bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of Interdiffusion From MCrAlY Overlay Coatings by Application of a Ni-Re Interlayer
Authors: Page Richard A. , Leverant Gerald R. 
Published: December 2014

The durability of protective coatings on combustion turbine blades and vanes is a critical issue in the power generation industry. Coating life usually dictates the refurbishment intervals for these components, and these intervals have generally been of shorter duration than desired by the operators of the equipment. Both MCrAlY and aluminide type coatings protect against oxidation and hot corrosion by forming a protective Al2O3 surface layer. Degradation of the coatings occurs by depletion of the aluminum content of the coating through interdiffusion with the substrate and through the formation and spallation of an external Al2O3 scale.
The results obtained in this study clearly show that the application of a thin interlayer of Ni-Re beneath the MCrAlY coating can significantly decrease the growth rate of the inner β-NiAl depletion zone. Order of magnitude reductions in the inner depletion zone thickness formed at 1000 hours were obtained with both the Ni-32 wt.% Re and the Ni-47 wt% Re interlayer coatings. Since formation of the inner depletion zone is believed to result from interdiffusion with the substrate, these results suggest that the Ni-Re interlayer provided a significant impediment to the inward diffusion of Al into the substrate.
CO2 Emission Abatement in IGCC Power Plants by Semiclosed Cycles: Part A — With Oxygen-Blown Combustion
Authors: Chiesa Paolo , Lozza Giovanni 
Published: December 2014

This paper analyzes the fundamentals of IGCC power plants where carbon dioxide produced by syngas combustion can be removed, liquefied and eventually disposed, to limit the environmental problems due to the “greenhouse effect”. To achieve this goal, a semiclosed-loop gas turbine cycle using an highly-enriched CO2 mixture as working fluid was adopted. As the oxidizer, syngas combustion utilizes oxygen produced by an air separation unit. Combustion gases mainly consist of CO2 and H2O: after expansion, heat recovery and water condensation, a part of the exhausts, highly concentrated in CO2, can be easily extracted, compressed and liquefied for storage or disposal.
A detailed discussion about the configuration and the thermodynamic performance of these plants is the aim of the paper. Proper attention was paid to: (i) the modelization of the gasification section and of its integration with the power cycle, (ii) the optimization of the pressure ratio due the change of the cycle working fluid, (iii) the calculation of the power consumption of the “auxiliary” equipment, including the compression train of the separated CO2 and the air separation unit. The resulting overall efficiency is in the 38–39% range, with status-of-the-art gas turbine technology, but resorting to a substantially higher pressure ratio. The extent of modifications to the gas turbine engine, with respect to commercial units, was therefore discussed. Relevant modifications are needed, but not involving changes in the technology.
A second plant scheme will be considered in the second part of the paper, using air for syngas combustion and a physical absorption process to separate CO2 from nitrogen-rich exhausts. A comparison between the two options will be addressed there.
Status of the European Gas Turbine Program — AGATA
Authors: Gabrielsson Rolf , Lundberg Robert , Avran Patrick 
Published: December 2014

The European Gas Turbine Program “AGATA” which started in 1993 now has reached its verification phase. The objective of the program is to develop three critical ceramic components aimed at a 60 kW turbogenerator in a hybrid electric vehicle — a catalytic combustor, a radial turbine wheel and a static heat exchanger. The AGATA partners represent car manufacturers as well as companies and research institutes in the turbine, catalyst and ceramic material fields in both France and Sweden. Each of the three ceramic components is validated separately during steady state and transient conditions in separate test rigs at ONERA, France, where the high pressure/temperature conditions can be achieved. A separate test rig for laser measurements downstream of the catalytic combustor is set up at Volvo Aero Turbines, Sweden.
The catalytic combustor design which includes preheater, premix duct and catalytic section operates at temperatures up to 1623 K. Due to this high temperature, the catalyst initially has undergone pilot tests including ageing, activity and strength tests. The premix duct flow field also has been evaluated by LDV measurements. The full scale combustion tests are ongoing.
The turbine wheel design is completed and the first wheels have been manufactured. FEM calculations have indicated that stress levels are below 300 MPa. The material used is a silicon nitride manufactured by AC Cerama (Grade CSN 101). Cold spin tests with complete wheels have started. Hot spin tests at TTT 1623 K will be performed in a modified turbo charger rig and are expected to start in February 1998.
The heat exchanger is of a high efficiency plate recuperator design using Cordierite material. Hot side inlet temperature is 1286 K. Therefore initial tests with test samples have been run to evaluate the thermomechanical properties at high temperatures. Tests are now proceeding with a 1/4 scale recuperator prototype to evaluate performance at steady state conditions. Manufacturing of the full scale heat exchanger is now in progress.
Strut Influences Within a Diffusing Annular S-Shaped Duct
Authors: Norris G. , Dominy R. G. , Smith A. D. 
Published: December 2014

Inter-turbine diffusers which provide flow continuity between the H.P. and L.P. turbines, are increasingly important within modern aero gas turbines, as the fan and hence L.P. turbine diameters increase with thrust. These gas turbines rely on struts within the inter-turbine diffuser to serve both as load bearing supports for inner spools and as passages to supply the engine with vital services such as cooling air and lubrication oil.
Experimental measurements have been made on a representative test rig in order to investigate the affect of a ring of struts on both the local and general flow phenomena as well as investigating their effect on overall duct performance. More realistic flow conditions are made available by the use of inlet wakes representative of those created by an upstream turbine row.
Measurements include static pressures on the strut and duct surfaces along with velocity and total pressure measurements at various axial locations. From these results calculations of total pressure loss have been made. The experimental results presented in this paper have been used to validate C.F.D. flow predictions on the duct with and without struts. The computational results included, capture the main physical features of the flow but clear limitations are observed and are discussed in this paper.
High Pressure Turbine Vane Annular Cascade Heat Flux and Aerodynamic Measurements With Comparisons to Predictions
Authors: Joe Christopher R. , Montesdeoca Xavier A. , Soechting Friedrich O. , MacArthur Charles D. , Meininger Matthew 
Published: December 2014

Experimental tests were performed at the USAF Turbine Research Facility (TRF) to obtain heat transfer and aerodynamic data on a first stage vane of a modern high pressure turbine. This is a transient blowdown facility that provides data from short duration tests. Data for a matrix of test conditions were obtained to document the effect of inlet Reynolds number, the stage pressure ratio across the vane, and the gas-to-wall temperature ratio. The objectives of these tests were to assess the capability of obtaining accurate aerodynamic total pressure loss measurements and airfoil static pressure measurements as well as determine the heat transfer coefficient distributions on the vanes. Results from these tests were compared to analytical predictions and are presented. The unique contribution of the work presented herein is: 1) demonstration of circumferential traversing temperature and pressure data in a short duration facility test, and 2) heat loss closure during a short duration test using heat flux gauges and the measured temperature loss. The transient heat loss during a short duration test is a fundamental requirement to determine turbine efficiency when work extraction is determined from the temperature drop across the turbine stage.
Heat transfer data were acquired from heat flux gauges that were fabricated using thin-film sputtering techniques and placed on the airfoil surfaces. The surface temperature of the gauge was measured and heat flux was determined from a closed form transient semi-infinite solution that included the resistance of the heat flux gauge and the underlying metal substrate.
Circumferentially, pressure measurements were obtained on the airfoil surfaces and on traversing rakes at the inlet and exit of the vane test section. Total and differential pressure rake instrumentation was required to obtain accurate aerodynamic loss measurements over a range of gas-to-wall temperature ratios.
NOx Dependency on Residence Time and Inlet Temperature for Lean-Premixed Combustion in Jet-Stirred Reactors
Authors: Rutar Teodora , Horning David C. , Lee John C. Y. , Malte Philip C. 
Published: December 2014

The effect of the residence time variation on NOx formation in high-intensity, lean-premixed (LP) methane combustion is explored through experiments conducted in a high-pressure jet-stirred reactor (HP-JSR) operated at 6.5 atm pressure. The residence time is varied between 0.5 ms and 4 ms, holding the measured reactor recirculation zone temperature constant at 1803 K. Air preheat is not used. The results indicate a minimum NOx level of 3.5 ppmvd (15% O2) for reactor mean residence times between 2 and 2.5 ms. As the residence time is reduced from 2.0 ms to 0.5 ms, the NOx increases, consistent with a spreading of super-equilibrium concentrations of free-radicals throughout the reactor. For the shortest residence times examined, PSR modeling agrees with the NOx measurements. At long residence times, (i.e., above 2.5 ms), the measured CO behavior indicates the super-equilibrium free radicals, and thus the rapid NOx production, are confined mainly to the jet zone of the reactor. For the long residence time range, the measured NOx increases with increasing residence time, and is significantly less than the PSR predictions. A simple two-zone model of the HP-JSR is used to interpret and evaluate the NOx formation.
Experiments exploring the effect of inlet temperature on NOx are conducted in an atmospheric pressure, methane-fired, jet-stirred reactor (A-JSR). The reactor temperature is held constant at 1788 K, and the inlet mixture temperature is varied between the no-preheat case and 623 K. These experiments show that increasing the inlet air temperature over the full range tested decreases the NOx by about 30%. Several explanations are offered for the behavior. For both reactors, i.e., the HP-JSR and A-JSR, single inlet jet nozzles are used. The results lead to a practical conclusion that very low NOx levels can be achieved for combustion in strongly back-mixed reaction cavities adjusted to optimal residence time and inlet temperature.
Computations of Discrete-Hole Film Cooling Over Flat and Convex Surfaces
Authors: Lin Y.-L. , Shih T. I-P. 
Published: December 2014

Computations were performed to investigate the three-dimensional flow and heat transfer about a flat surface and a convex surface cooled by jets, injected from a plenum through one row of film-cooling holes inclined at 35° with a density ratio of 1.6 and mass flux ratios of 0.5 and 1.0. The focus is on understanding how the mainflow distorts the jets issuing from the film-cooling holes and how the resulting interactions affect film cooling effectiveness and temperature distribution. Results are presented for the surface adiabatic effectiveness, normalized temperature, velocity vector field, and contours of the vorticity magnitude. The computed results for the surface effectiveness on a flat plate were compared with experimental data, and reasonably good agreements were obtained.
This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy closed by a low Reynolds number k-ω/SST turbulence model (i.e., wall functions were not used). Solutions were generated by a cell-centered finite-volume method that uses second-order accurate flux-difference splitting of Roe, multigrid acceleration of a diagonalized ADI scheme with local time stepping, and patched/overlapped structured grids. In the computations, the flow is resolved not just in the cooling-jet/mainflow interaction region, but also inside the film-cooling holes and in the plenum.
Numerical Simulation of a Film Cooled Nozzle Guide Vane Using an Injection Model
Authors: Dahlander Petter , Abrahamsson Hans , Mårtensson Hans , Håll Ulf 
Published: December 2014

Numerical simulations of film cooled nozzle guide vanes (NGV) are difficult since resolving the local flow near each cooling hole requires a very fine computational mesh. In this paper an injection model is used to include the coolant in the main flow by adding the influence of the coolant jets to the source terms in the governing equations.
The present method enables simulations of film cooled turbine stages using rather coarse meshes (i.e. not resolving the cooling holes) and gives the possibility to study, for example, the influence of the secondary flows on the coolant distribution. The disadvantage is that some parameters describing the injection need to be determined.
The development and validation of the injection model is performed using fully resolved 3D simulations and experimental data from single cooling jets. The present injection model is used to simulate the film cooled NGV of the research turbine stage MT1 at DERA, Pyestock, UK. Predictions of the heat transfer using the injection model show promising results.
Technology and Cost Options for Capture and Disposal of Carbon Dioxide From Gas Turbines: A System Study for Swedish Conditions
Authors: Ekström Clas , Cavani Adrin , Ericson Sven-Olov , Hinderson Anna , Westermark Mats 
Published: December 2014

The current and predicted global massive dependency on fossil fuels calls for the exploration of new options to limit the future carbon dioxide (CO2) emissions. One such option that has been studied within the IEA Greenhouse Gas Implementing Agreement, is the capture and disposal of CO2 from combustion gases. Such options for Sweden have been examined in a system study financed by NUTEK (The Swedish National Board for Industrial and Technical Development).
Aquifers that should be suitable for disposal of CO2, exist in the South of Sweden - Denmark and in the Baltic Sea close to Lithuania.
Based on commercially available technologies, CO2 can be captured from NGCC (natural gas combined cycle) and coal based IGCC (integrated gasification combined cycle) power plants. Most of the energy needed for the CO2 capture could then be recovered as district heating, thus maintaining the total energy efficiencies. At approximately 300 MW power production capacities, the heat quantities produced (55–85 MW heat) are likely to be suitable for a reasonable number of the Swedish district heating networks.
CO2 neutral production and utilisation of methanol as an automative fuel for the transport sector integrated with production of electric power and district heat, could be achieved with biomass combined with natural gas or coal as a raw material. An amount of CO2 corresponding to the carbon in the fossil fuel then has to be captured and disposed. Examples of possible process concepts have been examined.
The resulting estimated total costs for capture, transport and disposal of CO2, are in the same order of magnitude as the current Swedish carbon dioxide tax (365 SEK/ton CO2). Plant owners have to be credited for the captured and disposed CO2 in order to make this option economically justifiable and interesting for them.
It will be important for the total economy to find favourable combinations of energy conversion, CO2 capture and recovery, transport and disposal. There is also a need to reduce todays uncertainties in the available basis for estimation of costs for large scale transport, injection and disposal of CO2 into aquifers.
Hybrid Vehicle Turbine Engine Technology Support (HVTE-TS) Program 1997–98 Progress
Authors: Berenyi Steven G. , Sinnet George T. , French J. Mark 
Published: December 2014

The purpose of this program has been the development of advanced gas turbine engine technologies in support of U.S. Department of Energy (DoE) programs for use in generator sets for hybrid-electric automotive propulsion systems.
Initially the objective of this program had been the development of four key technologies to be applied 10 advanced turbogenerators:
• structural ceramic materials and processes
• low emissions combustion systems
• regenerator and seal systems
• insulation systems and processes.
Of these four, the lack of full program funding has limited 1997 activities to two technologies, i.e.: continued development of ceramics applications and continued regenerator and seal system development.
In late 1997, DoE Office of Transportation Technologies discontinued active sponsorship of this effort, and therefore, the potential application to automotive systems now appears to be delayed. However, the application to stationary engines is very relevant and will proceed.
Separated-Flow Transition: Part 3 — Primary Modes and Vortex Dynamics
Authors: Hatman Anca , Wang Ting 
Published: December 2014

This paper clearly identifies the possible modes of transition in the separated boundary layers and their specific characteristics. This study distinguishes between the short and long bubbles primarily based on the separated flow structure. A hypothetical description of the vortex structure and evolution for each separated-flow transition mode is provided.
The present approach in analyzing separated-flow transition is based on the assumption that the transition to turbulence in separated boundary layers is a result of the superposition of the effects of two different types of instability. The first type of instability is the Kelvin-Helmholtz (KH) instability. It occurs and develops in the shear layer at a specific location downstream of the separation point. The concentration of spanwise vorticity grows in time and remains in place through the vortex sheet roll-up mechanism. The roll-up vortex interacts with the wall and induces periodic ejection of near-wall fluid into the separated shear layer. The ejection process takes place at a location identifiable by the maximum displacement of shear layer, xMD.
The second type of instability is the (convective) Tollmien-Schlichting (TS) instability. It originates in the boundary layer prior to the separation point and continues to evolve in the separated shear layer. The mechanism for the TS instability also leads to roll-ups, but it involves viscous tuning of the instability waves. Thus, the separated-flow transition is the result of spatially developing, often competing instabilities. The ejection induces the onset of transition for laminar short and long bubble modes of transition and controls the mid-transition point of transitional separation mode. The ejection may be accompanied by vortex shedding. Shedding occurs in the laminar separation - short bubble mode and occasionally in the transitional separation mode; however, it is not present in the laminar separation - long bubble mode of transition.
The Design of an Improved Endwall Film-Cooling Configuration
Authors: Friedrichs S. , Hodson H. P. , Dawes W. N. 
Published: December 2014

The endwall film-cooling cooling configuration investigated by Friedrichs et al. (1996, 1997) had in principle sufficient cooling flow for the endwall, but in practice, the redistribution of this coolant by secondary flows left large endwall areas uncooled. This paper describes the attempt to improve upon this datum cooling configuration by redistributing the available coolant to provide a better coolant coverage on the endwall surface, whilst keeping the associated aerodynamic losses small.
The design of the new, improved cooling configuration was based on the understanding of endwall film-cooling described by Friedrichs et al. (1996, 1997). Computational fluid dynamics were used to predict the basic flow and pressure field without coolant ejection. Using this as a basis, the above described understanding was used to place cooling holes so that they would provide the necessary cooling coverage at minimal aerodynamic penalty. The simple analytical modelling developed in Friedrichs et al. (1997) was then used to check that the coolant consumption and the increase in aerodynamic loss lay within the limits of the design goal.
The improved cooling configuration was tested experimentally in a large scale, low speed linear cascade. An analysis of the results shows that the redesign of the cooling configuration has been successful in achieving an improved coolant coverage with lower aerodynamic losses, whilst using the same amount of coolant as in the datum cooling configuration.
The improved cooling configuration has reconfirmed conclusions from Friedrichs et al. (1996, 1997); firstly, coolant ejection downstream of the three-dimensional separation lines on the endwall does not change the secondary flow structures; secondly, placement of holes in regions of high static pressure helps reduce the aerodynamic penalties of platform coolant ejection; finally, taking account of secondary flow can improve the design of endwall film-cooling configurations.
Visualization and Measurements of Rub-Groove Leakage Effects on Straight-Through Labyrinth Seals
Authors: Rhode David L. , Allen Brian F. 
Published: December 2014

For the first time flow visualization images and leakage measurements were obtained and analyzed for an enhanced understanding of the effect of rub-grooves on straight-through labyrinth seal leakage. It was found that leakage resistance decreases sharply with increasing rub-groove axial width. Further, for small tooth clearances with medium- or large-width rub-grooves, the groove gives an approximate 50 percent drop in leakage resistance. At the medium clearance, the presence of medium- or large-width rub-grooves increases and decreases the resistance at low Re and high Re, respectively. At the large clearance, the presence of grooves increases the resistance by some 200 percent and 40 percent for low Re and high Re, respectively. However, large clearance applications generally give very high Re where the 40 percent increase occurs.
In addition, a vena contracta effect from the throughflow jet penetration into the rub-grooves was found on the flow pattern and on the leakage resistance. When penetration occurs, the trajectory angle of the jet entering the subsequent labyrinth cavity is sometimes dramatically altered, giving less kinetic energy carry-over to the subsequent tooth clearance.