Showing papers on "Turbine published in 2001"

Wind Energy Handbook

Abstract: As environmental concerns have focused attention on the generation of electricity from clean and renewable sources wind energy has become the world's fastest growing energy source. The Wind Energy Handbook draws on the authors' collective industrial and academic experience to highlight the interdisciplinary nature of wind energy research and provide a comprehensive treatment of wind energy for electricity generation. Features include: * An authoritative overview of wind turbine technology and wind farm design and development * In-depth examination of the aerodynamics and performance of land-based horizontal axis wind turbines * A survey of alternative machine architectures and an introduction to the design of the key components * Description of the wind resource in terms of wind speed frequency distribution and the structure of turbulence * Coverage of site wind speed prediction techniques * Discussions of wind farm siting constraints and the assessment of environmental impact * The integration of wind farms into the electrical power system, including power quality and system stability * Functions of wind turbine controllers and design and analysis techniques With coverage ranging from practical concerns about component design to the economic importance of sustainable power sources, the Wind Energy Handbook will be an asset to engineers, turbine designers, wind energy consultants and graduate engineering students.

Aerodynamics of Wind Turbines

Abstract: Aerodynamics of Wind Turbines is the established essential text for the fundamental solutions to efficient wind turbine design. Now in its third edition, it has been substantially updated with respect to structural dynamics and control. The new control chapter now includes details on how to design a classical pitch and torque regulator to control rotational speed and power, while the section on structural dynamics has been extended with a simplified mechanical system explaining the phenomena of forward and backward whirling modes. Readers will also benefit from a new chapter on Vertical Axis Wind Turbines (VAWT). Topics covered include increasing mass flow through the turbine, performance at low and high wind speeds, assessment of the extreme conditions under which the turbine will perform and the theory for calculating the lifetime of the turbine. The classical Blade Element Momentum method is also covered, as are eigenmodes and the dynamic behaviour of a turbine. The book describes the effects of the dynamics and how this can be modelled in an aeroelastic code, which is widely used in the design and verification of modern wind turbines. Furthermore, it examines how to calculate the vibration of the whole construction, as well as the time varying loads and global case studies.

Gas Turbine Heat Transfer and Cooling Technology

Abstract: Fundamentals Need for Turbine Blade Cooling Turbine-Cooling Technology Turbine Heat Transfer and Cooling Issues Structure of the Book Review Articles and Book Chapters on Turbine Cooling and Heat Transfer New Information from 2000 to 2010 References Turbine Heat Transfer Introduction Turbine-Stage Heat Transfer Cascade Vane Heat-Transfer Experiments Cascade Blade Heat Transfer Airfoil Endwall Heat Transfer Turbine Rotor Blade Tip Heat Transfer Leading-Edge Region Heat Transfer Flat-Surface Heat Transfer New Information from 2000 to 2010 2.10 Closure References Turbine Film Cooling Introduction Film Cooling on Rotating Turbine Blades Film Cooling on Cascade Vane Simulations Film Cooling on Cascade Blade Simulations Film Cooling on Airfoil Endwalls Turbine Blade Tip Film Cooling Leading-Edge Region Film Cooling Flat-Surface Film Cooling Discharge Coefficients of Turbine Cooling Holes 3.10 Film-Cooling Effects on Aerodynamic Losses 3.11 New Information from 2000 to 2010 3.12 Closure References Turbine Internal Cooling Jet Impingement Cooling Rib-Turbulated Cooling Pin-Fin Cooling Compound and New Cooling Techniques New Information from 2000 to 2010 References Turbine Internal Cooling with Rotation Rotational Effects on Cooling Smooth-Wall Coolant Passage Heat Transfer in a Rib-Turbulated Rotating CoolantPassage Effect of Channel Orientation with Respect to the RotationDirection on Both Smooth and Ribbed Channels Effect of Channel Cross Section on Rotating Heat Transfer Different Proposed Correlation to Relate the Heat Transferwith Rotational Effects Heat-Mass-Transfer Analogy and Detail Measurements Rotation Effects on Smooth-Wall Impingement Cooling Rotational Effects on Rib-Turbulated Wall ImpingementCooling New Information from 2000 to 2010 References Experimental Methods Introduction Heat-Transfer Measurement Techniques Mass-Transfer Analogy Techniques Liquid Crystal Thermography Flow and Thermal Field Measurement Techniques New Information from 2000 to 2010 Closure References Numerical Modeling Governing Equations and Turbulence Models Numerical Prediction of Turbine Heat Transfer Numerical Prediction of Turbine Film Cooling Numerical Prediction of Turbine Internal Cooling New Information from 2000 to 2010 References Final Remarks Turbine Heat Transfer and Film Cooling Turbine Internal Cooling with Rotation Turbine Edge Heat Transfer and Cooling New Information from 2000 to 2010 Closure Index

NREL Unsteady Aerodynamics Experiment in the NASA-Ames Wind Tunnel: A Comparison of Predictions to Measurements

Abstract: Currently, wind turbine designers rely on safety factors to compensate for the effects of unknown loads acting on the turbine structure. This results in components that are overdesigned because precise load levels and load paths are unknown. To advance wind turbine technology, the forces acting on the turbine structure must be accurately characterized because these forces translate directly into loads imparted to the wind turbine structure and resulting power production. Once these forces are more accurately characterized, we will better understand load paths and can therefore optimize turbine structures. To address this problem, the National Renewable Energy Laboratory (NREL) conducted the Unsteady Aerodynamics Experiment (UAE), which was a test of an extensively instrumented wind turbine in the giant NASA-Ames 24.4-m (80 feet) by 36.6-m (120 feet) wind tunnel. To maximize the benefits from testing, NREL formed a Science Panel of advisers comprised of wind turbine aerodynamics and modeling experts throughout the world. NREL used the Science Panel's guidance to specify the conditions and configurations under which the turbine was operated in the wind tunnel. The panel also helped define test priorities and objectives that would be effective for wind turbine modeling tool development and validation.

Dynamic modelling of a wind turbine with doubly fed induction generator

Abstract: As a result of increasing environmental concern, more and more electricity is generated from renewable sources. One way of generating electricity from renewable sources is to use wind turbines. A tendency to erect more and more wind turbines can be observed. As a result of this, in the near future wind turbines may start to influence the behaviour of electrical power systems. Therefore, adequate models to study the impact of wind turbines on electrical power system behaviour are needed. In this paper, a dynamic model of an important contemporary wind turbine concept is presented, namely a doubly fed (wound rotor) induction generator with a voltage source converter feeding the rotor. This wind turbine concept is equipped with rotor speed, pitch angle and terminal voltage controllers. After derivation of the model, the wind turbine response to two measured wind sequences is simulated.

Exhaust-gas turbocharger for an internal combustion engine

Abstract: An exhaust gas turbocharger for an internal combustion engine has an exhaust gas turbine in the exhaust gas train and a compressor in the intake tract, whereby an adjustable throttle device is provided upstream from the compressor wheel, for regulating the air mass stream to be supplied. The throttle device comprises a first guide grid and a second guide grid in the inflow region to the compressor wheel. Each guide grid possesses an adjustable grid geometry.

Using neural networks to estimate wind turbine power generation

Abstract: This paper uses data collected at Central and South West Services Fort Davis wind farm (USA) to develop a neural network based prediction of power produced by each turbine. The power generated by electric wind turbines changes rapidly because of the continuous fluctuation of wind speed and direction. It is important for the power industry to have the capability to perform this prediction for diagnostic purposes-lower-than-expected wind power may be an early indicator of a need for maintenance. In this paper, characteristics of wind power generation are first evaluated in order to establish the relative importance for the neural network. A four input neural network is developed and its performance is shown to be superior to the single parameter traditional model approach.

The Many Faces of Turbine Surface Roughness

Abstract: Results are presented for contact stylus measurements of surface roughness on in-service turbine blades and vanes. Nearly 100 turbine components were assembled from four land-based turbine manufacturers. Both coated and uncoated, cooled and uncooled components were measured, with part sizes varying from 2 to 20 cm. Spanwise and chordwise two-dimensional roughness profiles were taken on both pressure and suction surfaces. Statistical computations were performed on each trace to determine centerline averaged roughness, rms roughness, and peak to-valley height. In addition, skewness and kurtosis were calculated; as well as the autocorrelation length and dominant harmonics in each trace. Extensive three-dimensional surface maps made of deposits, pitting, erosion, and coating spallation expose unique features for each roughness type. Significant spatial variations are evidenced and transitions from rough to smooth surface conditions are shown to be remarkably abrupt in some cases. Film cooling sites are shown to be particularly prone to surface degradation.

Limits of the Turbine Efficiency for Free Fluid Flow

Abstract: An accurate estimate of the theoretical power limit of turbines in free fluid flows is important because of growing interest in the development of wind power and zero-head water power resources. The latter includes the huge kinetic energy of ocean currents, tidal streams, and rivers without dams. Knowledge of turbine efficiency limits helps to optimize design of hydro and wind power farms. An explicitly solvable new mathematical model for estimating the maximum efficiency of turbines in a free (nonducted) fluid is presented. This result can be used for hydropower turbines where construction of dams is impossible (in oceans) or undesirable (in rivers), as well as for wind power farms. The model deals with a finite two-dimensional, partially penetrable plate in an incompressible fluid. It is nearly ideal for two-dimensional propellers and less suitable for three-dimensional crossflow Darrieus and helical turbines. The most interesting finding of our analysis is that the maximum efficiency of the plane propeller is about 30 percent for free fluids. This is in a sharp contrast to the 60 percent given by the Betz limit, commonly used now for decades. It is shown that the Betz overestimate results from neglecting the curvature of the fluid streams. We also show that the three-dimensional helical turbine is more efficient than the two-dimensional propeller, at least in water applications. Moreover, well-documented tests have shown that the helical turbine has an efficiency of 35 percent, making it preferable for use in free water currents.

Semi-closed brayton cycle gas turbine power systems

Abstract: A combined cycle power system is provided which can convert an open combined cycle gas turbine into a reduced or zero emissions power system. The system includes a compressor which compresses air and combusts the air with a hydrocarbon fuel. The products of combustion and the remaining portions of the air form the exhaust which is expanded through a turbine. The turbine drives the compressor and outputs power. The exhaust exits the turbine and then is routed through a heat recovery steam generator. A bottoming cycle portion of the system includes a gas generator which combusts a hydrocarbon fuel with oxygen. Water is also entered into the gas generator where it is heated and combined with the products of combustion, before entering a bottoming turbine. The water is then separated and routed back to the gas generator after preheating within the heat recovery steam generator.

Convective Heat Transfer and Aerodynamics in Axial Flow Turbines

Abstract: The primary focus of this paper is convective heat transfer in axial flow turbines. Research activity involving heat transfer generally separates into two related areas: predictions and measurements. The problems associated with predicting heat transfer are coupled with turbine aerodynamics because proper prediction of vane and blade surface-pressure distribution is essential for predicting the corresponding heat transfer distribution. The experimental community has advanced to the point where time-averaged and time-resolved three-dimensional heat transfer data for the vanes and blades are obtained routinely by those operating full-stage rotating turbines. However, there are relatively few CFD codes capable of generating three-dimensional predictions of the heat transfer distribution, and where these codes have been applied the results suggest that additional work is required. This paper outlines the progression of work done by the heat transfer community over the last several decades as both the measurements and the predictions have improved to current levels. To frame the problem properly, the paper reviews the influence of turbine aerodynamics on heat transfer predictions. This includes a discussion of time-resolved surface-pressure measurements with predictions and the data involved in forcing function measurements. The ability of existing two-dimensional and three-dimensional Navier-Stokes codes to predict the proper trends of the time-averaged and unsteady pressure field for full-stage rotating turbines is demonstrated. Most of the codes do a reasonably good job of predicting the surface-pressure data at vane and blade midspan, but not as well near the hub or the tip region for the blade. In addition, the ability of the codes to predict surface-pressure distribution is significantly better than the corresponding heat transfer distributions. Heat transfer codes are validated against measurements of one type or another. Sometimes the measurements are performed using full rotating rigs, and other times a much simpler geometry is used. In either case, it is important to review the measurement techniques currently used. Heat transfer predictions for engine turbines are very difficult because the boundary conditions are not well known. The conditions at the exit of the combustor are generally not well known and a section of this paper discusses that problem. The majority of the discussion is devoted to external heat transfer with and without cooling, turbulence effects, and internal cooling. As the design community increases the thrust-to-weight ratio and the turbine inlet temperature, there remain many turbine-related heat transfer issues. Included are film cooling modeling, definition of combustor exit conditions, understanding of blade tip distress, definition of hot streak migration, component fatigue, loss mechanisms in the low turbine, and many others. Several suggestions are given herein for research and development areas for which there is potentially high payoff to the industry with relatively small risk.

Aircraft engine with inter-turbine engine frame

Abstract: An aircraft engine turbine frame includes a first structural ring, a second structural ring disposed co-axially with and radially spaced inwardly of the first structural ring about a centerline axis A plurality of circumferentially spaced apart struts extend between the first and second structural rings Forward and aft sump members having forward and aft central bores are fixedly joined to forward and aft portions of the turbine frame respectively A frame connecting means for connecting the engine to an aircraft is disposed on the first structural ring The frame connecting means may include a U-shaped clevis The frame may be an inter-turbine frame axially located between first and second turbines of first and second rotors of a gas turbine engine assembly An axial center of gravity of the second turbine passes though or very near a second turbine frame bearing supported by the aft sump member

Modelling and Prevention of Ice Accretion on Wind Turbines

Abstract: A numerical model that simulatesice accretion amounts and ice shapes on wind turbine blades is presented. The model simulates both rime icing due to fog droplets and glaze icing due to precipitation at all angles of droplet attack experienced by wind turbine blades. Icing can be simulated by the model also when the blade is heated. The sensitivity of ice accretions to meteorological variables is studied and predictions of the model are compared to data from icing wind tunnel experiments and from a field study of natural wind turbine icing. Applications of the model in the design of blade heating elementsfor anti-icing of wind turbines are described.

Wind turbine airfoil catalogue

Abstract: The aim of this work is two-sided. Firstly, experimental results obtained for numerous sets of airfoil measurements (mainly intended for wind turbine applications) are collected and compared with computational results from the 2D Navier-Stokes solver EllipSys2D, as well as results from the panel method code XFOIL. Secondly, we are interested in validating the code EllipSys2D and finding out for which air-foils it does not perform well compared to the experiments, as well as why, when it does so. The airfoils are classified according to the agreement between the numerical results and experimental data. A study correlating the available data and this classification is performed. It is found that transition modelling is to a large extent responsible for the poor quality of the computational results for most of the considered airfoils. The transition model mechanism that leads to these discrepancies is identified. Some advices are given for elaborating future airfoil design processes that would involve the numerical code EllipSys2D in particular, and transition modelling in general. (au)

Submersible electrical power generating plant

Abstract: A submersible generating plant for producing electricity from ocean currents. The apparatus consists of two counter-rotating, rear-facing turbines with a plurality of rotor blades extending radially outward from two separate horizontal axis that convey the kinetic energy from the two side-by-side turbine rotors through separate gearboxes to separate generators that are housed in two watertight nacelles that are located sufficiently far apart to provide clearance for the turbine rotors. The two generators and their gearboxes serve as ballast and are located below a streamlined buoyancy tank that extends fore and aft above and between them. A leverage system having no moving parts adjusts lifting forces to balance changing downward vector forces that result from changes in drag acting on the downward angled anchor line.

Limitations on Gas Turbine Performance Imposed by Large Turbine Cooling Flows

Abstract: Calculations of the performance of modern gas turbines usually include allowance for cooling air flow rate; assumptions are made for the amount of the cooling air bled from the compressor, as a fraction of the mainstream flow, but this fractional figure is often set in relatively arbitrary fashion. There are two essential effects of turbine blade cooling: (i) the reduction of the gas stagnation temperature at exit from the combustion chamber (entry to the first nozzle row) to a lower stagnation temperature at entry to the first rotor and (ii) a pressure loss resulting from mixing the cooling air with the mainstream, Similar effects occur in the following cooled blade rows. The paper reviews established methods for determining the amount of cooling air required and semi-empirical relations, for film cooled blading with thermal barrier coatings, are derived. Similarly, the pressure losses related to elements of cooling air leaving at various points round the blade surface are integrated over the whole blade. This gives another semi-empirical expression, this time for the complete mixing pressure loss in the blade row, as a function of the total cooling air used. These two relationships are then used in comprehensive calculations of the performance of a simple open-cycle gas turbine, for varying combustion temperature and pressure ratio. These calculations suggest that for maximum plant efficiency there may be a limiting combustion temperature (below that which would be set by stoichiometric combustion). For a given combustion temperature, the optimum pressure ratio is reduced by the effect of cooling air.

Method and apparatus for cooling high temperature components in a gas turbine

Abstract: A combustion turbine having a compressed air cooling circuit that is connected to a nitrogen source. Compressed air is provided to the cooling circuit upon start-up and gradually switched to nitrogen cooling, as the nitrogen becomes available. Transition from compressed air to nitrogen cooling is supplied to the hottest components first in accordance with a pre-selected control scheme. Upon shutdown of the plant, the process is reversed.

Optimum siting of wind turbine generators

Abstract: This paper investigates optimum siting of wind turbine generators from the viewpoint of site and wind turbine generator selection. The methodology of analysis is based on the accurate assessment of wind power potential of various sites. The analytical computations of annual and monthly capacity factors are done using the Weibull statistical model using cubic mean cube root of wind speeds. As many as fifty-four potential wind sites, with and without wind turbine installations, geographically distributed in different states of India are used for the siting analysis. As an outcome of this analysis several definitive conclusions of archival nature have been arrived at and are presented in the paper. If this analysis is done at the planning and development stages of installation of wind power stations, it will enable the wind power developer or the power utilities to make a judicious choice of potential site and wind turbine generator system from the available potential sites and wind turbine generators respectively.

Method and means for mounting a wind turbine on a tower

Abstract: The apparatus of this invention is utilized for mounting a wind turbine on the upper end of a wind turbine tower. The invention also relates to the method of erecting the same. The tower is provided with a pair of guide rails positioned on opposite sides thereof which extend from the lower end to the upper end of the tower. A sled is movably mounted on the guide rails and has a platform mounted thereon which is adapted to support the wind turbine thereon. In one form of the invention, the sled is self-contained in that it has an engine and a winch mounted thereon. In another form of the invention, the winch and engine are mounted on a self-propelled vehicle which is designed to transport the sled from one tower location to another. In another form of the invention, the winch is detachable from the self-propelled vehicle so that the winch may be anchored to the ground. When the wind turbine has been positioned at the upper end of the tower, a horizontally slidable platform moves the wind turbine from the sled to the upper end of the tower so that the wind turbine may be secured to the upper end of the tower.

WindPACT Turbine Design Scaling Studies Technical Area 1-Composite Blades for 80- to 120-Meter Rotor

Abstract: The United States Department of Energy (DOE) through the National Renewable Energy Laboratory (NREL) implemented the Wind Partnership for Advanced Component Technologies (WindPACT) program. As part of the WindPACT program, Global Energy Concepts, LLC (GEC), was awarded contract number YAM-0-30203-01 to examine Technical Area 1-Blade Scaling, Technical Area 2-Turbine Rotor and Blade Logistics, and Technical Area 3-Self-Erecting Towers. This report documents the results of GEC's Technical Area 1-Blade Scaling. The primary objectives of the Blade-Scaling Study are to assess the scaling of current materials and manufacturing technologies for blades of 40 to 60 meters in length, and to develop scaling curves of estimated cost and mass for rotor blades in that size range.

Generators and power electronics technology for wind turbines

Abstract: Due to the very fast development of power electronics, offering both higher capability and lower price/kW the applicability of power electronics in wind turbines increases rapidly. Moreover, new types of generators which may change the configuration of direct driven generators are being developed. This paper summarises the state of art regarding generator and power electronic concepts for wind turbines. The state of the art on wind turbine technology is established by a market oriented approach and the applied topologies are reviewed. Furthermore, trends for generators and power electronics are reviewed through technical and economical identifiers in terms of weight and price versus nominal power. New wind turbine designs are expected in the near future, exploiting the improved capabilities of generators and power electronics. Some of these new concepts are further discussed. Wind turbines are further being planned in big wind farms. These are subjected to quite high demands concerning power quality, controllability and safety. The paper also reviews potential concepts/technologies that can satisfy the defined restrictions.

Initialization of wind turbine models in power system dynamics simulations

Abstract: As a result of increasing environmental concern, increasing amounts of electricity are generated from renewable sources. One way of generating electricity from renewable sources is to use wind turbines. A tendency to erect more wind turbines can be observed. As a result of this, in the near future wind turbines may start to influence the behavior of electrical power systems. To investigate the impact of increasing wind turbine penetration, power system dynamics studies need to be carried out. To this end, power system dynamics simulation software is used, in which wind turbine models must be integrated to enable the investigation of increasing wind turbine penetration on power system behavior. If wind turbine models are to be integrated into power system dynamics simulation software, it must be possible to calculate the initial conditions of the dynamic model from load flow data to be able to initialize the dynamic simulation correctly. In this paper, a solution to this problem is presented.

Normalized Power Curves as a Tool for Identification of Optimum Wind Turbine Generator Parameters

Abstract: This paper presents a novel method of matching wind turbine generators to a site using normalized power and capacity factor curves. The site matching is based on identifying optimum turbine speed parameters from the turbine performance index curve, which is obtained from the normalized curves, so as to yield higher energy production at a higher capacity factor. The wind speeds are parameterized using a cubic mean cuberoot and statistically modeled using the Weibull probability density function. An expression for a normalized power and capacity factor, expressed entirely in normalized rated speed, is derived. The wind turbine performance index, a new ranking parameter, is defined to optimally match turbines to a potential wind site. The plots of normalized power, capacity factor, and turbine performance index versus normalized rated wind speed are drawn for a known value of the Weibull shape parameter of a site. Usefulness of these normalized curves for identifying optimum wind turbine generator parameters for a site is presented by means of two illustrative case studies. The generalized curves, if used at the planning and development stages of wind power stations, will serve as a useful tool to make a judicious choice of a wind turbine generator that yields higher energy at a higher capacity factor.

Comparative Analysis of Regression and Artificial Neural Network Models for Wind Turbine Power Curve Estimation

Abstract: This paper examines and compares regression and artificial neural network models used for the estimation of wind turbine power curves. First, characteristics of wind turbine power generation are investigated. Then, models for turbine power curve estimation using both regression and neural network methods are presented and compared. The parameter estimates for the regression model and training of the neural network are completed with the wind farm data, and the performances of the two models are studied. The regression model is shown to be function dependent, and the neural network model obtains its power curve estimation through learning. The neural network model is found to possess better performance than the regression model for turbine power curve estimation under complicated influence factors.

Segmented thermal barrier coating and method of manufacturing the same

Abstract: A thermal barrier coating ( 18 ) having a less dense bottom layer ( 20 ) and a more dense top layer ( 22 ) with a plurality of segmentation gaps ( 28 ) formed in the top layer to provide thermal strain relief. The top layer may be at least 95% of the theoretical density in order to minimize the densification effect during long term operation, and the bottom layer may be no more than 95% of the theoretical density in order to optimize the thermal insulation and strain tolerance properties of the coating. The gaps are formed by a laser engraving process controlled to limit the size of the surface opening to no more than 50 microns in order to limit the aerodynamic impact of the gaps for combustion turbine applications. The laser engraving process is also controlled to form a generally U-shaped bottom geometry ( 54 ) in the gaps in order to minimize the stress concentration effect.

Model Development and Simulation of Transient Behavior of Heavy Duty Gas Turbines

Abstract: This paper describes models for the transient analysis of heavy duty gas turbines, and presents dynamic simulation results of a modern gas turbine for electric power generation. Basic governing equations have been derived from integral forms of unsteady conservation equations. Mathematical models of each component are described with the aid of unsteady one-dimensional governing equations and steady-state component characteristics. Special efforts have been made to predict compressor characteristics including the effect of movable vanes, which govern the operating behavior of a whole engine. The derived equation sets are solved numerically by a fully implicit method. A controller model that maintains constant rotational speed and target temperature (turbine inlet or exhaust temperature) is used to simulate practical operations. Component models, especially those of the compressor, are validated through comparison with test data, The dynamic behavior of a 150 MW class engine is simulated. The time-dependent variations of engine parameters such as power, rotational speed, fuel, temperature, and guide vane angles are compared with field data. Simulated results are fairly close to the operation data.