bluuebunny/crossref_metadata_2025 huggingface dataset:
Proton Conducting Membrane Prepared by Cross-Linking Highly Sulfonated Peek for PEMFC Application
Authors: Luo Hongze , Vaivars Guntars , Mathe Mkhulu , Nonjola Shakes , Rohwer Mark
Published: February 2010

The proton conducting membrane was prepared by cross-linking highly sulfonated and sulfinated poly(etheretherketone) (SsPEEK). The cross-linked membrane is low cost due to its use of non-expensive chemical and simple production procedure. The membrane exhibited high proton conductivity (0.04 S/cm at 60 °C), extremely reduced water uptake, enhanced strength and stability compared with that of non-cross-linked membrane. These results suggested that the cross-linked PEEK membrane is a suitable candidate of proton conducting membranes for polymer electrolyte membrane fuel cell (PEMFC) applications, particularly promising to be used in direct methanol fuel cell (DMFC) due to its lower methanol crossover.
Effect of Conducting Oxide Coatings on Crofer22APU Used as Metallic Interconnects for Solid Oxide Fuel Cells
Authors: Pyo Seong-Soo , Lee Seung-Bok , Lim Tak-Hyoung , Song Rak-Hyun , Hyun Sang-Hoon , Shin Dong-Ryul
Published: February 2010

The conductive ceramic coating was used to improve an electrical performance of substrate steel, as well as to prevent the contamination of the chromium ion in SOFC. The (La0.8Sr0.2)0.98MnO3(LSM) conductive material was coated on Crofer22APU via a wet spray coating process. The adhesive strength of an interface between coated layer and metal substrate increased with the surface roughness of metallic interconnects. After the oxidation experiments of coated substrate during 8000 hours, the ASR showed a low value of 23 mΩ·cm2. These results shown that the coated oxides layer prevents the formation and the growth of scale (Cr2O3 and (Mn, Cr, Fe)3O4 layer) and enhance the long-term stability and electrical performance of metallic interconnect for SOFC.
Effect of Cathode Side Cationic Contamination on the Performance of an Operating PEFC
Authors: Serincan Mustafa Fazil , Pasaogullari Ugur , Molter Trent
Published: February 2010

A computational fluid dynamics model is developed to study the effect of cationic contamination on the performance of a polymer electrolyte fuel cell (PEFC). The fuel cell model incorporates mass, species, momentum and heat balances along with the ionic and electronic charge conservations. To model the transport of the cationic species, Nernst-Planck equations are used while taking into consideration of local electroneutrality in the ionomer phase. The diffusive fluxes of the cations are implemented in the Nernst-Planck equations such that they take into account adsorption of the species. A steady-state analysis is carried out to address the effects of contamination on the operating fuel cell performance. It is observed that contamination significantly reduces the output power density of the PEFC by occupying the available charge sites inside the ionomer.
Fuel Cell ASAP: Two Iterations of an Automated Stack Assembly Process and Ramifications for Fuel Cell Design-for-Manufacture Considerations
Authors: Laskowski Christina , Derby Stephen
Published: February 2010

Polymer-electrode membrane (PEM) fuel cell technology, a low-emissions power source receiving much attention for its efficiency, will need to progress from low-volume production to high-volume within the course of the next decade. To successfully achieve this transition, significant research progress has already been made towards developing a fully-functional fuel cell automatic stack assembly robotic station. Lessons can be drawn from this research with regards to design-for-manufacture (DFM) and design-for-assembly (DFA) considerations of fuel cells; however, more work still remains to be done. This document outlines both iterations of the robotic fuel cell assembly stations, other work to date, DFM and DFA lessons learned, and the anticipated future progression of automatic fuel cell stack assembly stations. A literature search reveals numerous patents pertaining to equipment and processes for fuel cell assembly as well as a great number of patents pertaining to fuel cell stack features to aid in manufacture or assembly. However, most of this is focused upon proper compression of the membrane material, with little thought given to overall assembly and throughput. Journal articles have begun to consider real-world manufacturing considerations pertinent to production scale-up, but much remains to be done. Therefore, there is a need for more contributions to stack manufacture and assembly. Work already completed (by the authors and their lab) towards the manufacturing workcell specifically includes the design and construction of two individual robotic fuel cell assembly stations, including custom-built end effectors and parts feeders. The second station incorporated numerous improvements, including overlapping work envelopes, elimination of a shuttle cart, software synchronization, fewer axes, and a better end effector. Consequentially, the second workcell achieved a four-fold improvement in cycle time over the previous iteration. Future improvements will focus in part upon improving the reliability of the overall system. Close study of the manufacturing workcell indicated that stack component design features are key for production and scale-up of fuel cell stack manufacturing processes. Critical features are discussed in this article, as well as their ramifications for the overall stack design. As the stack assembly workcell continues to improve, research will focus upon the ramifications and interplay of tolerances, stack failure modes, sealing, reliability, and the potential for component redesign specifically to optimize fuel cell manufacturing throughput.
Standard and Code Considerations for Stationary Fuel Cell Installations in the United States
Authors: Conmy Karla
Published: February 2010

Fuel cells power systems provide clean, efficient, and sustainable power. With the current push for sustainable green energy, interest in fuel cell power systems as alternate or supplemental power is high. For those intending to purchase and install stationary fuel cells, as well as for those responsible for permitting their operation, specific standards and codes should be reviewed.
Development of a Method for Determining the Two-Phase Relative Permeability Relationships in the Gas Diffusion Layers of PEM Fuel Cells
Authors: Sole J. D. , Ellis M. W.
Published: February 2010

A new method is demonstrated for the simultaneous determination of both the liquid phase relative permeability and the gas phase relative permeability as a function of compression in thin porous materials such as those used as gas diffusion layers (GDLs) in proton exchange membrane fuel cells (PEMFCs). In this method, multiple layers of the material of interest are inserted into the test section and the desired compression is achieved via pneumatic cylinders. The compression of the sample is maintained while both liquid and gas are forced through the medium at a known rate until a steady pressure differential across the compressed medium is achieved. Upon achieving a steady pressure differential, the pneumatic cylinders are retracted and the center layer of the sample material is released and suspended from an analytical balance. The mass measurement yields the liquid saturation of the material, while the flow rate of each component and the common pressure drop are used to determine the relative permeability of each phase. The process is repeated at different flow rates until the dependence of the relative permeability on saturation is established. The relative permeability of liquid water in GDL materials has long been assumed to follow a cubic relationship with saturation similar to what has been observed in packed sand. However, it is shown in this work for a variety of macroporous GDL materials including both carbon fiber paper and carbon fiber cloth, that the relative permeability function is actually a linear function of liquid water saturation. The slope of the linear function is highly dependent on the substrate type, the level of wetproofing that has been applied to the substrate, and the compression of the material. Results are presented for carbon paper and carbon cloth materials that are untreated (no wetproofing) and that have been treated with a wetproofing agent to a level of 20 wt%.
Coupled BEM and FDM Conjugate Analysis of a Three-Dimensional Air-Cooled Turbine Vane
Authors: Wang Zhenfeng , Yan Peigang , Huang Hongyan , Han Wanjin
Published: February 2010

A coupled boundary element method (BEM) and finite difference method (FDM) are applied to solve conjugate heat transfer problem of a three-dimensional air-cooled turbine blade. A loosely coupled strategy is adopted, in which each set of field equations is solved to provide boundary conditions for the other. In the fluid region, computation code (HIT-NS CODE) adopts the FDM to solve the Navier-Stokes equations. In the solid region, the BEM is adopted to resolve the conduction heat transfer equations. An iterated convergence criterion is the continuity of temperature and heat flux at the fluid-solid interface. The solid heat transfer computation code (3D-BEM CODE) is validated by comparing with the results of an analytic solution and the results of commercial code, the results from 3D-BEM CODE have a good agreement with the analytic solution and commercial code results. The BEM uses a weighted residual method to make the Laplace equation convert into a surface integral equation and the surface integral equation is discretized. The BEM avoids the complicated mesh needed in other computation methods and saves the computation time. In addition, the BEM has the characteristic of a combination of an analytic and a discrete solution. So the BEM solutions of heat conduction problems are more accurate. The results of the coupling computation code (HIT-NS-3DBEM CODE) have a good agreement with the experimental results. The adiabatic condition result is different from the results of experiment and code calculation. So the results from conjugate heat transfer analysis are more accurate and they are closer to realistic thermal environment of turbines. Four turbulence models are applied: K-epsilon model, K-omega model, K-omega (SST-Gamma Theta) model, and B-L model adopted by computation code. Different turbulence models gives different the results of vane wall temperature. Comparing the four turbulence models, the different turbulence models can exactly simulate the flow field, but they can not give exact values for the heat conduction simulation in the boundary layer. The result of K-Omega (SST-Gamma Theta) turbulence model is closer to the experimental data.
Foreign Object Damage in Gas-Turbine Grade Silicon Nitrides by Silicon Nitride Ball Projectiles
Authors: Choi Sung R.
Published: February 2010

Foreign object damage (FOD) behavior of two gas-turbine grade silicon nitrides (AS800 and SN282) was determined with a considerable sample size at ambient temperature using impact velocities ranging from 50 to 225 m/s by 1.59-mm diameter silicon nitride ball projectiles. The degree of impact damage as well as of post-impact strength degradation increased with increasing impact velocity, and was greater in SN282 than in AS800 silicon nitride. The critical impact velocity in which target specimens fractured catastrophically was remarkably low: about 200 and 130 m/s, respectively, for AS800 and SN282. The difference in the critical impact velocity and impact damage between the two target silicon nitrides was attributed to the fracture toughness of the target materials. The FOD by silicon nitride projectiles was significantly greater than that by steel ball projectiles. Prediction of impact force was made based on a yield model and compared with the conventional Hertzian contact-stress model.
Further Developments of a Variable Fuel Flow Automatic Mixing Valve for Prescribed Injection Ratio
Authors: Cerri Giovanni , Chennaoui Laila , Giovannelli Ambra , Miglioli Mauro
Published: February 2010

The production of an emulsion by emulsification plant without the addition of chemical additives always requires an injection device of the dispersed phase (water or ethanol) into the continuous phase (fuel oil). In this way, a preliminary mixture of immiscible liquids is produced at the right volume ratio. Such a mixture is processed downstream to have an emulsion with the dispersed phase drop mean diameters less than 4 μm. Since Gas Turbines have a variable fuel flow related to the delivered power, there is the necessity of maintaining a prescribed dispersed phase to continuous phase volumetric ratio when the fuel flow varies. This paper deals with an automatic device that is capable of producing the prescribed injection ratio of the dispersed phase into the fuel oil when the fuel oil flow rate changes. Such a device is developed to be coupled with an emulsification system that provides to break an immiscible part of fluid in a very small drops. The system is for feeding fuel into engines (S.I. Gasoline, Diesel, Gas Turbine combustors) operating at variable loadings i.e variable liquid fuel flow. The mixer (PMD, Pre-Mixer Device) has been presented at ASME Turbo Expo (Montreal 2007) for diesel #2 operating at 25°C with the viscosity being assumed as constant because of its variation is in a reduced range. In this paper, different fuels having different viscosities (diesel oil of different numbers, rapeseed oil, sunflower oil, etc) have been tested. The major modeling aspect concerns with the behavior of the annular orifice that produces a membrane displacement. A bibliographic analysis has been performed and the main results are reported in this paper. Since the architecture of the orifice, its geometry and the flow conditions were not reported in the bibliography, systematic experiments have been performed. Such experiments have been carried on for various liquids having various viscosities for different geometric arrangements and force acting on the membrane. The analysis of results led to formulate models to describe both the discharge flow and effective force coefficients. The paper gives a complete outlook of the experiments and of the above models. The viscosity dependent models have been introduced in to the PMD simulation code. Such models that take the influence of viscosity into account have been developed and some scale-up rules have been established. An amply description of the sizing and scale-up models is presented together with modifications to improve the prototype behavior operated with fluids having different viscosities. Experimental results concerning the influence of viscosity of the continuous phase are presented and widely discussed taking the model as reference.
Gas Turbines in Alternative Fuel Applications: Bio-Ethanol Field Test
Authors: Moliere Michel , Vierling Matthieu , Aboujaib Maher , Patil Prashant , Eranki Aditya , Campbell Anthony , Trivedi Raghav , Nainani Anil , Roy Subhendu , Pandey Nirjendu
Published: February 2010

There is a sustained interest worldwide for liquid biofuels that form a numerous and very contrasting family. Among biofuels, bio-ethanol is a natural candidate in regions such as Brazil and India, where similar petroleum-based fuels such as naphtha have been utilized as gas turbine fuels. While biodiesel is very similar to middle distillates (gasoil), ethanol has some commonalities with volatile petroleum fuels in terms of physical data; however, the small alcohol molecule displays a markedly distinct combustion behavior. As part of a development program devoted to biofuels and in collaboration with the major Indian utility Reliance Energy, GE Energy has carried out a preliminary characterization of the combustion of an extensive range of naphtha/bio-ethanol blends with up to 95% ethanol. This test was performed in Spring 2008 on a Frame 6B equipped with standard combustors at the Goa power plant, state of Goa, India. All blends showed excellent combustion performances, low NOx emissions and virtually zero emissions of carbon monoxide (CO), unburned hydrocarbons (UHC) and sulphur oxides (Sox).
The Control Strategy for a Solid Oxide Fuel Cell Hybrid System
Authors: Milewski Jarosław , Miller Andrzej , Dmowski Antoni , Biczel Piotr
Published: February 2010

Based on mathematical modelling and numerical simulations, the control strategy for a Solid Oxide Fuel Cell Hybrid System (SOFC-HS) is presented. Adequate maps of performances with three independent parameters are shown. These independent parameters are as follows: stack current, fuel mass flow and turbine-compressor shaft speed. To control external load, those parameters should be appropriately chosen. The control system is purposed to meet many constraints: e.g. stack temperature, steam-to-carbon ratio, compressor surge limitation etc. The aim is to achieve maximum efficiency of power generated within those constraints. Governing equations of SOFC-HS modelling are given. An adequate simulator for the SOFC module was produced and described. Based on this simulator, the control strategy was obtained. The performance of this SOFC-HS is shown in various working environments.
Electricity and Hydrogen Co-Production From Coal and Biomass
Authors: Galanti Leandro , Franzoni Alessandro , Traverso Alberto , Massardo Aristide F.
Published: February 2010

This paper presents and discusses the results of a complete thermoeconomic analysis of an integrated power plant for co-production of electricity and hydrogen via pyrolysis and gasification processes, applied to an existing large steam power plant (ENEL Brindisi power plant-660 MWe). The two considered technologies produce syngas with different characteristics in terms of temperature, pressure and composition, and this has a significant effect on the layouts of the complete systems proposed in the paper. Moreover, the proximity of a hydrogen production and purification plants to an existing steam power plant favour the inter-exchange of energy streams, mainly in the form of hot water and steam, which reduces the costs of auxiliary equipment. Various coals (Ashland, South African and Sardinian Sulcis coal) and mixtures of South African coal and biomass (Poplar) are considered in this study, in order to explore the real potential of mixed fuels in terms of impact on plant economics and reducing CO2 emissions. Furthermore, the high quality of the hydrogen, produced through a Pressure Swing Adsorption unit or a dense Membrane unit, allows it to be used for distributed generation (e.g. by microturbine, Stirling engine, etc.) as well as public transport (using PEM fuel cells). The results were obtained using WTEMP thermoeconomic software [9], developed by the TPG (Thermochemical Power Group) of the University of Genoa, and this project has been carried out within the framework of the FISR National project “Integrated systems for hydrogen production and utilization in distributed power generation” [10]. The complete systems proposed here can represent an attractive approach to flexible hydrogen-electricity co-production.
Investigation of Tangential Trapped Vortex Combustor
Authors: Zhang Chi , Lin Yuzhen , Xu Quanhong , Liu Gaoen
Published: February 2010

An innovative concept of Tangential Trapped Vortex Combustor (TTVC) applying a swirling flow to eliminate the guide vanes of the compressor and turbine in the future gas turbine engines is presented via theoretical analysis and experimental investigation. In TTVC, the airflow is mostly whirlblast, and the processes of evaporation, mixing, and chemical reaction for the liquid spray combustion take place along the tangential direction. It is shown that the TTVC operation has the potential of improving combustion efficiency, widening combustion stability range, and reducing emissions, mainly due to the effects of trapped vortex, high centrifugal force, and periodical mixing. Experimental results of the ignition and LBO limits in a small 4-cup annular TTVC operating at atmospheric pressure demonstrated that this innovative combustion technology has a good LBO limit performance to meet the requirements of advanced gas turbine engines.
Development of a µ-Scale Turbine Expander for Energy Recovery
Authors: Keding Marcus , Dudzinski Piotr , Tajmar Martin , Willinger Reinhard , Ka¨fer Klaus
Published: February 2010

Waste heat is a primary source of energy loss in many applications. A number of developments around a micro rocket engine at the Austrian Research Centers (ARC) promise innovative energy recovery and micro power generation solutions. Here we focus on the investigation of micro technologies for application in HVAC (heating, ventilating, and air conditioning) systems. The use of μ-scale turbine expanders for work recovery in transcritical CO2 heat pump processes has been identified as most interesting and promising for the application in HVAC cases. One of the main drawbacks of transcritical CO2 heat pumps is the lower COP (coefficient of performance) compared to conventional heat pump systems which originates from the non isothermal heat rejection in the gas cooler. This drawback can be compensated by utilizing the pressure difference between the high pressure and low pressure part of the heat pump for work recovery. This is feasible as the pressure difference is considerably larger in case of CO2 heat pumps compared to conventional systems. Work recovery can be realized by substituting the expansion valve between the high and low pressure side by an expansion machine. Due to the low flow rate of the working fluid, the turbine type is based on the Pelton turbine with specific two phase flow turbine blades. In addition to the turbine part a magnetic coupling, miniature bearings and a small scale generator are important parts of the system. Thermodynamic simulations showed an absolute microturbine power yield between 60 W and 150 W for a 2 kW heating system.
Integrated Fluid Network-Thermomechanical Approach for the Coupled Analysis of a Jet Engine
Authors: Muller Yannick
Published: February 2010

The present investigation aims at taking the existing interactions between secondary air properties (temperatures, pressures and mass flow rates) and material thermomechanical properties (temperature repartition and displacements) into consideration in a robust and modular analysis tool, combining air system, thermal and mechanical analysis. For air system calculations, a one-dimensional network representation is used. This network, the basic topology of which is presented in the paper, is coupled within a thermomechanical finite element model of the engine secondary air system structure within the free finite element software CalculiX®. The coupling process and boundary condition transfer between the different disciplines is carried out automatically. The fully coupled process is used to analyse a complete low pressure turbine general arrangement. Results of the coupled investigation show relevant and interesting dependence between each discipline as well as good agreement when compared with the current method and with test data.
Materials and Component Development for Advanced Turbine Systems
Authors: Alvin M. A.
Published: February 2010

Future hydrogen-fired or oxy-fuel turbines will likely experience an enormous level of thermal and mechanical loading, as turbine inlet temperatures (TIT) approach 1425–1760°C with pressures of 300–625 psig, respectively. Maintaining the structural integrity of future turbine components under these extreme conditions will require durable thermal barrier coatings (TBCs), high temperature creep resistant metal substrates, and effective cooling techniques. While advances in substrate materials have been limited for the past decades, thermal protection of turbine airfoils in future hydrogen-fired and oxy-fuel turbines will rely primarily on collective advances in TBCs and aerothermal cooling. To support the advanced turbine technology development, the National Energy Technology Laboratory (NETL) at the Office of Research and Development (ORD) has initiated a research project effort in collaboration with the University of Pittsburgh (UPitt), and West Virginia University (WVU), working in conjunction with commercial material and coating suppliers, to develop advanced materials, aerothermal configurations, as well as non-destructive evaluation techniques for use in advanced land-based gas turbine applications. This paper reviews technical accomplishments recently achieved in each of these areas.
The Effects of Simulated Particle Deposition on Film Cooling
Authors: Lawson S. A. , Thole K. A.
Published: February 2010

Diminishing natural gas resources has increased incentive to develop cleaner, more efficient combined cycle power plants capable of burning alternative fuels such as coal-derived synthesis gas (syngas). Although syngas is typically filtered, particulate matter still exists in the hot gas path that has proven to be detrimental to the life of turbine components. Solid and molten particles deposit on film cooled surfaces that can alter cooling dynamics and block cooling holes. To gain an understanding of the effects that particle deposits have on film cooling, a methodology was developed to simulate deposition in a low speed wind tunnel using a low melt wax, which can simulate solid and molten phases. A facility was constructed to simulate particle deposition on a flat plate with a row of film cooling holes. Infrared thermography was used to measure wall temperatures for quantifying spatially resolved adiabatic effectiveness values in the vicinity of the film cooling holes as deposition occurred. Results showed that deposition reduced cooling effectiveness by approximately 20% at momentum flux ratios of 0.23 and 0.5 and only 6% at a momentum flux ratio of 0.95.
Computational Design of Corrosion-Resistant Fe-Cr-Ni-Al Nanocoatings for Power Generation
Authors: Chan K. S. , Liang W. , Cheruvu N. S. , Gandy D. W.
Published: February 2010

A computational approach has been undertaken to design and assess potential Fe-Cr-Ni-Al systems to produce stable nanostructured corrosion-resistant coatings that form a protective, continuous scale of alumina or chromia at elevated temperatures. Phase diagram computation was modeled using the Thermo-Calc® software and database [1, 2] to generate pseudo-ternary Fe-Cr-Ni-Al phase diagrams to help identifying compositional ranges without undesirable brittle phases. Computational modeling of the grain growth process, sintering of voids, and interface toughness determination by indentation, assessed micro-structural stability and durability of the nanocoatings fabricated by a magnetron-sputtering process. Interdiffusion of Al, Cr, and Ni was performed using the DICTRA® diffusion code [3] to maximize the long-term stability of the nanocoatings. The computational results identified a new series of Fe-Cr-Ni-Al coatings that maintain long-term stability and a fine-grained microstructure at elevated temperatures. The formation of brittle sigma phase in Fe-Cr-Ni-Al alloys is suppressed for Al contents in excess of 4 wt.%. Grain growth modeling indicated that the columnar-grained structure with a high percentage of low-angle grain boundaries is resistant to grain growth. Sintering modeling indicated that the initial relative density of as-processed magnetron-sputtered coatings could achieve full density after a short thermal exposure or heat-treatment. Interface toughness computation indicated that Fe-Cr-Ni-Al nanocoatings exhibit high interface toughness in the range of 52–366 J/m2. Interdiffusion modeling using the DICTRA software package indicated that inward diffusion could result in substantial to moderate Al and Cr losses from the nanocoating to the substrate during long-term thermal exposures.
The Effect of Compound Angle on Nozzle Pressure Side Film Cooling
Authors: Zhang Luzeng , Yin Juan , Moon Hee Koo
Published: February 2010

The effect of film cooling hole compound angle on nozzle pressure side film cooling effectiveness was experimentally investigated using a single row of shaped hole injection. The engine operating conditions were simulated in a scaled warm cascade, which was built based on industrial gas turbine nozzle vanes. Local film effectiveness measurements were made using a computerized pressure sensitive paint (PSP) technique. Nitrogen gas was used to simulate cooling flow as well as a tracer gas to indicate oxygen concentration such that film effectiveness by the mass transfer analogy. Three separate nozzle test models were fabricated, which have same cooling supply plenum configurations. One of them has a row of shaped hole on the pressure surface without a compound angle. The other two test models have same size film holes at the same location, but one with a 30-degree compound angle in co-flow and the other in counter-flow direction to the cooling supply. Four cooling mass flow ratios (MFR, blowing ratio) were studied for each of the nozzle test models and two-dimensional film effectiveness distributions were measured. Then the film effectiveness distributions were spanwise averaged for comparison. For all three cases, the overall film effectiveness increased with the MFR (or the blowing ratio), but not significantly. Film effectiveness by a compound angle injection is higher compared to those without a compound angle near the injection, further downstream the difference is insignificant.
Comparison of Pre-Anode and Post-Anode Carbon Dioxide Separation for IGFC Systems
Authors: Liese Eric
Published: February 2010

This paper examines the arrangement of a solid oxide fuel cell (SOFC) within a coal gasification cycle, this combination generally being called an integrated gasification fuel cell cycle (IGFC). This work relies on a previous study performed by the National Energy Technology Laboratory (NETL) that details thermodynamic simulations of IGCC systems and considers various gasifier types and includes cases for 90% CO2 capture [1]. All systems in this study assume a Conoco Philips gasifier and cold gas clean up conditions for the coal gasification system (Cases 3 and 4 in the NETL IGCC report). Four system arrangements, cases, are examined. Cases 1 and 2 remove the CO2 after the SOFC anode. Case 3 assumes steam addition, a water-gas-shift (WGS) catalyst and a Selexol process to remove the CO2 in the gas cleanup section, sending a hydrogen-rich gas to the fuel cell anode. Case 4 assumes Selexol in the cold-gas cleanup section as in Case 3; however, there is no steam addition and the WGS takes places in the SOFC, and after the anode. Results demonstrate significant efficiency advantages compared to IGCC with CO2 capture. The hydrogen-rich case (Case 3) has better net electric efficiency compared to typical post-anode CO2 capture cases (Cases 1 and 2), with a simpler arrangement and similar SOFC area. Case 4 gives an efficiency similar to Case 3, but at a lower SOFC power density, or a lower efficiency at the same power density. Carbon deposition concerns are also discussed.
Role of Platinum in Thermal Barrier Coatings Used in Gas Turbine Blade Applications
Authors: Tawancy H. M. , Al-Hadhrami Luai M.
Published: February 2010

Current technology of thermal barrier coating systems used in gas turbine blade applications relies upon the use of a metallic bond coat, which has a two-fold function: i) it develops a thin layer of aluminum oxide enhancing the adhesion of the ceramic top coat, and ii) it provides an additional resistance to oxidation. It was the objective of this study to develop an understanding of the role of platinum in bond coats of the diffusion-type deposited on a nickel-base superalloy. Two Pt-containing bond coats were included in the study: i) a platinum-aluminide and ii) a bond coat formed by interdiffusion between an electroplated layer of platinum and the superalloy substrate. In both cases, the top ceramic coat was yttria-stabilized zirconia. For reference purposes, a simple aluminide bond coat free of Pt was also included in the study. Thermal exposure tests at 1150 °C with a 24-hour cycling period to room temperature were used to compare the coating performance. Microstructural features were characterized by various electron-optical techniques. Experimental results indicated that Pt acts as a “cleanser” of the oxide-bond coat interface by decelerating the kinetics of interdiffusion between the bond coat and superalloy substrate. This was found to promote selective oxidation of Al resulting in a purer Al2O3 scale of a slower growth rate increasing its effectiveness as “glue” holding the ceramic top coat to the underlying metallic substrate. However, the exact effect of Pt was found to be a function of the state of its presence within the outermost coating layer. Of the two bond coats studied, a surface layer of Pt-rich gamma prime phase (L12 superlattice) was found to provide longer coating life in comparison with a mixture of PtAl2 and beta phase. This could be related to the effectiveness of gamma prime phase as a sink for titanium minimizing its detrimental effect on the adherence of aluminum oxide.
Comparative Analysis of Field Performance Testing in Centrifugal and Reciprocating Compressors
Authors: Wilcox Melissa , Nored Marybeth , Brun Klaus , Kurz Rainer
Published: February 2010

Field testing of centrifugal compressors is often required by the operating company to determine compressor efficiency and power consumption over its speed range. Reciprocating compressors are also routinely tested to assure that adequate driver power is available and assess the losses associated with the compressor valves and pulsation controls. The uncertainties and test methods associated with field performance testing for these two compressors differ dramatically due to the field environment, unsteady flow field, and the traditional test methods used for compressor power. The field operating conditions, station piping and gas composition can influence the performance of both types but in different ways. Performance testing of a reciprocating compressor (typically based on pressure volume cards) differs dramatically from the more standardized approach to centrifugal compressor testing (based on enthalpy rise) mainly because of the effects of pulsating flow and the necessary volume bottles and pulsation filters in the reciprocating compressor installation. It is possible, however, to apply enthalpy rise methods to reciprocating compressor performance because the thermodynamic relationships still apply. In some cases, depending upon the influence of pulsations and the nozzle tap configuration, this measure of efficiency and power will introduce less uncertainty than measurements based on PV cards. Since the field test environment is less controlled than a manufacturer/third party test laboratory, uncertainty analysis must be used to validate or characterize the level of assurance in the measured performance. The uncertainty analysis can also provide an indication of the primary contributing measurements to an acceptably high uncertainty. For both reciprocating and centrifugal compressors, the uncertainty in the measured efficiency can be unacceptably high when some basic rules for proper test procedures and standards are violated. This paper presents an analysis of the requirements for proper field testing, examples of “near-ideal” test uncertainties for the two types of compressors and the primary causes of high test uncertainty in the field site test. These best practices are based on the recent industry guidelines published by the Gas Machinery Research Council (GMRC). Comparative illustrations are provided to highlight the differences in performance testing of centrifugal compressors and reciprocating compressor in terms of instrumentation, available test methods, and non-ideal effects on test uncertainty.
Filtration of Gas Turbine Intake Air in Offshore Installations: The Gap Between Test Standards and Actual Operating Conditions
Authors: Brekke Olaf , Bakken Lars E. , Syverud Elisabet
Published: February 2010

Gas turbine performance deterioration caused by fouling in the compressor section is a well known phenomenon in offshore installations. This performance deterioration not only increases fuel consumption and emissions but also has a severe economic impact when it reduces oil and gas production. Because fouling in the compressor section is commonly caused by intake air contamination, gas turbines offshore have air inlet filtration systems in order to limit the amount of ingested contaminants. Many different filtration systems from various suppliers are in operation offshore. Manufacturers supply documentation for their filtration system based on several international standards, and it can be challenging for the operator to make a direct comparison of different filtration systems. The comparison is further complicated by the fact that the characteristic offshore challenges related to salt and moisture in the intake air are not adequately covered in international standards, and these challenges are handled and documented differently among the manufacturers. This paper analyzes the challenges related to choosing the best filter solution for an offshore gas turbine installation based on data from offshore sites in the North Sea. The relevance of test requirements in applicable international standards and available supplier documentation is evaluated based on actual operating conditions offshore. Deviations among international test standard requirements, available manufacturer documentation, and actual operating conditions offshore are identified, and improved test requirements are suggested. In addition, this paper addresses the long-term effects of filter contamination and methods for intake filter monitoring based on data from offshore sites in the North Sea.
Emissions Modelling for the Optimization of Greener Aircraft Operations
Authors: Celis Cesar , Moss Barrie , Pilidis Pericles
Published: February 2010

This work focuses on the development and implementation of an emissions prediction model which allows the reliable calculation of emissions trends from current and potential future aircraft gas turbine combustors. The ultimate goal of the model developed involves its use in efficient aircraft trajectory optimisation processes, which eventually allow identifying aircraft “greener trajectories”, minimizing in that way both aircraft fuel consumption and the pollutants emitted. From the three broad strategies that can be adopted for combustor emissions prediction: empirical correlations, stirred reactor models, and comprehensive numerical simulations involving detailed Computational Fluid Dynamics calculations, the second one was chosen for the development of the model described in this work. Thus, critical zones within the combustor are represented by individual stirred reactors, incorporating the processes of mixing, combustion heat release, and pollutant formation. To take into account inhomogeneities in gas composition and temperature which influence directly the rates of pollutant formation, a stochastic representation of turbulent mixing in the combustor primary zone is utilized. Results obtained from the simulations of an actual combustor using the emissions prediction model developed in terms of NOx, CO, UHC, and soot/smoke emitted show reasonable agreement with experimental data, reproducing the trends observed in practice.
High Rotation Number Effect on Heat Transfer in a Triangular Channel With 45°, Inverted 45°, and 90° Ribs
Authors: Liu Yao-Hsien , Huh Michael , Han Je-Chin , Moon Hee-Koo
Published: February 2010

Heat transfer and pressure drop have been experimentally investigated in an equilateral triangular channel (Dh = 1.83cm), which can be used to simulate the internal cooling passage near the leading edge of a gas turbine blade. Three different rib configurations (45°, inverted 45°, and 90°) were tested at four different Reynolds numbers (10000–40000), each with five different rotational speeds (0–400 rpm). The rib pitch-to-height (P/e) ratio is 8 and the height-to-hydraulic diameter (e/Dh) ratio is 0.087 for every rib configuration. The rotation number and buoyancy parameter achieved in this study were 0–0.58 and 0–2.3, respectively. Both the rotation number and buoyancy parameter have been correlated to predict the rotational heat transfer in the ribbed equilateral triangular channel. For the stationary condition, staggered 45° angled ribs show the highest heat transfer enhancement. However, staggered 45° angled ribs and 90° ribs have the higher comparable heat transfer enhancement at rotating condition near the blade leading edge region.
Microstructural and Mechanical Characterization of a Hybrid Oxide CMC Combustor Liner After 25,000-Hour Engine Test
Authors: More Karren L. , Walker Larry R. , Wang Yanli , Lara-Curzio Edgar , Brummett Tracie M. , van Roode Mark , Price Jeffrey R. , Szweda Andy , Merrill Gary
Published: February 2010

A hybrid oxide ceramic matrix composite (CMC) outer combustor liner was tested in a Solar Turbines Incorporated Centaur® 50S engine between 2003 and 2006, accumulating >25,000 hours of field exposure. The hybrid CMC liner, which was ∼76 cm in diameter, had an alumina matrix with a Nextel 720 fiber-reinforcement (A/N720). The CMC, produced by ATK-COI Ceramics, Inc., was coated with a ceramic insulation layer known as FGI (Friable Graded Insulation) developed by Siemens Energy Incorporated. Post-test microstructural and mechanical evaluation was conducted on the field-exposed liner at Oak Ridge National Laboratory (ORNL) to determine the types of surface and structural damage that occurred to the combustor liner during engine exposure to elevated temperatures (>1200°C), thermal cycling (stop-start cycles), and combustion gases (especially water vapor). In this study, numerous sections were cut from the liner for mechanical and microstructural characterization that exhibited varying amounts of FGI and/or CMC degradation. In this way, damage accumulation was assessed (1) within the CMC and FGI layers, both on the gas-path surface and below the surface and (2) as a function of liner position (fore-to-aft) in the engine. The amount and type of damage observed was directly related to the starting CMC and FGI microstructures. The tensile strength of the hybrid liner after field exposure was found to be 19 MPa. The FGI layer remained well bonded to the CMC and the fracture surface of the CMC exhibited scissor-like features, which is typical of composites with ±45° fiber architecture. The stress acting on the CMC at failure was 53 MPa.
An Investigation of Turbine Wheelspace Cooling Flow Interactions With a Transonic Hot Gas Path—Part 1: Experimental Measurements
Authors: Bunker R. S. , Laskowski G. M. , Bailey J. C. , Palafox P. , Kapetanovic S. , Itzel G. M. , Sullivan M. A. , Farrell T. R.
Published: February 2010

The desire for higher power output combined with lower fuel consumption has focused recent design and research attention on the interaction of required secondary systems cooling flows with the turbine hot gas path. The flow physics associated with the rotor-stator wheelspaces, and in particular the trench and buffer cavity areas just inboard of the hot gas path, demand an increased level of design sophistication to account for the unsteady fluid and thermal effects associated with periodic vane wakes, circumferential pressure gradients, purge flows, and blade lead edge blockages. Part 1 of this study utilizes a wheelspace sector cascade rig for the purpose of gathering fundamental data on flow and thermal effects in a nonrotating environment. This experimental rig is a simplified screening tool for the investigation of basic geometry and flow effects that maintains the bulk of the correct flow physics in the absence of rotation. The test rig is also a validation data generation device for the unsteady CFD modeling efforts described in Part 2. The present cascade is composed of a five passage annular sector of a transonic turbine inlet guide vane, a complete sector of the upper wheelspace, buffer and trench cavities, and equivalent flow blockages for a blade row represented as leading edge cylinders. The geometry is three-dimensional including all sealing features of the wheelspace. The vane and blade rows can be clocked to any relative position. Secondary cooling flows are adjustable for the wheelspace purge flow and the leakage flow across the vane support. Detailed measurements in the form of static pressures throughout the interaction region, surface temperature distributions, and buffer cavity air temperatures are presented for various clocked positions. The circumferential pressure distribution peak-to-peak variations just aft of the vane are here as much as 18%. These variations are key to the resulting forcing of hot gas inboard of the rim seal. The blade leading edge bow wave is found to have an equal or even greater influence in generating this peak-to-peak variation than the vane trailing edge wake. Buffer cavity cooling effectiveness levels vary with the clocked positions and decrease as cylinder size is increased. Significantly, the effect of the leading edge blockage can reduce buffer cavity cooling effectiveness by a factor of 0.1.
Expanded Application of the Systematic Sensor Selection Strategy for Turbofan Engine Diagnostics
Authors: Sowers T. Shane , Fittje James E. , Kopasakis George , Simon Donald L.
Published: February 2010

Data acquired from system sensors form the foundation upon which any health management system is based, and the available sensor suite directly impacts the absolute diagnostic performance that can be achieved. While additional sensors may provide improved fault diagnostic performance, there are other factors that also need to be considered such as instrumentation cost, weight, and reliability. A systematic approach is desired to perform sensor selection from a holistic system-level perspective as opposed to performing decisions in an ad hoc or heuristic fashion. The Systematic Sensor Selection Strategy is a methodology that optimally selects sensor suites from a pool of sensors based on the system fault diagnostic approach, with the ability of taking cost, weight and reliability into consideration. This procedure was originally applied to a large turbofan engine simulation at a single operating point, considering fault conditions represented by single component health parameter shifts. In the current study, sensor selection is expanded to consider multiple operating conditions such as takeoff and cruise, and more representative fault conditions.