bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerodynamic Design of Exo-Skeletal Engine Fan Blades
Authors: Abumeri Galib H. , Schmidt James F. , Chamis Christos C.
Published: November 2008

The aerodynamic feasibility of fan rotor blades for the revolutionary Exo-Skeletal Engine (ESE) is assessed for a subsonic mission using the NASA Engine Structures Technology Benefit Estimator (EST/BEST) computational simulation system. The ESE calls for the elimination of the shafts and disks completely from the engine center, and places the attachment of the rotor blades in spanwise compression to a rotating casing. The preliminary aerodynamic design of the fan rotor blade estimated an overall adiabatic efficiency of 91.8%. The flow is supersonic near the blade leading edge but quickly transitions into a subsonic flow without any turbulent boundary layer separation on the blade. The performance map for the fan rotor blade is calculated using a 2D off-design code. The results show that the ESE fan blade has reasonable stall and choke margins. It will be demonstrated in this paper that a computational simulation capability is readily available to evaluate new and revolutionary technology such as the ESE.
Design Optimization Study of Isolation Mount Systems for Gas Turbine Engine Accessories
Authors: Sheridan William , Kazerounian Kazem
Published: November 2008

Design optimization has become increasingly important in today’s world. The ability to develop products that offer the best possible solution, distinguish industry leaders from those that lag behind. To reach this goal, optimization techniques are required which provide solutions in a timely and cost effective manner. This paper addresses a specific optimization process for designing isolation mount systems for gas turbine engine accessory components. This process enables the designer to quickly select an isolation system that will reduce the loads on components without the use of a time consuming Finite Element Analysis (FEA). Commercially available tools such as MATLAB [7] and MSC-WORKING MODEL 2D [6] are used to study a range of mount systems and help the designer focus his attention on the best choice of design variables. Gas Turbine engine accessory mount systems are generally sized by emergency conditions such as Fan Blade Out (FBO). These emergency conditions are rarely seen in service, but since they can drive the cost and weight of the mount system, an optimization process is needed to select the best configurations. References [8] through [10] discuss this in detail. Design Cycle time is just as important as cost and weight. The ability to size and package components quickly and accurately is vital to the design process. Poor utilization of space can drive cost and weight as much as poor component design. Knowing the correct size of the mount system in a rapid fashion offers further opportunities for surrounding components & systems to be optimized.
Results and Experience From GE Energy’s MS5002E Gas Turbine Testing and Evaluation
Authors: D’Ercole Michele , Biffaroni Giovanni , Grifoni Francesco , Zanobini Francesco , Pecchi Paolo
Published: November 2008

GE Energy’s new gas turbine, the MS5002E, is a 30 MW-class industrial gas turbine for mechanical drive and power generation applications. The MS5002E (fig.1) is the latest in the Frame5 two-shaft family and, while it retains some features from previous versions, the machine has been specifically designed for low environmental impact and high reliability, in direct response to customer demand for high efficiency and availability [1] & [2]. Main features for the MS5002E are: • 32 MW base load power at ISO inlet conditions (no losses); • 36% thermal efficiency; • 11-stage axial compressor and 17:1 pressure ratio; • reverse flow, six cans, Dry Low NOx (DLN2 technology) combustion system; • two-stages reaction type HP turbine; • two-stages PT leveraged from the LM2500+ HSPT (High Speed Power Turbine); • HP speed operating range 90% (6709rpm) / 101% (7529rpm); • PT speed operating range 50% (2857rpm) / 105% (6000rpm); • exhaust gas temperature (EGT): ∼510°C; • two-baseplates configuration (gas turbine flange-to-flange unit and auxiliary system); • integrated enclosure and baseplate, providing maximum accessibility for maintenance. The design of the MS5002E has been validated through an extensive test program which has included some key-test rigs such as the Rotordynamic Test, the CTV Test (full-scale axial compressor test) and numerous component and full-scale combustion tests in laboratory, conducted in advance of the First Engine to Test (FETT). The MS5002E First Engine to Test was initially started in January 2003 and the validation program has been completed with a full gas turbine teardown, dirty layout (visual and dimensional inspections for each major gas turbine component in as-is conditions) and NDT inspection in June 2004. During engine teardown, disassembly/assembly procedures and tools have been tested and validated. Additional endurance and operability testing is ongoing and will be completed by the end of 2005. The First Engine to Test is a complete equivalent-to-production package including gas turbine, auxiliaries and control system. For the test, a dedicated plateau has been built in Massa, Italy [3]. The gas turbine has been equipped with over 1400 direct measurement points (for a total of more than 2400 direct and indirect measurements) covering the flange-to flange, the package and auxiliaries. All critical-to-quality parameters, such as turbine gas path components temperatures and stresses, combustor temperatures and dynamics, performances and emissions, have been carefully verified by means of redundant instrumentation. This paper presents how the test program has been built on the GE Energy NPI (New Product Introduction) Development Process and how results from tests are fed back to the gas turbine design process. The paper discusses test rig and facilities layout, gas turbine operation experience and lessons learned. Results from the tests and measurements are also discussed.
Influence of Inlet Shape on Twin Intake Duct Performance
Authors: Saha K. , Singh S. N. , Seshadri V.
Published: November 2008

Performance of twin intake ducts with different inlet shapes has been analyzed using a commercial CFD (Computational Fluid Dynamics) code. The performance has been evaluated for incompressible flow at a fixed Reynolds number (1.4×105). The shapes studied are rectangular (Aspect ratio = 2), square, semicircular, elliptic-1, elliptic-2 (inverse-elliptic) and oval shape with all the other geometrical parameters remaining same. The performance of the twin intake ducts in terms of the static pressure recovery coefficient, total pressure loss coefficient and distortion coefficient, and the secondary motion at the merging plane and the downstream planes show that the inverse elliptic shape is the best followed by semi-circular inlet. The vectors plots of secondary motion at the merging plane and downstream have shown the presence of twin pairs of vortical motion possibly caused by the change in centerline curvature. The cross flow vector plots also show four distinct vortices after merger.
CFD Simulation of a Low NOx Oil Fired Boiler
Authors: Hochenauer C. , Brandstetter G.
Published: November 2008

This paper compares the results of an advanced CFD calculation with measurements of a heavy fuel oil fired low NOx boiler. First, a state of the art boiler was investigated and the impact of boiler load and excess air on the NOx emissions was measured. In a second test run a staged combustion technology was integrated using the over fire air concept. The over fire technology is well known and well tested in coal fired boilers. In this pilot boiler it was shown that the over fire air technology could be used for oil fired boilers, too — leading to an enormous NOx reduction without any increase in CO and soot emissions. It was shown that the influence of boiler load, excess air and over fire air on the NOx and CO emissions can be predicted very well in the CFD calculation. Detailed numerical investigations showed that two-phase effects, a good turbulence model, gas and soot radiation and a detailed chemical kinetics mechanism are a must when modeling (staged) heavy oil combustion. The results of the CFD calculation showed an excellent agreement with the measurements over a very wide range of boiler settings and load factors although NOx is extremely difficult to predict.
A CFD Model for Reacting Flows in an Aero-Engine Hot End Simulator
Authors: Ma L. , Pourkashanian M. C. , Wilson C. W.
Published: November 2008

This paper presents a three-dimensional CFD model that numerically simulates the physical and chemical species transformations in the aero-engine turbine and nozzle aimed at contributing to an improved understanding of the minor species emitted by the aircraft, in particular the production of the gaseous aerosol precursors such as SO3, H2SO4 and HONO within the aircraft engine. The results presented are for the model applications to an aero-engine Hot End Simulator (HES). The HES was designed in the PARTEMIS programme to recreate the thermodynamic profile in the turbine and nozzle through which the hot gases pass after leaving the combustor so that detailed measurements can be made within the HES providing key boundary conditions and validations to the CFD model predictions. A detailed sulphur reaction mechanism has been incorporated in the numerical model, together with hydrocarbon-air and nitrogen chemistry, so that the effect of both engine condition and fuel sulphur content on the sulphur IV to VI conversion, as well as NOx/NOy conversion, in the post combustor region can be numerically predicted. For the two operational conditions studied, it is noted that there is still a significant portion of sulphur conversions taking place within the HES, although they are smaller when compared with the sulphur conversions that take place in the combustor. Overall conversion efficiencies of about 3.2% and 2.8% have been predicted for the Cruise and the Modern conditions studied, respectively, of which 0.6% and 0.7% were predicted occurring within the HES, respectively. The CFD predictions compared well with the available data from the HES measurements, although considerable uncertainties in the model input exist. The modelling results suggest that reasonable predictions can be obtained for the fluid flow, heat transfer and the chemical species transformations that occur in the turbine and nozzle, particularly for some of the unstable species that are not readily obtained through measurements. These results could also provide useful information/boundary conditions for the subsequent post engine modelling of the new particulate materials formed within the aircraft wake.
Ejectors Design in the Rolls-Royce 1MW Hybrid System
Authors: Bernardi Davide , Bozzolo Michele , Marsano Francesco , Tarnowski Olivier , Agnew Gerry
Published: November 2008

Rolls-Royce Fuel Cell Systems Limited in the last few years has been developing a low cost hybrid system for electricity production based on planar SOFCs (Solide Oxide Fuel Cells). The novel cycle is based on the recycle of cathodic off-gas to pre-heat the oxidant flow, using ejectors. On the anode side, ejectors are used to recycle steam-rich off-gas to the reforming reactor. This paper describes the analysis process carried out to optimize the ejector geometry, from the preliminary sizing of lengths and sections, to the flow path optimisation. Further study has been carried out in order to evaluate the influence of altered geometries on the ejector performance varying the nozzle position relative to the ejector body. An extensive and successful use of CFD (Computational Fluid Dynamics) combined with experimental results allowed the validation of the basic design tools and the optimisation of the ejector performance.
The Training and Education of Application Engineers
Authors: Kurz Rainer , Andrade Hector
Published: November 2008

Project Application Engineers (PAE) are a critical link between the customer and the OEM. His knowledge of both internal capabilities and knowledge and the customers business make him an important contributor in developing new projects. Despite the fact that this position can be an important and satisfying career path for engineers, its existence is widely unknown amongst engineering graduates. Therefore, a description of the tasks, duties and challenges for Project Application Engineers is provided. Project Application Engineers require a solid foundation of knowledge to perform their work successfully. Using this foundation, the Application Engineering organization has to ensure that all the necessary knowledge, skills and tools are available to the application engineers. A structured process to meet this goal is outlined.
TRANSEO Code for the Dynamic Performance Simulation of Micro Gas Turbine Cycles
Authors: Traverso A.
Published: November 2008

In recent years microturbines and, more generally, small radial turbomachinery have been of great interest to the power industry due to their possible integration with advanced energy systems involving very high-tech components, such as high temperature fuel cells, high temperature ceramic heat exchangers and air saturators, which are still under development. Even if microturbine technology is already commercially available, when such an engine is inserted into a more complex plant there are at least two difficulties to be faced: firstly, guaranteeing the safe operation of the microturbine at all the operating points, including start-up and shut-down; and secondly, ensuring the proper feeding conditions to the main components of the cycle. In fact, additional components bring new variables to be monitored and require additional control devices and control systems. As a result, a flexible and modular simulation tool is extremely useful for the actual development of new cycles, where attention is mainly paid to the interaction of quasi-conventional turbomachinery with advanced components integrated in the same cycle. The TRANSEO code is a MATLAB-based modular tool for the transient performance simulation of conventional and advanced energy systems based on gas turbine and microturbine technology. This paper presents the theoretical background and the organization of the tool, showing the validation of results for a conventional recuperated microturbine.
Control System for Solid Oxide Fuel Cell Hybrid Systems
Authors: Ferrari Mario L. , Magistri Loredana , Traverso Alberto , Massardo Aristide F.
Published: November 2008

The aim of this work is the development and testing of a control system for solid oxide fuel cell hybrid systems through dynamic simulation. Because of the complexity of these cycles, several parameters, such as the turbine rotational speed, the temperatures within the fuel cell, the differential pressure between the anodic and the cathodic side, the Steam-To-Carbon Ratio, need to be monitored and kept within safe limits. On the other hand, the system response to load variations is required to be as quick as possible in order to meet the energy demand. The plant component models and their integration were carried out in previous works. This paper focuses on the control strategy to regulate the net electrical power from the hybrid system, avoiding malfunctions or damage. Once the control system had been developed, its performance was evaluated simulating the transient behavior of the whole hybrid cycle: the results for several operating conditions are presented and discussed.
Results From the Research on Microturbine-CHP-Applications in Flanders
Authors: Liekens Johan , Van Bael Johan , Desmedt Johan , Robeyn Nico , Jannis Peter
Published: November 2008

Since 2002, Vito is exploring the market opportunities for microturbine-CHP in Flanders. In the theoretical research, the effect of the efficiencies of microturbine-CHP on the economical feasibility of the project was investigated. In Flanders, cogeneration can obtain financial support proportional to the primary energy saving. The significant impact of this support will be shown from the results of three feasibility studies on microturbine-CHP. This paper also explains that microturbine based cooling does not realize primary energy savings and therefore will hardly be financially attractive in Flanders. In our Thermotechnical laboratory, we have performed tests on the C30 LF/DG-microturbine-CHP. These tests were done with different fuel gas compositions. The turbine performed very good, but emissions increased with lower methane content of the fuel. At the end, one turbine blade seemed to be broken. Nevertheless, the performance or vibrations of the turbine were not affected.
Advances in the Computed Tomography of Turbine Blades
Authors: Allen Martin , Ramsey Andrew T.
Published: November 2008

Recent advances in virtually all areas of industrial Computed Tomography (CT) now allow faster, higher resolution, and increasingly economic CT inspection of turbine blades than ever before. CT is now used for a wide range of Non Destructive Testing and Evaluation (NDT&E) applications including first article inspection, defect detection, internal measurement, wear (and failure) analysis, and reverse engineering. Improvements range from the introduction of international standards on CT, through improvements in acquisition, reconstruction, and data extraction. Some of the most significant advances have been made in the ability to process the data generated by the CT systems. Today, CT is an increasingly practical method for the Non Destructive Testing and Evaluation of turbine blades.
Calculation of the Expansion Through a Cooled Gas Turbine Stage
Authors: Torbidoni Leonardo , Horlock J. H.
Published: November 2008

In recent work by the same authors [1], a new method for calculating the coolant flow requirements of a high temperature gas turbine blade was described. It involved consideration of successive chord-wise strips of blading; the coolant required in each strip was obtained by detailed study of the heat transfer processes across the wall of the blade and then setting limits on the maximum blade metal temperature. In the present paper, the gas state paths, involving viscous losses, heat transfer and mixing of the coolant with the mainstream, are determined strip-by-strip along the whole blade chord for the stator and rotor of the stage and illustrated on an enthalpy-entropy chart. The work output from each rotor strip is obtained together with the losses [entropy creation] through the whole stage. It is then possible to calculate the thermodynamic efficiency for the cooled turbine stage and compare it with that of the uncooled stage. Illustrative calculations are given, a main calculation being based on the mean flow across the blade pitch. But, in a second supplementary calculation, allowance is also made for flow variations across the blade pitch. By comparing these two calculations it is shown that the mean flow calculation is usually adequate.
Turbofan Engine Robust H-∞ Dynamical Output Feedback Control Design Based on LMI Method
Authors: Wang Xi , Tan Daoliang , Zheng Tiejun
Published: November 2008

This paper presents an approach to turbofan engine dynamical output feedback controller (DOFC) design in the framework of LMI (Linear Matrix Inequality)-based H∞ control. In combination with loop shaping and internal model principle, the linear state space model of a turbofan engine is converted into that of some augmented plant, which is used to establish the LMI formulations of the standard H∞ control problem with respect to this augmented plant. Furthermore, by solving optimal H∞ controller for the augmented plant, we indirectly obtain the H∞ DOFC of turbofan engine which successfully achieves the tracking of reference instructions and effective constraints on control inputs. This design method is applied to the H∞ DOFC design for the linear models of an advanced multivariate turbofan engine. The obtained H∞ DOFC is only in control of the steady state of this turbofan engine. Simulation results from the linear and nonlinear models of this turbofan engine show that the resulting controller has such properties as good tracking performance, strong disturbance rejection, and satisfying robustness.
Experimental Study of the Fundamental Mistuning Model for Probabilistic Analysis
Authors: Rossi M. R. , Feiner D. M. , Griffin J. H.
Published: November 2008

FMM is a reduced order model for efficiently calculating the forced response of a mistuned bladed disk. FMM ID is a companion program that determines the mistuning in a particular rotor. Together, these methods provide a way to acquire data on the mistuning in a population of bladed disks and then simulate the forced response of the fleet. This process is tested experimentally, and the simulated results are compared with laboratory measurements of a “fleet” of test rotors. The method is shown to work quite well. It is found that accuracy of the results depends on two factors: the quality of the statistical model used to characterize mistuning, and the sensitivity of the system to errors in the statistical modeling.
Vapor-Phase Slurry Aluminide Coating for Gas Turbine Components
Authors: McConnell Jeffrey J. , Kircher Thomas A. , McMordie Bruce G.
Published: November 2008

Diffusion aluminide coatings have long been used to protect gas turbine components made of nickel, steel, and cobalt alloys from oxidation and corrosion at high temperatures. The most common method for producing aluminide coatings is to “pack” parts within a powdered mixture of aluminum metal, halide compounds and inert oxide. When this mixture is heated, the halide reacts with the aluminum to form aluminum-rich vapor that migrates to the part and forms protective intermetallic aluminide layers. Similar aluminide coatings can be produced from “vapor-phase” slurries that incorporate aluminum pigments and halide activators. Unlike slurries long used to locally repair pack aluminides via a liquid-phase reaction with molten (or semi-molten) aluminum, the thickness of an aluminide formed from a vapor-phase slurry depends primarily upon the diffusion cycle used, not upon the amount of slurry applied to the surface. By eliminating the need for a powder pack, the vapor-phase slurry reduces thermal mass of the furnace load, increases batch flexibility and simplifies masking. Examples of aluminide coatings that may be produced by this method are presented. It is also shown that the oxidation resistance of an aluminide produced from a vapor-phase slurry is comparable to that of a coating of similar composition formed by pack aluminization. Consequently, the properties and advantages of vapor-phase slurry aluminization make this method an attractive option for coating the entire gas path surfaces of many components.
A New Assumed PDF Turbulent Combustion Model for Multi-Step Chemistry
Authors: Zuo Baifang , Black David L. , Smith Clifford E.
Published: November 2008

The effect of turbulence on chemical reactions is known to be important in many gas turbine combustor applications. There are only a few established models that can capture turbulence-combustion interaction in CFD codes, and all of these models are either very expensive (e.g. Monte Carlo PDF model) or limited in what types of flames can be analyzed (e.g. laminar flamelet). Assumed PDF models have been a popular choice because they are inexpensive and can handle all flame types (e.g. diffusion, premixed and partially premixed). However, assumed PDF models are typically restricted to single, one-step global mechanisms; or are a function of species and quickly become computationally expensive. CFD Research Corporation has recently developed and validated a new assumed PDF turbulence chemistry interaction model for multi-step chemistry. The model adopts an assumed, two-variable joint-PDF to model a wide-range of turbulent reacting flows. The two variables defining the PDF are the mixture fraction and reaction progress, representing species diffusion and flame propagation. A significant advantage of this new approach is its wide range of applicability for premixed, diffusion, and partially premixed flames. Allowing more detailed chemistry for species and combustion predictions enables complex chemical reaction processes including pollutant formation, flame ignition, and flame quenching to be studied. The model is also computationally efficient, with only a minor increase in computational expense with either species or number of global reaction steps. The newly developed model was first validated using a diffusion flame from a piloted burner developed at the University of Sydney. Three different methane bulk jet velocities were used to investigate the model’s behavior on turbulent diffusion flames. Simulation data were compared with the experimental measurements and the simulation results performed by Pope (Masri and Pope, 1990) using a velocity-composition joint PDF transport equation solved by the Monte Carlo method. To validate the model on premixed flames, the data of Moreau et al. (Moreau et al., 1974, 1976, 1977) were used. Data were collected on a mixing layer stabilized burner, where the main flow into the combustor was a premixed mixture of methane and air. Parallel to the main stream, a pilot stream of hot combustion products at 2000 K was injected for flame stabilization. The results demonstrate the wide applicability of the new model for practical, turbulent combustion applications.
Numerical Study of Thermo-Acoustic Waves Generation by a Swirling Flame Using a New Approach Based on Large Eddy Simulation
Authors: Duwig Christophe , Gherman Bogdan , Mihaescu Mihai , Salewski Mirko , Fuchs Laszlo
Published: November 2008

The new challenge of the Gas Turbine industry is to develop new technologies for meeting electricity demand growth and reducing harmful emissions. Thus, a better understanding of the combustion phenomenon and an improvement in simulation capabilities are needed. In this paper, we present a new technique that is computationally efficient, for capturing the thermo-acoustic waves in low Mach number combustors. The idea is to utilize the fact that the acoustic related pressure fluctuations are small as compared to the dynamic pressure. Semi-compressible LES of reacting flow is performed and while the pressure perturbations related to the acoustic-wave propagation are handled separately. The equations are solved individually while allowing interaction between the two systems. The technique has been applied to the study of the generation and propagation of thermo-acoustic waves in a combustion chamber. A sensitivity analysis is presented and most important instability modes are identified.
Gas Path Analysis Study for Overhaul Engines
Authors: Co´rdoba Oscar
Published: November 2008

This paper could be considered as a sequel to current studies in overhaul steady state engine gas path diagnostic field. What is new in this work is the diagnostic system tuning based on experience gained over the years. Some heuristic rules will be presented to fit the statistical information required by the Iterated Extended Kalman Filters (IEKF) methodology. Taking into account that no engine performance models from the manufacturer are usually available in maintenance workshops, several details about gas path modeling techniques will be shown. Turbofan engine results derived from experiments carried out in a test cell will be presented. They show how the maintenance actions may be quantified and how their prediction helps the overhaul decisions with a high economical impact.
Measurement of the Inlet Gas Temperature of a Gas Turbine
Authors: Lechner Christof , Bothien Mirko R.
Published: November 2008

The measurement of the inlet gas temperature of a gas turbine using intrusive measuring techniques has to face the fundamental problem, that there is a deviation between the temperature of the sensor, which is indicated, and the gas temperature. The paper collates all phenomena, which have an influence on this deviation. Furthermore, it presents methodologies, which allow the calculation of the gas temperature from the indicated temperature of the sensor. The impacts of the relevant heat flux mechanisms are quantified for a typical gas turbine application, and the overall uncertainty of the method is estimated. Additionally, the uncertainty of the measuring chain determining the indicated temperature is estimated. Combining the two uncertainties a total uncertainty of the gas temperature measurement is given.
An Adaptation Approach for Gas Turbine Design-Point Performance Simulation
Authors: Li Y. G. , Pilidis P. , Newby M. A.
Published: November 2008

Accurate simulation and understanding of gas turbine performance is very useful for gas turbine users. Such a simulation and performance analysis must start from a design point. When some of the engine component parameters for an existing engine are not available, they must be estimated in order that the performance analysis can be carried out. However, the initially simulated design point performance of the engine using estimated engine component parameters may give a result that is different from the actual measured performance. This difference may be reduced with better estimation of these unknown component parameters. However, this can become a difficult task for performance engineers, let alone those without enough engine performance knowledge and experience, when the number of design point component parameters and the number of measurable/target performance parameters become large. In this paper, a gas turbine design point performance adaptation approach has been developed to best estimate the unknown design point component parameters and match the available design point engine measurable/target performance. In the approach, the initially unknown component parameters may be compressor pressure ratios and efficiencies, turbine entry temperature, turbine efficiencies, air mass flow rate, cooling flows, by-pass ratio, etc. The engine target (measurable) performance parameters may be thrust and SFC for aero engines, shaft power and thermal efficiency for industrial engines, gas path pressures and temperatures, etc. To select initially the design point component parameters, a bar chart has been used to analyze the sensitivity of the engine target performance parameters to the design point component parameters. The developed adaptation approach has been applied to a design point performance matching problem of an industrial gas turbine engine GE LM2500+ operating in Manx Electricity Authority (MEA), UK. The application shows that the adaptation approach is very effective and fast to produce a set of design point component parameters of a model engine that matches the actual engine performance very well. Theoretically the developed techniques can be applied to other gas turbine engines.
The Potential of Electronic High Temperature Devices Based Upon Polymer Derived Ceramics
Authors: Xu Weixing , Kapat Jayanta , Chow Louis C. , An Linan , Zhang Wenge
Published: November 2008

In this paper, we describe the potential use of polymer-derived ceramics (PDCs) for micro-sensors for high-temperature gas turbine applications. PDCs have several unique properties such as ease of microfabrication, excellent mechanical, materials and thermal properties, and tunable electrical conductivity. The electrical conductivity of PDCs with varied composition is measured as a function of temperature from room temperature upon to 700°C. Our results reveal that with suitable doping, the electrical conductivity could be controlled from insulating to semiconducting. Next, we measure the cure depth of the precursors as a function of UV intensity and exposure time. A model is developed to predict the cure depth as a function of photoinitiator concentration and light intensity. Good agreement between theory and experimental data is obtained. Finally, a few typical micro parts are fabricated by lithography technique.
Case History: Generator Rotor Shorted Turn Induced Vibration Excursion
Authors: Palmer Ken A.
Published: November 2008

The diagnosis of a generator rotor vibration in a 1,000 MW nuclear plant unit is presented. Several vibration excursions were recorded between July and August 2002. The excursions were somewhat repetitive in shape, but erratic and presented a clearly worsening trend, which threatened the continuous operation of the unit. In addition to high bearing vibration levels, the vibration force was transmitted to the Generator’s Current Transformers showing vibration levels in excess of 18 mils. The diagnosis of the rotor vibration excursions was simultaneously conducted by the Original Equipment Manufacturer (OEM) and a third party. An existing rubbing condition in the exciter and the generator hydrogen seals is presumed to have contributed to the elevated vibration levels reached during the excursion. A flat orbit in the generator side of one of the low pressure rotors was also recorded during the investigation. The existing rubbing condition caused discrepancy in the diagnostic between both parties. The OEM attributed the excursions to that rubbing condition while the third party attributed it to Generator Rotor Shorted Turns. Later inspection of the generator rotor revealed that the second diagnostic was correct. The characteristics of the vibration condition, the trouble shooting approach and the solution are described in this article.
An Investigation of the Effect of Swirl Vane Angle on Fuel Concentration and Velocity Fields in Gas Turbine Mixers
Authors: Turek Louis J. , Dawson Robert W. , Chaos Marcos , Chen Ruey-Hung
Published: November 2008

The flow fields of two different Siemens-Westinghouse gas turbine mixers were studied experimentally in an effort to better understand fuel-air mixing in confined swirling flows found in industrial applications. The mixers consist of an annular flow region and mixing is achieved using swirl vanes, the pressure side of which is used to inject the fuel. The difference between the two mixers studied is the degree of swirl imparted on the flow by the swirl vanes (45° vs. 55°). Velocity (both axial and azimuthal) and fuel concentration profiles were obtained for non-reacting, atmospheric pressure flows at several axial and radial locations downstream of the swirl vanes by the use of LDV and infrared laser light absorption techniques, respectively. The fuel used in this work was a methane/air mixture, which was injected at a momentum flux ratio comparable to that under operational conditions. Results show that flow uniformity, as evidenced by velocity and fuel concentration profiles, is reached further downstream of the swirl vanes for the 45° mixer than for the 55° mixer. This indicates a lesser mixing performance in the 45° mixer. The axial and azimuthal RMS velocities were consistently higher for the 55° degree mixer and this was a likely contributor to its superior mixing performance. High velocity and fuel concentration gradients are common for both mixers and present in the near-field region close to the swirl vanes. The data obtained indicates that the flow behavior in the region near the swirl vanes strongly influences the mixing of the fuel and air. Frequency analysis of the fuel concentration data shows that some turbulent structures prevail throughout the mixing region in both mixers, revealing that some large scale flow features emanating from the swirl vanes are not dissipated even in the high degree of swirl hardware. Lastly, unmixedness levels in both mixers tested are calculated and compared with a discussion on how they might impact NOx emission levels.
Unsteady Fluid Structure Interaction in a Turbine Blade
Authors: Reddy Gorla Rama Subba , Pai Shantaram S. , Blankson Isaiah , Tadepalli Srinivas C. , Reddy Gorla Sreekantha
Published: November 2008

An unsteady, three dimensional Navier-Stokes solution in rotating frame formulation for turbomachinery applications has been described. Casting the governing equations in a rotating frame enables the freezing of grid motion and results in substantial savings in computer time. Heat transfer to a gas turbine blade was computationally simulated by finite element methods and probabilistically evaluated in view of the several uncertainties in the performance parameters. The interconnection between the CFD code and finite element structural analysis code was necessary to couple the thermal profiles with the structural design. The stresses and their variations were evaluated at critical points on the turbine blade. Cumulative distribution functions and sensitivity factors were computed for stresses due to the aerodynamic, geometric, material and thermal random variables. These results can be used to quickly identify the most critical design variables in order to optimize the design and make it cost effective. The analysis leads to the selection of the appropriate materials to be used and to the identification of both the most critical measurements and parameters.
Analysis of Highly Swirled, Turbulent Flows in Dump Combustor With Exit Contraction
Authors: Nickolaus Daniel A. , Smith Clifford E.
Published: November 2008

Highly swirled flows are commonly used in gas turbine combustors to stabilize the flame and enhance fuel-air mixing. Experiments by D. G. Lilley, 1985 have shown that swirling flow patterns (i.e. recirculation zones) are dramatically impacted by a downstream contraction. For unconstricted swirling flow, a large, central recirculation zone is formed, while for constricted swirling flows, the recirculation zone can be annular in shape and high (positive) axial velocity is seen on the centerline of the combustor. Over the past 20 years, steady-state Reynolds Averaged Navier Stokes (RANS) solutions with various turbulence models have not been able to mimic the flowfield patterns for swirling flow with a downstream contraction. In this study, Large Eddy Simulation (LES) calculations were performed that correctly predicted the recirculation flow patterns for swirling flow with a downstream contraction. In addition, LES predicted radial profiles of swirl velocity agreed well with measurements, including the solid body vortex core on the centerline of the combustor. RANS produced inferior predictions. Two cases with 45° swirlers and a dump combustor with and without a downstream contraction were modeled. The LES predictions were compared with RANS predictions and Lilley’s measurements. The computational domain included flow through the swirl vanes, the combustor, and the contraction area. The unstructured, parallel CFD-ACE+ code was used, with the Localized Dynamic kinetic Energy Model (LDKM) for subgrid turbulence.
Design of State Space Controllers for Industrial Twin Shaft Gas Turbines
Authors: Beukenberg Markus , Brodmann Michael , Weibel Hans , Mu¨ller Detlef
Published: November 2008

This paper depicts the development of a new control strategy for industrial gas turbines to improve the control accuracy in the entire operating range. In the first step, a complex mathematical model has been developed, which is implemented into the controller dynamic simulation. An automatic operating point dependent linearization process permits the model to be displayed in a linear state space description. Three established controller design procedures have been applied to the process. In the past, only a small number of state space control designs have been presented for industrial gas turbines. These approaches use low order mathematical descriptions, which often do not describe the system behavior in detail. This paper presents a controller design for a more detailed mathematic model of the 15th order. It is indicated, that certain controller designs are difficult to realize or even fail. These effects result from unfavourable numerical conditions (depending on the operating point) in combination with the high order of the approximated linear system description. The tested pole placement designs show favorable closed loop system dynamic behavior and were improved by adding an integrating part to the controller.
Gas Turbine High Temperature Casing Upgrade
Authors: Orberg Alexei N. , Soudarev Vladimir B.
Published: November 2008

Due to enormous material losses in the case of emergency, it is vital to ensure the operation reliability of the natural gas pipeline compressor stations (CS). The risk of breakdown is rather high for gas turbines (GT) with total operation time approaching the design-estimated life and particularly for those in which the actual period of operation exceeds this value. Over 25% of turbine drives working on natural gas transportation net in Russia have exceeded their design life [1]. For instance, around 600 gas turbines of the GTC-10-4 type (10MW power) are still in service despite their 120,000–160,000 hours of operation (more than 1,000 gas turbines GTC-10 type have been made and installed at natural gas pumping stations in the seventies in Russia). These gas turbines contain several critical components. Most of them are related to the high temperature parts, including inner high-temperature turbine casing (ITC). This ITC is a kind of a collector (duct) connecting a combustion chamber outlet and the turbine’s entry. Combined with an insulation layer, it serves as a protective shield for outer (main) turbine casing against the effect of hot gases. Notwithstanding the fact that the GTC-10-4 turbine has a modest inlet gas temperature (TIT∼800°C), there are various problems with the ITC shape and state during the turbine’s operation. The ITC operates under conditions of dramatic temperature changes, pressure drops, extended periods of high temperature. All these factors can cause the ITC shell deformations, which results in poor turbine performances. Regular maintenance inspections including opening a turbine do not permit to establish reasons for dramatic changes in the ITC shape. A detailed numerical analysis has been performed to better understand the ITC dynamics over its service period of operation. Moreover, it should be observed that ITC forms a flow prior to entering a turbine. Then, gas flow is directed to the first stage nozzles of the turbine. Advanced numerical flow investigation methods were applied to improve hot gas distribution in front of the turbine. A considerable decrease in velocity nonuniformity was achieved both radially and circumferentially through the ITC shape optimization. Great need in this component stimulated introduction of a new manufacturing technology aimed at production of new ITCs and replacement of numerous defective ones still used at natural gas pumping stations across Russia. Results of thermo-deformation analysis and numerical flow investigation for various ITC configurations are presented in the paper. It also contains proposals for improving the state of the ITC and outer turbine casing (OTC) in the result of the fixing unit development and applying a new insulation material.
Advancements in Gas Turbine Fuels From 1943 to 2005
Authors: Edwards Tim
Published: November 2008

The first jet fuel specifications were published in 1943 in England (RDE/F/KER/210) and 1944 in the U.S. (AN-F-32a). Jet fuel has undergone many changes in subsequent years, with current specifications for JP-5 and JP-8 for the military in the U.S. and Jet A/Jet A-1 for commercial use world-wide. Jet fuel specifications are subject to constant tension between performance requirements and availability/cost considerations. This paper will discuss how jet fuels have evolved over the years from the first engines to current gas turbine engines. Jet fuels derived from non-petroleum sources will also be discussed.
Polymer Derived SiAlCN for Environmental Barrier Coatings
Authors: Wang Yiguang , An Linan
Published: November 2008

Silicon-based ceramics and composites are one of the most promising candidates for high temperature structural components in next generation gas turbines due to their excellent thermo-mechanical properties. However, these materials severely degraded when used in high temperature oxidizing environments, particularly, in the presence of corrosive species such as alkali elements or water vapor. Currently, the most promising approach with near-term benefits is to employ environmental barrier coatings (EBCs) that prevent direct contact between silicon-based materials and aggressive environments exist in turbine engines. Previous work on EBCs has primarily focused on using oxide coatings because oxides are in general more resistant to corrosive environments than Silicon-based ceramics. In this study, we propose to develop polymer-derived SiAlCN amorphous ceramics for EBC applications. Our research revealed that the oxidation rate of the SiAlCN ceramics is about 10 times lower than the lowest values observed on chemical vapor deposition (CVD) silicon carbide/nitride. Furthermore, the SiAlCN also exhibited good corrosion resistance to alkali salt at elevated temperatures.
Gas Turbine Fuel Injection Technology
Authors: Mansour Adel
Published: November 2008

This paper discusses the major drivers for innovation in the gas turbine fuel injection market with a major emphasis on a historical account of the progress made to date and the expected drivers for innovation in the coming years. A number of novel injector designs are presented that include Lean Direct Injection (LDI) Macrolaminate Modules, and various Lean Prevaporized Premixer (LPP) designs for power generation applications. The challenges that face fuel injection manufacturers are outlined.
Nonlinear Rotordynamics of Automotive Turbochargers: Predictions and Comparisons to Test Data
Authors: San Andre´s Luis , Rivadeneira Juan Carlos , Chinta Murali , Gjika Kostandin , LaRue Gerry
Published: November 2008

Passenger vehicle turbochargers (TCs) offer increased engine power and efficiency in an ever-competitive marketplace. Turbochargers operate at high rotational speeds and use engine oil to lubricate fluid film bearing supports (radial and axial). However, TCs are prone to large amplitudes of sub-synchronous shaft motion over wide ranges of their operating speed. Linear rotordynamic tools cannot predict the amplitudes and multiple frequency shaft motions. A comprehensive nonlinear rotordynamics model coupled to a complete fluid-film-bearing model solves in real time the dynamics of automotive turbochargers. The computational design tool predicts the limit cycle response for several inner and outer film clearances and operating conditions including rotor speed and lubricant feed pressure. Substantial savings in product development and prototype testing are the benefits of the present development. The paper presents predictions of the linear and nonlinear shaft motion of an automotive turbocharger supported on a semi-floating ring bearing. The shaft motion predictions are compared to measurements of shaft motion at the compressor nose for speeds up to 240 krpm, and for lubricant inlet pressure of 4 bar at 150°C. Linear and nonlinear rotordynamic models reproduce very well the test data for synchronous response to imbalance. The nonlinear results show two sub-synchronous whirl frequencies whose large magnitudes agree well with the measurements. A large side load predicted for this turbocharger must be considered for accurate prediction of the rotordynamic response.
Impact Fracture Behavior of Turbine-Grade Silicon Nitride Ceramic Under Tensile Stress at Elevated Temperatures
Authors: Yoshida Hiro , Chaudhri M. Munawar , Fukudome Takero , Tsuruzono Sazo
Published: November 2008

A series of particle impact tests was carried out at elevated temperatures up to 1400°C and under tensile stresses up to 200 MPa using a gas turbine-grade silicon nitride (SN282-Kyocera Corporation). It was found that: 1) At room temperature, 100 MPa tensile stress brings 8% strength degradation. 2) Regarding the effect of the temperature without applying tensile stress, similar to the case of quasi-static loading, the fracture toughness seems to play a predominant role under the dynamic loading also. 3) At 1350°C under 100 MPa tensile stress, effect of the stress on the degradation increases by 15%. 4) The effects of temperature and tensile stress on the strength degradation seem to be additive for temperatures up to 1350°C. Above 1350°C, remarkable strength degradation appears.