bluuebunny/crossref_metadata_2025 huggingface dataset:
Computational Towing Tank Procedures for Single Run Curves of Resistance and Propulsion
Authors: Xing Tao , Carrica Pablo , Stern Frederick
Published: September 2008

A procedure is proposed to perform ship hydrodynamics computations for a wide range of velocities in a single run, herein called the computational towing tank. The method is based on solving the fluid flow equations using an inertial earth-fixed reference frame, and ramping up the ship speed slowly such that the time derivatives become negligible and the local solution corresponds to a quasi steady-state. The procedure is used for the computation of resistance and propulsion curves, in both cases allowing for dynamic calculation of the sinkage and trim. Computational tests are performed for the Athena R/V model DTMB 5365, in both bare hull with skeg and fully appended configurations, including two speed ramps and extensive comparison with experimental data. Comparison is also performed against steady-state points, demonstrating that the quasisteady solutions obtained match well the single-velocity computations. A verification study using seven systematically refined grids was performed for one Froude number, and grid convergence for resistance coefficient, sinkage, and trim were analyzed. The verification study concluded that finer grids are needed to reach the asymptotic range, though validation was achieved for resistance coefficient and sinkage but not for trim. Overall results prove that for medium and high Froude numbers the computational towing tank is an efficient and accurate tool to predict curves of resistance and propulsion for ship flows using a single run. The procedure is not possible or highly difficult using a physical towing tank suggesting a potential of using the computational towing tank to aid the design process.
Accelerated Numerical Test of Liquid Behavior Across Gas Diffusion Layer in Proton Exchange Membrane Fuel Cell Cathode
Authors: Jiao Kui , Zhou Biao
Published: September 2008

Liquid water transport inside proton exchange membrane (PEM) fuel cells is one of the key challenges for water management in a PEM fuel cell. Investigation of the air-water flow patterns inside fuel cell gas flow channels with gas diffusion layer (GDL) would provide valuable information that could be used in fuel cell design and optimization. This paper presents an accelerated numerical investigation of air-water flow across a GDL with a serpentine channel on PEM fuel cell cathode by use of a commercial computational fluid dynamics software package FLUENT. Detailed flow patterns with air-water across the porous media were investigated and discussed.
Simultaneous Large Scale Sheet Metal Geometry and Strain Measurement
Authors: Spence A. D. , Capson D. W. , Sklad M. P. , Chan H.-L. , Mitchell J. P.
Published: September 2008

The need to simultaneously measure sheet metal geometry and strain arises during research, die tryout, statistical process control production part approval, or in response to manufacturing exceptions. Several optical systems have been developed for strain and geometry measurement of small specimens. Large scale geometric measurement is possible using coordinate measuring machines equipped with touch probes. This Technical Brief summarizes the extension of these methods using three dimensional gray level point clouds obtained from either laser digitizers or an in-house developed stereo vision system.
Multiphase Finite Element Modeling of Machining Unidirectional Composites: Prediction of Debonding and Fiber Damage
Authors: Dandekar Chinmaya R. , Shin Yung C.
Published: September 2008

A multiphase finite element model using the commercial finite element package ABAQUS/EXPLICIT is developed for simulating the orthogonal machining of unidirectional fiber reinforced composite materials. The composite materials considered for this study are a glass fiber reinforced epoxy and a tube formed carbon fiber reinforced epoxy. The effects of varying the fiber orientation angle and tool rake angle on the cutting force and damage during machining are considered for the glass fiber reinforced epoxy. In the case of carbon fiber reinforced epoxy, only the effect of fiber orientation on the measured cutting force and damage during machining is considered. Two major damage phenomena are predicted: debonding at the fiber-matrix interface and fiber pullout. In the multiphase approach, the fiber and matrix are modeled as continuum elements with isotropic properties separated by an interfacial layer, while the tool is modeled as a rigid body. The cohesive zone modeling approach is used for the interfacial layer to simulate the extent of debonding below the work surface. Bulk deformation and shear failure are considered in the matrix for both the models and the glass fiber. A brittle failure criterion is used for the carbon fiber specimen and is coded in FORTRAN as a user defined material (VUMAT). The brittle failure of the carbon fibers is modeled using the Marigo model for brittle failure. For validation purposes, simulation results of the multiphase approach are compared with experimental measurements of the cutting force and damage. The model is successful in predicting cutting forces and damage at the front and rear faces with respect to the fiber orientation. A successful prediction of fiber pullout is also demonstrated in this paper.
Comparative Investigation of Advanced Combined Cycles
Authors: Khaledi Hiwa , Sarabchi Kazem
Published: September 2008

Combined cycles, at present, have a prominent role in the power generation and advanced combined cycles efficiencies have now reached to 60 percent. Examination of thermodynamic behavior of these cycles is still carried out to determine optimum configuration and optimum design conditions for any cycle arrangement. Actually the performance parameters of these cycles are under the influence of various parameters and therefore the recognition of the optimum conditions is quiet complicated. In this research an extensive thermodynamic model was developed for analyzing major parameters variations on gas turbine performance and different configurations of advanced steam cycles: dual and triple pressure cycles with and without reheating in steam turbine sections. In this model it is attempted to consider all factors that affect on actual behavior of these cycles such as blade cooling (air cooling) in gas turbine and different formulations for Heat Recovery Steam Generator (HRSG) performance calculation. Results show good agreement with manufactures data. In the case of gas turbine cycle, location of coolant extraction has large influence on cycle performance. For extraction from compressor end, improving blade cooling technology is suitable than increasing TIT. For mid stage extraction, improving blade cooling technology and TIT has similar effects on efficiency, while power is more sensitive to TIT. Coolant air precooling has large positive effect in high TIT and medium blade cooling technology, but always it increases power. Turbine exhaust temperature has large influence on optimum layout and configuration of HRSG, while for low exhaust temperatures increasing number of pressure levels increase power and heat recovery greatly, for high exhaust temperatures this leads lower enhancement in power and recovery. Second law efficiency of HRSG is proportional to power production in steam cycle. It decreases with increasing gas turbine exhaust temperature.
Co-Utilization of Biomass and Natural Gas in an Existing Powerplant Through Primary Steam Reforming of Natural Gas
Authors: Delattin Frank , Bram Svend , De Ruyck Jacques
Published: September 2008

Power production from biomass can occur through external combustion (e.g. steam cycles, Organic Rankine Cycles, Stirling engines), or internal combustion after gasification or pyrolysis (e.g. gas engines, IGCC). External combustion has the disadvantage of delivering limited conversion efficiencies (max 35%). Internal combustion has the potential of high efficiencies, but it always needs a severe and mostly problematic gas cleaning. The present article proposes an alternative route where advantages of external firing are combined with potential high efficiency of combined cycles through co-utilization of natural gas and biomass. Biomass is burned to provide heat for partial reforming of the natural gas feed. In this way, biomass energy is converted into chemical energy contained in the produced syngas. Waste heat from the reformer and from the biomass combustor is recovered through a waste heat recovery system. It has been shown in previous papers that in this way biomass can replace up to 5% of the natural gas in steam injected gas turbines and combined cycles, whilst maintaining high efficiencies [1,2]. The present paper proposes the application of this technique as retrofit of an existing combined cycle power plant (Drogenbos, Belgium) where 1% of the natural gas input would be replaced by wood pellets. This represents an installed biomass capacity of 5 MWth from biomass which could serve as a small scale demonstration. The existing plant cycle is first simulated and validated. The simulated cycle is next adapted to partially run on biomass and a retrofit power plant cycle layout is proposed.
Kinetics of Kerosene Combustion Over Extended Conditions: Experimental and Modeling
Authors: Dagaut Philippe
Published: September 2008

The oxidation of kerosene (Jet-A1) and that of surrogate mixtures have been studied experimentally in a jet-stirred reactor at 1 to 40 atm and constant residence time, over the high temperature range 800–1300 K, and for variable equivalence ratio 0.5<φ<2). Concentration profiles of the reactants, stable intermediates, and final products have been obtained by probe sampling followed by on-line and off-line GC analyses. The oxidation of kerosene in these conditions was modeled using a detailed kinetic reaction mechanism (209 species and 1673 reactions, most of them reversible). In the modeling, kerosene was represented by four surrogate model fuels: 100% n-decane, n-decane-n-propylbenzene (74% / 26% mole), n-decane-n-propylcyclohexane (74% / 26% mole), and n-decane-n-propylbenzene-n-propylcyclohexane (74% / 15% / 11% mole). The 3-components model fuel was the most appropriate for simulating the JSR experiments. It was also successfully used to simulate the structure of a fuel-rich premixed kerosene-oxygen-nitrogen flame and ignition delays taken from the literature.
A Comparison of Cylindrical and Fan-Shaped Film-Cooling Holes on a Vane Endwall at Low and High Freestream Turbulence Levels
Authors: Colban W. , Thole K. A. , Haendler M.
Published: September 2008

Fan-shaped film-cooling holes have been shown to provide superior cooling performance to cylindrical holes along flat-plates and turbine airfoils over a large range of different conditions. Benefits of fan-shaped holes include less required cooling air for the same performance, increased part lifetime, and fewer required holes. The major drawback however, is increased manufacturing cost and manufacturing difficulty, particularly for the vane platform region. To this point, there have only been extremely limited comparisons between cylindrical and shaped holes on a turbine endwall at either low or high freestream turbulence conditions. This study presents film-cooling effectiveness measurements on an endwall surface in a large-scale, low-speed, two-passage, linear vane cascade. Results showed that film-cooling effectiveness decreased with increasing blowing rate for the cylindrical holes, indicating jet lift-off. However, the fan-shaped passage showed increased film-cooling effectiveness with increasing blowing ratio. Overall, fan-shaped holes increased film-cooling effectiveness by an average of 75% over cylindrical holes for constant cooling flow.
Design Concept for Large Output Graz Cycle Gas Turbines
Authors: Jericha H. , Sanz W. , Go¨ttlich E.
Published: September 2008

Introduction of closed cycle gas turbines with their capability of retaining combustion generated CO2 can offer a valuable contribution to the Kyoto goal and to future power generation. Therefore research and development work at Graz University of Technology since the nineties has led to the Graz Cycle, a zero emission power cycle of highest efficiency. It burns fossil fuels with pure oxygen which enables the cost-effective separation of the combustion CO2 by condensation. The efforts for the oxygen supply in an air separation plant are partly compensated by cycle efficiencies far higher than for modern combined cycle plants. Upon the basis of the previous work the authors present the design concept for a large power plant of 400 MW net power output making use of the latest developments in gas turbine technology. The Graz Cycle configuration is changed insofar, as condensation and separation of combustion generated CO2 takes place at the 1 bar range in order to avoid the problems of condensation of water out of a mixture of steam and incondensable gases at very low pressure. A final economic analysis shows promising CO2 mitigation costs in range of 20–30 $/ton CO2 avoided. The authors believe that they present here a partial solution regarding thermal power production for the most urgent problem of saving our climate.
De-Oiler System for Improved Oil Containment
Authors: Sheridan William G. , Swayze Sarah T. , Glahn J. Axel
Published: September 2008

Oil containment is a critical design requirement that affects overall system safety and reliability of gas turbine engines. This paper examines a new method to enhance oil containment by use of an improved de-oiler that creates a favorable bearing compartment differential pressure environment even at low power settings. Typically gas turbine engines require seals to contain oil within the bearing compartment. These seals, both contacting and non-contacting configuration styles, rely on secondary airflow to buffer the sealing interface and force oil mist and droplets back into the compartment. This is not difficult to achieve at high or moderate power conditions since there is generally sufficient air flow and pressure available to meet the sealing requirements. However, at idle conditions, the engine low-pressure compressor (LPC) may not turn fast enough to produce sufficient airflow to buffer the seals. To address these concerns the authors propose a method where the de-oiler creates a vacuum at idle speed, which results in favorable compartment seal differential pressures and also acts as a restrictor at higher speeds, where limiting the contact pressure and increasing the service life of mechanical seals become desirable design goals. The paper will examine a specific case study with both analytical and experimental results.
Requirements and Advances in Simulating Aircraft Inlet Total Pressure Distortion in Turbine Engine Ground Tests
Authors: Beale Dave , Davis Milt , Sirbaugh Jim
Published: September 2008

The development of high-performance aircraft demands the successful integration of the airframe, engine, and control systems. Advancements in aircraft technologies bring with them the need to improve the computational and experimental tools applied to the airframe-engine compatibility evaluations. This paper focuses on the need to improve one of these tools, the direct-connect turbine engine test method. In particular, the paper advocates improving the direct-connect test simulation of the total-pressure distortion induced in flight by the external airframe and the inlet system. To meet the needs of future direct-connect tests, AEDC embarked on the development of a transient total-pressure distortion generator. The paper first introduces specific total pressure pattern simulation requirements that form the basis for the development and results of the distortion generator development process. Included are sample distortion generator concept test results and a description of a fully functional prototype that is in fabrication. Next, the paper summarizes a parallel development of computational fluid dynamics (CFD) tools that will be applied to adapting the prototype design to specific test facilities and to the operation of the distortion generator in turbine engine tests. The paper concludes with a look ahead from the total-pressure distortion methodology to test and computational methodologies for other parameters, with emphasis on swirl.
Modeling of Heat Transfer and Clearance Changes in Transient Performance Calculations: A Comparison
Authors: Merkler Rasmus S. , Staudacher Stephan
Published: September 2008

This paper provides an overview of the models used in transient performance calculations relative to heat exchange between the fluid flows and the material as well as clearance changes due to centifugal forces and thermal loads. It entails a summary of the three basic modeling approaches recorded in literature noting their advantages and disadvantages. The most important criterions for the assesment of these modeling methods for their use in performance calculation programs is derived. The different modeling methods are then assessed with the derived criterions. And finally, further investigations on the most appealing aproach for use in performance calculations are presented.
Heat-Flux Measurements and Predictions for the Blade Tip Region of a High-Pressure Turbine
Authors: Molter S. M. , Dunn M. G. , Haldeman C. W. , Bergholz R. F. , Vitt P.
Published: September 2008

High-pressure turbine blade tips operate in a highly complex flow environment that makes designing new blades for increased life difficult. Computational fluid dynamics simulations of the tip flow field may be able to guide new designs to improve the blade life, but the analysis techniques need to be verified against detailed measurements before they can be applied. The current paper presents measurements of heat flux and pressure in the blade tip region of a modern one-and-one-half stage high-pressure turbine operating at design corrected conditions in a rotating rig. Both flat tip and recessed, or squealer, tip blades were used in the experiments. The measurements indicate that the recessed tip, used in the majority of modern turbines to minimize blade damage from rubs, increases the blade heat load overall, and creates several hot spots on the floor of the recess for an uncooled airfoil. The tip data also showed there were significant unsteady variations in the heat load at the vane passing frequency. Steady state CFD calculations were completed for both flat and squealer tip configurations to examine if the analysis could capture the details that were measured. The CFD, while not capable of estimating the unsteady heat load component and generally over predicting the overall heat flux by 10–25%, did capture the measured heat flux trends in the recessed tip. These results show that steady-state CFD analysis can be useful in predicting the complex flow field and heat load distribution in turbine blade tips to help guide future blade designs.
On Active Control of Film-Cooling Flows
Authors: Nikitopoulos Dimitris E. , Acharya Sumanta , Oertling Jeremiah , Muldoon Frank H.
Published: September 2008

A technical assessment of the potential improvements resulting from the application of active control of film cooling is discussed in this paper. Two methods of film-cooling jet excitation are theoretically evaluated. Film-cooling control through pulsation of the coolant stream mass flow rate is further examined on the basis of existing experimental and preliminary computational results. A potentially optimal range of coolant pulsation parameters are identified through theoretical and mechanistic arguments based on understanding of basic physical phenomena occurring in pulsed film-cooling flow, i.e. that of a pulsed jet in cross-flow. Guidelines for the choice of potentially optimum frequency and duty cycle windows of the controlling flow pulsations are identified, as well as the related mean and peak-to-peak blowing ratios. Evidence from existing experimental data and computations are invoked to validate these guidelines. Because of the limited experimental/computational data on this subject further work is necessary in order to fully verify the aforementioned flow-pulsing parameter ranges.
Mass/Heat Transfer in Rotating, Smooth, High-Aspect Ratio (4:1) Coolant Channels With Curved Walls
Authors: Sethuraman Eashwar , Nikitopoulos Dimitris E. , Acharya Sumanta
Published: September 2008

The paper presents an experimental study of heat/mass transfer coefficient in 4:1 aspect ratio smooth channels with non-uniform cross-sections. Curved leading and trailing edges are studied, for two curvatures of 9.06 m−1 (0.23 in−1) and 15.11 m−1 (0.384 in−1) and for two different curvature configurations. One configuration has curved walls with curvature corresponding to the blade profile (positive curvature on both leading and trailing walls), and the other configuration has leading and trailing walls that curve inwards into the coolant passage (negative curvature on the leading surface and positive curvature on the trailing surface). A detailed study at Re = 10,000 with rotation numbers in the range of 0–0.07 is undertaken for the two different curvature configurations. All experiments are done for a 90° passage-orientation with respect to the plane of rotation. The experiments are conducted in a rotating two-pass coolant channel facility using the naphthalene sublimation technique. Only the radially outward flow is considered for the present study. The span-wise mass transfer distributions of fully developed regions of the channel walls are also presented. The mass transfer data from the curved wall channels is compared to those from a smooth 4:1 rectangular duct with similar flow parameters. The local mass transfer data is analyzed mainly for the fully developed region, and area-averaged results are presented to delineate the effect of the rotation number. Heat transfer enhancement especially in the leading wall is seen for the lower curvature channels, and there is a subsequent reduction in the higher curvature channel, when compared to the 4:1 rectangular smooth channel. This indicates that an optimal channel wall curvature exists for which heat transfer is the highest.
Effects of Temperature and Hydroxyl Radical Concentration Distributions on Emissions of Partially Premixed Flames From Elliptical Burners
Authors: Baird Benjamin D. , Gollahalli S. R.
Published: September 2008

Non-circular burner geometries have shown some promise of reducing pollutant emissions form combustion systems. The use of non-axisymmetric geometries has the potential to alter the behavior of a flame through modification of the flow field. To investigate these flow field effects on combustion performance, a study of the partially premixed flames emitted from a circular burner and a 3:1 aspect ratio (major axis / minor axis) elliptical burner of equal exit area was performed. For laminar conditions, the elliptical and circular burner produced similar global emissions of carbon monoxide and nitric oxide. In turbulent flames, the elliptical burner produced a larger amount of carbon monoxide, but reduced nitric oxide production. In turbulent flames, the enhanced mixing facilitated by elliptical burners froze the CO oxidation reaction and thus increased its emission. In laminar flames, the elasticity did not significantly affect mixing rates, and thus resulted in similar CO emissions between the burners. The hypothesis on CO reaction freezing was confirmed with inflame structure measurements of CO, OH, and temperature. The decreased NO production in turbulent flame was attributed to a reduction of the flame length of the 3:1 aspect ratio elliptical burner and thus a decrease of residence time compared to the circular burner.
Effects of Sand Ingestion on the Blockage of Film-Cooling Holes
Authors: Walsh W. S. , Thole K. A. , Joe Chris
Published: September 2008

Gas turbines are often subjected to conditions where dirt and sand are ingested into the engine during takeoffs and landings. Given most aero engines do not have filtration systems, particulates can be present in both the main gas path and coolant streams. Particulates can block coolant passages and film-cooling holes that lead to increased airfoil temperatures caused by reduced coolant available for a given pressure ratio across the cooling holes. This study investigated the effects of sand blockage on film-cooling holes placed in a leading edge coupon. The coupon was tested to determine the reduction in flow parameter for a range of pressure ratios, coolant temperatures, metal temperatures, number of cooling holes, sand amounts, and sand diameters. Depending upon conditions, blockages characterized by reduced coolant flow can be as high as 10%.
Performance Analysis of APT (Atmospheric Pressure Turbine): Molten Carbonate Fuel Cell Hybrid System
Authors: Tsujikawa Y. , Kaneko K. , Yamauchi T. , Katsura S.
Published: September 2008

Molten Carbonate Fuel Cell (MCFC) has been extensively developed in many countries as a high efficient energy converter. Such high temperature fuel cell can be operated as a hybrid system of integrating of turbo machinery. A major decision is whether to place the cell stack in pressurized or unpressurized section. This paper discusses the exhaust energy recovery from fuel cells by use of turbo machines under unpressurized conditions, working with inverted Brayton cycle in which turbine expansion, cooling by heat exchanger and draft by compressor are made in an open cycle mode. It is denoted as “atmospheric pressure turbine (APT)”.
A Turbomachinery Design Tool for Teaching Design Concepts for Axial-Flow Fans, Compressors, and Turbines
Authors: Turner Mark G. , Merchant Ali , Bruna Dario
Published: September 2008

A new turbomachinery design system, T-AXI, is described and demonstrated. It is intended primarily for use by educators and students, although it is sophisticated enough for actual designs. The codes, example cases and a user’s manual are available through the authors’ web sites. The design system can be used to design multistage compressors and turbines from a small number of physical design parameters. Students can understand the connection between these physical parameters such as Mach number and flow angles to the cross sectional area and angular momentum. There is also a clear connection between the angular momentum, work and blade loadings. Loss models are built-in and results are compared against tested geometries. The code also has a built-in blade geometry generator and the geometry can be output for running the MISES blade-to-blade solver on each section or visualizing the blades. A single stage compressor from the US Air Force Stage Matching Investigation rig, the 10 stage NASA/GE EEE high pressure compressor and the NASA/GE EEE 5 stage low pressure turbine have been used to validate T-AXI as a design tool.
Film Effectiveness Performance of an Arrowhead-Shaped Film Cooling Hole Geometry
Authors: Okita Yoji , Nishiura Masakazu
Published: September 2008

This paper presents the first experimental and numerical work of film effectiveness performance for a novel film cooling method with an arrowhead-shaped hole geometry. Experimental results demonstrate that the proposed hole geometry improves the film effectiveness on both suction and pressure surface of a generic turbine airfoil. Film effectiveness data for a row of the holes are compared with that of fan-shaped holes at the same inclination angle of 35° to the surface on a large-scale airfoil model at engine representative Reynolds number and Mach number in a high speed tunnel with moderately elevated temperature mainstream flow. The film effectiveness data are collected using pressure sensitive paint (PSP). Numerical results show that the coolant film with the proposed hole geometry remains well attached to the surface and diffuses in the lateral direction in comparison with the conventional laidback fan-shaped holes for coolant to mainstream blowing ratios of 0.6 to 3.5.
The Coarsening Kinetic of γ′ Particles in Single Crystal Superalloys During Aging at High Temperatures
Authors: Mammoliti Fabrizio , Mastromatteo Francesco , Giannozzi Massimo , Iozzelli Federico , Lucci Daniele
Published: September 2008

Turbine blades are subjected to a complex combination of elevated temperatures, high stresses and aggressive environment. With exposure to these operating conditions the service lives of the components are limited by fatigue, hot corrosion and creep. For this reason in the last years single crystal superalloys have been developed and used in aeronautic but also in land based gas turbine. In particular in this paper CMSX-4® and SCB® Nickel-based superalloys are analyzed. The properties of these materials are due obviously to their single crystal structure, combined with the well known strengthening effect of second phase (γ′) precipitates in the nickel matrix (γ). These precipitates increase their size during aging. In this work a comparison between the growth kinetic of γ′ precipitates of these alloys has been carried out. Samples of both materials have been aged using the same test temperatures for times up to 5000 hours and the mean particle size measured by means of image analysis. Growth kinetic laws for both alloys have been developed, but they don’t take into account rafting of γ′ particles, that has been observed to occur in the two materials in different ways. In order to better understand this aspect, creep tests with variable load have been carried out and the relative structures have been examined.
Characterization and Oxidation Damage Modelling of MCrAlY
Authors: Pietrangeli Emanuele , Cappuccini Filippo , Bellacci Michelangelo , Iozzelli Federico , Romanelli Marco
Published: September 2008

Overlay coatings based on the MCrAlY alloy system (M is Ni, CO or both) are among the most important protective coating materials applied in the hottest section of gas turbine to counteract hot corrosion and high temperature oxidation. MCrAlY coatings are arranged in γ/β-phase system, where β-phase is the Al reserve for the surface oxide layer formation. Like any coating designed to resist oxidative environments at high temperatures, MCrAlYs should be capable of developing a thermodynamically stable, slow-growing and adherent surface oxide layer. In the current paper, two HVOF thermal sprayed MCrAlYs deposited on a Ni-based superalloy have been investigated in order to assess the different high temperature oxidation resistance. Isothermal oxidation tests were performed on NiCoCrAlY coating (GT33®) and CoNiCrAlY coating (Amdry995®) at four temperatures for thousand hours. Coating damage was evaluated by measures of outer and inner β-phase depletion, interdiffusion zone thickness and Al reduction. Both coatings have shown optimal microstructural stability but NiCoCrAlY coating, in virtue of greater Ni and Al content, proved superior high temperature oxidation resistance. A useful model for life assessment of gas turbine buckets coatings was extrapolated from microstructure evolution data.
The Application of µ-Fan Instead of the Ejector in Tubular SOFC Module
Authors: Milewski Jaroslaw , Miller Andrzej , Mozer Ewa
Published: September 2008

The possibility of using a μ-fan in tubular SOFC module is shown. The μ-fan is placed instead of the ejector and has the same role. Main advantages of this new solution are: lower power demanded by fuel compressor (blower), more stable working characteristic, and possibility of control of re-cycled part of anode gas during part load operation. Comparison of two SOFC Modules: with and without the ejector is also shown and commented.
Full Scale Testing of a Low Swirl Fuel Injector Concept for Ultra-Low NOx Gas Turbine Combustion Systems
Authors: Nazeer Waseem , Smith Kenneth , Sheppard Patrick , Cheng Robert , Littlejohn David
Published: September 2008

The continued development of a low swirl injector for ultra-low NOx gas turbine applications is described. An injector prototype for natural gas operation has been designed, fabricated and tested. The target application is an annular gas turbine combustion system requiring twelve injectors. High pressure rig test results for a single injector prototype are presented. On natural gas, ultra-low NOx emissions were achieved along with low CO. A turndown of approximately 100°F in flame temperature was possible before CO emissions increased significantly. Subsequently, a set of injectors was evaluated at atmospheric pressure using a production annular combustor. Rig testing again demonstrated the ultra-low NOx capability of the injectors on natural gas. An engine test of the injectors will be required to establish the transient performance of the combustion system and to assess any combustor pressure oscillation issues.
The Influence of Aero-Derivative Combustor Turbulence and Reynolds Number on Vane Aerodynamics Losses, Secondary Flows, and Wake Growth
Authors: Ames F. E. , Johnson J. D. , Fiala N. J.
Published: September 2008

Exit surveys detailing total pressure loss, turning angle, and secondary velocities have been acquired for a fully loaded vane profile in a large scale low speed cascade facility. Exit surveys have been taken over a four-to-one range in Reynolds numbers based on exit conditions and for both a low turbulence condition and a high turbulence condition. The high turbulence condition was generated using a mock aero-derivative combustor. Exit loss, angle, and secondary velocity measurements were acquired in the facility using a five-hole cone probe at two stations representing axial chord spacings of 0.25 and 0.50. Substantial differences in the level of losses, distribution of losses, and secondary flow vectors are seen with the different turbulence conditions and at the different Reynolds numbers. The higher turbulence condition produces a significantly broader wake than the low turbulence case and shows a measurable total pressure loss in the region outside the wakes. Generally, total pressure losses are about 0.02 greater for the high turbulence case compared with the low turbulence case primarily due to the state of the suction surface boundary layers. Losses decrease moderately with increasing Reynolds number. Cascade inlet velocity distributions have been previously documented in an endwall heat transfer study of this same geometry. These exit survey measurements support our understanding of the endwall heat transfer distributions, the secondary flows in the passage, and the origin of losses.
The Influence of Reynolds Number and Row Position on Surface Pressure Distributions in Staggered Pin Fin Arrays
Authors: Ames F. E. , Dvorak L. A.
Published: September 2008

Full surface pressure distributions over the endwall and pin in a staggered pin fin array have been acquired over a ten to one range in Reynolds numbers. These pressure distributions allow us to visualize the strong inertial pressure gradients that are responsible for driving secondary flows in pin fin passages. These strong pressure gradients include endwall regions near the pin stagnation region and near the pin at 90° from the stagnation region. Pressure distributions have been acquired on pin and endwall surfaces at eight consecutive rows using conventional static pressure measurement techniques. Pressures have been taken at 380 locations per row and, assuming symmetry, provide a well resolved visualization of surface pressure. Generally, surface and pin pressure distributions vary significantly from row to row in the entrance of the array at a given Reynolds number but stay relatively consistent after row four. Dimensionless pressure distributions are quite similar for row one for all Reynolds numbers but vary significantly at a given row downstream with Reynolds number. These data are expected to enhance our understanding of pin array fluid dynamics and to compliment full surface heat transfer data presented in a future paper.
Analysis of the Fuel Injection in Gas Turbine Premixing Systems by Experimental Correlations and Numerical Simulations
Authors: Riccio G. , Schoepflin L. , Adami P. , Martelli F.
Published: September 2008

This paper presents the aerodynamic study of two premixing systems for gas turbine combustion chamber based on detailed CFD 3-D simulations. The work was carried out with the aim to describe the aerodynamic and the mixing process in two different premixing system schemes, typical for DLE gas turbine combustion chamber. Results from different numerical tools (CFD 3-D and 0/1-D) for the estimation of the fuel jet pathway were compared. Both the premixer configurations analysed are related to the cross-flow injection scheme. The first one considers the fuel injection orthogonal to a low swirled air stream while the second one considers the fuel injection directly from hole rows drilled on the suction and pressure side of the swirler blades. The aerodynamic analysis of the premixing devices was focused on the fuel injection in terms of the jets pathway and air/fuel mixing in steady-state conditions. The aerodynamic investigations were performed by CFD 3-D “full Navier-Stokes” codes. Calculations were repeated, on the same mesh, by an in-house developed code (HybFlow) and by commercial codes also. Some previous experimental results were exploited to tune and validate the calculations. Results of the simulation were post-processed in order to allow a quantitative evaluation of the air/fuel mixing. Moreover the calculations were used to verify the accuracy of 0/1-D models, taken from the literature, for the estimation of the maximum penetration and the trajectory for the cross-flow of gaseous fuel jet, considering typical working conditions for gas turbine premixing system. Finally, preliminary considerations related to the fuel injection schemes and to the influence of the main injection conditions on the mixing were carried out.
Numerical Investigations of Geometric Design Parameters Defining Nozzle Guide Vane Endwall Heat Transfer
Authors: Rubensdo¨rffer Frank G. , Fransson Torsten H.
Published: September 2008

The objective of this work is to compare the predicted flow field and the endwall heat transfer of a baseline nozzle guide vane configuration with a combustion chamber variant, a heat shield variant without and with additional cooling air, and a cavity variant without and with additional cooling air. The comparison is carried out numerically using the commercial 3D Navier-Stokes software package Fluent [1]. For the turbulence modeling the v2-f model by Durbin [2] been used. The detailed comparison of the flow field and the endwall heat transfer shows major differences between the baseline and heat shield configuration. The heat shield in front of the airfoil of the nozzle guide vane cascade influences the secondary flow field and the endwall heat transfer pattern strongly. The additional cooling air, released under the heat shield also has a distinctive influence. The cavity between the combustion chamber and the nozzle guide vane affects the secondary flow field and the endwall heat transfer pattern. Here the influence of the additional cavity cooling air is more decisive.
Advances in Engine Test Capabilities at the NASA Glenn Research Center’s Propulsion Systems Laboratory
Authors: Pachlhofer Peter M. , Panek Joseph W. , Dicki Dennis J. , Piendl Barry R. , Lizanich Paul J. , Klann Gary A.
Published: September 2008

The Propulsion Systems Laboratory at the National Aeronautics and Space Administration (NASA) Glenn Research Center is one of the premier U.S. facilities for research on advanced aeropropulsion systems. The facility can simulate a wide range of altitude and Mach number conditions while supplying the aeropropulsion system with all the support services necessary to operate at those conditions. Test data are recorded on a combination of steady-state and high-speed data-acquisition systems. Recently a number of upgrades were made to the facility to meet demanding new requirements for the latest aeropropulsion concepts and to improve operational efficiency. Improvements were made to data-acquisition systems, facility and engine-control systems, test-condition simulation systems, video capture and display capabilities, and personnel training procedures. This paper discusses the facility’s capabilities, recent upgrades, and planned future improvements.
Correlation of Pre-Swirl Effectiveness With the Turbulent Flow Parameter and Application to the Mitsubishi MF111 Up-Grade
Authors: Laurello V. , Masada J. , Araki M. , Ishizaka K. , Nakamura T.
Published: September 2008

Analysis and testing were carried out to investigate the effectiveness of a turbine cooling air pre-swirl system and to determine the relationship with the turbulent flow parameter. The pre-swirler consisted of a low number of discrete round nozzles. The low nozzle count was the result of geometric constraints of an existing engine, the 15 MW Mitsubishi MF111. The incorporation of the pre-swirler allowed a significant increase in rotor inlet temperature while maintaining blade metal temperature levels. The increased rotor inlet temperature provided the desired increase in output. The increased output, with the low cost pre-swirler, provides a high value to MF111 up-grade customers.
An Integrated Gasification Zero Emission Plant Using Oxygen Produced in a Mixed Conducting Membrane Reactor
Authors: Lindfeldt Erik G. , Westermark Mats O.
Published: September 2008

Integrated gasification combined cycles (IGCCs) exhibit conditions favourable to CO2 sequestration. In this article, simulations of the Integrated Gasification Zero Emission Plant (IGZEP) concept are presented. The idea behind this concept is to use oxygen produced in a Mixed Conducting Membrane (MCM) reactor in an IGCC. Previous studies have shown that it is beneficial to integrate an MCM reactor in a natural gas fired cycle, and the objective of this article is to quantify the advantages of integrating the same type of reactor with an IGCC the way it is suggested in the IGZEP concept. The core of the membrane reactor is a ceramic membrane, which separates oxygen from air exiting the gas turbine compressor. The reactor operates at temperatures around 900 °C and is driven by a difference in oxygen partial pressure. The oxygen permeating the membrane is used in a Texaco gasifier, whereas the oxygen-depleted air is sent to a high temperature combustor. The rest of the cycle is essentially similar to a “standard” IGCC. The simulations performed resulted in a CO2 capture penalty of 6.4% points (Lower Heating Value, LHV) and a net cycle efficiency of 32.5% (LHV). Despite this quite low efficiency, the IGZEP concept is interesting since one of the main reasons for the low net efficiencies is the low efficiency of the Texaco gasifier model used. Other models for Texaco gasifiers with higher efficiency have been found in literature. Nevertheless, it is judged more interesting to compare IGZEP’s penalty for oxygen generation with that of existing competitors. It is shown that the total oxygen production penalty can be decreased from 4.9% points in the reference case to 4.3% points in IGZEP. That is, about 0.6% points in net efficiency may be gained by replacing a standard (non-integrated) cryogenic air distillation unit with an MCM reactor. Other studies have also shown that this strategy may entail lower investment and electricity production costs.
Local Internal Impingement Heat Transfer Near a 30 and 90 Deg Row of Film Cooling Holes: Part 1 — Effect of Flow Parameters
Authors: Xu Lei , Chang Haiping , Zhang Jingyang
Published: September 2008

Experimental investigations of local impingement heat transfer characteristics near a row of film cooling holes in a simulated internal midchord region of gas turbine blade have been carried out. The research of heat transfer characteristics is focused on three film cooling hole diameter area located upstream and downstream a row of film holes. There is a line of equally spaced film cooling holes whose angles are 30 or 90 degrees. When there is no impingement, the investigation about the effect of the film cooling bleed has been carried out under different cross flow Reynolds Numbers and film outflow-to-crossflow mass flux ratios based on each film cooling hole/channel section area. The results indicate that the local heat transfer near the film cooling holes is enhanced with the increase of the crossflow Reynolds Numbers and film outflow-to-crossflow mass flux ratios based on each film cooling hole/channel-section area. The local heat transfer characteristic downstream film cooling holes is better than that upstream film cooling holes. The average Nusselt number of one time diameter area downstream the row of film holes is generally 40% more than that upstream the row of film cooling holes. The place closer to the hole will have stronger heat transfer whether upstream film cooling holes or downstream film cooling holes. When there is impingement, the impinging air is provided by a single line of equally spaced jets. The spacing of the jet holes is twice that of the film cooling holes with staggered arrangements. The local heat transfer near the row of film cooling holes has been studied experimentally through changing flow parameters, such as impinging Reynolds Numbers and mass flux ratios of crossflow-to-jet based on each channel/jet hole section area etc. A great number of experimental data has been obtained. Based on this, the effects of the flow parameters on the heat transfer characteristics have been obtained qualitatively and quantitatively. It can be the important reference for accurately designing gas turbine blade.
Internal Air Systems Experimental Rig Best Practice
Authors: Childs Peter , Dullenkopf Klaus , Bohn Dieter
Published: September 2008

This paper reports best practice principles for experimental rig design and operation arising from a European Commision funded programme of research on internal air systems. The Internal Cooling Air Systems for Gas Turbines 2 (ICAS-GT2) research programme, ran from April 2001 to June 2005, and was undertaken by a consortium of ten gas turbine manufacturing companies and four universities. The programme of research involved both design and operation of a series of high pressure, high speed rotating rigs in order to deliver data at or near engine representative conditions. The rigs concerned cover the pre-swirl system, turbine rim seals, turbine stator wells, compressor rotor-rotor disc cavities, bolt windage and real engine parts experiments. Operation of these rigs has presented a wide range of challenges, particularly with respect to optical access in rotor-rotor and rotor-stator disc cavities and measurement of disc heat transfer. This paper explores the best practice principles developed for internal air system experimental rig design, operation and associated instrumentation.
Large Eddy Simulation of Fully Developed Flow and Heat Transfer in a Rotating Duct With 45° Ribs
Authors: Viswanathan Aroon K. , Tafti Danesh K.
Published: September 2008

This paper concerns itself with investigating the effect of rotation on flow and heat transfer in a 45° ribbed square duct. Large-Eddy Simulations (LES) are used to investigate why rotation does not have any effect on heat transfer augmentation unlike 90 degree ribs, in which considerable changes are observed in augmentation at the trailing and leading walls of the duct. It is found that unlike 90 degree ribbed ducts, in which the heat transfer augmentation is strongly dependent on streamwise momentum, spanwise momentum dominates heat transfer in skewed ribs. Since Coriolis forces under orthogonal rotation about the z-axis do not directly contribute to spanwise momentum, they do not have as much of an effect on heat transfer at the ribbed walls at the trailing and leading sides. However, because of the augmentation of turbulence at the trailing side, the vortices which are produced in the separated shear layer of the rib and which move from the inside to the outside of the duct, break down and diffuse before they can impinge on the outer wall. Turbulence attenuation at the leading wall has the opposite effect which allows the vortices to maintain their coherence and impinge on the outer wall. This effect taken together with the streamwise flow being pushed to the leading side, produces an extended region of high heat transfer at the outer wall near the leading side. This is countered by lower heat transfer at the trailing side of the outer wall. Hence, although local variations are present due to rotation, the overall augmentation remains the same.