bluuebunny/crossref_metadata_2025 huggingface dataset:
Combined Cycle Power Augmentation by Inlet Fogging
Authors: Chiang Hsiao-Wei D. , Wang Pai-Yi
Published: November 2008

Inlet fogging of gas turbine engines has attained considerable popularity due to the ease of installation and the relatively low first cost compared to other inlet cooling methods. With increasing demand for power and with shortages envisioned especially during the peak load times during the summers, there is a need to boost gas turbine power. In Taiwan, most gas turbines operate with combined cycle for base load. Only a small portion operates with simple-cycle for peak load. To recover lost power output due to increased ambient temperature in hot days, the power augmentation strategies for combined-cycles need to be studied in advance. Therefore, the objective is to study the effects caused by adding inlet fogging to an existing gas turbine-based combined-cycle power plant. Simulation runs were made for adding inlet fogging to a combined cycle with two Alstom gas turbines, two heatrecovery steam generators, and one steam turbine. Results show that the power output will be increased by 1% to 5% in typical hot summer days. Since there are seventeen combined-cycle power plants located in different areas in Taiwan, total extra power output gained by inlet fogging can make up the power loss in hot summer days. This paper also includes a parametric study of performance to provide guidelines for combined-cycle power augmentation by inlet fogging.
Inverse Model Control of a Three Spool Gas Turbine Engine
Authors: Mahmood Shahid , Griffin Ian A. , Fleming Peter J. , Shutler Arthur J.
Published: November 2008

The Rolls-Royce Inverse Model (RRIM) controller is a nonlinear, model-based fuel control algorithm. This paper compares the model-based design procedures and resulting performance of RRIM control to those of Classical Gain Scheduled (CGS) control for a three-spool gas turbine. It was observed that similar performance levels can be achieved using the RRIM with a significant decrease in tuning effort and design time when compared to CGS control. The RRIM controller also showed improved performance for the case of transient control. The paper indicates how and why the RRIM controller is robust across the operating envelope and highlights the practical advantages it affords to the industrial designer.
A NOx Reduction Project for a GT11 Type Gas Turbine
Authors: Nord Lars O. , Schoemaker David R. , Andersen Helmer G.
Published: November 2008

A study was initiated to investigate the possibility of significantly reducing the NOx emissions at a power plant utilizing, among other manufacturers, ALSTOM GT11 type gas turbines. This study is limited to one of the GT11 type gas turbines on the site. After the initial study phase, the project moved on to a mechanical implementation stage, followed by thorough testing and tuning. The NOx emissions were to be reduced at all ambient conditions, but particularly at cold conditions (below 0°C) where a NOx reduction of more than 70% was the goal. The geographical location of the power plant means cold ambient conditions for a large part of the year. The mechanical modifications included the addition of Helmholtz damper capacity with an approximately 30% increase in volume for passive thermo-acoustic instability control, significant piping changes to the fuel distribution system in order to change the burner configuration, and installation of manual valves for throttling of the fuel gas to individual burners. Subsequent to the mechanical modifications, significant time was spent on testing and tuning of the unit to achieve the wanted NOx emissions throughout a major part of the load range. The tuning was, in addition to the main focus of the NOx reduction, also focused on exhaust temperature spread, combustion stability, CO emissions, as well as other parameters. The measurement data was acquired through a combination of existing unit instrumentation and specific instrumentation added to aid in the tuning effort. The existing instrumentation readings were polled from the control system. The majority of the added instrumentation was acquired via the FieldPoint system from National Instruments. The ALSTOM AMODIS plant-monitoring system was used for acquisition and analysis of all the data from the various sources. The project was, in the end, a success with low NOx emissions at part load and full load. As a final stage of the project, the CO emissions were also optimized resulting in a nice compromise between the important parameters monitored, namely NOx emissions, CO emissions, combustion stability, and exhaust temperature distribution.
Engine Testing of an Advanced Alloy for Microturbine Primary Surface Recuperators
Authors: Matthews Wendy J. , Bartel Terry , Klarstrom Dwaine L. , Walker Larry R.
Published: November 2008

HAYNES® alloy HR-120® has been identified as a potential alloy for the manufacture of primary surface recuperators. Primary surface recuperator components have been manufactured from HR-120, and actual microturbine testing is on going. Initial engine test results indicate the formation of a protective oxide scale that is resistant to both steady-state and cyclic operation with no evidence of accelerated attack, and which is likely to meet or exceed the desired 80,000 hour component life.
Evaluation of Hydrogen Addition to Natural Gas on the Stability and Emissions Behavior of a Model Gas Turbine Combustor
Authors: Yoshimura Tomoshi , McDonell Vincent , Samuelsen Scott
Published: November 2008

In recent years, the potential for utilization of hydrogen as a strategy to optimize the performance of gas turbine combustors has been recognized. In this study, a swirl stabilized model combustor operating under lean premixed conditions with a centerline pilot injector is utilized to study how hydrogen addition to natural gas impacts performance. The relatively effectiveness of hydrogen addition to the pilot vs main fuel is examined in terms of overall stability and CO and NOx emissions. In addition, the relationship between the relative amount of hydrogen utilized and (1) the overall stability limits and (2) the ability to achieve both low CO and low NOx emissions is established. The role of hydrogen on the general flowfield and reaction structure is also examined. Also, the effect of hydrogen addition to the main fuel on flashback tendencies is examined. The results show that hydrogen addition can extend stability limits and allow for NOx reduction. The results also show that, for the system studied, pilot injection offers a more significant opportunity for using hydrogen to improve overall system emissions performance.
A New Ni-Base Single Crystal Superalloy TMS-82+
Authors: Yoshioka Yomei , Hino Takehisa , Fukuda Masafumi , Koizumi Yutaka , Kobayashi Toshiharu , Harada Hiroshi
Published: November 2008

A new single crystal (SC) superalloy TMS-82+ which contains only 2.4% Re has been developed by using a computer aided alloy design program (ADP) developed in the National Institute for Materials Science (NIMS). The compositions were designed as follows; a large negative lattice misfit at operated temperature, 60 vol.% of γ′, solution heat treatment window of >50°C, and creep strength better than 2nd generation superalloys. Corrosion resistance was also considered. A brief explanation of the NIMS-ADP and the whole development works of SC alloy TMS-82+, such as alloy selection, metallurgical and mechanical tests, a full-scale production test and an engine test in the 15MW gas turbine, will be described here.
Monitoring Microturbine Generators Installed in the South Coast Air Basin
Authors: Medrano Marc , Hack Richard L. , Lee Steve , McDonell Vincent G. , Samuelsen Scott , Kay Martin , Lange Howard
Published: November 2008

Microturbine generators offer an interesting early commercial strategy for implementation of distributed generation. Through a program sponsored by the South Coast Air Quality Management District (SCAQMD), 207 microturbines of 30 and 60kW output are deployed or in the process of being deployed at 47 sites throughout the SCAQMD. These units are being monitored for general operational characteristics such as hours operated, number of starts, total output. In addition, several of the sites have been outfitted with additional sensors that facilitate the collection of efficiency information. Performance results from two of these sites are presented along with corresponding economic evaluation. The results indicate that actual performance does not reach the manufacturer’s specifications and that the recent increases in natural gas prices have increased the projected payback period for the equipment.
The GT24/26 Combustion Technology and High Hydrocarbon (“C2+”) Fuels
Authors: Riccius Oliver , Smith Richard , Gu¨the Felix , Flohr Peter
Published: November 2008

In 1998 ALSTOM launched a development program to burn fuels containing high hydrocarbons in the GT24/26 gas turbines. These fuels are found in different parts of the world as for example in Brazil, Algeria or in the gulf of Bengal and Thailand. After validation in the GT26 gas turbine in the ALSTOM power plant in Birr (Switzerland) the combustion of fuel gases with up to 16 Vol% of high hydrocarbons was released in 2001. First field engines started to operate in 2001 and today 18 units are running commercially successful burning high hydrocarbon fuel gases. The engines operate without any hardware modifications compared against standard natural gas fuel, however with an advanced engine control system based on a fast gas composition monitoring system. This achievement is particularly remarkable in view of the sequential combustion system with a high pressure (30bar) first combustor stage, and a high inlet temperature (1000°C) second combustor stage. The paper discusses fundamental aspects of burning high hydrocarbon fuels and in particular its impact on the ignition process. It outlines the careful development and validation procedure which has been applied at ALSTOM. Finally, evidence is given of today’s reliable engine operation with 200’000 operating hours on high hydrocarbon fuel supplies at remarkably low emission levels.
Impact of Operating Regime on Economic Performamnce of Combined Cycle Power Plants
Authors: Fetescu Mircea
Published: November 2008

It is accepted that CCPP has the highest fuel conversion efficiency among fossil fuel fired generation technologies. The extensive installed base of CCPP worldwide is justified by additional advantages: low capital investment, short construction time, low environmental impact and high operating flexibility. The operating flexibility, with fast loading and deloading and short start-up and shutdown durations, allows CCPPs to fulfill a wide range of operating duties, such cycling, intermediate load to base load, grid frequency or voltage control and part load operation; mostly on a competitively generated cost basis. The traditional approach to CCPP development is to design an optimised plant, taking into consideration the technical and economic boundary conditions of a specific project. This includes assumptions for operating regime: base load, intermediate load or cycling with daily start-up and shutdown. In a deregulated environment, plants are dispatched on merit. The assumptions related to operating regime and used for optimising the configuration of a particular CCPP, often deviate significantly during commercial operation. The objective of this work is to evaluate the impact of the operating regime on CCPP economic performance. During the economic feasibility evaluation of a power project it is frequently considered that the main factors affecting the electricity generation cost, are capital cost and fuel cost. As far as the operating regime is concerned, a number for yearly operating hours is then assumed and eventually sensitivity is considered. The content of this work is an investigation on how the capital, fuel and O&M costs, components of the generation costs, are affected by the utilisation factor, by operating modes and loads, frequency and duration of start-up and shudown [s&s] of the plant. The conclusion of the paper is that both, operating regime and operating procedure have an important impact on economic performance of combined cycle plants. Annual operating hours and the number of s&s influence the factors which contribute to the profitability and competitiveness of the plant, such as EOH, availability, performance degradation, O&M costs and directly the average plant output and efficiency. Finally the economic performance of combined cycle plants can be significantly improved by re-visiting the conceptual design and the operating concept.
A Test Rig for Air Bearings Rotordynamic Coeffcients Measurement
Authors: Bellabarba Ernesto , Di´az Sergio , Rastelli Victor
Published: November 2008

This paper describes the design and manufacturing of an experimental facility for measurement of equivalent stiffness and damping of air bearings. For these preliminary tests, the shaft moves only in two perpendicular directions, laying in the rotation plane, thus producing 2×2 characteristic matrices. However, the rig can be easily modified to measure rotordynamic characteristics related to angular motion of the journal and measuring 4×4 matrices. The testing facility uses an experimental magnetic bearing suspension system that allows imposing any given orbit to the shaft, during the testing experiments. All individual parts, as well as the assembly, were dynamically studied to determine their modal response and optimize it according to the test rig’s operating frequency range. The principle of operation is to produce a shaft orbit using the magnetic suspension system and measuring the forces generated on the test bearing housing. Then, the stiffness and damping coefficients are calculated using an iterative parameter identification algorithm (a modification of the IVF method). The force measurement is performed via three load cells placed in a triangle configuration around the test bearing housing. All data is gathered and processed using PC based data acquisition boards and software. The present design allows testing air bearings up to 44 mm in external diameter and a bandwidth of 0 Hz to 1.000 Hz. Preliminary testing was performed on this research that demonstrates the capability of the apparatus to measure the dynamic properties with ease and accuracy.
An Optimal Orthogonal Decomposition Method for Kalman Filter-Based Turbofan Engine Thrust Estimation
Authors: Litt Jonathan S.
Published: November 2008

A new linear point design technique is presented for the determination of tuning parameters that enable the optimal estimation of unmeasured engine outputs such as thrust. The engine’s performance is affected by its level of degradation, generally described in terms of unmeasurable health parameters related to each major engine component. Accurate thrust reconstruction depends upon knowledge of these health parameters, but there are usually too few sensors to be able to estimate their values. In this new technique, a set of tuning parameters is determined which accounts for degradation by representing the overall effect of the larger set of health parameters as closely as possible in a least squares sense. The technique takes advantage of the properties of the singular value decomposition of a matrix to generate a tuning parameter vector of low enough dimension that it can be estimated by a Kalman filter. A concise design procedure to generate a tuning vector that specifically takes into account the variables of interest is presented. An example demonstrates the tuning parameters’ ability to facilitate matching of both measured and unmeasured engine outputs, as well as state variables. Additional properties of the formulation are shown to lend themselves well to diagnostics.
Developing and Deploying ICAS-Capable CBM Software Modules: Best Practices and Lessons Learned
Authors: Watson Matthew J. , Byington Carl S. , Donovan Bryan , Kacprzynski Greg , Krichene Assaad , Savage Christopher
Published: November 2008

The U.S. Navy’s Integrated Condition Assessment System (ICAS) is a shipboard monitoring system that helps enable the Navy’s Condition Based Maintenance (CBM) initiative. ICAS is installed on a large number of Navy Surface Combatants and provides data acquisition, display, and logging, as well as equipment diagnostic analysis for troubleshooting and maintenance tasking of hull mechanical and electrical systems. In recent years, it has been desirable to integrate specialized, third party diagnostic or prognostic software as plug ‘n play modules within the ICAS environment. A specific effort focused on such modules for shipboard LM2500 and Allison 501K gas turbine engines is well underway. Over the course of this three-year Prognostic Enhancement to Diagnostic System (PEDS) program, many lessons have been learned, best practices for ICAS integration have been identified, and the important steps required to field ICAS-capable modules have been realized. This paper summarizes these lessons and processes for future 3rd party integration efforts and provides specific examples for the developed gas turbine modules. The successful deployment of these modules aboard Navy ships is used to validate the ideas presented.
Significant Performance Improvements of GE-Built, Frame No.7, Model EA, GT
Authors: Hawley Scott , Ingistov Steve
Published: November 2008

This Paper describes the efforts implemented in performance enhancements of CGT, Frame No7, Model EA. The CGT is operating in Watson Cogeneration Company (WCC), Carson, California, USA. The better-than-expected improvements were achieved after MI of CGT Unit 4, in October 2004. The significant increase in CGT power and simultaneous reduction in HR was obtained by introduction of OEM-improved design details, by increasing FT from 2,020 degrees F to 2,055 degrees F and also by reduction of parasitic, internal to CGT, losses.
Corrosion Studies of High and Low Pressure Compressor Blades of a Gas Turbine
Authors: Boschetti A. , Kawachi E. Y. , Oliveira M. A. S.
Published: November 2008

This work presents preliminary results of corrosion studies for three blades, one of the low pressure compressor and two of two different stages of the high pressure compressor of a gas turbine, which has been operating for 5,000 hours. Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray diffraction (XRD), Electrochemical Impedance Spectroscopy (EIS) in aqueous solution containing chloride, and Atomic Absorption Spectrometry (AAS) were used to characterize the blades surfaces. The SEM and EDS results showed that the homogeneity and amount of contaminants, such as sodium, potassium, calcium, magnesium, chloride and sulphur are bigger in the high pressure compressor blade surfaces than in the low pressure compressor blade surface. The EIS results showed that the degradation process in turbine compressor blades increases with the temperature and pressure increase inside the compressors and depends of the blade composition. The low pressure compressor blade, which was made of a Ti base superalloy exhibited smaller corrosion resistance (smallest charge transfer resistance value (Rct)) than the two high pressure compressor blades, which were made of a Fe base superalloy. However, despite of its lower resistance to corrosion, after 5,000 hours of service, the low pressure compressor blade did not present pitting corrosion while the high pressure compressor blades did.
Cast Iron-Nickel Alloy for Industrial Gas Turbine Engine Applications
Authors: Neyhouse Jeffrey R. , Aurrecoechea Jose M. , Montague J. Preston , Lilley John D.
Published: November 2008

Austenitic ductile iron castings have traditionally been used for gas turbine exhaust components that require castability, good machinability, low thermal expansion, and high strength at elevated temperatures. The achievement of optimum properties in austenitic ductile irons hinges on the ability of the foundry to produce nodular graphite in the microstructure throughout the component. In large, complex components, consistently producing nodular graphite is challenging. A high-nickel steel alloy that is suitable for sand castings has been recently developed for industrial gas turbine engine applications. The alloy exhibits similar mechanical and physical properties to austenitic ductile irons, but with improved processability and ductility. This alloy is weldable and exhibits no secondary graphite phase. This paper presents the results of a characterization program conducted on a 35% nickel, high-alloy steel. The results are compared with an austenitic ductile iron of similar composition. Tensile and creep properties from ambient temperature to 760°C (1400°F) are included, along with fabrication experience gained during the manufacture of several sand cast components at Solar Turbines Incorporated. The alloy has been successfully adopted for gas turbine exhaust system components and other applications where austenitic ductile irons have traditionally been utilized. The low carbon content of austenitic steels permits improved weldabilty and processing characteristics over austenitic ductile irons. The enhancements provided by the alloy indicate that additional applications, as both austenitic ductile iron replacements and new components, will arise in the future.
Finite Element Analysis of Coupled Lateral and Torsional Vibrations of a Rotor With Multiple Cracks
Authors: Wu Xi , Sawicki Jerzy T. , Friswell Michael I. , Baaklini George Y.
Published: November 2008

The coupling between lateral and torsional vibrations has been investigated for a rotor dynamic system with breathing crack model. The stiffness matrix has been developed for the shaft element which accounts for the effect of the crack and all six degrees of freedom per node. Since the off-diagonal terms of the stiffness matrix represent the coupling of the respective modes, the special attention has been paid on accurate determination of their values. Based on the concepts of fracture mechanics, the variation of the stiffness matrix over the full shaft revolution is represented by the truncated cosine series where the fitting coefficient matrices are extracted from the stiffness matrices of the cracked shaft for a number of its different angular positions. The variation of the system eigenfrequencies and dynamic response of the rotor with two cracks have been studied for various shaft geometries, crack axial locations, and relative phase of cracks.
Low-NOx Emissions Over an Enlarged Range of Overall Equivalence Ratios by Staged Lean Premixed Tubular Flame Combustion
Authors: Yamada Hideshi , Takagi Hideyuki , Hayashi Shigeru
Published: November 2008

One of the inherent problems of lean premixed combustion is a narrow range of combustion-zone fuel-air ratios where low NOx emissions and complete combustion can be simultaneously achieved. The use of the reaction of lean to ultra-lean mixtures injected into the hot burned gas produced in the upstream lean-burn combustion zone can alleviate the abovementioned problem. The combustion characteristics of staged model gas turbine combustors with arranging two or three cylindrical swirl combustion chambers in series were investigated at atmospheric pressure. Tubular flame was stabilized in the primary stage and homogeneous mixture was injected into the burned gas from the upstream stage. It is shown that the lean multi-staged premixed tubular flame combustion has a potential to extend the range of gas turbine operation where both complete combustion and ultra-low NOx emissions can be achieved.
Modification of the Reaction Zone Using a Smart Fuel Injector for Control of Instabilities in Liquid Fueled Combustors
Authors: Conrad T. , Bibik A. , Shcherbik D. , Lubarsky E. , Zinn B. T.
Published: November 2008

This paper describes an experimental investigation of suppressing combustion instabilities in a liquid fueled (n-heptane) atmospheric combustor incorporating an array of “smart” fuel injectors. These injectors were designed so that their spray properties could be manipulated without changing the overall operating conditions (power, mass flow rates, equivalence ratio, etc.) of the combustor. The dependence of these spray properties upon the smart injector settings was determined for a single injector using a series of cold flow experiments, including spray images and PDPA measurements of spray velocities and droplet sizes. The stability characteristics of a combustor incorporating seven such injectors were then determined and correlations were drawn between these characteristics, the single injector spray properties, and combustion behavior measurements taken for a single injector. It was shown that both longitudinal and tangential instability modes were excited in this combustor; the mechanisms of excitation and damping of these modes were then further investigated using high speed photography and spectroscopy measurements. Finally, suppression of both modes of instabilities in this combustor were demonstrated by slow tuning of the injector spray properties.
Catalytic Detection of Fuel Leaks in Gas Turbines Units: Gaseous and Volatile Hydrocarbon Based Fuels
Authors: Molie`re Michel , Cozzarin Philippe , Bouchet Se´bastien , Rech Philippe
Published: November 2008

Gas/vapor detection is a critical function in Gas Turbines (GT) units as it allows to take appropriate steps in case of incipient fuel leaks in the confined volume of enclosures. This important subject is being actively revisited by the GT community and safety organizations, namely under the impulse of the HSE of UK. Historically the catalytic detection technology that is of common use in stationary GT, has been applied to detect leakages of gaseous fuels — and more especially Natural Gas (NG) — since the catalytic detectors or “pellistors” are most sensitive to methane. Indeed, the response of catalytic detectors is specific to each individual hydrocarbon molecule and decrease with the size of the latter. After years this technology has been extended to the detection of rich NG (containing some amounts of C3-C4) then to hydrogen and liquefied petroleumliquids (LPG). The use of alternative gas turbine fuels such as LPG, syngas and volatile fuels is becoming increasingly popular in some world regions and requires to adapt the leak detection systems. Especially, volatile liquid fuels that comprise naphtha, “natural gas liquids”, gas condensates (and alcohols) are critical in safety terms. Indeed these fuels exhibit both low initial boiling points (IBP as low as 30°C) and Flash Points (down to-20°C); in case of leak, they generate — as liquids — large masses of flammable substances. In addition, vapors of liquid fuels have a more complex response in catalytic detection than gases due to their complex composition with tens of HC molecules of various size and structure. In this context, the behavior of commercial detectors in presence of not only gas fuels but also of synthetic vapors of naphtha has been the matter of a comprehensive evaluation at the laboratory of INERIS, a French Institute devoted to safety and environment. This work that targets the detection of hydrocarbon (CnHm) fuels is the first phase of an overall, GE-INERIS joint evaluation program covering both hydrocarbon and non-hydrocarbon GT fuels, i.e. the complete CnHm/CO/H2/N2(CO2) spectrum. The first part of this program phase addressed the lightest terms of the paraffin series (C1 to C4) and some mixtures of the same that are involved in the detection of NG and LPG vapors. The second part was dedicated to the higher paraffins terms (C5 to C8) including various mixtures of the same and 2 synthetic naphtha compositions. Particular emphasis has been placed on the capability to detect hydrocarbons at the levels (as low as 5%) that result from recent safety codes. After a record of principles, the paper summarizes the results of these tests that confirm the general capability of the catalytic technology for the detection of LPG and naphtha vapors.
Model Calibration of Anisotropic Rotordynamic Systems With Speed Dependent Parameters
Authors: Younan A. A. , El-Shafei A.
Published: November 2008

In this paper, a method for calibrating rotordynamic models of speed dependent systems supported on anisotropic supports is presented. The method is based on the comparison between the calculated eigenvalues and the ones extracted from the synchronous frequency response functions. An eigensensitivity analysis is conducted to calculate the sensitivity of the computed eigenvalues to the selected elements to be updated. This method is suitable for field application since it requires simple coast down tests. The method is illustrated on a test rig with fluid film bearings, and is shown to be effective in the calibration of rotordynamic models at the speeds of the modes excited within the operating speed range.
Model-Based Control of Combustion Instabilities
Authors: Morgans Aimee S. , Dowling Ann P.
Published: November 2008

Model-based control has been successfully implemented on an atmospheric pressure lean premixed combustion rig. The rig incorporated a pressure transducer in the combustor to provide a sensor measurement, with actuation provided by a fuel valve. Controller design was based on experimental measurement of the open loop transfer function. This was achieved using a valve input signal which was the sum of an identification signal and a control signal from an empirical controller to eliminate the non-linear limit cycle. The transfer function was measured for the main instability occurring at a variety of operating conditions, and was found to be fairly similar in all cases. Using Nyquist and H∞-loop shaping techniques, several robust controllers were designed, based on a mathematical approximation to the measured transfer function. These were implemented experimentally on the rig, and were found to stabilise it under a variety of operating conditions, with a greater reduction in the pressure spectrum than had been achieved by the empirical controller.
Multidimensional Model of a Viscoelastic Sliding Bearing Support
Authors: Ja´uregui-Correa J. C. , Urbiola-Soto L. , Aboites-Da´vila F.
Published: November 2008

A multidimensional finite element model of a viscoelastic sliding bearing is presented. The model resulted into a simplified finite element model composed by an elastic matrix and a damping matrix. These matrices are independent from each other since the viscoelastic material properties are assumed to be of Kelvin type material. Kelvin type materials are approximated as a linear combination of an elastic modulus and a viscous coefficient. This simple model describes accurately most rubbers used in machine components. The model combines the linearity of the Kelvin type material plus the finite element interpolation scheme. Thus, the advantages of the finite element discretization can be applied to any geometry. In order to obtain Kelvin’s coefficients a test rig was built. Material properties were experimentally determined and the model was validated. Afterwards, a discretized model was developed for a radial support bearing with and embedded sandwich-like rubber band. From this model, it was possible to analyze bearing stiffness and damping properties. Then, damping and stiffness coefficients were input to a rotordynamic model of a single-mass rotor with a slender shaft to assess imbalance response characteristics obtained with viscoelastic sliding bearings. This procedure allows the designer to evaluate alternative damping mechanisms that can be added to sliding bearings.
Influence of Flow Characteristics on the Discharge Coefficient of a Multiperforated Wall
Authors: Champion Jean-Louis , Di Martino Pasquale , Coron Xavier
Published: November 2008

The aim of this study is to determine the discharge coefficient of a multiperforated wall sample designed by AVIO, and more precisely to show the influence of each surrounding flow (inside holes, coolant and main flows). Results obtained are compared to correlations from literature. As previously observed, it is found that the discharge coefficient is strongly dependent on the Reynolds number relative to the hole flow (Reh). The influence of the coolant flow has been proved. The comparison with classical correlations shows many differences: i) on the expected asymptotic value ii) on the rate of increase for the lowest values of Reh. This influence is not taken into account by classical correlations deduced from experiments carried out without crossflow. Based on our experiments, we determined a general expression of Cd. Experimental data are fitted with a function of type Cd = A(1−exp(−B.Reh)), where A and B are expressed as functions of the Reynolds number (Re2) of the coolant flow.
Comparative Evaluation of SOFC/Gas Turbine Hybrid System Options
Authors: Litzinger Kevin P. , Veyo Stephen E. , Shockling Larry A. , Lundberg Wayne L.
Published: November 2008

Solid Oxide Fuel Cell [SOFC]/Gas Turbine [GT] hybrid power systems can synergistically exploit the high operating temperature and high electrical generation efficiency of the solid oxide fuel cell and the high power density and simplicity of the gas turbine engine generator. Continued studies at Siemens Westinghouse seek practical system configurations with commercialization potential. Pressurized SOFC [PSOFC]/GT system concepts [directly heated Brayton cycles] can yield electrical power generation at the highest efficiency [circa 70%] {net ac/LHV} with concomitant complexity in configuration, operation and installation. Indirectly heated Brayton cycles utilizing an atmospheric pressure SOFC [ASOFC] can achieve a more modest electrical power generation efficiency [circa 55%] with considerably less complexity. Co-firing of the GT combustor to yield state-of-the-art [SOA] turbine inlet temperature [TIT] can most fully exploit the capability of SOA turbine technology yielding a hybrid system of lesser efficiency, but also of lesser cost ($/kWe). The ideal gas turbine and/or system configuration remains elusive however. Recent studies have focused on the indirectly heated cycle wherein the gas turbine exhaust serves directly as the SOFC oxidant. Consequently, the GT exhaust flow rate and temperature must be compatible with SOFC generator inlet requirements. This compatibility can be difficult to achieve with a state-of-the-art micro gas turbine generator [MTG] that typically operates with relatively low pressure ratio [3 to 4]. Alternatives ranging from the ideal GT to system level feature additions allowing SOA GTs have been analyzed. These alternatives are identified and discussed, and results of a comparative performance and cost evaluation are reviewed.
Laminar Flame Speeds of Synthetic Gas Fuel Mixtures
Authors: Natarajan J. , Nandula S. , Lieuwen T. , Seitzman J.
Published: November 2008

Laminar flame speeds of H2/CO/CO2 mixtures have been measured over a range of fuel compositions, lean equivalence ratios, and reactant preheat temperature (up to 700 K). The measurements are compared to numerical flame speed predictions based on two reaction mechanisms: GRI Mech 3.0 and a H2/CO mechanism. For undiluted and nonpreheated mixtures, the current results agree with previous data and the numerical calculations over most of the range tested. The measured flame speeds increase as the H2 content of the fuel rises and for higher equivalence ratios. The most significant difference between the measurements and models is for high CO content fuel with the H2/CO mechanism, and the high H2 content fuel at the leanest conditions with the GRI mechanism. For CO2 diluted fuels, measured flame speeds decrease as predicted. However, agreement between the measurements and predictions worsens with increasing CO2 dilution. Deviations as large as 40% are observed at lean equivalence ratios and 20% CO2 levels. For reactant preheat temperatures below ∼400K, the measured flame speeds generally match the calculated flame speeds within 10%. At higher preheat temperatures, however, the discrepancy between the measurements and the calculations increases, reaching levels of ∼30% at 700 K. The measured temperature dependence is closer to the predictions from GRI Mech 3.0 than from the H2/CO mechanism.
A CFD Based Off-Design Study of Micro-Gas Turbines Combustors
Authors: Cameretti Maria Cristina , Tuccillo Raffaele
Published: November 2008

The authors examine different off-design conditions induced in a lean-premixed combustor by some typical transient processes of a micro-gas turbine. The latter is subject to frequent changes in both thermal and mechanical load and the unsteady transition from one regime to a different one produces significant variation in the boundary conditions and in the fuel/air equivalence ratio as well. After a proper definition of the computational domains, a CFD based simulation allows examination of typical situations within full-to-part or part-to-full load transitions. Some results discussed in the paper suggest substantial modifications of the fuel supply laws for a more effective control of both temperature rise and pollutant production.
Hot Gas Filtration Meeting Turbine Requirements for Particulate Matter
Authors: Gardner Ben , Guan Xiaofeng , Martin Ruth Ann , Spain Jack
Published: November 2008

The Power Systems Development Facility (PSDF) is an engineering scale demonstration of advanced coal-fired power systems and high-temperature, high-pressure gas filtration systems. The PSDF was designed at sufficient scale so that advanced power systems and components can be tested in an integrated fashion to provide data for commercial scale-up. The PSDF is funded by the U.S. Department of Energy, the Electric Power Research Institute, Southern Company Services, Kellogg Brown & Root, Inc. (KBR), Siemens-Westinghouse, and Peabody Energy. Gasification at the PSDF is based on KBR’s Transport Gasifier, which is an advanced circulating fluidized-bed gasifier. Hot gas filtration is a critical process in the gasification system to clean up the particulate matter before the synthesis gas (syngas) is fed to the turbine. A Siemens-Westinghouse particulate control device (PCD) is used for syngas cleanup. The PCD contains 91 candle-style filter elements. More than twenty types of filter elements, categorized as monolithic ceramic, composite ceramic, sintered-metal powder, and sintered-metal fiber, have been tested in the gasification environment at the PSDF. Up to January 2005, the longest exposure time for individual filters has been 5783 hours. The particulate loading in the clean syngas during most stable operating periods has been demonstrated to be consistently below 0.1 ppmw, which is the lower detection limit of Southern Research Institute’s sampling system. Safeguard devices (failsafes) have also been tested and developed at the PSDF. Failsafes are used to block the particulate leaking through the PCD in the case of filter element failure to eliminate damage to the turbine. Demonstration of reliable failsafes is a critical factor to the hot gas filtration technology. Several types of currently available failsafes and PSDF-developed failsafes have been tested in the PCD with gasification ash injection to simulate filter element leakage. A typical failsafe was also tested in a device equipped with a quick-open mechanism to simulate a complete filter failure during a test run operation. The testing showed promising results for certain types of failsafes. Further failsafe testing and better understanding of turbine requirements for particulate loading are needed to evaluate the PCD performance and increase readiness towards commercialization of the technology.
Overview of Creep Strength and Oxidation of Heat-Resistant Alloy Sheets and Foils for Compact Heat-Exchangers
Authors: Maziasz Philip J. , Shingledecker John P. , Pint Bruce A. , Evans Neal D. , Yamamoto Yukinori , More Karren , Lara-Curzio Edgar
Published: November 2008

The Oak Ridge National Laboratory (ORNL) has been involved in research and development related to improved performance of recuperators for industrial gas turbines since about 1996, and in improving recuperators for advanced microturbines since 2000. Recuperators are compact, high efficiency heat-exchangers that improve the efficiency of smaller gas turbines and microturbines. Recuperators were traditionally made from 347 stainless steel and operated below or close to 650°C, but today are being designed for reliable operation above 700°C. The Department of Energy (DOE) sponsored programs at ORNL have helped defined the failure mechanisms in stainless steel foils, including creep due to fine grain size, accelerated oxidation due to moisture in the hot exhaust gas, and loss of ductility due to aging. ORNL has also been involved in selecting and characterizing commercial heat-resistant stainless alloys, like HR120 or the new AL20-25+Nb, that should offer dramatically improved recuperator capability and performance at a reasonable cost. This paper summarizes research on sheets and foils of such alloys over the last few years, and suggests the next likely stages for manufacturing recuperators with upgraded performance for the next generation of larger 200–250 kW advanced microturbines.
Effects of Damping and Varying Contact Area at Blade-Disc Joints in Forced Response Analysis of Bladed Disc Assemblies
Authors: Petrov E. P. , Ewins D. J.
Published: November 2008

In this paper, an approach is developed to analyse the multiharmonic forced response of large-scale finite element models of bladed discs taking account of the nonlinear forces acting at the contact interfaces of blade roots. Area contact interaction is modelled by area friction contact elements which allow for friction stresses under variable normal load, unilateral contacts, clearances and interferences. Examples of application of the new approach to analysis of root damping and forced response levels are given and numerical investigations of effects of contact conditions at root joints and excitation levels are explored for practical bladed discs.
Model-Based Data Reconciliation to Improve Accuracy and Reliability of Performance Evaluation of Thermal Power Plants
Authors: Hartner Peter , Petek Josef , Pechtl Peter , Hamilton Patrick
Published: November 2008

Accurate on-line plant and equipment performance evaluation is becoming critical in the power generation industry as operators seek to optimize their plants, particularly in competitive power markets. The analysis accuracy of an on-line performance monitoring system is directly dependent on the quality of the input data and usually suffers because installed plant sensors are not high-precision instruments. The inherent measurement uncertainties can be overcome by using a readily available heat balance program in combination with a least square solver. This data reconciliation system will provide the performance evaluation system with data that better reflects the plant’s current operating point, thus improving the performance evaluation system’s output and allowing for better plant optimization. Additionally, the reconciliation system can identify broken, biased or highly noisy sensors. These improvements can be obtained without installing additional precision sensors or putting unreasonable efforts into sensor calibration.
The Solution Precursor Plasma Spray Process for Making Durable Thermal Barrier Coatings
Authors: Gell Maurice , Wu Fang , Jordan Eric H. , Padture Nitin P. , Cetegen Baki M. , Xie Liangde , Ozturk Alper , Jadhav Amol , Chen Dianying , Ma Xinqing
Published: November 2008

The Solution Precursor Plasma Spray (SPPS) process involves the injection of atomized droplets of precursor into the plasma plume, instead of powder that is used in conventional plasma spray. The resultant thermal barrier coating (TBC) microstructure consists of (1) through-coating-thickness cracks, (2) ultra-fine splats, and (3) nanometer and micrometer-sized dispersed pores. These unique SPPS microstructural features provide highly durable TBCs. The SPPS TBCs in 1121°C /1 hour cyclic furnace tests exhibit a significantly improved spallation life compared to APS, DVC, and EB-PVD/Pt-Al TBCs. Extensive process diagnostic and modeling studies have been conducted to provide a foundation for understanding and control of the process. Process/microstructure/property relationships have been defined. Extension of the process for making thick coatings (> 3mm) and low thermal conductivity coatings are described.
Influence of Humid Air on Gaseous Combustion of Gasturbines
Authors: Wang Yue , Xu Gang , Nie Chaoqun , Xiao Yunhan , Huang Weiguang , Zhang Zhedian , Cui Yufeng
Published: November 2008

Combustion with humid air is a key process of humid air turbine (HAT) cycle. In the present study, the influence of humid air on gas turbine combustion was studied both experimentally and numerically. Performance of a full-scale can-type combustor equipped with a diffusion burner was investigated when burning propane and syn-gas with various humidity of intake air. The results indicate that the effect of humid air on pollutant emission depends on fuel type due to the difference of chemical mechanisms. For the syn-gas flames, moisture addition can effectively reduce NO emission without increasing CO. A numerical model was developed to simulate the 3D flow field in the combustor when burning syn-gas. The mixture fraction approach and the laminar flamelet model were applied to simulate the diffusion flame. The thermochemical quantities of the flamelets were computed by adopting a detailed chemical reaction mechanism for the H2-CO-N2-O2 system. The numerical results show that an oval hot zone above 2100 K is formed near the axis of the combustor due to flow recirculation. The hot zone mainly accounts for the thermal NO in the syn-gas flames. With the moisture addition into intake air, the volume of this zone is substantially decreased, and, therefore, the NO production is suppressed. This explains the NO reduction due to humid air observed in the experiment.
Inverted Turbo-Jet Engine for Hypersonic Propulsion
Authors: Tsujikawa Yoshiharu , Kaneko Ken-Ichi , Tokumoto Shusuke
Published: November 2008

This paper concerns to the inverted turbo-jet engine intended for operation in the range of Mach numbers from 0 to 6. In the present engine configuration, which is based on the inverted Brayton cycle, the sequence of the core-engine components was arranged in the order: turbine - heat exchanger - compressor - combustor. It should also be noted that the inverted Brayton cycle has also been considered for application to stationary power generation systems in the role of a bottoming cycle. An improved version of the inverted turbo-jet engine (ITE), has also been proposed in the present paper, incorporates an additional combustor installed between the inlet and the turbine. At low speeds this additional burner allows a heat input upstream of the initial turbine to augment thrust. The fuel-rich mode of operation is expected to be beneficial, as speed increases. In summary, the inverted turbojet engine can produce sufficient thrust compared to another engine concepts and it reveals high energy efficiency over the wide speed of range.