Showing papers on "Turbine blade published in 2003"

Trends in the Design, Manufacture and Evaluation of Wind Turbine Blades

Abstract: Wind turbine blades continue to be the target of technological improvements by the use of better designs, materials, manufacturing, analysis and testing. As the size of turbines has grown over the past decade, designers have restrained the associated growth in blade weight to less than would have been possible through simple scaling-up of past approaches. These past improvements are briefly summarized. Manufacturing trends and design drivers are presented, as are the ways these design drivers have changed. Issues related to blade material choices are described, first for the currently dominant glass fibre technology and then for the potential use of carbon fibres. Some possible directions for future blade design options are presented, namely new planforms, aerofoils and aeroelastic tailoring. The significant improvement in sophistication of stress analysis and full-scale blade testing are also discussed. Copyright © 2003 John Wiley & Sons, Ltd.

Aerodynamic Analysis of Blunt Trailing Edge Airfoils

Abstract: The adoption of blunt trailing edge airfoils for the inboard region of large wind turbine blades has been proposed. Blunt trailing edge airfoils would not only provide a number of structural benefits, such as increased structural volume and ease of fabrication and handling, but they have also been found to improve the lift characteristics of airfoils. Therefore, the incorporation of blunt trailing edge airfoils would allow blade designers to more freely address the structural demands without having to sacrifice aerodynamic performance. Limited experimental data make it difficult for wind turbine designers to consider and conduct tradeoff studies using these section shapes and has provided the impetus for the present analysis of blunt trailing edge airfoils using computational fluid dynamics. Several computational techniques are applied, including a viscous/inviscid interaction method and three Reynolds-averaged Navier-Stokes methods.

Turbine shroud segment

Abstract: A shroud segment for being incorporated in a gas turbine engine so as to suppress influence of hot combustion gas on a turbine case of the gas turbine engine is provided with a back plate having first and second plate portions formed in an arc shape and supported by the turbine case, a touching member integrally formed on an inner surface of the back plate for touching with a rotating turbine blade, a pair of first seal slots for receiving a pair of first spline seal plate, a pair of second seal slots for receiving a pair of second spline seal plate and a pair of seal gaps respectively communicating with the first seal slots and the second seal slots. The seal gaps are respectively provided with abutment surfaces recessed from front surfaces of the second seal slots so as to receive front ends of the first spline seal plates.

Integrated bypass turbojet engines for aircraft and other vehicles

Abstract: A turbo jet engine comprises a fan unit (10a) which combines a fan (11a), centrifugal compressor cells (11b), and turbine blades (11c). Air flowing through the centrifugal compressor cells (11b) is supplied to a peripheral combustor (12), and air flowing through the fan (11a) cools the air flowing through the compressor cells (11b) and bypasses the combustor (12). Turbine exhaust and bypass air are then ejected through a common nozzle (9).

Large-Eddy Simulation of Flow Around Low-Pressure Turbine Blade with Incoming Wakes

Abstract: The flow around a low-pressure turbine rotor blade with periodically incoming wakes at a realistic Reynolds number is computed by means of large-eddy simulation (LES). The computed results are discussed in terms of phase-averaged and mean quantities. A comparison is made with an existing direct numerical simulation (DNS) for the same geometry and operating conditions. Particular attention is devoted to flow structures associated with the incoming wakes and their effect on the boundary layers. The analysis of the flowfield reveals patterns similar to those encountered in DNS and in LES of flow in the same geometry at a lower Reynolds number. Noticeable differences occur in the suction-side boundary layer, which exhibits a complete transition to turbulence for the present case

Using Hydrogen as Gas Turbine Fuel

Abstract: This paper addresses the possibility to burn hydrogen in a large size, heavy–duty gas turbine designed to run on natural gas, as a possible short-term measure to reduce greenhouse emissions of the power industry. The process used to produce hydrogen is not discussed here: we mainly focus on the behavior of the gas turbine, by analyzing the main operational aspects related to switching from natural gas to hydrogen. We will consider the effects of variations of volume flow rate and of thermo-physical properties on the matching between turbine and compressor and on the blade cooling of the hot rows of the gas turbine. In the analysis we will keep into account that those effects are largely emphasized by the abundant dilution of the fuel by inert gases (steam or nitrogen), necessary to control the NOx emissions. Three strategies will be considered to adapt the original machine, designed to run on natural gas, to operate properly with diluted hydrogen (VGV operations, increased pressure ratio, re-engineered machine). The performance analysis, carried out by a calculation method including a detailed model the cooled gas turbine expansion, shows that moderate efficiency decays can be predicted with elevated dilution rates (nitrogen is preferable to steam under this point of view). The combined cycle power output substantially increases if not controlled by VGV operations. It represents an opportunity if some moderate re-design is accepted (turbine blade height modifications or HP compressor stages addition).© 2003 ASME

Cooling system for a tip of a turbine blade

Abstract: A turbine blade for a turbine engine having a cooling system in at least the tip portion of the turbine blade. The cooling system includes one or more vortex chambers in a tip section of the blade. The vortex chambers receive cooling fluids from metering slots that provide a pathway between internal cooling cavities of the blade and the vortex chambers. The cooling fluids may be exhausted through one or more film cooling holes. The vortex chambers, metering slots, and film cooling holes may include a tip cap attached to the tip section of the blade. At least a portion of the vortex chambers, metering slots, and film cooling holes may be formed from impressions in the tip cap or the turbine blade, or both.

Gas turbine high temperature turbine blade outer air seal assembly

Abstract: A turbine shroud assembly includes forward and aft hangers, an axisymmetric plenum assembly, ceramic shroud segments, ceramic spacers, and forward and aft rope seals. The plenum assembly supplies impingement cooling to the shroud and the hangers. The impingement cooling to the forward and aft hangers is controlled independently to improve blade tip clearance. The rope seals are radially inward from the hangers and reduce cooling flow leakage. The turbine shroud assembly can operate in a higher temperature environment using less cooling flow than the prior art.

Heat Transfer Coefficients on the Squealer Tip and Near-Tip Regions of a Gas Turbine Blade With Single or Double Squealer

Abstract: Detailed heat transfer coefficient distributions on a gas turbine squealer tip blade were measured using a hue detection based transient liquid crystals technique. The heat transfer coefficients on the shroud and near tip regions of the pressure and suction sides of a blade were also measured. Squealer rims were located along (a) the camber line, (b) the pressure side, (c) the suction side, (d) the pressure and suction sides, (e) the camber line and the pressure side, and (f) the camber line and the suction side, respectively. Tests were performed on a five-bladed linear cascade with a blow down facility. The Reynolds number based on the cascade exit velocity and the axial chord length of a blade was 1.1×106 and the overall pressure ratio was 1.2. Heat transfer measurements were taken at the three tip gap clearances of 1.0%, 1.5% and 2.5% of blade span. Results show that the heat transfer coefficients on the blade tip and the shroud were significantly reduced by using a squealer tip blade. Results also showed that a different squealer geometry arrangement changed the leakage flow path and resulted in different heat transfer coefficient distributions. The suction side squealer tip provided the lowest heat transfer coefficient on the blade tip and near tip regions compared to the other squealer geometry arrangements.Copyright © 2003 by ASME

Embedded micromachined fiber-optic Fabry-Perot pressure sensors in aerodynamics applications

Abstract: Small size, high bandwidth pressure sensors are required for instrumentation of probes and test models in aerodynamic studies of complex unsteady flows. Optical-fiber pressure sensors promise potential advantages of small size and low cost in comparison with their electrical counterparts. We describe miniature Fabry-Perot cavity pressure sensors constructed by micromachining techniques in a turbine test application. The sensor bodies are 500 /spl mu/m squared, 300 /spl mu/m deep with a /spl sim/2 /spl mu/m-thick copper diaphragm electroplated on one face. The sensor cavity is formed between the diaphragm and the cleaved end of a single mode fiber sealed to the sensor by epoxy. Each sensor is addressed interferometrically in reflection by three wavelengths simultaneously, giving an unambiguous phase determination; a pressure sensitivity of 1.6 radbar/sup -1/ was measured, with a typical range of vacuum to 600 kPa. Five sensors were embedded in the trailing edge of a nozzle guide vane installed upstream of a rotor in a full-scale turbine stage transient test facility. Pressure signals in the trailing edge flow show marked structure at the 8 kHz blade passing frequency. To our knowledge, this is the first report of sensors located at the trailing edge of a normal-sized turbine blade.

Alternative Composite Materials for Megawatt-Scale Wind Turbine Blades: Design Considerations and Recommended Testing

Abstract: As part of the U.S. Department of Energy’s Wind Partnerships for Advanced Component Technologies program, Global Energy Concepts LLC (GEC) is performing a study concerning blades for wind turbines in the multi-megawatt range. Earlier in this project constraints were identified to cost-effective scaling-up of the current commercial blade designs and manufacturing methods, and candidate innovations in composite materials, manufacturing processes and structural configurations were assessed. In the present work, preliminary structural designs are developed for hybrid carbon fiber / fiberglass blades at system ratings of 3.0 and 5.0 megawatts. Structural performance is evaluated for various arrangements of the carbon blade spar. Critical performance aspects of the carbon material and blade structure are discussed. To address the technical uncertainties identified, recommendations are made for new testing of composite coupons and blade sub-structure

High-Resolution Large-Eddy Simulation of Flow Around Low-Pressure Turbine Blade

Abstract: Large-eddy simulation ofcompressible Navier-Stokes equations is used to study flows where a laminar boundary-layer separation is followed by a turbulent reattachment. The aim of the present work is to predict and describe the transition process and its interaction with the wake dynamics for a subsonic blade turbine configuration. Indeed, a better knowledge of this mechanism can help to improve the accuracy of a Reynolds-averaged Navier-Stokes turbulence model for such a flow case. High-resolution large-eddy-simulation-type computations have been carried out for the T106 low-pressure blade turbine at inlet Mach number of 0.1 and chord Reynolds number of 1.6 x 10 5 based on the exit isentropic velocity. The simulated mean and turbulent quantities compare well with the available experimental data. The primary two-dimensional instability that originates from the free shear in the bubble is unstable via the Kelvin-Helmholtz mechanism. Then, the three-dimensional motions spread on the boundary layer, leading to full breakdown to turbulence after the reattachment point

Deicing device for wind turbine blades

Abstract: Methods and Apparatuses for deicing a wind turbine blade are described herein. In one embodiment, an exemplary process includes detecting an icy condition on a wind turbine blade and causing at least a portion of the wind turbine blade to vibrate, causing the ice built up on the wind turbine blade to break off.

Transition zone in wind turbine blade

Abstract: The invention relates to a wind turbine blade and a transitional shell blank for the manufacture of the shell of a wind turbine blade, the blade or the transitional shell blank being made of fibre-reinforced polymer including a first type of fibres (1, 3, 6) of a first stiffness and a first elongation at breakage, and a second type of fibres (2, 5, 7) of a different stiffness and a different elongation at breakage. According to the invention the two types of fibres are distributed in the polymer matrix. When seen in a sectional view perpendicular to longitudinal direction of the blade or the transitional shell blank, the quantitative ratio of the two types of fibres varies continuously in the longitudinal direction of the blade or of the transition shell blank.

Turbine blade having angled squealer tip

Abstract: A turbine blade (18) for a gas turbine engine, including an airfoil (24) and integral dovetail (22) for mounting the airfoil (24) along a radial axis (17) to a rotor disk (16) inboard of a turbine shroud (20). The airfoil (24) further includes: first and second sidewalls (28, 30) joined together at a leading edge (32) and a trailing edge (34), where the first and second sidewalls (28,30) extend from a root (36) disposed adjacent the dovetail (22) to a tip plate (48) for channeling combustion gases (12) thereover; and, at least one tip rib (50/52) extending outwardly from the tip plate (48) between the leading and trailing edges (32, 34). The tip rib (50/52) is oriented so that an axis (58/82) extending longitudinally therethrough is at an angle (6/Phi) respect to the radial axis (17) for at least a designated portion (60) of an axial length of the turbine blade (18). Such angle (6/Phi) varies across the designated portion (60).

Development of an axial microturbine for a portable gas turbine generator

Abstract: A miniature gas turbine is under development with the aim of generating electrical energy from fuel. This system consists of a compressor, combustion chamber, turbine and generator. The turbine is a single-stage axial impulse turbine (Laval turbine) with a rotor diameter of 10 mm, made of stainless steel using die-sinking electro-discharge machining. It has been tested with compressed air to speeds up to 160 000 rpm and generates a maximum mechanical power of 28 W with an efficiency of 18.4%. When coupled to a small generator, it generates 16 W of electrical power, which corresponds to an efficiency for the total system of 10.5%. The power density is mainly limited by the maximal speed of the ball bearings. The main losses are the blade profile losses and the exit losses. Higher speeds can considerably reduce the exit losses and therefore increase efficiency and power density. An improved turbine has been tested at temperatures up to 360 °C and generates up to 44 W of electrical energy with a total efficiency of 16%. A 20 mm diameter centrifugal compressor matching the pressure and flow characteristics of the turbine has been designed and is currently under construction.

Method of manufacturing a wind turbine blade, wind turbine blade, front cover and use of a front cover

Abstract: The invention relates to a method of manufacturing a wind turbine blade, said method comprising the steps of: casting at least two wind turbine shells and preferably one or more load bearing structures, forming a wind turbine blade structure including at least two longitudinal joints by adhering said at least two wind turbine shells and said one or more load bearing structures together, forming one or more front covers to a shape substantially corresponding to said wind turbine blade structure or sections hereof, positioning said one or more front covers in relation to said wind turbine blade structure, and fastening said one or more front covers to said wind turbine blade structure with adhering means. The invention also relates to a wind turbine blade, front cover and the use of a front cover as a unit for supplementary mounting on a wind turbine blade.

Method of controlling a wind turbine connected to an electric utility grid during malfunction in said electric utility grid, control system, wind turbine and family hereof

Abstract: The invention relates to a method of controlling a wind turbine connected to an electric utility grid during malfunction in said electric utility grid, said method comprising the steps of detecting a malfunction in said electric utility grid and monitoring at least one physical work property of at least one component of said wind turbine. Further, the method controls the pitch of one or more win turbine blades of said wind turbine in order too keep said least one physical work property below at least one predefined limit in a time period of said malfunction. The invention also relates to a control system for a wind turbine connected and supplying electric power to a utility grid as well as a wind turbine and park hereof.

Heat transfer coefficients on the squealer tip and near squealer tip regions of a gas turbine blade

Abstract: Detailed heat transfer coefficient distributions on a squealer tip of a gas turbine blade were measured using a hue detection based transient liquid crystals technique. The heat transfer coefficients on the shroud and near tip regions of the pressure and suction sides of a blade were also measured. Tests were performed on a five-bladed linear cascade with a blow-down facility. The blade was a two-dimensional model of a first stage gas turbine rotor blade with a profile of a GE-E 3 aircraft gas turbine engine rotor blade. The Reynolds number based on the cascade exit velocity and axial chord length of a blade was 1.1 ×10 6 and the total turning angle of the blade was 97.7 deg. The overall pressure ratio was 1.2 and the inlet and exit Mach number were 0.25 and 0.59, respectively. The turbulence intensity level at the cascade inlet was 9. 7 percent. The heat transfer measurements were taken at the three different tip gap clearances of 1.0 percent, 1.5 percent, and 2.5 percent of blade span

Method of servicing the outer components of a wind turbine such as the wind turbine blades and the tower with a work platform and work platform

Abstract: The invention relates to a method of servicing the outer components of a wind turbine such as the wind turbine blades and the tower with a work platform, said method comprises the steps of: positioning the work platform at the wind turbine tower and connecting the work platform to an upper part of the wind turbine with at least one cable. Further the method comprises the steps of raising the work platform with the cable and cable winding means to a position of use, and holding the work platform to the side of the wind turbine tower with holding means. The invention also relates to a work platform for servicing the outer components of a wind turbine.

Wind power system

Abstract: A system for the generation of electrical power using an improved 600-watt to 900-watt wind turbine system. The system comprises a wind driven generator utilizing an array of uni-directional carbon fiber turbine blades, an air-ducting nose cone, and a supporting tower structure. Additionally, a method of blade fabrication utilizing expanding foam, to achieve improved blade edge strength, is disclosed. The support tower utilizes a compressive coupler that permits standard fence pipe to be joined without welding or drilling.

New Fatigue Data for Wind Turbine Blade Materials

Abstract: This paper reports on recent fatigue data of interest to the wind turbine industry in several areas: (a) very high cycle S-N data; (b) refined Goodman Diagram; (c) effects of fiber waviness; and (d) large tow carbon fi bers. Tensile fatigue results from a specialized high frequency small strand testing facility have been carried out to 10 10 cycles in some cases, beyond the expected cycle range for turbines. While the data cannot be used directly in design due to the specialized test specimen, the data trends help to clarify t he pr oper models for extrapolating f rom standard coupons to higher cycles. The results for various fiber and matrix systems also provide insight into basic failure mechanisms. For spectrum loading predictions, a more detailed Goodman Diagram has been developed with additional R-values (R is the ratio of m inimum to maximum stress in a cycle). The data of greatest interest were obtained for tensile fatigue with low cyclic amplitudes, close to R=1.0, to clarify the shape of the diagram as the cyclic amplitude approaches zero. These data may significantly shorten lifetime predictions compared with traditional Goodman Diagram constructions based on more limited data. The effects of material/process i nduced flaws on properties continues to be a m ajor concern, particularly with large tow carbon fabrics. The results of a study o f fiber waviness effects on compressive st rength s how significant strength reductions for severe waviness which can be introduced in resin infusion processes. The final section presents new fatigue results for large tow carbon/fiberglass hybrid composites. Epoxy resin laminates show marginally higher compressive strength and fatigue resistance with car bon fibers. Improve d compressive static and fatigue performance is found with stitched fabrics as compared with woven fabrics.

Design of heterogeneous turbine blade

Abstract: Constantly rising operating pressure and temperature in turbine drivers push the material capabilities of turbine blades to the limit. The recent development of heterogeneous objects by layered manufacturing offers new potentials for the turbine blades. In heterogeneous turbine blades, multiple materials can be synthesized to provide better properties than any single material. A critical task of such synthesis in turbine blade design is an effective design method that allows a designer to design geometry and material composition simultaneously. This paper presents a new approach for turbine blade design, which ties B-spline representation of a turbine blade to a physics (diffusion) process. In this approach, designers can control both geometry and material composition. Meanwhile, material properties are directly conceivable to the designers during the design process. The designer's role is enhanced from merely interpreting the optimization result to explicitly controlling both material composition and geometry according to the acquired experience (material property constraints). The mathematical formulation of the approach includes three steps: using B-spline to represent the turbine blade, using diffusion equation to generate material composition variation, using finite element method to solve the constrained diffusion equation. The implementation and examples are presented to validate the effectiveness of this approach for heterogeneous turbine blade design.

Turbine blade platform cooling system

Abstract: Aspects of the invention relate to a cooling system for a blade platform that can provide cooling to and reduce stress on the platform. Aspects of the invention relate to including one or more channels in the blade platform such that the channels extend from the trailing edge face of the platform toward, but terminate prior to, the leading edge face of the platform. The channels can be generally oval or oblong in conformation. Extending between the hollow shank and the channels can be a plurality of cooling holes. During engine operation, coolant is supplied to the shank of the blade assembly. Because the pressure at the shank is greater than the pressure at the trailing edge of the platform, coolant flow is induced through the cooling holes and into the channels. After flowing through the channels, the coolant can be dumped at the trailing edge.

BEM/FVM conjugate heat transfer analysis of a three‐dimensional film cooled turbine blade

Abstract: We report on the progress in the development and application of a coupled boundary element/finite volume method temperature‐forward/flux‐back algorithm developed to solve conjugate heat transfer arising in 3D film‐cooled turbine blades We adopt a loosely coupled strategy where each set of field equations is solved to provide boundary conditions for the other Iteration is carried out until interfacial continuity of temperature and heat flux is enforced The NASA‐Glenn explicit finite volume Navier‐Stokes code Glenn‐HT is coupled to a 3D BEM steady‐state heat conduction solver Results from a CHT simulation of a 3D film‐cooled blade section are compared with those obtained from the standard two temperature model, revealing that a significant difference in the level and distribution of metal temperatures is found between the two Finally, current developments of an iterative strategy accommodating large numbers of unknowns by a domain decomposition approach is presented An iterative scheme is developed along with a physically‐based initial guess and a coarse grid solution to provide a good starting point for the iteration Results from a 3D simulation show the process that converges efficiently and offers substantial computational and storage savings

Effect of Internal Coolant Crossflow on the Effectiveness of Shaped Film-Cooling Holes

Abstract: Film-cooling was the subject of numerous studies during the past decades. However, the flow conditions on the entry side of the film-cooling hole have not received much attention up to now. A stagnant plenum which is widely used in experimental and numerical studies to feed the holes is not necessarily a right means to represent real engine conditions. For this reason, the present paper reports on an experimental study investigating the effect of a coolant crossflow feeding the holes that is oriented perpendicular to the hot gas flow direction to model a flow situation that is, for instance, of common use in the mid-portion of turbine blades. A comprehensive set of experiments was performed to evaluate the effect of perpendicular coolant supply direction on film-cooling effectiveness over a wide range of blowing ratios (M = 0.5{hor{underscore}ellipsis}2.0) and coolant crossflow Mach numbers (Ma{sub c} = 0{hor{underscore}ellipsis}0.6). The coolant to hot gas density ratio, however, was kept constant at 1.85 which can be assumed to be representative for typical gas turbine applications. Three different hole geometries, including a cylindrical hole as well as two holes with expanded exits, were considered. Particularly, two-dimensional distributions of local film-cooling effectiveness acquired by means of anmore » infrared camera system were used to give detailed insight into the governing flow phenomena. The results of the present investigation show that there is a profound effect of how the coolant is supplied to the hole on the film-cooling performance in the near hole region. Therefore, crossflow at the hole entry side must be taken into account when modeling film-cooling at engine representative conditions.« less

The Transition Mechanism of Highly-Loaded LP Turbine Blades

Abstract: A detailed experimental investigation was conducted into the interaction of a convected wake and a separation bubble on the rear suction surface of a highly loaded low-pressure (LP) turbine blade. Boundary layer measurements, made with 2D LDA, revealed a new transition mechanism resulting from this interaction. Prior to the arrival of the wake, the boundary layer profiles in the separation region are inflexional. The perturbation of the separated shear layer caused by the convecting wake causes an inviscid Kelvin-Helmholtz rollup of the shear layer. This results in the breakdown of the laminar shear layer and a rapid wake-induced transition in the separated shear layer.Copyright © 2003 by ASME

Aerodynamic structures and processes in rotationally augmented flow fields

Abstract: Rotational augmentation of horizontal axis wind turbine blade aerodynamics currently remains incompletely characterized and understood. To address this, the present study concurrently analysed experimental measurements and computational predictions, both of which were unique and of high quality. Experimental measurements consisted of surface pressure data statistics used to infer sectional boundary layer state and to quantify normal force levels. Computed predictions included high-resolution boundary layer topologies and detailed above-surface flow field structures. This synergy was exploited to reliably identify and track pertinent features in the rotating blade boundary layer topology as they evolved in response to varying wind speed. Subsequently, boundary layer state was linked to above-surface flow field structure and used to deduce mechanisms underlying augmented aerodynamic force production during rotating conditions. Copyright © 2007 John Wiley &Sons, Ltd.