bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the Segmented Displaced Trapezoidal Winding for Force and Torque Production as a Self Bearing Motor
Authors: Stephens Lyndon Scott , Impellizzeri Daniel
Published: November 2008

Self bearing motors have been identified as a potential technology for oil free turbomachinery where integral starter generator (ISG) technology may be used, among others. One of the key advantages of self bearing motors is that they reduce the shaft length of machines, hence increasing the rotordynamic performance. Until now, research has yielded self bearing motors that produce motoring torque and active force control of either the radial forces or the thrust force. In this paper, a new self bearing motor winding is analyzed for its potential to simultaneously produce actively controlled torque, radial forces and thrust force. The benefit of such a design is that the shaft length can be reduced even further as both the radial bearing and thrust bearing functions are performed by the motor. Experimental results are presented that verify the force and torque production capability of the motor to within 14% of the theoretical predictions. Another benefit of the motor is its ability to be used for large axial (thrust) movements, such that it could be used in precision axial positioning of high speed rotating loads over a large range (up to 25 mm or so for a 25 mm diameter rotor).
Analysis of the Segmented Displaced Trapezoidal Winding for Self Sensing Using Back EMF Waveforms
Authors: Stephens Lyndon Scott , Impellizzeri Daniel
Published: November 2008

In our companion paper, the trapezoidal winding is proposed for use as a self bearing motor that is capable of actively controlling motoring torque, radial force and axial thrust. Of course, this assumes that sensor signals are available for control of these axes. Conventionally, this is done using encoders and proximity sensors. In this paper the authors propose a self sensing approach that uses the back-EMF waveforms of the trapezoidal winding to estimate the angular, radial and thrust positions of the rotor, as well as rotor speed. Both simulated and experimental results are presented that demonstrate the potential of the approach and identify its limitations when applied to a closed loop feedback system. The experimental results indicate that the x, y, z and θ positions can be completely decoupled and estimated using the phase difference information in the back-EMF waveforms. A test actuator demonstrates that large axial displacements in excess of 5–10mm are achievable with the new actuator layout.
A High-Pressure Water Mist System: Clean Fire Protection for Gas Turbines
Authors: Voutilainen Heikki , Rohrbacher Herbert
Published: November 2008

Modern high-pressure water mist systems are an advanced choice for rotating machinery fire protection. High-pressure water mist systems can provide: • Proven extinguishing efficiency, • Proven capability to protect equipment from thermal stresses, • Tolerance to poor enclosure integrity, • A safe and reliable alternative to gaseous systems, and • An environmentally friendly alternative to dry chemicals, halons and halon alternatives. Generally, the systems have total flooding design, which is the most appropriate for protecting rotating equipment in their purpose-built enclosures. Fine water mist with a specific application rate, droplet size distribution and high discharge momentum is used to fill the enclosure quickly and completely. For all fire protection systems, third party testing and appraisal is important. FM and VdS have approved gas turbine fire protection systems for enclosures up to 500m3, while systems for enclosures up to 3300 m3 are (2004) within approval process. This paper explains the water mist system basic terminology and fundamentals. The paper then discusses system design requirements and features. In the end, health and safety, as well as environmental aspects are reviewed.
Experimental Results and Transient Model Validation of an Externally Fired Micro Gas Turbine
Authors: Traverso Alberto , Scarpellini Riccardo , Massardo Aristide
Published: November 2008

This paper presents the performance of the world’s first Externally Fired micro Gas Turbine (EFmGT) demonstration plant based on micro gas turbine technology. The plant was designed by Ansaldo Ricerche (ARI) s.r.l. and the Thermochemical Power Group (TPG) of the Universita` di Genova, using the in-house TPG codes TEMP (Thermoeconomic Modular Program) and TRANSEO. The plant was based on a recuperated 80 kW micro gas turbine (Elliott TA-80R), which was integrated with the externally fired cycle at the ARI laboratory. The first goal of the plant construction was the demonstration of the EFmGT system at full and part-load operations, mainly from the control point of view. The performance obtained in the field can be improved in the near future using high-temperature heat exchangers and apt external combustors, which should allow the system to operate at the actual micro gas turbine inlet temperature (900–950 °C). This paper presents the plant layout and the control system employed for regulating the microturbine power and rotational speed. The experimental results obtained by the pilot plant in early 2004 are shown: the feasibility of such a plant configuration has been demonstrated, and the control system has successfully regulated the shaft speed in all the tests performed. Finally, the plant model in TRANSEO, which was formerly used to design the control system, is shown to accurately simulate the plant behavior both at steady-state and transient conditions.
Improvements to Compressor Prognostics Algorithm for US Navy Ship Service Gas Turbine Generator Sets
Authors: Caguiat Daniel E. , Patterson Jeffrey S. , Scharschan John , Millsaps Knox
Published: November 2008

The Naval Surface Warfare Center Gas Turbine Emerging Technologies section conducted land-based testing on a gas turbine generator set in December 2003. The purpose of this testing, which was conducted on a Rolls Royce/Allison 501-K17 gas turbine, was to collect data that could be used to improve a previously developed computer program for predicting optimal compressor wash time intervals. For the purpose of Phase I of this testing, fouling was accomplished by injecting salt into the gas turbine inlet air stream. Phase II of this testing will consist of fouling the middle and back regions of the compressor. Influence coefficients can then be developed for each of these regions indicating how a given region affects overall performance. Typically, in a marine environment, fouling of the front stages occurs due to ingested salt while fouling in middle and rear regions occurs from a combination of ingested salt and oil seal leakage. A number of sensors, including compressor inlet and discharge condition probes, bleed air flow and fuel flow meters, were added in order to monitor engine performance during the testing. In addition, hardware was added to both ingest and monitor the concentration of salt in gas turbine inlet air. For Phase II testing, middle and rear stages of the 14-stage compressor shall be accessed through existing 5th and 10th stage bleed ports. A salt solution will be physically applied to the blades while the compressor is rotated by hand. Results from Phase I indicate that front stage compressor fouling causes a clear increase in inlet static pressure. This is due to the mass flow restriction through the compressor. Additional results are currently being summarized, and data is being utilized to improve the 501-K17 compressor wash prognostics algorithm previously noted.
On-Line Performance Evaluation of CHP Plant With Cooled Gas Turbine Supported by Off-Line Analysis Results
Authors: Chmielniak Tadeusz , Kosman Wojciech , Kosman Gerard
Published: November 2008

This paper presents a methodology of diagnostic investigations for gas turbines. The key feature is that the analysis is carried out in two modes: off-line and on-line. The first mode is performed periodically. It involves detailed measurements. Values obtained from measurements create the input data for further analysis. Health state of a gas turbine is then evaluated. The evaluation bases on calculation of several health state parameters. The on-line diagnostic mode uses these parameters as a reference state. The usual lack of measurements available in the on-line investigations creates the need for additional input data for the analysis. Therefore diagnostic investigations are supported by the results from the off-line mode. One of the main problems to be solved in diagnostic analysis is the appropriate modeling of gas turbine operation. An approach presented here regards the operation in various conditions, meaning also off-design operation.
Bottoming Organic Cycle for Gas Turbines
Authors: Bronicki Lucien Y. , Schochet Daniel N.
Published: November 2008

Organic Rankine Cycle (ORC) systems are not new; prototypes have been tested for about a century. The theoretical investigation and practical applications in the past are briefly presented and referenced. This paper presents the applications of this technology, which matured mainly in geothermal applications, to the recovery of exhaust heat of simple cycle gas turbines driving compressors on gas pipelines and gas processing plant. Most of the compressor stations have a capacity below 50 MW and operate basically unattended. The complexity and the necessity of an operator prevents the use of bottoming steam systems (combined cycle) on this size of plant. In these applications, which are mainly retrofits, the ease of operation of the ORC made its use possible where steam turbines were unsuccessful. Two applications are described: the Enterprise Products’ Neptune plant in Louisiana, and the Gold Creek gas compressor station in Alberta, Canada.
Adaptation and Modification of Gas Turbines for Solar Energy Applications
Authors: Sinai Joseph , Sugarmen Chemi , Fisher Uriyel
Published: November 2008

Adapting a gas turbine to high-temperature solar receivers and solar tower technology constitutes real progress towards commercial solar power utilization with high efficiency combined cycle power system. Solar gas turbine systems can also be adapted to hybrid solar/fossil fuel operation, thanks to its high efficiency conversion, relatively small solar field, and quick response to load fluctuations, low CO2 emissions, easy start, and more effective equipment utilization. ORMAT initiated adaptation and modification of gas turbines for solar energy applications in the early 1990s in cooperation with the Weizmann Institute of Science and later with the Boeing Corporation, with the support of the United States Israel Science and Technology Foundation (USISTF). Ultimately, the concept reached its successful realization (2001–2004) in the solar tower Plataforma Solar de Almeria (Spain) which has three solar receivers and a receiving system designed and supplied by the German Aerospace Center DLR.
A Reduced Order Model for Transient Analysis of Bladed Disk Forced Response
Authors: Ayers J. P. , Feiner D. M. , Griffin J. H.
Published: November 2008

A method for predicting the vibratory response of bladed disks under high engine acceleration rates is developed. The method is based on the Fundamental Mistuning Model, an existing reduced order model for predicting the steady-state vibratory response. In addition, a criterion is developed for a critical engine acceleration rate, above which transient effects play a large role in the response. It is shown that military engines operate at acceleration rates above this critical value and therefore transient effects are important in practice.
Revolutionizing Gas Turbine Maintenance in LNG Service
Authors: Raymer Stephen G. , Gautschy Charles A. , Evans B. Fred , Andrich Anthony S.
Published: November 2008

Atlantic LNG has developed a proven method for LNG turbine maintenance, which will revolutionize the industry. Over the life of Atlantic’s 4-Train facility, this method will reduce planned downtime by over a year. This paper details the innovative approach that the authors took to reduce Atlantic LNGs first major gas turbine overhaul from 29 days to 23 days, and the second major overhaul from 23 days to 18 days, with the ultimate goal of a 12 day turnaround (TAR). Atlantic LNG will soon begin a cycle in which a major overhaul is required approximately every 6 months as we cycle through our fleet of 26 Frame 5s. Using Gantry System technology, the company will be able to achieve a 50% reduction in downtime, which equates to approximately 1 year of additional production over the life of the plant.
A Comparison of a Single- and Multiphase Jets in a Crossflow Using LES
Authors: Salewski Mirko , Stankovic Dragan , Fuchs Laszlo
Published: November 2008

Large eddy simulations are performed for a single- and multiphase jets in crossflow (JICF). The multiphase JICF are compared to the single-phase case for the same momentum and mass flow ratios but with droplets of different sizes. Multiphase JICF have stronger counter-rotating vortex pairs (CVPs) than a corresponding single-phase JICF. Moreover, their trajectories are higher and their induced wakes weaker. The smaller the Stokes number of the droplets, the more the solution approaches the solution for single-phase flow. The computed results show the formation of a CVP and horseshoe vortices which are convected downstream. LES reveals also the intermittent formation of upright wake vortices from the horseshoe vortices on the ground towards the CVP. The dispersion of polydisperse spray droplets is computed using the stochastic parcel method. Atomization and droplet breakup are modeled by a combination of the breakup model by Reitz and the Taylor analogy breakup model. Evaporation and droplet collision are also modeled. The flow solver uses two-way coupling. Averages of the velocity and gaseous fuel mass fraction are computed. The single-phase JICF is validated against experimental data obtained by PIV. Additionally, the PDFs and frequency spectra are presented.
Numerical Analysis of Combustion Instability and Its Suppression in Gas Turbine Combustor With Swirlers Modeled on EV Premix Burners
Authors: Sohn Chae Hoon , Cho Han Chang
Published: November 2008

Pressure oscillation in an industrial gas-turbine combustor is numerically investigated based on thermo-acoustic instability. The combustor has 37 EV premix burners through which methane and air are mixed and then injected into the chamber. First, acoustic eigenmodes and frequencies of the chamber are examined by adopting linear acoustic analysis. Next, combustion instabilities are simulated. In simulating instabilities, first, steady fuel/air mixing and flow characteristics established by the burner are investigated by numerical analysis with single burner. And then, based on the calculated flow data, the burners are modeled numerically via equivalent swirlers, which facilitates the numerical analysis with the whole combustion system including the chamber and numerous burners. Finally, reactive flow fields within the chamber are investigated numerically by unsteady analysis and thereby spontaneous instability is simulated. Based on the numerical results, scaling analysis is conducted to find out the instability mechanism in the combustor and a passive control method to suppress the instability is proposed and verified numerically.
Numerical Design and Study of a MEMS-Based Micro Turbine
Authors: Onishi Tatsuo , Burguburu Ste´phane , Dessornes Olivier , Ribaud Yves
Published: November 2008

A full three dimensional Navier-Stokes solver elsA developed by ONERA is used to design and study the aerothermodynamics of a MEMS-based micro turbine. This work is performed in the framework of micro turbomachinery project at ONERA. A few millimeter scale micro turbine is operated in a low Reynolds number regime (Re = 5,000∼50,000), which implies a more important influence of skin friction and heat transfer than the conventional large-scale gas turbine. The 2D geometry constraints due to the limitation of fabrication technology also distinguish the aerothermodynamic characteristics of a micro turbine from that of conventional turbomachinery. Thus, for the foundation of aerothermodynamic design of micro turbomachinery, understanding of low Reynolds number effects on the performance is required and then the design of the turbine geometry can be optimized. In this study, aero-thermodynamic effects at low Reynolds number and different stator/rotor configurations are examined with a prescribed wall temperature. Losses due to heat transfer to walls and skin friction are estimated and their effects on the operating performance are discussed. Power delivery to turbine blades is checked and found satisfactory to give the objective design value of more than 100W. The effects of turbine exhaust geometry and the number of blades on turbine performance are also discussed.
Use of Hybrid Engine Modeling for On-Board Module Performance Tracking
Authors: Volponi Allan J.
Published: November 2008

A practical consideration for implementing a real-time on-board Module performance tracking system is the development of a high fidelity engine model capable of providing a reference level from which performance changes can be tracked. Real-time engine models made their advent with the State Variable Model (SVM) in the mid-80’s which provided a piecewise linear model that granted a reasonable representation of the engine during steady state operation and mild transients. Increased processor speeds over the next decade allowed more complex models to be considered which were combinations of linear and non-linear physics based components. While the latter may provide greater fidelity over transient operation and flight envelope excursions, it bears the limitation of potential model obsolescence as performance improvements in the form of hardware modifications, bleed and stator vane schedules alterations, cooling flow adjustments, and the like are made during an engine’s life cycle. Over time, these models may deviate enough from the actual engine being monitored that the module performance estimations are inaccurate and misleading. This paper describes an alternate approach to engine modeling by applying a hybrid engine model architecture that incorporates both physics-based and empirical components. This methodology provides a means to tune the engine model to a particular configuration as the engine development matures and furthermore, aligns the model to the particular engine being monitored to insure accurate performance tracking while not compromising real-time operation.
Advanced Services for Turbomachinery Asset Management
Authors: Quercioli Valter
Published: November 2008

Operations have a key role to play in today’s highly competitive environment, as they must provide the utmost effectiveness in asset management practices to boost the Return on Capital Employed (ROCE) back to the asset Owners. Asset Management Effectiveness (AME) can be rooted in a certain number of Operator-controllable leverages, that this paper is aimed to show thru a simple model. The model ties the identified operational leverages to the ROCE, providing guidance for the Operators to communicate properly with the asset Owners for demonstrating the financial benefits of their operational practices. A certain number of advanced services available to the Operators are shown and described, that can support both Operations and asset Owners in their search for the highest financial returns from existing assets.
Rough Set and Neural Network Based Fault Diagnosis for Aeroengine Gas Path
Authors: Chen Tian , Sun Jian-Guo
Published: November 2008

Aeroengine is a very complex nonlinear object. Traditional methods for its fault diagnosis are proved time-consuming and low efficient. A new system based on rough sets and neural networks for the fault diagnosis of aeroengine gas path is presented in this paper. At first, the rough set theory is used to determine qualitatively fault and isolate the fault. It consists of three steps: discretizing sensed data, reducing the decision table and generating rules. After that, feed-forward neural networks are added into the system to construct several sub-systems, which take the engine sensible data pretreated by rough sets as inputs and compute damage degrees of the aeroengine fault state. Last, the noise rejection abilities of the engine fault diagnosis system are analyzed. The test results show that the system can quantitatively diagnose the faults of aeroengine gas path with precision and efficiency, while it is robust for noise rejection.
Automated Repair and Overhaul of Aero-Engine and Industrial Gas Turbine Components
Authors: Bremer Claus
Published: November 2008

Automated repair processes and adaptive machining strategies constitute an important task in today’s aero-engine and industrial gas turbine maintenance, repair and overhaul (MRO) industry (figure 1). Currently, the repair of blisks is a central issue whenever consideration is given to replacing bladed stages with blisks; the feasibility of such a step hinges on the available capabilities for automated repair. The standard repairs are also influenced by these innovative approaches. Today, most of the processes for the MRO of engine components are carried out manually. In many cases, however, manual operations are not satisfactory from the point of view of costs and reliability. The MRO steps which are especially time consuming and require a high degree of accuracy are inspection, welding, milling and polishing. Adaptive machining methods can compensate for part-to-part variation as well as inaccurate clamping positions and keep the tolerances for the actual parts within a minimal range. The geometrical adaptation of the NC paths to the actual part geometry is performed automatically using in-process measuring techniques, mathematical best-fit strategies and adaptation methods. With the present state-of-the-art, it is possible to automate MRO work steps currently performed manually and to reduce costs and throughput times while boosting quality and precision. A further important aspect for the automation of component repair is the data management which should constitute the core of automated overhaul systems. As part of an innovative data management solution, the single repair process modules are integrated to build an automated repair cell for aero engine components. Furthermore, it is possible to establish “virtual” MRO workshops. The data management system generates a data set for each individual component and handles the logistics of the components and the accompanying data sets. As result, different MRO processes can be carried out at different facilities without loss of information, efficiency or quality. In addition, the approach described supports efficient life cycle monitoring.
Effects of Bearing Stiffness Anisotropy on Hydrostatic Micro Gas Journal Bearing Dynamic Behavior
Authors: Liu L. X. , Spakovszky Z. S.
Published: November 2008

The high-speed micro hydrostatic gas journal bearings used in the high-power density MIT micro-engines are of very low aspect ratio with an L/D of less than 0.1 and are running at surface speeds of order 500 m/s. These ultra-short high-speed bearings exhibit whirl instability limits and a dynamic behavior much different from conventional hydrostatic gas bearings. The design space for stable high-speed operation is confined to a narrow region and involves singular behavior (Spakovszky and Liu (2003)). This together with the limits on achievable fabrication tolerance that can be achieved in the silicon chip manufacturing technology severely affects bearing operability and limits the maximum achievable speeds of the micro turbomachinery. This paper introduces a novel variation of the axial-flow hydrostatic micro-gas journal bearing concept which yields anisotropy in bearing stiffness. By departing from axial symmetry and introducing biaxial symmetry in hydrostatic stiffness, the bearing’s top speed is increased and fabrication tolerance requirements are substantially relieved making more feasible extended stable high-speed bearing operation. The objectives of this work are: (1) to characterize the underlying physical mechanisms and the dynamic behavior of this novel bearing concept, and (2) to report on the design, implementation and test of this new micro-bearing technology. The technical approach involves the combination of numerical simulations, experiment, and simple, first principles based modeling of the gas bearing flow field and the rotordynamics. A simple description of the whirl instability threshold with stiffness anisotropy is derived explaining the instability mechanisms and linking the governing parameters to the whirl ratio and stability limit. An existing analytical hydrostatic gas bearing model is extended and modified to guide the bearing design with stiffness anisotropy. Numerical simulations of the full non-linear governing equations are conducted to validate the theory and the novel bearing concept. Experimental results obtained from a micro-bearing test device are presented and show good agreement between the theory and the measurements. The theoretical increase in achievable bearing top speed and the relief in fabrication tolerance requirements due to stiffness anisotropy are quantified and important design implications and guidelines for micro gas journal bearings are discussed.
Insertion of Shock Wave Compression Technology Into Micro Turbines for Increased Efficiency and Reduced Costs
Authors: Steele Robert , Baldwin Peter , Kesseli James
Published: November 2008

The following analysis is presented to serve as a preliminary design guide for micro turbine engine designers to consider the potential advantages of incorporating the Rampressor into their recuperated engine designs. It is shown that the increase in compressor efficiency and the shift in optimum pressure will increase the efficiency of the engine and lower the recuperator inlet temperature and specific cost. This also provides the opportunity to increase the turbine inlet temperature and specific power without incorporating more costly air-cooled metal or ceramic components into the turbine design. Ramgen Power Systems, Inc. (RPS) is developing a family of high performance supersonic compressor designs that combine many of the aspects of shock compression systems, commonly used in supersonic flight inlet design, with turbo-machinery design practices employed in conventional axial and centrifugal compressor design. The result is a high efficiency compressor that is capable of single stage pressure ratios in excess of those available in existing axial or centrifugal compressor designs. This technology provides a tremendous opportunity for replacement and/or de-staging of multi-stage centrifugal or axial compressors in gas turbines for greater efficiency, less cost, fewer parts, lower weight, and reduced footprint. A conceptual single-stage supersonic compressor has been defined for integration with a micro turbine in the 200 to 500 kWe class. This configuration offers the potential to achieve the DOE Advanced Micro Turbine Systems goals of greater than 40% LHV electric efficiency and $500 per kWe package selling price.
Modeling and Experimental Investigation of Micro-Hydrostatic Gas Thrust Bearings for Micro-Turbomachines
Authors: Teo C. J. , Spakovszky Z. S.
Published: November 2008

One of the major challenges for the successful operation of high-power-density micro-devices lies in the stable operation of the bearings supporting the high-speed rotating turbomachinery. Previous modeling efforts by Piekos [1], Liu et al. [2] and Spakovszky and Liu [3] have mainly focused on the operation and stability of journal bearings. However, since thrust bearings play the vital role of providing axial support and stiffness, there is a need to gain a fuller understanding of their behavior. In this work, a rigorous theory is presented to analyze the effects of compressibility in micro-flows (characterized by low Reynolds numbers and high Mach numbers) through hydrostatic thrust bearings for application to microturbomachines. The analytical model, which combines a 1-D compressible flow model with Finite-Element Analysis, serves as a useful tool for establishing operating protocols and assessing the stability characteristics of hydrostatic thrust bearings. The model is capable of predicting key steady-state performance indicators, such as bearing mass flow, axial stiffness and natural frequency as a function of the hydrostatic supply pressure and thrust bearing geometry. The model has been applied to investigate the static stability of hydrostatic thrust bearings in micro-turbine-generators, where the electrostatic attraction between the stator and rotor gives rise to a negative axial stiffness contribution and may lead to device failure. Thrust bearing operating protocols have been established for a micro-turbopump, where the bearings also serve as an annular seal preventing the leakage of pressurized liquid from the pump to the gaseous flow in the turbine. The dual role of the annular pad poses challenges in the operation of both the device and the thrust bearing. The operating protocols provide essential information for the required thrust bearing supply pressures and axial gaps required to prevent the leakage of water into the thrust bearings for various pump outlet pressures. Good agreement is observed between the model predictions and experimental results. In addition, a dynamic stability analysis is also performed, which indicates the occurrence of unstable axial oscillations due to flow choking effects in both forward and aft thrust bearings. These a-priori dynamic stability predictions were subsequently verified experimentally on a micro-turbocharger. The frequencies of unstable axial oscillations predicted using the model compare favorably to those determined experimentally, thus vindicating the validity of the model. A simple and useful dynamic stability criterion is established, where the occurrence of flow choking in both thrust bearings give rise to dynamic instability.
Analysis of Tilting Effects and Geometric Non-Uniformities in Micro-Hydrostatic Gas Thrust Bearings
Authors: Teo C. J. , Spakovszky Z. S.
Published: November 2008

The MIT microengine rotors are supported by hydrostatic gas journal and hydrostatic gas thrust bearings. Due to the low length-to-diameter ratio of the devices, the thrust bearings play an important role in providing sufficient tilting stiffness to resist any tilting motion about the spinning axis of the rotor. The performance of the thrust bearings can be influenced by geometric nonuniformities such as thrust bearing clearances and orifice diameters and profiles which arise in the process of microfabrication. To enable stable high speed operation of the micro-devices, it is important to quantify these effects. Furthermore, a thrust bearing analysis tool needs to be developed that is able to explore different thrust bearing arrangements and configurations. In this work, an analytical model is established for analyzing the effects of rotor tilt and geometric non-uniformities in micro-hydrostatic gas thrust bearings for application to microturbomachinery. A previously developed model (Teo and Spakovszky [1]) is generalized and extended for application to thrust bearings with orifices arranged in non-axisymmetric configurations. As a consequence of rotor tilt or geometric non-uniformities, the flow through individual orifices of the thrust bearing becomes non-uniform. The orifice flows are in turn coupled to the hydrostatic pressure field in the thrust bearing pad, and a Green’s function approach is adopted to solve the coupled system. The hydrodynamic thrust bearing forces induced by the pumping action of the rotor rotation are determined by solving the Reynolds equation. The model is able to predict thrust bearing tilting stiffness and variations in the thrust bearing mass flow rates as a function of rotor tilting angle for a variety of orifice arrangements. The model can be applied to analyze the effects of non-uniformities in orifice diameter and the presence of clogged orifices on tilting and the concomitant reduction in tilting stiffness. In addition, the effects of orifice taper are analyzed using an influence-coefficient technique for 1-D compressible flows. Results obtained for various taper ratios are presented and discussed. The model serves as a useful tool for specifying design tolerances during the fabrication of micro-hydrostatic gas thrust bearings and is used in the experiments to estimate the tilting angle of the rotor during operation.
Ceramic Matrix Composite Turbine Vanes for Gas Turbine Engines
Authors: Vedula Venkat , Shi Jun , Jarmon David , Ochs Scott , Oni Lola , Lawton Thomas , Green Kevin , Prill Lisa , Schaff Jeffery , Linsey Gary , Zadrozny Gary
Published: November 2008

Ceramic matrix composite (CMC) turbine vanes, due to their high temperature capability, allow significantly higher firing temperatures with minimal cooling. Turbine vanes were designed for a gas turbine engine with special attention to attachment methods that minimize thermal stresses due to large differences in coefficients of thermal expansion between the CMC airfoil and metal platforms. Detailed aerodynamic, thermal and structural analyses were performed to ensure component reliability. The paper describes the component design, analysis, fabrication, and rig testing of a silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) turbine vane.
Suppression of Combustion Noise and Combustion Oscillation by Thermo-Acoustic Active Control Using Secondary Flame
Authors: Ikame Masaru , Kishi Takeyuki , Harumi Kazuyoshi , Hiraoka Katsuhide , Oka Hideyuki , Sato Hiroyuki , Hayashi A. Koichi , Nishidome Chiaki , Kajiwara Itsuro , Ogawa Satoru
Published: November 2008

A feedback combustion control system based on the active noise control (ANC) principle was investigated with an experimental lean premixed dump combustor. In the control system, secondary diffusion flames were used as the sound source to attenuate pressure fluctuation in the combustion system. Piezo-valves with fast response were used to modulate the flow rate of the fuel for the secondary flames and to generate controlled sound by heat release oscillation. We investigated two kinds of controllers, that is, a time delay type controller and a model-based type one. In the experiment of the former, the dominant resonant mode of the combustion noise was suppressed more than 10dB in maximum. Clear periodicity of the suppression effect according to delay time indicates that the suppression is due to the acoustic interaction between the main flame and the secondary flames. In the model-based controller, robust control algorithms (mixed H2/H∞) were used. In addition, the gain-scheduled control was implemented to tune in to the shift of the dominant mode of the combustion noise, which resulted from variation of equivalence ratio. This control system effectively suppressed the dominant mode by more than 25dB without increase in other modes.
Investigation of Thermoacoustic Stability Limits of an Annular Gas Turbine Combustor Test-Rig With and Without Helmholtz-Resonators
Authors: Lepers Joachim , Krebs Werner , Prade Bernd , Flohr Patrick , Pollarolo Giacomo , Ferrante Antonio
Published: November 2008

Providing gas turbine combustion chambers with Helmholtz-resonators is a promising approach for extending the operating range of gas turbines towards higher thermal power input whilst minimizing the risk of thermoacoustic instabilities. The work currently being reported gives an overview of experimental and computational analyses carried out for a full annular combustor test-rig located at Gioia del Colle in Italy. The thermoacoustic stability characteristics of this test-rig were thoroughly analyzed both for a base configuration without Helmholtz-resonators and for an extended configuration with 14 Helmholtz-resonators. An increase of power input to the combustor by 8.5–20% can be realized when the test-rig is equipped with resonators. The experimental analyses are reproduced by a computational model.
Effects of Inlet Air Cooling, Blade Coolant Air Cooling and Recuperation on the Performance of Combined Cycle Power Plants
Authors: Yadav R. , Bhattacharya Somnath
Published: November 2008

In this work, the effects of inlet air cooling by vapor compression refrigeration cycle and evaporative water-cooling system, the cooling of blade coolant air by fuel before entering the combustor and recuperation on the combined cycle power plant performance have been studied. The present results show substantial improvements in the value of specific work and plant efficiency in the presence of cooling of inlet air and blade coolant air compared to a system without such cooling effects. However, implementation of recuperation alone reduces plant efficiency and specific work but recuperation combined with cooling effects increases plant efficiency. Design engineers might find presented results useful in optimizing a combined cycle system.
25 Years of BBC/ABB/Alstom Lean Premix Combustion Technologies
Authors: Do¨bbeling Klaus , Hellat Jaan , Koch Hans
Published: November 2008

The paper will show the development of lean premix combustion technologies in BBC, ABB and Alstom gas turbines. Different technologies have been developed and applied in Brown Boveri Company (BBC) before 1990. Considerable improvements with respect to NOx emissions as compared to gas turbines with a single combustor and a single diffusion burner for liquid and gaseous fuel have been achieved with burners with extended premixing sections and with multi injection burners for annular combustors. Between 1990 and 2005 burners with short but effective premixing zones (EV burners: environmental friendly V-shaped burners) have been implemented in all new gas turbines of the ABB (and later Alstom) fleet with NOx levels well below 25 vppmd (@15%O2). In addition to this, three variants of premix technologies have been successfully developed and deployed into Alstom GT engines: the sequential EV burners — a technology that allows premixing of natural gas and oil into a hot exhaust stream to reheat the exhaust gases of a first high pressure turbine; the MBtu EV burners that are used to burn syngas in a premix flame with low NOx emissions; and the advanced EV burners (AEV) that are capable to prevaporize and premix liquid fuel prior to combustion and burn it with very low NOx emissions without water injection. The paper will give an overview of these technologies and their usage in Alstom gas turbines over the last 25 years.
Operation Modes and Economic Performance Study of 100kW Microturbine Building Cooling, Heating and Power Systems
Authors: Huang Jintao , Feng Zhenping , Yue Chen , Liu Li
Published: November 2008

Microturbines are one of the most promising DG (Distributed Generation) technologies for Building Cooling, Heating and Power (BCHP) systems. They have advantages over other kinds of heat engines in terms of atmospheric emissions, fuel flexibility, noise, size, and vibration levels. The characteristics of the overall microturbine BCHP system may be different under various system configurations and operation modes which depend on the consumers and outdoor conditions. In this paper, on the basis of the authors’ previous work, the various possible operation modes are discussed under different external loads. The optimal operation modes are suggested to the microturbine BCHP schemes considering the various energy demands of a hotel in Xi’an. In the later part of this paper, the thermodynamic analyses and economic performance of microturbine BCHP system based on the first and the second laws of thermodynamics are carried out. The results show that even though the BCHP cogeneration system has the better economic performance both from the first and second laws evaluation, the benefits are affected by the operation modes because of the load uncertainty. The influence factors on the performance, such as power rate, natural gas price, operation time, are analyzed and compared for microturbine and gas engine BCHP systems. With the increase of natural gas price, or with the decrease of power rate, the economic performance advantages of both microturbine BCHP system and gas engine system are weakened, and the longer the cooling time, the shorter the payback periods for the system.
Advanced Interactive Cost Analysis Tool (AICAT): An Environment for Evaluating Affordability
Authors: Evans Jerry W. , Mehta Paul P. , Ludwig Arthur L.
Published: November 2008

AICAT encompasses innovative software architecture linked to a relational database. The system is based on a methodology (U.S. Patent #6775647) American Technology & Services previously developed for estimating and modeling the cost of advanced technology hardware for the “next-generation” fighter engine [1]. The AICAT offers a universal platform or software environment for developing and utilizing various types of cost models ideally suited for analyzing Life Cycle Cost (LCC) elements for all types of gas turbine engines. These cost models are comprised of algorithms and logic for mapping to specific elements such as features and design parameters associated with various hardware types, as well as cost elements related to gas turbine development or maintenance. The AICAT architecture is designed to be readily expandable and easily modified. Unlike other cost modeling software, AICAT does not require logic to be written in software code and recompiled in order to add models for new cost elements or for updating existing cost models.
Reduced Reaction Mechanisms for Methane and Syngas Combustion in Gas Turbines
Authors: Slavinskaya N. , Braun-Unkhoff M. , Frank P.
Published: November 2008

Two reduced reaction mechanisms were established which predict reliably for pressures up to about 20 bar the heat release for different syngas mixtures including initial concentrations of methane. The mechanisms were validated on the base of laminar flame speed data covering a wide range of preheat temperature, pressure and fuel-air mixtures. Additionally, a global reduced mechanism for syngas, which comprises only two steps, was developed and validated, too. This global reduced and validated mechanism can be incorporated into CFD codes for modelling turbulent combustion in stationary gas turbines.
Factory and Process Simulation in Aero-Engine Component Manufacturing
Authors: Franke Benedict Y. , Staudacher Stephan , Spieler Stefan , Gebser Dirk
Published: November 2008

This paper deals with factory and process simulation at an early stage of product introduction. During this stage basic considerations about producibility and impact on factory and supply chain logistics are of utter importance. Steps required to develop a realistic imitation of an (in this case) engine manufacturer plant are discussed. It is laid out how time variances, machine breakdowns as well as historic process capability and quality data can be included to create a model, which is able to realistically predict the impact of the introduction of new products. A feature-based approach to evaluate process capability for new products which have to be introduced is described. An example is given by the application of this approach to a modern engine high pressure compressor drum.
Supply Chain Simulation and Economical Evaluation of Forged Titanium Discs for Aircraft Engines
Authors: Boll Christopher , Staudacher Stephan , Spieler Stefan , Gebser Dirk
Published: November 2008

A top level investigation of the supply chain of forged titanium discs resulted in the fact that about 60% of the value-add and about 50% of the time used up in the supply-chain result from the titanium forgers. Engine manufacturers should focus on these companies when optimising their supply chain. The tool factory simulation with an attached economic evaluation tool is able to contribute to this supply chain optimization. It is presented and discussed on the basis of a titanium supply chain optimization from the view of an engine OEM. Two examples show the ability of this approach to predict the impact of future scenarios. Opportunities and weaknesses of this approach are discussed as well as ways and possibilities to bring a forging factory as well as the supply chain closer to optimal performance are evaluated and explained.
Performance of Oxidation and Creep Resistant Alloys for Primary Surface Recuperators for the Mercury 50 Gas Turbine
Authors: Rakowski James M. , Stinner Charles P. , Bergstrom David S. , Lipschutz Mark , Montague J. Preston
Published: November 2008

Recuperation is a means for increasing the efficiency of a simple-cycle gas turbine, allowing for heat transfer between the exhaust and compressor discharge gas streams to occur in a highly efficient, relatively compact package. The primary surface recuperator operates at high temperatures and gas pressures and is constructed from thin metal sections, presenting challenges for high temperature materials selection. This paper discusses a joint Solar Turbines-ATI Allegheny Ludlum project which was undertaken to address the issue of elevated temperature attack in the presence of high levels of water vapor and its relevance to alloys intended for use in primary surface recuperators. An overview of the alloy selection process will be presented, followed by a detailed study of the two most promising alloy candidates. Breakaway oxidation was mitigated by using alloys with higher nickel and chromium content, and oxide scale evaporation was controlled with selected minor element additions.
Low Pressure Fogger System for Power Augmentation of Industrial Gas Turbine
Authors: Levy Y. , Sherbaum V. , Ovcharenko V. , Sotsenko Y. , Zlochin I.
Published: November 2008

Based on three patented innovations (air-assist atomizer, wetness sensor, closed loop PLC), a new low-pressure power GT augmentation system was developed. Two modifications of air-assist atomizer were tested in the Jet Engine Laboratory of the Technion. The tests were performed to investigate influence of thermodynamic parameters on spray characteristics, as droplet size and velocity distribution of the spray. The system as a whole has passed field test in a gas turbine of a power station. Droplet characteristics, conceptual design aspects and tests results are the subject of this paper.