bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Contact Kinematics and Application to the Design of Wedge Dampers in Turbomachinery Blading: Part 2—Prediction of Forced Response and Experimental Verification
Authors: Yang B. D. , Menq C. H.
Published: February 2008

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 of a test beam is examined. The prediction is also compared with the results of lab tests to validate the proposed dual-interface friction force model.
Transition of a Technology Base for Advanced Aircraft Gas Turbine Control Systems
Authors: McGlone M. E.
Published: February 2008

Technology assessments during the 1980s projected the development of advanced military fighter aircraft that would require propulsion systems that could accommodate multimission capability with super maneuverability. These propulsion systems would be required to provide significantly improved thrust to weight, reduced thrust specific fuel consumption, and up and away thrust vectoring capabilities. Digital electronic control systems with significantly expanded capabilities would be required to handle these multifunction control actuation systems, to integrate them with flight control systems, and to provide fail-operational capability. This paper will discuss the challenges that were presented to propulsion system control designers, the innovation of technology to address these challenges, and the transition of that technology to production readiness. Technology advancements will be discussed in the area of digital electronic control capability and packaging, advanced fuel management systems, high pressure fuel hydraulic actuation systems for multifunction nozzles, integrated flight propulsion controls, and higher-order language software development tools. Each of these areas provided unique opportunities where technology development programs and flight prototyping carried concepts to reality.
Numerical Simulations of Nonreacting Flows for Industrial Gas Turbine Combustor Geometries
Authors: Relation H. L. , Battaglioli J. L. , Ng W. F.
Published: February 2008

This study evaluates the application of the computational fluid dynamics (CFD) to calculate the flowfields in industrial combustors. Two-burner test cases, which contain the elemental flow characteristics of an industrial gas turbine combustor, are studied. Comparisons were made between the standard k-epsilon turbulence model and a modified version of the k-epsilon turbulence model. The modification was based on the work of Chen and Kim in which a second time scale was added to the turbulent dissipation equation. Results from the CFD calculations were compared to experimental data. For the two-burner test cases under study, the standard k-epsilon model diffuses the swirl and axial momentum, which results in the inconsistent prediction of the location of the recirculation zone for both burner test cases. However, the modified k-epsilon model shows an improved prediction of the location, shape, and size of the primary centerline recirculation zone for both cases. The large swirl and axial velocity gradients, which are diffused by the standard k-epsilon; model, are preserved by the modified model, and good agreements were obtained between the calculated and measured axial and swirl velocities. The overprediction of turbulent eddy viscosity in regions of high shear, which is characteristic of the standard k-epsilon model, is controlled by the modified turbulence model.
Reaction of Fuel NOx Formation for Gas Turbine Conditions
Authors: Nakata T. , Sato M. , Hasegawa T.
Published: February 2008

Ammonia contained in coal-gasified fuel is converted to nitrogen oxides (NOx) in the combustion process of a gas turbine in integrated coal gasification combined cycle (IGCC) system. Research data on fuel-NOx formation are insufficient, and there still remains a wide explored domain. The present research aims at obtaining fundamental knowledge of fuel-NOx formation characteristics by applying reaction kinetics to gas turbine conditions. An instantaneous mixing condition was assumed in the cross section of a gas turbine combustor and both gradual mixing condition and instantaneous mixing condition were assumed at secondary air inlet section. The results may be summarized as follows: (1) in the primary combustion zone under fuel rich condition, HCN and other intermediate products are formed as ammonia contained in the fuel decomposes; (2) formation characteristics of fuel-NOx are affected by the condition of secondary air mixing; and (3) the conversion ratio from ammonia to NOx declines as the pressure inside the combustor rises under the condition of gradual mixing at the secondary air inlet. These results obtained agreed approximately with the experimentation.
Effect of Swirl on Combustion Characteristics in Premixed Flames
Authors: Gupta A. K. , Lewis M. J. , Qi S.
Published: February 2008

A double concentric premixed swirl burner is used to examine the structure of two different methane-air premixed flames. Direct flame photography together with local temperature data provides an opportunity to investigate the effects of swirl number distribution in each annulus on the global and local flame structure, flame stability and local distribution of thermal signatures. An R-type thermocouple compensated for high-frequency response is used to measure the local distribution of thermal signatures in two different flames, each of which represents a different of thermal signatures in two different flames, each of which represents a different of thermal signatures in two combination of swirl number in the swirl burner. In order to improve the accuracy of the temperature data at high-frequency conditions, information on the thermocouple time constant are also obtained under prevailing conditions of local temperature and velocity by compensating the heat loss from the thermocouple sensor bead. These results assist in quantifying the degree of thermal nonuniformities in the flame signatures as affected by the distribution of swirl and to develop strategies for achievinguniform distribution of temperatures in flames.
The GE Rich-Quench-Lean Gas Turbine Combustor
Authors: Feitelberg A. S. , Lacey M. A.
Published: February 2008

The General Electric Company has developed and successfully tested a full-scale, F-class (2550°F combustor exit temperature), rich-quench-lean (RQL) gas turbine combustor, designated RQL2, for low heating value (LHV) fuel and integrated gasification combined cycle applications. Although the primary objective of this effort was to develop an RQL combustor with lower conversion of fuel bound nitrogen to NOx than a conventional gas turbine combustor, the RQL2 design can be readily adapted to natural gas and liquid fuel combustion. RQL2 is the culmination of a 5 year research and development effort that began with natural gas tests of a 2” diameter perforated plate combustor and included LHV fuel tests of RQL1, a reduced scale (6” diameter) gas turbine combustor. The RQL2 combustor includes a 14” diameter converging rich stage liner, an impingement cooled 7” diameter radially-stratified-quench stage, and a backward facing step at the entrance to a 10” diameter film cooled lean stage. The rich stage combustor liner has a novel double-walled structure with narrow circumferential cooling channels to maintain metal wall temperatures within design limits. Provisions were made to allow independent control of the air supplied to the rich and quench/lean stages. RQL2 has been fired for almost 100 hours with LHV fuel supplied by a pilot scale coal gasification and high temperature desulfurization system. At the optimum rich stage equivalence ration NOx emissions were about 50 ppmv (on a dry, 15 percent O2 basis), more than a factor of 3 lower than expected from a conventional diffusion flame combustor burning the same fuel. With 4600 ppmv NH3 in the LHV fuel, this corresponds to a conversion of NH3 to NOx of about 5 percent. As conditions were shifted away from the optimum, RQL2 NOx emissions gradually increased until they were comparable to a standard combustor. A chemical kinetic model of RQL2, constructed from a series of ideal chemical reactors, matched the measured NOx emissions fairly well. The CO emissions were between 5 and 30 ppmv (on a dry, 15 percent O2 basis) under all conditions.
Gas Turbine Exhaust Emissions Monitoring Using Nonintrusive Infrared Spectroscopy
Authors: Hilton M. , Lettington A. H. , Wilson C. W.
Published: February 2008

Infrared (IR) spectra of the exhaust emissions from a static gas turbine engine have been studied using Fourier Transform (FT) spectroscopic techniques. Passive detection of the infrared emission from remote (range ∼ 3 m) hot exhaust gases was obtained nonintrusively using a high spectral resolution (0.25 cm−1) FTIR spectrometer. Remote gas temperatures were determined from their emission spectra using the total radiant flux method or by analysis of rotational line structure. The HITRAN database of atmospheric species was used to model the emission from gas mixtures at the relevant temperatures. The spatial distribution of molecular species across a section transverse to the exhaust plume ∼10 cm downstream of the jet pipe nozzle was studied using a tomographic reconstruction procedure. Spectra of the infrared emission from the plume were taken along a number of transverse lines of sight from the centerline of the engine outwards. A mathematical matrix inversion technique was applied to reconstruct the molecular concentrations of CO and CO2 in concentric regions about the centerline. Quantitative measurement of the molecular species concentrations determined nonintrusively were compared with results from conventional extractive sampling techniques.
An Efficient Computational Model for Premixed Turbulent Combustion at High Reynolds Numbers Based on a Turbulent Flame Speed Closure
Authors: Zimont V. , Polifke W. , Bettelini M. , Weisenstein W.
Published: February 2008

Theoretical background, details of implementation, and validation results for a computational model for turbulent premixed gaseous combustion at high turbulent Reynolds numbers are presented. The model describes the combustion process in terms of a single transport equation for a progress variable; turbulent closure of the progress variable’s source term is based on a model for the turbulent flame speed. The latter is identified as a parameter of prime significance in premixed turbulent combustion and determined from theoretical considerations and scaling arguments, taking into account physico-chemical properties and local turbulent parameters of the combustible mixture. Specifically, phenomena like thickening, wrinkling, and straining of the flame front by the turbulent velocity field are considered, yielding a closed form expression for the turbulent flame speed that involves, e.g., speed, thickness, and critical gradient of a laminar flame, local turbulent length scale, and fluctuation intensity. This closure approach is very efficient and elegant, as it requires only one transport equation more than the non reacting flow case, and there is no need for costly evaluation of chemical source terms or integration over probability density functions. The model was implemented in a finite-volume-based computational fluid dynamics code and validated against detailed experimental data taken from a large-scale atmospheric gas turbine burner test stand. The predictions of the model compare well with the available experimental results. It has been observed that the model is significantly more robust and computationally efficient than other combustion models. This attribute makes the model particularly interesting for applications to large three-dimensional problems in complicated geometries.
Thickness Measurement of MCrAlY High-Temperature Coatings by Frequency Scanning Eddy Current Technique
Authors: Antonelli G. , Ruzzier M. , Necci F.
Published: February 2008

Nondestructive characterization of nonserviced, high-temperature coatings can be considered one of the important factors to achieve a higher level of structural integrity of advanced gas turbines. The present paper describes an innovative eddy current technique especially developed for measuring the thickness of metallic (MCrAlY) coatings applied by vacuum plasma spray on Ni-base superalloys. Conventional eddy current techniques, well established for quality control of coating thickness, are not applicable in this case because of the low differences of electrical conductivities of coating and base materials, which is a consequence of their quite similar physical and chemical properties. The new technique employs fast frequency scanning of the electromagnetic field in the range 100 kHz–10 MHz, corresponding to probing depths from 1 mm to 0.1 mm. Dedicated hardware has been developed featuring high sensitivity, stability, and harmonic rejection. Analysis of the measured data (i.e., probe impedance versus frequency), in order to estimate the relevant diagnostic parameters (coating thickness, coating, and base metal electrical conductivities), is carried out on the basis of a theoretical model of interaction between a plane electromagnetic wave and test piece. The results of tests performed on a nonserviced first stage blade are reported and compared with reference destructive data. Reliability, accuracy and practical applicability of the method meets the requirements for in-shop quality control.
Blade Fault Recognition Based on Signal Processing and Adaptive Fluid Dynamic Modeling
Authors: Stamatis A. , Aretakis N. , Mathioudakis K.
Published: February 2008

An approach for identification of faults in blades of a gas turbine, based on physical modelling, is presented. A measured quantity is used as an input, and the deformed blading configuration is produced as an output. This is achieved without using any kind of “signature,” as is customary in diagnostic procedures for this kind of faults. A fluid dynamic model is used in a manner similar to what is known as “inverse design methods”: the solid boundaries that produce a certain flow field are calculated by prescribing this flow field. In the present case, a signal, corresponding to the pressure variation on the blade-to-blade plane, is measured. The blade cascade geometry that has produced this signal is then produced by the method. In the paper, the method is described, and applications to test cases are presented. The test cases include theoretically produced faults as well as experimental cases where actual measurement data are shown to produce the geometrical deformations that existed in the test engine.
Fundamental Heat Transfer Experiments of Heat Pipes for Turbine Cooling
Authors: Yamawaki S. , Yoshida T. , Taki M. , Mimura F.
Published: February 2008

Fundamental heat transfer experiments were carried out for three kinds of heat pipes that may be applied to turbine cooling in future aero-engines. In the turbine cooling system with a heat pipe, heat transfer rate and start-up time of the heat pipe are the most important performance criteria to evaluate and compare with conventional cooling methods. Three heat pipes are considered, called heat pipe A, B, and C, respectively. All heat pipes have a stainless steel shell and nickel sintered powder metal wick. Sodium (Na) was the working fluid for heat pipes A and B; heat pipe C used eutectic sodium-potassium (NaK). Heat pipes B and C included noncondensible gas for rapid start-up. There were fins on the cooling section of heat pipes. In the experiments, and infrared image furnace supplied heat to the heat pipe simulating turbine blade surface conditions. In the results, heat pipe B demonstrated the highest heat flux of 17 to 20 W/cm2. The start-up time was about 6 minutes for heat pipe B and about 16 minutes for heat pipe A. Thus, adding noncondensible gas effectively reduced start-up time. Although NaK is a liquid phase at room temperature, the startup time of heat pipe C (about 7 to 8 minutes) was not shorter than the heat pipe B. The effect of a gravitational force on heat pipe performance was also estimated by inclining the heat pipe at an angle of 90 deg. There was no significant gravitational dependence on heat transport for heat pipes including noncondensible gas.
Experience in Applying the New UK Procedure for Creep Rupture Data Assessment to Gas Turbine Materials
Authors: Bullough C. K.
Published: February 2008

A new procedure being developed in British Standards for the assessment of creep-rupture data is described and evaluated with trial data sets of gas turbine blading materials. The procedure is applied in phases. An important development by statistical experts is a framework for the main assessment phase that uses maximum-likelihood fitting methods for the treatment of unfailed test points and error variance. The framework selects models from a standard suite (together with any other linear models supplied by the assessor) using statistical criteria, but also incorporates metallurgical judgement. The improved representation of the experimental data compared with previous fitting methods and the associated statistical tests indicate that the new procedure can be used to derive rupture strength values for gas turbine materials with confidence.
Development and Turbine Engine Performance of Three Advanced Rhenium Containing Superalloys for Single Crystal and Directionally Solidified Blades and Vanes
Authors: Broomfield R. W. , Ford D. A. , Bhangu J. K. , Thomas M. C. , Frasier D. J. , Burkholder P. S. , Harris K. , Erickson G. L. , Wahl J. B.
Published: February 2008

Turbine inlet temperatures over the next few years will approach 1650°C (3000°F) at maximum power for the latest large commercial turbofan engines, resulting in high fuel efficiency and thrust levels approaching 445 KN (100,000 lbs.). High reliability and durability must be intrinsically designed into these turbine engines to meet operating economic targets and ETOPS certification requirements. This level of performance has been brought about by a combination of advances in air cooling for turbine blades and vanes, design technology for stresses and airflow, single crystal and directionally solidified casting process improvements, and the development and use of rhenium (Re) containing high γ′ volume fraction nickel-base superalloys with advanced coatings, including full-airfoil ceramic thermal barrier coatings. Re additions to cast airfoil superalloys not only improves creep and thermo-mechanical fatigue strength, but also environmental properties including coating performance. Re dramatically slows down diffusion in these alloys at high operating temperatures. A team approach has been used to develop a family of two nickel-base single crystal alloys (CMSX-4® containing 3 percent Re and CMSX®-10 containing 6 percent Re) and a directionally solidified, columnar grain nickel-base alloy (CM 186 LC® containing 3 percent Re) for a variety of turbine engine applications. A range of critical properties of these alloys is reviewed in relation to turbine component engineering performance through engine certification testing and service experience. Industrial turbines are now commencing to use this aero developed turbine technology in both small and large frame units in addition to aero-derivative industrial engines. These applications are demanding, with high reliability required for turbine airfoils out to 25,000 hours, with perhaps greater than 50 percent of the time spent at maximum power. Combined cycle efficiencies of large frame industrial engines are scheduled to reach 60 percent in the U. S. ATS programme. Application experience to a total 1.3 million engine hours and 28,000 hours individual blade set service for CMSX-4 first stage turbine blades is reviewed for a small frame industrial engine.
Reducing Lateral Vibrations of a Rotor Passing Through Critical Speeds by Acceleration Scheduling
Authors: Millsaps K. T. , Reed G. L.
Published: February 2008

A method is presented for reducing the lateral response of an imbalanced rotor accelerating or decelerating through its first lateral bending critical speed by using a variable acceleration rate. A lumped parameter model along with a numerical integration scheme is used to simulate the response of a simply supported, single disk rotor during fast acceleration and deceleration through critical speed. The results indicate that the maximum response and/or the total vibrational energy of a rotor passing through the critical speed can be reduced significantly by using a variable acceleration schedule. That is, reducing the acceleration rate after the nominal critical speed is passed. These predictions were verified experimentally for a single disk rotor.
Model Predictive Control of a Combined Heat and Power Plant Using Local Linear Models
Authors: Kikstra J. F. , Roffel B. , Schoen P.
Published: February 2008

Model predictive control has been applied to control of a combined heat and power plant. One of the main features of this plant is that it exhibits nonlinear process behavior due to large throughput swings. In this application, the operating window of the plant has been divided into a number of smaller windows in which the nonlinear process behavior has been approximated by linear behavior. For each operating window, linear step weight models were developed from a detailed nonlinear first principles model, and the model prediction is calculated based on interpolation between these linear models. The model output at each operating point can then subsequently be calculated from four basic linear models, and the required control action can subsequently be calculated with the standard model predicative control approach using quadratic programming.
Application of Active Combustion Instability Control to a Heavy Duty Gas Turbine
Authors: Seume J. R. , Vortmeyer N. , Krause W. , Hermann J. , Hantschk C.-C. , Zangl P. , Gleis S. , Vortmeyer D. , Orthmann A.
Published: February 2008

During the prototype shop tests, the Model V84.3A ring combustor gas turbine unexpectedly exhibited a noticeable “humming” caused by self-excited flame vibrations in the combustion chamber for certain operating conditions. The amplitudes of the pressure fluctuations in the combustor were unusually high when compared to the previous experience with silo combustor machines. As part of the optimization program, the humming was investigated and analyzed. To date, combustion instabilities in real, complex combustors cannot be predicted analytically during the design phase. Therefore, and as a preventive measure against future surprises by “humming,” a feedback system was developed which counteracts combustion instabilities by modulation of the fuel flow rate with rapid valves (active instability control, AIC). The AIC achieved a reduction of combustion-induced pressure amplitudes by 86 percent. The Combustion instability in the Model V84.3A gas turbine was eliminated by changes of the combustor design. Therefore, the AIC is not required for the operation of customer gas turbines.
Numerical Analysis of Heat Pipe Turbine Vane Cooling
Authors: Zuo Z. J. , Faghri A. , Langston L.
Published: February 2008

A numerical model was developed to simulate transient performance of a heat pipe turbine vane under typical gas turbine engine conditions. Curvilinear coordinates were used to describe the three-dimensional wall and wick heat conduction coupled with the quasi-one-dimensional vapor flow. A unique numerical procedure including two iterative “estimate-correction” processes was proposed to efficiently solve the governing equations along with the boundary conditions. Comparisons with experimental results validated the numerical model and the solution method. A detailed numerical simulation of the heat pipe vane’s transient performance indicated the benefits of incorporating heat pipe vane cooling as well as the areas where precautions should be taken while designing heat pipe vanes.
Steady-State Response of Continuous Nonlinear Rotor-Bearing Systems Using Analytical Approach
Authors: Zu J. W. , Ji Z. Y.
Published: February 2008

A continuous modeling of nonlinear rotor-bearing systems is presented in this paper. The shaft is treated as a distributed parameter system using Timoshenko beam theory. A close form, steady-state response of the system is solved analytically for the first time. For cubic nonlinear bearings, the response is composed of three components, synchronous vibration, subsynchronous, and supersynchronous vibration. The harmonic balance method is used to calculate the nonlinear bearing forces. Two examples of nonlinear rotor-bearing systems are shown to illustrate the analysis procedure and the nonlinear characteristics of the system. Solutions from simplified systems are also derived for comparison.
Analysis of Interfacial Cracks in a TBC/Superalloy System Under Thermomechanical Loading
Authors: Nusier S. Q. , Newaz G. M.
Published: February 2008

In thermal barrier coatings (TBC) residual stresses develop during cool down from processing temperature due to the thermal expansion mismatch between the different layers (substrate, bond coat, and TBC). These residual stresses can initiate micro-cracks at the bond coat/TBC interface and can lead to debonding at the bond coat/TBC interface. The effect of voids or crack-like flaws at the interface can be responsible for initiating debonding and accelerating the oxidation process. Effect of oxide layer growth between bond coat and ceramic layer (TBC) can be modeled as volume increase. In this work we represent this change in volume as an induced pressure across the interface. Mixed-mode fracture analysis of a thin circular delamination in an-axisymmetrically multi-layer circular plate is developed. Geometrical nonlin-earity is included in the analysis, since we have a large deflection case. The elastic deformation problem of a circular plate subjected to a clamped boundary condition at the edge of the delamination, an out of plane pressure load, and a compressive stress due to thermal mismatch between different layers, was solved numerically using a Rayleigh–Ritz method. The strain energy release rate was evaluated by means of the path-independent M-integral. The numerical results of this problem based on the energy method were verified using finite element method. Both methods correlate well in predicting the energy release rate for Mode I and Mode II, deflection, and postbuckling solutions. The energy release rates G, for both Mode I and Mode II using virtual crack extension method, were evaluated. The specimen was cooled down from processing temperature of 1000°C to 0°C. The variation of the properties as a function of temperature was used for analysis. It was found that the use of temperature dependent properties in contrast to constant properties provides significantly different values of J-integral and G.
Influence of the Exhaust System on Performance of a 4-Cylinder Supercharged Engine
Authors: Trenc F. , Bizjan F. , Hribernik A.
Published: February 2008

Twin entry radial turbines are mostly used to drive compressors of small and medium size 6-cylinder diesel engines where the available energy of the undisturbed exhaust pulses can be efficiently used to drive the turbine of a turbocharger. Three selected cylinders feed two separated manifold branches and two turbine inlets and prevent negative interaction of pressure waves and its influence on the scavenging process of the individual cylinders. In the case of a four-stroke, 4-cylinder engine, two selected cylinders, directed by the firing order, can be connected to one (of the two) separated manifold branches that feeds one turbine entry. Good utilization of the pressure pulse energy, together with typically longer periods of reduced exhaust flow can lead to good overall efficiency of the “two-pulse” system. Sometimes this system can be superior to the single manifold system with four cylinders connected to one singleentry turbine. The paper describes advantages and disadvantages of the above described exhaust systems applied to a turbocharged and aftercooled 4-cylinder Diesel engine. Comparisons supported by the analyses of the numerical and experimental results are also given in the presented paper.
Optical Measurement of Wet Steam in Turbines
Authors: Wang N. N. , Wei J. M. , Cai X. S. , Zhang Z. W. , Zheng G. , Yu X. H.
Published: February 2008

The wetness fraction of steam causes dangerous erosion of turbine blades and other components, and decreases efficiency of stages. The instrumentation of wet steam has, therefore, attracted growing interest from the point of safety and economical operation of power stations. Based on the light scattering technique, a method is presented that is capable of measuring the wetness fraction of steam, the mean water droplet diameter as well as their full size distribution. An optical probe has been constructed that can be used in the turbines in operation. Its main characteristic and features are discussed in this paper. Experimental results in a 200 MW condensing steam turbine are also given.
A Parametric Starting Study of an Axial-Centrifugal Gas Turbine Engine Using a One-Dimensional Dynamic Engine Model and Comparisons to Experimental Results: Part II—Simulation Calibration and Trade-Off Study
Authors: Owen A. K. , Daugherty A. , Garrard D. , Reynolds H. C. , Wright R. D.
Published: February 2008

A generic one-dimensional gas turbine engine model, developed at the Arnold Engineering Development Center, has been configured to represent the gas generator of a General Electric axial-centrifugal gas turbine engine in the six-kg/sec airflow class. The model was calibrated against experimental test results for a variety of initial conditions to insure that the model accurately represented the engine over the range of test conditions of interest. These conditions included both assisted (with a starter motor) and unassisted (altitude windmill) starts. The model was then exercised to study a variety of engine configuration modifications designed to improve its starting characteristics and thus quantify potential starting improvements for the next generation of gas turbine engines. This paper presents the model calibration results and the results of the trade-off study. A companion paper discusses the model development and describes the test facilities used to obtain the calibration data.
Combined Biomass and Black Liquor Gasifier/Gas Turbine Cogeneration at Pulp and Paper Mills
Authors: Larson E. D. , Kreutz T. G. , Consonni S.
Published: February 2008

Kraft pulp and paper mills generate large quantities of black liquor and byproduct biomass suitable for gasification. These fuels are used today for onsite cogeneration of heat and power in boiler/steam turbine systems. Gasification technologies under development would enable these fuels to be used in gas turbines. This paper reports results of detailed full-load performance modeling of pulp-mill cogeneration systems, based on gasifier/gas turbine technologies and, for comparison, on conventional steam-turbine cogeneration technologies. Pressurized, oxygen-blown black liquor gasification, the most advanced of proposed commercial black liquor gasifier designs, is considered, together with three alternative biomass gasifier designs under commercial development (high-pressure air-blown, low-pressure air-blown, and low-pressure indirectly-heated). Heavy-duty industrial gas turbines of the 70-MWe and 25-MWe class are included in the analysis. Results indicate that gasification-based cogeneration with biomass-derived fuels would transform a typical pulp mill into a significant power exporter and would also offer possibilities for net reductions in emissions of carbon dioxide relative to present practice.
Status of Westinghouse Hot Gas Filters for Coal and Biomass Power Systems
Authors: Newby R. A. , Lippert T. E. , Alvin M. A. , Burck G. J. , Sanjana Z. N.
Published: February 2008

Several advanced, coal and biomass-based combustion turbine power generation technologies using solid fuels (IGCC, PFBC, Topping-PFBC, HIPPS) are currently under development and demonstration. A key developing technology in these power generation systems is the hot gas filter. These power generation technologies must utilize highly reliable and efficient hot gas filter systems if their full thermal efficiency and cost potential is to be realized. This paper reviews the recent test and design progress made by Westinghouse in the development and demonstration of hot gas ceramic barrier filters toward the goal of reliability. The objective of this work is to develop and qualify, through analysis and testing, practical hot gas ceramic barrier filter systems that meet the performance and operational requirements for these applications.
An Assessment of the Performance of Closed Cycles With and Without Heat Rejection at Cryogenic Temperatures
Authors: Agazzani A. , Massardo A. F. , Korakianitis T.
Published: February 2008

This paper presents optimized cycle performance that can be obtained with systems including a closed cycle gas turbine (CCGT). The influence of maximum temperature, minimum temperature, and recuperator effectiveness on cycle performance is illustrated, Several power-plant arrangements are analyzed and compared based on thermodynamic performance (thermal efficiency and specific work); enabling technologies (available at present); and developing technologies (available in the near term or future). The work includes the effects of utilization of high temperature ceramic heat exchangers and of coupling of CCGT systems with plants vaporizing liquid hydrogen (LH2) or liquefied natural gas (LNG). Given the versatility of energy addition and rejection sources that can be utilized in closed gas-cycle systems, the thermodynamic performance of power plants shown in this paper indicate the remarkable capabilities and possibilities for closed gas-cycle systems.
Reaction Diffusion Behaviors for Interface Between Ni-Based Super Alloys and Vacuum Plasma Sprayed MCrAlY Coatings
Authors: Itoh Y. , Tamura M.
Published: February 2008

The object of this study is overlay coatings of MCrAlY alloy sprayed by a vacuum plasma spray (VPS) process for the protection against high-temperature corrosion and oxidation in the field of gas turbine components. Reaction diffusion behaviors at the interface between the MCrAlY coatings and the substrate, which have an important effect on coating degradation, have not always been clarified. Three kinds of substrate, equiaxis IN738LC, directional solidified CM247LC and single-crystal CMSX-2, and the four kinds of vacuum plasma sprayed MCrAlY coating have been selected for these experiments. The experimental results showed that the reaction diffusion layers consisted of aluminum compound layer and aluminum depleted layer, excepting that the aluminum depleted layer could not be observed in the case of CoNiCrAlY and NiCoCrAlY coatings. It also indicated that the diffusion thickness could be observed to follow a parabolic time dependence. The order of reaction diffusion rate was NiCrAlY > CoCrAlY > CoNiCrAlY > NiCoCrAlY independent of the substrates. A convenient computer-aided system was developed for analyzing the reaction diffusion behaviors at the interface between coating and substrate. It was also clear that the estimated results of long time diffusion behaviors by simulation analysis was in good agreement with experiments.
Coating Life Prediction for Combustion Turbine Blades
Authors: Chan K. S. , Cheruvu N. S. , Leverant G. R.
Published: February 2008

A life prediction method for combustion turbine blade coatings has been developed by modeling coating degradation mechanisms including oxidation, spallation, and aluminum loss due to inward diffusion. Using this model, the influence of cycle time on coating life is predicted for GTD-111 coated with an MCrAlY, PtAl, or aluminide coating. The results are used to construct a coating life diagram that depicts failure and safe regions for the coating in a log-log Plot of number of startup cycles versus cycle time. The regime where failure by oxidation, spallation, and inward diffusion dominates is identified and delineated from that dominated by oxidation and inward diffusion only. A procedure for predicting the remaining life of a coating is developed. The utility of the coating life diagram for predicting the failure and useful life of MCrAlY, aluminide, or PtAl coatings on the GTD-111 substrate is illustrated and compared against experimental data.
Fault Tolerant Magnetic Bearings
Authors: Maslen E. H. , Sortore C. K. , Gillies G. T. , Williams R. D. , Fedigan S. J. , Aimone R. J.
Published: February 2008

A fault tolerant magnetic bearing system was developed and demonstrated on a large flexible-rotor test rig. The bearing system comprises a high speed, fault tolerant digital controller, three high capacity radial magnetic bearings, one thrust bearing, conventional variable reluctance position sensors, and an array of commercial switching amplifiers. Controller fault tolerance is achieved through a very high speed voting mechanism which implements triple modular redundancy with a powered spare CPU, thereby permitting failure of up to three CPU modules without system failure. Amplifier/cabling/coil fault tolerance is achieved by using a separate power amplifier for each bearing coil and permitting amplifier reconfiguration by the controller upon detection of faults. This allows hot replacement of failed amplifiers without any system degradation and without providing any excess amplifier kVA capacity over the nominal system requirement. Implemented on a large (2440 mm in length) flexible rotor, the system shows excellent rejection of faults including the failure of three CPUs as well as failure of two adjacent amplifiers (or cabling) controlling an entire stator quadrant.
Reduced Order Modeling and Vibration Analysis of Mistuned Bladed Disk Assemblies With Shrouds
Authors: Bladh R. , Castanier M. P. , Pierre C.
Published: February 2008

This paper presents important improvements and extensions to a computationally efficient reduced order modeling technique for the vibration analysis of mistuned bladed disks. In particular, this work shows how the existing modeling technique is readily extended to turbomachinery rotors with shrouded blades. The modeling technique employs a component mode synthesis approach to systematically generate a reduced order model (ROM) using component modes calculated from a finite element model (FEM) of the rotor. Based on the total number of degrees of freedom, the ROM is typically two or three orders of magnitude smaller than the FEM. This makes it feasible to predict the forced response statistics of mistuned bladed disks using Monte Carlo simulations. In this work, particular attention is devoted to the introduction of mistuning into the ROM of a shrouded assembly. Mistuning is modeled by projecting the mistuned natural frequencies of a single, cantilever blade with free shrouds onto the harmonic modes of the shrouded blade assembly. Thus, the necessary mistuning information may be measured by testing individual blades.
Prediction of Resonant Response of Shrouded Blades With Three-Dimensional Shroud Constraint
Authors: Yang B. D. , Chen J. J. , Menq C. H.
Published: February 2008

In this paper, the three-dimensional shroud contact kinematics of a shrouded blade system is studied. The assumed blade motion has three components, namely axial, tangential, and radial components, which result in a three dimensional relative motion across the shroud interface. The resulting relative motion can be decomposed into two components. The first one is on the contact plane and can induce stick-slip friction. The other component is perpendicular to the contact plane and can cause variation of the contact normal load and, in extreme circumstances, separation of the two contacting surfaces. In order to estimate the equivalent stiffness and damping of the shroud contact an approach is proposed. In this approach, the in-plane slip motion is assumed to be elliptical and is decomposed into two linear motions along the principal major and minor axes of the ellipse. A variable normal load friction force model (Yang and Menq, 1996) is then applied separately to each individual linear motion, and the equivalent stiffness and damping of the shroud contact can be approximately estimated. With the estimated stiffness and damping, the developed shroud contact model is applied to the prediction of the resonant response of a shrouded blade system. The effects of two different shroud constraint conditions, namely two-dimensional constraint and three-dimensional constraint, on the resonant response of a shrouded blade system are compared and the results are discussed.
Reduction of Nitric Oxide in Diesel Exhaust With the Addition of Methylamine
Authors: Nakanishi Y. , Yoshihara Y. , Nishiwaki K. , Tanaka T.
Published: February 2008

A Chemical gas-phase process capable to reduce the nitric oxide in diesel engine exhaust was studied. In this process, monomethylamine (CH3NH2) was added to the exhaust gas in a molar ration to NO varying between 1:1 and 4:1, Experiments were conducted in electrically heated quartz, reactors in a temperature range of 200°C to 600°C. Diesel exhaust gas and simulated exhaust gas were used in this experiment. The results showed thorough mixing of methylamine into the exhaust effectively breaks NO down into nitrogen and water, enabling more than 80 percent NO reduction in a reactor temperature range of 400°C to 540°C and at a molar ratio of 1. On the other hand, imperfect mixing between methylamine and exhaust gases results in excess ammonia and reduced NO decomposition. Consequently, it is suggested that the mixing is a very important factor in this technique. The results also show that the coexisting gases such as carbon monoxide, carbon dioxide, hydrocarbons, and water vapor in the diesel exhaust have no effect on NO reduction by methylamine. However, the presence of oxygen in excess of 10 percent in the exhaust is needed for an 80 percent NOx reduction. Furthermore, the mechanisms of the methylamine process were discussed.
Multixial Creep Life Prediction of Ceramic Structures Using Continuum Damage Mechanics and the Finite Element Method
Authors: Jadaan O. M. , Powers L. M. , Gyekenyesi J. P.
Published: February 2008

High temperature and long duration applications of monolithic ceramics can place their failure mode in the creep rupture regime. A previous model advanced by the authors described a methodology by which the creep rupture life of a loaded component can be predicted. That model was based on the life fraction damage accumulation rule in association with the modified Monkman-Grant creep rupture criterion. However, that model did not take into account the deteriorating state of the material due to creep damage (e.g., cavitation) as time elapsed. In addition, the material creep parameters used in that life prediction methodology, were based on uniaxial creep curves displaying primary and secondary creep behavior, with no tertiary regime. The objective of this paper is to present a creep life prediction methodology based on a modified form of the Kachanov-Rabotnov continuum damage mechanics (CDM) theory. In this theory, the uniaxial creep rate is described in terms of stress, temperature, time, and the current state of material damage. This scalar damage state parameter is basically an abstract measure of the current state of material damage due to creep deformation. The damage rate is assumed to vary with stress, temperature, time, and the current state of damage itself. Multiaxial creep and creep rupture formulations of the CDM approach are presented in this paper. Parameter estimation methodologies based on nonlinear regression analysis are also described for both, isothermal constant stress states and anisothermal variable stress conditions. This creep life prediction methodology was preliminarily added to the integrated design code named Ceramics Analysis and Reliability Evaluation of Structures/Creep (CARES/Creep), which is a postprocessor program to commercially available finite element analysis (FEA) packages. Two examples, showing comparisons between experimental and predicted creep lives of ceramic specimens, are used to demonstrate the viability of this methodology and the CARES/Creep program.
Feedstock Blending Studies With Laboratory Indirectly Heated Gasifiers
Authors: Green A. E. S. , Mullin J. P.
Published: February 2008

To support the further-development of indirectly heated gasifiers intended to provide fuels for advanced gas turbines, several indirectly heated laboratory gasifiers were constructed. During many comparative tests, advantages and problems with each system were observed. The most useful systems make use of laboratory tube furnaces in conjunction with temperature, time, and pressure or volume yield measuring systems and a gas chromatograph with a thermal conductivity detector. In this paper, high temperature pyrolysis results obtained with the latest system are presented. Contrasting feedstocks suitable for commercial systems separately or in blends are used. Yield versus time measurements are used to determine relevant rate constants and outputs. Since the rate constants are mainly reflective of heat transfer effects, cylindrical dowel sticks of varying radii were volatilized. The data set leads to an analytic heat transfer model that considers the hemicellulose, cellulose, and lignin components of the dowels. Also developed from the dowel experiments is an approximate procedure for estimating the proportionate releases of CO, CO2, CH4, and H2 for any type of biomass whose component proportions are known.
The Application of Expert Systems and Neural Networks to Gas Turbine Prognostics and Diagnostics
Authors: DePold H. R. , Gass F. D.
Published: February 2008

Condition monitoring of engine gas generators plays an essential role in airline fleet management. Adaptive diagnostic systems are becoming available that interpret measured data, furnish diagnosis of problems, provide a prognosis of engine health for planning purposes, and rank engines for scheduled maintenance. More than four hundred operations worldwide currently use versions of the first or second generation diagnostic tools. Development of a third generation system is underway which will provide additional system enhancements and combine the functions of the existing tools. Proposed enhancements include the use of artificial intelligence to automate, improve the quality of the analysis, provide timely alerts, and the use of an Internet link for collaboration. One objective of these enhancements is to have the intelligent system do more of the analysis and decision making, while continuing to support the depth of analysis currently available at experienced operations. This paper presents recent developments in technology and strategies in engine condition monitoring including: (1) application of statistical analysis and artificial neural network filters to improve data quality, (2) neural networks for trend change detection, and classification to diagnose performance change, and (3) expert systems to diagnose, provide alerts and to rank maintenance action recommendations.