bluuebunny/crossref_metadata_2025 huggingface dataset:
Isoprenaline and Atropine Effect on Atrial Arrhythmias Study
Authors: Ahmad Anita , Schlindwein Fernando S. , Tuan Jiun H. , Ng G. Andre
Published: January 2011

Atrial Fibrillation (AF) is the most common disorder of the heart rhythms. There are about 2.3 million people in United States and 4.5 million people in the European Union with AF [Go et.al, 2001]. It is also one of the factors that may contribute to mortality and morbidity. Researchers who apply spectral techniques show that certain areas of the atria can have higher activation frequencies than other areas. Frequency analysis is used to measure changes in Dominant Frequency (DF). We access the electrical propagation inside the atria by spectrogram plotting and examining the effect of isoprenaline and atropine on frequency changes.
Usability Test in a Virtual Environment: A Case Study Based on a Mining Machine
Authors: Yousefi Hassan , Handroos Heikki , Soleimani Amir
Published: January 2011

Put During the concept phase of product development, designers must evaluate complex engineering scenarios. The usability test is an effective method to find out the design correctness regarding to use of the certain technical solutions. The commonly used usability test is performed on the physical mock-ups, and it is expensive test for new designed machines. Performance predictions and functional evaluations are possible long before real prototype test results become available. However, with the rise in model complexity, data quantity, computing performance, and accuracy, we increasingly find ourselves lacking the tools, methods, and metaphors to deal with the information generated. One of the most important applications of virtual reality (VR) technology has been for requirements analysis using virtual prototypes. The appeal of using VR is from saving the cost of physical mock-ups and prototypes, especially for complex systems. The paper presents a Virtual Reality (VR) technique as environment for the 3D model of the new designed systems and performs the usability tests to improve the designed system performance. The paper presents and investigates the results of applying usability test in a virtual environment for a sample mining machine.
Experiments on the Nonlinear Dynamics of Parallel Plates Subjected to Squeeze-Film Forces
Authors: Piteau Philippe , Antunes Jose´
Published: January 2011

Squeeze film dynamical effects are relevant in many industrial components, bearings and seals being the most conspicuous applications. But they also arise in other industrial contexts, for instance when dealing with the seismic excitation of spent fuel racks. The significant nonlinearity of the squeeze-film forces prevents the use of linearised flow models, therefore a fully nonlinear formulation must be used for adequate computational predictions. Because it can accommodate laminar and turbulence flow effects, a simplified bulk-flow model — based on gap-averaged Navier-Stokes equations and incorporating all relevant inertial and dissipative terms — was previously developed by the authors (Antunes & Piteau, 2010), assuming a constant skin-friction coefficient. In this paper we introduce an improved theoretical formulation, fully developed elsewhere (Piteau & Antunes, 2010), such that the dependence of the friction coefficient on the local flow velocity is explicitly accounted for, so that it can be applied to laminar, turbulent and mixed flows. The main part of the paper is then devoted to the presentation and discussion of the results from an extensive series of experiments performed at CEA/Saclay. The test rig consisted on a long gravity-driven instrumented plate of rectangular shape colliding with a planar surface. Theoretical results stemming from both analytical flow models are compared with the experimental measurements, in order to assert the strengths and drawbacks of the simpler original model, as well as the improvements brought by the new but more involved flow formulation.
Development of a 3kW Micro Turbine for CHP Applications
Authors: Visser W. P. J. , Shakariyants S. A. , Oostveen M.
Published: January 2011

Combined heat and power (CHP) concepts for small scale distributed power generation offer significant potential for saving energy and reducing CO2 emissions. Micro turbines are an interesting candidate for small CHP systems with advantages in terms of performance, size, noise and costs. MTT is developing a 3kW recuperated micro turbine for micro CHP applications for large households and for truck combined APU-heating systems. To minimize costs, off-the-shelf automotive turbocharger technology has been used for the turbomachinery. During recent years, turbocharger turbomachinery performance and efficiencies have significantly increased, even for very small sizes. At the same time, efficient high-speed motor-generators have become available at relatively low prices. The development of a concept demonstrator started in May 2008. This program phase included a cycle analysis and component selection study around off-the-shelf turbomachinery, design of a custom combustor, recuperator and generator and a test program. In this paper, results of the cycle definition, conceptual design and component matching study are presented. Next, the development of a detailed performance model is described and performance prediction results are given. Also, results of the test program and test analysis work are presented. Finally, from the conclusion of the demonstrator phase an outlook is given on the prototype design and performance, which will be the next phase of the development program.
Analyses of the Compressor Performance Impacts of Centrifugal Compressor Scroll Deformation Due to Installation
Authors: Xu C. , Amano R. S.
Published: January 2011

Centrifugal compressors have widely applications in industrial gas compression processes. Limitations of installation and compressor package always request to modify the compressor geometry to fit certain constrains. Very often, the modifications of the scroll were performed to meet the space constrains. To meet the installation and package requirements, we always modify the scroll and discharge pipe of the compressors. In this study, an original designed scroll and a modified scroll were analyzed by using the Computational Fluid Dynamics (CFD). The study is focused on the performance impacts of the scroll local deformation due to installation constrains. The CFD showed favorable agreements with experiments for original scroll. The detailed flow characters and performance impacts were discussed and results showed that current modifications of the scroll did not have significant impacts to the compressor performance. The study results can be used as a basic guidance for a compressor manufactures.
Transient Pressure Loss in Compressor Station Piping Systems
Authors: Brun Klaus , Nored Marybeth , Tweten Dennis , Kurz Rainer
Published: January 2011

“Dynamic pressure loss” is often used to describe the added loss associated with the time varying components of an unsteady flow through a piping system in centrifugal and reciprocating compressor stations. Conventionally, dynamic pressure losses are determined by assuming a periodically pulsating 1-D flow profile and calculating the transient pipe friction losses by multiplying a friction factor by the average flow dynamic pressure component. In reality, the dynamic pressure loss is more complex and is not a single component but consists of several different physical effects, which are affected by the piping arrangement, structural supports, piping diameter, and the level of unsteadiness in the flow stream. The pressure losses due to fluid-structure interactions represent one of these physical loss mechanisms and are presently the most misrepresented loss term. The dynamic pressure losses, dominated at times by the fluid-structure interactions, have not been previously quantified for transient flows in compressor piping systems. A number of experiments were performed by SwRI utilizing an instrumented piping system in a compressor closed loop facility to determine this loss component. Steady and dynamic pressure transducers and on-pipe accelerometers were utilized to study the dynamic pressure loss. This paper describes findings from reciprocating compressor experiments and the various fluid modeling studies undertaken for the same piping system. The objective of the research was to quantitatively assess the individual pressure loss components which contribute to dynamic pressure (non-steady) loss based on their physical basis as described by the momentum equation. Results from these experiments were compared to steady state and dynamic pressure loss predictions from 1-D and 3-D fluid models (utilizing both steady and transient flow conditions to quantify the associated loss terms). Comparisons between the fluid model predictions and experiments revealed that pressure losses associated with the piping fluid-structure interactions can be significant and may be unaccounted for by advanced 3-D fluid models. These fluid-to-structure losses should not be ignored when predicting dynamic pressure loss. The results also indicated the ability of an advanced 1-D Navier Stokes solution at predicting inertial momentum losses. Correspondingly, the three-dimensional fluid models were able to capture boundary layer losses affected by 3-D geometries.
On Gas Turbine Performance With Pulse Jet for Air Filters Cleaning
Authors: Brusca S. , Lanzafame R.
Published: January 2011

The present paper deals with the performance analysis of gas turbines with online pulse jet system for air filter cleaning. In order to evaluate the engine performance before, during and after the cleaning procedure, a mathematical model of GE MS6001FA gas turbine has been implemented using GateCycle software. The model was calibrated and tested using real engine monitoring data. A comparison of the engine behavior from the model and experimental data shows that the results can be calculated with errors below 2% for the input conditions simulated in the present study. The GateCycle model was used to evaluate engine performance before, during and after engine pulse jet activation. On the basis of the results it is possible to state that air filter cleaning slightly increase engine performance in normal industrial environment.
Application of Fiber-Optical Microphone for Thermo-Acoustic Measurements
Authors: Konle Holger J. , Paschereit Christian O. , Ro¨hle Ingo
Published: January 2011

A high temperature resistant fiber optical microphone (FOM) was developed and successfully applied in a combustion chamber at a thermal power of 8.4kW to measure thermo-acoustic oscillations at a frequency of 85Hz and a sound pressure level of 154dB. The sensor head temperature was estimated to ∼ 1000K. The core of the optical setup used for the FOM is a Fabry-Perot interferometer. To create an acoustical sensor based on this type of interferometer, a new method of generation and postprocessing of the interference signal was developed. The simple replaceability of the sensor membrane reduces the requirements concerning the sensor handling compared to conventional condenser microphones and allows the adaption of the sensor sensitivity to its application case changing the membrane stiffness.
Centrifugal Compressors During Fast Transients
Authors: Blieske Matthew , Garcia Hernandez Augusto , Kurz Rainer , Brun Klaus
Published: January 2011

Transient studies for compressor systems allow the prediction of the compressor system behavior during fast transients such as they occur during emergency shutdowns. For the system simulations, the compressor behavior is assumed to be quasi steady state. This means in particular that the steady state compressor flow-head-efficiency-speed map remains valid. During well instrumented emergency shutdown tests conducted on a centrifugal compressor system under realistic operating conditions, data showing the head-flow-speed relationship of the rapidly decelerating compressor was taken. This data is compared to steady state head-flow relationships taken at a number of speeds. This allows to determine the relative deviation between the transient and steady state head-flow-relationships, and thus answers the question of the validity of steady state assumptions during rapid transients. The impact of the fast transients on efficiency and consumed power, which can be derived from the speed decay of the system, as well as the impact of non-stationary heat transfer are also evaluated and reported.
Aerodynamic Optimization of an Impulse Turbine Cascade Including Laminar/Turbulent Transition Prediction
Authors: Benini Ernesto , Comis da Ronco Claudio , Ponza Rita
Published: January 2011

Aerodynamic optimization of an impulse turbine rotor cascade is described in this paper. The aim of the optimization is to minimize the total pressure losses through the cascade by reshaping the turbine airfoil. For a more realistic calculation of the boundary layer and the associated losses, laminar/turbulent transition is computed by means of the commercial CFD code Fluent. The solver underwent an accurate validation before it is inserted into the optimization loop. A proper optimization procedure is developed which is based on a sequential use of two modules: first, a global search is performed using a genetic algorithm, then a local optimization is carried out by means of a Sequential Quadratic Programming (SQP) algorithm. The benefits of this approach are demonstrated, in that the total pressure coefficient of the cascade can be lowered up to 25%.
Influence of Titanium in Nickel-Base Superalloys on the Performance of Thermal Barrier Coatings Utilizing γ-γ′ Platinum Bond Coats
Authors: Tawancy H. M. , Al-Hadhrami Luai M.
Published: January 2011

Titanium is a key element in nickel-base superalloys needed with aluminum to achieve the desired volume fraction of the strengthening γ′-phase. However, depending upon its concentration, titanium can degrade the adherence of aluminum oxide by forming TiO2 particles near the oxidemetal interface. This effect is extended to thermal barrier coating systems where in this case, the bond coat replaces the superalloy as the underlying substrate. Noting that the onset of failure of thermal barrier coating systems coincides with the first spall of the thermally grown oxide, titanium level in the superalloy can have an important effect on the useful life of the coating. Therefore, this study was undertaken to examine the effect of titanium on the performance of a thermal barrier coating system. Included in the study were two Ni-base superalloys with similar chemical composition except for the Ti content, and a Pt-containing bond coat consisting of γ′+γ-phases all top coated with zirconia stabilized by 7 weight % yttria. Coating performance was evaluated from thermal exposure tests at 1150 °C with a 24-hour cycling period to room temperature. Various electron-optical techniques were used to characterize the microstructure. The coating system on the low-Ti alloy was found to outperform that on the high-Ti alloy. However, for both alloys, failure was observed to occur by loss of adhesion between the thermally-grown oxide and underlying bond coat.
Advanced Mathematical Model of SOFC for System Optimization
Authors: Milewski Jaroslaw
Published: January 2011

The advanced mathematical model of Solid Oxide Fuel Cell (SOFC) is presented. Electrochemical, thermal, electrical and flow parameters are collected in the 0D mathematical model. The aim was to combine all cell working conditions in as low number factors as possible, which can be relatively easy to determine. A validation process for various experimental data was made and adequate results are shown.
Dynamics of a Prescribed Mixing Ratio Variable Fuel Flow Valve
Authors: Basilicata Carmine , Cerri Giovanni , Chennaoui Laila , Giovannelli Ambra , Miglioli Mauro
Published: January 2011

The production of emulsions on board of engines in real time with the fuel needs for the actual loading requires the development of a mixer that is capable to give the right volumetric ratio between the dispersed phase (water or ethanol) and the continuous phase (fuel). A Prescribed Mixing Device (PMD) has been developed to follow in real time the fuel request of a Gas Turbine or other engines. Previous investigations have demonstrated the stable steady state behavior at the various fuel flow rates ranging from idle to full load. Moreover, the influence of fuel viscosity variations (due to fuel temperature and quality changes) on the PMD response has been studied. This paper deals with the dynamic behavior of such a PMD. A physical model has been developed and accordingly, an amply series of tests have been carried on to check the PMD response to step and sinusoidal changes in the fuel request. A stable behavior has been evidenced thus the water content of the emulsion produced does not show significant drift in its value versus time.
Calibrated Non Linear Dissipative Model of Fan Bladed Disk
Authors: Lombard Jean-Pierre , Jean Pierrick , Lubrina Pascal
Published: January 2011

The results of non linear modeling of mechanical damped behavior of fan bladed disk are presented in the paper. A combined test/modeling strategy dedicated to the prediction of behavior of bladed disk in all operating flight range is proposed. The proposed methodology is applied on 2 configurations: firstly, on a well known fan stage (wide chord titanium blade with curvilinear attachment) and secondly, on a new one based on woven composite technology. This strategy needs to perform efficient and precise modal tests able to measure as well as possible the damping parameters. The test procedure is set up after trying of different test configurations: the robustness/repeatability of measure is verified and the scatter is quantified. A non linear tool (Snecma in-house code) is used to predict the behavior of the test configuration and allows the identification of damping parameters. These damping parameters are then used to assess the dissipative behavior in operating conditions. This tool is based on DLFT method derived from classical harmonic balance method and allows fast calculations of NL responses. The results presented illustrate the quality of tests measurement and the validity of the non linear model used to predict the characterized physics. The calibration is based on the damping parameters updated on a wide test configurations.
A Moving Load Finite Element-Based Approach to Determination of Case Load in a Blade-on-Casing Incursion
Authors: Ferguson Jeremy , Dunn Michael G. , Padova Corso , Manwaring Steve , Turner Alan
Published: January 2011

This paper presents a method for determination of case load by modeling blade-on-casing incursions using a moving load, finite element based approach. The blade is represented as a load moving at constant speed, imparting both tangential and radial forces to the casing. This approach also forms the basis for future work in the determination of the blade tip forces during such an event. A description of the future work required to use this approach to determine blade tip forces is presented.
A Numerical Approach for the Resonance Passage Computation
Authors: Hartung Andreas
Published: January 2011

This paper describes a numerical approach to compute the passage through the resonance with one of the natural frequencies and provides analytical proof of this. The numerical approach was used to compute the resonance passage of a turbine blade. The results are compared with complete resonance passages of a simplified multi body model and showed a very good agreement with the test results. In addition some parameter studies, such as structure damping resonance passage time and excitation amplitude, are presented.
Non-Equilibrium Plasma Assisted Combustion of Low BTU Fuels
Authors: Hu Hongbin , Xu Gang , Fang Aibing , Huang Weiguang
Published: January 2011

This paper presents preliminary experimental results of non-equilibrium plasma assisted combustion of low BTU fuels. The air flow and the fuel flow are separated by two co-axial tubes in which the air flow is excited by dielectric barrier discharge (DBD) plasma. A non-premixed simple jet flame is observed immediately when the DBD plasma-excited air flow mixed with the fuel flow. The measurements of the flame indicate that addition of a very small amount of energy in the form of DBD plasma can provide self-ignition in harsher conditions in contrast to usual spark ignition, and significantly improve the flame stability and combustion efficiency. The results also show that the effect of DBD plasma on the flame is most efficient in combustion at low equivalence ratios, and the chemical reactions can even occur at the equivalence ratios well below the lean flammability limit.
Secondary Flow Reduction by Blade Redesign and Endwall Contouring Using an Adjoint Optimization Method
Authors: Luo Jiaqi , Xiong Juntao , Liu Feng , McBean Ivan
Published: January 2011

For low-aspect-ratio turbine blades secondary loss reduction is important for improving performance. This paper presents the application of a viscous adjoint method to reduce secondary loss of a linear cascade. A scalable wall function is implemented in an existing Navier-Stokes flow solver to simulate the secondary flow with reduced requirements on grid density. The simulation result is in good agreement with the experimental data. Entropy production through a blade row is used as the objective function in the optimization of blade redesign and endwall contouring. With the adjoint method, the complete gradient information needed for optimization can be obtained by solving the governing flow equations and their corresponding adjoint equations only once, regardless of the number of design parameters. Three design cases are performed with a low-aspect-ratio steam turbine blade tested by Perdichizzi and Dossena. The results demonstrate that it is feasible to reduce flow loss through the redesign of the blade while maintaining the same mass-averaged turning angle. The effects on the profile loss and secondary loss due to the geometry modification of stagger angle, blade shape and endwall profile are presented and analyzed.
Minimizing Dynamic Response of Counter-Rotating Engines Through Optimized Node Placement
Authors: Hylton Peter D.
Published: January 2011

It has been previously proposed that a low-speed rotor balancing procedure can be suitable for supercritical shafting (GT2008-50077). That paper documented the necessity of taking into account nodal locations in the bending mode shapes of a supercritical rotor when designing an optimum balance process for such a rotor. This is due to the fact that balance correction forces (or for that matter, any forces) have the least impact when applied near the nodes of a particular mode. This result led to consideration that node location optimization could help with another issue, i.e. the excitation of backward excited whirl modes in a counter-rotating system. When designing a two rotor gas turbine, there are distinct advantages to having the two rotors turn in opposite directions. Among these are the ability to shorten and lighten the engine by reducing the length of the engine since a row of static turning vanes can be eliminated. The engine can be further lightened by inclusion of an inter-shaft bearing which eliminates static bearing support structure. Additional reduction in gyroscopic maneuver loads and deflections can also be achieved, thus resulting in multiple benefits to a counter-rotating system with an inter-shaft bearing. Unfortunately, the excitation of backward whirl modes of one rotor, which would normally not be a major concern in a co-rotating engine, can be a significant issue when excited in such a counter-rotating engine through the inter-shaft bearing, which serves as a conduit for forces from the other rotor. However, the logic of the earlier statement regarding the effectiveness of forces applied at, or near, a nodal point led to the hypothesis that optimizing the nodal locations relative to the interface points between the rotors could minimize the responsiveness of the system. This led to the hypothesis that by optimizing the node placement relative to the inter-shaft bearing, it should be possible to minimize the excitation of the backward modes. This paper examines that proposition and demonstrates that considering this aspect during the design of such an engine could lead to significant benefit in terms of minimized dynamic responses.
Numerical Study of Wet Compression Using Methanol Injection in Axial Compressor
Authors: El-Said A. F. , El-Salmawy H. A. , Gobran M. H. , Gad Ragab R. M.
Published: January 2011

A numerical model has been developed to study the impact of wet compression on the performance of three stages axial compressors. The CFD code, “FLUENT” was used to solve the governing equations in three dimensional, unsteady, turbulent flow scheme. Considering their advantages as volatile, non-corrosive, less erosive and renewable, Methanol droplets were considered for wet compression. They are introduced as a dispersed phase and are tracked in a Lagrangian frame. The model accounts for droplet-flow, droplet-droplet, and droplet-wall interactions. The compressor performance is analyzed in terms of; variation of air properties, characteristics of the operating point, and consumed power, due to wet compression. Parametric study has been conducted to find out the impact of different parameters on the performance of the compressor. These include the effect of; injection ratio, droplet size, and droplets agglomerations. It has been found that increasing the injection ratio reduces the temperature in both axial and radial directions. This in turn reduces the compressor specific power consumption. On the other hand, increasing the injected droplet size has an adverse effect on droplet evaporation rate and hence on specific power consumption. Droplets agglomerations tend to increase droplets sizes especially at rear stages of the compressor. This is also attributed to the omission of the smaller droplet due to early evaporation. Effect of agglomeration is emphasized as a result of higher loading ratio.
The Influence of Tip Clearance on the Acoustic and Aerodynamic Characteristics of Fans
Authors: Karstadt Sascha , Hess Michael , Matyschok Berthold , Pelz Peter F.
Published: January 2011

In addition to developing fans as aerodynamically efficient as possible, acoustic optimization gains more and more importance for the purpose of reducing fan noise exposure. In order to combine good aerodynamic properties with a silent fan, this experimental research investigates the acoustic and aerodynamic characteristics of an axial fan. In this case, a fan with skewed blades is tested in view of its aerodynamic efficiency and noise exposure in dependence on its tip clearance and stagger angle. For this purpose, six different stagger angles and five tip clearance gaps per angle were measured in a fan test rig (according to ISO 5136). Interpretation of the recorded data shows a clear trend toward higher aerodynamic efficiency and less noise with a down-sizing of the tip clearance gap. As the cost of manufacture rises with the decrease of the tip clearance, the efficiency of these measures can be calculated with the results of this study under consideration of aerodynamic and acoustic aspects.
The Impact of Geometric Scatter on High-Cycle-Fatigue of Compressor Blades
Authors: Heinze Kay , Vogeler Konrad , Friedl Winfried-Hagen
Published: January 2011

The geometric parameters of manufactured compressor blades do not exactly comply with the design intention. These deviations result from the abrasion of the forging and milling machines as well as variations of the material properties or the blank part geometries. Using probabilistic methods, the geometric deviations can be considered within the design process. This paper presents the results of a probabilistic High-Cycle-Fatigue investigation under consideration of the geometric parameter scatter of the entire compressor blade. Based on a previous paper of the authors, the geometric parametrization as well as the process chain to apply the geometric scatter to an existing FE-mesh was supplemented by the radii and the geometric dimensions of the compressor blade root. Thus, the impact of all geometric parameter scatter on the High-Cycle-Fatigue strength, the eigenfrequencies and the mode shapes can be evaluated.
Fatigue Properties of Narrow and Wide Gap Braze Repaired Joints
Authors: Henhoeffer Thomas , Huang Xiao , Yandt Scott , Au Peter
Published: January 2011

With the increasing utilization of braze repair in the gas turbine industry, the properties of braze joints under simulated service conditions become vital in selecting braze repair over other processes. While braze repair has often been claimed to deliver mechanical properties equivalent to that of the parent material; this is largely based on the results of tensile or accelerated creep tests. For most gas turbine hot section components failure occurs as a result of thermal fatigue or thermomechanical fatigue. The damage that occurs under such conditions cannot be assessed from tensile or creep testing. This study was undertaken to characterize the fatigue properties of narrow and wide gap brazed X-40 cobalt-based superalloy and compare these properties to that of the X-40 parent material. Butt joint narrow gap and wide gap specimens were vacuum brazed using BNi-9 braze alloy. X-40 and IN-738 were used as additive materials in wide gap braze joints. To characterize the fatigue properties of the braze joints and parent material, isothermal fatigue tests were conducted at 950°C and under load control using a fully reversed sinusoidal wave form having stress amplitude of 75% of the yield strength of the parent material. The braze specimens were fatigue tested in the as-brazed condition. The fatigue test results showed the fatigue lives of the brazed specimens were lower than that of the parent material, particularly for the narrow gap samples and wide gap samples containing IN-738 additive alloy. All fatigue failures in the brazed samples occurred in the braze joints. Analysis of the fracture surfaces using SEM revealed that porosity was the major contributing factor to fatigue failures in the wide gap braze joints. The testing life debit observed in the narrow gap braze samples can be attributed to the presence of brittle boride phases in the braze joint. This study also included examination of techniques for reducing the aforementioned porosity and presence of brittle intermetallic phases.
Study of Gas Turbine Exhaust Diffuser Performance and Its Enhancement by Shape Modifications
Authors: Pradeep A. M. , Roy Bhaskar , Vaibhav V. , Srinuvasu D.
Published: January 2011

In this paper, results of studies on typical gas turbine exhaust diffuser geometry have been reported. This diffuser consists of an annular diffuser followed by a conical diffuser. The annular diffuser has 5 radial, backward swept struts. The studies were carried out at a Reynolds number of 7.7 × 105 based on the diffuser inlet diameter (hydraulic). Two inflow boundary conditions corresponding to (i) full load (low swirl) and (ii) part load (high swirl) operations of a typical gas turbine exit were separately simulated. The performance of the diffuser was assessed in terms of total pressure loss and static pressure recovery coefficient along the diffuser. It was observed that the baseline diffuser geometry had substantial losses owing to separation of the boundary layer, beginning as early as in the annular diffuser and continuing all the way up to the exit of the conical diffuser. The performance was found to worsen with higher inlet swirl. It was observed that the divergence angle in the annular part of the diffuser plays an important role in the initiation of flow separation. Interaction of inlet flow swirl with the struts also initiates considerable asymmetry in the flow pattern within the conical diffuser. Based on observations from the baseline geometry, several new annular diffuser geometries with different divergence angles and shapes were numerically studied. The shroud shapes were manipulated at specific locations like the plane of the strut leading edge, maximum airfoil thickness and the trailing edge of the struts. Significant performance improvements were observed in these simulated diffuser configurations. Two such annular diffuser geometries have been discussed in detail in this paper.
A Methodology for Predicting the Response of Blades With Non-Linear Coatings
Authors: Filippi Sergio , Torvik Peter J.
Published: January 2011

Ceramic coatings applied by air plasma spray or electron beam techniques as thermal barrier coatings or to improve the erosion or corrosion resistance of blades in gas turbine engines are found to add damping to the system. However, such coatings display non-linear mechanical properties in that the Young’s modulus and the measure of damping are dependent on the amplitude of cyclic strain. To account for the coating nonlinearity, a new methodology for predicting blade response was developed and applied to an actual component coated with a titania-alumina blend ceramic infiltrated with a viscoelastic material. Resonant frequencies, mode shapes, and the forced response of a one blade segment of an integrated disk from a fan stage rotor were computed and compared with results from bench tests. Predicted frequencies agreed satisfactorily with measured values; predicted and observed values of system damping agreed to within 10%. The results of these comparisons are taken to indicate that it is possible to use laboratory-determined material properties together with an iterative finite element analysis to obtain satisfactory predictions of the response of an actual blade with a nonlinear coating.
The Development and Operational Experience With the Latest Siemens SGT6-5000F Gas Turbine at the Great River Energy Elk River Peaking Plant
Authors: Herda Vince , Gallagher William , McQuiggan Gerry
Published: January 2011

Siemens recently introduced the latest version of its popular SGT6-5000F (formerly known as the W501F) gas turbine. This paper will describe the new features of the engine (F4) and give details of the operational experience of the first engine to go into operation at the Elk River Peaking Station. Since the merging of Siemens and Westinghouse Power Generation divisions in 1998, Siemens has been working on consolidating the best technology of the two companies. This latest engine combines the best technologies from Siemens and Westinghouse.
Study of Tip Flows in High Hub-to-Tip Ratio Axial Compressors at Low Speed With Varying Tip Gaps, Inflow Conditions and Tip Shapes
Authors: Roy Bhaskar , Pradeep A. M. , Suzith A. , Bhatia Dinesh , Mulmule Aditya
Published: January 2011

The present study involves simulation of a single compressor rotor with a high hub-to-tip ratio blade. The study includes the effect of variation of tip gap, of tip shapes and of inlet axial velocity profiles, with inflows simulated similar to that of a typical rear stage environment of a multi-stage axial compressor. Numerical studies were carried out on a baseline rotor blade (without sweep or dihedral) and then on blades with sweep and dihedral applied at the tip region of the rotor. Simulation of these part-span sweep and dihedral shapes are done to study their effects on blade tip leakage flow. Results show that sweep and dihedral, in some cases, produce favorable tip flows, improving blade aerodynamics. Positive dihedral caused weakening of tip leakage vortex at design point as well as at peak pressure point. Negative dihedral may help postpone stall at the high pressure, low flow operation. Backward sweep weakened tip vortex at the design point. Contrary to some of the studies reported earlier forward sweep, when applied at the tip region, showed performance deterioration over the most of the operating range of the high hub-to-tip rotor.
USAF Enterprise-Wide Initiative to Improve Aeropropulsion Test and Evaluation
Authors: Kidman David S. , Dent Michael L. , Malloy Donald J.
Published: January 2011

In October of 2009, the United States Air Force (USAF) Test and Evaluation (T&E) community initiated work on an enterprise-wide initiative to improve collaboration across all phases of T&E. This paper provides an overview of the USAF aeropropulsion T&E capabilities and the way forward which are 1) an aligned T&E Enterprise using coordinated tactical and strategic goals, 2) a seamless T&E approach using independent Air Force assessments, 3) state-of-the-art T&E capabilities capable of testing current and future generation propulsion systems, and 4) improved propulsion acquisition and development processes. This paper includes a discussion of past difficulties and successes and focuses on the approach employed to realize USAF goals.
Characteristics of Tip Clearance Flow Instability in a Transonic Compressor
Authors: Hah Chunill , Voges Melanie , Mueller Martin , Schiffer Heinz-Peter
Published: January 2011

In the present study, unsteady flow phenomena due to tip clearance flow instability in a modern transonic axial compressor rotor are studied in detail. First, unsteady flow characteristics due the oscillating tip clearance vortex measured with the particle image velocimetry (PIV) and casing-mounted unsteady pressure transducers are analyzed and compared to numerical results with a large eddy simulation (LES). Then, measured characteristic frequencies of the unsteady flow near stall operation are investigated. The overall purpose of the study is to advance the current understanding of the unsteady flow field near the blade tip in an axial transonic compressor rotor near the stall operating condition. Flow interaction between the tip leakage vortex and the passage shock is inherently unsteady in a transonic compressor. The currently applied PIV measurements indicate that the flow near the tip region is unsteady even at the design condition. This self-induced unsteadiness increases significantly as the compressor operates toward the stall condition. PIV data show that the tip clearance vortex oscillates substantially near stall. The calculated unsteady characteristics from LES agree well with the PIV measurements. Calculated unsteady flow fields show that the formation of the tip clearance vortex is intermittent and the concept of vortex breakdown from steady flow analysis does not seem to apply in the current flow field. Fluid with low momentum near the pressure side of the blade close to the leading edge periodically spills over into the adjacent blade passage. The spectral analysis of measured end wall and blade surface pressure shows that there are two dominant frequencies near stall. One frequency is about 40–60% of the rotor rotation and the other dominant frequency is about 40–60% of the blade passing frequency (BPF). The first frequency represents the movement of a large blockage over several consecutive blade passages against the rotor rotation. The second frequency represents traditional tip flow instability, which has been widely observed in subsonic compressors. The LES simulations show that the second frequency is due to movement of the instability vortex.
An Experimental Investigation of Shrouded and Cantilevered Compressor Stators at Varying Clearance Sizes
Authors: Lange Martin , Mailach Ronald , Vogeler Konrad
Published: January 2011

This paper presents measurements conducted at a 4-stage low speed axial research compressor with cantilevered and shrouded stator vanes. The aim of the work is to compare these two design philosophies under rear stage conditions. To achieve blockage levels typical for rear compressor stages, the hub clearance of the first and second vane row were kept constant at 4% of channel height. The investigation were done within the third and fourth stage of the compressor. Tests were conducted at 4 different hub clearances over the third and fourth stator and subsequently with 3 different mass flow rates through the cavity of the shrouded third stator. Overall performance data and flow field traverses upstream and downstream of stator 3 and rotor 4 will be discussed.
Operating Experience on the First MS5002E Unit to Exceed 16000 Running Hours at Yara Sluiskil, Netherlands
Authors: Russo Alessandro , Forte Annalisa , Paci Mariateresa , Rossi Marco , D’Ercole Michele , Olivieri Tommaso , Ciofini Maurizio , van Graefschepe Marco
Published: January 2011

The MS5002E is a 32 MW-class, two-shaft gas turbine suitable for both mechanical and generator drive applications. Its design, based on the latest heavy-duty gas turbine technology, delivers 36% of thermal efficiency and maintains NOx emissions below 25 ppm. After an extensive validation program performed on the First Engine to Test (FETT), the first production unit was shipped to the Yara fertilizer company for its ammonia and nitrate fertilizer plant at Sluiskil in the Netherlands. Yara is the world’s largest supplier of crop nutrients, with sales to more than 120 countries. The unit entered into commercial operation on November 2007, supporting Yara in meeting its environmental plan by replacing an existing, less efficient gas turbine. The engine is operated in generator drive mode, producing 30+ MW of electric power and 50 tons per hour of steam, which is used in the plant process. As of this writing, the unit has exceeded 18,000 hours of continuous service. The performance results and reliability are unusually high for a new machine. This article reports the experience accumulated on the gas turbine during field operations, based both on the day-by-day activity (condition monitoring) and on the special introductory inspection program carried on to date. The improvements already introduced and being introduced on subsequent fleet units are discussed as well. The day-by-day monitoring is supported by an extensive quantity of data collected from the machine and sent via Internet connection to the GE Oil&Gas Remote Monitoring & Diagnostic Center in Florence.
Design and Operational Aspects of Gas and Steam Turbines for the Novel Solar Hybrid Combined Cycle SHCC®
Authors: Heide Stephan , Gampe Uwe , Orth Ulrich , Beukenberg Markus , Gericke Bernd , Freimark Manfred , Langnickel Ulrich , Pitz-Paal Robert , Buck Reiner , Giuliano Stefano
Published: January 2011

Solar hybrid power plants are characterized by a combination of heat input both of high temperature solar heat and heat from combustion of gaseous or liquid fuel which enables to supply the electricity market according to its requirements and to utilize the limited and high grade natural resources economically. The SHCC® power plant concept integrates the high temperature solar heat into the gas turbine process and in addition — depending on the scheme of the process cycle — downstream into the steam cycle. The feed-in of solar heat into the gas turbine is carried out between compressor outlet and combustor inlet either by direct solar thermal heating of the pressurized air inside the receivers of the solar tower or by indirectly heating via interconnection of a heat transfer fluid. Thus, high shares of solar heat input referring to the total heat input of more than 60% in design point can be achieved. Besides low consumption of fossil fuels and high efficiency, the SHCC® concept is aimed for a permanent availability of the power plant capacity due to the possible substitution of solar heat by combustion heat during periods without sufficient solar irradiation. In consequence, no additional standby capacity is necessary. SHCC® can be conducted with today’s power plant and solar technology. One of the possible variants has already been demonstrated in the test field PSA in Spain using a small capacity gas turbine with location in the head of the solar tower for direct heating of the combustion air. However, the authors present and analyze also alternative concepts for power plants of higher capacity. Of course, the gas turbine needs a design which enables the external heating of the combustion air. Today only a few types of gas turbines are available for SHCC® demonstration. But these gas turbines were not designed for solar hybrid application at all. Thus, the autors present finally some reflections on gas turbine parameters and their consequences for SHCC® as basis for evaluation of potentials of SHCC®.
Effects of Blade Loading Distribution on Aerodynamic Performance of Ultra-High Lift LP Turbine Airfoils Under the Influences of Wake Passing and Freestream Turbulence
Authors: Funazaki Ken-ichi , Shiba Takahiro , Tanimitsu Haruyuki
Published: January 2011

This paper deals with studies on the flow field around three types of linear cascades of low pressure turbine (LPT) airfoils with different chordwise loading distributions, while keeping the aerodynamic loading index almost the same. The purpose of the low-speed linear cascade study is to clarify the performance of newly designed two ultra high-lift blade (UHL blade) and compare each of them to that of the conventional LPT blade (Base Model) with low solidity through the measurements of boundary layers accompanied by separation bubble for low Reynolds number conditions. Cylindrical bars on the timing belts work as wake generator to emulate upstream stator wakes that impact the boundary layer on the airfoil suction surface. Freestream turbulence is also enhanced by use of passive turbulence grid. In addition to the pneumatic probe measurements of the midspan loss characteristics of each of the cascades, hot-wire probe measurement is conducted over the blade suction surface to understand to what extent and how the interaction of incoming wakes as well as freestream turbulence affect the boundary layer and separation bubble. Computational Fluid Dynamics (CFD) analyses are also applied to the flow fields around the cascades, mainly using Large-Eddy Simulation (LES) with dynamic Smagorinsky subgrid scale model.
Parker-Type Acoustic Resonances in the Return Guide Vane Cascade of a Centrifugal Compressor: Theoretical Modeling and Experimental Verification
Authors: Ko¨nig Sven , Petry Nico
Published: January 2011

The potential of acoustic resonances within vane arrays of turbomachinery has been known since the fundamental investigations of Parker back in the sixties and seventies. In his basic studies on flat plate arrays (and later on for an axial compressor) he could show that vortex shedding from the respective trailing edges may excite acoustic resonances that are localized to the vaned flow region. In principle, such phenomena are conceivable for any kind of turbomachinery; however, no such investigations are publicly available for the centrifugal type. The current investigation is one part of an extended research program to gain a better understanding of excitation and noise generating mechanism in centrifugal compressors, and focuses on Parker-type acoustic resonances within the return guide vane cascade of a high-pressure centrifugal compressor. A simplified model to calculate the respective acoustic eigenfrequencies is presented, and the results are compared with finite element analyses. Furthermore, the calculated mode shapes and frequencies are compared with experimental results. It is shown that for high-pressure centrifugal compressors, according to the nomenclature of Parker, acoustic modes of the α, β, γ, and δ type exist over a wide operating range within the return guide vane cascade. For engine representative Reynolds numbers, the experimental results indicate that the vortex shedding frequencies from the vane trailing edges cannot be characterized by a definite Strouhal number; the excitation of the Parker-type acoustic modes is mostly broadband due to the flow turbulence. No lock-in phenomenon between vortex shedding and acoustic modes takes place, and the amplitudes of the acoustic resonances are too small to cause machines failures or excessive noise levels.