bluuebunny/crossref_metadata_2025 huggingface dataset:
Shift Reactors and Physical Absorption for Low-CO2 Emission IGCCs
Authors: Chiesa Paolo , Consonni Stefano
Published: December 2014

Integrated Gasification Combined Cycles (IGCC) exhibit conditions particularly favourable to the sequestration of CO2. The concept pursued in this paper is the generation of syngas low in carbon, where most of the heating value of the coal fuel is carried by hydrogen. Catalytic shift reactors convert most of the CO in the syngas into CO2, which is subsequently removed by physical absorption and then compressed to make it suitable for transport and permanent storage.

Energy balances, performance and cost of electricity are evaluated for two plants based on a Texaco gasifier and a large, heavy-duty gas turbine giving an overall IGCC power output between 350 and 400 MW. In one plant the raw syngas exiting the gasifier is cooled in a high-temperature, radiative cooler; in the other it is quenched by the injection of liquid water.

With respect to “conventional” Texaco IGCCs, the reduction of specific CO2 emissions by 90% reduces LHV efficiency from 5 to 7 percentage points and increases the cost of electricity of about 45%. These penalties can be reduced by accepting lower reductions of CO2 emissions. Compared to the semi-closed cycle considered by other authors, where CO2 is the main component of the gas turbine working fluid, the plants analyzed here exhibit higher efficiency over the whole range of specific CO2 emissions.
Heat Transfer on a Film-Cooled Blade — Effect of Hole Physics
Authors: Garg Vijay K. , Rigby David L.
Published: December 2014

A multi-block, three-dimensional Navier-Stokes code has been used to study the within-hole and near-hole physics in relation to heat transfer on a film-cooled blade. The flow domain consists of the coolant flow through the plenum and hole-pipes for the three staggered rows of shower-head holes on the VKI rotor, and the main flow over the blade. A multi-block grid is generated that is nearly orthogonal to the various surfaces. It may be noted that for the VKI rotor the shower-head holes are inclined at 30° to the spanwise direction, and are normal to the streamwise direction on the blade. Wilcox’s k-ω turbulence model is used. The present study provides a much better comparison for the span-averaged heat transfer coefficient on the blade surface with the experimental data than an earlier analysis wherein coolant velocity and temperature distributions were specified at the hole exits rather than extending the computational domain into the hole-pipe and plenum. Details of the distributions of coolant velocity, temperature, k and ω at the hole exits are also presented.
Adaptive Vibration Control of Industrial Turbomachinery
Authors: Hope R. Winston , Tessier Lynn P. , Knospe Carl , Miyaji Toshikazu
Published: December 2014

This paper presents test results from the application of Adaptive Vibration Control (AVC) to a magnetic bearing equipped 6-stage hydrogen process compressor which operates at 20.6 MPa (3000 psi). This application represents the first time AVC has been demonstrated on a fully functional industrial machine. The results demonstrate the reduction in vibration levels possible with AVC operating in each of the two vibration control modes: synchronous position reduction which reduces the synchronous displacement of the shaft as measured at the bearing and synchronous current reduction which reduces the synchronous control effort by the bearings, allowing the shaft to rotate about its inertial center. A discussion is also included on future developments planned for AVC.
A High Bandwidth, Low Loss Magnetic Suspension System for Turbomachinery
Authors: Kondoleon Anthony S. , Kelleher William P.
Published: December 2014

Magnetic bearings, unlike traditional mechanical bearings, consist of a series of components that, when mated together, form a stabilized system. The correct design of the magnetic bearing actuators will provide a cost effective device with low power requirements. The necessity of stability, which a magnetic suspension control system requires in both gain and phase margin, demands the actuators have sufficient bandwidth over the operating range. This paper presents designs for both radial and axial actuators which have attained both high bandwidth and low loss in operation. Test data which verifies the actuator models are presented. Applications of this technology for turbomachinery are described. These include fully magnetically levitated rotor systems, tip clearance control systems and noise and vibration control systems.
LM2500+ Single Shaft Combined Cycle With Frequency Stabilization
Authors: Kolp Donald A. , Levey Charles E.
Published: December 2014

Zorlu Enerji needed 35 MW of reliable power at a stable frequency to maintain constant speed on the spindles producing thread at its parent company’s textile plant in Bursa, Turkey. In December of 1996, Zorlu selected an LM2500+ combined cycle plant to fill its power-generating requirements.

The LM2500+ has output of 26,810 KW at a heat rate of 9,735 Kj/Kwh. The combined cycle plant has an output of 35,165 KW and a heat rate of 7,428 Kj/Kwh.

The plant operates in the simple cycle mode utilizing the LM2500+ and a bypass stack and in combined cycle mode using the 2-pressure heat recovery steam generator and single admission, 9.5 MW condensing steam turbine. The generator is driven through a clutch by the steam turbine from the exciter end and by the gas turbine from the opposing end. The primary fuel for the plant is natural gas; the backup fuel is naphtha.

Utilizing a load bank, the plant is capable of accepting a 12 MW load loss when the utility breaker trips open; it can sustain this loss while maintaining frequency within 1% on the mill load. The frequency stabilizing capability prevents overspeeding of the spindles, breakage of thousands of strands of thread and a costly shutdown of the mill.

A description of the equipment, operation and performance illustrates the unique features of this versatile, compact and efficient generating unit.
Comparative Analysis of Gas Turbine Engine Starting
Authors: Beyene Asfaw , Fredlund Terry
Published: December 2014

Electric, pneumatic, combustion, and hydraulic systems are commonly used as gas turbine engine starters. All such starters must allow full-load engine operation to be reached within few or several minutes, depending on the size and type of the engine. This contrast in the power source of these starters imposes a variation in their operations including control procedures and safety measures such as blow-downs and on/off sequences. Driving characteristics such as dynamic and static behaviors of these starters also vary significantly, depending on the type of starter and the size or configuration (single or multiple shafts) of the engine to be started.

This paper provides an overall comparative background of the commonly available gas turbine engine starters. It also presents numerical results comparing hot start characteristics of single, two, and three shaft engines with cold and hot ends. The possibility of a safe engine hot starting is a valid asset in some service areas, mainly military applications. The comparisons include starter power and gas producer speed (NGP) as the function of engine acceleration, and also starter torque as a function of the % NGP. Fuel consumption of the engine during the hot start is simulated and presented as a function of the load. The impact of an engine configuration on engine starting characteristics is implicated.
Effect of Coolant Injection on Heat Transfer for a Simulated Turbine Airfoil Leading Edge
Authors: Yuki Ushio M. , Bogard David G. , Cutbirth J. Michael
Published: December 2014

This paper presents an experimental study of the heat transfer on the leading edge of a simulated film cooled turbine airfoil. Previous studies have shown that use of film cooling on the leading edge of an airfoil can significantly increase the heat transfer coefficients around the leading edge which counter-acts the benefits of the adiabatic effectiveness provided by the coolant film. These heat transfer results complement our earlier study of the adiabatic effectiveness for this leading edge and film cooling hole geometry. Heat transfer and adiabatic effectiveness results were combined to determine the overall performance of the film cooling in terms of the net heat flux reduction. Heat transfer coefficients were found to be significantly increased by the film cooling flow in a narrow region which followed the path of the coolant flow. However, heat transfer coefficients were maximum to one side of the coolant jet, consistent with a streamwise vortex flow which is believed to be generated by the interaction of the mainstream with the coolant jet. Overall performance in terms of the net heat flux reduction was found to be unaffected by the large heat transfer coefficients in the vicinity of the holes, but was significantly diminished farther downstream.
Flow Measurement in a Multistage Large Scale Low Speed Axial Flow Research Compressor
Authors: Boos P. , Möckel H. , Henne J. M. , Seimeler R.
Published: December 2014

In this paper the newly built large scale low speed axial flow research compressor at Dresden University of Technology is presented. This compressor rig serves three main purposes. Firstly, it shall improve the understanding of compressor aerodynamics (especially secondary flows) by allowing detailed flow field measurements without heavily disturbing the flow. Secondly, it will be used to examine new design concepts. Thirdly, the detailed measurements in the absolute and relative system will be used for the calibration of existing CFD-codes.

The design and the construction of the test rig which will allow an easy variation of the test configuration is described. A short view of the different data acquisition units for steady and unsteady measurement in the stationary and rotating system will be given.

The blading of the compressor in the first series of test runs simulates a middle stage of a contemporary high-pressure compressor. Measurement data will be compared with results of 3D-Navier-Stokes calculations that were performed at MTU München.
Ultra-High Efficiency Power Systems With Near-Term Commercial Availability
Authors: Ali Sy A. , Zeh Charles
Published: December 2014

Power generation technologies of the twenty first century will offer diverse energy options for electric power generation. These would include many high efficiency, environmentally friendly systems. Fuel cell/gas turbine hybrid power packages meet these objectives. Fuel cells, when pressurized, produce very high efficiency, clean and quiet electric power. The unique features of pressurized fuel cells will be unmatched by any other power generation sources.
CFD Analysis of High Pressure Turbines
Authors: Liamis N. , Duboue J.-M.
Published: December 2014

The purpose of this contribution is to report on the aerodynamical performance calculations carried out around single stage high pressure turbines including rotor blade tip clearance effects. Three different turbine configurations are considered: a low lift case with two different tip gap heights and a high lift case. A multistage approach based on the ONERA-Snecma 3D Navier-Stokes code CANARI is used to investigate the turbine flow behaviour. The computational results are compared with experimental data and with results obtained by single blade row simulations.
Heat Load on the Walls of an Annular DLE Combustor Calculation and Comparison With Experiments
Authors: Janczewski Jacek , Nilsson Ulf , Strand Torsten , Troger Christian
Published: December 2014

The knowledge of the hot gas side heat load is a necessary prerequisite for the design of the advanced cooling scheme of a dry low-NOx combustor and the mechanical integrity (MIT) calculations of the combustor walls. The magnitude and the spatial distribution of the heat fluxes has to be known in the very early phase of the design, where there is no hardware available.

The evaluation of a combustor wall design has to be based on known process data, thermodynamic and combustion parameters and has to rely on computational methods and experience.

A stepwise computational approach is presented to reach this target utilising

• 1D flow and Nusselt-Number correlations

• 2-D boundary layer code

• computational fluid dynamics (CFD)

For the validation of the method atmospheric and pressurised single burner combustor tests were performed.

The relative merits and pitfalls of the different methods are discussed in detail. Recommendations for their utilisation within the design process and for their further development are given.
Separated-Flow Transition: Part 2 — Experimental Results
Authors: Hatman Anca , Wang Ting
Published: December 2014

The present paper focuses on presenting the results of the experimental investigation of the transition process in separated boundary layers on a flat plate at zero incidence, with imposed adverse pressure gradients. The combined effects of Reynolds number and adverse pressure gradient strength on the transition mechanism, bubble geometry, and bubble bursting process are studied. The flow structures and the unsteady aspects associated with separated-flow transition are analyzed for three representative experimental cases. Surface pressure results and detailed boundary layer measurements using hot-wire anemometry are presented as mean and rms velocity profiles, and Reynolds shear stress distribution. Turbulent intermittency and spectral analysis results are briefly introduced.
Complementary Velocity and Heat Transfer Measurements in a Rotating Cooling Passage With Smooth Walls
Authors: Bons Jeffrey P. , Kerrebrock Jack L.
Published: December 2014

An experimental investigation was conducted on the internal flowfield of a simulated smooth-wall turbine blade cooling passage. The square cross-sectioned passage was manufactured from quartz for optical accessibility. Velocity measurements were taken using Particle Image Velocimetry for both heated and non-heated cases. Thin film resistive heaters on all four exterior walls of the passage allowed heat to be added to the coolant flow without obstructing laser access. Under the same conditions, an infrared detector with associated optics collected wall temperature data for use in calculating local Nusselt number. The test section was operated with radial outward flow and at values of Reynolds number and Rotation number typical of a small turbine blade. The density ratio was 0.27. Velocity data for the non-heated case document the evolution of the coriolis-induced double vortex. The vortex has the effect of disproportionately increasing the leading side boundary layer thickness. Also, the streamwise component of the coriolis acceleration creates a considerably thinned side wall boundary layer. Additionally, these data reveal a highly unsteady, turbulent flowfield in the cooling passage. Velocity data for the heated case show a strongly distorted streamwise profile indicative of a buoyancy effect on the leading side. The coriolis vortex is the mechanism for the accumulation of stagnant flow on the leading side of the passage. Heat transfer data show a maximum factor of two difference in the Nusselt number from trailing side to leading side. A first-order estimate of this heat transfer disparity based on the measured boundary layer edge velocity yields approximately the same factor of two. A momentum integral model was developed for data interpretation which accounts for coriolis and buoyancy effects. Calculated streamwise profiles and secondary flows match the experimental data well. The model, the velocity data, and the heat transfer data combine to strongly suggest the presence of separated flow on the leading wall starting at about five hydraulic diameters from the channel inlet for the conditions studied.
A Parametric Starting Study of an Axial-Centrifugal Gas Turbine Engine Using a One-Dimensional Dynamic Engine Model and Comparisons to Experimental Results: Part 2 — Simulation Calibration and Trade-Off Study
Authors: Owen A. Karl , Daugherty Anne , Garrard Doug , Reynolds Howard C. , Wright Richard D.
Published: December 2014

A generic one-dimensional gas turbine engine model, developed at the Arnold Engineering Development Center, has been configured to represent the gas generator of a General Electric axial-centrifugal gas turbine engine in the six-kg/sec airflow class. The model was calibrated against experimental test results for a variety of initial conditions to insure that the model accurately represented the engine over the range of test conditions of interest. These conditions included both assisted (with a starter motor) and unassisted (altitude windmill) starts. The model was then exercised to study a variety of engine configuration modifications designed to improve its starting characteristics and thus quantify potential starting improvements for the next generation of gas turbine engines. This paper presents the model calibration results and the results of the trade-off study. A companion paper discusses the model development and describes the test facilities used to obtain the calibration data.
A Computational Model for Short Wavelength Stall Inception and Development in Multi-Stage Compressors
Authors: Gong Y. , Tan C. S. , Gordon K. A. , Greitzer E. M.
Published: December 2014

This paper presents a computational model for simulating axial compressor stall inception and development via disturbances with length scales on the order of several (typically about three) blade pitches. The model was designed for multi-stage compressors in which stall is initiated by these “short wavelength” disturbances, also referred to as spikes. The inception process described is fundamentally nonlinear, in contrast to the essentially linear behavior seen in so called “modal stall inception”. The model was able to capture the following experimentally observed phenomena: (1) development of rotating stall via short wavelength disturbances, (2) formation and evolution of localized short wavelength stall cells in the first stage of a mismatched compressor, (3) the switch from long to short wavelength stall inception resulting from the re-staggering of the inlet guide vane, (4) the occurrence of rotating stall inception on the negatively sloped portion of the compressor characteristic. Parametric investigations indicated that (1) short wavelength disturbances were supported by the rotor blade row, (2) the disturbance strength was attenuated within the stators, and (3) the reduction of inter-blade row gaps can suppress the growth of short wavelength disturbances. It is argued that each local component group (rotor plus neighboring stators) has its own instability point (i.e. conditions at which disturbances are sustained) for short wavelength disturbances, with the instability point for the compressor set by the most unstable component group.
Vortex Generators in Lean-Premix Combustion
Authors: Eroglu Adnan , Döbbeling Klaus , Joos Franz , Brunner Philipp
Published: December 2014

A novel fuel-air mixing technique on the basis of vortex generators has been developed and successfully implemented in the worlds first lean-premix reheat combustor of ABB’s GT24/GT26 series industrial gas turbines. This technique uses a special arrangement of delta-wing type vortex generators to achieve rapid mixing through longitudinal vortices, which produce low pressure drop and no recirculation zones along the mixing section. In this paper, after a short introduction to the topic, the motivation for utilizing vortex generators and the main considerations in their design are explained. A detailed analysis of the flow field, pressure drop and the strength of the vortices generated by a single vortex generator are presented as one of the three main geometrical parameters is varied. The results obtained through water model tests indicate that an optimum vortex generator geometry exists, which produces the maximum circulation at a relatively low pressure drop price. Moreover, the axial velocity distribution along the mixing section stays uniform enough to assure flash-back free operation despite the elevated inlet temperatures encountered in a reheat combustor. After selecting this optimized geometry, the process of the arrangement of multiple vortex generators in an annular combustor segment is described. The optimum arrangement presented here is suitable both for gaseous and liquid fuel injection, since it requires only one injection location per combustor segment.
Multiaxial Creep Life Prediction of Ceramic Structures Using Continuum Damage Mechanics and the Finite Element Method
Authors: Jadaan Osama M. , Powers Lynn M. , Gyekenyesi John P.
Published: December 2014

High temperature and long duration applications of monolithic ceramics can place their failure mode in the creep rupture regime. A previous model advanced by the authors described a methodology by which the creep rupture life of a loaded component can be predicted. That model was based on the life fraction damage accumulation rule in association with the modified Monkman-Grant creep rupture criterion. However, that model did not take into account the deteriorating state of the material due to creep damage (e.g., cavitation) as time elapsed. In addition, the material creep parameters used in that life prediction methodology, were based on uniaxial creep curves displaying primary and secondary creep behavior, with no tertiary regime. The objective of this paper is to present a creep life prediction methodology based on a modified form of the Kachanov-Rabotnov continuum damage mechanics (CDM) theory. In this theory, the uniaxial creep rate is described in terms of stress, temperature, time, and the current state of material damage. This scalar damage state parameter is basically an abstract measure of the current state of material damage due to creep deformation. The damage rate is assumed to vary with stress, temperature, time, and the current state of damage itself. Multiaxial creep and creep rupture formulations of the CDM approach are presented in this paper. Parameter estimation methodologies based on nonlinear regression analysis are also described for both, isothermal constant stress states and anisothermal variable stress conditions This creep life prediction methodology was preliminarily added to the integrated design code. CARES/Creep (Ceramics Analysis and Reliability Evaluation of Structures/Creep), which is a postprocessor program to commercially available finite element analysis (FEA) packages. Two examples, showing comparisons between experimental and predicted creep lives of ceramic specimens, are used to demonstrate the viability of this methodology and the CARES/Creep program.
PSP Measurement of Stator Vane Surface Pressures in a High Speed Fan
Authors: Lepicovsky Jan
Published: December 2014

This paper presents measurements of static pressures on the stator vane suction side of a high-speed single stage fan using the technique of pressure sensitive paint (PSP). The paper illustrates development in application of the relatively new experimental technique to the complex environment of internal flows in turbomachines. First, there is a short explanation of the physics of the PSP technique and a discussion of calibration methods for pressure sensitive paint in the turbomachinery environment. A description of the image conversion process follows. The recorded image of the stator vane pressure field is skewed due to the limited optical access and must be converted to the meridional plane projection for comparison with analytical predictions. The experimental results for seven operating conditions along an off-design rotational speed line are shown in a concise form, including performance map points, midspan static tap pressure distributions, and vane suction side pressure fields. Then, a comparison between static tap and pressure sensitive paint data is discussed. Finally, the paper lists shortcomings of the pressure sensitive paint technology and lessons learned in this high-speed fan application.
Numerical Simulation and Aerothermal Physics of Leading Edge Film Cooling
Authors: Chernobrovkin A. , Lakshminarayana B.
Published: December 2014

A viscous flow solver based on the Runge-Kutta scheme has been modified for the numerical investigation of the aerothermal field due to the leading edge film cooling at a compound angle. An existing code has been modified to incorporate multi-block capabilities. Good agreement with the measured data has been achieved. Results of the numerical investigation have been used to analyze the vortex structure associated with the coolant jet-freestream interaction to understand the contribution of different vortices on the cooling effectiveness and aerothermal losses. Two counter-rotating vortices generated by the interaction between the mainflow and the coolant jet have been found to have a major influence in decreasing the cooling efficiency through strong entrainment of the hot fluid. Numerical simulation was carried out to investigate the influence of the inlet Mach number, inlet turbulence intensity, and length scale on the aerothermal field due to the leading edge film cooling. Variation of the inlet Mach number leads to a minor modification of the cooling effectiveness, and this is predominantly caused by the modified pressure gradient. Increased turbulence intensity has profound effect on the cooling near the leading edge. Adiabatic effectiveness downstream of the second row of coolant holes is less sensitive to a change in turbulence intensity. Results of the numerical simulation indicate that the turbulence length scale has a significant effect on the accuracy of the numerical prediction of film cooling. Not only the inlet turbulence intensity but also the turbulence length scale should be accurately set to achieve a reliable numerical prediction of the heat and mass transfer due to film cooling.
On 3D Inverse Design of Centrifugal Compressor Impellers With Splitter Blades
Authors: Zangeneh M.
Published: December 2014

In the design of centrifugal compressor impellers with splitter blades it is quite common to use the same blade shapes on the full and splitter blades with the splitters placed at the mid-pitch location. However, recent results using conventional design methodology have indicated that by moving the pitchwise location of the leading edge of the splitter it is possible to improve splitter performance.

In this paper a 3D inverse design method is developed for the design of compressor impellers with splitters. In this design method the blades are designed subject to a specified distribution of the circulation on the full and splitter blades. The paper describes the choice of loading (or derivative of circulation with respect to meridional distance) and stacking condition to limit the complexity of the blade shape. Two different generic impellers are designed with different splitter leading edge location. The performance of these inverse designed impellers is then compared with the corresponding conventional impellers by using a 3D viscous code at design and off-design conditions.
Long Term Thermal Stability of INCONEL Alloy 783
Authors: Mannan Sarwan , deBarbadillo John
Published: December 2014

Recently developed INCONEL® alloy 783 (nominal composition of Ni-34Co-26Fe-5.4Al-3Nb-3Cr) is precipitation strengthened by Ni3Al-type Gamma Prime and NiAl-type Beta Phases. Due to its low co-efficient of thermal expansion (CTE), high strength, and good oxidation resistance alloy 783 has been specified for use in aircraft gas turbine components such as rings, casings, shrouds, and seals and has been considered for use in a number of other critical industrial turbine components.

In this study, commercially produced alloys 783, 718, and 909 were annealed and aged following recommended heat treatments. The materials were then isothermally exposed at 1100°F (593°C) for times up to 10,000 hours. At 1000 hour intervals, specimens of these alloys were removed from the furnace and subjected to room temperature tensile (RTT) and high temperature tensile (HTT) testing at 1200°F (649°C). The microstructure of as-produced and exposed materials was characterized using optical microscopy, Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). Variation in tensile properties with isothermal exposure time was correlated with the microstructure.
The Technology of Multipurpose Optimization of Gas-Turbine Engines and Their Components
Authors: Egorov I. N. , Kretinin G. V. , Leshchenko I. A. , Kostiuk S. S.
Published: December 2014

This paper presents the technology of searching for the most effective (optimal) engineering solutions for gas-turbine engines and their components at the stages of their designing, development and modernization. The distinctive feature of the technology is the possibility to solve optimization problems with large dimensionality (tens and hundreds of variables), with single or multiple criteria (search of Pareto-optimal solutions set), with minimal number of researched object mathematical simulator direct calls.
Characteristics of an Annular Turbine Cascade at Low Reynolds Numbers
Authors: Matsunuma Takayuki , Abe Hiroyuki , Tsutsui Yasukata , Murata Koji
Published: December 2014

The aerodynamic characteristics of turbine cascades are thought to be relatively satisfactory due to the favorable pressure gradient of the accelerating flow. But within the low Reynolds number region of approximately 6×104 where the 300kW ceramic gas turbines which are being developed under the New Sunshine Project of Japan operate, the characteristics such as boundary layer separation, reattachment and secondary flow which lead to prominent power losses can not be easily predicted.

In this research, experiments have been conducted to evaluate the performance of an annular turbine stator cascade. Wakes of the cascade were measured using a single hot wire and five hole pressure tube, for a range of blade chord Reynolds numbers based on the inlet condition from 2×104 to 12×104. Flow visualizations on the suction surface of the blade were carried out using oil film method. At low Reynolds numbers, the flow structure in the annular cascade was quite complex and three-dimensional. The separation line on the suction surface moved upstream due to the decrease of Reynolds number. In addition, the growth of secondary flows, i.e., passage vortices and leakage vortex, was extremely under the influence of Reynolds number.
ABB’s Advanced EV Burner — A Dual Fuel Dry Low NOx Burner for Stationary Gas Turbines
Authors: Steinbach Christian , Ruck Thomas , Lloyd Jonathan , Jansohn Peter , Döbbeling Klaus , Sattelmayer Thomas , Strand Torsten
Published: December 2014

A dual fuel burner has been developed to meet stringent NOx goals without the use of water or steam injection. This combustion system is based on the proven ABB EV burner dry low NOx technology and uses the same type of aerodynamic vortex breakdown flame stabilization. A more advanced aerodynamic design improves the quality of the fuel air mixture for both gaseous and liquid fuels. The design of the liquid fuel injection and the fuel-air-mixture preparation is described in this paper. Fuel air mixture homogeneity was improved with the help of experimental and numerical tools. This way an optimization in fuel atomizer design was possible. Distinct differences in fuel distribution were observed for different designs of pressure atomizers. Combustion tests of the burner were performed at pressures up to 20 bars. The NOx levels measured under gas turbine full load conditions are <25 vppm using oil no. 2 and <10 vppm using natural gas. These results highlight the potential for achieving similar combustion low emission performance for gaseous and liquid fuels near perfect lean premix conditions.

Operating parameters and test results at part load conditions are discussed as well in this paper. The wide operating range of the burner in the full premix mode restricts the need for pilot application or burner staging to low load (<50 %) conditions. This allows for low emissions on NOx, CO and UHC in the entire load range.
Steady and Unsteady Three-Dimensional Flow Field Downstream of an Embedded Stator in a Multistage Axial Flow Compressor: Part 1 — Unsteady Velocity Field
Authors: Prato J. , Lakshminarayana B. , Suryavamshi N.
Published: December 2014

A comprehensive investigation of the three-dimensional unsteady flow and thermal field downstream of an embedded stator in a multistage compressor, acquired with a high-response hot-film probe and aspirating probe, is presented and analyzed. Some of the earlier data (five-hole probe and high-response Kulite probe) from the same compressor is used with the present data to provide an integrated and comprehensive interpretation of the flow and thermal fields. The emphasis is on the unsteady flow, unsteady thermal, and integrated flow fields. Part 1 covers the description of the facility and the development of the hot-film technique for multistage flow field measurement. In addition, the unsteady velocity field is presented and interpreted. Part 2 provides an integrated assessment of the stagnation pressure, temperature and velocity fields to derive a comprehensive understanding of the time-averaged flow features. The final part covers velocity-velocity and velocity-temperature correlations and the assessment of their magnitudes in the average-passage equations.

The results from an area traverse of the unsteady velocity field derived from a 45 degree slanted film probe downstream of the second stator of a three-stage axial flow compressor are presented and discussed in this paper. The measurements were conducted at the peak efficiency operating point using a four-rotation method. The ensemble-averaged unsteady three-dimensional velocity data is resolved into the time-averaged component, revolution and blade periodic, and aperiodic components. Some of the features of the rotor 2 flow, measured at the exit of stator 2, reveal the extent of the spread of the upstream rotor wakes and the unsteadiness due to rotor hub and leakage flow regions and levels of periodic and aperiodic unsteadiness. Both the revolution and blade periodic velocity fluctuations are seen to be significantly greater than the aperiodic fluctuations.
Quasi-3D Numerical Computations on a Film-Cooled Gas Turbine Nozzle
Authors: Bassi F. , Rebay S. , Savini M.
Published: December 2014

The aim of this work is to assess the accuracy of a “quasi-3d” Navier-Stokes solver equipped with the k-ω turbulence model in the computation of a film-cooled gas turbine blade under a variety of flow conditions. The “quasi-3d” formulation was chosen as a cheap approach to investigate a large number of test conditions for a nozzle of complex geometry (around 400 cooling holes) which would require a large computational effort for a truly 3d simulation. The developed code has been used to investigate the influence of various cooling geometries and blowing conditions (mass flow rate and/or density ratios) on the aerodynamic behaviour of the cascade (in terms of loading, losses and flow angles) and their impact on the mixing process downstream of the trailing edge. The investigated nozzle is an advanced design turbine vane working in high subsonic regime. It is characterized by a marked endwall contouring at the casing and by the presence of 12 rows of holes (including a trailing edge row of slots) so as to obtain full-coverage film-cooling of the solid surfaces. This vane has been extensively tested in the Politecnico di Milano Fluid Dynamics Laboratory (formerly C.N.P.M.) blowdown transonic wind tunnel and a great amount of data are therefore available for validation purposes. The uselfulness of the proposed approach is fully analyzed and discussed throughout the paper and it is shown that the relation between the cascade performance and the variation of the investigated parameters is correctly described. In addition we address and discuss which ejection boundary conditions and which loss definitions are best suited for a meaningful comparison with the experimental measurements. In conclusion, in the case considered the developed code seems to be a valuable tool to determine the impact of film-cooling on the aerodynamic performance of a gas turbine blade.
Experimental Analysis of Fluid Flow and Surface Heat Transfer in a Three-Pass Trapezoidal Serpentine Smooth Passage
Authors: Cravero C. , Giusto C. , Massardo A. F.
Published: December 2014

The fluid-dynamic and heat transfer experimental analysis of a gas turbine internal three-pass blade cooling channel is presented.

The passage is composed of three rectilinear channels joined by two sharp 180 degree turns; moreover the channel section is trapezoidal instead of the rectangular configuration already analysed in depth in literature. The trapezoidal section is more representative of the actual geometrical configuration of the blade and, in comparison with the rectangular section, it shows significant aspect ratio and hydraulic diameter variations along the channel. These variations have a strong impact on the flow field and the heat transfer coefficient distributions.

The flow analysis experimental results — wall pressure distributions, flow visualisations — are presented and discussed. The heat transfer coefficient distributions, Nusselt enhancement factor, obtained using Thermocromic Liquid Crystals (TLC), have been studied as well.

In order to understand the influence of the cooling mass flow rate, a wide range of flow regimes-Reynolds numbers- has been considered.
HIPed Silicon Nitride Components for AGATA — Properties and Evaluation
Authors: Lundberg Robert , Moret Mona P. , Garguet-Duport Luc
Published: December 2014

The European EUREKA project, EU 209, otherwise known as AGATA (Advanced Gas Turbine for Automobiles), is a programme dedicated to the development of three critical ceramic components — a catalytic combustor, a radial turbine wheel and a static heat exchanger — for a 60 kW turbogenerator in an hybrid electric vehicle. These three components, which are of critical importance to the achievement of low emissions and high efficiency, have been designed, developed, manufactured and tested as part of a full scale feasibility study. AGATA is a joint project conducted by eight commercial companies and four research institutes in France and Sweden. Silicon nitride ceramics play an important role both in the development of the catalytic combustor and for the radial turbine wheel. This paper outlines the main results of the AGATA project with special emphasis to the development of HIPed Si3N4 combustor and turbine wheel. AC Cerama has developed a HIPed Si3N4 material designated CSN 101. This material has been selected for the catalytic combustor afterburner as well as for the radial turbine wheel. Mechanical properties of the CSN 101 Si3N4 have been found to be at the level of the best available high temperature Si3N4 materials. A new glass encapsulation technique using an interlayer between the glass and the silicon nitride has been shown to give material with excellent strength, oxidation resistance and creep resistance with as-HIPed surface finish.
Effects of Steam Reheat in Advanced Steam Injected Gas Turbine Cycles
Authors: Hofstädter A. , Frutschi H. U. , Haselbacher H.
Published: December 2014

Steam injection is a well-known principle for increasing gas turbine efficiency by taking advantage of the relatively high gas turbine exhaust temperatures. Unfortunately, performance is not sufficiently improved compared with alternative bottoming cycles. However, previously investigated supplements to the STIG-principle — such as sequential combustion and consideration of a back pressure steam turbine — led to a remarkable increase in efficiency. The cycle presented in this paper includes a further improvement: The steam, which exits from the back pressure steam turbine at a rather low temperature, is no longer led directly into the combustion chamber. Instead, it reenters the boiler to be further superheated. This modification yields additional improvement of the thermal efficiency due to a significant reduction of fuel consumption. Taking into account the simpler design compared with combined-cycle power plants, the described type of an advanced STIG-cycle (A-STIG) could represent an interesting alternative regarding peak and medium load power plants.
3D Flow Field Measurement Around a Rotating Stall Cell
Authors: Palomba C. , Puddu P. , Nurzia F.
Published: December 2014

Rotating stall is an unsteady phenomenon that arises in axial and radial flow compressors. Under certain operating conditions a more or less regular cell of turbulent flow develops and propagates around the annulus at a speed lower than rotor speed. Recently little work has been devoted to the understanding of the flow field pattern inside a rotating cell. However, this knowledge could be of help in the understanding of the interaction between the cell and the surrounding flow. Such information could be extremely important during the modelling process when some hypothesis have to be made about the cell behaviour.

A detailed experimental investigation has been conducted during one cell operation of an isolated low-speed axial flow compressor rotor using a slanted hot wire and an ensemble average technique based on the cell revolution time. The three flow field components have been measured on 9 axial section for 800 circumferential points and on 21 radial stations to give a complete description of the flow field upstream and downstream of the rotor. Interpretation of data can give a description of the mean flow field patterns inside and around the rotating cell.
Reliability Evaluation of Structural Ceramics Under Multiaxial Stress State
Authors: Ono Takashi , Kaji Masaki , Nishimura Michiaki
Published: December 2014

Strength and fatigue lifetime of structural ceramics under multiaxial stress state have been estimated and compared with experimental data. Biaxial strength tests were done by an anticlastic bending test method at room temperature. Biaxial fatigue tests were done by anticlastic bending and also ring-on-ring test method at 1200°C in air. Fracture probability and lifetime were predicted on the basis of a Weibull multiaxial distribution function and subcritical crack growth, using the results of stress analyses by the finite element method. Modified maximum hoop stress theory including an empirical parameter, T, was applied to the equivalent normal stress in the multiaxial distribution function. The empirical parameter T represents a shear stress sensitivity to mixed-mode fracture due to a grain interlocking effect. It has been confirmed that the predicted fracture probability and the fatigue lifetime agrees well with the experimental data if grain interlocking effects are taking into account.
Metal-HfO2-Ge capacitor: Its enhanced charge trapping properties with S-treated substrate and atomic-layer-deposited HfO2 layer
Authors: Park In-Sung , Jung Yong Chan , Seong Sejong , Ahn Jinho , Lee Sung Bo
Published: December 2014

The charge trapping properties of metal-HfO2-Ge capacitor as a nonvolatile memory have been investigated with (NH4)2S-treated Ge substrate and atomic-layer-deposited HfO2 layer. The interfacial layer generated by (NH4)2S-treated Ge substrate reveals a trace of -S- bonding, very sharp interface edges, and smooth surface morphology. The Ru-HfO2-Ge capacitor with (NH4)2S-treated Ge substrate shows an enhanced interface state with little frequency dispersion, a lower leakage current, and very reliable properties with the enhanced endurance and retention than Ru-HfO2-Ge capacitor with cyclic-cleaned Ge substrate.
Cyclopentadienyliron dicarbonyl dimer carbon nanotube synthesis
Authors: Zeidell Andrew M. , Cox Nathanael D. , Huston Shawn M. , Rossi Jamie E. , Landi Brian J. , Conrad Brad R.
Published: December 2014

Well-aligned multiwalled carbon nanotubes (MWCNTs) were synthesized from a cyclopentadienyliron dicarbonyl dimer precursor using chemical vapor deposition and were systematically characterized over a variety of growth conditions. The injection volume of the precursor was found to affect both the MWCNT diameter distribution and the amount of residual iron catalyst found in the sample. Low injection volumes produced relatively low impurity samples. Synthesized materials contained as little as 2.47% catalyst impurity by weight and were grown without predeposition of catalyst materials onto the substrate, reducing the need for damaging purification processes necessary to remove the substrate. Scanning electron microscopy was used to investigate catalyst contamination, synthesized MWCNT diameters, and growth morphology. Additionally, transmission electron microscopy was employed to qualitatively examine nanotube wall formation and sidewall defects. Longer growth times resulted in a higher quality product. Raman spectroscopy was used in conjunction with thermogravimetric analysis to confirm sample quality. The relative efficacy of the precursor and material quality are evaluated.
Adjusting the forming step for resistive switching in Nb2O5 by ion irradiation
Authors: Wylezich Helge , Mähne Hannes , Heinrich Anett , Slesazeck Stefan , Rensberg Jura , Ronning Carsten , Zahn Peter , Mikolajick Thomas
Published: December 2014

Resistive switching devices with Nb2O5 as a switching layer are treated with argon ion irradiation, which generates defects in the oxide layer that support the electroforming step. To distinguish between the effects of layer thinning by sputtering and that of defect generation, devices with different thicknesses of deposited oxide are investigated. It is found that the defect-rich interfaces allow the formation of thick oxides at low forming voltages, and therefore, the effects of the ion irradiation are comparable to the use of reactive electrodes.
A universal dose–response curve for radiochromic films
Authors: Martín‐Viera Cueto J. A. , Parra Osorio V. , Moreno Sáiz C. , Navarro Guirado F. , Casado Villalón F. J. , Galán Montenegro P.
Published: December 2014

Purpose:

This paper presents a model for dose–response curves of radiochromic films. It is based on a modified version of single‐hit model to take into account the growth experienced by lithium salt of pentacosa‐10,12‐diynoic acid polymers after irradiation.

Methods:

Polymer growth in radiochromic films is a critical phenomenon that can be properly described by means of percolation theory to provide an appropriate distribution function for polymer sizes. Resulting functional form is a power function featuring a critical exponent and two adjustable parameters. Moreover, these parameters act as scaling factors setting a natural scale for sensitometric curves where the dependence on channel sensitivity is removed. A unique reduced response curve is then obtained from all the color channels describing film behavior independently of film dosimetry system.

Results:

Resulting functional form has been successfully tested in several sensitometric curves from different Gafchromic EBT models, providing excellent agreement with experimental data in a wide dose range up to about 40 Gy and low dose uncertainty.

Conclusions:

The model presented in this paper describes accurately the sensitometric curves of radiochromic films in wide dose ranges covering all typical ranges used in external radiotherapy. Resulting dose uncertainty is low enough to render a reasonably good performance in clinical applications. Due to cross‐correlation, only one of the adjustable parameters is totally independent and characterizes film batches.
Kepler unbound: Some elegant curiosities of classical mechanics
Authors: MacKay Niall J. , Salour Sam
Published: December 2014

We explain two exotic systems of classical mechanics: the McIntosh-Cisneros-Zwanziger (“MICZ”) Kepler system, of motion of a charged particle in the presence of a modified dyon; and Gibbons and Manton's description of the slow motion of well-separated solitonic (“BPS”) monopoles using Taub-NUT space. Each system is characterized by the conservation of a Laplace-Runge-Lenz vector, and we use elementary vector techniques to show that each obeys a subtly different variation on Kepler's three laws for the Newton-Coulomb two-body problem, including a new modified Kepler third law for BPS monopoles.
Shifting T Cells into Action
Authors: Ferrarelli Leslie K.
Published: December 2014

Blocking multiple inhibitory receptors on T cells may enable the immune system to more effectively fight cancer and chronic infection.