascades with the turning angles of 113°and 160°, and each with 7 bowed blade angles 0°(straight),±10°, ±20° and ±30° were experimentally investigated. Both internal flow field measurement and flow visualization on the blade surfaces were conducted, and the effects of blade bowing on the flow topology, distribution of vorticity and the flow energy loss were discussed. The results show that, for the cascade with the turning angle of 113°, the appropriately positive bow angle could reduce the flow energy loss; whereas for the cascade with the turning angle of 160°, the well selected negative bow angle can give the better aerodynamic performance.

  1. Evaluation of a Blade Force Measurement System for a Vertical Axis Wind Turbine Using Load Cells

    Morgan Rossander


    Full Text Available Unique blade force measurements on an open site straight-bladed vertical axis wind turbine have been performed. This paper presents a method for measuring the tangential and normal forces on a 12-kW vertical axis wind turbine prototype with a three-bladed H-rotor. Four single-axis load cells were installed in-between the hub and the support arms on one of the blades. The experimental setup, the measurement principle, together with the necessary control and measurement system are described. The maximum errors of the forces and accompanying weather data that can be obtained with the system are carefully estimated. Measured forces from the four load cells are presented, as well as the normal and tangential forces derived from them and a comparison with theoretical data. The measured torque and bending moment are also provided. The influence of the load cells on the turbine dynamics has also been evaluated. For the aerodynamic normal force, the system provides periodic data in agreement with simulations. Unexpected mechanical oscillations are present in the tangential force, introduced by the turbine dynamics. The measurement errors are of an acceptable size and often depend on the measured variable. Equations are presented for the calculation of measurement errors.

  2. A low-order model for analysing effects of blade fatigue load control

    Kallesoee, B.S. [Technical Univ. of Denmark, Dept. of Mechanical Engineering, Lyngby (Denmark)


    A new low-order mathematical model is introduced to analyse blade dynamics and blade load-reducing control strategies for wind turbines. The model consists of a typical wing section model combined with a rotor speed model, leading to four structural degrees of freedom (flapwise, edgewise and torsional blade oscillations and rotor speed). The aerodynamics is described by an unsteady aerodynamic model. The equations of motion are derived in non-linear and linear form. The linear equations of motion are used for stability analysis and control design. The non-linear equations of motion are used for time simulations to evaluate control performance. The stability analysis shows that the model is capable of predicting classical flutter and stall-induced vibrations. The results from the stability analysis are compared with known results, showing good agreement. The model is used to compare the performance of one proportional-integral-derivative controller and two full-state feedback controllers. (Author)

  3. Application of Load Carrying Sandwich Elements in Wind Turbine Blades

    Jensen, Jacob Fisker; Schultz, Jacob Pagh; Berggreen, Carl Christian;


    The present work investigates the possibilities and drawbacks when applying sandwich as opposed to single skin composites in the flanges of the load carrying spar in a future 180 m wind turbine rotor. FEA is applied to investigate two basic designs with single skin and sandwich flanges respectively...... wrinkling and large tip deflection. Geometric non-linear analysis showed sensitivity to imperfections....

  4. Novelty detection applied to vibration data from a CX-100 wind turbine blade under fatigue loading

    Dervilis, N.; Choi, M.; Antoniadou, I.; Farinholt, K. M.; Taylor, S. G.; Barthorpe, R. J.; Park, G.; Worden, K.; Farrar, C. R.


    The remarkable evolution of new generation wind turbines has led to a dramatic increase of wind turbine blade size. In turn, a reliable structural health monitoring (SHM) system will be a key factor for the successful implementation of such systems. Detection of damage at an early stage is a crucial issue as blade failure would be a catastrophic result for the entire wind turbine. In this study the SHM analysis will be based on experimental measurements of Frequency Response Functions (FRFs) extracted by using an input/output acquisition technique under a fatigue loading of a 9m CX-100 blade at the National Renewable Energy Laboratory (NREL) and National Wind Technology Center (NWTC) performed in the Los Alamos National Laboratory. The blade was harmonically excited at its first natural frequency using a Universal Resonant Excitation (UREX) system. For analysis, the Auto-Associative Neural Network (AANN) is a non-parametric method where a set of damage sensitive features gathered from the measured structure are used to train a network that acts as a novelty detector. This traditionally has a highly complex "bottleneck" structure with five layers in the AANN. In the current paper, a new attempt is also exploited based on an AANN with one hidden layer in order to reduce the theoretical and computational difficulties. Damage detection of composite bodies of blades is a "grand challenge" due to varying aerodynamic and gravitational loads and environmental conditions. A study of the noise tolerant capability of the AANN which is associated to its generalisation capacity is addressed. It will be shown that vibration response data combined with AANNs is a robust and powerful tool, offering novelty detection even when operational and environmental variations are present. The AANN is a method which has not yet been widely used in the structural health monitoring of composite blades.

  5. Novelty detection applied to vibration data from a CX-100 wind turbine blade under fatigue loading

    The remarkable evolution of new generation wind turbines has led to a dramatic increase of wind turbine blade size. In turn, a reliable structural health monitoring (SHM) system will be a key factor for the successful implementation of such systems. Detection of damage at an early stage is a crucial issue as blade failure would be a catastrophic result for the entire wind turbine. In this study the SHM analysis will be based on experimental measurements of Frequency Response Functions (FRFs) extracted by using an input/output acquisition technique under a fatigue loading of a 9m CX-100 blade at the National Renewable Energy Laboratory (NREL) and National Wind Technology Center (NWTC) performed in the Los Alamos National Laboratory. The blade was harmonically excited at its first natural frequency using a Universal Resonant Excitation (UREX) system. For analysis, the Auto-Associative Neural Network (AANN) is a non-parametric method where a set of damage sensitive features gathered from the measured structure are used to train a network that acts as a novelty detector. This traditionally has a highly complex 'bottleneck' structure with five layers in the AANN. In the current paper, a new attempt is also exploited based on an AANN with one hidden layer in order to reduce the theoretical and computational difficulties. Damage detection of composite bodies of blades is a 'grand challenge' due to varying aerodynamic and gravitational loads and environmental conditions. A study of the noise tolerant capability of the AANN which is associated to its generalisation capacity is addressed. It will be shown that vibration response data combined with AANNs is a robust and powerful tool, offering novelty detection even when operational and environmental variations are present. The AANN is a method which has not yet been widely used in the structural health monitoring of composite blades.

  6. Failure Test and Finite Element Simulation of a Large Wind Turbine Composite Blade under Static Loading

    Xiao Chen


    Full Text Available This study presented a failure analysis of a 52.3 m composite wind turbine blade under static loading. Complex failure characteristics exhibited at the transition region of the blade were thoroughly examined and typical failure modes were indentified. In order to predict multiple failure modes observed in the tests and gain more insights into the failure mechanisms of the blade, a Finite Element (FE simulation was performed using a global-local modeling approach and Progressive Failure Analysis (PFA techniques which took into account material failure and property degradation. Failure process and failure characteristics of the transition region were satisfactorily reproduced in the simulation, and it was found that accumulated delamination in spar cap and shear web failure at the transition region were the main reasons for the blade to collapse. Local buckling played an important role in the failure process by increasing local out-of-plane deformation, while the Brazier effect was found not to be responsible for the blade failure.

  7. Reduction of aerodynamic load fluctuation on wind turbine blades through active flow control

    Velarde, John-Michael; Coleman, Thomas; Magstadt, Andrew; Aggarwal, Somil; Glauser, Mark


    The current set of experiments deals with implementing active flow control on a Bergey Excel 1, 1kW turbine. The previous work in our group demonstrated successfully that implementation of a simple closed-loop controller could reduce unsteady aerodynamic load fluctuation by 18% on a vertically mounted wing. Here we describe a similar flow control method adapted to work in the rotating frame of a 2.5m diameter wind turbine. Strain gages at the base of each blade measure the unsteady fluctuation in the blades and pressure taps distributed along the span of the blades feed information to the closed-loop control scheme. A realistic, unsteady flow field has been generated by placing a cylinder upstream of the turbine to induce shedding vortices at frequencies in the bandwidth of the first structural bending mode of the turbine blades. The goal of these experiments is to demonstrate closed-loop flow control as a means to reduce the unsteady fluctuation in the blades and increase the overall lifespan of the wind turbine.

  8. Combining Unsteady Blade Pressure Measurements and a Free-Wake Vortex Model to Investigate the Cycle-to-Cycle Variations in Wind Turbine Aerodynamic Blade Loads in Yaw

    Moutaz Elgammi


    Full Text Available Prediction of the unsteady aerodynamic flow phenomenon on wind turbines is challenging and still subject to considerable uncertainty. Under yawed rotor conditions, the wind turbine blades are subjected to unsteady flow conditions as a result of the blade advancing and retreating effect and the development of a skewed vortical wake created downstream of the rotor plane. Blade surface pressure measurements conducted on the NREL Phase VI rotor in yawed conditions have shown that dynamic stall causes the wind turbine blades to experience significant cycle-to-cycle variations in aerodynamic loading. These effects were observed even though the rotor was subjected to a fixed speed and a uniform and steady wind flow. This phenomenon is not normally predicted by existing dynamic stall models integrated in wind turbine design codes. This paper couples blade pressure measurements from the NREL Phase VI rotor to a free-wake vortex model to derive the angle of attack time series at the different blade sections over multiple rotor rotations and three different yaw angles. Through the adopted approach it was possible to investigate how the rotor self-induced aerodynamic load fluctuations influence the unsteady variations in the blade angles of attack and induced velocities. The hysteresis loops for the normal and tangential load coefficients plotted against the angle of attack were plotted over multiple rotor revolutions. Although cycle-to-cycle variations in the angles of attack at the different blade radial locations and azimuth positions are found to be relatively small, the corresponding variations in the normal and tangential load coefficients may be significant. Following a statistical analysis, it was concluded that the load coefficients follow a normal distribution at the majority of blade azimuth angles and radial locations. The results of this study provide further insight on how existing engineering models for dynamic stall may be improved through

  9. Application of Load Carrying Sandwich Elements in Wind Turbine Blades

    Jensen, Jacob Fisker; Schultz, Jacob Pagh; Berggreen, Carl Christian; Branner, Kim

    The present work investigates the possibilities and drawbacks when applying sandwich as opposed to single skin composites in the flanges of the load carrying spar in a future 180 m wind turbine rotor. FEA is applied to investigate two basic designs with single skin and sandwich flanges respectively....... For a single skin design, buckling is critical compared to other design criterions. By introducing sandwich, a significant weight reduction and increased buckling capacity is obtained. Tower clearance now becomes critical. Proper choice of core material and thickness is important to prevent face...

  10. Loads and Performance Data from a Wind-Tunnel Test of Generic Model Helicopter Rotor Blades

    Yeager, William T., Jr.; Wilbur, Matthew L.


    An investigation was conducted in the NASA Langley Transonic Dynamics Tunnel to acquire data for use in assessing the ability of current and future comprehensive analyses to predict helicopter rotating-system and fixed-system vibratory loads. The investigation was conducted with a generic model helicopter rotor system using blades with rectangular planform, no built-in twist, uniform radial distribution of mass and stiffnesses, and a NACA 0012 airfoil section. Rotor performance data, as well as mean and vibratory components of blade bending and torsion moments, fixed-system forces and moments, and pitch link loads were obtained at advance ratios up to 0.35 for various combinations of rotor shaft angle-of-attack and collective pitch. The data are presented without analysis.

  11. Design optimization of blade stiffened laminated composite plates for maximum buckling load

    Achenbach, Mark R.


    Approved for public release; distribution unlimited. The buckling load of a blade stiffened laminated composite plate having midplane symmetry is maximized for a given total weight. The thickness of the layers and the width and height of the stiffener are taken as the design variables. Buckling analysis is carried out using a finite element method. The optimization problem is solved using commercially available optimization packages. Due to the highly nonlinear nature of the optimality equ...

  12. Rotor hub vibration and blade loads reduction, and energy harvesting via embedded radial oscillator

    Austruy, Julien

    An embedded radial absorber is investigated to control helicopter rotor hub vibration and blade loads. The absorber is modeled as a discrete mass moving in the spanwise direction within the blade. The absorber is retained in place and tuned with a spring and a damper. The radial absorber couples with lead-lag dynamic through Coriolis forces. The embedded radial absorber coupled to the helicopter is analyzed with a comprehensive rotorcraft model. The blade is modeled as an elastic beam undergoing flap bending, lag bending and elastic torsion, and a radial degree of freedom is added for the absorber. The tuning of the embedded radial absorber to a frequency close to 3/rev with no damping is shown to reduce significantly (up to 86%) the 4/rev in-plane hub forces of a 4-bladed hingeless rotor similar to a MBB BO-105 in high speed flight. The simulation shows that the absorber modifies the in-plane blade root shears to synchronize them to cancel each other in the transmission from rotating frame to fixed frame. A design of an embedded radial absorber experiment for hub vibration control is presented and it is concluded that for such high tuning frequencies as 3/rev, it is feasible to use a regular coil spring to compensate for the steady centrifugal force. Large reduction of blade lag shear (85%) and lag bending moment (71%) is achieved by tuning the embedded radial absorber close to 1/rev (also shown for a BO-105 like helicopter in high speed flight). The absorber reduces the amplitude of the lag bending moment at 1/rev, thus reducing the blade lead-lag motion and reducing the blade drag shear and lag bending moment. Finally, the use of the embedded radial absorber is investigated as a source electrical power when combined with an electromagnetic circuit. A model of the electromagnetic system is developed and validated, and an evaluation of the amount of power harvestable for different configurations is presented. The maximum power harvested was calculated to be 133

  13. A Two-Bladed Teetering Hub configuration for the DTU 10 MW RWT: loads considerations

    Bergami, Leonardo; Aagaard Madsen, Helge; Rasmussen, Flemming


    frequency and the rotational forcing, the tower mode frequency is lowered with a modified tower stiffness distributions. The loads caused by the aerodynamic unbalance are instead addressed by introducing a teetering hub configuration. The load alleviation potential of the teetering hub, and the required...... study on an alternative downwind two-bladed rotor configuration. The study is based on a model representative of next generation multi-MW wind turbines: the DTU 10-MW Reference Wind Turbine (RWT). As a first design iteration, the aerodynamic characteristics of the original rotor are maintained, and the...

  14. A Two-Bladed Teetering Hub configuration for the DTU 10 MW RWT: loads considerations

    Bergami, Leonardo; Aagaard Madsen, Helge; Rasmussen, Flemming

    frequency and the rotational forcing, the tower mode frequency is lowered with a modified tower stiffness distributions. The loads caused by the aerodynamic unbalance are instead addressed by introducing a teetering hub configuration. The load alleviation potential of the teetering hub, and the required...... study on an alternative downwind two-bladed rotor configuration. The study is based on a model representative of next generation multi-MW wind turbines: the DTU 10-MW Reference Wind Turbine (RWT). As a first design iteration, the aerodynamic characteristics of the original rotor are maintained, and the...

  15. Investigation of the effect of bending twisting coupling on the loads in wind turbines with superelement blade definition

    Bending-twisting coupling in the composite blades is exploited for load alleviation in the whole turbine system. For the purpose of the study, inverse design of a reference blade is performed such that sectional beam properties of the 3D blade design approximately match the sectional beam properties of NREL's 5MW turbine blade. In order to appropriately account for the bending-twisting coupling effect, dynamic superelement of the blade is created and introduced into the multi-body dynamic model of the wind turbine system. Initially, a comparative study is conducted on the performance of wind turbines which have blades defined as superelements and geometrically nonlinear beams, and conclusions are inferred with regard to the appropriateness of the use of superelement blade definition in the transient analysis of the 5MW wind turbine system that is set up in the present study. Multi-body dynamic simulations of the wind turbine system are performed for the power production load case with the constant wind and the normal turbulence model as external wind loadings. For the internal loads, fatigue damage equivalent load is used as the metric to assess the effect of bending-twisting coupling on the load alleviation in the whole wind turbine system. Results show that in the overall, through the bending-twisting coupling induced with the use of off-axis plies in the main spar caps of the blade, damage equivalent loads associated with the critical load components can be reduced in the wind turbine system

  16. Full scale test SSP 34m blade, edgewise loading LTT. Extreme load and PoC{sub I}nvE Data report

    Nielsen, Magda; Roczek-Sieradzan, A.; Jensen, Find M. (and others)


    This report is the second report covering the research and demonstration project 'Experimental blade research: Structural mechanisms in current and future large blades under combined loading', supported by the EUDP program. A 34m wind turbine blade from SSP-Technology A/S has been tested in edgewise direction (LTT). The blade has been submitted to thorough examination by means of strain gauges, displacement transducers and a 3D optical measuring system. This data report presents results obtained during full scale testing of the blade up to 80% Risoe load, where 80% Risoe load corresponds to 100% certification load. These pulls at 80% Risoe load were repeated and the results from these pulls were compared. The blade was reinforced according to a Risoe DTU invention, where the trailing edge panels are coupled. The coupling is implemented to prevent the out of plane deformations and to reduce peeling stresses in the adhesive joints. Test results from measurements with the reinforcement have been compared to results without the coupling. The report presents only the relevant results for the 80% Risoe load and the results applicable for the investigation of the influence of the invention on the profile deformation. (Author)

  17. Effect of the flap and edgewise bending moment phase relationships on the fatigue loads of a typical HAWT blade

    Sutherland, H. J.

    The load spectrum unposed upon a horizontal-axis wind turbine blade is typically decomposed into two primary bending moments; flap and edgewise bending. The critical fatigue loads (stress cycles) imposed on the blade may not be on one of these axes, especially if die two bending loads are in-phase with one another. To quantify the correlation of these two bending moments and determine the impact of this correlation on off-axis fatigue loads, an extensive data set for a typical wind turbine blade is examined. The results are compared using their respective cycle count matrices. These results illustrate that the harmonic components of die principal bending stresses are correlated, and that the random components are not. The analysis techniques described in the paper provide the turbine designer with a spectral technique for combining primary bending spectra into off-axis fatigue loads.

  18. A new method for dual-axis fatigue testing of large wind turbine blades using resonance excitation and spectral loading

    White, Darris L.

    The demand for cost effective renewable energy sources has resulted in the continual refinement of modern wind turbine designs. These refinements generally result in larger wind turbines and wind turbine blades. In order to reduce maintenance expenses, and improve quality and reliability, each new blade design must be subjected to a high cycle fatigue test. With blades expected to soon reach 70 meters in length, traditional fatigue test systems and methods are becoming less practical. Additionally, the relationship between the flap and lead-lag bending moments has not been well understood. This work explores the accuracy of current test methods compared to service loads, presents a new method for fatigue testing larger blades and experimentally validates the analysis. A dynamic model of a generic wind turbine blade and test system has been developed to evaluate the strain profiles during testing, evaluate control strategies and optimize the test accuracy. The relationship between the flap and lead-lag strains resulting from service bending moments has been analyzed. A load spectrum based on the relationship between the flap and lead-lag loads has been developed and compared to traditional test conditions. The effect of using the load spectrum on the test system stability has been analyzed and a new state-space controller has been designed. A 3-D finite element model of a generic wind turbine blade has been used to evaluate the damage accumulation for current test load conditions and the proposed load spectrum. A nonlinear damage accumulation model has been derived to evaluate the effects of load sequencing. Additionally, a new method for applying the fatigue loads to the blades has been developed and implemented. A system that applies a harmonic force at the resonance frequency of the blade in the flap direction has been designed. The new system will reduce the costs and time associated with performing a fatigue test on wind turbine blades. The new system is also


    CAO Qing-ming; HONG Fang-wen; TANG Deng-hai; HU Fang-lin; LU Lin-zhang


    This article presents an approach which employs a commercial Reynolds-Averaged Navier-Stokes (RANS) solver to predict the steady wake field and loading distributions for a rim driven thruster.Four different cases of propeller blades are chosen to be calculated with the presented method.The propeller blade radial circulation and chordwise circulation density distributions are analyzed.The maximum radial circulation is found at the blade tip,which is different from conventional shaft drven propeller.The numerical results indicate that there is no tip leakage vortex in rim driven propulors.But there exist the tip joint vortex and the root region vortex.Bollard characteristics are calculated by taking rim surface effect into account.From the predicted results the second case in this paper is selected as the final one to perform hydrodynamic experiment.The calculation results with empirical rim surface corrections are compared with the measurement.It shows that the developed numerical method can well predict hydrodynamic performances of the rim driven thruster.

  20. Non-steady dynamics of atmospheric turbulence interaction with wind turbine loadings through blade-boundary-layer-resolved CFD

    Vijayakumar, Ganesh

    Modern commercial megawatt-scale wind turbines occupy the lower 15-20% of the atmospheric boundary layer (ABL), the atmospheric surface layer (ASL). The current trend of increasing wind turbine diameter and hub height increases the interaction of the wind turbines with the upper ASL which contains spatio-temporal velocity variations over a wide range of length and time scales. Our interest is the interaction of the wind turbine with the energetic integral-scale eddies, since these cause the largest temporal variations in blade loadings. The rotation of a wind turbine blade through the ABL causes fluctuations in the local velocity magnitude and angle of attack at different sections along the blade. The blade boundary layer responds to these fluctuations and in turn causes temporal transients in local sectional loads and integrated blade and shaft bending moments. While the integral scales of the atmospheric boundary layer are ˜ O(10--100m) in the horizontal with advection time scales of order tens of seconds, the viscous surface layer of the blade boundary layer is ˜ O(10 -- 100 mum) with time scales of order milliseconds. Thus, the response of wind turbine blade loadings to atmospheric turbulence is the result of the interaction between two turbulence dynamical systems at extremely disparate ranges of length and time scales. A deeper understanding of this interaction can impact future approaches to improve the reliability of wind turbines in wind farms, and can underlie future improvements. My thesis centers on the development of a computational framework to simulate the interaction between the atmospheric and wind turbine blade turbulence dynamical systems using a two step one-way coupled approach. Pseudo-spectral large eddy simulation (LES) is used to generate a true (equilibrium) atmospheric boundary layer over a flat land with specified surface roughness and heating consistent with the stability state of the daytime lower troposphere. Using the data from the

  1. CFD computations of wind turbine blade loads during standstill operation KNOW-BLADE, Task 3.1 report

    Soerensen, N.N.; Johansen, J.; Conway, S.


    Two rotors blades are computed during standstill conditions, using two different Navier-Stokes solvers EDGE and EllipSys3D. Both steady and transient linear {kappa} - {omega} RANS turbulence models are applied, along with steady non-linear RANS and transient DES simulations. The STORK 5.0 WPX blade is computed a three different tip pitch angles, 0, 26 and 50 degrees tip pitch angle, while the NREL Phase-VI blade is computed at 90 degrees tip pitch angle. Generally the CFD codes reproduce the measured trends quite well and the two involved CFD codes give very similar results. The discrepancies observed can be explained by the difference in the applied turbulence models and the fact that the results from one of the solvers are presented as instantaneous values instead of averaged values. The comparison of steady and transient RANS results show that the gain of using time true computations are very limited for this case, with respect to mean quantities. The same can be said for the RANS/DES comparison performed for the NREL rotor, even though the DES computation shows improved agreement at the tip and root sections. Finally, it is shown that the DES methodology provides a much more physical representation of the heavily stalled part of the flow over blades at high angles of attack. (au)

  2. Non-intrusive aerodynamic loads analysis of an aircraft propeller blade

    Ragni, D.; Oudheusden, B.W. van; Scarano, F. [Delft University of Technology, Faculty of Aerospace Engineering, Delft (Netherlands)


    The flow field in a cross-sectional plane of a scaled Beaver DHC aircraft propeller has been measured by means of a stereoscopic PIV setup. Phase-locked measurements are obtained in a rotational frequency range from 18,900 to 21,000 rpm, at a relative Mach number of 0.6 at 3/4 propeller radius. The use of an adapted formulation of the momentum equation in differential form for rotating frame of references, integrated with isentropic relations as boundary conditions, allowed to compute the pressure field around the blade and the surface pressure distribution directly from the velocity data in the compressible regime. The procedure, extended to the computation of the aerodynamic lift and drag coefficients by a momentum contour integral approach, proved to be able to couple the aerodynamical loads to the flow field on the moving propeller blade, comparing favorably with a numerical simulation of the entire scaled model. Results are presented for two propeller rotation speeds and three different yawing angles. (orig.)

  3. Comprehensive Forced Response Analysis of J2X Turbine Bladed-Discs with 36- Degree Variation in CFD Loading

    Elrod, David; Christensen, Eric; Brown, Andrew


    At NASA/MSFC, Structural Dynamics personnel continue to perform advanced analysis for the turbomachinery in the J2X Rocket Engine, which is under consideration for the new Space Launch System. One of the most challenging analyses in the program is predicting turbine blade structural capability. Resonance was predicted by modal analysis, so comprehensive forced response analyses using high fidelity cyclic symmetric finite element models were initiated as required. Analysis methodologies up to this point have assumed the flow field could be fully described by a sector, so the loading on every blade would be identical as it travelled through it. However, in the J2X the CFD flow field varied over the 360 deg of a revolution because of the flow speeds and tortuous axial path. MSFC therefore developed a complex procedure using Nastran Dmap's and Matlab scripts to apply this circumferentially varying loading onto the cyclically symmetric structural models to produce accurate dynamic stresses for every blade on the disk. This procedure is coupled with static, spin, and thermal loading to produce high cycle fatigue safety factors resulting in much more accurate analytical assessments of the blades.

  4. Investigation of Rotor Performance and Loads of a UH-60A Individual Blade Control System

    Yeo, Hyeonsoo; Romander, Ethan A.; Norman, Thomas R.


    Wind tunnel measurements of performance, loads, and vibration of a full-scale UH-60A Black Hawk main rotor with an individual blade control (IBC) system are compared with calculations obtained using the comprehensive helicopter analysis CAMRAD II and a coupled CAMRAD II/OVERFLOW 2 analysis. Measured data show a 5.1% rotor power reduction (8.6% rotor lift to effective-drag ratio increase) using 2/rev IBC actuation with 2.0 amplitude at = 0.4. At the optimum IBC phase for rotor performance, IBC actuator force (pitch link force) decreased, and neither flap nor chord bending moments changed significantly. CAMRAD II predicts the rotor power variations with the IBC phase reasonably well at = 0.35. However, the correlation degrades at = 0.4. Coupled CAMRAD II/OVERFLOW 2 shows excellent correlation with the measured rotor power variations with the IBC phase at both = 0.35 and = 0.4. Maximum reduction of IBC actuator force is better predicted with CAMRAD II, but general trends are better captured with the coupled analysis. The correlation of vibratory hub loads is generally poor by both methods, although the coupled analysis somewhat captures general trends.

  5. Wind Turbine Blade Design

    Richard J. Crossley; Peter J. Schubel


    A detailed review of the current state-of-art for wind turbine blade design is presented, including theoretical maximum efficiency, propulsion, practical efficiency, HAWT blade design, and blade loads. The review provides a complete picture of wind turbine blade design and shows the dominance of modern turbines almost exclusive use of horizontal axis rotors. The aerodynamic design principles for a modern wind turbine blade are detailed, including blade plan shape/quantity, aerofoil selection ...

  6. Rotordynamic analysis of asymmetric turbofan rotor due to fan blade-loss event with contact-impact rub loads

    Sinha, Sunil K.


    Loss of a blade from a running turbofan rotor introduces not only huge imbalance into the dynamical system rather it makes the entire rotor asymmetric as well. In a nonsymmetric rotor, the various terms of mass, gyroscopic and stiffness matrices also become time-dependent. In this paper, all the dynamical equations include the effect of the rotary inertia and gyroscopic moments as a result of both shaft bending as well as staggered blades flexing in-and-out of the plane of the disk. The governing equations also account for internal material damping in the shaft and the external damping in the support bearing system. In addition to the unbalance load at the disk location, the shaft may also be subjected to a torque and axial forces. Here, the fan blades are modeled as pre-twisted thin shallow shells. They have coupled flexural-torsional motion in the lateral out-of-plane direction as well as extensional degrees-of-freedom in the longitudinal spanwise direction of the blade airfoil. The effect of blade tip rub forces being transmitted to the shaft are analyzed in terms of the dynamic stability of the rotor, especially during windmilling.

  7. Measurement of Unsteady Aerodynamics Load on the Blade of Field Horizontal Axis Wind Turbine

    Kamada, Yasunari; Maeda, Takao; Naito, Keita; Ouchi, Yuu; Kozawa, Masayoshi

    This paper describes an experimental field study of the rotor aerodynamics of wind turbines. The test wind turbine is a horizontal axis wind turbine, or: HAWT with a diameter of 10m. The pressure distributions on the rotating blade are measured with multi point pressure transducers. Sectional aerodynamic forces are analyzed from pressure distribution. Blade root moments are measured simultaneously by a pair of strain gauges. The inflow wind is measured by a three component sonic anemometer, the local inflow of the blade section are measured by a pair of 7 hole Pitot tubes. The relation between the aerodynamic moments on the blade root from pressure distribution and the mechanical moment from strain gauges is discussed. The aerodynamic moments are estimated from the sectional aerodynamic forces and show oscillation caused by local wind speed and direction change. The mechanical moment shows similar oscillation to the aerodynamic excepting the short period oscillation of the blade first mode frequency. The fluctuation of the sectional aerodynamic force triggers resonant blade oscillations. Where stall is present along the blade section, the blade's first mode frequency is dominant. Without stall, the rotating frequency is dominant in the blade root moment.

  8. Design, manufacturing and characterization of aero-elastically scaled wind turbine blades for testing active and passive load alleviation techniques within a ABL wind tunnel

    In the research described in this paper, a scaled wind turbine model featuring individual pitch control (IPC) capabilities, and equipped with aero-elastically scaled blades featuring passive load reduction capabilities (bend-twist coupling, BTC), was constructed to investigate, by means of wind tunnel testing, the load alleviation potential of BTC and its synergy with active load reduction techniques. The paper mainly focus on the design of the aero-elastic blades and their dynamic and static structural characterization. The experimental results highlight that manufactured blades show desired bend-twist coupling behavior and are a first milestone toward their testing in the wind tunnel

  9. A Critical Evaluation of Structural Analysis Tools used for the Design of Large Composite Wind Turbine Rotor Blades under Ultimate and Cycle Loading

    Lekou, D.J.; Bacharoudis, K. C.; Farinas, A. B.;


    , the material properties of the constitutive layers and the aero-elastic loads formed the base by which global and local blade stiffness and strength are evaluated and compared. Static, modal, buckling and fatigue analysis of the blade were performed by each partner using their own tools; fully in...

  10. Wind Turbine Blade Design

    Richard J. Crossley


    Full Text Available A detailed review of the current state-of-art for wind turbine blade design is presented, including theoretical maximum efficiency, propulsion, practical efficiency, HAWT blade design, and blade loads. The review provides a complete picture of wind turbine blade design and shows the dominance of modern turbines almost exclusive use of horizontal axis rotors. The aerodynamic design principles for a modern wind turbine blade are detailed, including blade plan shape/quantity, aerofoil selection and optimal attack angles. A detailed review of design loads on wind turbine blades is offered, describing aerodynamic, gravitational, centrifugal, gyroscopic and operational conditions.

  11. Comprehensive Forced Response Analysis of J2X Turbine Bladed-Discs with 360 Degree Variation in CFD Loading

    Elrod, David; Christensen, Eric; Brown, Andrew


    The temporal frequency content of the dynamic pressure predicted by a 360 degree computational fluid dynamics (CFD) analysis of a turbine flow field provides indicators of forcing function excitation frequencies (e.g., multiples of blade pass frequency) for turbine components. For the Pratt and Whitney Rocketdyne J-2X engine turbopumps, Campbell diagrams generated using these forcing function frequencies and the results of NASTRAN modal analyses show a number of components with modes in the engine operating range. As a consequence, forced response and static analyses are required for the prediction of combined stress, high cycle fatigue safety factors (HCFSF). Cyclically symmetric structural models have been used to analyze turbine vane and blade rows, not only in modal analyses, but also in forced response and static analyses. Due to the tortuous flow pattern in the turbine, dynamic pressure loading is not cyclically symmetric. Furthermore, CFD analyses predict dynamic pressure waves caused by adjacent and non-adjacent blade/vane rows upstream and downstream of the row analyzed. A MATLAB script has been written to calculate displacements due to the complex cyclically asymmetric dynamic pressure components predicted by CFD analysis, for all grids in a blade/vane row, at a chosen turbopump running speed. The MATLAB displacements are then read into NASTRAN, and dynamic stresses are calculated, including an adjustment for possible mistuning. In a cyclically symmetric NASTRAN static analysis, static stresses due to centrifugal, thermal, and pressure loading at the mode running speed are calculated. MATLAB is used to generate the HCFSF at each grid in the blade/vane row. When compared to an approach assuming cyclic symmetry in the dynamic flow field, the current approach provides better assurance that the worst case safety factor has been identified. An extended example for a J-2X turbopump component is provided.

  12. Direct Embedding of Fiber-Optical Load Sensors into Wind Turbine Blades

    Glavind, Lars; Buggy, Stephen; Olesen, Ib S.;

    Long Period Gratings were embedded into the adhesive utilized in the matrix of a wind turbine blade. The LPGs were subsequently subjected to temperature-testing in order to assess their performance, which illustrates good embedding capabilities.......Long Period Gratings were embedded into the adhesive utilized in the matrix of a wind turbine blade. The LPGs were subsequently subjected to temperature-testing in order to assess their performance, which illustrates good embedding capabilities....

  13. Numerical investigation of optimal yaw misalignment and collective pitch angle for load imbalance reduction of rigid and flexible HAWT blades under sheared inflow

    Wind shear can strongly influence the cyclic loading on horizontal axis wind turbine blades. These load fluctuation causes a variation of power output and introduces fatigue load. Thus, individual pitch controllers have been developed that are focused on the load alleviations, however, comes at a price of actuator requirements for control. Moreover, these controllers are unable to apply to already existing wind turbines with active yaw and collective pitch control system. Therefore, the investigations for minimizing load imbalance through the adjustments of yaw misalignment and collective pitch angle are implemented for the rigid and flexible blades under the sheared inflow. By applying the optimization process based on a sequential quadratic programming approach, the optimal yaw and pitch angle can be estimated. Then, the numerical simulations for predicting the performance are performed. The results showed that the fluctuation range of the root flapwise bending moment for the rigid blades can be reduced by 84.5%, whereas the vibratory bending moment for the flexible blades can be reduced by up to approximately 82.4% in the best case. Therefore, the magnitudes of load imbalance can be minimized by the adjustment of the optimal yaw misalignment and collective pitch angle without any power loss. - Highlights: • We propose a novel method for the reduction of load imbalance under sheared inflow. • We estimate optimal yaw misalignment and collective pitch angle through optimization. • Numerical results of performance are predicted for rigid and flexible blades. • By applying optimal angles, load variations are reduced without any power loss

  14. Exit blade geometry and part-load performance of small axial flow propeller turbines: An experimental investigation

    Singh, Punit; Nestmann, Franz [Institute for Water and River Basin Management (IWG), University of Karlsruhe, Kaiser Str. 12, D 76128 Karlsruhe (Germany)


    A detailed experimental investigation of the effects of exit blade geometry on the part-load performance of low-head, axial flow propeller turbines is presented. Even as these turbines find important applications in small-scale energy generation using micro-hydro, the relationship between the layout of blade profile, geometry and turbine performance continues to be poorly characterized. The experimental results presented here help understand the relationship between exit tip angle, discharge through the turbine, shaft power, and efficiency. The modification was implemented on two different propeller runners and it was found that the power and efficiency gains from decreasing the exit tip angle could be explained by a theoretical model presented here based on classical theory of turbomachines. In particular, the focus is on the behaviour of internal parameters like the runner loss coefficient, relative flow angle at exit, mean axial flow velocity and net tangential flow velocity. The study concluded that the effects of exit tip modification were significant. The introspective discussion on the theoretical model's limitation and test facility suggests wider and continued experimentation pertaining to the internal parameters like inlet vortex profile and exit swirl profile. It also recommends thorough validation of the model and its improvement so that it can be made capable for accurate characterization of blade geometric effects. (author)

  15. FE Modeling of Blade Couple with Friction Contacts under Dynamic Loading

    Pešek, Luděk; Půst, Ladislav; Vaněk, František; Veselý, Jan

    Guanajuato : IFToMM, 2011, s. 1-8. [World Congress in Mechanism and Machine Science /13/. Guanajuato (MX), 19.06.2011-23.06.2011] R&D Projects: GA ČR GA101/09/1166 Institutional research plan: CEZ:AV0Z20760514 Keywords : blade wheel * dynamics * contact problem * friction Subject RIV: BI - Acoustics

  16. FE Modeling of Blade Couple with Friction Contacts Under Dynamic Loading

    Pešek, Luděk; Půst, Ladislav; Vaněk, František; Veselý, Jan


    Roč. 2, č. 3 (2014), s. 229-238. ISSN 2321-3558 R&D Projects: GA ČR GA101/09/1166 Institutional support: RVO:61388998 Keywords : turbine blades * dry friction * damping Subject RIV: BI - Acoustics

  17. Measurement of the tower wake of the Swedish prototype Wind Energy Conversion System (WECS) Maglarp (Sweden) and calculations of its effect on noise and blade loading

    Barman, K.; Dahlberg, J. A.; Meijer, S.

    Hot-wire measurements of the velocity deficit in the wake behind the tower of a wind turbine are presented. The measurements were performed at one height and at three distances from the tower center when the turbine was not running. The low frequency noise caused by the passage of a turbine blade through the wake of the tower is calculated using wake data from the measurements. A comparision with noise emission measurements is included. The variation in blade loading and turbine power output caused by the wake are also calculated. Results show that wake deficits can be of the same order of magnitude as the freestream velocity.

  18. Fatigue behaviour of fiberglass wind turbine blade material under variable amplitude loading

    Delft, D.R.V. Van; Winkel, G.D. de [Delft Univ. of Technology, STEVIN Lab., Delft (Netherlands); Joosse, P.A. [Stork Product Engineering b.v., Amsterdam (Netherlands)


    In the work presented here fatigue tests with the WISPER and WISPERX load sequence have been carried out and analysed. The test programme includes tests at low stress levels which results in fatigue lives of 50 millions of cycles. The results are compared with constant amplitude tests in the very high cycle range, carried out in a previous programme. The results are also compared with ECN results in the lower cycle range (on identical specimens). It appeared, that the difference between the fatigue life of the specimens tested with the WISPER and the WISPERX load sequence is larger than can be expected from the theoretical damage rates. Moreover, the slope of the S-N data differs from theoretical values obtained by using commonly applied design rules. (au)

  19. Effect of bow-type initial imperfection on the buckling load and mass of graphite-epoxy blade-stiffened panels

    Stroud, W. J.; Anderson, M. S.; Hennessy, K. W.


    A structural synthesis computer code which accounts for first order effects of an initial bow and which can be used for sizing stiffened composite panels having an arbitrary cross section is used to study graphite blade-stiffened panels. The effect of a small initial bow on both the load carrying ability of panels and on the mass of panels designed to carry a specified load is examined. Large reductions in the buckling load caused by a small initial bow emphasize the need for considering a bow when a panel is designed.

  20. Helicopter rotor blade design for minimum vibration

    Taylor, R. B.


    The importance of blade design parameters in rotor vibratory response and the design of a minimum vibration blade based upon this understanding are examined. Various design approaches are examined for a 4 bladed articulated rotor operating at a high speed flight condition. Blade modal shaping, frequency placement, structural and aerodynamic coupling, and intermodal cancellation are investigated to systematically identify and evaluate blade design parameters that influence blade airloads, blade modal response, hub loads, and fuselage vibration. The relative contributions of the various components of blade force excitation and response to the vibratory hub loads transmitted to the fuselage are determined in order to isolate primary candidates for vibration alleviation. A blade design is achieved which reduces the predicted fuselage vibration from the baseline blade by approximately one half. Blade designs are developed that offer significant reductions in vibration (and fatigue stresses) without resorting to special vibration alleviation devices, radical blade geometries, or weight penalties.

  1. Pultrusion of a vertical axis wind turbine blade part-II: combining the manufacturing process simulation with a subsequent loading scenario

    Baran, Ismet; Hattel, Jesper Henri; Tutum, Cem Celal;


    modulus is implemented by employing the cure hardening instantaneous linear elastic (CHILE) model in the process simulation. The subsequent bent-in place simulation of the pultruded blade profile is performed taking the residual stresses into account. The integrated numerical simulation tool predicts the......This paper in particular deals with the integrated modeling of a pultruded NACA0018 blade profile being a part of EU funded DeepWind project. The manufacturing aspects of the pultrusion process are associated with the preliminary subsequent service loading scenario. A 3D thermochemical analysis of...... the pultrusion process is sequentially coupled with a 2D quasi-static mechanical analysis in which the process induced residual stresses and distortions are predicted using the generalized plane stain elements in a commercial finite element software ABAQUS. The temperature- and cure-dependent resin...

  2. Comparison of the lifting-line free vortex wake method and the blade-element-momentum theory regarding the simulated loads of multi-MW wind turbines

    Design load simulations for wind turbines are traditionally based on the blade- element-momentum theory (BEM). The BEM approach is derived from a simplified representation of the rotor aerodynamics and several semi-empirical correction models. A more sophisticated approach to account for the complex flow phenomena on wind turbine rotors can be found in the lifting-line free vortex wake method. This approach is based on a more physics based representation, especially for global flow effects. This theory relies on empirical correction models only for the local flow effects, which are associated with the boundary layer of the rotor blades. In this paper the lifting-line free vortex wake method is compared to a state- of-the-art BEM formulation with regard to aerodynamic and aeroelastic load simulations of the 5MW UpWind reference wind turbine. Different aerodynamic load situations as well as standardised design load cases that are sensitive to the aeroelastic modelling are evaluated in detail. This benchmark makes use of the AeroModule developed by ECN, which has been coupled to the multibody simulation code SIMPACK

  3. Study on testing method of mechanical load of blade root%一种叶根机械载荷测试方法的研究

    邢作霞; 薛田威; 张军阳


    A method to measure load of wind turbine blade is introduced. To overcome difficulties of load signals collection, foil strain gauge is introduced to measure the loads of wind turbine blade. The principle of strain gauge is described, the method of choosing gauges and determining measurement point are explained. Wheatstone bridge method is used in the measurement in this paper. The influencing factors are summarized and the methods to reduce interference are developed in the results of blade measurements so as to ensure the accuracy and the reliability of the results.%提出了一种风机叶片应变量的测量方法.在测量过程中,载荷信号的采集难度较大,一旦采集不准确,将直接影响到整个软件系统的分析结果.文章主要讨论了如何利用箔式应变片进行测量的相关问题,阐述了箔式应变片的选择方法以及测点位置的确定方法,介绍了应变片的工作原理,并将惠斯通电桥法引入到叶片载荷测试中.在不同叶片的测量结果的比较中,分析了测量结果的影响因素,并指出了减小测量干扰的方法,提高了测量结果的准确性、可靠性.

  4. Wide bandsaw blade under cutting conditions. Part I: Vibration of a plate moving in its plane while subjected to tangential edge loading

    Lengoc, L.; McCallion, H.


    The cutting span of a bandsaw blade is modelled as a moving plate and a simple, yet powerful, method is presented for analyzing its vibration when subjected to various in-plane stresses, including stresses due to tangential cutting forces. Time-independent tangential edge-loading couples modes of vibration and can lead to divergent buckling. The effects of transport velocity, "back-crowning" and "prestressing" on the vibration of a moving plate under tangential cutting forces are also investigated. Graphical representations of the modes of vibration are presented.

  5. Blade lock for a rotor disk and rotor blade assembly

    Moore, Jerry H. (Inventor)


    A rotor disk 18 and rotor blade 26 assembly is disclosed having a blade lock 66 which retains the rotor blade against axial movement in an axially extending blade retention slot 58. Various construction details are developed which shield the dead rim region D.sub.d and shift at least a portion of the loads associated with the locking device from the dead rim. In one detailed embodiment, a projection 68 from the live rim D.sub.1 of the disk 18 is adapted by slots 86 to receive blade locks 66.

  6. Snubber assembly for turbine blades

    Marra, John J


    A snubber associated with a rotatable turbine blade in a turbine engine, the turbine blade including a pressure sidewall and a suction sidewall opposed from the pressure wall. The snubber assembly includes a first snubber structure associated with the pressure sidewall of the turbine blade, a second snubber structure associated with the suction sidewall of the turbine blade, and a support structure. The support structure extends through the blade and is rigidly coupled at a first end portion thereof to the first snubber structure and at a second end portion thereof to the second snubber structure. Centrifugal loads exerted by the first and second snubber structures caused by rotation thereof during operation of the engine are at least partially transferred to the support structure, such that centrifugal loads exerted on the pressure and suctions sidewalls of the turbine blade by the first and second snubber structures are reduced.

  7. 载荷分布规律对混流泵叶轮设计的影响%Influences of blade loading distribution law on design of mixed-flow pump impeller

    常书平; 王永生; 靳栓宝; 苏永生


    Based on three-dimensional inverse design theory, the meridional gradient of circulation vur was adopted as control parameter of blade loading distributions. Two parabolic curves were proposed to describe blade loading distributions along meridional streamlines. In order to analyze influences of blade loading distributions on design of mixed-flow pump impellers, three impellers respectively with fore-loaded, mid-loaded and aft-loaded blade loading distributions were designed. Based on the RANS equations, SST turbulence model and multiple-reference-frame model, flow fields of the impellers were simulated and the impeller performances and blade surface pressure distributions were analyzed. The results show that it's practicable to apply two parabolic curves to describe blade loading distributions. Three-dimensional inverse design theory with adjustable blade loading distributions can effectively control pressure distributions on blade surfaces. As the location of blade loading peak approaches leading edges, impellers performances of head, power and efficiency all increase. At the design flow rate, differences of head, power and efficiency between fore-loaded impellers and aft-loaded impellers are 18.3% , 16.4% and 2.01% respectively. With different loading distributions, differences of three impeller performances are gradually obvious as flow rate increases.%基于三元反设计理论,将环量vur沿轴面流线的变化梯度作为载荷分布的控制参数,采用两段抛物线来描述载荷沿轴面流线的分布规律.为了分析载荷分布规律对混流泵叶轮设计结果的影响,建立了“前载型”、“中载型”和“后载型”3种混流泵叶轮.基于雷诺时均的Navier-Stokes方程、SST湍流模型和多参考坐标系模型对3种叶轮内流场进行数值模拟,对叶轮的能量性能和叶片表面压力分布进行分析.结果表明:采用两段抛物线表示载荷沿轴面流线的分布规律是合理的,基于载荷分布

  8. Rotor blade vortex interaction noise

    Yu, Yung H.


    Blade-vortex interaction noise-generated by helicopter main rotor blades is one of the most severe noise problems and is very important both in military applications and community acceptance of rotorcraft. Research over the decades has substantially improved physical understanding of noise-generating mechanisms, and various design concepts have been investigated to control noise radiation using advanced blade planform shapes and active blade control techniques. The important parameters to control rotor blade-vortex interaction noise and vibration have been identified: blade tip vortex structures and its trajectory, blade aeroelastic deformation, and airloads. Several blade tip design concepts have been investigated for diffusing tip vortices and also for reducing noise. However, these tip shapes have not been able to substantially reduce blade-vortex interaction noise without degradation of rotor performance. Meanwhile, blade root control techniques, such as higher-harmonic pitch control (HHC) and individual blade control (IBC) concepts, have been extensively investigated for noise and vibration reduction. The HHC technique has proved the substantial blade-vortex interaction noise reduction, up to 6 dB, while vibration and low-frequency noise have been increased. Tests with IBC techniques have shown the simultaneous reduction of rotor noise and vibratory loads with 2/rev pitch control inputs. Recently, active blade control concepts with smart structures have been investigated with the emphasis on active blade twist and trailing edge flap. Smart structures technologies are very promising, but further advancements are needed to meet all the requirements of rotorcraft applications in frequency, force, and displacement.

  9. 定向凝固涡轮叶片高温低周疲劳的破坏特点%Failure Characteristics of Directional Solidification Turbine Blade Under High Temperature Low Cycle Fatigue Load

    孙瑞杰; 闫晓军; 聂景旭


    针对几何形状完全相同但材料不同的两种涡轮叶片,采用相同的试验方法进行高温低周疲劳试验,普通铸造K403合金叶片和定向凝固DZ22B合金叶片却在不同的部位破坏,K403合金叶片在试验考核的榫齿部位断裂,而DZ22B合金叶片的榫齿在叶身根部断裂前均未出现裂纹.为了解释上述试验结果,展开了两类叶片试验条件应力场的有限元分析和定向凝同叶片晶粒形貌的数值模拟.研究结果表明:相同几何结构的普通铸造叶片和定向凝固叶片,其应力分布趋势相似,应力峰值均出现在叶片第一榫齿处;定向凝固叶片的失效模式与普通铸造叶片不同,其破坏不仅与应力场分布有关,而且受叶片各部位的晶粒形貌影响,叶片的失效不一定发生在应力最大的部位.%Under high temperature Iow cycle fatigue (LOF) loads, directional solidification (DS) turbine blades present quite different failure features as compared with equiaxed (EQ) turbine blades with identical geometry and similar stress distribution. All the EQ blade specimens fractured in the key section located at the serration part of the blade. However, this part of the DS blade specimens exhibited no microcrack before the fracture in the root of the blade body. Obviously, the damage characteristic of the DS blade is different from that of the conventional EQ blade, which fractures at the highest stress point. Further theoretical investigation indicates that grain structure of the DS blade has a significant impact on both the properties of the material and its subsequent load capacity. For the DS blade, the LCF damage is not only related to its stress field, but also affected by the microstructure of various parts.

  10. Low-Noise Rotorcraft Blades

    Brooks, Thomas F.


    Blades of helicopter rotors, tilt rotors, and like reshaped to reduce noise, according to proposal. Planform features combination of rearward and forward sweep. Forward sweep over large outer portion of blade constitutes primary noise-reduction feature. Relieves some of compressive effect in tip region, with consequent reduction of noise from compressive sources. Performance at high advance ratio improved. Cabin vibration and loading noise reduced by load-averaging effect of double-sweep planform. Aft-swept section provides balancing of aerodynamic and other dynamic forces on blade along 1/4-chord line of straight inboard section and along projection of line to outermost blade radius. Possible for hub-hinge forces and moments to remain within practical bounds. Provides stabilizing blade forces and moments to counteract any instability caused by forward sweep.

  11. Active Aerodynamic Blade Distributed Flap Control Design Procedure for Load Reduction on the UpWind 5MW Wind Turbine

    Wilson, D.G.; Resor, B.R.; Berg, D.E.; Barlas, T.K.; Van Kuik, G.A.M.


    This paper develops a system identification approach and procedure that is employed for distributed control system design for large wind turbine load reduction applications. The primary goal of the study is to identify the process that can be used with multiple sensor inputs of varying types (such a

  12. A Critical Evaluation of Structural Analysis Tools used for the Design of Large Composite Wind Turbine Rotor Blades under Ultimate and Cycle Loading

    Lekou, D.J.; Bacharoudis, K. C.; Farinas, A. B.; Branner, Kim; Berring, Peter; CROCE, A.; Philippidis, T.P.; De Winkel, G.D.


    Rotor blades for 10-20MW wind turbines may exceed 120m. To meet the demanding requirements of the blade design, structural analysis tools have been developed individually and combined with commercial available ones by blade designers. Due to the various available codes, understanding and estimating the uncertainty introduced in the design calculations by using these tools is needed to allow assessment of the effectiveness of any future design modification. For quantifying the introduced uncer...

  13. Dynamic response of active twist rotor blades

    Cesnik, Carlos E. S.; Shin, Sang Joon; Wilbur, Matthew L.


    Dynamic characteristics of active twist rotor (ATR) blades are investigated analytically and experimentally in this paper. The ATR system is intended for vibration and potentially for noise reductions in helicopters through individual blade control. An aeroelastic model is developed to identify frequency response characteristics of the ATR blade with integral, generally anisotropic, strain actuators embedded in its composite construction. An ATR prototype blade was designed and manufactured to experimentally study the vibration reduction capabilities of such systems. Several bench and hover tests were conducted and those results are presented and discussed here. Selected results on sensitivity of the ATR system to collective setting (i.e. blade loading), blade rpm (i.e. centrifugal force and blade station velocity), and media density (i.e. altitude) are presented. They indicated that the twist actuation authority of the ATR blade is independent of the collective setting up to approximately 10P, and dependent on rotational speed and altitude near the torsional resonance frequency due to its dependency on the aerodynamic damping. The proposed model captures very well the physics and sensitivities to selected test parameters of the ATR system. The numerical result of the blade torsional loads show an average error of 20% in magnitude and virtually no difference in phase for the blade frequency response. Overall, the active blade model is in very good agreement with the experiments and can be used to analyze and design future active helicopter blade systems.

  14. Forces and Moments on Flat Plates of Small Aspect Ratio with Application to PV Wind Loads and Small Wind Turbine Blades

    Xavier Ortiz


    Full Text Available To improve knowledge of the wind loads on photovoltaic structures mounted on flat roofs at the high angles required in high latitudes, and to study starting flow on low aspect ratio wind turbine blades, a series of wind tunnel tests were undertaken. Thin flat plates of aspect ratios between 0.4 and 9.0 were mounted on a sensitive three-component instantaneous force and moment sensor. The Reynolds numbers varied from 6 × 104 to 2 × 105. Measurements were made for angles of attack between 0° and 90° both in the free stream and in wall proximity with increased turbulence and mean shear. The ratio of drag to lift closely follows the inverse tangent of the angle of incidence for virtually all measurements. This implies that the forces of interest are due largely to the instantaneous pressure distribution around the plate and are not significantly influenced by shear stresses. The instantaneous forces appear most complex for the smaller aspect ratios but the intensity of the normal force fluctuations is between 10% and 20% in the free-steam but can exceed 30% near the wall. As the wind tunnel floor is approached, the lift and drag reduce with increasing aspect ratio, and there is a reduction in the high frequency components of the forces. It is shown that the centre of pressure is closer to the centre of the plates than the quarter-chord position for nearly all cases.

  15. Structural Testing of the Blade Reliability Collaborative Effect of Defect Wind Turbine Blades

    Desmond, M. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Hughes, S. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Paquette, J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)


    Two 8.3-meter (m) wind turbine blades intentionally constructed with manufacturing flaws were tested to failure at the National Wind Technology Center (NWTC) at the National Renewable Energy Laboratory (NREL) south of Boulder, Colorado. Two blades were tested; one blade was manufactured with a fiberglass spar cap and the second blade was manufactured with a carbon fiber spar cap. Test loading primarily consisted of flap fatigue loading of the blades, with one quasi-static ultimate load case applied to the carbon fiber spar cap blade. Results of the test program were intended to provide the full-scale test data needed for validation of model and coupon test results of the effect of defects in wind turbine blade composite materials. Testing was part of the Blade Reliability Collaborative (BRC) led by Sandia National Laboratories (SNL). The BRC seeks to develop a deeper understanding of the causes of unexpected blade failures (Paquette 2012), and to develop methods to enable blades to survive to their expected operational lifetime. Recent work in the BRC includes examining and characterizing flaws and defects known to exist in wind turbine blades from manufacturing processes (Riddle et al. 2011). Recent results from reliability databases show that wind turbine rotor blades continue to be a leading contributor to turbine downtime (Paquette 2012).

  16. Preliminary blade design using integrated computer codes

    Ryan, Arve


    Loads on the root of a horizontal axis wind turbine (HAWT) rotor blade were analyzed. A design solution for the root area is presented. The loads on the blades are given by different load cases that are specified. To get a clear picture of the influence of different parameters, the whole blade is designed from scratch. This is only a preliminary design study and the blade should not be looked upon as a construction reference. The use of computer programs for the design and optimization is extensive. After the external geometry is set and the aerodynamic loads calculated, parameters like design stresses and laminate thicknesses are run through the available programs, and a blade design optimized on basis of facts and estimates used is shown.

  17. Forward sweep, low noise rotor blade

    Brooks, Thomas F. (Inventor)


    A forward-swept, low-noise rotor blade includes an inboard section, an aft-swept section and a forward-swept outboard section. The rotor blade reduces the noise of rotorcraft, including both standard helicopters and advanced systems such as tiltrotors. The primary noise reduction feature is the forward sweep of the planform over a large portion of the outer blade radius. The rotor blade also includes an aft-swept section. The purpose of the aft-swept region is to provide a partial balance to pitching moments produced by the outboard forward-swept portion of the blade. The rotor blade has a constant chord width; or has a chord width which decreases linearly along the entire blade span; or combines constant and decreasing chord widths, wherein the blade is of constant chord width from the blade root to a certain location on the rotor blade, then decreases linearly to the blade tip thereafter. The noise source showing maximum noise reduction is blade-vortex interaction (BVI) noise. Also reduced are thickness, noise, high speed impulsive noise, cabin vibration and loading noise.

  18. Simulation of Flexible Mechanisms in a Rotating Blade for Smart-Blade Applications

    Paternoster, A.R.A.; Loendersloot, R.; Boer; Akkerman, R.


    The active Gurney flap technology is investigated to improve the performance of rotorblades by allowing helicopter blades to further control the lift unbalance that rises at high speed and by damping vibration loads on the rotor hub. This technology needs validation by wind tunnel testing of a scaled model blade under rotational loading. An optimised geometry of a flexible actuation system has been designed to provide motion for the deployment of the Gurney flap for a Mach-scale model blade [...

  19. Optimal design of wind turbine blades equipped with flaps

    Wiratama, I. Kade; Maheri, Alireza


    As a result of the significant growth of wind turbines in size, blade load control has become the main challenge for large wind turbines. Many advanced techniques have been investigated aiming at developing control devices to ease blade loading. Amongst them, trailing edge flaps have been proven as effective devices for load alleviation. The present study aims at investigating the potential benefits of flaps in enhancing the energy capture capabilities rather than blade load alleviation. A so...

  20. Dynamic Response of Flexible Wind Turbine Blade

    Yu-qiao Zheng; Rong-zhen ZHAO; Hong liu


    Aiming at the non-stationary and stall flutter problems of wind turbine blade caused by transient load fluctuations, the dynamic properties of wind turbine were studied, the blade was simplify to a cantilever beam in case of the action of shear deformation and cross section rotating effect were considered in this analysis, equations of the blade were established based on D'Alemberts' principle and the principle of virtual displacement. The dynamic response of the wind turbine was solved by us...

  1. Optimization of the hydraulic pre formance of a centrifugal pump impeller based on the blade load distribution%基于叶片载荷分布的离心泵叶轮水力性能优化

    江伟; 李国君; 张新盛


    The load distribution of a blade is the key parameter of the 3-D inverse design method.In order to analyze the influence of the load distribution of blade on the hydraulic and cavitation performance of the impeller of centrifu-gal pump, the software CFX is used to simulate internal flow field of three impellers of centrifugal pump with different blade load distributions, i.e.impeller a, impeller b and impeller c.Analysis results showed that different blade load distributions have great influence on the hydraulic and cavitation performance of the centrifugal pump.The impeller has a better external characteristic performance and the maximum static pressure at the inlet of the suction face of blade.The impeller b has the best external characteristic performance, but the static pressure at the inlet of the suc-tion face of blade is the minimum.Therefore, under the conditions of considering both the impeller efficiency and cavitation performance of the impeller of centrifugal pump, the impeller has the optimum load distribution, i.e.the external characteristic and cavitation are the best.On the basis of the optimum load, the load distribution is optimized again and the load distribution of the impeller a-3 has better hydraulic and cavitation performance.The results provid-ed a reference for 3-D inverse design of impeller in a centrifugal pump.%载荷分布是三元反问题设计中的关键参数,为分析叶片载荷分布规律对离心泵叶轮水力性能和气蚀性能的影响,采用软件CFX对叶轮a、b和c 3种不同叶片载荷方式的离心泵叶轮内流场进行数值模拟。由分析结果可知:不同叶片载荷对离心泵叶轮外特性存在较大影响,外特性性能最好的是叶轮b,但其吸力面进口处静压值最小,外特性性能其次的为叶轮a,其吸力面进口处静压值最大,所以在兼顾离心泵叶轮效率与气蚀性能的条件下,优化出最佳载荷分布方式为叶轮a,即外特性和气蚀

  2. Investigation of guide blade vibrations induced by transient loads with flow indentations in the wake. DMS multistage axial compressor; Erfassen der Schwingungsanregung der Leitschaufeln bedingt durch die instationaere Beaufschlagung mit Nachlaufdellen. DMS Mehrstufiger Axialverdichter

    Theobald, K. [RWTH Aachen (Germany). Inst. fuer Strahlenantriebe und Turboarbeitsmaschinen; Michel, A. [MTU Aero Engines GmbH, Muenchen (Germany)


    For investigating 3D flow phenomena in turbomachinery, a 3.5-stage axial compressor with CDA blading was constructed at the Institute of Jet Propulsion Systems and Turbo-Engines, and vibrations in the guide blades were investigated on selected guide blades of all four guide wheels on which semiconductor straing gauges had been attached in positions calculated according to a NASTRAN calculation. The data provided by the strain gauges were recorded digitally. The harmonics of the rotor wheels were clearly identified as the main influencing factors of guide blade vibration. The effects of flow indentations in the wake was more pronounced than the effects of potential-theoretic flow effects. The vibration characteristics of the guide blades are first of all determined by the rotational speed of the compressor; the throttle state has hardly any effect. Within one guide blade row, differences in their intrinsic frequencies were observed. As the measuring system had not been calibrated, mechanical stress in the strain gauges and material stress in the blades were estimated only, using the known basic equations and assuming worst case. The estimates showed that the values are safely below the limiting load. (orig.) [German] Zur Untersuchung der dreidimensionalen Stroemungsvorgaenge in Turbomaschinen wurde am Institut fuer Strahlantriebe und Turboarbeitsmaschinen ein 3,5 stufiger Axialverdichter mit CDA-Beschaufelung aufgebaut. Anliegen des hier vorgestellten Kurzprojektes war die schwingungsmechanische Untersuchung der Leitschaufeln der Maschine. Dazu wurden ausgewaehlte Leitschaufeln aus allen vier Leitraedern mit Halbleiter-Dehnungsmessstreifen bestueckt. Die HL-DMS wurden an durch eine NASTRAN-Rechnung ermittelte Positionen auf die Schaufeln geklebt. Die gemessenen Spannungen der DMS wurden nach Verstaerkung mit einem digitalen Bandgeraet aufgezeichnet. Die Harmonischen der Laufraeder zeichneten sich klar als der Haupteinflussfaktor fuer die Schwingungen der

  3. A Two-Bladed Concept Wind Turbine

    Kim, Taeseong

    This article shows the potential for reducing extreme loads with an innovative design of wind turbine, a partial pitch two-bladed concept turbine. The most extreme conditions to test a turbine are considered to be stand-still combined with a grid failure in which the wind comes from all directions...... from 0 to 360 degrees. All aeroelastic load simulations are done by using the aeroelastic code HAWC2. From the load comparisons between the partial pitch two-bladed turbine and a conventional three-bladed turbine it is observed that the partial pitch two-bladed turbine can reduce the extreme tower...... bottom bending moment by approximately 33% compared to the three-bladed turbine....

  4. Load Measurements

    Kock, Carsten Weber; Vesth, Allan

    The report describes Load measurements carried out on a given wind turbine. The aim of the measurement program regarding the loads on the turbine is to verify the basic characteristics of the wind turbine and loads on the blades, the rotor and the tower, using [Ref 1], [Ref2] and [Ref 3]. Regarding...

  5. Development of smart blade technology - trailing edge flaps

    Aagaard Madsen, Helge


    With blade lengths presently up to 80+ m there is a need for a supplement to the standard pitch system for control of power and loads. Distributed load control along the blade span with trailing edge flaps is a promising concept where numerical simulations have shown considerable load alleviation...

  6. Advances in wind turbine blade design and materials

    well as the requirements and challenges for composite materials used in both current and future designs of wind turbine blades. Part one outlines the challenges and developments in wind turbine blade design, including aerodynamic and aeroelastic design features, fatigue loads on wind turbine blades...... fatigue resistance of wind turbine blades. The final part of the book describes advances in wind turbine blade materials, development and testing, including biobased composites, surface protection and coatings, structural performance testing and the design, manufacture and testing of small wind turbine...... materials scientists and engineers, wind turbine blade manufacturers and maintenance technicians, scientists, researchers and academics....

  7. Rotor blade full-scale fatigue testing technology and research

    Nielsen, Per Hørlyk; Berring, Peter; Pavese, Christian; Branner, Kim

    Full scale fatigue test is an important part of the development and design of wind turbine blades. Testing is also needed for the approval of the blades in order for them to be used on large wind turbines. However, usually only one prototype blade is tested. Fatigue test of wind turbine blades was...... presented in this report giving the blade test facility operator a guide to choose the method that best fit the needs and economic constraints. The state of the art method is currently dual axis mass resonance, where the purpose of the test is to emulate the loads the blades encounter in operation....

  8. Design and Analysis of Composite Propeller Blade for Aircraft

    Madhusudhan BM; Dr P.V Srihari


    Fiber reinforced composites is used for twin blade propeller because of its high strength, low temperature applications. Fiber has to be oriented in the loading direction while designing the composite propeller blade. The blade geometry and design are more complex involving many controlling parameters. In the present work a methodology to design a composite propeller to analyze its strength and deformation using ANSYS software. The weight of the composite blade is reduced comp...

  9. 涡轮叶片复合疲劳特性曲线及其规律的试验%Experimental study on fatigue curve law of turbine blade under combined high and low cycle loading

    闫晓军; 孙瑞杰; 邓瑛; 刘芝娜; 聂景旭


    为了解高周振动载荷对于涡轮叶片高温疲劳性能的影响,对某型涡轮叶片进行高低周复合疲劳试验.试验结果表明,在低周载荷基础上叠加高频振动载荷,显著缩短了叶片的疲劳寿命;复合疲劳的分散性很大,且不存在疲劳极限,当叶片高周循环次数超过10^7时,继续试验叶片仍会发生断裂;在双对数坐标下,叶片的振动应力与其高周循环寿命成线性关系,即复合疲劳特性曲线(应力-寿命曲线、概率应力-寿命曲线)服从双对数线性规律,进一步研究发现该规律对于高温合金材料的复合疲劳特性曲线具有普遍性.%The effect of the high cycle vibration load on the high-temperature fatigue properties of the turbine blade were addressed. Combined high and low cycle fatigue tests were carried out on several blade specimens. The results show that the superposition of high-frequency vibration on low-cycle load can significantly reduce the fatigue life of the blade. It is noteworthy that combined high and low cycle fatigue has two features: great dispersion and no fatigue limit. The former is exhibited by much broader life range than the low cycle fatigue (LCF) test, and the latter indicated by fracture of the blades over 107 high cycles (which is considered as the life limit of the metal materials for the invariable-amplitude fatigue). In addition, the fatigue data suggest a double logarithmic linear relationship between vibration stress level and the combined fatigue life. Further research has found that the law for superalloys operates universally .

  10. Test evaluation of a laminated wood wind turbine blade concept

    Faddoul, J. R.


    A series of tests conducted on a root end section of a laminated wood wind turbine blade are reported. The blade to hub transition of the wood blade uses steel studs cast into the wood D spar with a filled epoxy. Both individual studs and a full scale, short length, root section were tested. Results indicate that the bonded stud concept is more than adequate for both the 30 year life fatigue loads and for the high wind or hurricane gust loads.

  11. Individual blade pitch for yaw control

    Individual pitch control (IPC) for reducing blade loads has been investigated and proven successful in recent literature. For IPC, the multi-blade co-ordinate (MBC) transformation is used to process the blade load signals from the rotating to a stationary frame of reference. In the stationary frame of reference, the yaw error of a turbine can be appended to generate IPC actions that are able to achieve turbine yaw control for a turbine in free yaw. In this paper, IPC for yaw control is tested on a high-fidelity numerical model of a commercially produced wind turbine in free yaw. The tests show that yaw control using IPC has the distinct advantage that the yaw system loads and support structure loading are substantially reduced. However, IPC for yaw control also shows a reduction in IPC blade load reduction potential and causes a slight increase in pitch activity. Thus, the key contribution of this paper is the concept demonstration of IPC for yaw control. Further, using IPC for yaw as a tuning parameter, it is shown how the best trade-off between blade loading, pitch activity and support structure loading can be achieved for wind turbine design

  12. Turbine blade cooling: the blade temperature distribution

    Horlock, J. [Cambridge University (United Kingdom). Whittle Laboratory; Torbidoni, L. [Ansaldo Energia, Genoa (Italy)


    Air cooling of high-temperature gas turbines is a standard practice; the air first cools the blading by internal convection and then by external film cooling, after ejection through holes and slots in the blade surface. In some 'conventional' analyses of turbine blade cooling, a 'standard blade' is invoked, which has a uniform blade temperature equal to the average temperature of the real blade, and estimates are made of the cooling flow required to hold the standard blade temperature to a limit set by material considerations. However, early analytical work by Ainley (for convective cooling of thin-walled blades) showed that both the coolant and blade temperatures should increase along the blade span. The current paper develops Ainley's original analysis to allow for finite blade wall thickness and thermal barrier coatings, film cooling, and variation in the mainstream gas temperature along the span. This new analysis should enable more accurate estimates to be made of cooling air flow requirements. (author)

  13. Wavy-Planform Helicopter Blades Make Less Noise

    Brooks, Thomas F.


    Wavy-planform rotor blades for helicopters have been investigated for the first time in an effort to reduce noise. Two of the main sources of helicopter noise are blade/vortex interaction (BVI) and volume displacement. (The noise contributed by volume displacement is termed thickness noise.) The reduction in noise generated by a wavyplanform blade, relative to that generated by an otherwise equivalent straight-planform blade, affects both main sources: (1) the BVI noise is reduced through smoothing and defocusing of the aerodynamic loading on the blade and (2) the thickness noise is reduced by reducing gradients of thickness with respect to listeners on the ground.

  14. Helicopter Rotor Blade With Free Tip

    Stroub, Robert H.; Young, Larry; Cawthorne, Matthew; Keys, Charles


    Free-tip rotor blades improve fuel efficiency and performance characteristics of helicopters. Outermost portion of blade pivots independently with respect to inboard portion about pitch axis parallel to blade axis, located forward of aerodynamic center. Centrifugal force acts on tension/torsion strap and biases tip nose-up. Airstream turns tip nose-down, other torques cause tip to "weathervane" to intermediate angular position resulting in net lift. Reduces fluctuations in lift, with two effects: flapwise vibratory loads on blade and vibratory loads on pitch-control mechanism reduced; negative lift produced by advancing fixed tip eliminated, reducing power required to achieve same overall lift. Applies to tilt rotors and tail rotors as well.

  15. Resonant vibration control of wind turbine blades

    Svendsen, Martin Nymann; Krenk, Steen; Høgsberg, Jan Becker


    The paper deals with introduction of damping to specific vibration modes of wind turbine blades, using a resonant controller with acceleration feedback. The wind turbine blade is represented by three-dimensional, two-node finite elements in a local, rotating frame of reference. The element....... The efficiency of the resonant controller is demonstrated for a representative turbine blade exposed to turbulent wind loading. It is found that the present explicit tuning procedure yields close to optimal tuning, with very limited modal spill-over and effective reduction of the vibration amplitudes....

  16. Growian rotor blades: Production development, construction and test

    Thiele, H. M.


    Development and construction of three 50 m rotor blades for a 3 MW wind turbine are described. A hybrid concept was chosen, i.e., a load carrying inflexible steel spar and a glass fiber reinforced plastic skin. A test blade was constructed and static loading tests, dynamic vibration tests and fatigue tests on critical welds as well as at the connection between spar and blade skin were performed. All test results show good accordance with calculated values, and were taken into consideration during the construction of two rotor blades.


    Baumann, K.


    A means is given of holding open-sided impeller blades in a turbo-rotor. Two half blades, with dovetail roots of sufficient weight to contain the center of gravity, are fitted into slots cut in the rotor so as to form the desired angle between the blade faces. The adjoining edges of the half blades are welded to form one solid blade that is securely locked an the rotor. This design permits the manufacture of a V shaped impeller blade without the need of machining the entire V shaped contour from a single blank, and furthermore provides excellent locking characteristics for attachment to the rotor.

  18. Effects of splitter blades on the flows and characteristics in centrifugal impellers

    Miyamoto, Hiroyuki; Nakashima, Yukitoshi; Ohba, Hideki


    A five-flow pressure probe was used to perform flow measurements in an unshrouded impeller and in a shrouded impeller with splitter blades. The effect of the splitter blade on passage flow and impeller performance was analyzed by comparing the results with those of impellers without splitter blades. It is found that, in impellers with splitter blades, the blade loadings tend to become smaller, and the absolute circumferential velocities and total pressures become considerably larger than those in impellers without splitter blades. It is noted that the splitter blade effect on static pressure differs between the unshrouded and shrouded impellers.

  19. Blade system design studies volume II : preliminary blade designs and recommended test matrix.

    Griffin, Dayton A. (Global Energy Concepts, LLC, Kirkland, WA)


    As part of the U.S. Department of Energy's Wind Partnerships for Advanced Component Technologies (WindPACT) program, Global Energy Concepts, LLC is performing a Blade System Design Study (BSDS) concerning innovations in materials, processes and structural configurations for application to wind turbine blades in the multi-megawatt range. The BSDS Volume I project report addresses issues and constraints identified to scaling conventional blade designs to the megawatt size range, and evaluated candidate materials, manufacturing and design innovations for overcoming and improving large blade economics. The current report (Volume II), presents additional discussion of materials and manufacturing issues for large blades, including a summary of current trends in commercial blade manufacturing. Specifications are then developed to guide the preliminary design of MW-scale blades. Using preliminary design calculations for a 3.0 MW blade, parametric analyses are performed to quantify the potential benefits in stiffness and decreased gravity loading by replacement of a baseline fiberglass spar with carbon-fiberglass hybrid material. Complete preliminary designs are then presented for 3.0 MW and 5.0 MW blades that incorporate fiberglass-to-carbon transitions at mid-span. Based on analysis of these designs, technical issues are identified and discussed. Finally, recommendations are made for composites testing under Part I1 of the BSDS, and the initial planned test matrix for that program is presented.

  20. Study on T-bolt and pin-loaded bearing strengths and damage accumulation in E-glass/epoxy blade applications

    Briggs, Alexander JE Ashworth; Zhang, Zhong; Dhakal, Hom Nath


    In this paper, the ultimate bearing strengths of pin-loaded double shear and T-bolt loaded connections were studied in thick composites, where the diameter of the pin equates to the thickness of the laminate. These bearing strengths were obtained for E-glass / Epoxy laminates of [(±45, 03)n ,±45], and a Vf of 54%. It is found that the values for ultimate bearing failure and first non-linearity of pin-loaded connections should be reduced by 25% and 38% respectively, when applied to T-Bolt conn...

  1. Innovative design approaches for large wind turbine blades : final report.


    The goal of the Blade System Design Study (BSDS) was investigation and evaluation of design and manufacturing issues for wind turbine blades in the one to ten megawatt size range. A series of analysis tasks were completed in support of the design effort. We began with a parametric scaling study to assess blade structure using current technology. This was followed by an economic study of the cost to manufacture, transport and install large blades. Subsequently we identified several innovative design approaches that showed potential for overcoming fundamental physical and manufacturing constraints. The final stage of the project was used to develop several preliminary 50m blade designs. The key design impacts identified in this study are: (1) blade cross-sections, (2) alternative materials, (3) IEC design class, and (4) root attachment. The results show that thick blade cross-sections can provide a large reduction in blade weight, while maintaining high aerodynamic performance. Increasing blade thickness for inboard sections is a key method for improving structural efficiency and reducing blade weight. Carbon/glass hybrid blades were found to provide good improvements in blade weight, stiffness, and deflection when used in the main structural elements of the blade. The addition of carbon resulted in modest cost increases and provided significant benefits, particularly with respect to deflection. The change in design loads between IEC classes is quite significant. Optimized blades should be designed for each IEC design class. A significant portion of blade weight is related to the root buildup and metal hardware for typical root attachment designs. The results show that increasing the number of blade fasteners has a positive effect on total weight, because it reduces the required root laminate thickness.

  2. Structural Analysis and Design of the Composite Wind Turbine Blade

    Wu, Wen-Hsiang; Young, Wen-Bin


    The wind turbine blade sustains various kinds of loadings during the operation and parking state. Due to the increasing size of the wind turbine blade, it is important to arrange the composite materials in a sufficient way to reach the optimal utilization of the material strength. Most of the composite blades are made of glass fibers composites while carbon fibers are also employed in recent years. Composite materials have the advantages of high specific strength and stress. This study develops a GUI interface to construct the blade model for the stress analysis using ANSYS. With the aid of visualization interface, the geometric model of the blade can be constructed by only a few data inputs. Based on the numerical stress analysis of the turbine blade, a simple iterative method was proposed to design the structure of the composite blade.

  3. Sweep-twist adaptive rotor blade : final project report.

    Ashwill, Thomas D.


    Knight & Carver was contracted by Sandia National Laboratories to develop a Sweep Twist Adaptive Rotor (STAR) blade that reduced operating loads, thereby allowing a larger, more productive rotor. The blade design used outer blade sweep to create twist coupling without angled fiber. Knight & Carver successfully designed, fabricated, tested and evaluated STAR prototype blades. Through laboratory and field tests, Knight & Carver showed the STAR blade met the engineering design criteria and economic goals for the program. A STAR prototype was successfully tested in Tehachapi during 2008 and a large data set was collected to support engineering and commercial development of the technology. This report documents the methodology used to develop the STAR blade design and reviews the approach used for laboratory and field testing. The effort demonstrated that STAR technology can provide significantly greater energy capture without higher operating loads on the turbine.

  4. Design optimization for active twist rotor blades

    Mok, Ji Won

    This dissertation introduces the process of optimizing active twist rotor blades in the presence of embedded anisotropic piezo-composite actuators. Optimum design of active twist blades is a complex task, since it involves a rich design space with tightly coupled design variables. The study presents the development of an optimization framework for active helicopter rotor blade cross-sectional design. This optimization framework allows for exploring a rich and highly nonlinear design space in order to optimize the active twist rotor blades. Different analytical components are combined in the framework: cross-sectional analysis (UM/VABS), an automated mesh generator, a beam solver (DYMORE), a three-dimensional local strain recovery module, and a gradient based optimizer within MATLAB. Through the mathematical optimization problem, the static twist actuation performance of a blade is maximized while satisfying a series of blade constraints. These constraints are associated with locations of the center of gravity and elastic axis, blade mass per unit span, fundamental rotating blade frequencies, and the blade strength based on local three-dimensional strain fields under worst loading conditions. Through pre-processing, limitations of the proposed process have been studied. When limitations were detected, resolution strategies were proposed. These include mesh overlapping, element distortion, trailing edge tab modeling, electrode modeling and foam implementation of the mesh generator, and the initial point sensibility of the current optimization scheme. Examples demonstrate the effectiveness of this process. Optimization studies were performed on the NASA/Army/MIT ATR blade case. Even though that design was built and shown significant impact in vibration reduction, the proposed optimization process showed that the design could be improved significantly. The second example, based on a model scale of the AH-64D Apache blade, emphasized the capability of this framework to

  5. Turbomachine blade reinforcement

    Garcia Crespo, Andres Jose


    Embodiments of the present disclosure include a system having a turbomachine blade segment including a blade and a mounting segment coupled to the blade, wherein the mounting segment has a plurality of reinforcement pins laterally extending at least partially through a neck of the mounting segment.

  6. Wind Turbine Blade


    The invention relates to a blade for a wind turbine, particularly to a blade that may be produced by an advanced manufacturing process for producing a blade with high quality structural components. Particularly, the structural components, which are preferably manufactured from fibre reinforced...

  7. Effects of diffuser blade geometry at leading edge on a highly-loaded centrifugal compressor%高负荷离心压气机扩压器叶片前缘结构分析

    王毅; 卢新根; 赵胜丰; 朱俊强


    为拓宽离心压气机稳定工作范围,以某高负荷离心压气机为研究对象,对径向扩压器叶片前缘进行盘侧开槽处理,借助数值模拟手段,探讨了开槽处理对离心压气机性能和稳定工作范围的影响,并对开槽结构进行了参数化研究,确定了主要开槽参数对离心压气机的影响.数值计算表明,径向扩压器前缘盘侧开槽能够在一定程度上提高离心压气机的稳定工作裕度,但同时伴随着压气机性能的降低.详细对比分析了开槽结构引人前后离心压气机内部流场结构,揭示了径向扩压器叶片前缘开槽提高离心压气机稳定工作裕度机理.%To extend the stable operating range of centrifugal compressor, a series of numerical simulations were performed for a highly - loaded centrifugal compressor with slotted radial diffuser blade at the bottom of leading edge, and the effects of slotted radial diffuser blade on performance and stable operating range of the centrifugal compressor were investigated in detail. In addition, parametric studies on slot depth and slot width were conducted in order to explore the key role parameters for optimum performance. The simulation results indicate that slotted radial diffuser blade at leading edge could extend the stable operating range, but slightly decrease the pressure ratio and efficiency. Detailed analysis of the flow visualization has exposed the different tip flow topologies between the cases with original radial diffuser and slotted radial diffuser, therefore led to some preliminary conclusions as to the flow physics involved in the stall margin improvements afforded by the use of slotted radial diffuser.

  8. Stress analysis and life prediction of gas turbine blade

    Hsiung, H. C.; Dunn, A. J.; Woodling, D. R.; Loh, D. L.


    A stress analysis procedure is presented for a redesign of the Space Shuttle Main Engine high pressure fuel turbopump turbine blades. The analysis consists of the one-dimensional scoping analysis to support the design layout and the follow-on three-dimensional finite element analysis to confirm the blade design at operating loading conditions. Blade life is evaluated based on high-cycle fatigue and low-cycle fatigue.

  9. Bistable devices for morphing rotor blades

    Johnson, Terrence

    This dissertation presents two bistable concepts for morphing rotor blades. These concepts are simple and are composed of bistable devices that act as coupling structures between an actuator and the rotor blade. Bistable or "snap-through" mechanisms have two stable equilibrium states and are a novel way to achieve large actuation output stroke at relatively modest effort for gross rotor morphing applications. This is because in addition to the large actuation stroke associated with the snap-through (relative to conventional actuator/ amplification systems) coming at relatively low actuation effort, no locking is required in either equilibrium state (since they are both stable). The first concept that is presented in this dissertation is a that is composed of a bistable twisting device that twists the tip of helicopter rotor blades. This work examines the performance of the presented bistable twisting device for rotor morphing, specifically, blade tip twist under an aerodynamic lift load. The device is analyzed using finite element analysis to predict its load carrying capability and bistable behavior. The second concept that is presented is a concept that is composed of a bistable arch for rotor blade chord extension. The bistable arch is coupled to a thin flat plate that is supported by rollers. Increasing the chord of the rotor blade is expected to generate more lift-load and improve helicopter performance. In this work, a methodology is presented to design the bistable arches for chord morphing using the finite element analysis and pseudo-rigid body model method. This work also examines the effect of different arches, arch hinge size and shape, inertial loads and rigidity on arch performance. Finally, this work shows results from an experiment that was conducted to validate the developed numerical model and demonstrates how the arch can be actuated using a Nitinol Shape Memory Alloy (SMA) wire to extend the chord of a helicopter rotor blade.

  10. Analysis of three-dimensional blading influence on highly loaded transonic fan stator%三维造型对高负荷跨声风扇静子的影响分析

    徐朋飞; 刘宝杰; 赵斌


    以负荷系数高达0.42的跨声风扇进口级为背景,利用三维数值模拟手段,研究了叶片三维气动造型技术对高负荷跨声风扇静子气动性能的影响,并深入地分析了其影响机理.结果表明:由于激波在静子叶根有垂直于轮毂端壁的趋势,因此前掠造型对于激波/端壁附面层所主导的静子角区分离的控制效果并不明显;相比之下,正弯静子通过加入叶片力使得角区中的低速流体向叶中发生径向迁移,显著地改善了静子的性能;而复合弯掠进一步提高了静子的性能,说明单纯使用前掠造型收效不佳,需要配合正弯造型才能达到最佳效果.%Under the background of highly loaded transonic inlet fan stage, which pro- duces loading coefficient of 0.42, three-dimensional (3-D) blading influence on transonic stator aerodynamic performance was analyzed as well as its mechanism with numerical simu lation technology. The result indicates that the forward sweep is not effective to control the corner separation conducted by shock/endwall boundary layer interaction because of the trend that the shock always tends to remain perpendicular to the endwall. Positive bow mod- ifies the stator performance obviously through adding the blade force to migrate the low speed corner fluid toward to mid-span. Sweep/bow composition improves the stator per- formance further, illustrating that the benefit from pure forward sweep is limited and for ward sweep can attain optimum effect when combining the positive bow.

  11. Blade by Blade Tip Clearance Measurement

    A. G. Sheard


    This paper describes a capacitance-based tip clearance measurement system which engineers have used in the most demanding turbine test applications. The capacitance probe has survived extended use in a major European gas turbine manufacturer's high-temperature demonstrator unit, where it functioned reliably at a turbine entry temperature in excess of 1800 degrees Kelvin. This paper explores blade by blade tip clearance measurement techniques and examines probe performance under laboratory con...

  12. Model Predictive Control of Trailing Edge Flaps on a wind turbine blade

    Castaignet, Damien; Poulsen, Niels Kjølstad; Buhl, Thomas; Wedel-Heinen, Jens Jakob

    blade root. The design model is based on a modal model of the blade structure and a steady state aerodynamic model of the blade airfoils. Depending on the output filter, loads within different frequency range are decreased. A fine tuning of the Kalman filter and of the cost function allows to decrease...

  13. Reliability analysis of rotor blades of tidal stream turbines

    Tidal stream turbines are used for converting kinetic energy of tidal currents into electricity. There are a number of uncertainties involved in the design of such devices and their components. To ensure safety of the turbines these uncertainties must be taken into account. The paper shows how this may be achieved for the design of rotor blades of horizontal-axis tidal stream turbines in the context of bending failure due to extreme loading. Initially, basic characteristics of such turbines in general and their blades in particular are briefly described. A probabilistic model of tidal current velocity fluctuations, which are the main source of load uncertainty, is then presented. This is followed by the description of reliability analysis of the blades, which takes into account uncertainties associated with tidal current speed, the blade resistance and the model used to calculate bending moments in the blades. Finally, the paper demonstrates how results of the reliability analysis can be applied to set values of the partial factors for the blade design. - Highlights: • A probabilistic model of the maximum of tidal current velocity fluctuations is proposed. • Reliability analysis of rotor blades of a tidal stream turbine is described. • Influence of pitch control system on the blade reliability is investigated. • Partial safety factors for the design of tidal turbine rotor blades are calibrated

  14. Rotor blade dynamic design

    Pritchard, Jocelyn I.; Adelman, Howard M.; Mantay, Wayne R.


    The rotor dynamic design considerations are essentially limitations on the vibratory response of the blades which in turn limit the dynamic excitation of the fuselage by forces and moments transmitted to the hub. Quantities which are associated with the blade response and which are subject to design constraints are discussed. These include blade frequencies, vertical and inplane hub shear, rolling and pitching moments, and aeroelastic stability margin.

  15. Design and Analysis of Composite Propeller Blade for Aircraft

    Madhusudhan BM


    Full Text Available Fiber reinforced composites is used for twin blade propeller because of its high strength, low temperature applications. Fiber has to be oriented in the loading direction while designing the composite propeller blade. The blade geometry and design are more complex involving many controlling parameters. In the present work a methodology to design a composite propeller to analyze its strength and deformation using ANSYS software. The weight of the composite blade is reduced compared to wooden blade by adopting the shell model. The present work is to carryout the static analysis of composite propeller which is a combination CFRP (Carbon Fiber Reinforced Plastics and epoxy resin materials. In order to evaluate the effectiveness of the composite blade over wooden stress analysis is performed on both the blades. To define the orientation and number of layers in the composite blade ANSYS classic software is used. From the results, the stresses of composite propeller obtained in static analysis are within the allowable stress limit. The deflection of the composite blade is less compared to the wooden blade.

  16. An investigation of the vibration characteristics of shrouded-bladed-disk rotor stages

    Chen, L.-T.; Dugundji, J.


    Coupled differential equations of motion are given for application to a rotating, pretwisted and heated beam under the effects of thermal stresses and gas bending loads. The circumferential modes of the multi-blade vibration of a bladed-disk rotor stage were studied. A finite element method was developed for the dynamic and static deformation analysis of the blade. The deformations of a bladed disk and a shrouded-bladed disk were studied by introducing a special bladed-disk element and a special shrouded-blade element. Some features of the vibration of part-span-shrouded, bladed-disk rotor stages are discussed. The static deformation, thermal stress and gas bending effects on the blade vibration were presented previously.

  17. Optimization Design and Experimental Study of Low-Pressure Axial Fan with Forward-Skewed Blades

    Li Yang


    Full Text Available This paper presents an experimental study of the optimization of blade skew in low pressure axial fan. Using back propagation (BP neural network and genetic algorithm (GA, the optimization was performed for a radial blade. An optimized blade is obtained through blade forward skew. Measurement of the two blades was carried out in aerodynamic and aeroacoustic performance. Compared to the radial blade, the optimized blade demonstrated improvements in efficiency, total pressure ratio, stable operating range, and aerodynamic noise. Detailed flow measurement was performed in outlet flow field for investigating the responsible flow mechanisms. The optimized blade can cause a spanwise redistribution of flow toward the blade midspan and reduce tip loading. This results in reduced significantly total pressure loss near hub and shroud endwall region, despite the slight increase of total pressure loss at midspan. In addition, the measured spectrums show that the broadband noise of the impeller is dominant.

  18. Application of Acoustic Emission Testing for the Assessment of Wind Turbine Blade

    Lee, Sang Il; Yun, Dong Jin; Hur, Yong Jin; Kim, Dong Jin [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)


    The purpose of this study was to verify the applicability of acoustic emission (AE) to detect damage in wind turbine blade. Nondestructive behavior of a GFRP wind turbine blade (WTB) was evaluated using AE analysis under stepwise cyclic loading. AE hits of the blade were correspondence with strain change within 80% of the maximum load. From the analysis of AE signals, the low energy signals due to electrical/mechanical noise were well distinguished from the signals of the blade delamination with higher amplitude or energy. When the AE test is performed with full blade test, AE will play an important role as a major nondestructive technique to assess damages of the WTB.

  19. Sandwich materials for wind turbine blades

    Thybo Thomsen, O. [Aalborg Univ., Dept. of Mechanical Engineering, Aalborg (Denmark)


    Wind turbine blades are being manufactured using polymer matrix composite materials (PMC), in a combination of monolithic (single skin) and sandwich composites. Present day designs are mainly based on glass fibre reinforced composites (GFRP), but for very large blades carbon fibre reinforced composites (CFRP) are being used increasingly, in addition to GFRP by several manufacturers to reduce the weight. The size of wind turbines have increased significantly over the last 25 years, and this trend is expected to continue in the future. Thus, it is anticipated that wind turbines with a rated power output in the range of 8-10 MW and a rotor diameter about 170-180 m will be developed and installed within the next 10-15 years. The paper presents an overview of current day design principles and materials technology applied for wind turbine blades, and it highlights the limitations and important design issues to be addressed for up-scaling of wind turbine blades from the current maximum length in excess of 61 m to blade lengths in the vicinity of 90 m as envisaged for future very large wind turbines. In particular, the paper discusses the potential advantages and challenges of applying sandwich type construction to a larger extent than is currently being practiced for the load carrying parts of wind turbine blades. (au)

  20. Aeroelastic stability predictions for a MW-sized blade

    Lobitz, Don W. [Sandia National Labs., Albuquerque, NM (United States)


    Classical aeroelastic flutter instability historically has not been a driving issue in wind turbine design. In fact, rarely has this issue even been addressed in the past. Commensurately, among the wind turbines that have been built, rarely has classical flutter ever been observed. However, with the advent of larger turbines fitted with relatively softer blades, classical flutter may become a more important design consideration. In addition, innovative blade designs involving the use of aeroelastic tailoring, wherein the blade twists as it bends under the action of aerodynamic loads to shed load resulting from wind turbulence, may increase the blade's proclivity for flutter. With these considerations in mind it is prudent to revisit aeroelastic stability issues for a MW-sized blade with and without aeroelastic tailoring. Focusing on aeroelastic stability associated with the shed wake from an individual blade turning in still air, the frequency domain technique developed by Theodorsen for predicting classical flutter in fixed wing aircraft has been adapted for use with a rotor blade. Results indicate that the predicted flutter speed of a MW-sized blade is slightly greater than twice the operational speed of the rotor. When a moderate amount of aeroelastic tailoring is added to the blade, a modest decrease (12%) in the flutter speed is predicted. By comparison, for a smaller rotor with relatively stiff blades the predicted flutter speed is approximately six times the operating speed. When frequently used approximations to Theodorsen's method are implemented, drastic underpredictions result, which, while conservative, may adversely impact blade design. These underpredictions are also evident when this MW-sized blade is analysed using time domain methods. (Author)

  1. Stall Flutter Control of a Smart Blade Section Undergoing Asymmetric Limit Oscillations

    Nailu Li; Balas, Mark J.; Pourya Nikoueeyan; Hua Yang; Naughton, Jonathan W.


    Stall flutter is an aeroelastic phenomenon resulting in unwanted oscillatory loads on the blade, such as wind turbine blade, helicopter rotor blade, and other flexible wing blades. Although the stall flutter and related aeroelastic control have been studied theoretically and experimentally, microtab control of asymmetric limit cycle oscillations (LCOs) in stall flutter cases has not been generally investigated. This paper presents an aeroservoelastic model to study the microtab control of the...

  2. Methods and apparatus for twist bend coupled (TCB) wind turbine blades

    Moroz, Emilian Mieczyslaw; LeMieux, David Lawrence; Pierce, Kirk Gee


    A method for controlling a wind turbine having twist bend coupled rotor blades on a rotor mechanically coupled to a generator includes determining a speed of a rotor blade tip of the wind turbine, measuring a current twist distribution and current blade loading, and adjusting a torque of a generator to change the speed of the rotor blade tip to thereby increase an energy capture power coefficient of the wind turbine.

  3. Multiple piece turbine rotor blade

    Jones, Russell B; Fedock, John A


    A multiple piece turbine rotor blade with a shell having an airfoil shape and secured between a spar and a platform with the spar including a tip end piece. a snap ring fits around the spar and abuts against the spar tip end piece on a top side and abuts against a shell on the bottom side so that the centrifugal loads from the shell is passed through the snap ring and into the spar and not through a tip cap dovetail slot and projection structure.

  4. Dynamic Response of Flexible Wind Turbine Blade

    Yu-qiao Zheng


    Full Text Available Aiming at the non-stationary and stall flutter problems of wind turbine blade caused by transient load fluctuations, the dynamic properties of wind turbine were studied, the blade was simplify to a cantilever beam in case of the action of shear deformation and cross section rotating effect were considered in this analysis, equations of the blade were established based on D'Alemberts' principle and the principle of virtual displacement. The dynamic response of the wind turbine was solved by using the finite element method under the transient load environment. A 29.2 m rotor blade, previously reported in specialized literature, was chosen as a case study to validate dynamic behaviour predicted by a Timoshenko beam model. It is concluded that despite its simplicity, The cross-sectional shear-deformation  has great influence on  dynamic response of the blade.Dynamic model is sufficiently accurate to serve as a design tool for the recursive analyses required during design and optimization stages of wind turbines using only readily available computational tools.

  5. Reliability of wind turbine blades: An overview of materials testing

    Holmes, John W.; Sørensen, Bent F.; Brøndsted, Povl


    when wind turbines are located in remote regions where the cost of inspections and repairs can be very high. From a structural viewpoint, wind turbine blades are subjected to very complex loading histories with coupled deformation modes. The long-term reliability of wind turbine blades requires an...... understanding of how damage develops in composite structures, composite materials and adhesives. Designing reliable wind turbine blades also requires the further development of laboratory scale and full scale test methods to evaluate the structural response and durability of new materials under various loading...

  6. Acoustic design of rotor blades using a genetic algorithm

    Wells, V. L.; Han, A. Y.; Crossley, W. A.


    A genetic algorithm coupled with a simplified acoustic analysis was used to generate low-noise rotor blade designs. The model includes thickness, steady loading and blade-vortex interaction noise estimates. The paper presents solutions for several variations in the fitness function, including thickness noise only, loading noise only, and combinations of the noise types. Preliminary results indicate that the analysis provides reasonable assessments of the noise produced, and that genetic algorithm successfully searches for 'good' designs. The results show that, for a given required thrust coefficient, proper blade design can noticeably reduce the noise produced at some expense to the power requirements.

  7. Aeroelastic tailoring in wind-turbine blade applications

    Veers, P.; Lobitz, D. [Sandia National Labs., Albuquerque, NM (United States); Bir, G. [National Renewable Energy Lab., Golden, CO (United States). National Wind Technology Center


    This paper reviews issues related to the use of aeroelastic tailoring as a cost-effective, passive means to shape the power curve and reduce loads. Wind turbine blades bend and twist during operation, effectively altering the angle of attack, which in turn affects loads and energy production. There are blades now in use that have significant aeroelastic couplings, either on purpose or because of flexible and light-weight designs. Since aeroelastic effects are almost unavoidable in flexible blade designs, it may be desirable to tailor these effects to the authors advantage. Efforts have been directed at adding flexible devices to a blade, or blade tip, to passively regulate power (or speed) in high winds. It is also possible to build a small amount of desirable twisting into the load response of a blade with proper asymmetric fiber lay up in the blade skin. (Such coupling is akin to distributed {delta}{sub 3} without mechanical hinges.) The tailored twisting can create an aeroelastic effect that has payoff in either better power production or in vibration alleviation, or both. Several research efforts have addressed different parts of this issue. Research and development in the use of aeroelastic tailoring on helicopter rotors is reviewed. Potential energy gains as a function of twist coupling are reviewed. The effects of such coupling on rotor stability have been studied and are presented here. The ability to design in twist coupling with either stretching or bending loads is examined also.

  8. Structural experiment of wind turbine blades; Fushayo blade no zairyo rikigakuteki jikken kenkyu

    Seki, K.; Shimizu, Y.; Kuroyanagi, H. [Tokai University, Tokyo (Japan)


    Aluminum, GFRP and composite of aluminum coated with carbon as structural materials for wind turbine blades were bending-tested, to improve blade bending stiffness, understand stress conditions at each position, and clarify structural dynamic strength by the bending-failure test. It is possible to estimate stress conditions at each position from the test results of displacement and strain at each load. The test results with GFRP are well explained qualitatively by the boundary theory, known as a theory for composite materials. The test gives reasonable material strength data, useful for designing wind turbines of high functions and safety. The results of the blade bending-failure test are in good agreement with the calculated structural blade strength. It is also found that GFRP is a good material of high structural strength for wind turbines. 8 refs., 6 tabs.

  9. Flutter control of incompressible flow turbomachine blade rows by splitter blades

    Splitter blades as a passive flutter control technique are investigated by developing a mathematical model to predict the stability of an aerodynamically loaded splittered-rotor operating in an incompressible flow field. The splitter blades, positioned circumferentially in the flow passage between two principal blades, introduce aerodynamic and/or combined aerodynamic-structural detuning into the rotor. The two-dimensional oscillating cascade unsteady aerodynamics, including steady loading effects, are determined by developing a complete first-order unsteady aerodynamic analysis together with an unsteady aerodynamic influence coefficient technique. The torsion mode flutter of both uniformly spaced tuned rotors and detuned rotors are predicted by incorporating the unsteady aerodynamic influence coefficients into a single-degree-of-freedom aeroelastic model. This model is then utilized to demonstrate that incorporating splitters into unstable rotor configurations results in stable splittered-rotor configurations. (orig.)

  10. Instability of a penetrating blade

    Bigoni, D.; Bosi, F.; Dal Corso, F.; Misseroni, D.


    Application of a dead compressive load at the free end of an elastic rod (the ‘blade') induces its penetration into a sliding sleeve ending with a linear elastic spring. Bifurcation and stability analysis of this simple elastic system shows a variety of unexpected behaviors: (i) an increase of buckling load at decreasing of elastic stiffness; (ii) a finite number of buckling loads for a system with infinite degrees of freedom (leading to a non-standard Sturm-Liouville problem); (iii) more than one bifurcation load associated to each bifurcation mode; (iv) a restabilization of the straight configuration after the second bifurcation load associated to the first instability mode; (v) the presence of an Eshelby-like (or configurational) force, deeply influencing stability. Only the first of these behaviors was previously known, the second and third ones disprove common beliefs, the fourth highlights a sort of ‘island of instability', and the last one shows surprising phenomena and effects on stability.

  11. Construction of low-cost, Mod-OA wood composite wind turbine blades

    Lark, R. F.


    Two sixty-foot, low-cost, wood composite blades for service on 200 kW Mod-OA wind turbines were constructed. The blades were constructed of epoxy resin-bonded Douglas fir veneers for the leading edge sections, and paper honeycombcored, birch plywood faced panels for the afterbody sections. The blades were joined to the wind turbine hub by epoxy resin-bonded steel load take-off studs embedded into the root end of the blades. The blades were installed on the 200 kW Mod-OA wind turbine facility at Kahuku, Hawaii, The blades completed nearly 8,000 hours of operation over an 18 month period at an average power of 150 kW prior to replacement with another set of wood composite blades. The blades were replaced because of a corrosion failure of the steel shank on one stud. Inspections showed that the wood composite structure remained in excellent condition.

  12. Swept Blade Aero-Elastic Model for a Small Wind Turbine (Presentation)

    Damiani, R.; Lee, S.; Larwood, S.


    A preprocessor for analyzing preswept wind turbines using the in-house aero-elastic tool coupled with a multibody dynamic simulator was developed. A baseline 10-kW small wind turbine with straight blades and various configurations that featured bend-torsion coupling via blade-tip sweep were investigated to study their impact on ultimate loads and fatigue damage equivalent loads.

  13. Mitigating the Long term Operating Extreme Load through Active Control

    Koukoura, Christina; Natarajan, Anand


    the blades. Through gain scheduling of the controller (modifications of the proportional Kp and the integral Ki gains) the extreme loads are mitigated, ensuring minimum instantaneous variations in the power production for operation above rated wind speed. The response of the blade load is examined for...... blade azimuth location are shown to affect the extreme blade load magnitude during operation in normal turbulence wind input. The simultaneously controlled operation of generator torque variation and pitch variation at low blade pitch angles is detected to be responsible for very high loads acting on...

  14. Wind-tunnel evaluation of an advanced main-rotor blade design for a utility-class helicopter

    Yeager, William T., Jr.; Mantay, Wayne R.; Wilbur, Matthew L.; Cramer, Robert G., Jr.; Singleton, Jeffrey D.


    An investigation was conducted in the Langley Transonic Dynamics Tunnel to evaluate differences between an existing utility-class main-rotor blade and an advanced-design main-rotor blade. The two rotor blade designs were compared with regard to rotor performance oscillatory pitch-link loads, and 4-per-rev vertical fixed-system loads. Tests were conducted in hover and over a range of simulated full-scale gross weights and density altitude conditions at advance ratios from 0.15 to 0.40. Results indicate that the advanced blade design offers performance improvements over the baseline blade in both hover and forward flight. Pitch-link oscillatory loads for the baseline rotor were more sensitive to the test conditions than those of the advanced rotor. The 4-per-rev vertical fixed-system load produced by the advanced blade was larger than that produced by the baseline blade at all test conditions.

  15. Simulation of Flexible Mechanisms in a Rotating Blade for Smart-Blade Applications

    Paternoster, A.R.A.; Loendersloot, R.; Boer, de A.; Akkerman, R.


    The active Gurney flap technology is investigated to improve the performance of rotorblades by allowing helicopter blades to further control the lift unbalance that rises at high speed and by damping vibration loads on the rotor hub. This technology needs validation by wind tunnel testing of a scale

  16. Blade attachment assembly

    Garcia-Crespo, Andres Jose; Delvaux, John McConnell; Miller, Diane Patricia


    An assembly and method for affixing a turbomachine rotor blade to a rotor wheel are disclosed. In an embodiment, an adaptor member is provided disposed between the blade and the rotor wheel, the adaptor member including an adaptor attachment slot that is complementary to the blade attachment member, and an adaptor attachment member that is complementary to the rotor wheel attachment slot. A coverplate is provided, having a coverplate attachment member that is complementary to the rotor wheel attachment slot, and a hook for engaging the adaptor member. When assembled, the coverplate member matingly engages with the adaptor member, and retains the blade in the adaptor member, and the assembly in the rotor wheel.

  17. Improving Bending Moment Measurements on Wind Turbine Blades

    Post, Nathan L.


    Full-scale fatigue testing of wind turbine blades is conducted using resonance test techniques where the blade plus additional masses is excited at its first resonance frequency to achieve the target loading amplitude. Because there is not a direct relationship between the force applied by an actuator and the bending moment, the blade is instrumented with strain gauges that are calibrated under static loading conditions to determine the sensitivity or relationship between strain and applied moment. Then, during dynamic loading the applied moment is calculated using the strain response of the structure. A similar procedure is also used in the field to measure in-service loads on turbine blades. Because wind turbine blades are complex twisted structures and the deflections are large, there is often significant cross-talk coupling in the sensitivity of strain gauges placed on the structure. Recent work has shown that a sensitivity matrix with nonzero cross terms must be employed to find constant results when a blade is subjected to both flap and lead-lag loading. However, even under controlled laboratory conditions, potential for errors of 3 percent or more in the measured moment exist when using the typical cross-talk matrix approach due to neglecting the influence of large deformations and torsion. This is particularly critical when considering a biaxial load as would be applied on the turbine or during a biaxial fatigue test. This presentation describes these results demonstrating errors made when performing current loads measurement practices on wind turbine blades in the lab and evaluating potential improvements using enhanced cross-talk matrix approaches and calibration procedures.

  18. Blade Testing Trends (Presentation)

    Desmond, M.


    As an invited guest speaker, Michael Desmond presented on NREL's NWTC structural testing methods and capabilities at the 2014 Sandia Blade Workshop held on August 26-28, 2014 in Albuquerque, NM. Although dynamometer and field testing capabilities were mentioned, the presentation focused primarily on wind turbine blade testing, including descriptions and capabilities for accredited certification testing, historical methodology and technology deployment, and current research and development activities.

  19. Structural characterization of rotor blades through photogrammetry

    Bernardini, Giovanni; Serafini, Jacopo; Enei, Claudio; Mattioni, Luca; Ficuciello, Corrado; Vezzari, Valerio


    This paper deals with the use of photogrammetry for the experimental identification of structural and inertial properties of helicopter rotor blades4. The identification procedure is based upon theoretical/numerical algorithms for the evaluation of mass and flexural stiffness distributions which are an extension of those proposed in the past by Larsen, whereas the torsional properties (stiffness and shear center position) are determined through the Euler–Bernoulli beam theory. The identification algorithms require the knowledge of the blade displacement field produced by known steady loads. These data are experimentally obtained through photogrammetric detection technique, which allows the identification of 3D coordinates of labeled points (markers) on the structure through the correlation of 2D digital photos. Indeed, the displacement field is simply evaluated by comparing the markers positions on the loaded configuration with those on the reference one. The proposed identification procedure, numerically and experimentally validated in the past by the authors, has been here applied to the structural characterization of two main rotor blades, designed for ultra-light helicopters. Strain gauges measurements have been used to assess the accuracy of the identified properties through natural frequencies comparison as well as to evaluate the blades damping characteristics.

  20. Control of LP Turbine Rotor Blade Underloading Using Stator Blade Compound Lean at Root



    Due to a large gradient of reaction,LP rotor blades remain underloaded at the root over some range of volumetric flow rates.An interesting design to control the flow through the root passage of the overloaded stator and underloaded moving blade row is compound lean at the root of stator blades.The paper describes results of numerical investigations from a 3D NS solver FlowER conducted for several configurations of stator blade compund lean.The computations are carried out for a wide range of volumetric flow rates.accounting for the nominal operating regime as well as low and high load.It is found that compund lean induces additional blade force.streamwise curature and redistribution of flow parameters in the stage,including pressure and mass flow rate spanwise that can improve the flow conditions in both the stator and the rotor.The obtained efficiency improvements depend greatly on the flow regime,with the highest gains in the region of low load.

  1. Design and evaluation of low-cost laminated wood composite blades for intermediate size wind turbines: Blade design, fabrication concept, and cost analysis

    Lieblein, S.; Gaugeon, M.; Thomas, G.; Zueck, M.


    As part of a program to reduce wind turbine costs, an evaluation was conducted of a laminated wood composite blade for the Mod-OA 200 kW wind turbine. The effort included the design and fabrication concept for the blade, together with cost and load analyses. The blade structure is composed of laminated Douglas fir veneers for the primary spar and nose sections, and honeycomb cored plywood panels for the trailing edges sections. The attachment of the wood blade to the rotor hub was through load takeoff studs bonded into the blade root. Tests were conducted on specimens of the key structural components to verify the feasibility of the concept. It is concluded that the proposed wood composite blade design and fabrication concept is suitable for Mod-OA size turbines (125-ft diameter rotor) at a cost that is very competitive with other methods of manufacture.

  2. Blade design and operating experience on the MOD-OA 200 kW wind turbine at Clayton, New Mexico

    Linscott, B. S.; Shaltens, R. K.


    Two 60 foot long aluminum wind turbine blades were operated for over 3000 hours on the MOD-OA wind turbine. The first signs of blade structural damage were observed after 400 hours of operation. Details of the blade design, loads, cost, structural damage, and repair are discussed.

  3. The SNL100-03 Blade: Design Studies with Flatback Airfoils for the Sandia 100-meter Blade.

    Griffith, Daniel; Richards, Phillip William


    A series of design studies were performed to inv estigate the effects of flatback airfoils on blade performance and weight for large blades using the Sandi a 100-meter blade designs as a starting point. As part of the study, the effects of varying the blade slenderness on blade structural performance was investigated. The advantages and disadvantages of blad e slenderness with respect to tip deflection, flap- wise & edge-wise fatigue resistance, panel buckling capacity, flutter speed, manufacturing labor content, blade total weight, and aerodynamic design load magn itude are quantified. Following these design studies, a final blade design (SNL100-03) was prod uced, which was based on a highly slender design using flatback airfoils. The SNL100-03 design with flatback airfoils has weight of 49 tons, which is about 16% decrease from its SNL100-02 predecessor that used conventional sharp trailing edge airfoils. Although not systematically optimized, the SNL100 -03 design study provides an assessment of and insight into the benefits of flatback airfoils for la rge blades as well as insights into the limits or negative consequences of high blade slenderness resulting from a highly slender SNL100-03 planform as was chosen in the final design definition. This docum ent also provides a description of the final SNL100-03 design definition and is intended to be a companion document to the distribution of the NuMAD blade model files for SNL100-03, which are made publicly available. A summary of the major findings of the Sandia 100-meter blade development program, from the initial SNL100-00 baseline blade through the fourth SNL100-03 blade study, is provided. This summary includes the major findings and outcomes of blade d esign studies, pathways to mitigate the identified large blade design drivers, and tool development that were produced over the course of this five-year research program. A summary of large blade tec hnology needs and research opportunities is also presented.

  4. Optical Measurements of Axial and Tangential Steady-State Blade Deflections Obtained Simultaneously

    Kurkov, Anatole P.; Dhadwal, Harbans S.


    Case-mounted fiber-optic sensors have been used by aircraft engine manufacturers mainly to monitor blade vibration in fans and compressors. The simplest probe arrangement is a spot probe where, typically, a center fiber transmits laser light, and the outer fibers collect the reflected light from the blade tips and transmit it to a photodetector. Because the spot of incident light is fixed in space, whereas the blade deflects dynamically, the reflected light will originate from slightly different portions of the blade tip under different operating conditions. Unless corrections are developed to compensate for this effect, some error in vibratory tangential amplitude will occur. For monitoring vibrations, this error is usually not critical. However, when steady-state blade deflections are being measured, it is very important to fix the spot on the blade tip at a particular location because the operating speed blade deflections are evaluated against a low-speed reference run. The change in speed usually implies a significant change in the blade orientation and possibly its shape brought about by the aerodynamic and centrifugal loading. It is most convenient to select the blade s leading and trailing edges as the fixed points for which deflections will be evaluated. To capture the blade edges at various speeds, the light probe must be movable. This was achieved by mounting the probe in an eccentric hole in a bushing that fit the fan case in the region that overlapped the path of the blade edge. The probe was actuated to search for a blade edge while all the blades were viewed on an oscilloscope. The blade edge was considered to be captured when a pulse associated with a particular blade was significantly reduced in magnitude but was clearly distinguishable from the background noise level. By tracing the axial position of either blade edge, one could extend the deflection measurement to two dimensions: axial and tangential. These blade deflection measurements were

  5. Effect of blade outlet angle on radial thrust of single-blade centrifugal pump

    Nishi, Y.; Fukutomi, J.; Fujiwara, R.


    Single-blade centrifugal pumps are widely used as sewage pumps. However, a large radial thrust acts on a single blade during pump operation because of the geometrical axial asymmetry of the impeller. This radial thrust causes vibrations of the pump shaft, reducing the service life of bearings and shaft seal devices. Therefore, to ensure pump reliability, it is necessary to quantitatively understand the radial thrust and clarify the behavior and generation mechanism. This study investigated the radial thrust acting on two kinds of single-blade centrifugal impellers having different blade outlet angles by experiments and computational fluid dynamics (CFD) analysis. Furthermore, the radial thrust was modeled by a combination of three components, inertia, momentum, and pressure, by applying an unsteady conservation of momentum to this impeller. As a result, the effects of the blade outlet angle on both the radial thrust and the modeled components were clarified. The total head of the impeller with a blade outlet angle of 16 degrees increases more than the impeller with a blade outlet angle of 8 degrees at a large flow rate. In this case, since the static pressure of the circumference of the impeller increases uniformly, the time-averaged value of the radial thrust of both impellers does not change at every flow rate. On the other hand, since the impeller blade loading becomes large, the fluctuation component of the radial thrust of the impeller with the blade outlet angle of 16 degrees increases. If the blade outlet angle increases, the fluctuation component of the inertia component will increase, but the time-averaged value of the inertia component is located near the origin despite changes in the flow rate. The fluctuation component of the momentum component becomes large at all flow rates. Furthermore, although the time-averaged value of the pressure component is almost constant, the fluctuation component of the pressure component becomes large at a large flow rate

  6. Life assessment of gas turbine blades after long term service

    Auerkari, Pertti; Salonen, Jorma [VTT, Espoo (Finland); Maekinen, Sari [Helsingin Energia, Helsinki (Finland); Karvonen, Ikka; Tanttari, Heikki [Lappeenrannan Laempoevoima, Lappeenranta (Finland); Kangas, Pekka [Neste Oil, Kilpilahti (Finland); Scholz, Alfred [Technische Univ. Darmstadt (Germany); Vacchieri, Erica [Ansaldo Richerche, Genoa (Italy)


    Turbine blade samples from three land based gas turbines have been subjected to systematic condition and life assessment after long term service (88000 - 109000 equivalent operating hours, eoh), when approaching the nominal or suggested life limits. The blades represent different machine types, materials and design generations, and uncooled blading outside the hottest front end of the turbine, i.e. blades with relatively large size and considerable expected life. For a reasonable assessment, a range of damage mechanisms need to be addressed and evaluated for the impact in the residual life. The results suggested significant additional safe life for all three blade sets. In some cases this could warrant yet another life cycle comparable to that of new blades, even after approaching the nominal end of life in terms of recommended equivalent operating hours. This is thought to be partly because of base load combined cycle operation and natural gas fuel, or modest operational loading if the design also accounted for more intensive cycling operation and more corrosive oil firing. In any case, long term life extension is only appropriate if not intervened by events of overloading, overheating or other sudden events such as foreign object damage (FOD), and if supported by the regular inspection and maintenance program to control in-service damage. Condition based assessment therefore remains an important part of the blade life management after the decision of accepted life extension. (orig.)

  7. Vibrational analyses of cracked pre-twisted blades

    Chen, L. W.; Jeng, C. H.


    A finite element model is utilized to analyze the vibrational behavior of a pre-twisted rotating blade with a single edge crack. This model can satisfy both geometric boundary conditions and natural boundary conditions of the blade. The effects of the transverse shear deformation, rotary inertia and the pre-twisted angle are taken into account. The influences of the crack location and the crack size on natural frequencies, buckling loads and dynamic instability regions are studied. It is found that a crack has great influences on these dynamic characteristics of the rotating blade.

  8. Ultimate strength of a large wind turbine blade

    Jensen, Find Mølholt; Stang, Henrik; Branner, Kim


    The present PhD project contains a study of the structural static strength of wind turbine blades loaded in flap-wise direction. A combination of experimental and numerical work has been used to address the most critical failure mechanisms and to get an understanding of the complex structural behaviour of wind turbine blades. Four failure mechanisms observed during the fullscale tests and the corresponding FE-analysis are presented. Elastic mechanisms associated with failure, such as buckling...

  9. Blade dynamic stress analysis of rotating bladed disks

    Kellner J.


    Full Text Available The paper deals with mathematical modelling of steady forced bladed disk vibrations and with dynamic stress calculation of the blades. The blades are considered as 1D kontinuum elastic coupled with three-dimensional elastic disk centrally clamped into rotor rotating with constant angular speed. The steady forced vibrations are generated by the aerodynamic forces acting along the blade length. By using modal synthesis method the mathematical model of the rotating bladed disk is condensed to calculate steady vibrations. Dynamic stress analysis of the blades is based on calculation of the time dependent reduced stress in blade cross-sections by using Hubert-Misses-Hencky stress hypothesis. The presented method is applied to real turbomachinery rotor with blades connected on the top with shroud.

  10. Deflection estimation of a wind turbine blade using FBG sensors embedded in the blade bonding line

    Estimating the deflection of flexible composite wind turbine blades is very important to prevent the blades from hitting the tower. Several researchers have used fiber Bragg grating (FBG) sensors—a type of optical fiber sensor (OFS)—to monitor the structural behavior of the blades. They can be installed on the surface and/or embedded in the interior of composites. However, the typical installation positions of OFSs present several problems, including delamination of sensing probes and a higher risk of fiber breakage during installation. In this study, we proposed using the bonding line between the shear web and spar cap as a new installation position of embedded OFSs for estimating the deflection of the blades. Laboratory coupon tests were undertaken preliminarily to confirm the strain measuring capability of embedded FBG sensors in adhesive layers, and the obtained values were verified by comparison with results obtained by electrical strain gauges and finite element analysis. We performed static loading tests on a 100 kW composite wind turbine blade to evaluate its deflections using embedded FBG sensors positioned in the bonding line. The deflections were estimated by classical beam theory considering a rigid body rotation near the tip of the blade. The evaluated tip deflections closely matched those measured by a linear variable differential transformer. Therefore, we verified the capability of embedded FBG sensors for evaluating the deflections of wind turbine blades. In addition, we confirmed that the bonding line between the shear web and spar cap is a practical location to embed the FBG sensors. (paper)

  11. Non-linear ultimate strength and stability limit state analysis of a wind turbine blade

    Rosemeier, Malo; Berring, Peter; Branner, Kim


    According to the design codes for wind turbine blades, it is sufficient to evaluate the blade's limit states using solely a linear analysis. This study, however, shows the need of non-linear analyses in blade design. Therefore, a geometrically non-linear structural response of a 34 m blade under...... flap-wise loading has been compared with a linear response to determine the blade's resistance in the ultimate strength and stability limit states. The linear analysis revealed an unrealistic failure mechanism and failure mode. Further, it did not capture the highly non-linear response of the blade...... application of an imperfection. The more realistic non-linear approaches yielded more optimistic results than the mandatory linear bifurcation analysis. Consequently, the investigated blade designed after the lesser requirements was sufficient. Using the non-linear approaches, considering inter-fibre failure...


    LI Yang; LIU Jie; OUYANG Hua; DU Zhao-Hui


    This article presents the flow mechanism analysis and experimental study of a forward-skewed impeller and a radial impeller in low pressure axial fan. The forward-skewed blade was obtained by the optimization design of the radial blade and CFD technique. Measurement of the two blades was carried out in aerodynamic and aeroacoustic performance. Compared to the radial blade, the forward-skewed blade has demonstrated the improvements in efficiency, total pressure ratio, Stable Operating Range (SOR) and less aerodynamic noise. Detailed flow measurement and computation were performed for outlet flow field for investigating the responsible flow mechanisms. The results show the forward-skewed blade can cause a spanwise redistribution of flow toward the blade mid-span and reduce tip loading. This results in reduced significantly total pressure loss near hub and shroud endwall region, despite the slight increase of total pressure loss at mid-span.

  13. Particle swarm-based structural optimization of laminated composite hydrokinetic turbine blades

    Li, H.; Chandrashekhara, K.


    Composite blade manufacturing for hydrokinetic turbine application is quite complex and requires extensive optimization studies in terms of material selection, number of layers, stacking sequence, ply thickness and orientation. To avoid a repetitive trial-and-error method process, hydrokinetic turbine blade structural optimization using particle swarm optimization was proposed to perform detailed composite lay-up optimization. Layer numbers, ply thickness and ply orientations were optimized using standard particle swarm optimization to minimize the weight of the composite blade while satisfying failure evaluation. To address the discrete combinatorial optimization problem of blade stacking sequence, a novel permutation discrete particle swarm optimization model was also developed to maximize the out-of-plane load-carrying capability of the composite blade. A composite blade design with significant material saving and satisfactory performance was presented. The proposed methodology offers an alternative and efficient design solution to composite structural optimization which involves complex loading and multiple discrete and combinatorial design parameters.

  14. Cooled snubber structure for turbine blades

    Mayer, Clinton A; Campbell, Christian X; Whalley, Andrew; Marra, John J


    A turbine blade assembly in a turbine engine. The turbine blade assembly includes a turbine blade and a first snubber structure. The turbine blade includes an internal cooling passage containing cooling air. The first snubber structure extends outwardly from a sidewall of the turbine blade and includes a hollow interior portion that receives cooling air from the internal cooling passage of the turbine blade.

  15. Blade System Design Studies Volume I: Composite Technologies for Large Wind Turbine Blades



    As part of the U.S. Department of Energy's Wind Partnerships for Advanced Component Technologies (WindPACT) program, Global Energy Concepts LLC (GEC) is performing a study concerning innovations in materials, processes and structural configurations for application to wind turbine blades in the multi-megawatt range. The project team for this work includes experts in all areas of wind turbine blade design, analysis, manufacture, and testing. Constraints to cost-effective scaling-up of the current commercial blade designs and manufacturing methods are identified, including self-gravity loads, transportation, and environmental considerations. A trade-off study is performed to evaluate the incremental changes in blade cost, weight, and stiffness for a wide range of composite materials, fabric types, and manufacturing processes. Fiberglass/carbon fiber hybrid blades are identified as having a promising combination of cost, weight, stiffness and fatigue resistance. Vacuum-assisted resin transfer molding, resin film infision, and pre-impregnated materials are identified as having benefits in reduced volatile emissions, higher fiber content, and improved laminate quality relative to the baseline wet lay-up process. Alternative structural designs are identified, including jointed configurations to facilitate transportation. Based on the results to date, recommendations are made for further evaluation and testing under this study to verify the predicted material and structural performance.

  16. Simulation of realistic rotor blade-vortex interactions using a finite-difference technique

    Hassan, Ahmed A.; Charles, Bruce D.


    A numerical finite-difference code has been used to predict helicopter blade loads during realistic self-generated three-dimensional blade-vortex interactions. The velocity field is determined via a nonlinear superposition of the rotor flowfield. Data obtained from a lifting-line helicopter/rotor trim code are used to determine the instantaneous position of the interaction vortex elements with respect to the blade. Data obtained for three rotor advance ratios show a reasonable correlation with wind tunnel data.

  17. Vibrations of blades bunches

    Půst, Ladislav; Pešek, Luděk

    Brno: Brno University of Technology, 2014 - (Fuis, V.), s. 520-523 ISBN 978-80-214-4871-1. ISSN 1805-8248. [Engineering Mechanics 2014 /20./. Svratka (CZ), 12.05.2014-15.05.2014] Institutional support: RVO:61388998 Keywords : damping * dry friction * five-blades-bunch * harmonic excitation * response curve Subject RIV: BI - Acoustics

  18. Database about blade faults

    Branner, Kim; Ghadirian, Amin

    This report deals with the importance of measuring the reliability of the rotor blades and describing how they can fail. The Challenge is that very little non-confidential data is available and that the quality and detail in the data is limited....

  19. In-flight rotorcraft blade elastic twist sensor

    A novel sensor network for measuring rotorcraft blade elastic twist in flight using an expansion of strain gage theory is proposed and demonstrated. The embedded sensor has negligible weight, small power draw, high bandwidth (≥100 kHz), works in the high centrifugal force environment of the rotating blade and does not disturb the blade airflow or structure. The sensor network can also be used to measure lead–lag and flap bending. The blade is idealized as an Euler–Bernoulli beam in bending and a rod in torsion. The theory is rigorously derived from first principles and shows that a sawtooth shaped sensor will measure twist directly without any numerical integration. The network is modeled computationally for a blade undergoing arbitrary torsional and bending moments. The model shows the twist sensor is not affected by arbitrary loading or noise or local structural discontinuities. The twist sensor is then embedded in a Mach scale rotor blade. The elastic twist measurement from the sensor exactly matched the actual twist angle on the benchtop for small (±0.08°), moderate (±0.3°) and large (±2.5°) elastic twist angles over a 4.6 in span (16% of total span). For the large twist deflections, the blade also had flap bending deflections of ±0.34 in (±7% of span). (paper)

  20. Optimization design of spar cap layup for wind turbine blade


    Based on the aerodynamic shape and structural form of the blade are fixed,a mathematical model of optimization design for wind turbine blade is established.The model is pursued with respect to minimum the blade mass to reduce the cost of wind turbine production.The material layup numbers of the spar cap are chosen as the design variables;while the demands of strength,stiffness and stability of the blade are employed as the constraint conditions.The optimization design for a 1.5 MW wind turbine blade is carried out by combing above objective and constraint conditions at the action of ultimate flapwise loads with the finite element software ANSYS.Compared with the original design,the optimization design result achieves a reduction of 7.2% of the blade mass,the stress and strain distribution of the blade is more reasonable,and there is no occurrence of resonance,therefore its effectiveness is verified.

  1. Strength Reliability Analysis of Turbine Blade Using Surrogate Models

    Wei Duan


    Full Text Available There are many stochastic parameters that have an effect on the reliability of steam turbine blades performance in practical operation. In order to improve the reliability of blade design, it is necessary to take these stochastic parameters into account. In this study, a variable cross-section twisted blade is investigated and geometrical parameters, material parameters and load parameters are considered as random variables. A reliability analysis method as a combination of a Finite Element Method (FEM, a surrogate model and Monte Carlo Simulation (MCS, is applied to solve the blade reliability analysis. Based on the blade finite element parametrical model and the experimental design, two kinds of surrogate models, Polynomial Response Surface (PRS and Artificial Neural Network (ANN, are applied to construct the approximation analytical expressions between the blade responses (including maximum stress and deflection and random input variables, which act as a surrogate of finite element solver to drastically reduce the number of simulations required. Then the surrogate is used for most of the samples needed in the Monte Carlo method and the statistical parameters and cumulative distribution functions of the maximum stress and deflection are obtained by Monte Carlo simulation. Finally, the probabilistic sensitivities analysis, which combines the magnitude of the gradient and the width of the scatter range of the random input variables, is applied to evaluate how much the maximum stress and deflection of the blade are influenced by the random nature of input parameters.

  2. Wind turbine blade tip comparison using CFD

    The effect of wind turbine blade tip geometry is numerically analysed using Computational Fluid Dynamics (CFD). Three different rotating blade tips are compared for attached flow conditions and the flow physics around the geometries are analysed. To this end, the pressure coefficient (Cp) is defined based on the stagnation pressure rather than on the inflow dynamic pressure. The tip geometry locally modifies the angles of attack (AOA) and the inflow dynamic pressure at each of the studied sections. However not all 3D effects could be reduced to a change of these two variables. An increase in loadings (particularly the normal force) towards the tip seem to be associated to a spanwise flow component present for the swept-back analysed tip. Integrated loads are ranked to asses wind turbine tip overall performance. It results from the comparison that a better tip shape that produced better torque to thrust ratios in both forces and moments is a geometry that has the end tip at the pitch axis. The work here presented shows that CFD may prove to be useful to complement 2D based methods on the design of new wind turbine blade tips

  3. Using Pretwist to Reduce Power Loss of Bend-Twist Coupled Blades

    Stäblein, Alexander; Tibaldi, Carlo; Hansen, Morten Hartvig


    Bend-twist coupling of wind turbine blades is known as a means to reduce the structural loads of the turbine. While the load reduction is desirable, bend-twist coupling also leads to a decrease in the annual energy production of the turbine. The reduction is mainly related to a no longer optimal...... twist distribution along the blade due to the coupling induced twist. Some of the power loss can be compensated by pretwisting the blade. This paper presents a pretwisting procedure for large blade deflections and investigates the effect of pretwisting on blade geometry, annual energy production, and...... fatigue load for the DTU 10 MW Reference Wind Turbine. The analysis was carried out by calculating the nonlinear steady state rotor deflection in an uniform inflow over the operational range of the turbine. The steady state power curve together with a Rayleigh wind speed distribution has been used to...

  4. BWR control blade replacement strategies

    The reactivity control elements in a BWR, the control blades, perform three significant functions: provide shutdown margin during normal and accident operating conditions; provide overall core reactivity control; and provide axial power shaping control. As such, the blades are exposed to the core's neutron flux, resulting in irradiation of blade structural and absorber materials. Since the absorber depletes with time (if B4C is used, it also swells) and the structural components undergo various degradation mechanisms (e.g., embrittlement, corrosion), the blades have limits on their operational lifetimes. Consequently, BWR utilities have implemented strategies that aim to maximize blade lifetimes while balancing operational costs, such as extending a refuelling outage to shuffle high exposure blades. This paper examines the blade replacement strategies used by BWR utilities operating in US, Europe and Asia by assembling information related to: the utility's specific blade replacement strategy; the impact the newer blade designs and changes in core operating mode were having on those strategies; the mechanical and nuclear limits that determined those strategies; the methods employed to ensure that lifetime limits were not exceeded during operation; and blade designs used (current and replacement blades). (author)

  5. Damage detection in turbine wind blades by vibration based methods

    Dolinski, L; Krawczuk, M, E-mail:, E-mail: mk@imp.gda.p [Gdansk University of Technology, Faculty of Electrical and Control Engineering, Narutowicza 11/12, 80-233 Gdansk (Poland)


    The paper describes results of numerical simulation for damage localization in the composite coat of a wind turbine blade using modal parameters and a modern damage detection method (wavelet transform). The presented results were obtained in the first period of research on the diagnostic method, which is aimed at detecting damage in the blades of large wind turbines during normal operation. A blade-modelling process including the geometry, loads and failures has been introduced in the paper. A series of simulations has been carried out for different localizations and size of damage for finding the method's limits. To verify the results of numeric simulations a subscale blade has been built which has geometric features and mechanical properties similar to the computer model.

  6. Comparison of damping treatments for gas turbine blades

    Gordon, Robert W.; Hollkamp, Joseph J.


    High frequency vibration of gas turbine fan blades is a high cycle fatigue concern. Friction damping devices are ineffective in suppressing high frequency vibration modes and external damping treatments are plagued by creep concerns. An alternative approach is to apply viscoelastic material internally in the blades. In this paper, an analytical comparison of internal damping treatments for fan blades is presented. The fan blade is modeled as a solid, flat, cantilevered titanium plate. Internal portions are removed producing cavities that are filled with viscoelastic material. Configurations with one, two, and three cavities are modeled using the modal strain energy method in conjunction with finite element analysis to estimate damping. Results show that appreciable damping levels for high frequency modes are possible with stiff viscoelastic material. Other design criteria are also considered. Results indicate that the hydrostatic load from the viscoelastic material on the cavity walls may be a concern.

  7. Structural Evaluation of Exo-Skeletal Engine Fan Blades

    Kuguoglu, Latife; Abumeri, Galib; Chamis, Christos C.


    The available computational simulation capability is used to demonstrate the structural viability of composite fan blades of innovative Exo-Skeletal Engine (ESE) developed at NASA Glenn Research Center for a subsonic mission. Full structural analysis and progressive damage evaluation of ESE composite fan blade is conducted through the NASA in-house computational simulation software system EST/BEST. The results of structural assessment indicate that longitudinal stresses acting on the blade are in compression. At a design speed of 2000 rpm, pressure and suction surface outer most ply stresses in longitudinal, transverse and shear direction are much lower than the corresponding composite ply strengths. Damage is initiated at 4870 rpm and blade fracture takes place at rotor speed of 7735 rpm. Damage volume is 51 percent. The progressive damage, buckling, stress and strength results indicate that the design at hand is very sound because of the factor of safety, damage tolerance, and buckling load of 6811 rpm.

  8. Interdependence of centrifugal compressor blade geometry and relative flow field

    Krain, H.


    The influence of the impeller blade geometry on the calculated relative flow field has been studied by means of an impeller design program available at DFVLR (Krain, 1984). Several geometrical parameters were varied, however, the meridional channel geometry was always kept constant. By this approach the blade wrap angle has been found to react significantly on the relative flow which is illustrated by comparing two designs with different wrap angles. Primarily in the hub/leading edge area a better boundary layer flow connected with a reduction of blade loading was obtained by increasing the wrap angle. But also in the shroud/pressure side area the increased blade looping attributed to an additional flow stabilization.

  9. Quiet Clean Short-haul Experimental Engine (QCSEE) under-the-wing engine composite fan blade design


    The design and analysis of a composite fan blade for the under the wing (UTW) QCSEE is presented. The blade is designed for a variable pitch, 18 bladed rotor and is constructed from a hybrid composite combination of materials consisting of Kevlar-49, type AS graphite, boron, and S-glass fibers in a PR288 epoxy resin matrix. The blade has an attached platform which is constructed of AS-graphite, PR288 epoxy resin matrix and aluminum honeycomb. The blade is designed to satisfy aerostability and cyclic life and strength requirements with a light weight construction. The attached platform is designed for a fail-safe condition in that it is retainable by the blade, under centrifugal force loading, even in the event of blade to platform bond separation. Details of the blade design and the results of stress, vibration, and impact analysis are included.

  10. Materials of large wind turbine blades: Recent results in testing and modeling

    Mishnaevsky, Leon; Brøndsted, Povl; Nijssen, Rogier;


    input data for advanced design of wind turbine blades were collected. For assessing the residual strength and stiffness of wind turbine blades subjected to irregular cyclic loads, a shell-based finite element numerical methodology was developed, taking into account the non-linear response of plies, and...

  11. New morphing blade section designs and structural solutions for smart blades

    Karakalas, Anargyros A.; Machairas, Theodore; Solomou, Alexandros;


    Within INNWIND.EU new concepts are investigated having the ultimate goal to reduce the cost per kilowatt-hour of the produced energy. With increasing size of wind turbines, new approaches to load control are required to reduce the stresses in blades. Experimental and numerical studies in the fields...... turbine system. As these efforts mature from an aeroelastic and control point of view, in order to get to the next stage of applying the solutions on wind turbine systems evaluation of the structural needs of the various proposed solutions and quantification of their potential is required. The report...... includes the efforts performed within Task 2.2 “Lightweight structural design” of INNWIND.Eu work-package WP2 “Lightweight Rotor” regarding the structural solutions necessary to accommodate the requirements of smart blades developed within work-package WP2 Task 2.3 “Active and passive loads control and...

  12. Fluid-structure interaction of a wind turbine blade employing a refined finite element model coupled with a blade-element momentum method

    Peeters, Mathijs; Van Paepegem, Wim


    Typically the aero-elastic simulation tools that are used in industry employ simple beam models to represent the blades of a wind turbine. The aerodynamic loads are usually calculated using a fast blade-element momentum (BEM) method. These models allow relatively fast calculation of the aero-elastic behavior of the blade which is required in order to allow the simulation of a large number of load cases as required by the IEC 61400 [1] and GL [2] standards in a feasible amount of time. Such b...

  13. Correlation of airloads on a two-bladed helicopter rotor

    Fernandez, Francisco J.; Johnson, Wayne


    Airloads measured on a two-bladed helicopter rotor in flight during the Ames' Tip Aerodynamic and Acoustic Test are compared with calculations from a comprehensive helicopter analysis (CAMRAD/JA), and the pressures compared with calculations from a full-potential rotor code (FPR). The flight-test results cover an advance ratio range of 0.19 to 0.38. The lowest-speed case is characterized by the presence of significant blade-vortex interactions. Good correlation of peak-to-peak vortex-induced loads and the corresponding pressures is obtained. Results of the correlation for this two-bladed rotor are substantially similar to those for three- and four-bladed rotors, including the tip-vortex core size for best correlation, calculation of the peak-to-peak loads on the retreating side, and calculation of vortex iduced loads on inboard radial stations. The higher-speed cases are characterized by the presence of transonic flow on the outboard sections of the blade. Comparison of calculated and measured airloads on the advancing side is not considered appropriate because the presence of shocks makes chordwise integration of the measured data difficult. However, good correlation of the corresponding pressures is obtained.

  14. Experimental Blade Research

    Eder, Martin Alexander; Branner, Kim; Berring, Peter;

    This report is a summary of the results obtained in the project: Experimental Blade Research – phase 2 (EBR2). The project was supported by the Danish Energy Authority through the 2010 Energy Technology Development and Demonstration Program (EUDP 2010-II) and has journal no. 64011-0006. The proje...... has been running from spring 2011 to the end of 2014. Being a summary report, this report only contains a collection of the research topics and the major results. For more details, see the publications listed at the end of this report.......This report is a summary of the results obtained in the project: Experimental Blade Research – phase 2 (EBR2). The project was supported by the Danish Energy Authority through the 2010 Energy Technology Development and Demonstration Program (EUDP 2010-II) and has journal no. 64011-0006. The project...

  15. Blade Vibration Measurement System

    Platt, Michael J.


    The Phase I project successfully demonstrated that an advanced noncontacting stress measurement system (NSMS) could improve classification of blade vibration response in terms of mistuning and closely spaced modes. The Phase II work confirmed the microwave sensor design process, modified the sensor so it is compatible as an upgrade to existing NSMS, and improved and finalized the NSMS software. The result will be stand-alone radar/tip timing radar signal conditioning for current conventional NSMS users (as an upgrade) and new users. The hybrid system will use frequency data and relative mode vibration levels from the radar sensor to provide substantially superior capabilities over current blade-vibration measurement technology. This frequency data, coupled with a reduced number of tip timing probes, will result in a system capable of detecting complex blade vibrations that would confound traditional NSMS systems. The hardware and software package was validated on a compressor rig at Mechanical Solutions, Inc. (MSI). Finally, the hybrid radar/tip timing NSMS software package and associated sensor hardware will be installed for use in the NASA Glenn spin pit test facility.

  16. Engineered wood wind turbine blades : final report : design project MECH 4020

    Beck, J.; Donaldson, M.; Mader, C.; Myatt, E.; Rent, J.; Sandler, A. [Group 8 (Canada)


    A project to redesign a wind turbine blade for manufacturing out of engineered wood was presented. The aim of the Aeolus Blades design project was to reduce typical manufacturing costs of $3000 for wind turbine blades to $1000 per blade using cheaper materials and less intensive manufacturing processes. The wooden blades were designed to meet the same design standards as typical wind turbine blades. The project also aimed to reduce startup costs for wind turbine applications in remote locations as well as for the residential sector. Baseline stiffness data were obtained through a series of benchmark tests on existing fiberglass and carbon fiber blades. Wooden billets were used to re-orient veneer planes and avoid interlaminar shear stress. The blades were produced from 2 machined billets. The wood blade was tested experimentally, and compared to the benchmark data and a series of finite element analyses (FEA). Results indicated that the laminated veneer lumber (LVL) was not stiff enough to support design wind pressure loads of up to 5000 Pa. Carbon fiber strips were inserted onto the outer surfaces of the blade. Results of further tests showed that overall stiffness compared to carbon fiber and fiberglass blades. Total tip deflection predicted by the FEA was within 1.5 per cent of the measured tests. The results of an economic analysis showed that the wood blades could be produced for approximately $1000 each in a 50-blade batch manufacturing run. It was concluded that engineered wood is a suitable material for wind turbine blades. 20 refs., 8 tabs., 75 figs.

  17. Bondlines – Online blade measurements (October 2012 and January 2013)

    McGugan, Malcolm; Chiesura, Gabriele

    Some local deformations in an operating Wind Turbine blade (V80) have been measured during October 2012. Displacement and load values generated between the trailing edge panels at blade radius R9.2m, R10,2m, and R11,2m were obtained. A fluctuating loading of between 100 - 200N existed when the tw...... for the on-site measurements. The data output is then summarised. The full data files will be used to improve models and sub-component testing of these structures, as well as the continuing development of the reinforcement approaches designed to prolong structural life....... edge displacement was re-measured (during January 2013) following a reinforcement of the blade to prevent trailing edge distortion. This trial showed that the new displacement values were below 1mm during similar operating conditions. This report describes the planning for and procurement of hardware...

  18. Ultimate strength of a large wind turbine blade

    Jensen, Find Mølholt


    behaviour of wind turbine blades. Four failure mechanisms observed during the fullscale tests and the corresponding FE-analysis are presented. Elastic mechanisms associated with failure, such as buckling, localized bending and the Brazier effect, are studied. In the thesis six different types of structural......The present PhD project contains a study of the structural static strength of wind turbine blades loaded in flap-wise direction. A combination of experimental and numerical work has been used to address the most critical failure mechanisms and to get an understanding of the complex structural...... reinforcements helping to prevent undesired structural elastic mechanisms are presented. The functionality of two of the suggested structural reinforcements was demonstrated in full-scale tests and the rest trough FE-studies. The blade design under investigation consisted of an aerodynamic airfoil and a load...

  19. OPTIMAT Blades. Reliable Optimal Use of Materials for Wind Turbine Rotor Blades. Final Report

    Janssen, L.G.J. [ECN Wind Energy, Petten (Netherlands); Van Wingerde, A.M.; Nijssen, R.P.L. [Knowledge Centre Wind Trubine Materials and Constructions, Delft (Netherlands); Philippidis, T.P. [University of Patras, Patras (Greece); Broendsted, P. [Risoe National Laboratory, Roskilde (Denmark); Dutton, A.G. [Council for the Central Laboratory of Research Councils CCLRC, Chilton, Didcot (United Kingdom); Kensche, C.W. [Deutsches Zentrum fuer Luft- und Raumfahrt, Berlin (Germany)


    As the required financial investments to achieve the expansion of the installed capacity of wind turbine grow, the economical pressure on reliable and structurally optimised blades, that are fit for their designed life, will increase. Very large blades may even become practically impossible without further knowledge of the material behaviour since the dominating loads on the material are caused by the blade mass. Therefore, a sound and accurate understanding of the structural behaviour of the material under all for wind turbine applications possible loading conditions is necessary. The project aims to provide accurate design recommendations for the optimised use of materials within wind turbine rotor blades and to achieve improved reliability. The major deliverable of the project will be improved design recommendations for the next generation of rotor blades. With the accurate and reliable design recommendations resulting from this project, reliable blades with optimised use of materials can be designed. The increased reliability and weight reduction of the blades will stimulate further the offshore exploitation with large capacity wind turbines. This supports the increase in wind energy and by that helps to reach the White Paper target of 40GW of installed power by 2010. The possible reduction of the material use will lower the impact on earth's resources and environment. The reduction can result from direct weight saving and from the increased reliability which prevents the need for replacements and waste of material. To execute the research activities a consortium was formed consisting of 10 research institutes from 7 EU countries; 5 wind turbine and/or blade manufactures from 3 EU countries; and the two leading certification bodies that carry out wind turbine certification throughout the world today. Over 3000 individual tests have been carried out on epoxy GFRP coupons, with numerous technical reports being issued to analyse and understand this data. The

  20. The Effect of Composite Flexures on Aeroelastic Stability of a Hingeless Rotor Blade

    Shi; Qinghua


    The effects of ply orientation angle of composite flexures on stability of hingeless rotor blade system are studied.The composite hingeless rotor blade system is simplified as a hub,a flap flexure and a lag flexure.pitch bearing and main blade.The kinematics formulations are inferred by employing the moderate deflection beam theory.The shear deformation and warping related to torsion are considered.The quasi-steady strip theory with dynamic inflow effects is applied to obtain the aerodynamic loads acting on the blade.Based on these.the set of finite element formulations of a hingeless rotor blade system is worked out.The numerical results show that the ply angle of the composite flexures has great effects on the aeroelastic stability of rotor blade.

  1. Investigation of Structural Behavior due to Bend-Twist Couplings in Wind Turbine Blades

    Fedorov, Vladimir; Dimitrov, Nikolay Krasimirov; Berggreen, Christian;


    One of the problematic issues concerning the design of future large composite wind turbine blades is the prediction of bend-twist couplings and torsion behaviour. The current work is a continuation of a previous work [1,2], and it examines different finite element modelling approaches for...... predicting the torsional response of the wind turbine blades with built-in bend-twist couplings. Additionally, a number of improved full-scale tests using an advanced bi-axial servo-hydraulic load control have been performed on a wind turbine blade section provided by Vestas Wind Systems A/S. In the present...... the blade cross section as the defining surface, off-setting the location of the shell elements according to the specified thickness. The experimental full-scale tests were carried out on an 8 m section of a 23 m wind turbine blade with specially implemented bend-twist coupling. The blade was tested...

  2. Experimental wind tunnel testing of linear individual pitch control for two-bladed wind turbines

    In this paper Linear Individual Pitch Control (LIPC) is applied to an experimental small-scale two-bladed wind turbine. LIPC is a recently introduced Individual Pitch Control (IPC) strategy specifically intended for two-bladed wind turbines. The LIPC approach is based on a linear coordinate transformation, with the special property that only two control loops are required to potentially reduce all periodic blade loads. In this study we apply LIPC to a control-oriented small-scale two-bladed wind turbine, equipped with, among others, two high- bandwidth servomotors to regulate the blade pitch angles and strain gauges to measure the blade moments. Experimental results are presented that indicate the effectiveness of LIPC

  3. Constructal blade shape in nanofluids

    Bai Chao; Wang Liqiu


    Abstract Blade configuration of nanofluids has been proven to perform much better than dispersed configuration for some heat conduction systems. The analytical analysis and numerical calculation are made for the cylinder--shaped and regular-rectangular-prism--shaped building blocks of the blade-configured heat conduction systems (using nanofluids as the heat conduction media) to find the optimal cross-sectional shape for the nanoparticle blade under the same composing materials, composition r...

  4. Unsteady potential flow past a propeller blade section

    Takallu, M. A.


    An analytical study was conducted to predict the effect of an oscillating stream on the time dependent sectional pressure and lift coefficients of a model propeller blade. The assumption is that as the blade sections encounter a wake, the actual angles of attack vary in a sinusoidal manner through the wake, thus each blade is exposed to an unsteady stream oscillating about a mean value at a certain reduced frequency. On the other hand, an isolated propeller at some angle of attack can experience periodic changes in the value of the flow angle causing unsteady loads on the blades. Such a flow condition requires the inclusion of new expressions in the formulation of the unsteady potential flow around the blade sections. These expressions account for time variation of angle of attack and total shed vortices in the wake of each airfoil section. It was found that the final expressions for the unsteady pressure distribution on each blade section are periodic and that the unsteady circulation and lift coefficients exhibit a hysteresis loop.

  5. Useful life consumption analysis of the blades of a gas turbine by thermofluency during constant load operation; Analisis de consumo de vida util por termofluencia en alabes de turbinas de gas durante operacion con carga constante

    Ortega Quiroz, Gerardo Daniel


    A new analytical model for creep life prediction of gas turbine blades is proposed. The ultimate tensile strength is included to reflect heat-to-heat variations in strength. A thermo mechanical analysis is made using the finite element method. With the stress distribution obtained, some creep life prediction models as the Norton-Bailey and Dorn-Bailey models were reviewed as well as the Larson-Miller parameter. The time to failure data obtained with the previous analysis, was used to determine the new creep life prediction model coefficients. The results obtained are in good concordance with experimental data for IN-738-LN gas turbine blades. [Spanish] En el presente trabajo se propone un nuevo modelo analitico para predecir la vida util por termofluencia en alabes de turbinas de gas, donde se incluye el esfuerzo ultimo de tension para reflejar el efecto que tiene la variacion de la temperatura en la rigidez del material. Para lograr esto, primero se hizo un analisis termomecanico del alabe, utilizando el metodo de elementos finitos. Con los esfuerzos obtenidos, se hizo una revision de los modelos de consumo de vida de Norton-Bailey y de Dorn-Bailey. Tambien se utilizo el parametro Larson-Miller para obtener datos de consumo de vida. Con los resultados de los analisis anteriores, fue posible determinar los coeficientes del modelo propuesto. Los resultados obtenidos estan en buena concordancia con los datos experimentales del alabe, y muestran un error menor que el de los modelos revisados.

  6. Structural response of fiber composite fan blades

    Chamis, C. C.; Minich, M. D.


    A fiber composite airfoil, typical for high-tip speed compressor applications, is subjected to load conditions anticipated to be encountered in such applications, and its structural response is theoretically investigated. The analysis method used consists of composite mechanics embedded in pre- and post-processors and coupled with NASTRAN. The load conditions examined include thermal due to aerodynamic heating, pressure due to aerodynamic forces, centrifugal, and combinations of these. The various responses investigated include root reactions due to various load conditions, average composite and ply stresses, ply delaminations, and the fundamental modes and the corresponding reactions. The results show that the thermal and pressure stresses are negligible compared to those caused by the centrifugal forces. Also, the core-shell concept for composite blades is an inefficient design (core plies not highly stressed) and appears to be sensitive to interply delaminations. The results are presented in graphical and tabular forms to illustrate the types and amount of data required for such an analysis, and to provide quantitative data of the various responses which can be helpful in designing such composite blades.

  7. Structural damage identification in wind turbine blades using piezoelectric active sensing with ultrasonic validation

    Claytor, Thomas N [Los Alamos National Laboratory; Ammerman, Curtt N [Los Alamos National Laboratory; Park, Gyu Hae [Los Alamos National Laboratory; Farinholt, Kevin M [Los Alamos National Laboratory; Farrar, Charles R [Los Alamos National Laboratory; Atterbury, Marie K [Los Alamos National Laboratory


    This paper gives a brief overview of a new project at LANL in structural damage identification for wind turbines. This project makes use of modeling capabilities and sensing technology to understand realistic blade loading on large turbine blades, with the goal of developing the technology needed to automatically detect early damage. Several structural health monitoring (SHM) techniques using piezoelectric active materials are being investigated for the development of wireless, low power sensors that interrogate sections of the wind turbine blade using Lamb wave propagation data, frequency response functions (FRFs), and time-series analysis methods. The modeling and sensor research will be compared with extensive experimental testing, including wind tunnel experiments, load and fatigue tests, and ultrasonic scans - on small- to mid-scale turbine blades. Furthermore, this study will investigate the effect of local damage on the global response of the blade by monitoring low-frequency response changes.

  8. Integral Twist Actuation of Helicopter Rotor Blades for Vibration Reduction

    Shin, SangJoon; Cesnik, Carlos E. S.


    Active integral twist control for vibration reduction of helicopter rotors during forward flight is investigated. The twist deformation is obtained using embedded anisotropic piezocomposite actuators. An analytical framework is developed to examine integrally-twisted blades and their aeroelastic response during different flight conditions: frequency domain analysis for hover, and time domain analysis for forward flight. Both stem from the same three-dimensional electroelastic beam formulation with geometrical-exactness, and axe coupled with a finite-state dynamic inflow aerodynamics model. A prototype Active Twist Rotor blade was designed with this framework using Active Fiber Composites as the actuator. The ATR prototype blade was successfully tested under non-rotating conditions. Hover testing was conducted to evaluate structural integrity and dynamic response. In both conditions, a very good correlation was obtained against the analysis. Finally, a four-bladed ATR system is built and tested to demonstrate its concept in forward flight. This experiment was conducted at NASA Langley Tansonic Dynamics Tunnel and represents the first-of-a-kind Mach-scaled fully-active-twist rotor system to undergo forward flight test. In parallel, the impact upon the fixed- and rotating-system loads is estimated by the analysis. While discrepancies are found in the amplitude of the loads under actuation, the predicted trend of load variation with respect to its control phase correlates well. It was also shown, both experimentally and numerically, that the ATR blade design has the potential for hub vibratory load reduction of up to 90% using individual blade control actuation. Using the numerical framework, system identification is performed to estimate the harmonic transfer functions. The linear time-periodic system can be represented by a linear time-invariant system under the three modes of blade actuation: collective, longitudinal cyclic, and lateral cyclic. A vibration

  9. Aeroelastic behavior of twist-coupled HAWT blades

    Lobitz, D.W.; Veers, P.S.


    As the technology for horizontal axis wind turbines (HAWT) development matures, more novel techniques are required for the capture of additional amounts of energy, alleviation of loads and control of the rotor. One such technique employs the use of an adaptive blade that could sense the wind velocity or rotational speed in some fashion and accordingly modify its aerodynamic configuration to meet a desired objective. This could be achieved in either an active or passive manner, although the passive approach is much more attractive due to its simplicity and economy. As an example, a blade design might employ coupling between bending and/or extension, and twisting so that, as it bends and extends due to the action of the aerodynamic and inertial loads, it also twists modifying the aerodynamic performance in some way. These performance modifications also have associated aeroelastic effects, including effects on aeroelastic instability. To address the scope and magnitude of these effects a tool has been developed for investigating classical flutter and divergence of HAWT blades. As a starting point, an adaptive version of the uniform Combined Experiment Blade will be investigated. Flutter and divergence airspeeds will be reported as a function of the strength of the coupling and also be compared to those of generic blade counterparts.

  10. Structural integrity design for an active helicopter rotor blade with piezoelectric flap actuators

    Lee, Jaehwan; Shin, SangJoon


    Helicopter uses a rotor system to generate lift, thrust and forces, and its aerodynamic environment is generally complex. Unsteady aerodynamic environment arises such as blade vortex interaction. This unsteady aerodynamic environment induces vibratory aerodynamic loads and high aeroacoustic noise. The aerodynamic load and aeroacoustic noise is at N times the rotor blade revolutions (N/rev). But conventional rotor control system composed of pitch links and swash plate is not capable of adjusting such vibratory loads because its control is restricted to 1/rev. Many active control methodologies have been examined to alleviate the problem. The blade using active control device manipulates the blade pitch angle with N/rev. In this paper, Active Trailing-edge Flap blade, which is one of the active control methods, is designed to reduce the unsteady aerodynamic loads. Active Trailing-edge Flap blade uses a trailing edge flap manipulated by an actuator to change camber line of the airfoil. Piezoelectric actuators are installed inside the blade to manipulate the trailing edge flap.

  11. Fretting Stresses in Single Crystal Superalloy Turbine Blade Attachments

    Arakere, Nagaraj K.; Swanson, Gregory


    Single crystal nickel base superalloy turbine blades are being utilized in rocket engine turbopumps and turbine engines because of their superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal nickel base turbine blade superalloys are PWA 1480/1493 and PWA 1484. These alloys play an important role in commercial, military and space propulsion systems. High Cycle Fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Blade attachment regions are prone to fretting fatigue failures. Single crystal nickel base superalloy turbine blades are especially prone to fretting damage because the subsurface shear stresses induced by fretting action at the attachment regions can result in crystallographic initiation and crack growth along octahedral planes. Furthermore, crystallographic crack growth on octahedral planes under fretting induced mixed mode loading can be an order of magnitude faster than under pure mode I loading. This paper presents contact stress evaluation in the attachment region for single crystal turbine blades used in the NASA alternate Advanced High Pressure Fuel Turbo Pump (HPFTP/AT) for the Space Shuttle Main Engine (SSME). Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. Blades and the attachment region are modeled using a large-scale 3D finite element (FE) model capable of accounting for contact friction, material orthotrophy, and variation in primary and secondary crystal orientation. Contact stress analysis in the blade attachment regions is presented as a function of coefficient of friction and primary and secondary crystal orientation, Stress results are used to discuss fretting fatigue failure analysis of SSME blades. Attachment stresses are seen to reach

  12. Structural Design of a Horizontal-Axis Tidal Current Turbine Composite Blade

    Bir, G. S.; Lawson, M. J.; Li, Y.


    This paper describes the structural design of a tidal composite blade. The structural design is preceded by two steps: hydrodynamic design and determination of extreme loads. The hydrodynamic design provides the chord and twist distributions along the blade length that result in optimal performance of the tidal turbine over its lifetime. The extreme loads, i.e. the extreme flap and edgewise loads that the blade would likely encounter over its lifetime, are associated with extreme tidal flow conditions and are obtained using a computational fluid dynamics (CFD) software. Given the blade external shape and the extreme loads, we use a laminate-theory-based structural design to determine the optimal layout of composite laminas such that the ultimate-strength and buckling-resistance criteria are satisfied at all points in the blade. The structural design approach allows for arbitrary specification of the chord, twist, and airfoil geometry along the blade and an arbitrary number of shear webs. In addition, certain fabrication criteria are imposed, for example, each composite laminate must be an integral multiple of its constituent ply thickness. In the present effort, the structural design uses only static extreme loads; dynamic-loads-based fatigue design will be addressed in the future. Following the blade design, we compute the distributed structural properties, i.e. flap stiffness, edgewise stiffness, torsion stiffness, mass, moments of inertia, elastic-axis offset, and center-of-mass offset along the blade. Such properties are required by hydro-elastic codes to model the tidal current turbine and to perform modal, stability, loads, and response analyses.

  13. SERI advanced wind turbine blades

    Tangler, J.; Smith, B.; Jager, D.


    The primary goal of the Solar Energy Research Institute's (SERI) advanced wind turbine blades is to convert the kinetic energy in the wind into mechanical energy in an inexpensive and efficient manner. To accomplish this goal, advanced wind turbine blades have been developed by SERI that utilize unique airfoil technology. Performance characteristics of the advanced blades were verified through atmospheric testing on fixed-pitch, stall-regulated horizontal-axis wind turbines (HAWTs). Of the various wind turbine configurations, the stall-regulated HAWT dominates the market because of its simplicity and low cost. Results of the atmospheric tests show that the SERI advanced blades produce 10 percent to 30 percent more energy than conventional blades.

  14. Design of centrifugal impeller blades

    Betz, A; Flugge-Lotz, I


    This paper restricts itself to radial impellers with cylindrical blades since, as Prasil has shown, the flow about an arbitrarily curved surface of revolution may be reduced to this normal form we have chosen by a relatively simple conformal transformation. This method starts from the simple hypotheses of the older centrifugal impeller theory by first assuming an impeller with an infinite number of blades. How the flow is then modified is then investigated. For the computation of flow for a finite number of blades, the approximation method as developed by Munk, Prandtl and Birnbaum, or Glauert is found suitable. The essential idea of this method is to replace the wing by a vortex sheet and compute the flow as the field of these vortices. The shape of the blades is then obtained from the condition that the flow must be along the surface of the blade.

  15. Experimental Investigation of the Influence of Local Flow Features on the Aerodynamic Damping of an Oscillating Blade Row

    Sanz Luengo, Antonio


    The general trend of efficiency increase, weight and noise reduction has derived in the design of more slender, loaded, and 3D shaped blades. This has a significant impact on the stability of fan, and low pressure turbine blades, which are more prone to aeroelastic phenomena such as flutter. The flutter phenomenon is a self-excited, self-sustained unstable vibration produced by the interaction of flow and structure. These working conditions will induce either blade overload, or High Cycle Fat...

  16. A smart segmented blade system for reducing weight of the wind turbine rotor

    Highlights: • A segmented blade system to light the wind turbine rotor is proposed. • The experiments in the wind tunnel and the numerical calculation are combined to validate the effectiveness of the design. • The moment of the blade below the hinged location are alleviated. • The mounting locations of the hinged rods significantly affect the moment distribution on the blade. • The gross weight of the blade can be reduced by 35.4%. - Abstract: The paper proposes a novel design concept for the wind turbine rotors. The design is composed of the segmented blades and a hinged-rods support structure (SBHR) as a means of reducing weight through alleviating the moment on the blade. A prototype of the design is manufactured. Focusing on the hinged-rods support structure (HRSS), a method combining the experiments and numerical calculation is developed to analyze its feasibility. The experiments in the wind tunnel platform were conducted to measure the loads at the root of the isolated blade and in the rods. A numerical model was developed to describe the designed wind turbine rotor using the measured loads in experiments. In the model, the mounting locations of the hinged rods significantly affected the moment distribution on the blade. Thus, two dimensionless indexes were determined to analyze its influences. The model perfectly explain the characteristics of the novel structure under different configurations. The results demonstrated that the moment of the blade below the hinged location were alleviated, which reduced the requirements for the material. A 43.1% reduction of the maximum moment can be achieved in the design. In addition, the gross reduced weight of the blade was estimated to be 35.4% based on the blade mass distribution along the span

  17. Evaluation of Aeroelastically Tailored Small Wind Turbine Blades Final Project Report

    Griffin, Dayton A.


    Evaluation of Aeroelastically Tailored Small Wind Turbine Blades Final Report Global Energy Concepts, LLC (GEC) has performed a conceptual design study concerning aeroelastic tailoring of small wind turbine blades. The primary objectives were to evaluate ways that blade/rotor geometry could be used to enable cost-of-energy reductions by enhancing energy capture while constraining or mitigating blade costs, system loads, and related component costs. This work builds on insights developed in ongoing adaptive-blade programs but with a focus on application to small turbine systems with isotropic blade material properties and with combined blade sweep and pre-bending/pre-curving to achieve the desired twist coupling. Specific goals of this project are to: (A) Evaluate and quantify the extent to which rotor geometry can be used to realize load-mitigating small wind turbine rotors. Primary aspects of the load mitigation are: (1) Improved overspeed safety affected by blades twisting toward stall in response to speed increases. (2) Reduced fatigue loading affected by blade twisting toward feather in response to turbulent gusts. (B) Illustrate trade-offs and design sensitivities for this concept. (C) Provide the technical basis for small wind turbine manufacturers to evaluate this concept and commercialize if the technology appears favorable. The SolidWorks code was used to rapidly develop solid models of blade with varying shapes and material properties. Finite element analyses (FEA) were performed using the COSMOS code modeling with tip-loads and centripetal accelerations. This tool set was used to investigate the potential for aeroelastic tailoring with combined planform sweep and pre-curve. An extensive matrix of design variables was investigated, including aerodynamic design, magnitude and shape of planform sweep, magnitude and shape of blade pre-curve, material stiffness, and rotor diameter. The FEA simulations resulted in substantial insights into the structural

  18. Vibration reduction in helicopter rotors using an active control surface located on the blade

    Millott, T. A.; Friedmann, P. P.


    A feasibility study of vibration reduction in a four-bladed helicopter rotor using individual blade control (IBC), which is implemented by an individually controlled aerodynamic surface located on each blade, is presented. For this exploratory study, a simple offset-hinged spring restrained model of the blade is used with fully coupled flap-lag-torsional dynamics for each blade. Deterministic controllers based on local and global system models are implemented to reduce 4/rev hub loads using both an actively controlled aerodynamic surface on each blade as well as conventional IBC, where the complete blade undergoes cyclic pitch change. The effectiveness of the two approaches for simultaneous reduction of the 4/rev hub shears and hub moments is compared. Conventional IBC requires considerably more power to achieve approximately the same level of vibration reduction as that obtained by implementing IBC using an active control surface located on the outboard segment of the blade. The effect of blade torsional flexibility on the vibration reduction effectiveness of the actively controlled surface was also considered and it was found that this parameter has a very substantial influence.

  19. A tip deflection calculation method for a wind turbine blade using temperature compensated FBG sensors

    The tip deflections of wind turbine blades should be monitored continuously to prevent catastrophic failures of wind turbine power plants caused by blades hitting the tower. In this paper, a calculation method for wind turbine blade tip deflection is proposed using a finite difference method based on arbitrary beam bending and moment theory using measured strains. The blade strains were measured using fiber optic Bragg grating sensors. In order to confirm this method, a 100 kW composite wind turbine blade was manufactured with epoxy molded fiber optic Bragg grating (FBG) sensors installed in the shear web of the blade. A number of these sensors, normal FBG probes, were fabricated to only measure strains and the other sensors, temperature compensated FBG probes, were prepared to also measure strain and temperature. Because the output signals of FBG sensors are dependent on strains as well as temperatures, the sensor output signals should be compensated by the temperatures to obtain accurate strains. These FBG sensors were attached on the lower and upper parts of the web at one meter intervals throughout the entire length of the blade. To evaluate the measurement accuracy of the FBG sensors, conventional electrical strain gauges were also bonded onto the surface of the web beside each FBG sensor. By performing a static load test of the blade, the calculated tip deflection of the blade was well determined within an average error of 2.25%. (paper)

  20. Sources of fatigue damage to passive yaw wind turbine blades

    Laino, D.J. [Univ. of Utah, Salt Lake City, UT (United States)


    Using an integrated computer analysis approach developed at the University of Utah, fatigue damage sources to passive yaw wind turbine blades have been investigated. Models of a rigid hub and teetering hub machine reveal the parameters important to the fatigue design of each type. The teetering hub proved much less susceptible to fatigue damage from normal operation loads. As a result, extreme events were critical to the teetering hub fatigue life. The rigid hub blades experienced extremely large gyroscopic load cycles induced by rapid yaw rates during normal operation. These yaw rates stem from turbulence activity which is shown to be dependent upon atmospheric stability. Investigation revealed that increasing yaw damping is an effective way of significantly reducing these gyroscopic fatigue loads.

  1. Environmental and mechanical fatigue of composite wind turbine blades

    Caprile, C.; Sala, G.; Buzzi, A. [Politecnico di Milano (Italy). Aerospace Engineering Dept.; Botta, G.; Cavaliere, M. [ENEL, Cologno Monzese (Italy)


    The problem relevant to fatigue design and analysis of wind turbine blades made of composite materials is studied taking into account the mid-size single-blade wind turbine. Static and fatigue load conditions are defined; hygrothermal conditions are identified as well, in terms of yearly statistical distribution of wind speed and air temperature, relative humidity, solar radiation and atmospheric pressure daily variations; the occurrence of low-energy impacts due to hailstones is also considered. A FEM structural analysis is carried out to compute stress and strain distributions all along the blade: hot spots are identified; the stress critical values, along with fatigue spectra, are used to design fatigue tests. Some preliminary tests are performed on composite specimens previously dry and wet conditioned, as well as on low-energy impacted coupons, considering both mechanical and hygrothermal effects; finally some preliminary fatigue tests on both adhesive and riveted composite joints are carried out.

  2. Failure analysis of turbine blades

    Two 20 MW gas turbines suffered damage in blades belonging to the 2nd. stage of the turbine after 24,000 hours of duty. From research it arises that the fuel used is not quite adequate to guarantee the blade's operating life due to the excess of SO3, C and Na existing in combustion gases which cause pitting to the former. Later, the corrosion phenomenon is presented under tension produced by working stress enhanced by pitting where Pb is its main agent. A change of fuel is recommended thus considering the blades will reach the operational life they were designed for. (Author)

  3. Rotating vibration behavior of the turbine blades with different groups of blades

    Tsai, Gwo-Chung


    The rotating vibration behaviors of full cycle of 60 blades are studied in this report. The dynamic analysis of two different structures in one of which there are 10 groups of 6 blades and in the other 5 groups of 12 blades, is performed to investigate behavior deviation. In this research, the following jobs are considered: (1) collect the geometric dimensions and material properties of a single blade, (2) create the finite element model of a single blade, a group of 6 blades and 12 blades, and full cycle of 60 blades, (3) perform the vibration analyses of a single blade, a group of blades and a full circle of 60 blades, (4) perform the steady state stress analysis of the blade with different rotating speed; (5) get the Campbell diagram for the full circle of blades, and (6) make comparisons between a group of 6 blades and a group of 12 blades. The conclusions from the analyses are the following: (1) the contact elements are applied to groups of 6 and 12 blades systems and the highest stresses are observed at the location of the first neck of the blade root. These results completely agree very well with in-site observations. (2) The big differences were present in the Campbell diagram: resonant frequencies are observed in the first vibration group for the full system comprising the group of 6 blades and resonant frequencies are not found in the first vibration group of the full blade system made of the group of 12 blades. (3) The dynamic behavior of the full blade system comprised of a group of 6 blades was found much different from that of the full blade system made is of a group of 12 blades. (4) Excellent agreements for the vibration frequencies and mode shapes of a single blade and a full circle of blades are obtained between the FEA results and experimental data.

  4. Incipient Crack Detection in Composite Wind Turbine Blades

    Taylor, Stuart G. [Los Alamos National Laboratory; Choi, Mijin [Chonbuk National University, Korea; Jeong, Hyomi [Chonbuk National University, Korea; Jang, Jae Kyeong [Chonbuk National University, Korea; Park, Gyuhae [Chonnam National University, Korea; Farinholt, Kevin [Commonwealth Center for Advanced Manufacturing, VA; Farrar, Charles R. [Los Alamos National Laboratory; Ammerman, Curtt N. [Los Alamos National Laboratory; Todd, Michael D. [Los Alamos National Laboratory; Lee, Jung-Ryul [Chonbuk National University, Korea


    This paper presents some analysis results for incipient crack detection in a 9-meter CX-100 wind turbine blade that underwent fatigue loading to failure. The blade was manufactured to standard specifications, and it underwent harmonic excitation at its first resonance using a hydraulically-actuated excitation system until reaching catastrophic failure. This work investigates the ability of an ultrasonic guided wave approach to detect incipient damage prior to the surfacing of a visible, catastrophic crack. The blade was instrumented with piezoelectric transducers, which were used in an active, pitchcatch mode with guided waves over a range of excitation frequencies. The performance results in detecting incipient crack formation in the fiberglass skin of the blade is assessed over the range of frequencies in order to determine the point at which the incipient crack became detectable. Higher excitation frequencies provide consistent results for paths along the rotor blade's carbon fiber spar cap, but performance falls off with increasing excitation frequencies for paths off of the spar cap. Lower excitation frequencies provide more consistent performance across all sensor paths.

  5. Design and optimization for strength and integrity of tidal turbine rotor blades

    Tidal turbine rotor blade fractures and failures have resulted in substantial damage and hence cost of repair and recovery. The present work presents a rotor blade design and optimization method to address the blade structural strength design problem. The generic procedure is applicable to both turbine rotors and propellers. The optimization method seeks an optimum blade thickness distribution across the span with a prescribed constant safety factor for all the blade sections. This optimization procedure serves two purposes: while maintaining the required structural strength and integrity for an ultimate inflow speed, it aims to reduce the material to a minimum and to maintain power generation efficiency or improve the hydrodynamic efficiency. The value of the chosen minimum safety factor depends on the actual working conditions of the turbine in which the sectional peak loading and frequency are used: the harsher the environment, the larger the required safety factor. An engineering software tool with both hydrodynamic and structural capabilities was required to predict the instantaneous loading acting on all the blade sections, as well as the strength of a local blade section with a given blade geometry and chosen material. A time-domain, 3D unsteady panel method was then implemented based on a marine propeller software tool and used to perform the optimization. A 3-blade 20-m tidal turbine that was prototyped in parallel with the current work for the Bay of Fundy was used as an example for optimization. The optimum thickness distribution for a required safety factor at the ultimate possible inflow speed resulted in 37.6% saving in blade material. The blade thickness and distribution as a function of a maximum inflow speed of 6 m/s is also presented. The blade material used in the example was taken as nickel–aluminium–bronze (NAB) but the procedure was developed to be applicable to propeller or turbine blades of basically any material. -- Highlights: ► A

  6. Partial Safety Factors for Fatigue Design of Wind Turbine Blades

    Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

    accumulation is determined from variable amplitude fatigue tests with the Wisper and Wisperx spectra. The statistical uncertainty for the assessment of the fatigue loads is also investigated. The partial safety factors are calibrated for design load case 1.2 in IEC 61400-1. The fatigue loads are determined......In the present paper calibration of partial safety factors for fatigue design of wind turbine blades is considered. The stochastic models for the physical uncertainties on the material properties are based on constant amplitude fatigue tests and the uncertainty on Miners rule for linear damage...

  7. Stall Flutter Control of a Smart Blade Section Undergoing Asymmetric Limit Oscillations

    Nailu Li


    Full Text Available Stall flutter is an aeroelastic phenomenon resulting in unwanted oscillatory loads on the blade, such as wind turbine blade, helicopter rotor blade, and other flexible wing blades. Although the stall flutter and related aeroelastic control have been studied theoretically and experimentally, microtab control of asymmetric limit cycle oscillations (LCOs in stall flutter cases has not been generally investigated. This paper presents an aeroservoelastic model to study the microtab control of the blade section undergoing moderate stall flutter and deep stall flutter separately. The effects of different dynamic stall conditions and the consequent asymmetric LCOs for both stall cases are simulated and analyzed. Then, for the design of the stall flutter controller, the potential sensor signal for the stall flutter, the microtab control capability of the stall flutter, and the control algorithm for the stall flutter are studied. The improvement and the superiority of the proposed adaptive stall flutter controller are shown by comparison with a simple stall flutter controller.

  8. A practical approach to fracture analysis at the trailing edge of wind turbine rotor blades

    Eder, Martin Alexander; Bitsche, Robert; Nielsen, Magda;


    Wind turbine rotor blades are commonly manufactured from composite materials by a moulding process. Typically, the wind turbine blade is produced in two halves, which are eventually adhesively joined along their edges. Investigations of operating wind turbine blades show that debonding of the...... virtual crack closure technique (VCCT) is proposed, which can be used to identify critical areas in the adhesive joint of a trailing edge. The paper gives an overview of methods applicable for fracture cases comprising non-parallel crack faces in the realm of linear fracture mechanics. Furthermore, the...... VCCT is discussed in detail and validated against numerical analyses in 2D and 3D. Finally, the SERR of a typical blade section subjected to various loading conditions is investigated and assessed in order to identify potential design drivers for trailing edge details. Analysis of the blade section...


    YUAN Shouqi; ZHANG Jinfeng; YUAN Jianping; HE Youshi; FU Yuedeng


    Analysis on the inner flow field of a centrifugal pump impeller with splitter blades is carried out by numerical simulation. Based on this analysis, the principle of increasing pump head and efficiency are discussed. New results are obtained from the analysis of turbulence kinetic energy and relative velocity distribution: Firstly, unreasonable length or deviation design of the splitter blades may cause great turbulent fluctuation in impeller channel, which has a great effect on the stability of impeller outlet flow; Secondly, it is found that the occurrence of flow separation can be decreased or delayed with splitter blades from the analysis of blade loading; Thirdly, the effect of splitter blades on reforming the structure of "jet-wake" is explained from the relative velocity distribution at different flow cross-sections, which shows the flow process in the impeller. The inner flow analysis verifies the results of performance tests results and the PIV test.

  10. Spline for blade grids design

    Korshunov, Andrei; Shershnev, Vladimir; Korshunova, Ksenia


    Methods of designing blades grids of power machines, such as equal thickness shape built on middle-line arc, or methods based on target stress spreading were invented long time ago, well described and still in use. Science and technology has moved far from that time and laboriousness of experimental research, which were involving unique equipment, requires development of new robust and flexible methods of design, which will determine the optimal geometry of flow passage.This investigation provides simple and universal method of designing blades, which, in comparison to the currently used methods, requires significantly less input data but still provides accurate results. The described method is purely analytical for both concave and convex sides of the blade, and therefore lets to describe the curve behavior down the flow path at any point. Compared with the blade grid designs currently used in industry, geometric parameters of the designs constructed with this method show the maximum deviation below 0.4%.

  11. Dynamic behavior analysis of floating offshore wind turbine including flexible effects of tower and blade

    To establish a floating offshore wind turbine simulation model, a tension leg platform is added to an onshore wind turbine. The wind load is calculated by using meteorological administration data and a power law that defines the wind velocity according to the height from the sea surface. The wind load is applied to the blade and wind tower at a regular distance. The relative Morison equation is employed to generate the wave load. The rated rotor speed (18rpm) is applied to the hub as a motion. The dynamic behavior of a 2MW floating offshore wind turbine subjected to the wave excitation and wind load is analyzed. The flexible effects of the wind tower and the blade are analyzed. The flexible effects of the wind tower and the blade are analyzed. The flexible model of the wind tower and blade is established to examine the natural frequency of the TLP type offshore wind turbine. To study the effect of the flexible tower and blade on the floating offshore wind turbine, we modeled the flexible tower model and flexible tower blade model and compared it with a rigid model

  12. Blade tip timing (BTT) uncertainties

    Russhard, Pete


    Blade Tip Timing (BTT) is an alternative technique for characterising blade vibration in which non-contact timing probes (e.g. capacitance or optical probes), typically mounted on the engine casing (figure 1), and are used to measure the time at which a blade passes each probe. This time is compared with the time at which the blade would have passed the probe if it had been undergoing no vibration. For a number of years the aerospace industry has been sponsoring research into Blade Tip Timing technologies that have been developed as tools to obtain rotor blade tip deflections. These have been successful in demonstrating the potential of the technology, but rarely produced quantitative data, along with a demonstration of a traceable value for measurement uncertainty. BTT technologies have been developed under a cloak of secrecy by the gas turbine OEM's due to the competitive advantages it offered if it could be shown to work. BTT measurements are sensitive to many variables and there is a need to quantify the measurement uncertainty of the complete technology and to define a set of guidelines as to how BTT should be applied to different vehicles. The data shown in figure 2 was developed from US government sponsored program that bought together four different tip timing system and a gas turbine engine test. Comparisons showed that they were just capable of obtaining measurement within a +/-25% uncertainty band when compared to strain gauges even when using the same input data sets.

  13. Implementation of a Biaxial Resonant Fatigue Test Method on a Large Wind Turbine Blade

    Snowberg, D.; Dana, S.; Hughes, S.; Berling, P.


    A biaxial resonant test method was utilized to simultaneously fatigue test a wind turbine blade in the flap and edge (lead-lag) direction. Biaxial resonant blade fatigue testing is an accelerated life test method utilizing oscillating masses on the blade; each mass is independently oscillated at the respective flap and edge blade resonant frequency. The flap and edge resonant frequency were not controlled, nor were they constant for this demonstrated test method. This biaxial resonant test method presented surmountable challenges in test setup simulation, control and data processing. Biaxial resonant testing has the potential to complete test projects faster than single-axis testing. The load modulation during a biaxial resonant test may necessitate periodic load application above targets or higher applied test cycles.

  14. Ultimate strength of a large wind turbine blade

    Moelholt Jensen, Find


    The present PhD project contains a study of the structural static strength of wind turbine blades loaded in flap-wise direction. A combination of experimental and numerical work has been used to address the most critical failure mechanisms and to get an understanding of the complex structural behaviour of wind turbine blades. Four failure mechanisms observed during the fullscale tests and the corresponding FE-analysis are presented. Elastic mechanisms associated with failure, such as buckling, localized bending and the Brazier effect, are studied. Six different types of structural reinforcements helping to prevent undesired structural elastic mechanisms are presented. The functionality of two of the suggested structural reinforcements was demonstrated in full-scale tests and the rest trough FE-studies. The blade design under investigation consisted of an aerodynamic airfoil and a load carrying box girder. In total, five full-scale tests have been performed involving one complete blade and two shortened box girders. The second box girder was submitted to three independent tests covering different structural reinforcement alternatives. The advantages and disadvantages of testing a shortened load carrying box girder vs. an entire blade are discussed. Changes in the boundary conditions, loads and additional reinforcements, which were introduced in the box girder tests in order to avoid undesired structural elastic mechanisms, are presented. New and advanced measuring equipment was used in the fullscale tests to detect the critical failure mechanisms and to get an understanding of the complex structural behaviour. Traditionally, displacement sensors and strain gauges in blade tests are arranged based on an assumption of a Bernoulli-Euler beam structural response. In the present study it is shown that when following this procedure important information about distortions of the cross sections is lost. In the tests presented here, one of the aims was to measure distortion

  15. Actuator control of edgewise vibrations in wind turbine blades

    Staino, A.; Basu, B.; Nielsen, S. R. K.


    Edgewise vibrations with low aerodynamic damping are of particular concern in modern multi-megawatt wind turbines, as large amplitude cyclic oscillations may significantly shorten the life-time of wind turbine components, and even lead to structural damages or failures. In this paper, a new blade design with active controllers is proposed for controlling edgewise vibrations. The control is based on a pair of actuators/active tendons mounted inside each blade, allowing a variable control force to be applied in the edgewise direction. The control forces are appropriately manipulated according to a prescribed control law. A mathematical model of the wind turbine equipped with active controllers has been formulated using an Euler-Lagrangian approach. The model describes the dynamics of edgewise vibrations considering the aerodynamic properties of the blade, variable mass and stiffness per unit length and taking into account the effect of centrifugal stiffening, gravity and the interaction between the blades and the tower. Aerodynamic loads corresponding to a combination of steady wind including the wind shear and the effect of turbulence are computed by applying the modified Blade Element Momentum (BEM) theory. Multi-Blade Coordinate (MBC) transformation is applied to an edgewise reduced order model, leading to a linear time-invariant (LTI) representation of the dynamic model. The LTI description obtained is used for the design of the active control algorithm. Linear Quadratic (LQ) regulator designed for the MBC transformed system is compared with the control synthesis performed directly on an assumed nominal representation of the time-varying system. The LQ regulator is also compared against vibration control performance using Direct Velocity Feedback (DVF). Numerical simulations have been carried out using data from a 5-MW three-bladed Horizontal-Axis Wind Turbine (HAWT) model in order to study the effectiveness of the proposed active controlled blade design in

  16. Load prediction of stall regulated wind turbines

    Bjoerck, A.; Dahlberg, J.Aa. [Aeronautical Research Inst. of Sweden, Bromma (Sweden); Carlen, I. [Chalmers Univ. of Technology, Goeteborg (Sweden). Div. of Marine Structural Engineering; Ganander, H. [Teknikgruppen AB, Sollentua (Sweden)


    Measurements of blade loads on a turbine situated in a small wind farm shows that the highest blade loads occur during operation close to the peak power i.e. when the turbine operates in the stall region. In this study the extensive experimental data base has been utilised to compare loads in selected campaigns with corresponding load predictions. The predictions are based on time domain simulations of the wind turbine structure, performed by the aeroelastic code VIDYN. In the calculations a model were adopted in order to include the effects of dynamic stall. This paper describes the work carried out so far within the project and key results. 5 refs, 10 figs

  17. Steady and unsteady blade stresses within the SSME ATD/HPOTP inducer

    Gross, R. Steven


    There were two main goals of the ATD HPOTP (alternate turbopump development)(high pressure oxygen turbopump). First, determine the steady and unsteady inducer blade surface strains produced by hydrodynamic sources as a function of flow capacity (Q/N), suction specific speed (Nss), and Reynolds number (Re). Second, to identify the hydrodynamic source(s) of the unsteady blade strains. The reason the aforementioned goals are expressed in terms of blade strains as opposed to blade hydrodynamic pressures is because of the interest regarding the high cycle life of the inducer blades. This report focuses on the first goal of the test program which involves the determination of the steady and unsteady strain (stress) values at various points within the inducer blades. Strain gages were selected as the strain measuring devices. Concurrent with the experimental program, an analytical study was undertaken to produce a complete NASTRAN finite-element model of the inducer. Computational fluid dynamics analyses were utilized to provide the estimated steady-state blade surface pressure loading needed as load input to the NASTRAN inducer model.


    ZENG Zhi-bo; KUIPER Gert


    Kuiper and Jessup (1993) developed a design method for propellers in a wake based on the Eppler foil design method.The optimized section is transformed into the three-dimensional propeller flow using the approach of the effective blade sections.Effective blade sections are two-dimensional sections in two-dimensional flow which have the same chordwise loading distribution as the three-dimensional blade sections of a propeller.However,the design procedure is laborious in two aspects:finding an optimum blade section using the Eppler program requires much skill of the designer,and transforming the two-dimensional blade section into a propeller blade section in three-dimensional flow is complex.In this work,these two problems were coped with.A blade section design procedure was presented using an optimization technique and an alternative procedure for the effective blade section is developed using a lifting surface design method.To validate the method a benchmark model of a naval ship was used.This benchmark model was extended by new appendices and a reference propeller,and designed using conventional design methods.This reference propeller was optimized using the new design procedure and model tests were carried out.Special attention was given to the data of the model and the reference propeller,to make the configuration suitable for the Reynolds-Averaged Navier-Stokes (RANS) calculations.

  19. Fabrication of low-cost Mod-OA wood composite wind turbine blades

    Lark, R. F.; Gougeon, M.; Thomas, G.; Zuteck, M.


    The wood composite blades were fabricated by using epoxy resin-bonded laminates of Douglas fir veneers for the leading edge spar sections and honeycomb-cored birch plywood panels for the blade trailing edge or afterbody sections. The blade was joined to the wind turbine hub assembly by epoxy resin-bonded steel load take-off studs. The wood composite blades were installed in the Mod-OA wind turbine test facility at Kahuku, Hawaii. The wood composite blades have successfully completed high power (average of 150 kW) operations for an eighteen month period (nearly 8,000 hr) before replacement with another set of wood composite blades. The original set of blades was taken out of service because of the failure of the shank on one stud. An inspection of the blades at NASA-Lewis showed that the shank failure was caused by a high stress concentration at a corrosion pit on the shank fillet radius which resulted in fatigue stresses in excess of the endurance limit.

  20. The Analysis of the Aerodynamic Character and Structural Response of Large-Scale Wind Turbine Blades

    Jie Zhu


    Full Text Available A process of detailed CFD and structural numerical simulations of the 1.5 MW horizontal axis wind turbine (HAWT blade is present. The main goal is to help advance the use of computer-aided simulation methods in the field of design and development of HAWT-blades. After an in-depth study of the aerodynamic configuration and materials of the blade, 3-D mapping software is utilized to reconstruct the high fidelity geometry, and then the geometry is imported into CFD and structure finite element analysis (FEA software for completely simulation calculation. This research process shows that the CFD results compare well with the professional wind turbine design and certification software, GH-Bladed. Also, the modal analysis with finite element method (FEM predicts well compared with experiment tests on a stationary blade. For extreme wind loads case that by considering a 50-year extreme gust simulated in CFD are unidirectional coupled to the FE-model, the results indicate that the maximum deflection of the blade tip is less than the distance between the blade tip (the point of maximum deflection and the tower, the material of the blade provides enough resistance to the peak stresses the occur at the conjunction of shear webs and center spar cap. Buckling analysis is also included in the study.

  1. Numerical simulation of turbulent flows past the RoBin helicopter with a four-bladed rotor

    The current paper presents a turbulent flow simulation study past a generic helicopter RoBin with a four-bladed rotor using the Chimera moving grid approach. The aerodynamic performance of the rotor blades and their interactions with the RoBin fuselage are investigated using the k - ω SST turbulence model contained in the WIND code. The rotor is configured as a Chimera moving grid in a quasisteady flow field. The rotor blades are rectangular, untapered, linearly twisted and are made from NACA 0012 airfoil profile. The blade motion (rotation and cyclic pitching) schedule is specified in the NASA wind tunnel testing of a generic helicopter RoBin. The aerodynamic radial load distributions in the rotor plane are generated by integrating the pressure on each blade surfaces along the blade chordwise direction. The rotor flow interacts strongly with the flow coming off from the fuselage and thus has a significant impact on helicopter aerodynamic performance. (author)

  2. Assessment Report on Innovative Rotor Blades (MAREWINT WP1,D1.3)

    McGugan, Malcolm; Leble, Vladimir; Pereira, Gilmar Ferreira

    The offshore wind energy industry faces many challenges in the short to medium term if it is to meet the ambitions of the global community for sustainable energy supply in the future. Not least among these challenges is the issue of rotor blades. Innovative design for “smart” rotor blades with...... innovative concept development for wind turbine blades. This covers models and experiments with damage measurement systems embedded within the composite material/structure and numerical methods investigating the effects of leading and trailing edge flaps on modifying the aerodynamic loads on the operating...

  3. Model predictive control of trailing edge flaps on a wind turbine blade

    Castaignet, Damien Bruno

    with three trailing edge flaps on one blade, located on DTU’s Risø Campus in Roskilde, Denmark. This thesis is divided into three parts: the controller design, results from simulations, and results from the experiments. The trailing edge flaps controller designed for this project is based on a frequency......, in Roskilde, Denmark. One blade of the turbine was equipped with three independent trailing edge flaps. In spite of the failure of several sensors and actuators, the test of the trailing edge flaps controller described in this thesis showed a consistent flapwise blade root fatigue load reduction. An average...

  4. Investigation of Dynamic Aerodynamics and Control of Wind Turbine Sections Under Relevant Inflow/Blade Attitude Conditions

    Naughton, Jonathan W. [University of Wyoming


    The growth of wind turbines has led to highly variable loading on the blades. Coupled with the relative reduced stiffness of longer blades, the need to control loading on the blades has become important. One method of controlling loads and maximizing energy extraction is local control of the flow on the wind turbine blades. The goal of the present work was to better understand the sources of the unsteady loading and then to control them. This is accomplished through an experimental effort to characterize the unsteadiness and the effect of a Gurney flap on the flow, as well as an analytical effort to develop control approaches. It was planned to combine these two efforts to demonstrate control of a wind tunnel test model, but that final piece still remains to be accomplished.

  5. Is blade element momentum theory (BEM) enough for smart rotor design

    Yu, W.; Simao Ferreira, C.J.; van Kuik, G.A.M.


    Smart rotor emerges as an innovation technique to reduce the impact of dynamic loading on wind turbines. Local movements of distributed aerodynamic devices will enhance the non-uniformity and dynamic effects of loading, which will challenge the applicability of the blade element momentum theory (BEM

  6. Comparative analysis of steady state heat transfer in a TBC and functionally graded air cooled gas turbine blade

    Nilanjan Coomar; Ravikiran Kadoli


    Internal cooling passages and thermal barrier coatings (TBCs) are presently used to control metal temperatures in gas turbine blades. Functionally graded materials (FGMs), which are typically mixtures of ceramic and metal, have been proposed for use in turbine blades because they possess smooth property gradients thereby rendering them more durable under thermal loads. In the present work, a functionally graded model of an air-cooled turbine blade with airfoil geometry conforming to the NACA0012 is developed which is then used in a finite element algorithm to obtain a non-linear steady state solution to the heat equation for the blade under convection and radiation boundary conditions. The effects of external gas temperature, coolant temperature, surface emissivity changes and different average ceramic/metal content of the blade on the temperature distributions are examined. Simulations are also carried out to compare cooling effectiveness of functionally graded blades with that of blades having TBC. The results highlight the effect of including radiation in the simulation and also indicate that external gas temperature influences the blade heat transfer more strongly. It is also seen that graded blades with about 70% ceramic content can deliver better cooling effectiveness than conventional blades with TBC.

  7. Two LQRI based Blade Pitch Controls for Wind Turbines

    Yoonsu Nam


    Full Text Available As the wind turbine size has been increasing and their mechanical components are built lighter, the reduction of the structural loads becomes a very important task of wind turbine control in addition to maximum wind power capture. In this paper, we present a separate set of collective and individual pitch control algorithms. Both pitch control algorithms use the LQR control technique with integral action (LQRI, and utilize Kalman filters to estimate system states and wind speed. Compared to previous works in this area, our pitch control algorithms can control rotor speed and blade bending moments at the same time to improve the trade-off between rotor speed regulation and load reduction, while both collective and individual pitch controls can be designed separately. Simulation results show that the proposed collective and individual pitch controllers achieve very good rotor speed regulation and significant reduction of blade bending moments.

  8. Improved design for large wind turbine blades of fibre composites (Phase 4) - Summary report

    Sørensen, Bent F; Toftegaard, Helmuth Langmaack; Goutianos, Stergios; Branner, Kim; Berring, Peter; Lund, E.; Wedel-Heinen, J.; Garm, J.H.


    Results are summarised for the project "Improved design for large wind turbine blades (Phase 4)", partially supported by the Danish Energy Agency under the Ministry of Climate and Energy through the EUDP journal no.: 33033-0267. The aim of the project was to develop new and better design methods for wind turbine blades, so that uncertainties associated with damage and defects can be reduced. The topics that are studied include buckling-driven delamination of flat load-carrying laminates, crac...

  9. Load alleviation of wind turbines by yaw misalignment

    Kragh, Knud Abildgaard; Hansen, Morten Hartvig


    Vertical wind shear is one of the dominating causes of load variations on the blades of a horizontal axis wind turbine. To alleviate the varying loads, wind turbine control systems have been augmented with sensors and actuators for individual pitch control. However, the loads caused by a vertical...... wind shear can also be affected through yaw misalignment. Recent studies of yaw control have been focused on improving the yaw alignment to increase the power capture at below rated wind speeds. In this study, the potential of alleviating blade load variations induced by the wind shear through yaw...... applied without power loss for wind speeds above rated wind speed. In deterministic inflow, it is shown that the range of the steady-state blade load variations can be reduced by up to 70%. For turbulent inflows, it is shown that the potential blade fatigue load reductions depend on the turbulence level...

  10. Large, low cost composite wind turbine blades

    Gewehr, H. W.


    A woven roving E-glass tape, having all of its structural fibers oriented across the tape width was used in the manufacture of the spar for a wind turbine blade. Tests of a 150 ft composite blade show that the transverse filament tape is capable of meeting structural design requirements for wind turbine blades. Composite blades can be designed for interchangeability with steel blades in the MOD-1 wind generator system. The design, analysis, fabrication, and testing of the 150 ft blade are discussed.