bluuebunny/crossref_metadata_2025 huggingface dataset:
Impingement Cooling Experiments With Flat Plate and Pin Plate Target Surfaces
Authors: Hoecker Rainer , Johnson Bruce V. , Hausladen Josef , Rothbrust Matthias , Weigand Bernhard
Published: December 2014

Heat transfer experiments were conducted with three (3) different target plate configurations: a baseline copper flat smooth plate, a copper plate model with copper pins and a copper plate model with Teflon pins, to determine average heat transfer coefficients on the flat and pin surfaces for application with different plate materials. For each target plate surface configuration, the heat transfer experiments were conducted with selected impingement orifice plate configurations and with selected spacing between the orifice plate and the heat transfer target plate. The heat transfer results for the baseline copper smooth flat plate were in good agreement with a well-recognized correlation for the flow regions used in the correlation. An analytical procedure, similar to that used by Metzger et al. for pin-fins in coolant channels, was developed to separate the average heat transfer coefficients on the flat and pin surfaces. The results with the copper pins showed modest increases of approximately 35 percent in heat transfer at lower Reynolds numbers, decreasing with increased Reynolds number. Application of the experimental results to an analysis for high-pressure engine conditions with modest thermal conductivity materials showed that the overall heat transfer coefficient can decrease with pin surfaces for some conditions, compared to flat plates.
An Implicit Scheme for Cascade Flow and Heat Transfer Analysis
Authors: Xu C. , Amano R. S.
Published: December 2014

A new efficient implicit scheme, based on the second-order time and spatial difference algorithm for solving steady flow by using time-marching Navier-Stokes equations, was developed for predicating turbine cascade flows and heat transfer. The difference scheme comprises an explicit part in the intermediate time-step and an implicit part in the local time-step. The viscous flux-vectors are decomposed to simplify the flow calculation in the explicit step. The time difference terms are expressed in terms of the viscous dependent terms which appear in the diffusion terms in the form by adding eigenvalues of viscous flux matrices into the time derivation term. In the presently proposed scheme, the two-sweep procedure is used in the implicit step instead of employing a traditional matrix operation to save the computational time. This method has been used to calculate the flow around C3X and VKI cascades. The computed results were compared with experimental data as well as with other published computations. The comparisons for both surface pressure and heat transfer coefficient showed good agreement with the experiments.
Comparison of Computational Velocity and Heat Transfer Predictions to Experimental Measurements in a Rotating Cooling Passage With Smooth Walls
Authors: Bons Jeffrey P.
Published: December 2014

Numerical predictions of the turbulent velocity field and wall heat transfer for a simulated turbine blade cooling passage are presented. The square cross-sectioned, smooth-walled passage is identical to one for which velocity and heat transfer data are available for comparison. Reynolds number (8000), rotation number (0.2), and buoyancy numbers (0 and 0.49) are typical of gas turbine applications. Predictions are presented for three turbulence models: standard k-ε, Renormalization Group k-ε, and Reynolds Stress. In addition, two wall treatments are evaluated: wall functions and a two-layer zonal model. Results from the three models are comparable, however the two-layer zonal wall treatment provides the best match to both the experimental flowfield data and the Nusselt distribution. Wall functions are shown to be unsuitable for this flowfield. General flow features in the passage are adequately captured by the zonal model including the Coriolis-induced double vortex and the distorted streamwise velocity profile due to the buoyancy effect. Agreement between the calculated and measured streamwise velocity profile (from leading to trailing wall) is particularly remarkable and contributes to an impressive leading and trailing Nu match with the data. This agreement suggests that the model adequately accounts for the buoyancy effect on the bulk flow without any buoyancy terms in the k or ε conservation equations. The model is less effective, however, at capturing the specific vortex position and strength. Specifically, the model vortex has only half the measured vortex maximum velocity and is located forward or aft of the passage centerline (depending on the density ratio of the flow).
Variable Geometry Fuel Injector for Low Emissions Gas Turbines
Authors: Smith K. , Steele R. , Rogers J.
Published: December 2014

To extend the stable operating range of a lean premixed combustion system, variable geometry can be used to adjust the combustor air flow distribution as gas turbine operating conditions vary. This paper describes the design and preliminary testing of a lean premixed fuel injector that provides the variable geometry function. Test results from both rig and engine evaluations using natural gas are presented. The variable geometry injector has proven successful in the short-term testing conducted to date. Longer term field tests are planned to demonstrate durability.
Computations of Film Cooling From Holes With Struts
Authors: Shih T. I-P. , Lin Y.-L. , Chyu M. K. , Gogineni S.
Published: December 2014

Computations were performed to study the three-dimensional flow and heat transfer on a flat plate cooled by jets, injected from a plenum through one row of film-cooling holes in which each hole is fitted with a strut in the form of a circular cylinder. Three different configurations of the film-cooling hole were investigated: without strut, with streamwise strut, and with spanwise strut. For all configurations, the film-cooling holes are inclined at 35°, and the coolant-to-mainflow density and mass-flux ratios are 1.6 and 0.5, respectively. The focus of this study is to understand how struts in holes affect film cooling jets and their interactions with the mainflow in forming a protective layer of cooler fluid over the plate.

This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy. Effects of turbulence was modeled by a low Reynolds number k-ω closure known as the shear-stress-transport (SST) model. Solutions were generated by a cell-centered finite-volume method that uses third-order accurate flux-difference splitting of Roe with limiters, multigrid acceleration of a diagonalized ADI scheme with local time stepping, and patched/overlapped structured grids. In the computations, the flow is resolved not just in the cooling-jet/mainflow interaction region, but also inside the film-cooling holes and in the plenum. Computed results for adiabatic effectiveness for the case without struts were compared with experimental data, and reasonably good agreements were obtained.
Stress Relaxation Testing of Service Exposed IN738 for Creep Strength Evaluation
Authors: Woodford David A.
Published: December 2014

Standard size and miniature specimens of IN738 were taken from a service exposed turbine blade and vane for comparative stress relaxation testing at 800C, 850C and 900C. Base data taken from root section material were used to construct stress vs. creep rate parametric curves which could be used directly in design. Up to five decades in creep rates were obtained at each temperature from tests lasting less than one day. The data were also presented in the form of stress vs. predicted times to 0.5% creep which compared well with available long time creep data. Differences were noted in specimens taken from different locations in the airfoil regions which probably resulted from differences in grain size or orientation. Based on these measurements it was concluded that there was no significant effect of section size on creep strength as defined by this test, and that the alloy was quite insensitive to prior deformation and thermal exposures. A life management procedure, using a combination or creep strength evaluation based on the stress relaxation test and a separate fracture evaluation measurement, is outlined in which end of useful life is defined in terms of minimum acceptable performance levels.
Application of Integrated Electronic Control on Gas Turbine Marine Direct Drive Propulsion
Authors: Murphy Gregory L.
Published: December 2014

The use of digital controls in marine gas turbine propulsion has not been as widespread as in other applications. Although these controls have been used in marine applications such as gas turbine electric and water jet drive systems, digital controls have not been applied to a gas turbine direct drive application. This paper describes the use of digital control technology in a marine direct drive application.
Prediction of Periodic Response of Blades Having 3D Nonlinear Shroud Constraints
Authors: Chen J. J. , Menq C. H.
Published: December 2014

In this paper, a 3D shroud contact model is employed to predict the periodic response of blades having 3D nonlinear shroud constraint. When subjected to periodic excitation, the resulting relative motion at the shroud contact is assumed to be periodic in three-dimensional space. Based on the 3D shroud contact model, analytical criteria are used to determine the transitions between stick, slip, and separation of the contact interface and are used to simulate hysteresis loops of the induced constrained force, when experiencing periodic relative motion. The constrained force can be considered as a feedback force that influences the response of the shrouded blade. By using the Multi-Harmonic Balance Method along with Fast Fourier Transform, the constrained force can be approximated by a series of harmonic functions so as to predict the periodic response of a shrouded blade. This approach results in a set of nonlinear algebraic equations, which can be solved iteratively to yield the periodic response of blades having 3D nonlinear shroud constraint. In order to validate the proposed approach, the predicted results are compared with those of the direct time integration method. The resonant frequency shift, the damping effect, and the jump phenomenon due to nonlinear shroud constraint are examined. The implications of the developed solution procedure to the design of shroud contact are also discussed.
An Advanced Spray Model for Application to the Prediction of Gas Turbine Combustor Flowfields
Authors: Tolpadi Anil K. , Aggarwal Suresh K. , Mongia Hukam C.
Published: December 2014

It is well known that fuel preparation, its method of injection into a combustor and its atomization characteristics have a significant impact on emissions. A simple dilute spray model which assumes that droplet heating and vaporization occur in sequence has been implemented in the past within computational fluid dynamics (CFD) codes at GE and has been used extensively for combustion applications. This spray model coupled with an appropriate combustion model makes reasonable predictions of the combustor pattern factor and emissions. In order to improve upon this predictive ability, a more advanced quasi-steady droplet vaporization model has been considered. This paper describes the evaluation of this advanced model. In this new approach, droplet heating and vaporization take place simultaneously (which is more realistic). In addition, the transport properties of both the liquid and vapor phases are allowed to vary as a function of pressure, gas phase temperature and droplet temperature. These transport properties which are most up to date have been compiled from various sources and appropriately curve-fit in the form of polynomials. Validation of this new approach for a single droplet was initially performed. Subsequently, calculations of the flow and temperature field were conducted and emissions (NOx, CO and UHC) were predicted for a modern single annular turbofan engine combustor using both the standard spray model and the advanced spray model. The effect of the number of droplet size ranges as well as the effect of stochastic treatment of the droplets were both investigated.
Thermoeconomic Analysis of Gas Turbine Based Cycles
Authors: Massardo A. F. , Scialò M.
Published: December 2014

The thermoeconomic analysis of gas turbine based cycles is presented and discussed in this paper. The thermoeconomic analysis has been performed using the ThermoEconomic Modular Program (TEMP V.5.0) developed by the Authors (Agazzani and Massardo, 1997). The modular structure of the code allows the thermoeconomic analysis for different scenarios (turbine inlet temperature, pressure ratio, fuel cost, installation costs, operating hours per year, etc.) of a large number of advanced gas turbine cycles to be obtained in a fast and reliable way. The simple cycle configuration results have been used to assess the cost functions and coefficient values.

The results obtained for advanced gas turbine based cycles (intercooled, re-heated, regenerated and their combinations) are presented using new and useful representations: cost vs. efficiency, cost vs. specific work, and cost vs. pressure ratio. The results, including productive diagram configurations, are discussed in detail and compared to one another.
Design and Initial Development of Monolithic Cross-Flow Ceramic Hot-Gas Filters
Authors: Vaubert Virginie , Stinton David P. , Barra Chris , Limaye Santosh
Published: December 2014

Advanced, coal-fueled, power generation systems utilizing pressurized fluidized bed combustion (PFBC) and integrated gasification combined cycle (IGCC) technologies are currently being developed for high-efficiency, low emissions, and low-cost power generation. In spite of the advantages of these promising technologies, the severe operating environment often leads to material degradation and loss of performance in the barrier filters used for particle entrapment. To address this problem, LoTEC Inc., and Oak Ridge National Laboratory are jointly designing and developing a monolithic cross-flow ceramic hot-gas filter. The filter concept involves a truly monolithic cross-flow design that is resistant to delamination, can be easily fabricated, and offers flexibility of geometry and material make-up.

During Phase I of the program, a thermo-mechanical analysis was performed to determine how a cross-flow filter would respond both thermally and mechanically to a series of thermal and mechanical loads. The cross-flow filter mold was designed accordingly, and the materials selection was narrowed down to Ca0.5Sr0.5Zr4P6O24 (CS-50) and 2Al2O3−3SiO2 (mullite). A fabrication process was developed using gelcasting technology and monolithic cross-flow filters were fabricated. The program focuses on obtaining optimum filter permeability and testing the corrosion resistance of the candidate materials.
A Comparative View of Engineering Training in the US, Germany, and France With Special Focus on Turbomachinery-Relevant Skills
Authors: von Hoyningen-Huene Martin , Wedig Walter , Jeanpert Julie , Edel André
Published: December 2014

In this study, the status quo of university engineering education in the US, Germany, and France is presented. The different ways of training mechanical and aeronautical engineers are compared. Based on this, the strengths and weaknesses of their “products”, the outcoming engineers at Bachelor’s and Master’s level, are analyzed in respect to the needs in industry.

After a presentation of new tendencies and concepts in engineering education in the three countries under concern, the authors outline their vision of an engineer’s training. Some of these proposals are currently under realization in the Department of Mechanical Engineering of the University of Karlsruhe and at the Grande Ecole ENSAM in Paris that jointly have pursued this broad study.
An Interactive Method for Teaching Turbine Design
Authors: Ramsden K. W.
Published: December 2014

The implementation of new technology in the gas turbine industry is accelerating at a rate which demands increasing specialisation by its engineering design staff. Simultaneously, this industry has been adopting concurrent engineering practices to reduce product lead-time. Accordingly, the industry now requires its engineers to acquire competence in a wide range of technological disciplines together with a thorough understanding of the demands of design optimisation for the whole engine.

Against this background, educational providers must respond to these increasing demands with teaching programmes that enable a more rapid and deeper understanding of a very complex product. The ambition of the teacher, however, to prepare the student will continue to be limited by time constraints within lecture courses. Hitherto, this has normally resulted in class worked examples which are necessarily narrow in scope and confined to a limited range of design cases.

To overcome these limitations, a portfolio of multimedia computer programs has been developed specifically for rapid and relevant learning purposes. Each is structured to facilitate in-depth understanding of the key interactions between aerodynamics, thermodynamics and mechanical integrity needed in gas turbine design and performance assessment.

This paper describes an interactive teaching method for turbine design optimisation using only the multimedia turbine design and performance module. Through the example of a case study, the preliminary design of a high pressure and low pressure turbine combination is undertaken initially by hand.

This first pass design leaves substantial scope for design optimisation through a series of workshops using only the software. Final design recommendations are subsequently based on comprehensive tutor led but fully interactive discussion. Particular emphasis is placed on the impact of design decisions on both the various technology issues and on the performance of other engine components.
A Student-Executed Industrial Gas Turbine Design Project
Authors: Miller T. F. , Evanko J. M. , Camci C. , Glezer B. , Fox M.
Published: December 2014

Practical training that readies the university graduate to deal with real life problems from the beginning of their engineering career is considered by many leading companies to be a critically important factor for future technological progress. An aggressive design project was undertaken by a unique collaboration between the Pennsylvania State University and Solar Turbines, Inc., an industrial gas turbine company. What made this project unusual was the requirement that the design effort had to be completed by students within the tight scheduling of this industry. It is becoming clear, as our students complete their formal education and leave, that the specific educational environment provided within this project to undergraduate and graduate level engineering students was effective, practical, and beneficial in terms of both educational value and practical outcome. Insights into undertaking such a project are described here.
Linear Vibrations of Statically Indeterminate Rotors on Angular Misaligned Hydrodynamic Bearings
Authors: Zachariadis Demetrio C.
Published: December 2014

The influence of journal’s static and dynamic angular misalignment on the synchronous unbalance response and linear stability threshold of statically indeterminate rotors is analysed. Both short and finite bearing models are considered in order to calculate hydrodynamic reactions, and rotating parts are modeled using beam finite elements. The results provide descriptions of the effects of the consideration of the 32 coefficient bearing model on linear vibrations analyses, together with guidelines for early design stage identification of rotor systems sensitive to angular misalignments.
Numerical and Experimental Study of Unsteady Flow Field and Vibration in Radial Inflow Turbines
Authors: Kreuz-Ihli T. , Filsinger D. , Schulz A. , Wittig S.
Published: December 2014

The blades of turbocharger impellers are exposed to unsteady aerodynamic forces, which cause blade vibrations and may lead to failures. An indispensable requirement for a safe design of radial inflow turbines is a detailed knowledge of the exciting forces. Up to now, only few investigations relating to unsteady aerodynamic forces in radial turbines were presented. To give a detailed insight into the complex phenomena, a comprehensive research project was initiated at the Institut für Thermische Strömungsmaschinen, at the University of Karlsruhe.

A turbocharger test rig was installed in the high pressure, high temperature laboratory of the institute. The present paper gives a description of the test rig design and the measuring techniques. The flow field in a vaneless radial inflow turbine was analyzed using laser Doppler anemometry. First results of unsteady flow field investigations in the turbine scroll and unsteady phase resolved measurements of the flow field in the turbine rotor will be discussed. Moreover, results from finite element calculations analyzing frequencies and mode shapes are presented.

As vibrations in turbines of turbochargers are assumed to be predominantly excited by unsteady aerodynamic forces, a method to predict the actual transient flow in a radial turbine utilizing the commercial Navier Stokes solver TASCflow3d was developed. Results of the unsteady calculations are presented and comparisons with the measured unsteady flow field are made. As a major result, the excitation effect of the tongue region in a vaneless radial inflow turbine can be demonstrated.
Computational Simulation of Gas Turbines: Part II — Extensible Domain Framework
Authors: Reed John A. , Afjeh Abdollah A.
Published: December 2014

This paper describes the design concepts and object-oriented architecture of Onyx, an extensible domain framework for computational simulation of gas turbine engines. Onyx provides a flexible environment for defining, modifying and simulating the component-based gas turbine models described in Part 1 of this paper. Using advanced object-oriented technologies such as design patterns and frameworks, Onyx enables users to customize and extend the framework to add new functionality or adapt simulation behavior as required. A customizable visual interface provides high-level symbolic control of propulsion system construction and execution. For computationally-intensive analysis, components may be distributed across heterogeneous computing architectures and operating systems. A distributed gas turbine engine model is developed and simulated to illustrate the use of the framework.
Deformation of Plasma Sprayed Thermal Barrier Coatings
Authors: Senturk Ufuk , Lima Rogerio S. , Lima Carlos R. C. , Berndt Christopher C.
Published: December 2014

The deformation behavior of thermally sprayed partially stabilized zirconia (PSZ) coatings are investigated using Hertzian indentation and four-point bend testing, with in situ acoustic emission monitoring. The experimental deformation curves, together with the corresponding acoustic emission responses and the fracture properties of the material are used in defining the deformation characteristics of the coating (ceramic overlay with metallic bond coal where applicable) and substrate composite system. Experiments are aimed in examining the influence of the bond coat and the coating properties on the form of deformation. Substrate temperature and pauses during spraying are demonstrated to strongly effect the coating properties and the resulting fracture/failure characteristics of the composite system.
Predictions of NOx Formation Under Combined Droplet and Partially Premixed Reaction of Diffusion Flame Combustors
Authors: Rizk Nader K. , Chin Ju S. , Marshall Andre W. , Razdan Mohan K.
Published: December 2014

A methodology is presented in this paper on the modeling of NOx formation in diffusion flame combustors where both droplet burning and partially premixed reaction proceed simultaneously. The model simulates various combustion zones with an arrangement of reactors that are coupled with a detailed chemical reaction scheme. In this model, the primary zone of the combustor comprises a reactor representing contribution from droplet burning under stoichiometric conditions and a mixing reactor that provides additional air or fuel to the primary zone. The additional flow allows forming a fuel vapor/air mixture distribution that reflects the unmixedness nature of the fuel injection process. Expressions to estimate the extent of deviation in fuel/air ratios from the mean value, and the duration of droplet burning under stoichiometric conditions were derived. The derivation of the expressions utilized a data base obtained in a parametric study performed using a conventional gas turbine combustor where the primary zone equivalence ratio varied over a wide range of operation. The application of the developed model to a production combustor indicated that most of the NOx produced under the engine takeoff mode occurred in the primary as well as the intermediate regions. The delay in NOx formation is attributed to the operation of the primary zone under fuel rich conditions resulting in a less favorable condition for NOx formation. The residence time for droplet burning increased with a decrease in engine power. The lower primary zone gas temperature that limits the spray evaporation process coupled with the leaner primary zone mixtures under idle and low power modes increases the NOx contribution from liquid droplet combustion in diffusion flames. Good agreement was achieved between the measured and calculated NOx emissions for the production combustor. This indicates that the simulation of the diffusion flame by a combined droplet burning and fuel vapor/air mixture distribution offers a promising approach for estimating NOx emissions in combustors, in particular for those with significant deviation from traditional stoichiometry in the primary combustion zone.
Technical Development Issues and Dynamic Modeling of Gas Turbine and Fuel Cell Hybrid Systems
Authors: Liese Eric A. , Gemmen Randall S. , Jabbari Faryar , Brouwer Jacob
Published: December 2014

This paper describes safety issues important to the operation of combined fuel cell and gas turbine (hybrid) systems, and provides motivation for building dynamic modeling tools to support their development. It also describes two models — a steam reformer and a fuel cell — that will be used to investigate the dynamic performance of a hybrid system. The present goals are to develop dynamic models for these two components, ensure their reliability, and obtain a basic understanding of their performance prior to integration into a complete hybrid system model. Because of the large physical domain to be analyzed in the integrated hybrid system, both reformer and fuel cell models are simplified to a one-dimensional system of equations. Model results are presented for a tubular, counterflow steam reformer showing methane conversion and temperature behavior during initial startup, and following several step change perturbations. For the fuel cell model, a generic planar type is analyzed showing voltage and current behavior following step changes in load resistance and fuel input. The results provide confidence in each model’s reliability, enabling them to be integrated for hybrid system simulation. Results from the integrated simulations will provide guidance on future hybrid technology development needs.
Assessing the Effects of Deposits on Turbine Blading in a Twin Shaft Gas Turbine
Authors: Stamatis A. , Mathioudakis K. , Papailiou K.
Published: December 2014

This paper presents a procedure for assessing the condition of gas turbines and their components and particularly the hot section. The case of performance alteration due to deposits on the turbine is considered in more detail. Methods of elaborating on test data for achieving this purpose are presented. Testing under the guideline of current standards and parameter corrections are also discussed. Data from testing an operating twin shaft gas turbine are used to demonstrate the methods presented in the paper.
Diagnosing the Sources of Overall Performance Deterioration in CCGT Plants
Authors: Mathioudakis K. , Stamatis A. , Bonataki E.
Published: December 2014

A method for diagnosing which parts of a Combined Cycle Gas Turbine (CCGT) power plant are responsible for performance deviations is presented. When the overall power output and efficiency deviate from their baseline value, application of the method allows the determination of the component(s) of the plant, responsible for this deviation. The level of depth of this assessment depends on the number of quantities measured. It is demonstrated that a minimal number of measurements can be used to allocate differences between the gas turbine and the steam part of the plant. Additional data can then be used to identify deviating components in more detail. The influence of measurement uncertainty and the exploitation of different measurements in order to check consistency and improve reliability of the results are discussed.
Continuous Monitoring of Binary Gas Mixture Concentration With Application to Turbine Blade Cooling Experiments
Authors: Strilka Tomas , Sajben Miklos , Nagy Peter
Published: December 2014

Turbine blade cooling experiments often use mixtures of air and a heavy gas (CO2, SF6) to simulate coolant/mainstream density ratios. If the mixing of the mainstream with the coolant ejected from the blade is of interest, then it may be necessary to determine the spatial distribution of the heavy gas concentration in the flowfield. Commercial analyzers are too slow and have other disadvantages when used for this purpose. To meet this special need, a device has been developed to continuously monitor the heavy gas concentration in a small sample stream by determining the speed of sound in the sample. Together with the temperature of the sample, the information is sufficient to determine the concentration. The device measures the time of propagation for an ultrasonic burst transverse to the stream. The temperature of the gas contained in the device is controlled and measured. Calibration with several gas mixtures (air and CO2, SF6, He) has shown an uncertainty (Cmeas-Ctrue) of 2% over the full concentration range of 0–100%, for CO2 and SF6. The device is operable in the pressure range from −50 to 100 kPa gauge and in the temperature range from 0 to 40 °C. The instrument is rugged and will survive in noisy, turbulent environments.
300 KW Class, Semi-Closed Cycle Gas Turbine Engine Design Considerations
Authors: Rodgers C.
Published: December 2014

The thermodynamic performances and relative sizing of small single shaft and two spool semi-closed cycle turbine engines (SCTE), for propulsion needs were studied relative to the conventional intercooled recuperative (ICR) open cycle gas turbine. The study indicated that the basic attributes of the SCTE are higher specific power, hp/pps inlet flow, a flat specific fuel consumption (SFC) characteristic, and potentially reduced exhaust emissions, at the expense of slightly higher SFC, lower power to weight ratio, and increased cost $/hp relative to the ICR.

The combustor is paramount to the successful operation of the SCTE in that the feedback (recirculated) flow, must be clean and devoid of particulates that could deposit on the heat transfer surfaces and turbo machinery. Additionally if high specific power is the primary design constraint high reticulation flow ratio combustor technology must be researched.

A conservative cycle analysis was conducted with current small gas turbine state-of-art component efficiencies and temperature limits for metallic hot-end components. The analysis was simplified by using existing gas properties for hydrocarbon air mixtures without oxygen depletion, or exhaust products in compression. Although the assumption that the intercooler and recuperator effectiveness and pressure drops remained constant provided a common datum, the part load performance analysis could benefit from the supplementation of improved heat exchanger algorithms.
Predicting Coating Degradation Under Variable Peak Temperatures
Authors: Chan Kwai S. , Cheruvu N. Sastry , Leverant Gerald R.
Published: December 2014

The cyclic oxidation behavior of a CoCrAlY coating on a GTD-111 substrate was characterized by thermal cycling between ambient temperature and a variable peak temperature. The initial peak temperature of the thermal cycle was 954°C (1750°F) and tested for n1 cycles. The peak temperature was then increased to 1010°C (1850°F) for n2 cycles. Finally, the peak temperature was raised again to 1066°C (1950°F) for n3 cycles, where n1, n2, and n3 are in the range of a few hundred to a few thousand cycles. In all three cases, thermal cycles consisting of 55 minutes at the peak temperature and 5 minutes heating/cooling were used. Weight change of the test specimens was measured as a function of thermal cycle. The results were compared against a coating life model that treats coating degradation mechanisms including oxidation, spallation, and aluminum loss due to both inward and outward diffusion. Using this model, the influence of the variable peak temperature on coating life was predicted in accordance with experimental results.
A Time-Linearized Navier-Stokes Analysis of Stall Flutter
Authors: Clark William S. , Hall Kenneth C.
Published: December 2014

A computational method for accurately and efficiently predicting unsteady viscous flow through two-dimensional cascades is presented. The method is intended to predict the onset of the aeroelastic phenomenon of stall flutter. In stall flutter, viscous effects significantly impact the aeroelastic stability of a cascade. In the present effort, the unsteady flow is modeled using a time-linearized Navier-Stokes analysis. Thus, the unsteady flow field is decomposed into a nonlinear spatially varying mean flow plus a small-perturbation harmonically varying unsteady flow. The resulting equations that govern the perturbation flow are linear, variable coefficient partial differential equations. These equations are discretized on a deforming, multi-block, computational mesh and solved using a finite-volume Lax-Wendroff integration scheme. Numerical modelling issues relevant to the development of the unsteady aerodynamic analysis, including turbulence modelling, are discussed. Results from the present method are compared to experimental stall flutter data, and to a nonlinear time-domain Navier-Stoke analysis. The results presented demonstrate the ability of the present time-linearized analysis to model accurately the unsteady aerodynamics associated with turbomachinery stall flutter.
Shunted Piezoelectric Control of Airfoil Vibrations
Authors: Cross Charles J. , Fleeter Sanford
Published: December 2014

The application of shunted piezoelectric elements to provide passive structural damping is investigated by means of experiments performed in the Purdue High Speed Axial Compressor Research Facility. Piezoelectric elements are bonded to three airfoils in the stator row. This airfoil is excited by the wakes generated by an upstream rotor. As the wakes drive the airfoil vibrations, the piezoelectrics experience a strain and in response produce an electric field. Tuned electrical circuits connected to the piezoelectrics as shunts dissipate this electrical energy, with multiple shunting techniques utilized. This electrical energy dissipation and the corresponding reduction in the airfoil mechanical energy result in a reduction in the magnitude of the resonant vibrations. Thus, these passive vibration control experiments demonstrate that shunted piezoelectrics have significant damping capability and could be practical for the elimination or minimization of gas turbine blading flow induced vibrations.
Quantifying Fuel/Air Unmixedness in Premixing Nozzles Using an Acetone Fluorescence Technique
Authors: Stufflebeam John H. , Kendrick Donald W. , Sowa William A. , Snyder Timothy S.
Published: December 2014

The ability of a lean-premixed combustion system to minimize emissions while maintaining combustion stability over the operating curve relies upon how well the fuel nozzle premixes the fuel and air. As the level of premixing increases, NOx emissions at a given flame temperature decrease until a perfectly premixed condition is achieved. The objective of this paper is to quantify the level of premixing achieved by a premixing nozzle using an acetone fluorescence technique and determine its relationship to NOx emissions and combustion stability.

The technique of using acetone fluorescence has been used as a fast and quantitative diagnostic to map the fuel-air distribution. This technique has been applied to the development of a lean premixing nozzle to measure the fuel air distribution at the fuel nozzle exit plane. In this study, the fuel air distribution is presented as 2-D images. The average fuel/air ratio and the standard deviation are calculated at various annular regions to determine the distribution as a function of radius. A single unmixedness parameter (σ/μ) over the entire annulus is also calculated to allow relative ranking of the various fuel nozzle configurations.

The fluorescence data is acquired for various nozzle hardware configurations in an atmospheric test facility. Fuel and air flow conditions are determined by scaling engine conditions to cold flow conditions and matching the fuel to air momentum ratio at the fuel injection site. Measured fuel/air distributions, 6 mm downstream of the nozzle exit plane, from the acetone fluorescence technique are correlated to emissions and acoustic measurements made at full pressure and temperature conditions in a single-nozzle test rig.

The paper includes a description of the acetone fluorescence technique, the method for optimizing the fuel/air distribution through changes to the main gas fuel injection array, and correlations made between the fuel/air distribution, nozzle geometry, power setting, emissions and combustor acoustics.
GT24/26 Advanced Cycle System Power Plant Progress for the New Millenium
Authors: Mayer Albrecht , van der Linden Septimus
Published: December 2014

The GT24/26 Advance Cycle System ‘ACS’ was announced in 1993 as the first modern single shaft reheat combustion turbine to serve the power generation market. The ACS goal was to have higher efficiency and higher specific output than ‘F’ class machines already providing the first step to improved efficiency.

The innovative sequential combustion system (reheat) technology raised overall plant efficiencies to 58% LHV, a substantial improvement over the state of the art plant performance of 55% LHV at that time, without pushing the turbine inlet temperature envelope.

This paper will review progress of the power plant concepts that will serve the emerging Merchant Power market as a result of deregulation of the industry not only in the United States but in other countries as well. Operating experience as well as improvements will be reviewed of the current and future plants that will account for over 10 GW’s in the year 2000. Improvements to meet the challenges of the New Millenium continue through ABB R&D efforts as well as contributions to the DOE ATS program.
Experimental Investigations of Stall Flutter in a Transonic Cascade
Authors: Ellenberger Karsten , Gallus Heinz E.
Published: December 2014

The design of modern gas turbines is more and more based on flow simulations by numerical calculation models. Due to the different influence parameters the development and verification of these codes requires detailed data bases, which can only be provided by experimental investigations. The demand of increasing power density leads to higher Mach Numbers up to transonic ranges. Due to the thin blade profiles the risk of stall flutter becomes an extraordinary point of interest. Therefore, in a transonic wind tunnel a cascade of nine compressor blades designed by MTU Munich were investigated at different inlet Mach numbers and incidence angles. To get information about flow behavior at steady state, profile pressure distribution was measured at midspan with pressure taps on profile surface. In order to provide information about the overall flow field oil flow visualization and Schlieren technique were applied for the investigation at steady state. For flutter simulation the blade in the middle position of the cascade was forced to torsional oscillating movement by an electromagnetic shaker system with a frequency of f = 310.0 Hz. The flow behavior with oscillating and fixed center blade was investigated at midspan by means of dynamic pressure transducers and hot films glued on profile probes. The results of these investigations are presented in this paper especially up to the appearance of stall flutter.
Assessment of Turbine Engine Structural Integrity Using the Structural Dynamic Response Analysis Code (SDRAC)
Authors: Nichol Kurt L. , Sensmeier Mark D. , Tibbals Thomas F.
Published: December 2014

AEDC has developed a model-based analysis tool that merges real time processed dynamic engine vibration data with finite element models (FEM) and pretest analysis results. The tool, called the Structural Dynamics Response Analysis Capability, or SDRAC, performs this merge, displays the analysis results via an interactive graphical user interface (GUI) and presents an assessment of structural capability in real time. The tool also features a model modification routine to insure that the mathematical simulation adequately reflects results from the test. The adequacy of the simulation is displayed via error measures.
Deposition and Testing of Thermal Barrier Coatings on Gas Turbine Vanes
Authors: Tului M. , Gualco G. C. , Scarpellini R.
Published: December 2014

An innovative methodology to deposit, by plasma spraying, ceramic thermal barrier coatings on gas turbine blades and vanes was developed. Such a methodology produces a pattern of microcracks in the coating, thus improving its thermal shock resistance.

After a laboratory campaign of process optimization and coating characterization, real components were coated with a 150 μm thick layer of NiCoCrAlY as a bond coat and a 300 μm thick layer of ZrO2, partially stabilised with 8%of Y2O3, as a top coat. In particular, four vanes, taken from the first stage of a land based gas turbine (V64.3, produced by Ansaldo), were coated on the whole airfoil.

The four vanes were submitted to a cyclic oxidation test in a burner rig simulating the operative conditions of a gas turbine. In particular, they were exposed to a gas flow with the same composition, temperature and speed of the inlet gas of a real gas turbine; moreover, they were cooled by an internal stream of compressed air for obtaining the same temperature profile of a vane in operation. The surface temperature of the vanes was monitored during the test by an optical pyrometer and the internal temperature by a thermocouple.

After 550 hours of test, corresponding to 550 cycles, the four vanes did not show any sign of damage.
Life Management System for Hot-Gas-Path Components of Gas Turbines
Authors: Hayasaka Yasushi , Isobe Nobuhiro , Sakurai Shigeo , Kumata Kazuhiko
Published: December 2014

Recently the number of gas-turbine-powered combined-cycle plants has been increasing because of their efficiency and environmental compatibility. Gas turbine operating conditions are severe, especially for hot-gas-path components. To improve the reliability of such components and to extend their life, we have developed a life management system based on a residual-life-assessment method. The system makes possible integrated residual-life-assessment based on numerical analyses, material destructive-tests, nondestructive inspections, statistical analyses of field machine data, and the use of a database. To develop the system, the primary damage mechanism for each component is clarified and material degradation is evaluated. For nozzles, the system describes a method of predicting the maximum surface crack growth. The validity of the methods is verified by assessment of the inspection data. This paper also describes optimization of operating cost and RAM (reliability, availability and maintainability).
The Hybrid Cycle: Integration of a Fuel Cell With a Gas Turbine
Authors: Leeper John D.
Published: December 2014

The integration of a fuel cell and a gas turbine is a natural evolution in the quest for improved generation efficiency with clean emissions. Integration is achieved by using the gas turbine compressor as the air mover for the fuel cell, and using the high temperature exhaust of the fuel cell to supplant the gas turbine combustor.

Edison Technology Solutions (ETS), the California Energy Commission, the U. S. Department of Energy (DOE), and Siemens Westinghouse Power Corporation are jointly sponsoring a project to design and fabricate a hybrid cycle power system that couples a Pressurized Solid Oxide Fuel Cell (SOFC) generator module with a Micro Turbine Generator (MTG), to yield a system with a nominal capacity of 250 kW and a power generation efficiency approaching 60%. The SOFC will supply approximately 80% of the output power and the MTG 20%. The MTG functions primarily as a turbo charger for the SOFC with some additional shaft power available to turn an integral generator. The demonstration will be conducted at the University of California at Irvine. Startup is scheduled for the summer of 1999.

This project is expected to be the first demonstration of a hybrid cycle employing a pressurized SOFC to supplant the combustor of a gas turbine generator. The parameters of evaluation are the power output, electric generation efficiency, degradation characteristics, operability, and operating power range.

The primary project objective is to demonstrate successful startup and operation over the design power range at efficiencies approaching 60%. Secondary objectives are to evaluate operability, component reliability, and to conduct a design evaluation to develop improvements for subsequent designs.
Unsteady Transition Characteristics of Rotating Stall in a Single-Stage Transonic Axial Compressor
Authors: Nie Chaoqun , Chen Jingyi , Gui Xingmin , Yu Qing , Wang Tongqing
Published: December 2014

The unsteady transition characteristics of rotating stall have been studied experimentally in a single-stage transonic axial compressor. Three tested conditions in the near design and below design speed range, at tip relative Mach numbers from 1.26 to 1.0, were performed. The characteristics of rotating stall were studied by its dynamic behavior on the scale of compressor circumference and also by the flow field details in the blade passage. The dynamic behavior was analyzed by the technique of successive frequency spectrum and the flow field details were studied through internal transient pressure patterns in the blade passage plotted by the dynamic pressure data measured on the compressor shroud. It has been shown that intermittent pre-stall perturbations are evident for all the tested speeds and distinct by the different time and length scale of their existence. These are also interpreted by the difference of pressure loading and shock structure visualized in the pressure plots in the blade passage during stall inception. The pre-stall perturbations, with rather scattered frequency spectra, grow into fully developed stall abruptly. Nevertheless, the frequency spectrum of rotating stall falls into constant fraction of the frequency of compressor rotation for all the tested conditions. The increasing trend of the amplitude of pressure oscillation of rotating stall while gathering at its frequency spectrum could be detected in the stage of stall inception. Based on these two observations, there is a possibility of warning the stall precursors even for the high speed transonic compressor like the one tested in this paper.