bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling of Three-Dimensional Flow in Turning Channels
Authors: Khalil I. M. , Weber H. G.
Published: October 2009

The structure of developing flows inside curved channels has been investigated numerically using the time-averaged Navier Stokes equations in three dimensions. The equations are solved in primitive variables using finite difference techniques. The solution procedure involves a combination of repeated space-marching integration of the governing equations and correction for elliptic effects between two marching sweeps. Type-dependent differencing is used to permit downstream marching even in the reverse-flow regions. The procedure is shown to allow efficient calculations of turbulent flow inside strongly curved channels as well as laminar flow inside a moderately curved passage. Results obtained in both cases indicate that the flow structure is strongly controlled by local imbalance between centrifugal forces and pressure gradients. Furthermore, distortion of primary flow due to migration of low momentum fluid caused by secondary flow is found to be largely dependent on the Reynolds number and Dean number. Comparison with experimental data is also included.
The Integrated Approach to a Gas Turbine Topping Cycle Cogeneration System
Authors: Leibowitz H. , Tabb E.
Published: October 2009

Under Gas Research Institute (GRI) sponsorship, a new gas turbine cogeneration system was developed by Mechanical Technology, Inc., (MTI) for installation at a General Motors plant in early 1985. Specific emphasis was placed on system integration. A single, prime-reliable drive train and a single control center replace a wide assortment of nonintegrated, free-standing power drives and control centers. On-line availability, installation costs, and overall user acceptance are improved. The cogeneration set produces 3 MWe and 8,860 kg/hr (19,500 lb/hr) of 1825 kPa (250 psig) saturated steam using an Allison 501-KH gas turbine and a natural circulation waste heat boiler. The system is designed for multifuel operation using either natural gas or distillate oil. A steam injection feature is employed to increase output to 4 MWe when process steam demand diminishes. The system is prepackaged, skid mounted, and delivered in four modules: one each for the machinery, duct burner, waste heat boiler, and controls.
Thermodynamics of an Isothermal Gas Turbine Combined Cycle
Authors: El-Masri M. A. , Magnusson J. H.
Published: October 2009

The isothermal (or multiple-reheat) gas turbine performs the combustion/work extraction process at a sustained, elevated temperature. This has distinct thermodynamic advantages in combined cycles for given peak temperature constraints. A thermodynamic model for this cycle is developed. Although based on a simple CO/CO2/O2 chemcial system the results are applicable to other reactants and dilutants. Combined cycle efficiency is reported for different gas turbine pressure ratios, peak temperatures, reactant dilution and steam cycle conditions. The range of parameters investigated starts from present-day advanced technologies and examines the potential of higher pressures and temperatures. Balances of thermodynamic availability are used to interpret the results. They show that for a given steam cycle and gas turbine pressure ratio, increasing peak temperature beyond a certain value provides sharply diminishing return. This is because the reduction in combustion irreversibility is offset by increased heat transfer irreversibility. Higher pressure ratios or steam cycle temperatures can raise this optimum peak temperature. In view of the various technological constraints, the authors’ conclusion is that an isothermal gas turbine with a peak temperature and pressure-ratio of about 1600K and 100:1, respectively, represents the most promising next step in technology. Coupled with existing advanced steam cycles this should provide efficiencies in the 60 percent range.
A Numerical Model of Moist Plume Thermodynamics
Authors: Becker B. R.
Published: October 2009

Evaporative cooling towers and cooling ponds are in ever-increasing use for the dissipation of waste heat. The modeling of moist plumes from these facilities has received considerable attention in recent years. The simulation of plume thermodynamics is a necessary part of the modeling of a moist plume. This paper describes an algorithm which, when supplied with the ambient atmospheric distribution of various thermodynamic properties, performs the necessary psychrometric calculations to simulate the thermodynamics within the moist plume. A unique feature of this algorithm is the modeling of the condensation of “excess” water vapor, which simulates the formation and deposition of water droplets from the moist plume.
Total Absorptivities and Emissivities of Particulate Coal Ash From Spectral Band Emissivity Measurements
Authors: Wall T. F. , Becker H. B.
Published: October 2009

Previous measurements of the spectral emissivity of coal ashes are converted to total absorptivities and emissivities. Below the temperature at which ash sinters, the total absorptivity of an ash layer—which is necessary for the estimation of radiative transfer in furnaces—is shown to depend on both the source (flame) temperature and the ash temperature. Synthetic mixtures of the oxides Al2O3, SiO2, and Fe2O3 are shown to give the same trends as those for ashes of the same Fe2O3 content.
Development of a Dry Low NOx Combustor for a 120-MW Gas Turbine
Authors: Aoyama K. , Mandai S.
Published: October 2009

Two stage premixed combustor with variable geometry has been developed to meet stringent NOx goals in Japan without the use of water or steam injection. This combustion system is planned to be applied for 120-MW gas turbine in 1090-MW LNG combined cycle plant. The full-pressure, full-scale combustion tests were conducted over a wide range of operating conditions for this gas turbine. The combustion tests proved that NOx levels as well as mechanical characteristics were well within the goals.
Repowering in Steel Works by Introducing a Blast-Furnace, Gas-Firing Gas Turbine
Authors: Muyama A. , Hiura H. , Morimoto K.
Published: October 2009

A 14-MW, high-temperature gas turbine firing extremely low-BTU, blast-furnace gas was developed and installed in a steel works of Japan as a repowering unit. Field tests proved the stable combustion up to 590 Kcal/Nm3 calorific value and plant efficiency improvement of up to 60 percent on existing steam plant. Design features and two years operational experiences are presented.
Crude Oil Burning Experience in MS5001P Gas Turbines
Authors: Bunz W. J. , Ziady G. N. , Doering H. vonE. , Radice R. J.
Published: October 2009

At Qaisumah, Saudi Arabia, there are four GE MS5001P Gas Turbines operated by the Saudi Consolidated Electric Company in the Eastern Province (SCECO East). The Power Plant is not connected to the main SCECO grid and experiences near-capacity peak load demands in the summer months. Its remoteness and proximity to the Trans-Arabian Pipeline (TAPLINE) dictates the burning of Light Saudi Arabian Crude Oil which is desalted by centrifugal purification without the addition of wash water. Eliminating the need for wash water is important because of the scarcity of water at this site. Power loss is controlled and shutdowns minimized during the critical summer months by removing the ash accumulation on the turbine components by on-line nutshell cleaning. This paper describes the first application of this waterless (dry centrifuge) fuel purification system and the impact of various turbine cleaning methods (particularly on-line nutshelling) on turbine performance, availability, and maintenance.
An Experimentally Verified NOx Prediction Algorithm Incorporating the Effects of Steam Injection
Authors: Touchton G. L.
Published: October 2009

A Perfectly Stirred Reactor model, kinetic rate data, and equilibrium adiabatic flame temperatures have been incorporated into a closed form NOx prediction algorithm. The algorithm accounts for combustor inlet parameters and steam injection. Combining this model with the operating map for the gas turbine allows prediction of NOx with variation in parameters such as inlet guide vane angle, ambient temperature, and load. If the actual values of the model input variables are measured, real time prediction of NOx emissions may be generated using a microcomputer. This signal may then be used as an input to NOx abatement systems such as Selective Catalytic Reduction. The semitheoretical technique is based upon the extended Zeldovich chain reaction kinetics for the production of NOx in the post-flame zone. The temperature and concentration of major product species in the post-flame zone are taken to be those appropriate to equilibrium. Steam injection and inlet effects enter the model through their influence on the abiabatic equilibrium flame temperature. Mixing effects are accounted for empirically.
Water-Ethanol-Gasoline Blends—Physical Properties, Power, and Pollution Characteristics
Authors: Rajan S.
Published: October 2009

Factors relevant to the utilization of nonanhydrous ethanol as a blending component with gasoline for use in current on-the-road spark ignition engines are investigated. Miscibility limits are determined and key physical properties important for proper engine operation are measured. Dynamometer tests on an unmodified production engine with hydrated ethanol-gasoline blends containing varying percentages of water show potential for increased thermal efficiency and reduced oxides of nitrogen emissions.
Simulation of Fuel Droplet Gasification in SI Engines
Authors: Liu X. Q. , Wang C. H. , Law C. K.
Published: October 2009

The heating and gasification of a fuel droplet during the intake and compression strokes of an SI engine are modeled. Results show that the simultaneous increases in the gas temperature and pressure during compression tend to have compensatory effects on the droplet gasification rate such that it remains somewhat insensitive to changes in the cylinder environment. Generalized results are presented allowing for the assessment of the lower and upper bounds in the initial size of the droplet that can achieve complete gasification prior to the end of the compression stroke.
Centrifugal Fan Performance With Distorted Inflows
Authors: Wright T. , Madhavan S. , DiRe J.
Published: October 2009

Efforts to quantify degradation of the performance of a centrifugal fan subjected to distorted inflows are presented. The study centered on examination of pressure rise, efficiency, and onset of stall for a backwardly-inclined, airfoil-bladed fan. Nonuniform flow patterns were generated in an adjustable countervane damper assembly installed upstream of the inlet box, and systematic families of performance curves were generated. Results of these tests show that significant degradation in efficiency and pressure rise—as much as 10 to 15 percent—may result from moderately to severely distorted inflow patterns. Onset of stall was significantly influenced by severely distorted inflows.
Centrifugal Fan Performance With Inlet Clearance
Authors: Wright T.
Published: October 2009

This paper describes a systematic study of the influence of the inlet clearance gap on the performance of a centrifugal fan. Overall fan performance in terms of volume flow rate, pressure rise, stall margin, and efficiency were measured over a range of values of the radial clearance between the impeller and the stationary inlet cone. These data have been correlated as functions of lumped clearance parameters. Additional data on velocity surveys in the impeller discharge are presented and discussed in relation to overall performance.
Effects of Cooling Films on the Heat Transfer Coefficient on a Flat Plate With Zero Mainstream Pressure Gradient
Authors: Hay N. , Lampard D. , Saluja C. L.
Published: October 2009

The influence of injection of cooling films through a row of holes on the heat transfer coefficient on a flat plate is investigated for a range of mass flux ratio using a heat-mass transfer analogy. Injection angles of 35 deg and 90 deg are covered. The experimental technique employed uses a swollen polymer surface and laser holographic interferometry. The results presented show the change in local heat transfer coefficient over the no-injection values at the centerline and off-centerline locations for various streamwise stations. The effect of injection on laterally averaged heat transfer coefficients is also assessed.
Effect of Surface Roughness on Film Cooling Performance
Authors: Goldstein R. J. , Eckert E. R. G. , Chiang H. D. , Elovic E.
Published: October 2009

An experimental investigation of film cooling on a rough surface has been performed using a mass transfer technique. Two injection geometries (one and two rows of holes) and six roughness patterns were used. The density of the injected gas was close to that of the free-stream air. The presence of roughness causes a decrease in the spanwise-averaged effectiveness for both injection geometries at low blowing rates, and an increase in the effectiveness for one-row injection at high blowing rates, but not for two-row injection. The results for two-row injection (with or without roughness) can be correlated by a parameter used to correlate slot-injection data. The influence of roughness pattern on the average effectiveness and on the lateral uniformity of the effectiveness is described.
Acoustic Emission Evaluation of Plasma-Sprayed Thermal Barrier Coatings
Authors: Berndt C. C.
Published: October 2009

Acoustic emission techniques have recently been used in a number of studies to investigate the performance and failure behavior of plasma-sprayed thermal barrier coatings. Failure of the coating is a complex phenomena, especially when the composite nature of the coating is considered in the light of possible failure mechanisms. Thus it can be expected that both the metal and ceramic components (i.e., the bond coat and ceramic overlay) of a composite thermal protection system influence the macroscopic behavior and performance of the coating. The aim of the present work is to summarize the “state-of-the-art” in terms of this initial work and indicate where future progress may be made.
Vibration Characteristics of the HPOTP (High-Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine)
Authors: Childs D. W. , Moyer D. S.
Published: October 2009

A review is presented of various rotordynamic problems which have been encountered and eliminated in developing the current flight engines and of continuing subsynchronous problems which are being encountered in developing a 109 percent power level engine. The basic model for the HPOTP, including the structural dynamic model for the rotor and housing and component models for the liquid and gas seals, turbine-clearance excitation forces, and impeller-diffuser forces, are discussed. Results from a linear model are used to examine the synchronous response and stability characteristics of the HPOTP, examining bearing load and stability problems associated with the second critical speed. Various seal modifications are examined and shown to have favorable consequences with respect to bearing reactions and stability. Differences between linear and nonlinear model results are discussed and explained in terms of simple models. The transient nonlinear model is used to demonstrate forced subsynchronous motion similar to that observed in test data for models which are lightly damped but stable. The subsynchronous motion results from bearing clearance nonlinearities. Simulation results indicates that synchronous bearing loads can be reduced but that sub-synchronous motion is not eliminated by seal modifications.
Experimental Analysis of Damper Behavior of Squeeze Film Dampers for Gas Turbine Engines
Authors: Kaushal S. C. , Kumar V. A. , Lakshmikantan K.
Published: October 2009

This paper discusses the experimental evaluation of performance of squeeze film dampers without centralizing retaining springs. Rotor amplitudes in the damper plane and damping coefficient have been considered to assess the system performance. Tests were conducted on two damper configurations that were to go in the rotor assembly of a certain gas turbine engine. Land width and film thickness were varied, and experiments were conducted for different values of excitation frequency, oil supply pressure, and unbalance. The test program showed that the parameters are to be individually optimized to obtain better overall performance in the damper systems without centralizing springs. The damper configurations subjected to severe dynamic conditions due to unbalance on overhung mass were also experimentally analyzed.
An Experimental Investigation of Oil-Buffered Shaft Seal Flow Rates
Authors: Shade W. N. , Hampshire D. E.
Published: October 2009

An experimental investigation was conducted to identify an optimum oil-buffered shaft seal for use on centrifugal compressors, with the primary objective being minimal seal oil exposure to process gases that cause seal oil degradation or are toxic. Types of seals tested included smooth bore cylindrical bushings, spiral groove cylindrical bushings, radial outward-flow face seals, and radial inward-flow face seals. The influence of shaft speed, gas pressure, seal oil differential pressure, oil bypass flow rate, and oil supply temperature on process side seal oil flow rate was determined. The investigation revealed some surprising relationships between seal oil flow rates and the escape of process gas.
Thrust Load Measurement on Aero-Engine Bearing
Authors: Jimboh K. , Aono H. , Chikata T. , Hagiwara Y. , Nakasu K. , Hoshino T.
Published: October 2009

Aero-engine bearings operate in an extraordinarily high speed range (high DN number) and severe conditions. It is especially necessary to measure and adjust the bearing thrust load in the engine development phase, but it is very difficult to measure the thrust load accurately, because bearings and bearing housings are subjected to elevated temperature and oil environment. Open space permitted for installation of thrust measurement transducers is small and limited around the bearing housing. We tried to measure the thrust load by applying “Unit Cells,” which are installed between bearing and bearing housing. “Unit Cells” which have been specially designed to measure the bearing thrust load are very small and temperature-compensated load cells. We have been successful in measuring the actual thrust load using the above “Unit Cells,” both in the steady-state and transient condition. Repeatability and hysteresis of the data have been satisfactory. We have established the effect of seal clearance on the thrust load by the measurement. We also have obtained the dynamic characteristics of the thrust load versus rotor speed in low bypass fan engines. Procedure and obtained data are presented in detail.
A Blade Loss Response Spectrum for Flexible Rotor Systems
Authors: Alam M. , Nelson H. D.
Published: October 2009

A shock spectrum procedure is developed to estimate the peak displacement response of linear flexible rotor-bearing systems subjected to a step change in unbalance (i.e., a blade loss). A progressive and a retrograde response spectrum are established. These blade loss response spectra are expressed in a unique non-dimensional form and are functions of the modal damping ratio and the ratio of rotor spin speed to modal damped whirl speed. Modal decomposition using complex modes is utilized to make use of the unique feature of the spectra for the calculation of the peak blade loss displacement response of the rotor system. The procedure is applied to three example systems using several modal superposition strategies. The results of each are compared to true peak displacements obtained by a separate transient response program.
The Interaction Between Mistuning and Friction in the Forced Response of Bladed Disk Assemblies
Authors: Griffin J. H. , Sinha A.
Published: October 2009

This paper summarizes the results of an investigation to establish the impact of mistuning on the performance and design of blade-to-blade friction dampers of the type used to control the resonant response of turbine blades in gas turbine engines. In addition, it discusses the importance of friction slip force variations on the dynamic response of shrouded fan blades.
Observations on the Interaction of High Mean Stress and Type II Hot Corrosion on the Fatigue Behavior of a Nickel Base Superalloy
Authors: Allen J. M. , Whitlow G. A.
Published: October 2009

A study measuring the effects of a molten sulfate/chloride salt on the creep/fatigue behavior of a nickel base turbine blade superalloy, Udimet 720, at 1300°F (704°C) is described. Cyclic stress–cycles to failure (S-N) curves were generated at high mean stress levels, with mean stress, maximum stress, or the ratio of minimum to maximum stress (R ratio) held constant. In salt, it was found that when maximum stress is above the yield, with the cyclic component 20 percent of the maximum, failure occurs by stress corrosion fatigue in orders of magnitude less time than for corresponding loading conditions in air. It is significant, from a failure analysis point of view, that fatigue fracture is intergranular in these circumstances. Similar fatigue behavior may be expected for other nickel base alloys, however, at substantially lower maximum stresses in as much as Udimet 720 exhibits superior short time rupture strength, i.e., resistance to this form of stress corrosion, over the other blade alloys evaluated in this environment.
Deformation of Curved Bars With Creep
Authors: Lau J. H. , Hu C. K.
Published: October 2009

An exact analysis is presented for the creep deformation of a curved bar subjected to the simultaneous actions of bending moment and axial force. Dimensionless interaction curves and charts, which relate the variables, axial force, location of neutral axis, maximum stress and strain rate, bending moment, and change in curvature rate, are also provided for engineering practice convenience. The constitutive relationship of the curved bar is described by the Prandtl-Nadai Creep Law.
Some Practical Aspects of Staged Premixed, Low Emissions Combustion
Authors: Sotheran A. , Pearce D. E. , Overton D. L.
Published: October 2009

An experimental program to research, develop, and demonstrate an axially staged, premixed low emissions combustor is described, with particular emphasis on the many mechanical and thermal problems which were encountered and which seem characteristic of the type. Of these, the risks of autoignition and flashback in the premixing duct were perhaps, the most severe. Their elimination imposed severe constraints on premixing duct geometry and indeed, dictated the layout of the whole combustor. Nevertheless, it proved possible to retain conventional technology to a large extent including the basic combustor structure and mounting arrangements and normal fuel injector accessibility. Large emissions reduction capability was demonstrated to be possible though not within conventional combustor dimensions.
Optical Measurements of Soot Size and Number Density in a Spray-Atomized, Swirl-Stabilized Combustor
Authors: Wood C. P. , Samuelsen G. S.
Published: October 2009

In-flame optical measurements of soot particulates in a turbulent, recirculating (i.e., complex flow) model laboratory combustor are described. A nonintrusive optical probe based on large-angle (60 and 20 deg) intensity ratio scattering was used to yield a point measurement of soot particulate in the size range of 0.08 to 0.38 μm. A shale-derived JP-8 stock, isooctane, and mixtures of isooctane with various ring and aromatic compounds blended to yield the smoke point of the JP-8 stock were separately injected as a liquid spray through a twin-fluid atomizer. One blend was also introduced prevaporized through a hollow-cone nozzle. The addition of ring compounds to the base isooctane as well as operation on JP-8 increased the amount of soot produced, although the total amount of soot produced depended on fuel type for those fuels of equivalent smoke point. The spatial distribution of soot as well as the amount produced was found to be sensitive to nozzle atomization quality and injection momentum. The amount of soot produced was reduced by a reduction in fuel loading. However, injection of fuel in a prevaporized state both increased the amount of soot produced and changed spatially the region over which soot was distributed. Scanning electron micrographs of extracted samples established that the optical technique resolved the large particle wing of the soot size distribution.
Free-Stream Turbulence and Pressure Gradient Effects on Heat Transfer and Boundary Layer Development on Highly Cooled Surfaces
Authors: Rued K. , Wittig S.
Published: October 2009

Heat transfer and boundary layer measurements were derived from flows over a cooled flat plate with various free-stream turbulence intensities (Tu = 1.6–11 percent), favorable pressure gradients (k = νe/ue2•due/dx = 0÷6•10−6) and cooling intensities (Tw/Te = 1.0–0.53). Special interest is directed towards the effects of the dominant parameters, including the influence on laminar to turbulent boundary layer transition. It is shown, that free-stream turbulence and pressure gradients are of primary importance. The increase of heat transfer due to wall cooling can be explained primarily by property variations as transition, and the influence of free-stream parameters are not affected.
Effects of the Condition of the Approach Boundary Layer and of Mainstream Pressure Gradients on the Heat Transfer Coefficient on Film-Cooled Surfaces
Authors: Hay N. , Lampard D. , Saluja C. L.
Published: October 2009

This paper describes an investigation of the sensitivity of the heat transfer coefficient under the film to the state of the approach boundary layer for injection through a row of holes on a flat plate. The investigation is done for a range of blowing parameters using a heat-mass transfer analogy. Injection angles of 35 deg and 90 deg are covered. Additionally, for the same injection geometries, the effect of injection in the presence of mild adverse, mild favorable, and strong favorable mainstream pressure gradients is investigated. The results indicate that the heat transfer coefficient under the film is sensitive neither to the condition of the approach boundary layer nor to the presence of a mild adverse pressure gradient, but it is significantly lowered by a favorable pressure gradient, particularly at low blowing parameters.
Calculation of the Three-Dimensional, Steady, Inviscid Flow in a Transonic Axial Turbine Stage
Authors: Arts T.
Published: October 2009

The aim of this paper is to develop an approach to compute the three-dimensional, rotational, adiabatic, inviscid flow of a perfect gas in a transonic axial turbine stage. The time-dependent Euler equations, expressed in a cylindrical coordinate system, are solved using a time-marching method and a finite volume approach. The absolute flow is calculated in the stator, whereas the relative flow is computed in the rotor. A time-averaged blade row interaction is assumed. The method is applied to a transonic single-stage turbine. The calculated results agree well with the measured performance and three-dimensional aspects of the flow appear clearly.
Solution of Transonic S1 Surface Flow by Successively Reversing the Direction of Integration of the Stream Function Equation
Authors: Wang Zhengming
Published: October 2009

In the solution of the stream function equation on an S1 relative stream surface with transonic velocities, the occurrence of two values of the density is avoided by using a method of combining simple iteration with an integration method. In this method, the direction of integration is successively reversed, i.e., the starting line for the integration is varied from iteration to iteration. The governing equations are therefore satisfied as fully as possible during each iteration, and the procedure leads to rapid convergence. The method uses nonorthogonal curvilinear coordinates and artificial compressibility. The technique can be used to calculate transonic S1 surface flows, with either subsonic or supersonic inlet velocities. Example calculations indicate that the method is very effective.
Computation of Potential Flow on S2 Stream Surface for a Transonic Axial-Flow Compressor Rotor
Authors: Lu¨ Pan-Ming , Wu Chung-Hua
Published: October 2009

A set of conservative full potential function equations governing the fluid flow along a given S2 streamsurface in a transonic axial compressor rotor was obtained. By the use of artificial density and a potential function/density iteration, this set of equations can be solved, and the passage shock on the S2 streamsurface can be captured. A computer program for this analysis problem has been developed and used to compute the flow field along a mean S2 streamsurface in the DFVLR transonic axial compressor rotor. A comparison of computed results with DFVLR L2F measurement at 100 percent design speed shows fairly good agreement.
An Inviscid Blade-to-Blade Prediction of a Wake-Generated Unsteady Flow
Authors: Hodson H. P.
Published: October 2009

This paper describes a time-marching calculation of the unsteady flow generated by the interaction of upstream wakes with a moving blade row. The inviscid equations of motion are solved using a finite volume technique. Wake dissipation is modeled using an artificial viscosity. Predictions are presented for the rotor mid-span section of an axial turbine. Reasonable agreement is found between the predicted and measured unsteady blade surface static pressures and velocities. These and other results confirm that simple theories can be used to explain the phenomena of rotor-stator wake interactions.
An Experimental Study of the Compressor Rotor Blade Boundary Layer
Authors: Pouagare M. , Galmes J. M. , Lakshminarayana B.
Published: October 2009

The three-dimensional turbulent boundary layer developing on a rotor blade of an axial flow compressor was measured using a minature “x” configuration hot-wire probe. The measurements were carried out at nine radial locations on both surfaces of the blade at various chordwise locations. The data derived includes streamwise and radial mean velocities and turbulence intensities. The validity of conventional velocity profiles such as the “power law profile” for the streamwise profile, and Mager and Eichelbrenner’s for the radial profile, is examined. A modification to Mager’s crossflow profile is proposed. Away from the blade tip, the streamwise component of the blade boundary layer seems to be mainly influenced by the streamwise pressure gradient. Near the tip of the blade, the behavior of the blade boundary layer is affected by the tip leakage flow and the annulus wall boundary layer. The “tangential blockage” due to the blade boundary layer is derived from the data. The profile losses are found to be less than that of an equivalent cascade, except in the tip region of the blade.
Surface Static Pressures in an Inlet Vortex Flow Field
Authors: Liu W. , Greitzer E. M. , Tan C. S.
Published: October 2009

An experimental investigation of the three-dimensional flow field associated with an inlet vortex is reported. The specific configuration investigated is an inlet, in proximity to a ground plane, in crosswind. Parametric data are presented to define the regimes of vortex formation in this configuration, as a function of inlet height to diameter ratio and inlet velocity ratio. The detailed static pressure distribution on the inlet is given for two quite different flow regimes, one with a strong inlet vortex and one with no inlet vortex. These new quantitative data are supplemented by flow visualization studies that allow an estimate to be made of the circulation around the inlet vortex. It is argued that the static pressure distributions in both cases can be clearly interpreted using the basic ideas of inlet vortex formation that were previously developed from (qualitative) water tunnel studies.
Optimization and Mechanisms of Mistuning in Cascades
Authors: Crawley E. F. , Hall K. C.
Published: October 2009

An inverse design procedure has been developed for the optimum mistuning of a high bypass ratio shroudless fan. The fan is modeled as a cascade of blades, each with a single torsional degree of freedom. Linearized supersonic aerodynamic theory is used to compute the unsteady aerodynamic forces in the influence coefficient form at a typical blade section. The mistuning pattern is then numerically optimized using the method of nonlinear programming via augmented Lagrangians. The objective of the mistuning is to achieve a specified increase in aeroelastic stability margin with a minimum amount of mistuning. It is shown that a necessary but not sufficient condition for aeroelastic stability is that the blades be self-damped. If this condition is met, an optimized mistuning pattern can be found that achieves a given stability margin for a much lower level of mistuning than is required for the alternate mistuning pattern. However, small errors in the implementation of the optimum mistuning pattern severely reduce the anticipated gains in stability margin. These small errors are introduced by the manufacturing process and by the approximation of the optimum mistuning pattern by patterns of a few discrete blade frequencies. Alternate mistuning, which requires only two blade frequencies, is shown to be relatively insensitive to errors in implementation.
Investigation of Flow Phenomena in a Transonic Fan Rotor Using Laser Anemometry
Authors: Strazisar A. J.
Published: October 2009

Several flow phenomena, including flow field periodicity, rotor shock oscillation, and rotor shock system geometry have been investigated in a transonic low aspect ratio fan rotor using laser anemometry. Flow periodicity is found to increase with increasing rotor pressure rise and to correlate with blade geometry variations. Analysis of time-accurate laser anemometer data indicates that the rotor shock oscillates about its mean location with an amplitude of 3–4 percent of rotor chord. The shock surface is nearly two-dimensional for levels of rotor pressure rise at and above the peak efficiency level but becomes more complex for lower levels of pressure rise. Spanwise shock lean generates radial flows due to streamline deflection in the hub-to-shroud streamsurface.
Axial Compressor Stator Aerodynamics
Authors: Joslyn H. D. , Dring R. P.
Published: October 2009

Axisymmetric, through-flow calculations, currently the “backbone” of most multistage turbomachinery design systems, are being pushed to their limit. This is due to the difference between the complex, three-dimensional flows that actually occur in turbomachinery and the two-dimensional flow assumed in this type of analysis. To foster the development of design analyses that account more accurately for these three-dimensional effects, there is a need for detailed flow field data in a multistage environment. This paper presents a survey of the initial results from a detailed experimental study of the aerodynamics of the second stage of a large scale, two-stage axial compressor. Data were acquired over a range of flow coefficients. The data presented here are for the second stator and include airfoil and endwall flow visualization, and radial-circumferential traverse measurements presented in the form of fullspan contour plots of total pressure. Also presented are the spanwise distributions of total and static pressures, axial velocity, air angles, and blockage. The effect of increased loading on the growth of the hub corner stall and its impact on these parameters is discussed.
A Theoretical Model for Rotating Stall in the Vaneless Diffuser of a Centrifugal Compressor
Authors: Frigne P. , Van den Braembussche R.
Published: October 2009

A theoretical model for rotating stall in the vaneless diffuser of a centrifugal compressor is presented. It consists of a time-evolutive calculation of the strong interaction between the inviscid flow core and the unsteady boundary layers along the walls. It is shown that, depending on the diffuser geometry and the diffuser inlet flow angle, a transient perturbation of the outlet static pressure will generate a rotating flow pattern, if the periodicity of this perturbation corresponds to the experimentally observed number of cells. The relative rotational speed and the phase relation between the velocity and the flow angle variations are also in agreement with experimental data.
Rotating Stall Induced in Vaneless Diffusers of Very Low Specific Speed Centrifugal Blowers
Authors: Kinoshita Y. , Senoo Y.
Published: October 2009

The limit of rotating stall was experimentally determined for three very small specific speed centrifugal blowers. The impellers were specially designed for stall-free at very small flow rates, so that the cause of rotating stall could be attributed to the vaneless diffusers. Experimental results demonstrated that the blowers did not stall until the flow coefficient was reduced to very small values, which had never been reported in the literature. The critical flow coefficient for rotating stall agreed very well with the prediction based on a flow analysis and a criterion for rotating stall in vaneless diffusers developed by the authors.
The Effects of Reynolds Number on the Efficiency of Centrifugal Compressor Stages
Authors: Casey M. V.
Published: October 2009

An analysis of the friction losses in a centrifugal compressor stage is used to suggest a new form of correction equation for the effect of Reynolds number on efficiency. This equation relates the effect of Reynolds number to the surface roughness, the impeller outlet width ratio and the work input coefficient. Systematic tests on a wide range of compressor stages are used to calibrate the single empirical coefficient in the equation. Despite its simplicity this equation provides more accurate predictions of the Reynolds number effects than existing empirical methods.
A Universal Correlation for the Thermal Efficiency of Open Gas Turbine Cycle With Different Fuels
Authors: Leung E. Y. W.
Published: October 2009

It is well known that, unlike the thermal efficiency of closed gas turbine cycles, the thermal efficiency of open gas turbine cycles varies with the fuel used in the combustion process. Presented in this paper is a thorough investigation of the effects of hydrocarbon fuels and alcohol fuels on the thermal efficiency of open gas turbine cycle. Among the open cycles with different fuels and otherwise identical specifications, the computed thermal efficiencies show a variation of about 2 percent between the extremes, which is appreciable. It was found that the thermal efficiency increases with a parameter of the fuel, c1 + c2, taken from the equation of reaction, c(Fuel)+O2→c1(CO2)+c2(H2O), and that the thermal efficiency of open gas turbine cycles is likely to be higher if the original fuel is replaced by a fuel which has a higher fuel parameter, c1 + c2. A universal correlation for both hydrocarbon fuels and alcohol fuels is presented in Fig. 1, plotting the thermal efficiency maximized from the pressure ratio variation, versus the parameter, c1 + c2. Alternatively, this correlation is also generalized by equation (2).
Steam Cycle Regeneration Influence on Combined Gas-Steam Power Plant Performance
Authors: Cerri G. , Colage´ A.
Published: October 2009

The influence of steam cycle regeneration on combined plant performance has been analyzed from the thermodynamic point of view. A mathematical model has been developed and calculations have been performed according to a cycle analysis criterion. The higher the number of extractions the lower the relative efficiency gain. The influence of the intermediate feedwater temperatures is very small when these temperatures are slightly changed in relation to the equally spaced values. Results are given for a gas turbine firing temperature equal to 1000°C. They show a positive influence on combined cycle efficiency for small regeneration degrees. Gas turbine firing temperature in the range of 800–1400°C has been considered. The influence of the economizer inlet temperature lower limit is shown.
Power Plant Spray Cooling: Design and Performance Studies
Authors: Palaszewski S. J. , Weinbaum S. , Jiji L. M.
Published: October 2009

A new three-dimensional model for determining the flow and thermal characteristics of spray units is utilized in an effort to predict and improve the cooling efficiency of spray units. In a marked departure from present theories, which are based on the behavior of an average droplet in a uniform average environment, the model examines the local variation in properties of both the air and the droplets throughout the flow field encompassing the spray umbrella. Model predictions of droplet return temperature along the spray perimeter, downwind wet-bulb temperature, and downwind air-velocity were compared with field data on a commercial spray. Good agreement was observed. A parametric study was then performed to determine the optimum droplet size and discharge angle for a spray unit. It was found that substantial improvements in the cooling obtained for a given spray power input can be achieved over currently used floating spray units.
Heat Exchanger Fires and the Ignition of Solid Metals
Authors: Theoclitus G.
Published: October 2009

Solid metals can ignite and burn from the heat released through the oxidation reaction and related to the rate in which heat is dispersed. The fires can be promoted by the preignition of combustible accumulations at temperatures normally considered as relatively safe oxidation conditions. Experimental studies for fire and theoretical ignition temperatures are described in the paper.
A Model for Convective Boiling in a Narrow Eccentric Annular Gap
Authors: Tong C. R. , Tan M. J. , Bankoff S. G.
Published: October 2009

A steady-state model is developed for convective boiling and dryout in an eccentric annulus with line contact between the heated inner wall and the adiabatic outer wall. The geometry and heat transfer conditions resemble those in a PWR steam generator, except for the lower pressure. Good agreement is shown with experimental data reported elsewhere.
The Transpired Turbulent Boundary Layer in Various Pressure Gradients and the Blow-Off Condition
Authors: Georgiou D. P. , Louis J. F.
Published: October 2009

An experimental study of the reduction in heat transfer to a transpiration-cooled flat surface subjected to pressure gradients (zero, negative, and positive) is presented for flow conditions similar to those encountered in gas turbines. The investigation is carried out for high injection rates and determines the blow-off conditions under which the boundary layer is lifted away from the wall by the transpired coolant. The study was conducted in a hot blow-down wind tunnel facility. The transient nature of the facility ensures that the wall remains isothermal. The Reynolds number, the ratio of the gas to wall temperatures, and the pressure gradient parameters K are chosen to be representative of the conditions found in advanced gas turbines. The effect of the pressure gradient was found to be small. However, a local strong acceleration can reduce the cooling effectiveness. The heat transfer rates or Stanton numbers on a solid surface downstream of a transpiration cooled wall are found to be sensitive to the upstream injection ratio (b) and to the pressure gradient parameter. The data indicate that the ratio of Stanton numbers with and without cooling is nonzero for values of the injection parameters larger than values obtained theoretically by Kutateladze. The predicted value of the critical injection ratio (bcr) determined from this study agrees well with the experimental data of Liepmann and Laufer for a free mixing layer, which is similar to a transpired boundary layer near blow-off as pointed out by Coles.
Performance and Flowrate Control of the Kinetic Extruder Coal Powder Pump
Authors: Meyer J. W. , Bonin J. H.
Published: October 2009

The kinetic extruder is a novel centrifugal machine for feeding powdered material, in particular coal, against gas back pressure. The nonmechanical method of flow-rate control in the machine is described. Performance data obtained in tests of the kinetic extruder are presented and compared with theoretical predictions. It is found that a one-dimensional model of the material flow through the device gives accurate predictions of most aspects of the machine’s performance. However, some details of the limiting behavior evidently require a more refined analysis.
Characterization of Solid Particle Erosion Resistance of Ductile Metals Based on Their Properties
Authors: Rao P. V. , Buckley D. H.
Published: October 2009

This paper presents experimental results pertaining to spherical glass bead and angular crushed glass particle impingement. A concept of energy absorption to explain the failure of material is proposed and is correlated with the erosion characteristics of several pure metals. Analyses of extensive erosion data indicate that the properties—surface energy, specific melting energy, strain energy, melting point, bulk modulus, hardness, atomic volume—and the product of the parameters—linear coefficient of thermal expansion × bulk modulus × temperature rise required for melting, and ultimate resilience × hardness—exhibit the best correlations. The properties of surface energy and atomic volume are suggested for the first time for correlation purposes and are found to correlate well with erosion rates at different angles of impingement. It further appears that both energy and thermal properties contribute to the total erosion.
Combustion Efficiency of a Premixed Continuous Flow Combustor
Authors: Anand M. S. , Gouldin F. C.
Published: October 2009

Experimental data in the form of radial profiles of mean temperature, gas composition and velocity at the combustor exit and combustion efficiency are reported and discussed for a swirling flow, continuous combustor. The combustor is composed of two confined, concentric independently swirling jets: an outer, annular air jet and a central premixed fuel-air jet, the fuel being propane or methane. Combustion is stabilized by a swirl-generated central recirculation zone. The primary objective of this research is to determine the effect of fuel substitution and of changes in outer flow swirl conditions on combustor performance. Results are very similar for both methane and propane. Changes in outer flow swirl cause significant changes in exit profiles, but, surprisingly, combustion efficiency is relatively unchanged. A combustion mechanism is proposed which qualitatively explains the results and identifies important flow characteristics and physical processes determining combustion efficiency. It is hypothesized that combustion occurs in a thin sheet, similar in structure to a premixed turbulent flame, anchored on the combustor centerline just upstream of the recirculation zone and swept downstream with the flow. Combustion efficiency depends on the extent of the radial propagation, across mean flow streamtubes, of this reaction sheet. It is concluded that, in general, this propagation and hence efficiency are extremely sensitive to flow conditions.
The Prediction of Several Residual Oil Flames
Authors: Abbas A. S. , Lockwood F. C.
Published: October 2009

This paper describes the application of a general computational procedure to predict four residual oil trials conducted at the International Flame Research Foundation. These trials were conducted in an attempt to isolate scaling criteria based on conventional similarity arguments. However, it is here demonstrated that, after a single preliminary calibration limited to one of the model constants, very acceptable and detailed predictions can be obtained using the present method for all of the trials.