Showing papers on "Turbine blade published in 1998"

Progress in coatings for gas turbine airfoils

Abstract: The development of ever more efficient gas turbines has always been paced by the results of research and development in the concurrent fields of design and materials technology. Improved structural design and airfoil cooling technology applied to higher strength-at-temperature alloys cast by increasingly complex methods, and coated with steadily improved coating systems, have led to remarkably efficient turbine engines for aircraft propulsion and power generation. For first stage turbine blades, nickel-based superalloys in various wrought and cast forms, and augmented by coatings since the 1960s, have been singularly successful materials systems for the past 50 years—and still no real world substitutes are on the horizon. This paper traces the history of protective coatings for superalloy airfoils beginning with the simple aluminides, followed by modifications with silicon, chromium and platinum, then MCrAlY overlay coatings, and finally the elegant electron beam vapor deposited ceramic thermal barrier coatings recently introduced to service. The publicly available results of several decades of research supporting these advances are highlighted. These include generic research on oxidation and hot corrosion mechanisms of superalloys and coatings, the intricacies of protective oxide adherence, mechanisms of low temperature (Type II) hot corrosion, and of aluminide coating formation and mechanical properties of alloy–coating systems. With no promising turbine materials beyond coated nickel-base superalloys apparent in the foreseeable future, continued progress will likely be made by further refinement of control of thermally grown oxide adherence, and by more cost effective manufacturing processes for contemporary types of protective coatings.

A 3-D stall-delay model for horizontal axis wind turbine performance prediction

Abstract: Most design and analysis methods widely used for horizontal axis wind turbine performance prediction, such as the PROP code, are based on the traditional 2-D blade element/momentum theory (BEMT) methods, which are inadequate and underpredict the wind turbine rotor power output in the high-wind/peak-power condition, owing to effects of rotation on the wind turbine blade boundary layer. Although the deficiencies of the methods have been known for some time, this area has been neglected. The continued development of viable and well-established stall-regulated wind-turbine technology makes this research topic timely and particularly relevant to reducing the cost of wind energy. The main aim of the present paper is to describe and analyze the fundamental flow phenomena that characterize the boundary layer on rotating blades, and to develop a preliminary stall-delay model that modifies the 2-D airfoil data so as to simulate the 3-D stall-delay effects. The following steps were taken in the development of the model: 1) analysis of the 3-D integral boundarylayer equations for a reference system rotating with the blade, 2) description of the effects of rotor rotation on the separation point and its causes, and 3) determination of a simple correction formula to obtain rotating rotor lift coefficient Ci(a) and drag coefficient Cd(a) data from measured 2-D airfoil data. The preliminary 3-D stall-delay model consists of two key parameters (the ratio of local chord to local radius c/r the ratio of rotation speed to freestream velocity A) and three empirical correction factors Copyright © 1998 by the American Institute of Aeronautics and Astronautics, Inc. and the American Society of Mechanical Engineering. All rights reserved. ^Visiting Scholar. 'Assistant Professor, Senior Member AIAA. (a, b, d}. The stall-delay model is consistent with the blade element/momentum theory method and the Viterna/Tangler model, and the 3-D stall-delay model can be incorporated into the state of the art performance prediction codes, such as PROP. Through comparison with the field test data, the new model for 3-D stall-delay shows good agreement between predictions and experiments. The new model should be of great use in existing codes for horizontal axis wind turbine design and analysis.

Three-Dimensional Wind Simulation

Abstract: A method for numerically simulating a three-dimensional field of turbulent windspeed (the “Sandia method”) for use in the aerodynamic and structural analyses of wind turbines is presented. The required inputs are single point power spectral densities (PSDs) and the coherence function. Suggestions for appropriate inputs and an example calculation are included. The simulation method is used to obtain “rotationally sampled” PSDs, which are compared with measurements obtained by Pacific Northwest Laboratories. The results show that the Sandia method is capable of producing simulations that agree with the measurements, especially when the coherence function is augmented from the usual form to include the ratio of spatial separation over height raised to the 0.25 power. The method is specialized for horizontal axis wind turbine analysis by phase lagging the simulations at each point in space so that wind speeds are simulated only when the turbine blade passes the point, reducing storage requirements and computation time by about an order of magnitude. For vertical axis applications, where interpolation will be required, the error induced by the interpolation is estimated and eliminated by the addition of white noise.

Turbulence properties of the impeller stream of a Rushton turbine

Abstract: The structure of the flow in a vessel stirred by a Rushton turbine was investigated using laser Doppler anemometry measurement techniques. The time and length scales of turbulence were determined and used to estimate the dissipation rate of turbulence energy. The levels of turbulence energy and dissipation are high near the turbine and decrease rapidly with increasing distance from the turbine blades. The turbulence in the impeller stream is mostly anisotropic close to the blades. The results are compared with the findings of earlier investigations, and their implications for computational fluid dynamics (CFD) predictions of the flows are discussed.

Heat Transfer Contributions of Pins and Endwall in Pin-Fin Arrays: Effects of Thermal Boundary Condition Modeling

Abstract: Short pin-fin arrays are often used for cooling turbine airfoils, particularly near the trailing edge. An accurate heat transfer estimation from a pin-fin array should account for the total heat transfer over the entire wetted surface, which includes the pin surfaces and uncovered endwalls. One design question frequently raised is the actual magnitudes of heat transfer coefficients on both pins and endwalls. Results from earlier studies have led to different and often contradicting conclusions. This variation, in part, is caused by imperfect or unrealistic thermal boundary conditions prescribed in the individual test models. Either pins or endwalls, but generally not both, were heated in those previous studies. Using a mass transfer analogy based on the naphthalene sublimation technique, the present experiment is capable of revealing the individual heat transfer contributions from pins and endwalls with the entire wetted surface thermally active. The particular pin-fin geometry investigated, S/D = X/D = 2.5 and H/D = 1.0, is considered to be one of the optimal array arrangement for turbine airfoil cooling. Both inline and staggered arrays with the identical geometric parameters are studied for 5000 < Re < 25,000. The present results reveal that the general trends of the row-resolved heat transfer coefficients on either pins or endwalls are somewhat insensitive to the nature of thermal boundary conditions prescribed on the test surface. However, the actual magnitudes of heat transfer coefficients can be substantially different, due to variations in the flow bulk temperature. The present study also concludes that the pins have consistently 10 to 20 percent higher heat transfer coefficient than the endwalls. However, such a difference in heat transfer coefficient imposes very insignificant influence on the overall array-averagea heat transfer, since the wetted area of the uncovered endwalls is nearly four times greater than that of the pins.

Trailing vortices around a 45° pitched‐blade impeller

Abstract: The trailing vortex system near impeller blades has been identified as the major flow mechanism responsible for mixing and dispersion in stirred vessels, and high turbulence levels in the vortices have an important impact on such phenomena as drop breakup and cell damage in bioreactors. Numerical computations of the flows require more detailed information on the velocity characteristics generated by different impeller designs than is available in the literature. The study on the mean flow and turbulence structure generated by a pitched-blade turbine with four 45° inclined blades found that single trailing vortex is formed around each turbine blade. The vortex axis spread out radially by less than 0.0015 T and was inclined at 20° to the horizontal plane. The vortices merged into the bulk flow structure at around 135° behind each blade. Periodicity of the mean flow due to the crossing of the individual blades and high levels of kinetic energy of turbulence (k) are contained within a radial distance of around r/T=0.23 from the axis and a vertical distance of z/T=0.07-0.46 from the bottom of the vessel. The k levels decay to nearly-uniform and low values outside this region. The results are compared with earlier investigations, and their implications for mixing processes and CFD predictions of the flows are discussed. The data identify flow regions accurately where intense turbulence is present and thus give useful indications for the optimization of mixing processes.

Unsteady Wake-Induced Boundary Layer Transition in High Lift LP Turbines

Abstract: The development of the unsteady suction side boundary layer of a highly loaded LP turbine blade has been investigated in a rectilinear cascade experiment. Upstream rotor wakes were simulated with a moving-bar wake generator. A variety of cases with different wake-passing frequencies, different wake strength, and different Reynolds numbers were tested. Boundary layer surveys have been obtained with a single hot-wire probe. Wall shear stress has been investigated with surface-mounted hot-film gages. Losses have been measured. The suction surface boundary layer development of a modern highly loaded LP turbine blade is shown to be dominated by effects associated with unsteady wake-passing. Whereas without wakes the boundary layer features a large separation bubble at a typical cruise Reynolds number, the bubble was largely suppressed if subjected to unsteady wake-passing at a typical frequency and wake strength. Transitional patches and becalmed regions, induced by the wake, dominated the boundary layer development. The becalmed regions inhibited transition and separation and are shown to reduce the loss of the wake-affected boundary layer. An optimum wake-passing frequency exists at cruise Reynolds numbers. For a selected wake-passing frequency and wake strength, the profile loss is almost independent of Reynolds number. This demonstrates a potential to design highly loaded LP turbine profiles without suffering large losses at low Reynolds numbers.

A Survey of Blade Tip-Timing Measurement Techniques for Turbomachinery Vibration

Abstract: This paper aims at providing a comparative survey of current analysis methods for the interpretation of vibration data measured at turbomachinery rotor blade tips using optical laser probes. The methods are classified by the form of the vibration that they attempt to identify, namely, asynchronous and synchronous with respect to rotor speed. The performance of the various techniques is investigated by using both actual assembly measurements and simulated response data. In the latter case, synchronous vibration data are obtained via a multidegree-of-freedom numerical simulator that includes the structural and geometric properties of the bladed-disk assembly, the external forcing terms, and the characteristics of the optical probe. When using experimental data, the results of the tip timing analysis are compared to those obtained from standard strain-gauge tests and the relative merits of the two approaches are discussed with emphasis on the effects of blade mistuning. Existing industry standard, tip-timing analysis techniques are found to exhibit a number of inherent limitations and suggestions were made to address these deficiencies, A detailed tip-timing case study for a steam turbine rotor is presented in some detail, and other potential application areas are explored. Of particular note is the introduction of a new indirect analysis method for identifying the characteristics of synchronous vibration modes using measurements from two probes. Finally, new avenues for future analysis methods and further developments in tip-timing systems are also discussed.

Analysis of thermal radiation effects on temperatures in turbine engine thermal barrier coatings

Abstract: Thermal barrier coatings on combustor liners and on turbine vanes and rotating blades are important for reducing metal temperatures in current and advanced turbine engines. Some coating materials such as zirconia are partially transparent to thermal radiation, and radiation within a coating will increase as temperatures are raised for higher efficiency engines. Hence, it is necessary to determine if radiation effects in a coating are a design consideration. For this purpose, the engine thermal environment is first summarized with regard to factors affecting radiative heat transfer. Radiative and thermal properties of zirconia are then considered, and methods of radiative analysis are briefly discussed. Typical temperature distributions and heat fluxes are given from the analysis of zirconia thermal barrier coatings on vanes and rotating blades, and on a combustor liner where the coating surface is expected to be covered with soot. The effects of various thermal conditions and heat transfer parameters are examined to indicate when radiation effects might be significant within a coating in a turbine engine. The largest effects were found in the combustor where coatings are subjected to large incident radiation. For coatings on turbine blades away from the combustor, and hence without large incident radiation, effects of radiation were found to be very small.

Thermal barrier coating ceramic structure

Abstract: A multilayered ceramic topcoat of a thermal barrier coating system is useful for high temperature corrosive applications such as hot section components in gas turbine engines. The ceramic topcoat includes at least two layers, each having generally columnar grain microstructures with different grain orientation directions. A preferred method of producing the multilayered ceramic topcoat includes positioning a superalloy substrate at a first angled orientation relative to a ceramic vapor cloud in an electron beam physical vapor deposition apparatus for a time sufficient to grow a first ceramic layer. The substrate is then reoriented to a second, different angled orientation for a time sufficient to grow a second ceramic layer. The ceramic layers exhibit columnar microstructures having respective grain orientation directions which are related to the first and second substrate orientations. For uniformly coating a complex contoured surface such as a turbine blade airfoil, the blade can be rotated during coating deposition at each angled orientation. Alternatively, the article may be continuously reoriented according to a predetermined speed cycle to produce generally arcuate, sinusoidal, helical, or other columnar grain microstructures.

Aeroelastic behavior of twist-coupled hawt blades

Abstract: 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.

Turbine blades made from multiple single crystal cast superalloy segments

Abstract: Large gas turbine blades (10) made from separate cast segments (12, 14. 16, 18) of superalloys are disclosed. The turbine blade is designed such that bond lines between adjacent segments are placed in low stress regions of the blade. The cast superalloy segments of the blades are aligned and fitted together with specified tolerances. The turbine blade segments are then joined by transient liquid phase bonding, followed by a controlled heat treatment which produces the desired microstructure in the bond region. The method allows for the production of large, high quality turbine blades (10) by joining small, high quality cast superalloy sections (12, 14, 16, 18), in comparison with prior attempts to cast large turbine blades as single pieces which have produced very low yields and high individual component costs.

Three-dimensional inverse method for turbomachinery blading design

Abstract: An iterative procedure for three-dimensional blade design is presented, in which the three-dimensional blade shape is modified using a physical algorithm, based on the transpiration model. The transpiration flux is computed by means ofa modified Euler solver, in which the target pressure distribution is imposed along the blade surfaces. Only a small number of modifications is needed to obtain the final geometry. The method is based on a high-resolution three-dimensional Euler solver. An upwind biased evaluation of the advective fluxes allows for a very low numerical entropy generation, and sharp shock capturing. Non-reflecting boundary conditions are applied along the inlet/outlet boundaries. The capabilities of the method are illustrated by redesigning a transonic compressor rotor blade, to achieve, for the same mass flow and outlet flow angle, a shock-free deceleration along the suction side. The second example concerns the design of a low aspect ratio turbine blade, with a positive compound lean to reduce the intensity of the passage vortices. The final blade is designed for an optimized pressure distribution, taking into account the forces resulting from the blade lean angle.

Experience with bicoherence of electrical power for condition monitoring of wind turbine blades

Abstract: The authors explore the application of the normalised bispectrum or bicoherence to the problem of condition monitoring of wind turbine blades. Background information is provided on this type of condition monitoring, how it differs from more conventional condition monitoring of turbo machinery, and the motivation for selecting bicoherence. Bicoherence is defined and compared with the power spectral density. Complications in collecting suitable data, and estimating the bicoherence from that data are investigated; including the requirements of very long stationary data sets for consistent estimates, and computational difficulties in handling such large data sets. Bicoherence is then applied to electrical power output data obtained from a 45 kW wind turbine. The turbine is operated in three configurations to represent normal and fault conditions. A blade with less flapwise stiffness but identical outer dimensions to the matched set of blades was fitted to simulate a damaged blade. Comparison of the results from the power spectral density and bicoherence indicates how the bicoherence might be employed for condition monitoring purposes. Slices of the bicoherence with one frequency fixed at the rate of rotation show clear differences between the configurations and substantially reduce the computational effort required to calculate the estimate.

Device and method for heating and deicing wind energy turbine blades

Abstract: The invention relates to heatable wind energy turbine blades and to a method of heating and deicing the turbine blades using conductive fabrics to displace and/or cease the buildup of ice on the turbine blades by electrothermal fabric heater disposed or integrated on the turbines for effectively deicing the blades. Multiple turbine blade design methods are explored as well as heater materials and the application of such materials.

Tapered tip turbine blade

Abstract: A turbine blade includes a hollow airfoil extending from an integral dovetail. The airfoil includes sidewalls extending between leading and trailing edges and longitudinally between a root and a tip. The sidewalls are spaced apart to define a flow channel for channeling cooling air through the airfoil. The tip is tapered longitudinally above at least one of the sidewalls and decreases in thickness.

Effects of Tip Clearance and Casing Recess on Heat Transfer and Stage Efficiency in Axial Turbines

Abstract: Calculations were performed to assess the effect of the tip leakage flow on the rate of heat transfer to blade, blade tip and casing. The effect on exit angle and efficiency was also examined. Passage geometries with and without casing recess were considered. The geometry and the flow conditions of the GE-E 3 first stage turbine, which represents a modem gas turbine blade were used for the analysis. Clearance heights of 0%, 1%, 1.5% and 3% of the passage height were considered. For the two largest clearance heights considered, different recess depths were studied. There was an increase in the thermal load on all the heat transfer surfaces considered due to enlargement of the clearance gap. Introduction of recessed casing resulted in a drop in the rate of heat transfer on the pressure side but the picture on the suction side was found to be more complex for the smaller tip clearance height considered. For the larger tip clearance height the effect of casing recess was an orderly reduction in the suction side heat transfer as the casing recess height was increased. There was a marked reduction of heat load and peak values on the blade tip upon introduction of casing recess, however only a small reduction was observed on the casing itself. It was reconfirmed that there is a linear relationship between the efficiency and the tip gap height. It was also observed that the recess casing has a small effect on the efficiency but can have a moderating effect on the flow underturning at smaller tip clearances.

Cooling system for turbine blade platforms

Abstract: A cooling system is disclosed for cooling the platforms of turbine blades fixed to the periphery of a turbine rotor, each turbine blade having an airfoil portion, a platform with opposite longitudinal edges, a root portion affixed to the turbine rotor, and a shank portion connecting the root portion to the platform. Adjacent turbine blades are located such that a longitudinal edge of one platform is adjacent to a longitudinal edge of an adjacent platform. A cavity is formed bounded by a portion of the periphery of the turbine rotor, the shank portions of the adjacent turbine blades, and the platforms of the adjacent turbine blades. A cooling air passage supplies cooling air to the cavity. One or more cooling channels are formed in a side of the platform facing the turbine rotor, each cooling channel having a cooling air collector at an end located adjacent to the air supply passage and communicating with the cavity. The cooling channels also include venting holes distributed along each of the cooling channels. A sealing plate extends across surfaces of adjacent platforms facing toward the turbine rotor so as to seal any gap existing between the adjacent longitudinal edges of the platform. The sealing plate covers the cooling channels to form cooling passages, the sealing plate having an orifice aligned with the cooling air collector of the cooling channel to enable cooling air from the cavity to enter the cooling channel and exit through the plurality of venting holes to cool the blade platform. The cavities are, in known fashion, sealed at their forward and rear ends by annular seals affixed to the turbine rotor.

Characterization of Contact Kinematics and Application to the Design of Wedge Dampers in Turbomachinery Blading: Part 1—Stick-Slip Contact Kinematics

Abstract: Friction dampers are often used in turbine design to attenuate blade vibration to acceptable levels so as to prolong blades’ service life. A wedge damper, also called a self-centering, blade-to-blade damper, can provide more design flexibility to meet various needs in different operating conditions when compared with conventional platform dampers. However, direct coupling of the two inclined friction interfaces of the wedge damper often leads to very complex contact kinematics. In Part I of this two-part paper, a dual-interface friction force model is proposed to investigate the coupling contact kinematics. The key issue of the model formulation is to derive analytical criteria for the stick-slip transitions that can be used to precisely simulate the complex stick-slip motion and, thus, the induced friction force as well. When considering cyclic loading, the induced periodic friction forces can be obtained to determine the effective stiffness and damping of the interfaces over a cycle of motion. In Part II of this paper, the estimated stiffness and damping are then incorporated with the harmonic balance method to predict the forced response of a blade constrained by wedge dampers.

Aeroelastic tailoring in wind-turbine blade applications

Abstract: 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.

Tapered tip-rib turbine blade

Abstract: A gas turbine engine rotor blade 18 includes a dovetail 22 and integral airfoil 24. The airfoil includes a pair of sidewalls 28,30 extending between leading and trailing edges 32,34, and longitudinally between a root 36 and tip 38. The sidewalls are spaced laterally apart to define a flow channel 40 for channeling cooling air through the airfoil. The tip includes a floor 48 atop the flow channel, and a pair of ribs 50,52 laterally offset from respective sidewalls. The ribs are longitudinally tapered for increasing cooling conduction thereof.

Blades Forced Response Analysis With Friction Dampers

Abstract: A multiharmonic frequency domain analysis combined with a Craig-Bampton component mode synthesis is presented to compute the dry friction damped forced response of blades. The accuracy of the analysis is established, for a cantilever beam with a dry friction damper attached, by comparison with experimental results and time domain analysis. The method has then been applied to a model fan blade damped by a blade to ground damper.

On the interpretation of measured profile losses in unsteady wake-turbine blade interaction studies

Abstract: The interaction of wakes shed by a moving blade row with a downstream blade row causes unsteady flow. The meaning of the free-stream stagnation pressure and stagnation enthalpy in these circumstances has been examined using simple analyses, measurements, and CFD. The unsteady flow in question arises from the behavior of the wakes as so-called negative jets. The interactions of the negative jets with the downstream blades lead to fluctuations in static pressure, which in turn generate fluctuations in the stagnation pressure and stagnation enthalpy. It is shown that the fluctuations of the stagnation quantities created by unsteady effects within the blade row are far greater than those within the incoming wake. The time-mean exit profiles of the stagnation pressure and stagnation enthalpy are affected by these large fluctuations. This phenomenon of energy separation is much more significant than the distortion of the time-mean exit profiles that is caused directly by the cross-passage transport associated with the negative jet, as described by Kerrebrock and Mikolajczak. Finally, it is shown that if only time-averaged values of loss are required across a blade row, it is nevertheless sufficient to determine the time-mean exit stagnation pressure.

Flutter Mechanisms in Low Pressure Turbine Blades

Abstract: Keywords: Unsteady Flows ; Turbomachinery ; GTT ; LTT Reference LTT-CONF-1998-005View record in Web of Science Record created on 2007-04-18, modified on 2017-05-10

Characterization of Contact Kinematics and Application to the Design of Wedge Dampers in Turbomachinery Blading: Part 2—Prediction of Forced Response and Experimental Verification

Abstract: In the second part of this paper, the application of the proposed dual-interface model to the prediction of the forced response of a blade constrained by wedge dampers will be presented. When considering cyclic loading, the induced friction forces and contact normal loads are combined so as to determine the effective stiffness and damping of the friction interfaces over a cycle of motion. The harmonic balance method is then used to impose the approximate stiffness and damping of the friction interfaces to a linear structure model of the blade. This approach results in a set of nonlinear algebraic equations that can be solved to yield the forced response of the blade excited by harmonic external forces. The predicted forced response can then be used to optimize a given damper design, namely to determine the dynamic weight at which the maximum reduction of resonant response is obtained. In order to illustrate the capacity of the proposed method and to examine its accuracy, the forced response ofa test beam is examined. The prediction is also compared with the results of lab tests to validate the proposed dual-interface friction force model.

Turbomachinery Blade Design Using a Navier-Stokes Solver and Artificial Neural Network

Abstract: This paper describes a knowledge-based method for the automated design of more efficient turbine blades. Two-dimensional blade sections, defined by BPzier curves as a function of 15 parameters, are first optimized by means of Simulated Annealing (SA) and an Artificial Neural Network (ANN). The later one is an approximate model (response surface) of the 2D Navier-Stokes solutions of previous designs stored in a database. Depending on the performance predicted by a Navier Stokes analysis the procedure will be stopped or the design cycle will be repeated after the newly designed blade has been added to the database. This extended database allows a more reliable optimization of the blade at next iteration. This procedure results in a considerable speed-up of the design process by reducing both the interventions of the operator and the computational effort. It is also shown how such a method allows the design of more efficient blades while satisfying both the aerodynamic and mechanical constraints. In this paper, emphasis is put on the formulation of a new objective function and its validation by means of three different blade designs.

Turbine blade with trailing edge root section cooling

Abstract: A convectively cooled turbine blade 10 has two distinct cooling air passage systems. The first system 30 cools the blade leading edge and emits cooling air through outlet passageways 36 in the leading edge arranged in showerhead array. The second system 38 includes a five-pass series flow passage comprising five cooling passage sections 41-45 that extend in series through the remainder of the blade. One of the passage sections includes a plurality of recesses 92,94 near the trailing edge 20 of the turbine blade to retain cooling air flow to the trailing edge adjacent the root portion of the blade.

Aerodynamic Analysis and Monitoring of the Vortec 7 Diffuser-augmented Wind Turbine

Abstract: The Vortec 7 is the first full scale diffuser augmented wind turbine (DAWT) to be built. A DAWT has a duct which surrounds the wind turbine blades and increases in cross-sectional area farther downstream. The aerodynamics of a diffuser are such that more air flows through the blade plane, and more power can be generated compared to a 'bare turbine' of the same rotor blade diameter. The idea of using a diffuser to augment the power of a wind turbine had been considered earlier, but received a big boost from research directed by K.M. Foreman at Grumman Aerospace Corporation into innovative wind energy conversion systems. The design of the Vortec 7 is based on the best model as determined by wind tunnel tests on a host of various DAWT options performed by Grumman in the 1970's and early I980's. This paper reports on the work performed at the Grumman Aerospace Corporation and presents a simplified theoretical analysis of the design, and results from a computational fluid dynamic (CFD) analysis. Preliminary field results from monitoring the Vortec 7 are presented. It is found that the simplified theoretical analysis and the CFD results show significant differences, but that the CFD agrees quite well with the field measurements. Many of the field results also agree with the Grumman measurements, including wind speed up at inlet near the blade tips. Preliminary measurements show that the speed up across the blade plane is not uniform as assumed by Foreman, decreasing towards the hub, and hence the power output of a DAWT would be less than predicted by Foreman. Improvements to the inlet velocity profile are anticipated after retrofitting a bullnose to the primary diffuser slot and a parabolic nose cone ahead of the rotor hub. This performance optimisation work has been guided by the CFD, blade & diffuser performance codes presented in this paper.

An infrared thermography imaging system for convective heat transfer measurements in complex flows

Abstract: An infrared thermography imaging system is described for spatially resolved convective heat transfer measurements when used in conjunction with thermocouples, energy balances, digital image processing, zinc-selenide windows, and unique in situ calibration procedures. The usefulness of the system and the techniques developed are demonstrated by measurements made in two different environments with complex, three-dimensional flow features. First, spatial variations of surface Nusselt numbers are measured along the concave surfaces of a swirl chamber whose geometry models an internal passage used to cool the leading edge of a turbine blade. Second, spatially resolved distributions of the adiabatic film-cooling effectiveness are measured downstream of film-cooling holes on a symmetric turbine blade in transonic flow.