Showing papers on "Turbine blade published in 2009"

A review of surface engineering issues critical to wind turbine performance

Abstract: Wind turbine performance can be significantly reduced when the surface integrity of the turbine blades is compromised. Many frontier high-energy regions that are sought for wind farm development including Nordic, warm-humid, and desert-like environments often provide conditions detrimental to the surface of the turbine blade. In Nordic climates ice can form on the blades and the turbine structure itself through a variety of mechanisms. Initial ice adhesion may slightly modify the original aerodynamic profile of the blade; continued ice accretion can drastically affect the structural loading of the entire rotor leading to potentially dangerous situations. In warmer climates, a humid wind is desirable for its increased density; however, it can come at a price when the region supports large populations of insects. Insect collisions with the blades can foul blade surfaces leading to a marked increase in skin drag, reducing power production by as much as 50%. Finally, in more arid regions where there is no threat from ice or insects, high winds can carry soil particles eroded from the ground (abrasive particles). Particulate-laden winds effectively sand-blast the blade surfaces, and disrupt the original skin profile of the blade, again reducing its aerodynamic efficiency. While these problems are challenging, some mitigative measures presently exist and are discussed in the paper. Though, many of the current solutions to ice or insect fouling actually siphon power from the turbine itself to operate, or require that the turbine be stopped, in either case, profitability is diminished. Our survey of this topic in the course of our research suggests that a desirable solution may be a single surface engineered coating that reduces the incidence of ice adhesion, insect fouling, and protects the blade surface from erosive deterioration. Research directions that may lead to such a development are discussed herein.

Control of wind turbines: Past, present, and future

Abstract: We review the objectives and techniques used in the control of horizontal axis wind turbines at the individual turbine level, where controls are applied to the turbine blade pitch and generator. The turbine system is modeled as a flexible structure operating in the presence of turbulent wind disturbances. Some overview of the various stages of turbine operation and control strategies used to maximize energy capture in below rated wind speeds is given, but emphasis is on control to alleviate loads when the turbine is operating at maximum power. After reviewing basic turbine control objectives, we provide an overview of the common basic linear control approaches and then describe more advanced control architectures and why they may provide significant advantages.

A comparison of smart rotor control approaches using trailing edge flaps and individual pitch control

Abstract: Modern wind turbines have been steadily increasing in size, and have now become very large, with recent models boasting rotor diameters greater than 120 m. Reducing the loads experienced by the wind turbine rotor blades is one means of lowering the cost of energy of wind turbines. Wind turbines are subjected to signiflcant and rapid ∞uctuating loads, which arise from a variety of sources including: turbulence in the wind, tower shadow, wind shear, and yawed ∞ow conditions. \Smart rotor control" concepts have emerged as a major topic of research in the attempt to reduce fatigue loads on wind turbines. In this approach, aerodynamic load control devices are distributed along the span of the wind turbine blade, and through a combination of sensing, control, and actuation, these devices dynamically control the loads on the blades. This research investigates the load reduction potential of smart rotor control devices, namely trailing edge ∞aps (TEFs), in the operation of a 5 MW wind turbine in the aeroelastic design code \GH Bladed." Speciflcally in this paper, the fatigue load reductions achieved using trailing edge ∞aps are evaluated, and the performance is compared to another promising load reduction technique, individual pitch control. A feedback control approach is implemented for load reduction, which utilizes a multiblade coordinate transformation, so that variables in the rotating frame of reference can be mapped into a flxed frame of reference. Single input single output (SISO) control techniques for linear time invariant (LTI) systems are then employed to determine the appropriate response of the TEFs based on the loads on the blades. The use of TEFs and this control approach is shown to efiectively reduce the fatigue loads on the blades, relative to a baseline controller. The load reduction potential is also compared to an alternative individual pitch control approach, in the time and frequency domain. The efiects on the pitch and power systems are brie∞y evaluated, and the limitations of the analysis are assessed.

Column-stabilized offshore platform with water-entrapment plates and asymmetric mooring system for support of offshore wind turbines

Abstract: A floating wind turbine platform includes a floatation frame (105) that includes three columns (102, 103) that are coupled to each other with horizontal main beams (115). A wind turbine tower (111) is mounted above a tower support column (102) to simplify the system construction and improve the structural strength. The turbine blades (101) are coupled to a nacelle (125) that rotates on top of the tower (111). The turbine's gearbox generator and other electrical gear can be mounted either traditionally in the nacelle, or lower in the tower (11 1) or in the top of the tower-supporting column (102). The floatation frame (105) includes a water ballasting system that pumps water between the columns (102, 103) to keep the tower ( 1 1 1 ) in a 10 vertical alignment regardless of the wind speed. Water-entrapment plates (107) are mounted to the bottoms of the columns (102, 103) to minimize the rotational movement of the floatation frame (105) due to waves.

Shape Optimization of Wind Turbine Blades

Abstract: This paper presents a design tool for optimizing wind turbine blades. The design model is based on an aerodynamic/aero-elastic code that includes the structural dynamics of the blades and the Blade Element Momentum (BEM) theory. To model the main aero-elastic behaviour of a real wind turbine, the code employs 11 basic degrees of freedom corresponding to 11 elastic structural equations. In the BEM theory, a refined tip loss correction model is used. The objective of the optimization model is to minimize the cost of energy which is calculated from the annual energy production and the cost of the rotor. The design variables used in the current study are the blade shape parameters, including chord, twist and relative thickness. To validate the implementation of the aerodynamic/aero-elastic model, the computed aerodynamic results are compared to experimental data for the experimental rotor used in the European Commision-sponsored project Model Experiments in Controlled Conditions, (MEXICO) and the computed aero-elastic results are examined against the FLEX code for flow past the Tjaereborg 2 MW rotor. To illustrate the optimization technique, three wind turbine rotors of different sizes (the MEXICO 25 kW experimental rotor, the Tjaereborg 2 MW rotor and the NREL 5 MW virtual rotor) are applied. The results show that the optimization model can reduce the cost of energy of the original rotors, especially for the investigated 2 MW and 5 MW rotors. Copyright © 2009 John Wiley & Sons, Ltd.

Sandwich Materials for Wind Turbine Blades — Present and Future

Abstract: Wind turbine blades are being manufactured using polymer matrix composite materials, in a combination of monolithic (single skin) and sandwich composites. Present day designs are mainly based on glass fiber-reinforced composites (GFRP), but for very large blades carbon fiber-reinforced composites 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 article 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 len...

Blade Offset and Pitch Effects on a High Solidity Vertical Axis Wind Turbine

Abstract: A high solidity, small scale, 2.5m diameter by 3m high Vertical Axis Wind Turbine (VAWT) consisting of three NACA 0015 profile blades, each with a span of 3m and a chord length of 0.4m, was tested in an open-air wind tunnel facility to investigate the effects of preset toe-in and toe-out turbine blade pitch. The effect of blade mount-point offset was also investigated. The results from these tests are presented for a range of tip speed ratios, and compared with an extensive base data set obtained for a nominal wind speed of 10m/s. Results show measured performance decreases of up to 47% for toe-in, and increases of up to 29% for toe-out blade pitch angles, relative to the zero preset pitch case. Also, blade mount-point offset tests indicate decreases in performance as the mount location is moved from mid-chord towards the leading edge, as a result of an inherent toe-in condition. Observations indicate that these performance decreases may be minimized by compensating for the blade mount offset with a toe-o...

Multiharmonic Forced Response Analysis of a Turbine Blading Coupled by Nonlinear Contact Forces

Abstract: The rotor blades of a low pressure (LP) steam turbine stage are subjected to high static and dynamic loads during operation. The static loads are mainly due to the centrifugal force and thermal strains, whereas the dynamic loads are caused by fluctuating gas forces resulting in forced vibrations of the blades. The forced vibrations can lead to high cycle fatigue (HCF) failures causing substantial damage and high maintenance effort. Thus, one of the main tasks in the design of LP steam turbine blading is the vibration amplitude reduction in order to avoid high dynamic stresses that could damage the blading. The vibration amplitudes of the blades in a LP steam turbine stage can be reduced significantly to a reasonable amount if adjacent blades are coupled by shroud contacts that reinforce the blading, see Fig. 1. Furthermore, in the case of blade vibrations, relative displacements between neighboring blades occur in the contacts and friction forces are generated that provide additional damping to the structure due to the energy dissipation caused by micro- and macroslip effects. Therefore, the coupling of the blades increases the overall mechanical damping. A three-dimensional structural dynamics model including an appropriate spatial contact model is necessary to predict the contact forces generated by the shroud contacts and to describe the vibrational behavior of the blading with sufficient accuracy. To compute the nonlinear forced vibrations of the coupled blading, the nonlinear equations of motion are solved in the frequency domain owing to the high computational efficiency of this approach. The transformation of the nonlinear equations of motion into the frequency domain can be carried out by representing the steady-state displacement in terms of its harmonic components. After that transformation, the nonlinear forced response is computed as a function of the excitation frequency in the frequency domain.Copyright © 2009 by ASME

Turbine Blade Tip Heat Transfer in Low Speed and High Speed Flows

Abstract: In this paper, high and low speed tip flows are investigated for a high-pressure turbine blade. Previous experimental data are used to validate a CFD code, which is then used to study the tip heat transfer in high and low speed cascades. The results show that at engine representative Mach numbers the tip flow is predominantly transonic. Thus, compared to the low speed tip flow, the heat transfer is affected by reductions in both the heat transfer coefficient and the recovery temperature. The high Mach numbers in the tip region (M>1.5) lead to large local variations in recovery temperature. Significant changes in the heat transfer coefficient are also observed. These are due to changes in the structure of the tip flow at high speed. At high speeds, the pressure side corner separation bubble reattachment occurs through supersonic acceleration which halves the length of the bubble when the tip gap exit Mach number is increased from 0.1 to 1.0. In addition, shock/boundary-layer interactions within the tip gap lead to large changes in the tip boundary-layer thickness. These effects give rise to significant differences in the heat-transfer coefficient within the tip region compared to the low-speed tip flow. Compared to the low speed tip flow, the high speed tip flow is much less dominated by turbulent dissipation and is thus less sensitive to the choice of turbulence model. These results clearly demonstrate that blade tip heat transfer is a strong function of Mach number, an important implication when considering the use of low speed experimental testing and associated CFD validation in engine blade tip design

Direct adaptive control of a utility-scale wind turbine for speed regulation

Abstract: The accurate modeling of wind turbines is an extremely challenging problem due to the tremendous complexity of the machines and the turbulent and unpredictable conditions in which they operate. Adaptive control techniques are well suited to nonlinear applications, such as wind turbines, which are difficult to accurately model and which have effects from poorly known operating environments. In this paper, we extended the direct model reference adaptive control (DMRAC) approach to track a reference point and to reject persistent disturbances. This approach was then used to design an adaptive collective pitch controller for a high-fidelity simulation of a variable-speed horizontal axis wind turbine. The objective of the adaptive pitch controller was to regulate generator speed in Region 3 and to reject step disturbances. The control objective was accomplished by collectively pitching the turbine blades. The turbine simulation models the controls advanced research turbine (CART) of the National Renewable Energy Laboratory in Golden, Colorado. The CART is a utility-scale wind turbine that has a well-developed and extensively verified simulator. This novel application of adaptive control was compared in simulations with a classical proportional integrator (PI) collective pitch controller. In the simulations, the adaptive pitch controller showed improved speed regulation in Region 3 when compared with the PI pitch controller. Copyright © 2008 John Wiley & Sons, Ltd.

Gas turbine engine temperature modulated cooling flow

Abstract: A gas turbine engine cooling system includes a heat exchanger in fluid communication with a source of cooling air, a first cooling circuit including a first heat exchanger circuit in the heat exchanger and a first bypass circuit with a first bypass valve for selectively bypassing at least a portion of first airflow around the first heat exchanger circuit. A second cooling circuit may be used having a second heat exchanger circuit in the heat exchanger and a shutoff control valve operably disposed in the second cooling circuit upstream of the second heat exchanger circuit and the heat exchanger. A circuit inlet of the first cooling circuit may be used to bleed a portion of compressor discharge bleed air for the first airflow to cool turbine blades mounted on a rotor disk using an annular flow inducer downstream of the first bypass valve and the heat exchanger.

Development and Validation of a CFD Technique for the Aerodynamic Analysis of HAWT

Abstract: This paper demonstrates the potential of a compressible Navier–Stokes CFD method for the analysis of horizontal axis wind turbines. The method was first validated against experimental data of the NREL/NASA-Ames Phase VI (Hand, , 2001, “Unsteady Aerodynamics Experiment Phase, VI: Wind Tunnel Test Configurations and Available Data Campaigns,” NREL, Technical Report No. TP-500-29955) wind-tunnel campaign at 7 m/s, 10 m/s, and 20 m/s freestreams for a nonyawed isolated rotor. Comparisons are shown for the surface pressure distributions at several stations along the blades as well as for the integrated thrust and torque values. In addition, a comparison between measurements and CFD results is shown for the local flow angle at several stations ahead of the wind turbine blades. For attached and moderately stalled flow conditions the thrust and torque predictions are fair, though improvements in the stalled flow regime are necessary to avoid overprediction of torque. Subsequently, the wind-tunnel wall effects on the blade aerodynamics, as well as the blade/tower interaction, were investigated. The selected case corresponded to 7 m/s up-wind wind turbine at 0 deg of yaw angle and a rotational speed of 72 rpm. The obtained results suggest that the present method can cope well with the flows encountered around wind turbines providing useful results for their aerodynamic performance and revealing flow details near and off the blades and tower.

Efficiency Improvement of Centrifugal Reverse Pumps

Abstract: Pumps as turbines have been successfully applied in a wide range of small hydrosites in the world. Since the overall efficiency of these machines is lower than the overall efficiency of conventional turbines, their application in larger hydrosites is not economical. Therefore, the efficiency improvement of reverse pumps is essential. In this study, by focusing on a pump impeller, the shape of blades was redesigned to reach a higher efficiency in turbine mode using a gradient based optimization algorithm coupled by a 3D Navier-Stokes flow solver. Also, another modification was done by rounding the blades' leading edges and hub/shroud interface in turbine mode. After each modification, a new impeller was manufactured and tested in the test rig. The efficiency was improved in all measured points by the optimal design of the blade and additional modification as the rounding of the blade's profile in the impeller inlet and hub/shroud inlet edges in turbine mode. Experimental results confirmed the numerical efficiency improvement in all measured points. This study illustrated that the efficiency of the pump in reverse operation can be improved just by impeller modification.

A critical assessment of computer tools for calculating composite wind turbine blade properties

Abstract: The purpose of this paper is to critically assess several computer tools for calculating the inertial and structural properties of wind turbine blades. The theoretical foundation of each tool is briefly summarized, and the advantages and disadvantages of each tool are pointed out. Several benchmark examples, including a circular aluminium tube, a highly heterogeneous section, a multi-layer composite pipe, an isotropic blade-like section and a realistic composite wind turbine blade are used to evaluate the performance of different tools. Such a systematic and critical assessment provides guidance for wind turbine blade engineers to choose the right tool for effective design and analysis of wind turbine blades. Copyright © 2009 John Wiley & Sons, Ltd.

NDT of wind turbine blades using adapted ultrasonic and radiographic techniques

Abstract: The objective of this study was to adapt ultrasonic and radiographic techniques for the inspection of wind turbine blades and to compare the obtainedresults The measurements performed show that radiographic techniques are capable of reliably detecting a number of structural defects within the blade The adapted air-coupled ultrasonic technique, using Lamb waves, proved to be the most promising in terms of implementation as it only requires access to one side However, the novel combination of contact pulse-echo and immersion techniques using a moving container of water identified the shape and size of defects better Through comparisons of images obtained using both radiographic and ultrasonic techniques, different defect properties can be identified Hence, the best results are achieved when both techniques are combined together

Segmented ceramic matrix composite turbine airfoil component

Abstract: A segmented component for use with a gas turbine engine comprises a radially extending gas path portion. The gas path portion is for interacting with gas flow from the gas turbine engine. The component is divided into axially aligned segments comprising a forward segment, an aft segment, and a plurality of middle segments disposed between the forward segment and the aft segment. The middle segments comprise radially elongate ceramic matrix composite material plates. In one embodiment, the gas path portion comprises an airfoil for a turbine blade. In another embodiment, the gas path portion comprises a removable platform for a turbine blade. In another embodiment, the gas path portion comprises an airfoil for a turbine vane.

Biformal platform turbine blade

Abstract: A turbine blade includes an airfoil and integral platform. The platform is biformally contoured in elevation to include bilaterally disposed elevated ridges and depressed troughs on opposite sides of the airfoil.

Geared differential speed counter-rotatable low pressure turbine

Abstract: A counter-rotatable low pressure turbine (26) includes counter-rotatable outer and inner drum rotors (68, 78). The outer drum rotor (68) is connected to a sole shaft for transmitting torque and power out of the low pressure turbine (26). Low pressure outer drum turbine blade rows (70) extend radially inwardly from an outer shell (66) of the outer drum rotor (68). Low pressure inner drum turbine blade rows (80) extend radially outwardly from the low pressure inner drum rotor (78). The outer drum turbine blade rows (70) are interdigitated with the inner drum turbine blade rows (80). The drum rotors (68, 78) are geared together through an epicyclic gearbox (56) for transmitting all the torque and power produced by the drum rotors (68, 78) to the shaft (74). The gearbox (56) may be located aft of the drum rotors (68, 78). A differential thrust bearing (112) is disposed between the drum rotors (68, 78). A single stage fan section (12) of an engine (10) is connected to the turbine (26) by the shaft (74).

A wind turbine rotor, a wind turbine and use thereof

Abstract: The invention relates a wind turbine rotor. The rotor comprises at least one wind turbine blade, at least one image capturing device, and one or more markers arranged on the blade so that the at least one image capturing device may detect the position of the markers. The invention further relates to a wind turbine and use thereof.

Design Study of 10 kW Superconducting Generator for Wind Turbine Applications

Abstract: We have performed a design study of a 10 kW superconducting slow rotating generator suitable for demonstration in a small scale wind turbine, where the drive train only consists of the turbine blades connected directly to the generator. The flux density in the superconducting rotor is chosen as B = 1 Tesla to be similar to the performance of permanent magnets and to represent a layout, which can be scaled up in future off-shore wind turbines. The proposed generator is a 8 pole synchronous machine based on race-track coils of high temperature superconducting tapes and an air cored copper stator enclosed in an iron shield.

Curved platform turbine blade

Abstract: A turbine blade (10) includes an airfoil (16) and integral platform at the root thereof. The platform (18) is contoured in elevation from a ridge (36, 48) to a trough (38), and is curved axially to complement the next adjacent curved platform.

Late lean injection fuel staging configurations

Abstract: A gas turbine engine (10) is provided and includes a combustor (70) having a first interior (21) in which a first fuel supplied thereto is combustible, a turbine (50), including rotating turbine blades, into which products of at least the combustion of the first fuel are receivable to power a rotation of the turbine blades, a transition zone (43), including a second interior (41) in which a second fuel supplied thereto and the products of the combustion of the first fuel are combustible, the transition zone (43) being disposed to fluidly couple the combustor (20) and the turbine (50) to one another, and a plurality of fuel injectors (60), which are supported by the transition zone (43) and coupled to a fuel circuit (70), and which are configured to supply the second fuel to the second interior (41) in any one or more of a single axial stage, multiple axial stages, a single axial circumferential stage and multiple axial circumferential stages.

A Review of Modern Wind Turbine Technology

Abstract: This article deals with a review of modern wind turbine technology. Wind energy for electricity production today is a mature, competitive, and virtually pollution-free technology widely used in many areas of the world. Wind technology converts the energy available in wind to electricity or mechanical power through the use of wind turbines. A wind turbine is a machine for converting the mechanical energy in wind into electrical energy. Wind turbines capture the power from the wind by means of aerodynamically designed blades and convert it into rotating mechanical power. Wind turbine blades use airfoils to develop mechanical power. Recent advances in technology and performance have resulted in current wind turbine designs being increasingly efficient, cost effective, and reliable.