bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of Sediment Sources in Forested Watersheds With Surface Coal Mining Disturbance Using Carbon and Nitrogen Isotopes1
Authors: Fox James F.
Published: October 2009

Abstract:  Sediments and soils were analyzed using stable carbon and nitrogen isotope ratio mass spectrometry and carbon and nitrogen elemental analyses to evaluate the their ability to indicate land‐use and land management disturbance and pinpoint loading from sediment transport sources in forested watersheds disturbed by surface coal mining. Samples of transported sediment particulate organic matter were collected from four watersheds in the Southern Appalachian forest region of southeastern Kentucky. The four watersheds had different surface coal mining history that were classified as undisturbed, active mining, and reclaimed conditions. Soil samples were analyzed including reclaimed grassland soils, undisturbed forest soils, geogenic organic matter associated with coal fragments in mining spoil, and soil organic matter from un‐mined grassland soils. Statistically significant differences were found for all biogeochemical signatures when comparing transported sediments from undisturbed watersheds and surface coal mining disturbed watersheds, and the results were attributed to differences in erosion sources and the presence of geogenic organic matter. Sediment transport sources in the surface coal mining watersheds were analyzed using Monte Carlo mass balance un‐mixing and it was found that: δ15N showed the ability to differentiate streambank erosion and surface soil erosion; and δ13C showed the ability to differentiate soil organic matter and geogenic organic matter. Results from the analyses suggest that streambank erosion downstream of surface coal mining sites is an especially significant source of sediment in coal mining disturbed watersheds. Further, the results suggest that the sediment transport processes governing streambank erosion loads are taking longer to reach geomorphologic equilibrium in the watershed as compared with the surface erosion processes. The dual‐isotope technique provides a useful method for further investigation of the impact of surface coal mining in the uplands of the watershed upon the geomorphologic state of the channel and the source of organic matter in aquatic systems impacted by surface coal mining.
Lack of effect of subtherapeutic vitamin D treatment on glycemic and lipid parameters in Type 2 diabetes: A pilot prospective randomized trial
Authors: PATEL Parini , PORETSKY Leonid , LIAO Emilia
Published: October 2009

Background:  Epidemiological studies suggest a higher prevalence of metabolic syndrome and its components among individuals with vitamin D deficiency. The aim of the present study was to determine whether vitamin D treatment improves glucose control and insulin sensitivity in Type 2 diabetes mellitus (T2DM).

Methods:  Subjects with T2DM and serum 25‐hydroxyvitamin D (25(OH)D) concentrations <25 ng/mL were randomized to receive 400 IU (Group 1) or 1200 IU (Group 2) cholecalciferol for 4 months. Fasting plasma glucose, glycosylated hemoglobin (HbA1c), Quantitative Insulin Sensitivity Check Index (QUICKI), serum lipid levels and serum adiponectin were measured at baseline and at 4 months.

Results:  Mean 25(OH)D levels increased in both groups (from 17.6 ± 1.5 to 25.5 ± 1.8 ng/mL in Group 1 and from 15.6 ± 1.4 to 27.4 ± 2.4 ng/mL in Group 2; P ≤ 0.001 vs baseline for each group). No significant differences were noted in fasting plasma glucose, HbA1c, QUICKI, serum adiponectin, and lipid levels compared with baseline within groups or between the two groups.

Conclusions:  In the present pilot study, conventional vitamin D treatment at a level improving, but not optimizing, serum 25(OH)D did not improve glycemia, insulin sensitivity, or lipid profile. However, diabetes and lipids were relatively well controlled at baseline. Future studies should be designed to achieve optimal concentrations of serum 25(OH)D (at least >32 ng/mL) and should include subjects showing more abnormal parameters of glycemia, lipid, and insulin sensitivity at baseline.
DnaSAM: Software to perform neutrality testing for large datasets with complex null models
Authors: ECKERT ANDREW J. , LIECHTY JOHN D. , TEARSE BRANDON R. , PANDE BARNALY , NEALE DAVID B.
Published: October 2009

Patterns of DNA sequence polymorphisms can be used to understand the processes of demography and adaptation within natural populations. High‐throughput generation of DNA sequence data has historically been the bottleneck with respect to data processing and experimental inference. Advances in marker technologies have largely solved this problem. Currently, the limiting step is computational, with most molecular population genetic software allowing a gene‐by‐gene analysis through a graphical user interface. An easy‐to‐use analysis program that allows both high‐throughput processing of multiple sequence alignments along with the flexibility to simulate data under complex demographic scenarios is currently lacking. We introduce a new program, named DnaSAM, which allows high‐throughput estimation of DNA sequence diversity and neutrality statistics from experimental data along with the ability to test those statistics via Monte Carlo coalescent simulations. These simulations are conducted using the ms program, which is able to incorporate several genetic parameters (e.g. recombination) and demographic scenarios (e.g. population bottlenecks). The output is a set of diversity and neutrality statistics with associated probability values under a user‐specified null model that are stored in easy to manipulate text file.
Analytical and Experimental Studies of the Mechanics of Deformation in a Solid With a Wavy Surface Profile
Authors: Xiao J. , Carlson A. , Liu Z. J. , Huang Y. , Rogers J. A.
Published: October 2009

The analytical solution is obtained for a semi-infinite linear elastic solid with a sinusoidal, “wavy” surface profile subject to applied strain. The amplitude A of a deformed wavy surface is related to the initial amplitude A0 and the applied strain εa through the simple expression A=A0(1−εa). This relation is confirmed independently by finite element analyses and experimental measurements of strained wavy poly(dimethylsiloxane) surfaces. Analytical solutions are also obtained for a wavy solid subject to stretch and lateral displacement.
Inelastic Analysis of Fracture Propagation in Distal Radius
Authors: Pietruszczak S. , Gdela K.
Published: October 2009

The focus of this paper is on the description of progressive fracture in distal radius in the event of a fall onto an outstretched hand. The inception of fracture, which involves formation of a macrocrack in the cortical tissue, is defined by invoking a macroscopic failure criterion that accounts for inherent anisotropy of the material. The subsequent propagation of damage is described by employing a homogenization procedure in which the average properties of cortical tissue intercepted by a macrocrack are established. The framework is verified by performing a series of nonlinear finite element analyses. In particular, the experimental tests recently conducted by the authors and their colleagues on a number of cadaver radii under boundary conditions leading to Colles’ fracture are simulated, and the results are compared with the experimental outcome.
The Bounds on the Coefficients of Restitution for the Frictional Impact of Rigid Pendulum Against a Fixed Surface
Authors: Lubarda V. A.
Published: October 2009

Upper bounds on Newton’s, Poisson’s, and energetic coefficients of normal restitution for the frictional impact of rigid pendulum against a fixed surface are derived, demonstrating that the upper bound on Newton’s coefficient is smaller than 1, while the upper bound on Poisson’s coefficient is greater than 1. The upper bound on the energetic coefficient of restitution, which is a geometric mean of Newton’s and Poisson’s coefficients of normal restitution, is equal to 1. Lower bound on all three coefficients is equal to zero. The bounds on the tangential impact coefficient, defined by the ratio of the frictional and normal impulses, are also derived. Its lower bound is negative, while its upper bound is equal to the kinetic coefficient of friction. Simplified bounds in the case of a nearly vertical impact are also derived.
Constitutive Modeling of Electrostrictive Polymers Using a Hyperelasticity-Based Approach
Authors: Richards A. W. , Odegard G. M.
Published: October 2009

The use of constitutive equations to describe the electromechanical behavior of electrostrictive materials began over 100 years ago. While these equations have been used to model a host of ceramic-based and polymer-based electroactive materials, a fully characterized model has not yet been developed to predict the response of transversely isotropic polymer electrostrictives. A constitutive model is developed within a thermodynamic and hyperelastic framework that incorporates the transversely isotropic material symmetry that is present in many polymer-based electrostrictives. The resulting constitutive model is characterized for three electrostrictive polymer systems using empirical data that are available in the literature. The model has a relatively simple functional form that is easily adaptable to other polymer electrostrictive material systems.
Diagnostic-Photographic Determination of Drag/Lift/Torque Coefficients of a High Speed Rigid Body in a Water Column
Authors: Chu Peter C. , Fan Chenwu , Gefken Paul R.
Published: October 2009

Prediction of a rigid body falling through water column with a high speed (such as Mk-84 bomb) needs formulas for drag/lift and torque coefficients, which depend on various physical processes such as free surface penetration and bubbles. A semi-empirical method is developed in this study to determine the drag/lift and torque coefficients for a fast-moving rigid body in a water column. The theoretical part is to derive the relationships (called diagnostic relationships) between (drag, lift, and torque) coefficients and (position and orientation) of the rigid body from the three momentum equations and the three moment of momentum equations. The empirical part is to collect data of trajectory and orientation of a fast-moving rigid body using multiple high-speed video cameras (10,000 Hz). Substitution of the digital photographic data into the theoretical relationships leads to semi-empirical formulas of drag/lift and torque coefficients, which are functions of the Reynolds number, attack angle, and rotation rate. This method was verified by 1/12th Mk-84 bomb strike experiment with various tail configurations (tail section with four fins, two fins, and no fin and no-tail section) conducted at the SRI test site. The cost of this method is much lower than the traditional method using the wind tunnel. Various trajectory patterns are found for different tail configurations.
A Mean Line Prediction Method for Axial Flow Turbine Efficiency
Authors: Kacker S. C. , Okapuu U.
Published: October 2009

A mean line loss system is described, capable of predicting the design point efficiencies of current axial turbines of gas turbine engines. This loss system is a development of the Ainley/Mathieson technique of 1951. The prediction method is tested against the “Smith’s chart” and against the known efficiencies of 33 turbines of recent design. It is shown to be able to predict the efficiencies of a wide range of axial turbines of conventional stage loadings to within ± 1 1/2 percent.
Endwall Boundary Layer Flows and Losses in an Axial Turbine Stage
Authors: Hunter I. H.
Published: October 2009

In order to gain an insight into boundary layer phenomena in axial flow turbines, experimental studies were carried out on a large-scale, low speed, single stage machine. Low and high frequency instrumentation supplemented by flow visualizations were used to determine the details of the flows and losses in the stator and rotor blade rows. Measurements of the turbine stator flows, which were obtained at two different inlet wall boundary layer thicknesses, were generally consistent with typical linear cascade observations. A major difference concerned the presence of appreciable radially directed flow. Hot-wire anemometry measurements at the turbine rotor exit, revealed strong secondary flows at the high turning hub section. The flow pattern was seen to be influenced by the spacing between the two rows of blades and by the rotor’s instantaneous position with respect to the periodic flow field arising from the upstream stator row.
A Generalized Mathematical Model to Estimate Gas Turbine Starting Characteristics
Authors: Agrawal R. K. , Yunis M.
Published: October 2009

The paper describes a generalized mathematical model to estimate gas turbine performance in the starting regime of the engine. These estimates are then used to calculate the minimum engine starting torque requirements, thereby defining the specifications for the aircraft starting system. Alternatively, the model can also be used to estimate the start up time at any ambient temperature or altitude for a given engine/aircraft starting system combination.
Preliminary Study on Reheat Combustors for Advanced Gas Turbines
Authors: Mori Kenji , Kitajima Junichi , Kimura Takeshi , Miki Sansei
Published: October 2009

Feasibility studies carried out by the Engineering Research Association for Advanced Gas Turbines under the sponsorship of the Agency of Industrial Science and Technology of Japan have indicated that the thermal efficiency of the combined cycle plant incorporating a high temperature reheat gas turbine and a steam turbine can exceed 50 percent. One of the engine components being investigated is the high temperature reheat combustor which will operate under high temperature (973 K) and heavily vitiated (12.4 percent O2) inlet-air conditions. This paper describes the design considerations on the reheat combustor and the results of the near-atomospheric pressure tests (0.1 ∼ 0.3 MPa) under vitiated conditions, using a conventional can-type combustor and a full scale model of the reheat combustor. Effects of air vitiation on inflammability limits, combustion efficiency, NOx and wall temperatures of gas turbine combustors are discussed.
Rotor Wake Mixing Effects Downstream of a Compressor Rotor
Authors: Ravindranath A. , Lakshminarayana B.
Published: October 2009

An experimental study of rotor wake was conducted in the trailing-edge and near-wake regions of a moderately loaded compressor rotor blade using a rotating triaxial hot-wire probe in a rotating frame of reference. The flow-field was surveyed very close to the trailing-edge as well as inside the annulus and hub-wall boundary layers. The large amount of data acquired during this program has been analyzed to discern the decay effects as well as the spanwise variation of three components of velocity, three components of intensities and three components of shear stresses. The data set also include extensive information on the variation of the flow properties downstream. The other derived quantities include wake momentum thickness and deviation angles at various spanwise and downstream locations. These data are presented and interpreted, with emphasis on the downstream mixing as well as endwall-wake interaction effects.
Premixing and Flash Vaporization in a Two-Stage Combustor
Authors: Sjo¨blom B. G. A.
Published: October 2009

A double recirculation zone two-stage combustor fitted with airblast atomizers has been investigated in a previous work. The present paper describes further tests with premixing tubes in the secondary combustion zone. Flash vaporization was employed to ensure complete vaporization of the secondary fuel, which was heated to 600K by the combustor inlet air. The combustor was run at conditions corresponding to four different engine power settings, and the effect of primary/secondary fuel flow split on emissions was investigated. Tests were also performed with unheated secondary fuel, and comparisons were made with flash vaporization data. The best configuration reduced the oxides of nitrogen by 54 percent, carbon monoxide by 59 percent and unburned hydrocarbons by 97 percent as compared to emission levels for the standard JT8D combustor, which was used as a reference.
Formation of SO3 in Gas Turbines
Authors: Hunter S. C.
Published: October 2009

Sulfur trioxide in gas turbine exhaust contributes to particulate emissions; reduction of this compound is a means for control of particulate emissions. The chemical kinetics of SO3 formation were analyzed for a large stationary gas turbine. The source of SO3 is the reaction of SO2 with oxygen atoms in the downstream end of the combustor primary zone. The primary zone produces SO3 levels of 1 to 2 percent of total SOx. SO3 increases above 1 to 2 percent during air dilution from an equivalence ratio of about 0.5 to 0.35; formation times are on the order of 1 to 10 ms. Reduction of primary zone air flow and more rapid dilution air mixing were identified as means for SO3 reduction. Dilution air mixing in 1 ms was identified as an objective; but would be a difficult task with current combustor designs.
Development of a Small-Scale Catalytic Gas Turbine Combustor
Authors: Anderson S. J. , Friedman M. A. , Krill W. V. , Kesselring J. P.
Published: October 2009

Catalytically supported thermal combustion can provide low NOx emissions with gaseous and distillate fuels while maintaining high combustion efficiency. For stationary gas turbines, catalytic combustion may be the only emerging technology that can cost effectively meet recent federal regulations for NOx emissions. Under EPA sponsorship, a small-scale, catalytic gas turbine combustor was developed to evaluate transient and steady state combustor performance. The combustor consisted of a multiple air-atomizing fuel injector, an opposed jet igniter, and a graded-cell monolithic reactor. System startup, including opposed jet ignition and catalyst stabilization, was achieved in 250 seconds. This time interval is comparable to conventional gas turbines. Steady state operation was performed at 0.505 MPa (5 atmospheres) pressure and 15.3 m/s (50 ft/s) reference velocities. Thermal NOx emissions were measured below 10 ppmv, while fuel NOx conversion ranged from 75 to 95 percent. At catalyst bed temperatures greater than 1422K (2100°F), total CO and UHC emissions were less than 50 ppmv indicating combustion efficiency greater than 99.9 percent. Compared with conventional gas turbine combustors, the catalytic reactor operates only within a relatively narrow range of fuel/air ratios. As a result, modified combustor air distribution or fuel staging will be required to achieve the wide turndown required in large stationary systems.
Use of Cascade and Small Turbine Tests to Determine Erosion of Utility Turbines
Authors: Wenglarz R. A. , Menguturk M.
Published: October 2009

Experiments using cascades and small turbines have been conducted or are being considered to simulate large utility turbine operation with future coal-fired power plants. The purpose of these experiments is to evaluate utility turbine tolerances to particulates and to determine gas cleanup requirements for successful turbine performance. Since these tests do not fully reproduce the flow and erosion conditions in large utility turbines, this paper explores the interpretation of data from simulation experiments to assess erosion in large utility turbines. Effects of physical scale, rotation speed, and pressure differences between test cascades and small test turbines and large utility turbines are considered.
A Theory for Fine Particle Deposition in Two-Dimensional Boundary Layer Flows and Application to Gas Turbines
Authors: Mengu¨turk M. , Sverdrup E. F.
Published: October 2009

A theory is presented to predict deposition rates of fine particles in two-dimensional compressible boundary layer flows. The mathematical model developed accounts for diffusion due to both molecular and turbulent fluctuations in the boundary layer flow. Particle inertia is taken into account in establishing the condition on particle flux near the surface. Gravitational settling and thermophoresis are not considered. The model assumes that the fraction of particles sticking upon arrival at the surface is known, and thus, treats it as a given parameter. The theory is compared with a number of pipe and cascade experiments, and a reasonable agreement is obtained. A detailed application of the model to a turbine is also presented. Various regimes of particle transport are identified, and the range of validity of the model is discussed. An order of magnitude estimate is obtained for the time the turbine stage can be operated without requiring cleaning.
Dual Pressure Steam/Immiscible Liquid Cycles for Gas Turbine Exhaust Heat Recovery
Authors: Burnside B. M.
Published: October 2009

A dual pressure steam/immiscible liquid cycle gas turbine bottoming plant is described. Three variants of the cycle are analysed. It is shown that under typical conditions one of these shows a 5 percent higher output than the conventional steam/steam cycle with only a 5 percent increase in heat extraction from the gas turbine exhaust. A larger LP preheater and condenser are required. Attention is drawn to the flexibility this type of cycle brings to the task of matching bottoming plant to gas turbine exhaust of combined cycles.
An Investigation of Axial Compressor Rotor Aerodynamics
Authors: Dring R. P. , Joslyn H. D. , Hardin L. W.
Published: October 2009

The detailed nature of the three-dimensional flow over the blading, and in the wake, of an isolated compressor rotor has been studied experimentally in a large scale rotating rig. A variety of flow properties were measured including (1) blade profile and endwall surface flow visualization, (2) radial-circumferential arrays of pneumatic wake data acquired in the rotating frame and (3) full-span blade pressure distribution data. Data have been obtained over a wide range of blade loading and downstream location. These results show a hub corner stall at lower blade loadings and full-span blade separation at higher blade loadings. Under both conditions there is strong radial flow on the airfoil. The radial flow in the wake, however, increases dramatically when the blade undergoes full-span separation. The impact of these flow phenomena on the blade pressure distribution is also illustrated.
Spanwise Mixing in Axial-Flow Turbomachines
Authors: Adkins G. G. , Smith L. H.
Published: October 2009

Flow measurements taken in multistage axial-flow turbomachines suggest that substantial spanwise mixing of flow properties often occurs. In addition, measured blade row turnings often show considerable deviation from two-dimensional cascade theory, particularly in the end-wall regions. An approximate method is presented with which both of these effects can be included in design through-flow calculations. The method is based on inviscid, small-perturbation secondary flow theory. Frictional effects are not directly included but secondary flows caused by annulus wall and blade boundary layers are included in an approximate way. The secondary flow model includes effects of 1) main-stream nonfree-vortex flow, 2) end-wall boundary layers, 3) blade end clearances, 4) blade end shrouding, and 5) blade boundary layer and wake centrifugation. The spanwise mixing phenomenon is modeled as a diffusion process, where the mixing coefficient is related to the calculated spanwise secondary velocities. Empirical adjustments are employed to account for the dissipation of the secondary velocities and interactions with downstream blade rows. The induced blade row overturnings are related to the calculated cross-passage secondary velocities. The nature of the assumptions employed restricts the method to design-point-type applications for which losses are relatively small and significant regions of separated flow are not present.
The Reheat Gas Turbine With Steam-Blade Cooling—A Means of Increasing Reheat Pressure, Output, and Combined Cycle Efficiency
Authors: Rice I. G.
Published: October 2009

The reheat (RH) pressure can be appreciably increased by applying steam cooling to the gas-generator (GG) turbine blading which in turn allows a higher RH firing temperature for a fixed exhaust temperature. These factors increase gas turbine output and raise combined-cycle efficiency. The GG turbine blading will approach “uncooled expansion efficiency”. Eliminating cooling air increases the gas turbine RH pressure by 10.6 percent. When steam is used (injected) as the blade coolant, additional GG work is also developed which further increases the RH pressure by another 12.0 percent to yield a total increase of approximately 22.6 percent. The 38-cycle pressure ratio 2400° F (1316° C) TIT GG studied produces a respectable 6.5 power turbine expansion ratio. The higher pressure also noticeably reduces the physical size of the RH combustor. This paper presents an analysis of the RH pressure rise when applying steam to blade cooling.
Cooling Air Flow Characteristics in Gas Turbine Components
Authors: Jen H. F. , Sobanik J. B.
Published: October 2009

An analytical model for the prediction of cooling air flow characteristics (mass flow rate and internal pressure distribution) in gas turbine components is discussed. The model addresses a number of basic flow elements typical to gas turbine components such as orifices, frictional passages, labyrinth seals, etc. Static bench test measurements of the flow characteristics were in good agreement with the analysis. For the turbine blade, the concept of equivalent pressure ratio is introduced and shown to be useful for predicting (i) the cooling air flow rate through the rotor blade at engine conditions from the static rig and (ii) cooling air leakage rate at the rotor serration at engine conditions. This method shows excellent agreement with a detailed analytical model at various rotor speeds. A flow calibration procedure preserving flow similarity for blades and rotor assemblies is recommended.
Interactive Multimode Blade Impact Analysis
Authors: Alexander A.
Published: October 2009

This paper describes the theoretical methodology used in developing an analysis for the response of turbine engine fan blades subjected to soft body (bird) impacts and the computer program that was developed using this methodology as its basis. This computer program is an outgrowth of two programs that were previously developed for the purpose of studying problems of a similar nature (a three-mode beam impact analysis and a multimode beam impact analysis). The present program utilizes an improved missile model that is interactively coupled with blade motion which is more consistent with actual observations. It takes into account local deformation at the impact area, blade camber effects, and the spreading of the impacted missile mass on the blade surface. In addition, it accommodates plate-type mode shapes. The analysis capability in this computer program represents a significant improvement in the development of the methodology for evaluating potential fan blade materials and designs with regard to foreign object impact resistance.
Low NOx and Fuel Flexible Gas Turbine Combustors
Authors: Lew H. G. , DeCorso S. M. , Vermes G. , Carl D. , Havener W. J. , Schwab J. , Notardonato J.
Published: October 2009

The work described in this paper is a part of the DOE/LeRC “Advanced Conversion Technology Project” (ACT). The program is a multiple contract effort with funding provided by the Department of Energy and technical program management provided by NASA LeRC. Testing has been done burning a petroleum distillate fuel (ERBS fuel), a coal derived fuel (SRC II middle distillate), a petroleum residual fuel, and various blends of these fuels. Measurements are made of NOx CO, and UHC emissions, and other measurements are made to evaluate combustor performance. Results to date indicate that rich-lean diffusion flames, with low fuel bound nitrogen conversion, are achievable with very high combustion efficiencies.
Combined Gas and Steam Cycle for a Gas-Cooled Solar Tower Power Plant
Authors: Becker B. , Finckh H. H. , Meyer-Pittroff R.
Published: October 2009

In gas-cooled solar power plants the radiant energy of the sun is transferred to the cycle fluid in a cavity type solar receiver and converted into electric energy by means of a combined gas and steam turbine cycle incorporating a waste heat steam generator. The design and optimization of the energy conversion system in accordance with solar-specific considerations are described with particular regard to the gas turbine. In designing the energy conversion system several variants on the combined cycle with waste heat steam generator are investigated and special measures for the improvement of the cycle efficiency, such as the refinement of the steam process through the addition of pressure stages are introduced. It is demonstrated that the solar power plant meets the requirements both for straight solar and constant load operation with fossil fuel substitution. In order to establish the possibilities of attaining high part-load efficiencies in straight solar operation, two modes, variable and constant speed of the gas turbine, are compared with one another.
Modified Brayton Cycles Utilizing Alcohol Fuels
Authors: Bardon M. F.
Published: October 2009

It is already well known that alcohols can be burned in open-cycle gas turbines by direct firing in the combustor. This paper demonstrates however, that there are significant improvements in thermal efficiency possible by modifying the manner in which alcohols are used in Brayton cycle engines. It is shown that injection of the alcohol during the compression process can materially improve both thermal efficiency and specific work because of the intercooling effect of evaporation. Calculations are given which demonstrate the improvement theoretically possible at representative values of peak turbine inlet temperature. It is also shown that the optimum pressure ratio for both regenerated and unregenerated cycles is different when such compressor evaporative intercooling is used rather than simply injecting the fuel into the combustor.
Nonlinear Damage Cumulation in Solution-Treated and Aged Titanium 6Al-4V
Authors: Adams J. H.
Published: October 2009

A procedure for determining the functional form of the exponent in the nonlinear damage equation from a limited number of block loading fatigue tests is presented. The theory and experimental details are demonstrated for solution-treated and aged Ti 6-4 at 278°C1. The predictive accuracy of the derived functional fit is then shown for additional independent block loading fatigue tests.
Design and Preliminary Results of a Fuel Flexible Industrial Gas Turbine Combustor
Authors: Novick A. S. , Troth D. L. , Yacobucci H. G.
Published: October 2009

The work described in this paper is a part of the DOE/LeRc “Advanced Conversion Technology Project” (ACT). The program is a multiple contract effort with funding provided by the Department of Energy and Technical Program Management provided by NASA LeRc. It is anticipated that future industrial gas turbine engines will require fuel flexibility. The emphasis in this paper is the fuel flexible combustor technology developed under the “Low NOx Heavy Fuel Combustor Concept Program” for application to the Detroit Diesel Allison (DDA) Model 570-K industrial gas turbine engine. The technology, to achieve emission goals, emphasizes dry NOx reduction methods. Due to the high levels of fuel bound nitrogen (FBN) control of NOx can be effected through a staged combustor with a rich initial combustion zone. A RICH/QUENCH/LEAN (RQL) variable geometry combustor is the technology that will be presented to achieve low NOx from alternate fuels containing FBN. The results will focus on emissions and durability for fuel flexible operation.
Low NOx Combustion Systems for Burning Heavy Residual Fuels and High-Fuel-Bound Nitrogen Fuels
Authors: White D. J. , Batakis A. , LeCren R. T. , Yacobucci H. G.
Published: October 2009

The work described in this paper is a part of the Department of Energy/Lewis Research Center (DOE/LeRC) “Advanced Conversion Technology” (ACT) project. The program is a multiple contract effort with funding provided by the Department of Energy and technical program management provided by NASA LeRC. The increasingly critical situation concerning the world’s petroleum supply necessitates the investigation of alternate fuels for use in industrial gas turbines. Environmentally acceptable operation with minimally processed petroleum based heavy residual and coal derived synthetic fuels requires advanced combustor technology. The technology described in this paper was developed under the DOE/NASA Low NOx Heavy Fuel Combustor Concept Program (Contract DEN3-145). Novel combustor concepts were designed for dry reduction of thermal NOx, control of NOx from fuels containing high levels of organic nitrogen, and control of smoke from low hydrogen content fuels. These combustor concepts were tested by burning a wide variety of fuels including a middle distillate (ERBS), a petroleum based heavy residual, a coal derived synthetic (SRC-II), and various ratios of blends of these fuels which included nitrogen doping with pyridine. The results of these tests show promise that low NOx emissions and high efficiencies can be obtained over most of the operating range of a typical industrial gas turbine engine.
Computation of Three-Dimensional Flow Fields Through Rotating Blade Rows and Comparison With Experiment
Authors: Sarathy K. P.
Published: October 2009

A three-dimensional inviscid time-marching calculation solving the unsteady Euler equations in a coordinate system rotating with the blade row has been developed, based on the Denton flow solver. This calculation was used to compute the flow field through the rotor of a transonic axial compressor and compared to measurements made with an advanced laser velocimeter at DFVLR. The comparison is made at design speed at pressure ratio corresponding to peak efficiency. Comparisons of the calculated and experimentally determined Mach number contours indicate excellent agreement in the entrance region where the viscous blockage effects are small. The methodology of the analysis is also described in this paper.
Evaluation of Methods for the Treatment of Mean Stress Effects on Low-Cycle Fatigue
Authors: Doner M. , Bain K. R. , Adams J. H.
Published: October 2009

Several methods proposed for the treatment of mean stress effects on time-independent low cycle fatigue (LCF) lifetime were critically evaluated using LCF crack initiation data on a number of materials used in gas turbine design. The methods evaluated included Jaske’s equivalent strain (εeq) formulation, Manson ’s mean stress correction method and nonlinear Goodman diagram representation of the strain-controlled LCF data. LCF crack initiation data on STA Ti-6-4 (533K), Ti-5522S (783K), IN-706 (866K) and MAR-M246 (1033K) were utilized in the evaluations. The evaluations were carried out in terms of each method’s capability to back-predict the experimetnal data used in its construction. Also considered were the implications associated with the type and the extent of data required for each method.
New Correlations of the Two-Dimensional Turbine Cascade Aerodynamic Performance
Authors: Qiang K. F. , Chen N. X.
Published: October 2009

Theoretical evaluation and experimental research have been conducted to verify the performance of steam and gas turbines, including exhaust turbines of superchargers. The simplified channel method and hydroelectrical analog method have been used to calculate blade surface velocity distribution. Based on the “fully developed turbulence” assumption, viscous effects are approximately taken into account by using the boundary layer theory. Theoretical optimum profile loss coefficients are given. Effects of velocity profile on losses are analyzed. Turbine cascades have the characteristics of high solidity, high setting angle, and high air turning angle, which facilitate the use of the channel concept. On this basis, K. W. Todd’s “passage convergent gradient,” modified O. Zweifel’s “tangential load coefficient” and other effective criteria have been chosen and cascade data correlated. Some relatively accurate semiempirical formulas for predicting the aerodynamic performance of cascades are formulated.
Study of Secondary Flows in Blade Cascades of Turbomachines
Authors: Bario F. , Leboeuf F. , Papailiou K. D.
Published: October 2009

Experiments have been performed with two cascades of turbomachines. The first cascade is composed of highly loaded turbine blades, and has been used in the low subsonic Mach number range. The second cascade consists of highly loaded compressor blades, of the DCA type. The Mach number was then in the high subsonic range. The experimental results are presented in the form of mean values in the pitch direction. Detailed local values are also described. The growth of a passage vortex and a corner effect are presented in the compressor case. Their interactions with the whole flow are analyzed. In the turbine case, the passage vortex is found to be a dominant effect. Results obtained with a theoretical method of calculation of the flow in the blade passage are used to complete the analysis.
Development of Screening Criteria for Selecting Long-Distance Heat Transmission Fluids
Authors: Szepe S. , Calm J. M.
Published: October 2009

Selection criteria are developed for screening liquids for long-distance thermal energy transport. The model used in developing these criteria employs power function approximations for physical and economical relations. Its simplified version provides analytical insights into the optimal allocation of major cost components, as well as a solution for the total transmission cost. The resulting hierarchy of selection criteria can be used for fast screening and ranking of a large number of fluids, thereby eliminating the need for detailed engineering, economic, environmental, and safety studies on fluids which would ultimately prove undesirable. Representative fluids are discussed and compared with transmission by hot water. It is found that most thermal fluids can be rejected, because of less desirable physical properties compared with those of hot water, with the simplest of the criteria presented.
Component Mode Synthesis of Large Rotor Systems
Authors: Li D. F. , Gunter E. J.
Published: October 2009

A scheme is presented for calculating the vibrations of large multi-component flexible rotor systems based on the component mode synthesis method. It is shown that, by a modal expansion of the elastic interconnecting elements, the system modal equation can be conveniently constructed from the undamped eigen representations of the component subsystems. The capability of the component mode method is demonstrated in two examples: a transient simulation of a two-spool gas turbine engine equipped with a squeeze-film damper; and an unbalance response analysis of the Space Shuttle Main Engine oxygen turbopump in which the dynamics of the rotor and the housing are both considered.
Turbulence Characteristics in the Annulus-Wall Boundary Layer and Wake Mixing Region of a Compressor Rotor Exit
Authors: Davino R. , Lakshminarayana B.
Published: October 2009

The flow at the exit of a turbomachinery rotor near the annulus wall is three-dimensional with a varying degree of turbulence and nonisotropic characteristics. The characteristics of the turbulence vary considerably with radial and axial location, blade loading, Reynolds number, free-stream turbulence, and the rotor blade geometry. This paper is concerned with the turbulence properties near the annulus wall region of a moderately loaded compressor blade. The variation of the streamwise, normal, and radial intensities as well as the stresses across the wake, its profile and decay characteristics, were determined with a tri-axial hot-wire probe in the stationary frame of reference. The turbulence characteristics in the annulus-wall region of the rotor exit were found to be highly complex due to the interaction of the blade wake and the annulus wall.
Equivalent Performance Testing of Multisection Compressors
Authors: Strite M. A. , Samurin N. A.
Published: October 2009

Equivalent performance testing of multisection compressors has largely been ignored by the various test codes. Existing code methods have been modified and adapted for testing multisection compressors by the manufacturers and users. The performance testing of two types of multisection units—the externally cooled and the sideload compressor—are discussed here. Each compressor type has had specific test difficulties that require identification and resolution. Prior to the start of testing, an overview of the problems, along with some solutions, is presented.
Engine Dynamic Analysis With General Nonlinear Finite-Element Codes, Part 1: Overall Approach and Development of Bearing Damper Element
Authors: Adams M. L. , Padovan J. , Fertis D. G.
Published: October 2009

There is currently a considerable interest and level of activity in developing computational schemes to predict general engine dynamic behavior. The general feeling among researchers working on engine vibration problems is that various modes of operation, such as blade-loss events, require a high level of analysis sophistication to realistically model the engine. Proper account of system nonlinearities (particularly at the bearings, dampers and rubs) appears to be necessary if analytical predictions are to be realistic. The approach described in this paper seeks to make use of already proven general finite-element nonlinear time-transient computer codes which are available on the open market. The work specifically described in this paper covers the first phase of a three-phase NASA-Lewis-sponsored research grant on engine dynamic simulation with available finite element codes. The first phase was concentrated on the development of a bearing-damper element computer software package suitable for “plug-in” to available finite element codes.
Ceramic to Metal Attachment Using Low Modulus BRUNSBOND® Pad
Authors: Tolokan R. P. , Nablo J. C. , Brady J. B.
Published: October 2009

BRUNSBOND® Pad is a low modulus sintered fiber metal material developed for attaching high temperature ceramic coatings to metal substrates. The fiber metal pad acts as a compliant strain absorbing interlayer to accomodate the differences in thermal expansivity and operating temperature between the ceramic and metal substrate. Ceramic coatings, 0.060 – 0.125 in. thick, remain intact on metal substrates through severe multiple cycle thermal excursions. The fiber metal pad is comparable in insulating value to the ceramic coating. Applications include ceramic thermal barrier coatings for high temperature gas turbine engine seals and combustors, MHD electrodes, and internal combustion engine insulators.
Fabrication of Injection Molded Sintered Alpha SiC Turbine Components
Authors: Storm R. S. , Ohnsorg R. W. , Frechette F. J.
Published: October 2009

Fabrication of a sintered alpha Silicon Carbide turbine blade by injection molding is described. An extensive process variation matrix was carried out to define the optimum fabrication conditions. Variation of molding parameters had a significant impact on yield. Turbine blades were produced in a reasonable yield which met a rigid quality and dimensional specification. Application of injection molding technology to more complex components such as integral rotors is also described.
Water-Cooled Gas Turbine Monometallic Nozzle Fabrication and Testing
Authors: Schilke P. W. , DeGeorge C. L.
Published: October 2009

This paper describes the fabrication and testing of the second-stage monometallic water-cooled nozzles for the Department of Energy funded High-Temperature Turbine Technology (HTTT) program. The materials and processes development work required to fabricate these nozzles has been reported in an earlier paper. The fabrication of these nozzles—including investment casting, Shaped Tube Electrolytic Machining (STEM), Electrode discharge Machining (EDM), conventional machining, and brazing—is described. The testing of these nozzles in a static hot-gas path development test stand is also described, and the results of this testing are discussed in terms of the overall component design goals.
The Effect of Bending-Torsion Coupling on Fan and Compressor Blade Flutter
Authors: Bendiksen O. O. , Friedmann P. P.
Published: October 2009

A study of the effects of bending-torsion interaction of the flutter boundaries of turbomachinery blading is presented. The blades are modeled as equivalent sections, and the equations of motion allow for the general case of structural, inertial and aerodynamic coupling, in the presence of structural damping. Two different speed regimes are investigated: incompressible flow, and supersonic flow with a subsonic leading edge locus. Flutter boundaries are presented for cascade design parameters representative of current technology fan rotors. These results illustrate that bending-torsion interaction has a pronounced effect on the flutter boundaries for both speed regimes, although the mode frequencies show no appreciable tendency to coalesce as flutter is approached. Several cases of bending branch instability were observed, without incorporating the effects of finite mean lift or strong shocks in the analysis.
Nuclear Blast Response of Airbreathing Propulsion Systems: Laboratory Measurements With an Operational J-85-5 Turbojet Engine
Authors: Dunn M. G. , Rafferty J. M.
Published: October 2009

This paper describes an experimental technique that has been developed for the performance of controlled laboratory measurements of the nuclear blast response of airbreathing propulsion systems. The experiments utilize an available G.E. J-85-5 turbojet engine located in the test section of the Calspan Ludwieg-tube facility. Significant modifications, described herein, were made to this facility in order to adapt it to the desired configuration. The J-85 engine had previously been used at Calspan for other purposes and thus came equipped with eight pressure transducers at four axial locations along the compressor section. These transducers have a frequency response on the order of 40 KHz. Pressure histories obtained at several circumferential and axial locations along the compressor are presented for blast-wave equivalent overpressures up to 17.2 kPa (2.5 psi) at corrected engine speeds on the order of 94 percent of maximum speed.
The Influence of Blade Number Ratio and Blade Row Spacing on Axial-Flow Compressor Stator Blade Dynamic Load and Stage Sound Pressure Level
Authors: Gallus H. E. , Grollius H. , Lambertz J.
Published: October 2009

In axial-flow turbomachines considerable dynamic blade loads and noise production occur as a result of the unsteady blade row interaction between rotor and stator blades. This paper presents results of midspan measurements of the dynamic pressure distribution on the stator blade surface (fixed number of blades) for various rotor-blade numbers and various axial clearances between rotor and stator. For this purpose, one stator blade had been provided with eleven semiconductor pressure transducers in the midspan section. Simultaneously, the sound pressure level was measured at two axial distances downstream of the stator by four condensator microphones distributed along the circumference in each of the two sections and mounted flush with the wall surface. The wake-flow distribution downstream of the rotor could be obtained by a rotating three-hole pressure probe. The results of the corresponding dynamic pressure-measurements and noise measurements are discussed and compared with results from theory.